PHOSPHORYLATION OF MEMBRANE-BOUND ACETYLCHOLINE-RECEPTOR BY PROTEIN KINASE-C - CHARACTERIZATION AND SUBUNIT SPECIFICITY

Acetylcholine receptor (AChR) from Torpedo electric organ in its membrane-bound or solubilized form is phosphorylated by the Ca2+/phospholipid-dependent protein kinase (PKC). The subunit specificity for PKC is different from that observed for cAMP-dependent protein kinase (PKA). Whereas PKC phosphorylates predominantly the δ subunit and the phosphorylation of the γ subunit by this enzyme is very low, PKA phosphorylates both subunits to a similar high extent. We have extended our phosphorylation studies to a synthetic peptide from the γ subunit, corresponding to residues 346–359, which contains a consensus PKA phosphorylation site. This synthetic peptide is phosphorylated by both PKA and PKC, suggesting that in the intact receptor both kinases may phosphorylate the γ subunit at a similar site, as has been previously demonstrated by us for the δ subunit [Safran, A., et al. (1987) J. Biol. Chem. 262, 10506–10510]. The diverse pattern of phosphorylation of AChR by PKA and PKC may play a role in the regulation of its function. © 1990, American Chemical Society. All rights reserved.