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TRESK background potassium channel is not gated at the helix bundle crossing near the cytoplasmic end of the pore

Fig 1

Barium ions can be trapped in the Kv1.3 channel pore.

Kv1.3 channels were expressed in HEK293T cells. The currents were recorded in inside-out excised patches. Voltage-dependent currents were measured by depolarizing the membrane to +40 mV for 250 ms. The holding potential was -80 mV. Currents were measured at the end of the +40 mV voltage step. Kv1.3 current was calculated by subtracting the current measured in K+-free bath solution from the value measured in the high K+ solution. The currents after the administration of Ba2+ were normalized to the value measured before the application of the blocker (on panel C). A, Representative recording showing the application of Ba2+ (1 mM) to the intracellular surface of the patches while keeping the holding potential at -80 mV (constant hyperpolarization). Afterwards the blocker was removed from the bath solution and the current was measured every 30 s by depolarizing steps to +40 mV. B, Representative recording showing the effect of Ba2+ (1 mM) applied to the intracellular surface of inside-out patches when the membrane was depolarized to +40 mV (transient depolarization). Barium was then removed from the bath solution while the holding potential was -80 mV. Voltage-gated K+ currents were measured every 30 s, as in panel A. C, The normalized currents after the application of Ba2+ are plotted as a function of time. The channels were opened by transient depolarization to +40 mV (black circles) or closed at constant -80 mV (grey squares) in the presence of Ba2+. Data are plotted as scatter plot, the averages of the different groups are plotted as columns. The differences between the groups were significant at all examined time points (p<0.05, statistical analysis was performed using Kruskal-Wallis ANOVA followed by pairwise comparison using the Mann-Whitney U test).

Fig 1