101. Ca2+ Activates Cystic Fibrosis Transmembrane Conductance Regulator- and Cl−-dependent HCO3− Transport in Pancreatic Duct Cells
- Author
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Sung Won Kwon, Won Sun Han, Duk Sun Ahn, Min Goo Lee, Wooin Ahn, Jin Ah Lee, Wan Namkung, and Kyung Hwan Kim
- Subjects
Pancreatic duct ,biology ,Bicarbonate ,Purinergic receptor ,chemistry.chemical_element ,Cell Biology ,Calcium ,Biochemistry ,Cystic fibrosis transmembrane conductance regulator ,Calcium in biology ,Cell biology ,chemistry.chemical_compound ,medicine.anatomical_structure ,BAPTA ,chemistry ,biology.protein ,medicine ,Molecular Biology ,Calcium signaling - Abstract
Pancreatic duct cells secrete bicarbonate-rich fluids, which are important for maintaining the patency of pancreatic ductal trees as well as intestinal digestive function. The bulk of bicarbonate secretion in the luminal membrane of duct cells is mediated by a Cl−-dependent mechanism (Cl−/HCO exchange), and we previously reported that the mechanism is CFTR-dependent and cAMP-activated (Lee, M. G., Choi, J. Y., Luo, X., Strickland, E., Thomas, P. J., and Muallem, S. (1999)J. Biol. Chem. 274, 14670–14677). In the present study, we provide comprehensive evidence that calcium signaling also activates the same CFTR- and Cl−-dependent HCO transport. ATP and trypsin evoked intracellular calcium signaling in pancreatic duct-derived cells through the activation of purinergic and protease-activated receptors, respectively. Cl−/HCO exchange activity was measured by recording pHi in response to [Cl−]o changes of the perfusate. In perfusate containing high concentrations of K+, which blocks Cl− movement through electrogenic or K+-coupled pathways, ATP and trypsin highly stimulated luminal Cl−/HCO exchange activity in CAPAN-1 cells expressing wild-type CFTR, but not in CFPAC-1 cells that have defective (ΔF508) CFTR. Notably, adenoviral transfection of wild-type CFTR in CFPAC-1 cells completely restored the stimulatory effect of ATP on luminal Cl−/HCO exchange. In addition, the chelation of intracellular calcium by 1,2-bis(2-aminophenoxy)ethane-N,N,N,N′-tetraacetic acid (BAPTA) treatment abolished the effect of calcium agonists on luminal Cl−/HCO exchange. These results provide a molecular basis for calcium-induced bicarbonate secretion in pancreatic duct cells and highlight the importance of CFTR in epithelial bicarbonate secretion induced by various stimuli.
- Published
- 2003