Parkinson's disease (PD) is associated with the aggregation and misfolding of alpha‐synuclein in midbrain dopaminergic neurons. The gene for alpha‐synuclein has six known mutations that directly cause familial forms of PD. The pathological determinants of three of these mutants (A30P, E46K, and A53T) are well characterized in diverse model systems and they that reveal that each mutant affects cellular toxicity in distinctive ways. The three more recently discovered familial mutants (H50Q, G51D, and A53E) are not extensively studied. We expressed H50Q, G51D, and A53E mutants in budding and fission yeasts model systems and hypothesized that each would generate toxicity by altering their membrane association and aggregation properties, and by disrupting cellular pathways including nitrative stress responses and endocytosis, but each would do so in distinctive ways. First, we found that the H50Q and A53E mutants were toxic to yeast, and bound membranes and aggregated within yeast, while G51D was cytoplasmically diffuse and nontoxic. Secondly, and surprisingly, we found that G51D mutant dominated over H50Q and A53E when these mutants were combined in double/triple mutants. Thirdly, we asked whether the loss of the original amino acid or the gain of the new amino acid in each new familial mutant is responsible for disease. We created four substitution mutations for H50Q, G51D, and A53E in both yeasts models corresponding to the four functional classes of amino acids. We found that H50D was cytoplasmically diffuse and nontoxic, G51A bound membranes and aggregated like WT, G51E was cytoplasmically diffuse and nontoxic like G51D, and A53R was cytoplasmically diffuse and nontoxic, suggesting both the loss of the original amino acid and the gain of the new amino acid are key. Finally, we are currently characterizing these familial mutants in yeast strains altered for endocytosis, nitrative stress, and sumoylation. Collectively, this work adds insight into the pathogenicity of different familial PD mutants of alpha‐synuclein.Support or Funding InformationE.O. was funded by Parkinson's Disease Foundation

Parkinson's disease (PD) is characterized by a‐synuclein misfolding and the death of midbrain neurons. PD can be described as familial, or sporadic, both of which are influenced by a multitude of environmental and genetic factors. Familial PD is directly caused by a mutation in one of at least ten genes, including SNCA, DJ‐1, VPS35, and ATP13A2. SNCA, which encodes a‐synuclein, has six identified missense mutations (A30P, E46K, H50Q, G51D, A53E, and A53T) that each cause autosomal dominant PD. Sporadic PD is linked with several risk genes and loci, including VPS13, the Sac I domain of SYNJ1, and the Swa2 domain of DNAJC6. Using our previously established budding yeast model system for α‐synuclein, we first show that wild‐type (WT), E46K, A53T, H50Q, and A53E a‐synuclein are toxic to yeast and show varying degrees of membrane binding and aggregation, while A30P and G51D a‐synuclein are relatively non‐toxic and shows cytoplasmic diffuse localization. What is still not well understood is whether the other PD‐causing and risk genes mentioned above can influence toxicity and localization properties of WT a‐synuclein and these six familial PD mutants. To test the hypothesis that they do influence a‐synuclein, WT and familial mutant forms of a‐synuclein were studied in haploid yeast strains that were singly deleted for these six PD‐linked genes (all of which are linked to loss‐of‐function in PD). Results show that some gene deletions increase (Δhsp31) or decrease (Δatp13, Δvps35) a‐synuclein toxicity and alter its localization in a highly familial mutant specific way, while others more broadly increase a‐synuclein toxicity or aggregation (Δvps13, Δsac1), while still others no effect (Δswa2). Our findings suggest that WT and each familial mutant of a‐synuclein create cellular toxicity and alter localization in distinct ways and that each is likely regulated by different subsets of genes, opening doors for mutant‐specific mechanistic insight into the varying modes of a‐synuclein toxicity.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.