Divergent effects of pathological α-synuclein truncations and mutations on phase separation

ABSTRACT Phase separated condensates can accelerate α-synuclein (α-Syn) amyloid fibril formation implicated in Parkinson’s disease pathogenesis. The effects of pathological modifications, i.e., truncations and familial mutations on the thermodynamics, material properties, and the extent of amyloid aggregation within α-Syn condensates remain elusive. Here, we quantitatively demonstrate that terminal truncations significantly alter α-Syn phase separation, while familial mutations impart minimal effects. Spontaneous sol-gel phase transitions of the truncated α-Syn variants could give rise to amyloid fibrils almost instantly within condensates, suggesting similarities between molecular interactions driving both processes. Extending our study to model coacervate and condensate systems where α-Syn acts as a client, we find α-Syn can dissolve coacervates and form Pickering clusters on condensate surfaces—regulating their size. Additionally, the C-terminal region of α-Syn modulates nucleic acid sequestration within condensates. Together, our findings reveal diverse effects of α-Syn modifications on phase separation, both in pathological and physiological contexts. GRAPHICAL ABSTRACT