Expression and functional characterisation of a human chimeric nicotinic receptor with α6β4 properties

Abstract Despite being cloned several years ago, the expression of functional nicotinic acetylcholine receptors containing the human α6 subunit in recombinant mammalian cell lines has yet to be demonstrated. The resulting lack of selective ligands has hindered the evaluation of the role of α6-containing nicotinic receptors. We report that functional channels were recorded following co-transfection of human embryonic kidney (HEK-293) cells with a chimeric α6/α4 subunit and the β4 nicotinic receptor subunit. They displayed an agonist rank order potency of epibatidine≫1,1-dimethyl-4-phenylpiperazinium (DMPP)≥cytisine>acetylcholine>nicotine measured in a fluorescent imaging plate reader assay. Nicotine, cytisine, DMPP and epibatidine displayed partial agonist properties whilst α-conotoxin MII and methyllycaconitine blocked the functional responses elicited by acetylcholine stimulation. Co-transfection of the α6/α4 chimera with the β2 nicotinic receptor subunit did not result in functional receptors. The human α6/α4β4 chimeric nicotinic receptor expressed in HEK-293 cells may provide a valuable tool for the generation of subtype specific ligands.