Abstract
TRPC6 is one of major TRP isoforms in vascular tissues and acts as a nonselective cation channel associated with vascular tone generation and remodeling. There is good evidence to suggest that activation and inactivation of TRP6 channel are effectively regulated via its phosphorylation by Ca2+-calmodulin dependent kinase II and protein kinase C, respectively. In this study, we show evidence that nitric oxide (NO)/cGMP/ PKG pathway may serve as another potent mechanism that would tonically inhibit TRPC6 channel activity.HEK293 cell expressing mouse TRPC6 protein responded to carhachol (100μM) to generate a non-selective cationic current with S-shaped double rectifying property (ITRPC6). The magnitude of ITRPC6 was greatly inhibited by pretreatment with a NO donor, S-nitrosoacetyl penicillamine (SNAP) (by 70% at 100μM) in a voltage-independent manner, but cell-surface expression of TRPC6 protein was not appreciably reduced. Similar extent of inhibition was produced by a membrane-permeable analogue of cGMP 8-bromo cGMP (8-Br-cGMP; 100μM). Both the inhibitory effects of SNAP and 8-Br-cGMP were nearly abolished by simultaneous administration of the PKG inhibitor KT5823 (10μM) or alanine substitution for one of PKG phophorylation motifs in murine TRPC6, T69. These results suggest that PKG-mediated phosphorylation is another powerful mechanism to control TRPC6 channel activity, which may in situ operate as a tonic negative feedback from adjacent endothelial cells which are producing NO continuously. [J Physiol Sci. 2007;57 Suppl:S78]
