Regulation of CFTR channels by HCO3-sensitive soluble adenylyl cyclase in human airway epithelial cells

• Published in: American Journal of Physiology: Cell Physiology Vol. 58; no. 5; pp. C1145 - C1151
• Main Authors: Wang, Yan, Lam, Chak Sum, Wu, Fan, Wang, Wen
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Physiological Society 01.11.2005
• Subjects: Biological and medical sciences; Cell membranes. Ionic channels. Membrane pores; Cell structures and functions; Cells; Cellular biology; Cystic fibrosis; Enzymes; Fundamental and applied biological sciences. Psychology; Gastroenterology. Liver. Pancreas. Abdomen; Liver. Biliary tract. Portal circulation. Exocrine pancreas; Medical sciences; Molecular and cellular biology; Other diseases. Semiology; Respiratory system; Signal transduction; Human; Adenosine; 2-hydroxyestradiol; bicarbonate: adenosine 3',5'-cyclic monophosphate; Epithelial cell; Cystic fibrosis transmembrane conductance regulator; Hydrogencarbonates
• ISSN: 0363-6143; 1522-1563

CFTR channels conduct HCO3- in addition to Cl- in airway epithelial cells. A defective HCO3--transporting function of CFTR may underlie the pathogenesis of cystic fibrosis. In the present study, we have investigated whether a HCO3--sensitive soluble adenylyl cyclase (sAC) is functionally coupled with CFTR and thus forms an autoregulatory mechanism for HCO3- 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. HCO3- 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 HCO3- 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 HCO3- 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 HCO3-/CO2 and the modulation of HCO3--conductive CFTR function by cAMP/PKA. [PUBLICATION ABSTRACT]