FIGURE 6.
The scorpion toxin BeKm-1 protects ERG channels against PK-mediated cleavage. A, hERG current traces in control (Ctrl) or PK-treated (200 μg/ml, 20 min) hERG-HEK cells in the absence or presence of BeKm-1 (1 μm). IhERG is summarized in the bar graph below the current traces for each group. The numbers above the bar graphs indicate the number of cells examined from three independent experiments. B, Western blot demonstrating hERG expression in control or PK-treated hERG-HEK cells in the absence or presence of BeKm-1 (1 μm). hERG was detected using an anti-hERG antibody targeting the C terminus. The band intensities of the 155-kDa hERG in PK-treated cells are normalized to that of control and summarized below the Western blot image (n = 4). C, families of Cs+-mediated IKr in neonatal rat ventricular myocytes in control or in PK treatment with or without BeKm-1 (1 μm). The maximal tail currents upon repolarization to −80 mV are summarized below the current traces. The numbers above the bar graphs indicate the number of cells examined from three independent experiments. D, diagram illustrating that BeKm-1 protects the hERG S5-pore linker from being digested by PK. **, p < 0.01 versus control. Error bars, S.E.