Calcium Release - Activated Calcium Current Icrac

典型的储存操作钙内流途径ICRAC（即“钙释放激活钙电流”）最初是在1992年由Penner教授实验室确定的。从那时起，本实验室和其他实验室获得了关于ICRAC生理和临床重要性的大量信息，然而，CRAC通道的分子组成仍然是难以捉摸的2。直到最近才有一个重要的发现，一种被称为基质相互作用分子（STIM1）的蛋白质，作为存储Ca2+含量的传感器，是功能性存储操作的Ca2+流入所必需的。这一令人兴奋的发现之后，我们的研究小组又发现了另一种储存性钙进入的必需蛋白质，称为CRAC调节剂1 (CRACM1)， Rao和Lewis实验室的一项独立研究发现了Orai1。RNAi抑制该蛋白可消除CRAC通道活性，一些患有严重联合免疫缺陷（SCID）的患者淋巴细胞中CRACM1点突变也是如此。STIM1和CRACM1的联合过表达极大地放大了储存操作电流，这些电流具有ICRAC 7最明显的特征。来自三个实验室（Cahalan， Rao和我们的团队）的工作确定了CRACM1跨膜和环结构域中影响离子选择性的氨基酸，证明CRACM1代表了CRAC通道的一个成孔亚基。我的数据显示，CRACM1同源物CRACM2和CRACM38也形成具有不同属性的存储操作通道。我的建议侧重于CRACM1及其同源物，作为一组介导具有不同功能特性的存储操作Ca2+进入的蛋白质。我提出生物物理，分子和功能方法来研究这些蛋白质的结构和机制方面及其在储存操作的Ca2+进入中的作用。

The prototypical store-operated calcium-influx pathway ICRAC (for “calcium-release activated calcium current”) originally was identified in Prof. Penner laboratory in 19921. Since then this lab, and others have acquired substantial information about ICRAC’s physiological and clinical importance, however, the molecular composition of the CRAC channels has remained elusive2. Only recently did a significant finding establish that a protein called stromal interaction molecule (STIM1), acting as the sensor for store Ca2+ content, is required for functional store-operated Ca2+ influx3, 4. This exciting finding was followed by the identification of another essential protein for store-operated calcium entry called CRAC Modulator 1 (CRACM1) by our group5 and Orai1 by an independent study from the Rao and Lewis laboratories6. Suppression of this protein by RNAi abolishes CRAC channel activity, as does a point mutation of CRACM1 in lymphocytes of some patients suffering from Severe Combined Immune Deficiency (SCID). The combined overexpression of STIM1 and CRACM1 greatly amplifies store-operated currents and these currents possess the most defining characteristics of ICRAC 7. Work from three laboratories (Cahalan, Rao, and our group) identified amino acids in transmembrane and loop domains of CRACM1 that affect ion selectivity, demonstrating that CRACM1 represents a pore-forming subunit of the CRAC channel. My data show that the CRACM1 homologs CRACM2 and CRACM38 also form store-operated channels with distinct properties. My proposal focuses on CRACM1 and its homologs, as a group of proteins that mediate store-operated Ca2+ entry with distinct functional properties. I propose biophysical, molecular and functional approaches to investigate the structural and mechanistic aspects of these proteins and their roles in store-operated Ca2+ entry.