Yuan Joseph P, Zeng Weizhong, Dorwart Michael R, Choi Young-Jin, Worley Paul F, Muallem Shmuel
Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Nat Cell Biol. 2009 Mar;11(3):337-43. doi: 10.1038/ncb1842. Epub 2009 Feb 1.
Influx of Ca(2+) through store-operated Ca(2+) channels (SOCs) is a central component of receptor-evoked Ca(2+) signals. Orai channels are SOCs that are gated by STIM1, a Ca(2+) sensor located in the ER but how it gates and regulates the Orai channels is unknown. Here, we report the molecular basis for gating of Orais by STIM1. All Orai channels are fully activated by the conserved STIM1 amino acid fragment 344-442, which we termed SOAR (the STIM1 Orai activating region). SOAR acts in combination with STIM1 (450-485) to regulate the strength of interaction with Orai1. Activation of Orai1 by SOAR recapitulates all the kinetic properties of Orai1 activation by STIM1. However, mutations of STIM1 within SOAR prevent activation of Orai1 but not co-clustering of STIM1 and Orai1 in response to Ca(2+) store depletion, indicating that STIM1-Orai1 co-clustering is not sufficient for Orai1 activation. An intact carboxy terminus alpha-helicial region of Orai is required for activation by SOAR. Deleting most of the Orai1 amino terminus impaired Orai1 activation by STIM1, but Orai1(Delta1-73) interacted with and was fully activated by SOAR. Accordingly, the characteristic inward rectification of Orai is mediated by an interaction between the polybasic STIM1 (672-685) and a Pro-rich region in the N terminus of Orai1. Hence, the essential properties of Orai1 function can be rationalized by interactions with discrete regions of STIM1.
通过储存操纵性钙通道（SOCs）的Ca(2+)内流是受体诱发的Ca(2+)信号的核心组成部分。Orai通道是由内质网中的Ca(2+)传感器STIM1门控的SOCs，但STIM1如何门控和调节Orai通道尚不清楚。在此，我们报告了STIM1门控Orai通道的分子基础。所有Orai通道都被保守的STIM1氨基酸片段344 - 442完全激活，我们将其称为SOAR（STIM1 Orai激活区域）。SOAR与STIM1（450 - 485）共同作用以调节与Orai1相互作用的强度。SOAR对Orai1的激活概括了STIM1对Orai1激活的所有动力学特性。然而，SOAR内的STIM1突变阻止了Orai1的激活，但不影响STIM1和Orai1在Ca(2+)储存耗竭时的共聚集，这表明STIM1 - Orai1共聚集不足以激活Orai1。Orai完整的羧基末端α螺旋区域是SOAR激活所必需的。删除大部分Orai1氨基末端会损害STIM1对Orai1的激活，但Orai1(Delta1 - 73)与SOAR相互作用并被其完全激活。因此，Orai的特征性内向整流是由多碱性的STIM1（672 - 685）与Orai1 N末端富含脯氨酸区域之间的相互作用介导的。因此，Orai1功能的基本特性可以通过与STIM1离散区域的相互作用来解释。
