FIGURE 4.

The interaction of GSKIP with both GSK3β and PKA is required for enhancing Wnt signaling in the presence of a Wnt stimulus. A, HEK293 cells expressing the indicated proteins were subjected to TOPflash/FOPflash (TOP/FOP) luciferase assays to detect Wnt signaling activity in the presence of Wnt-conditioned medium. n = 4, mean ± S.E., ANOVA, *, p < 0.05. B, cytosolic fractions were purified, and the indicated proteins were detected by Western blotting. C, the signals were semi-quantitatively analyzed by densitometry; n = 5, mean ± S.E., ANOVA, *, p < 0.05, **, p < 0.01, ***, p < 0.001. D, HEK293 cells expressing an empty vector control or wild type CFP-GSKIP were stimulated with increasing amounts of recombinant Wnt3a, and TOPflash/FOPflash luciferase assays were performed to determine Wnt signaling activity; n = 4, mean ± S.E., ANOVA, ***, p < 0.001.