G-protein βγ subunits are positive regulators of Kv7.4 and native vascular Kv7 channel activity.

Abstract

Kv7.4 channels are a crucial determinant of arterial diameter both at rest and in response to endogenous vasodilators. However, nothing is known about the factors that ensure effective activity of these channels. We report that G-protein βγ subunits increase the amplitude and activation rate of whole-cell voltage-dependent K(+) currents sensitive to the Kv7 blocker linopirdine in HEK cells heterologously expressing Kv7.4, and in rat renal artery myocytes. In excised patch recordings, Gβγ subunits (2-250 ng /mL) enhanced the open probability of Kv7.4 channels without changing unitary conductance. Kv7 channel activity was also augmented by stimulation of G-protein-coupled receptors. Gallein, an inhibitor of Gβγ subunits, prevented these stimulatory effects. Moreover, gallein and two other structurally different Gβγ subunit inhibitors (GRK2i and a β-subunit antibody) abolished Kv7 channel currents in the absence of either Gβγ subunit enrichment or G-protein-coupled receptor stimulation. Proximity ligation assay revealed that Kv7.4 and Gβγ subunits colocalized in HEK cells and renal artery smooth muscle cells. Gallein disrupted this colocalization, contracted whole renal arteries to a similar degree as the Kv7 inhibitor linopirdine, and impaired isoproterenol-induced relaxations. Furthermore, mSIRK, which disassociates Gβγ subunits from α subunits without stimulating nucleotide exchange, relaxed precontracted arteries in a linopirdine-sensitive manner. These results reveal that Gβγ subunits are fundamental for Kv7.4 activation and crucial for vascular Kv7 channel activity, which has major consequences for the regulation of arterial tone.