miR-3940-5p reduces amyloid β production via selectively targeting PSEN1

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid beta (A beta) in brain. Mounting evidence has revealed critical roles of microRNAs (miRNAs) in AD pathogenesis; however, the miRNAs directly targeting presenilin1 (PSEN1), which encodes the catalytic core subunit of gamma-secretase that limits the production of A beta from amyloid precursor protein (APP), are extremely understudied. The present study aimed to identify miRNAs targeting PSEN1 and its effect on A beta production. This study first predicted 5 candidate miRNAs that may target PSEN1,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 PSEN1 transcription and translation in the tested cells were detected using RT-qPCR and Western Blot, respectively. Finally, to explore whether miR-3940-5p affects A beta production, SH-SY5Y APP(swe) cells overexpressing the Swedish mutant type of APP were transiently transfected with miR-3940-5p mimics, and the expression level of A beta was detected using ELISA. The results are as follows: The dual-luciferase reporter assays validated the targeting specificity of miR-3940-5p for PSEN1. Overexpression of miR-3940-5p significantly reduced the mRNA and protein levels of PSEN1 in SH-SY5Y cells. Conversely, inhibition of miR-3940-5p led to an increase in PSEN1 mRNA levels. Transfection of miR-3940-5p mimics into SH-SY5Y-APP(swe) cells resulted in a significant reduction in A beta(42) and A beta(40). Lentiviral-mediated overexpression of miR-3940-5p significantly decreased the expression of PSEN1 and did not significantly affect the expression of other predicted target genes. Furthermore, stable overexpression of miR-3940-5p in SH-SY5Y-APP(swe) cells mediated by lentivirus significantly reduced the expression of PSEN1 and the production of A beta(42) and A beta(40). Therefore, our study demonstrates for the first time the functional importance of miR-3940-5p in antagonizing A beta production through specific and direct targeting of PSEN1.