Aberrant CFTR-dependent HCO3- Transport in Mutations Associated With Cystic Fibrosis

Nature. 2001 Mar 1;410(6824):94-7. doi: 10.1038/35065099.

Abstract

Cystic fibrosis (CF) is a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Initially, Cl- conductance in the sweat duct was discovered to be impaired in CF, a finding that has been extended to all CFTR-expressing cells. Subsequent cloning of the gene showed that CFTR functions as a cyclic-AMP-regulated Cl- channel; and some CF-causing mutations inhibit CFTR Cl- channel activity. The identification of additional CF-causing mutants with normal Cl- channel activity indicates, however, that other CFTR-dependent processes contribute to the disease. Indeed, CFTR regulates other transporters, including Cl(-)-coupled HCO3- transport. Alkaline fluids are secreted by normal tissues, whereas acidic fluids are secreted by mutant CFTR-expressing tissues, indicating the importance of this activity. HCO3- and pH affect mucin viscosity and bacterial binding. We have examined Cl(-)-coupled HCO3- transport by CFTR mutants that retain substantial or normal Cl- channel activity. Here we show that mutants reported to be associated with CF with pancreatic insufficiency do not support HCO3- transport, and those associated with pancreatic sufficiency show reduced HCO3- transport. Our findings demonstrate the importance of HCO3- transport in the function of secretory epithelia and in CF.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bicarbonates / metabolism*
  • Biological Transport
  • Cell Line
  • Chlorides / metabolism
  • Cystic Fibrosis / metabolism*
  • Cystic Fibrosis Transmembrane Conductance Regulator / genetics
  • Cystic Fibrosis Transmembrane Conductance Regulator / metabolism*
  • Humans
  • Membrane Potentials
  • Membranes / metabolism
  • Mutagenesis, Site-Directed
  • Mutation
  • Pancreas / metabolism
  • Transfection

Substances

  • Bicarbonates
  • CFTR protein, human
  • Chlorides
  • Cystic Fibrosis Transmembrane Conductance Regulator