Controlling Amyloid Beta Peptide Aggregation and Toxicity by Protease-Stable Ligands.

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Alzheimer's disease (AD) pathogenesis involves amyloid beta (Aβ) peptide polymerization into insoluble fibrils.
• The N-terminal hydrophobic fragment (16KLVFF20) of Aβ is crucial for β-sheet formation and aggregation.
• Understanding Aβ aggregation mechanisms is key to developing AD therapies.

Purpose of the Study:

• To investigate the impact of single amino acid mutations in the Aβ N-terminal region on Aβ aggregation.
• To identify specific Aβ peptide mutants that inhibit fibril formation.
• To evaluate the neuroprotective effects of these modified peptides against Aβ-induced toxicity.

Main Methods:

• Designed and synthesized 14 hydrophobic peptides (NT-01 to NT-14) with single mutations at the 18Val position of the Aβ fragment (KLVFFAE).
• Utilized circular dichroism (CD) spectroscopy and Fourier transform infrared (FTIR) spectroscopy to analyze changes in Aβ secondary structure.
• Assessed Aβ aggregation inhibition using thioflavin-T (ThT) binding assays, Congo red staining, and electron microscopy.
• Evaluated neuroprotection in PC-12 differentiated neurons exposed to Aβ and NT peptides.

Main Results:

• Mutant peptides NT-02, NT-03, and NT-13 significantly altered Aβ aggregate formation.
• Coincubation with NT peptides reduced Aβ β-sheet content and increased random coil conformation.
• Inhibition of Aβ fibril formation was confirmed by ThT, Congo red, and electron microscopy.
• NT peptides demonstrated neuroprotective effects against Aβ-induced toxicity and apoptosis in vitro.

Conclusions:

• Single amino acid mutations in the Aβ N-terminal region can effectively inhibit Aβ aggregation.
• Promoting random coil conformation over β-sheet structure in Aβ is a viable strategy to control fibril formation.
• Protease-stable ligands targeting Aβ secondary structure represent a promising therapeutic avenue for Alzheimer's disease.