scholarly journals An anti-Aβ (amyloid β) single-chain variable fragment prevents amyloid fibril formation and cytotoxicity by withdrawing Aβ oligomers from the amyloid pathway

2011 ◽  
Vol 437 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Marta Marín-Argany ◽  
Geovanny Rivera-Hernández ◽  
Joaquim Martí ◽  
Sandra Villegas
Keyword(s):  
Conformational Changes ◽  
Amyloid Fibril ◽  
Recombinant Expression ◽  
Neuroblastoma Cell ◽  
Amyloid Β ◽  
Antibody Fragment ◽  
Temperature Perturbation ◽  
Single Chain ◽  
Aβ Oligomers ◽  
Aβ Amyloid

Aβ (amyloid β) immunotherapy has been revealed as a possible tool in Alzheimer's disease treatment. In contrast with complete antibodies, the administration of scFvs (single-chain variable fragments) produces neither meningoencephalitis nor cerebral haemorrhage. In the present study, the recombinant expression of scFv-h3D6, a derivative of an antibody specific for Aβ oligomers, is presented, as well as the subsequent proof of its capability to recover the toxicity induced by the Aβ1–42 peptide in the SH-SY5Y neuroblastoma cell line. To gain insight into the conformational changes underlying the prevention of Aβ toxicity by this antibody fragment, the conformational landscape of scFv-h3D6 upon temperature perturbation is also described. Heating the native state does not lead to any extent of unfolding, but rather directly to a β-rich intermediate state which initiates an aggregation pathway. This aggregation pathway is not an amyloid fibril pathway, as is that followed by the Aβ peptide, but rather a worm-like fibril pathway which, noticeably, turns out to be non-toxic. On the other hand, this pathway is thermodynamically and kinetically favoured when the scFv-h3D6 and Aβ1–42 oligomers form a complex in native conditions, explaining how the scFv-h3D6 withdraws Aβ1–42 oligomers from the amyloid pathway. To our knowledge, this is the first description of a conformational mechanism by which a scFv prevents Aβ-oligomer cytotoxicity.

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.

Synaptic memory mechanisms: Alzheimer's disease amyloid β-peptide-induced dysfunction

2007 ◽  
Vol 35 (5) ◽  
pp. 1219-1223 ◽  
Author(s):  
M.J. Rowan ◽  
I. Klyubin ◽  
Q. Wang ◽  
N.W. Hu ◽  
R. Anwyl
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Synaptic Plasticity ◽  
Nitrosative Stress ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Amyloid Β Peptide ◽  
Aβ Oligomers ◽  
Aβ Amyloid

There is growing evidence that mild cognitive impairment in early AD (Alzheimer's disease) may be due to synaptic dysfunction caused by the accumulation of non-fibrillar, oligomeric Aβ (amyloid β-peptide), long before widespread synaptic loss and neurodegeneration occurs. Soluble Aβ oligomers can rapidly disrupt synaptic memory mechanisms at extremely low concentrations via stress-activated kinases and oxidative/nitrosative stress mediators. Here, we summarize experiments that investigated whether certain putative receptors for Aβ, the αv integrin extracellular cell matrix-binding protein and the cytokine TNFα (tumour necrosis factor α) type-1 death receptor mediate Aβ oligomer-induced inhibition of LTP (long-term potentiation). Ligands that neutralize TNFα or genetic knockout of TNF-R1s (type-1 TNFα receptors) prevented Aβ-triggered inhibition of LTP in hippocampal slices. Similarly, antibodies to αv-containing integrins abrogated LTP block by Aβ. Protection against the synaptic plasticity-disruptive effects of soluble Aβ was also achieved using systemically administered small molecules targeting these mechanisms in vivo. Taken together, this research lends support to therapeutic trials of drugs antagonizing synaptic plasticity-disrupting actions of Aβ oligomers in preclinical AD.

scholarly journals Near-Atomic Resolution Structure of a Highly Neutralizing Fab Bound to Canine Parvovirus

2016 ◽  
Vol 90 (21) ◽  
pp. 9733-9742 ◽  
Author(s):  
Lindsey J. Organtini ◽  
Hyunwook Lee ◽  
Sho Iketani ◽  
Kai Huang ◽  
Robert E. Ashley ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Receptor Binding ◽  
Conformational Changes ◽  
De Novo ◽  
Mutational Analysis ◽  
Antibody Fragment ◽  
Canine Parvovirus ◽  
Single Chain ◽  
Cryo Electron Microscopy ◽  
Resolution Structure

ABSTRACT Canine parvovirus (CPV) is a highly contagious pathogen that causes severe disease in dogs and wildlife. Previously, a panel of neutralizing monoclonal antibodies (MAb) raised against CPV was characterized. An antibody fragment (Fab) of MAb E was found to neutralize the virus at low molar ratios. Using recent advances in cryo-electron microscopy (cryo-EM), we determined the structure of CPV in complex with Fab E to 4.1 Å resolution, which allowed de novo building of the Fab structure. The footprint identified was significantly different from the footprint obtained previously from models fitted into lower-resolution maps. Using single-chain variable fragments, we tested antibody residues that control capsid binding. The near-atomic structure also revealed that Fab binding had caused capsid destabilization in regions containing key residues conferring receptor binding and tropism, which suggests a mechanism for efficient virus neutralization by antibody. Furthermore, a general technical approach to solving the structures of small molecules is demonstrated, as binding the Fab to the capsid allowed us to determine the 50-kDa Fab structure by cryo-EM. IMPORTANCE Using cryo-electron microscopy and new direct electron detector technology, we have solved the 4 Å resolution structure of a Fab molecule bound to a picornavirus capsid. The Fab induced conformational changes in regions of the virus capsid that control receptor binding. The antibody footprint is markedly different from the previous one identified by using a 12 Å structure. This work emphasizes the need for a high-resolution structure to guide mutational analysis and cautions against relying on older low-resolution structures even though they were interpreted with the best methodology available at the time.

scholarly journals Amphiphilic Distyrylbenzene Derivatives as Potential Therapeutic and Imaging Agents for the Soluble Amyloid-β Oligomers in Alzheimer’s Disease

2021 ◽  
Author(s):  
Liang Sun ◽  
Hong-Jun Cho ◽  
Soumyo Sen ◽  
Andres S. Arango ◽  
Truc T. Huynh ◽  
...  
Keyword(s):  
Binding Affinity ◽  
Electrostatic Interactions ◽  
Amyloid Fibril ◽  
Amyloid Β ◽  
Amyloid Plaques ◽  
Aβ Peptide ◽  
Aβ Oligomers ◽  
5Xfad Mice ◽  
Soluble Aβ Oligomers

Alzheimer’s Diseases (AD) is the most common neurodegenerative disease, but efficient therapeutic and early diagnosis agents for this neurological disorder are still lacking. <a>Herein, we report the development of a novel amphiphilic compound, LS-4, generated linking a hydrophobic amyloid fibril-binding fragment with a hydrophilic azamacrocycle that can dramatically increase the binding affinity towards various amyloid β (Aβ) peptide aggregates. The developed compound exhibits uncommon fluorescence turn-on and high binding affinity for Aβ aggregates, especially for soluble Aβ oligomers. Moreover, upon the administration of LS-4 to 5xFAD mice, fluorescence imaging of the LS-4-treated brain sections reveals that LS-4 can readily penetrate the blood-brain-barrier (BBB) and bind to the Aβ oligomers <i>in vivo</i>, as confirmed by immunostaining with an Aβ oligomer-specific antibody. In addition, the treatment of 5xFAD mice with LS-4 significantly reduces the amount of both amyloid plaques and associated phosphorylated tau (p-tau) aggregates vs. the vehicle-treated 5xFAD mice, while microglia activation is also reduced. Furthermore, molecular dynamics simulations corroborate the observation that introducing a hydrophilic moiety into the molecular structure can significantly enhance the electrostatic interactions with the polar residues of the Aβ peptide species. Finally, taking advantage of the strong Cu-chelating property of the azamacrocycle, we performed a series of radioimaging and biodistribution studies that show the <sup>64</sup>Cu-LS-4 complex binds to the amyloid plaques and can accumulate a significantly larger extent in the 5xFAD mice brains vs. the WT controls. Overall, these <i>in vitro</i> and <i>in vivo</i> studies illustrate that the novel strategy to employ an amphiphilic molecule containing a hydrophilic fragment attached to a hydrophobic amyloid fibril-binding fragment </a><a>can increase the binding affinity of these compounds for the soluble Aβ oligomers and can thus be used </a>to detect and regulate the soluble Aβ species in AD.

scholarly journals Modulation of β-Amyloid Fibril Formation in Alzheimer’s Disease by Microglia and Infection

2020 ◽  
Vol 13 ◽  
Author(s):  
Madeleine R. Brown ◽  
Sheena E. Radford ◽  
Eric W. Hewitt
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Fibril ◽  
Amyloid Β ◽  
Aβ Peptides ◽  
Aβ Amyloid ◽  
Aβ Fibrils ◽  
The Brain

Amyloid plaques are a pathological hallmark of Alzheimer’s disease. The major component of these plaques are highly ordered amyloid fibrils formed by amyloid-β (Aβ) peptides. However, whilst Aβ amyloid fibril assembly has been subjected to detailed and extensive analysis in vitro, these studies may not reproduce how Aβ fibrils assemble in the brain. This is because the brain represents a highly complex and dynamic environment, and in Alzheimer’s disease multiple cofactors may affect the assembly of Aβ fibrils. Moreover, in vivo amyloid plaque formation will reflect the balance between the assembly of Aβ fibrils and their degradation. This review explores the roles of microglia as cofactors in Aβ aggregation and in the clearance of amyloid deposits. In addition, we discuss how infection may be an additional cofactor in Aβ fibril assembly by virtue of the antimicrobial properties of Aβ peptides. Crucially, by understanding the roles of microglia and infection in Aβ amyloid fibril assembly it may be possible to identify new therapeutic targets for Alzheimer’s disease.

The role of cell-derived oligomers of Aβ in Alzheimer's disease and avenues for therapeutic intervention

2005 ◽  
Vol 33 (5) ◽  
pp. 1087-1090 ◽  
Author(s):  
D.M. Walsh ◽  
I. Klyubin ◽  
G.M. Shankar ◽  
M. Townsend ◽  
J.V. Fadeeva ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Size Exclusion ◽  
Amyloid Β Protein ◽  
Aβ Oligomers ◽  
Aβ Peptides ◽  
Aβ Amyloid

Burgeoning evidence suggests that soluble oligomers of Aβ (amyloid β-protein) are the earliest effectors of synaptic compromise in Alzheimer's disease. Whereas most other investigators have employed synthetic Aβ peptides, we have taken advantage of a β-amyloid precursor protein-overexpressing cell line (referred to as 7PA2) that secretes sub-nanomolar levels of low-n oligomers of Aβ. These are composed of heterogeneous Aβ peptides that migrate on SDS/PAGE as dimers, trimers and tetramers. When injected into the lateral ventricle of rats in vivo, these soluble oligomers inhibit hippocampal long-term potentiation and alter the memory of a complex learned behaviour. Biochemical manipulation of 7PA2 medium including immunodepletion with Aβ-specific antibodies and fractionation by size-exclusion chromatography allowed us to unambiguously attribute these effects to low-n oligomers. Using this paradigm we have tested compounds directed at three prominent amyloid-based therapeutic targets: inhibition of the secretases responsible for Aβ production, inhibition of Aβ aggregation and immunization against Aβ. In each case, compounds capable of reducing oligomer production or antibodies that avidly bind Aβ oligomers also ameliorate the synaptotoxic effects of these natural, cell-derived oligomers.

scholarly journals Both Amyloid-β Peptide and Tau Protein Are Affected by an Anti-Amyloid-β Antibody Fragment in Elderly 3xTg-AD Mice

2020 ◽  
Vol 21 (18) ◽  
pp. 6630 ◽  
Author(s):  
Alejandro R. Roda ◽  
Laia Montoliu-Gaya ◽  
Gabriel Serra-Mir ◽  
Sandra Villegas
Keyword(s):  
Psychological Symptoms ◽  
Early Stage ◽  
Amyloid Β ◽  
Antibody Fragment ◽  
Amyloid Β Peptide ◽  
Single Chain ◽  
Female Mice ◽  
Apolipoprotein J ◽  
Inflammatory State ◽  
Behavioral And Psychological Symptoms

Alzheimer’s disease (AD) is the most common dementia worldwide. According to the amyloid hypothesis, the early accumulation of the Aβ-peptide triggers tau phosphorylation, synaptic dysfunction, and eventually neuronal death leading to cognitive impairment, as well as behavioral and psychological symptoms of dementia. ScFv-h3D6 is a single-chain variable fragment that has already shown its ability to diminish the amyloid burden in 5-month-old 3xTg-AD mice. However, tau pathology is not evident at this early stage of the disease in this mouse model. In this study, the effects of scFv-h3D6 on Aβ and tau pathologies have been assessed in 22-month-old 3xTg-AD mice. Briefly, 3xTg-AD female mice were treated for 2 weeks with scFv-h3D6 and compared with 3xTg-AD and non-transgenic (NTg) mice treated with PBS. The treatment with scFv-h3D6 was unequivocally effective in reducing the area of Aβ staining. Furthermore, a tendency for a reduction in tau levels was also observed after treatment that points to the interplay between Aβ and tau pathologies. The pro-inflammatory state observed in the 3xTg-AD mice did not progress after scFv-h3D6 treatment. In addition, the treatment did not alter the levels of apolipoprotein E or apolipoprotein J. Thus, a 2-week treatment with scFv-h3D6 was able to reduce AD-like pathology in elderly 3xTg-AD female mice.

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

2021 ◽  
Vol 12 (1) ◽  
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 kDa, termed AβOs, 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 Atomic-resolution structure of a disease-relevant Aβ(1–42) amyloid fibril

2016 ◽  
Vol 113 (34) ◽  
pp. E4976-E4984 ◽  
Author(s):  
Marielle Aulikki Wälti ◽  
Francesco Ravotti ◽  
Hiromi Arai ◽  
Charles G. Glabe ◽  
Joseph S. Wall ◽  
...  
Keyword(s):  
Amyloid Fibrils ◽  
Senile Plaque ◽  
3D Structure ◽  
Amyloid Β ◽  
Aβ Oligomers ◽  
Aβ Amyloid ◽  
Combining Data ◽  
Distance Restraints ◽  
Β Sheet ◽  
Resolution Structure

Amyloid-β (Aβ) is present in humans as a 39- to 42-amino acid residue metabolic product of the amyloid precursor protein. Although the two predominant forms, Aβ(1–40) and Aβ(1–42), differ in only two residues, they display different biophysical, biological, and clinical behavior. Aβ(1–42) is the more neurotoxic species, aggregates much faster, and dominates in senile plaque of Alzheimer’s disease (AD) patients. Although small Aβ oligomers are believed to be the neurotoxic species, Aβ amyloid fibrils are, because of their presence in plaques, a pathological hallmark of AD and appear to play an important role in disease progression through cell-to-cell transmissibility. Here, we solved the 3D structure of a disease-relevant Aβ(1–42) fibril polymorph, combining data from solid-state NMR spectroscopy and mass-per-length measurements from EM. The 3D structure is composed of two molecules per fibril layer, with residues 15–42 forming a double-horseshoe–like cross–β-sheet entity with maximally buried hydrophobic side chains. Residues 1–14 are partially ordered and in a β-strand conformation, but do not display unambiguous distance restraints to the remainder of the core structure.

Synaptic plasticity disruption by amyloid β protein: modulation by potential Alzheimer's disease modifying therapies

2005 ◽  
Vol 33 (4) ◽  
pp. 563-567 ◽  
Author(s):  
M.J. Rowan ◽  
I. Klyubin ◽  
Q. Wang ◽  
R. Anwyl
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Synaptic Plasticity ◽  
Medial Temporal Lobe ◽  
Amyloid Β ◽  
Long Term Potentiation ◽  
Soluble Form ◽  
Amyloid Β Protein ◽  
Aβ Oligomers ◽  
Aβ Amyloid

AD (Alzheimer's disease) is characterized by a progressive and devastating mental decline that is usually presaged by impairment of a form of memory dependent on medial temporal lobe structures, including the hippocampus. The severity of clinical dementia correlates positively with the cerebral load of the AD-related protein Aβ (amyloid β), particularly in its soluble form rather than the insoluble fibrillar Aβ found in amyloid plaques. Recent research in animal models of AD has pointed to a potentially important role for rapid disruptive effects of soluble species of Aβ on neural function in causing a relatively selective impairment of memory early in the disease. Our experiments assessing the mechanisms of Aβ inhibition of LTP (long-term potentiation), a correlate of memory-related synaptic plasticity, in the rodent hippocampus showed that low-n oligomers were the soluble Aβ species primarily responsible for the disruption of synaptic plasticity in vivo. Exogenously applied and endogenously generated anti-Aβ antibodies rapidly neutralized and prevented the synaptic plasticity disrupting effects of these very potent Aβ oligomers. This suggests that active or passive immunotherapeutic strategies for early AD should target Aβ oligomers in the brain. The ability of agents that reduce nitrosative/oxidative stress or antagonize stress-activated kinases to prevent Aβ inhibition of LTP in vitro points to a key role of these cellular mechanisms at very early stages in Aβ-induced neuronal dysfunction. A combination of antibody-mediated inactivation of Aβ oligomers and pharmacological prevention of cellular stress mechanisms underlying their synaptic plasticity disrupting effects provides an attractive strategy in the prevention of early AD.

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