Liquid-liquid phase separation of α-synuclein is highly sensitive to sequence complexity

Area of Science:

• Biochemistry
• Neuroscience
• Protein Misfolding Diseases

Background:

• Alpha-synuclein (α-syn) aggregation into amyloid fibrils is a hallmark of Parkinson's disease (PD).
• Alpha-synuclein undergoes liquid-liquid phase separation (LLPS), a process linked to fibrillation, complicating the study of unique LLPS determinants.
• Dissecting the biological roles of α-syn LLPS independent of fibrillation requires strategies to selectively perturb LLPS.

Approach:

• Investigated the role of sequence complexity in α-syn LLPS using subtle missense mutations.
• Quantified the impact of specific mutations (e.g., V16I, V15I, A18T) on α-syn LLPS propensity.
• Developed α-syn variants with differential LLPS and fibrillation propensities.

Key Points:

• LLPS of α-syn is highly sensitive to its sequence complexity; even conservative mutations altering complexity significantly impact LLPS.
• A PD-associated mutation (A18T) that enhances sequence complexity reduces LLPS, suggesting complexity's role in α-syn pathogenicity.
• Demonstrated that α-syn fibrillation does not necessarily correlate with LLPS, identifying mutations that selectively perturb one process over the other.

Conclusions:

• Sequence complexity is a critical determinant of α-syn LLPS.
• The ability to selectively perturb LLPS or fibrillation of α-syn provides novel tools to disentangle their respective roles.
• These findings will advance research into the distinct pathobiological functions of α-syn LLPS and fibrillation in Parkinson's disease.