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  • Rapid tau aggregation and delayed hippocampal neuronal death induced by persistent thrombin signaling. 12821672

    Tau hyperphosphorylation, leading to self-aggregation, is widely held to underlie the neurofibrillary degeneration found in Alzheimer's disease (AD) and other tauopathies. However, it is unclear exactly what environmental factors may trigger this pathogenetic tau hyperphosphorylation. From several perspectives, the coagulation serine protease, thrombin, has been implicated in AD and activates several different protein kinase pathways but has not previously been shown how it may contribute to AD pathogenesis. Here we report that nanomolar thrombin induced rapid tau hyperphosphorylation and aggregation in murine hippocampal neurons via protease-activated receptors, which was followed by delayed synaptophysin reduction and apoptotic neuronal death. Mechanistic study revealed that a persistent thrombin signaling via protease-activated receptor 4 and prolonged downstream p44/42 mitogenactivated protein kinase activation are at least in part responsible. These results pathogenetically linked thrombin to subpopulations of AD and other tauopathies associated with cerebrovascular damage. Such knowledge may be instrumental in transforming therapeutic paradigms.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB1518
    Nombre del producto:
    Anti-Neurofibrillary Tangles Antibody

  • Tau aggregation and toxicity in a cell culture model of tauopathy. 17428800

    Intracellular aggregation of the microtubule-associated protein tau into filamentous inclusions is a defining characteristic of Alzheimer disease. Because appearance of tau-aggregate bearing lesions correlates with both cognitive decline and neurodegeneration, it has been hypothesized that tau aggregation may be directly toxic to cells that harbor them. Testing this hypothesis in cell culture has been complicated by the resistance of full-length tau isoforms to aggregation over experimentally tractable time periods. To overcome this limitation, a small-molecule agonist of the tau aggregation reaction, Congo red, was used to drive aggregation within HEK-293 cells expressing full-length tau isoform htau40. Formation of detergent-insoluble aggregates was both time and agonist concentration dependent. At 10 microM Congo red, detergent-insoluble aggregates appeared with pseudo-first order kinetics and a half-life of approximately 5 days. By 7 days in culture, total tau levels increased 2-fold, with approximately 30% of total tau converted into detergent-insoluble aggregates. Agonist addition also led to rapid losses in the tubulin binding activity of tau, although tau was not hyperphosphorylated as judged by occupancy of phosphorylation sites Ser396/Ser404. Tau aggregation was associated with decreased viability as detected by ToPro-3 uptake. The results, which establish a new approach for analysis of tau aggregation in cells independent of tau hyperphosphorylation, suggest that conformational changes associated with aggregation are incompatible with microtubule binding, and that toxicity associated with intracellular tau aggregation is not acute but develops over a period of days.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Cleavage of tau by asparagine endopeptidase mediates the neurofibrillary pathology in Alzheimer's disease. 25326800

    Neurofibrillary tangles (NFTs), composed of truncated and hyperphosphorylated tau, are a common feature of numerous aging-related neurodegenerative diseases, including Alzheimer's disease (AD). However, the molecular mechanisms mediating tau truncation and aggregation during aging remain elusive. Here we show that asparagine endopeptidase (AEP), a lysosomal cysteine proteinase, is activated during aging and proteolytically degrades tau, abolishes its microtubule assembly function, induces tau aggregation and triggers neurodegeneration. AEP is upregulated and active during aging and is activated in human AD brain and tau P301S-transgenic mice with synaptic pathology and behavioral impairments, leading to tau truncation in NFTs. Tau P301S-transgenic mice with deletion of the gene encoding AEP show substantially reduced tau hyperphosphorylation, less synapse loss and rescue of impaired hippocampal synaptic function and cognitive deficits. Mice infected with adeno-associated virus encoding an uncleavable tau mutant showed attenuated pathological and behavioral defects compared to mice injected with adeno-associated virus encoding tau P301S. Together, these observations indicate that AEP acts as a crucial mediator of tau-related clinical and neuropathological changes. Inhibition of AEP may be therapeutically useful for treating tau-mediated neurodegenerative diseases.
    Tipo de documento:
    Referencia
    Referencia del producto:
    ABN1703
    Nombre del producto:
    Anti-Tau, AEP-cleaved (N368) Antibody

  • Co-occurrence of Alzheimer's disease beta-amyloid and tau pathologies at synapses. 18771816

    Although beta-amyloid (Abeta) plaques and tau neurofibrillary tangles are hallmarks of Alzheimer's disease (AD) neuropathology, loss of synapses is considered the best correlate of cognitive decline in AD, rather than plaques or tangles. How pathological Abeta and tau aggregation relate to each other and to alterations in synapses remains unclear. Since aberrant tau phosphorylation occurs in amyloid precursor protein (APP) Swedish mutant transgenic mice, and since neurofibrillary tangles develop in triple transgenic mice harboring mutations in APP, tau and presenilin 1, we utilized these well-characterized mouse models to explore the relation between Abeta and tau pathologies. We now report that pathological accumulation of Abeta and hyperphosphorylation of tau develop concomitantly within synaptic terminals.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB5078P
    Nombre del producto:
    Anti-Beta-Amyloid 1-42 Antibody

  • Characterization of prefibrillar Tau oligomers in vitro and in Alzheimer disease. 21550980

    Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers self-associate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB5320
    Nombre del producto:
    Anti-Synuclein α Antibody, clone 7B12.2

  • Abnormal Tau Phosphorylation in the Thorny Excrescences of CA3 Hippocampal Neurons in Patients with Alzheimer\'s Disease. 21677375

    A key symptom in the early stages of Alzheimer\'s disease (AD) is the loss of declarative memory. The anatomical substrate that supports this kind of memory involves the neural circuits of the medial temporal lobe, and in particular, of the hippocampal formation and adjacent cortex. A main feature of AD is the abnormal phosphorylation of the tau protein and the presence of tangles. The sequence of cellular changes related to tau phosphorylation and tangle formation has been studied with an antibody that binds to diffuse phosphotau (AT8). Moreover, another tau antibody (PHF-1) has been used to follow the pathway of neurofibrillary (tau aggregation) degeneration in AD. We have used a variety of quantitative immunocytochemical techniques and confocal microscopy to visualize and characterize neurons labeled with AT8 and PHF-1 antibodies. We present here the rather unexpected discovery that in AD, there is conspicuous abnormal phosphorylation of the tau protein in a selective subset of dendritic spines. We identified these spines as the typical thorny excrescences of hippocampal CA3 neurons in a pre-tangle state. Since thorny excrescences represent a major synaptic target of granule cell axons (mossy fibers), such aberrant phosphorylation may play an essential role in the memory impairment typical of AD patients.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB5905
    Nombre del producto:
    Anti-Vesicular Glutamate Transporter 1 Antibody

  • Long-term overexpression of heme oxygenase 1 promotes tau aggregation in mouse brain by inducing tau phosphorylation. 21613741

    Intracellular tau aggregates composed of neurofibrillary tangles (NFTs) are a defining feature of Alzheimer's disease (AD). Increased expression of heme oxygenase-1 (HO-1) is a common phenomenon in AD. Interestingly, the spatial distribution of HO-1 expression is essentially identical to that of pathological accumulation of tau in AD. In this study, we developed a new transgenic mouse overexpressing HO-1, called CAG-HO-1 Tg mice, to explore the relationship between HO-1 and tau aggregation. In this model, we found that long-term overexpression of HO-1 significantly promoted tau aggregation in brain, by analyzing changes in morphology and insoluble tau expression levels. Moreover, our research provides the first in vivo evidence that HO-1 can enhance iron loading and tau (Ser199/202/396) phosphorylation in brains of transgenic mice. Cellular evidence indicates that HO-1 can induce the phosphorylation of tau through iron accumulation in Neuro2a cells stably transfected with HO-1. Our data suggest that long-term overexpression of HO-1 can promote tau aggregation. This mechanism involves excessive iron production mediated by HO-1 overexpression, which induces tau phosphorylation. Our results provide a potential pathway for the pathogenesis of tauopathies, which remains largely unknown.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB361
    Nombre del producto:
    Anti-Tau Antibody, a.a. 210-241, clone Tau-5

  • Identification of oligomers at early stages of tau aggregation in Alzheimer's disease. 22253473

    Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease (AD); however, the relationship between NFTs and disease progression remains controversial. Analyses of tau animal models suggest that phenotypes coincide with accumulation of soluble aggregated tau species but not the accumulation of NFTs. The pathological role of prefilamentous tau aggregates, e.g., tau oligomeric intermediates, is poorly understood, in part because of methodological challenges. Here, we engineered a novel tau oligomer-specific antibody, T22, and used it to elucidate the temporal course and biochemical features of oligomers during NFT development in AD brain. We found that tau oligomers in human AD brain samples were 4-fold higher than those in the controls. We also revealed the role of oligomeric tau conformers in pretangles, neuritic plaques, and neuropil threads in the frontal cortex tissue from AD brains; this analysis uncovers a consistent code that governs tau oligomerization with regard to degree of neuronal cytopathology. These data are the first to characterize the role of tau oligomers in the natural history of NFTs, and they highlight the suitability of tau oligomers as therapeutic targets in AD and related tauopathies.
    Tipo de documento:
    Referencia
    Referencia del producto:
    ABN454
    Nombre del producto:
    Anti-Tau (T22), oligomeric Antibody

  • Extracellular Vesicles Isolated from the Brains of rTg4510 Mice Seed Tau Protein Aggregation in a Threshold-dependent Manner 27030011

    The microtubule-associated protein tau has a critical role in Alzheimer disease and related tauopathies. There is accumulating evidence that tau aggregates spread and replicate in a prion-like manner, with the uptake of pathological tau seeds causing misfolding and aggregation of monomeric tau in recipient cells. Here we focused on small extracellular vesicles enriched for exosomes that were isolated from the brains of tau transgenic rTg4510 and control mice. We found that these extracellular vesicles contained tau, although the levels were significantly higher in transgenic mice that have a pronounced tau pathology. Tau in the vesicles was differentially phosphorylated, although to a lower degree than in the brain cells from which they were derived. Several phospho-epitopes (AT8, AT100, and AT180) thought to be critical for tau pathology were undetected in extracellular vesicles. Despite this, when assayed with FRET tau biosensor cells, extracellular vesicles derived from transgenic mice were capable of seeding tau aggregation in a threshold-dependent manner. We also observed that the dye used to label extracellular vesicle membranes was still present during nucleation and formation of tau inclusions, suggesting either a role for membranes in the seeding or in the process of degradation. Together, we clearly demonstrate that extracellular vesicles can transmit tau pathology. This indicates a role for extracellular vesicles in the transmission and spreading of tau pathology. The characteristics of tau in extracellular vesicles and the seeding threshold we identified may explain why tau pathology develops very slowly in neurodegenerative diseases such as Alzheimer disease.
    Tipo de documento:
    Referencia
    Referencia del producto:
    ABC40
    Nombre del producto:
    Anti-AIP1/Alix Antibody

  • Distinct α-synuclein strains differentially promote tau inclusions in neurons. 23827677

    Many neurodegenerative diseases are characterized by the accumulation of insoluble protein aggregates, including neurofibrillary tangles comprised of tau in Alzheimer's disease and Lewy bodies composed of α-synuclein in Parkinson's disease. Moreover, different pathological proteins frequently codeposit in disease brains. To test whether aggregated α-synuclein can directly cross-seed tau fibrillization, we administered preformed α-synuclein fibrils assembled from recombinant protein to primary neurons and transgenic mice. Remarkably, we discovered two distinct strains of synthetic α-synuclein fibrils that demonstrated striking differences in the efficiency of cross-seeding tau aggregation, both in neuron cultures and in vivo. Proteinase K digestion revealed conformational differences between the two synthetic α-synuclein strains and also between sarkosyl-insoluble α-synuclein extracted from two subgroups of Parkinson's disease brains. We speculate that distinct strains of pathological α-synuclein likely exist in neurodegenerative disease brains and may underlie the tremendous heterogeneity of synucleinopathies.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo