The Gβ1 and Gβ3 Subunits Differentially Regulate Rat Vascular Kv7 Channels

Within the vasculature Kv7 channels are key regulators of basal tone and contribute to a variety of receptor mediated vasorelaxants. The Kv7.4 isoform, abundant within the vasculature, is key to these processes and was recently shown to have an obligatory requirement of G-protein beta gamma subunits for its voltage dependent activity. There is an increasing appreciation that with 5 G beta subunits and 12 G gamma subunits described in mammalian cells that different G beta(x)gamma(x) combinations can confer selectivity in G beta gamma effector stimulation. Therefore, we aimed to characterize the G beta subunit(s) which basally regulate Kv7.4 channels and native vascular Kv7 channels. In Chinese Hamster Ovary cells overexpressing Kv7.4 and different G beta x subunits only G beta 1, G beta 3, and G beta 5 enhanced Kv7.4 currents, increasing the activation kinetics and negatively shifting the voltage dependence of activation. In isolated rat renal artery myocytes, proximity ligation assay detected an interaction of Kv7.4 with G beta 1 and G beta 3 subunits, but not other isoforms. Morpholino directed knockdown of G beta 1 in rat renal arteries did not alter Kv7 dependent currents but reduced Kv7.4 protein expression. Knockdown of G beta 3 in rat renal arteries resulted in decreased basal K+ currents which were not sensitive to pharmacological inhibition of Kv7 channels. These studies implicate the G beta 1 subunit in the synthesis or stability of Kv7.4 proteins, whilst revealing that the G beta 3 isoform is responsible for the basal activity of Kv7 channels in native rat renal myocytes. These findings demonstrate that different G beta subunits have important individual roles in ion channel regulation.