| First Author | Alkhatib O | Year | 2019 |
| Journal | J Neurosci | Volume | 39 |
| Issue | 40 | Pages | 7840-7852 |
| PubMed ID | 31451581 | Mgi Jnum | J:282016 |
| Mgi Id | MGI:6363281 | Doi | 10.1523/JNEUROSCI.0882-19.2019 |
| Citation | Alkhatib O, et al. (2019) Promiscuous G-Protein-Coupled Receptor Inhibition of Transient Receptor Potential Melastatin 3 Ion Channels by Gbetagamma Subunits. J Neurosci 39(40):7840-7852 |
| abstractText | Transient receptor potential melastatin 3 (TRPM3) is a nonselective cation channel that is inhibited by Gbetagamma subunits liberated following activation of Galphai/o protein-coupled receptors. Here, we demonstrate that TRPM3 channels are also inhibited by Gbetagamma released from Galphas and Galphaq Activation of the Gs-coupled adenosine 2B receptor and the Gq-coupled muscarinic acetylcholine M1 receptor inhibited the activity of TRPM3 heterologously expressed in HEK293 cells. This inhibition was prevented when the Gbetagamma sink betaARK1-ct (C terminus of beta-adrenergic receptor kinase-1) was coexpressed with TRPM3. In neurons isolated from mouse dorsal root ganglion (DRG), native TRPM3 channels were inhibited by activating Gs-coupled prostaglandin-EP2 and Gq-coupled bradykinin B2 (BK2) receptors. The Gi/o inhibitor pertussis toxin and inhibitors of PKA and PKC had no effect on EP2- and BK2-mediated inhibition of TRPM3, demonstrating that the receptors did not act through Galphai/o or through the major protein kinases activated downstream of G-protein-coupled receptor (GPCR) activation. When DRG neurons were dialyzed with GRK2i, which sequesters free Gbetagamma protein, TRPM3 inhibition by EP2 and BK2 was significantly reduced. Intraplantar injections of EP2 or BK2 agonists inhibited both the nocifensive response evoked by TRPM3 agonists, and the heat hypersensitivity produced by Freund's Complete Adjuvant (FCA). Furthermore, FCA-induced heat hypersensitivity was completely reversed by the selective TRPM3 antagonist ononetin in WT mice and did not develop in Trpm3 (-/-) mice. Our results demonstrate that TRPM3 is subject to promiscuous inhibition by Gbetagamma protein in heterologous expression systems, primary neurons and in vivo, and suggest a critical role for this ion channel in inflammatory heat hypersensitivity.SIGNIFICANCE STATEMENT The ion channel TRPM3 is widely expressed in the nervous system. Recent studies showed that Galphai/o-coupled GPCRs inhibit TRPM3 through a direct interaction between Gbetagamma subunits and TRPM3. Since Gbetagamma proteins can be liberated from other Galpha subunits than Galphai/o, we examined whether activation of Gs- and Gq-coupled receptors also influence TRPM3 via Gbetagamma. Our results demonstrate that activation of Gs- and Gq-coupled GPCRs in recombinant cells and sensory neurons inhibits TRPM3 via Gbetagamma liberation. We also demonstrated that Gs- and Gq-coupled receptors inhibit TRPM3 in vivo, thereby reducing pain produced by activation of TRPM3, and inflammatory heat hypersensitivity. Our results identify Gbetagamma inhibition of TRPM3 as an effector mechanism shared by the major Galpha subunits. |
