PKCα mediates acetylcholine-induced activation of TRPV4-dependent calcium influx in endothelial cells

Adapala RK, Talasila PK, Bratz IN, Zhang DX, Suzuki M, Meszaros JG, Thodeti CK. PKC alpha mediates acetylcholine-induced activation of TRPV4-dependent calcium influx in endothelial cells. Am J Physiol Heart Circ Physiol 301: H757-H765, 2011. First published June 24, 2011; doi:10.1152/ajpheart.00142.2011.-Transient receptor potential vanilloid channel 4 (TRPV4) is a polymodally activated nonselective cationic channel implicated in the regulation of vasodilation and hypertension. We and others have recently shown that cyclic stretch and shear stress activate TRPV4-mediated calcium influx in endothelial cells (EC). In addition to the mechanical forces, acetylcholine (ACh) was shown to activate TRPV4-mediated calcium influx in endothelial cells, which is important for nitric oxide-dependent vasodilation. However, the molecular mechanism through which ACh activates TRPV4 is not known. Here, we show that ACh-induced calcium influx and endothelial nitric oxide synthase (eNOS) phosphorylation but not calcium release from intracellular stores is inhibited by a specific TRPV4 antagonist, AB-159908. Importantly, activation of store-operated calcium influx was not altered in the TRPV4 null EC, suggesting that TRPV4-dependent calcium influx is mediated through a receptor-operated pathway. Furthermore, we found that ACh treatment activated protein kinase C (PKC) alpha, and inhibition of PKC alpha activity by the specific inhibitor Go-6976, or expression of a kinase-dead mutant of PKC alpha but not PKC epsilon or downregulation of PKC alpha expression by chronic 12-O-tetradecanoylphorbol-13-acetate treatment, completely abolished ACh-induced calcium influx. Finally, we found that ACh-induced vasodilation was inhibited by the PKC alpha inhibitor Go-6976 in small mesenteric arteries from wild-type mice, but not in TRPV4 null mice. Taken together, these findings demonstrate, for the first time, that a specific isoform of PKC, PKC alpha, mediates agonist-induced receptor-mediated TRPV4 activation in endothelial cells.