TRPC5 Is a Ca2+-activated Channel Functionally Coupled to Ca2+-selective Ion Channels
TRPC5 Is a Ca2+-activated Channel Functionally Coupled to Ca2+-selective Ion Channels
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DOI：
10.1074/jbc.m109.018192
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发表时间：
2009-12-04
影响因子：
4.8
通讯作者：
Cavalie, Adolfo
中科院分区：
文献类型：
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作者：
Gross, Stefan Alfred;Guzman, Gustavo Adolfo;Cavalie, Adolfo
TRPC5 形成非选择性阳离子通道。在这里，我们研究了内部Ca2+在激活人胚胎肾细胞中异源表达的鼠TRPC5中的作用。使用不同Ca2+浓度(Ca-i(2+))的细胞透析显示内部Ca2+对TRPC5通道的激活具有剂量依赖性，在负膜电位和正膜电位下EC50分别为635.1和358.2 nM。笼内Ca2+光解诱导的Ca-i(2+)逐步增加表明，TRPC5通道的Ca2+激活遵循快速指数时间过程，在Ca-i(2+)低于10 μM时，时间常数为8.6+/-0.2 ms，表明内部Ca2+的作用是TRPC5通道激活的主要机制。在高于 10 μM 的 Ca-i(2+) 处还观察到了第二个缓慢激活阶段，达到峰值时间为 1.4 +/- 0.1 s。为了支持 Ca2+ 激活机制，毒胡萝卜素诱导的 Ca2+ 从内部储存释放短暂激活了 TRPC5 通道，随后的 Ca2+ 进入产生了持续的 TRPC5 激活，这反过来又支持了持久的膜去极化。通过共表达 STIM1 和 ORAI1 或 L 型 Ca2+ 通道的 α C-1 和 beta(2) 亚基，我们发现 Ca2+ 通过钙释放激活钙通道或电压依赖性 Ca2+ 通道进入足以激活 TRPC5 通道。 Ca2+ 进入在 EGTA 的内部 Ca2+ 缓冲下激活 TRPC5 通道，但 BAPTA 则不然。我们的数据支持这样的假设：TRPC5 形成 Ca2+ 激活的阳离子通道，该通道通过质膜下方局部 Ca2+ 增加与 Ca2+ 选择性离子通道功能耦合。
TRPC5 forms non-selective cation channels. Here we studied the role of internal Ca2+ in the activation of murine TRPC5 heterologously expressed in human embryonic kidney cells. Cell dialysis with various Ca2+ concentrations (Ca-i(2+)) revealed a dose-dependent activation of TRPC5 channels by internal Ca2+ with EC50 of 635.1 and 358.2 nM at negative and positive membrane potentials, respectively. Stepwise increases of Ca-i(2+) induced by photolysis of caged Ca2+ showed that the Ca2+ activation of TRPC5 channels follows a rapid exponential time course with a time constant of 8.6 +/- 0.2 ms at Ca-i(2+) below 10 mu M, suggesting that the action of internal Ca2+ is a primary mechanism in the activation of TRPC5 channels. A second slow activation phase with a time to peak of 1.4 +/- 0.1 s was also observed at Ca-i(2+) above 10 mu M. In support of a Ca2+-activation mechanism, the thapsigargin-induced release of Ca2+ from internal stores activated TRPC5 channels transiently, and the subsequent Ca2+ entry produced a sustained TRPC5 activation, which in turn supported a long-lasting membrane depolarization. By co-expressing STIM1 plus ORAI1 or the alpha C-1 and beta(2) subunits of L-type Ca2+ channels, we found that Ca2+ entry through either calcium-release-activated-calcium or voltage-dependent Ca2+ channels is sufficient for TRPC5 channel activation. The Ca2+ entry activated TRPC5 channels under buffering of internal Ca2+ with EGTA but not with BAPTA. Our data support the hypothesis that TRPC5 forms Ca2+-activated cation channels that are functionally coupled to Ca2+-selective ion channels through local Ca2+ increases beneath the plasma membrane.