Probing neuroserpin polymerization and interaction with amyloid-beta peptides using single molecule fluorescence

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Neuroserpin, a serine proteinase inhibitor, can form polymers linked to dementia.
• Wild-type neuroserpin inhibits amyloid-beta peptide toxicity, relevant to Alzheimer's disease.

Purpose of the Study:

• To determine the rate-limiting steps in early-stage neuroserpin polymerization.
• To assess how amyloid-beta(1-40) affects neuroserpin polymerization.

Main Methods:

• Single molecule fluorescence spectroscopy.
• Two-color coincidence detection.
• Utilized fluorophore-labeled neuroserpin and amyloid-beta(1-40) peptides.

Main Results:

• Neuroserpin polymerization initiates with unimolecular active monomer formation.
• Competing polymerization and latent monomer formation occur from the active species.
• Amyloid-beta(1-40) forms a weak complex with neuroserpin, increasing active monomer and polymerization rate.
• Amyloid-beta(1-40) acts as a catalyst and is not incorporated into polymers.

Conclusions:

• Findings contradict the proposed domain swap model for neuroserpin polymer formation.
• Amyloid-beta(1-40) catalyzes neuroserpin polymerization, suggesting a potential therapeutic mechanism in Alzheimer's disease.