SERCA2a controls the mode of agonist-induced intracellular Ca2+ signal, transcription factor NFAT and proliferation in human vascular smooth muscle cells

In blood vessels, tone is maintained by agonist-induced cytosolic Ca2+ oscillations of quiescent/contractile vascular smooth muscle cells (VSMCs). However, in synthetic/proliferative VSMCs, Gq/phosphoinositide receptor-coupled agonists trigger a steady-state increase in cytosolic Ca2+ followed by a Store Operated Calcium Entry (SOCE) which translates into activation of the proliferation-associated transcription factor NFAT. Here, we report that in human coronary artery smooth muscle cells (hCASMCs), the sarco/endoplasmic reticulum calcium ATPase type 2a (SERCA2a) expressed in the contractile form of the hCASMCs, controls the nature of the agonist-induced Ca2+ transient and the resulting down-stream signaling pathway. Indeed, restoring SERCA2a expression by gene transfer in synthetic hCASMCs 1) increased Ca2+ storage capacity; 2) modified agonist-induced IP3R Ca2+ release from steady-state to oscillatory mode (the frequency of agonist-induced IP3R Ca2+ signal was 11.66 ± 1.40/100 s in SERCA2a-expressing cells (n = 39) vs 1.37 ± 0.20/100 s in control cells (n = 45), p < 0.01); 3) suppressed SOCE by preventing interactions between SR calcium sensor STIM1 and pore forming unit ORAI1; 4) inhibited calcium regulated transcription factor NFAT and its down-stream physiological function such as proliferation and migration. This study provides evidence for the first time that oscillatory and steady-state patterns of Ca2+ transients have different effects on calcium-dependent physiological functions in smooth muscle cells.

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► SERCA2a controls the kinetic of agonist-induced Ca2+ transient in VSMC.
► Steady-state Ca2+ transient results in STIM1/ORAI association and SOCE opening.
► Oscillatory Ca2+ transient prevents STIM1/ORAI association and SOCE opening.
► SERCA2a expression inhibits proliferation-associated SOCE/NFAT pathway.