Activation of chloride channels in normal and cystic fibrosis airway epithelial cells by multifunctional calcium/calmodulin-dependent protein kinase.
Cystic fibrosis is associated with defective regulation of apical membrane chloride channels in airway epithelial cells. These channels in normal cells are activated by cyclic AMP-dependent protein kinase and protein kinase C. In cystic fibrosis these kinases fail to activate otherwise normal Cl- channels. But Cl- flux in cystic fibrosis cells, as in normal cells, can be activated by raising intracellular Ca2+ (refs 5-10). We report here whole-cell patch clamp studies of normal and cystic fibrosis-derived airway epithelial cells showing that Cl- channel activation by Ca2+ is mediated by multifunctional Ca2+/calmodulin-dependent protein kinase. We find that intracellular application of activated kinase and ATP activates a Cl- current similar to that activated by a Ca2+ ionophore, that peptide inhibitors of either the kinase or calmodulin block Ca2(+)-dependent activation of Cl- channels, and that a peptide inhibitor of protein kinase C does not block Ca2(+)-dependent activation. Ca2+/calmodulin activation of Cl- channels presents a pathway with therapeutic potential for circumventing defective regulation of Cl- channels in cystic fibrosis.
Wagner
J A
JA
Department of Medicine, Falk CVRC, Stanford University School of Medicine, California 94305.
Cozens
A L
AL
Schulman
H
H
Gruenert
D C
DC
Stryer
L
L
Gardner
P
P
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin / Q000494:pharmacology; D018118:Chloride Channels; D003550:Cystic Fibrosis / Q000503:physiopathology*; D004848:Epithelium / Q000502:physiology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D015759:Ionomycin / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism*; D012016:Reference Values; D012143:Respiratory Physiological Phenomena; D012137:Respiratory System / Q000503:physiopathology
D002147:Calmodulin; D018118:Chloride Channels; D007473:Ion Channels; D008565:Membrane Proteins; D015759:Ionomycin; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases