Potential Protective Function of Aβ₄₂ Monomer on Tauopathies.

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Soluble amyloid-beta (Aβ) and Tau proteins interact to drive neurodegeneration in Alzheimer's disease (AD).
• Disulfide bond cross-linking is critical for Tau oligomer stability and prion-like spread.
• The precise role of Aβ in regulating Tau cross-linking and propagation remains unclear.

Purpose of the Study:

• To investigate how Aβ42 regulates disulfide bond formation in Tau.
• To explore the potential protective role of nonamyloidogenic Aβ species against Tau aggregation.
• To assess the differential toxicity of Aβ42 and TauPHF43 in neuronal models.

Main Methods:

• Studied interactions between Aβ42 and TauPHF43 (a Tau construct).
• Utilized disulfide bond assays and assessed dimer/oligomer disassembly.
• Employed antioxidant experiments with Aβ and cystine.
• Investigated the effect of cyclosporine A (CycA) on Aβ-Tau interactions.
• Assessed peptide toxicity in acute brain slices.

Main Results:

• Fresh Aβ42 protected Tau against disulfide-linked dimer formation.
• Monomeric and small Aβ oligomers disassembled Tau dimers and heparin-induced Tau oligomers.
• Aβ exhibited antioxidant properties, preventing disulfide bond formation in Tau.
• Cyclosporine A did not impede Aβ42-driven Tau disassembly.
• Aβ42 demonstrated higher acute toxicity than TauPHF43 in brain slices.

Conclusions:

• Aβ42 monomers and small oligomers may have a protective role in AD by preventing Tau cross-linking.
• Aβ acts as an antioxidant, inhibiting Tau disulfide bond formation.
• Targeting amyloidogenic Aβ with CycA does not interfere with this protective Aβ-Tau interaction.
• Aβ42 exhibits greater acute neurotoxicity than TauPHF43.