Barttin increases surface expression and changes current properties of ClC-K channels

Pflugers Arch. 2002 Jun;444(3):411-8. doi: 10.1007/s00424-002-0819-8. Epub 2002 Apr 9.


The term Bartter syndrome encompasses a heterogeneous group of autosomal recessive salt-losing nephropathies that are caused by disturbed transepithelial sodium chloride reabsorption in the distal nephron. Mutations have been identified in the NKCC2 (Na(+)-K(+)-2Cl(-)) cotransporter and ROMK potassium channel, which cooperate in the process of apical sodium chloride uptake, and ClC-Kb chloride channels, which mediate basolateral chloride release. Recently, mutations in barttin, a protein not related to any known ion transporter or channel, were described in BSND, a variant of Bartter syndrome associated with sensorineural deafness. Here we show that barttin functions as an activator of ClC-K chloride channels. Expression of barttin together with ClC-K in Xenopus oocytes increased ClC-K current amplitude, changed ClC-K biophysical properties, and enhanced ClC-K abundance in the cell membrane. Co-immunoprecipitation revealed a direct interaction of barttin with ClC-K. We performed in situ hybridization on rat kidney slices and RT-PCR analysis on microdissected nephron segments to prove co-expression of barttin, ClC-K1 and ClC-K2 along the distal nephron. Functional analysis of BSND-associated point mutations revealed impaired ClC-K activation by barttin. The results demonstrate regulation of a CLC chloride channel by an accessory protein and indicate that ClC-K activation by barttin is required for adequate tubular salt reabsorption.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anion Transport Proteins*
  • Bartter Syndrome / genetics
  • Bartter Syndrome / metabolism
  • Cell Line
  • Chloride Channels / genetics
  • Chloride Channels / metabolism*
  • Membrane Potentials / physiology
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism*
  • Nephrons / metabolism
  • Oocytes / physiology
  • Patch-Clamp Techniques
  • Point Mutation*
  • RNA, Messenger / analysis
  • Xenopus Proteins*
  • Xenopus laevis


  • Anion Transport Proteins
  • BSND protein, human
  • CLCNKA protein, human
  • Chloride Channels
  • Clcnkb protein, rat
  • Membrane Proteins
  • RNA, Messenger
  • Xenopus Proteins
  • bsnd protein, rat
  • clcnka protein, Xenopus