scholarly journals Change in tau phosphorylation associated with neurodegeneration in the ME7 model of prion disease

2010 ◽  
Vol 38 (2) ◽  
pp. 545-551 ◽  
Author(s):  
Ayodeji A. Asuni ◽  
V. Hugh Perry ◽  
Vincent O'Connor
Keyword(s):  
Axonal Transport ◽  
Prion Disease ◽  
Neuronal Loss ◽  
Brain Homogenate ◽  
Tau Phosphorylation ◽  
Synaptic Dysfunction ◽  
Normal Brain ◽  
Hyperphosphorylated Tau ◽  
Ad Alzheimer’S Disease ◽  
End Stage

Hyperphosphorylation of the microtubule-associated protein tau is a significant determinant in AD (Alzheimer's disease), where it is associated with disrupted axonal transport and probably causes synaptic dysfunction. Although less well studied, hyperphosphorylation has been observed in prion disease. We have investigated the expression of hyperphosphorylated tau in the hippocampus of mice infected with the ME7 prion agent. In ME7-infected animals, there is a selective loss of CA1 synapse, first discernable at 13 weeks of disease. There is a potential that dysfunctional axonal transport contributes to this synaptopathy. Thus investigating hyperphosphorylated tau that is dysfunctional in AD could illuminate whether and how they are significant in prion disease. We observed no differences in the levels of phosphorylated tau (using MC1, PHF-1 and CP13 antibodies) in detergent-soluble and detergent-insoluble fractions extracted from ME7- and NBH- (normal brain homogenate) treated animals across disease. In contrast, we observed an increase in phospho-tau staining for several epitopes using immunohistochemistry in ME7-infected hippocampal sections. Although the changes were not of the magnitude seen in AD tissue, clear differences for several phospho-tau species were seen in the CA1 and CA3 of ME7-treated animals (pSer199−202>pSer214>PHF-1 antibody). Temporally, these changes were restricted to animals at 20 weeks and none of the disease-related staining was associated with the axons or dendrites that hold CA1 synapses. These findings suggest that phosphorylation of tau at the epitopes examined does not underpin the early synaptic dysfunction. These data suggest that the changes in tau phosphorylation recorded here and observed by others relate to end-stage prion pathology when early dysfunctions have progressed to overt neuronal loss.

scholarly journals Amphiphysin I cleavage by asparagine endopeptidase leads to tau hyperphosphorylation and synaptic dysfunction

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Xingyu Zhang ◽  
Li Zou ◽  
Lanxia Meng ◽  
Min Xiong ◽  
Lina Pan ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Cognitive Deficits ◽  
Neurofibrillary Tangles ◽  
Molecular Mechanisms ◽  
Cysteine Proteinase ◽  
Tau Phosphorylation ◽  
Synaptic Dysfunction ◽  
Hyperphosphorylated Tau ◽  
Tau Hyperphosphorylation ◽  
Terminal Fragment

Neurofibrillary tangles composed of hyperphosphorylated tau and synaptic dysfunction are characteristics of Alzheimer’s disease (AD). However, the underlying molecular mechanisms remain poorly understood. Here, we identified Amphiphysin I mediates both tau phosphorylation and synaptic dysfunction in AD. Amphiphysin I is cleaved by a cysteine proteinase asparagine endopeptidase (AEP) at N278 in the brains of AD patients. The amount of AEP-generated N-terminal fragment of Amphiphysin I (1-278) is increased with aging. Amphiphysin I (1-278) inhibits clathrin-mediated endocytosis and induces synaptic dysfunction. Furthermore, Amphiphysin I (1-278) binds p35 and promotes its transition to p25, thus activates CDK5 and enhances tau hyperphosphorylation. Overexpression of Amphiphysin I (1-278) in the hippocampus of Tau P301S mice induces synaptic dysfunction, tau hyperphosphorylation, and cognitive deficits. However, overexpression of the N278A mutant Amphiphysin I, which resists the AEP-mediated cleavage, alleviates the pathological and behavioral defects. These findings suggest a mechanism of tau hyperphosphorylation and synaptic dysfunction in AD.

Inhibition of neuroinflammatory nitric oxide signalling supresses protein glycation and recovers neuronal dysfunction in prion disease

2020 ◽  
Author(s):  
Julie-Myrtille Bourgognon ◽  
Jereme G. Spiers ◽  
Sue Robinson ◽  
Hannah Scheiblich ◽  
Catharine Ortori ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Prion Protein ◽  
Prion Disease ◽  
Protein Misfolding ◽  
Brain Homogenate ◽  
Protein Glycation ◽  
Therapeutic Effects ◽  
Normal Brain ◽  
Gene And Protein Expression ◽  
Nos Inhibitor

Abstract Background: Several neurodegenerative diseases associated with protein misfolding (Alzheimer’s, Parkinson’s disease) exhibit oxidative and nitrergic stress following initiation of neuroinflammatory pathways. Associated nitric oxide (NO)-mediated post-translational modifications impact upon protein functions that can exacerbate pathology. Non-enzymatic and irreversible glycation signalling has been implicated as an underlying pathway that promotes protein misfolding, but the direct interactions between both pathways are poorly understood. Methods: Here we investigated the potential therapeutic effects of supressing neurotoxic NO signalling during early progression of prion disease. Tg37 mice aged 3-4 weeks were inoculated by intracerebral injection with either 1% brain homogenate of Rocky Mountain Laboratory (RML) scrapie prion protein or control normal brain homogenate (NBH). Hippocampal gene and protein expression levels of oxidative and nitrergic stress markers were analysed and electrophysiological characterisations of pyramidal neurons were performed in 6-10 weeks old RML and NBH mice. Mice were injected with a NO synthase (NOS) inhibitor and the time course of disease markers was compared to controls. Electrophysiology, immunoblotting and immunocytochemistry studies were performed to identify the effects of NOS inhibition on neurophysiology, glycation, prion protein misfolding and cell death. Statistical analyses employed two-tailed unpaired Student’s t-test, one-way or two-way ANOVA as required and data were considered significant with P<0.05.Results: Increased neuroinflammatory signalling was observed in mice between 6 and 10 weeks post inoculation (w.p.i.) with scrapie prion protein which was characterised by enhanced nitrergic stress and associated with a decline in hippocampal neuronal function by 9 w.p.i.. Daily in vivo administration of the NOS inhibitor L-NAME between 6 and 9 w.p.i. at 20 mg/kg abolished the functional degeneration of hippocampal neurons in prion mice. We further found that this intervention in diseased mice ameliorated 3-nitrotyrosination of triose-phosphate isomerase, an enzyme involved in the formation of disease-associated glycation signalling. Furthermore, L-NAME application reduced the expression of the receptor for advanced glycation end products and the accumulation of hippocampal prion misfolding. Conclusions: Our data suggest that alleviating nitrergic stress during early phases of neurodegeneration reduces neurotoxic post-translational NO signalling and glycation-assisted prion misfolding in the hippocampus, a mechanism which might be applicable to other protein misfolding neurodegenerative conditions.

Disruption of neuronal function by soluble hyperphosphorylated tau in a Drosophila model of tauopathy

2010 ◽  
Vol 38 (2) ◽  
pp. 564-570 ◽  
Author(s):  
Catherine M. Cowan ◽  
Francis Chee ◽  
David Shepherd ◽  
Amritpal Mudher
Keyword(s):  
Axonal Transport ◽  
Neuronal Death ◽  
Synaptic Function ◽  
Hyperphosphorylated Tau ◽  
Neuronal Function ◽  
Synaptic Loss ◽  
Early Stages ◽  
Mediated Effects ◽  
Drosophila Model ◽  
Ad Alzheimer’S Disease

Axonal microtubules are essential for transport of materials to the synapse. Compromised microtubules and synaptic loss have been demonstrated in AD (Alzheimer's disease), which is believed to contribute to cognitive dysfunction before neuronal death in the early stages of the disease. The mechanism by which hyperphosphorylated tau, the building block of neurofibrillary tangles, one of the pathological hallmarks of AD, disrupts neuronal and synaptic function is unclear. There is a theory that hyperphosphorylated tau does not bind effectively to microtubules and is no longer able to function in stabilizing them, thus axonal transport can no longer proceed efficiently. This leads to synaptic dysfunction. We have tested this theory in a Drosophila model of tauopathies in which we expressed human tau (h-tau). Using this model, we have tested all aspects of this hypothesis and have demonstrated that axonal transport does become compromised in the presence of hyperphosphorylated h-tau and this leads to synaptic and behavioural defects. We are currently investigating the mechanism by which hyperphosphorylated h-tau mediates this effect and are preliminary data indicate that this entails phospho-tau-mediated effects that are predicted by the tau–microtubule hypothesis, as well as novel effects. These deleterious effects of h-tau occur in the absence of tau filaments and before neuronal death. This sequence of pathogenic events may constitute the mechanism by which abnormal tau disrupts neuronal and synaptic function and contributes to cognitive impairment before neuronal death in the early stages of tauopathies such as AD.

Dysfunction and recovery of synapses in prion disease: implications for neurodegeneration

2010 ◽  
Vol 38 (2) ◽  
pp. 482-487 ◽  
Author(s):  
Julie A. Moreno ◽  
Giovanna R. Mallucci
Keyword(s):  
Cell Death ◽  
Prion Disease ◽  
Neurodegenerative Disorders ◽  
Neuronal Death ◽  
Neuronal Loss ◽  
Adult Brain ◽  
Synaptic Dysfunction ◽  
Synapse Loss ◽  
Physiological Processes ◽  
Temporal Segregation

Synaptic dysfunction is a key early process in many neurodegenerative diseases, but how this ultimately leads to neuronal loss is not clear. In health, there is ongoing remodelling of synapses and spines in the adult brain: their elimination and formation are continual physiological processes fundamental to learning and memory. But in neurodegenerative disease, including prion disease, lost synapses are not replaced, and their loss is followed by neuronal death. These two processes are separately regulated, with mechanistic, spatial and temporal segregation of the respective death routines of synapses and cell bodies. Mice with prion disease can be cured at the stage of early synaptic dysfunction, when they have reversible impairments at neurophysiological, behavioural and morphological levels. Critically, reversing synaptic dysfunction at this stage of disease rescues neurons, preventing its otherwise inevitable progression to synapse loss and cell death. These findings call for a deeper analysis of the mechanisms underlying neurotoxicity at the synapse, and have important implications for the therapy of prion and other neurodegenerative disorders.

scholarly journals Contribution of TMS and TMS-EEG to the Understanding of Mechanisms Underlying Physiological Brain Aging

2021 ◽  
Vol 11 (3) ◽  
pp. 405
Author(s):  
Andrea Guerra ◽  
Lorenzo Rocchi ◽  
Alberto Grego ◽  
Francesca Berardi ◽  
Concetta Luisi ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Brain Aging ◽  
Cortical Excitability ◽  
Motor Evoked Potentials ◽  
Neurological Diseases ◽  
Physiological Activity ◽  
Neuronal Loss ◽  
Normal Brain ◽  
Potential Contribution ◽  
Brain Degeneration

In the human brain, aging is characterized by progressive neuronal loss, leading to disruption of synapses and to a degree of failure in neurotransmission. However, there is increasing evidence to support the notion that the aged brain has a remarkable ability to reorganize itself, with the aim of preserving its physiological activity. It is important to develop objective markers able to characterize the biological processes underlying brain aging in the intact human, and to distinguish them from brain degeneration associated with many neurological diseases. Transcranial magnetic stimulation (TMS), coupled with electromyography or electroencephalography (EEG), is particularly suited to this aim, due to the functional nature of the information provided, and thanks to the ease with which it can be integrated with behavioral manipulation. In this review, we aimed to provide up to date information about the role of TMS and TMS-EEG in the investigation of brain aging. In particular, we focused on data about cortical excitability, connectivity and plasticity, obtained by using readouts such as motor evoked potentials and transcranial evoked potentials. Overall, findings in the literature support an important potential contribution of TMS to the understanding of the mechanisms underlying normal brain aging. Further studies are needed to expand the current body of information and to assess the applicability of TMS findings in the clinical setting.

scholarly journals Ultramicroscopy Reveals Axonal Transport Impairments in Cortical Motor Neurons at Prion Disease

2009 ◽  
Vol 96 (8) ◽  
pp. 3390-3398 ◽  
Author(s):  
Vladimir Ermolayev ◽  
Mike Friedrich ◽  
Revaz Nozadze ◽  
Toni Cathomen ◽  
Michael A. Klein ◽  
...  
Keyword(s):  
Axonal Transport ◽  
Prion Disease ◽  
Motor Neurons ◽  
Cortical Motor

scholarly journals Bile Acids Reduce Prion Conversion, Reduce Neuronal Loss, and Prolong Male Survival in Models of Prion Disease

2015 ◽  
Vol 89 (15) ◽  
pp. 7660-7672 ◽  
Author(s):  
Leonardo M. Cortez ◽  
Jody Campeau ◽  
Grant Norman ◽  
Marian Kalayil ◽  
Jacques Van der Merwe ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Neurodegenerative Diseases ◽  
Bile Acids ◽  
Prion Disease ◽  
Prion Diseases ◽  
Neuronal Loss ◽  
Disease Models ◽  
Orally Bioavailable ◽  
Prion Conversion ◽  
Lateral Sclerosis

ABSTRACTPrion diseases are fatal neurodegenerative disorders associated with the conversion of cellular prion protein (PrPC) into its aberrant infectious form (PrPSc). There is no treatment available for these diseases. The bile acids tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) have been recently shown to be neuroprotective in other protein misfolding disease models, including Parkinson's, Huntington's and Alzheimer's diseases, and also in humans with amyotrophic lateral sclerosis. Here, we studied the therapeutic efficacy of these compounds in prion disease. We demonstrated that TUDCA and UDCA substantially reduced PrP conversion in cell-free aggregation assays, as well as in chronically and acutely infected cell cultures. This effect was mediated through reduction of PrPScseeding ability, rather than an effect on PrPC. We also demonstrated the ability of TUDCA and UDCA to reduce neuronal loss in prion-infected cerebellar slice cultures. UDCA treatment reduced astrocytosis and prolonged survival in RML prion-infected mice. Interestingly, these effects were limited to the males, implying a gender-specific difference in drug metabolism. Beyond effects on PrPSc, we found that levels of phosphorylated eIF2α were increased at early time points, with correlated reductions in postsynaptic density protein 95. As demonstrated for other neurodegenerative diseases, we now show that TUDCA and UDCA may have a therapeutic role in prion diseases, with effects on both prion conversion and neuroprotection. Our findings, together with the fact that these natural compounds are orally bioavailable, permeable to the blood-brain barrier, and U.S. Food and Drug Administration-approved for use in humans, make these compounds promising alternatives for the treatment of prion diseases.IMPORTANCEPrion diseases are fatal neurodegenerative diseases that are transmissible to humans and other mammals. There are no disease-modifying therapies available, despite decades of research. Treatment targets have included inhibition of protein accumulation, clearance of toxic aggregates, and prevention of downstream neurodegeneration. No one target may be sufficient; rather, compounds which have a multimodal mechanism, acting on different targets, would be ideal. TUDCA and UDCA are bile acids that may fulfill this dual role. Previous studies have demonstrated their neuroprotective effects in several neurodegenerative disease models, and we now demonstrate that this effect occurs in prion disease, with an added mechanistic target of upstream prion seeding. Importantly, these are natural compounds which are orally bioavailable, permeable to the blood-brain barrier, and U.S. Food and Drug Administration-approved for use in humans with primary biliary cirrhosis. They have recently been proven efficacious in human amyotrophic lateral sclerosis. Therefore, these compounds are promising options for the treatment of prion diseases.

scholarly journals Stabilization of dynamic microtubules by mDia1 drives Tau-dependent Aβ1–42 synaptotoxicity

2017 ◽  
Vol 216 (10) ◽  
pp. 3161-3178 ◽  
Author(s):  
Xiaoyi Qu ◽  
Feng Ning Yuan ◽  
Carlo Corona ◽  
Silvia Pasini ◽  
Maria Elena Pero ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Axonal Transport ◽  
Dendritic Spines ◽  
Posttranslational Modifications ◽  
Hippocampal Neurons ◽  
Neuronal Damage ◽  
Driving Factors ◽  
Hyperphosphorylated Tau ◽  
Tau Hyperphosphorylation

Oligomeric Amyloid β1–42 (Aβ) plays a crucial synaptotoxic role in Alzheimer’s disease, and hyperphosphorylated tau facilitates Aβ toxicity. The link between Aβ and tau, however, remains controversial. In this study, we find that in hippocampal neurons, Aβ acutely induces tubulin posttranslational modifications (PTMs) and stabilizes dynamic microtubules (MTs) by reducing their catastrophe frequency. Silencing or acute inhibition of the formin mDia1 suppresses these activities and corrects the synaptotoxicity and deficits of axonal transport induced by Aβ. We explored the mechanism of rescue and found that stabilization of dynamic MTs promotes tau-dependent loss of dendritic spines and tau hyperphosphorylation. Collectively, these results uncover a novel role for mDia1 in Aβ-mediated synaptotoxicity and demonstrate that inhibition of MT dynamics and accumulation of PTMs are driving factors for the induction of tau-mediated neuronal damage.

scholarly journals Role of Cofilin in Alzheimer’s Disease

2020 ◽  
Vol 8 ◽  
Author(s):  
Qiang Wang ◽  
Wei Yuan ◽  
Xiaohang Yang ◽  
Yuan Wang ◽  
Yongfeng Li ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Plaques ◽  
Executive Dysfunction ◽  
Actin Binding ◽  
Synaptic Dysfunction ◽  
Hyperphosphorylated Tau ◽  
Hirano Bodies ◽  
Visual Spatial ◽  
Β Amyloid

Alzheimer’s disease (AD) is a degenerative neurological disease and has an inconspicuous onset and progressive development. Clinically, it is characterized by severe dementia manifestations, including memory impairment, aphasia, apraxia, loss of recognition, impairment of visual-spatial skills, executive dysfunction, and changes in personality and behavior. Its etiology is unknown to date. However, several cellular biological signatures of AD have been identified such as synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies which are related to the actin cytoskeleton. Cofilin is one of the most affluent and common actin-binding proteins and plays a role in cell motility, migration, shape, and metabolism. They also play an important role in severing actin filament, nucleating, depolymerizing, and bundling activities. In this review, we summarize the structure of cofilins and their functional and regulating roles, focusing on the synaptic dysfunction, β-amyloid plaques, hyperphosphorylated tau, cofilin-actin rods, and Hirano bodies of AD.

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