Pathways of Amyloid-β Aggregation Depend on Oligomer Shape.

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• Alzheimer's disease research focuses on amyloid-beta (Aβ) peptide aggregation.
• Two main Aβ alloforms, Aβ40 and Aβ42, exhibit distinct aggregation pathways.
• Specific oligomer sizes are implicated as key toxic agents in early aggregation.

Purpose of the Study:

• To investigate the molecular mechanisms underlying Aβ40 and Aβ42 aggregation pathways.
• To correlate oligomer conformations with experimentally observed aggregation patterns.
• To elucidate the structural basis for the differential toxicity of Aβ alloforms.

Main Methods:

• Utilized transition networks derived from all-atom molecular dynamics simulations.
• Analyzed oligomer conformations and their contribution to aggregation pathways.
• Compared aggregation dynamics between Aβ40 and Aβ42 alloforms.

Main Results:

• Oligomers originating from compact conformations lead to experimentally observed distributions.
• Extended oligomers contribute significantly to the formation of larger aggregates.
• Distinct aggregation differences between Aβ40 and Aβ42 emerge at the dimer stage.
• Increased solvent exposure of hydrophobic residues in Aβ42 oligomers influences aggregation and toxicity.

Conclusions:

• Oligomer conformation dictates aggregation pathway and product.
• Early-stage dimer interactions are critical for differential Aβ alloform aggregation.
• Structural differences in Aβ42 contribute to its enhanced neurotoxicity in Alzheimer's disease.