| First Author | Klasen K | Year | 2012 |
| Journal | Pflugers Arch | Volume | 463 |
| Issue | 6 | Pages | 779-97 |
| PubMed ID | 22460725 | Mgi Jnum | J:321456 |
| Mgi Id | MGI:6862076 | Doi | 10.1007/s00424-012-1098-7 |
| Citation | Klasen K, et al. (2012) The TRPM8 ion channel comprises direct Gq protein-activating capacity. Pflugers Arch 463(6):779-97 |
| abstractText | The transient receptor potential (TRP) family of ion channels comprises receptors that are activated by a vast variety of physical as well as chemical stimuli. TRP channels interact in a complex manner with several intracellular signaling cascades, both up- and downstream of receptor activation. Investigating cascades stimulated downstream of the cold and menthol receptor TRPM8, we found evidence for both, functional and structural interaction of TRPM8 with Galphaq. We demonstrated menthol-evoked increase in intracellular Ca(2+) under extracellular Ca(2+)-free conditions, which was blocked by the PLC inhibitors U73122 or edelfosine. This metabotropic Ca(2+) signal could be observed also in cells expressing a channel-dead (i.e. non-conducting) or a chloride-conducting TRPM8 pore mutant. However, this intracellular metabotropic Ca(2+) signal could not be detected in Galphaq deficient cells or in the presence of dominant-negative GalphaqX. Evidence for a close spatial proximity necessary for physical interaction of TRPM8 and Galphaq was provided by acceptor bleaching experiments demonstrating FRET between TRPM8-CFP and Galphaq-YFP. A Galphaq-YFP mobility assay (FRAP) revealed a restricted diffusion of Galphaq-YFP under conditions when TRPM8 is immobilized in the plasma membrane. Moreover, a menthol-induced and TRPM8-mediated G protein activation could be demonstrated by FRET experiments monitoring the dissociation of Galphaq-YFP from a Gbeta/Ggamma-CFP complex, and by the exchange of radioactive [(35)S]GTPgammaS for GDP. Our observations lead to a view that extends the operational range of the TRPM8 receptor from its function as a pure ion channel to a molecular switch with additional metabotropic capacity. |
