TASK1 (K 2P 3.1) K + channel inhibition by endothelin‐1 is mediated through Rho kinase‐dependent phosphorylation

BACKGROUND AND PURPOSE TASK1 (K 2P 3.1) two‐pore‐domain K + channels contribute substantially to the resting membrane potential in human pulmonary artery smooth muscle cells (hPASMC), modulating vascular tone and diameter. The endothelin‐1 (ET‐1) pathway mediates vasoconstriction and is an established target of pulmonary arterial hypertension (PAH) therapy. ET‐1‐mediated inhibition of TASK1 currents in hPASMC is implicated in the pathophysiology of PAH. This study was designed to elucidate molecular mechanisms underlying inhibition of TASK1 channels by ET‐1. EXPERIMENTAL APPROACH Two‐electrode voltage clamp and whole‐cell patch clamp electrophysiology was used to record TASK1 currents from hPASMC and Xenopus oocytes. KEY RESULTS ET‐1 inhibited TASK1‐mediated I KN currents in hPASMC, an effect attenuated by Rho kinase inhibition with Y‐27632. In Xenopus oocytes, TASK1 current reduction by ET‐1 was mediated by endothelin receptors ET A (IC 50 = 0.08 nM) and ET B (IC 50 = 0.23 nM) via Rho kinase signalling. TASK1 channels contain two putative Rho kinase phosphorylation sites, Ser 336 and Ser 393 . Mutation of Ser 393 rendered TASK1 channels insensitive to ET A ‐ or ET B ‐mediated current inhibition. In contrast, removal of Ser 336 selectively attenuated ET A ‐dependent TASK1 regulation without affecting the ET B pathway. CONCLUSIONS AND IMPLICATIONS ET‐1 regulated vascular TASK1 currents through ET A and ET B receptors mediated by downstream activation of Rho kinase and direct channel phosphorylation. The Rho kinase pathway in PASMC may provide a more specific therapeutic target in pulmonary arterial hypertension treatment.