Electrophysiological and biochemical evidence that DEG/ENaC cation channels are composed of nine subunits

Abstract

Members of the DEG/ENaC protein family form ion channels with diverse functions. DEG/ENaC subunits associate as hetero- and homomultimers to generate channels; however the stoichiometry of these complexes is unknown. To determine the subunit stoichiometry of the human epithelial Na+ channel (hENaC), we expressed the three wild-type hENaC subunits (α, β, and γ) with subunits containing mutations that alter channel inhibition by methanethiosulfonates. The data indicate that hENaC contains three α, three β, and three γ subunits. Sucrose gradient sedimentation of αhENaC translated in vitro, as well as α-, β-, and γhENaC coexpressed in cells, was consistent with complexes containing nine subunits. FaNaCh and BNC1, two related DEG/ENaC channels, produced complexes of similar mass. Our results suggest a novel nine-subunit stoichiometry for the DEG/ENaC family of ion channels.