Distinct α-Synuclein strains and implications for heterogeneity among α-Synucleinopathies

The deposition of misfolded β-sheet enriched amyloid protein is a shared feature of many neurodegenerative diseases. Recent studies demonstrated the existence of conformationally diverse strains as a common property for multiple amyloidogenic proteins including α-Synuclein (α-Syn). α-Syn is misfolded and aggregated in a group of neurodegenerative diseases collectively known as α-Synucleinopathies, which include Parkinson's disease (PD), dementia with Lewy body, multiple system atrophy and also a subset of Alzheimer's disease patients with concomitant PD-like Lewy bodies and neurites. While sharing the same pathological protein, different α-Synucleinopathies demonstrate distinct clinical and pathological phenotypes, which could result from the existence of diverse pathological α-Syn strains in patients. In this review, we summarized the characteristics of different α-Synucleinopathies and α-Syn strains generated with recombinant α-Syn monomers. We also make predictions of α-Syn strains that could potentially exist in patients based on the knowledge from other amyloid proteins and the clinical and pathological features of different α-Synucleinopathies.