CFTR-adenylyl cyclase I association responsible for UTP activation of CFTR in well-differentiated primary human bronchial cell cultures

Chloride secretion by airway epithelial cells is defective in cystic fibrosis (CF). The conventional paradigm is that CFTR is activated through cAMP and protein kinase A (PKA), whereas the Ca(2+)-activated chloride channel (CaCC) is activated by Ca(2+) agonists like UTP. We found that most chloride...

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Bibliographic Details
Published in:Molecular biology of the cell 2010-08, Vol.21 (15), p.2639-2648
Main Authors: Namkung, Wan, Finkbeiner, Walter E, Verkman, A S
Format: Article
Language:English
Subjects:
Adenylyl Cyclases - metabolism
Bronchi - cytology
Calcium - agonists
Calcium - metabolism
Cell Differentiation - drug effects
Cell Membrane - drug effects
Cell Membrane - metabolism
Cell Polarity - drug effects
Cells, Cultured
Chlorides - metabolism
Cyclic AMP - metabolism
Cyclic AMP-Dependent Protein Kinases - metabolism
Cystic Fibrosis Transmembrane Conductance Regulator - metabolism
Electric Conductivity
Enzyme Activation - drug effects
Epithelial Cells - cytology
Epithelial Cells - drug effects
Epithelial Cells - enzymology
Epithelial Cells - metabolism
Humans
Ion Channel Gating - drug effects
Potassium Channels - metabolism
Protein Transport - drug effects
Signal Transduction - drug effects
Uridine Triphosphate - pharmacology
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Summary:Chloride secretion by airway epithelial cells is defective in cystic fibrosis (CF). The conventional paradigm is that CFTR is activated through cAMP and protein kinase A (PKA), whereas the Ca(2+)-activated chloride channel (CaCC) is activated by Ca(2+) agonists like UTP. We found that most chloride current elicited by Ca(2+) agonists in primary cultures of human bronchial epithelial cells is mediated by CFTR by a mechanism involving Ca(2+) activation of adenylyl cyclase I (AC1) and cAMP/PKA signaling. Use of selective inhibitors showed that Ca(2+) agonists produced more chloride secretion from CFTR than from CaCC. CFTR-dependent chloride secretion was reduced by PKA inhibition and was absent in CF cell cultures. Ca(2+) agonists produced cAMP elevation, which was blocked by adenylyl cyclase inhibition. AC1, a Ca(2+)/calmodulin-stimulated adenylyl cyclase, colocalized with CFTR in the cell apical membrane. RNAi knockdown of AC1 selectively reduced UTP-induced cAMP elevation and chloride secretion. These results, together with correlations between cAMP and chloride current, suggest that compartmentalized AC1-CFTR association is responsible for Ca(2+)/cAMP cross-talk. We further conclude that CFTR is the principal chloride secretory pathway in non-CF airways for both cAMP and Ca(2+) agonists, providing a novel mechanism to link CFTR dysfunction to CF lung disease.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.e09-12-1004