Figure 6.

IBP promotes ubiquitin degradation of PAK1

(A) A549 cells were treated with the indicated concentrations of IBP (0, 5, 10, and 20 μg/mL) for 48 h. PAK1 mRNA expression was evaluated by RT-PCR. (B) Cells were treated with 10 μg/mL IBP alone or combine treated with 10 mM MG132 for 48 h. Protein levels of PAK1 in A549 and H460 were determined by immunoblotting. (C) A549 cells were cotransfected with Flag-ubiquitin (Ub) and PAK1-HA plasmids for 24 h and then were treated as in (B). (D and E) A549 cells were cotransfected with Flag-Ub, and PAK1-HA plasmids contained one lysine mutant (D) and five mutations (E). Interaction between HA and PAK1-Ub in indicated A549 cells (C–E) was determined by coimmunoprecipitation assay. (F) Proposed model for the role of IBP in regulating the autophagy in lung cancer cells. WT, wild type; KO, knockout. Data are a representation of 3 independent experiments. One-way ANOVA (Tukey’s post hoc); ∗p < 0.05; ∗∗p < 0.01.