Zinc as chaperone-mimicking agent for retardation of amyloid β peptide fibril formation

Metal ions have emerged to play a key role in the aggregation process of amyloid β (Aβ) peptide that is closely related to the pathogenesis of Alzheimer’s disease. A detailed understanding of the underlying mechanistic process of peptide–metal interactions, however, has been challenging to obtain. By applying a combination of NMR relaxation dispersion and fluorescence kinetics methods we have investigated quantitatively the thermodynamic Aβ–Zn2+ binding features as well as how Zn2+ modulates the nucleation mechanism of the aggregation process. Our results show that, under near-physiological conditions, substoichiometric amounts of Zn2+ effectively retard the generation of amyloid fibrils. A global kinetic profile analysis reveals that in the absence of zinc Aβ40 aggregation is driven by a monomer-dependent secondary nucleation process in addition to fibril-end elongation. In the presence of Zn2+, the elongation rate is reduced, resulting in reduction of the aggregation rate, but not a complete inhibition of amyloid formation. We show that Zn2+ transiently binds to residues in the N terminus of the monomeric peptide. A thermodynamic analysis supports a model where the N terminus is folded around the Zn2+ ion, forming a marginally stable, short-lived folded Aβ40 species. This conformation is highly dynamic and only a few percent of the peptide molecules adopt this structure at any given time point. Our findings suggest that the folded Aβ40–Zn2+ complex modulates the fibril ends, where elongation takes place, which efficiently retards fibril formation. In this conceptual framework we propose that zinc adopts the role of a minimal antiaggregation chaperone for Aβ40.

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Characterization of amyloid β fibril formation under microgravity conditions

10.1101/2020.03.23.004341 ◽

2020 ◽

Author(s):

Maho Yagi-Utsumi ◽

Saeko Yanaka ◽

Chihong Song ◽

Tadashi Satoh ◽

Chiaki Yamazaki ◽

...

Keyword(s):

Amyloid Fibrils ◽

Protein Crystallization ◽

Space Station ◽

Amyloid Β ◽

Fibril Formation ◽

Formation Mechanisms ◽

Amyloid Formation ◽

Functional Roles ◽

Solution Condition ◽

Microgravity Conditions

AbstractAmyloid fibrils are self-assembled and ordered proteinaceous supramolecules structurally characterized by the cross-β spine. Amyloid formation is known to be related to various diseases typified by neurogenerative disorders and involved in a variety of functional roles. Whereas common mechanisms for amyloid formation have been postulated across diverse systems, the mesoscopic morphology of the fibrils is significantly affected by the type of solution condition in which it grows. Amyloid formation is also thought to share a phenomenological similarity with protein crystallization. While many studies have demonstrated the effect of gravity on protein crystallization, its effect on amyloid formation has not been reported. In this study, we conducted an experiment at the International Space Station (ISS) to characterize fibril formation of 40-residue amyloid β (Aβ(1-40)) under microgravity conditions. Our comparative analyses revealed that the Aβ(1-40) fibrilization progresses much more slowly on the ISS than on the ground, similarly to protein crystallization. Furthermore, microgravity promoted the formation of distinct morphologies of Aβ(1-40) fibrils. Our findings demonstrate that the ISS provides an ideal experimental environment for detailed investigations of amyloid formation mechanisms by eliminating the conventionally uncontrollable factors derived from gravity.

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Assembling amyloid fibrils from designed structures containing a significant amyloid β-peptide fragment

Biochemical Journal ◽

10.1042/bj20020229 ◽

2002 ◽

Vol 366 (1) ◽

pp. 343-351 ◽

Cited By ~ 38

Author(s):

Lars O. TJERNBERG ◽

Agneta TJERNBERG ◽

Niklas BARK ◽

Yuan SHI ◽

Bela P. RUZSICSKA ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Amyloid Fibrils ◽

Amyloid Β ◽

Structural Features ◽

Fibril Formation ◽

Amyloid Β Peptide ◽

Detailed Model ◽

Aβ Fibrils ◽

Β Sheet

The amyloid plaque, consisting of amyloid β-peptide (Aβ) fibrils surrounded by dystrophic neurites, is an invariable feature of Alzheimer's disease. The determination of the molecular structure of Aβ fibrils is a significant goal that may lead to the structure-based design of effective therapeutics for Alzheimer's disease. Technical challenges have thus far rendered this goal impossible. In the present study, we develop an alternative methodology. Rather than determining the structure directly, we design conformationally constrained peptides and demonstrate that only certain ‘bricks’ can aggregate into fibrils morphologically identical to Aβ fibrils. The designed peptides include variants of a decapeptide fragment of Aβ, previously shown to be one of the smallest peptides that (1) includes a pentapeptide sequence necessary for Aβ—Aβ binding and aggregation and (2) can form fibrils indistinguishable from those formed by full-length Aβ. The secondary structure of these bricks is monitored by CD spectroscopy, and electron microscopy is used to study the morphology of the aggregates formed. We then made various residue deletions and substitutions to determine which structural features are essential for fibril formation. From the constraints, statistical analysis of side-chain pair correlations in β-sheets and experimental data, we deduce a detailed model of the peptide strand alignment in fibrils formed by these bricks. Our results show that the constrained decapeptide dimers rapidly form an intramolecular, antiparallel β-sheet and polymerize into amyloid fibrils at low concentrations. We suggest that the formation of an exposed β-sheet (e.g. an Aβ dimer formed by interaction in the decapeptide region) could be a rate-limiting step in fibril formation. A theoretical framework that explains the results is presented in parallel with the data.

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Rationally Designed Bicyclic Peptides Prevent the Conversion of Aβ42 Assemblies Into Fibrillar Structures

Frontiers in Neuroscience ◽

10.3389/fnins.2021.623097 ◽

2021 ◽

Vol 15 ◽

Author(s):

Tatsuya Ikenoue ◽

Francesco A. Aprile ◽

Pietro Sormanni ◽

Michele Vendruscolo

Keyword(s):

Drug Discovery ◽

Molecular Recognition ◽

Kinetic Analysis ◽

Amyloid Β ◽

Amyloid Β Peptide ◽

Amyloid Formation ◽

Aggregation Process ◽

Structural Studies ◽

Recognition Ability ◽

Amyloidogenic Region

There is great interest in drug discovery programs targeted at the aggregation of the 42-residue form of the amyloid β peptide (Aβ42), since this molecular process is closely associated with Alzheimer’s disease. The use of bicyclic peptides may offer novel opportunities for the effective modification of Aβ42 aggregation and the inhibition of its cytotoxicity, as these compounds combine the molecular recognition ability of antibodies with a relatively small size of about 2 kD. Here, to pursue this approach, we rationally designed a panel of six bicyclic peptides targeting various epitopes along the sequence of Aβ42 to scan its most amyloidogenic region (residues 13–42). Our kinetic analysis and structural studies revealed that at sub-stoichiometric concentrations the designed bicyclic peptides induce a delay in the condensation of Aβ42 and the subsequent transition to a fibrillar state, while at higher concentrations they inhibit such transition. We thus suggest that designed bicyclic peptides can be employed to inhibit amyloid formation by redirecting the aggregation process toward amorphous assemblies.

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Endo-lysosomal Aβ concentration and pH enable formation of Aβ oligomers that potently induce Tau missorting

10.1101/2020.06.28.175885 ◽

2020 ◽

Author(s):

Marie P. Schützmann ◽

Filip Hasecke ◽

Sarah Bachmann ◽

Mara Zielinski ◽

Sebastian Hänsch ◽

...

Keyword(s):

Amyloid Fibrils ◽

Amyloid Β ◽

Amyloid Β Peptide ◽

Tau Pathology ◽

Aβ Oligomers ◽

Lysosomal Ph ◽

Amyloid Fibril Formation ◽

Aβ Amyloid ◽

Key Factor ◽

Lysosomal System

AbstractAmyloid-β peptide (Aβ) forms metastable oligomers >50 kD, termed AβOs or protofibrils, that are more effective than Aβ amyloid fibrils at triggering Alzheimer’s disease-related processes such as synaptic dysfunction and Tau pathology, including Tau mislocalization. In neurons, Aβ accumulates in endo-lysosomal vesicles at low pH. Here, we show that the rate of AβO assembly is accelerated 8,000-fold upon pH reduction from extracellular to endo-lysosomal pH, at the expense of amyloid fibril formation. The pH-induced promotion of AβO formation and the high endo-lysosomal Aβ concentration together enable extensive AβO formation of Aβ42 under physiological conditions. Exploiting the enhanced AβO formation of the dimeric Aβ variant dimAβ we furthermore demonstrate targeting of AβOs to dendritic spines, potent induction of Tau missorting, a key factor in tauopathies, and impaired neuronal activity. The results suggest that the endosomal/lysosomal system is a major site for the assembly of pathomechanistically relevant AβOs.

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A sulfated proteoglycan aggregation factor mediates amyloid-β peptide fibril formation and neurotoxicity

Amyloid ◽

10.3109/13506129909007334 ◽

1999 ◽

Vol 6 (4) ◽

pp. 233-243 ◽

Cited By ~ 27

Author(s):

Joanne McLaurin ◽

Trudy Franklin ◽

William J Kuhns ◽

Paul E. Fraser

Keyword(s):

Amyloid Β ◽

Fibril Formation ◽

Amyloid Β Peptide ◽

Aggregation Factor

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Restored degradation of the Alzheimer’s amyloid-β peptide by targeting amyloid formation

Journal of Neurochemistry ◽

10.1111/j.1471-4159.2009.05870.x ◽

2009 ◽

Vol 108 (5) ◽

pp. 1198-1207 ◽

Cited By ~ 57

Author(s):

Peter J. Crouch ◽

Deborah J. Tew ◽

Tai Du ◽

Diem Ngoc Nguyen ◽

Aphrodite Caragounis ◽

...

Keyword(s):

Amyloid Β ◽

Amyloid Β Peptide ◽

Amyloid Formation

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Structural origin of polymorphism of Alzheimer's amyloid β-fibrils

Biochemical Journal ◽

10.1042/bj20120034 ◽

2012 ◽

Vol 447 (1) ◽

pp. 43-50 ◽

Cited By ~ 20

Author(s):

Audrey Agopian ◽

Zhefeng Guo

Keyword(s):

Amyloid Fibrils ◽

Spin Exchange ◽

Electron Paramagnetic Resonance Spectroscopy ◽

Senile Plaques ◽

Amyloid Β ◽

Side Chain ◽

Resonance Spectroscopy ◽

Amyloid Β Peptide ◽

Amyloid Proteins ◽

Aβ Amyloid

Formation of senile plaques containing amyloid fibrils of Aβ (amyloid β-peptide) is a pathological hallmark of Alzheimer's disease. Unlike globular proteins, which fold into unique structures, the fibrils of Aβ and other amyloid proteins often contain multiple polymorphs. Polymorphism of amyloid fibrils leads to different toxicity in amyloid diseases and may be the basis for prion strains, but the structural origin for fibril polymorphism is still elusive. In the present study we investigate the structural origin of two major fibril polymorphs of Aβ40: an untwisted polymorph formed under agitated conditions and a twisted polymorph formed under quiescent conditions. Using electron paramagnetic resonance spectroscopy, we studied the inter-strand side-chain interactions at 14 spin-labelled positions in the Aβ40 sequence. The results of the present study show that the agitated fibrils have stronger inter-strand spin–spin interactions at most of the residue positions investigated. The two hydrophobic regions at residues 17–20 and 31–36 have the strongest interactions in agitated fibrils. Distance estimates on the basis of the spin exchange frequencies suggest that inter-strand distances at residues 17, 20, 32, 34 and 36 in agitated fibrils are approximately 0.2 Å (1 Å=0.1 nm) closer than in quiescent fibrils. We propose that the strength of inter-strand side-chain interactions determines the degree of β-sheet twist, which then leads to the different association patterns between different cross β-units and thus distinct fibril morphologies. Therefore the inter-strand side-chain interaction may be a structural origin for fibril polymorphism in Aβ and other amyloid proteins.

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