Stromal interaction molecule 2 regulates C2C12 myoblast differentiation

BACKGROUND: Enhanced intracellular Ca(2+) signaling by stromal interaction molecule 1 (STIM1)-mediated store-operated Ca(2+) entry (SOCE) is required for skeletal muscle differentiation. However, the contribution of STIM2, STIM1's analogue protein, on muscle cell differentiation has not been clearly elucidated. The present study aimed to explore the contribution of STIM2-mediated SOCE on C2C12 myoblast differentiation. METHODS: Changes in STIM2 expression level (reverse transcription-polymerase chain reaction and Western blotting) and SOCE activity ([Ca(2+)](i) measurement) were measured during 3 days of in vitro differentiation of C2C12 skeletal myoblast. Transcriptional regulation of STIM2 by nuclear factor of activated T cells, cytoplasmic (NFATc) overexpression was observed, and the effect of STIM2 knockdown on NFAT transcriptional activity (luciferase assay) and myoblast differentiation was quantified. RESULTS: Increase of STIM2 protein level and enhanced SOCE activity were observed in differentiating myoblasts. Treatment with a SOCE blocker (2-APB) inhibited the differentiation. Overexpression of NFATc1 increased STIM2 expression and SOCE activity. Knockdown of STIM2 decreased NFAT transcriptional activity, SOCE activity, and differentiation of C2C12 myoblast. CONCLUSION: It is suggested that STIM2-activated SOCE controls C2C12 myoblast differentiation.