Figure 2
Electrophysiological characterization of TRPM8-Y745H mutant sensitivity to menthol, cold and voltage. A, Whole-cell current-voltage relationships of TRPM8-wt and TRPM8-Y745H expressing HEK293 cells in control and menthol-containing solutions at 33°C. Note the different current scale. B, Summary histogram of experiments seen in A showing menthol-induced whole-cell currents at various potentials, normalized with the current in control conditions. Note the logarithmic current scale. The responses of TRPM8-wt vs. Y745H were compared with repeated-measures 2-way ANOVA in combination with Bonferroni's post test with respect to the effect of the mutation at each potential: *** p < 0.001; * p < 0.05; n = 7 (TRPM8-wt) and n = 13 (TRPM8-Y745H). C-E, Parameters obtained from fits of I-V data of experiments such as the ones showed in A to equation (i), n = 4-19. C, Average values of the apparent gating charge in control (33°C), menthol (100 μM), cooling (20°C) and cooling + menthol, of the TRPM8-wt vs. TRPM8-Y745H. D, Average maximum conductance (g) of cells expressing TRPM8-wt and TRPM8-Y745H during cooling and menthol application. The data are normalized with the value of g of the same cells in control solution at 33°C. E, Agonist-induced shifts of the midpoint of voltage activation (V1/2) of TRPM8-wt vs. TRPM8-Y745H. The data are represented with respect to the value of V1/2 in control solution at 33°C. In panels C-E, statistical significance was assessed with Student's unpaired t-test: *** p < 0.001; ** p < 0.01; * p < 0.05.