Quantifying Co-Oligomer Formation by α-Synuclein

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Small oligomers of alpha-synuclein (αS) are cytotoxic and implicated in Parkinson's disease (PD).
• αS can form co-aggregates with its variants and other proteins like amyloid-β (Aβ) and tau, linked to Alzheimer's disease.
• Studying αS self- and co-oligomerization quantitatively is challenging.

Purpose of the Study:

• To quantitatively measure equilibrium populations of αS oligomers formed in vitro.
• To investigate co-oligomerization of wild-type αS with its mutational variants and with Aβ40, Aβ42, and tau fragments.
• To understand the thermodynamic and biophysical properties of αS oligomer formation.

Main Methods:

• Utilized single-molecule techniques to analyze protein oligomerization.
• Applied a statistical mechanical model to interpret equilibrium populations.
• Measured in vitro formation of oligomers from mixtures of αS, its variants, Aβ, and tau.

Main Results:

• Co-oligomer formation of αS is generally more thermodynamically favorable than self-oligomer formation at equilibrium.
• αS self-oligomers exhibit higher potency in disrupting lipid membranes compared to co-oligomers.
• The greater propensity for co-oligomer formation can outweigh the membrane disruption difference when multiple proteins are present.

Conclusions:

• Co-oligomerization of αS with other proteins is a significant process.
• The formation propensity and membrane disruptive properties of αS oligomers vary based on co-assembly.
• Co-oligomer formation may be a crucial factor in the pathogenesis of Parkinson's disease and related neurodegenerative disorders.