Dataset Information

Site-specific structural order in Alzheimer's A?42 fibrils.

ABSTRACT: Deposition of amyloid fibrils is a pathological hallmark of Alzheimer's disease. A?42 is the major protein whose aggregation leads to the formation of these fibrils. Understanding the detailed structure of A?42 fibrils is of particular importance for delineating the mechanism of A?42 aggregation and developing specific amyloid-targeting drugs. Here, we use site-directed spin labelling and electron paramagnetic resonance spectroscopy to study the site-specific structural order at each and every residue position in A?42 fibrils. Strong interactions between spin labels indicate highly ordered protein backbone at the labelling site, while weak interactions suggest disordered local structure. Our results show that A?42 consists of five ?-strands (residues 2-7, 10-13, 17-20, 31-36, 39-41), three turns (residues 7-8, 14-16, 37-38) and one ordered loop (residues 21-30). Spin labels introduced at ?-strand sites show strong spin-spin interactions, while spin labels at turn or loop sites show weak interactions. However, residues 24, 25 and 28 also show strong interactions between spin labels, suggesting that the loop 21-30 is partly ordered. In the context of recent structural work using solid-state NMR and cryoEM, the site-specific structural order revealed in this study provides a different perspective on backbone and side chain dynamics of A?42 fibrils.

SUBMITTER: Wang H

PROVIDER: S-EPMC6083707 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Site-specific structural order in Alzheimer's Aβ42 fibrils.

Wang Hongsu H Lee Yoon Kyung YK Xue Christine C Guo Zhefeng Z

Royal Society open science 20180704 7

Deposition of amyloid fibrils is a pathological hallmark of Alzheimer's disease. Aβ42 is the major protein whose aggregation leads to the formation of these fibrils. Understanding the detailed structure of Aβ42 fibrils is of particular importance for delineating the mechanism of Aβ42 aggregation and developing specific amyloid-targeting drugs. Here, we use site-directed spin labelling and electron paramagnetic resonance spectroscopy to study the site-specific structural order at each and every r ...[more]

PMID: 30109072

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Project description:BackgroundIn Alzheimer's disease (AD), amyloid-β 1-42 (Aβ42) neurotoxicity stems mostly from its soluble oligomeric aggregates. Studies of such aggregates have been hampered by the lack of oligomer-specific research tools and their intrinsic instability and heterogeneity. Here, we developed a monoclonal antibody with a unique oligomer-specific binding profile (ALZ-201) using oligomer-stabilising technology. Subsequently, we assessed the etiological relevance of the Aβ targeted by ALZ-201 on physiologically derived, toxic Aβ using extracts from post-mortem brains of AD patients and controls in primary mouse neuron cultures.MethodsMice were immunised with stable oligomers derived from the Aβ42 peptide with A21C/A30C mutations (AβCC), and ALZ-201 was developed using hybridoma technology. Specificity for the oligomeric form of the Aβ42CC antigen and Aβ42 was confirmed using ELISA, and non-reactivity against plaques by immunohistochemistry (IHC). The antibody's potential for cross-protective activity against pathological Aβ was evaluated in brain tissue samples from 10 individuals confirmed as AD (n=7) and non-AD (n=3) with IHC staining for Aβ and phosphorylated tau (p-Tau) aggregates. Brain extracts were prepared and immunodepleted using the positive control 4G8 antibody, ALZ-201 or an isotype control to ALZ-201. Fractions were biochemically characterised, and toxicity assays were performed in primary mouse neuronal cultures using automated high-content microscopy.ResultsAD brain extracts proved to be more toxic than controls as demonstrated by neuronal loss and morphological determinants (e.g. synapse density and measures of neurite complexity). Immunodepletion using 4G8 reduced Aβ levels in both AD and control samples compared to ALZ-201 or the isotype control, which showed no significant difference. Importantly, despite the differential effect on the total Aβ content, the neuroprotective effects of 4G8 and ALZ-201 immunodepletion were similar, whereas the isotype control showed no effect.ConclusionsALZ-201 depletes a toxic species in post-mortem AD brain extracts causing a positive physiological and protective impact on the integrity and morphology of mouse neurons. Its unique specificity indicates that a low-abundant, soluble Aβ42 oligomer may account for much of the neurotoxicity in AD. This critical attribute identifies the potential of ALZ-201 as a novel drug candidate for achieving a true, clinical therapeutic effect in AD.

Dataset Information

Site-specific structural order in Alzheimer's A?42 fibrils.

Publications

Site-specific structural order in Alzheimer's Aβ42 fibrils.

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