Subtype-specific regulation of P2X3 and P2X2/3 receptors by phosphoinositides in peripheral nociceptors

• Main Authors: Logothetis Diomedes, Ase Ariel R, Chabot-Doré Anne-Julie, Zhao Qi, Bernier Louis-Philippe, Mo Gary, Cao Chang-Qing, Séguéla Philippe
• Format: Article
• Language: English
• Published: SAGE Publishing 2009-08-01
• Series: Molecular Pain
• Online Access: http://www.molecularpain.com/content/5/1/47

<p>Abstract</p> <p>Background</p> <p>P2X3 and P2X2/3 purinergic receptor-channels, expressed in primary sensory neurons that mediate nociception, have been implicated in neuropathic and inflammatory pain responses. The phospholipids phosphatidylinositol 4,5-bisphosphate (PIP₂) and phosphatidylinositol 3,4,5-trisphosphate (PIP₃) are involved in functional modulation of several types of ion channels. We report here evidence that these phospholipids are able to modulate the function of homomeric P2X3 and heteromeric P2X2/3 purinoceptors expressed in dorsal root ganglion (DRG) nociceptors and in heterologous expression systems.</p> <p>Results</p> <p>In dissociated rat DRG neurons, incubation with the PI3K/PI4K inhibitor wortmannin at 35 μM induced a dramatic decrease in the amplitude of ATP- or α,β-meATP-evoked P2X3 currents, while incubation with 100 nM wortmannin (selective PI3K inhibition) produced no significant effect. Intracellular application of PIP₂was able to fully reverse the inhibition of P2X3 currents induced by wortmannin. In <it>Xenopus </it>oocytes and in HEK293 cells expressing recombinant P2X3, 35 μM wortmannin incubation induced a significant decrease in the rate of receptor recovery. Native and recombinant P2X2/3 receptor-mediated currents were inhibited by incubation with wortmannin both at 35 μM and 100 nM. The decrease of P2X2/3 current amplitude induced by wortmannin could be partially reversed by application of PIP₂or PIP₃, indicating a sensitivity to both phosphoinositides in DRG neurons and <it>Xenopus </it>oocytes. Using a lipid binding assay, we demonstrate that the C-terminus of the P2X2 subunit binds directly to PIP₂, PIP₃and other phosphoinositides. In contrast, no direct binding was detected between the C-terminus of P2X3 subunit and phosphoinositides.</p> <p>Conclusion</p> <p>Our findings indicate a functional regulation of homomeric P2X3 and heteromeric P2X2/3 ATP receptors by phosphoinositides in the plasma membrane of DRG nociceptors, based on subtype-specific mechanisms of direct and indirect lipid sensing.</p>