Store-Operated Ca2+ Entry Activates the CREB Transcription Factor in Vascular Smooth Muscle

Ca-regulated gene transcription is a critical component of arterial responses to injury, hypertension, and tumor-stimulated angiogenesis. The Ca/cAMP response element binding protein (CREB), a transcription factor that regulates expression of many genes, is activated by Ca-induced phosphorylation. Multiple Ca entry pathways may contribute to CREB activation in vascular smooth muscle including voltage-dependent Ca channels and store-operated Ca entry (SOCE). To investigate a role for SOCE in CREB activation, we measured CREB phosphorylation using immunofluorescence, intracellular Ca levels using a fluorescence resonance energy transfer (FRET)–based Cameleon indicator, and c-fos transcription using RT-PCR. In this study, we report that SOCE activates CREB in both cultured smooth muscle cells and intact arteries. Depletion of intracellular Ca stores with thapsigargin increased nuclear phospho-CREB levels, intracellular Ca concentration, and transcription of c-fos. These effects were abolished by inhibiting SOCE through lowering extracellular Ca concentration or by application of 2-aminoethoxydiphenylborate and Ni. Inhibition of Ca influx through voltage-dependent Ca channels using nimodipine partially blocked intact artery responses, but was without effect in cultured smooth muscle cells. Our findings indicate that Ca entry through store-operated Ca channels leads to CREB activation, suggesting that SOCE contributes to the regulation of gene expression in vascular smooth muscle.