Referenced in: none

Automatically associated channels: Kv1.4 , Kv3.1 , Kv4.3 , Slo1

Title: Time- and voltage-dependent components of Kv4.3 inactivation.

Authors: Shimin Wang, Vladimir E Bondarenko, Yu-Jie Qu, Glenna C L Bett, Michael J Morales, Randall L Rasmusson, Harold C Strauss

Journal, date & volume: Biophys. J., 2005 Nov , 89, 3026-41

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/16100281

Abstract
Kv4.3 inactivation is a complex multiexponential process, which can occur from both closed and open states. The fast component of inactivation is modulated by the N-terminus, but the mechanisms mediating the other components of inactivation are controversial. We studied inactivation of Kv4.3 expressed in Xenopus laevis oocytes, using the two-electrode voltage-clamp technique. Inactivation during 2000 ms pulses at potentials positive to the activation threshold was described by three exponents (46 +/- 3, 152 +/- 13, and 930 +/- 50 ms at +50 mV, n = 7) whereas closed-state inactivation (at potentials below threshold) was described by two exponents (1079 +/- 119 and 3719 +/- 307 ms at -40 mV, n = 9). The fast component of open-state inactivation was dominant at potentials positive to -20 mV. Negative to -30 mV, the intermediate and slow components dominated inactivation. Inactivation properties were dependent on pulse duration. Recovery from inactivation was strongly dependent on voltage and pulse duration. We developed an 11-state Markov model of Kv4.3 gating that incorporated a direct transition from the open-inactivated state to the closed-inactivated state. Simulations with this model reproduced open- and closed-state inactivation, isochronal inactivation relationships, and reopening currents. Our data suggest that inactivation can proceed primarily from the open state and that multiple inactivation components can be identified.