title: Uncovering the Early Assembly Mechanism for Amyloidogenic β2-Microglobulin Using Cross-linking and Native Mass Spectrometry.
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.
authors.affiliation: From 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.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Hall
authors.affiliation: Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom, and.
authors.forename: Carla
authors.initials: C
authors.lastname: Schmidt
authors.affiliation: Department of Chemistry, King's College London, 7 Trinity Street, London SE1 1DB, United Kingdom argyris.politis@kcl.ac.uk.
authors.forename: Argyris
authors.initials: A
authors.lastname: Politis
mesh_terms: D000465:Algorithms; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000737:chemistry; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D019281:Dimerization; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010449:Peptide Mapping; D066329:Protein Aggregates; D066263:Protein Aggregation, Pathological / Q000378:metabolism*; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013388:Succinimides / Q000737:chemistry; D053719:Tandem Mass Spectrometry; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000682:Amyloid; D003432:Cross-Linking Reagents; D010446:Peptide Fragments; D066329:Protein Aggregates; D011994:Recombinant Proteins; D013388:Succinimides; D001613:beta 2-Microglobulin; C035760:bis(sulfosuccinimidyl)suberate
keywords: amyloid; mass spectrometry; mass spectrometry (MS); molecular modeling; protein cross-linking; structural model