Jardín Isaac, López José J, Redondo Pedro C, Salido Ginés M, Rosado Juan A
Department of Physiology (Cellular Physiology Research Group), University of Extremadura, 10071 Cáceres, Spain.
Biochim Biophys Acta. 2009 Oct;1793(10):1614-22. doi: 10.1016/j.bbamcr.2009.07.003. Epub 2009 Jul 23.
Store-operated Ca(2+) entry (SOCE) is a major mechanism for Ca(2+) influx in platelets and other cells activated by a reduction in Ca(2+) concentration in the intracellular stores. SOCE has been reported to be regulated by extracellular Ca(2+), although the underlying mechanism remains unclear. Here we have examined the involvement of plasma membrane-located STIM1 (PM-STIM1) in the regulation of SOCE by extracellular Ca(2+). Treatment of platelets with the SERCA inhibitor thapsigargin (TG) induced Mn(2+) entry, which was inhibited by extracellular Ca(2+) in a concentration-dependent manner. Incubation of platelets with a specific antibody, which recognizes the extracellular amino acid sequence 25-139 of PM-STIM1 that contains the Ca(2+)-binding domain, prevented the inactivation of Ca(2+) entry induced by extracellular Ca(2+). TG induced translocation of STIM1 to the plasma membrane (PM), an event that was found to be Ca(2+)-dependent. In addition, TG stimulated association of PM-STIM1 with Orai1, an event that was not prevented by stabilization of the membrane cytoskeleton using jasplakinolide. These findings suggest that PM-STIM1 is important for the inactivation of SOCE by extracellular Ca(2+), an event that is likely to be mediated by interaction with Orai1.
钙库操纵性钙内流（SOCE）是血小板及其他因细胞内钙库中钙浓度降低而被激活的细胞中钙内流的主要机制。据报道，SOCE受细胞外钙调节，但其潜在机制仍不清楚。在此，我们研究了质膜定位的基质相互作用分子1（PM-STIM1）在细胞外钙对SOCE调节中的作用。用肌浆网Ca2+-ATP酶抑制剂毒胡萝卜素（TG）处理血小板可诱导锰离子内流，而细胞外钙以浓度依赖的方式抑制这种内流。用识别包含钙结合结构域的PM-STIM1细胞外氨基酸序列25-139的特异性抗体孵育血小板，可阻止细胞外钙诱导的钙内流失活。TG诱导STIM1转位至质膜（PM），这一事件被发现是依赖钙的。此外，TG刺激PM-STIM1与Orai1结合，而使用茉莉酮酸酯稳定膜细胞骨架并不能阻止这一事件。这些发现表明，PM-STIM1对细胞外钙使SOCE失活很重要，这一事件可能是由与Orai1相互作用介导的。
