Fig. 7.

WD4- and WD6-peptides reduce CFTR surface expression. WD peptides were delivered into Calu-3 cells using BioPORTER reagent. The apical membrane was biotinylated, and biotinylated proteins were recovered by streptavidin pulldown. Proteins were probed for CFTR, RACK1, and FlnA. In A–C: −BioP, no BioPORTER or peptide added to cells; +BioP, BioPORTER but no peptide added to cells. A: WD4 and WD6 peptides. Representative results from biotinylation experiment, showing recovery of CFTR, RACK1 and FlnA with streptavidin beads. As a control, blots were reprobed for actin, as shown at bottom, which indicate, as expected, a weak signal on beads and much stronger signal in the supernatant. B: percent surface CFTR is calculated from densitometry values as bead value/(bead + total supernatant values) × 100. means ± SE for 3 different experiments. **P < 0.01, suppression of CFTR surface expression by WD4 and WD6 repeats is very significant. C: WD1 and WD2 peptides. Representative experiment showing recovery of CFTR relative to -BioP control. D: summary of data of the effects of WD1 and WD2 peptides on recovery of biotinylated CFTR. Statistical test by ANOVA yielded a P = 0.63 indicating that WD1 and WD2 do not affect CFTR surface expression.