Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.
Br J Pharmacol. 2012 Mar;165(5):1467-75. doi: 10.1111/j.1476-5381.2011.01626.x.
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.
Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record TASK1 currents from hPASMC and Xenopus oocytes.
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.
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.
TASK1（K（2P）3.1）双孔钾通道在人肺动脉平滑肌细胞（hPASMC）中对静息膜电位有重要贡献，调节血管张力和直径。内皮素-1（ET-1）途径介导血管收缩，是肺动脉高压（PAH）治疗的既定靶点。ET-1 介导的 hPASMC 中 TASK1 电流的抑制与 PAH 的病理生理学有关。本研究旨在阐明 ET-1 抑制 TASK1 通道的分子机制。
使用双电极电压钳和全细胞膜片钳电生理学技术记录 hPASMC 和非洲爪蟾卵母细胞中的 TASK1 电流。
ET-1 抑制 hPASMC 中的 TASK1 介导的 I（KN）电流，该效应可被 Rho 激酶抑制剂 Y-27632 减弱。在非洲爪蟾卵母细胞中，ET-1 通过 Rho 激酶信号转导抑制 TASK1 电流，这是由内皮素受体 ET（A）（IC（50）= 0.08 nM）和 ET（B）（IC（50）= 0.23 nM）介导的。TASK1 通道包含两个假定的 Rho 激酶磷酸化位点，Ser（336）和 Ser（393）。Ser（393）突变使 TASK1 通道对 ET（A）或 ET（B）介导的电流抑制不敏感。相反，Ser（336）的去除选择性地减弱了 ET（A）依赖性 TASK1 调节，而不影响 ET（B）途径。
ET-1 通过下游 Rho 激酶激活和直接通道磷酸化，通过 ET（A）和 ET（B）受体调节血管 TASK1 电流。PASMC 中的 Rho 激酶途径可能为肺动脉高压治疗提供更特异的治疗靶点。
