Secondary nucleation and elongation occur at different sites on Alzheimer’s amyloid-β aggregates

Abstract

The aggregates of the Aβ peptide associated with Alzheimer’s disease are able to both grow in size as well as generate, through secondary nucleation, new small oligomeric species, that are major cytotoxins associated with neuronal death. Despite the importance of these amyloid fibril-dependent processes, their structural and molecular underpinnings have remained challenging to elucidate. Here, we consider two molecular chaperones: the Brichos domain, which suppresses specifically secondary nucleation processes, and clusterin which our results show is capable of inhibiting, specifically, the elongation of Aβ fibrils at remarkably low substoichiometric ratios. Microfluidic diffusional sizing measurements demonstrate that this inhibition originates from interactions of clusterin with fibril ends with high affinity. Kinetic experiments in the presence of both molecular chaperones reveal that their inhibitory effects are additive and noncooperative, thereby indicating that the reactive sites associated with the formation of new aggregates and the growth of existing aggregates are distinct.

Augmentation of Bri2 molecular chaperone activity against amyloid-β reduces neurotoxicity in mouse hippocampus in vitro

“…The molecular size of the Bri2 BRICHOS R221E dimer matches well the surface of the cross sectional area of recently published Aβ42 fibril structures 57,58 , providing a possible explanation why the Bri2 BRI-CHOS dimer, besides the secondary nucleation rate k 2 , also efficiently attenuates the elongation rate k + . The different specificity of the Bri2 BRICHOS dimer compared to the monomer also support that secondary nucleation and elongation events occur at distinct sites on Aβ42 aggregates, as recently reported 59 . While structural details about the soluble neurotoxic Aβ42 species are still missing, a β-structure state of toxic Aβ42 species/oligomers has been reported 55,60 .…”

NMR unveils an N-terminal interaction interface on acetylated-α-synuclein monomers for recruitment to fibrils

“…Previous approaches to inhibit different aspects of amyloid fibril seeding have largely targeted the structured amyloid core. Such methods include using chaperones to block fibril ends or fibril surfaces (9), treating with natural products that promote fibril clustering to reduce fibril fragmentation and hide binding sites for monomer addition (14,15), and creating high affinity interactions with amyloidogenic monomers to sequester monomers from self-assembly (16). However, all of these approaches introduce foreign molecules and can only interfere with single microscopic steps.…”

Rational Design of a Cocktail of Inhibitors against Aβ Aggregation

“…Therefore, we have achieved our goal for at least two kinds of cocktails, since the identification and selection of molecules with different binding sites and different inhibitory mechanisms at the very beginning is designed to avoid possible unwanted interferences between the various components in the mixture. We note that a similar strategy has been applied to the mix of Brichos domain and Clusterin mixture for Aβ aggregation inhibition . To further elucidate the molecular binding sites for inhibitors and Aβ aggregates, we carried out molecular docking simulations (Figure ).…”

“…We note that as imilar strategy has been applied to the mix of Brichos domain and Clusterin mixturef or Ab aggregation inhibition. [15] To further elucidatet he molecular binding sites for inhibitors and Ab aggregates,w ec arried out molecular docking simulations ( Figure 5). By using Autodock Vina, [16] Figure 3.…”