FIGURE 5.

Wild-type hKv7.4 and the transmembrane mutant F182L channels were expressed in CHO cells. A, exemplary outward hKv7.4 current traces recorded from a holding potential of −80 to 30 mV using voltage increment of 10 mV in depolarizing and hyperpolarizing step voltages. B–D, current traces recorded from CHO cells, which were transfected with MT-F182L alone (B), WT-hKv7.4:MT-F182L (1:1) (C), and (1:3) (D). E, group data of current density-voltage curves (mean ± S.D.) for co-expression of WT-hKv7.4 alone (●) with WT-hKv7.4:MT-F182L (1:1, ○), (1:3, △), and (0:1,▿). F, summary data of the steady-state voltage-dependent activation of WT-hKv7.4 alone (●), WT:F182L (1:1, ○), (1:3, △), and (0:1, ▿). The V½ of the steady-state activation curves of the four combinatorial expression and the ensuing currents were not statistically different. The V½ (in mV) of WT-hKv7.4 alone and WT:F182L (1:1, 1:3, and 0:1 ratios) were −32.5 ± 0.5, −30.4 ± 1.0, −30.8 ± 0.7, and −32.1 ± 0.6, (n = 11, p = 0.3), respectively. The slope factors (k) of the resulting Boltzmann function curves were also not statistically different. The k values (in mV) of WT-hKv7.4 alone (●) and WT:F182L (1:1, 1:3, and 0:1 ratios) were 12.1 ± 0.5, 11.9 ± 0.8, 11.2 ± 1.0, and 12.0 ± 0.6 (n = 11; p = 0.2), respectively. G, deactivation time constants (τ) of the current at −20 mV as a function of voltage for the wild-type and F182L channel currents are shown.