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Novel CLCNKB Mutations Causing Bartter Syndrome Affect Channel Surface Expression

Authors

  • Mathilde Keck,

    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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  • Olga Andrini,

    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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  • Olivier Lahuna,

    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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  • Johanna Burgos,

    1. Centro de Estudios Científicos, Avenida Arturo Prat 514, Valdivia, Chile
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  • L. Pablo Cid,

    1. Centro de Estudios Científicos, Avenida Arturo Prat 514, Valdivia, Chile
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  • Francisco V. Sepúlveda,

    1. Centro de Estudios Científicos, Avenida Arturo Prat 514, Valdivia, Chile
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  • Sébastien L‘Hoste,

    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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  • Anne Blanchard,

    1. Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Centre d'Investigation Clinique, Paris, France
    2. Université Paris-Descartes, Faculté de Médecine, Paris, France
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  • Rosa Vargas-Poussou,

    1. Université Paris-Descartes, Faculté de Médecine, Paris, France
    2. Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, département de génétique, Paris, France
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  • Stéphane Lourdel,

    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
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  • Jacques Teulon

    Corresponding author
    1. UPMC Université Paris 06, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    2. INSERM, UMR_S 872, Laboratoire de génomique, physiologie et physiopathologie rénales, Paris, France
    • Address for correspondence: Jacques Teulon, UMR_S 872, team 3, 15 rue de l'Ecole de Médecine, 75720 Paris Cedex 06, France. E-mail: jacques.teulon@upmc.fr

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  • Communicated by Claude Férec

  • Contract Grant Sponsors: Agence Nationale de la Recherche (ANR07-PHYSIO-008–2, BLAN 2010–111201); Ministry of Foreign Affairs (ECOS-sud C10S03). Centers of Excellence Base Financing Program of Conicyt.

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 Ca2+ 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.

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