A long‐lived Aβ oligomer resistant to fibrillization

Abstract

The hydrophobic Aβ peptide is highly aggregation prone; it first forms soluble oligomers, which then convert into the amyloid fibrils found in the cerebral plaques of Alzheimer's disease. It is generally understood that as the peptide concentration of Aβ increases, the fibrillization process is accelerated, but we examine the limits on this phenomenon. We found that once a threshold concentration of Aβ is exceeded, a stable oligomer is formed at the expense of fibril formation. The suppression of fibril formation was observed by amyloid-binding dye Thioflavin T and solution nuclear magnetic resonance (NMR). Small-angle X-ray scattering, size exclusion chromatography, and analytical ultracentrifugation demonstrated that Aβ peptides form a range of compact species, with a dimer being an early highly populated oligomer. Solution NMR allowed us to define the secondary structure of this Aβ dimer, which shows interlocking contacts between C-terminal peptide strands. Thus, we present a novel Aβ oligomer that resists conversion to fibrils and remains stable for more than one year.

The effects of fluorescent labels on Aβ42 aggregation detected by fluorescence correlation spectroscopy

“…The aggregation and neurotoxicity of Aβ oligomers, especially for Aβ 42 oligomers, are subjects of intense AD research. Several techniques can be used to analyze Aβ oligomers, including fluorescence correlation spectroscopy (FCS), fluorescence resonance energy transfer, magic angle spinning (MAS) NMR spectroscopy (MAS NMR), total internal reflection fluorescence microscopy, SDS polyacrylamide gel electrophoresis (SDS‐PAGE), size‐exclusion chromatography, mass spectrometry (MS), dynamic light scattering, atomic force microscopy (AFM), and Thioflavin T spectroscopic assay …”

“…Several techniques can be used to analyze Aβ oligomers, including fluorescence correlation spectroscopy (FCS), [13][14][15][16] fluorescence resonance energy transfer, [17,18] magic angle spinning (MAS) NMR spectroscopy (MAS NMR), [19] total internal reflection fluorescence microscopy, [20][21][22] SDS polyacrylamide gel electrophoresis (SDS-PAGE), [23] size-exclusion chromatography, [24] mass spectrometry (MS) [25,26] , dynamic light scattering, [27] atomic force microscopy (AFM), [28,29] and Thioflavin T spectroscopic assay. [30] Fluorescence-based detection methods are more sensitive and selective than other methods and have the capacity to detect single molecules. However, to perform fluorescence-based techniques, fluorescent dyes must be used to label the Aβ.…”

Origin of metastable oligomers and their effects on amyloid fibril self-assembly

“…2A and C ). Prior reports of biphasic ThT kinetics for Aβ 43 , 63 , 66 and Sup35 yeast protein 42 suggest that biphasic kinetics represent a generic mode for amyloid assembly. Similarly, there are previous reports associating a micelle-like transition in Aβ40, 64 , 76 , 77 amylin, 78 β-microglobulin, 21 and lysozyme, 46 with the formation of gO/CFs.…”

“…Aβ40 and Aβ42 were previously shown to exhibit biphasic assembly kinetics at elevated protein concentrations. 63 – 66 The linkage of two Aβ units was chosen to increase the local Aβ concentration, thereby promoting the highly concentration-dependent gO/CF formation. Compared to Aβ40 and Aβ42, this provides the separation of the two kinetics phases, i.e.…”

Stability analysis of a steady state of a model describing Alzheimer’s disease and interactions with prion proteins

“…The second pathway corresponds to the Aβ oligomerization pathway. As for fibrillation, the oligomerization process follows a nucleation elongation mechanism with the difference that the oligomerization pathway leads to the formation of highly stable Aβ assemblies structurally distinct from Aβ fibrils (Nick et al (2018); Barz et al (2017)). Regarding the literature, several neurotoxic pathways not mutually exclusive and all involving specifically Aβ oligomers have been proposed (Kessels et al (2010); James (2013); Kandel et al (2017)).…”