Ca2+-dependent inactivation of acetylcholine receptors by an endogenous transglutaminase.

The nicotinic acetylcholine receptor (nAChR) from Torpedo californica and T. marmorata electric tissue polymerises irreversibly when DTE and Ca2+ are added to receptor-rich membranes. The polymerisation is time-dependent and complete within 3 h at 30 degrees C. It can be completely prevented by EGTA or the transglutaminase inhibitor cystamine. Transglutaminase activity can also be monitored with the exogenous substrates [3H]putrescine and dimethylcasein. This assay can also be inhibited by EGTA or cystamine.