Direct Gαq Gating Is the Sole Mechanism for TRPM8 Inhibition Caused by Bradykinin Receptor Activation

Activation of Gα q -coupled receptors by inflammatory mediators inhibits cold-sensing TRPM8 channels, aggravating pain and inflammation. Both Gα q and the downstream hydrolysis of phosphatidylinositol 4, 5-bisphosphate (PIP 2 ) inhibit TRPM8. Here, I demonstrate that direct Gα q gating is essential for both the basal cold sensitivity of TRPM8 and TRPM8 inhibition elicited by bradykinin in sensory neurons. The action of Gα q depends on binding to three arginine residues in the N terminus of TRPM8. Neutralization of these residues markedly increased sensitivity of the channel to agonist and membrane voltage and completely abolished TRPM8 inhibition by both Gα q and bradykinin while sparing the channel sensitivity to PIP 2 . Interestingly, the bradykinin receptor B2R also binds to TRPM8, rendering TRPM8 insensitive to PIP 2 depletion. Furthermore, TRPM8-Gα q binding impaired Gα q coupling and signaling to PLCβ-PIP 2 . The crosstalk in the TRPM8-Gα q -B2R complex thus determines Gα q gating rather than PIP 2 as a sole means of TRPM8 inhibition by bradykinin.