Uncovering the Early Assembly Mechanism for Amyloidogenic β2-Microglobulin Using Cross-linking and Native Mass
Zoe Hall1, Carla Schmidt2, Argyris Politis3
1From the Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom, and.
Abstract:
β2-Microglobulin (β2m), a key component of the major histocompatibility class I complex, can aggregate into fibrils with severe clinical consequences. As such, investigating the structural aspects of the formation of oligomeric intermediates of β2m and their subsequent progression toward fibrillar aggregates is of great importance. However, β2m aggregates are challenging targets in structural biology, primarily due to their inherent transient and heterogeneous nature. Here we study the oligomeric distributions and structures of the early intermediates of amyloidogenic β2m and its truncated variant ΔN6-β2m. We established compact oligomers for both variants by integrating advanced mass spectrometric techniques with available electron microscopy maps and atomic level structures from NMR spectroscopy and x-ray crystallography. Our results revealed a stepwise assembly mechanism by monomer addition and domain swapping for the oligomeric species of ΔN6-β2m. The observed structural similarity and common oligomerization pathway between the two variants is likely to enable ΔN6-β2m to cross-seed β2m fibrillation and allow the formation of mixed fibrils. We further determined the key subunit interactions in ΔN6-β2m tetramer, revealing the importance of a domain-swapped hinge region for formation of higher order oligomers. Overall, we deliver new mechanistic insights into β2m aggregation, paving the way for future studies on the mechanisms and cause of amyloid fibrillation.
Insights
Researchers investigated the early stages of beta2-microglobulin (β2m) aggregation, revealing a stepwise assembly mechanism. This work provides crucial insights into amyloid fibrillation pathways and potential cross-seeding events.
Area of Science:
- Structural Biology
- Biochemistry
- Molecular Medicine
Background:
- Beta2-microglobulin (β2m) aggregation into fibrils is linked to severe clinical outcomes.
- Understanding the structural intermediates of β2m aggregation is critical for disease research.
- The transient and heterogeneous nature of β2m aggregates presents significant structural biology challenges.
Purpose of the Study:
- To investigate the oligomeric distributions and structures of early amyloidogenic intermediates of β2m and its variant ΔN6-β2m.
- To elucidate the stepwise assembly mechanism and key subunit interactions in β2m oligomers.
- To provide mechanistic insights into β2m aggregation and amyloid fibrillation.
Main Methods:
- Integration of advanced mass spectrometry with electron microscopy maps.
- Utilizing atomic-level structures from NMR spectroscopy and x-ray crystallography.
- Analysis of oligomeric distributions and structural characterization of β2m variants.
Main Results:
- Compact oligomers were established for both β2m and ΔN6-β2m.
- A stepwise assembly mechanism involving monomer addition and domain swapping was revealed for ΔN6-β2m oligomers.
- Key subunit interactions in ΔN6-β2m tetramer highlighted the role of a domain-swapped hinge region.
Conclusions:
- Structural similarity and common oligomerization pathways exist between β2m and ΔN6-β2m.
- ΔN6-β2m may cross-seed β2m fibrillation, leading to mixed fibril formation.
- New mechanistic insights into β2m aggregation advance the study of amyloid fibrillation.
