STOICHIOMETRY OF THE RECOMBINANT 910 NICOTINIC ACETYLCHOLINE RECEPTOR.

PLAZAS PV ; ELGOYHEN AB.

Congreso; Society for Neuroscience 35th Annual Meeting; 2005

The a9 and a10 nicotinic cholinergic subunits assemble to form the receptor that mediates synaptic transmission between efferent olivocochlear fibers and hair cells of the cochlea, one of the few verified examples of postsynaptic function for a non-muscle nicotinic acetylcholine receptor (nAChR). When co-expressed in Xenopus oocytes, a9 and a10 subunits form functional receptors the stoichiometry of which remains unknown. We probed the stoichiometry of the a9a10 nAChR by site-directed mutagenesis of a conserved valine (V13’) to threonine, in the second transmembrane domain of the rat a9 and a10 subunits. Co-expression of wild type and mutant subunits of each class (e.g. a9 and a9V13´T), along with their wild type counterparts (e.g. a10), in Xenopus oocytes resulted in mixed populations of receptors with distinct acetylcholine sensitivities. This is consistent with the interpretation that the V13’T mutation increased the ACh sensitivity in proportion to the number of incorporated mutant subunits. The apparent number of incorporated mutant subunits for each class could then be determined from the number of components comprising the compound acetylcholine dose-response relationships. Our results suggest that the recombinant a9a10 nAChR is a pentamer composed of two a9 and three a10 subunits. Supported by ANPCyT, NOHR and HHMI.