title: 14-3-3 gamma associates with muscle specific kinase and regulates synaptic gene transcription at vertebrate neuromuscular synapse.
abstract: The muscle-specific receptor tyrosine kinase (MuSK) is part of a receptor complex, activated by neural agrin, that orchestrates the differentiation of the neuromuscular junction (NMJ). To gain insight into the function of the MuSK complex, we have developed a proteomic approach to identify new MuSK partners. MS analysis of MuSK crosslink products from postsynaptic membranes of the Torpedo electrocytes identified the adaptor protein 14-3-3 gamma. The 14-3-3 gamma protein was found localized at the adult rat NMJ. Cotransfection experiments in COS-7 cells showed that MuSK codistributed with the 14-3-3 gamma protein at the plasma membrane. Furthermore, 14-3-3 gamma was copurified by affinity chromatography with MuSK from transfected COS-7 cells and myotubes. The 14-3-3 gamma protein did not colocalize with agrin-elicited acetylcholine receptor (AChR) aggregates in cultured myotubes, suggesting that it is not involved in AChR clustering. Expression of 14-3-3 gamma specifically repressed the transcription of several synaptic reporter genes in cultured myotubes. This repression was potentiated by MuSK expression. Moreover, the expression of 14-3-3 gamma in muscle fibers in vivo caused both the repression of synaptic genes transcription and morphological perturbations of the NMJ. Our data extend the notion that, apart from its well documented role in AChR clustering, the MuSK complex might also be involved in the regulation of synaptic gene expression at the NMJ.
authors.affiliation: Biologie Cellulaire des Membranes, Institut Jacques Monod, Unité Mixte de Recherche 7592, Centre National de la Recherche Scientifique, Universités Paris 6 et 7, 75251 Paris, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Strochlic
authors.forename: Annie
authors.initials: A
authors.lastname: Cartaud
authors.forename: Alexandre
authors.initials: A
authors.lastname: Mejat
authors.forename: Régis
authors.initials: R
authors.lastname: Grailhe
authors.forename: Laurent
authors.initials: L
authors.lastname: Schaeffer
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Changeux
authors.forename: Jean
authors.initials: J
authors.lastname: Cartaud
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism / Q000502:physiology*; D018171:Agrin / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002845:Chromatography; D003432:Cross-Linking Reagents; D004573:Electrolytes / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D009132:Muscles / Q000378:metabolism; D009469:Neuromuscular Junction / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D011485:Protein Binding; D040901:Proteomics; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D011950:Receptors, Cholinergic / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013569:Synapses / Q000473:pathology*; D013997:Time Factors; D014101:Torpedo; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D048948:14-3-3 Proteins; D018171:Agrin; D003432:Cross-Linking Reagents; D004573:Electrolytes; D011950:Receptors, Cholinergic; D049452:Green Fluorescent Proteins; C095714:MUSK protein, human; D020794:Receptor Protein-Tyrosine Kinases