Functional and structural analysis of ClC-K chloride channels involved in renal disease

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Item Type:	Article
Title:	Functional and structural analysis of ClC-K chloride channels involved in renal disease
Creators Name:	Waldegger, S. and Jentsch, T.J.
Abstract:	ClC-K channels belong to the CLC family of chloride channels and are predominantly expressed in the kidney. Genetic evidence suggests their involvement in transepithelial transport of chloride in distal nephron segments; ClC-K1 gene deletion leads to nephrogenic diabetes insipidus in mice, and mutations of the hClC-Kb gene cause Bartter's syndrome type III in humans. Expression of rClC-K1 in Xenopus oocytes yielded voltage-independent currents that were pH-sensitive, had a Br(-) > NO(3)(-) = Cl(-) > I(-) conductance sequence, and were activated by extracellular calcium. A glutamate for valine exchange at amino acid position 166 induced strong voltage dependence and altered the conductance sequence of ClC-K1. This demonstrates that rClC-K1 indeed functions as an anion channel. By contrast, we did not detect currents upon hClC-Kb expression in Xenopus oocytes. Using a chimeric approach, we defined a protein domain that, when replaced by that of rClC-K1, allowed the functional expression of a chimera consisting predominantly of hClC-Kb. Its currents were linear and were inhibited by extracellular acidification. Contrasting with rClC-K1, they displayed a Cl(-) > Br(-)> I(-) > NO(3)(-) conductance sequence and were not augmented by extracellular calcium. Insertion of point mutations associated with Bartter's syndrome type III destroyed channel activity. We conclude that ClC-K proteins form constitutively open chloride channels with distinct physiological characteristics.
Keywords:	Amino Acid Substitution, Anion Transport Proteins, Bartter Syndrome, Chloride Channels, Gene Deletion, Kidney Diseases, Membrane Potentials, Membrane Proteins, Molecular Models, Oocytes, Patch-Clamp Techniques, Point Mutation, Protein Conformation, Recombinant Fusion Proteins, Xenopus Proteins, Animals, Mice, Xenopus Laevis
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	275
Number:	32
Page Range:	24527-24533
Date:	11 August 2000
Official Publication:	https://doi.org/10.1074/jbc.M001987200
PubMed:	View item in PubMed

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