TASK1 (K 2P3.1) K + channel inhibition by endothelin-1 is mediated through Rho kinase-dependent phosphorylation

Abstract

BACKGROUND AND PURPOSE TASK1 (K 2P3.1) 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. © 2011 The Authors. British Journal of Pharmacology.