S-Nitrosylation of STIM1 by Neuronal Nitric Oxide Synthase Inhibits Store-Operated Ca Entry.

Store-operated Ca entry (SOCE) mediated by stromal interacting molecule-1 (STIM1) and Orai1 represents a major route of Ca entry in mammalian cells and is initiated by STIM1 oligomerization in the endoplasmic or sarcoplasmic reticulum. However, the effects of nitric oxide (NO) on STIM1 function are unknown. Neuronal NO synthase is located in the sarcoplasmic reticulum of cardiomyocytes. Here, we show that STIM1 is susceptible to S-nitrosylation. Neuronal NO synthase deficiency or inhibition enhanced Ca release-activated Ca channel current (I) and SOCE in cardiomyocytes. Consistently, NO donor S-nitrosoglutathione inhibited STIM1 puncta formation and I 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 depletion-dependent oligomerization of the luminal Ca-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.