Figure 2. Experiments performed to determine the effects of Dab2 on the cell membrane abundance of WT-CFTR and r∆F508-CFTR in human airway epithelial cells (CFBE41o-). Cells were transfected with siRNA specific for the human Dab2 gene (siDab2) or with a non-silencing siRNA control (siCTRL). The Dab2 gene is alternatively spliced to produce two proteins, p96 and p67 (30). Because the Dab2 p96 functions as an endocytic adaptor, it was specifically targeted by the siRNA. CFBE41o- cells expressing ∆F508-CFTR were cultured at 27°C for 36 h before experiments to increase biosynthetic processing and thus enhance the cell membrane abundance of rescued ∆F508-CFTR (r∆F508-CFTR). Representative western blots (A, middle row) and summary of experiments (B) demonstrate that siDab2 decreased the Dab2 p96 protein abundance in postnuclear supernatants (PNS) by ~70%. Silencing Dab2 increased the steady-state plasma membrane (PM) abundance of WT-CFTR and r∆F508-CFTR (A, top row; C). PM CFTR was isolated by cell membrane biotinylation. siDab2 did not alter ezrin expression in PNS. *, p < 0.05 vs. siCTRL. Summary data reflect 4 experiments (WT-CFTR) or 6 experiments (r∆F508-CFTR). Error bars, SE.