MiR-124 acts as a target for Alzheimer's disease by regulating BACE1

Abstract

Although large numbers of microRNAs (miRNAs) expressed in Alzheimer disease (AD) have been detected, their functions and mechanisms of regulation remain to be fully clarified. Beta-site Amyloid precursor protein Cleaving Enzyme 1 (BACE1) has been one of the prime therapeutic targets for AD. Here, we identified that miR-124 levels are gradually decreased in AD. In addition, we demonstrated that miR-124 suppresses BACE1 expression by directly targeting the 3'UTR of Bace1 mRNA in vitro. Inhibition of miR-124 significantly increased BACE1 levels in neuronal cells. In contrast, miR-124 overexpression significantly suppressed BACE1 expression in cells. And finally we determined that downregulation of miR-124 alleviated Aβ-induced viability inhibition and decreased apoptosis in SH-SY5Y cells. Our results demonstrated that miR-124 is a potent negative regulator of BACE1 in the cellular AD phenotype and might be involved in the pathogenesis of AD.

Keywords: Alzheimer’s disease; BACE1; cell apoptosis; cell viability; miR-124.

Figure 1. The relative expression of miR-124 and BACE1 were determined by qRT-PCR and western blot in AD patients

(A) miR-124 expression levels were significantly lower in sporadic AD brain tissues than control tissues; (B) BACE mRNA expression levels were significantly higher in sporadic AD brain tissues than control tissues; (C) BACE1 protein expression levels were significantly higher in AD group than in control group.

Figure 2

(A) MTT assay results showed that Aβ inhibited the viability of SH-SY5Y cells and downregulation of BACE1 enhanced the inhibitory effects of Aβ; (B) downregulation of miR-124 relieved Aβ-induced viability inhibition of SH-SY5Y cells; (C) flow cytometric analysis results showed that Aβ-induced apoptosis of SH-SY5Y cells and downregulation of BACE1 enhanced the induced effects of Aβ; (D) downregulation of miR-124 decreased apoptosis of SH-SY5Y cells in the presence of Aβ.

Figure 3. BACE1 is one of the candidates because miR-124 includes its potential binding sequences of the BACE1 mRNA 3′-UTR; miR-124 regulates BACE1 expression by directly binding to the 3′-UTR of BACE1 mRNA

(A) The putative binding sites of miR-124 in the wild-type 3′-UTR of BACE1 (BACE1 3′-UTR-WT) and mutated target sites of BACE1 (BACE1 3′-UTR-MUT). (B) Relative luciferase activity in HEK293 cells co-transfected with pGL3-BACE1–3′-UTRWT/MUT and miR-124 mimics or miRNA scramble control (miRcon).

Figure 4. The relative levels of BACE1 mRNA and protein in SH-SY5Y cells transfected with miR-124 mimics, miRNA mimic negative control (miR-con), miR-124 inhibitors (anti-miR-124), or miRNA inhibitor negative control (anti-miR-con)

(A) At 48 h posttransfection, the relative levels of BACE1 mRNA were measured using qRT-PCR. (B) At 48 h posttransfection, the relative levels of BACE1 protein were measured using western blotting. Data are shown as means ± standard deviation (SD). ^**P < 0.01.