Ligand induced changes in stability and distribution of acetylcholine receptors on surface membranes of muscle cells

Distribution and stability of acetylcholine receptor (AChR) in cultured muscle cells was studied following the binding to these cells of concanavalin A (Con A) and specific antibodies against the receptor molecules. Con A (10 μg/ml) significantly slowed the rate of receptor degradation. In contrast, the rate of AChR degradation was enhanced 4-fold in the presence of the antibodies while the monovalent antibody fragments (Fab) were without effect. Divalent antibodies induced formation of large clusters on the surface of the muscle cultures within 2 h of incubation at 37°C. Monovalent antibody fragments and Con A had no effect on receptor distribution. It is suggested that receptor aggregation and turnover can be modulated by specific ligands acting at the cell surface.