Oligomeric Protein Complexes Formed by Beta Amyloid Peptides and Their Molecular Associates

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Amyloid-beta (Aβ) peptide aggregation and dysregulation are central to Alzheimer's disease (AD) pathogenesis.
• Zinc ions (Zn²⁺) and TDP-43 are known binding partners of Aβ implicated in neurodegenerative diseases.

Purpose of the Study:

• To investigate reverse micelles (RMs) as a nanoscale environment for encapsulating Aβ peptides.
• To explore the interactions of encapsulated Aβ peptides with Zn²⁺ and a TDP-43 variant.
• To elucidate the structural consequences of these interactions on Aβ oligomers.

Main Methods:

• Encapsulation of Aβ peptides within reverse micelles (RMs).
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy for structural analysis.
• Site-specific ¹³C chemical shift analysis to probe conformational changes.

Main Results:

• RMs stabilize Aβ peptides in oligomeric forms, promoting β-sheet structure.
• Zn²⁺ induces conformational changes in specific Aβ oligomer residues (E11, E22).
• A stable protein complex forms between Aβ₄₀ and the TDP-43 variant, persisting under harsh conditions.
• Aβ₄₀ oligomers adopt a β₁-loop-β₂ motif, with alterations primarily in loop and charged residues, while hydrophobic regions remain stable.

Conclusions:

• Reverse micelles provide a suitable environment for studying Aβ oligomer structure and interactions.
• Zn²⁺ and TDP-43 binding modulate Aβ₄₀ conformation in distinct ways, highlighting their roles in neurodegeneration.
• Structural insights into Aβ-protein and Aβ-ion interactions are crucial for understanding Alzheimer's disease.