Figure 5.
Gαq Gates TRPM8 through Three Arginine Residues on TRPM8
(A) Representative inward and outward currents of TRPM8 and TRPM8-TM activated by menthol (200 μM, 5 s).
(B) Summary of currents of TRPM8 and TRPM8-TM with or without 3Gαqi from experiments similar to those in (A). Data are mean ± SEM. ∗∗p < 0.01; ∗∗∗p < 0.001.
(C) Dose-response relationship of TRPM8 and TRPM8-TM expressed in HEK293 and Gαq/11−/− MEF cells in response to menthol. Curves are fitted with the Hill equation. TRPM8 (♦), EC50 = 148.8 μM ± 8.1 μM; TRPM8-TM (▲), EC50 = 40.6 μM ± 5.3 μM; TRPM8 in Gαq/11−/− MEF (□), EC50 = 75.1 μM ± 2.8 μM; TM in Gαq/11−/− (△), EC50 = 61.4 μM ± 5.0 μM). n = 7–15.
(D) Average I-V relationship of TRPM8-TM with (pink, n = 13) or without (black, n = 14) 3Gαqi.
(E) Example currents of TRPM8 and TRPM8-TM evoked by voltage steps from −120 mV up to 200 mV in 20-mV increments. Maximal current was evoked at 140 mV for TRPM8-TM.
(F) Normalized conductance (G)-voltage relationship from the cells in (E) fitted with the Boltzmann equation, giving rise to V1/2 and slope factor as follows: TRPM8, 103.5 mV and 36.2 mV; TRPM8-TM, 62.0 mV and 36.3 mV.
(G) Collective results of V1/2 from experiments similar to those in (E) and (F). The number of experiments is shown above each bar.
(H) Side stereoview of a ribbon representation of the TRPM8 structure (6BPQ).
(I) Side stereoview of central cavity formed by the N terminus of two opposite TRPM8 subunits. Distance measurements between domains and residues are indicated.
Error bars represent mean ± SEM. ∗∗p < 0.01; NS, not significant. See also Figure S2.