Figure 2.

ERα is responsible for E2-induced downregulation of BACE1 promoter activity. A, We treated the stable BACE1 wild-type promoter-driven luciferase-expressing HEK293 cell line with a combination of vehicle, TNFα, E2, ICI-182780, PPT, and DPN for 24 h at doses indicated in the label below the x-axis (A). Note that TNFα induces BACE1, while E2 or the ERα agonist PPT represses it. The ER antagonist ICI-182780 blocks the E2 repression of BACE1. Unlike the ERα agonist, the ERβ-selective agonist DPN did not affect BACE1 activity. B, C, We used siRNA to knock down ERα (B) or ERβ (C) in the same cell line to confirm their relative contribution to BACE1 regulation. Western blots demonstrate the reduction of the two ER receptors after siRNA treatment (B, C, right panels). Once again, ERα, but not Erβ, knockdown blocked E2-mediated repression of BACE1 promoter activity. Data are expressed as a percentage of control (vehicle alone) normalized to 100% in each experiment and are represented as the mean and SEM of at least three independent experiments. *p < 0.05, versus control; **p < 0.01, versus control; #p < 0.05.