PINK1 SUMOylation regulates basal mitophagy

The detection and removal of damaged mitochondria is essential for cells to maintain a healthy mitochondrial network. PTEN-induced kinase 1 (PINK1) is a critical sensor that detects mitochondrial damage. PINK1 is subject to several post-translational modifications including phosphorylation, ubiquitination, and S-nitrosylation, each playing a key role in regulating its stability, subcellular localization, and/or function. Here, we show that PINK1 is additionally modified by non-canonical, lysine-independent SUMOylation, mediated by mitochondrial anchored protein ligase (MAPL). Levels of PINK1 SUMOylation are reduced by the mitochondrial uncoupler CCCP, whereas they are increased by the inhibitor of proteasomal degradation MG132. MAPL knockdown increases mitophagy in wild-type, but not PINK1 ^-/- HEK293T cells. Moreover, selective deSUMOylation of PINK1 also increases mitophagy. These findings indicate that SUMOylation of PINK1 is a key factor in the regulation of mitophagy and mitochondrial quality control.