miR-34a-5p regulates PINK1-mediated mitophagy via multiple modes.

AIMS: PTEN induced putative kinase 1 (PINK1)-mediated mitophagy process is tightly associated with various age-dependent diseases in mammals. The roles of miRNAs (miRNAs) in the PINK1-mediated mitophagy process are not fully understood. Here we discovered that miR-34a-5p suppresses PINK1 expression directly though two post-transcriptional non-classical binding modes, resulting in inhibition of PINK1-mediated mitophagy process. MAIN METHODS: For in vivo experiments, brains were dissected from 8 weeks old and 40 weeks old C57BL/6 male mice to measure miR-34a-5p expression and PINK1 expression. For in vitro experiments, overexpression of miR-34a-5p mimics in HEK293 cells was performed to investigate the effect of miR-34a-5p on PINK1 expression and its regulatory mechanism, parkin recruitment and mitophagy process. KEY FINDINGS: The level of miR-34a-5p was upregulated and the level of PINK1 mRNA was downregulated in brains of aged mice. Both the 3'-untranslated region (3'UTR) and the Coding DNA sequence (CDS) of PINK1 mRNA were bound to the non-seed region of miR-34a-5p, rather than the seed region, resulting in a decrease in PINK1 expression. Endogenous miR-34a-5p knockout increased PINK1 expression. Further results indicated that miR-34a-5p inhibits mitophagy process by reduction of PINK1. miR-34a-5p hinders phosphorylated Ser65-ubiquitin (pS65-Ub) accumulation, prevents the mitochondrial recruitment of Parkin, attenuates ubiquitination and delays the clearance of damaged mitochondria. SIGNIFICANCE: We firstly found that miR-34a-5p suppresses PINK1 directly and further regulates mitophagy through non-canonical modes. This finding hints at a crucial role of miR-34a-5p implicated in accelerating the pathogenesis of age-related neurological diseases.