title: GTP-binding proteins inhibit cAMP activation of chloride channels in cystic fibrosis airway epithelial cells.
abstract: Cystic fibrosis (CF) is a genetic disease characterized, in part, by defective regulation of Cl- secretion by airway epithelial cells. In CF, cAMP does not activate Cl- channels in the apical membrane of airway epithelial cells. We report here whole-cell patch-clamp studies demonstrating that pertussis toxin, which uncouples heterotrimeric GTP-binding proteins (G proteins) from their receptors, and guanosine 5'-[beta-thio]diphosphate, which prevents G proteins from interacting with their effectors, increase Cl- currents and restore cAMP-activated Cl- currents in airway epithelial cells isolated from CF patients. In contrast, the G protein activators guanosine 5'-[gamma-thio]triphosphate and AlF4- reduce Cl- currents and inhibit cAMP from activating Cl- currents in normal airway epithelial cells. In CF cells treated with pertussis toxin or guanosine 5'-[beta-thio]diphosphate and in normal cells, cAMP activates a Cl- conductance that has properties similar to CF transmembrane-conductance regulator Cl- channels. We conclude that heterotrimeric G proteins inhibit cAMP-activated Cl- currents in airway epithelial cells and that modulation of the inhibitory G protein signaling pathway may have the therapeutic potential for improving cAMP-activated Cl- secretion in CF.
mesh_terms: D000535:Aluminum / Q000494:pharmacology; D017607:Aluminum Compounds; D002460:Cell Line; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D018118:Chloride Channels; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D003550:Cystic Fibrosis / Q000235:genetics / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004848:Epithelium / Q000502:physiology; D005459:Fluorides; D005461:Fluorine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005838:Genotype; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D037342:Pertussis Toxin; D012143:Respiratory Physiological Phenomena; D012137:Respiratory System / Q000503:physiopathology; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D017607:Aluminum Compounds; C505032:CFTR protein, human; D018118:Chloride Channels; D007473:Ion Channels; D008565:Membrane Proteins; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D006153:Guanosine Diphosphate; C050992:tetrafluoroaluminate; D005461:Fluorine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; C023427:guanosine 5'-O-(2-thiodiphosphate); D000535:Aluminum; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D005459:Fluorides