title: Novel CLCNKB mutations causing Bartter syndrome affect channel surface expression.
abstract: Mutations in the CLCNKB gene encoding the ClC-Kb Cl(-) channel cause Bartter syndrome, which is a salt-losing renal tubulopathy. Here, we investigate the functional consequences of seven mutations. When expressed in Xenopus laevis oocytes, four mutants carried no current (c.736G>C, p.Gly246Arg; c.1271G>A, p.Gly424Glu; c.1313G>A, p.Arg438His; c.1316T>C, p.Leu439Pro), whereas others displayed a 30%-60% reduction in conductance as compared with wild-type ClC-Kb (c.242T>C, p.Leu81Pro; c.274C>T, p.Arg92Trp; c.1052G>C, p.Arg351Pro). Anion selectivity and sensitivity to external Ca(2+) and H(+), typical of the ClC-Kb channel, were not modified in the partially active mutants. In oocytes, we found that all the mutations reduced surface expression with a profile similar to that observed for currents. In HEK293 cells, the currents in the mutants had similar profiles to those obtained in oocytes, except for p.Leu81Pro, which produced no current. Furthermore, p.Arg92Trp and p.Arg351Pro mutations did not modify the unit-conductance of closely related ClC-K1. Western blot analysis in HEK293 cells showed that ClC-Kb protein abundance was lower for the nonconducting mutants but similar to wild-type for other mutants. Overall, two classes of mutants can be distinguished: nonconducting mutants associated with low total protein expression, and partially conducting mutants with unaltered channel properties and ClC-Kb protein abundance.
authors.affiliation: UPMC Université Paris 06, UMR_S 872, Laboratoire de Génomique, Physiologie et Physiopathologie Rénales, Paris, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Keck
authors.forename: Olga
authors.initials: O
authors.lastname: Andrini
authors.forename: Olivier
authors.initials: O
authors.lastname: Lahuna
authors.forename: Johanna
authors.initials: J
authors.lastname: Burgos
authors.forename: L Pablo
authors.initials: LP
authors.lastname: Cid
authors.forename: Francisco V
authors.initials: FV
authors.lastname: Sepúlveda
authors.forename: Sébastien
authors.initials: S
authors.lastname: L'hoste
authors.forename: Anne
authors.initials: A
authors.lastname: Blanchard
authors.forename: Rosa
authors.initials: R
authors.lastname: Vargas-Poussou
authors.forename: Stéphane
authors.initials: S
authors.lastname: Lourdel
authors.forename: Jacques
authors.initials: J
authors.lastname: Teulon
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D027321:Anion Transport Proteins / Q000378:metabolism / Q000502:physiology*; D001477:Bartter Syndrome / Q000235:genetics* / Q000378:metabolism*; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007223:Infant; D008297:Male; D009865:Oocytes / Q000378:metabolism; D017354:Point Mutation; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism; D055815:Young Adult
chemical_list: D027321:Anion Transport Proteins; C489932:CLCNKA protein, human; C412733:CLCNKB protein, human; D018118:Chloride Channels
keywords: Bartter; CLCNKB; ClC family; chloride channel; kidney