Basal Ca2+ Entry Controls NFAT Transcriptional Activity, Proliferation And Migration Of Human Vascular Smooth Muscle Cells

Abstract

We have previously shown that in the rat the sarco/endoplasmic reticulum calcium ATPase, SERCA2a, controls vascular smooth muscle cell (VSMC) proliferation through modulation of the activity of the transcription factor NFAT. Here we tested the hypothesis that SERCA2a, controls human VSMC proliferation by inhibiting voltage-independent Ca2+ entry and the NFAT transcription pathway.Single-channel recording showed that proliferating VSMC possessed high spontaneous voltage-independent basal channel activity (nPo: 0.415 ± 0.050; n=31). SERCA2a gene transfer, using an adenoviral vector, to proliferating VSMCs abolished the activity of these channels (0.091 ± 0.096; n=26) compared to control cells infected with an adenovirus encoding GFP (0.315 ± 0.035; n=42). SERCA 2a gene transfer also down-regulated expression of transient receptor potential channels TRPC4, TRPC5 and stromal interacting molecule 1 (STIM1) suggesting their involvement in the channel activity.SERCA2a gene transfer also inhibited VSMC proliferation and migration as well as the NFAT activity. Furthermore, NFAT activity was inhibited by depolarization-induced Ca2+ influx and by several calcium channel inhibitors such as nifedipine, mibefradil, carboxyamidotriazole and 2-aminoethoxydiphenyl, suggesting involvement of different types of Ca2+ channels in the control of NFAT and proliferation. Our data suggest that different types of Ca2+ channels are involved in the control of NFAT transcriptional activity and proliferation. By controlling submembrane Ca2+ concentration, SERCA2a finely regulated basal Ca2+ current via regulation of translocation and/or expression of STIM1 and TRPCs.