N-Terminal Acetylation Affects α-Synuclein Fibril Polymorphism.

Area of Science:

• Biochemistry
• Neuroscience
• Structural Biology

Background:

• Parkinson's disease pathogenesis involves amyloid formation by alpha-synuclein (αSyn).
• αSyn undergoes constitutive N-terminal acetylation in vivo.
• The impact of N-terminal acetylation on αSyn aggregation kinetics and fibril structure remains incompletely understood.

Purpose of the Study:

• To investigate the aggregation properties of N-terminally acetylated αSyn (Ac-αSyn) compared to non-acetylated αSyn (NH3-αSyn).
• To characterize the structural differences and seeding capabilities of Ac-αSyn and NH3-αSyn fibrils.
• To determine how N-terminal acetylation modulates αSyn aggregation and fibril polymorphism.

Main Methods:

• Thioflavin T (ThT) binding assays to monitor fibril formation.
• Transmission electron microscopy (TEM) for fibril morphology.
• Circular dichroism (CD) spectroscopy for secondary structure analysis.
• Limited proteolysis to assess structural stability.

Main Results:

• Ac-αSyn exhibited slower aggregation kinetics and reduced ThT sensitivity compared to NH3-αSyn.
• TEM and CD revealed distinct fibril structures for Ac-αSyn and NH3-αSyn.
• Ac-αSyn fibrils formed a stable polymorph that faithfully propagated seeding characteristics.
• NH3-αSyn fibrils showed reduced fidelity in propagating seeding characteristics over generations.

Conclusions:

• N-terminal acetylation of αSyn significantly alters its aggregation pathway and leads to the formation of a distinct, stable fibril polymorph.
• Despite being outside the canonical amyloid core, the N-terminus plays a crucial role in modulating αSyn aggregation and fibril polymorphism.
• These findings offer insights into the structural diversity of αSyn fibrils and their potential implications in Parkinson's disease etiology.