S-Nitrosylation of STIM1 by neuronal nitric oxide synthase inhibits store-operated Ca 2+ entry

Store-operated Ca 2+ entry (SOCE) mediated by stromal interacting molecule-1 (STIM1) and Orai1 represents a major route of Ca 2+ entry in mammalian cells and is initiated by STIM1 oligomerization in the endoplasmic or sarcoplasmic reticulum (ER/SR). However, the effects of nitric oxide (NO) on STIM1 function are unknown. Neuronal NO synthase (nNOS) is located in the SR of cardiomyocytes. Here, we show that STIM1 is susceptible to S-nitrosylation. nNOS deficiency or inhibition enhanced Ca 2+ release-activated Ca 2+ channel current ( I CRAC ) and SOCE in cardiomyocytes. Consistently, NO donor S-nitrosoglutathione (GSNO) inhibited STIM1 puncta formation and I CRAC in HEK293 cells, but this effect was absent in cells expressing the Cys49Ser/Cys56Ser STIM1 double mutant. Furthermore, NO donors caused Cys49 and Cys56-specific structural changes associated with reduced protein backbone mobility, increased thermal stability and suppressed Ca 2+ -depletion-dependent oligomerization of the luminal Ca 2+ -sensing region of STIM1. Collectively, our data show that S-nitrosylation of STIM1 suppresses oligomerization via enhanced luminal domain stability and rigidity, and inhibits SOCE in cardiomyocytes.