MicroRNA-149 is downregulated in Alzheimer's disease and inhibits β-amyloid accumulation and ameliorates neuronal viability through targeting BACE1

Abstract

Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) plays a critical role in Alzheimer's disease (AD) pathogenesis. This study aimed to investigate the relationship between microRNA-149 (miR-149) and BACE1, and evaluate the clinical significance and biological function of miR-149 in AD progression. Bioinformatics analysis and a luciferase reporter assay were used to confirm the interaction between miR-149 and BACE1. Expression of miR-149 and BACE1 was estimated using quantitative real-time PCR. The clinical significance of miR-149 in AD diagnosis and severity determination was evaluated using ROC analysis. The effect of miR-149 on Aβ accumulation and neuronal viability was analyzed in Aβ-treated SH-SY5Y cells. miR-149 was found directly binding the 3'-UTR of BACE1 and was negatively correlated with BACE1 in AD patients and cell model. Serum miR-149 expression was downregulated in AD patients and served as a potential diagnostic biomarker. The overexpression of miR-149 in Aβ-treated SH-SY5Y cells resulted in inhibited Aβ accumulation and enhanced neuronal viability. This study demonstrated that serum miR-149 is decreased in AD patients and serves as a candidate diagnostic biomarker, and that the overexpression of miR-149 may suppress Aβ accumulation and promote neuronal viability by targeting BACE1 in AD model cells.

Figure 1 -. miR-149 directly binds the 3’-UTR of BACE1. A. The putative binding site of miR-149 at the 3’-UTR of BACE1. B. The luciferase activity results to confirm the interaction between miR-149 and BACE1. C. Serum expression of miR-149 detected by qRT-PCR. D. Serum mRNA expression of BACE1 measured by qRT-PCR. E. A negative correlation between serum miR-149 and BACE1 (r = -0.797, P < 0.001). F. A negative correlation between CF miR-149 and BACE1 (r = -0.780, P < 0.001). CF: cerebrospinal fluid; **P < 0.01; ***P < 0.001.

Figure 2 -. Expression of miR-149 in AD patients with different degree of dementia and its correlation with MMSE scores of AD patients. A. Expression of miR-149 was decreased as disease severity increased. B. A positive correlation between miR-149 and MMSE score (r = 0.738, P < 0.001). ***P < 0.001 vs. Mild; ^&&& P < 0.001 vs. Moderate.

Figure 3 -. ROC curves based on serum miR-149 levels in AD patients. A. A ROC curve based on serum miR-149 to distinguish AD patients from healthy volunteers. B. A ROC curve based on serum miR-149 to screen AD cases with severe dementia from AD patients with mild and moderate dementia. AUC, area under the curve.

Figure 4 -. Differential expression of serum miR-149 between AD and PD patients. A. Serum miR-149 was significantly lower in AD patients than that in PD patients. B. A ROC curve based serum miR-149 expression to distinguish AD cases from PD cases. AUC, area under the curve.

Figure 5 -. Expression of miR-149 in Aβ-treated SH-SY5Y cells and its negative regulatory effect on BACE1 expression. A. Aβ treatment in SH-SY5Y led to inhibited miR-149 expression, but cell transfection with miR-149 mimic significantly promoted the expression miR-149. B. The increased mRNA expression of BACE1 in Aβ-treated cells was inhibited by the overexpression of miR-149. C. The protein expression of BACE1 in Aβ-treated cells with miR-149 overexpression. **P < 0.01, ***P < 0.001 vs. Control; ^&& P < 0.01, ^&&& P < 0.001 vs. Aβ.

Figure 6 -. Effect of miR-149 on Aβ accumulation and neuronal viability in Aβ-treated SH-SY5Y cells. A. The increased APP protein expression by Aβ treatment was reversed by the overexpression of miR-149. B. The decreased neuronal viability induced by Aβ was promoted by the upregulation of miR-149. ***P < 0.001 vs. Control; ^&&& P < 0.001 vs. Aβ.