Rescue of F508-CFTR trafficking and gating in human cystic fibrosis airway primary cultures by small molecules

Van Goor, Fredrick, Kimberly S. Straley, Dong Cao, Jesús González, Sabine Hadida, Anna Hazlewood, John Joubran, Tom Knapp, Lewis R. Makings, Mark Miller, Timothy Neuberger, Eric Olson, Victor Panchenko, James Rader, Ashvani Singh, Jeffrey H. Stack, Roger Tung, Peter D. J. Grootenhuis, and Paul Negulescu. Rescue of F508-CFTR trafficking and gating in human cystic fibrosis airway primary cultures by small molecules. Am J Physiol Lung Cell Mol Physiol 290: L1117–L1130, 2006. First published January 27, 2006; doi:10.1152/ajplung.00169.2005.—Cystic fibrosis (CF) is a fatal genetic disease caused by mutations in cftr, a gene encoding a PKA-regulated Cl channel. The most common mutation results in a deletion of phenylalanine at position 508 ( F508-CFTR) that impairs protein folding, trafficking, and channel gating in epithelial cells. In the airway, these defects alter salt and fluid transport, leading to chronic infection, inflammation, and loss of lung function. There are no drugs that specifically target mutant CFTR, and optimal treatment of CF may require repair of both the folding and gating defects. Here, we describe two classes of novel, potent small molecules identified from screening compound libraries that restore the function of F508-CFTR in both recombinant cells and cultures of human bronchial epithelia isolated from CF patients. The first class partially corrects the trafficking defect by facilitating exit from the endoplasmic reticulum and restores F508-CFTRmediated Cl transport to more than 10% of that observed in non-CF human bronchial epithelial cultures, a level expected to result in a clinical benefit in CF patients. The second class of compounds potentiates cAMP-mediated gating of F508-CFTR and achieves single-channel activity similar to wild-type CFTR. The CFTR-activating effects of the two mechanisms are additive and support the rationale of a drug discovery strategy based on rescue of the basic genetic defect responsible for CF.