Smith MA

References (19)

Title : A dynamic loop provides dual control over the catalytic and membrane binding activity of a bacterial serine hydrolase - Smith_2018_Biochim.Biophys.Acta_1866_925
Author(s) : Smith MA , Phillips WK , Rabin PL , Johnson RJ
Ref : Biochimica & Biophysica Acta , 1866 :925 , 2018
Abstract : The bacterial acyl protein thioesterase (APT) homologue FTT258 from the gram-negative pathogen Francisella tularensis exists in equilibrium between a closed and open state. Interconversion between these two states is dependent on structural rearrangement of a dynamic loop overlapping its active site. The dynamics and structural properties of this loop provide a simple model for how the catalytic activity of FTT258 could be spatiotemporally regulated within the cell. Herein, we characterized the dual roles of this dynamic loop in controlling its catalytic and membrane binding activity. Using a comprehensive library of loop variants, we determined the relative importance of each residue in the loop to these two biological functions. For the catalytic activity, a centrally located tryptophan residue (Trp66) was essential, with the resulting alanine variant showing complete ablation of enzyme activity. Detailed analysis of Trp66 showed that its hydrophobicity in combination with spatial arrangement defined its essential role in catalysis. Substitution of other loop residues congregated along the N-terminal side of the loop also significantly impacted catalytic activity, indicating a critical role for this loop in controlling catalytic activity. For membrane binding, the centrally located hydrophobic residues played a surprising minor role in membrane binding. Instead general electrostatic interactions regulated membrane binding with positively charged residues bracketing the dynamic loop controlling membrane binding. Overall for FTT258, this dynamic loop dually controlled its biological activities through distinct residues within the loop and this regulation provides a new model for the spatiotemporal control over FTT258 and potentially homologous APT function.
ESTHER : Smith_2018_Biochim.Biophys.Acta_1866_925
PubMedSearch : Smith_2018_Biochim.Biophys.Acta_1866_925
PubMedID: 29857162
Gene_locus related to this paper: fratt-q5ni32

Title : Long noncoding miRNA gene represses wheat beta-diketone waxes - Huang_2017_Proc.Natl.Acad.Sci.U.S.A_114_E3149
Author(s) : Huang D , Feurtado JA , Smith MA , Flatman LK , Koh C , Cutler AJ
Ref : Proc Natl Acad Sci U S A , 114 :E3149 , 2017
Abstract : The cuticle of terrestrial plants functions as a protective barrier against many biotic and abiotic stresses. In wheat and other Triticeae, beta-diketone waxes are major components of the epicuticular layer leading to the bluish-white glaucous trait in reproductive-age plants. Glaucousness in durum wheat is controlled by a metabolic gene cluster at the WAX1 (W1) locus and a dominant suppressor INHIBITOR of WAX1 (Iw1) on chromosome 2B. The wheat D subgenome from progenitor Aegilops tauschii contains W2 and Iw2 paralogs on chromosome 2D. Here we identify the Iw1 gene from durum wheat and demonstrate the unique regulatory mechanism by which Iw1 acts to suppress a carboxylesterase-like protein gene, W1-COE, within the W1 multigene locus. Iw1 is a long noncoding RNA (lncRNA) containing an inverted repeat (IR) with >80% identity to W1-COE The Iw1 transcript forms a miRNA precursor-like long hairpin producing a 21-nt predominant miRNA, miRW1, and smaller numbers of related sRNAs associated with the nonglaucous phenotype. When Iw1 was introduced into glaucous bread wheat, miRW1 accumulated, W1-COE and its paralog W2-COE were down-regulated, and the phenotype was nonglaucous and beta-diketone-depleted. The IR region of Iw1 has >94% identity to an IR region on chromosome 2 in Ae. tauschii that also produces miRW1 and lies within the marker-based location of Iw2 We propose the Iw loci arose from an inverted duplication of W1-COE and/or W2-COE in ancestral wheat to form evolutionarily young miRNA genes that act to repress the glaucous trait.
ESTHER : Huang_2017_Proc.Natl.Acad.Sci.U.S.A_114_E3149
PubMedSearch : Huang_2017_Proc.Natl.Acad.Sci.U.S.A_114_E3149
PubMedID: 28351975

Title : A clinical study of lupron depot in the treatment of women with Alzheimer's disease: preservation of cognitive function in patients taking an acetylcholinesterase inhibitor and treated with high dose lupron over 48 weeks - Bowen_2015_J.Alzheimers.Dis_44_549
Author(s) : Bowen RL , Perry G , Xiong C , Smith MA , Atwood CS
Ref : J Alzheimers Dis , 44 :549 , 2015
Abstract : To test the efficacy and safety of leuprolide acetate (Lupron Depot) in the treatment of Alzheimer's disease (AD), we conducted a 48-week, double-blind, placebo-controlled, dose-ranging study in women aged 65 years or older with mild to moderate AD. A total of 109 women with mild to moderate AD and a Mini-Mental State Examination score between 12 and 24 inclusive were randomized to low dose Lupron Depot (11.25 mg leuprolide acetate), high dose Lupron Depot (22.5 mg leuprolide acetate), or placebo injections every 12 weeks. There were no statistically significant differences in primary efficacy parameters (ADAS-Cog and ADCS-CGIC), although there was a non-statistically significant trend in favor of the high dose Lupron group on the ADAS-Cog. There were no statistically significant differences in secondary efficacy parameters (NPI, ADCS-ADL, BI, and ADCS-Severity Rating). However, in the a priori designated subgroup analysis of patients taking an acetylcholinesterase inhibitor (AChEI), there was a statistically significant benefit in the high dose group compared to both the low dose and placebo groups as determined by ADAS-Cog (mean decline: 0.18, 4.21, and 3.30), ADCS-CGIC (% subjects experiencing decline: 38, 82, and 63), and ADCS-ADL (mean decline: -0.54, -8.00, and -6.85), respectively. No differences between treatment groups were seen on the NPI, ADCS-CGI Severity Rating, or the BI in the subgroup analysis. These data indicate that cognitive function is preserved in patients treated with high dose Lupron who were already using AChEIs. The positive interaction between Lupron and AChEIs warrants further investigation for the treatment of AD.
ESTHER : Bowen_2015_J.Alzheimers.Dis_44_549
PubMedSearch : Bowen_2015_J.Alzheimers.Dis_44_549
PubMedID: 25310993

Title : Reduced homocysteine-thiolactonase activity in Alzheimer's disease - Suszynska_2010_J.Alzheimers.Dis_19_1177
Author(s) : Suszynska J , Tisonczyk J , Lee HG , Smith MA , Jakubowski H
Ref : J Alzheimers Dis , 19 :1177 , 2010
Abstract : Elevated plasma homocysteine (Hcy) is a risk factor for Alzheimer's disease (AD). Bleomycin hydrolase (BLH), a thiol-dependent enzyme that has Hcy-thiolactonase (HTase) and aminopeptidease (APase) activities, has also been implicated in Alzheimer's disease (AD). In order to examine its role in AD, BLH activities were measured in postmortem brain tissue from twelve AD patients and twelve control patients who died from non-neurological causes. We found that HTase and APase activities in human brain extracts were strongly correlated and sensitive to the thiol reagent iodoacetamide, indicating that they are associated with BLH. Both activities were significantly decreased in brain tissue extracts from AD patients relative to controls (7.6 +/- 4.2 vs. 13.5 +/- 5.5 units, p= 0.003 for HTase, and 3.82 +/- 1.27 vs. 5.33 +/- 1.68 units, p=0.010 for APase). HTase and APase activities were positively correlated with N-linked protein Hcy, but not with tHcy, in AD and control brains. Levels of brain total Hcy and N-linked protein Hcy did not differ between AD cases and controls. These results suggest that diminished functional BLH activity could contribute to the pathology of AD.
ESTHER : Suszynska_2010_J.Alzheimers.Dis_19_1177
PubMedSearch : Suszynska_2010_J.Alzheimers.Dis_19_1177
PubMedID: 20308784

Title : Nanoparticle and iron chelators as a potential novel Alzheimer therapy - Liu_2010_Methods.Mol.Biol_610_123
Author(s) : Liu G , Men P , Perry G , Smith MA
Ref : Methods Mol Biol , 610 :123 , 2010
Abstract : Current therapies for Alzheimer disease (AD) such as the acetylcholinesterase inhibitors and the latest NMDA receptor inhibitor, Namenda, provide moderate symptomatic delay at various stages of the disease, but do not arrest the disease progression or bring in meaningful remission. New approaches to the disease management are urgently needed. Although the etiology of AD is largely unknown, oxidative damage mediated by metals is likely a significant contributor since metals such as iron, aluminum, zinc, and copper are dysregulated and/or increased in AD brain tissue and create a pro-oxidative environment. This role of metal ion-induced free radical formation in AD makes chelation therapy an attractive means of dampening the oxidative stress burden in neurons. The chelator desferrioxamine, FDA approved for iron overload, has shown some benefit in AD, but like many chelators, it has a host of adverse effects and substantial obstacles for tissue-specific targeting. Other chelators are under development and have shown various strengths and weaknesses. Here, we propose a novel system of chelation therapy through the use of nanoparticles. Nanoparticles conjugated to chelators show unique ability to cross the blood-brain barrier (BBB), chelate metals, and exit through the BBB with their corresponding complexed metal ions. This method may provide a safer and more effective means of reducing the metal load in neural tissue, thus attenuating the harmful effects of oxidative damage and its sequelae. Experimental procedures are presented in this chapter.
ESTHER : Liu_2010_Methods.Mol.Biol_610_123
PubMedSearch : Liu_2010_Methods.Mol.Biol_610_123
PubMedID: 20013176

Title : Current approaches in the treatment of Alzheimer's disease - Shah_2008_Biomed.Pharmacother_62_199
Author(s) : Shah RS , Lee HG , Xiongwei Z , Perry G , Smith MA , Castellani RJ
Ref : Biomed Pharmacother , 62 :199 , 2008
Abstract : The management of Alzheimer's disease (AD) has been a long-standing challenge and area of interest. Advances in knowledge of the pathogenesis of disease and an increase in disease burden have prompted investigation into innovative therapeutics over the last two decades. This article reviews the various treatments of AD including those targeted towards cholinergic deficiency, oxidative stress, the amyloid cascade, inflammation, and excitotoxicity. Second generation cholinesterase inhibitors remain the preferred therapy for early and intermediate AD while the glutamate antagonist, memantine, is also approved for advanced stages of disease. Antioxidants may delay disease progression, while data on other experimental therapies remain equivocal at best. Gene therapy directed at neurotropins is currently under investigation with some intriguing preliminary results; however, the number of patients examined is too few to be conclusive. Drugs directly targeting amyloid-beta, particularly the amyloid-beta vaccine, continue to be investigated and their forthcoming results are eagerly anticipated.
ESTHER : Shah_2008_Biomed.Pharmacother_62_199
PubMedSearch : Shah_2008_Biomed.Pharmacother_62_199
PubMedID: 18407457

Title : The discovery and early validation of novel plasma biomarkers in mild-to-moderate Alzheimer's disease patients responding to treatment with rosiglitazone - Akuffo_2008_Biomarkers_13_618
Author(s) : Akuffo EL , Davis JB , Fox SM , Gloger IS , Hosford D , Kinsey EE , Jones NA , Nock CM , Roses AD , Saunders AM , Skehel JM , Smith MA , Cutler P
Ref : Biomarkers , 13 :618 , 2008
Abstract : Recent advances in clinical, pathological and neuroscience studies have identified disease-modifying therapeutic approaches for Alzheimer's disease that are now in clinical trials. This has highlighted the need for reliable and convenient biomarkers for both early disease diagnosis and a rapid signal of drug efficacy. We describe the identification and assessment of a number of candidate biomarkers in patients with Alzheimer's disease and the correlation of those biomarkers with rosiglitazone therapeutic efficacy, as represented by a change in the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog). Plasma from 41 patients with Alzheimer's disease were analysed by open platform proteomics at baseline and after receiving 8 mg rosiglitazone for 24 weeks. From a comparison of protein expression following treatment with rosiglitazone, 97 proteins were observed to be differentially expressed with a p-value<0.01. From this analysis and comparison to recently published data from our laboratory, a prioritized list of 10 proteins were analysed by immunoassay and/or functional assay in a wider set of samples from the same clinical study, representing a rosiglitazone dose response, in order to verify the changes observed. A number of these proteins appeared to show a correlation with change in ADAS-Cog at the higher treatment doses compared with the placebo. Alpha-2-macroglobulin, complement C1 inhibitor, complement factor H and apolipoprotein E expression showed a correlation with ADAS-Cog score at the higher doses (4 mg and 8 mg). These results are discussed in light of the pathology and other recently published data.
ESTHER : Akuffo_2008_Biomarkers_13_618
PubMedSearch : Akuffo_2008_Biomarkers_13_618
PubMedID: 18830857

Title : Therapeutic options in Alzheimer's disease - Moreira_2006_Expert.Rev.Neurother_6_897
Author(s) : Moreira PI , Zhu X , Nunomura A , Smith MA , Perry G
Ref : Expert Rev Neurother , 6 :897 , 2006
Abstract : Alzheimer's disease (AD) places an enormous burden on individuals, families and society. Consequently, a tremendous effort is being devoted to the development of drugs that prevent or delay neurodegeneration. Current pharmacological treatments are based on the use of acetylcholinesterase inhibitors or memantine, a N-methyl-D-aspartate channel blocker. However, new therapeutic approaches, including those more closely targeted to the pathogenesis of the disease, are being developed. These potentially disease-modifying therapeutics include secretase inhibitors, cholesterol-lowering drugs, amyloid-beta immunotherapy, nonsteroidal anti-inflammatory drugs, hormonal modulation and the use of antioxidants. The possibility that oxidative stress is a primary event in AD indicates that antioxidant-based therapies are perhaps the most promising weapons against this devastating neurodegenerative disorder.
ESTHER : Moreira_2006_Expert.Rev.Neurother_6_897
PubMedSearch : Moreira_2006_Expert.Rev.Neurother_6_897
PubMedID: 16784412

Title : Comparative genome sequencing of Drosophila pseudoobscura: chromosomal, gene, and cis-element evolution - Richards_2005_Genome.Res_15_1
Author(s) : Richards S , Liu Y , Bettencourt BR , Hradecky P , Letovsky S , Nielsen R , Thornton K , Hubisz MJ , Chen R , Meisel RP , Couronne O , Hua S , Smith MA , Zhang P , Liu J , Bussemaker HJ , van Batenburg MF , Howells SL , Scherer SE , Sodergren E , Matthews BB , Crosby MA , Schroeder AJ , Ortiz-Barrientos D , Rives CM , Metzker ML , Muzny DM , Scott G , Steffen D , Wheeler DA , Worley KC , Havlak P , Durbin KJ , Egan A , Gill R , Hume J , Morgan MB , Miner G , Hamilton C , Huang Y , Waldron L , Verduzco D , Clerc-Blankenburg KP , Dubchak I , Noor MA , Anderson W , White KP , Clark AG , Schaeffer SW , Gelbart W , Weinstock GM , Gibbs RA
Ref : Genome Res , 15 :1 , 2005
Abstract : We have sequenced the genome of a second Drosophila species, Drosophila pseudoobscura, and compared this to the genome sequence of Drosophila melanogaster, a primary model organism. Throughout evolution the vast majority of Drosophila genes have remained on the same chromosome arm, but within each arm gene order has been extensively reshuffled, leading to a minimum of 921 syntenic blocks shared between the species. A repetitive sequence is found in the D. pseudoobscura genome at many junctions between adjacent syntenic blocks. Analysis of this novel repetitive element family suggests that recombination between offset elements may have given rise to many paracentric inversions, thereby contributing to the shuffling of gene order in the D. pseudoobscura lineage. Based on sequence similarity and synteny, 10,516 putative orthologs have been identified as a core gene set conserved over 25-55 million years (Myr) since the pseudoobscura/melanogaster divergence. Genes expressed in the testes had higher amino acid sequence divergence than the genome-wide average, consistent with the rapid evolution of sex-specific proteins. Cis-regulatory sequences are more conserved than random and nearby sequences between the species--but the difference is slight, suggesting that the evolution of cis-regulatory elements is flexible. Overall, a pattern of repeat-mediated chromosomal rearrangement, and high coadaptation of both male genes and cis-regulatory sequences emerges as important themes of genome divergence between these species of Drosophila.
ESTHER : Richards_2005_Genome.Res_15_1
PubMedSearch : Richards_2005_Genome.Res_15_1
PubMedID: 15632085
Gene_locus related to this paper: drome-BEM46 , drome-GH02439 , drops-ACHE , drops-b5dhd2 , drops-b5di70 , drops-b5djn7 , drops-b5dk96 , drops-b5dm12 , drops-b5dpe3 , drops-b5drp9 , drops-b5du62 , drops-b5dud8 , drops-b5dwa7 , drops-b5dwa8 , drops-b5dy09 , drops-b5dz85 , drops-b5dz86 , drops-b5e1k7 , drops-CG4390 , drops-est5a , drops-est5b , drops-est5c , drops-nrtac , drops-q2lyp3 , drops-q2lyp4 , drops-q2lyu3 , drops-q2lz68 , drops-q2m0u9 , drops-q2m169 , drops-q28wj5 , drops-q28wt2 , drops-q28wt8 , drops-q28zi3 , drops-q28zz1 , drops-q29a22 , drops-q29ad8 , drops-q29ad9 , drops-q29ae0 , drops-q29ae1 , drops-q29ay7 , drops-q29ay8 , drops-q29ay9 , drops-q29bq2 , drops-q29br3 , drops-q29d59 , drops-q29dc9 , drops-q29dd7 , drops-q29dp4 , drops-q29dw3 , drops-q29dw4 , drops-q29e16 , drops-q29ew0 , drops-q29f35 , drops-q29f66 , drops-q29fi0 , drops-q29fw0 , drops-q29fw9 , drops-q29g93 , drops-q29gb0 , drops-q29gs6 , drops-q29h54 , drops-b5dmp7 , drops-q29hd2 , drops-q29hu2 , drops-q29hu3 , drops-q29hv0 , drops-q29i09 , drops-q29js9 , drops-q29jt5 , drops-q29jt6 , drops-q29jy5 , drops-q29k25 , drops-q29kd5 , drops-q29kd6 , drops-q29ke5 , drops-q29kq9 , drops-q29kr1 , drops-q29kr3 , drops-q29kr5 , drops-q29kr8 , drops-q29kr9 , drops-q29ks6 , drops-q29kz0 , drops-q29kz1 , drops-q29l31 , drops-q29lf8 , drops-q29lv0 , drops-q29m07 , drops-q29m08 , drops-q29m27 , drops-q29m66 , drops-q29m81 , drops-q29mj7 , drops-q29mv2 , drops-q29mx0 , drops-q29n87 , drops-q29na5 , drops-q29na6 , drops-q29pe4 , drops-q29pk4 , drops-q290i1 , drops-q290k3 , drops-q290v8 , drops-q290v9 , drops-q290w0 , drops-q290z8 , drops-q291d5 , drops-q291e8 , drops-q291y3 , drops-q292f5 , drops-q292g6 , drops-q293n1 , drops-q293n4 , drops-q293n5 , drops-q293n6 , drops-q293y7 , drops-q294n3 , drops-q294n6 , drops-q294n7 , drops-q294n9 , drops-q294p0 , drops-q294p1 , drops-q294p3 , drops-q294p4 , drops-q294u9 , drops-q295h3 , drops-q296h2 , drops-q296x1 , drops-q296x2 , drops-q297h5 , drops-q298u8 , drope-b4gkk1

Title : Alzheimer's disease and the cell cycle - Raina_2004_Acta.Neurobiol.Exp.(Wars)_64_107
Author(s) : Raina AK , Zhu X , Smith MA
Ref : Acta Neurobiol Exp (Wars) , 64 :107 , 2004
Abstract : Current views associate the reappearance of cell cycle markers with early events in Alzheimer's disease. Even though, the cell cycle was implicated early in the study of this disease, only recently has it been associated with selective early vulnerability of neurons. The pathological hallmarks of Alzheimer's disease namely tau and amyloid have been associated with having effects on or being affected by cell cycle progression. Indeed the mitogenic component looms large early in the onset of Alzheimer's disease. Although quite a number of markers of reentry have been catalogued, the common denominator is abortosis, the unalterable march towards neuronal dysfunction, stasis and eventually death. We feel that complete understanding of the mechanisms, acting either positively by stimulation or through removal of inhibitory signals will provide promising molecular targets for pharmacological interventions which have been static for a number of years by being relegated to inhibition of the enzyme cholinesterase. In our opinion, investigating more proximal mechanisms will provide answers to changing the natural course of this illness.
ESTHER : Raina_2004_Acta.Neurobiol.Exp.(Wars)_64_107
PubMedSearch : Raina_2004_Acta.Neurobiol.Exp.(Wars)_64_107
PubMedID: 15190685

Title : Genes for chlorogenate and hydroxycinnamate catabolism (hca) are linked to functionally related genes in the dca-pca-qui-pob-hca chromosomal cluster of Acinetobacter sp. strain ADP1 - Smith_2003_Appl.Environ.Microbiol_69_524
Author(s) : Smith MA , Weaver VB , Young DM , Ornston LN
Ref : Applied Environmental Microbiology , 69 :524 , 2003
Abstract : Hydroxycinnamates are ubiquitous in the environment because of their contributions to the structure and defense mechanisms of plants. Additional plant products, many of which are formed in response to stress, support the growth of Acinetobacter sp. strain ADP1 through pathways encoded by genes in the dca-pca-qui-pob chromosomal cluster. In an appropriate genetic background, it was possible to select for an Acinetobacter strain that had lost the ability to grow with caffeate, a commonly occurring hydroxycinnamate. The newly identified mutation was shown to be a deletion in a gene designated hcaC and encoding a ligase required for conversion of commonly occurring hydroxycinnamates (caffeate, ferulate, coumarate, and 3,4-dihydroxyphenylpropionate) to thioesters. Linkage analysis showed that hcaC is linked to pobA. Downstream from hcaC and transcribed in the direction opposite the direction of pobA transcription are open reading frames designated hcaDEFG. Functions of these genes were inferred from sequence comparisons and from the properties of knockout mutants. HcaD corresponded to an acyl coenzyme A (acyl-CoA) dehydrogenase required for conversion of 3,4-dihydroxyphenylpropionyl-CoA to caffeoyl-CoA. HcaE appears to encode a member of a family of outer membrane proteins known as porins. Knockout mutations in hcaF confer no discernible phenotype. Knockout mutations in hcaG indicate that this gene encodes a membrane-associated esterase that hydrolyzes chlorogenate to quinate, which is metabolized in the periplasm, and caffeate, which is metabolized by intracellular enzymes. The chromosomal location of hcaG, between hcaC (required for growth with caffeate) and quiA (required for growth with quinate), provided the essential clue that led to the genetic test of HcaG as the esterase that produces caffeate and quinate from chlorogenate. Thus, in this study, organization within what is now established as the dca-pca-qui-pob-hca chromosomal cluster provided essential information about the function of genes in the environment.
ESTHER : Smith_2003_Appl.Environ.Microbiol_69_524
PubMedSearch : Smith_2003_Appl.Environ.Microbiol_69_524
PubMedID: 12514037
Gene_locus related to this paper: aciad-q8rlz8

Title : Developmental expression of alpha 7 neuronal nicotinic receptor messenger RNA in rat sensory cortex and thalamus - Broide_1995_Neurosci_67_83
Author(s) : Broide RS , O'Connor LT , Smith MA , Smith JA , Leslie FM
Ref : Neuroscience , 67 :83 , 1995
Abstract : The distribution of alpha 7 messenger RNA expression was characterized in developing rat cortex and thalamus. Northern blot analysis of neonatal and adult cortex revealed a single messenger RNA transcript of 5.7 kb. Using in situ hybridization with both full length and short 35S-labeled alpha 7 riboprobes, a distinct transient expression of messenger RNA within sensory cortex and thalamus, during early postnatal development, was observed. alpha 7 transcripts were expressed in low levels as early as embryonic day 13 in the ventricular zone of the neocortex, and as early as embryonic day 15 in the thalamic neuroepithelium. A marked increase in messenger RNA levels was observed during the late prenatal period in both sensory and non-sensory regions of the cortex and thalamus. Moderate to high levels of messenger RNA were maintained into the first postnatal week, followed by a decline into adulthood. alpha 7 messenger RNA expression was significantly higher in the anterodorsal, lateral dorsal, ventral posterior medial and ventral posterior lateral thalamic nuclei of postnatal day 7 pups than in adult brains. Expression of messenger RNA within dorsal lateral geniculate, ventral lateral geniculate and medial geniculate did not show a significant reduction with age. Within the developing cortex, messenger RNA expression delineated the primary somatosensory, auditory and visual cortices in a unique laminar pattern that was consistently and significantly higher than in the adult in superficial layer VI. Higher levels of expression were also observed in retrosplenial cortex at postnatal day 7 than in the adult. Tangential sections through postnatal day 7 cortex revealed low levels of alpha 7 messenger RNA expression delineating the primary sensory areas in layer IV, corresponding to acetylcholinesterase-labeled thalamocortical afferents. However, these sensory areas exhibited higher levels of alpha 7 messenger RNA expression and were more clearly defined in layer VI, but not by acetylcholinesterase staining. The distribution of alpha 7 messenger RNA within the developing thalamocortical system parallels the distribution of alpha-bungarotoxin binding sites and suggests that the receptor is localized on both thalamic cells and their cortical target neurons. This transient and distinct pattern of distribution of the alpha 7 neuronal nicotinic receptor, which coincides with the major phase of thalamocortical development, suggests that it may play a functional role in the development of cortical circuitry.
ESTHER : Broide_1995_Neurosci_67_83
PubMedSearch : Broide_1995_Neurosci_67_83
PubMedID: 7477913

Title : Identification of agrin in electric organ extracts and localization of agrin-like molecules in muscle and central nervous system - Smith_1987_J.Exp.Biol_132_223
Author(s) : Smith MA , Yao YM , Reist NE , Magill C , Wallace BG , McMahan UJ
Ref : J Exp Biol , 132 :223 , 1987
Abstract : The portion of the muscle fibre's basal lamina that occupies the synaptic cleft at the neuromuscular junction contains molecules that cause the aggregation of acetylcholine receptors and acetylcholinesterase on regenerating muscle fibres. Agrin, which is extracted from basal lamina-containing fractions of the Torpedo electric organ and causes the formation of acetylcholine receptor and acetylcholinesterase aggregates on cultured myotubes, may be similar, if not identical, to the acetylcholine receptor- and acetylcholinesterase-aggregating molecules at the neuro-muscular junction. Here we summarize experiments which led to the identification of agrin and established that the basal lamina at the neuromuscular junction contains molecules antigenically similar to agrin. We also discuss results which raise the possibility that agrin-like molecules at the neuromuscular junction are produced by motor neurones.
ESTHER : Smith_1987_J.Exp.Biol_132_223
PubMedSearch : Smith_1987_J.Exp.Biol_132_223
PubMedID: 2828510

Title : Identification of agrin, a synaptic organizing protein from Torpedo electric organ - Nitkin_1987_J.Cell.Biol_105_2471
Author(s) : Nitkin RM , Smith MA , Magill C , Fallon JR , Yao YM , Wallace BG , McMahan UJ
Ref : Journal of Cell Biology , 105 :2471 , 1987
Abstract : Extracts of the electric organ of Torpedo californica contain a proteinaceous factor that causes the formation of patches on cultured myotubes at which acetylcholine receptors (AChR), acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) are concentrated. Results of previous experiments indicate that this factor is similar to the molecules in the synaptic basal lamina that direct the aggregation of AChR and AChE at regenerating neuromuscular junctions in vivo. We have purified the active components in the extracts 9,000-fold. mAbs against four different epitopes on the AChR/AChE/BuChE-aggregating molecules each immunoprecipitated four polypeptides from electric organ extracts, with molecular masses of 150, 135, 95, and 70 kD. Gel filtration chromatography of electric organ extracts revealed two peaks of AChR/AChE/BuChE-aggregation activity; one comigrated with the 150-kD polypeptide, the other with the 95-kD polypeptide. The 135- and 70-kD polypeptides did not cause AChR/AChE/BuChE aggregation. Based on these molecular characteristics and on the pattern of staining seen in sections of muscle labeled with the mAbs, we conclude that the electric organ-aggregating factor is distinct from previously identified molecules, and we have named it "agrin".
ESTHER : Nitkin_1987_J.Cell.Biol_105_2471
PubMedSearch : Nitkin_1987_J.Cell.Biol_105_2471
PubMedID: 2826489

Title : Cholinergic modulation of an acetylcholine receptor-like antigen on the surface of chick ciliary ganglion neurons in cell culture - Smith_1986_J.Neurosci_6_946
Author(s) : Smith MA , Margiotta JF , Franco A, Jr. , Lindstrom JM , Berg DK
Ref : Journal of Neuroscience , 6 :946 , 1986
Abstract : Chick ciliary ganglion neurons have a membrane component that shares an antigenic determinant with the "main immunogenic region" of the alpha subunits in nicotinic ACh receptors from skeletal muscle and electric organ. Ultrastructural studies on antibody binding in the ganglion have shown that the cross-reacting antigen on the neuron surface is located predominantly in synaptic membrane. Biochemical studies have shown that the cross-reacting component has a number of other properties expected for the ganglionic nicotonic ACh receptor and that it is distinct from the alpha-bungarotoxin binding component in the tissue. Here we show that ciliary ganglion neurons grown in dissociated cell culture express a similar component that cross-reacts with monoclonal antibodies to ACh receptors, and that the number of antibody-binding sites on the neurons can be modulated by exposure to cholinergic agonists and a protein neurotoxin that reversibly inhibits ACh receptors on the neurons. In most, though not all, cases, levels of ACh sensitivity associated with the neurons are specifically comodulated in parallel with the changes in number of antibody binding sites. The results suggest that at least a portion of the cross-reacting sites on the surface of ciliary ganglion neurons is likely to represent nicotinic ACh receptors. The fact that in some instances levels of ACh sensitivity can be altered without changing the number of cross-reacting sites, however, leaves open the possibility that not all of the sites are associated with receptors or that the neurons can alter the proportion of receptors that is functional.
ESTHER : Smith_1986_J.Neurosci_6_946
PubMedSearch : Smith_1986_J.Neurosci_6_946
PubMedID: 2422330

Title : Characterization of a component in chick ciliary ganglia that cross-reacts with monoclonal antibodies to muscle and electric organ acetylcholine receptor - Smith_1985_J.Neurosci_5_2726
Author(s) : Smith MA , Stollberg J , Lindstrom JM , Berg DK
Ref : Journal of Neuroscience , 5 :2726 , 1985
Abstract : Chick ciliary ganglion neurons have previously been shown to contain a component that shares an antigenic determinant with the "main immunogenic region" of the alpha-subunit in nicotinic acetylcholine receptor from skeletal muscle and electric organ. Ultrastructural studies of antibody binding in the ganglion have shown that the cross-reacting antigen exposed on the surface of the neurons is located predominantly in synaptic membrane. Here we show that the neuronal antigen can be identified in detergent extracts of ciliary and sympathetic ganglia, but not in extracts of heart, liver, spinal cord, retina, or dorsal root ganglia. In the ciliary ganglion the component is present as an integral membrane constituent, and, when detergent solubilized, it sediments as a 10 S species and binds to concanavalin A. The component is distinct from the alpha-bungarotoxin-binding site on the neurons since toxin-binding sites and antibody-binding sites can be precipitated separately in ganglion extracts. The component reaches peak levels per ganglionic protein between embryonic days 8 and 12. These are some of the properties expected for the nicotinic acetylcholine receptor on ciliary ganglion neurons.
ESTHER : Smith_1985_J.Neurosci_5_2726
PubMedSearch : Smith_1985_J.Neurosci_5_2726
PubMedID: 2413185

Title : The absence of calcium blocks impulse-evoked release of acetylcholine but not de novo formation of functional neuromuscular synaptic contacts in culture - Henderson_1984_J.Neurosci_4_3140
Author(s) : Henderson LP , Smith MA , Spitzer NC
Ref : Journal of Neuroscience , 4 :3140 , 1984
Abstract : We have examined the role of calcium-dependent, impulse-evoked release of acetylcholine (ACh) in the formation of functional neuromuscular contacts. Dissociated cell cultures prepared from Xenopus laevis embryos were maintained either in standard medium containing calcium or in calcium-free medium. Both the number of neuron-myocyte contacts and the number of terminations of neurites on myocytes were reduced in Ca-free medium. Intracellular recordings from neuron-myocyte pairs during perfusion with a standard saline revealed that functional synaptic contacts were formed in Ca-free medium, although with a reduced frequency (approximately 30% of controls). Postsynaptic potentials elicited by neuronal action potentials were smaller than those observed after growth in standard medium. The frequency of small, spontaneously occurring potentials was reduced by a factor of 10. Ca-free saline prevented the impulse-evoked release of transmitter from neurons in Ca-free and control cultures. Labeling with alpha-bungarotoxin and iontophoretic application of ACh revealed no ACh receptor clusters in the membrane of myocytes grown in Ca-free medium. Our results suggest that evoked, vesicular release is not required for the initial formation of neuromuscular contacts, although it may be involved in further maturation of synapses. Roles for spontaneous quantal or non-quantal release have not been excluded.
ESTHER : Henderson_1984_J.Neurosci_4_3140
PubMedSearch : Henderson_1984_J.Neurosci_4_3140
PubMedID: 6094749

Title : Differential regulation of acetylcholine sensitivity and alpha-bungarotoxin-binding sites on ciliary ganglion neurons in cell culture - Smith_1983_J.Neurosci_3_2395
Author(s) : Smith MA , Margiotta JF , Berg DK
Ref : Journal of Neuroscience , 3 :2395 , 1983
Abstract : Levels of acetylcholine (ACh) sensitivity and numbers of alpha-bungarotoxin (alpha-Bgt)-binding sites have been measured for chick ciliary ganglion neurons grown in cell culture under various conditions. The two properties were found not to change in parallel. Neurons maintained in culture medium supplemented with embryonic eye extract developed high levels of ACh sensitivity and low numbers of alpha-Bgt-binding sites, whereas neurons grown in medium containing elevated K+ concentrations displayed the reverse. Neurons from media containing both eye extract and elevated K+ concentrations had both low levels of sensitivity and low numbers of toxin sites. The growth conditions do not alter the basic binding properties of the ACh receptors and alpha-Bgt-binding sites. Both the ACh receptor dose-response characteristics and the pharmacological properties of the toxin-binding sites were similar for neurons grown in media containing eye extract or elevated K+ concentrations. The inhibitory effects of eye extract on development of alpha-Bgt-binding sites appeared to be specific: eye extract had previously been shown to stimulate neuronal growth and cholinergic development, and in the present study eye extract enhanced development of ACh sensitivity and had no effect on mechanisms responsible for binding and accumulation of tetanus toxin. Eye extract did not block alpha-Bgt binding in competition binding experiments and did not cause redistribution of toxin sites away from the neuronal soma. These results demonstrate that ACh sensitivity and alpha-Bgt-binding sites can be independently regulated on the neurons and suggest that the two membrane properties are associated with separate membrane components.
ESTHER : Smith_1983_J.Neurosci_3_2395
PubMedSearch : Smith_1983_J.Neurosci_3_2395
PubMedID: 6631487

Title : Spatial distribution of acetylcholine receptors at developing chick neuromuscular junctions - Smith_1983_J.Neurocytol_12_993
Author(s) : Smith MA , Slater CR
Ref : Journal of Neurocytology , 12 :993 , 1983
Abstract : The development of high-density clusters of acetylcholine receptors (AChRs) and the relationship of these clusters to nerve contacts on embryonic chick wing muscle fibres has been studied. Fluorescent labelling of AChRs with rhodamine-conjugated alpha-bungarotoxin (R-Bgt) revealed the presence of irregularly shaped AChR clusters in wing buds at 4 1/2-5 days of incubation. This is within a day of when myotubes first appear in the wing bud, and close to the time when functional innervation becomes established. At 10 days of incubation AChR clusters present on muscle cells in anterior and posterior latissimus dorsi appear as round or oval, uniformly labelled plaques. At about the time of hatching, however, these plaques break into numerous smaller clusters. Similar changes in the morphology of AChR clusters have been observed previously in mammalian skeletal muscle during development. Using horseradish peroxidase labelled alpha-bungarotoxin (HRP-Bgt), the relationship between AChR clusters and motor nerve terminals was studied at the ultrastructural level. At all stages of development nerve-muscle contacts were labelled with HRP-Bgt. In wing buds, however, the majority (90%) of labelled clusters observed were not in contact with a motor nerve terminal. The incidence of AChR clusters with axon contacts increased sharply during development such that by 10 days more than 50% and by hatching more than 90% of all sections through labelled AChR clusters contained nerve terminal profiles. At all times studied nerve-contacted receptor clusters were longer (about 5 micron) than non-contacted clusters (about 2 micron).
ESTHER : Smith_1983_J.Neurocytol_12_993
PubMedSearch : Smith_1983_J.Neurocytol_12_993
PubMedID: 6363632