Parvez Suhel, Beck Andreas, Peinelt Christine, Soboloff Jonathan, Lis Annette, Monteilh-Zoller Mahealani, Gill Donald L, Fleig Andrea, Penner Reinhold
Center for Biomedical Research and John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96813, USA.
FASEB J. 2008 Mar;22(3):752-61. doi: 10.1096/fj.07-9449com. Epub 2007 Sep 28.
STIM1 and CRACM1 (or Orai1) are essential molecular components mediating store-operated Ca2+ entry (SOCE) and Ca2+ release-activated Ca2+ (CRAC) currents. Although STIM1 acts as a luminal Ca2+ sensor in the endoplasmic reticulum (ER), the function of STIM2 remains unclear. Here we reveal that STIM2 has two distinct modes of activating CRAC channels: a store-operated mode that is activated through depletion of ER Ca2+ stores by inositol 1,4,5-trisphosphate (InsP3) and store-independent activation that is mediated by cell dialysis during whole-cell perfusion. Both modes are regulated by calmodulin (CaM). The store-operated mode is transient in intact cells, possibly reflecting recruitment of CaM, whereas loss of CaM in perfused cells accounts for the persistence of the store-independent mode. The inhibition by CaM can be reversed by 2-aminoethoxydiphenyl borate (2-APB), resulting in rapid, store-independent activation of CRAC channels. The aminoglycoside antibiotic G418 is a highly specific and potent inhibitor of STIM2-dependent CRAC channel activation. The results reveal a novel bimodal control of CRAC channels by STIM2, the store dependence and CaM regulation, which indicates that the STIM2/CRACM1 complex may be under the control of both luminal and cytoplasmic Ca2+ levels.
基质相互作用分子1（STIM1）和钙释放激活钙通道蛋白1（CRACM1，即Orai1）是介导钙库操纵性钙内流（SOCE）和钙释放激活钙（CRAC）电流的关键分子成分。尽管STIM1在内质网（ER）中作为管腔钙传感器发挥作用，但STIM2的功能仍不清楚。在此我们揭示，STIM2具有两种激活CRAC通道的不同模式：一种是通过肌醇1,4,5-三磷酸（InsP3）消耗ER钙库而激活的钙库操纵模式，以及在全细胞灌流期间由细胞透析介导的不依赖钙库的激活模式。这两种模式均受钙调蛋白（CaM）调节。在完整细胞中，钙库操纵模式是短暂的，这可能反映了CaM的募集，而在灌流细胞中CaM的缺失则导致了不依赖钙库模式的持续存在。CaM的抑制作用可被2-氨基乙氧基二苯硼酸盐（2-APB）逆转，从而导致CRAC通道迅速发生不依赖钙库的激活。氨基糖苷类抗生素G418是STIM2依赖性CRAC通道激活的一种高度特异性和强效抑制剂。这些结果揭示了STIM2对CRAC通道的一种新型双峰控制，即对钙库的依赖性和CaM调节，这表明STIM2/CRACM1复合物可能受管腔和细胞质钙水平的共同控制。
