Lewy-MSA hybrid fold drives distinct neuronal a-synuclein pathology
The ordered assembly of -synuclein protein into filaments encoded by SNCA characterizes neurodegenerative diseases called synucleinopathies. Lewy body disease (LBD) shows predominantly neuronal -synuclein pathology and multiple system atrophy (MSA) predominantly oligodendrocytic -synuclein pathology affecting subcortical brain structures. Based on cryo-electron microscopy, it was reported that structures of -synuclein filaments from LBD differ from MSA and juvenile onset synucleinopathy (JOS) caused by a 21-nucleotide duplication in the second exon of one allele of SNCA gene 1-3. Importantly, a rare subtype of MSA, called atypical MSA4 shows abundant neuronal argyrophilic -synuclein inclusions in the limbic system. Current concepts indicate that disease entities are characterized by unique protofilament folds. Here we demonstrate that in addition to the MSA fold, -synuclein can form a new Lewy-MSA hybrid fold in the same brain region, leading to the atypical histopathological form of MSA. Distinct biochemical characteristics of -synuclein, as demonstrated by protease-sensitivity digestion assay, seed amplification assays (SAAs) and conformational stability assay (CSA), are also linked to cytopathological differences (e.g. neuronal or oligodendroglial). We expand the current structure-based classification of -synucleinopathies and propose that cell-specific protein pathologies can be associated with distinct filament folds.