cAMP-inducible chloride conductance in mouse fibroblast lines stably expressing the human cystic fibrosis transmembrane conductance regulator.
A cAMP-inducible chloride permeability has been detected in mouse fibroblast (L cell) lines upon stable integration of a full-length cDNA encoding the human cystic fibrosis transmembrane conductance regulator (CFTR). As indicated by a Cl(-)-indicator dye, the Cl- permeability of the plasma membrane increases by 10- to 30-fold within 2 min after treatment of the cells with forskolin, an activator of adenylyl cyclase. The properties of the conductance are similar to those described in secretory epithelial cells; the whole-cell current-voltage relationship is linear and there is no evidence of voltage-dependent inactivation or activation. In contrast, this cAMP-dependent Cl- flux is undetectable in the untransfected cells or cells harboring defective cDNA constructs, including one with a phenylalanine deletion at amino acid position 508 (delta F508), the most common mutation causing cystic fibrosis. These observations are consistent with the hypothesis that the CFTR is a cAMP-dependent Cl- channel. The availability of a heterologous (nonepithelial) cell type expressing the CFTR offers an excellent system to understand the basic mechanisms underlying this CFTR-associated ion permeability and to study the structure and function of the CFTR.
Rommens
J M
JM
Department of Genetics, Hospital for Sick Children, Toronto, ON, Canada.
Dho
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Bear
C E
CE
Kartner
N
N
Kennedy
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D
Riordan
J R
JR
Tsui
L C
LC
Foskett
J K
JK
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D000242:Cyclic AMP / Q000502:physiology*; D003550:Cystic Fibrosis / Q000235:genetics / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005091:Exons; D005347:Fibroblasts / Q000502:physiology; D015870:Gene Expression; D005822:Genetic Vectors; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes; D010957:Plasmids; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D014162:Transfection
C505032:CFTR protein, human; D018118:Chloride Channels; D002712:Chlorides; D003062:Codon; D007473:Ion Channels; D008565:Membrane Proteins; D015345:Oligonucleotide Probes; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D008668:Metallothionein; D000242:Cyclic AMP