Novel CLCNKB mutations causing Bartter syndrome affect channel surface expression

Hum Mutat. 2013 Sep;34(9):1269-78. doi: 10.1002/humu.22361. Epub 2013 Jun 12.


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.

Keywords: Bartter; CLCNKB; ClC family; chloride channel; kidney.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Anion Transport Proteins / metabolism
  • Anion Transport Proteins / physiology*
  • Bartter Syndrome / genetics*
  • Bartter Syndrome / metabolism*
  • Chloride Channels / genetics*
  • Chloride Channels / metabolism*
  • Female
  • HEK293 Cells
  • Humans
  • Infant
  • Male
  • Oocytes / metabolism
  • Point Mutation
  • Xenopus laevis / genetics
  • Xenopus laevis / metabolism
  • Young Adult


  • Anion Transport Proteins
  • CLCNKA protein, human
  • CLCNKB protein, human
  • Chloride Channels