Aggregation of Beta-Amyloid Peptides Proximal to Zwitterionic Lipid Bilayers

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Alzheimer's disease (AD) is characterized by amyloid plaque deposition.
• Amyloid-beta (Aβ) peptides aggregate into fibrils, forming plaques.
• The formation mechanism of nonfibrillar Aβ intermediates remains poorly understood.

Purpose of the Study:

• To investigate the formation mechanism of amyloid-beta (Aβ) fibril intermediates.
• To explore the role of zwitterionic lipids in trapping Aβ40 on-pathway intermediates.
• To establish a liposome-Aβ model for studying fibril formation.

Main Methods:

• Incubation of Aβ40 peptides with liposomes composed of zwitterionic lipids.
• Preparation of Aβ40 aggregates at low peptide concentrations (<10 μm).
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to analyze aggregate conformation.

Main Results:

• On-pathway β-sheet intermediates of Aβ40 were successfully trapped using zwitterionic liposomes.
• Solid-state NMR confirmed that the backbone conformation of liposome-bound aggregates closely resembles that of fibrils formed in solution.
• Zwitterionic lipids, unlike anionic lipids, did not induce significant conformational changes in Aβ40 fibrils.

Conclusions:

• Zwitterionic liposomes can effectively trap Aβ40 on-pathway intermediates, providing a model for studying early fibril formation.
• The liposome-Aβ system offers a valuable tool for elucidating the molecular mechanisms underlying amyloidogenesis in Alzheimer's disease.
• Understanding these early aggregation steps is crucial for developing therapeutic strategies against Alzheimer's disease.