Regulation of CFTR channels by HCO(3)--sensitive soluble adenylyl cyclase in human airway epithelial cells.
CFTR channels conduct HCO(3)(-) in addition to Cl(-) in airway epithelial cells. A defective HCO(3)(-)-transporting function of CFTR may underlie the pathogenesis of cystic fibrosis. In the present study, we have investigated whether a HCO(3)(-)-sensitive soluble adenylyl cyclase (sAC) is functionally coupled with CFTR and thus forms an autoregulatory mechanism for HCO(3)(-) transport in human airway epithelial Calu-3 cells. A reverse transcriptase-polymerase chain reaction showed that transcripts of both full-length and truncated sACs are present in Calu-3 cells. Truncated sAC protein is the predominant, if not the only, isoform expressed in Calu-3 cells. HCO(3)(-) stimulated a modest increase in cAMP production, and the increase was sensitive to 2-hydroxyestradiol (2-HE), a sAC inhibitor, but not to SQ22,536, a blocker of conventional transmembrane adenylyl cyclases. These results suggest that sAC is functional in Calu-3 cells. Adding 25 mM HCO(3)(-) to the bath stimulated CFTR-mediated whole cell currents in the absence, but not in the presence, of 2-HE. In cell-attached membrane patches, 25 or 50 mM HCO(3)(-) in the bath markedly increased the product of channel number and open probability of CFTR, and this activation was attenuated by 2-HE. These findings demonstrate that sAC signaling pathway is involved in the regulation of CFTR function in human airway epithelium and thereby provides a link between the level of intracellular HCO(3)(-)/CO(2) and the modulation of HCO(3)(-)-conductive CFTR function by cAMP/PKA.
Wang
Yan
Y
Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China.
Lam
Chak Sum
CS
Wu
Fan
F
Wang
Wen
W
Duan
Yuanyuan
Y
Huang
Pingbo
P
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001639:Bicarbonates / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors / Q000502:physiology*; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D020545:Respiratory Mucosa / Q000166:cytology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction
D000067956:Adenylyl Cyclase Inhibitors; D001639:Bicarbonates; C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D005905:Glyburide