Tyrosine phosphorylation of the nicotinic acetylcholine receptor (AChR) may be involved in AChR desensitization and clustering. Torpedo AChR γ-subunit is phosphorylated at Tyr365. Using overlapping synthetic peptides, we have precisely mapped the epitopes of five anti-γ-subunit monoclonal antibodies (mAbs) and found that the epitope(s) for the mAbs 154, 165 and 168 (γ365–370) all contain Tyr365. mAb 168 is a known blocker of AChR channel function. Using peptide analogues, Tyr365. was found to be indispensable for mAb165 binding; furthermore its binding was selectively inhibited by in vitro AChR tyrosine phosphorylation. The possible connection between γ-subunit phosphorylation and regulation of AChR function and the proven usefulness of these mAbs as tools should facilitate functional studies of AChR γ-subunit phosphorylation.
