Calcium inhibition and calcium potentiation of Orai1, Orai2, and Orai3 calcium release-activated calcium channels
Calcium inhibition and calcium potentiation of Orai1, Orai2, and Orai3 calcium release-activated calcium channels
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DOI：
10.1074/jbc.m611374200
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发表时间：
2007-06-15
影响因子：
4.8
通讯作者：
Putney, James W., Jr.
中科院分区：
文献类型：
--
作者：
DeHaven, Wayne I.;Smyth, Jeremy T.;Putney, James W., Jr.
最近发现的Stim 1和奥赖蛋白分别揭示了内质网Ca 2+传感器和钙释放激活的钙（CRAC）通道的分子组成。在这项研究中，我们研究了CRAC通道功能的调节细胞外Ca 2+的主要组成的通道Orai 1，Orai 2，和Orai 3，通过共表达这些蛋白质与Stim 1，以及内源性通道HEK 293细胞。如前所述，Orai 1或Orai 2导致CRAC电流（I-crac）的大幅增加，但Orai 3未能产生任何可检测的Ca 2+选择性电流。然而，在表达Orai 3的HEK 293细胞中测量的钠电流的电流密度显著大于表达Stim 1的细胞。此外，在切换到二价游离外部溶液时，Orai 3电流比Orai 1或Orai 2稳定得多，表明Orai 3通道经历较低程度的去电位。此外，对于Orai 3，来自Ca 2+和Ba 2+或Mg 2+溶液的去电位之间的差异显著小于Orai 1或-2。尽管如此，通过Orai 1，Orai 2和Orai 3的Na+电流，以及HEK 293细胞中的内源性储存操纵的Na+电流，都被细胞外Ca 2+抑制，其半最大浓度类似于20 μ M。我们得出结论，Orai 1，-2，和-3通道被细胞外Ca 2+类似地抑制，这表明在选择性过滤器内对Ca 2+有类似的亲和力。Orai 3通道似乎与Orai 1和-2不同，对Ca 2+去增强过程有一定的抗性。
The recent discoveries of Stim1 and Orai proteins have shed light on the molecular makeup of both the endoplasmic reticulum Ca2+ sensor and the calcium release-activated calcium ( CRAC) channel, respectively. In this study, we investigated the regulation of CRAC channel function by extracellular Ca2+ for channels composed primarily of Orai1, Orai2, and Orai3, by coexpressing these proteins together with Stim1, as well as the endogenous channels in HEK293 cells. As reported previously, Orai1 or Orai2 resulted in a substantial increase in CRAC current ( I-crac), but Orai3 failed to produce any detectable Ca2+ selective currents. However, sodium currents measured in the Orai3-expressing HEK293 cells were significantly larger in current density than Stim1-expressing cells. Moreover, upon switching to divalent free external solutions, Orai3 currents were considerably more stable than Orai1 or Orai2, indicating that Orai3 channels undergo a lesser degree of depotentiation. Additionally, the difference between depotentiation from Ca2+ and Ba2+ or Mg2+ solutions was significantly less for Orai3 than for Orai1 or -2. Nonetheless, the Na+ currents through Orai1, Orai2, and Orai3, as well as the endogenous store-operated Na+ currents in HEK293 cells, were all inhibited by extracellular Ca2+ with a half-maximal concentration of similar to 20 mu M. We conclude that Orai1, -2, and -3 channels are similarly inhibited by extracellular Ca2+, indicating similar affinities for Ca2+ within the selectivity filter. Orai3 channels appeared to differ from Orai1 and -2 in being somewhat resistant to the process of Ca2+ depotentiation.