Distinct Filament Conformation for Receptor-Bound Amyloid-ß from Alzheimer's Disease Brain

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Alzheimer's disease (AD) pathogenesis is linked to amyloid-ß (Aß) and synapse loss.
• Oligomeric Aß is suspected as the cause, but its molecular details remain elusive.
• Existing research often overlooks receptor-bound Aß species.

Purpose of the Study:

• To define the molecular characteristics of receptor-bound Aß in Alzheimer's disease brains.
• To investigate the role of receptor-bound Aß in synaptic dysfunction and prion protein interaction.
• To differentiate receptor-bound Aß from plaque-associated Aß filaments.

Main Methods:

• Isolation and purification of receptor-bound Aß using a receptor antagonist.
• Cryo-electron microscopy (Cryo-EM) for structural determination.
• Analysis of prion protein binding and synaptic damage potential.

Main Results:

• A distinct pool of receptor-bound Aß filaments (65 nm) was identified, 10x more abundant than free Aß.
• These filaments feature prion protein binding at their tips and consist of S-shaped monomers.
• Structural analysis revealed unique features distinguishing them from plaque-associated Aß.
• No evidence of oligomeric Aß interacting with human brain receptors was found.

Conclusions:

• Receptor-bound Aß filaments, not oligomers, are critical for prion protein interaction and synaptic damage in AD.
• The high tip:length ratio of these filaments is key to their neurotoxic mechanism.
• Understanding receptor-bound Aß offers insights into neuronal dysfunction distinct from plaque pathology.