Abstract
Soluble oligomers of the amyloid-β (Aβ) peptide play a key role in the pathogenesis of Alzheimer's disease, but their elusive nature makes their detection challenging. Here we describe a novel immunoassay based on surface plasmon resonance (SPR) that specifically recognizes biologically active Aβ oligomers. As a capturing agent, we immobilized on the sensor chip the monoclonal antibody 4G8, which targets a central hydrophobic region of Aβ. This SPR assay allows specific recognition of oligomeric intermediates that rapidly appear and disappear during the incubation of synthetic Aβ(1-42), discriminating them from monomers and higher order aggregates. The species recognized by SPR generate ionic currents in artificial lipid bilayers and inhibit the physiological pharyngeal contractions in Caenorhabditis elegans, a new method for testing the toxic potential of Aβ oligomers. With these assays we found that the formation of biologically relevant Aβ oligomers is inhibited by epigallocatechin gallate and increased by the A2V mutation, previously reported to induce early onset dementia. The SPR-based immunoassay provides new opportunities for detection of toxic Aβ oligomers in biological samples and could be adapted to study misfolding proteins in other neurodegenerative disorders.
Highlights
A oligomers are major players in Alzheimer disease, but the tools for their detection are not satisfactory
We describe here a new surface plasmon resonance (SPR)-based immunoassay that selectively recognizes a subpopulation of biologically active A oligomers
SPR studies were done with the anti-A antibody 6E10, which, proved unsuitable for distinguishing monomers from oligomers because both species bound the antibody with strong affinities and very slow dissociation rates [30]
Summary
A oligomers are major players in Alzheimer disease, but the tools for their detection are not satisfactory. We immobilized on the sensor chip the monoclonal antibody 4G8, which targets a central hydrophobic region of A This SPR assay allows specific recognition of oligomeric intermediates that rapidly appear and disappear during the incubation of synthetic A1–42, discriminating them from monomers and higher order aggregates. The species recognized by SPR generate ionic currents in artificial lipid bilayers and inhibit the physiological pharyngeal contractions in Caenorhabditis elegans, a new method for testing the toxic potential of A oligomers. With these assays we found that the formation of biologically relevant A oligomers is inhibited by epigallocatechin gallate and increased by the A2V mutation, previously reported to induce early onset dementia. One of the two interacting partners is immobilized on a sensor chip
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