CFTR channels in immortalized human airway cells.
The cystic fibrosis (CF) gene codes for CF transmembrane regulator (CFTR), a small-conductance linear Cl- channel, but numerous studies have identified a larger conductance, rectifying Cl- channel as the adenosine 3',5'-cyclic monophosphate (cAMP)-regulated channel that is defective in airway cells. We examined Cl- conductance in a bronchial epithelial cell line that expresses CFTR, 16HBE14o-, (CFTR+) and in an airway cell line that does not, 9HTEo-/S, (CFTR-). Ionomycin or hypotonic Ringer increased iodide efflux from both cell lines; however, forskolin increased iodide efflux or whole cell Cl- currents only in CFTR+ cells. Forskolin-stimulated whole cell currents were linear, voltage independent, and blocked by iodide. Cell-attached and outside-out patches from confluent CFTR+ but not CFTR- cells revealed 6-pS channels having linear current-voltage relations, permselectivity Cl > I (partial block by external iodide), and little or no inhibition by 5-nitro-2-(3-phenylpropylamino)-benzoate. The number of active channels per patch increased from 0.6 to 3.0 after forskolin. Channels closed after excision with tau = 4 s, but activity could be prolonged with ATP or protein kinase A plus ATP. Channels were modeled with one open and four closed states and show apparent cooperativity in gating. Rectifying Cl- channels previously implicated in CF were not seen in cell-attached recordings from either cell line but were abundant in excised patches from both cell lines. Thus CFTR channels are the pathway for cAMP-mediated Cl- conductance in these human airway cells, Ca2+ and swelling-induced channels do not require CFTR, and CFTR-cells display a CF phenotype.
D000838:Anions / Q000378:metabolism; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D002461:Cell Line, Transformed; D018118:Chloride Channels; D002712:Chlorides / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D004553:Electric Conductivity; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007454:Iodides / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*
D000838:Anions; C505032:CFTR protein, human; D018118:Chloride Channels; D002712:Chlorides; D007038:Hypotonic Solutions; D007454:Iodides; D007473:Ion Channels; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D015759:Ionomycin; D000242:Cyclic AMP