alpha(5) subunit forms functional alpha(3)beta(4)alpha(5) nAChRs in transfected human cells

NACHRS heterologously expressed in human cells after transient transfection with alpha(3) beta(4) alpha(5) or alpha(3) beta(4) subunit cDNAs exhibited similar sensitivities to antagonists and comparable functional channel profiles. However, the sum of two Hill equations was required for best fitting the ACh dose-current response curves after co-expression of alpha(5), alpha(3) and beta(4) subunits. One component was comparable to that obtained in alpha(3) beta(4)-transfected cells, while the additional component, putatively attributed to an alpha(3) beta(4) alpha(5) nAChR population, showed a Hill coefficient >2 and a nine-fold greater half-maximal ACh concentration (EC50). These results suggest that the alpha(5) subunit participates in the assembly of alpha(3) beta(4) alpha(5) nAChRs complexes in human cells, adding a new member to the family of neuronal nicotinic receptors.