Received for publication August 9, 2007.
Revised October 17, 2007.
Accepted for publication November 1, 2007.

Structural analogue of sildenafil identified as a novel corrector of the F508del-CFTR trafficking defect

Abstract

The F508del mutation impairs trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) to the plasma membrane and results in a partially functional chloride channel that is retained in the endoplasmic reticulum and degraded. We recently used a novel High Throughput Screening (HTS) assay to identify small molecule correctors of F508del CFTR trafficking and found several classes of hits in a screen of 2000 compounds (Carlile et al., 2007). In the present study we have extended the screen to 42,000 compounds and confirmed sildenafil as a corrector using this assay. We evaluated structural analogues of sildenafil and found that one such molecule called KM11060 (7-chloro-4-{4-[(4-chlorophenyl) sulfonyl] piperazino}quinoline) was surprisingly potent. It partially restored F508del trafficking and increased maturation significantly when baby hamster kidney (BHK) cells were treated with 10 nM for 24 h or 10 µM for 2 h. Partial correction was confirmed by the appearance of mature CFTR in Western blots and by using halide flux, patch-clamp and short-circuit current measurements in unpolarized BHK cells, monolayers of human airway epithelial cells (CFBE41o-), and intestines isolated from F508del-CFTR mice ( Cftr ^tm1Eur) treated ex-vivo. Small molecule correctors such as KM11060 may serve as useful pharmacologic tools in studies of the F508del-CFTR processing defect and in the development of CF therapeutics.

Key words: cAMP, cGMP, Phosphodiesterases, Ion transporters (SERCA, Na/K ATPase, CFTR), Func. analysis receptor/ion channel mutants, Fluorescence techniques, Regulation - post-transcriptional