Lake Forest College, Neuroscience, Biology, Lake Forest, IL 60045
Parkinson's disease (PD) is a hypokinetic neurodegenerative disease that arises from the selective death of midbrain dopaminergic neurons. This cell death is linked to misfolding and accumulation of the abundant brain protein, alpha-synuclein. Genetic mutations account for 10% of familial PD cases and the best studied mutant gene is alpha-synuclein itself, where the familial point mutants are A53T, A30P and E46K. The PD-linked properties of each alpha-synuclein familial mutant are widely studied and reported. Our lab too has previously published each familial mutant's pathology-related properties using two types of yeast models (Sharma et al, 2006; Brandis et al, 2006; Fiske et al, 2011), where each mutant distinctively affects α-synuclein’s localization, aggregation, and cell survival properties, indicating each amino acid's strategic importance to controlling pathology. In this study, we hypothesized that combining these three familial mutations (evaluated as double or triple mutants) will blend individual mutant's cellular localization and aggregation properties, and they will lead to higher cellular toxicity. We tested our hypothesis in fission yeast (which best models alpha-synuclein aggregation) and budding yeast (which best models alpha-synuclein membrane association). Surprisingly, we found one mutant (A30P) dominated over the other two mutants (A53T, E46K) in controlling alpha-synuclein localization in both organisms, and that the exact pattern of localization depended on the type of yeast. Moreover, the combination of double or triple mutations did increase cellular toxicity over what was achieved by individual mutants in either organism. Our findings illustrate that each of these individual amino acids within alpha-synuclein cooperatively exert differential influence over cellular pathology and that organismal context is also a determinant to this pathology. Currently, as our final analysis, we are investigating the single and combinatorial familial mutant properties once again in budding yeast using an eGFP vector system that not only much higher alpha-synuclein expression, but prominently displays both membrane localization and intracellular aggregation over a time course.
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