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

Xuming Zhang

doi:10.1016/j.celrep.2019.05.080

Abstract

SummaryActivation of Gαq-coupled receptors by inflammatory mediators inhibits cold-sensing TRPM8 channels, aggravating pain and inflammation. Both Gαq and the downstream hydrolysis of phosphatidylinositol 4, 5-bisphosphate (PIP2) inhibit TRPM8. Here, I demonstrate that direct Gαq gating is essential for both the basal cold sensitivity of TRPM8 and TRPM8 inhibition elicited by bradykinin in sensory neurons. The action of Gαq 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 Gαq and bradykinin while sparing the channel sensitivity to PIP2. Interestingly, the bradykinin receptor B2R also binds to TRPM8, rendering TRPM8 insensitive to PIP2 depletion. Furthermore, TRPM8-Gαq binding impaired Gαq coupling and signaling to PLCβ-PIP2. The crosstalk in the TRPM8-Gαq-B2R complex thus determines Gαq gating rather than PIP2 as a sole means of TRPM8 inhibition by bradykinin.

Highlights

TRPM8 channels detect a wide range of cold temperatures, spanning from innocuous cooling to noxious cold (Madrid et al, 2009; McKemy et al, 2002; Peier et al, 2002)
Gaq Is Crucial for the Cold Sensitivity of TRPM8 in Sensory Neurons We have previously shown that activated Gaq directly inhibits TRPM8 channels in vitro (Zhang et al, 2012), but it remains unknown whether this mechanism occurs to sensory neurons
To verify that cold-elicited firing is mediated by TRPM8, dorsal root ganglia (DRG) neurons were exposed to PBMC, a specific TRPM8 antagonist (Knowlton et al, 2011), during the second cold ramp

Summary

Introduction

TRPM8 channels detect a wide range of cold temperatures, spanning from innocuous cooling to noxious cold (Madrid et al, 2009; McKemy et al, 2002; Peier et al, 2002). It is activated by cooling-mimetic compounds, such as menthol and its derivative, WS-12. Activation of TRPM8 inhibits inflammatory and neuropathic pain, mediating an analgesic effect (Dhaka et al, 2007; Knowlton et al, 2013; Liu et al, 2013; Proudfoot et al, 2006), though it causes cold hypersensitivity in some cases (Colburn et al, 2007; De Caro et al, 2018; Knowlton et al, 2013). Activation of TRPM8, inhibits both pain and inflammation, which may underlie cold therapy that has been used to relieve pain and inflammation for hundreds of years

Results

Discussion

Conclusion