Dimerization and Structural Stability of Amyloid Precursor Proteins Affected by the Membrane Microenvironments

Area of Science:

• Biochemistry
• Neuroscience
• Computational Biology

Background:

• Lipid rafts are crucial microenvironments influencing amyloid precursor protein (APP) processing.
• APP transmembrane domain (C99) dimerization is structurally dynamic and affected by membrane composition.
• The role of lipid rafts in C99 dimerization and amyloidogenesis remains unclear.

Purpose of the Study:

• To investigate the behavioral preference and dimerization of the APP transmembrane domain (C99) within lipid raft microenvironments.
• To elucidate the molecular mechanisms by which lipid rafts influence C99 structural dynamics and packing.
• To compare C99 dimerization in raft-forming versus bulk fluid lipid bilayers.

Main Methods:

• Coarse-grained (CG) molecular dynamics simulations were employed.
• Simulations explored C99 behavior in various membrane compositions, including lipid rafts.
• Analysis focused on C99 anchoring, dimerization, and conformational changes.

Main Results:

• C99 anchors to lipid raft boundaries via a conserved hydrophobic motif (VxxAxxxVxxxV).
• Lipid rafts significantly destabilize C99 dimerization, leading to altered packing conformations.
• Dimerization changes are driven by combined effects of saturated lipids and cholesterol, not just cholesterol binding.

Conclusions:

• Lipid rafts promote amyloidogenic processing by destabilizing C99 dimerization.
• Membrane composition, particularly saturated lipids and cholesterol, dictates C99 structural dynamics.
• Understanding these molecular details aids in comprehending APP processing and potential therapeutic targets.