Figure 6.

DKK1 signaling through JNK attenuates p-Akt, resulting in inhibition of nuclear β-catenin translocation. A: Cordycepin-mediated p-JNK upregulation enhances Dkk1. TK-10 cells were treated with cordycepin or cordycepin and 10 mM SP600125 for 48 h. TK-10 cells were incubated with siRNA directed against DUSP5 (si-DUSP5) or negative control siRNA for 48 h. B: TK-10 cells were incubated with siRNA directed against Dkk1 (si-Dkk1) or negative control siRNA for 48 h, and transfected with a DUSP5-overexpressing construct for 48 h. Bar graphs represent densitometric analysis of at least three separate experiments (means ± SD). *P<0.05, **P<0.01, and ***P<0.001. C: TK-10 cells were grown on glass coverslips and treated with cordycepin or cordycepin with DUSP5 overexpression for 48 h. Samples were analyzed by indirect immunofluorescence with confocal microscopy. The cellular localization of β-catenin (cytosol, green; nucleus, blue) is shown in the middle panels. The right panels are merged images. The bar indicates 20 μm. D: Analysis of apoptotic protection by DUSP5 overexpression using double-labeled flow cytometry in TK-10 cells treated with cordycepin. Control (left panel) and DUSP5 over-expressing (right panel) constructs were transfected into TK-10 cells, which were then treated with cordycepin for 24 h.