A critical role for the self-assembly of Amyloid-β1-42 in neurodegeneration

Abstract

Amyloid β1-42 (Aβ1-42) plays a central role in Alzheimer’s disease. The link between structure, assembly and neuronal toxicity of this peptide is of major current interest but still poorly defined. Here, we explored this relationship by rationally designing a variant form of Aβ1-42 (vAβ1-42) differing in only two amino acids. Unlike Aβ1-42, we found that the variant does not self-assemble, nor is it toxic to neuronal cells. Moreover, while Aβ1-42 oligomers impact on synaptic function, vAβ1-42 does not. In a living animal model system we demonstrate that only Aβ1-42 leads to memory deficits. Our findings underline a key role for peptide sequence in the ability to assemble and form toxic structures. Furthermore, our non-toxic variant satisfies an unmet demand for a closely related control peptide for Aβ1-42 cellular studies of disease pathology, offering a new opportunity to decipher the mechanisms that accompany Aβ1-42-induced toxicity leading to neurodegeneration.

Dityrosine cross-link trapping of amyloid-β intermediates reveals that self-assembly is required for Aβ-induced cytotoxicity

“…To investigate the influence of DiY cross-linking on Ab assembly, we compared the effect of metal-catalysed oxidation (MCO) using CuCl2 and H202, on wild-type Ab42 and variant Ab42 (henceforth called Ab and vAb, respectively). vAb is a variant of Ab1-42 with F19S and G37D mutations which render the peptide assembly incompetent (see 3…”

“…Recombinant Aβ42 (Aβ) and variant Aβ42 (vAβ) were purchased in Hexafluoroisopropanol (HFIP) films from rPeptide and JPT, respectively. The peptides were prepared using an established protocol, and all procedures were done using protein LoBind Eppendorfs and tips 3 . 0.2 mg/mL of the peptides were solubilized in 200 μL HFIP (Sigma-Aldrich), vortexed for 1 min and sonicated in 50/60 Hz bath sonicator for 5 min.…”

“…Many pieces of evidence have subsequently shown that the oligomeric form of Ab is the most toxic species, resulting in a reformulated amyloid cascade hypothesis in which Ab oligomers are proposed to be central to AD pathogenesis 2 . Indeed, accumulated evidence shows that Ab oligomers disrupt cellular function in cultured cells and animal models [2][3][4][5][6] . Numerous studies have searched for the elusive "toxic" species and tried to characterise its structure.…”

“…Using MCO and UV-induced oxidation to induce DiY cross-linking, here we show that DiY formation results in the stabilisation of Ab42 assemblies and prevents or very significantly slows further elongation of the assemblies. To specifically address the impact of DiY cross-linking on Aβ assembly, we compared the effect of oxidation on an non-assembly competent variant Aβ (vAβ) 3 and revealed that DiY cross-linking does not induce or promote its assembly. We show that in the absence of H202, CuCl2 at a concentration found around Ab plaques (~ 400 µM) 25 , is sufficient to facilitate the formation and cross-linking of Ab42 oligomers into a long-lived oligomer population.…”

The diversity and utility of amyloid fibrils formed by short amyloidogenic peptides

“…Importantly, small changes in the sequence of amyloidogenic peptides can result in different morphologies arising from different packing arrangements. Furthermore, substitutions can result in changes in the propensity to self-assemble [14][15][16][17].…”