Side-chain moieties from the N-terminal region of Aβ are Involved in an oligomer-stabilizing network of interactions

PLoS One. 2018 Aug 6;13(8):e0201761. doi: 10.1371/journal.pone.0201761. eCollection 2018.

Abstract

Oligomeric forms of the Aβ peptide represent the most probable neurotoxic agent in Alzheimer's disease. The dynamic and heterogeneous character of these oligomers makes their structural characterization by classic methods difficult. Native mass spectrometry, when supported by additional gas phase techniques, like ion mobility separation and hydrogen-deuterium exchange (IM-HDX-MS), enable analysis of different oligomers coexisting in the sample and may provide species-specific structural information for each oligomeric form populated in the gas phase. Here, we have combined these three techniques to obtain insight into the structural properties of oligomers of Aβ1-40 and two variants with scrambled sequences. Gas-phase HDX-MS revealed a sequence-specific engagement of the side-chains of residues located at the N-terminal part of the peptide in a network of oligomer-stabilizing interactions. Oligomer-specific interactions were no longer observed in the case of the fully scrambled sequence. Also, the ability to form alternative structures, observed for WT Aβ peptide, was lost upon scrambling. Our data underscore a role for the N-terminal residues in shaping the equilibria of oligomeric forms. Although the peptide lacking the N-terminal 1-16 residues (p3 peptide) is thought to be benign, the role of the N-terminus has not been sufficiently characterized yet. We speculate that the interaction networks revealed here may be crucial for enabling structural transitions necessary to obtain mature parallel cross-β structures from smaller antiparallel oligomers. We provide a hypothetical molecular model of the trajectory that allows a gradual conversion from antiparallel to parallel oligomers without decomposition of oligomers. Oligomer-defining interactions involving the Aβ peptide N-terminus may be important in production of the neurotoxic forms and thus should not be neglected.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid beta-Peptides / chemistry
  • Amyloid beta-Peptides / genetics
  • Amyloid beta-Peptides / metabolism*
  • Escherichia coli
  • Molecular Dynamics Simulation
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism*
  • Protein Conformation
  • Protein Multimerization
  • Protein Stability

Substances

  • Amyloid beta-Peptides
  • Peptide Fragments
  • amyloid beta-protein (1-40)

Grants and funding

Funded by National Science Centre: MAESTRO (2014/14/A/NZ1/00306) to MD and KP, Centre of Preclinical Research and Technology (POIG.02.02.00-14-024/08-00) to MD, National Multidisciplinary Laboratory of Functional Nanomaterials (POIGT.02.02.00-00-025/09-00) to MD, and European Cooperation in Science and Technology Short-Term Scientific Mission (STSM TD1207) to KP. The DLS equipment used was sponsored in part by the Centre for Preclinical Research and Technology (POIG.02.02.00-14-024/08-00), a project co-sponsored by European Regional Development Fund and Innovative Economy, The National Cohesion Strategy of Poland. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.