Identification Of N-Terminal Extracellular Domain Determinants In Nicotinic Acetylcholine Receptor (Nachr) Î±6 Subunits That Influence Effects Of Wild-Type Or Mutant Î²3 Subunits On Function Of Î±6Î²2*- Or Î±6Î²4*-Nachr
Despite the apparent function of naturally expressed mammalian Î±6*-nicotinic acetylcholine receptors (Î±6*-nAChR; where*indicates the known or possible presence of additional subunits), their functional and heterologous expression has been difficult. Here, we report that coexpression with wild-type Î²3 subunits abolishes the small amount of function typically seen for all-human or all-mouse Î±6Î²4*-nAChR expressed in Xenopus oocytes. However, levels of function and agonist potencies are markedly increased, and there is atropine-sensitive blockade of spontaneous channel opening upon coexpression of Î±6 and Î²4 subunits with mutant Î²3 subunits harboring valine-to-serine mutations at 9â€²- or 13â€²-positions. There is no function when Î±6 and Î²2 subunits are expressed alone or in the presence of wild-type or mutant Î²3 subunits. Interestingly, hybrid nAChR containing mouse Î±6 and human (h) Î²4 subunits have function potentiated rather than suppressed by coexpression with wild-type hÎ²3 subunits and potentiated further upon coexpression with hÎ²3 V9,S subunits. Studies using nAChR chimeric mouse/human Î±6 subunits indicated that residues involved in effects seen with hybrid nAChR are located in the Î±6 subunit N-terminal domain. More specifically, nAChR hÎ±6 subunit residues Asn-143 and Met-145 are important for dominant-negative effects of nAChR hÎ²3 subunits on hÎ±6hÎ²4-nAChR function. Asn-143 and additional residues in the N-terminal domain of nAChR hÎ±6 subunits are involved in the gain-of-function effects of nAChR hÎ²3 V9,S subunits on Î±6Î²2*-nAChR function. These studies illuminate the structural bases for effects of Î²3 subunits on Î±6*-nAChR function and suggest that unique subunit interfaces involving the complementary rather than the primary face of Î±6 subunits are involved. Â© 2011 by The American Society for Biochemistry and Molecular Biology, Inc.
Journal of Biological Chemistry
Digital Object Identifier (DOI)
Dash, Bhagirathi; Bhakta, Minoti; Chang, Yongchang; and Lukas, Ronald J., "Identification Of N-Terminal Extracellular Domain Determinants In Nicotinic Acetylcholine Receptor (Nachr) Î±6 Subunits That Influence Effects Of Wild-Type Or Mutant Î²3 Subunits On Function Of Î±6Î²2*- Or Î±6Î²4*-Nachr" (2011). Neurobiology. 231.