TY - JOUR T1 - The SUMO conjugase Ubc9 protects Dopaminergic cells from cytotoxicity and enhances the stability of α-synuclein in Parkinson’s disease models JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0134-20.2020 SP - ENEURO.0134-20.2020 AU - Dinesh Kumar Verma AU - Anurupa Ghosh AU - Lindsey Ruggiero AU - Etienne Cartier AU - Eric Janezic AU - Dionne Williams AU - Eui-Gil Jung AU - Michael Moore AU - Jong Bok Seo AU - Yong-Hwan Kim Y1 - 2020/09/04 UR - http://www.eneuro.org/content/early/2020/09/03/ENEURO.0134-20.2020.abstract N2 - Small Ubiquitin-like Modifier (SUMO) is a widespread regulatory mechanism of post-translational modification that induces rapid and reversible changes in protein function and stability. 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 (PFF) of alpha-synuclein induced toxicities in cell viability and cytotoxicity assays. In the mechanism of protection, Ubc9 overexpression significantly suppressed the MPP+ or PFF-induced ROS generation, while Ubc9-RNAi enhanced the toxicity-induced ROS production. Further, PFF-mediated protein aggregation was exacerbated by Ubc9-RNAi in Thioflavin T staining, compared to NC1 controls. In cycloheximide-based protein stability assays, higher protein level of α-synuclein was identified in Ubc9-EGFP than in EGFP cells. Since there was no difference in endogenous mRNA levels of α-synuclein between Ubc9 and EGFP cells in qRT-PCR, we assessed the mechanisms of SUMO-mediated delayed α-synuclein degradation via MG132, proteasomal inhibitor and PMA, lysosomal degradation inducer. Ubc9-mediated SUMOylated α-synuclein avoided PMA-induced lysosomal degradation due to its high solubility. Our results suggest that Ubc9 enhances the levels of SUMO1 and Ubiquitin on α-synuclein and interrupts SUMO1 removal from α-synuclein. In immunohistochemistry, dopaminergic axon tips in the striatum and cell bodies in the Substantia Nigra from Ubc9-overexpressing transgenic mice were protected from MPTP toxicities compared to WT siblings. Our results support that SUMOylation can be a regulatory target to protect dopaminergic neurons from oxidative stress and protein aggregation, with the implication that high levels of SUMOylation in dopaminergic neurons can prevent the pathological progression of PD.Significance Statement We tested if SUMOylation enhances the solubility of aggregation-prone proteins such as α-synuclein to prevent protein aggregation induced by oxidative stress and/or preformed fibrils (PFF) of α-synuclein. Here, we demonstrate that high levels of SUMOylation mediated by Ubc9 overexpression protect dopaminergic cells from MPTP- (MPP+) or PFF-induced toxicities. The protective effects are derived from the inhibition of ROS generation and protein aggregation. Interestingly, SUMOylated α-synuclein avoided lysosomal degradation, which was not detrimental. Ubiquitin binding to lysine residues may not compete with SUMO binding to determine the protein half-life of α-synuclein. Our findings strongly suggest that the regulation of SUMO conjugation to α-synuclein can be a novel therapeutic target to prevent the formation of Lewy bodies and ROS generation. ER -