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Amyloid oligomers

Natarajan Suganthy, Dicson Sheeja Malar, Kasi Pandima Devi
OBJECTIVE: Amyloid hypothesis states that endogenous β-amyloid peptides (Aβ), especially its aggregated oligomers and fibrils are the key pathogenic factors leading to Alzheimer's disease (AD). Therefore, inhibition of Aβ fibrillation rather than blocking its production is considered promising therapeutic intervention. Hence, the present study was carried out to assess the effect of methanolic leaf extract of R. mucronata (MERM) and its bioactive compound catechin on in vitro fibrillation of Aβ (25-35)...
October 21, 2016: Neurological Research
Przemyslaw Jurczak, Patrick Groves, Aneta Szymanska, Sylwia Rodziewicz-Motowidlo
Human cystatin C (hCC) is a small protein belonging to the cystatin family of papain-like cysteine proteinase inhibitors. We review the recent literature concerning structural aspects of hCC related to disease. We focus on the mechanisms of hCC dimerization, oligomerization and amyloid formation. Amyloid formation is associated with a number of neurodegenerative diseases that affect the independence and quality of life of aging populations. hCC is one of the second wave proteins that have been found to undergo amyloidosis associated with disease...
October 19, 2016: FEBS Letters
Anna V Glyakina, Nikolai K Balabaev, Oxana V Galzitskaya
The amyloidogenic peptide VDSWNVLVAG from Bgl2p-glucantransferase of Saccharomyces cerevisiae cell wall and its modifying analog VESWNVLVAG were taken for the construction of four types of bilayers which differ by orientation of the peptides in the layers and of the layers relative to each other. These bilayers were used as starting models for the molecular dynamics (MD) at three charge states (neutral, pH3, and pH5). The changes of the fraction of secondary structure during 1 ns simulations were received for 96 MD trajectories...
December 2016: Data in Brief
Qin Qiao, Ruxi Qi, Guanghong Wei, Xuhui Huang
Amyloid deposits of human islet amyloid polypeptide (hIAPP) are identified in 95% of type II diabetes patients. The oligomers during the early stage of hIAPP aggregation are believed to be more cytotoxic than the mature fibrils. However, the structural details during the initial stage of hIAPP aggregation are still under debate experimentally. To understand its initial nucleation mechanism, we investigate the thermodynamics and kinetics of hIAPP(11-25) dimerization, which is the first manifestation of the interplay between intra- and inter-molecular interactions, via the construction of Markov state models from extensive molecular dynamics simulations...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Ying Wei, Jun Lu, Tong Lu, Feihong Meng, Jia Xu, Li Wang, Yang Li, Liping Wang, Fei Li
Prefibrillar amyloid aggregates of proteins are known as cytotoxic species and a common pathogenic factor for many degenerative diseases. The mechanism underlying the formation and cytotoxicity of prefibrillar aggregates is believed to be independent of the actual nature of the amyloid protein. In this study, we monitored the formation of the peptide oligomers and examined the disruptive effects of the oligomers on liposomes using the human islet amyloid polypeptide fragment hIAPP18-27 as a model peptide. We observed various morphologies of oligomers formed at different aggregation stages that precede the formation of mature amyloid fibrils...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Alessandro Sinopoli, Alessandro Giuffrida, Marianna Flora Tomasello, Maria Laura Giuffrida, Marilisa Leone, Francesco Attanasio, Filippo Caraci, Paolo De Bona, Irina Naletova, Michele Saviano, Agata Copani, Giuseppe Pappalardo, Enrico Rizzarelli
No abstract text is available yet for this article.
October 17, 2016: Chembiochem: a European Journal of Chemical Biology
Asad Jan, Brandon Jansonius, Alberto Delaidelli, Syam Prakash Somasekharan, Forum Bhanshali, Milène Vandal, Gian Luca Negri, Don Moerman, Ian MacKenzie, Frédéric Calon, Michael R Hayden, Stefan Taubert, Poul H Sorensen
Soluble oligomers of amyloid-β (Aβ) impair synaptic plasticity, perturb neuronal energy homeostasis, and are implicated in Alzheimer's disease (AD) pathogenesis. Therefore, significant efforts in AD drug discovery research aim to prevent the formation of Aβ oligomers or block their neurotoxicity. The eukaryotic elongation factor-2 kinase (eEF2K) plays a critical role in synaptic plasticity, and couples neurotransmission to local dendritic mRNA translation. Recent evidence indicates that Aβ oligomers activate neuronal eEF2K, suggesting a potential link to Aβ induced synaptic dysfunction...
October 17, 2016: Acta Neuropathologica
Claudia Balducci, Angelisa Frasca, Margherita Zotti, Pietro La Vitola, Emanuela Mhillaj, Emanuele Grigoli, Martina Iacobellis, Federica Grandi, Massimo Messa, Laura Colombo, Monica Molteni, Luigia Trabace, Carlo Rossetti, Mario Salmona, Gianluigi Forloni
[Background] Amyloid-β oligomers (AβO) are species mainly involved in the synaptic and cognitive dysfunction in Alzheimer's disease. Although their action has been described mainly at neuronal level, it is now clear that glial cells govern synaptic activity in their resting state, contributing to new learning and memory establishment. In contrast, when activated, they may lead to synaptic and cognitive dysfunction. Using a reliable acute AβO-mediated mouse model of AD, we explored whether the memory alteration AβOs induce relies on the activation of glial cells, and if Toll-like receptor 4 (TLR4), pivotal in the initiation of an immune response, is involved...
October 14, 2016: Brain, Behavior, and Immunity
Koning Shen, Barbara Calamini, Jonathan A Fauerbach, Boxue Ma, Sarah H Shahmoradian, Ivana L Serrano Lachapel, Wah Chiu, Donald C Lo, Judith Frydman
Many neurodegenerative diseases are linked to amyloid aggregation. In Huntington's disease (HD), neurotoxicity correlates with increased aggregation propensity of a polyglutamine (polyQ) expansion in exon 1 of mutant huntingtin protein (mHtt). Here we establish how the domains flanking the polyQ tract shape the mHtt conformational landscape in vitro and in neurons. In vitro, the flanking domains have opposing effects on the conformation and stabilities of oligomers and amyloid fibrils. The N-terminal N17 promotes amyloid fibril formation, while the C-terminal Proline Rich Domain destabilizes fibrils and enhances oligomer formation...
October 18, 2016: ELife
Hu Shi, Baotao Kang, Jin Yong Lee
Histidine state (deprotonated, neutral, and protonated) is considered an important factor influencing the structural properties and aggregation mechanisms in amyloid β-peptides which are associated with the pathogenesis of Alzheimer's disease. Understanding the structural properties and aggregation mechanisms is a great challenge because two forms (the Nε-H or Nδ-H tautomer) can exist in the free neutral state of histidine. Here, replica exchange molecular dynamics simulation was performed to elucidate the changes of structure and mechanism of aggregation influenced by tautomeric behaviors of histidine in Aβ (1-40)...
October 17, 2016: Journal of Physical Chemistry. B
Xiaotian T Fang, Jonas Eriksson, Gunnar Antoni, Ulrika Yngve, Linda Cato, Lars Lannfelt, Dag Sehlin, Stina Syvänen
Alzheimer's disease (AD) is characterized by aggregation of amyloid beta (Aβ) into insoluble plaques. Intermediates, Aβ oligomers (Aβo), appear to be the mechanistic cause of disease. The de facto PET AD ligand, [(11)C]PIB, binds and visualizes Aβ plaque load, which does not correlate well with disease severity. Therefore, finding a dynamic target that changes with pathology progression in AD is of great interest. Aβo alter synaptic plasticity, inhibit long-term potentiation, and facilitate long-term depression; key mechanisms involved in memory and learning...
October 12, 2016: Neuropharmacology
Farron L McIntee, Patrizia Giannoni, Steven Blais, George Sommer, Thomas A Neubert, Agueda Rostagno, Jorge Ghiso
Amyloid β (Aβ) is the major constituent of the brain deposits found in parenchymal plaques and cerebral blood vessels of patients with Alzheimer's disease (AD). Several lines of investigation support the notion that synaptic pathology, one of the strongest correlates to cognitive impairment, is related to the progressive accumulation of neurotoxic Aβ oligomers. Since the process of oligomerization/fibrillization is concentration-dependent, it is highly reliant on the homeostatic mechanisms that regulate the steady state levels of Aβ influencing the delicate balance between rate of synthesis, dynamics of aggregation, and clearance kinetics...
2016: Frontiers in Aging Neuroscience
Yanli Zhou, Huanqing Zhang, Lantao Liu, Congming Li, Zhu Chang, Xu Zhu, Baoxian Ye, Maotian Xu
Amyloid β-peptide (Aβ) in its oligomeric form is often considered as the most toxic species in Alzheimer's disease (AD), and thus Aβ oligomer is a potentially promising candidate biomarker for AD diagnosis. The development of a sensitive and reliable method for monitoring the Aβ oligomer levels in body fluids is an urgent requirement in order to predict the severity and progression at early or preclinical stages of AD. Here, we show a proof of concept for a sensitive and specific detection of Aβ oligomers by an antibody-aptamer sandwich assay...
October 11, 2016: Scientific Reports
Darrell Sawmiller, Ahsan Habib, Song Li, Donna Darlington, Huayan Hou, Jun Tian, R Douglas Shytle, Adam Smith, Brian Giunta, Takashi Mori, Jun Tan
Naturally-occurring bioactive flavonoids such as diosmin significantly reduces amyloid beta (Aβ) associated pathology in Alzheimer's disease (AD) mouse models. In the present study, oral administration of diosmin reduced cerebral Aβ oligomer levels, tau-hyperphosphorylation and cognitive impairment in the 3xTg-AD mouse model through glycogen synthase kinase-3 (GSK-3) and transient receptor potential canonical 6-related mechanisms. Diosmetin, one major bioactive metabolite of diosmin, increased inhibitory GSK-3β phosphorylation, while selectively reducing γ-secretase activity, Aβ generation, tau hyperphosphorylation and pro-inflammatory activation of microglia in vitro, without altering Notch processing...
October 15, 2016: Journal of Neuroimmunology
O S Levin, E E Vasenina
Amyloid hypothesis of Alzheimer's disease (AD) has been long the primary one. During the 25-year history the concept has been dramatically changed. Accumulation of β-amyloid is associated not only with the disruption of its synthesis (as it seemed after the discovery of genetic mechanisms of some familial cases of AD) but rather with the disruption of its clearance and elimination from the brain tissue via the microcirculatory system. It has been recognized that soluble oligomers of β-amyloid, but not senile plaques that consisted of insoluble conjugates described by A...
2016: Zhurnal Nevrologii i Psikhiatrii Imeni S.S. Korsakova
John J Chen, Joseph C Genereux, Eul Hyun Suh, Vincent F Vartabedian, Bibiana Rius, Song Qu, Maria T A Dendle, Jeffery W Kelly, R Luke Wiseman
Transthyretin (TTR) is a tetrameric serum protein associated with multiple systemic amyloid diseases. In these disorders, TTR aggregates in extracellular environments through a mechanism involving rate-limiting dissociation of the tetramer to monomers, which then misfold and aggregate into soluble oligomers and amyloid fibrils that induce toxicity in distal tissues. Using an assay established herein, we show that highly destabilized, aggregation-prone TTR variants are secreted as both native tetramers and non-native conformations that accumulate as high-molecular-weight oligomers...
October 20, 2016: Cell Chemical Biology
Nor Faeizah Ibrahim, Daijiro Yanagisawa, Lina Wati Durani, Hamizah Shahirah Hamezah, Hanafi Ahmad Damanhuri, Wan Zurinah Wan Ngah, Mayumi Tsuji, Yuji Kiuchi, Kenjiro Ono, Ikuo Tooyama
Alzheimer's disease (AD) is the most common cause of dementia. The cardinal neuropathological characteristic of AD is the accumulation of amyloid-β (Aβ) into extracellular plaques that ultimately disrupt neuronal function and lead to neurodegeneration. One possible therapeutic strategy therefore is to prevent Aβ aggregation. Previous studies have suggested that vitamin E analogs slow AD progression in humans. In the present study, we investigated the effects of the tocotrienol-rich fraction (TRF), a mixture of vitamin E analogs from palm oil, on amyloid pathology in vitro and in vivo...
October 1, 2016: Journal of Alzheimer's Disease: JAD
Zijian Zhao, Ling Zhu, Haiyun Li, Peng Cheng, Jiaxi Peng, Yudan Yin, Yang Yang, Chen Wang, Zhiyuan Hu, Yanlian Yang
The oligomerization and aggregation of amyloid β (Aβ) play central role in the pathogenesis of Alzheimer's disease (AD). Molecular binding agents for modulating the formation of Aβ oligomers and fibrils have promising application potential in AD therapies. By screening a peptoid library using surface plasmon resonance imaging, amyloid inhibitory peptoid 1 (AIP1) that has high affinity to Aβ42 is identified. AIP1 is demonstrated to inhibit Aβ42 oligomerization and fibrillation and to rescue Aβ42-induced cytotoxicity through decreasing the content of Aβ42 oligomers that is related to cell membrane permeability...
October 7, 2016: Small
Ane Wyssenbach, Tania Quintela, Francisco Llavero, Jose L Zugaza, Carlos Matute, Elena Alberdi
Astrogliosis is a hallmark of Alzheimer's disease (AD) and may constitute a primary pathogenic component of that disorder. Elucidation of signaling cascades inducing astrogliosis should help characterizing the function of astrocytes and identifying novel molecular targets to modulate AD progression. Here, we describe a novel mechanism by which soluble amyloid-β modulates β1-integrin activity and triggers NADPH oxidase (NOX)-dependent astrogliosis in vitro and in vivo. Amyloid-β oligomers activate a PI3K/classical PKC/Rac1/NOX pathway which is initiated by β1-integrin in cultured astrocytes...
October 5, 2016: Aging Cell
Niels R Reinders, Yvonne Pao, Maria C Renner, Carla M da Silva-Matos, Tessa R Lodder, Roberto Malinow, Helmut W Kessels
Amyloid-β (Aβ) is a prime suspect for causing cognitive deficits during the early phases of Alzheimer's disease (AD). Experiments in AD mouse models have shown that soluble oligomeric clusters of Aβ degrade synapses and impair memory formation. We show that all Aβ-driven effects measured in these mice depend on AMPA receptor (AMPAR) subunit GluA3. Hippocampal neurons that lack GluA3 were resistant against Aβ-mediated synaptic depression and spine loss. In addition, Aβ oligomers blocked long-term synaptic potentiation only in neurons that expressed GluA3...
October 5, 2016: Proceedings of the National Academy of Sciences of the United States of America
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