Tekarli_2025_J.Biol.Chem__108182

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels. In mammals, there are 16 individual nAChR subunits allowing for numerous possible heteromeric compositions. nAChRs assembled from alpha7 or alpha9 subunits will form as homopentamers. In contrast, the structurally related alpha10 nAChR subunit has historically been thought to require alpha9 subunits for function. Recently, however, strychnine was shown to enable expression of human alpha10 nAChRs in Xenopus laevis oocytes or mammalian cells, prompting a re-examination of whether the human alpha10 subunit can self-assemble in the absence of strychnine. In the present study, acetylcholine-evoked ionic currents were obtained by co-expression of human alpha10 nAChR subunits with the transmembrane protein resistance to inhibitors of cholinesterase-3 (RIC-3) in Xenopus oocytes. Furthermore, creation of a gain-of-function reporter mutation, V13'T, in the second transmembrane domain demonstrated that alpha10 subunits can self-assemble in the presence or absence of RIC-3. The antagonist sensitivity of the homomeric alpha10 nAChR is distinct from that of the closely related alpha7 and alpha9alpha10 subtypes. alpha10 homomers were blocked by alpha-bungarotoxin but were insensitive to alpha-conotoxin [V11L;V16D]ArIB and RgIA-5474, which potently block alpha7 nAChRs and alpha9alpha10 nAChRs, respectively. These studies yield insight into the assembly of functional human alpha10 homomers and provide tools for the development of alpha10 -nAChR-selective ligands.