Conformational Effects of the A21G Flemish Mutation on the Aggregation of Amyloid β Peptide

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Familial Alzheimer's disease (AD) involves hereditary mutations in amyloid-beta (Aβ).
• The Flemish A21G mutant of Aβ exhibits distinct deposition patterns, primarily Aβ1-40 in vascular walls, differing from typical Aβ1-42 brain deposition.
• Understanding the structural and kinetic impact of the A21G mutation is crucial for elucidating Flemish AD pathogenesis.

Purpose of the Study:

• To structurally characterize the Flemish A21G mutant Aβ1-40 peptide.
• To compare its conformation and aggregation kinetics with wild-type Aβ1-40.
• To investigate the mutation's effect on Aβ1-40's interaction with membrane mimics.

Main Methods:

• Kinetic analysis of peptide aggregation using thioflavin T fluorescence.
• Spectroscopic analysis of peptide structure in the presence of lyso-GM1 micelles.
• Comparison of Flemish mutant (A21G) with wild-type Aβ1-40.

Main Results:

• The A21G mutation significantly inhibits the initial nucleation step in Aβ1-40 fibril formation.
• Compared to wild-type Aβ1-40, the Flemish mutant exhibits reduced α-helical structure when bound to lyso-GM1 micelles.
• The mutation alters the membrane-binding properties and conformational behavior of Aβ1-40.

Conclusions:

• The A21G mutation disrupts the normal nucleation pathway of Aβ1-40 aggregation.
• Changes in membrane binding affinity and secondary structure are associated with the Flemish mutation.
• These findings link altered membrane interactions to modified nucleation behavior in Aβ fibril formation, potentially explaining Flemish AD's unique pathology.