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Rationally Designed Antibodies as Research Tools to Study the Structure-Toxicity Relationship of Amyloid-? Oligomers.

ABSTRACT: Alzheimer's disease is associated with the aggregation of the amyloid-? peptide (A?), resulting in the deposition of amyloid plaques in brain tissue. Recent scrutiny of the mechanisms by which A? aggregates induce neuronal dysfunction has highlighted the importance of the A? oligomers of this protein fragment. Because of the transient and heterogeneous nature of these oligomers, however, it has been challenging to investigate the detailed mechanisms by which these species exert cytotoxicity. To address this problem, we demonstrate here the use of rationally designed single-domain antibodies (DesAbs) to characterize the structure-toxicity relationship of A? oligomers. For this purpose, we use Zn2+-stabilized oligomers of the 40-residue form of A? (A?40) as models of brain A? oligomers and two single-domain antibodies (DesAb18-24 and DesAb34-40), designed to bind to epitopes at residues 18-24 and 34-40 of A?40, respectively. We found that the DesAbs induce a change in structure of the Zn2+-stabilized A?40 oligomers, generating a simultaneous increase in their size and solvent-exposed hydrophobicity. We then observed that these increments in both the size and hydrophobicity of the oligomers neutralize each other in terms of their effects on cytotoxicity, as predicted by a recently proposed general structure-toxicity relationship, and observed experimentally. These results illustrate the use of the DesAbs as research tools to investigate the biophysical and cytotoxicity properties of A? oligomers.

SUBMITTER: Limbocker R

PROVIDER: S-EPMC7352524 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Rationally Designed Antibodies as Research Tools to Study the Structure-Toxicity Relationship of Amyloid-β Oligomers.

Limbocker Ryan R Mannini Benedetta B Cataldi Rodrigo R Chhangur Shianne S Wright Aidan K AK Kreiser Ryan P RP Albright J Alex JA Chia Sean S Habchi Johnny J Sormanni Pietro P Kumita Janet R JR Ruggeri Francesco S FS Dobson Christopher M CM Chiti Fabrizio F Aprile Francesco A FA Vendruscolo Michele M

International journal of molecular sciences 20200625 12

Alzheimer's disease is associated with the aggregation of the amyloid-β peptide (Aβ), resulting in the deposition of amyloid plaques in brain tissue. Recent scrutiny of the mechanisms by which Aβ aggregates induce neuronal dysfunction has highlighted the importance of the Aβ oligomers of this protein fragment. Because of the transient and heterogeneous nature of these oligomers, however, it has been challenging to investigate the detailed mechanisms by which these species exert cytotoxicity. To ...[more]

PMID: 32630615

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Project description:Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the pathological aggregation of the amyloid-? peptide (A?). Monomeric soluble A? can switch from helicoidal to ?-sheet conformation, promoting its assembly into oligomers and subsequently to amyloid fibrils. Oligomers are highly toxic to neurons and have been reported to induce synaptic transmission impairments. The progression from oligomers to fibrils forming senile plaques is currently considered a protective mechanism to avoid the presence of the highly toxic oligomers. Protein nitration is a frequent post-translational modification under AD nitrative stress conditions. A? can be nitrated at tyrosine 10 (Y10) by peroxynitrite. Based on our analysis of ThT binding, Western blot and electron and atomic force microscopy, we report that A? nitration stabilizes soluble, highly toxic oligomers and impairs the formation of fibrils. We propose a mechanism by which fibril elongation is interrupted upon Y10 nitration: Nitration disrupts fibril-forming folds by preventing H14-mediated bridging, as shown with an A? analog containing a single residue (H to E) replacement that mimics the behavior of nitrated A? related to fibril formation and neuronal toxicity. The pathophysiological role of our findings in AD was highlighted by the study of these nitrated oligomers on mouse hippocampal neurons, where an increased NMDAR-dependent toxicity of nitrated A? oligomers was observed. Our results show that A? nitrotyrosination is a post-translational modification that increases A? synaptotoxicity. SIGNIFICANCE STATEMENT:We report that nitration (i.e., the irreversible addition of a nitro group) of the Alzheimer-related peptide amyloid-? (A?) favors the stabilization of highly toxic oligomers and inhibits the formation of A? fibrils. The nitrated A? oligomers are more toxic to neurons due to increased cytosolic calcium levels throughout their action on NMDA receptors. Sustained elevated calcium levels trigger excitotoxicity, a characteristic event in Alzheimer's disease.

Dataset Information

Rationally Designed Antibodies as Research Tools to Study the Structure-Toxicity Relationship of Amyloid-? Oligomers.

Publications

Rationally Designed Antibodies as Research Tools to Study the Structure-Toxicity Relationship of Amyloid-β Oligomers.

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