Parkinson'S Disease-Related Phosphorylation At Tyr39 Rearranges Alpha-Synuclein Amyloid Fibril Structure Revealed By Cryo-Em

Posttranslational modifications (PTMs) of alpha-synuclein (alpha-syn), e.g., phosphorylation, play an important role in modulating alpha-syn pa-thology in Parkinson's disease (PD) and alpha-synucleinopathies. Accu-mulation of phosphorylated alpha-syn fibrils in Lewy bodies and Lewy neurites is the histological hallmark of these diseases. However, it is unclear how phosphorylation relates to alpha-syn pathology. Here, by combining chemical synthesis and bacterial expression, we obtained homogeneous alpha-syn fibrils with site-specific phosphory-lation at Y39, which exhibits enhanced neuronal pathology in rat primary cortical neurons. We determined the cryo-electron micros-copy (cryo-EM) structure of the pY39 alpha-syn fibril, which reveals a fold of alpha-syn with pY39 in the center of the fibril core forming an electrostatic interaction network with eight charged residues in the N-terminal region of alpha-syn. This structure composed of resi-dues 1 to 100 represents the largest alpha-syn fibril core determined so far. This work provides structural understanding on the pathology of the pY39 alpha-syn fibril and highlights the importance of PTMs in defining the polymorphism and pathology of amyloid fibrils in neurodegenerative diseases.