title: Phosphorylation fails to activate chloride channels from cystic fibrosis airway cells.
abstract: Chloride impermeability of epithelial cells can account for many of the experimental and clinical manifestations of cystic fibrosis (CF). Activation of apical-membrane Cl- channels by cyclic AMP-mediated stimuli is defective in CF airway epithelial cells, despite normal agonist-induced increases in cellular cAMP levels. This defect in Cl- channel regulation has been localized to the apical membrane by exposing the cytoplasmic surface of excised membrane patches to the catalytic subunit (C subunit) of cAMP-dependent protein kinase and ATP. In membranes from normal cells, C-subunit activated Cl- channels with properties identical to those stimulated by cAMP-dependent agonists during cell-attached recording. Activation by the C subunit was not observed in CF membranes, but the presence of Cl- channels was verified by voltage-induced activation. The failure of the C subunit to activate the Cl- channels of CF membranes indicates that the block in their cAMP-mediated activation lies distal to induction of cAMP-dependent protein kinase activity and focuses our attention on the Cl- channel and its membrane-associated regulatory proteins as the probable site of the CF defect.
mesh_terms: D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D003550:Cystic Fibrosis / Q000503:physiopathology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology; D014132:Trachea / Q000503:physiopathology*
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D000242:Cyclic AMP; D011494:Protein Kinases