Abstract 1100 Insight into Synucleinopathies: Molecular Dissection of β- and γ-Synuclein for potential toxicity in a yeast model

The family of synucleinopathies are linked to the misfolding and aggregation of proteins within the family of the synucleins (α-, β-, and γ-), include Parkinson's Disease (PD), the second most prevalent neurodegenerative disease. While α-synuclein is well-studied for its direct contribution to PD, less is known about the role in neurodegeneration and toxicity potential of β- and γ-synuclein. Two β-synuclein mutants (P123H and V70M) were recently linked with Dementia with Lewy Bodies (DLB), and recently, γ-synuclein inclusions were reported observed with ALS pathology. Lessons from α-synuclein pathogenicity demonstrate that it is not only enhanced by point mutations within it, but modified by post-translational modifications and altered cellular environments linked with mitochondrial dysfunction, altered lysosomal pathways, nitrative stress, and lipid metabolism. Here, we further evaluated the toxicity potential of β- and γ-synuclein in these various neurodegeneration-related cellular environment strains and post-translational modification mutants (for phosphorylation, nitration, SUMOylation, acetylation), using our Saccharomyces cerevisiae (budding yeast) PD model system. Additionally, we evaluated substitution mutants for V70M and P123H β-synuclein, where the original amino acid was mutated to representatives of all four amino acid classes (A, R, N, E), for whether loss of the original amino acid (V70, P123) or gain of the new mutant (70M, 123H) is key to toxicity. Finally, we swapped several known familial mutations in α-synuclein and β-synuclein onto each other and onto γ-synuclein as assessed their toxicities. We report that: 1) V70M and P123H β-synuclein mutants aggregate and are more toxic than WT β-synuclein, in a strain- and expression-dependent manner. 2) Evaluation of β-synuclein substitution mutants demonstrate that that gain of histidine is key to P123H-β-synuclein toxicity. 3) The V70M b-synuclein mutation when swapped into a-synuclein makes the latter differentially more toxic than swapping in the P123H mutation. 4) WT and mutant β-synuclein toxicities are differentially aggravated by altered nitrative stress. Overall, this study expands the evaluation of β- and γ-synuclein, as well as genetically modified mutants in a yeast model, to understand mechanisms of toxicity for these two nervous system proteins and illuminates mutant toxicity in β-synuclein. We would like to thank ASBMB for the Undergraduate Research Award and Nu Rho Psi grant, whose generosity and research grants allow for the progress and continuation of all research in the lab.