INDUCTION OF ACETYLCHOLINE-RECEPTOR CLUSTER FORMATION BY LOCAL APPLICATION OF GROWTH-FACTORS IN CULTURED XENOPUS MUSCLE-CELLS

A survey of several growth factors was carried out to determine their effect on the formation of acetylcholine receptor (AChR) clusters in c ultured Xenopus muscle cells. Factors were locally applied via polysty rene beads and AChR clustering at bead-muscle contacts was assessed. A mong the factors tested, basic fibroblast growth factor, insulin and i nsulin-like growth factor-I, as well as several polycations, were foun d to be effective in inducing AChR clusters. The action of these molec ules appears to be mediated by tyrosine kinase receptors, since it can be blocked by a tyrosine kinase inhibitor. These results suggest that local ligand-mediated tyrosine phosphorylation is involved in the for mation of AChR clusters.