Prolonged treatment of cells with genistein modulates the expression and function of the cystic fibrosis transmembrane conductance regulator

Background and purpose: Cystic fibrosis (CF) is caused by dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. In the search for new CF therapies, small molecules have been identified that rescue the defective channel gating of CF mutants (termed CFTR potentiators). Here, we investigate the long‐term effects of genistein, the best‐studied CFTR potentiator, on the expression and function of CFTR. Experimental approach: We pre‐treated baby hamster kidney (BHK) cells expressing wild‐type or F508del‐CFTR (the most common CF mutant) with concentrations of genistein that potentiate (30 μM) or inhibit (100 μM) CFTR function for 2 or 24 h at 37 °C before examining CFTR maturation, expression and single‐channel activity. Key results: Using the iodide efflux technique, we found that genistein pre‐treatment failed to restore function to F508del‐CFTR, but altered that of wild‐type CFTR. Pre‐treatment of cells with genistein for 2 h had little effect on CFTR processing, whereas pre‐treatment for 24 h either augmented (30 μM genistein) or impaired (100 μM genistein) CFTR maturation. Using immunocytochemistry, we found that all genistein pre‐treatments increased the localization of CFTR protein to the cell surface. However, following the incubation of cells with genistein (100 μM) for 2 h, individual CFTR Cl− channels exhibited characteristics of channel block upon channel activation. Conclusions and implications: Genistein pre‐treatment alters the maturation, cell surface expression and single‐channel function of CFTR in ways distinct from its acute effects. Thus, CFTR potentiators have the potential to influence CFTR by mechanisms distinct from their effects on channel gating. British Journal of Pharmacology (2008) 153, 1311–1323; doi:10.1038/sj.bjp.0707663; published online 28 January 2008