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Expression in mammalian cells and electrophysiological characterization of two mutant Kv1.1 channels causing episodic ataxia type 1 (EA‐1)
Author(s) -
Bretschneider Frank,
Wrisch Anja,
LehmannHorn Frank,
Grissmer Stephan
Publication year - 1999
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1999.00659.x
Subject(s) - mutant , wild type , tetraethylammonium , potassium channel , patch clamp , transmembrane domain , biophysics , chemistry , point mutation , protein subunit , mutation , electrophysiology , biology , genetics , amino acid , gene , neuroscience , potassium , organic chemistry
Episodic ataxia type 1 (EA‐1) is a rare neurological disorder and was the first ionic channel disease to be associated with defects in a potassium channel. Until now 10 different point mutations in the KCNA1‐gene have been reported to cause this disorder. We have investigated the functional consequences of two mutations leading to amino acid substitutions in the first and sixth transmembrane segments of a Kv1.1 channel subunit, by means of the patch‐clamp technique; we injected cRNA coding for, respectively, F184C and V408A mutant Kv1.1 channels into mammalian cells and compared the resulting currents with those in the wild‐type. The expression levels of F184C and V408A mutant channels relative to that of the wild‐type was 38 and 68%, respectively. Since the single‐channel conductance of the F184C mutant was similar to that of the wild‐type (12 pS) without an apparent change in the maximum open probability, we conclude that the lower expression level in the F184C mutant channels is due to a reduced number of functional channels on the cell surface. F184C activated slower, and at more depolarized potentials, and deactivated faster compared with the wild‐type. V408A channels deactivated and inactivated faster compared with the wild‐type. Studies with different extracellular cations and tetraethylammonium gave no indication that the pore structure was changed in the mutant channels. Acetazolamide, that is helpful in some patients suffering from EA‐1, was without effect on Kv1.1 wild‐type or mutant channels. This study confirms and extends earlier studies on the functional consequences of Kv1.1 mutations associated with EA‐1, in an attempt to understand the pathophysiology of the disease.