γ-secretase inhibition decreases AICD-Gal4 levels and AICD-Gal4 mediated luciferase activity in SY5Y-APP-Gal4 cells. (A) Inhibition of γ-secretase by L-685,458 (5 mM) decreases AICD-Gal4 levels and increases C83-Gal4 levels as detected by Western blot analysis. (B) Quantification of Western blot densitometry in panel A. Normalization for loading differences was achieved by dividing the densitometry values for individual bands by the densitometry values for β-actin in the same lane. (C) Dose-dependent decreases in AICD-Gal4-mediated luciferase activity with increasing concentrations of L-685,458. For the luciferase experiments, points represent mean normalized luciferase activity (+/- standard error) of three independent trials, with luciferase levels normalized to total cell numbers using SYBR Green. Student's t-tests with sequential Bonferroni correction for multiple comparisons was utilized to test for significance. * indicates p < 0.05; ** indicates p < 0.01. "Control" uses the same media as the treatments, and also contains the same amount of DMSO.