Calcium Release - Activated Calcium Current Icrac

典型的储存操作的钙内流途径ICRAC(“钙释放激活的钙电流”)最初是在19921由彭纳教授实验室发现的。从那时起，这个实验室和其他实验室已经获得了关于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难以捉摸。直到最近的一项重要发现才证实，一种名为基质相互作用分子(STIM1)的蛋白质，作为存储钙含量的传感器，是功能存储操作的钙内流所必需的。这一令人兴奋的发现之后，我们的小组5和Orai1通过来自Rao和Lewis实验室的独立研究鉴定了另一种存储操作的钙内流所必需的蛋白质，称为CRAC调制器1(CRACM1)。通过RNAi抑制该蛋白可以取消CRAC通道的活性，一些严重联合免疫缺陷(SCID)患者的淋巴细胞中CRACM1的点突变也是如此。STIM1和CRACM1的联合过表达极大地放大了存储操作电流，这些电流具有ICRAC 7的最具决定性的特征。来自三个实验室(Cahalan、Rao和我们的团队)的工作发现，CRACM1的跨膜区和环区中的氨基酸影响离子选择性，证明CRACM1是CRAC通道的一个成孔亚基。我的数据显示，CRACM1同源物CRACM2和CRACM38也形成了具有不同性质的商店运营渠道。我的建议集中在CRACM1及其同系物上，作为一组具有不同功能特性的蛋白质，它们介导着商店操作的钙离子进入。我提出了生物物理、分子和功能的方法来研究这些蛋白质的结构和机制方面，以及它们在存储操作的钙离子进入中的作用。

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.