Referenced in: none

Automatically associated channels: Kv2.1 , Slo1

Title: Shab K (+) channel slow inactivation: a test for U-type inactivation and a hypothesis regarding K (+) -facilitated inactivation mechanisms.

Authors: Elisa Carrillo, Imilla I Arias-Olguín, León D Islas, Froylan Gómez-Lagunas

Journal, date & volume: Channels (Austin), 2013 Mar-Apr , 7, 97-108

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/23419584

Abstract
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.