scholarly journals Molecular chaperone ability to inhibit amyloid-derived neurotoxicity, but not amorphous protein aggregation, depends on a conserved pH-sensitive Asp residue

2021 ◽  
Author(s):  
Gefei Chen ◽  
Yuniesky Andrade-Talavera ◽  
Xueying Zhong ◽  
Sameer Hassan ◽  
Henrik Biverstal ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Molecular Chaperone ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Small Heat Shock Protein ◽  
Amyloid Toxicity ◽  
Amyloid Fibril Formation ◽  
Pka Value ◽  
Aspartate Residue

Proteins can self-assemble into amyloid fibrils or amorphous aggregates and thereby cause disease. Molecular chaperones can prevent both these types of protein aggregation, but the respective mechanisms are not fully understood. The BRICHOS domain constitutes a disease-associated small heat shock protein-like chaperone family, with activities against both amyloid toxicity and amorphous protein aggregation. Here, we show that the activity of two BRICHOS domain families against Alzheimer’s disease associated amyloid-β neurotoxicity to mouse hippocampi in vitro depends on a conserved aspartate residue, while the ability to suppress amorphous protein aggregation is unchanged by Asp to Asn mutations. The conserved Asp in its ionized state promotes structural flexibility of the BRICHOS domain and has a pKa value between pH 6.0–7.0, suggesting that chaperone effects against amyloid toxicity can be affected by physiological pH variations. Finally, the Asp is evolutionarily highly conserved in >3000 analysed BRICHOS domains but is replaced by Asn in some BRICHOS families and animal species, indicating independent evolution of molecular chaperone activities against amyloid fibril formation and non-fibrillar amorphous protein aggregation.

scholarly journals Are amyloid diseases caused by protein aggregates that mimic bacterial pore-forming toxins?

2006 ◽  
Vol 39 (2) ◽  
pp. 167-201 ◽  
Author(s):  
Hilal A. Lashuel ◽  
Peter T. Lansbury
Keyword(s):  
Neurodegenerative Diseases ◽  
Protein Aggregation ◽  
Amyloid Fibril ◽  
Amyloid Β ◽  
Fibril Formation ◽  
Common Mechanism ◽  
Spongiform Encephalopathy ◽  
Amyloid Fibril Formation ◽  
Amyloid Diseases

1. Introduction 22. What is the significance of the shared structural properties of disease-associated protein fibrils? 32.1 Mechanism of amyloid fibril formation in vitro 62.1.1 In vitro fibril formation involves transient population of ordered aggregates of intermediate stability, or protofibrils 63. Toxic properties of protofibrils 73.1 Protofibrils, rather than fibrils, are likely to be pathogenic 73.2 The toxic protofibril may be a mixture of related species 83.3 Morphological similarities of protofibrils suggest a common mechanism of toxicity 93.4 Are the amyloid diseases a subset of a much larger class of previously unrecognized protofibril diseases? 93.5 Fibrils, in the form of aggresomes, may function to sequester toxic protofibrils 94. Amyloid pores, a common structural link among protein aggregation neurodegenerative diseases 104.1 Mechanistic studies of amyloid fibril formation reveal common features, including pore-like protofibrils 104.1.1 Amyloid-β (Aβ) (Alzheimer's disease) 104.1.2 α-Synuclein (PD and diffuse Lewy body disease) 124.1.3 ABri (familial British dementia) 134.1.4 Superoxide dismutase-1 (amyotrophic lateral sclerosis) 134.1.5 Prion protein (Creutzfeldt–Jakob disease, bovine spongiform encephalopathy, etc.) 144.1.6 Huntingtin (Huntington's disease) 144.2 Amyloidogenic proteins that are not linked to disease also from pore-like protofibrils 154.3 Amyloid proteins form non-fibrillar aggregates that have properties of protein channels or pores 154.3.1 Aβ ‘channels’ 154.3.2 α-Synuclein ‘pores’ 164.3.3 PrP ‘channels’ 164.3.4 Polyglutamine ‘channels’ 174.4 Nature uses β-strand-mediated protein oligomerization to construct pore-forming toxins 175. Mechanisms of protofibril induced toxicity in protein aggregation diseases 195.1 The amyloid pore can explain the age-association and cell-type selectivity of the neurodegenerative diseases 195.2 Protofibrils may promote their own accumulation by inhibiting the proteasome 206. Testing the amyloid pore hypothesis by attempting to disprove it 217. Acknowledgments 228. References 22Protein fibrillization is implicated in the pathogenesis of most, if not all, age-associated neurodegenerative diseases, but the mechanism(s) by which it triggers neuronal death is unknown. Reductionist in vitro studies suggest that the amyloid protofibril may be the toxic species and that it may amplify itself by inhibiting proteasome-dependent protein degradation. Although its pathogenic target has not been identified, the properties of the protofibril suggest that neurons could be killed by unregulated membrane permeabilization, possibly by a type of protofibril referred to here as the ‘amyloid pore’. The purpose of this review is to summarize the existing supportive circumstantial evidence and to stimulate further studies designed to test the validity of this hypothesis.

scholarly journals Acid-denatured small heat shock protein HdeA from Escherichia coli forms reversible fibrils with an atypical secondary structure

2018 ◽  
Vol 294 (5) ◽  
pp. 1590-1601 ◽  
Author(s):  
Shiori Miyawaki ◽  
Yumi Uemura ◽  
Kunihiro Hongo ◽  
Yasushi Kawata ◽  
Tomohiro Mizobata
Keyword(s):  
Escherichia Coli ◽  
Heat Shock ◽  
Secondary Structure ◽  
Heat Shock Protein ◽  
Molecular Chaperone ◽  
Protein Function ◽  
Amyloid Fibrils ◽  
Small Heat Shock Protein ◽  
Chaperone Activity

The periplasmic small heat shock protein HdeA from Escherichia coli is inactive under normal growth conditions (at pH 7) and activated only when E. coli cells are subjected to a sudden decrease in pH, converting HdeA into an acid-denatured active state. Here, using in vitro fibrillation assays, transmission EM, atomic-force microscopy, and CD analyses, we found that when HdeA is active as a molecular chaperone, it is also capable of forming inactive aggregates that, at first glance, resemble amyloid fibrils. We noted that the molecular chaperone activity of HdeA takes precedence over fibrillogenesis under acidic conditions, as the presence of denatured substrate protein was sufficient to suppress HdeA fibril formation. Further experiments suggested that the secondary structure of HdeA fibrils deviates somewhat from typical amyloid fibrils and contains α-helices. Strikingly, HdeA fibrils that formed at pH 2 were immediately resolubilized by a simple shift to pH 7 and from there could regain molecular chaperone activity upon a return to pH 1. HdeA, therefore, provides an unusual example of a “reversible” form of protein fibrillation with an atypical secondary structure composition. The competition between active assistance of denatured polypeptides (its “molecular chaperone” activity) and the formation of inactive fibrillary deposits (its “fibrillogenic” activity) provides a unique opportunity to probe the relationship among protein function, structure, and aggregation in detail.

scholarly journals Modulators of amyloid protein aggregation and toxicity: EGCG and CLR01

2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Aida Attar ◽  
Farid Rahimi ◽  
Gal Bitan
Keyword(s):  
Protein Aggregation ◽  
Drug Targets ◽  
Amyloid Fibrils ◽  
Specific Binding ◽  
Amyloid Β ◽  
Amyloid Β Protein ◽  
Amyloid Protein ◽  
Islet Amyloid

AbstractAbnormal protein folding and self-assembly causes over 30 cureless human diseases for which no disease-modifying therapies are available. The common side to all these diseases is formation of aberrant toxic protein oligomers and amyloid fibrils. Both types of assemblies are drug targets, yet each presents major challenges to drug design, discovery, and development. In this review, we focus on two small molecules that inhibit formation of toxic amyloid protein assemblies — the green-tea derivative (−)-epigallocatechin-3-gallate (EGCG), which was identified through a combination of epidemiologic data and a compound library screen, and the molecular tweezer CLR01, whose inhibitory activity was discovered in our group based on rational reasoning, and subsequently confirmed experimentally. Both compounds act in a manner that is not specific to one particular protein and thus are useful against a multitude of amyloidogenic proteins, yet they act via distinct putative mechanisms. CLR01 disrupts protein aggregation through specific binding to lysine residues, whereas the mechanisms underlying the activity of EGCG are only recently beginning to unveil. We discuss current in vitro and, where available, in vivo literature related to EGCG and CLR01’s effects on amyloid β-protein, α-synuclein, transthyretin, islet amyloid polypeptide, and calcitonin. We also describe the toxicity, pharmacokinetics, and mechanism of action of each compound.

scholarly journals The Effect of Oxidized Dopamine on the Structure and Molecular Chaperone Function of the Small Heat-Shock Proteins, αB-Crystallin and Hsp27

2021 ◽  
Vol 22 (7) ◽  
pp. 3700
Author(s):  
Junna Hayashi ◽  
Jennifer Ton ◽  
Sparsh Negi ◽  
Daniel E. K. M. Stephens ◽  
Dean L. Pountney ◽  
...  
Keyword(s):  
Heat Shock ◽  
Protein Aggregation ◽  
Molecular Chaperone ◽  
Cross Linking ◽  
Αb Crystallin ◽  
The Cross ◽  
Shock Proteins ◽  
And Function

Oxidation of the neurotransmitter, dopamine (DA), is a pathological hallmark of Parkinson’s disease (PD). Oxidized DA forms adducts with proteins which can alter their functionality. αB-crystallin and Hsp27 are intracellular, small heat-shock molecular chaperone proteins (sHsps) which form the first line of defense to prevent protein aggregation under conditions of cellular stress. In vitro, the effects of oxidized DA on the structure and function of αB-crystallin and Hsp27 were investigated. Oxidized DA promoted the cross-linking of αB-crystallin and Hsp27 to form well-defined dimer, trimer, tetramer, etc., species, as monitored by SDS-PAGE. Lysine residues were involved in the cross-links. The secondary structure of the sHsps was not altered significantly upon cross-linking with oxidized DA but their oligomeric size was increased. When modified with a molar equivalent of DA, sHsp chaperone functionality was largely retained in preventing both amorphous and amyloid fibrillar aggregation, including fibril formation of mutant (A53T) α-synuclein, a protein whose aggregation is associated with autosomal PD. In the main, higher levels of sHsp modification with DA led to a reduction in chaperone effectiveness. In vivo, DA is sequestered into acidic vesicles to prevent its oxidation and, intracellularly, oxidation is minimized by mM levels of the antioxidant, glutathione. In vitro, acidic pH and glutathione prevented the formation of oxidized DA-induced cross-linking of the sHsps. Oxidized DA-modified αB-crystallin and Hsp27 were not cytotoxic. In a cellular context, retention of significant chaperone functionality by mildly oxidized DA-modified sHsps would contribute to proteostasis by preventing protein aggregation (particularly of α-synuclein) that is associated with PD.

scholarly journals The Amyloid Fibril-Forming β-Sheet Regions of Amyloid β and α-Synuclein Preferentially Interact with the Molecular Chaperone 14-3-3ζ

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6120
Author(s):  
Danielle M. Williams ◽  
David C. Thorn ◽  
Christopher M. Dobson ◽  
Sarah Meehan ◽  
Sophie E. Jackson ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Chaperones ◽  
Protein Unfolding ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Parkinson’S Diseases ◽  
Amino Acid Form ◽  
Shock Proteins

14-3-3 proteins are abundant, intramolecular proteins that play a pivotal role in cellular signal transduction by interacting with phosphorylated ligands. In addition, they are molecular chaperones that prevent protein unfolding and aggregation under cellular stress conditions in a similar manner to the unrelated small heat-shock proteins. In vivo, amyloid β (Aβ) and α-synuclein (α-syn) form amyloid fibrils in Alzheimer’s and Parkinson’s diseases, respectively, a process that is intimately linked to the diseases’ progression. The 14-3-3ζ isoform potently inhibited in vitro fibril formation of the 40-amino acid form of Aβ (Aβ40) but had little effect on α-syn aggregation. Solution-phase NMR spectroscopy of 15N-labeled Aβ40 and A53T α-syn determined that unlabeled 14-3-3ζ interacted preferentially with hydrophobic regions of Aβ40 (L11-H21 and G29-V40) and α-syn (V3-K10 and V40-K60). In both proteins, these regions adopt β-strands within the core of the amyloid fibrils prepared in vitro as well as those isolated from the inclusions of diseased individuals. The interaction with 14-3-3ζ is transient and occurs at the early stages of the fibrillar aggregation pathway to maintain the native, monomeric, and unfolded structure of Aβ40 and α-syn. The N-terminal regions of α-syn interacting with 14-3-3ζ correspond with those that interact with other molecular chaperones as monitored by in-cell NMR spectroscopy.

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

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.

scholarly journals Monomeric amyloid β-peptide (1-42) significantly populates compact fibril-like conformations

2020 ◽  
Author(s):  
Bogdan Barz ◽  
Alexander K. Buell ◽  
Soumav Nath
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Random Coil ◽  
Amyloid Β Peptide ◽  
Secondary Nucleation ◽  
Fibril Structure ◽  
Amyloid Fibril Formation ◽  
Dynamics Simulations ◽  
The Individual ◽  
Structural Ensemble

AbstractThe aggregation of the amyloid β (Aβ) peptide is a major hallmark of Alzheimer’s disease. This peptide can aggregate into oligomers, proto-fibrils, and mature fibrils, which eventually assemble into amyloid plaques. The peptide monomers are the smallest assembly units, and play an important role in most of the individual processes involved in amyloid fibril formation, such as primary and secondary nucleation and elongation. The structure of the Aβ monomer has been shown to be very dynamic and mostly disordered, both in experimental and in computational studies, similar to a random coil. This structural state of the monomer contrasts with the very stable and well defined structural core of the amyloid fibrils. An important question is whether the monomer can adopt transient fibril-like conformations in solution and what role such conformations might play in the aggregation process. Here we use enhanced and extensive molecular dynamics simulations to study the Aβ42 monomer structural flexibility with different force fields, water models and salt concentrations. We show that the monomer behaves as a random coil under different simulation conditions. Importantly, we find a conformation with the N-terminal region structured very similarly to that of recent experimentally determined fibril models. This is to the best of our knowledge the first monomeric structural ensemble to show such a similarity with the fibril structure.

scholarly journals Lithium ions display weak interaction with amyloid-beta (Aβ) peptides and have minor effects on their aggregation

2021 ◽  
Author(s):  
Elina Berntsson ◽  
Suman Paul ◽  
Faraz Vosough ◽  
Sabrina B. Sholts ◽  
Jüri Jarvet ◽  
...  
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Underlying Mechanism ◽  
Aβ Peptides ◽  
Beneficial Effects ◽  
Incurable Disease ◽  
Age Related ◽  
Aβ Aggregation ◽  
In Vitro Interactions

Alzheimer’s disease (AD) is an incurable disease and the main cause of age-related dementia worldwide, despite decades of research. Treatment of AD with lithium (Li) has showed promising results, but the underlying mechanism is unclear. The pathological hallmark of AD brains is deposition of amyloid plaques, consisting mainly of amyloid-β (Aβ) peptides aggregated into amyloid fibrils. The plaques contain also metal ions of e.g. Cu, Fe, and Zn, and such ions are known to interact with Aβ peptides and modulate their aggregation and toxicity. The interactions between Aβ peptides and Li+ ions have however not been well investigated. Here, we use a range of biophysical techniques to characterize in vitro interactions between Aβ peptides and Li+ ions. We show that Li+ ions display weak and non-specific interactions with Aβ peptides, and have minor effects on Aβ aggregation. These results indicate that possible beneficial effects of Li on AD pathology are not likely caused by direct interactions between Aβ peptides and Li+ ions.

scholarly journals 6-gingerol interferes with amyloid-beta (Aβ) peptide aggregation

2021 ◽  
Author(s):  
Elina Berntsson ◽  
Suman Paul ◽  
Sabrina B. Sholts ◽  
Jüri Jarvet ◽  
Andreas Barth ◽  
...  
Keyword(s):  
Animal Studies ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Nutritional Supplement ◽  
Aβ Oligomers ◽  
Microscopy Imaging ◽  
Positive Effects ◽  
Age Related ◽  
Soluble Aβ Oligomers

AbstractAlzheimer’s disease (AD) is the most prevalent age-related cause of dementia. AD affects millions of people worldwide, and to date there is no cure. The pathological hallmark of AD brains is deposition of amyloid plaques, which mainly consist of amyloid-β (Aβ) peptides, commonly 40 or 42 residues long, that have aggregated into amyloid fibrils. Intermediate aggregates in the form of soluble Aβ oligomers appear to be highly neurotoxic. Cell and animal studies have previously demonstrated positive effects of the molecule 6-gingerol on AD pathology. Gingerols are the main active constituents of the ginger root, which in many cultures is a traditional nutritional supplement for memory enhancement. Here, we use biophysical experiments to characterize in vitro interactions between 6-gingerol and Aβ40 peptides. Our experiments with atomic force microscopy imaging, and nuclear magnetic resonance and Thioflavin-T fluorescence spectroscopy, show that the hydrophobic 6-gingerol molecule interferes with formation of Aβ40 aggregates, but does not interact with Aβ40 monomers. Thus, together with its favourable toxicity profile, 6-gingerol appears to display many of the desired properties of an anti-AD compound.

Sign in / Sign up

Export Citation Format

Share Document