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

Abstract

Multiple chemical reactions, such as the production of reactive oxygen species (ROS) can lead to dityrosine (DiY) formation via the cross-linking of closely spaced tyrosine residues and this can serve as a marker for aging. Amyloid-β (Aβ) has been found to be DiY cross-linked in the brains of AD patients. In vitro, Aβ forms DiY cross-links via metal-catalysed oxidation (Cu 2+ and H202) (MCO) leading to the formation of fibrils that are resistant to formic acid denaturation.However, copper is well known to influence and enhance self-assembly. Here, to investigate the interplay between self-assembly and DiY cross-linking we have utilised a non-assembly competent variant of Aβ (vAβ). MCO and UV oxidation experiments using vAβ and wild-type Aβ, revealed that DiY cross-linking stabilises, but does not induce or promote Aβ assembly.Cu 2+ alone, without H202, facilitates the formation and DiY cross-linking of wild-type Aβ into long-lived oligomers. Our work reveals DiY formation halts further Aβ self-assembly. DiY cross-linked Aβ is non-toxic to neuroblastoma cells at all stages of self-assembly in contrast to oligomeric non-cross-linked Aβ. These findings point to a mechanism of toxicity that necessitates continuing self-assembly of the Aβ peptide, whereby trapped DiY Aβ assemblies and assembly incompetent variant Aβ are unable to result in cell death.

Dityrosine Crosslinking of Collagen and Amyloid-β Peptides Is Formed by Vitamin B12 Deficiency-Generated Oxidative Stress in Caenorhabditis elegans

“…Sitkiewicz et al [ 34 ] demonstrated that tyrosine crosslinking shifts the equilibrium toward more compact oligomer types, leading to highly toxic fibrils. Maina et al [ 35 ] suggest that dityrosine crosslinking, specifically, promotes the stabilization, but not the induction or facilitation, of Aβ assembly, and Aβ exerts high-level toxicity at a stage when self-assembly is high. These observations and the results presented in worms suggest that the dityrosine crosslinking formed during B 12 deficiency promotes the formation and stabilization of the compact Aβ oligomers that facilitate self-assembly to induce high toxicity, probably in neuronal cells specifically located in the pharynx and tail ( Figure 6 D).…”

Nucleation-dependent aggregation kinetics of YeastSup35 fragment GNNQQNY

“…PGQ 9 I and PGQ 9 A peptides were solubilised using established protocols. [22][23][24][25][26] Mass spectrometry 5 µL of GNNQQNY peptide solubilized in water-HCl (pH 2.0) was injected into time-offlight (TOF) mass analyzer provided with electrospray ionization (ESI) source (Waters Q-TOF premier HAB213). The m/z spectrum recorded at a mass range of 50-3500 Da was plotted using OriginPro 8.5 data analysis and graphing software and the purity was estimated by analyzing the observed molecular ionization states of the peptide.…”