Functional role of vanilloid transient receptor potential 4-canonical transient receptor potential 1 complex in flow-induced Ca2+ influx.

OBJECTIVE The present study is aimed at investigating the interaction of TRPV4 with TRPC1 and the functional role of such an interaction in flow-induced Ca(2+) influx. Hemodynamic blood flow is an important physiological factor that modulates vascular tone. One critical early event in this process is a cytosolic Ca(2+) ([Ca(2+)](i)) rise in endothelial cells in response to flow. METHODS AND RESULTS With the use of fluorescence resonance energy transfer, coimmunoprecipitation, and subcellular colocalization methods, it was found that TRPC1 interacts physically with TRPV4 to form a complex. In functional studies, flow elicited a transient [Ca(2+)](i) increase in TRPV4-expressing human embryonic kidney (HEK) 293 cells. Coexpression of TRPC1 with TRPV4 markedly prolonged this [Ca(2+)](i) transient; it also enabled this [Ca(2+)](i) transient to be negatively modulated by protein kinase G. Furthermore, this flow-induced [Ca(2+)](i) increase was markedly inhibited by anti-TRPC1-blocking antibody T1E3 and a dominant-negative construct TRPC1 Delta 567-793 in TRPV4-C1-coexpressing HEK cells and human umbilical vein endothelial cells. T1E3 also inhibited flow-induced vascular dilation in isolated rat small mesenteric artery segments. CONCLUSIONS This study shows that TRPC1 interacts physically with TRPV4 to form a complex, and this TRPV4-C1 complex may mediate flow-induced Ca(2+) influx in vascular endothelial cells. The association of TRPC1 with TRPV4 prolongs the flow-induced [Ca(2+)](i) transient, and it also enables this [Ca(2+)](i) transient to be negatively modulated by protein kinase G. This TRPV4-C1 complex plays a key role in flow-induced endothelial Ca(2+) influx.