TY - JOUR T1 - A chemical corrector modifies the channel function of F508del-CFTR JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.110.065862 SP - mol.110.065862 AU - Patrick Kim Chiaw AU - Leigh Wellhauser AU - Ling Jun Huan AU - Mohabir Ramjeesingh AU - Christine Bear Y1 - 2010/05/25 UR - http://molpharm.aspetjournals.org/content/early/2010/05/25/mol.110.065862.abstract N2 - The deletion of Phe-508 (F508del) constitutes the most prevalent Cystic Fibrosis causing mutation. This mutation leads to CFTR misfolding and retention in the endoplasmic reticulum, as well as altered channel activity in mammalian cells. This folding defect can however be partially overcome by growing cells expressing this mutant protein at low (27°C) temperature. Chemical "correctors" have been identified that are also effective in rescuing the biosynthetic defect in F508del-CFTR, thereby permitting its functional expression at the cell surface. The mechanism of action of chemical correctors remains unclear but it has been suggested that certain correctors (including VRT-325) may act to promote trafficking by interacting directly with the mutant protein. To test this hypothesis, we assessed the effect of VRT-325 addition on the channel activity of F508del-CFTR after its surface expression had been "rescued" by low temperature. Interestingly, acute pre-treatment with VRT-325 (but not an inactive analog (VRT-186)), caused a modest, but significant inhibition of cAMP-mediated halide flux. Further, VRT-325 decreased the apparent ATP affinity of purified and reconstituted F508del-CFTR in our ATPase activity assay, an effect which may account for the decrease in channel activity by temperature rescued F508del-CFTR. These findings suggest that biosynthetic rescue mediated by VRT-325 may be conferred (at least in part) by direct modification of the structure of the mutant protein, leading to a decrease in its ATP dependent conformational dynamics. Therefore, the challenge for therapy discovery will be the design of small molecules which bind to promote biosynthetic maturation of the major mutant without compromising its activity in-vivo.The American Society for Pharmacology and Experimental Therapeutics ER -