REGULATION OF A SODIUM CHANNEL-ASSOCIATED G-PROTEIN BY ALDOSTERONE

The action of aldosterone to increase apical membrane permeability in responsive epithelia is thought to be due to activation of sodium chan nels. This channel is regulated, in part, by G-proteins, but it is not known if this mechanism is regulated by aldosterone. We report that a ldosterone stimulates the expression of the 41-kDa alpha(i3) subunit o f the heterotrimeric GTP-binding proteins in A-6 cells. Both mRNA and the total amount of this protein are increased by aldosterone. The G-p rotein is palmitoylated in response to the steroid, and the newly synt hesized subunit is found to co-localize with the sodium channel. Aldos terone stimulation of sodium transport is significantly inhibited by i nhibition of palmitoylation. These results suggest that aldosterone re gulates sodium channel activity in epithelia through stimulation of th e expression and post-translational targeting of a channel regulatory G-protein subunit.