Variable K(+) channel subunit dysfunction in inherited mutations of KCNA1.

TY - JOUR

T1 - Variable K(+) channel subunit dysfunction in inherited mutations of KCNA1.

AU - Rea, Ruth

AU - Spauschus, Alexander

AU - Eunson, Louise H

AU - Hanna, Michael G

AU - Kullmann, Dimitri M

PY - 2002

Y1 - 2002

N2 - Mutations of KCNA1, which codes for the K(+) channel subunit hKv1.1, are associated with the human autosomal dominant disease episodic ataxia type 1 (EA1). Five recently described mutations are associated with a broad range of phenotypes: neuromyotonia alone or with seizures, EA1 with seizures, or very drug-resistant EA1. Here we investigated the consequences of each mutation for channel assembly, trafficking, gating and permeation. We related data obtained from co-expression of mutant and wild-type hKv1.1 to the results of expressing mutant-wild-type fusion proteins, and combined electrophysiological recordings in Xenopus oocytes with a pharmacological discrimination of the contribution of mutant and wild-type subunits to channels expressed at the membrane. We also applied confocal laser scanning microscopy to measure the level of expression of either wild-type or mutant subunits tagged with green fluorescent protein (GFP). R417stop truncates most of the C-terminus and is associated with severe drug-resistant EA1. Electrophysiological and pharmacological measurements indicated that the mutation impairs both tetramerisation of R417stop with wild-type subunits, and membrane targeting of heterotetramers. This conclusion was supported by confocal laser scanning imaging of enhanced GFP (EGFP)-tagged hKv1.1 subunits. Co-expression of R417stop with wild-type hKv1.2 subunits yielded similar results to co-expression with wild-type hKv1.1. Mutations associated with typical EA1 (V404I) or with neuromyotonia alone (P244H) significantly affected neither tetramerisation nor trafficking, and only altered channel kinetics. Two other mutations associated with a severe phenotype (T226R, A242P) yielded an intermediate result. The phenotypic variability of KCNA1 mutations is reflected in a wide range of disorders of channel assembly, trafficking and kinetics.

AB - Mutations of KCNA1, which codes for the K(+) channel subunit hKv1.1, are associated with the human autosomal dominant disease episodic ataxia type 1 (EA1). Five recently described mutations are associated with a broad range of phenotypes: neuromyotonia alone or with seizures, EA1 with seizures, or very drug-resistant EA1. Here we investigated the consequences of each mutation for channel assembly, trafficking, gating and permeation. We related data obtained from co-expression of mutant and wild-type hKv1.1 to the results of expressing mutant-wild-type fusion proteins, and combined electrophysiological recordings in Xenopus oocytes with a pharmacological discrimination of the contribution of mutant and wild-type subunits to channels expressed at the membrane. We also applied confocal laser scanning microscopy to measure the level of expression of either wild-type or mutant subunits tagged with green fluorescent protein (GFP). R417stop truncates most of the C-terminus and is associated with severe drug-resistant EA1. Electrophysiological and pharmacological measurements indicated that the mutation impairs both tetramerisation of R417stop with wild-type subunits, and membrane targeting of heterotetramers. This conclusion was supported by confocal laser scanning imaging of enhanced GFP (EGFP)-tagged hKv1.1 subunits. Co-expression of R417stop with wild-type hKv1.2 subunits yielded similar results to co-expression with wild-type hKv1.1. Mutations associated with typical EA1 (V404I) or with neuromyotonia alone (P244H) significantly affected neither tetramerisation nor trafficking, and only altered channel kinetics. Two other mutations associated with a severe phenotype (T226R, A242P) yielded an intermediate result. The phenotypic variability of KCNA1 mutations is reflected in a wide range of disorders of channel assembly, trafficking and kinetics.

M3 - SCORING: Zeitschriftenaufsatz

VL - 538

SP - 5

EP - 23

JO - J PHYSIOL-LONDON

JF - J PHYSIOL-LONDON

SN - 0022-3751

IS - 1

M1 - 1

ER -