The Neuroprotective Effects of Sumo Conjugase, Ubc9, in Dopaminergic Cells and Neurons
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Abstract
Parkinson’s disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and related to alpha-synuclein mediated protein aggregation. These protein aggregates are known as Lewy bodies. The Small Ubiquitin Modifier (SUMO) is a form of post-translational modification that regulates protein function and stability. Although SUMOylation may increase the solubility of alpha-synuclein, the role of SUMOylation in dopaminergic neurons remains unclear for PD pathology. Our preliminary studies show that the SUMO conjugase, Ubc9, protects rat dopaminergic cells against 1-methyl-4-phenylpyridinium (MPP+) toxicity and prevents the protein degradation of dopamine transporter (DAT) (Cartier et al., manuscript under review). We hypothesize that the overexpression of Ubc9 protects dopaminergic neurons against oxidative stress. For in vitro studies, N27 rat dopaminergic cells overexpressing Ubc9-EGFP showed higher cell viability and lower cytotoxicity against MPP+ induced toxicity, compared to EGFP only cells. In vitro studies include cell viability (MTT) and cytotoxicity assay (LDH), reactive oxygen species (ROS) detection, and mitochondrial respiration, to determine the protective role of Ubc9 in dopaminergic cells against oxidative stress (MPP+). We also established transgenic C57Bl/6 mice overexpressing Ubc9 or wildtype C57Bl/6 mice in the lab. Chronic intraperitoneal injection of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been utilized to induce parkinsonism for both transgenic and wildtype C57BL/6 mice. Using immunhistological staining of tyrosine hydroxylase (TH) as a marker for dopaminergic neurons. We found that the pan-Ubc9 overexpression protected dopaminergic neurons in the striatum and the Substantia Nigra from MPTP-toxicities, compared to wildtype littermate mice. Our study supports that SUMOylation can be a potential therapeutic target to prevent oxidative stress-induced PD pathology. Currently we are assessing the neuroprotective mechanisms of Ubc9-mediated SUMOylation in PD models.