Large store-operated calcium selective currents due to co-expression of Orai1 or Orai2 with the intracellular calcium sensor, Stim1
Large store-operated calcium selective currents due to co-expression of Orai1 or Orai2 with the intracellular calcium sensor, Stim1
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DOI：
10.1074/jbc.m604589200
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发表时间：
2006-08-25
影响因子：
4.8
通讯作者：
Putney, James W., Jr.
中科院分区：
文献类型：
--
作者：
Mercer, Jason C.;DeHaven, Wayne I.;Putney, James W., Jr.
钙离子选择性通道的分子本质仍然是一个谜，这主要是因为仍然不能令人信服地证明已知基因的外源表达导致的钙选择性通道电流。最近的研究表明，STIM1和Orai1这两种蛋白质在钙离子跨膜转运过程中起着重要的作用。然而，这些蛋白质本身的瞬时过表达导致商店操作的进入很少或没有增加。在这里，我们展示了这两种介体之间的戏剧性协同作用；将STIM1和Orai1共同转染HEK293细胞，可以使钙离子进入和钙离子选择性电流增加约20倍。这表明，这两种蛋白都限制了钙离子选择性储存操作的钙离子进入的信号和渗透机制。Orai1有三个哺乳动物同源物，在表达实验中，它们都产生或增加了商店操作的钙离子进入，其效果顺序为Orai1&>Orai2&>Orai3。STIM1显然是通过作为内质网中的钙感受器启动信号传递过程的。这导致STIM1在细胞内重排，并向质膜迁移，以某种方式调节位于质膜中的Orai1。然而，我们证明STIM1不结合在表膜上，因此可能在质膜和细胞内含有STIM1的细胞器之间紧密结合的位置调节或与Orai1相互作用。
The molecular nature of store-operated Ca2+-selective channels has remained an enigma, due largely to the continued inability to convincingly demonstrate Ca2+-selective store-operated currents resulting from exogenous expression of known genes. Recent findings have implicated two proteins, Stim1 and Orai1, as having essential roles in store-operated Ca2+ entry across the plasma membrane. However, transient overexpression of these proteins on their own results in little or no increase in store-operated entry. Here we demonstrate dramatic synergism between these two mediators; co-transfection of HEK293 cells with Stim1 and Orai1 results in an approximate 20-fold increase in store-operated Ca2+ entry and Ca2+-selective current. This demonstrates that these two proteins are limiting for both the signaling and permeation mechanisms for Ca2+-selective store-operated Ca2+ entry. There are three mammalian homologs of Orai1, and in expression experiments they all produced or augmented store-operated Ca2+ entry with efficacies in the order Orai1 > Orai2 > Orai3. Stim1 apparently initiates the signaling process by acting as a Ca2+ sensor in the endoplasmic reticulum. This results in rearrangement of Stim1 within the cell and migration toward the plasma membrane to regulate in some manner Orai1 located in the plasma membrane. However, we demonstrate that Stim1 does not incorporate in the surface membrane, and thus likely regulates or interacts with Orai1 at sites of close apposition between the plasma membrane and an intracellular Stim1-containing organelle.