miR-3940-5p reduces amyloid β production via selectively targeting .

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid beta (Aβ) in brain. Mounting evidence has revealed critical roles of microRNAs (miRNAs) in AD pathogenesis; however, the miRNAs directly targeting (), which encodes the catalytic core subunit of γ-secretase that limits the production of Aβ from amyloid precursor protein (APP), are extremely understudied. The present study aimed to identify miRNAs targeting and its effect on Aβ production. This study first predicted 5 candidate miRNAs that may target ,through websites such as TargetScan, miRDB, and miRwalk. Subsequently, the targeting specificity of the candidate miRNAs towards PS1 was validated using dual-luciferase reporter assays. To investigate the regulatory effect of miR-3940-5p on gene expression based on its targeting of PS1, miR-3940-5p mimics or inhibitors were transiently transfected into SH-SY5Y cells. Changes in transcription and translation in the tested cells were detected using RT-qPCR and Western Blot, respectively. Finally, to explore whether miR-3940-5p affects Aβ production, SH-SY5Y APP cells overexpressing the Swedish mutant type of APP were transiently transfected with miR-3940-5p mimics, and the expression level of Aβ was detected using ELISA. The results are as follows: The dual-luciferase reporter assays validated the targeting specificity of miR-3940-5p for . Overexpression of miR-3940-5p significantly reduced the mRNA and protein levels of in SH-SY5Y cells. Conversely, inhibition of miR-3940-5p led to an increase in mRNA levels. Transfection of miR-3940-5p mimics into SH-SY5Y-APP cells resulted in a significant reduction in Aβ and Aβ. Lentiviral-mediated overexpression of miR-3940-5p significantly decreased the expression of and did not significantly affect the expression of other predicted target genes. Furthermore, stable overexpression of miR-3940-5p in SH-SY5Y-APP cells mediated by lentivirus significantly reduced the expression of and the production of Aβ and Aβ. Therefore, our study demonstrates for the first time the functional importance of miR-3940-5p in antagonizing Aβ production through specific and direct targeting of .