Caveolin‐1 Scaffolding Domain Regulates Store‐Operated Calcium Influx by Interacting with IP3R and TRPC1 in endothelial cells

Caveolin‐1 (Cav1) expression is required for store‐operated Ca 2+ entry in endothelial cells. We have shown previously Cav1 scaffolding domain (CSD) peptide interacted with the C‐terminus of TRPC1 and inhibited Ca 2+ influx in endothelial cells ( Mol Pharmacol.70:1174–1183, 2006 ). To understand the basis of Cav1 regulation of Ca 2+ influx, we ectopically expressed CSD truncated Cav1 (Cav1ΔCSD) and TRPC1 C‐terminus truncated (TRPC1‐CΔ781–789) mutants in endothelial cells. We observed >2‐fold increase in thrombin‐induced store Ca 2+ release‐activated Ca 2+ influx in Cav‐1ΔCSD expressing cells compared to controls. In contrast, TRPC1‐CΔ781–789 mutant expression abolished thrombin‐induced Ca 2+ influx. Immunoprecipitation studies revealed that WT‐Cav‐1 and WT‐TRPC1 interacted with endogenous IP 3 R. Whereas expression of TRPC1‐CΔ781–789 with WT‐Cav1 resulted in ∼50% reduction in the ability of IP 3 R binding to TRPC1. Interestingly, expression of Cav1ΔCSD with WT‐TRPC1 caused >80% reduction in the ability of IP 3 R binding to TRPC1. We also assessed the direct binding of IP 3 R with Cav1. Importantly WT‐Cav1 but not the Cav1ΔCSD interacted with endogenous IP 3 R. Co‐expression of TRPC1‐CΔ781–789 and WT‐Cav1 increased Cav1 binding to IP 3 R. These results suggest that Cav1 interacts with IP 3 R and TRPC1 through CSD to form IP 3 R‐Cav1‐TRPC1 complex and thus regulates store‐operated Ca 2+ entry in endothelial cells.