Figure 1. Specific inhibition of GSK3 reduces BACE1 cleavage of APP.
(A) Swedish mutant APP stable cell line 20E2 was cultured and treated with ARA for 24 hours, and cell lysates subjected to Western blot analysis. Full-length APP and the APP CTFs were detected with C20 antibody. β-Catenin was detected by anti–β-catenin antibody. β-Actin was detected by anti-actin antibody AC-15 as the internal control. (B) Quantification of APP C99 generation in 20E2 cells. ARA treatment significantly increased β-catenin levels in a dose-dependent manner, while APP C99 production decreased with increasing ARA dosage. n = 6; *P < 0.05 and **P < 0.01, ANOVA. Aβ ELISA detection of Aβ40 (C) and Aβ42 (D) in conditioned medium from 20E2 cells treated with ARA for 24 hours. ARA treatment reduced Aβ levels in the conditioned medium in a dose-dependent manner. The values are expressed as mean ± SEM. n = 4; *P < 0.05, ANOVA. (E) γ-Secretase activity in 20E2 cells was inhibited by the pharmacological inhibitor L685,458 (GSI). Co-treatment with specific GSK3 inhibitors ARA and G2 reduced C99. Con, control. (F) Quantification of C99 levels. n = 6; *P < 0.05, ANOVA.