Gardner PD

References (17)

Title : Nicotinic acetylcholine receptors containing the alpha4 subunit modulate alcohol reward - Liu_2013_Biol.Psychiatry_73_738
Author(s) : Liu L , Hendrickson LM , Guildford MJ , Zhao-Shea R , Gardner PD , Tapper AR
Ref : Biological Psychiatry , 73 :738 , 2013
Abstract : BACKGROUND: Nicotine and alcohol are the two most co-abused drugs in the world, suggesting a common mechanism of action might underlie their rewarding properties. Although nicotine elicits reward by activating ventral tegmental area dopaminergic (DAergic) neurons via high-affinity neuronal nicotinic acetylcholine receptors (nAChRs), the mechanism by which alcohol activates these neurons is unclear.
METHODS: Because most high-affinity nAChRs expressed in ventral tegmental area DAergic neurons contain the alpha4 subunit, we measured ethanol-induced activation of DAergic neurons in midbrain slices from two complementary mouse models, an alpha4 knock-out (KO) mouse line and a knock-in line (Leu9'Ala) expressing alpha4 subunit-containing nAChRs hypersensitive to agonist compared with wild-type (WT). Activation of DAergic neurons by ethanol was analyzed with both biophysical and immunohistochemical approaches in midbrain slices. The ability of alcohol to condition a place preference in each mouse model was also measured.
RESULTS: At intoxicating concentrations, ethanol activation of DAergic neurons was significantly reduced in alpha4 KO mice compared with WT. Conversely, in Leu9'Ala mice, DAergic neurons were activated by low ethanol concentrations that did not increase activity of WT neurons. In addition, alcohol potentiated the response to ACh in DAergic neurons, an effect reduced in alpha4 KO mice. Rewarding alcohol doses failed to condition a place preference in alpha4 KO mice, paralleling alcohol effects on DAergic neuron activity, whereas a sub-rewarding alcohol dose was sufficient to condition a place preference in Leu9'Ala mice.
CONCLUSIONS: Together, these data indicate that nAChRs containing the alpha4 subunit modulate alcohol reward.
ESTHER : Liu_2013_Biol.Psychiatry_73_738
PubMedSearch : Liu_2013_Biol.Psychiatry_73_738
PubMedID: 23141806

Title : Activation of GABAergic neurons in the interpeduncular nucleus triggers physical nicotine withdrawal symptoms - Zhao-Shea_2013_Curr.Biol_23_2327
Author(s) : Zhao-Shea R , Liu L , Pang X , Gardner PD , Tapper AR
Ref : Current Biology , 23 :2327 , 2013
Abstract : BACKGROUND: Chronic exposure to nicotine elicits physical dependence in smokers, yet the mechanism and neuroanatomical bases for withdrawal symptoms are unclear. As in humans, rodents undergo physical withdrawal symptoms after cessation from chronic nicotine characterized by increased scratching, head nods, and body shakes.
RESULTS: Here we show that induction of physical nicotine withdrawal symptoms activates GABAergic neurons within the interpeduncular nucleus (IPN). Optical activation of IPN GABAergic neurons via light stimulation of channelrhodopsin elicited physical withdrawal symptoms in both nicotine-naive and chronic-nicotine-exposed mice. Dampening excitability of GABAergic neurons during nicotine withdrawal through IPN-selective infusion of an NMDA receptor antagonist or through blockade of IPN neurotransmission from the medial habenula reduced IPN neuronal activation and alleviated withdrawal symptoms. During chronic nicotine exposure, nicotinic acetylcholine receptors containing the beta4 subunit were upregulated in somatostatin interneurons clustered in the dorsal region of the IPN. Blockade of these receptors induced withdrawal signs more dramatically in nicotine-dependent compared to nicotine-naive mice and activated nonsomatostatin neurons in the IPN.
CONCLUSIONS: Together, our data indicate that therapeutic strategies to reduce IPN GABAergic neuron excitability during nicotine withdrawal, for example, by activating nicotinic receptors on somatostatin interneurons, may be beneficial for alleviating withdrawal symptoms and facilitating smoking cessation.
ESTHER : Zhao-Shea_2013_Curr.Biol_23_2327
PubMedSearch : Zhao-Shea_2013_Curr.Biol_23_2327
PubMedID: 24239118

Title : Nicotinic acetylcholine receptors mediate lung cancer growth - Improgo_2013_Front.Physiol_4_251
Author(s) : Improgo MR , Soll LG , Tapper AR , Gardner PD
Ref : Front Physiol , 4 :251 , 2013
Abstract : Ion channels modulate ion flux across cell membranes, activate signal transduction pathways, and influence cellular transport-vital biological functions that are inexorably linked to cellular processes that go awry during carcinogenesis. Indeed, deregulation of ion channel function has been implicated in cancer-related phenomena such as unrestrained cell proliferation and apoptotic evasion. As the prototype for ligand-gated ion channels, nicotinic acetylcholine receptors (nAChRs) have been extensively studied in the context of neuronal cells but accumulating evidence also indicate a role for nAChRs in carcinogenesis. Recently, variants in the nAChR genes CHRNA3, CHRNA5, and CHRNB4 have been implicated in nicotine dependence and lung cancer susceptibility. Here, we silenced the expression of these three genes to investigate their function in lung cancer. We show that these genes are necessary for the viability of small cell lung carcinomas (SCLC), the most aggressive type of lung cancer. Furthermore, we show that nicotine promotes SCLC cell viability whereas an alpha3beta4-selective antagonist, alpha-conotoxin AuIB, inhibits it. Our findings posit a mechanism whereby signaling via alpha3/alpha5/beta4-containing nAChRs promotes lung carcinogenesis.
ESTHER : Improgo_2013_Front.Physiol_4_251
PubMedSearch : Improgo_2013_Front.Physiol_4_251
PubMedID: 24062692

Title : Nicotine persistently activates ventral tegmental area dopaminergic neurons via nicotinic acetylcholine receptors containing alpha4 and alpha6 subunits - Liu_2012_Mol.Pharmacol_81_541
Author(s) : Liu L , Zhao-Shea R , McIntosh JM , Gardner PD , Tapper AR
Ref : Molecular Pharmacology , 81 :541 , 2012
Abstract : Nicotine is reinforcing because it activates dopaminergic (DAergic) neurons within the ventral tegmental area (VTA) of the brain's mesocorticolimbic reward circuitry. This increase in activity can occur for a period of several minutes up to an hour and is thought to be a critical component of nicotine dependence. However, nicotine concentrations that are routinely self-administered by smokers are predicted to desensitize high-affinity alpha4beta2 neuronal nicotinic acetylcholine receptors (nAChRs) in seconds. Thus, how physiologically relevant nicotine concentrations persistently activate VTA DAergic neurons is unknown. Here we show that nicotine can directly and robustly increase the firing frequency of VTA DAergic neurons for several minutes. In mouse midbrain slices, 300 nM nicotine elicited a persistent inward current in VTA DAergic neurons that was blocked by alpha-conotoxin MII[H9A;L15A], a selective antagonist of nAChRs containing the alpha6 subunit. alpha-conotoxin MII[H9A;L15A] also significantly reduced the long-lasting increase in DAergic neuronal activity produced by low concentrations of nicotine. In addition, nicotine failed to significantly activate VTA DAergic neurons in mice that did not express either alpha4 or alpha6 nAChR subunits. Conversely, selective activation of nAChRs containing the alpha4 subunit in knock-in mice expressing a hypersensitive version of these receptors yielded a biphasic response to nicotine consisting of an acute desensitizing increase in firing frequency followed by a sustained increase that lasted several minutes and was sensitive to alpha-conotoxin MII[H9A;L15A]. These data indicate that nicotine persistently activates VTA DAergic neurons via nAChRs containing alpha4 and alpha6 subunits.
ESTHER : Liu_2012_Mol.Pharmacol_81_541
PubMedSearch : Liu_2012_Mol.Pharmacol_81_541
PubMedID: 22222765

Title : Nicotinic acetylcholine receptor-mediated mechanisms in lung cancer - Improgo_2011_Biochem.Pharmacol_82(8)_1015
Author(s) : Improgo MR , Tapper AR , Gardner PD
Ref : Biochemical Pharmacology , 82 :1015 , 2011
Abstract : Despite the known adverse health effects associated with tobacco use, over 45 million adults in the United States smoke. Cigarette smoking is the major etiologic factor associated with lung cancer. Cigarettes contain thousands of toxic chemicals, many of which are carcinogenic. Nicotine contributes directly to lung carcinogenesis through the activation of nicotinic acetylcholine receptors (nAChRs). nAChRs are ligand-gated ion channels, expressed in both normal and lung cancer cells, which mediate the proliferative, pro-survival, angiogenic, and metastatic effects of nicotine and its nitrosamine derivatives. The underlying molecular mechanisms involve increases in intracellular calcium levels and activation of cancer signal transduction pathways. In addition, acetylcholine (ACh) acts as an autocrine or paracrine growth factor in lung cancer. Other neurotransmitters and neuropeptides also activate similar growth loops. Recent genetic studies further support a role for nAChRs in the development of lung cancer. Several nAChR antagonists have been shown to inhibit lung cancer growth, suggesting that nAChRs may serve as valuable targets for biomarker-guided lung cancer interventions.
ESTHER : Improgo_2011_Biochem.Pharmacol_82(8)_1015
PubMedSearch : Improgo_2011_Biochem.Pharmacol_82(8)_1015
PubMedID: 21640716

Title : Bioluminescence-based high-throughput screen identifies pharmacological agents that target neurotransmitter signaling in small cell lung carcinoma - Improgo_2011_PLoS.One_6_e24132
Author(s) : Improgo MR , Johnson CW , Tapper AR , Gardner PD
Ref : PLoS ONE , 6 :e24132 , 2011
Abstract : BACKGROUND: Frontline treatment of small cell lung carcinoma (SCLC) relies heavily on chemotherapeutic agents and radiation therapy. Though SCLC patients respond well to initial cycles of chemotherapy, they eventually develop resistance. Identification of novel therapies against SCLC is therefore imperative. METHODS AND FINDINGS: We have designed a bioluminescence-based cell viability assay for high-throughput screening of anti-SCLC agents. The assay was first validated via standard pharmacological agents and RNA interference using two human SCLC cell lines. We then utilized the assay in a high-throughput screen using the LOPAC(1280) compound library. The screening identified several drugs that target classic cancer signaling pathways as well as neuroendocrine markers in SCLC. In particular, perturbation of dopaminergic and serotonergic signaling inhibits SCLC cell viability.
CONCLUSIONS: The convergence of our pharmacological data with key SCLC pathway components reiterates the importance of neurotransmitter signaling in SCLC etiology and points to possible leads for drug development.
ESTHER : Improgo_2011_PLoS.One_6_e24132
PubMedSearch : Improgo_2011_PLoS.One_6_e24132
PubMedID: 21931655

Title : Nicotine-mediated activation of dopaminergic neurons in distinct regions of the ventral tegmental area - Zhao-Shea_2011_Neuropsychopharmacology_36_1021
Author(s) : Zhao-Shea R , Liu L , Soll LG , Improgo MR , Meyers EE , McIntosh JM , Grady SR , Marks MJ , Gardner PD , Tapper AR
Ref : Neuropsychopharmacology , 36 :1021 , 2011
Abstract : Nicotine activation of nicotinic acetylcholine receptors (nAChRs) within the dopaminergic (DAergic) neuron-rich ventral tegmental area (VTA) is necessary and sufficient for nicotine reinforcement. In this study, we show that rewarding doses of nicotine activated VTA DAergic neurons in a region-selective manner, preferentially activating neurons in the posterior VTA (pVTA) but not in the anterior VTA (aVTA) or in the tail VTA (tVTA). Nicotine (1 muM) directly activated pVTA DAergic neurons in adult mouse midbrain slices, but had little effect on DAergic neurons within the aVTA. Quantification of nAChR subunit gene expression revealed that pVTA DAergic neurons expressed higher levels of alpha4, alpha6, and beta3 transcripts than did aVTA DAergic neurons. Activation of nAChRs containing the alpha4 subunit (alpha4(*) nAChRs) was necessary and sufficient for activation of pVTA DAergic neurons: nicotine failed to activate pVTA DAergic neurons in alpha4 knockout animals; in contrast, pVTA alpha4(*) nAChRs were selectively activated by nicotine in mutant mice expressing agonist-hypersensitive alpha4(*) nAChRs (Leu9'Ala mice). In addition, whole-cell currents induced by nicotine in DAergic neurons were mediated by alpha4(*) nAChRs and were significantly larger in pVTA neurons than in aVTA neurons. Infusion of an alpha6(*) nAChR antagonist into the VTA blocked activation of pVTA DAergic neurons in WT mice and in Leu9'Ala mice at nicotine doses, which only activate the mutant receptor indicating that alpha4 and alpha6 subunits coassemble to form functional receptors in these neurons. Thus, nicotine selectively activates DAergic neurons within the pVTA through alpha4alpha6(*) nAChRs. These receptors represent novel targets for smoking-cessation therapies.
ESTHER : Zhao-Shea_2011_Neuropsychopharmacology_36_1021
PubMedSearch : Zhao-Shea_2011_Neuropsychopharmacology_36_1021
PubMedID: 21289604

Title : A transcriptional regulatory element critical for CHRNB4 promoter activity in vivo - Scofield_2010_Neurosci_170_1056
Author(s) : Scofield MD , Tapper AR , Gardner PD
Ref : Neuroscience , 170 :1056 , 2010
Abstract : Genome-wide association studies have underscored the importance of the clustered neuronal nicotinic acetylcholine receptor (nAChR) subunit genes with respect to nicotine dependence as well as lung cancer susceptibility. CHRNB4, which encodes the nAChR beta4 subunit, plays a major role in the molecular mechanisms that govern nicotine withdrawal. Thus, elucidating how expression of the beta4 gene is regulated is critical for understanding the pathophysiology of nicotine addiction. We previously identified a CA box regulatory element, (5'-CCACCCCT-3') critical for beta4 promoter activity in vitro. We further demonstrated that a 2.3-kb fragment of the beta4 promoter region containing the 5'-CCACCCCT-3' regulatory element in the beta4 gene promoter (CA box) is capable of directing cell-type specific expression of a reporter gene to a myriad of brain regions that endogenously express the beta4 gene. To test the hypothesis that the CA box is critical for beta4 promoter activity in vivo, transgenic animals expressing a mutant form of the beta4 promoter were generated. Reporter gene expression was not detected in any tissue or cell type at embryonic day 18.5 (ED 18.5). Similarly, we observed drastically reduced reporter gene expression at postnatal day 30 (PD30) when compared to wild type (WT) transgenic animals. Finally, we demonstrated that CA box mutation results in decreased interaction of the transcription factor Sp1 with the mutant beta4 promoter. Taken together these results demonstrate that the CA box is critical for beta4 promoter activity in vivo.
ESTHER : Scofield_2010_Neurosci_170_1056
PubMedSearch : Scofield_2010_Neurosci_170_1056
PubMedID: 20696214

Title : Dopamine D2-receptor activation elicits akinesia, rigidity, catalepsy, and tremor in mice expressing hypersensitive {alpha}4 nicotinic receptors via a cholinergic-dependent mechanism - Zhao-Shea_2010_FASEB.J_24_49
Author(s) : Zhao-Shea R , Cohen BN , Just H , McClure-Begley TD , Whiteaker P , Grady SR , Salminen O , Gardner PD , Lester HA , Tapper AR
Ref : FASEB Journal , 24 :49 , 2010
Abstract : Recent studies suggest that high-affinity neuronal nicotinic acetylcholine receptors (nAChRs) containing alpha4 and beta2 subunits (alpha4beta2*) functionally interact with G-protein-coupled dopamine (DA) D(2) receptors in basal ganglia. We hypothesized that if a functional interaction between these receptors exists, then mice expressing an M2 point mutation (Leu9'Ala) rendering alpha4 nAChRs hypersensitive to ACh may exhibit altered sensitivity to a D(2)-receptor agonist. When challenged with the D(2)R agonist, quinpirole (0.5-10 mg/kg), Leu9'Ala mice, but not wild-type (WT) littermates, developed severe, reversible motor impairment characterized by rigidity, catalepsy, akinesia, and tremor. While striatal DA tissue content, baseline release, and quinpirole-induced DA depletion did not differ between Leu9'Ala and WT mice, quinpirole dramatically increased activity of cholinergic striatal interneurons only in mutant animals, as measured by increased c-Fos expression in choline acetyltransferase (ChAT)-positive interneurons. Highlighting the importance of the cholinergic system in this mouse model, inhibiting the effects of ACh by blocking muscarinic receptors, or by selectively activating hypersensitive nAChRs with nicotine, rescued motor symptoms. This novel mouse model mimics the imbalance between striatal DA/ACh function associated with severe motor impairment in disorders such as Parkinson's disease, and the data suggest that a D(2)R-alpha4*-nAChR functional interaction regulates cholinergic interneuron activity.
ESTHER : Zhao-Shea_2010_FASEB.J_24_49
PubMedSearch : Zhao-Shea_2010_FASEB.J_24_49
PubMedID: 19720621

Title : Activation of alpha4* nAChRs is necessary and sufficient for varenicline-induced reduction of alcohol consumption - Hendrickson_2010_J.Neurosci_30_10169
Author(s) : Hendrickson LM , Zhao-Shea R , Pang X , Gardner PD , Tapper AR
Ref : Journal of Neuroscience , 30 :10169 , 2010
Abstract : Recently, the smoking cessation therapeutic varenicline, a nicotinic acetylcholine receptor (nAChR) partial agonist, has been shown to reduce alcohol consumption. However, the mechanism and nAChR subtype(s) involved are unknown. Here we demonstrate that varenicline and alcohol exposure, either alone or in combination, selectively activates dopaminergic (DAergic) neurons within the posterior, but not the anterior, ventral tegmental area (VTA). To gain insight into which nAChR subtypes may be involved in the response to alcohol, we analyzed nAChR subunit gene expression in posterior VTA DAergic neurons. Ethanol-activated DAergic neurons expressed higher levels of alpha4, alpha6, and beta3 subunit genes compared with nonactivated neurons. To examine the role of nicotinic receptors containing the alpha4 subunit (alpha4* nAChRs) in varenicline-induced reduction of alcohol consumption, we examined the effect of the drug in two complementary mouse models, a knock-out line that does not express the alpha4 subunit (alpha4 KO) and another line that expresses alpha4* nAChRs hypersensitive to agonist (Leu9'Ala). While varenicline (0.1-0.3 mg/kg, i.p.) reduced 2% and 20% alcohol consumption in wild-type (WT) mice, the drug did not significantly reduce consumption in alpha4 KO animals. Conversely, low doses of varenicline (0.0125-0.05 mg/kg, i.p.) that had little effect in WT mice dramatically reduced ethanol intake in Leu9'Ala mice. Infusion of varenicline into the posterior, but not the anterior VTA was sufficient to reduce alcohol consumption. Together, our data indicate that activation of alpha4* nAChRs is necessary and sufficient for varenicline reduction of alcohol consumption.
ESTHER : Hendrickson_2010_J.Neurosci_30_10169
PubMedSearch : Hendrickson_2010_J.Neurosci_30_10169
PubMedID: 20668200

Title : ASCL1 regulates the expression of the CHRNA5\/A3\/B4 lung cancer susceptibility locus - Improgo_2010_Mol.Cancer.Res_8_194
Author(s) : Improgo MR , Schlichting NA , Cortes RY , Zhao-Shea R , Tapper AR , Gardner PD
Ref : Mol Cancer Research , 8 :194 , 2010
Abstract : Tobacco contains a variety of carcinogens as well as the addictive compound nicotine. Nicotine addiction begins with the binding of nicotine to its cognate receptor, the nicotinic acetylcholine receptor (nAChR). Genome-wide association studies have implicated the nAChR gene cluster, CHRNA5/A3/B4, in nicotine addiction and lung cancer susceptibility. To further delineate the role of this gene cluster in lung cancer, we examined the expression levels of these three genes as well as other members of the nAChR gene family in lung cancer cell lines and patient samples using quantitative reverse transcription-PCR. Overexpression of the clustered nAChR genes was observed in small-cell lung carcinoma (SCLC), an aggressive form of lung cancer highly associated with cigarette smoking. The overexpression of the genomically clustered genes in SCLC suggests their coordinate regulation. In silico analysis of the promoter regions of these genes revealed putative binding sites in all three promoters for achaete-scute complex homolog 1 (ASCL1), a transcription factor implicated in the pathogenesis of SCLC, raising the possibility that this factor may regulate the expression of the clustered nAChR genes. Consistent with this idea, knockdown of ASCL1 in SCLC, but not in non-SCLC, led to a significant decrease in expression of the alpha 3 and beta 4 genes without having an effect on any other highly expressed nAChR gene. Our data indicate a specific role for ASCL1 in regulating the expression of the CHRNA5/A3/B4 lung cancer susceptibility locus. This regulation may contribute to the predicted role that ASCL1 plays in SCLC tumorigenesis.
ESTHER : Improgo_2010_Mol.Cancer.Res_8_194
PubMedSearch : Improgo_2010_Mol.Cancer.Res_8_194
PubMedID: 20124469

Title : From smoking to lung cancer: the CHRNA5\/A3\/B4 connection - Improgo_2010_Oncogene_29_4874
Author(s) : Improgo MR , Scofield MD , Tapper AR , Gardner PD
Ref : Oncogene , 29 :4874 , 2010
Abstract : Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that modulate key physiological processes ranging from neurotransmission to cancer signaling. These receptors are activated by the neurotransmitter, acetylcholine, and the tobacco alkaloid, nicotine. Recently, the gene cluster encoding the alpha3, alpha5 and beta4 nAChR subunits received heightened interest after a succession of linkage analyses and association studies identified multiple single-nucleotide polymorphisms in these genes that are associated with an increased risk for nicotine dependence and lung cancer. It is not clear whether the risk for lung cancer is direct or an effect of nicotine dependence, as evidence for both scenarios exist. In this study, we summarize the body of work implicating nAChRs in the pathogenesis of lung cancer, with special focus on the clustered nAChR subunits and their emerging role in this disease state.
ESTHER : Improgo_2010_Oncogene_29_4874
PubMedSearch : Improgo_2010_Oncogene_29_4874
PubMedID: 20581870

Title : The nicotinic acetylcholine receptor CHRNA5\/A3\/B4 gene cluster: dual role in nicotine addiction and lung cancer - Improgo_2010_Prog.Neurobiol_92_212
Author(s) : Improgo MR , Scofield MD , Tapper AR , Gardner PD
Ref : Prog Neurobiol , 92 :212 , 2010
Abstract : More than 1 billion people around the world smoke, with 10 million cigarettes sold every minute. Cigarettes contain thousands of harmful chemicals including the psychoactive compound, nicotine. Nicotine addiction is initiated by the binding of nicotine to nicotinic acetylcholine receptors, ligand-gated cation channels activated by the endogenous neurotransmitter, acetylcholine. These receptors serve as prototypes for all ligand-gated ion channels and have been extensively studied in an attempt to elucidate their role in nicotine addiction. Many of these studies have focused on heteromeric nicotinic acetylcholine receptors containing alpha4 and beta2 subunits and homomeric nicotinic acetylcholine receptors containing the alpha7 subunit, two of the most abundant subtypes expressed in the brain. Recently however, a series of linkage analyses, candidate-gene analyses and genome-wide association studies have brought attention to three other members of the nicotinic acetylcholine receptor family: the alpha5, alpha3 and beta4 subunits. The genes encoding these subunits lie in a genomic cluster that contains variants associated with increased risk for several diseases including nicotine dependence and lung cancer. The underlying mechanisms for these associations have not yet been elucidated but decades of research on the nicotinic receptor gene family as well as emerging data provide insight on how these receptors may function in pathological states. Here, we review this body of work, focusing on the clustered nicotinic acetylcholine receptor genes and evaluating their role in nicotine addiction and lung cancer.
ESTHER : Improgo_2010_Prog.Neurobiol_92_212
PubMedSearch : Improgo_2010_Prog.Neurobiol_92_212
PubMedID: 20685379

Title : The armadillo repeat-containing protein, ARMCX3, physically and functionally interacts with the developmental regulatory factor Sox10 - Mou_2009_J.Biol.Chem_284_13629
Author(s) : Mou Z , Tapper AR , Gardner PD
Ref : Journal of Biological Chemistry , 284 :13629 , 2009
Abstract : Sox10 is a member of the group E Sox transcription factor family and plays key roles in neural crest development and subsequent cellular differentiation. Sox10 binds to regulatory sequences in target genes via its conserved high mobility group domain. In most cases, Sox10 exerts its transcriptional effects in concert with other DNA-binding factors, adaptor proteins, and nuclear import proteins. These interactions can lead to synergistic gene activation and can be cell type-specific. In earlier work, we demonstrated that Sox10 transactivates the nicotinic acetylcholine receptor alpha3 and beta4 subunit genes and does so only in neuronal-like cell lines, raising the possibility that Sox10 mediates its effects via interactions with co-regulatory factors. Here we describe the identification of the armadillo repeat-containing protein, ARMCX3, as a Sox10-interacting protein. Biochemical analyses indicate that ARMCX3 is an integral membrane protein of the mitochondrial outer membrane. Others have shown that Sox10 is a nucleocytoplasmic shuttling protein. We extend this observation and demonstrate that, in the cytoplasm, Sox10 is peripherally associated with the mitochondrial outer membrane. Both Sox10 and ARMCX3 are expressed in mouse brain and spinal cord as well as several cell lines. Overexpression of ARMCX3 increased the amount of mitochondrially associated Sox10. In addition, although ARMCX3 does not possess intrinsic transcriptional activity, it does enhance transactivation of the nicotinic acetylcholine receptor alpha3 and beta4 subunit gene promoters by Sox10. These results suggest that Sox10 is a membrane-associated factor whose transcriptional function is increased by direct interactions with ARMCX3 and raise the possibility of a signal transduction cascade between the nucleus and mitochondria through Sox10/ARMCX3 interactions.
ESTHER : Mou_2009_J.Biol.Chem_284_13629
PubMedSearch : Mou_2009_J.Biol.Chem_284_13629
PubMedID: 19304657

Title : Interactions between regulatory proteins that bind to the nicotinic receptor beta4 subunit gene promoter - Melnikova_2000_Eur.J.Pharmacol_393_75
Author(s) : Melnikova IN , Yang Y , Gardner PD
Ref : European Journal of Pharmacology , 393 :75 , 2000
Abstract : The genes encoding the alpha3, alpha5 and beta4 subunits of nicotinic acetylcholine receptors are tightly clustered within the genome. As these three subunits constitute the predominant acetylcholine receptor subtype expressed in the peripheral nervous system, their genomic proximity suggests a regulatory mechanism ensuring their coordinate expression. We previously identified two transcriptional regulatory elements within the beta4 promoter. One of these elements, a CT box, interacts with the regulatory factors heterogeneous nuclear ribonucleoprotein K and Puralpha. Another element, a CA box, interacts with Sp1 and Sp3. The binding site for a fifth factor, Sox10, overlaps the CT and CA boxes. As the CT and CA boxes are adjacent, we postulated that the proteins that bind to the elements interact. Here we report that the CT box-binding factors interact with each other as do the CA box-binding factors. However, there are no direct associations between the two pairs of proteins. Interestingly though, Sox10 directly interacts with all four proteins, suggesting a central role in beta4 gene expression for this member of the Sox family of regulatory factors.
ESTHER : Melnikova_2000_Eur.J.Pharmacol_393_75
PubMedSearch : Melnikova_2000_Eur.J.Pharmacol_393_75
PubMedID: 10771000

Title : Properties of embryonic and adult muscle acetylcholine receptors transiently expressed in COS cells - Gu_1990_Neuron_5_147
Author(s) : Gu Y , Franco A, Jr. , Gardner PD , Lansman JB , Forsayeth JR , Hall ZW
Ref : Neuron , 5 :147 , 1990
Abstract : We used transient transfection in COS cells to compare the properties of mouse muscle acetylcholine receptors (AChRs) containing alpha, beta, delta, and either gamma or epsilon subunits. gamma- and epsilon-AChRs had identical association rates for binding 125I-alpha-bungarotoxin, and identical curves for inhibition of toxin binding by d-tubocurarine, but epsilon-AChRs had a significantly longer half-time of turnover in the membrane than gamma-AChRs. A myasthenic serum specific for the embryonic form of the AChR reduced toxin binding to gamma-, but not epsilon-AChRs. The gamma-AChRs had channel characteristics of embryonic AChRs, whereas the major class of epsilon-AChR channels had the characteristics of adult AChRs. Two minor channel classes with smaller conductances were also seen with epsilon-AChR. Thus, some, but not all, of the differences between AChRs at adult endplates and those in the extrasynaptic membrane can be explained by the difference in subunit composition of gamma- and epsilon-AChRs.
ESTHER : Gu_1990_Neuron_5_147
PubMedSearch : Gu_1990_Neuron_5_147
PubMedID: 2383398

Title : Transcriptional regulation of nicotinic acetylcholine receptor genes: identification of control elements of a gamma-subunit gene - Gardner_1987_Brain.Res_427_69
Author(s) : Gardner PD , Heinemann S , Patrick J
Ref : Brain Research , 427 :69 , 1987
Abstract : The muscle nicotinic acetylcholine receptor undergoes profound changes in abundance and distribution in response to innervation and denervation. As a start towards understanding the detailed mechanisms of acetylcholine receptor gene regulation, we have identified transcriptional regulatory regions of a receptor subunit gene. A region of genomic DNA at the 5' end of the mouse acetylcholine receptor gamma-subunit gene has been shown to promote transcription of the bacterial chloramphenicol acetyltransferase gene in a cell-type specific manner. In addition, the transcriptional activity of this fragment is developmentally regulated in mouse muscle C2C12 cells. We propose that this fragment contains transcriptional control elements of the mouse muscle acetylcholine receptor gamma-subunit gene.
ESTHER : Gardner_1987_Brain.Res_427_69
PubMedSearch : Gardner_1987_Brain.Res_427_69
PubMedID: 3480767