Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center , Albuquerque, New Mexico.
Am J Physiol Cell Physiol. 2018 Feb 1;314(2):C166-C176. doi: 10.1152/ajpcell.00159.2017. Epub 2017 Oct 25.
Increases in pulmonary arterial smooth muscle cell (PASMC) intracellular Ca levels and enhanced RhoA/Rho kinase-dependent Ca sensitization are key determinants of PASMC contraction, migration, and proliferation accompanying the development of hypoxic pulmonary hypertension. We previously showed that acid-sensing ion channel 1a (ASIC1a)-mediated Ca entry in PASMC is an important constituent of the active vasoconstriction, vascular remodeling, and right ventricular hypertrophy associated with hypoxic pulmonary hypertension. However, the enhanced ASIC1a-mediated store-operated Ca entry in PASMC from pulmonary hypertensive animals is not dependent on an increase in ASIC1a protein expression, suggesting that chronic hypoxia (CH) stimulates ASIC1a function through other regulatory mechanism(s). RhoA is involved in ion channel trafficking, and levels of activated RhoA are increased following CH. Therefore, we hypothesize that activation of RhoA following CH increases ASIC1a-mediated Ca entry by promoting ASIC1a plasma membrane localization. Consistent with our hypothesis, we found greater plasma membrane localization of ASIC1a following CH. Inhibition of RhoA decreased ASIC1a plasma membrane expression and largely diminished ASIC1a-mediated Ca influx, whereas activation of RhoA had the opposite effect. A proximity ligation assay revealed that ASIC1a and RhoA colocalize in PASMC and that the activation state of RhoA modulates this interaction. Together, our findings show a novel interaction between RhoA and ASIC1a, such that activation of RhoA in PASMC, both pharmacologically and via CH, promotes ASIC1a plasma membrane localization and Ca entry. In addition to enhanced RhoA-mediated Ca sensitization following CH, RhoA can also activate a Ca signal by facilitating ASIC1a plasma membrane localization and Ca influx in pulmonary hypertension.
肺动脉平滑肌细胞（PASMC）细胞内 Ca 水平的增加和 RhoA/Rho 激酶依赖性 Ca 敏感性的增强是 PASMC 收缩、迁移和增殖的关键决定因素，这些变化伴随着低氧性肺动脉高压的发展。我们之前的研究表明，酸敏感离子通道 1a（ASIC1a）介导的 PASMC 内 Ca 内流是与低氧性肺动脉高压相关的主动血管收缩、血管重构和右心室肥厚的重要组成部分。然而，肺动脉高压动物的 PASMC 中增强的 ASIC1a 介导的储存操纵的 Ca 内流并不依赖于 ASIC1a 蛋白表达的增加，这表明慢性低氧（CH）通过其他调节机制刺激 ASIC1a 功能。RhoA 参与离子通道运输，CH 后激活的 RhoA 水平增加。因此，我们假设 CH 后 RhoA 的激活通过促进 ASIC1a 质膜定位来增加 ASIC1a 介导的 Ca 内流。与我们的假设一致，我们发现 CH 后 ASIC1a 更多地定位于质膜。RhoA 的抑制减少了 ASIC1a 的质膜表达，并在很大程度上减少了 ASIC1a 介导的 Ca 内流，而 RhoA 的激活则产生相反的效果。接近连接测定显示，ASIC1a 和 RhoA 在 PASMC 中共定位，并且 RhoA 的激活状态调节这种相互作用。总之，我们的研究结果显示了 RhoA 和 ASIC1a 之间的一种新的相互作用，即通过药理学和 CH 激活 PASMC 中的 RhoA 促进 ASIC1a 的质膜定位和 Ca 内流。除了 CH 后增强的 RhoA 介导的 Ca 敏感性外，RhoA 还可以通过促进 ASIC1a 质膜定位和 Ca 内流来激活肺动脉高压中的 Ca 信号。
