Characterization of two distinct Cl- conductances in fused human respiratory epithelial cells. II. Relation to cystic fibrosis gene product.
The present microelectrode experiments on fused respiratory epithelial cells of cystic fibrosis (CF) origin and non-CF origin aim at characterizing the molecular basis of the Cl- conductances regulated by cyclic adenosine monophosphate (cAMP) or respectively Ca2+, as described in the preceding publication. Cell membrane potential (Vm) and resistance (Rm) were recorded as well as their response to substitution of 90% of bath Cl- by isethionate (delta Vm,ISE), by I- (delta Vm,I), or by other halide anions. Fused CF cells had significantly (P < 0.05) higher control Vm values (-18.0 +/- 9.4 mV, +/- SD, n = 68) than fused non-CF cells (-12.5 +/- 6.6 mV, n = 69) and responded to the Ca2+ ionophore A23187 with an increase in the Vm response to Cl- substitution, but did not respond to forskolin. This indicates that CF cells express only the Ca(2+)-stimulated Cl- conductance. Injection of the antibody M3A7 against a fusion protein containing amino acids 1195 to 1480 of the CF gene product into young, forskolin-stimulated or old non-CF cells decreased delta Vm,ISE and delta Vm,I within 15 min to values observed in CF cells. This indicates inhibition of the cAMP-stimulated Cl- conductance and supports the molecular identity of this conductance with the CF gene product. However, the slow onset of inhibition does not allow secondary effects to be excluded and a slight fall in Rm remains unexplained. Stimulation of the Ca(2+)-regulated Cl- conductance was not impaired. Injection of M3A7 into CF cells or of a control antibody in non-CF cells had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
Schröder
U H
UH
Zentrum der Physiologie, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany.
Frömter
E
E
D000906:Antibodies / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002459:Cell Fusion; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004553:Electric Conductivity; D004848:Epithelium / Q000503:physiopathology; D006801:Humans; D008565:Membrane Proteins / Q000276:immunology / Q000502:physiology*; D009298:Nasal Polyps / Q000503:physiopathology; D012137:Respiratory System / Q000503:physiopathology*
D000906:Antibodies; C505032:CFTR protein, human; D018118:Chloride Channels; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000001:Calcimycin; D000242:Cyclic AMP; D002118:Calcium