Regulation of Rho/ROCK signaling in airway smooth muscle by membrane potential and [Ca2+]i
Regulation of Rho/ROCK signaling in airway smooth muscle by membrane potential and [Ca2+]i
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DOI：
10.1152/ajplung.00134.2005
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发表时间：
2005-10-01
影响因子：
4.9
通讯作者：
Janssen, LJ
中科院分区：
文献类型：
--
作者：
Liu, CQ;Zuo, JM;Janssen, LJ
最近，我们已经表明，Rho和Rho活化激酶（ROCK）可能被高毫摩尔的KCl激活，而以前广泛认为KCl仅通过打开电压依赖性Ca2+通道起作用。在这项研究中，我们更详细地探讨了膜去极化、Ca2+电流和牛气管平滑肌Rho/ROCK激活之间的关系。Ca2+电流在膜电压大于-40 mV时开始激活，在0 mV以上激活最大；同时，这些细胞经历了时间和电压依赖的失活。通过KCl刺激使完整组织去极化，引起的收缩同样被硝苯地平或ROCK抑制剂Y-27632以非加性方式阻断。其他通过独立于G蛋白偶联受体的途径提高细胞内钙浓度（[Ca2+](i)）的药物，即serca泵抑制剂环吡唑酸和Ca2+离子载体A-23187，引起的收缩也在很大程度上被Y-27632减少。KCl以浓度依赖性的方式直接增加Rho和ROCK活性，这与KCl对音调和[Ca2+]的影响密切相关(i)，以及在0-120 mM KCl诱发的电压范围内测量的电压依赖性Ca2+电流。通过使用各种药物抑制剂，我们排除了Ca2+/钙调素依赖性CaM激酶II、蛋白激酶C和蛋白激酶A在介导kc1刺激的音调和Rho/ROCK活性变化中的作用。总之，Rho被[Ca2+](i)的升高激活（尽管这种Ca2+依赖性的信号转导途径尚不清楚），也可能被膜去极化本身激活。
Recently, we have shown that Rho and Rho-activated kinase (ROCK) may become activated by high-millimolar KCl, which had previously been widely assumed to act solely through opening of voltage-dependent Ca2+ channels. In this study, we explored in more detail the relationship between membrane depolarization, Ca2+ currents, and activation of Rho/ROCK in bovine tracheal smooth muscle. Ca2+ currents began to activate at membrane voltages more positive than -40 mV and were maximally activated above 0 mV; at the same time, these underwent time- and voltage-dependent inactivation. Depolarizing intact tissues by KCl challenge evoked contractions that were blocked equally, and in a nonadditive fashion, by nifedipine or by the ROCK inhibitor Y-27632. Other agents that elevate intracellular calcium concentration ([Ca2+](i)) by pathways independent of G protein-coupled receptors, namely the SERCA-pump inhibitor cyclopiazonic acid and the Ca2+ ionophore A-23187, evoked contractions that were also largely reduced by Y-27632. KCl directly increased Rho and ROCK activities in a concentration-dependent fashion that paralleled closely the effect of KCl on tone and [Ca2+](i), as well as the voltage-dependent Ca2+ currents that were measured over the voltage ranges that are evoked by 0-120 mM KCl. Through the use of various pharmacological inhibitors, we ruled out roles for Ca2+/calmodulin-dependent CaM kinase II, protein kinase C, and protein kinase A in mediating the KC1-stimulated changes in tone and Rho/ROCK activities. In conclusion, Rho is activated by elevation of [Ca2+](i) (although the signal transduction pathway underlying this Ca2+ dependence is still unclear) and possibly also by membrane depolarization per se.