PP2A forestalls mitophagy by dephosphorylating Parkin and ubiquitin

Abstract

Mitophagy is a selective autophagic process that removes damaged mitochondria. PINK1-Parkin axis is primarily responsible for initiating mitophagy via feedforward mechanism, in which PINK1 phosphorylates ubiquitin and Parkin, and Parkin gains E3 ligase activity at the mitochondrial outer membrane. However, the phosphatase of pParkin is unknown, and the braking mechanism of mitophagy is incomplete. Here we report that protein phosphatase 2A (PP2A) catalyzes the dephosphorylation of Parkin and ubiquitin, with C, A, and B55, the catalytic scaffolding and regulatory subunits, respectively. Up- or down-regulation of PP2A protein level in cells by over-expression or transfection of specific siRNA decreases or increases Parkin and ubiquitin phosphorylation levels, respectively. Consequently, PP2A phosphatase activity negatively modulates mitochondrial translocation of Parkin and forestalls mitophagy. Our finding thus places PP2A, an enzyme already known for its involvement in the pathogenesis of neurodegenerative diseases, further intertwined with the PINK1-Parkin signaling pathway.