Identification and regulation of the cystic fibrosis transmembrane conductance regulator-generated chloride channel.
Cystic fibrosis transmembrane conductance regulator (CFTR) generates cAMP-regulated Cl- channels; mutations in CFTR cause defective Cl- channel function in cystic fibrosis epithelia. We used the patch-clamp technique to determine the single channel properties of Cl- channels in cell expressing recombinant CFTR. In cell-attached patches, an increase in cellular cAMP reversibly activated low conductance Cl- channels. cAMP-dependent regulation is due to phosphorylation, because the catalytic subunit of cAMP-dependent protein kinase plus ATP reversibly activated the channel in excised, cell-free patches of membrane. In symmetrical Cl- solutions, the channel had a channel conductance of 10.4 +/- 0.2 (n = 7) pS and a linear current-voltage relation. The channel was more permeable to Cl- than to I- and showed no appreciable time-dependent voltage effects. These biophysical properties are consistent with macroscopic studies of Cl- channels in single cells expressing CFTR and in the apical membrane of secretory epithelia. Identification of the single channel characteristics of CFTR-generated channels allows further studies of their regulation and the mechanism of ion permeation.
Berger
H A
HA
Howard Hughes Medical Institute, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
Anderson
M P
MP
Gregory
R J
RJ
Thompson
S
S
Howard
P W
PW
Maurer
R A
RA
Mulligan
R
R
Smith
A E
AE
Welsh
M J
MJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D018118:Chloride Channels; D003550:Cystic Fibrosis / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D011494:Protein Kinases / Q000494:pharmacology
C505032:CFTR protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; D011494:Protein Kinases