Solution NMR studies of Aβ monomer dynamics.

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Amyloid-beta (Aβ) aggregates, including oligomers and fibrils, are implicated in Alzheimer's disease neurotoxicity.
• Aβ40 and Aβ42 are the primary Aβ species in the human brain, with Aβ42 exhibiting faster aggregation.
• The molecular mechanisms underlying the differential aggregation propensity of Aβ40 and Aβ42 remain unclear.

Purpose of the Study:

• To investigate the role of monomer dynamics in the differential aggregation rates of Aβ40 and Aβ42.
• To explore how modifications affecting dynamics influence Aβ aggregation.
• To establish a link between protein dynamics and the mechanism of Aβ aggregation.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spin relaxation was used to probe the picosecond-to-nanosecond timescale dynamics of Aβ40 and Aβ42 monomers.
• Replica Exchange Molecular Dynamics (REMD) simulations were employed to determine the major monomer conformations.
• Methionine 35 (M35) oxidation was used to perturb Aβ42 dynamics.

Main Results:

• Aβ40 and Aβ42 monomers exhibit distinct backbone and sidechain dynamics.
• Aβ42 monomers are more rigid in the C-terminus, while Aβ40 monomers show increased rigidity in the central hydrophobic cluster.
• M35 oxidation in Aβ42 induced Aβ40-like dynamic changes and significantly reduced its aggregation rate.

Conclusions:

• Protein dynamics play a crucial role in the aggregation mechanism of amyloid-beta.
• Differences in monomer dynamics contribute to the varying aggregation propensities of Aβ40 and Aβ42.
• Modulating protein dynamics presents a potential strategy for controlling Aβ aggregation in Alzheimer's disease.