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Regulation by ATP and ADP of CFTR chloride channels that contain mutant nucleotide-binding domains

M P Anderson1, M J Welsh

  • 1Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.

Science (New York, N.Y.)
|September 18, 1992
PubMed

Insights

Cytosolic adenosine triphosphate (ATP) is crucial for opening phosphorylated cystic fibrosis transmembrane conductance regulator (CFTR) channels. Mutations affecting ATP binding in CFTR

Area of Science:

  • Molecular biology
  • Ion channel physiology
  • Biochemistry

Background:

  • The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel.
  • CFTR channel gating requires phosphorylation and cytosolic adenosine triphosphate (ATP).
  • CFTR possesses two predicted nucleotide-binding domains (NBDs).

Purpose of the Study:

  • To investigate the role of NBDs in ATP-dependent CFTR channel regulation.
  • To determine the functional equivalence of the two NBDs in ATP interaction.
  • To assess the impact of cystic fibrosis-associated mutations on CFTR function.

Main Methods:

  • Site-directed mutagenesis of CFTR NBDs.
  • Measurement of CFTR chloride channel activity in response to varying ATP concentrations.
  • Analysis of adenosine diphosphate (ADP) inhibition.

Main Results:

  • Mutations in both NBDs altered the ATP concentration-channel activity relationship, confirming direct ATP interaction.
  • The two NBDs are not functionally equivalent; adenosine diphosphate (ADP) competitively inhibited the channel via NBD2.
  • Four cystic fibrosis-associated mutations reduced channel activity, and one also decreased ATP potency.

Conclusions:

  • ATP directly interacts with both NBDs to stimulate CFTR channel activity.
  • Functional differences exist between the two NBDs.
  • Defective ATP-dependent stimulation of CFTR through NBDs may underlie some cases of cystic fibrosis.

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