Analysis and comparison of post-translational modifications of α-synuclein filaments in multiple system atrophy and dementia with Lewy bodies.

Our previous cryogenic electron microscopy (cryoEM) analysis showed that the core structures of α-synuclein filaments accumulated in brains of patients diagnosed with dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) patients are different. We analyzed the post-translational modifications (PTMs) in these filaments , and examined their relationship with the core filament structures and pathological features. Besides the common PTMs in MSA and DLB filaments, acetylation, methylation, oxidation and phosphorylation were frequently detected in MSA filaments, but not in DLB filaments. Furthermore, in DLB filament cases, the processing occurred at the C-terminal side of Asp at 119 residue and Asn at 122 residue, while in MSA cases, the processing occurred at multiple sites between residues 109-123. We have previously reported that PTMs in tau filaments depend on the filament core structure. This was considered to apply to α-synuclein filaments as well. As an example, PTMs including processing sites detected in α-synuclein filaments in early-onset DLB (an atypical form, now named juvenile-onset α-synucleinopathy) brain also supported this idea. These suggests that PTMs appeared to be closely related to the specific filament core structures.