Changeux JP


Full name : Changeux Jean-Pierre

First name : Jean-Pierre

Mail : Neurobiologie Moleculaire, CNRS URA 1284, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris

Zip Code :

City :

Country : France

Email :

Phone : 33 1 45 68 88 45

Fax : 33 1 45 68 88 36

Website : \/\/\/wiki\/Jean-Pierre_Changeux

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References (168)

Title : Do Nicotinic Receptors Modulate High-Order Cognitive Processing? - Koukouli_2020_Trends.Neurosci_43_550
Author(s) : Koukouli F , Changeux JP
Ref : Trends in Neurosciences , 43 :550 , 2020
Abstract : Recent studies provided strong evidence that deficits in cholinergic signaling cause disorders of cognition and affect conscious processing. Technical advances that combine molecular approaches, in vivo recordings in awake behaving animals, human brain imaging, and genetics have strengthened our understanding of the roles of nicotinic acetylcholine receptors (nAChRs) in the modulation of cognitive behavior and network dynamics. Here, we review the emergent role of nAChRs in high-order cognitive processes and discuss recent work implicating cholinergic circuits in cognitive control, including conscious processing.
ESTHER : Koukouli_2020_Trends.Neurosci_43_550
PubMedSearch : Koukouli_2020_Trends.Neurosci_43_550
PubMedID: 32591156

Title : Golden Anniversary of the Nicotinic Receptor - Changeux_2020_Neuron_107_14
Author(s) : Changeux JP
Ref : Neuron , 107 :14 , 2020
Abstract : The high-resolution structure of the nicotinic acetylcholine receptor from Torpedo electric tissue in association with the snake toxin alpha-bungarotoxin (Rahman et al., 2020) is presented 50 years after its identification as the first neurotransmitter receptor and ligand-gated ion channel.
ESTHER : Changeux_2020_Neuron_107_14
PubMedSearch : Changeux_2020_Neuron_107_14
PubMedID: 32645305

Title : Towards a cognitive neuroscience of self-awareness - Lou_2017_Neurosci.Biobehav.Rev_83_765
Author(s) : Lou HC , Changeux JP , Rosenstand A
Ref : Neurosci Biobehav Rev , 83 :765 , 2017
Abstract : Self-awareness is a pivotal component of conscious experience. It is correlated with a paralimbic network of medial prefrontal/anterior cingulate and medial parietal/posterior cingulate cortical "hubs" and associated regions. Electromagnetic and transmitter manipulation have demonstrated that the network is not an epiphenomenon but instrumental in generation of self-awareness. Thus, transcranial magnetic stimulation (TMS) targeting the hubs impedes different aspects of self-awareness with a latency of 160ms. The network is linked by approximately 40Hz oscillations and regulated by dopamine. The oscillations are generated by rhythmic GABA-ergic inhibitory activity in interneurons with an extraordinarily high metabolic rate. The hubs are richly endowed with interneurons and therefore highly vulnerable to disturbed energy supply. Consequently, deficient paralimbic activity and self-awareness are characteristic features of many disorders with impaired oxygen homeostasis. Such disorders may therefore be treated unconventionally by targeting interneuron function.
ESTHER : Lou_2017_Neurosci.Biobehav.Rev_83_765
PubMedSearch : Lou_2017_Neurosci.Biobehav.Rev_83_765
PubMedID: 27079562

Title : Climbing Brain Levels of Organisation from Genes to Consciousness - Changeux_2017_Trends.Cogn.Sci_21_168
Author(s) : Changeux JP
Ref : Trends Cogn Sci , 21 :168 , 2017
Abstract : Given the tremendous complexity of brain organisation, here I propose a strategy that dynamically links stages of brain organisation from genes to consciousness, at four privileged structural levels: genes; transcription factors (TFs)-gene networks; synaptic epigenesis; and long-range connectivity. These structures are viewed as nested and reciprocally inter-regulated, with a hierarchical organisation that proceeds on different timescales during the course of evolution and development. Interlevel bridging mechanisms include intrinsic variation-selection mechanisms, which offer a community of bottom-up and top-down models linking genes to consciousness in a stepwise manner.
ESTHER : Changeux_2017_Trends.Cogn.Sci_21_168
PubMedSearch : Changeux_2017_Trends.Cogn.Sci_21_168
PubMedID: 28161289

Title : Nicotine reverses hypofrontality in animal models of addiction and schizophrenia - Koukouli_2017_Nat.Med_23_347
Author(s) : Koukouli F , Rooy M , Tziotis D , Sailor KA , O'Neill HC , Levenga J , Witte M , Nilges M , Changeux JP , Hoeffer CA , Stitzel JA , Gutkin BS , DiGregorio DA , Maskos U
Ref : Nat Med , 23 :347 , 2017
Abstract : The prefrontal cortex (PFC) underlies higher cognitive processes that are modulated by nicotinic acetylcholine receptor (nAChR) activation by cholinergic inputs. PFC spontaneous default activity is altered in neuropsychiatric disorders, including schizophrenia-a disorder that can be accompanied by heavy smoking. Recently, genome-wide association studies (GWAS) identified single-nucleotide polymorphisms (SNPs) in the human CHRNA5 gene, encoding the alpha5 nAChR subunit, that increase the risks for both smoking and schizophrenia. Mice with altered nAChR gene function exhibit PFC-dependent behavioral deficits, but it is unknown how the corresponding human polymorphisms alter the cellular and circuit mechanisms underlying behavior. Here we show that mice expressing a human alpha5 SNP exhibit neurocognitive behavioral deficits in social interaction and sensorimotor gating tasks. Two-photon calcium imaging in awake mouse models showed that nicotine can differentially influence PFC pyramidal cell activity by nAChR modulation of layer II/III hierarchical inhibitory circuits. In alpha5-SNP-expressing and alpha5-knockout mice, lower activity of vasoactive intestinal polypeptide (VIP) interneurons resulted in an increased somatostatin (SOM) interneuron inhibitory drive over layer II/III pyramidal neurons. The decreased activity observed in alpha5-SNP-expressing mice resembles the hypofrontality observed in patients with psychiatric disorders, including schizophrenia and addiction. Chronic nicotine administration reversed this hypofrontality, suggesting that administration of nicotine may represent a therapeutic strategy for the treatment of schizophrenia, and a physiological basis for the tendency of patients with schizophrenia to self-medicate by smoking.
ESTHER : Koukouli_2017_Nat.Med_23_347
PubMedSearch : Koukouli_2017_Nat.Med_23_347
PubMedID: 28112735

Title : Allosteric Modulation as a Unifying Mechanism for Receptor Function and Regulation - Changeux_2016_Cell_166_1084
Author(s) : Changeux JP , Christopoulos A
Ref : Cell , 166 :1084 , 2016
Abstract : Four major receptor families enable cells to respond to chemical and physical signals from their proximal environment. The ligand- and voltage-gated ion channels, G-protein-coupled receptors, nuclear hormone receptors, and receptor tyrosine kinases are all allosteric proteins that carry multiple, spatially distinct, yet conformationally linked ligand-binding sites. Recent studies point to common mechanisms governing the allosteric transitions of these receptors, including the impact of oligomerization, pre-existing and functionally distinct conformational ensembles, intrinsically disordered regions, and the occurrence of allosteric modulatory sites. Importantly, synthetic allosteric modulators are being discovered for these receptors, providing an enriched, yet challenging, landscape for novel therapeutics.
ESTHER : Changeux_2016_Cell_166_1084
PubMedSearch : Changeux_2016_Cell_166_1084
PubMedID: 27565340

Title : Biased Allostery - Edelstein_2016_Biophys.J_111_902
Author(s) : Edelstein SJ , Changeux JP
Ref : Biophysical Journal , 111 :902 , 2016
Abstract : G-protein-coupled receptors (GPCRs) constitute a large group of integral membrane proteins that transduce extracellular signals from a wide range of agonists into targeted intracellular responses. Although the responses can vary depending on the category of G-proteins activated by a particular receptor, responses were also found to be triggered by interactions of the receptor with beta-arrestins. It was subsequently discovered that for the same receptor molecule (e.g., the beta-adrenergic receptor), some agonists have a propensity to specifically favor responses by G-proteins, others by beta-arrestins, as has now been extensively studied. This feature of the GPCR system is known as biased agonism and is subject to various interpretations, including agonist-induced conformational change versus selective stabilization of preexisting active conformations. Here, we explore a complete allosteric framework for biased agonism based on alternative preexisting conformations that bind more strongly, but nonexclusively, either G-proteins or beta-arrestins. The framework incorporates reciprocal effects among all interacting molecules. As a result, G-proteins and beta-arrestins are in steric competition for binding to the cytoplasmic surface of either the G-protein-favoring or beta-arrestin-favoring GPCR conformation. Moreover, through linkage relations, the strength of the interactions of G-proteins or beta-arrestins with the corresponding active conformation potentiates the apparent affinity for the agonist, effectively equating these two proteins to allosteric modulators. The balance between response alternatives can also be influenced by the physiological concentrations of either G-proteins or beta-arrestins, as well as by phosphorylation or interactions with positive or negative allosteric modulators. The nature of the interactions in the simulations presented suggests novel experimental tests to distinguish more fully among alternative mechanisms.
ESTHER : Edelstein_2016_Biophys.J_111_902
PubMedSearch : Edelstein_2016_Biophys.J_111_902
PubMedID: 27602718

Title : Nicotinic receptors in mouse prefrontal cortex modulate ultraslow fluctuations related to conscious processing - Koukouli_2016_Proc.Natl.Acad.Sci.U.S.A_113_14823
Author(s) : Koukouli F , Rooy M , Changeux JP , Maskos U
Ref : Proc Natl Acad Sci U S A , 113 :14823 , 2016
Abstract : The prefrontal cortex (PFC) plays an important role in cognitive processes, including access to consciousness. The PFC receives significant cholinergic innervation and nicotinic acetylcholine receptors (nAChRs) contribute greatly to the effects of acetylcholine signaling. Using in vivo two-photon imaging of both awake and anesthetized mice, we recorded spontaneous, ongoing neuronal activity in layer II/III in the PFC of WT mice and mice deleted for different nAChR subunits. As in humans, this activity is characterized by synchronous ultraslow fluctuations and neuronal synchronicity is disrupted by light general anesthesia. Both the alpha7 and beta2 nAChR subunits play an important role in the generation of ultraslow fluctuations that occur to a different extent during quiet wakefulness and light general anesthesia. The beta2 subunit is specifically required for synchronized activity patterns. Furthermore, chronic application of mecamylamine, an antagonist of nAChRs, disrupts the generation of ultraslow fluctuations. Our findings provide new insight into the ongoing spontaneous activity in the awake and anesthetized state, and the role of cholinergic neurotransmission in the orchestration of cognitive functions.
ESTHER : Koukouli_2016_Proc.Natl.Acad.Sci.U.S.A_113_14823
PubMedSearch : Koukouli_2016_Proc.Natl.Acad.Sci.U.S.A_113_14823
PubMedID: 27911815

Title : The nicotinic alpha6 subunit gene determines variability in chronic pain sensitivity via cross-inhibition of P2X2\/3 receptors - Wieskopf_2015_Sci.Transl.Med_7_287ra72
Author(s) : Wieskopf JS , Mathur J , Limapichat W , Post MR , Al-Qazzaz M , Sorge RE , Martin LJ , Zaykin DV , Smith SB , Freitas K , Austin JS , Dai F , Zhang J , Marcovitz J , Tuttle AH , Slepian PM , Clarke S , Drenan RM , Janes J , Al Sharari S , Segall SK , Aasvang EK , Lai W , Bittner R , Richards CI , Slade GD , Kehlet H , Walker J , Maskos U , Changeux JP , Devor M , Maixner W , Diatchenko L , Belfer I , Dougherty DA , Su AI , Lummis SC , Damaj MI , Lester HA , Patapoutian A , Mogil JS
Ref : Sci Transl Med , 7 :287ra72 , 2015
Abstract : Chronic pain is a highly prevalent and poorly managed human health problem. We used microarray-based expression genomics in 25 inbred mouse strains to identify dorsal root ganglion (DRG)-expressed genetic contributors to mechanical allodynia, a prominent symptom of chronic pain. We identified expression levels of Chrna6, which encodes the alpha6 subunit of the nicotinic acetylcholine receptor (nAChR), as highly associated with allodynia. We confirmed the importance of alpha6* (alpha6-containing) nAChRs by analyzing both gain- and loss-of-function mutants. We find that mechanical allodynia associated with neuropathic and inflammatory injuries is significantly altered in alpha6* mutants, and that alpha6* but not alpha4* nicotinic receptors are absolutely required for peripheral and/or spinal nicotine analgesia. Furthermore, we show that Chrna6's role in analgesia is at least partially due to direct interaction and cross-inhibition of alpha6* nAChRs with P2X2/3 receptors in DRG nociceptors. Finally, we establish the relevance of our results to humans by the observation of genetic association in patients suffering from chronic postsurgical and temporomandibular pain.
ESTHER : Wieskopf_2015_Sci.Transl.Med_7_287ra72
PubMedSearch : Wieskopf_2015_Sci.Transl.Med_7_287ra72
PubMedID: 25972004

Title : The nicotinic acetylcholine receptor and its prokaryotic homologues: Structure, conformational transitions & allosteric modulation - Cecchini_2015_Neuropharmacol_96_137
Author(s) : Cecchini M , Changeux JP
Ref : Neuropharmacology , 96 :137 , 2015
Abstract : Pentameric ligand-gated ion channels (pLGICs) play a central role in intercellular communications in the nervous system by converting the binding of a chemical messenger - a neurotransmitter - into an ion flux through the postsynaptic membrane. Here, we present an overview of the most recent advances on the signal transduction mechanism boosted by X-ray crystallography of both prokaryotic and eukaryotic homologues of the nicotinic acetylcholine receptor (nAChR) in conjunction with time-resolved analyses based on single-channel electrophysiology and Molecular Dynamics simulations. The available data consistently point to a global mechanism of gating that involves a large reorganization of the receptor mediated by two distinct quaternary transitions: a global twisting and a radial expansion/contraction of the extracellular domain. These transitions profoundly modify the organization of the interface between subunits, which host several sites for orthosteric and allosteric modulatory ligands. The same mechanism may thus mediate both positive and negative allosteric modulations of pLGICs ligand binding at topographically distinct sites. The emerging picture of signal transduction is expected to pave the way to new pharmacological strategies for the development of allosteric modulators of nAChR and pLGICs in general. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.
ESTHER : Cecchini_2015_Neuropharmacol_96_137
PubMedSearch : Cecchini_2015_Neuropharmacol_96_137
PubMedID: 25529272

Title : The nicotinic acetylcholine receptor: From molecular biology to cognition -
Author(s) : Changeux JP , Corringer PJ , Maskos U
Ref : Neuropharmacology , 96 :135 , 2015
PubMedID: 25842243

Title : Crystal structures of a pentameric ligand-gated ion channel provide a mechanism for activation - Sauguet_2014_Proc.Natl.Acad.Sci.U.S.A_111_966
Author(s) : Sauguet L , Shahsavar A , Poitevin F , Huon C , Menny A , Nemecz A , Haouz A , Changeux JP , Corringer PJ , Delarue M
Ref : Proc Natl Acad Sci U S A , 111 :966 , 2014
Abstract : Pentameric ligand-gated ion channels mediate fast chemical transmission of nerve signals. The structure of a bacterial proton-gated homolog has been established in its open and locally closed conformations at acidic pH. Here we report its crystal structure at neutral pH, thereby providing the X-ray structures of the two end-points of the gating mechanism in the same pentameric ligand-gated ion channel. The large structural variability in the neutral pH structure observed in the four copies of the pentamer present in the asymmetric unit has been used to analyze the intrinsic fluctuations in this state, which are found to prefigure the transition to the open state. In the extracellular domain (ECD), a marked quaternary change is observed, involving both a twist and a blooming motion, and the pore in the transmembrane domain (TMD) is closed by an upper bend of helix M2 (as in locally closed form) and a kink of helix M1, both helices no longer interacting across adjacent subunits. On the tertiary level, detachment of inner and outer beta sheets in the ECD reshapes two essential cavities at the ECD-ECD and ECD-TMD interfaces. The first one is the ligand-binding cavity; the other is close to a known divalent cation binding site in other pentameric ligand-gated ion channels. In addition, a different crystal form reveals that the locally closed and open conformations coexist as discrete ones at acidic pH. These structural results, together with site-directed mutagenesis, physiological recordings, and coarse-grained modeling, have been integrated to propose a model of the gating transition pathway.
ESTHER : Sauguet_2014_Proc.Natl.Acad.Sci.U.S.A_111_966
PubMedSearch : Sauguet_2014_Proc.Natl.Acad.Sci.U.S.A_111_966
PubMedID: 24367074

Title : Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement - Tolu_2013_Mol.Psychiatry_18_382
Author(s) : Tolu S , Eddine R , Marti F , David V , Graupner M , Pons S , Baudonnat M , Husson M , Besson M , Reperant C , Zemdegs J , Pages C , Hay YA , Lambolez B , Caboche J , Gutkin B , Gardier AM , Changeux JP , Faure P , Maskos U
Ref : Mol Psychiatry , 18 :382 , 2013
Abstract : Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or gamma-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.
ESTHER : Tolu_2013_Mol.Psychiatry_18_382
PubMedSearch : Tolu_2013_Mol.Psychiatry_18_382
PubMedID: 22751493

Title : Intermediate closed state for glycine receptor function revealed by cysteine cross-linking - Prevost_2013_Proc.Natl.Acad.Sci.U.S.A_110_17113
Author(s) : Prevost MS , Moraga-Cid G , Van Renterghem C , Edelstein SJ , Changeux JP , Corringer PJ
Ref : Proc Natl Acad Sci U S A , 110 :17113 , 2013
Abstract : Pentameric ligand-gated ion channels (pLGICs) mediate signal transmission by coupling the binding of extracellular ligands to the opening of their ion channel. Agonist binding elicits activation and desensitization of pLGICs, through several conformational states, that are, thus far, incompletely characterized at the structural level. We previously reported for GLIC, a prokaryotic pLGIC, that cross-linking of a pair of cysteines at both sides of the extracellular and transmembrane domain interface stabilizes a locally closed (LC) X-ray structure. Here, we introduced the homologous pair of cysteines on the human alpha1 glycine receptor. We show by electrophysiology that cysteine cross-linking produces a gain-of-function phenotype characterized by concomitant constitutive openings, increased agonist potency, and equalization of efficacies of full and partial agonists. However, it also produces a reduction of maximal currents at saturating agonist concentrations without change of the unitary channel conductance, an effect reversed by the positive allosteric modulator propofol. The cross-linking thus favors a unique closed state distinct from the resting and longest-lived desensitized states. Fitting the data according to a three-state allosteric model suggests that it could correspond to a LC conformation. Its plausible assignment to a gating intermediate or a fast-desensitized state is discussed. Overall, our data show that relative movement of two loops at the extracellular-transmembrane interface accompanies orthosteric agonist-mediated gating.
ESTHER : Prevost_2013_Proc.Natl.Acad.Sci.U.S.A_110_17113
PubMedSearch : Prevost_2013_Proc.Natl.Acad.Sci.U.S.A_110_17113
PubMedID: 24085847

Title : Modulation of the mouse prefrontal cortex activation by neuronal nicotinic receptors during novelty exploration but not by exploration of a familiar environment - Bourgeois_2012_Cereb.Cortex_22_1007
Author(s) : Bourgeois JP , Meas-Yeadid V , Lesourd AM , Faure P , Pons S , Maskos U , Changeux JP , Olivo-Marin JC , Granon S
Ref : Cerebral Cortex , 22 :1007 , 2012
Abstract : Organization of locomotor behavior is altered in mice knockout for the beta2 subunit of the nicotinic receptor-beta2-/- mice-during novelty exploration. We investigated the neuronal basis of this alteration by measuring activation of the immediate early gene c-fos in the brains of wild-type (WT) and beta2-/- mice after exploration of a novel or a familiar environment. Results show 1) no constitutive difference between WT and beta2-/- mice in c-fos gene expression in any brain region, 2) novelty exploration triggered activation of the hippocampus and the reward circuit while exploration of a familiar environment produced increased activation in the amygdala, and 3) in beta2-/- mice, exploration of novelty, but not familiarity, induced an increase in activation in the prelimbic prefrontal cortex (PFC) compared with WT mice. c-Fos immunoreactivity after different stages of learning in a maze increased similarly in the prelimbic area of both WT and beta2-/- mice, while their performance differed. In WT mice, exploration of a novel environment triggered an increase in c-Fos expression in the reward circuit and the hippocampus, while in beta2-/- mice, the amygdala and the motor cortex were additionally activated. We also highlight the role of nicotinic receptors during activation of the PFC, specifically during free exploration of a novel environment.
ESTHER : Bourgeois_2012_Cereb.Cortex_22_1007
PubMedSearch : Bourgeois_2012_Cereb.Cortex_22_1007
PubMedID: 21810785

Title : Prefrontal nicotinic receptors control novel social interaction between mice - Avale_2011_FASEB.J_25_2145
Author(s) : Avale ME , Chabout J , Pons S , Serreau P , De Chaumont F , Olivo-Marin JC , Bourgeois JP , Maskos U , Changeux JP , Granon S
Ref : FASEB Journal , 25 :2145 , 2011
Abstract : Social behavior is a defining mammalian feature that integrates emotional and motivational processes with external rewarding stimuli. It is thus an appropriate readout for complex behaviors, yet its neuronal and molecular bases remain poorly understood. In this study, we investigated the role of the mouse prefrontal area, particularly the involvement of beta2-subunit nicotinic receptors (beta2*-nAChRs) in a paradigm of social behavior with concurrent motivations. We previously observed that mice lacking beta2*-nAChRs (beta2(-/-)) display increased time in social contact and exaggerated approach movements toward the novel conspecific. Here, combining behavioral analysis, localized brain lesions, and lentiviral gene rescue, we found that c-Fos expression is specifically activated in the prelimbic (PrL) area of the prefrontal cortex (PFC) of mice exposed to a novel conspecific; lesions of the PrL area in wild-type mice produce the same social pattern as in beta2(-/-) mice; and virally mediated reexpression of the beta2-subunit in the PrL area of beta2(-/-) mice rescues behavioral components in the social interaction task up to normal levels. Together, these data reveal that social interactions particularly mobilize the PrL area of the mouse PFC and that the presence of functional PrL beta2*-nAChRs is necessary for this integrated behavior to emerge.
ESTHER : Avale_2011_FASEB.J_25_2145
PubMedSearch : Avale_2011_FASEB.J_25_2145
PubMedID: 21402717

Title : X-ray structures of general anaesthetics bound to a pentameric ligand-gated ion channel - Nury_2011_Nature_469_428
Author(s) : Nury H , Van Renterghem C , Weng Y , Tran A , Baaden M , Dufresne V , Changeux JP , Sonner JM , Delarue M , Corringer PJ
Ref : Nature , 469 :428 , 2011
Abstract : General anaesthetics have enjoyed long and widespread use but their molecular mechanism of action remains poorly understood. There is good evidence that their principal targets are pentameric ligand-gated ion channels (pLGICs) such as inhibitory GABA(A) (gamma-aminobutyric acid) receptors and excitatory nicotinic acetylcholine receptors, which are respectively potentiated and inhibited by general anaesthetics. The bacterial homologue from Gloeobacter violaceus (GLIC), whose X-ray structure was recently solved, is also sensitive to clinical concentrations of general anaesthetics. Here we describe the crystal structures of the complexes propofol/GLIC and desflurane/GLIC. These reveal a common general-anaesthetic binding site, which pre-exists in the apo-structure in the upper part of the transmembrane domain of each protomer. Both molecules establish van der Waals interactions with the protein; propofol binds at the entrance of the cavity whereas the smaller, more flexible, desflurane binds deeper inside. Mutations of some amino acids lining the binding site profoundly alter the ionic response of GLIC to protons, and affect its general-anaesthetic pharmacology. Molecular dynamics simulations, performed on the wild type (WT) and two GLIC mutants, highlight differences in mobility of propofol in its binding site and help to explain these effects. These data provide a novel structural framework for the design of general anaesthetics and of allosteric modulators of brain pLGICs.
ESTHER : Nury_2011_Nature_469_428
PubMedSearch : Nury_2011_Nature_469_428
PubMedID: 21248852

Title : Distinct contributions of nicotinic acetylcholine receptor subunit alpha4 and subunit alpha6 to the reinforcing effects of nicotine - Exley_2011_Proc.Natl.Acad.Sci.U.S.A_108_7577
Author(s) : Exley R , Maubourguet N , David V , Eddine R , Evrard A , Pons S , Marti F , Threlfell S , Cazala P , McIntosh JM , Changeux JP , Maskos U , Cragg SJ , Faure P
Ref : Proc Natl Acad Sci U S A , 108 :7577 , 2011
Abstract : Nicotine is the primary psychoactive component of tobacco. Its reinforcing and addictive properties depend on nicotinic acetylcholine receptors (nAChRs) located within the mesolimbic axis originating in the ventral tegmental area (VTA). The roles and oligomeric assembly of subunit alpha4- and subunit alpha6-containing nAChRs in dopaminergic (DAergic) neurons are much debated. Using subunit-specific knockout mice and targeted lentiviral re-expression, we have determined the subunit dependence of intracranial nicotine self-administration (ICSA) into the VTA and the effects of nicotine on dopamine (DA) neuron excitability in the VTA and on DA transmission in the nucleus accumbens (NAc). We show that the alpha4 subunit, but not the alpha6 subunit, is necessary for ICSA and nicotine-induced bursting of VTA DAergic neurons, whereas subunits alpha4 and alpha6 together regulate the activity dependence of DA transmission in the NAc. These data suggest that alpha4-dominated enhancement of burst firing in DA neurons, relayed by DA transmission in NAc that is gated by nAChRs containing alpha4 and alpha6 subunits, underlies nicotine self-administration and its long-term maintenance.
ESTHER : Exley_2011_Proc.Natl.Acad.Sci.U.S.A_108_7577
PubMedSearch : Exley_2011_Proc.Natl.Acad.Sci.U.S.A_108_7577
PubMedID: 21502501

Title : alpha-Conotoxin BuIA[T5A\;P6O]: a novel ligand that discriminates between alpha6ss4 and alpha6ss2 nicotinic acetylcholine receptors and blocks nicotine-stimulated norepinephrine release - Azam_2010_FASEB.J_24_5113
Author(s) : Azam L , Maskos U , Changeux JP , Dowell CD , Christensen S , De Biasi M , McIntosh JM
Ref : FASEB Journal , 24 :5113 , 2010
Abstract : alpha6* (asterisk indicates the presence of additional subunits) nicotinic acetylcholine receptors (nAChRs) are broadly implicated in catecholamine-dependent disorders that involve attention, motor movement, and nicotine self-administration. Different molecular forms of alpha6 nAChRs mediate catecholamine release, but receptor differentiation is greatly hampered by a paucity of subtype selective ligands. alpha-Conotoxins are nAChR-targeted peptides used by Conus species to incapacitate prey. We hypothesized that distinct conotoxin-binding kinetics could be exploited to develop a series of selective probes to enable study of native receptor subtypes. Proline6 of alpha-conotoxin BuIA was found to be critical for nAChR selectivity; substitution of proline6 with 4-hydroyxproline increased the IC(50) by 2800-fold at alpha6/alpha3beta2beta3 but only by 6-fold at alpha6/alpha3beta4 nAChRs (to 1300 and 12 nM, respectively). We used conotoxin probes together with subunit-null mice to interrogate nAChR subtypes that modulate hippocampal norepinephrine release. Release was abolished in alpha6-null mutant mice. alpha-Conotoxin BuIA[T5A;P6O] partially blocked norepinephrine release in wild-type controls but failed to block release in beta4(-/-) mice. In contrast, BuIA[T5A;P6O] failed to block dopamine release in the wild-type striatum known to contain alpha6beta2* nAChRs. BuIA[T5A;P6O] is a novel ligand for distinguishing between closely related alpha6* nAChRs; alpha6beta4* nAChRs modulate norepinephrine release in hippocampus but not dopamine release in striatum.
ESTHER : Azam_2010_FASEB.J_24_5113
PubMedSearch : Azam_2010_FASEB.J_24_5113
PubMedID: 20739611

Title : A versatile system for the neuronal subtype specific expression of lentiviral vectors - Tolu_2010_FASEB.J_24_723
Author(s) : Tolu S , Avale ME , Nakatani H , Pons S , Parnaudeau S , Tronche F , Vogt A , Monyer H , Vogel R , De Chaumont F , Olivo-Marin JC , Changeux JP , Maskos U
Ref : FASEB Journal , 24 :723 , 2010
Abstract : Lentiviral expression vectors are powerful tools for gene therapy and long-term gene expression/repression in the mammalian brain. However, no specificity of transduction has been reported so far in the central nervous system. Here we have developed a novel system to achieve a neuronal subtype specific expression in either dopaminergic (DA) or GABAergic neurons. We employed a delivery strategy by which the transgene is not expressed until its activation by Cre recombinase. We successfully tested the system in vitro and then used this novel lentivector, containing loxP sites, in 2 different transgenic mouse lines expressing Cre either in DA or in GABAergic neurons. In both lines the reporter gene was detected exclusively in Cre-positive cells, demonstrating that with this experimental approach we were able to achieve completely specific expression of transgenes delivered by lentiviral vectors. This universal system can be applied to all neural subtypes making use of the growing number of specific Cre driver lines.- Tolu, S., Avale, M. E., Nakatani, H., Pons, S., Parnaudeau, S., Tronche, F., Vogt, A., Monyer, H., Vogel, R., de Chaumont, F., Olivo-Marin, J.-C., Changeux, J.-P., Maskos, U. A versatile system for the neuronal subtype specific expression of lentiviral vectors.
ESTHER : Tolu_2010_FASEB.J_24_723
PubMedSearch : Tolu_2010_FASEB.J_24_723
PubMedID: 19858094

Title : One-microsecond molecular dynamics simulation of channel gating in a nicotinic receptor homologue - Nury_2010_Proc.Natl.Acad.Sci.U.S.A_107_6275
Author(s) : Nury H , Poitevin F , Van Renterghem C , Changeux JP , Corringer PJ , Delarue M , Baaden M
Ref : Proc Natl Acad Sci U S A , 107 :6275 , 2010
Abstract : Recently discovered bacterial homologues of eukaryotic pentameric ligand-gated ion channels, such as the Gloeobacter violaceus receptor (GLIC), are increasingly used as structural and functional models of signal transduction in the nervous system. Here we present a one-microsecond-long molecular dynamics simulation of the GLIC channel pH stimulated gating mechanism. The crystal structure of GLIC obtained at acidic pH in an open-channel form is equilibrated in a membrane environment and then instantly set to neutral pH. The simulation shows a channel closure that rapidly takes place at the level of the hydrophobic furrow and a progressively increasing quaternary twist. Two major events are captured during the simulation. They are initiated by local but large fluctuations in the pore, taking place at the top of the M2 helix, followed by a global tertiary relaxation. The two-step transition of the first subunit starts within the first 50 ns of the simulation and is followed at 450 ns by its immediate neighbor in the pentamer, which proceeds with a similar scenario. This observation suggests a possible two-step domino-like tertiary mechanism that takes place between adjacent subunits. In addition, the dynamical properties of GLIC described here offer an interpretation of the paradoxical properties of a permeable A13'F mutant whose crystal structure determined at 3.15 A shows a pore too narrow to conduct ions.
ESTHER : Nury_2010_Proc.Natl.Acad.Sci.U.S.A_107_6275
PubMedSearch : Nury_2010_Proc.Natl.Acad.Sci.U.S.A_107_6275
PubMedID: 20308576

Title : Relationships between structural dynamics and functional kinetics in oligomeric membrane receptors - Edelstein_2010_Biophys.J_98_2045
Author(s) : Edelstein SJ , Changeux JP
Ref : Biophysical Journal , 98 :2045 , 2010
Abstract : Recent efforts to broaden understanding of the molecular mechanisms of membrane receptors in signal transduction make use of rate-equilibrium free-energy relationships (REFERs), previously applied to chemical reactions, enzyme kinetics, and protein folding. For oligomeric membrane receptors, we distinguish between a), the Leffler parameter alpha(L), to characterize the global transition state for the interconversion between conformations; and b), the Fersht parameter, varphi(F), to assign the degree of progression of individual residue positions at the transition state. For both alpha(L) and varphi(F), insights are achieved by using harmonic energy profiles to reflect the dynamic nature of proteins, as illustrated with single-channel results reported for normal and mutant nicotinic receptors. We also describe new applications of alpha(L) based on published results. For large-conductance calcium-activated potassium channels, data are satisfactorily fit with an alpha(L) value of 0.65, in accord with REFERs. In contrast, results reported for the flip conformational state of glycine and nicotinic receptors are in disaccord with REFERs, since they yield alpha(L) values outside the usual limits of 0-1. Concerning published varphi(F) values underlying the conformational wave hypothesis for nicotinic receptors, we note that interpretations may be complicated by variations in the width of harmonic energy profiles.
ESTHER : Edelstein_2010_Biophys.J_98_2045
PubMedSearch : Edelstein_2010_Biophys.J_98_2045
PubMedID: 20483311

Title : Regional changes in the cholinergic system in mice lacking monoamine oxidase A - Grailhe_2009_Brain.Res.Bull_78_283
Author(s) : Grailhe R , Cardona A , Even N , Seif I , Changeux JP , Cloez-Tayarani I
Ref : Brain Research Bulletin , 78 :283 , 2009
Abstract : Elevated brain monoamine concentrations resulting from monoamine oxidase A genetic ablation (MAOA knock-out mice) lead to changes in other neurotransmitter systems. To investigate the consequences of MAOA deficiency on the cholinergic system, we measured ligand binding to the high-affinity choline transporter (CHT1) and to muscarinic and nicotinic receptors in brain sections of MAOA knock-out (KO) and wild-type mice. A twofold increase in [(3)H]-hemicholinium-3 ([(3)H]-HC-3) binding to CHT1 was observed in the caudate putamen, nucleus accumbens, and motor cortex in MAOA KO mice as compared with wild-type (WT) mice. There was no difference in [(3)H]-HC-3 labeling in the hippocampus (dentate gyrus) between the two genotypes. Binding of [(125)I]-epibatidine ([(125)I]-Epi), [(125)I]-alpha-bungarotoxin ([(125)I]-BGT), [(3)H]-pirenzepine ([(3)H]-PZR), and [(3)H]-AFDX-384 ([(3)H]-AFX), which respectively label high- and low-affinity nicotinic receptors, M1 and M2 muscarinic cholinergic receptors, was not modified in the caudate putamen, nucleus accumbens, and motor cortex. A small but significant decrease of 19% in M1 binding densities was observed in the hippocampus (CA1 field) of KO mice. Next, we tested acetylcholinesterase activity and found that it was decreased by 25% in the striatum of KO mice as compared with WT mice. Our data suggest that genetic deficiency in MAOA enzyme is associated with changes in cholinergic activity, which may account for some of the behavioral alterations observed in mice and humans lacking MAOA.
ESTHER : Grailhe_2009_Brain.Res.Bull_78_283
PubMedSearch : Grailhe_2009_Brain.Res.Bull_78_283
PubMedID: 19111597

Title : Nicotinic receptors: allosteric transitions and therapeutic targets in the nervous system - Taly_2009_Nat.Rev.Drug.Discov_8_733
Author(s) : Taly A , Corringer PJ , Guedin D , Lestage P , Changeux JP
Ref : Nat Rev Drug Discov , 8 :733 , 2009
Abstract : Nicotinic receptors - a family of ligand-gated ion channels that mediate the effects of the neurotransmitter acetylcholine - are among the most well understood allosteric membrane proteins from a structural and functional perspective. There is also considerable interest in modulating nicotinic receptors to treat nervous-system disorders such as Alzheimer's disease, schizophrenia, depression, attention deficit hyperactivity disorder and tobacco addiction. This article describes both recent advances in our understanding of the assembly, activity and conformational transitions of nicotinic receptors, as well as developments in the therapeutic application of nicotinic receptor ligands, with the aim of aiding novel drug discovery by bridging the gap between these two rapidly developing fields.
ESTHER : Taly_2009_Nat.Rev.Drug.Discov_8_733
PubMedSearch : Taly_2009_Nat.Rev.Drug.Discov_8_733
PubMedID: 19721446

Title : Differential role of nicotinic acetylcholine receptor subunits in physical and affective nicotine withdrawal signs - Jackson_2008_J.Pharmacol.Exp.Ther_325_302
Author(s) : Jackson KJ , Martin BR , Changeux JP , Damaj MI
Ref : Journal of Pharmacology & Experimental Therapeutics , 325 :302 , 2008
Abstract : It has been suggested that the negative effects associated with nicotine withdrawal promote continued tobacco use and contribute to the high relapse rate of smoking behaviors. Thus, it is important to understand the receptor-mediated mechanisms underlying nicotine withdrawal to aid in the development of more successful smoking cessation therapies. The effects of nicotine withdrawal are mediated through nicotinic acetylcholine receptors (nAChRs); however, the role of nAChRs in nicotine withdrawal remains unclear. Therefore, we used mecamylamine-precipitated, spontaneous, and conditioned place aversion (CPA) withdrawal models to measure physical and affective signs of nicotine withdrawal in various nAChR knockout (KO) mice. beta2, alpha7, and alpha5 nAChR KO mice were chronically exposed to nicotine through surgically implanted osmotic minipumps. Our results show a loss of anxiety-related behavior and a loss of aversion in the CPA model in beta2 KO mice, whereas alpha7 and alpha5 KO mice displayed a loss of nicotine withdrawal-induced hyperalgesia and a reduction in somatic signs, respectively. These results suggest that beta2-containing nAChRs are involved in the affective signs of nicotine withdrawal, whereas non-beta2-containing nAChRs are more closely associated with physical signs of nicotine withdrawal; thus, the nAChR subtype composition may play an important role in the involvement of specific subtypes in nicotine withdrawal.
ESTHER : Jackson_2008_J.Pharmacol.Exp.Ther_325_302
PubMedSearch : Jackson_2008_J.Pharmacol.Exp.Ther_325_302
PubMedID: 18184829

Title : Interplay of beta2* nicotinic receptors and dopamine pathways in the control of spontaneous locomotion - Avale_2008_Proc.Natl.Acad.Sci.U.S.A_105_15991
Author(s) : Avale ME , Faure P , Pons S , Robledo P , Deltheil T , David DJ , Gardier AM , Maldonado R , Granon S , Changeux JP , Maskos U
Ref : Proc Natl Acad Sci U S A , 105 :15991 , 2008
Abstract : Acetylcholine (ACh) is a known modulator of the activity of dopaminergic (DAergic) neurons through the stimulation of nicotinic ACh receptors (nAChRs). Yet, the subunit composition and specific location of nAChRs involved in DA-mediated locomotion remain to be established in vivo. Mice lacking the beta2 subunit of nAChRs (beta2KO) display striking hyperactivity in the open field, which suggests an imbalance in DA neurotransmission. Here, we performed the selective gene rescue of functional beta2*-nAChRs in either the substantia nigra pars compacta (SNpc) or the ventral tegmental area (VTA) of beta2KO mice. SNpc rescued mice displayed normalization of locomotor activity, both in familiar and unfamiliar environments, whereas restoration in the VTA only rescued exploratory behavior. These data demonstrate the dissociation between nigrostriatal and mesolimbic beta2*-nAChRs in regulating unique locomotor functions. In addition, the site-directed knock-down of the beta2 subunit in the SNpc by RNA interference caused hyperactivity in wild-type mice. These findings highlight the crucial interplay of nAChRs over the DA control of spontaneous locomotion.
ESTHER : Avale_2008_Proc.Natl.Acad.Sci.U.S.A_105_15991
PubMedSearch : Avale_2008_Proc.Natl.Acad.Sci.U.S.A_105_15991
PubMedID: 18832468

Title : Crucial role of alpha4 and alpha6 nicotinic acetylcholine receptor subunits from ventral tegmental area in systemic nicotine self-administration - Pons_2008_J.Neurosci_28_12318
Author(s) : Pons S , Fattore L , Cossu G , Tolu S , Porcu E , McIntosh JM , Changeux JP , Maskos U , Fratta W
Ref : Journal of Neuroscience , 28 :12318 , 2008
Abstract : The identification of the molecular mechanisms involved in nicotine addiction and its cognitive consequences is a worldwide priority for public health. Novel in vivo paradigms were developed to match this aim. Although the beta2 subunit of the neuronal nicotinic acetylcholine receptor (nAChR) has been shown to play a crucial role in mediating the reinforcement properties of nicotine, little is known about the contribution of the different alpha subunit partners of beta2 (i.e., alpha4 and alpha6), the homo-pentameric alpha7, and the brain areas other than the ventral tegmental area (VTA) involved in nicotine reinforcement. In this study, nicotine (8.7-52.6 microg free base/kg/inf) self-administration was investigated with drug-naive mice deleted (KO) for the beta2, alpha4, alpha6 and alpha7 subunit genes, their wild-type (WT) controls, and KO mice in which the corresponding nAChR subunit was selectively re-expressed using a lentiviral vector (VEC mice). We show that WT mice, beta2-VEC mice with the beta2 subunit re-expressed exclusively in the VTA, alpha4-VEC mice with selective alpha4 re-expression in the VTA, alpha6-VEC mice with selective alpha6 re-expression in the VTA, and alpha7-KO mice promptly self-administer nicotine intravenously, whereas beta2-KO, beta2-VEC in the substantia nigra, alpha4-KO and alpha6-KO mice do not respond to nicotine. We thus define the necessary and sufficient role of alpha4beta2- and alpha6beta2-subunit containing nicotinic receptors (alpha4beta2*- and alpha6beta2*-nAChRs), but not alpha7*-nAChRs, present in cell bodies of the VTA, and their axons, for systemic nicotine reinforcement in drug-naive mice.
ESTHER : Pons_2008_J.Neurosci_28_12318
PubMedSearch : Pons_2008_J.Neurosci_28_12318
PubMedID: 19020025

Title : Behavioral sequence analysis reveals a novel role for beta2* nicotinic receptors in exploration - Maubourguet_2008_PLoS.Comput.Biol_4_e1000229
Author(s) : Maubourguet N , Lesne A , Changeux JP , Maskos U , Faure P
Ref : PLoS Comput Biol , 4 :e1000229 , 2008
Abstract : Nicotinic acetylcholine receptors (nAChRs) are widely expressed throughout the central nervous system and modulate neuronal function in most mammalian brain structures. The contribution of defined nAChR subunits to a specific behavior is thus difficult to assess. Mice deleted for beta2-containing nAChRs (beta2-/-) have been shown to be hyperactive in an open-field paradigm, without determining the origin of this hyperactivity. We here develop a quantitative description of mouse behavior in the open field based upon first order Markov and variable length Markov chain analysis focusing on the time-organized sequence that behaviors are composed of. This description reveals that this hyperactivity is the consequence of the absence of specific inactive states or "stops". These stops are associated with a scanning of the environment in wild-type mice (WT), and they affect the way that animals organize their sequence of behaviors when compared with stops without scanning. They characterize a specific "decision moment" that is reduced in beta2-/- mutant mice, suggesting an important role of beta2-nAChRs in the strategy used by animals to explore an environment and collect information in order to organize their behavior. This integrated analysis of the displacement of an animal in a simple environment offers new insights, specifically into the contribution of nAChRs to higher brain functions and more generally into the principles that organize sequences of behaviors in animals.
ESTHER : Maubourguet_2008_PLoS.Comput.Biol_4_e1000229
PubMedSearch : Maubourguet_2008_PLoS.Comput.Biol_4_e1000229
PubMedID: 19023420

Title : Nicotinic acetylcholine receptor-subunit mRNAs in the mouse superior cervical ganglion are regulated by development but not by deletion of distinct subunit genes - Putz_2008_J.Neurosci.Res_86_972
Author(s) : Putz G , Kristufek D , Orr-Urtreger A , Changeux JP , Huck S , Scholze P
Ref : Journal of Neuroscience Research , 86 :972 , 2008
Abstract : Mice with deletions of nicotinic ACh receptor (nAChR) subunit genes are valuable models for studying nAChR functions. We could previously show in the mouse superior cervical ganglion (SCG) that the absence of distinct subunits affects the functional properties of receptors. Here, we have addressed the question of whether deletions of the subunits alpha5, alpha7, or beta2 are compensated at the mRNA level, monitored by reverse transcription and quantitative real-time polymerase chain reaction. Relative to our reference gene, alpha3, which is expressed in all SCG nAChRs, mRNA levels of beta4 showed little change from birth until adult ages in intact ganglia of wild-type mice. In contrast, alpha4 declined sharply after birth and was barely detectable in adult animals. alpha5, alpha7, and beta2 subunit message levels also declined, though more slowly and less completely than alpha4. The subunits alpha6 and beta3 were detected by conventional polymerase chain reaction at very low levels, if at all, whereas alpha2 was never seen in any of our samples. The developmental profile of nAChR mRNA levels in the three knockout strains did not differ markedly from that of wild-type mice. Likewise, message levels of nAChR subunits were similar in cultures prepared from either wild-type or knockout animals. Our observations indicate a developmental regulation of nAChR subunit mRNAs in the SCG of mice after birth that was not affected by the three knockouts under investigation.
ESTHER : Putz_2008_J.Neurosci.Res_86_972
PubMedSearch : Putz_2008_J.Neurosci.Res_86_972
PubMedID: 17975828

Title : Evaluating the suitability of nicotinic acetylcholine receptor antibodies for standard immunodetection procedures - Moser_2007_J.Neurochem_102_479
Author(s) : Moser N , Mechawar N , Jones I , Gochberg-Sarver A , Orr-Urtreger A , Plomann M , Salas R , Molles BE , Marubio L , Roth U , Maskos U , Winzer-Serhan U , Bourgeois JP , Le Sourd AM , De Biasi M , Schroder H , Lindstrom JM , Maelicke A , Changeux JP , Wevers A
Ref : Journal of Neurochemistry , 102 :479 , 2007
Abstract : Nicotinic acetylcholine receptors play important roles in numerous cognitive processes as well as in several debilitating central nervous system (CNS) disorders. In order to fully elucidate the diverse roles of nicotinic acetylcholine receptors in CNS function and dysfunction, a detailed knowledge of their cellular and subcellular localizations is essential. To date, methods to precisely localize nicotinic acetylcholine receptors in the CNS have predominantly relied on the use of anti-receptor subunit antibodies. Although data obtained by immunohistology and immunoblotting are generally in accordance with ligand binding studies, some discrepancies remain, in particular with electrophysiological findings. In this context, nicotinic acetylcholine receptor subunit-deficient mice should be ideal tools for testing the specificity of subunit-directed antibodies. Here, we used standard protocols for immunohistochemistry and western blotting to examine the antibodies raised against the alpha3-, alpha4-, alpha7-, beta2-, and beta4-nicotinic acetylcholine receptor subunits on brain tissues of the respective knock-out mice. Unexpectedly, for each of the antibodies tested, immunoreactivity was the same in wild-type and knock-out mice. These data imply that, under commonly used conditions, these antibodies are not suited for immunolocalization. Thus, particular caution should be exerted with regards to the experimental approach used to visualize nicotinic acetylcholine receptors in the brain.
ESTHER : Moser_2007_J.Neurochem_102_479
PubMedSearch : Moser_2007_J.Neurochem_102_479
PubMedID: 17419810

Title : A prokaryotic proton-gated ion channel from the nicotinic acetylcholine receptor family - Bocquet_2007_Nature_445_116
Author(s) : Bocquet N , Prado de Carvalho L , Cartaud J , Neyton J , Le Poupon C , Taly A , Grutter T , Changeux JP , Corringer PJ
Ref : Nature , 445 :116 , 2007
Abstract : Ligand-gated ion channels (LGICs) mediate excitatory and inhibitory transmission in the nervous system. Among them, the pentameric or 'Cys-loop' receptors (pLGICs) compose a family that until recently was found in only eukaryotes. Yet a recent genome search identified putative homologues of these proteins in several bacterial species. Here we report the cloning, expression and functional identification of one of these putative homologues from the cyanobacterium Gloeobacter violaceus. It was expressed as a homo-oligomer in HEK 293 cells and Xenopus oocytes, generating a transmembrane cationic channel that is opened by extracellular protons and shows slow kinetics of activation, no desensitization and a single channel conductance of 8 pS. Electron microscopy and cross-linking experiments of the protein fused to the maltose-binding protein and expressed in Escherichia coli are consistent with a homo-pentameric organization. Sequence comparison shows that it possesses a compact structure, with the absence of the amino-terminal helix, the canonical disulphide bridge and the large cytoplasmic domain found in eukaryotic pLGICs. Therefore it embodies a minimal structure required for signal transduction. These data establish the prokaryotic origin of the family. Because Gloeobacter violaceus carries out photosynthesis and proton transport at the cytoplasmic membrane, this new proton-gated ion channel might contribute to adaptation to pH change.
ESTHER : Bocquet_2007_Nature_445_116
PubMedSearch : Bocquet_2007_Nature_445_116
PubMedID: 17167423

Title : The role of nicotinic receptors in B-lymphocyte development and activation - Skok_2007_Life.Sci_80_2334
Author(s) : Skok MV , Grailhe R , Agenes F , Changeux JP
Ref : Life Sciences , 80 :2334 , 2007
Abstract : We studied the binding of [(3)H]-epibatidine and [(125)I-]alpha-bungarotoxin, as well as subunit-specific antibodies with purified B lymphocytes of C57Bl/6J mice and found that these cells contained 12,200+/-3200 of alpha4(alpha5)beta2 and 3130+/-750 of alpha7(alpha5beta4) nicotinic acetylcholine receptors per cell. According to flow cytometry data, the highest expression of alpha4(alpha5)beta2 receptors was observed in immature newly generated B lymphocytes of the bone marrow, while the number of alpha7(alpha5beta4) receptors grew up along with the B cell maturation in the spleen. By using alpha4, beta2 or alpha7 knockout and chimera mice, it was shown that both receptor subtypes supported the survival of B cell precursors and increased the size of B-lymphocyte population in the bone marrow. In contrast, propagation of mature B lymphocytes in the spleen was controlled by alpha7-containing subtype only. Moreover, mature B lymphocytes became sensitive to nicotine only in the absence of beta2-containing receptors. Knockout mice had less serum IgG, IgG-producing cells and natural IgG antibodies than their wild-type counterparts, while the absence of beta2-containing receptors resulted in increased B-lymphocyte activation and antibody immune response. The data obtained indicate that nicotinic receptors are involved in regulating B-lymphocyte development and activation, possibly, by affecting expression and/or signaling of CD40, the two subtypes playing different roles.
ESTHER : Skok_2007_Life.Sci_80_2334
PubMedSearch : Skok_2007_Life.Sci_80_2334
PubMedID: 17363009

Title : Intracellular complexes of the beta2 subunit of the nicotinic acetylcholine receptor in brain identified by proteomics - Kabbani_2007_Proc.Natl.Acad.Sci.U.S.A_104_20570
Author(s) : Kabbani N , Woll MP , Levenson R , Lindstrom JM , Changeux JP
Ref : Proc Natl Acad Sci U S A , 104 :20570 , 2007
Abstract : Nicotine acetylcholine receptors (nAChRs) comprise a family of ligand-gated channels widely expressed in the mammalian brain. The beta2 subunit is an abundant protein subunit critically involved in the cognitive and behavioral properties of nicotine as well as in the mechanisms of nicotine addiction. In this work, we used matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS/MS) to uncover protein interactions of the intracellular loop of the beta2 subunit and components of immunoprecipitated beta2-nAChR complexes from mouse brain. Using the beta2-knockout mouse to exclude nonspecific binding to the beta2 antibody, we identify 21 nAChR-interacting proteins (NIPs) expressed in brain. Western blot analysis confirmed the association between the beta2 subunit and candidate NIPs. Based on their functional profiles, the hypothesis is suggested that the identified NIPs can regulate the trafficking and signaling of the beta2-nAChR. Interactions of the beta2 subunit with NIPs such as G protein alpha, G protein-regulated inducer of neurite outgrowth 1, and G protein-activated K(+) channel 1 suggest a link between nAChRs and cellular G protein pathways. These findings reveal intracellular interactions of the beta2 subunit and may contribute to the understanding of the mechanisms of nAChR signaling and trafficking in neurons.
ESTHER : Kabbani_2007_Proc.Natl.Acad.Sci.U.S.A_104_20570
PubMedSearch : Kabbani_2007_Proc.Natl.Acad.Sci.U.S.A_104_20570
PubMedID: 18077321

Title : Loss of high-affinity nicotinic receptors increases the vulnerability to excitotoxic lesion and decreases the positive effects of an enriched environment - Zanardi_2007_FASEB.J_21_4028
Author(s) : Zanardi A , Ferrari R , Leo G , Maskos U , Changeux JP , Zoli M
Ref : FASEB Journal , 21 :4028 , 2007
Abstract : Pharmacological activation of nicotinic acetylcholine receptors (nAChRs) exerts neuroprotective effects in cultured neurons and the intact animal. Much less is known about a physiological protective role of nAChRs. To understand whether endogenous activation of beta2* nAChRs contributes to the maintenance of the functional and morphological integrity of neural tissue, adult beta2-/- mice were subjected to in vivo challenges that cause neurodegeneration and cognitive impairment (intrahippocampal injection of the excitotoxin quinolinic acid), or neuroprotection and cognitive potentiation (2-month exposure to an enriched environment). The excitotoxic insult caused an increased deficit in the Morris water maze learning curve and increased loss of hippocampal pyramidal cells in beta2-/- mice. Exposure to an enriched environment improved performance in contextual and cued fear conditioning and object recognition tests in beta2+/+, whereas the improvement was absent in beta2-/- mice. In addition, beta2+/+, but not beta2-/-, mice exposed to an enriched environment showed a significant hypertrophy of the CA1/3 regions. Thus, lack of beta2* nAChRs increased susceptibility to an excitotoxic insult and diminished the positive effects of an enriched environment. These results may be relevant to understanding the pathophysiological consequences of the marked decrease in nAChRs that occurs in neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease.
ESTHER : Zanardi_2007_FASEB.J_21_4028
PubMedSearch : Zanardi_2007_FASEB.J_21_4028
PubMedID: 17622669

Title : Catecholamine outflow from mouse and rat brain slice preparations evoked by nicotinic acetylcholine receptor activation and electrical field stimulation - Scholze_2007_Br.J.Pharmacol_151_414
Author(s) : Scholze P , Orr-Urtreger A , Changeux JP , McIntosh JM , Huck S
Ref : British Journal of Pharmacology , 151 :414 , 2007
Abstract : BACKGROUND AND PURPOSE: Mice with targeted deletions of neuronal nicotinic acetylcholine receptor (nAChR) subunit genes are valuable models to study nAChR function such as catecholamine outflow by presynaptic receptor activation. Contrary to the rat, our present knowledge on presynaptic nAChRs in mice primarily relies on observations made with synaptosomes. We have now used brain slices to investigate nicotine-induced catecholamine outflow in wild type (WT) and nAChR (beta2 and alpha5) knockout mice for a comparison with rat brain slice preparations. EXPERIMENTAL APPROACH: Brain slices from rat and mouse hippocampus, parieto-occipital neocortex, and corpus striatum were loaded with either [3H]-noradrenaline or [3H]-dopamine. We provoked catecholamine outflow by electrical field stimulation and nicotinic agonists. KEY
RESULTS: When set in relation to electrical field stimulation, nicotine-evoked catecholamine release was sizeable in the striatum but low in the neocortex of both rats and mice. [3H]-noradrenaline outflow was, on the other hand, substantial in the rat but low in the mouse hippocampus. About 10% (or less) of nicotine-induced catecholamine release persisted in the presence of tetrodotoxin in all our preparations. CONCLUSIONS AND IMPLICATIONS: Targeted deletion of the beta2 subunit gene essentially abolished the effect of nicotine, indicating that this subunit is an essential constituent of nAChRs that indirectly (via action potentials) induce catecholamine release from hippocampal and striatal slices in mice. The impact of nAChRs in catecholaminergic projection areas differs between species and has thus to be considered when extrapolating results from animal models to human conditions.
ESTHER : Scholze_2007_Br.J.Pharmacol_151_414
PubMedSearch : Scholze_2007_Br.J.Pharmacol_151_414
PubMedID: 17401441

Title : Live imaging of neural structure and function by fibred fluorescence microscopy - Vincent_2006_EMBO.Rep_7_1154
Author(s) : Vincent P , Maskos U , Charvet I , Bourgeais L , Stoppini L , Leresche N , Changeux JP , Lambert R , Meda P , Paupardin-Tritsch D
Ref : EMBO Rep , 7 :1154 , 2006
Abstract : Only a few methods permit researchers to study selected regions of the central and peripheral nervous systems with a spatial and time resolution sufficient to image the function of neural structures. Usually, these methods cannot analyse deep-brain regions and a high-resolution method, which could repeatedly probe dynamic processes in any region of the central and peripheral nervous systems, is much needed. Here, we show that fibred fluorescence microscopy-which uses a small-diameter fibre-optic probe to provide real-time images-has the spatial resolution to image various neural structures in the living animal, the consistency needed for a sequential, quantitative evaluation of axonal degeneration/regeneration of a peripheral nerve, and the sensitivity to detect calcium transients on a sub-second timescale. These unique features should prove useful in many physiological studies requiring the in situ functional imaging of tissues in a living animal.
ESTHER : Vincent_2006_EMBO.Rep_7_1154
PubMedSearch : Vincent_2006_EMBO.Rep_7_1154
PubMedID: 17008931

Title : Identification of two critical residues within the Cys-loop sequence that determine fast-gating kinetics in a pentameric ligand-gated ion channel - Grutter_2006_J.Mol.Neurosci_30_63
Author(s) : Grutter T , de Carvalho LP , Dufresne V , Taly A , Changeux JP
Ref : Journal of Molecular Neuroscience , 30 :63 , 2006
Abstract : Pentameric ligand-gated ion channels (LGICs) are fast-gating receptors, represented by cationic nicotinic acetylcholine (nAChR) and serotonin (5HT3R) receptors, and by anionic GABA and glycine (GlyR) receptors. Because of a highly conserved sequence of 13 amino acids flanked by two canonical cysteine residues shared by all members of the family, these receptors are also known as the Cys-loop family. These receptors are allosteric transmembrane proteins made of five identical (or not) subunits arranged (pseudo) symmetrically around a central ion pore in the membrane. In nAChR, upon ACh binding, the receptor interconverts into discrete allosteric states, with each state corresponding to a different physiological state: resting (closed), active (open), and desensitized (closed).
ESTHER : Grutter_2006_J.Mol.Neurosci_30_63
PubMedSearch : Grutter_2006_J.Mol.Neurosci_30_63
PubMedID: 17192629

Title : Hierarchical control of dopamine neuron-firing patterns by nicotinic receptors - Mameli-Engvall_2006_Neuron_50_911
Author(s) : Mameli-Engvall M , Evrard A , Pons S , Maskos U , Svensson TH , Changeux JP , Faure P
Ref : Neuron , 50 :911 , 2006
Abstract : Nicotine elicits dopamine release by stimulating nicotinic acetylcholine receptors (nAChRs) on dopaminergic neurons. However, a modulation of these neurons by endogenous acetylcholine has not been described. We recorded, in vivo, the spontaneous activity of dopaminergic neurons in the VTA of anaesthetized wt and nAChR knockout mice and their response to nicotine injections. Deleting alpha7 or beta2 subunits modified the spontaneous firing patterns, demonstrating their direct stimulation by endogenous acetylcholine. Quantitative analysis further revealed four principal modes of firing, each depending on the expression of particular nAChR subunits and presenting unique responses to nicotine. The prominent role of the beta2 subunit was further confirmed by its selective lentiviral reexpression in the VTA. These data suggest a hierarchical control of dopaminergic neuron firing patterns by nAChRs: activation of beta2*-nAChR switches cells from a resting to an excited state, whereas activation of alpha7*-nAChRs finely tunes the latter state but only once beta2*-nAChRs have been activated.
ESTHER : Mameli-Engvall_2006_Neuron_50_911
PubMedSearch : Mameli-Engvall_2006_Neuron_50_911
PubMedID: 16772172

Title : Nicotine enhances intracellular nicotinic receptor maturation: A novel mechanism of neural plasticity? - Corringer_2006_J.Physiol.Paris_99_162
Author(s) : Corringer PJ , Sallette J , Changeux JP
Ref : Journal de Physiologie (Paris) , 99 :162 , 2006
Abstract : Nicotine addiction, the primary cause of tobacco consumption, is mediated through nicotine binding to brain nicotinic acetylcholine receptor (nAChRs). Upon chronic exposure, nicotine elicits a cascade of events, starting with nAChR activation and desensitization, followed by a long term up-regulation that corresponds to an increase in the number of the high affinity nAChRs, a paradoxical process that occurs in the brain of smokers. Recent investigation of the maturation and trafficking of the major brain +/-42 nAChR demonstrates that up-regulation is initiated in the endoplasmic reticulum soon after protein translation. The data thus far accumulated provide evidence that nicotine elicits up-regulation by promoting maturation of nAChR precursors that would otherwise be degraded. This maturational enhancer action of nicotine probably contributes to the long term effect of chronic nicotine, and suggests a novel mechanism of neuronal plasticity through an yet unknown endogenous substance which would modulate the receptor expression under physiological conditions.
ESTHER : Corringer_2006_J.Physiol.Paris_99_162
PubMedSearch : Corringer_2006_J.Physiol.Paris_99_162
PubMedID: 16458492

Title : Implications of the quaternary twist allosteric model for the physiology and pathology of nicotinic acetylcholine receptors - Taly_2006_Proc.Natl.Acad.Sci.U.S.A_103_16965
Author(s) : Taly A , Corringer PJ , Grutter T , Prado de Carvalho L , Karplus M , Changeux JP
Ref : Proc Natl Acad Sci U S A , 103 :16965 , 2006
Abstract : Nicotinic acetylcholine receptors (nAChR) are pentameric ligand-gated ion channels composed of subunits that consist of an extracellular domain that carries the ligand-binding site and a distinct ion-pore domain. Signal transduction results from the allosteric coupling between the two domains: the distance from the binding site to the gate of the pore domain is 50 A. Normal mode analysis with a C(alpha) Gaussian network of a new structural model of the neuronal alpha7 nAChR showed that the lowest mode involves a global quaternary twist motion that opens the ion pore. A molecular probe analysis, in which the network is modified at each individual amino acid residue, demonstrated that the major effect is to change the frequency, but not the form, of the twist mode. The largest effects were observed for the ligand-binding site and the Cys-loop. Most (24/27) of spontaneous mutations known to cause congenital myasthenia and autosomal dominant nocturnal frontal lobe epilepsy are located either at the interface between subunits or, within a given subunit, at the interface between rigid blocks. These interfaces are modified significantly by the twist mode. The present analysis, thus, supports the quaternary twist model of the nAChR allosteric transition and provides a qualitative interpretation of the effect of the mutations responsible for several receptor pathologies.
ESTHER : Taly_2006_Proc.Natl.Acad.Sci.U.S.A_103_16965
PubMedSearch : Taly_2006_Proc.Natl.Acad.Sci.U.S.A_103_16965
PubMedID: 17077146

Title : Targeted in vivo expression of nicotinic acetylcholine receptors in mouse brain using lentiviral expression vectors - Molles_2006_J.Mol.Neurosci_30_105
Author(s) : Molles BE , Maskos U , Pons S , Besson M , Guiard P , Guilloux JP , Evrard A , Cormier A , Mameli-Engvall M , Cloez-Tayarani I , Nakatani H , Dufour N , Bemelmans AP , Mallet J , Cazala P , Gardier AM , David V , Faure P , Granon S , Changeux JP
Ref : Journal of Molecular Neuroscience , 30 :105 , 2006
Abstract : Nicotinic acetylcholine receptors (nAChRs) in the brain exhibit diverse functional properties and ubiquitous distribution. Yet, except for providing a receptor for the exogenously applied nicotine of tobacco products, their role in the normal functioning of the brain has remained elusive. We have used a lentiviral expression vector to re-express the beta2 subunit specifically in the ventral tegmental area (VTA) of beta2-/- mice. The viral vector efficiently expresses beta2- subunit protein leading to new nAChR-binding sites. VTA neurons transduced by the lentiviral vector are responsive to intravenous nicotine when analyzed using in vivo electrophysiology. Nicotine-induced dopamine release from the nucleus accumbens (NuAcc) was also restored in re-expressing beta2-/- mice. Intra-VTA injection of nicotine was found to be reinforcing in both wild-type and beta2-subunit re-expressing beta2-/- mice, but not in beta2-/- mice. Furthermore, in the absence of applied nicotine, the spontaneous slow exploratory behavior of the mice was restored, whereas fast navigation did not change. This latter behavioral analysis suggests a role for beta2* nAChR, specifically expressed in the VTA, in mammalian cognitive function.
ESTHER : Molles_2006_J.Mol.Neurosci_30_105
PubMedSearch : Molles_2006_J.Mol.Neurosci_30_105
PubMedID: 17192649

Title : Inhibition of both alpha7* and beta2* nicotinic acetylcholine receptors is necessary to prevent development of sensitization to cocaine-elicited increases in extracellular dopamine levels in the ventral striatum - Zanetti_2006_Psychopharmacology.(Berl)_187_181
Author(s) : Zanetti L , de Kerchove d'Exaerde A , Zanardi A , Changeux JP , Picciotto MR , Zoli M
Ref : Psychopharmacology (Berl) , 187 :181 , 2006
Abstract : RATIONALE: Several studies have suggested that nicotine treatment can modulate the behavioral and neurochemical responses to other psychostimulants, such as cocaine. OBJECTIVES: The current study examined the hypothesis that nicotinic acetylcholine receptor (nAChR) blockade influences the ability of cocaine to elicit increases in extracellular dopamine levels. MATERIALS AND
METHODS: Pharmacological studies using nicotinic antagonists as well as genetic inactivation of beta2* nAChRs were used to determine the effect of nAChR blockade on dopamine levels in ventral striatum elicited by acute or repeated administrations of cocaine in mice.
RESULTS: Administration of mecamylamine (a general nicotinic antagonist that is not highly selective for individual nAChR subtypes) or co-administration of methyllycaconitine (a more selective antagonist of alpha7* nAChRs) with dihydro-beta-erythroidine (a more selective antagonist of beta2* nAChRs and other heteromeric nAChR subtypes) prevented sensitization of cocaine-elicited increases in extracellular DA levels in the ventral striatum in wild-type mice. In contrast, neither of the more specific antagonists alone was effective in preventing sensitization. Finally, methyllycaconitine administration prevents sensitization in beta2-/- mice but not in beta2+/+ or wild-type mice.
CONCLUSIONS: These data indicate that inhibition of both alpha7* and beta2* nAChRs is necessary to prevent development of sensitization of cocaine-elicited increases in extracellular dopamine levels in the ventral striatum of mice.
ESTHER : Zanetti_2006_Psychopharmacology.(Berl)_187_181
PubMedSearch : Zanetti_2006_Psychopharmacology.(Berl)_187_181
PubMedID: 16826402

Title : The beta2 but not alpha7 subunit of the nicotinic acetylcholine receptor is required for nicotine-conditioned place preference in mice - Walters_2006_Psychopharmacology.(Berl)_184_339
Author(s) : Walters CL , Brown S , Changeux JP , Martin B , Damaj MI
Ref : Psychopharmacology (Berl) , 184 :339 , 2006
Abstract : RATIONALE: Tobacco use is implicated in approximately 440,000 deaths per year, making it the leading cause of preventable death in the United States. Although it is generally recognized that tobacco use is correlated with a variety of health-related complications, many smokers are unsuccessful in their efforts to stop smoking using current cessation therapies. OBJECTIVES: Given that nicotine is the addictive component of tobacco, successful smoking cessation therapies must address the various processes, including reward, which contribute to nicotine addiction. As such, determining the nicotinic receptor subtypes involved in nicotine reward is of utmost importance to understanding how nicotine addiction progresses.
METHODS: Conditioned place preference (CPP) in three-chamber conditioning boxes was performed. For antagonist studies, drug was given on all conditioning sessions 10 min before nicotine or saline injection and placement in the boxes.
RESULTS: We have demonstrated that a pretreatment with the alpha4beta2 subunit of the nicotinic acetylcholine receptor (nAChR) antagonist dihydro-beta-erythroidine (2.0 mg/kg, s.c.) blocked nicotine (0.5 mg/kg, s.c.) CPP in wild-type mice (C57BL/6 mice). In contrast, pretreatment with an antagonist of the alpha7 subunit of the nAChR, methyllycaconitine (MLA, 5.0 or 10.0 mg/kg, s.c.), had no effect on this behavior. Finally, we showed that mice lacking the beta2 subunit of the nAChR did not exhibit nicotine CPP while alpha7 knock-out mice did. CONCLUSION: Taken together, these data suggest that the beta2 subunit of the nAChR is critically involved in nicotine reward as measured by CPP.
ESTHER : Walters_2006_Psychopharmacology.(Berl)_184_339
PubMedSearch : Walters_2006_Psychopharmacology.(Berl)_184_339
PubMedID: 16416156

Title : Heterogeneity and selective targeting of neuronal nicotinic acetylcholine receptor (nAChR) subtypes expressed on retinal afferents of the superior colliculus and lateral geniculate nucleus: identification of a new native nAChR subtype alpha3beta2(alpha5 or beta3) enriched in retinocollicular afferents - Gotti_2005_Mol.Pharmacol_68_1162
Author(s) : Gotti C , Moretti M , Zanardi A , Gaimarri A , Champtiaux N , Changeux JP , Whiteaker P , Marks MJ , Clementi F , Zoli M
Ref : Molecular Pharmacology , 68 :1162 , 2005
Abstract : The activation of neuronal nicotinic acetylcholine receptors (nAChRs) has been implicated in the activity-dependent development and plasticity of retina and the refinement of retinal projections. Pharmacological and functional studies have also indicated that different presynaptic nAChRs can have a modulatory function in retinotectal synapses. We biochemically and pharmacologically identified the multiple nAChR subtypes expressed on retinal afferents of the superior colliculus (SC) and lateral geniculate nucleus (LGN). We found that the alpha6beta2(*) and alpha4(nonalpha6)beta2(*) nAChRs are the major receptor populations expressed in both SC and LGN. In addition, the LGN contains two minor populations of alpha2alpha6beta2(*) and alpha3beta2(*) subtypes, whereas the SC contains a relatively large population of a new native subtype, the alpha3beta2(alpha5/beta3) nAChR. This subtype binds the alpha-conotoxin MII with an affinity 50 times lower than that of the native alpha6beta2(*) subtype. Studies of tissues obtained from eye-enucleated animals allowed the identification of nAChRs expressed by retinal afferents: in SC alpha6beta2(*), alpha4alpha6beta2(*), and alpha3beta2(*) (approximately 45, 35, and 20%, respectively), in LGN, alpha4alpha6beta2(*), alpha6beta2(*), alpha4beta2(*), alpha2alpha6beta2(*), and alpha3beta2(*) (approximately 40, 30, 20, 5, and 5%, respectively). In both regions, more than 50% of nAChRs were not expressed by retinal afferents and belonged to the alpha4beta2(*) (90%) or alpha4alpha5beta2(*) (10%) subtypes. Moreover, studies of the SC tissues obtained from wild-type and alpha4, alpha6, and beta3 knockout mice confirmed and extended the data obtained in rat tissue and allowed a comprehensive dissection of the composition of nAChR subtypes present in this retinorecipient area.
ESTHER : Gotti_2005_Mol.Pharmacol_68_1162
PubMedSearch : Gotti_2005_Mol.Pharmacol_68_1162
PubMedID: 16049166

Title : A chimera encoding the fusion of an acetylcholine-binding protein to an ion channel is stabilized in a state close to the desensitized form of ligand-gated ion channels - Grutter_2005_C.R.Biol_328_223
Author(s) : Grutter T , Prado de Carvalho L , Virginie D , Taly A , Fischer M , Changeux JP
Ref : C R Biol , 328 :223 , 2005
Abstract : To understand the mechanism of allosteric coupling between the ligand-binding domain and the ion channel of the Cys-loop ligand-gated ion channels (LGICs), we fused the soluble acetylcholine-binding protein (AChBP), which lacks an ion channel, to either the cationic serotonin type-3A ion channel (5HT(3A)) or the anionic glycine ion channel. Both linear chimeras expressed in HEK-293 cells display high affinity for the nicotinic agonist epibatidine (K(D) = 0.2-0.5 nM), but are not targeted to the cell surface. Only after substituting a ring of three loops located at the putative membrane side of the AChBP three-dimensional structure by the homologous residues of 5HT(3A), the resulting chimera AChBP(ring)/5HT(3A) (i) still displayed on intact cells an apparent high affinity for epibatidine, yet with a fourfold decrease (K(D) = 2.1 nM), (ii) displayed a high proportion of low affinity sites (11 +/- 7 microM) for the resting state stabilizing competitive antagonist alpha-bungarotoxin and (iii) was successfully targeted to the cell surface, as seen by immunofluorescence labelling. The AChBP(ring)/5HT(3A) chimera forms a pentameric structure, as revealed by sucrose gradient sedimentation. However, no whole-cell patch-clamp currents were detectable. Interestingly, binding assays with membrane fragments prepared from cells expressing AChBP(ring)/5HT(3A) showed a decrease in the apparent affinity for the agonists nicotine and epibatidine (5-fold), concomitant with an increase in the proportion of high-affinity sites (48 +/- 1 nM) for alpha-bungarotoxin. These results indicate that fusion of AChBP to an ion channel forms a pentameric receptor exposed to the cell surface and able to convert between discrete allosteric states, but stabilized in a high affinity state for epibatidine that likely corresponds to a desensitized form of LGICs. These artificial chimeras might offer a useful system to investigate signal transduction in LGICs.
ESTHER : Grutter_2005_C.R.Biol_328_223
PubMedSearch : Grutter_2005_C.R.Biol_328_223
PubMedID: 15810546

Title : Nicotine reinforcement and cognition restored by targeted expression of nicotinic receptors - Maskos_2005_Nature_436_103
Author(s) : Maskos U , Molles BE , Pons S , Besson M , Guiard BP , Guilloux JP , Evrard A , Cazala P , Cormier A , Mameli-Engvall M , Dufour N , Cloez-Tayarani I , Bemelmans AP , Mallet J , Gardier AM , David V , Faure P , Granon S , Changeux JP
Ref : Nature , 436 :103 , 2005
Abstract : Worldwide, 100 million people are expected to die this century from the consequences of nicotine addiction, but nicotine is also known to enhance cognitive performance. Identifying the molecular mechanisms involved in nicotine reinforcement and cognition is a priority and requires the development of new in vivo experimental paradigms. The ventral tegmental area (VTA) of the midbrain is thought to mediate the reinforcement properties of many drugs of abuse. Here we specifically re-expressed the beta2-subunit of the nicotinic acetylcholine receptor (nAChR) by stereotaxically injecting a lentiviral vector into the VTA of mice carrying beta2-subunit deletions. We demonstrate the efficient re-expression of electrophysiologically responsive, ligand-binding nicotinic acetylcholine receptors in dopamine-containing neurons of the VTA, together with the recovery of nicotine-elicited dopamine release and nicotine self-administration. We also quantified exploratory behaviours of the mice, and showed that beta2-subunit re-expression restored slow exploratory behaviour (a measure of cognitive function) to wild-type levels, but did not affect fast navigation behaviour. We thus demonstrate the sufficient role of the VTA in both nicotine reinforcement and endogenous cholinergic regulation of cognitive functions.
ESTHER : Maskos_2005_Nature_436_103
PubMedSearch : Maskos_2005_Nature_436_103
PubMedID: 16001069

Title : Allosteric mechanisms of signal transduction - Changeux_2005_Science_308_1424
Author(s) : Changeux JP , Edelstein SJ
Ref : Science , 308 :1424 , 2005
Abstract : Forty years ago, a simple model of allosteric mechanisms (indirect interactions between distinct sites), used initially to explain feedback-inhibited enzymes, was presented by Monod, Wyman, and Changeux. We review the MWC theory and its applications for the understanding of signal transduction in biology, and also identify remaining issues that deserve theoretical and experimental substantiation.
ESTHER : Changeux_2005_Science_308_1424
PubMedSearch : Changeux_2005_Science_308_1424
PubMedID: 15933191

Title : Nicotine upregulates its own receptors through enhanced intracellular maturation - Sallette_2005_Neuron_46_595
Author(s) : Sallette J , Pons S , Devillers-Thiery A , Soudant M , Prado de Carvalho L , Changeux JP , Corringer PJ
Ref : Neuron , 46 :595 , 2005
Abstract : Chronic exposure to nicotine elicits upregulation of high-affinity nicotinic receptors in the smoker's brain. To address the molecular mechanism of upregulation, we transfected HEK293 cells with human alpha4beta2 receptors and traced the subunits throughout their intracellular biosynthesis, using metabolic labeling and immunoprecipitation techniques. We show that high-mannose glycosylated subunits mature and assemble into pentamers in the endoplasmic reticulum and that only pentameric receptors reach the cell surface following carbohydrate processing. Nicotine is shown to act inside the cell and to increase the amount of beta subunits immunoprecipitated by the conformation-dependent mAb290, indicating that nicotine enhances a critical step in the intracellular maturation of these receptors. This effect, which also takes place at concentrations of nicotine found in the blood of smokers upon expression of alpha4beta2 in SH-SY5Y neuroblastoma cells, may play a crucial role in nicotine addiction and possibly implement a model of neural plasticity.
ESTHER : Sallette_2005_Neuron_46_595
PubMedSearch : Sallette_2005_Neuron_46_595
PubMedID: 15944128

Title : Molecular tuning of fast gating in pentameric ligand-gated ion channels - Grutter_2005_Proc.Natl.Acad.Sci.U.S.A_102_18207
Author(s) : Grutter T , de Carvalho LP , Dufresne V , Taly A , Edelstein SJ , Changeux JP
Ref : Proc Natl Acad Sci U S A , 102 :18207 , 2005
Abstract : Neurotransmitters such as acetylcholine (ACh) and glycine mediate fast synaptic neurotransmission by activating pentameric ligand-gated ion channels (LGICs). These receptors are allosteric transmembrane proteins that rapidly convert chemical messages into electrical signals. Neurotransmitters activate LGICs by interacting with an extracellular agonist-binding domain (ECD), triggering a tertiary/quaternary conformational change in the protein that results in the fast opening of an ion pore domain (IPD). However, the molecular mechanism that determines the fast opening of LGICs remains elusive. Here, we show by combining whole-cell and single-channel recordings of recombinant chimeras between the ECD of alpha7 nicotinic receptor (nAChR) and the IPD of the glycine receptor (GlyR) that only two GlyR amino acid residues of loop 7 (Cys-loop) from the ECD and at most five alpha7 nAChR amino acid residues of the M2-M3 loop (2-3L) from the IPD control the fast activation rates of the alpha7/Gly chimera and WT GlyR. Mutual interactions of these residues at a critical pivot point between the agonist-binding site and the ion channel fine-tune the intrinsic opening and closing rates of the receptor through stabilization of the transition state of activation. These data provide a structural basis for the fast opening of pentameric LGICs.
ESTHER : Grutter_2005_Proc.Natl.Acad.Sci.U.S.A_102_18207
PubMedSearch : Grutter_2005_Proc.Natl.Acad.Sci.U.S.A_102_18207
PubMedID: 16319224

Title : Knockout and knockin mice to investigate the role of nicotinic receptors in the central nervous system - Champtiaux_2004_Prog.Brain.Res_145_235
Author(s) : Champtiaux N , Changeux JP
Ref : Prog Brain Res , 145 :235 , 2004
Abstract : The recent use of genetically engineered knockout (Ko) and knockin (Kin) animals for neurotransmitter receptor genes, in particular, nicotinic acetylcholine receptors (nAChRs) in the brain, has provided a powerful alternative to the classical pharmacological approach. These animal models are not only useful in order to reexamine and refine the results derived from pharmacological studies, but they do also provide a unique opportunity to determine the subunit composition of the nicotinic receptors which modulate various brain functions. Ultimately, this knowledge will be valuable in the process of designing new drugs that will mimic the effects of nicotine on several important pathologies or on smoking cessation therapies. In this review, we present recent data obtained from the studies of mutant animals that contributed to our understanding of the role and composition of nAChRs in the central nervous system (CNS). The advantages and pitfalls of Ko animal models will also be discussed.
ESTHER : Champtiaux_2004_Prog.Brain.Res_145_235
PubMedSearch : Champtiaux_2004_Prog.Brain.Res_145_235
PubMedID: 14650919

Title : Critical role of the C-terminal segment in the maturation and export to the cell surface of the homopentameric alpha 7-5HT3A receptor - Pons_2004_Eur.J.Neurosci_20_2022
Author(s) : Pons S , Sallette J , Bourgeois JP , Taly A , Changeux JP , Devillers-Thiery A
Ref : European Journal of Neuroscience , 20 :2022 , 2004
Abstract : Many neurological pathologies are related to misfolded proteins. During folding and assembly in the endoplasmic reticulum, the nicotinic acetylcholine receptor (nAChR) subunits undergo several conformational changes to acquire the ability to bind ligands. After folding and maturation, by mechanisms largely unknown, receptors are exported to the cell surface. We investigated the maturational role of the extracellular C-terminal segment located at the boundary between the extracellular and the transmembrane domains. In the functional chimeric alpha7-5HT3A receptor used as a model system, amino acids from the C-terminal segment were successively deleted or mutated. Upon progressive shortening of the peptide we observed less and less alpha-bungarotoxin binding sites until no sites could be detected when the entire peptide had been deleted (chimera Del 5). Protein synthesis and pentameric assembly were not altered. In Del 5 transfected cells, pentameric receptors present in the endoplasmic reticulum were not detected on the cell surface where Del 5 proteins appeared as patches. With the Del 5 chimera, export of proteins to the cell surface diminished to about half that of wild-type. We propose that the C-terminal segment plays a double role: (i) through an interaction between the penultimate tyrosine residue of the C-terminal segment and the Cys loop of the N-terminal domain, it locks the receptor in a mature alpha-bungarotoxin binding conformation; (ii) this mature conformation, in turn, masks a retention signal present in the first transmembrane segment allowing properly assembled and matured receptors to escape to the cell surface.
ESTHER : Pons_2004_Eur.J.Neurosci_20_2022
PubMedSearch : Pons_2004_Eur.J.Neurosci_20_2022
PubMedID: 15450081

Title : Reduction of withdrawal signs after chronic nicotine exposure of alpha-calcitonin gene-related peptide knock-out mice - Salmon_2004_Neurosci.Lett_360_73
Author(s) : Salmon AM , Evrard A , Damaj MI , Changeux JP
Ref : Neuroscience Letters , 360 :73 , 2004
Abstract : Nicotine, the main substance responsible for the addictive behavior of smokers, binds to a variety of nicotinic acetylcholine receptors (nAChRs) diversely distributed in the brain, notably in areas involved in motivation and reward mechanisms. The alpha-calcitonin gene-related peptide (alphaCGRP) has been previously shown to modulate the functions of nAChRs and is released in brain areas implicated in motivation, such as the amygdala or the ventral tegmental area. Interestingly, alphaCGRP -/- mice display a decrease in morphine withdrawal symptoms. In this context, we investigate the tolerance and withdrawal symptoms in alphaCGRP -/- mice exposed to acute and chronic nicotine. We report that these animals develop a normal tolerance to the antinociceptive effects of nicotine, but display an attenuation of somatic withdrawal symptoms.
ESTHER : Salmon_2004_Neurosci.Lett_360_73
PubMedSearch : Salmon_2004_Neurosci.Lett_360_73
PubMedID: 15082182

Title : An H-bond between two residues from different loops of the acetylcholine binding site contributes to the activation mechanism of nicotinic receptors - Grutter_2003_EMBO.J_22_1990
Author(s) : Grutter T , Prado de Carvalho L , Le Novere N , Corringer PJ , Edelstein SJ , Changeux JP
Ref : EMBO Journal , 22 :1990 , 2003
Abstract : The molecular mechanisms of nicotinic receptor activation are still largely unknown. The crystallographic structure of the acetylcholine binding protein (AChBP) reveals a single H-bond between two different acetylcholine binding loops. Within these homologous loops we systematically introduced alpha4 residues into the alpha7/5HT(3) chimeric receptor and found that the single point mutations G152K (loop B) and P193I (loop C) displayed a non-additive increase of equilibrium binding affinity for several agonists compared with the double mutant G152K/P193I. In whole-cell patch-clamp recordings, G152K, P193I and G152K/P193I mutants displayed an increase up to 5-fold in acetylcholine potency with a large decrease of the apparent Hill coefficients (significantly smaller than one). Concomitantly, the G152K/P193I mutant showed a dramatic loss of high-affinity alpha-bungarotoxin binding (100-fold decrease), thus pinpointing a new contact area for the toxin. Fitting the data with an allosteric-kinetic model, together with molecular dynamic simulations, suggests that the presence of the inter-backbone H-bond between positions 152 and 193, revealed in alpha4 and in alpha7 double mutant but not in alpha7, coincides with a large stabilization of both open and desensitized states of nicotinic receptors.
ESTHER : Grutter_2003_EMBO.J_22_1990
PubMedSearch : Grutter_2003_EMBO.J_22_1990
PubMedID: 12727867

Title : An in vitro study of the sub-cellular distribution of nicotinic receptors - Devillers-Thiery_2003_Biol.Cell_95_373
Author(s) : Devillers-Thiery A , Bourgeois JP , Pons S , Le Sourd A , Pucci B , Changeux JP
Ref : Biology of the cell , 95 :373 , 2003
Abstract : Nicotinic and serotoninergic 5HT3 receptors share important sequence identities except for their cytoplasmic loop. Both ends of this loop display conserved 3D helical structures with distinct primary sequences. We decided to check whether these two helices named F and G play a role in the sub-cellular distribution of different nicotinic receptors. We systematically exchanged each helix with the equivalent sequence of neuronal nicotinic and alpha4, beta2 and alpha7 subunits in the functional chimeric alpha7-5HT3 receptor used as a model system. The new chimeras were expressed in vitro in polarized epithelial cells from pig kidney. We quantified synthesis and export of the receptors to the cell surface by measuring alpha-bungarotoxin binding sites. Immunogold labelling was used, at the electron microscope level, to determine the amount of each chimera present at either domain, apical and/or basolateral, of these cells. We noticed that in epithelial cells the majority of alpha-bungarotoxin binding sites remained sequestered in the cytoplasm as already observed in neurons in vivo. The majority of the pentamers present at the cell surface were located at the apical domain. Our results suggest that helix F and G differently regulate assembly and export to the cell surface of alpha-bungarotoxin binding receptors.
ESTHER : Devillers-Thiery_2003_Biol.Cell_95_373
PubMedSearch : Devillers-Thiery_2003_Biol.Cell_95_373
PubMedID: 14519554

Title : Subunit composition of functional nicotinic receptors in dopaminergic neurons investigated with knock-out mice - Champtiaux_2003_J.Neurosci_23_7820
Author(s) : Champtiaux N , Gotti C , Cordero-Erausquin M , David DJ , Przybylski C , Lena C , Clementi F , Moretti M , Rossi FM , Le Novere N , McIntosh JM , Gardier AM , Changeux JP
Ref : Journal of Neuroscience , 23 :7820 , 2003
Abstract : Nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic (DA) neurons have long been considered as potential therapeutic targets for the treatment of several neuropsychiatric diseases, including nicotine and cocaine addiction or Parkinson's disease. However, DA neurons express mRNAs coding for most, if not all, neuronal nAChR subunits, and the subunit composition of functional nAChRs has been difficult to establish. Immunoprecipitation experiments performed on mouse striatal extracts allowed us to identify three main types of heteromeric nAChRs (alpha4beta2*, alpha6beta2*, and alpha4alpha6beta2*) in DA terminal fields. The functional relevance of these subtypes was then examined by studying nicotine-induced DA release in striatal synaptosomes and recording ACh-elicited currents in DA neurons fromalpha4, alpha6, alpha4alpha6, and beta2 knock-out mice. Our results establish that alpha6beta2* nAChRs are functional and sensitive to alpha-conotoxin MII inhibition. These receptors are mainly located on DA terminals and consistently do not contribute to DA release induced by systemic nicotine administration, as evidenced by in vivo microdialysis. In contrast, (nonalpha6)alpha4beta2* nAChRs represent the majority of functional heteromeric nAChRs on DA neuronal soma. Thus, whereas a combination of alpha6beta2* and alpha4beta2* nAChRs may mediate the endogenous cholinergic modulation of DA release at the terminal level, somato-dendritic (nonalpha6)alpha4beta2* nAChRs most likely contribute to nicotine reinforcement.
ESTHER : Champtiaux_2003_J.Neurosci_23_7820
PubMedSearch : Champtiaux_2003_J.Neurosci_23_7820
PubMedID: 12944511

Title : Rapsyn escorts the nicotinic acetylcholine receptor along the exocytic pathway via association with lipid rafts - Marchand_2002_J.Neurosci_22_8891
Author(s) : Marchand S , Devillers-Thiery A , Pons S , Changeux JP , Cartaud J
Ref : Journal of Neuroscience , 22 :8891 , 2002
Abstract : The 43 kDa receptor-associated protein rapsyn is a myristoylated peripheral protein that plays a central role in nicotinic acetylcholine receptor (AChR) clustering at the neuromuscular junction. In a previous study, we demonstrated that rapsyn is specifically cotransported with AChR via post-Golgi vesicles targeted to the innervated surface of the Torpedo electrocyte (Marchand et al., 2000). In the present study, to further elucidate the mechanisms for sorting and assembly of postsynaptic proteins, we analyzed the dynamics of the intracellular trafficking of fluorescently labeled rapsyn in the transient-expressing COS-7 cell system. Our approach was based on fluorescence, time-lapse imaging, and immunoelectron microscopies, as well as biochemical analyses. We report that newly synthesized rapsyn associates with the trans-Golgi network compartment and traffics via vesiculotubular organelles toward the cell surface of COS-7 cells. The targeting of rapsyn organelles appeared to be mediated by a microtubule-dependent transport. Using cotransfection experiments of rapsyn and AChR, we observed that these two molecules codistribute within distal exocytic routes and at the plasma membrane. Triton X-100 extraction on ice and flotation gradient centrifugation demonstrated that rapsyn and AChR are recovered in low-density fractions enriched in two rafts markers: caveolin-1 and flotillin-1. We propose that sorting and targeting of these two companion molecules are mediated by association with cholesterol-sphingolipid-enriched raft microdomains. Collectively, these data highlight rapsyn as an itinerant vesicular protein that may play a dynamic role in the sorting and targeting of its companion receptor to the postsynaptic membrane. These data also raise the interesting hypothesis of the participation of the raft machinery in the targeting of signaling molecules to synaptic sites.
ESTHER : Marchand_2002_J.Neurosci_22_8891
PubMedSearch : Marchand_2002_J.Neurosci_22_8891
PubMedID: 12388596

Title : Experimentally based model of a complex between a snake toxin and the alpha 7 nicotinic receptor - Fruchart-Gaillard_2002_Proc.Natl.Acad.Sci.U.S.A_99_3216
Author(s) : Fruchart-Gaillard C , Gilquin B , Antil-Delbeke S , Le Novere N , Tamiya T , Corringer PJ , Changeux JP , Menez A , Servent D
Ref : Proc Natl Acad Sci U S A , 99 :3216 , 2002
Abstract : To understand how snake neurotoxins interact with nicotinic acetylcholine receptors, we have elaborated an experimentally based model of the alpha-cobratoxin-alpha7 receptor complex. This model was achieved by using (i) a three-dimensional model of the alpha7 extracellular domain derived from the crystallographic structure of the homologous acetylcholine-binding protein, (ii) the previously solved x-ray structure of the toxin, and (iii) nine pairs of residues identified by cycle-mutant experiments to make contacts between the alpha-cobratoxin and alpha7 receptor. Because the receptor loop F occludes entrance of the toxin binding pocket, we submitted this loop to a dynamics simulation and selected a conformation that allowed the toxin to reach its binding site. The three-dimensional structure of the toxin-receptor complex model was validated a posteriori by an additional double-mutant experiment. The model shows that the toxin interacts perpendicularly to the receptor axis, in an equatorial position of the extracellular domain. The tip of the toxin central loop plugs into the receptor between two subunits, just below the functional receptor loop C, the C-terminal tail of the toxin making adjacent additional interactions at the receptor surface. The receptor establishes major contacts with the toxin by its loop C, which is assisted by principal (loops A and B) and complementary (loops D, F, and 1) functional regions. This model explains the antagonistic properties of the toxin toward the neuronal receptor and opens the way to the design of new antagonists.
ESTHER : Fruchart-Gaillard_2002_Proc.Natl.Acad.Sci.U.S.A_99_3216
PubMedSearch : Fruchart-Gaillard_2002_Proc.Natl.Acad.Sci.U.S.A_99_3216
PubMedID: 11867717

Title : The diversity of subunit composition in nAChRs: evolutionary origins, physiologic and pharmacologic consequences - Le_2002_J.Neurobiol_53_447
Author(s) : Le Novere N , Corringer PJ , Changeux JP
Ref : Journal of Neurobiology , 53 :447 , 2002
Abstract : Nicotinic acetylcholine receptors are made up of homologous subunits, which are encoded by a large multigene family. The wide number of receptor oligomers generated display variable pharmacological properties. One of the main questions underlying research in molecular pharmacology resides in the actual role of this diversity. It is generally assumed that the observed differences between the pharmacology of homologous receptors, for instance, the EC(50) for the endogenous agonist, or the kinetics of desensitization, bear some kind of physiologic relevance in vivo. Here we develop the quite challenging point of view that, at least within a given subfamily of nicotinic receptor subunits, the pharmacologic variability observed in vitro would not be directly relevant to the function of receptor proteins in vivo. In vivo responses are not expected to be sensitive to mild differences in affinities, and several examples of functional replacement of one subunit by another have been unravelled by knockout animals. The diversity of subunits might have been conserved through evolution primarily to account for the topologic diversity of subunit distribution patterns, at the cellular and subcellular levels. A quantitative variation of pharmacological properties would be tolerated within a physiologic envelope, as a consequence of a near-neutral genetic drift. Such a "gratuitous" pharmacologic diversity is nevertheless of practical interest for the design of drugs, which would specifically tackle particular receptor oligomers with a defined subunit composition among the multiple nicotinic receptors present in the organism.
ESTHER : Le_2002_J.Neurobiol_53_447
PubMedSearch : Le_2002_J.Neurobiol_53_447
PubMedID: 12436412

Title : Acute and long-term changes in the mesolimbic dopamine pathway after systemic or local single nicotine injections - Ferrari_2002_Eur.J.Neurosci_15_1810
Author(s) : Ferrari R , Le Novere N , Picciotto MR , Changeux JP , Zoli M
Ref : European Journal of Neuroscience , 15 :1810 , 2002
Abstract : We have examined several neurochemical and behavioural parameters related to the function of the mesolimbic dopamine (DA) pathway in animals treated with nicotine following three modes of drug administration, i.e. systemic intraperitoneal injection, intra-accumbens (Acb) infusion or intraventral tegmental area (intra-VTA) microinjection. The present modes of systemic, intra-Acb and intra-VTA nicotine administration elicited comparable acute increases in dialysate DA levels from the Acb. The increase in extracellular DA levels was paralleled by a significant enhancement of locomotion in a habituated environment in the case of systemic or intra-VTA nicotine administration, whereas unilateral or bilateral intra-Acb nicotine infusion was ineffective, showing that accumbal DA increase is not sufficient to elicit locomotion in this experimental paradigm. Intra-VTA, but not systemic or intra-Acb, nicotine administration caused a long-term (at least 24-h) increase in basal dialysate DA levels from the Acb. In addition, significant increases in tyrosine hydroxylase (TH) and GluR1 (but not dopamine transporter or NR1) mRNA levels in the VTA were detected 24 h after intra-VTA nicotine administration. Systemic nicotine injection caused only an increase in TH mRNA levels while intra-Acb infusion did not modify any of the mRNAs tested. The long-term increase in basal DA levels in the Acb and TH, and GluR1 mRNA levels in the VTA upon intra-VTA nicotine microinjection indicates that even a single nicotine injection can induce plastic changes of the mesolimbic DA pathway.
ESTHER : Ferrari_2002_Eur.J.Neurosci_15_1810
PubMedSearch : Ferrari_2002_Eur.J.Neurosci_15_1810
PubMedID: 12081661

Title : The role of nicotinic receptor beta-2 subunits in nicotine discrimination and conditioned taste aversion - Shoaib_2002_Neuropharmacol_42_530
Author(s) : Shoaib M , Gommans J , Morley A , Stolerman IP , Grailhe R , Changeux JP
Ref : Neuropharmacology , 42 :530 , 2002
Abstract : The subtypes of nicotinic receptors at which the behavioural effects of nicotine originate are not fully understood. These experiments use mice lacking the beta2 subunit of nicotinic receptors to investigate its role in nicotine discrimination and conditioned taste aversion (CTA). Wild-type and mutant mice were trained either in a two-lever nicotine discrimination procedure using a tandem schedule of food reinforcement, or in a counterbalanced two-flavour CTA procedure. Rates of lever-pressing of wild-type and mutant mice did not differ. Wild-type mice acquired discrimination of nicotine (0.4 or 0.8 mg/kg) rapidly and exhibited steep dose-response curves. Mutant mice failed to acquire these nicotine discriminations and exhibited flat dose-response curves. Both wild-type and mutant mice acquired discrimination of nicotine (1.6 mg/kg) although discrimination performance was weak in the mutants. Nicotine initially reduced response rates in wild-type and mutant mice, and tolerance developed to this effect in each genotype. Both genotypes acquired discrimination of morphine (3 mg/kg) with similar degrees of accuracy, and dose-response curves for morphine discrimination in the two genotypes were indistinguishable. Nicotine produced dose-related CTA in both genotypes, but the magnitude of the effect was less in the mutants than in the wild-type controls. It is concluded that nicotinic receptors containing the beta2 subunit play a major role in the discriminative stimulus and taste aversion effects of nicotine that may reflect psychological aspects of tobacco dependence. Such receptors appear to have a less crucial role in the response-rate, reducing effects of nicotine and in nicotine tolerance.
ESTHER : Shoaib_2002_Neuropharmacol_42_530
PubMedSearch : Shoaib_2002_Neuropharmacol_42_530
PubMedID: 11955523

Title : Desensitization of neuronal nicotinic acetylcholine receptors conferred by N-terminal segments of the beta 2 subunit - Bohler_2001_Biochemistry_40_2066
Author(s) : Bohler S , Gay S , Bertrand S , Corringer PJ , Edelstein SJ , Changeux JP , Bertrand D
Ref : Biochemistry , 40 :2066 , 2001
Abstract : Desensitization is a general property of ligand-gated ion channels. Because of a wide array of available subunit combinations, it generates different time constants for channel closure, thereby modulating the processing of information in the brain. Within the family of neuronal nicotinic acetylcholine receptors (nAChRs), alpha 3 beta 2 and alpha 3 beta 4 receptors display contrasting properties of desensitization. When measured using two-electrode voltage-clamp in Xenopus oocytes, desensitization results in current decreases 2 s after initiation of acetylcholine application by 94% for alpha 3 beta 2 receptors, but only by 6% in the case of alpha 3 beta 4 receptors. Desensitization was analyzed by inserting different portions of the beta2 into the beta 4 subunit. Residues 1--212 of the beta2 subunit were able to confer 78% desensitization in 2 s, while smaller chimeras revealed desensitization in 2 s conferred by residues 1--42 alone to a level of 50%, by residues 72--89 to a level of 74%, and by residues 96--212 to a level of 77%. Some long-term (25 min) effects of desensitization driven by acetylcholine were found to rely partially on the same elements, including an enhancement mediated by residues 1--95 and 96--212 of the beta 2 subunit individually. Our results reveal that desensitization relies independently on diverse portions of the extracellular domain of the beta 2 subunit. Phenotype of alpha 3 beta 4 involves, in contrast, complex structural requirements involving residues dispersed throughout the entire N-terminal domain of the beta 4 subunit.
ESTHER : Bohler_2001_Biochemistry_40_2066
PubMedSearch : Bohler_2001_Biochemistry_40_2066
PubMedID: 11329274

Title : Nicotinic agonists stimulate acetylcholine release from mouse interpeduncular nucleus: a function mediated by a different nAChR than dopamine release from striatum - Grady_2001_J.Neurochem_76_258
Author(s) : Grady SR , Meinerz NM , Cao J , Reynolds AM , Picciotto MR , Changeux JP , McIntosh JM , Marks MJ , Collins AC
Ref : Journal of Neurochemistry , 76 :258 , 2001
Abstract : Acetylcholine release stimulated by nicotinic agonists was measured as radioactivity released from perfused synaptosomes prepared from mouse interpeduncular nucleus (IPN) that had been loaded with [(3)H]choline. Agonist-stimulated release was dependent upon external calcium and over 90% of released radioactivity was acetylcholine. The release process was characterized by dose response curves for 13 agonists and inhibition curves for six antagonists. alpha-Conotoxin MII did not inhibit this release, while alpha-conotoxin AuIB inhibited 50% of agonist-stimulated release. Comparison of this process with [(3)H]dopamine release from mouse striatal synaptosomes indicated that different forms of nicotinic acetylcholine receptors (nAChRs) may mediate these processes. This was confirmed by assays using mice homozygous for the beta 2 subunit null mutation. The deletion of the beta 2 subunit had no effect on agonist-stimulated acetylcholine release, but abolished agonist-stimulated release of dopamine from striatal synaptosomes. Mice heterozygous for the beta 2 subunit null mutation showed decreased dopamine release evoked by L-nicotine with no apparent change in EC(50) value, as well as similar decreases in both transient and persistent phases of release with no changes in desensitization rates.
ESTHER : Grady_2001_J.Neurochem_76_258
PubMedSearch : Grady_2001_J.Neurochem_76_258
PubMedID: 11145999

Title : Targeting transcription to the neuromuscular synapse - Schaeffer_2001_Neuron_31_15
Author(s) : Schaeffer L , de Kerchove d'Exaerde A , Changeux JP
Ref : Neuron , 31 :15 , 2001
Abstract : Concomitant with innervation, genes coding for components of the neuromuscular junction become exclusively expressed in subsynaptic nuclei. A six-base pair element, the N box, can confer synapse-specific transcription to the acetylcholine nicotinic receptor delta and epsilon subunit, utrophin, and acetylcholine esterase genes. N box-dependent synaptic expression is stimulated by the nerve-derived signal agrin and the trophic factor neuregulin, which triggers the MAPK and JNK signaling pathways, to ultimately allow activation by the N box binding Ets transcription factor GABP.
ESTHER : Schaeffer_2001_Neuron_31_15
PubMedSearch : Schaeffer_2001_Neuron_31_15
PubMedID: 11498047

Title : Nicotine receptor inactivation decreases sensitivity to cocaine - Zachariou_2001_Neuropsychopharmacology_24_576
Author(s) : Zachariou V , Caldarone BJ , Weathers-Lowin A , George TP , Elsworth JD , Roth RH , Changeux JP , Picciotto MR
Ref : Neuropsychopharmacology , 24 :576 , 2001
Abstract : The reinforcing properties of nicotine and psychomotor stimulants are thought to be mediated through the mesolimbic dopamine (DA) system. This study investigates the role of high affinity nicotinic acetylcholine receptors (nAChRs) in cocaine place preference and examines some neurochemical changes in the mesolimbic DA system that might account for the interaction between nicotine and cocaine. 5 mg/kg is the lowest dose of cocaine able to condition a place preference in C57Bl/6 mice. Co-treatment with the nicotinic antagonist mecamylamine (1.0 mg/kg) disrupted place preference to 5 mg/kg cocaine. In addition, mice lacking the high affinity nAChR containing the beta2 subunit showed decreased place preference to 5 mg/kg cocaine, although higher doses of cocaine could condition a place preference in these knock out animals. In contrast, co-administration of a low dose of nicotine (0.2 mg/kg) potentiated place preference to a subthreshold dose of cocaine (3 mg/kg). DA turnover was monitored in several brain regions using tissue levels of DA and its primary metabolite DOPAC as an indication of DA release. Wild type mice showed decreased DA turnover following treatment with 5 mg/kg cocaine; whereas, this response was not seen in mice lacking the beta2 subunit of the nAChR. Induction of chronic fos-related antigens by cocaine was also reduced in mutant mice as compared to their wild type siblings, implying that downstream actions of cocaine were also affected by inactivation of the high affinity nAChR. These data indicate that activation of the high affinity nAChR may contribute to cocaine reinforcement.
ESTHER : Zachariou_2001_Neuropsychopharmacology_24_576
PubMedSearch : Zachariou_2001_Neuropsychopharmacology_24_576
PubMedID: 11282258

Title : Molecular characterization of the specificity of interactions of various neurotoxins on two distinct nicotinic acetylcholine receptors - Servent_2000_Eur.J.Pharmacol_393_197
Author(s) : Servent D , Antil-Delbeke S , Gaillard C , Corringer PJ , Changeux JP , Menez A
Ref : European Journal of Pharmacology , 393 :197 , 2000
Abstract : Snake curaremimetic toxins are currently classified as short-chain and long-chain toxins according to their size and their number of disulfide bonds. All these toxins bind with high affinity to muscular-type nicotinic acetylcholine receptor, whereas only long toxins recognize the alpha7 receptor with high affinity. On the basis of binding experiments with Torpedo or neuronal alpha7 receptors using wild-type and mutated neurotoxins, we characterized the molecular determinants involved in these different recognition processes. The functional sites by which long and short toxins interact with the muscular-type receptor include a common core of highly conserved residues and residues that are specific to each of toxin families. Furthermore, the functional sites through which alpha-cobratoxin, a long-chain toxin, interacts with muscular and alpha7 receptors share similarities but also marked differences. Our results reveal that the three-finger fold toxins have evolved toward various specificities by displaying distinct functional sites.
ESTHER : Servent_2000_Eur.J.Pharmacol_393_197
PubMedSearch : Servent_2000_Eur.J.Pharmacol_393_197
PubMedID: 10771013

Title : How well can molecular modelling predict the crystal structure: the case of the ligand-binding domain of glutamate receptors - Paas_2000_Trends.Pharmacol.Sci_21_87
Author(s) : Paas Y , Devillers-Thiery A , Teichberg VI , Changeux JP , Eisenstein M
Ref : Trends in Pharmacological Sciences , 21 :87 , 2000
Abstract : The concept that the ligand-binding domain of vertebrate glutamate receptor channels and bacterial periplasmic substrate-binding proteins (PBPs) share similar three-dimensional (3D) structures has gained increasing support in recent years. On the basis of a dual approach that included computer-assisted molecular modelling and functional studies of site-specific mutants, theoretical 3D models of this domain have been proposed. This article reviews to what extent these models could predict the crystal structure of the ligand-binding domain of an ionotropic glutamate receptor subunit recently determined at high resolution by X-ray diffraction studies.
ESTHER : Paas_2000_Trends.Pharmacol.Sci_21_87
PubMedSearch : Paas_2000_Trends.Pharmacol.Sci_21_87
PubMedID: 10689361

Title : Pharmacological and null mutation approaches reveal nicotinic receptor diversity - Whiteaker_2000_Eur.J.Pharmacol_393_123
Author(s) : Whiteaker P , Marks MJ , Grady SR , Lu Y , Picciotto MR , Changeux JP , Collins AC
Ref : European Journal of Pharmacology , 393 :123 , 2000
Abstract : We have developed an array of assays for nicotinic acetylcholine receptor binding and function. [125I]alpha-Bungarotoxin-, (-)-[3H]nicotine-, and [3H]epibatidine-binding nicotinic acetylcholine receptors were assayed in mouse brain membranes and sections. Nicotinic acetylcholine receptor function was quantified using synaptosomal [3H]dopamine, [3H]gamma-aminobutyric acid ([3H]GABA), and 86Rb(+) efflux techniques. Additionally, the effects of beta2 subunit deletion on each of the measures were assessed. Detailed pharmacological comparison revealed minimally six nicotinic binding subtypes: [125I]alpha-bungarotoxin-binding nicotinic acetylcholine receptors; beta2-subunit-dependent and -independent high-affinity (-)-[3H]nicotine-binding sites; beta2-dependent and -independent cytisine-resistant [3H]epibatidine-binding sites; and a beta2-dependent low-affinity [3H]epibatidine binding site. Comparative pharmacology suggested that [3H]GABA and dihydro-beta-erythroidine (DHbetaE)-sensitive 86Rb(+) efflux are mediated by the same (probably alpha4beta2) nicotinic acetylcholine receptor subtype, while other nicotinic acetylcholine receptor subtypes evoke [3H]dopamine and DHbetaE-resistant 86Rb(+) efflux. In whole-brain preparations, each measure of nicotinic acetylcholine receptor function was beta2 dependent. The majority of beta2-independent [3H]epibatidine binding was located in small, scattered brain nuclei, suggesting that individual nuclei may prove suitable for identification of novel, native nicotinic acetylcholine receptors.
ESTHER : Whiteaker_2000_Eur.J.Pharmacol_393_123
PubMedSearch : Whiteaker_2000_Eur.J.Pharmacol_393_123
PubMedID: 10771005

Title : Structural differences in the two agonist binding sites of the Torpedo nicotinic acetylcholine receptor revealed by time-resolved fluorescence spectroscopy - Martinez_2000_Biochemistry_39_6979
Author(s) : Martinez KL , Corringer PJ , Edelstein SJ , Changeux JP , Merola F
Ref : Biochemistry , 39 :6979 , 2000
Abstract : The nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata carries two nonequivalent agonist binding sites at the alphadelta and alphagamma subunit interfaces. These sites have been characterized by time-resolved fluorescence with the partial nicotinic agonist dansyl-C(6)-choline (Dnscho). When bound to the detergent-solubilized receptor, the fluorescence lifetime distribution of Dnscho displays a characteristic signature, with four separable components at 0.2, 1.8, 7.2, and 18.3 ns, respectively. Competition experiments with the antagonist d-tubocurarine (dTC), known to bind preferentially to the alphagamma site, result in substantial changes of this signature, associated with a strong decrease in average fluorescence lifetime. Comparisons with two other competitive antagonists, alpha-conotoxin M1 and alpha-bungarotoxin, demonstrate that Dnscho binds with a similar affinity to the two sites but that the microenvironment of the probe is different for each site. Using a two-site binding model together with published equilibrium constants to describe the competitive binding of dTC and Dnscho, we reach a satisfactory description of the changes in fluorescence lifetimes and propose characteristic fluorescence parameters of the probe bound to each type of site. This analysis indicates that Dnscho at the alphadelta site is principally associated with a 8.7 ns lifetime, while it has a 20.2 ns major lifetime at the alphagamma site. Therefore, the observed fluorescence heterogeneity arises in large part from the structural differences of the two binding sites. As a result, this signal can be used to identify the binding preferences of competitive ligands of unknown pharmacology.
ESTHER : Martinez_2000_Biochemistry_39_6979
PubMedSearch : Martinez_2000_Biochemistry_39_6979
PubMedID: 10841780

Title : Knockout Mice as Animal Models for Studying Nicotinic Acetylcholine Receptor Function -
Author(s) : Marubio LM , Changeux JP
Ref : Handbook of Experimental Pharmacology , 144 :525 , 2000

Title : Nicotinic-agonist stimulated (86)Rb(+) efflux and [(3)H]epibatidine binding of mice differing in beta2 genotype - Marks_2000_Neuropharmacol_39_2632
Author(s) : Marks MJ , Stitzel JA , Grady SR , Picciotto MR , Changeux JP , Collins AC
Ref : Neuropharmacology , 39 :2632 , 2000
Abstract : Nicotinic acetylcholine receptor function and binding was measured in 12 brain regions from mice differing in beta2 subunit expression. Function was measured by on-line detection of (86)Rb(+) efflux stimulated under conditions that measure two pharmacologically distinct nicotinic responses: (1) stimulation with 10 microM nicotine, a response that is relatively sensitive to inhibition by the antagonist, dihydro-beta-erythroidine (DHbetaE); and (2) stimulation with 10 microM epibatidine in the presence of 2 microM DHbetaE, a response that is relatively resistant to inhibition by DHbetaE. Deletion of the beta2 subunit profoundly reduced both DHbetaE-sensitive and -resistant (86)Rb(+) efflux in each brain region and essentially eliminated activity in regions such as cerebral cortex and thalamus. However, residual activity was observed in regions such as olfactory bulbs and inferior colliculus. [(3)H]Epibatidine binding was measured under conditions that allow estimation of both high- and low-affinity sites. High-affinity sites sensitive to inhibition by the nicotinic agonist, cytisine, were virtually eliminated in every region by the beta2 null mutation. In contrast, only a subset of the high-affinity sites insensitive to inhibition by cytisine were eliminated in beta2 null mutants, suggesting receptor heterogeniety. Similarly, low affinity [(3)H]epibatidine binding was heterogeneous in that a fraction of the sites required the beta2 subunit. Many remaining sites were sensitive to inhibition by alpha-bungarotoxin indicating that a subset of the low affinity [(3)H]epibatidine binding are of the alpha7* subtype. Distinct regional variation was observed among the 12 brain regions. These studies confirm important roles for beta2-containing receptors in mediating pharmacologically distinct functions and as components of several identifiable binding sites.
ESTHER : Marks_2000_Neuropharmacol_39_2632
PubMedSearch : Marks_2000_Neuropharmacol_39_2632
PubMedID: 11044733

Title : Molecular determinants by which a long chain toxin from snake venom interacts with the neuronal alpha 7-nicotinic acetylcholine receptor - Antil-Delbeke_2000_J.Biol.Chem_275_29594
Author(s) : Antil-Delbeke S , Gaillard C , Tamiya T , Corringer PJ , Changeux JP , Servent D , Menez A
Ref : Journal of Biological Chemistry , 275 :29594 , 2000
Abstract : Long chain curarimimetic toxins from snake venom bind with high affinities to both muscular type nicotinic acetylcholine receptors (AChRs) (K(d) in the pm range) and neuronal alpha 7-AChRs (K(d) in the nm range). To understand the molecular basis of this dual function, we submitted alpha-cobratoxin (alpha-Cbtx), a typical long chain curarimimetic toxin, to an extensive mutational analysis. By exploring 36 toxin mutants, we found that Trp-25, Asp-27, Phe-29, Arg-33, Arg-36, and Phe-65 are involved in binding to both neuronal and Torpedo (Antil, S., Servent, D., and Menez, A. (1999) J. Biol. Chem. 274, 34851-34858) AChRs and that some of them (Trp-25, Asp-27, and Arg-33) have similar binding energy contributions for the two receptors. In contrast, Ala-28, Lys-35, and Cys-26-Cys-30 selectively bind to the alpha 7-AChR, whereas Lys-23 and Lys-49 bind solely to the Torpedo AChR. Therefore, alpha-Cbtx binds to two AChR subtypes using both common and specific residues. Double mutant cycle analyses suggested that Arg-33 in alpha-Cbtx is close to Tyr-187 and Pro-193 in the alpha 7 receptor. Since Arg-33 of another curarimimetic toxin is close to the homologous alpha Tyr-190 of the muscular receptor (Ackermann, E. J., Ang, E. T. H., Kanter, J. R., Tsigelny, I., and Taylor, P. (1998) J. Biol. Chem. 273, 10958-10964), toxin binding probably occurs in homologous regions of neuronal and muscular AChRs. However, no coupling was seen between alpha-Cbtx Arg-33 and alpha 7 receptor Trp-54, Leu-118, and Asp-163, in contrast to what was observed in a homologous situation involving another toxin and a muscular receptor (Osaka, H., Malany, S., Molles, B. E., Sine, S. M., and Taylor, P. (2000) J. Biol. Chem. 275, 5478-5484). Therefore, although occurring in homologous regions, the detailed modes of toxin binding to alpha 7 and muscular receptors are likely to be different. These data offer a molecular basis for the design of toxins with predetermined specificities for various members of the AChR family.
ESTHER : Antil-Delbeke_2000_J.Biol.Chem_275_29594
PubMedSearch : Antil-Delbeke_2000_J.Biol.Chem_275_29594
PubMedID: 10852927

Title : Molecular basis of the charge selectivity of nicotinic acetylcholine receptor and related ligand-gated ion channels - Corringer_1999_Novartis.Found.Symp_225_215
Author(s) : Corringer PJ , Bertrand S , Galzi JL , Devillers-Thiery A , Changeux JP , Bertrand D
Ref : Novartis Found Symp , 225 :215 , 1999
Abstract : Nicotinic acetylcholine receptors are homo- or heteropentameric proteins belonging to the superfamily of receptor channels including the glycine and GABA-A receptors. Affinity labelling and mutagenesis experiments indicated that the M2 transmembrane segment of each subunit lines the ion channel and is coiled into an alpha-helix. Comparison of the M2 sequence of the cation-selective alpha 7 nicotinic receptor to that of the anion-selective alpha 1 glycine receptor identified amino acids involved in charge selectivity. Mutations of the alpha 7 homo-oligomeric receptor within (or near) M2, namely E237A, V251T and a proline insertion P236' were shown to convert the ionic selectivity of alpha 7 from cationic to anionic. Systematic analysis of each of these three mutations supports the notion that the conversion of ionic selectivity results from a local structural reorganization of the 234-238 loop. The 234-238 coiled loop, previously shown to lie near the narrowest portion of the channel, is thus proposed to contribute directly to the charge selectivity filter. A possible functional analogy with the voltage-gated ion channels and related receptors is discussed.
ESTHER : Corringer_1999_Novartis.Found.Symp_225_215
PubMedSearch : Corringer_1999_Novartis.Found.Symp_225_215
PubMedID: 10472058

Title : Mutational analysis of the charge selectivity filter of the alpha7 nicotinic acetylcholine receptor - Corringer_1999_Neuron_22_831
Author(s) : Corringer PJ , Bertrand S , Galzi JL , Devillers-Thiery A , Changeux JP , Bertrand D
Ref : Neuron , 22 :831 , 1999
Abstract : In the alpha7 nicotinic acetylcholine receptors, we analyze the contribution of mutations E237A and V251T, together with the proline insertion P236', in the conversion of the charge selectivity from cationic to anionic. We show that the triple mutant exhibits spontaneous openings displaying anionic selectivity. Furthermore, at position 251, hydrophilic or even negatively charged residues are compatible with an anionic channel. In contrast, the additional proline yields an anionic channel only when inserted between positions 234 and 237; insertion before 234 yields a cationic channel and after 238 alters the receptor surface expression. The coiled 234-238 loop thus directly contributes to the charge selectivity filter of the alpha7 channel.
ESTHER : Corringer_1999_Neuron_22_831
PubMedSearch : Corringer_1999_Neuron_22_831
PubMedID: 10230802

Title : Involvement of alpha6 nicotinic receptor subunit in nicotine-elicited locomotion, demonstrated by in vivo antisense oligonucleotide infusion - le Novere_1999_Neuroreport_10_2497
Author(s) : Le Novere N , Zoli M , Lena C , Ferrari R , Picciotto MR , Merlo-Pich E , Changeux JP
Ref : Neuroreport , 10 :2497 , 1999
Abstract : Enhanced locomotion in a habituated environment is a well documented effect of nicotine mediated by the mesotelencephalic dopaminergic system. The nicotinic receptor subunit alpha6 is, among other subunits, strongly expressed in the dopaminergic neurons of the mesencephalon. To examine the functional role of this subunit, we inhibited its expression in vivo using antisense oligonucleotides. In vitro treatments of embryonic mesencephalic neuron cultures demonstrated that the alpha6 antisense oligonucleotides caused a marked decrease in the level of alpha6 subunit protein. In vivo, 1 week infusion of alpha6 antisense oligonucleotides by osmotic mini-pump reduced the effect of nicotine on locomotor activity in habituated environment by 70%. These data support the notion that the effects of nicotine on the dopaminergic system involve alpha6 subunit containing nAChRs.
ESTHER : le Novere_1999_Neuroreport_10_2497
PubMedSearch : le Novere_1999_Neuroreport_10_2497
PubMedID: 10574359

Title : Reduced antinociception in mice lacking neuronal nicotinic receptor subunits - Marubio_1999_Nature_398_805
Author(s) : Marubio LM , del Mar Arroyo-Jimenez M , Cordero-Erausquin M , Lena C , Le Novere N , de Kerchove d'Exaerde A , Huchet M , Damaj MI , Changeux JP
Ref : Nature , 398 :805 , 1999
Abstract : Nicotine exerts antinociceptive effects by interacting with one or more of the subtypes of nicotinic acetylcholine receptors (nAChRs) that are present throughout the neuronal pathways that respond to pain. To identify the particular subunits involved in this process, we generated mice lacking the alpha4 subunit of the neuronal nAChR by homologous recombination techniques and studied these together with previously generated mutant mice lacking the beta2 nAChR subunit. Here we show that the homozygous alpha4-/- mice no longer express high-affinity [3H]nicotine and [3H]epibatidine binding sites throughout the brain. In addition, both types of mutant mice display a reduced antinociceptive effect of nicotine on the hot-plate test and diminished sensitivity to nicotine in the tail-flick test. Patch-clamp recordings further reveal that raphe magnus and thalamic neurons no longer respond to nicotine. The alpha4 nAChR subunit, possibly associated with the beta2 nAChR subunit, is therefore crucial for nicotine-elicited antinociception.
ESTHER : Marubio_1999_Nature_398_805
PubMedSearch : Marubio_1999_Nature_398_805
PubMedID: 10235262

Title : Use of knock-out mice to determine the molecular basis for the actions of nicotine - Picciotto_1999_Nicotine.Tob.Res_1 Suppl 2_S121
Author(s) : Picciotto MR , Zoli M , Changeux JP
Ref : Nicotine Tob Res , 1 Suppl 2 :S121 , 1999
Abstract : Recombinant DNA techniques have been used to identify the family of molecules that mediate nicotine's effects on the brain. Nicotine binds and activates nicotinic acetylcholine receptors (nAChRs) which are made up of combinations of individual nicotinic subunits. It is important to determine which of the many possible subunit combinations are responsible for the physiological and behavioral effects of nicotine that lead to addiction. Molecular genetic tools such as antisense strategies have been useful in elucidating the electrophysiological properties of nAChRs in different tissues. Use of knock-out mice lacking individual nAChR subunits has also begun to elucidate how nicotine exerts its actions from the molecular level to the behavioral level. Experiments using mice lacking the beta2 subunit of the nAChR have shown that binding of nicotine to receptors containing this subunit is the first step in a pathway leading to increased dopamine levels in the mesolimbic dopamine system, and ultimately to the behavioral effects of nicotine in a test of nicotine reinforcement. Mice deficient in various alpha subunits of the nAChR will identify the partners of beta2 mediating the addictive properties of nicotine. In addition, more data needs to be gathered on the electrophysiological properties of different subunit combinations, the effects of nicotine on different neurotransmitter systems and the links between the molecular biology of nicotine receptors, their physiology and the ultimate role of individual receptor subtypes in complex behaviors. Multidisciplinary approaches to nAChR function will be essential to answering these questions.
ESTHER : Picciotto_1999_Nicotine.Tob.Res_1 Suppl 2_S121
PubMedSearch : Picciotto_1999_Nicotine.Tob.Res_1 Suppl 2_S121
PubMedID: 11768168

Title : International Union of Pharmacology. XX. Current status of the nomenclature for nicotinic acetylcholine receptors and their subunits -
Author(s) : Lukas RJ , Changeux JP , Le Novere N , Albuquerque EX , Balfour DJ , Berg DK , Bertrand D , Chiappinelli VA , Clarke PB , Collins AC , Dani JA , Grady SR , Kellar KJ , Lindstrom JM , Marks MJ , Quik M , Taylor P , Wonnacott S
Ref : Pharmacol Rev , 51 :397 , 1999
PubMedID: 10353988

Title : Modulation of morphine analgesia in alphaCGRP mutant mice - Salmon_1999_Neuroreport_10_849
Author(s) : Salmon AM , Damaj MI , Sekine S , Picciotto MR , Marubio L , Changeux JP
Ref : Neuroreport , 10 :849 , 1999
Abstract : A homozygous CGRP-/- mouse line was generated by the targeted disruption of exon 5 in the calcitonin/alphaCGRP gene using homologous recombination. The mutant mice lack alphaCGRP mRNA. Furthermore CGRP immunoreactivity almost completely disappears from the spinal cord and is not at all observed in spinal ganglia and muscle synapses. However, motor end plates were still detected by acetylcholinesterase staining. Antinociceptive behavior tested by the tail flick and hot plate tests did not significantly differ in mutant and wild-type mice, except when challenged by morphine. Paradoxically, morphine analgesia was reduced in mutant mice compared with controls in the tail flick test, but not in the hot plate test. Thus, alphaCGRP differentially modulates opiate pain pathways.
ESTHER : Salmon_1999_Neuroreport_10_849
PubMedSearch : Salmon_1999_Neuroreport_10_849
PubMedID: 10208559

Title : Two pharmacologically distinct components of nicotinic receptor-mediated rubidium efflux in mouse brain require the beta2 subunit - Marks_1999_J.Pharmacol.Exp.Ther_289_1090
Author(s) : Marks MJ , Whiteaker P , Calcaterra J , Stitzel JA , Bullock AE , Grady SR , Picciotto MR , Changeux JP , Collins AC
Ref : Journal of Pharmacology & Experimental Therapeutics , 289 :1090 , 1999
Abstract : Nicotinic agonist-stimulated efflux of 86Rb+ from mouse brain synaptosomes was monitored continuously by on-line radioactivity detection. The concentration-effect curve following a 5-s stimulation with acetylcholine was biphasic (EC50 = 7.2 and 550 microM). alpha-Bungarotoxin (100 nM) did not inhibit the response, but dihydro-beta-erythroidine (DHbetaE) blocked both phases with differing potency (average IC50 =.22 and 8.9 microM for responses activated by low and high acetylcholine concentrations, respectively). Differential sensitivity DHbetaE inhibition was used to measure stimulation of 86Rb+ efflux by 17 nicotinic agonists, which differed markedly in potency and efficacy. All agonists were more potent at the DHbetaE-sensitive site. Both components were inhibited by the six antagonists tested. Methyllycaconitine and DHbetaE were more potent for the DHbetaE-sensitive component, whereas hexamethonium was more potent at the DHbetaE-resistant component. Both DHbetaE-sensitive and DHbetaE-resistant responses were reduced more than 95% in beta2-null mutant mice, establishing the requirement for the beta2 subunit for both components. Both components were widely, but not identically, distributed throughout the brain. The DHbetaE-sensitive component appears to be identical with agonist-stimulated 86Rb+ efflux described previously and is likely to be mediated by alpha4beta2 receptors. The DHbetaE-resistant component is a novel, active, and widely distributed response mediated by nicotinic receptor(s) that also require the beta2 subunit.
ESTHER : Marks_1999_J.Pharmacol.Exp.Ther_289_1090
PubMedSearch : Marks_1999_J.Pharmacol.Exp.Ther_289_1090
PubMedID: 10215692

Title : Assessment of nicotinic acetylcholine receptor subunit contributions to nicotine self-administration in mutant mice -
Author(s) : Epping-Jordan MP , Picciotto MR , Changeux JP , Pich EM
Ref : Psychopharmacology (Berl) , 147 :25 , 1999
PubMedID: 10591862

Title : Increased neurodegeneration during ageing in mice lacking high-affinity nicotine receptors - Zoli_1999_EMBO.J_18_1235
Author(s) : Zoli M , Picciotto MR , Ferrari R , Cocchi D , Changeux JP
Ref : EMBO Journal , 18 :1235 , 1999
Abstract : We have examined neuroanatomical, biochemical and endocrine parameters and spatial learning in mice lacking the beta2 subunit of the nicotinic acetylcholine receptor (nAChR) during ageing. Aged beta2(-/-) mutant mice showed region-specific alterations in cortical regions, including neocortical hypotrophy, loss of hippocampal pyramidal neurons, astro- and microgliosis and elevation of serum corticosterone levels. Whereas adult mutant and control animals performed well in the Morris maze, 22- to 24-month-old beta2(-/-) mice were significantly impaired in spatial learning. These data show that beta2 subunit-containing nAChRs can contribute to both neuronal survival and maintenance of cognitive performance during ageing. beta2(-/-) mice may thus serve as one possible animal model for some of the cognitive deficits and degenerative processes which take place during physiological ageing and in Alzheimer's disease, particularly those associated with dysfunction of the cholinergic system.
ESTHER : Zoli_1999_EMBO.J_18_1235
PubMedSearch : Zoli_1999_EMBO.J_18_1235
PubMedID: 10064590

Title : Structural discrimination between the two agonist binding sites of the Torpedo nicotinic acetylcholine receptor using time resolved fluorescence -
Author(s) : Martinez K , Corringer PJ , Merola F , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :466 , 1998

Title : Artificial toxins to explore new receptors? -
Author(s) : Menez A , Mourier G , Kessler P , Ducancel F , Bertrand D , Corringer PJ , Changeux JP , Servent D
Ref : Journal de Physiologie (Paris) , 92 :468 , 1998

Title : Involvement of protein kinases and protein phosphatases in the regulation of acetylcholine receptor gene expression -
Author(s) : Nghiem HO , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :475 , 1998

Title : Differential susceptibility of young and old rat neuromuscular junctions to antibody-mediated AChR degradation in experimental autoimmune myasthenia gravis -
Author(s) : Hoedemaekers A , Bessereau JL , Graus Y , Guyon T , Changeux JP , Berrih-Aknin S , Van Breda Vriesman P , de Baets M
Ref : Annals of the New York Academy of Sciences , 841 :550 , 1998
PubMedID: 9668293

Title : Role of the target organ in determining susceptibility to experimental autoimmune myasthenia gravis - Hoedemaekers_1998_J.Neuroimmunol_89_131
Author(s) : Hoedemaekers A , Bessereau JL , Graus Y , Guyon T , Changeux JP , Berrih-Aknin S , Van Breda Vriesman P , De Baets MH
Ref : Journal of Neuroimmunology , 89 :131 , 1998
Abstract : Injection of anti-AChR antibodies in passive transfer experimental autoimmune myasthenia gravis (EAMG) results in increased degradation of acetylcholine receptor (AChR) and increased synthesis of AChR alpha-subunit mRNA. Passive transfer of anti-Main Immunogenic Region (MIR) mAb 35 in aged rats does not induce clinical signs of disease nor AChR loss. The expression of the AChR subunit genes was analyzed in susceptible and resistant rats. In aged EAMG resistant rats, no increase in the amount of AChR alpha-subunit mRNA was measured. In vivo AChR degradation experiments did not show any increase in AChR degradation rates in aged resistant rats, in contrast to young susceptible rats. Taken together, these data demonstrate that resistance of the AChR protein to antibody-mediated degradation is the primary mechanism that accounts for the resistance to passive transfer EAMG in aged rats.
ESTHER : Hoedemaekers_1998_J.Neuroimmunol_89_131
PubMedSearch : Hoedemaekers_1998_J.Neuroimmunol_89_131
PubMedID: 9726835

Title : Analysis of developmental evolution of synapses in CGRP knock-out mice -
Author(s) : Salmon AM , Sekine S , Picciotto MR , Damaj MI , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :488 , 1998

Title : Implication of a multisubunit Ets related transcription factor in synaptic expression of the nicotinic acetylcholine receptor -
Author(s) : Schaeffer L , de Kerchove d'Exaerde A , Duclert N , Huchet-Dymanus M , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :489 , 1998

Title : An antibody specific for the neuronal nicotinic acetylcholine receptor alpha 4 subunit: High levels of expression in monoaminergic neurons -
Author(s) : Arroyo-Jimenez MM , Bourgeois JP , Le Sourd AM , Fairen A , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :405 , 1998

Title : Allosteric receptors after 30 years -
Author(s) : Changeux JP , Edelstein SJ
Ref : Neuron , 21 :959 , 1998
PubMedID: 9856454

Title : Regulation of desensitization by beta subunit in neuronal nAchR -
Author(s) : Bohler S , Corringer PJ , Changeux JP , Bertrand S , Bertrand D , Edelstein SJ
Ref : Journal de Physiologie (Paris) , 92 :414 , 1998

Title : Acetylcholine receptors containing the beta2 subunit are involved in the reinforcing properties of nicotine - Picciotto_1998_Nature_391_173
Author(s) : Picciotto MR , Zoli M , Rimondini R , Lena C , Marubio LM , Pich EM , Fuxe K , Changeux JP
Ref : Nature , 391 :173 , 1998
Abstract : Release of the neurotransmitter dopamine in the mesolimbic system of the brain mediates the reinforcing properties of several drugs of abuse, including nicotine. Here we investigate the contribution of the high-affinity neuronal nicotinic acetylcholine receptor to the effects of nicotine on the mesolimbic dopamine system in mice lacking the beta2 subunit of this receptor. We found that nicotine stimulates dopamine release in the ventral striatum of wild-type mice but not in the ventral striatum of beta2-mutant mice. Using patch-clamp recording, we show that mesencephalic dopaminergic neurons from mice without the beta2 subunit no longer respond to nicotine, and that self-administration of nicotine is attenuated in these mutant mice. Our results strongly support the idea that the beta2-containing neuronal nicotinic acetylcholine receptor is involved in mediating the reinforcing properties of nicotine.
ESTHER : Picciotto_1998_Nature_391_173
PubMedSearch : Picciotto_1998_Nature_391_173
PubMedID: 9428762

Title : Critical elements determining diversity in agonist binding and desensitization of neuronal nicotinic acetylcholine receptors - Corringer_1998_J.Neurosci_18_648
Author(s) : Corringer PJ , Bertrand S , Bohler S , Edelstein SJ , Changeux JP , Bertrand D
Ref : Journal of Neuroscience , 18 :648 , 1998
Abstract : To identify the molecular determinants underlying the pharmacological diversity of neuronal nicotinic acetylcholine receptors, we compared the alpha7 homo-oligomeric and alpha4beta2 hetero-oligomeric receptors. Sets of residues from the regions initially identified within the agonist binding site of the alpha4 subunit were introduced into the alpha7 agonist binding site, carried by the homo-oligomeric alpha7-V201-5HT3 chimera. Introduction of the alpha4 residues 183-191 into alpha7 subunit sequence (chimera C2) selectively increased the apparent affinities for equilibrium binding and for ion channel activation by acetylcholine, resulting in a receptor that no longer displays differences in the responses to acetylcholine and nicotine. Introduction of the alpha4 residues 151-155 (chimera B) produced a approximately 100-fold increase in the apparent affinity for both acetylcholine and nicotine in equilibrium binding measurements. In both cases electrophysiological recordings revealed a much smaller increase (three- to sevenfold) in the apparent affinity for activation, but the concentrations required to desensitize the mutant chimeras parallel the shifts in apparent binding affinity. The data were fitted by a two-state concerted model, and an alteration of the conformational isomerization constant leading to the desensitized state accounts for the chimera B phenotype, whereas alteration of the ligand binding site accounts for the chimera C2 phenotype. Point mutation analysis revealed that several residues in both fragments contribute to the phenotypes, with a critical effect of the G152K and T183N mutations. Transfer of alpha4 amino acids 151-155 and 183-191 into the alpha7-V201-5HT3 chimera thus confers physiological and pharmacological properties typical of the alpha4beta2 receptor.
ESTHER : Corringer_1998_J.Neurosci_18_648
PubMedSearch : Corringer_1998_J.Neurosci_18_648
PubMedID: 9425007

Title : Characterization of mice lacking the nicotinic receptoralpha4 subunit -
Author(s) : Cordero-Erausquin LM , Marubio LM , Arroyo-Jimenez MM , Le Novere N , Huchet M , Lena C , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :423 , 1998

Title : Critical elements determining diversity in agonist binding and desensitization of neuronal nAChR -
Author(s) : Corringer PJ , Bertrand S , Bohler S , Edelstein SJ , Bertrand D , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :424 , 1998

Title : Allosteric transitions of the acetylcholine receptor -
Author(s) : Edelstein SJ , Changeux JP
Ref : Advances in Protein Chemistry , 51 :121 , 1998
PubMedID: 9615170

Title : Identification of four classes of brain nicotinic receptors using beta2 mutant mice - Zoli_1998_J.Neurosci_18_4461
Author(s) : Zoli M , Lena C , Picciotto MR , Changeux JP
Ref : Journal of Neuroscience , 18 :4461 , 1998
Abstract : Although the expression patterns of the neuronal nicotinic acetylcholine receptor (nAChR) subunits thus far described are known, the subunit composition of functional receptors in different brain areas is an ongoing question. Mice lacking the beta2 subunit of the nAChR were used for receptor autoradiography studies and patch-clamp recording in thin brain slices. Four distinct types of nAChRs were identified, expanding on an existing classification [Alkondon M, Albuquerque EX (1993) Diversity of nicotinic acetylcholine receptors in rat hippocampal neurons. I. Pharmacological and functional evidence for distinct structural subtypes. J Pharmacol Exp Ther 265:1455-1473.], and tentatively identifying the subunit composition of nAChRs in different brain regions. Type 1 nAChRs bind alpha-bungarotoxin, are not altered in beta2 -/- mice, and contain the alpha7 subunit. Type 2 nAChRs contain the beta2 subunit because they are absent in beta2 -/- mice, bind all nicotinic agonists used with high affinity (excluding alpha-bungarotoxin), have an order of potency for nicotine >> cytisine in electrophysiological experiments, and are likely to be composed of alpha4 beta2 in most brain regions, with other alpha subunits contributing in specific areas. Type 3 nAChRs bind epibatidine with high affinity in equilibrium binding experiments and show that cytisine is as effective as nicotine in electrophysiological experiments; their distribution and persistence in beta2 -/- mice strongly suggest a subunit composition of alpha3 beta4. Type 4 nAChRs bind cytisine and epibatidine with high affinity in equilibrium binding experiments and persist in beta2 -/- mice; cytisine = nicotine in electrophysiological experiments. Type 4 nAChRs also exhibit faster desensitization than type 3 nAChRs at high doses of nicotine. Knock-out animals lacking individual alpha subunits should allow a further dissection of nAChR subclasses.
ESTHER : Zoli_1998_J.Neurosci_18_4461
PubMedSearch : Zoli_1998_J.Neurosci_18_4461
PubMedID: 9614223

Title : Predicted secondary structure of a nicotinic acetylcholine receptor subunit. Incorporation of predicted solvent accessibility and experimental data into a two dimensional representation -
Author(s) : Le Novere N , Corringer PJ , Changeux JP
Ref : Journal de Physiologie (Paris) , 92 :458 , 1998

Title : Nonmyogenic factors bind nicotinic acetylcholine receptor promoter elements required for response to denervation - Bessereau_1998_J.Biol.Chem_273_12786
Author(s) : Bessereau JL , Laudenbach V , Le Poupon C , Changeux JP
Ref : Journal of Biological Chemistry , 273 :12786 , 1998
Abstract : Nicotinic acetylcholine receptors (AChRs) belong to a class of muscle proteins whose expression is regulated by muscle electrical activity. In innervated muscle fiber, AChR genes are transcriptionally repressed outside of the synapse, while after denervation they become reexpressed throughout the fiber. The myogenic determination factors (MDFs) of the MyoD family have been shown to play a central role in this innervation-dependent regulation. In the chicken AChR alpha-subunit gene promoter, two E-boxes that bind MDFs are necessary to achieve the enhancement of transcription following muscle denervation. However, the deletion of promoter sequences located upstream to these E-boxes greatly impairs the response to denervation (Bessereau, J. L., Stratford- Perricaudet, L. D., Piette, J., Le Poupon, C. and Changeux, J. P. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 1304-1308). Here we identified two additional cis-regulatory elements of the alpha-subunit gene promoter that cooperate with the E-boxes in the denervation response. One region binds the Sp1 and Sp3 zinc finger transcription factors. The second region binds at least three distinct factors, among which we identified an upstream stimulatory factor, a b-ZIP-HLH transcription factor. We propose that among MDF-responsive muscle promoters, a specific combination between myogenic and nonmyogenic factors specify innervation-dependent versus innervation-independent promoters.
ESTHER : Bessereau_1998_J.Biol.Chem_273_12786
PubMedSearch : Bessereau_1998_J.Biol.Chem_273_12786
PubMedID: 9582305

Title : Paradoxical allosteric effects of competitive inhibitors on neuronal alpha7 nicotinic receptor mutants - Bertrand_1997_Neuroreport_8_3591
Author(s) : Bertrand S , Devillers-Thiery A , Palma E , Buisson B , Edelstein SJ , Corringer PJ , Changeux JP , Bertrand D
Ref : Neuroreport , 8 :3591 , 1997
Abstract : Mutation of the conserved leucine residue, in the second transmembrane domain of the neuronal alpha7 acetylcholine receptor to a threonine (L247T) causes pleiotropic alterations of receptor properties. In this study we examined the effects of competitive inhibitors on the alpha7-L247T physiological responses. While the alpha7 competitive inhibitor dihydro-beta-erythroidine evoked a current comparable to that induced by ACh, other inhibitors such as methyllycaconitine (MLA) and alpha-bungarotoxin (alpha-Bgt) caused a blockade of alpha7-L247T to ACh activation. When applied in the absence of ACh, MLA or alpha-Bgt reduced the cell leakage current, showing that alpha7-L247T displays a significant fraction (10%) of spontaneously open channels. These data can be interpreted in terms of an allosteric model, assuming that the L247T mutant possesses a low isomerization constant L and that MLA and alpha-Bgt stabilize the closed, resting state.
ESTHER : Bertrand_1997_Neuroreport_8_3591
PubMedSearch : Bertrand_1997_Neuroreport_8_3591
PubMedID: 9427332

Title : Contribution of nicotinic acetylcholine receptors containing the beta 2-subunit to the behavioural effects of nicotine -
Author(s) : Picciotto MR , Zoli M , Zachariou V , Changeux JP
Ref : Biochemical Society Transactions , 25 :824 , 1997
PubMedID: 9388554

Title : Enhanced hemicholinium binding and attenuated dendrite branching in cognitively impaired acetylcholinesterase-transgenic mice - Beeri_1997_J.Neurochem_69_2441
Author(s) : Beeri R , Le Novere N , Mervis R , Huberman T , Grauer E , Changeux JP , Soreq H
Ref : Journal of Neurochemistry , 69 :2441 , 1997
Abstract : In a search for behavioral, neuroanatomical, and metabolic characteristics of Alzheimer's disease that may result from cholinergic malfunction, we used transgenic mice overexpressing acetylcholinesterase (AChE) mRNA and active enzyme in brain neurons. Mapping by in situ hybridization revealed that transgenic and host AChE mRNAs were distributed similarly. In a Morris water maze working memory paradigm, adult transgenic mice did not display the characteristic improvement found in control mice either between or within test days and spent less time than control mice in the platform zone. In 5-week-old transgenic mice, the basilar dendritic trees of layer 5 pyramidal neurons from the frontoparietal cortex were essentially as developed as in age-matched controls. However, branching totally ceased after this age, whereas in control adults it continued up to at least 7 months. Therefore, dendritic arbors became smaller in adult transgenic mice than those of controls. Furthermore, the average number of spines was significantly lower on dendritic branches of 7-month-old but not 5-week-old transgenics as compared with controls. Binding of tritiated hemicholinium-3, a blocker of the high-affinity choline uptake characteristic of active cholinergic terminals, was over twofold enhanced in the brain of transgenic mice. In contrast, no differences were observed in the mRNA and ligand binding levels of several different subtypes of nicotinic and muscarinic acetylcholine receptors. These findings suggest that three different hallmarks associated with Alzheimer's disease--namely, progressive cognitive failure, cessation of dendrite branching and spine formation, and enhanced high-affinity choline uptake--are outcomes of cholinergic malfunction.
ESTHER : Beeri_1997_J.Neurochem_69_2441
PubMedSearch : Beeri_1997_J.Neurochem_69_2441
PubMedID: 9375677

Title : Myasthenic nicotinic receptor mutant interpreted in terms of the allosteric model - Edelstein_1997_C.R.Acad.Sci.III_320_953
Author(s) : Edelstein SJ , Schaad O , Changeux JP
Ref : Comptes Rendus de l Academie des Sciences , 320 :953 , 1997
Abstract : An extended Monod-Wyman-Changeux allosteric-type model is applied to human muscle nicotinic acetylcholine receptors expressed in HEK cells, for both the normal form and the high-affinity human myasthenic mutant, epsilon T264P. The model is based on a concerted transition between the basal (resting) B state and the active (open-channel) A state, with the equilibrium in the absence of ligand determined by the allosteric constant, L0 = [B0]/[A0]. For wild-type receptors the model with L0 = 9 x 10(8) provides a satisfactory representation of published patch-clamp recordings that yields a distribution of open-channel dwell times with a single peak at 0.7 ms. For the epsilon T264P mutant, the model with L0 = 100 accounts for the trimodal distribution reported for open-channel dwell times, with peaks at 0.15, 3.8 and 60 ms that correspond to non-, mono- and bi-liganded receptors, respectively. Possible applications of the allosteric model to other myasthenic mutants are considered.
ESTHER : Edelstein_1997_C.R.Acad.Sci.III_320_953
PubMedSearch : Edelstein_1997_C.R.Acad.Sci.III_320_953
PubMedID: 9587473

Title : Single binding versus single channel recordings: a new approach to study ionotropic receptors - Edelstein_1997_Biochemistry_36_13755
Author(s) : Edelstein SJ , Schaad O , Changeux JP
Ref : Biochemistry , 36 :13755 , 1997
Abstract : The observation of ligand binding to a single molecule has become feasible with recent developments in laser-based fluorescence microscopy. We have simulated such single ligand-binding events for the nicotinic acetylcholine receptor in order to provide comparisons with single channel events under pulsed agonist conditions. The binding events would be more complex than ionic events due to multiple interconversions between different conformational states at the same degree of ligation. Nevertheless, recording of such events could provide valuable new information concerning the role of ligand binding in stabilizing conformational changes and the degree of functional nonequivalence of the binding sites.
ESTHER : Edelstein_1997_Biochemistry_36_13755
PubMedSearch : Edelstein_1997_Biochemistry_36_13755
PubMedID: 9374851

Title : Identification of an extracellular motif involved in the binding of guanine nucleotides by a glutamate receptor - Paas_1996_EMBO.J_15_1548
Author(s) : Paas Y , Devillers-Thiery A , Changeux JP , Medevielle F , Teichberg VI
Ref : EMBO Journal , 15 :1548 , 1996
Abstract : The chick cerebellar kainate (KA) binding protein (KBP), a member of the family of ionotropic glutamate receptors, harbours a glycine-rich (GxGxxG) motif known to be involved in the binding of ATP and GTP to kinases and G proteins respectively. Here, we report that guanine, but not adenine, nucleotides interact with KBP by inhibiting [3H]KA binding in a competitive-like manner, displaying IC50 values in the micromolar range. To locate the GTP binding site, KBP was photoaffinity labelled with [alpha-32P]GTP. The reaction was blocked by KA, glutamate, 6-cyano-7-nitroquinoxaline-2,3-dione and antibodies raised against a peptide containing the glycine-rich motif. Site-directed mutagenesis of residues K72 and Y73 within the glycine-rich motif followed by the expression of the KBP mutants at the surface of HEK 293 cells showed a decrease in GTP binding affinity by factors of 10 and 100 respectively. The binding of [3H]KA to the K72A/T KBP mutants was not affected but binding to the Y73I KBP mutant was decreased by a factor of 10. Accordingly, we propose that the glycine-rich motif of KBP forms part of a guanine nucleotide binding site. We further suggest that the glycine-rich motif is the binding site at which guanine nucleotides inhibit the glutamate-mediated responses of various members of the subfamily of glutamate ionotropic receptors.
ESTHER : Paas_1996_EMBO.J_15_1548
PubMedSearch : Paas_1996_EMBO.J_15_1548
PubMedID: 8612578

Title : Allosteric proteins after thirty years: the binding and state functions of the neuronal alpha 7 nicotinic acetylcholine receptors - Edelstein_1996_Experientia_52_1083
Author(s) : Edelstein SJ , Changeux JP
Ref : Experientia , 52 :1083 , 1996
Abstract : A key statement of the 1965 Monod-Wyman-Changeux (MWC) model for allosteric proteins concerns the distinction between the ligand-binding function (Y) and the relevant state function (R). Sequential models predict overlapping behavior of the two functions. In contrast, a straightforward experimental consequence of the MWC model is that for an oligomeric protein the parameters which characterize the two functions should differ significantly. Two situations, where R > Y and the system is hyper-responsive or where R < Y and the system is hypo-responsive, have been encountered. Indeed, the hyper-responsive pattern was first observed for the enzyme aspartate transcarbamoylase, by comparing Y with R monitored by a change in sedimentation. Extensions of the theory to ligand-gated channels led to the suggestion that, on the one hand, hyper-responsive properties also occur with high-affinity mutants. On the other hand, native channels of the acetylcholine neuronal alpha 7 receptor and low-affinity mutants of the glycine receptor can be interpreted in terms of the hypo-responsive pattern. For the ligand-gated channels, whereas R is detected directly by ion flux, ligand binding has rarely been measured and the formation of desensitized states may complicate the analysis. However, stochastic models incorporating both binding and channel opening for single molecules predict differences that should be measurable with new experimental approaches, particularly fluorescence correlation spectroscopy.
ESTHER : Edelstein_1996_Experientia_52_1083
PubMedSearch : Edelstein_1996_Experientia_52_1083
PubMedID: 8988250

Title : A kinetic mechanism for nicotinic acetylcholine receptors based on multiple allosteric transitions - Edelstein_1996_Biol.Cybern_75_361
Author(s) : Edelstein SJ , Schaad O , Henry E , Bertrand D , Changeux JP
Ref : Biological Cybernetics , 75 :361 , 1996
Abstract : Nicotinic acetylcholine receptors are transmembrane oligomeric proteins that mediate interconversions between open and closed channel states under the control of neurotransmitters. Fast in vitro chemical kinetics and in vivo electrophysiological recordings are consistent with the following multi-step scheme. Upon binding of agonists, receptor molecules in the closed but activatable resting state (the Basal state, B) undergo rapid transitions to states of higher affinities with either open channels (the Active state, A) or closed channels (the initial Inactivatable and fully Desensitized states, I and D). In order to represent the functional properties of such receptors, we have developed a kinetic model that links conformational interconversion rates to agonist binding and extends the general principles of the Monod-Wyman-Changeux model of allosteric transitions. The crucial assumption is that the linkage is controlled by the position of the interconversion transition states on a hypothetical linear reaction coordinate. Application of the model to the peripheral nicotine acetylcholine receptor (nAChR) accounts for the main properties of ligand-gating, including single-channel events, and several new relationships are predicted. Kinetic simulations reveal errors inherent in using the dose-response analysis, but justify its application under defined conditions. The model predicts that (in order to overcome the intrinsic stability of the B state and to produce the appropriate cooperativity) channel activation is driven by an A state with a Kd in the 50 nM range, hence some 140-fold stronger than the apparent affinity of the open state deduced previously. According to the model, recovery from the desensitized states may occur via rapid transit through the A state with minimal channel opening, thus without necessarily undergoing a distinct recovery pathway, as assumed in the standard 'cycle' model. Transitions to the desensitized states by low concentration 'pre-pulses' are predicted to occur without significant channel opening, but equilibrium values of IC50 can be obtained only with long pre-pulse times. Predictions are also made concerning allosteric effectors and their possible role in coincidence detection. In terms of future developments, the analysis presented here provides a physical basis for constructing more biologically realistic models of synaptic modulation that may be applied to artificial neural networks.
ESTHER : Edelstein_1996_Biol.Cybern_75_361
PubMedSearch : Edelstein_1996_Biol.Cybern_75_361
PubMedID: 8983160

Title : Nicotinic receptors and brain plasticity -
Author(s) : Changeux JP , Bessis A , Bourgeois JP , Corringer PJ , Devillers-Thiery A , Eisele JL , Kerszberg M , Lena C , Le Novere N , Picciotto MR , Zoli M
Ref : Cold Spring Harbor Symposium on Quantitative Biology , 61 :343 , 1996
PubMedID: 9246464

Title : Developmental Regulation of Acetylcholinesterase mRNA in the Mouse Diaphragm -
Author(s) : Legay C , Huchet M , Massoulie J , Changeux JP
Ref : In Enzyme of the Cholinesterase Family - Proceedings of Fifth International Meeting on Cholinesterases , (Quinn, D.M., Balasubramanian, A.S., Doctor, B.P., Taylor, P., Eds) Plenum Publishing Corp. :47 , 1995

Title : Developmental regulation of acetylcholinesterase transcripts in the mouse diaphragm: alternative splicing and focalization - Legay_1995_Eur.J.Neurosci_7_1803
Author(s) : Legay C , Huchet M , Massoulie J , Changeux JP
Ref : European Journal of Neuroscience , 7 :1803 , 1995
Abstract : We studied the splicing and compartmentalization of acetylcholinesterase (AchE) mRNAs during muscle differentiation in the mouse, both in vitro and in vivo. We used the polymerase chain reaction (PCR) to analyse AChE mRNAs in cultures of the myogenic C2 and Sol8 cell lines, and in the developing diaphragm, from embryonic day 14 (E14). We characterized three types of alternatively spliced AChE mRNAs, encoding catalytic subunits that differ by their C-terminal regions (R, H and T). The T transcript is predominant in all cases and represents the only AChE mRNA in the adult muscle. We detected the presence of the minor R and H transcripts in the myogenic cell lines, both as myoblasts and differentiated myotubes, and also in the diaphragm from E14 until birth. At E14 the R transcript represents approximately 1% of AChE mRNA and the level of the H transcript is still lower. By in situ hybridization, we found that the T AChE mRNAs begin to preferentially accumulate at the level of the first neuromuscular contacts in the mouse diaphragm and other muscles as early as E14, e.g. concomitantly with mRNAs encoding the receptor subunits. This suggests that a common control mechanism ensures the synaptic focalization of mRNAs encoding the cholinergic proteins AChE and acetylcholine receptor during muscle development.
ESTHER : Legay_1995_Eur.J.Neurosci_7_1803
PubMedSearch : Legay_1995_Eur.J.Neurosci_7_1803
PubMedID: 7582132

Title : Abnormal avoidance learning in mice lacking functional high-affinity nicotine receptor in the brain - Picciotto_1995_Nature_374_65
Author(s) : Picciotto MR , Zoli M , Lena C , Bessis A , Lallemand Y , Le Novere N , Vincent P , Pich EM , Brulet P , Changeux JP
Ref : Nature , 374 :65 , 1995
Abstract : Nicotine affects many aspects of behaviour including learning and memory through its interaction with neuronal nicotinic acetylcholine receptors (nAChR). Functional nAChRs are pentameric proteins containing at least one type of alpha-subunit and one type of beta-subunit. The involvement of a particular neuronal nicotinic subunit in pharmacology and behaviour was examined using gene targeting to mutate beta 2, the most widely expressed nAChR subunit in the central nervous system. We report here that high-affinity binding sites for nicotine are absent from the brains of mice homozygous for the beta 2-subunit mutation. Further, electrophysiological recording from brain slices reveals that thalamic neurons from these mice do not respond to nicotine application. Finally, behavioural tests demonstrate that nicotine no longer augments the performance of beta 2-1- mice on passive avoidance, a test of associative memory. Paradoxically, mutant mice are able to perform better than their non-mutant siblings on this task.
ESTHER : Picciotto_1995_Nature_374_65
PubMedSearch : Picciotto_1995_Nature_374_65
PubMedID: 7870173

Title : ErbB3 and ErbB2\/neu mediate the effect of heregulin on acetylcholine receptor gene expression in muscle: differential expression at the endplate - Altiok_1995_EMBO.J_14_4258
Author(s) : Altiok N , Bessereau JL , Changeux JP
Ref : EMBO Journal , 14 :4258 , 1995
Abstract : Motor neurons modulate acetylcholine receptor (AChR) gene expression in skeletal muscle by two signalling pathways: the transmitter-evoked depolarization of muscle membrane inhibits AChR gene transcription throughout the myofibre presumably via activation of a serine/threonine kinase, while the transcription rates of AChR genes in the synaptic region are increased by nerve-derived trophic factors including AChR-inducing activity (ARIA). To gain further insight into these interactions we characterized the receptor for heregulin (HRG)/ARIA in muscle. We showed that HRG increases AChR alpha-subunit mRNA levels via tyrosine phosphorylation of ErbB3 and ErbB2/neu in myotubes. The protein tyrosine phosphatase inhibitor, pervanadate, potentiated the responses to HRG that were in turn blocked by the tyrosine kinase inhibitor erstatin, indicating the relevance of tyrosine phosphorylation to these events. The effects of HRG were inhibited by enhanced cellular serine/threonine phosphorylation which has been implicated in the repression of AChR genes by electrical activity. Immunocytochemical analysis of adult rat muscle revealed that while ErbB2/neu is present throughout the entire surface of the myofibre membrane, ErbB3 expression is exclusively restricted to the endplate suggesting its involvement in synapse-specific transcription of AChR genes by HRG/ARIA.
ESTHER : Altiok_1995_EMBO.J_14_4258
PubMedSearch : Altiok_1995_EMBO.J_14_4258
PubMedID: 7556067

Title : In vivo and in vitro analysis of electrical activity-dependent expression of muscle acetylcholine receptor genes using adenovirus - Bessereau_1994_Proc.Natl.Acad.Sci.U.S.A_91_1304
Author(s) : Bessereau JL , Stratford-Perricaudet LD , Piette J , Le Poupon C , Changeux JP
Ref : Proc Natl Acad Sci U S A , 91 :1304 , 1994
Abstract : Acetylcholine receptor (AChR) genes are repressed in extrajunctional domains of adult muscle fiber by neurally evoked electrical activity. Denervation elicits upregulation of AChR gene transcription in extrasynaptic areas. We have used an adenovirus (Ad)-based strategy to analyze in vitro and in vivo the electrical activity-dependent transcription of the chicken AChR alpha 1 subunit gene. The luciferase gene placed under the control of wild-type and mutated fragments of the alpha 1 subunit promoter was inserted in a defective Ad vector designed for the study of transcriptional regulation. Animals were infected by intramuscular injection and in vivo luciferase levels were normalized by coinfection with an Ad vector containing the chloramphenicol acetyltransferase gene driven by an electrical activity-insensitive promoter. Our results demonstrate that although both proximal MyoD binding sites of the alpha 1 promoter are required for muscle-specific expression of the alpha 1 gene, only one is necessary, albeit insufficient, to enhance alpha 1 promoter activity after denervation. Parallel results were obtained with cultured muscle cells in vitro following tetrodotoxin blocking of spontaneous electrical activity. These results substantiate a direct contribution of MyoD factors in electrical activity-dependent regulation of AChR expression and further indicate that Ad-based vectors constitute a powerful tool in the field of transcriptional regulation.
ESTHER : Bessereau_1994_Proc.Natl.Acad.Sci.U.S.A_91_1304
PubMedSearch : Bessereau_1994_Proc.Natl.Acad.Sci.U.S.A_91_1304
PubMedID: 8108406

Title : On allosteric mechanisms and acetylcholine receptors -
Author(s) : Changeux JP , Edelstein SJ
Ref : Trends in Biochemical Sciences , 19 :399 , 1994
PubMedID: 7817393

Title : Muscle-specific expression of the acetylcholine receptor alpha-subunit gene requires both positive and negative interactions between myogenic factors, Sp1 and GBF factors - Bessereau_1993_EMBO.J_12_443
Author(s) : Bessereau JL , Mendelzon D , LePoupon C , Fiszman M , Changeux JP , Piette J
Ref : EMBO Journal , 12 :443 , 1993
Abstract : The dependence of the muscle-specific enhancer of the acetylcholine receptor alpha-subunit gene on other domains of the promoter has been analysed by performing point mutagenesis and modular reconstitution of the enhancer--promoter sequences. The enhancer is inactive in the absence of the proximal region containing an Sp1 binding site and an overlapping G-C homopolymer binding factor site (referred to as GBF). The proximal region can be replaced by an Sp1 binding site from SV40 or an MEF-2 binding site from the muscle creatine kinase gene. Specific mutation of the Sp1 site markedly affects transactivation by CMD1 or myogenin. Mutation of the GBF binding site leads to higher promoter activity in primary cultures of chick myotubes or in quail fibroblasts. In addition, binding of a purified Sp1 protein prevents the binding of GBF in vitro. It is proposed that in the case of the alpha-subunit promoter, the myogenic factors activate transcription in cooperation with Sp1, and that GBF contributes to muscle-specific expression of the promoter by interfering with Sp1 binding in nonmuscle muscle cells or myoblasts.
ESTHER : Bessereau_1993_EMBO.J_12_443
PubMedSearch : Bessereau_1993_EMBO.J_12_443
PubMedID: 8382608

Title : Mutations at two distinct sites within the channel domain M2 alter calcium permeability of neuronal alpha 7 nicotinic receptor - Bertrand_1993_Proc.Natl.Acad.Sci.U.S.A_90_6971
Author(s) : Bertrand D , Galzi JL , Devillers-Thiery A , Bertrand S , Changeux JP
Ref : Proc Natl Acad Sci U S A , 90 :6971 , 1993
Abstract : The relative permeability for sodium, potassium, and calcium of chicken alpha 7 neuronal nicotinic receptor was investigated by mutagenesis of the channel domain M2. Mutations in the "intermediate ring" of negatively charged residues, located at the cytoplasmic end of M2 (site 1), reduce calcium permeability without significantly modifying other functional properties (activation and desensitization) of the receptor; a similar change of ion selectivity is also noticed when mutations at site 1 are done in the context of a receptor mutant that conducts ions in a desensitized state. Moreover, mutations of two adjacent rings of leucines at the synaptic end of M2 (site 2) have multiple effects. They abolish calcium permeability, increase the apparent affinity for acetylcholine by 10- to 100-fold, augment Hill numbers (up to 4.6-5.0) of acetylcholine dose-response relationships, slow rates of ionic response onset, and lower the extent of desensitization. Mutations at these two topographically distinct sites within M2 selectively alter calcium transport without affecting the relative permeabilities for sodium and potassium.
ESTHER : Bertrand_1993_Proc.Natl.Acad.Sci.U.S.A_90_6971
PubMedSearch : Bertrand_1993_Proc.Natl.Acad.Sci.U.S.A_90_6971
PubMedID: 7688468

Title : Stratification of the channel domain in neurotransmitter receptors - Bertrand_1993_Curr.Opin.Cell.Biol_5_688
Author(s) : Bertrand D , Galzi JL , Devillers-Thiery A , Bertrand S , Changeux JP
Ref : Current Opinion in Cell Biology , 5 :688 , 1993
Abstract : Analyses of the ionic pore of ligand-gated ion channels at the amino acid level reveal a structural and functional stratification of the M2 channel domain. Mutations in the equatorial and outer regions affect channel gating, whereas mutations of other amino acid rings alter ionic permeability or selectivity.
ESTHER : Bertrand_1993_Curr.Opin.Cell.Biol_5_688
PubMedSearch : Bertrand_1993_Curr.Opin.Cell.Biol_5_688
PubMedID: 7504932

Title : Negative regulatory elements upstream of a novel exon of the neuronal nicotinic acetylcholine receptor alpha 2 subunit gene - Bessis_1993_Nucleic.Acids.Res_21_2185
Author(s) : Bessis A , Savatier N , Devillers-Thiery A , Bejanin S , Changeux JP
Ref : Nucleic Acids Research , 21 :2185 , 1993
Abstract : The expression of the nicotinic acetylcholine receptor alpha 2 subunit gene is highly restricted to the Spiriform lateralis nucleus of the Chick diencephalon. As a first step toward understanding the molecular mechanism underlying this regulation, we have investigated the structural and regulatory properties of the 5' sequence of this gene. A strategy based on the ligation of an oligonucleotide to the first strand of the cDNA (SLIC) followed by PCR amplification was used. A new exon was found approximately 3kb upstream from the first coding exon, and multiple transcription start sites of the gene were mapped. Analysis of the flanking region shows many consensus sequences for the binding of nuclear proteins, suggesting that the 1 kb flanking region contains at least a portion of the promoter of the gene. We have analysed the negative regulatory elements present within this region and found that a silencer region located between nucleotide -144 and +76 is active in fibroblasts as well as in neurons. This silencer is composed of six tandem repeat Oct-like motifs (CCCCATGCAAT), but does not bind any member of the Oct family. Moreover these motifs were found to act as a silencer only when they were tandemly repeated. When two, four or five motifs were deleted, the silencer activity of the motifs unexpectedly became an enhancer activity in all cells we have tested.
ESTHER : Bessis_1993_Nucleic.Acids.Res_21_2185
PubMedSearch : Bessis_1993_Nucleic.Acids.Res_21_2185
PubMedID: 8502560

Title : Chicken neuronal acetylcholine receptor alpha 2-subunit gene exhibits neuron-specific expression in the brain and spinal cord of transgenic mice - Daubas_1993_Proc.Natl.Acad.Sci.U.S.A_90_2237
Author(s) : Daubas P , Salmon AM , Zoli M , Geoffroy B , Devillers-Thiery A , Bessis A , Medevielle F , Changeux JP
Ref : Proc Natl Acad Sci U S A , 90 :2237 , 1993
Abstract : Transgenic mice carrying the complete structural gene of the alpha 2 subunit of the chicken neuronal nicotinic acetylcholine receptor (nAChR) and 7 kilobase pairs (kbp) of 5' upstream and 3 kbp of 3' downstream sequences have been generated. The transgene was stably integrated in transgenic lines and transmitted to their progeny. Avian transgene expression was predominant in the central nervous system as detected by specific alpha 2-subunit cDNA amplification. Moreover, in at least two independent mouse lines, its expression appeared to be neuron-specific and reproducibly restricted to subregions in the brain and spinal cord, as revealed by in situ hybridization histochemistry. Most cranial motor nuclei were positive, and several of the alpha 2-subunit transgene-expressing structures corresponded to cholinergic areas in rodents. This study reveals that regulatory mechanisms giving rise to neuronal-specific gene expression have been conserved at least in part between birds and mammals.
ESTHER : Daubas_1993_Proc.Natl.Acad.Sci.U.S.A_90_2237
PubMedSearch : Daubas_1993_Proc.Natl.Acad.Sci.U.S.A_90_2237
PubMedID: 8460128

Title : Functional architecture of the nicotinic acetylcholine receptor: a prototype of ligand-gated ion channels -
Author(s) : Devillers-Thiery A , Galzi JL , Eisele JL , Bertrand S , Bertrand D , Changeux JP
Ref : J Membr Biol , 136 :97 , 1993
PubMedID: 7508983

Title : Chimaeric nicotinic-serotonergic receptor combines distinct ligand binding and channel specificities - Eisele_1993_Nature_366_479
Author(s) : Eisele JL , Bertrand S , Galzi JL , Devillers-Thiery A , Changeux JP , Bertrand D
Ref : Nature , 366 :479 , 1993
Abstract : The neuronal nicotinic alpha 7 (nAChR) and 5-hydroxytryptamine (5HT3) receptors are ligand-gated ion channels with a homologous topological organization and have activation and desensitization reactions in common. Yet these homo-oligomeric receptors differ in the pharmacology of their binding sites for agonists and competitive antagonists, and in their sensitivity to Ca2+ ions. The alpha 7 channel is highly permeable to Ca2+ ions and external Ca2+ ions potentiate, in an allosteric manner, the permeability response to acetylcholine, as shown for other neuronal nAChRs. The 5HT3 channel, in contrast, is not permeable to Ca2+ ions, but blocked by them. To assign these properties to delimited domains of the primary structure, we constructed several recombinant chimaeric alpha 7-5HT3 receptors. We report here that one of the constructs expresses a functional receptor that contains the serotonergic channel still blocked by Ca2+ ions, but is activated by nicotinic ligands and potentiated by external Ca2+ ions.
ESTHER : Eisele_1993_Nature_366_479
PubMedSearch : Eisele_1993_Nature_366_479
PubMedID: 8247158

Title : Unconventional pharmacology of a neuronal nicotinic receptor mutated in the channel domain - Bertrand_1992_Proc.Natl.Acad.Sci.U.S.A_89_1261
Author(s) : Bertrand D , Devillers-Thiery A , Revah F , Galzi JL , Hussy N , Mulle C , Bertrand S , Ballivet M , Changeux JP
Ref : Proc Natl Acad Sci U S A , 89 :1261 , 1992
Abstract : The putative channel-forming MII domains of the nicotinic, gamma-aminobutyric acid type A, and glycine receptors contain a highly conserved leucine residue. Mutation of this hydrophobic amino acid in the neuronal nicotinic receptor alpha 7 (Leu-247), reconstituted in Xenopus oocytes, modifies the ionic response to acetylcholine and alters desensitization. Furthermore, the Leu----Thr (L247T) mutant has two conducting states (46 pS and 80 pS), in contrast with the wild-type (WT) receptor, which has only one (45 pS). We now show that this mutant possesses a rather paradoxical pharmacology: antagonists of the WT receptor such as dihydro-beta-erythroidin, hexamethonium, or (+)-tubocurarine elicit ionic currents when applied to the L247T alpha 7 mutant and these responses are blocked by alpha-bungarotoxin. Furthermore, prolonged application of acetylcholine causes desensitization in the WT but leads to a potentiation of the responses to acetylcholine or dihydro-beta-erythroidin in the mutant. These data are consistent with a scheme in which mutation of Leu-247 renders a desensitized state in the WT channel a conducting state. They also strengthen the proposal that, in the WT, some competitive antagonists may stabilize desensitized states. Finally, these observations may shed light on properties of other ion channels, in particular the glutamate receptors, which display multiple conductance levels associated with various pharmacological agents.
ESTHER : Bertrand_1992_Proc.Natl.Acad.Sci.U.S.A_89_1261
PubMedSearch : Bertrand_1992_Proc.Natl.Acad.Sci.U.S.A_89_1261
PubMedID: 1741378

Title : Mutations in the channel domain of a neuronal nicotinic receptor convert ion selectivity from cationic to anionic - Galzi_1992_Nature_359_500
Author(s) : Galzi JL , Devillers-Thiery A , Hussy N , Bertrand S , Changeux JP , Bertrand D
Ref : Nature , 359 :500 , 1992
Abstract : Introduction by site-directed mutagenesis of three amino acids from the MII segment of glycine or gamma-aminobutyric acid (GABAA) receptors into the MII segment of alpha 7 nicotinic receptor was sufficient to convert a cation-selective channel into an anion-selective channel gated by acetylcholine. A critical mutation was the insertion of an uncharged residue at the amino-terminal end of MII, stressing the importance of protein geometrical constraints on ion selectivity.
ESTHER : Galzi_1992_Nature_359_500
PubMedSearch : Galzi_1992_Nature_359_500
PubMedID: 1383829

Title : Stratified organization of the nicotinic acetylcholine receptor channel - Devillers-Thiery_1992_Neuroreport_3_1001
Author(s) : Devillers-Thiery A , Galzi JL , Bertrand S , Changeux JP , Bertrand D
Ref : Neuroreport , 3 :1001 , 1992
Abstract : Mutations of leucine 247 within the M2 channel domain of the alpha 7 neuronal nicotinic receptor, confer electrophysiological and pharmacological properties, which allow one of the desensitized states to become conductive. Here we show that, in Xenopus oocytes, the effects of the mutations were preserved when 1,2-bis(2-aminophenoxy)-ethane N,N,N',N'-tetraacetic acid (BAPTA) was injected in the cytoplasm to block Ca(2+)-dependent chloride currents, and that in agreement with the proposed interpretation, the ionic currents do not desensitize and rise slowly, in the time-scale of seconds, upon agonist application. Interestingly, similar effects were observed when the two rings (T244, V251) neighbouring L247 on the alpha-helix, but not the more distant ones (S240, L254/255), were mutated, thus supporting the proposal of a functional stratification of the channel domain.
ESTHER : Devillers-Thiery_1992_Neuroreport_3_1001
PubMedSearch : Devillers-Thiery_1992_Neuroreport_3_1001
PubMedID: 1282832

Title : New mutants to explore nicotinic receptor functions -
Author(s) : Changeux JP , Devillers-Thiery A , Galzi JL , Bertrand D
Ref : Trends in Pharmacological Sciences , 13 :299 , 1992
PubMedID: 1384213

Title : The acetylcholine receptor: a model of an allosteric membrane protein mediating intercellular communication - Changeux_1992_Ciba.Found.Symp_164_66
Author(s) : Changeux JP , Devillers-Thiery A , Galzi JL , Revah F
Ref : Ciba Found Symp , 164 :66 , 1992
Abstract : Over the past 20 years the nicotinic acetylcholine receptor has become the prototype of a superfamily of ligand-gated ion channels. As a single macromolecular entity of M(r) about 300,000, the receptor protein mediates, altogether, the activation and the desensitization of the associated ion channel and the regulation of these processes by extracellular and intracellular signals. The notion is discussed that the acetylcholine receptor is a membrane-bound allosteric protein which possesses several categories of specific sites for neurotransmitters and for regulatory ligands, and undergoes conformational transitions which link these diverse sites together. At this elementary molecular level, interactions between signalling pathways may be mediated by membrane-bound allosteric receptors and/or by other categories of cytoplasmic allosteric proteins.
ESTHER : Changeux_1992_Ciba.Found.Symp_164_66
PubMedSearch : Changeux_1992_Ciba.Found.Symp_164_66
PubMedID: 1395936

Title : The functional architecture of the acetylcholine nicotinic receptor explored by affinity labelling and site-directed mutagenesis -
Author(s) : Changeux JP , Galzi JL , Devillers-Thiery A , Bertrand D
Ref : Q Rev Biophys , 25 :395 , 1992
PubMedID: 1293635

Title : An acetylcholine receptor alpha-subunit promoter conferring preferential synaptic expression in muscle of transgenic mice - Klarsfeld_1991_EMBO.J_10_625
Author(s) : Klarsfeld A , Bessereau JL , Salmon AM , Triller A , Babinet C , Changeux JP
Ref : EMBO Journal , 10 :625 , 1991
Abstract : We have obtained transgenic mice expressing nuclearly targeted beta-galactosidase (nls-beta-gal) under the control of a chicken acetylcholine receptor alpha-subunit promoter. The expression of the transgene was detected in early somites, starting before embryonic day 9.5. In 13-day embryos, the expression pattern of the transgene closely paralleled that of the endogenous mouse alpha-subunit gene, assessed by in situ hybridization. Our results illustrate, with single-cell resolution, the tissue specificity of this alpha-subunit promoter during embryogenesis. After birth, the overall beta-galactosidase activity rapidly decreased with age. However, in diaphragms of newborn animals, beta-galactosidase activity selectively persisted in nuclei underlying the motor endplates. The latter were revealed by an acetylcholinesterase stain. Nls-beta-gal was also visualized by indirect immunofluorescence, while endplates were labelled with fluorescent alpha-bungarotoxin. Confocal microscopy unambiguously identified the more intensely stained nuclei as synaptic 'fundamental nuclei', and allowed estimates of relative staining levels. Thus an 842 bp acetylcholine receptor gene promoter confers preferential synaptic expression to a reporter gene within myofibres in vivo.
ESTHER : Klarsfeld_1991_EMBO.J_10_625
PubMedSearch : Klarsfeld_1991_EMBO.J_10_625
PubMedID: 1900467

Title : Functional significance of aromatic amino acids from three peptide loops of the alpha 7 neuronal nicotinic receptor site investigated by site-directed mutagenesis - Galzi_1991_FEBS.Lett_294_198
Author(s) : Galzi JL , Bertrand D , Devillers-Thiery A , Revah F , Bertrand S , Changeux JP
Ref : FEBS Letters , 294 :198 , 1991
Abstract : Three aromatic amino acids, Tyr92, Trp148 and Tyr187 belonging to three separate domains of the alpha 7-subunit of neuronal nicotinic acetylcholine receptor were mutated to phenylalanine, and the electrophysiological response of the resulting mutant receptors analyzed in the Xenopus oocyte expression system. All mutations significantly decreased the apparent affinities for acetylcholine and nicotine, and to a lesser extent, those for the competitive antagonists dihydro-beta-erythroidine and alpha-bungarotoxin. Other properties investigated, such as the voltage dependency of the ion response as well as its sensitivity to the open channel blocker QX222, were not significantly changed, indicating that the mutations affected selectively the recognition of cholinergic ligands by the receptor protein. The maximal rates for the rapid desensitization process were slightly modified, suggesting that the contribution of Tyr92, Trp148 and Tyr187 to the binding area might differ in the various conformations of the nicotinic receptor. Other mutations at nearby positions (S94N, W153F, G151D and G82E) did not affect the properties of the electrophysiological response. These data point to the functional significance of Tyr92, Trp148 and Tyr187 in the binding of cholinergic ligands and ion channel activation of the nicotinic receptor, thus supporting a multiple loop model [(1990) J. Biol. Chem. 265, 10430-10437] for the ligand binding area.
ESTHER : Galzi_1991_FEBS.Lett_294_198
PubMedSearch : Galzi_1991_FEBS.Lett_294_198
PubMedID: 1756861

Title : Mutations in the channel domain alter desensitization of a neuronal nicotinic receptor - Revah_1991_Nature_353_846
Author(s) : Revah F , Bertrand D , Galzi JL , Devillers-Thiery A , Mulle C , Hussy N , Bertrand S , Ballivet M , Changeux JP
Ref : Nature , 353 :846 , 1991
Abstract : A variety of ligand-gated ion channels undergo a fast activation process after the rapid application of agonist and also a slower transition towards desensitized or inactivated closed channel states when exposure to agonist is prolonged. Desensitization involves at least two distinct closed states in the acetylcholine receptor, each with an affinity for agonists higher than those of the resting or active conformations. Here we investigate how structural elements could be involved in the desensitization of the acetylcholine-gated ion channel from the chick brain alpha-bungarotoxin sensitive homo-oligomeric alpha 7 receptor, using site-directed mutagenesis and expression in Xenopus oocytes. Mutations of the highly conserved leucine 247 residue from the uncharged MII segment of alpha 7 suppress inhibition by the open-channel blocker QX-222, indicating that this residue, like others from MII, faces the lumen of the channel. But, unexpectedly, the same mutations decrease the rate of desensitization of the response, increase the apparent affinity for acetylcholine and abolish current rectification. Moreover, unlike wild-type alpha 7, which has channels with a single conductance level, the leucine-to-threonine mutant has an additional conducting state active at low acetylcholine concentrations. It is possible that mutation of Leu 247 renders conductive one of the high-affinity desensitized states of the receptor.
ESTHER : Revah_1991_Nature_353_846
PubMedSearch : Revah_1991_Nature_353_846
PubMedID: 1719423

Title : Two adjacent MyoD1-binding sites regulate expression of the acetylcholine receptor alpha-subunit gene - Piette_1990_Nature_345_353
Author(s) : Piette J , Bessereau JL , Huchet M , Changeux JP
Ref : Nature , 345 :353 , 1990
Abstract : Several genes encoding putative myogenic regulatory factors have been isolated on the basis of their ability to convert nonmuscle cells into myoblasts. Four of these genes code for nuclear proteins that belong to a larger family characterized by a conserved helix-loop-helix motif required for DNA-binding and dimerization. At least one protein, MyoD1, can function as a transcription factor and activate muscle-specific genes during differentiation. But the promoter of the delta-subunit gene of the mouse acetylcholine receptor (AChR) was recently reported to be functional in the absence of MyoD1 binding sites and it has been suggested that the genes coding for the AChR could be regulated independently of MyoD1 protein. Here, we identify two functional MyoD1-binding sites in the muscle-specific enhancer of the chicken AChR alpha-subunit gene that are essential for full activity in transfected myotubes.
ESTHER : Piette_1990_Nature_345_353
PubMedSearch : Piette_1990_Nature_345_353
PubMedID: 2342565

Title : Chromosomal localization of the mouse genes coding for alpha 2, alpha 3, alpha 4 and beta 2 subunits of neuronal nicotinic acetylcholine receptor - Bessis_1990_FEBS.Lett_264_48
Author(s) : Bessis A , Simon-Chazottes D , Devillers-Thiery A , Guenet JL , Changeux JP
Ref : FEBS Letters , 264 :48 , 1990
Abstract : The chromosomal localization of four neuronal nicotinic acetylcholine receptor subunit genes was performed by following the mendelian segregation of their corresponding alleles in backcrosses involving the mouse species Mus spretus and the laboratory strains C57BL/6 or BALB/c. A similar analysis previously performed with muscle nicotinic acetylcholine receptor subunits revealed that the genes coding for the alpha and beta subunits are respectively located on chromosome 2 and 11, whereas the gamma and delta subunit coding genes are linked and located on mouse chromosome 1. In this study, we show that the genes coding for the neuronal nicotinic acetylcholine receptor alpha 2, alpha 3 and beta 2 subunits are dispersed on three different mouse chromosomes, viz. 14, 9 and 3 respectively. Moreover, the alpha 4 subunit gene is located on chromosome 2 but is not genetically linked to the alpha 1 subunit gene.
ESTHER : Bessis_1990_FEBS.Lett_264_48
PubMedSearch : Bessis_1990_FEBS.Lett_264_48
PubMedID: 2338144

Title : Differential expression of the neuronal acetylcholine receptor alpha 2 subunit gene during chick brain development - Daubas_1990_Neuron_5_49
Author(s) : Daubas P , Devillers-Thiery A , Geoffroy B , Martinez S , Bessis A , Changeux JP
Ref : Neuron , 5 :49 , 1990
Abstract : In situ hybridization histochemistry reveals localized expression of the nicotinic acetylcholine receptor (nAChR) alpha 2 subunit mRNA restricted to the lateral spiriform nucleus (SpL) of the chick diencephalon. The alpha 2 nAChR transcripts are not detected in immature SpL neurons at 4.5-5 days of embryonic development. They begin to accumulate in the SpL at embryonic day 11 and increase until the newborn stage. Specific alpha 2 cDNA amplification by the polymerase chain reaction shows that during this period, the absolute content of alpha 2 mRNA increases about 20-fold. The expression of the alpha 2 nAChR gene is thus developmentally regulated and appears concomitant with the entry of cholinergic fibers into the SpL, as demonstrated by choline acetyltransferase immunohistochemistry.
ESTHER : Daubas_1990_Neuron_5_49
PubMedSearch : Daubas_1990_Neuron_5_49
PubMedID: 2369520

Title : Compartmentalization of acetylcholine receptor gene expression during development of the neuromuscular junction -
Author(s) : Changeux JP , Babinet C , Bessereau JL , Bessis A , Cartaud A , Cartaud J , Daubas P , Devillers-Thiery A , Duclert A , Hill JA , et al.
Ref : Cold Spring Harbor Symposium on Quantitative Biology , 55 :381 , 1990
PubMedID: 2132828

Title : The acetylcholine receptor: functional architecture and regulation -
Author(s) : Changeux JP , Benoit P , Bessis A , Cartaud J , Devillers-Thiery A , Fontaine B , Galzi JL , Klarsfeld A , Laufer R , Mulle C , et al.
Ref : Adv Second Messenger Phosphoprotein Res , 24 :15 , 1990
PubMedID: 1698404

Title : Regulation of acetylcholine receptor gene expression by neural factors and electrical activity during motor endplate formation -
Author(s) : Changeux JP , Benoit P , Bessis A , Cartaud J , Devillers-Thiery A , Fontaine B , Galzi JL , Klarsfeld A , Laufer R , Mulle C , et al.
Ref : Biochemical Society Symposium , 56 :9 , 1990
PubMedID: 2256962

Title : Denervation of mouse skeletal muscle differentially affects the expression of the jun and fos proto-oncogenes - Bessereau_1990_New.Biol_2_375
Author(s) : Bessereau JL , Fontaine B , Changeux JP
Ref : New Biol , 2 :375 , 1990
Abstract : The mRNA levels of the jun and fos proto-oncogenes, whose products are part of the transcription regulatory complex AP1, were investigated after denervation of the lower-leg muscles of adult mice. The levels of the four transcripts studied varied in a non-coordinated manner after muscle denervation. As early as 1.5 h after sciatic nerve section, c-fos mRNA reached a maximum and then returned to basal level at 6 h, while c-jun and jun-B mRNA levels increased after 24 h and remained elevated for at least 8 days. In contrast, jun-D mRNA levels did not change after denervation. In situ hybridization experiments revealed different patterns of spatial localization of the c-jun and jun-D transcripts. Labeling of dividing cells by the thymidine analog bromo-deoxyuridine demonstrated that proliferating cells were at least 40-fold less abundant than those expressing c-jun. Thus, denervation rapidly and differentially modulates the expression of genes coding for the AP1 transcription factor subunits in differentiated muscle cells. The possibility that these proto-oncogenes might be involved in the trans-synaptic regulation of muscle-specific gene expression is discussed.
ESTHER : Bessereau_1990_New.Biol_2_375
PubMedSearch : Bessereau_1990_New.Biol_2_375
PubMedID: 2126956

Title : Acetylcholine receptor expression in primary cultures of embryonic chick myotubes--I. Discoordinate regulation of alpha-, gamma- and delta-subunit gene expression by calcitonin gene-related peptide and by muscle electrical activity - Osterlund_1989_Neurosci_32_279
Author(s) : Osterlund M , Fontaine B , Devillers-Thiery A , Geoffroy B , Changeux JP
Ref : Neuroscience , 32 :279 , 1989
Abstract : The neuropeptide calcitonin gene-related peptide calcitonin gene-related peptide, and muscle electrical activity regulate in opposite directions the content of nicotinic acetylcholine receptor alpha-subunit mRNA in primary cultures of chick embryonic myotubes. Indeed, treating the cells with calcitonin gene-related peptide or blocking the spontaneous activity of muscle cells by tetrodotoxin (an inhibitor of sodium channels) increases, although to different levels, the content of acetylcholine receptor alpha-subunit mRNA [Fontaine B., Klarsfeld A. and Changeux J. P. (1987) J. Cell Biol. 105, 1337-1342; Klarsfeld A. and Changeux J. P. (1985) Proc. natn. Acad. Sci. U.S.A. 82, 4558-4562]. In this paper, we demonstrate that, under these in vitro culture conditions, calcitonin gene-related peptide (0.1 microM) and tetrodotoxin (0.5 microM) regulate to a smaller extent (no more than 2.5-fold above control) the levels of acetylcholine receptor gamma- and delta-subunit mRNAs. No effect of either compound on acetylcholine receptor biosynthesis was observed during the initial three days of culture. The response to calcitonin gene-related peptide was already maximal when the cells were treated between days three and four after plating (about 3-fold increase of the alpha-subunit mRNA level). The effect of tetrodotoxin resulted in a six-fold increase of the acetylcholine receptor alpha-subunit mRNA level in cells treated between days three and four, and still increased when the cells were exposed to tetrodotoxin through days six and eight (up to a maximum of 20-fold).
ESTHER : Osterlund_1989_Neurosci_32_279
PubMedSearch : Osterlund_1989_Neurosci_32_279
PubMedID: 2586755

Title : Acetylcholine receptor expression in primary cultures of embryonic chick myotubes--II. Comparison between the effects of spinal cord cells and calcitonin gene-related peptide - Kirilovsky_1989_Neurosci_32_289
Author(s) : Kirilovsky J , Duclert A , Fontaine B , Devillers-Thiery A , Osterlund M , Changeux JP
Ref : Neuroscience , 32 :289 , 1989
Abstract : Spinal cord cells co-cultured with primary chick myotubes caused a 1.5-3-fold increase in the number of muscle surface acetylcholine receptors assayed with [125I]alpha-bungarotoxin. This increase did not result from the metabolic stabilization of the acetylcholine receptor protein and was at least partially due to a stimulation of acetylcholine receptor biosynthesis up to the level of the accumulation of alpha-subunit mature and partially spliced precursor mRNAs. A medium conditioned by spinal cord cells also caused a rise in acetylcholine receptor number. This increase did not coincide with an augmentation of the intracellular cyclic AMP level as reported for the neuropeptide calcitonin gene-related peptide. In contrast, spinal cord cells and the medium conditioned by them potentiated the effect of calcitonin gene-related peptide on acetylcholine receptor number. Stimulation of acetylcholine receptor synthesis by the conditioned medium was blocked by the protein kinase C activator 12-O-tetradecanoyl phorbol-13-acetate and by the calcium ionophore A23187. These two compounds have already been reported to block the increase of acetylcholine receptor number produced by the voltage sensitive sodium channel antagonist tetrodotoxin which stimulates acetylcholine receptor biosynthesis by blocking spontaneous electrical activity of the cultured muscle cells. The possibility that different neural factors and second messenger systems are involved in the regulation of acetylcholine receptor biosynthesis during the development of the neuromuscular junction is discussed.
ESTHER : Kirilovsky_1989_Neurosci_32_289
PubMedSearch : Kirilovsky_1989_Neurosci_32_289
PubMedID: 2586756

Title : Regulation of muscle AChR alpha subunit gene expression by electrical activity: involvement of protein kinase C and Ca2+ - Klarsfeld_1989_Neuron_2_1229
Author(s) : Klarsfeld A , Laufer R , Fontaine B , Devillers-Thiery A , Dubreuil C , Changeux JP
Ref : Neuron , 2 :1229 , 1989
Abstract : Using primary cultures of chicken myotubes, we investigated the involvement of protein kinase C and Ca2+ in the repression of nicotinic acetylcholine receptor (AChR) biosynthesis by electrical activity. Treatment with the Ca2+ channel blocker verapamil or the Na+ channel blocker tetrodotoxin increased alpha subunit mRNA levels 11.5- to 15-fold. The effect of tetrodotoxin was abolished in the presence of the Ca2+ ionophore A23187. Dantrolene, which blocks Ca2+ efflux from the sarcoplasmic reticulum, caused only a 1.7-fold increase in alpha subunit mRNA levels. Down regulation of protein kinase C by prolonged exposure to the phorbol ester TPA or inhibition of protein kinase C by staurosporine led to 8- to 10-fold increases in alpha subunit mRNA levels. Mature and precursor forms of AChR alpha subunit mRNA were found to vary in parallel throughout all of these treatments, suggesting that protein kinase C and Ca2+ ions may modulate AChR alpha subunit biosynthesis at the transcriptional level.
ESTHER : Klarsfeld_1989_Neuron_2_1229
PubMedSearch : Klarsfeld_1989_Neuron_2_1229
PubMedID: 2516449

Title : Asynchronous assembly of the acetylcholine receptor and of the 43-kD nu1 protein in the postsynaptic membrane of developing Torpedo marmorata electrocyte - Kordeli_1989_J.Cell.Biol_108_127
Author(s) : Kordeli E , Cartaud J , Nghiem HO , Devillers-Thiery A , Changeux JP
Ref : Journal of Cell Biology , 108 :127 , 1989
Abstract : The assembly of the nicotinic acetylcholine receptor (AchR) and the 43-kD protein (v1), the two major components of the post synaptic membrane of the electromotor synapse, was followed in Torpedo marmorata electrocyte during embryonic development by immunocytochemical methods. At the first developmental stage investigated (45-mm embryos), accumulation of AchR at the ventral pole of the newly formed electrocyte was observed within columns before innervation could be detected. No concomitant accumulation of 43-kD immunoreactivity in AchR-rich membrane domains was observed at this stage, but a transient asymmetric distribution of the extracellular protein, laminin, which paralleled that of the AchR, was noticed. At the subsequent stage studied (80-mm embryos), codistribution of the two proteins was noticed on the ventral face of the cell. Intracellular pools of AchR and 43-kD protein were followed at the EM level in 80-mm electrocytes. AchR immunoreactivity was detected within membrane compartments, which include the perinuclear cisternae of the endoplasmic reticulum and the plasma membrane. On the other hand, 43-kD immunoreactivity was not found associated with the AchR in the intracellular compartments of the cell, but codistributed with the AchR at the level of the plasma membrane. The data reported in this study suggest that AchR clustering in vivo is not initially determined by the association of the AchR with the 43-kD protein, but rather relies on AchR interaction with extracellular components, for instance from the basement membrane, laid down in the tissue before the entry of the electromotor nerve endings.
ESTHER : Kordeli_1989_J.Cell.Biol_108_127
PubMedSearch : Kordeli_1989_J.Cell.Biol_108_127
PubMedID: 2642909

Title : [Possible trophic role on the neuromuscular junction of a neuropeptide co-existing with acetylcholine in motor neurons of the spinal cord] - Fontaine_1989_Rev.Neurol.(Paris)_145_194
Author(s) : Fontaine B , Klarsfeld A , Laufer R , Hokfelt T , Changeux JP
Ref : Rev Neurol (Paris) , 145 :194 , 1989
Abstract : The Calcitonin-Gene Related Peptide (CGRP), a neuropeptide present in chick spinal cord motoneurons, increases the levels of surface acetylcholine receptor (AChR) and of the AChR alpha-subunit mRNA in cultured chick myotubes. Cholera toxin (CT), an activator of adenylate cyclase, produces a similar effect which does not add up with that of CGRP. Consistent with this observation, CGRP increases the content of cyclic AMP in chick muscle cells in culture. Tetrodotoxin (TTX), a blocker of voltage-sensitive Na+ channels, elevates the levels of AChR and of AChR alpha-subunit mRNA. This effect is additive with that of CGRP or CT. TPA (12-O-tetradecanoyl phorbol-13-acetate), an activator of protein kinase C, decreases the level of AChR but has no effect on the level of AChR alpha-subunit mRNA. Interestingly, TPA inhibits the increase of AChR alpha-subunit mRNA caused by TTX without affecting that produced by CGRP or CT. These data suggest that CGRP, which coexists with acetylcholine in spinal cord motoneurons, could be one of the anterograde factors (or a model of such factor) responsible for the enhanced expression of the genes coding for AChR subunits in subneural nuclei, via the activation of adenylate cyclase. Muscle electrical activity would then inhibit the expression of the same genes in extrajunctional nuclei, via another intracellular pathway.
ESTHER : Fontaine_1989_Rev.Neurol.(Paris)_145_194
PubMedSearch : Fontaine_1989_Rev.Neurol.(Paris)_145_194
PubMedID: 2546240

Title : Chromosomal localization of muscle nicotinic acetylcholine receptor genes in the mouse - Heidmann_1986_Science_234_866
Author(s) : Heidmann O , Buonanno A , Geoffroy B , Robert B , Guenet JL , Merlie JP , Changeux JP
Ref : Science , 234 :866 , 1986
Abstract : The chromosomal localization of the genes encoding the four subunits of muscle nicotinic receptor was determined by analyzing restriction fragment length polymorphisms between two mouse species Mus musculus domesticus (DBA/2) and Mus spretus (SPE). Analysis of the progeny of the interspecies mouse backcross (DBA/2 X SPE) X DBA/2 showed that the alpha-subunit gene cosegregates with the alpha-cardiac actin gene on chromosome 17, that the beta-subunit gene is located on chromosome 11, and that the gamma- and delta-subunit genes cosegregate and are located on chromosome 1.
ESTHER : Heidmann_1986_Science_234_866
PubMedSearch : Heidmann_1986_Science_234_866
PubMedID: 3022377

Title : Calcitonin gene-related peptide, a peptide present in spinal cord motoneurons, increases the number of acetylcholine receptors in primary cultures of chick embryo myotubes - Fontaine_1986_Neurosci.Lett_71_59
Author(s) : Fontaine B , Klarsfeld A , Hokfelt T , Changeux JP
Ref : Neuroscience Letters , 71 :59 , 1986
Abstract : Using immunohistochemical methods we show that calcitonin gene-related peptide (CGRP, a peptide encoded by the calcitonin gene) is present in chick spinal cord motoneurons. When added to cultured chicken myotubes, CGRP caused an average 1.5-fold increase in levels of surface acetylcholine receptors. Moreover, the effect of CGRP was independent of the one produced by tetrodotoxin, a blocker of membrane electrical activity but not of that caused by cholera toxin, an activator of adenylate cyclase.
ESTHER : Fontaine_1986_Neurosci.Lett_71_59
PubMedSearch : Fontaine_1986_Neurosci.Lett_71_59
PubMedID: 3491345

Title : Transmembrane topology of acetylcholine receptor subunits probed with photoreactive phospholipids - Giraudat_1985_Biochemistry_24_3121
Author(s) : Giraudat J , Montecucco C , Bisson R , Changeux JP
Ref : Biochemistry , 24 :3121 , 1985
Abstract : The domains of the acetylcholine receptor subunits that contact the lipid phase were investigated by hydrophobic photolabeling of receptor-rich membrane fragments prepared from Torpedo marmorata and Torpedo californica electric organs. The radioactive arylazido phospholipids used carry a photoreactive group, either at the level of the lipid polar head group (PCI) or at the tip of the aliphatic chain (PCII), and thus probe respectively the "superficial" and "deep" regions of the lipid bilayer. The four subunits of T. marmorata and T. californica acetylcholine receptor reacted with both the PCI and PCII probes and thus are all exposed to the lipid phase. Ligands known to stabilize different conformations of the acetylcholine receptor (nicotinic agonists, snake alpha-toxin, and noncompetitive blockers) did not cause any significant change in the labeling pattern. The acetylcholine receptor associated 43 000-dalton v1 protein did not react with any of the probes. A striking difference in labeling between T. marmorata and T. californica acetylcholine receptors occurred at the level of the alpha-subunit when the superficial PCI probe was used. An approximately 5-fold higher labeling of the alpha-subunit as compared to the beta-, gamma-, and delta-subunits was observed by using receptor-rich membranes from T. marmorata but not from T. californica. The same difference persisted after purification of the labeled receptors from the two species and was restricted to an 8000-dalton C-terminal tryptic peptide. The only mutation observed in this region of the complete alpha-subunit sequence of the two species is the substitution of cysteine-424 in T. marmorata by serine-424 in T. californica.
ESTHER : Giraudat_1985_Biochemistry_24_3121
PubMedSearch : Giraudat_1985_Biochemistry_24_3121
PubMedID: 4027235

Title : Molecular genetics of Torpedo marmorata acetylcholine receptor -
Author(s) : Devillers-Thiery A , Giraudat J , Bentaboulet M , Klarsfeld A , Changeux JP
Ref : Advances in Experimental Medicine & Biology , 181 :17 , 1984
PubMedID: 6549423

Title : A single gene codes for the nicotinic acetylcholine receptor alpha-subunit in Torpedo marmorata: structural and developmental implications - Klarsfeld_1984_EMBO.J_3_35
Author(s) : Klarsfeld A , Devillers-Thiery A , Giraudat J , Changeux JP
Ref : EMBO Journal , 3 :35 , 1984
Abstract : We have used Southern blot hybridization to analyze the genomic structure encoding the alpha-subunit of the acetylcholine receptor (AChR) in Torpedo marmorata, with cDNA probes isolated from the electric organ. Four different radiolabelled probes, corresponding to various parts of the alpha-subunit mRNA, hybridized to several genomic fragments of T. marmorata DNA generated by digestion with the restriction enzymes SstI, PvuII and PstI. The same hybridization pattern was observed after washing the blots under low- or high-stringency conditions. As a check for detection sensitivity of heterologous sequences, the same probes were hybridized to PvuII-digested chicken DNA, revealing bands at low stringency which disappeared at higher stringencies. Unambiguously, two of our probes (one of them entirely within the coding region) hybridized to a single genomic fragment from T. marmorata DNA. This feature, as well as the results of an extensive study of the whole hybridization pattern, points towards the uniqueness of alpha-subunit-specific sequences in the genome of T. marmorata. Since overall more bands were found than expected from the cDNA sequence, this alpha-subunit gene must be split by several introns (at least four, possibly more). The length of this gene is at least 20 kb. The existence of a single alpha-subunit gene is consistent with the absence of chemical heterogeneity in the NH2-terminal sequence of the purified alpha-chain, and supports the view that the two alpha-chains belonging to one AChR oligomer have an identical primary structure. It also suggests that localization and stabilization of the AChR in well-defined post-synaptic areas of T. marmorata electric organ basically relies, during development, on 'epigenetic' mechanisms.
ESTHER : Klarsfeld_1984_EMBO.J_3_35
PubMedSearch : Klarsfeld_1984_EMBO.J_3_35
PubMedID: 6323168

Title : Lipid-dependent recovery of alpha-bungarotoxin and monoclonal antibody binding to the purified alpha-subunit from Torpedo marmorata acetylcholine receptor. Enhancement by noncompetitive channel blockers - Tzartos_1984_J.Biol.Chem_259_11512
Author(s) : Tzartos SJ , Changeux JP
Ref : Journal of Biological Chemistry , 259 :11512 , 1984
Abstract : Recently the purified alpha-subunit from Torpedo marmorata acetylcholine receptor was shown to bind alpha-bungarotoxin with a KD approximately 3 nM in the presence of sodium dodecyl sulfate (Tzartos, S.J., and Changeux, J.P. (1983) EMBO J. 2, 381-387). Here we describe a further significant step toward renaturation of the alpha-subunit as judged by toxin and monoclonal antibody binding. Purified T. marmorata receptor subunits were diluted with 1% lipids (asolectin) plus 0.5% Na+ cholate. An anion-exchange resin eliminated most of the detergents, leaving approximately 0.1% Na+ cholate and the lipids. After this treatment, about 20% of the alpha-subunit recovered (but not the beta-, gamma-, or delta-subunit) exhibited a high affinity for radioiodinated alpha-bungarotoxin with a KD approximately 0.5 nM. The 34,000- and 27,000-dalton proteolytic peptides of the alpha-subunit conserved this lipid-dependent toxin binding. Unlabeled alpha-toxins, hexamethonium, and carbamylcholine competed with alpha-bungarotoxin for the renatured alpha-subunit. Noncompetitive channel blockers doubled the lipid-dependent toxin-binding capacity of the alpha-subunit but had no effect on the 27,000-dalton peptide. The binding of several monoclonal antibodies to the main immunogenic region (which is particularly sensitive to denaturation) significantly increased. In particular, binding of antibody 16 changed from 1% to denatured to 100% to the lipid-renaturated alpha-subunit. The binding of these antibodies was lost with the lipid-renatured 34,000- and 27,000-dalton peptides.
ESTHER : Tzartos_1984_J.Biol.Chem_259_11512
PubMedSearch : Tzartos_1984_J.Biol.Chem_259_11512
PubMedID: 6088547

Title : Complete nucleotide sequence of Torpedo marmorata mRNA coding for the 43,000-dalton nu 2 protein: muscle-specific creatine kinase - Giraudat_1984_Proc.Natl.Acad.Sci.U.S.A_81_7313
Author(s) : Giraudat J , Devillers-Thiery A , Perriard JC , Changeux JP
Ref : Proc Natl Acad Sci U S A , 81 :7313 , 1984
Abstract : DNA sequences coding for the muscle-specific subunit of creatine kinase have been isolated from cDNA libraries constructed from Torpedo marmorata electric organ. Clones were screened by differential in situ hybridization and hybrid-selected translation. The in vitro translation product of the selected mRNA was immunoprecipitated by anti-chicken creatine kinase antibodies and comigrated with Torpedo muscle creatine kinase on two-dimensional gels at the same position as the cytosolic 43,000-dalton protein referred to as nu 2. The cDNA inserts hybridized to a mRNA species present in adult Torpedo muscle but not in brain. The complete sequence of the mRNA was determined on one of the clones except for the 78 nucleotides of the mRNA 5' terminal sequence, which were identified by the primer extension method. The amino acid sequence of muscle-specific creatine kinase from T. marmorata was deduced and analyzed. It includes the known sequence of a peptide from the active site of rabbit muscle-specific creatine kinase.
ESTHER : Giraudat_1984_Proc.Natl.Acad.Sci.U.S.A_81_7313
PubMedSearch : Giraudat_1984_Proc.Natl.Acad.Sci.U.S.A_81_7313
PubMedID: 6095285

Title : Acetylcholine receptor: an allosteric protein - Changeux_1984_Science_225_1335
Author(s) : Changeux JP , Devillers-Thiery A , Chemouilli P
Ref : Science , 225 :1335 , 1984
Abstract : The nicotine receptor for the neurotransmitter acetylcholine is an allosteric protein composed of four different subunits assembled in a transmembrane pentamer alpha 2 beta gamma delta. The protein carries two acetylcholine sites at the level of the alpha subunits and contains the ion channel. The complete sequence of the four subunits is known. The membrane-bound protein undergoes conformational transitions that regulate the opening of the ion channel and are affected by various categories of pharmacologically active ligands.
ESTHER : Changeux_1984_Science_225_1335
PubMedSearch : Changeux_1984_Science_225_1335
PubMedID: 6382611

Title : Rapid kinetics of agonist binding and permeability response analyzed in parallel on acetylcholine receptor rich membranes from Torpedo marmorata - Heidmann_1983_Biochemistry_22_5452
Author(s) : Heidmann T , Bernhardt J , Neumann E , Changeux JP
Ref : Biochemistry , 22 :5452 , 1983
Abstract : Excitable acetylcholine receptor rich membrane fragments from Torpedo marmorata have been used to measure, in parallel, (1) the permeability response to the fluorescent cholinergic agonist Dns-C6-Cho (in the 0.1 microM to millimolar concentration range) characterized by both the initial rate of Li+ transport and the rate of channel closure using the rapid-mixing quench-flow technique and (2) the kinetics of interaction of Dns-C6-Cho with the acetylcholine receptor sites using the rapid-mixing stopped-flow technique. Analysis of the kinetics of Dns-C6-Cho binding in the millisecond to minute time scale leads to the identification of at least three conformational states of the acetylcholine receptor: a "low-affinity" one (approximately 50 microM) that can be interconverted in the fraction of a second to a transient state of "intermediate affinity" (approximately 1 microM), followed by the final stabilization, in the second to minute time range, of a state of "high affinity" (approximately 3 nM). Comparison of Dns-C6-Cho binding data with the permeability response to the same agonist demonstrates that the binding to the low-affinity conformation(s) of the acetylcholine receptor sites coincides with the triggering of the permeability increase--or "activation"--and the transitions to the intermediate- and high-affinity states with the two-step process of channel closing--or "desensitization". The data are interpreted in terms of a minimum four-state "allosteric" model for the acetylcholine receptor.
ESTHER : Heidmann_1983_Biochemistry_22_5452
PubMedSearch : Heidmann_1983_Biochemistry_22_5452
PubMedID: 6652072

Title : Complete mRNA coding sequence of the acetylcholine binding alpha-subunit of Torpedo marmorata acetylcholine receptor: a model for the transmembrane organization of the polypeptide chain - Devillers-Thiery_1983_Proc.Natl.Acad.Sci.U.S.A_80_2067
Author(s) : Devillers-Thiery A , Giraudat J , Bentaboulet M , Changeux JP
Ref : Proc Natl Acad Sci U S A , 80 :2067 , 1983
Abstract : A 1,350-base-pair-long cDNA clone, named p alpha-2, was isolated by hybridization to the previously characterized clone p alpha-1 and found to be specific for the alpha-subunit of the Torpedo marmorata acetylcholine receptor. The nucleotide sequences of both cDNA inserts were analyzed and the sequence of the complete coding region and part of the 5' and 3' untranslated regions of the alpha-chain mRNA was determined. The complete amino acid sequence of the alpha-chain precursor is presented and used to develop a model for the transmembrane organization of the polypeptide.
ESTHER : Devillers-Thiery_1983_Proc.Natl.Acad.Sci.U.S.A_80_2067
PubMedSearch : Devillers-Thiery_1983_Proc.Natl.Acad.Sci.U.S.A_80_2067
PubMedID: 6572962

Title : Allosteric properties of the acetylcholine receptor protein from Torpedo marmorata -
Author(s) : Changeux JP , Bon F , Cartaud J , Devillers-Thiery A , Giraudat J , Heidmann T , Holton B , Nghiem HO , Popot JL , Van Rapenbusch R , et al.
Ref : Cold Spring Harbor Symposium on Quantitative Biology , 48 Pt 1 :35 , 1983
PubMedID: 6327163

Title : Identification of a cDNA clone coding for the acetylcholine binding subunit of Torpedo marmorata acetylcholine receptor - Giraudat_1982_EMBO.J_1_713
Author(s) : Giraudat J , Devillers-Thiery A , Auffray C , Rougeon F , Changeux JP
Ref : EMBO Journal , 1 :713 , 1982
Abstract : A recombinant DNA plasmid has been constructed that contains sequences of the gene coding for the acetylcholine binding subunit (alpha-subunit, 40 000 daltons) of Torpedo marmorata acetylcholine receptor protein (AChR). Polyadenylated RNA purified from Torpedo electric organ was used to construct a cDNA library. The AChR alpha-subunit cDNA clone was then identified by a two-step screening of 700 recombinant clones. As AChR is present in Torpedo electric organ but not in Torpedo liver or spleen, differential screening led to the selection of 12 clones specific for the electric organ. We then tested the ability of cDNA inserts to hybridize alpha-subunit mRNA specifically, as judged by cell-free translation and immunoprecipitation. The insert from one clone, p alpha-1, selectively hybridized with a mRNA species which elicited the synthesis of a 38 000 mol. wt. polypeptide. This polypeptide was precipitated by: (1) a rabbit serum raised against purified denatured alpha-subunit (the pure alpha-subunit displaced the complex); and (2) a rat monoclonal antibody specific for the denatured alpha-subunit. It was thus identified as a precursor of the alpha chain. Blot hybridization analysis of polyadenylated RNA from Torpedo electric organ with the p alpha-1 probe revealed a major species of 2.0 kb, which thus contains approximately 800 non-coding nucleotides.
ESTHER : Giraudat_1982_EMBO.J_1_713
PubMedSearch : Giraudat_1982_EMBO.J_1_713
PubMedID: 6897919

Title : [Effects of chronic medullary stimulation on the total number of sites of acetylcholinesterase activity of the posterior latissimus dorsi muscle of chick embryo]. [French] - Toutant_1981_C.R.Acad.Sci.III_292_771
Author(s) : Toutant M , Toutant JP , Renaud D , Le Douarin GH , Changeux JP
Ref : Comptes Rendus de l Academie des Sciences , 292 :771 , 1981
Abstract : From incubation day 10 to 15, the spinal cord of Chick embryos are electrically stimulated in ovo at 0.5 Hz at the level of the motor roots innervating the latissimus dorsi muscles. As a consequence, the total number of spots of acetylcholinesterase determined on serial sections of posterior latissimus dorsi muscle increased 2.3 fold. This increase parallels that of acetylcholine receptor clusters, supporting the interpretation that these clusters are of synaptic origin.
ESTHER : Toutant_1981_C.R.Acad.Sci.III_292_771
PubMedSearch : Toutant_1981_C.R.Acad.Sci.III_292_771
PubMedID: 6788396

Title : Chronic stimulation of the spinal cord in developing chick embryo causes the differentiation of multiple clusters of acetylcholine receptor in the posterior latissimus dorsi muscle -
Author(s) : Toutant M , Bourgeois JP , Toutant JP , Renaud D , Le Douarin GH , Changeux JP
Ref : Developmental Biology , 76 :384 , 1980
PubMedID: 7390009

Title : The amino-terminal sequence of the 40,000 molecular weight subunit of the acetylcholine receptor protein from Torpedo marmorata -
Author(s) : Devillers-Thiery A , Changeux JP , Paroutaud P , Strosberg AD
Ref : FEBS Letters , 104 :99 , 1979
PubMedID: 477982

Title : Effects of a snake alpha-neurotoxin on the development of innervated skeletal muscles in chick embryo - Giacobini_1973_Proc.Natl.Acad.Sci.U.S.A_70_1708
Author(s) : Giacobini G , Filogamo G , Weber M , Boquet P , Changeux JP
Ref : Proc Natl Acad Sci U S A , 70 :1708 , 1973
Abstract : The evolution of the cholinergic (nicotinic) receptor in chick muscles is monitored during embryonic development with a tritiated alpha-neurotoxin from Naja nigricollis and compared with the appearance of acetylcholinesterase. The specific activity of these two proteins reaches a maximum around the 12th day of incubation. By contrast, choline acetyltransferase reaches an early maximum of specific activity around the 7th day of development, and later continuously increases until hatching. Injection of alpha-toxin in the yolk sac at early stages of development causes an atrophy of skeletal and extrinsic ocular-muscles and of their innervation. In 16-day embryos treated by the alpha-toxin, the endplates revealed by the Koelle reaction are almost completely absent. The total content and specific activities of acetylcholinesterase and choline acetyltransferase in atrophic muscles are markedly reduced.
ESTHER : Giacobini_1973_Proc.Natl.Acad.Sci.U.S.A_70_1708
PubMedSearch : Giacobini_1973_Proc.Natl.Acad.Sci.U.S.A_70_1708
PubMedID: 4515929

Title : Immunological characterisation of the cholinergic receptor protein from Electrophorus electricus -
Author(s) : Sugiyama H , Benda P , Meunier JC , Changeux JP
Ref : FEBS Letters , 35 :124 , 1973
PubMedID: 4201666

Title : In Vitro excitation of purified membrane fragments by cholinergic agonists : I. Pharmalogical properties of the excitable membrane fragments - Kasai_1971_J.Membr.Biol_6_1
Author(s) : Kasai M , Changeux JP
Ref : J Membr Biol , 6 :1 , 1971
Abstract : Excitation of membrane fragments by cholinergic agonists is measuredin vitro by a filtration technique. Membrane fragments which contain high levels of the enzyme acetylcholinesterase and presumably originate from the innervated excitable faces of electroplax are first purified from homogenates of electric organ ofElectrophorus electricus by centrifugation in a sucrose gradient. Then the fragments, which make closed vesicles or microsacs, are equilibrated overnight with a medium containing(22)Na(+). After equilibration of the inside of the microsacs with the outside medium, the suspension is diluted into a nonradioactive medium. The(22)Na(+) content of the microsacs as a function of time is then followed by rapid filtration on Millipore filters. In the presence of cholinergic agonists, the time course of(22)Na(+) release changes: the rate of(22)Na(+) release increases. This increase is blocked byd-tubocurarine and is absent with microsacs derived from the non-innervated inexcitable membrane of the electroplax. The response to cholinergic agonists is thus followed on a completely cell-free system, in a well-defined environment. The dose-response curves to cholinergic agents obtainedin vitro agree, quantitatively, with the dose-response curves recordedin vivo by electrophysiological methods. In particular, the dose-response curve to agonists is sigmoid, the antagonism betweend-tubocurarine and carbamylcholine competitive, and the antagonism between tetracaine and carbamylcholine noncompetitive. The effects of two different affinity labeling reagents on the response to agonists and on the catalytic activity of acetylcholinesterase are followed in parallel on the same microsac preparation. The effects of dithiothreitol and of gramicidin A on the microsacs are studied and are found to be similar to those observedin vivo with the isolated electroplax.
ESTHER : Kasai_1971_J.Membr.Biol_6_1
PubMedSearch : Kasai_1971_J.Membr.Biol_6_1
PubMedID: 24173287

Title : In vitro excitation of purified membrane fragments by cholinergic agonists. III. Comparison of the dose response curves to decamethonium with the corresponding binding curves of decamethonium to the cholinergic receptor - Kasai_1971_J.Membr.Biol_6_58
Author(s) : Kasai M , Changeux JP
Ref : J Membr Biol , 6 :58 , 1971
Abstract : The reversible binding of(14)C-decamethonium (Deca) to excitable microsacs prepared from the electric tissue ofElectrophorus electricus is followed by an ultracentrifugal assay. alpha-Bungarotoxin, a snake venom toxin, blocks irreversibly the binding of(14)C-Deca. The displacement is partial. The fraction of(14)C-Deca displaced by alpha-bungarotoxin corresponds to molecules of Deca bound to the cholinergic receptor site, whereas the fraction of(14)C-Deca bound in the presence of alpha-bungarotoxin corresponds to molecules bound to the catalytic site of acetylcholinesterase (AcChE). The total number of cholinergic receptor sites is found to be close but not identical to the total number of catalytic sites of AcChE.On the same preparation of microsacs, the binding of(14)C-Deca and the permeability response corresponding to a given concentration of Deca are measured as a function of increased concentration of Deca. The dose-response curve and the binding curve superimpose almost exactly; in other words, the "apparent" affinity of Deca coincides with its "real" affinity. Displacement of(14)C-Deca byd-tubocurarine gives an "apparent" affinity ford-tubocurarine which coincides as well with its "real" affinity.The transport properties of the ionophore controlled by one Deca binding site are estimated.
ESTHER : Kasai_1971_J.Membr.Biol_6_58
PubMedSearch : Kasai_1971_J.Membr.Biol_6_58
PubMedID: 24173289

Title : In vitro excitation of purified membrane fragments by cholinergic agonists : IV. Ultrastructure, at high resolution, of the AcChE-Rich and ATPase-rich microsacs - Cartaud_1971_J.Membr.Biol_6_81
Author(s) : Cartaud J , Benedetti EL , Kasai M , Changeux JP
Ref : J Membr Biol , 6 :81 , 1971
Abstract : Membrane fragments rich in acetylcholinesterase (AcChE) or in Na(+)-K(+)-ATPase are observed under the electron microscope on thin sections after fixation, after negative staining of unfixed material, and after freeze-etching. Both classes of membrane fragments make closed approximately spherical vesicles, or microsacs. The preparation appears to be free from mitochondria, nuclear envelopes or other cytoplasmic contamination. A subunit structure is seen with both kinds of microsacs by freeze-etching and negative staining, but the size, shape and arrangement of the subunits are different in the two classes of membrane fragments. On thin sections, globular repeating units are seen only with the AcChE-rich microsacs; the membrane of the ATPase-rich microsacs shows a classic triple-layered structure.
ESTHER : Cartaud_1971_J.Membr.Biol_6_81
PubMedSearch : Cartaud_1971_J.Membr.Biol_6_81
PubMedID: 24173290

Title : Use of a snake venom toxin to characterize the cholinergic receptor protein - Changeux_1970_Proc.Natl.Acad.Sci.U.S.A_67_1241
Author(s) : Changeux JP , Kasai M , Lee CY
Ref : Proc Natl Acad Sci U S A , 67 :1241 , 1970
Abstract : alpha-Bungarotoxin, a polypeptide of mol wt 8000 purified from the venom of Bungarus multicinctus, blocks irreversibly and specifically the excitation by cholinergic agonists on the isolated electroplax and on purified membrane fragments in vitro. The toxin also blocks the in vitro binding of decamethonium to a protein recently isolated from electric tissue. This observation strengthens our earlier conclusion that this protein is the cholinergic receptor macromolecule.
ESTHER : Changeux_1970_Proc.Natl.Acad.Sci.U.S.A_67_1241
PubMedSearch : Changeux_1970_Proc.Natl.Acad.Sci.U.S.A_67_1241
PubMedID: 5274453

Title : On the association of tyrocidine with acetylcholinesterase - Changeux_1969_Proc.Natl.Acad.Sci.U.S.A_62_986
Author(s) : Changeux JP , Ryter A , Leuzinger W , Barrand P , Podleski T
Ref : Proc Natl Acad Sci U S A , 62 :986 , 1969
Abstract : In studies of several polypeptide antibiotics with a high affinity for a variety of biological membranes, tyrocidine was found to bind specifically to acetylcholinesterase, an enzyme localized in excitable membranes. Several other polypeptides tested were not bound. Tyrocidine reversibly inhibits acetylcholinesterase formed by homogeneous protein, but seems to have no effect on the activity of the enzyme bound to the eel electroplax membrane. This inhibition is accompanied by a reversible association of the soluble enzyme in to ordered and rapidly sedimenting aggregates of large molecular weight. Electron micrographs of acetylcholinesterase are shown which are consistent with the chemical evidence of the existence of four subunits.
ESTHER : Changeux_1969_Proc.Natl.Acad.Sci.U.S.A_62_986
PubMedSearch : Changeux_1969_Proc.Natl.Acad.Sci.U.S.A_62_986
PubMedID: 5257018

Title : Affinity labelling of the acetylcholine-receptor -
Author(s) : Changeux JP , Podleski TR , Wofsy L
Ref : Proceedings of the National Academy of Sciences of the United States of America , 58 :2063 , 1967
PubMedID: 5237500

Title : [Effects of ionic forces and curarizing agents on the acetylcholine esterase properties of the electric tissue of Torpedo marmorata] -
Author(s) : Changeux JP
Ref : Comptes Rendus Hebdomadaires des Seances de l Academie des Sciences D: Sciences Naturelles , 262 :937 , 1966
PubMedID: 4956272

Title : Responses of acetylcholinesterase from Torpedo marmorata to salts and curarizing drugs -
Author(s) : Changeux JP
Ref : Molecular Pharmacology , 2 :369 , 1966
PubMedID: 5970686

Title : Allosteric proteins and cellular control systems -
Author(s) : Monod J , Changeux JP , Jacob F
Ref : Journal of Molecular Biology , 6 :306 , 1963