Rescue of Delta F508 and other misprocessed CFTR mutants by a novel quinazoline compound

Cystic fibrosis (CF) is most commonly caused by deletion of Phe508 in the cystic fibrosis transmembrane conductance regulator protein (Delta F508 CFTR). The misfolded Delta F508 CFTR protein is retained in the endoplasmic reticulum (misprocessed mutant) and is rapidly degraded. Studies on misprocessed mutants of P-glycoprotein (P-gp), a sister protein of CFTR, however, have shown that specific substrates and modulators can act as specific chemical/pharmacological chaperones to rescue the protein. A major goal in CF research is the identification of compounds that can be used at low concentrations to rescue misprocessed CFTR mutants. Here, we show that a novel quinazoline derivative, 4-cyclohexyloxy-2-{1-[4-(4-methoxy-benzenesulfonyl)piperazin-1-yl]ethyl}quinazoline (CFcor-325), rescued Delta F508 CFTR. Incubation of BHK cells stably expressing human Delta F508 CFTR with 1-10 mu M CFcor-325 resulted in maturation and delivery of a functional molecule to the cell surface as determined by the iodide efflux assay. The misprocessed CFTR mutants R258G, S945L, and H949Y were also rescued by CFcor-325 in either BHK or HEK 293 cells. CFcor-325 appeared to be specific for Delta F508 CFTR because another quinazoline derivative, prazosin, did not rescue the misprocessed CFTR mutants. CFcor-325 could also rescue misprocessed mutants of P-gp. The compound was a P-gp inhibitor as it inhibited vinblastine-stimulated ATPase activity. P-gp-mediated vinblastine resistance was also reduced about 10-fold with 300 nM CFcor-325. These results show that CFcor-325 is a particularly important lead compound for treatment of CF because low concentrations can be used to rescue many misprocessed CFTR mutants.