Inhibition of native TRPC6 channel activity by phosphatidylinositol 4,5-bisphosphate in mesenteric artery myocytes

The present work investigates the effect of phosphatidylinositol-4,5-bisphosphate (PIP(2)) on native TRPC6 channel activity in freshly dispersed rabbit mesenteric artery myocytes using patch clamp recording and co-immunoprecipitation methods. Inclusion of 100 microM diC8-PIP(2) in the patch pipette and bathing solutions, respectively, inhibited angiotensin II (Ang II)-evoked whole-cell cation currents and TRPC6 channel activity by over 90%. In inside-out patches diC8-PIP(2) also inhibited TRPC6 activity induced by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) with an IC(50) of 7.6 microM. Anti-PIP(2) antibodies potentiated Ang II- and OAG-evoked TRPC6 activity by about 2-fold. Depleters of tissue PIP(2) wortmannin and LY294002 stimulated TRPC6 activity, as did the polycation PIP(2) scavenger poly-L-lysine. Wortmannin reduced Ang II-evoked TRPC6 activity by over 75% but increased OAG-induced TRPC6 activity by over 50-fold. Co-immunoprecipitation studies demonstrated association between PIP(2) and TRPC6 proteins in tissue lysates. Pre-treatment with Ang II, OAG and wortmannin reduced TRPC6 association with PIP(2). These results provide for the first time compelling evidence that constitutively produced PIP(2) exerts a powerful inhibitory action on native TRPC6 channels.