title: Agrin induces phosphorylation of the nicotinic acetylcholine receptor.
abstract: Agrin causes acetylcholine receptors (AChRs) on chick myotubes in culture to aggregate, forming specializations that resemble the postsynaptic apparatus at the vertebrate skeletal neuromuscular junction. Here we report that treating chick myotubes with agrin caused an increase in phosphorylation of the AChR beta, gamma, and delta subunits. H-7, a potent inhibitor of several protein serine kinases, blocked agrin-induced phosphorylation of the gamma and delta subunits, but did not prevent either agrin-induced AChR aggregation or phosphorylation of the beta subunit. Experiments with anti-phosphotyrosine antibodies demonstrated that agrin caused an increase in tyrosine phosphorylation of the beta subunit that began within 30 min of adding agrin to the myotube cultures, reached a plateau by 3 hr, and was blocked by treatments known to block agrin-induced AChR aggregation. Anti-phosphotyrosine antibodies labeled agrin-induced specializations as they do the postsynaptic apparatus. These results suggest that agrin-induced tyrosine phosphorylation of the beta subunit may play a role in regulating AChR distribution.
authors.affiliation: Department of Physiology, University of Colorado Health Sciences Center, Denver 80262.
authors.forename: B G
authors.initials: BG
authors.lastname: Wallace
authors.forename: Z
authors.initials: Z
authors.lastname: Qu
authors.forename: R L
authors.initials: RL
authors.lastname: Huganir
mesh_terms: D018171:Agrin; D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007700:Kinetics; D046911:Macromolecular Substances; D009132:Muscles / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D013570:Synaptic Membranes / Q000502:physiology; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D018171:Agrin; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D011978:Receptors, Nicotinic; D019000:Phosphotyrosine; D014443:Tyrosine