A self-limiting regulation of vasoconstrictor-activated TRPC3/C6/C7 channels coupled to PI(4,5)P2-diacylglycerol signalling

作者：Imai Yuko; Itsuki Kyohei; Okamura Yasushi; Inoue Ryuji; Mori Masayuki X^*

来源：The Journal of Physiology, 2012, 590(5): 1101-1119.

DOI：10.1113/jphysiol.2011.221358

Activation of transient receptor potential (TRP) canonical TRPC3/ C6/ C7 channels by diacylglycerol (DAG) upon stimulation of phospholipase C (PLC)-coupled receptors results in the breakdown of phosphoinositides (PIPs). The critical importance of PIPs to various ion-transporting molecules is well documented, but their function in relation to TRPC3/ C6/ C7 channels remains controversial. By using an ectopic voltage-sensing PIP phosphatase (DrVSP), we found that dephosphorylation of PIPs robustly inhibits currents induced by carbachol (CCh), 1-oleolyl-2-acetyl-sn-glycerol (OAG) or RHC80267 in TRPC3, TRPC6 and TRPC7 channels, though the strength of the DrVSP-mediated inhibition (VMI) varied among the channels with a rank order ofC7%26gt; C6%26gt; C3. Pharmacological and molecular interventions suggest that depletion of phosphatidylinositol 4,5-bisphosphate (PI(4,5) P2) ismost likely the critical event for VMI in all three channels. When the PLC catalytic signal was vigorously activated through overexpression of themuscarinic type-I receptor (M1R), the inactivation of macroscopic TRPC currents was greatly accelerated in the same rank order as the VMI, and VMI of these currents was attenuated or lost. VMIwas also rarely detected in vasopressin-inducedTRPC6-like currents inA7r5 vascular smooth muscle cells, indicating that the inactivation by PI(4,5) P2 depletion underlies the physiological condition. Simultaneous fluorescence resonance energy transfer (FRET)-based measurement of PI(4,5) P2 levels and TRPC6 currents confirmed that VMI magnitude reflects the degree of PI(4,5) P2 depletion. These results demonstrate that TRPC3/ C6/ C7 channels are differentially regulated by depletion of PI(4,5)P-2, and that the bimodal signal produced by PLC activation controls these channels in a self-limiting manner.

• 出版日期2012-2