Résumé :
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Cytosolic Ca2+ signals encoded by repetitive Ca2+ releases rely on two processes to refill Ca2+ stores: (i) Ca2+ re-uptake from the cytosol and (ii) activation of a Ca2+ influx via Store Operated Calcium Entry (SOCE). SOCE activation is, however, a slow process. It is delayed by approximately 1 minute following store depletion because STIM1, the Ca2+-sensor of the intracellular stores, must form clusters before being able to open Orai1, the plasma membrane Ca2+ channel. Here, we identified a new protein - STIM1L - which colocalizes with Orai1 Ca2+-channels and interacts with actin to form permanent clusters. This property allows the immediate activation of SOCE, a characteristic required for generating repetitive Ca2+ signals with frequencies within seconds such as those frequently observed in excitable cells. STIM1L is expressed in a number of mammalian tissues, suggesting that many cell types rely on this Ca2+-sensor for their Ca2+-homeostasis and intracellular signaling.
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