Store-operated calcium entry (SOCE) through the Ca2+ release–activated Ca2+ (CRAC) channel is a central mechanism by which cells generate Ca2+ signals and mediate Ca2+-dependent gene expression. The molecular basis for CRAC channel regulation by the SOCE-associated regulatory factor (SARAF) remained insufficiently understood. Here we found that following ER Ca2+ depletion, SARAF facilitates a conformational change in the ER Ca2+ sensor STIM1 that relieves an activation constraint enforced by the STIM1 inactivation domain (ID; aa 475–483) and promotes initial activation of STIM1, its translocation to ER–plasma membrane junctions, and coupling to Orai1 channels. Following intracellular Ca2+ rise, cooperation between SARAF and the STIM1 ID controls CRAC channel slow Ca2+-dependent inactivation. We further show that in T lymphocytes, SARAF is required for proper T cell receptor evoked transcription. Taking all these data together, we uncover a dual regulatory role for SARAF during both activation and inactivation of CRAC channels and show that SARAF fine-tunes intracellular Ca2+ responses and downstream gene expression in cells.
Bidirectional regulation of calcium release–activated calcium (CRAC) channel by SARAF
- Award Id(s): 1048/18
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Elia Zomot, Hadas Achildiev Cohen, Inbal Dagan, Ruslana Militsin, Raz Palty; Bidirectional regulation of calcium release–activated calcium (CRAC) channel by SARAF. J Cell Biol 6 December 2021; 220 (12): e202104007. doi: https://doi.org/10.1083/jcb.202104007
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