N-terminal Domain of Amyloid-β Impacts Fibrillation and Neurotoxicity

Abstract

Alzheimer’s disease is characterized by the presence of distinct amyloid-β peptide (Aβ) assemblies with diverse sizes, shapes, and toxicity. However, the primary determinants of Aβ aggregation and neurotoxicity remain unknown. Here, the N-terminal amino acid residues of Aβ42 that distinguished between humans and rats were substituted. The effects of these modifications on the ability of Aβ to aggregate and its neurotoxicity were investigated using biochemical, biophysical, and cellular techniques. The Aβ-derived diffusible ligand, protofibrils, and fibrils formed by the N-terminal mutational peptides, including Aβ42(R5G), Aβ42(Y10F), and rat Aβ42, were indistinguishable by conventional techniques such as size-exclusion chromatography, negative-staining transmission electron microscopy and silver staining, whereas the amyloid fibrillation detected by thioflavin T assay was greatly inhibited in vitro. Using circular dichroism spectroscopy, we discovered that both Aβ42 and Aβ42(Y10F) generated protofibrils and fibrils with a high proportion of parallel β-sheet structures. Furthermore, protofibrils formed by other mutant Aβ peptides and N-terminally shortened peptides were incapable of inducing neuronal death, with the exception of Aβ42 and Aβ42(Y10F). Our findings indicate that the N-terminus of Aβ is important for its fibrillation and neurotoxicity.

Transition Metal Ion FRET-Based Probe to Study Cu(II)-Mediated Amyloid-β Ligand Binding

“…The contrast observed between the two flexible termini correlates with their possible involvement in oligomerization dynamics. 63 We note that labeling may alter the intrinsic properties of biomolecules of interest, 64,65 however, there were only insignificant differences in the conformational ensembles of unlabeled monomeric Aβ and each labeling isomer (Supporting Information Figures S9− S10), as well as identical copper ion binding sites and similar affinities (Supporting Information Figure S3).…”

“…Additionally, one or multiple carboxylic acids of the NTA moiety may be deprotonated, possibly affecting the transition dipole moment orientation and the spectral properties (e.g., absorption). 63 Consequently, the gas-phase R 0 value had to be re-estimated since the spectral overlap (J) of cR6G and Cu(II) could be altered by NTA (creating a different chemical microenvironment). A reduced gas-phase R 0 value with the NTA-binding motif was estimated to be 19.5 Å (Supporting Information Figure S19), compared to 26.0 Å for the bihistidine motif, rendering it more suitable for short interchromophore distances.…”

“…Contrary to P1 , less fluorescence quenching was observed for the Cu-bound P2 species, hinting at an extended peptide structure as a result of Coulombic repulsion and the use of an extended linker for the NTA moiety (Figure a). Additionally, one or multiple carboxylic acids of the NTA moiety may be deprotonated, possibly affecting the transition dipole moment orientation and the spectral properties (e.g., absorption) . Consequently, the gas-phase R 0 value had to be re-estimated since the spectral overlap ( J ) of cR6G and Cu­(II) could be altered by NTA (creating a different chemical microenvironment).…”

Modulation of Alzheimer’s Disease Aβ40 Fibril Polymorphism by the Small Heat Shock Protein αB-Crystallin

“…P1-induced cytotoxicity is less affected by the chaperone due to the lack of the fuzzy coat. Electrostatic interactions, along with specific interactions with various cell receptors such as integrin, were suggested to play an important role in the interaction of Aβ with cell membranes. − Various experiments with deletions and mutations in the N-terminus verified that the N-terminus plays not only an important role in Aβ fibrillation but also impacts on cellular toxicity. , In Narayanan et al, we have speculated that the Aβ aromatic hydrophobic core region contributes mostly to the interaction with αBC . In the analysis of the saturation transfer difference NMR spectroscopy (STD) experiments, however, a potential shift of equilibrium between different Aβ aggregation states induced by αBC has not been taken into account.…”

Transient interactions between the fuzzy coat and the cross-β core of brain-derived Aβ42 filaments

“…The prominent role of the N-terminal region of Aβ42 fibrils in the aggregation process and the stability of the amyloid fibrils has been documented in several studies. This is substantiated by the observed influence of various N-terminal mutants on the aggregation process and the subsequent neurotoxic effects of the peptide (32)(33)(34)(35)(36). Nevertheless, our understanding of the impact of the fuzzy coat region on various functionalities and characteristics of the amyloid filaments, such as its interactions with the cross-β core, its contribution to the binding between the amyloid filaments and other biologically relevant components, and the solubility of the amyloid filaments, remains elusive.…”