How the amyloid-β peptide and membranes affect each other: an extensive simulation study

Area of Science:

• Biophysics
• Neuroscience
• Computational Biology

Background:

• Alzheimer's disease etiology involves amyloid-beta (Aβ) interactions with neural membranes.
• Experimental studies show Aβ affects lipid behavior, but structural details and causality are unclear.

Purpose of the Study:

• Investigate amyloid-beta (Aβ)(42) behavior in lipid bilayers using molecular dynamics.
• Determine factors influencing Aβ stability and water translocation across membranes.

Main Methods:

• Atomistic molecular dynamics simulations (over 6 μs).
• Simulated Aβ(42) in zwitterionic and anionic lipid bilayers.
• Analyzed transmembrane β-sheets (monomer, tetramer) and helical structures.

Main Results:

• Aβ(42) remained embedded in bilayers; stability depended on surface charge and lipid type.
• Unsaturated lipids and zwitterionic surfaces promoted Aβ(42) stability.
• The β-sheet tetramer was the most stable conformation due to interpeptide interactions.
• Water translocation was generally fast but slower than in peptide-free bilayers.
• Translocation rate depended on lipid type, temperature, and Aβ conformation.

Conclusions:

• Membrane permeabilization in Alzheimer's disease is likely caused by membrane-bound Aβ oligomers, not monomers.
• The Aβ(42) β-sheet tetramer facilitates greater water passage than monomers.
• Interactions with the hydrophobic core slow water permeation through Aβ-bilayer systems.