Referenced in: none

Automatically associated channels: ClC1 , ClC4 , Slo1

Title: The myotonia congenita mutation A331T confers a novel hyperpolarization-activated gate to the muscle chloride channel ClC-1.

Authors: Maike Warnstedt, Chen Sun, Barbara Poser, Maria Jose Escriva, Lisbeth Tranebjaerg, Torberg Torbergsen, Marijke van Ghelue, Christoph Fahlke

Journal, date & volume: J. Neurosci., 2002 Sep 1 , 22, 7462-70

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/12196568

Abstract
Mutations in the muscle chloride channel gene CLCN1 cause myotonia congenita, an inherited disorder of skeletal muscle excitability leading to a delayed relaxation after muscle contraction. Here, we examine the functional consequences of a novel disease-causing mutation that predicts the substitution of alanine by threonine at position 331 (A331T) by whole-cell patch-clamp recording of recombinant mutant channels. A331T hClC-1 channels exhibit a novel slow gate that activates during membrane hyperpolarization and closes at positive potentials. This novel gate acts in series with fast opening and closing transitions that are common to wild-type (WT) and mutant channels. Under conditions at which this novel gate is not activated, i.e., a holding potential of 0 mV, the typical depolarization-induced activation gating of WT hClC-1 was only slightly affected by the mutation. In contrast, A331T hClC-1 channels with an open slow gate display an altered voltage dependence of open probability. These novel gating features of mutant channels produce a decreased open probability at -85 mV, the normal muscle resting potential, leading to a reduced resting chloride conductance of affected muscle fibers. The A331T mutation causes an unprecedented alteration of ClC-1 gating and reveals novel processes defining transitions between open and closed states in ClC chloride channels.