Phosphatase Inhibitors Activate Normal and Defective CFTR Chloride Channels

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 91; no. 19; pp. 9160 - 9164
• Main Authors: Becq, Frederic, Jensen, Timothy J., Chang, Xiu-Bao, Savoia, Anna, Rommens, Johanna M., Tsui, Lap-Chee, Buchwald, Manuel, Riordan, John R., Hanrahan, John W.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 13-09-1994; National Acad Sciences; National Academy of Sciences
• Subjects: 1-Methyl-3-isobutylxanthine - pharmacology; Animals; Cell membranes; Cellular biology; Chloride channels; Chloride Channels - drug effects; CHO Cells; Cricetinae; Cystic fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Epithelial cells; Humans; In Vitro Techniques; Laboratory animals; Medical research; Membrane Proteins - drug effects; Membrane Proteins - genetics; Membranes; Mutation; P branes; Phosphatases; Phosphoric Monoester Hydrolases - antagonists & inhibitors; Phosphorylation; Physiological regulation; Recombinant Proteins; Theophylline - pharmacology; Vanadates; Vanadates - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.19.9160

The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is regulated by phosphorylation and dephosphorylation at multiple sites. Although activation by protein kinases has been studied in some detail, the dephosphorylation step has received little attention. This report examines the mechanisms responsible for the dephosphorylation and spontaneous deactivation ("rundown") of CFTR chloride channels excised from transfected Chinese hamster ovary (CHO) and human airway epithelial cells. We report that the alkaline phosphatase inhibitors bromotetramisole, 3-isobutyl-1-methylxanthine, theophylline, and vanadate slow the rundown of CFTR channel activity in excised membrane patches and reduce dephosphorylation of CFTR protein in isolated membranes. It was also found that in unstimulated cells, CFTR channels can be activated by exposure to phosphatase inhibitors alone. Most importantly, exposure of mammalian cells to phosphatase inhibitors alone activates CFTR channels that have disease-causing mutations, provided the mutant channels are present in the plasma membrane (R117H, G551D, and Δ F508 after cooling). These results suggest that CFTR dephosphorylation is dynamic and that membrane-associated phosphatase activity may be a potential therapeutic target for the treatment of cystic fibrosis.