Abstract
Amyloid fibrils found in plaques in Alzheimer's disease (AD) brains are composed of amyloid-β peptides. Oligomeric amyloid-β 1-42 (Aβ42) is thought to play a critical role in neurodegeneration in AD. Here, we determine how size and conformation affect neurotoxicity and internalisation of Aβ42 assemblies using biophysical methods, immunoblotting, toxicity assays and live-cell imaging. We report significant cytotoxicity of Aβ42 oligomers and their internalisation into neurons. In contrast, Aβ42 fibrils show reduced internalisation and no toxicity. Sonicating Aβ42 fibrils generates species similar in size to oligomers but remains nontoxic. The results suggest that Aβ42 oligomers have unique properties that underlie their neurotoxic potential. Furthermore, we show that incubating cells with Aβ42 oligomers for 24h is sufficient to trigger irreversible neurotoxicity.
Highlights
Internalisation and toxicity of amyloid-b 1-42 are influenced by its conformation and assembly state rather than size
Five minutes was not sufficient to fragment the fibrils, whereas by 20 min no species were present by transmission electron microscopy
These results show that sonicating Ab fibrils produces species that are comparable in size to Ab oligomers
Summary
Internalisation and toxicity of amyloid-b 1-42 are influenced by its conformation and assembly state rather than size. Amyloid fibrils found in plaques in Alzheimer’s disease (AD) brains are composed of amyloid-b peptides. We determine how size and conformation affect neurotoxicity and internalisation of Ab42 assemblies using biophysical methods, immunoblotting, toxicity assays and live-cell imaging. Plaque deposits in AD brains are composed of self-assembled forms of the amyloid-b (Ab) peptide arranged into cross-b amyloid fibrils [2,3,4]. Ab42 self-assembly in vitro involves the formation of oligomers, protofibrils and mature fibrils. This process has been shown to occur via nucleated polymerisation, and intermediates are thought to be critical in cytotoxicity [5,6,7,8]. Abbreviations AD, Alzheimer’s disease; Ab, amyloid-b; BME, b-mercaptoethanol; CD, circular dichroism; cryo-EM, cryo-electron microscopy; DMSO, dimethyl sulfoxide; HRP, horseradish peroxidase; ssNMR, solid-state nuclear magnetic resonance; TEM, transmission electron microscopy
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