Probing the Mechanism of Correction in DeltaF508-CFTR.

摘要

Cystic Fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which cause loss function of the CFTR channel on the apical surface of epithelial cells. ΔF508-CFTR, the major mutation in patients, is misfolded, retained in the endoplasmic reticulum (ER) and degraded. Small molecule corrector compounds partially rescue the trafficking defect of ΔF508-CFTR by allowing escape from the ER and trafficking to the plasma membrane where it exhibits partial function. These compounds may bind directly to the mutant protein and rescue the biosynthetic defect by inducing improved protein conformation. We tested this hypothesis by evaluating the consequence of corrector compound on the conformation of each nucleotide-binding domain (NBD) in the context of the full-length mutant protein in limited proteolytic digest studies. We found that VRT-325 was capable in partially restoring compactness only in NBD1. In comparison, ablation of the arginine framed peptide sequence: R553XR555 (ΔF508-KXK-CFTR) modified the protease resistance of NBD1, NBD2 and the full-length protein. Singly, each intervention led to a partial correction of the processing defect. Together these interventions restored processing of ΔF508-CFTR to near wild-type levels. Importantly however, a defect in NBD1 conformation persisted, as did a defect in channel activation after the combined interventions. This defect in channel activation can be fully corrected by addition of the potentiator: VX-770. The experiments performed partly elucidated the molecular mechanism of action for drug therapy and suppressor mutation. It is important to understand these basic concepts in hopes to layout a blue print for future drug design.