Monoclonal antibodies against the acetylcholine receptor γ‐subunit as site specific probes for receptor tyrosine phosphorylation

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Abstract
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.