Phosphorylation and Alanine-76 Contribute to α-Synuclein’s Plasma Membrane Binding and Aggregation

Parkinson’s disease (PD) is an incurable neurodegenerative disease, which afflicts nearly 4 million people worldwide. The hallmark symptom of PD is the formation of Lewy bodies containing aggregated, phosphorylated, and membrane phospholipid associated α-synuclein. The molecular determinants for α-synuclein aggregation and membrane association are still unknown. Past studies suggest that alanine-76 and phosphorylation at serines 87 and 129 may contribute to aggregation and membrane-association, which we tested here in two yeast models. By studying phosphorylation mutants (S87D and S129D), we found evidence that phosphorylation increases α-synuclein plasma membrane association in budding yeast and intracellular vesicular aggregation in fission yeast. Study of an A76R and A76E mutant demonstrated that this site promotes α-synuclein membrane association in budding yeast and aggregation in fission yeast, but the extent of aggregation is sensitive to the charge of the side chain. Thus, both yeast models help illuminate the molecular basis of α-synuclein pathology.