Department of Surgery, The Keenan Research Centre for Biomedical Science at St. Michael's Hospital, 209 Victoria Street, M5B 1T8, Toronto, ON, Canada.
Department of Physiology, Institute of Physiology, Charité - Universitaetsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
Cardiovasc Res. 2017 Jul 1;113(8):869-878. doi: 10.1093/cvr/cvx076.
Hypoxic pulmonary vasoconstriction (HPV) redistributes blood flow from poorly ventilated to better aerated areas in the lung, thereby optimizing ventilation-perfusion ratio (V/Q). Pulmonary artery smooth muscle cell (PASMC) contraction in response to hypoxia is triggered by Ca2+ influx via transient receptor potential canonical 6 (TRPC6) cation channels that have translocated to caveolae in the plasma membrane. Since phosphatase and tensin homolog (PTEN) was suggested to regulate TRPC6 in endothelial cells, we aimed to define its role in the hypoxic response of PASMCs and as a putative mediator of HPV.
In isolated perfused mouse lungs, smooth muscle specific PTEN deficiency attenuated pulmonary vasoconstriction in response to hypoxia but not to angiotensin II (Ang II). Analogously, siRNA-mediated knock down of PTEN in human PASMC inhibited the hypoxia-induced increase in cytosolic Ca2+ concentration ([Ca2+]i). Co-immunoprecipitation and proximity ligation assays revealed increased interaction of PTEN with TRPC6 in human PASMC and murine lungs in response to hypoxia. In hypoxic PASMC, both PTEN and TRPC6 translocated to caveolae, and this response was blocked by pharmacological inhibition of Rho-associated protein kinase (ROCK) which in parallel prevented PTEN-TRPC6 interaction, hypoxia-induced [Ca2+]i increase, and HPV in PASMC and murine lungs, respectively.
Our data indicate a novel interplay between ROCK and [Ca2+]i signalling in HPV via PTEN, in that ROCK mediates interaction of PTEN and TRPC6 which then conjointly translocate to caveolae allowing for Ca2+ influx into and subsequent contraction of PASMC.
低氧性肺血管收缩（HPV）将血流从通气不良的区域重新分配到通气良好的区域，从而优化通气-灌注比（V/Q）。肺动脉平滑肌细胞（PASMC）对缺氧的反应性收缩是由通过瞬时受体电位经典型 6（TRPC6）阳离子通道的 Ca2+内流触发的，这些通道已转移到质膜中的小窝。由于磷酸酶和张力蛋白同源物（PTEN）被认为在内皮细胞中调节 TRPC6，因此我们旨在确定其在 PASMC 对低氧的反应中的作用以及作为 HPV 的潜在介质。
在分离的灌注小鼠肺中，平滑肌特异性 PTEN 缺乏减弱了对缺氧的肺血管收缩反应，但对血管紧张素 II（Ang II）无反应。类似地，siRNA 介导的人 PASMC 中 PTEN 的敲低抑制了缺氧诱导的细胞浆 Ca2+浓度增加([Ca2+]i)。共免疫沉淀和接近连接测定显示，PTEN 与 TRPC6 在人 PASMC 和低氧小鼠肺中的相互作用增加。在低氧性 PASMC 中，PTEN 和 TRPC6 均转移到小窝中，该反应被 Rho 相关蛋白激酶（ROCK）的药理学抑制阻断，该反应平行地阻止了 PTEN-TRPC6 相互作用、缺氧诱导的[Ca2+]i 增加以及 PASMC 和小鼠肺中的 HPV。
我们的数据表明，ROCK 和[Ca2+]i 信号在 HPV 中通过 PTEN 之间存在新的相互作用，ROCK 介导了 PTEN 和 TRPC6 的相互作用，然后共同转移到小窝中，允许 Ca2+内流入 PASMC 并随后收缩。
