TY - JOUR T1 - Direct Modulation of P2X<sub>1</sub> Receptor-Channels by the Lipid Phosphatidylinositol 4,5-Bisphosphate JF - Molecular Pharmacology JO - Mol Pharmacol SP - 785 LP - 792 DO - 10.1124/mol.108.047019 VL - 74 IS - 3 AU - Louis-Philippe Bernier AU - Ariel R. Ase AU - Xinkang Tong AU - Edith Hamel AU - Dominique Blais AU - Qi Zhao AU - Diomedes E. Logothetis AU - Philippe Séguéla Y1 - 2008/09/01 UR - http://molpharm.aspetjournals.org/content/74/3/785.abstract N2 - The P2X1 receptor-channels activated by extracellular ATP contribute to the neurogenic component of smooth muscle contraction in vascular beds and genitourinary tracts of rodents and humans. In the present study, we investigated the interactions of plasma membrane phosphoinositides with P2X1 ATP receptors and their physiological consequences. In an isolated rat mesenteric artery preparation, we observed a strong inhibition of P2X1-mediated constrictive responses by depletion of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] with the phosphatidylinositol 4-kinase inhibitor wortmannin. Using the Xenopus laevis oocyte expression system, we provided electrophysiological evidence that lowering PI(4,5)P2 levels with wortmannin significantly decreases P2X1 current amplitude and recovery. Previously reported modulation of recovery of desensitized P2X1 currents by phospholipase C-coupled 5-hydroxytryptamine2A metabotropic receptors was also found to be wortmannin-sensitive. Treatment with wortmannin alters the kinetics of P2X1 activation and inactivation without changing its sensitivity to ATP. The functional impact of wortmannin on P2X1 currents could be reversed by addition of intracellular PI(4,5)P2, but not phosphatidylinositol 3,4,5-trisphosphate, and direct application of PI(4,5)P2 to excised inside-out macropatches rescued P2X1 currents from rundown. We showed that the proximal region of the intracellular C terminus of P2X1 subunit directly binds to PI(4,5)P2 and other anionic phospholipids, and we identified the basic residue Lys364 as a critical determinant for phospholipid binding and sensitivity to wortmannin. Overall, these results indicate that PI(4,5)P2 plays a key role in the expression of full native and heterologous P2X1 function by regulating the amplitude, recovery, and kinetics of ionotropic ATP responses through direct receptor-lipid interactions. ER -