GPD activates the AMPKα and/or JNK pathways in SK-MEL-28 human melanoma cells.

(A) Phosphorylation of AMPKα is increased by GPD in a dose-dependent manner. (B) GPD upregulates phosphorylated JNK1/2 in a dose-dependent manner. (C) Levels of phosphorylated c-Jun, a well-known downstream of JNK, peak at 24 h after GPD treatment. (D) The phosphorylation of c-Jun after GPD treatment was dramatically decreased by co-treatment with the JNK inhibitor SP600125, whereas it decreased slightly in the presence of SB202180, a p38 inhibitor. (E) Activated AMPKα negatively regulated the phosphorylation of mTOR in a time-dependent manner. Cells (5×105/100 mm dish) were incubated with various concentrations of GPD for the indicated durations. (F) GPD induces the phosphorylation of Bcl-2 and the dissociation of Beclin-1 from Bcl-2. Western blot analysis was performed using specific antibodies as described in Materials and Methods. β-actin was used to verify equal protein leading.