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ShakerIR and Kv1.5 mutant channels with enhanced slow inactivation also exhibit K(+) o-dependent resting inactivation.
MedLine Citation:
PMID:  23708835     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Previous studies have shown that in N-type inactivation-removed Shaker (ShakerIR) channels, the T449K and T449A mutations result in enhanced slow inactivation. These mutant channels also show a loss of conductance in 0 mM K(+) o that was attributed to an inactivation process occurring from the closed, resting state and which we refer to as resting inactivation. Similar behavior has also been observed in the Kv1.5 H463G mutant channel. To date, the time courses for the onset of and recovery from resting inactivation have been unknown, but a comparison of the kinetics for resting inactivation induced at -80 mV and slow inactivation evoked at +50 mV may provide information on whether these two processes are mechanistically related. Here, we present an analysis of the time courses for the onset of and recovery from [K(+)]o-dependent resting inactivation and depolarization-induced inactivation of these mutant channels. Despite the enhancement of slow inactivation in the ShakerIR T449K, T449A, and Kv1.5 H463G mutants, the time constant for slow inactivation at +50 mV (τ inact) was relatively insensitive to the increases or decreases of [K(+)]o, confirming that accelerated inactivation from the open state does not underlie the loss of conductance in 0 mM K(+). For all three mutants, the time constant for resting inactivation (τ RI), induced by exposure to 0 mM K(+) o solution at -80 mV, was at least an order of magnitude larger than τ inact. On the other hand, the time course of recovery at -80 mV of each mutant from 0 mM K(+) o-induced resting inactivation was the same as that from depolarization-induced slow inactivation. This latter result suggests that the 0 mM K(+) o-induced resting inactivation of these mutant ShakerIR and Kv1.5 channels is mechanistically related to slow inactivation.
Authors:
Yen May Cheng; David Fedida; Steven J Kehl
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-5-26
Journal Detail:
Title:  Pflugers Archiv : European journal of physiology     Volume:  -     ISSN:  1432-2013     ISO Abbreviation:  Pflugers Arch.     Publication Date:  2013 May 
Date Detail:
Created Date:  2013-5-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0154720     Medline TA:  Pflugers Arch     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada, yenmayc@sfu.ca.
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