Factors Driving Amyloid Beta Fibril Recognition by Cell Surface Receptors: A Computational Study

Area of Science:

• Neuroscience
• Immunology
• Biochemistry

Background:

• Alzheimer's disease (AD) is characterized by neurotoxic beta-amyloid (Aβ) plaques.
• Insoluble Aβ fibrils (fAβ) activate microglia via receptors like RAGE, TLR2, TLR4, and CD14, leading to inflammation.

Purpose of the Study:

• To elucidate binding patterns of fAβ with RAGE, TLR2, TLR4, and CD14.
• To investigate the influence of fAβ structure (type I vs. II) and pH on receptor binding.
• To explore the impact of familial AD mutations on fAβ structure and receptor interactions.

Main Methods:

• Utilized experimentally resolved fAβ structures (type I and II) from AD brain tissue.
• Performed binding assays with RAGE, TLR2, TLR4, and CD14.
• Investigated the effects of familial mutations (Arctic, Dutch, Iowa, Italian, Flemish) on fAβ structure and binding affinity using in silico modeling.

Main Results:

• TLR2 and RAGE tightly bound both fibril types; TLR4 preferred type I; CD14 preferred type II.
• Binding affinity was pH-dependent for CD14, TLR4, and RAGE, but not TLR2.
• Familial mutations showed varied effects: Arctic, Dutch, and Iowa had similar binding impacts, Italian abrogated binding, and Flemish mutations were not feasible.

Conclusions:

• Immune receptors exhibit adaptability in recognizing fAβ, with fibril structure and pH as key determinants.
• In silico analysis suggests certain familial mutations can form aggregates resembling type I and II structures.
• Findings provide insights into molecular recognition mechanisms in Alzheimer's disease progression.