Tolhurst Gwen, Carter Richard N, Amisten Stefan, Holdich Jon P, Erlinge David, Mahaut-Smith Martyn P
Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge CB23EG, UK.
Platelets. 2008 Jun;19(4):308-13. doi: 10.1080/09537100801935710.
Store-operated Ca2+ influx represents a major route by which cytosolic Ca2+ can be elevated during platelet activation, yet its molecular identity in this cell type remains highly controversial. Using quantitative RT-PCR analysis of candidate receptor-operated cation entry pathways in human platelets, we show a >30-fold higher expression of message for the recently discovered Orai1 store-operated Ca2+ channel, and also the store Ca2+ sensor STIM1, when compared to the non-selective cation channels TRPC1, TRPC6 and TRPM2. Orai1 and STIM1 gene transcripts were also detected at higher levels than TRPC1, TRPC6 and TRPM2 in primary murine megakaryocytes and human megakaryocytic cell lines. In direct electrophysiological recordings from murine megakaryocytes, Ca2+ ionophore-induced store depletion stimulated CRAC currents, which are known to require Orai1, and these overlapped with TRPC6-like currents following P2Y receptor activation. Together with recent transgenic studies, these data provide evidence for STIM1:Orai1 as a primary pathway for agonist-evoked Ca2+ influx in the platelet and megakaryocyte.
钙库操纵性钙离子内流是血小板激活过程中细胞溶质钙离子浓度升高的主要途径，然而其在这种细胞类型中的分子身份仍极具争议。通过对人血小板中候选受体操纵性阳离子内流途径进行定量逆转录聚合酶链反应分析，我们发现，与非选择性阳离子通道TRPC1、TRPC6和TRPM2相比，最近发现的Orai1钙库操纵性钙离子通道以及钙库钙离子传感器STIM1的信使核糖核酸表达量要高出30倍以上。在原代小鼠巨核细胞和人巨核细胞系中，Orai1和STIM1基因转录本的检测水平也高于TRPC1、TRPC6和TRPM2。在对小鼠巨核细胞进行的直接电生理记录中，钙离子载体诱导的钙库耗竭刺激了钙释放激活钙电流（CRAC电流），已知该电流需要Orai1，并且这些电流与P2Y受体激活后的TRPC6样电流重叠。结合最近的转基因研究，这些数据为STIM1:Orai1作为激动剂诱发血小板和巨核细胞钙离子内流的主要途径提供了证据。
