COEXPRESSION OF 2 DISTINCT MUSCLE ACETYLCHOLINE-RECEPTOR ALPHA-SUBUNITS DURING DEVELOPMENT

THE nicotinic acetylcholine receptor is a ligand-gated channel that mediates signalling at the vertebrate neuromuscular junction. It is a pentameric complex of four different subunits, assembled with a stoichiometry of α2βγΔMuscle-like α-subunits have been cloned from Torpedo, mouse, calf, rat, chicken, human and Xenopus, and only a single α-subunit complementary DNA from each species has been detected (reviewed in ref. 1). We report here the cloning and characterization of a second muscle α-subunit cDNA from Xenopus, and show that this and a previously reported Xenopus α-subunit cDNA2 are encoded by distinct genes. The novel α-subunit reported here is expressed uniquely in oocytes; but both types of a-subunit are coexpressed throughout muscle development. This latter observation indicates that the expression of these two α-subunits is different from a previously reported developmental 'su burnt-switch' mechanism used to generate channel diversity. © 1990 Nature Publishing Group.