Figure 4.

I_A G_max is significantly decreased in HEK-Kv4.2g cells transiently transfected with SUMO+Ubc9 compared to control. Whole cell patch clamp experiments were performed on HEK-Kv4.2g cells that were or were not transiently transfected with SUMO+Ubc9 to produce a ~60% increase in mean Kv4.2 SUMOylation. (A) Representative current traces (upper panel) and voltage steps (lower panel) used to obtain the voltage dependence of activation. (B) Representative current traces (upper panel) and voltage steps (lower panel) used to obtain the voltage dependence of steady-state inactivation. (C) Plots of normalized I_A G_max for control and SUMO+Ubc9 treatment groups. Each data point represents one cell. Cells in each treatment groups were obtained from ≥3 independent transfections. All data points were normalized by the mean value for the control treatment group. Asterisk, significantly different; control, 1.0 ± 0.079; SUMO+Ubc9, 0.78 ± 0.068; Mann-Whitney U p = 0.044. (D) Activation and steady-state inactivation curves for control and SUMO+Ubc9 treatment groups. Each point represents the mean ± SEM for all cells shown in panel (C). (E,F) Inactivation τ for all cells shown in panel (C). Asterisk, significantly different; t-test p = 0.018.