title: Rapsyn may function as a link between the acetylcholine receptor and the agrin-binding dystrophin-associated glycoprotein complex.
abstract: The 43 kDa AChR-associated protein rapsyn is required for the clustering of nicotinic acetylcholine receptors (AChRs) at the developing neuromuscular junction, but the functions of other postsynaptic proteins colocalized with the AChR are less clear. Here we use a fibroblast expression system to investigate the role of the dystrophin-glycoprotein complex (DGC) in AChR clustering. The agrin-binding component of the DGC, dystroglycan, is found evenly distributed across the cell surface when expressed in fibroblasts. However, dystroglycan colocalizes with AChR-rapsyn clusters when these proteins are coexpressed. Furthermore, dystroglycan colocalizes with rapsyn clusters even in the absence of AChR, indicating that rapsyn can cluster dystroglycan and AChR independently. Immunofluorescence staining using a polyclonal antibody to utrophin reveals a lack of staining of clusters, suggesting that the immunoreactive species, like the AChR, does not mediate the observed rapsyndystroglycan interaction. Rapsyn may therefore be a molecular link connecting the AChR to the DGC. At the neuromuscular synapse, rapsyn-mediated linkage of the AChR to the cytoskeleton-anchored DGC may underlie AChR cluster stabilization.
authors.affiliation: Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Apel
authors.forename: S L
authors.initials: SL
authors.lastname: Roberds
authors.forename: K P
authors.initials: KP
authors.lastname: Campbell
authors.forename: J P
authors.initials: JP
authors.lastname: Merlie
mesh_terms: D018171:Agrin / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D049030:Dystroglycans; D016189:Dystrophin / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D009124:Muscle Proteins / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000648:ultrastructure; D011485:Protein Binding / Q000502:physiology; D011784:Quail; D011817:Rabbits; D011978:Receptors, Nicotinic / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D049411:Utrophin
chemical_list: D018171:Agrin; D003598:Cytoskeletal Proteins; D016189:Dystrophin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D011978:Receptors, Nicotinic; D011994:Recombinant Proteins; C483600:Utrn protein, mouse; D049411:Utrophin; C051609:peripheral membrane protein 43K; D049030:Dystroglycans