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      STIM is a Ca2+ sensor essential for Ca2+-store-depletion-triggered Ca2+ influx.

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          Abstract

          Ca(2+) signaling in nonexcitable cells is typically initiated by receptor-triggered production of inositol-1,4,5-trisphosphate and the release of Ca(2+) from intracellular stores. An elusive signaling process senses the Ca(2+) store depletion and triggers the opening of plasma membrane Ca(2+) channels. The resulting sustained Ca(2+) signals are required for many physiological responses, such as T cell activation and differentiation. Here, we monitored receptor-triggered Ca(2+) signals in cells transfected with siRNAs against 2,304 human signaling proteins, and we identified two proteins required for Ca(2+)-store-depletion-mediated Ca(2+) influx, STIM1 and STIM2. These proteins have a single transmembrane region with a putative Ca(2+) binding domain in the lumen of the endoplasmic reticulum. Ca(2+) store depletion led to a rapid translocation of STIM1 into puncta that accumulated near the plasma membrane. Introducing a point mutation in the STIM1 Ca(2+) binding domain resulted in prelocalization of the protein in puncta, and this mutant failed to respond to store depletion. Our study suggests that STIM proteins function as Ca(2+) store sensors in the signaling pathway connecting Ca(2+) store depletion to Ca(2+) influx.

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          Author and article information

          Journal
          Curr Biol
          Current biology : CB
          Elsevier BV
          0960-9822
          0960-9822
          Jul 12 2005
          : 15
          : 13
          Affiliations
          [1 ] Department of Molecular Pharmacology, Stanford University Medical School, California 94305, USA.
          Article
          S0960-9822(05)00570-1 NIHMS180879
          10.1016/j.cub.2005.05.055
          3186072
          16005298
          f07f54f8-b5b1-468c-840b-0c3da0918bd9
          History

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