Nanoaggregates Derived from Amyloid-beta and Alpha-synuclein Characterized by Sequential Quadruple Force Mapping.

Area of Science:

• Neuroscience
• Biochemistry
• Structural Biology

Background:

• Alzheimer's disease (AD) and Parkinson's disease (PD) pathologies involve amyloid-beta (Aβ) and alpha-synuclein (α-syn) proteins.
• The formation of hetero-oligomers between Aβ and α-syn is implicated in the overlapping symptoms of AD and PD.
• The high-resolution structure of these hetero-oligomers remains poorly understood.

Purpose of the Study:

• To elucidate the surface structure of Aβ/α-syn hetero-oligomers at high resolution.
• To investigate the accessibility and orientation of peptide termini within these aggregates.
• To develop novel methodologies for studying protein aggregate structures at the single-molecule level.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) with multi-tip functionalization.
• Employed antibodies targeting the N-terminus and C-terminus of Aβ and α-syn peptides.
• Analyzed the surface topography and antibody binding patterns of individual aggregates.

Main Results:

• Confirmed the presence of hetero-oligomers composed of both Aβ and α-syn.
• Observed a significantly higher probability of recognizing peptide termini in hetero-oligomers compared to homo-oligomers.
• Inferred that termini are more exposed or flexible at the surface of hetero-oligomers, possibly due to looser packing.

Conclusions:

• The study provides a novel high-resolution method for characterizing complex protein aggregates.
• Findings suggest distinct structural features of hetero-oligomers, with more accessible termini.
• This approach can be extended to study other intrinsically disordered protein aggregates relevant to various diseases.