Shab K+channel slow inactivation

• DOI: 10.4161/chan.23569
• Publication Date: 2013-03-15T20:03:22Z
• Authors: Elisa Carrillo; Imilla I. Arias-O...; León D. Islas; Froylan Gómez-Lag...
• Keywords: 0303 health sciences; Tetraethylammonium; Spodoptera; Quinidine; Protein Structure, Tertiary; 03 medical and health sciences; Drosophila melanogaster; Shab Potassium Channels; Potassium; Potassium Channel Blockers; Sf9 Cells; Animals; Drosophila Proteins; Ion Channel Gating

Herein, we report the first characterization of Shab slow inactivation. Open Shab channels inactivate within seconds, with two voltage-independent time constants. Additionally, Shab presents significant closed-state inactivation. We found that with short depolarizing pulses, shorter than the slowest inactivation time constant, the resulting inactivation curve has a marked U-shape, but as pulse duration increases, approaching steady-state conditions, the U-shape vanishes, and the resulting inactivation curves converge to the classical Boltzmann h∞ curve. Regarding the mechanism of inactivation, we found that external K (+) and TEA facilitate both open- and closed-state inactivation, while the cavity blocker quinidine hinders inactivation. These results together with our previous observations regarding the K (+) -dependent stability of the K (+) conductance, suggest the novel hypothesis that inactivation of Shab channels, and possibly that of other Kv channels whose inactivation is facilitated by K (+) , does not involve a significant narrowing of the extracellular entry of the pore. Instead, we hypothesize that there is only a rearrangement of a more internal segment of the pore that affects the central cavity and halts K (+) conduction.