Using SUMO conjugase Ubc9-overexpressing or knock-down cells in Parkinson’s disease (PD) models, we demonstrate that SUMOylation protects dopaminergic cells against MPP+ or preformed fibrils (PFFs) of α-synuclein (α-syn)-induced toxicities in cell viability and cytotoxicity assays. Here, SNCA is linked to Parkinson disease.