title: CFTR-adenylyl cyclase I association responsible for UTP activation of CFTR in well-differentiated primary human bronchial cell cultures.
abstract: 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.
authors.affiliation: Department of Medicine and Physiology, University of California, San Francisco, CA 94143, USA.
authors.forename: Wan
authors.initials: W
authors.lastname: Namkung
authors.forename: Walter E
authors.initials: WE
authors.lastname: Finkbeiner
authors.forename: A S
authors.initials: AS
authors.lastname: Verkman
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology*; D002118:Calcium / Q000819:agonists / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D016764:Cell Polarity / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004553:Electric Conductivity; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D015221:Potassium Channels / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014544:Uridine Triphosphate / Q000494:pharmacology*
chemical_list: D002712:Chlorides; D015221:Potassium Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D002118:Calcium; D014544:Uridine Triphosphate