Soluble adenylyl cyclase links Ca entry to Ca/cAMP-response element binding protein (CREB) activation in vascular smooth muscle.

Ca-transcription coupling controls gene expression patterns that define vascular smooth muscle cell (VSMC) phenotype. Although not well understood this allows normally contractile VSMCs to become proliferative following vessel injury, a process essential for repair but which also contributes to vascular remodelling, atherogenesis and restenosis. Here we show that the Ca/HCO-sensitive enzyme, soluble adenylyl cyclase (sAC), links Ca influx in human coronary artery smooth muscle cells (hCASMCs) to 3',5'-cyclic adenosine monophosphate (cAMP) generation and phosphorylation of the transcription factor Ca/cAMP response element binding protein (CREB). Store-operated Ca entry (SOCE) into hCASMCs expressing the FRET-based cAMP biosensor H187 induced a rise in cAMP that mirrored cytosolic [Ca]. SOCE also activated the cAMP effector, protein kinase A (PKA), as determined by the PKA reporter, AKAR4-NES, and induced phosphorylation of vasodilator-stimulated phosphoprotein (VASP) and CREB. Transmembrane adenylyl cyclase inhibition had no effect on the SOCE-induced rise in cAMP, while sAC inhibition abolished SOCE-generated cAMP and significantly reduced SOCE-induced VASP and CREB phosphorylation. This suggests that SOCE in hCASMCs activates sAC which in turn activates the cAMP/PKA/CREB axis. sAC, which is insensitive to G-protein modulation but responsive to Ca, pH and ATP, may therefore act as an overlooked regulatory node in vascular Ca-transcription coupling.