Study The Role Of MiR-181a In Regulating Mitophagy

Autophagy is a cellular catabolic pathway in which damaged or superfluous proteins and organelles are degraded when cells are under stress.Mitochondria are one of the most important organelles that synthesize ATP via electron transport chain together with oxidative phosphorylation.Mitophagy serves as a controller that regulates mitochondria quantity and quality when mitochondria are excess or damaged,maintaining cellular homeostasis.Mitophagy abnormalities are involved in multiple human diseases,such as neurodegenerative disease and cancer.MicroRNAs are a class of small non-coding RNAs about 22 nt that are involved in mediating the degradation or regulating the translation by targeting 3’-UTR sequence of mRNA,resulting in the decrease of protein level.miRNAs regulate many important cellular processes such as cell growth,cell proliferation,cell differentiation,and apoptosis.Several lines of evidence indicate that miRNAs also regulate different autophagic stages,however,the roles of miRNA in regulating mitophagy are not well understood.In this study,we systemtically investigate the role of miR-181 a in regulating mitophagy.Mitochondrial uncouplers,FCCP and CCCP are used as mitophagy inducers.We demonstrate that miR-181 a is down-regulated by FCCP/CCCP in human neuroblastoma SH-SY5 Y cells,glioma A172 cells and human primary neurons.Overexpression of miR-181 a inhibits mitochondrial uncouple-induced mitophagy by inhibiting the degradation of mitochondrial membrane proteins without affecting global autophagy.Knocking down endogenous miR-181 a accelerates autophagic degradation of damaged mitochondria.miR-181 a directly targets Parkin E3 ubiquitin ligase and blocks colocalization of mitochondria and autophagosomes/lysosomes.Re-expression of exogenous Parkin restores the inhibitory effect of miR-181 a on mitophagy.Furthermore,miR-181 a increases the sensitivity of neuroblastoma cells to mitochondrial toxinsinduced apoptosis,whereas miR-181 a antagomir prevents cell death.Together,these findings show that miR-181 a is a novel inhibitor of mitophagy by directly downregulating the expression of Parkin.And this study attempts to provide some guidance for the research of the disease.