Altered Biogenesis of DeltaF508-CFTR Following Treatment with Doxorubicin

Abstract

Cystic fibrosis (CF) is caused by mutations to the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The most common of these mutations is deletion of a phenylalanine residue at position 508 (DeltaF508), which accounts for n70% of all CF alleles. This mutation interferes with the biogenesis and maturation of DeltaF508-CFTR to the plasma membrane. However, DeltaF508-CFTR can partially function upon proper localization. Thus, pharmacological correction of DeltaF508-CFTR maturation holds promise in CF therapy. Our previous studies indicate that a single non-cytotoxic dose of the anthracycline doxorubicin (Dox) significantly increase DeltaF508-CFTR-associated chloride secretion in MDCK cells by increasing the expression of this protein at the apical plasma membrane. We report here that Dox alters the biogenesis of DeltaF508-CFTR. Treatment with Dox increases the resistance of DeltaF508-CFTR to trypsin digestion, possibly by expediting protein folding. Further, treatment with Dox reduces the amount of polyubiquitinated DeltaF508-CFTR in cells and prolongs the half-life of this protein. Concomitantly, treatment with Dox decreases the association of DeltaF508-CFTR with HSP70 but does not alter the expression of major HSP70 family members. Based on these results, we propose that Dox expedites the folding and maturation of DeltaF508-CFTR by acting as a pharmacological chaperone, which consequently promotes the functional expression of this protein in MDCK cells. Copyright (c) 2007 S. Karger AG, Basel