Liu Heng, Chen Shuai, Sun Qian, Sha Qingquan, Tang Yu, Jia Wenming, Chen Long, Zhao Juan, Wang Tan, Sun Xiulian
School of Medicine, Cheeloo College of Medicine, Shandong University Jinan 250012, Shandong, China.
NHC Key Laboratory of Otorhinolaryngology, Qilu Hospital of Shandong University Jinan 250012, Shandong, China.
Am J Transl Res. 2022 Feb 15;14(2):899-908. eCollection 2022.
MicroRNAs (miRNAs) are highly conserved, non-coding transcripts that regulate gene expression in various ways. Evidence suggests that miRNAs may be a contributory factor in neurodegeneration, including Alzheimer's disease (AD), Parkinson's disease (PD), and triplet repeat disorders. In order to further understand the potential roles of miRNAs in the pathogenesis of AD, we analyzed Down syndrome (DS), a special model of AD, by using a TaqMan microRNA array and found that miRNA let-7c was up-regulated in both DS and AD. ELISA assay showed that let-7c reduced the expression level of Aβ significantly. Real-time quantitative-polymerase chain reaction (RT-qPCR) was conducted to reveal that the expression level of let-7c increased dramatically in DS cells, patients with DS and mice with AD compared with normal ones respectively. Additionally, western blotting illustrated that let-7c suppressed the expression of Aβ by inducing BACE2 to cut C99 and increase the content of C83/80. BACE2 expression was inhibited by let-7c and luciferase reporter gene assay revealed that let-7c increased the activity of wild-type BACE2 promoter but not 3'UTR. Furthermore, promoter analysis of BACE2 confirmed that let-7c could bind to BACE2 in the sequence between -1368 and -1347. In addition, immunoblotting assay demonstrated that let-7c induced BACE2 expression by RNAa. To the best of our knowledge, our study revealed for the first time that let-7c up-regulated BACE2 expression and decreased Aβ production.
微小RNA（miRNA）是高度保守的非编码转录本，可通过多种方式调节基因表达。有证据表明，miRNA可能是神经退行性疾病（包括阿尔茨海默病（AD）、帕金森病（PD）和三联体重复序列疾病）的一个促成因素。为了进一步了解miRNA在AD发病机制中的潜在作用，我们使用TaqMan微小RNA芯片分析了AD的特殊模型——唐氏综合征（DS），发现miRNA let-7c在DS和AD中均上调。酶联免疫吸附测定（ELISA）显示，let-7c显著降低了Aβ的表达水平。进行实时定量聚合酶链反应（RT-qPCR）以揭示，与正常细胞相比，let-7c的表达水平在DS细胞、DS患者和AD小鼠中分别显著增加。此外，蛋白质印迹法表明，let-7c通过诱导β-分泌酶2（BACE2）切割C99并增加C83/80的含量来抑制Aβ的表达。let-7c抑制BACE2的表达，荧光素酶报告基因测定显示let-7c增加野生型BACE2启动子的活性，但不增加3'非翻译区（3'UTR）的活性。此外，BACE2的启动子分析证实，let-7c可在-1368至-1347之间的序列中与BACE2结合。此外，免疫印迹测定表明，let-7c通过RNA激活（RNAa）诱导BACE2表达。据我们所知，我们的研究首次揭示let-7c上调BACE2表达并减少Aβ生成。
