title: Phosphoinositides regulate P2X4 ATP-gated channels through direct interactions.
abstract: P2X receptors are ATP-gated nonselective cation channels highly permeable to calcium that contribute to nociception and inflammatory responses. The P2X(4) subtype, upregulated in activated microglia, is thought to play a critical role in the development of tactile allodynia following peripheral nerve injury. Posttranslational regulation of P2X(4) function is crucial to the cellular mechanisms of neuropathic pain, however it remains poorly understood. Here, we show that the phosphoinositides PI(4,5)P(2) (PIP(2)) and PI(3,4,5)P(3) (PIP(3)), products of phosphorylation by wortmannin-sensitive phosphatidylinositol 4-kinases and phosphatidylinositol 3-kinases, can modulate the function of native and recombinant P2X(4) receptor channels. In BV-2 microglial cells, depleting the intracellular levels of PIP(2) and PIP(3) with wortmannin significantly decreased P2X(4) current amplitude and P2X(4)-mediated calcium entry measured in patch clamp recordings and ratiometric ion imaging, respectively. Wortmannin-induced depletion of phosphoinositides in Xenopus oocytes decreased the current amplitude of P2X(4) responses by converting ATP into a partial agonist. It also decreased their recovery from desensitization and affected their kinetics. Injection of phosphoinositides in wortmannin-treated oocytes reversed these effects and application of PIP(2) on excised inside-out macropatches rescued P2X(4) currents from rundown. Moreover, we report the direct interaction of phospholipids with the proximal C-terminal domain of P2X(4) subunit (Cys(360)-Val(375)) using an in vitro binding assay. These results demonstrate novel regulatory roles of the major signaling phosphoinositides PIP(2) and PIP(3) on P2X(4) function through direct channel-lipid interactions.
authors.affiliation: Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, Montréal, Québec, Canada H3A 2B4.
authors.forename: Louis-Philippe
authors.initials: LP
authors.lastname: Bernier
authors.forename: Ariel R
authors.initials: AR
authors.lastname: Ase
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Chevallier
authors.forename: Dominique
authors.initials: D
authors.lastname: Blais
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhao
authors.forename: Eric
authors.initials: E
authors.lastname: Boué-Grabot
authors.forename: Diomedes
authors.initials: D
authors.lastname: Logothetis
authors.forename: Philippe
authors.initials: P
authors.lastname: Séguéla
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology; D007249:Inflammation / Q000378:metabolism* / Q000503:physiopathology; D015640:Ion Channel Gating / Q000502:physiology*; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010523:Peripheral Nervous System Diseases / Q000378:metabolism / Q000503:physiopathology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D018048:Receptors, Purinergic P2 / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D058848:Receptors, Purinergic P2X4; D000077191:Wortmannin; D014982:Xenopus laevis
chemical_list: D000730:Androstadienes; C548227:P2rx4 protein, mouse; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010726:Phosphodiesterase Inhibitors; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; C060974:phosphatidylinositol 3,4,5-triphosphate; D000255:Adenosine Triphosphate; D000077191:Wortmannin