Effects of monoclonal antibodies on the function of acetylcholine receptors purified from Torpedo californica and reconstituted into vesicles

Abstract

The effects of 62 monoclonal antibodies (mAb) to acetylcholine receptors from T. californica on the function of receptor reconstituted into lipid vesicles were tested. Two of these mAb, mAb 148 and 168, inhibited carbamylcholine-induced 22Na+ uptake into vesicles. The rate of 125I-labeled .alpha.-bungarotoxin (125I-.alpha.BGT) binding to the reconstituted liposomes was also reduced, although 125I-.alpha.BGT binding at equilibrium was not affected. Agonist-induced desensitization of the receptor was also affected by these mAb. mAb 148 binds to the .beta. subunit of receptor, and mAb 168 binds to the .gamma. subunit. Both mAb bind to the cytoplasmic surface of the receptor; correspondingly, both block function when added before reconstitution, and both were found to have no effect on function when added to preformed vesicles. Their effects were not due to interference with the reconstitution process. Both mAb were capable of cross-linking receptors. In contrast to the bivalent mAb, monovalent Fab fragments of these 2 mAb had little effect on receptor function, which suggests that the effects of the bivalent mAb resulted primarily from cross-linking receptors.