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.

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.

p35 Deficiency Accelerates HMGB-1-mediated Neuronal Death in the Early Stages of an Alzheimer’s disease Mouse Model

2013 ◽  
Vol 10 (8) ◽  
pp. 829-843 ◽  
Author(s):  
Ahram Jang ◽  
Hyunjeong Liew ◽  
Yun-Mi Kim ◽  
Heesoon Choi ◽  
Saeromi Kim ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mouse Model ◽  
Neuronal Death ◽  
Early Stages

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 Esculetin Provides Neuroprotection against Mutant Huntingtin-Induced Toxicity in Huntington’s Disease Models

2021 ◽  
Vol 14 (10) ◽  
pp. 1044
Author(s):  
Letizia Pruccoli ◽  
Carlo Breda ◽  
Gabriella Teti ◽  
Mirella Falconi ◽  
Flaviano Giorgini ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Neuronal Death ◽  
Trinucleotide Repeat ◽  
Neurodegenerative Disorder ◽  
Positive Impact ◽  
Neuroprotective Effects ◽  
Drosophila Model ◽  
Exon 1 ◽  
Transgenic Drosophila

Huntington’s disease (HD) is a neurodegenerative disorder caused by an abnormal CAG trinucleotide repeat expansion within exon 1 of the huntingtin (HTT) gene. This mutation leads to the production of mutant HTT (mHTT) protein which triggers neuronal death through several mechanisms. Here, we investigated the neuroprotective effects of esculetin (ESC), a bioactive phenolic compound, in an inducible PC12 model and a transgenic Drosophila melanogaster model of HD, both of which express mHTT fragments. ESC partially inhibited the progression of mHTT aggregation and reduced neuronal death through its ability to counteract the oxidative stress and mitochondria impairment elicited by mHTT in the PC12 model. The ability of ESC to counteract neuronal death was also confirmed in the transgenic Drosophila model. Although ESC did not modify the lifespan of the transgenic Drosophila, it still seemed to have a positive impact on the HD phenotype of this model. Based on our findings, ESC may be further studied as a potential neuroprotective agent in a rodent transgenic model of HD.

scholarly journals Dynein efficiently navigates the dendritic cytoskeleton to drive the retrograde trafficking of BDNF/TrkB signaling endosomes

2017 ◽  
Vol 28 (19) ◽  
pp. 2543-2554 ◽  
Author(s):  
Swathi Ayloo ◽  
Pedro Guedes-Dias ◽  
Amy E. Ghiretti ◽  
Erika L. F. Holzbaur
Keyword(s):  
Real Time ◽  
Axonal Transport ◽  
Hippocampal Neurons ◽  
Cytoplasmic Dynein ◽  
Microtubule Dynamics ◽  
Neuronal Function ◽  
Retrograde Trafficking ◽  
Basic Understanding ◽  
Dependent Transport ◽  
Dynamic Microtubule

The efficient transport of cargoes within axons and dendrites is critical for neuronal function. Although we have a basic understanding of axonal transport, much less is known about transport in dendrites. We used an optogenetic approach to recruit motor proteins to cargo in real time within axons or dendrites in hippocampal neurons. Kinesin-1, a robust axonal motor, moves cargo less efficiently in dendrites. In contrast, cytoplasmic dynein efficiently navigates both axons and dendrites; in both compartments, dynamic microtubule plus ends enhance dynein-dependent transport. To test the predictions of the optogenetic assay, we examined the contribution of dynein to the motility of an endogenous dendritic cargo and found that dynein inhibition eliminates the retrograde bias of BDNF/TrkB trafficking. However, inhibition of microtubule dynamics has no effect on BDNF/TrkB motility, suggesting that dendritic kinesin motors may cooperate with dynein to drive the transport of signaling endosomes into the soma. Collectively our data highlight compartment-specific differences in kinesin activity that likely reflect specialized tuning for localized cytoskeletal determinants, whereas dynein activity is less compartment specific but is more responsive to changes in microtubule dynamics.

scholarly journals Synaptic tau: A pathological or physiological phenomenon?

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Miranda Robbins ◽  
Emma Clayton ◽  
Gabriele S. Kaminski Schierle
Keyword(s):  
Neurofibrillary Tangles ◽  
Declarative Memory ◽  
Synaptic Function ◽  
Current Evidence ◽  
Tau Pathology ◽  
Research Focus ◽  
Synaptic Loss ◽  
Physiological Phenomenon ◽  
Synaptic Pathology

AbstractIn this review, we discuss the synaptic aspects of Tau pathology occurring during Alzheimer’s disease (AD) and how this may relate to memory impairment, a major hallmark of AD. Whilst the clinical diagnosis of AD patients is a loss of working memory and long-term declarative memory, the histological diagnosis is the presence of neurofibrillary tangles of hyperphosphorylated Tau and Amyloid-beta plaques. Tau pathology spreads through synaptically connected neurons to impair synaptic function preceding the formation of neurofibrillary tangles, synaptic loss, axonal retraction and cell death. Alongside synaptic pathology, recent data suggest that Tau has physiological roles in the pre- or post- synaptic compartments. Thus, we have seen a shift in the research focus from Tau as a microtubule-stabilising protein in axons, to Tau as a synaptic protein with roles in accelerating spine formation, dendritic elongation, and in synaptic plasticity coordinating memory pathways. We collate here the myriad of emerging interactions and physiological roles of synaptic Tau, and discuss the current evidence that synaptic Tau contributes to pathology in AD.

Cells of the Nervous System

2017 ◽  
Author(s):  
Peggy Mason
Keyword(s):  
Nervous System ◽  
Axonal Transport ◽  
Information Transfer ◽  
Common Mechanism ◽  
Neuronal Function ◽  
Synaptic Terminals ◽  
System P ◽  
Paraneoplastic Disease ◽  
Mature Neurons ◽  
The Brain

The nervous system is made up of neurons and glia that derive from neuroectoderm. Since neurons are terminally differentiated and do not divide, primary intracranial tumors do not arise from mature neurons. Tumors outside the nervous system may metastasize inside the brain or may release a substance that negatively affects brain function, termed paraneoplastic disease. Neurons receive information through synaptic inputs onto dendrites and soma and send information to other cells via a synaptic terminal. Most neurons send information to faraway locations and for this, an axon that connects the soma to synaptic terminals is required. Glial cells wrap axons in myelin, which speeds up information transfer. Axonal transport is necessary to maintain neuronal function and health across the long distances separating synaptic terminals and somata. A common mechanism of neurodegeneration arises from impairments in axonal transport that lead to protein aggregation and neuronal death.

scholarly journals Electroacupuncture Improves Synaptic Function in SAMP8 Mice Probably via Inhibition of the AMPK/eEF2K/eEF2 Signaling Pathway

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Weiguo Dong ◽  
Wendan Yang ◽  
Feifei Li ◽  
Wanqing Guo ◽  
Changhui Qian ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Elongation Factor ◽  
Synaptic Function ◽  
Control Group ◽  
Synaptic Loss ◽  
Elongation Factor 2 ◽  
Eukaryotic Elongation Factor 2 ◽  
Eukaryotic Elongation Factor ◽  
Samp8 Mice ◽  
Senescence Accelerated Mouse

Synaptic loss and dysfunction is associated with cognitive impairment in Alzheimer’s disease (AD). Recent evidence indicates that the AMP-activated protein kinase (AMPK)/eukaryotic elongation factor-2 kinase (eEF2K)/eukaryotic elongation factor-2 (eEF2) pathway was implicated in synaptic plasticity in AD. Therapeutic strategies for AD treatment are currently limited. Here, we investigate the effects of electroacupuncture (EA) on synaptic function and the AMPK/eEF2K/eEF2 signaling pathway in male senescence-accelerated mouse-prone 8 (SAMP8) mice. Male 7-month-old SAMP8 and SAMR1 mice (senescence-accelerated mouse resistant 1) were randomly divided into 3 groups: SAMR1 control group (Rc), SAMP8 control group (Pc), and SAMP8 electroacupuncture group (Pe). The Pe group was treated with EA for 30 days. Transmission electron microscopy (TEM) was used to observe the structure of synapse. The protein and mRNA expression of synaptophysin (SYN) and postsynaptic density 95 (PSD95) was examined by immunohistochemistry, western blot, and real-time RT-PCR. The activity of AMPK and eEF2K was studied by western blot. Our results showed that EA ameliorated synaptic loss, increased the expression of SYN and PSD95, and inhibited AMPK activation and eEF2K activity. Collectively, these findings suggested that the mechanisms of EA improving synaptic function in AD may be associated with the inhibition of the AMPK/eEF2K/eEF2 signaling pathway.

scholarly journals Brain Death and the Persistent Vegetative State: Similarities and Contrasts

1989 ◽  
Vol 16 (4) ◽  
pp. 388-393 ◽  
Author(s):  
Bryan Young ◽  
Warren Blume ◽  
Abbyann Lynch
Keyword(s):  
Cerebral Cortex ◽  
Brain Death ◽  
Neuronal Death ◽  
Vegetative State ◽  
Persistent Vegetative State ◽  
Neuronal Function ◽  
Medical Support ◽  
Specific Test ◽  
Brainstem Death ◽  
The Brain

ABSTRACT:Brain death and the persistent vegetative state (PVS) share the following features: 1.) There is death of neurons in the brain; 2.) Both require an etiology which is capable of causing neuronal death. 3.) The potential for cognition is totally and permanently lost; 4.) Intensive medical support is usually withdrawn. In contrast, the diagnosis of brain death depends on death of the brainstem, while PVS implies permanent and total loss of forebrain function. While brainstem death can be diagnosed clinically, accurate prognosis in PVS requires additional investigation. Thus far, the EEG is the most specific test of neuronal function in the cerebral cortex. Brain death is equivalent to death, while PVS is not; management of the latter is more complex because of medical, social, ethical and legal factors.

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