Mitochondrial and lysosomal biogenesis are activated following PINK1/parkin-mediated mitophagy.

Impairment of the autophagy-lysosome pathway is implicated with the changes in α-synuclein and mitochondrial dysfunction observed in Parkinson's disease ( PD). Damaged mitochondria accumulate PINK1, which then recruits parkin, resulting in ubiquitination of mitochondrial proteins. These can then be bound by the autophagic proteins p62/ SQSTM1 and LC3, resulting in degradation of mitochondria by mitophagy. Mutations in PINK1 and parkin genes are a cause of familial PD. We found a significant increase in the expression of p62/ SQSTM1 m RNA and protein following mitophagy induction in human neuroblastoma SH- SY5Y cells. p62 protein not only accumulated on mitochondria, but was also greatly increased in the cytosol. Increased p62/ SQSMT1 expression was prevented in PINK1 knock-down cells, suggesting increased p62 expression was a consequence of mitophagy induction. The transcription factors Nrf2 and TFEB, which play roles in mitochondrial and lysosomal biogenesis, respectively, can regulate p62/ SQSMT1. We report that both Nrf2 and TFEB translocate to the nucleus following mitophagy induction and that the increase in p62 m RNA levels was significantly impaired in cells with Nrf2 or TFEB knockdown. TFEB translocation also increased expression of itself and lysosomal proteins such as glucocerebrosidase and cathepsin D following mitophagy induction. We also report that cells with increased TFEB protein have significantly higher PGC-1α m RNA levels, a regulator of mitochondrial biogenesis, resulting in increased mitochondrial content. Our data suggests that TFEB is activated following mitophagy to maintain autophagy-lysosome pathway and mitochondrial biogenesis. Therefore, strategies to increase TFEB may improve both the clearance of α-synuclein and mitochondrial dysfunction in PD. [ABSTRACT FROM AUTHOR]