Nucleoside triphosphates are required to open the CFTR chloride channel.
The CFTR Cl- channel contains two predicted nucleotide-binding domains (NBD1 and NBD2); therefore, we examined the effect of ATP on channel activity. Once phosphorylated by cAMP-dependent protein kinase (PKA), channels required cytosolic ATP to open. Activation occurred by a PKA-independent mechanism. ATP gamma S substituted for ATP in PKA phosphorylation, but it did not open the channel. Several hydrolyzable nucleotides (ATP greater than GTP greater than ITP approximately UTP greater than CTP) reversibly activated phosphorylated channels, but nonhydrolyzable analogs and Mg(2+)-free ATP did not. Studies of CFTR mutants indicated that ATP controls channel activity independent of the R domain and suggested that hydrolysis of ATP by NBD1 may be sufficient for channel opening. The finding that nucleoside triphosphates regulate CFTR begins to explain why CF-associated mutations in the NBDs block Cl- channel function.
Anderson
M P
MP
Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Berger
H A
HA
Rich
D P
DP
Gregory
R J
RJ
Smith
A E
AE
Welsh
M J
MJ
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology; D000818:Animals; D001665:Binding Sites; D018118:Chloride Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004252:DNA Mutational Analysis; D004553:Electric Conductivity; D006801:Humans; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D009711:Nucleotides / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology; D013329:Structure-Activity Relationship
C505032:CFTR protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D009711:Nucleotides; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate; D011494:Protein Kinases