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VASCULAR BIOLOGY

Caveolin-1 scaffold domain interacts with TRPC1 and IP₃R3 to regulate Ca²⁺ store release-induced Ca²⁺ entry in endothelial cells

Department of Pharmacology and Center for Lung and Vascular Biology, College of Medicine, University of Illinois, Chicago, Illinois

Submitted 11 September 2008 ; accepted in final form 30 November 2008

Caveolin-1 (Cav-1) regulates agonist-induced Ca²⁺ entry in endothelial cells; however, how Cav-1 regulates this process is poorly understood. Here, we describe that Cav-1 scaffold domain (NH₂-terminal residues 82–101; CSD) interacts with transient receptor potential canonical channel 1 (TRPC1) and inositol 1,4,5-trisphosphate receptor 3 (IP₃R3) to regulate Ca²⁺ entry. We have shown previously that the TRPC1 COOH-terminal residues 781-789 bind to CSD. In the present study, we show that the TRPC1 COOH-terminal residues 781-789 truncated (TRPC1-C781-789) mutant expression abolished Ca²⁺ store release-induced Ca²⁺ influx in human dermal microvascular endothelial cell line (HMEC) and human embryonic kidney (HEK-293) cells. To understand the basis of loss of Ca²⁺ influx, we determined TRPC1 binding to IP₃R3. We observed that the wild-type (WT)-TRPC1 but not TRPC1-C781-789 effectively interacted with IP₃R3. Similarly, WT-TRPC1 interacted with Cav-1, whereas TRPC1-C781-789 binding to Cav-1 was markedly suppressed. We also assessed the direct binding of Cav-1 with TRPC1 and observed that the WT-Cav-1 but not the Cav-1CSD effectively interacted with TRPC1. Since the interaction between TRPC1 and Cav-1CSD was reduced, we measured Ca²⁺ store release-induced Ca²⁺ influx in Cav-1CSD-transfected cells. Surprisingly, Cav-1CSD expression showed a gain-of-function in Ca²⁺ entry in HMEC and HEK-293 cells. We observed a similar gain-of-function in Ca²⁺ entry when Cav-1CSD was expressed in lung endothelial cells of Cav-1 knockout mice. Immunoprecipitation results revealed that WT-Cav-1 but not Cav-1CSD interacted with IP₃R3. Furthermore, we observed using confocal imaging the colocalization of IP₃R3 with WT-Cav-1 but not with Cav-1CSD on Ca²⁺ store release in endothelial cells. These findings suggest that CSD interacts with TRPC1 and IP₃R3 and thereby regulates Ca²⁺ store release-induced Ca²⁺ entry in endothelial cells.

transient receptor potential channel 1; inositol 1,4,5-trisphosphate receptor; caveolin-1 knockout mice

This article has been cited by other articles:

				C. D. Hardin and J. Vallejo Dissecting the functions of protein-protein interactions: caveolin as a promiscuous partner. Focus on "Caveolin-1 scaffold domain interacts with TRPC1 and IP3R3 to regulate Ca2+ store release-induced Ca2+ entry in endothelial cells" Am J Physiol Cell Physiol, March 1, 2009; 296(3): C387 - C389. [Full Text] [PDF]