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Roos TT, Garcia MG, Martinsson I, Mabrouk R, Israelsson B, Deierborg T, Kobro-Flatmoen A, Tanila H, Gouras GK. Neuronal spreading and plaque induction of intracellular Aβ and its disruption of Aβ homeostasis. Acta Neuropathol 2021; 142:669-687. [PMID: 34272583 PMCID: PMC8423700 DOI: 10.1007/s00401-021-02345-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/18/2021] [Accepted: 07/07/2021] [Indexed: 01/11/2023]
Abstract
The amyloid-beta peptide (Aβ) is thought to have prion-like properties promoting its spread throughout the brain in Alzheimer’s disease (AD). However, the cellular mechanism(s) of this spread remains unclear. Here, we show an important role of intracellular Aβ in its prion-like spread. We demonstrate that an intracellular source of Aβ can induce amyloid plaques in vivo via hippocampal injection. We show that hippocampal injection of mouse AD brain homogenate not only induces plaques, but also damages interneurons and affects intracellular Aβ levels in synaptically connected brain areas, paralleling cellular changes seen in AD. Furthermore, in a primary neuron AD model, exposure of picomolar amounts of brain-derived Aβ leads to an apparent redistribution of Aβ from soma to processes and dystrophic neurites. We also observe that such neuritic dystrophies associate with plaque formation in AD-transgenic mice. Finally, using cellular models, we propose a mechanism for how intracellular accumulation of Aβ disturbs homeostatic control of Aβ levels and can contribute to the up to 10,000-fold increase of Aβ in the AD brain. Our data indicate an essential role for intracellular prion-like Aβ and its synaptic spread in the pathogenesis of AD.
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Affiliation(s)
- Tomas T Roos
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden.
| | - Megg G Garcia
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Isak Martinsson
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Rana Mabrouk
- A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland
| | - Bodil Israelsson
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Tomas Deierborg
- Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | | | - Heikki Tanila
- A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland
| | - Gunnar K Gouras
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden.
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2
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The 'a, b, c's of pretangle tau and their relation to aging and the risk of Alzheimer's Disease. Semin Cell Dev Biol 2021; 116:125-134. [PMID: 33674223 DOI: 10.1016/j.semcdb.2020.12.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/07/2020] [Accepted: 12/21/2020] [Indexed: 12/11/2022]
Abstract
Braak has described the beginnings of Alzheimer's Disease as occurring in the locus coeruleus. Here we review these pretangle stages and relate their expression to recently described normal features of tau biology. We suggest pretangle tau depends on characteristics of locus coeruleus operation that promote tau condensates. We examine the timeline of pretangle and tangle appearance in locus coeruleus. We find catastrophic loss of locus coeruleus neurons is a late event. The strong relationship between locus coeruleus neuron number and human cognition underscores the utility of a focus on locus coeruleus. Promoting locus coeruleus health will benefit normal aging as well as aid in the prevention of dementia. Two animal models offering experimental approaches to understanding the functional change initiated by pretangles in locus coeruleus neurons are discussed.
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Braak H, Del Tredici K. Top-Down Projections Direct the Gradual Progression of Alzheimer-Related Tau Pathology Throughout the Neocortex. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1184:291-303. [PMID: 32096045 DOI: 10.1007/978-981-32-9358-8_22] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In sporadic Alzheimer's disease (sAD), tau pathology gradually but relentlessly progresses from the transentorhinal region of the temporal lobe into both the allocortex and temporal high order association areas of the neocortex. From there, it ultimately reaches the primary sensory and motor fields of the neocortex. The brunt of the changes seen during neurofibrillary stages (NFT) I-VI is borne by top-down projection neurons that contribute to cortico-cortical connectivities between different neocortical fields. Very early changes develop in isolated pyramidal cells in layers III and V, and these cells are targets of top-down projections terminating in association areas of the first temporal gyrus or in peristriate regions of the occipital lobe. Neurofibrillary pathology in these regions is routinely associated with late NFT stages. Sequential changes occur in different cell compartments (dendritic, somatic, axonal) of these early-involved neurons. Tau pathology first develops in distal segments of basal dendrites, then in proximal dendrites, the soma, and, finally, in the axon of affected pyramidal neurons. This sequence of abnormal changes supports the concept that axons of cortico-cortical top-down neurons may carry and spread abnormal tau seeds in a focused manner (transsynaptically) into the distal dendritic segments of nerve cells directly following in the neuronal chain, thereby sustaining tau-seeded templating in sAD.
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Affiliation(s)
- Heiko Braak
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Ulm, Germany
| | - Kelly Del Tredici
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Ulm, Germany.
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Braak H, Del Tredici K. Spreading of Tau Pathology in Sporadic Alzheimer's Disease Along Cortico-cortical Top-Down Connections. Cereb Cortex 2018; 28:3372-3384. [PMID: 29982389 PMCID: PMC6095209 DOI: 10.1093/cercor/bhy152] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 05/11/2018] [Accepted: 06/06/2018] [Indexed: 02/02/2023] Open
Abstract
By using AT8-immunocytochemistry that visualizes hyperphosphorylated tau protein, we examined neurofibrillary changes related to sporadic Alzheimer's disease (AD) in N = 40 individuals at neurofibrillary tangle (NFT) stages I-IV. We report the presence of abnormal tau changes within solitary pyramidal neurons in layers III and V of the neocortex. These pyramidal cells showed pathology in different cell compartments (dendritic, somatic, axonal) that appeared to occur sequentially: Tau pathology was seen in distal segments of the basal dendrites, then in proximal dendrites, the soma, and, finally, in the axon of affected neurons. These findings are remarkable in that they point to the existence of neurofibrillary changes in regions routinely associated with later NFT stages. In addition, they lend support to the idea that it may be the axons of cortico-cortical top-down neurons in neocortical fields involved in AD that carry and spread abnormal tau seeds in a focused manner (transsynaptically) into the distal dendritic segments of nerve cells following directly in the neuronal chain, thereby sustaining further tau-seeded templating.
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Affiliation(s)
- Heiko Braak
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Helmholtzstrasse 8/1, Ulm, Germany
| | - Kelly Del Tredici
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Helmholtzstrasse 8/1, Ulm, Germany
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5
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Schiel KA. A new etiologic model for Alzheimers Disease. Med Hypotheses 2018; 111:27-35. [DOI: 10.1016/j.mehy.2017.12.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 11/19/2017] [Accepted: 12/12/2017] [Indexed: 01/26/2023]
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Eira J, Silva CS, Sousa MM, Liz MA. The cytoskeleton as a novel therapeutic target for old neurodegenerative disorders. Prog Neurobiol 2016; 141:61-82. [PMID: 27095262 DOI: 10.1016/j.pneurobio.2016.04.007] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 04/13/2016] [Accepted: 04/13/2016] [Indexed: 12/12/2022]
Abstract
Cytoskeleton defects, including alterations in microtubule stability, in axonal transport as well as in actin dynamics, have been characterized in several unrelated neurodegenerative conditions. These observations suggest that defects of cytoskeleton organization may be a common feature contributing to neurodegeneration. In line with this hypothesis, drugs targeting the cytoskeleton are currently being tested in animal models and in human clinical trials, showing promising effects. Drugs that modulate microtubule stability, inhibitors of posttranslational modifications of cytoskeletal components, specifically compounds affecting the levels of tubulin acetylation, and compounds targeting signaling molecules which regulate cytoskeleton dynamics, constitute the mostly addressed therapeutic interventions aiming at preventing cytoskeleton damage in neurodegenerative disorders. In this review, we will discuss in a critical perspective the current knowledge on cytoskeleton damage pathways as well as therapeutic strategies designed to revert cytoskeleton-related defects mainly focusing on the following neurodegenerative disorders: Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis and Charcot-Marie-Tooth Disease.
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Affiliation(s)
- Jessica Eira
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal
| | - Catarina Santos Silva
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal
| | - Mónica Mendes Sousa
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal; Nerve Regeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal
| | - Márcia Almeida Liz
- Neurodegeneration Group, IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200 Porto, Portugal.
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Bamburg JR, Bernstein BW. Actin dynamics and cofilin-actin rods in alzheimer disease. Cytoskeleton (Hoboken) 2016; 73:477-97. [PMID: 26873625 DOI: 10.1002/cm.21282] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 12/18/2022]
Abstract
Cytoskeletal abnormalities and synaptic loss, typical of both familial and sporadic Alzheimer disease (AD), are induced by diverse stresses such as neuroinflammation, oxidative stress, and energetic stress, each of which may be initiated or enhanced by proinflammatory cytokines or amyloid-β (Aβ) peptides. Extracellular Aβ-containing plaques and intracellular phospho-tau-containing neurofibrillary tangles are postmortem pathologies required to confirm AD and have been the focus of most studies. However, AD brain, but not normal brain, also have increased levels of cytoplasmic rod-shaped bundles of filaments composed of ADF/cofilin-actin in a 1:1 complex (rods). Cofilin, the major ADF/cofilin isoform in mammalian neurons, severs actin filaments at low cofilin/actin ratios and stabilizes filaments at high cofilin/actin ratios. It binds cooperatively to ADP-actin subunits in F-actin. Cofilin is activated by dephosphorylation and may be oxidized in stressed neurons to form disulfide-linked dimers, required for bundling cofilin-actin filaments into stable rods. Rods form within neurites causing synaptic dysfunction by sequestering cofilin, disrupting normal actin dynamics, blocking transport, and exacerbating mitochondrial membrane potential loss. Aβ and proinflammatory cytokines induce rods through a cellular prion protein-dependent activation of NADPH oxidase and production of reactive oxygen species. Here we review recent advances in our understanding of cofilin biochemistry, rod formation, and the development of cognitive deficits. We will then discuss rod formation as a molecular pathway for synapse loss that may be common between all three prominent current AD hypotheses, thus making rods an attractive therapeutic target. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- James R Bamburg
- Department of Biochemistry and Molecular Biology and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO.
| | - Barbara W Bernstein
- Department of Biochemistry and Molecular Biology and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO
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8
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Sonoda Y, Tooyama I, Mukai H, Maeda K, Akiyama H, Kawamata T. S6 kinase phosphorylated at T229 is involved in tau and actin pathologies in Alzheimer's disease. Neuropathology 2015; 36:325-32. [PMID: 26582459 DOI: 10.1111/neup.12275] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/18/2015] [Accepted: 10/19/2015] [Indexed: 01/15/2023]
Abstract
The 70-kDa ribosomal protein S6 kinase (S6K), a serine/threonine kinase that modulates the phosphorylation of the 40S ribosomal protein S6, regulates cell cycle progression and is known as a tau kinase in Alzheimer's disease (AD). In AD brains, neurofibrillary tangles (NFTs) have been shown to be positively stained with antibodies against S6K proteins phosphorylated at T389 (pT389-S6K) or T421/S424 (pT421/S424-S6K) by the mammalian target of rapamycin and mitogen-activated protein kinase pathways, respectively. However, there is little information available about S6K proteins directly phosphorylated at T229 (pT229-S6K) by the PI3K-PDK1 pathway. In the present study, we investigated the distribution of pT229-S6K in post mortem human brain tissues from elderly (control) and patients with AD using immnunoblotting and immunohistochemistry. pT229-S6K immunoreactivity was localized to small granular structures in neurons and endothelial cells in control and AD brains. In AD brains, intense pT229-S6K immunoreactivity was detected in 16.3% of AT8-positive NFTs, neuropil threads, and dystrophic neurites in the hippocampus and other vulnerable brain areas. In addition, Hirano bodies were also positive for pT229-S6K but were negative for pT389-S6K or pT421/S424-S6K. The present results indicate that S6K phosphorylation via the PI3K-PD1 pathway is involved in tau pathology in NFTs and abnormal neurites as well as actin pathology in Hirano bodies.
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Affiliation(s)
- Yuma Sonoda
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, Kobe, Japan.,Rehabilitation Units, Shiga University of Medical Science, Otsu, Japan
| | - Ikuo Tooyama
- Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Japan
| | | | - Kiyoshi Maeda
- Department of Medical Rehabilitation, Kobe Gakuin University, Kobe, Japan
| | - Haruhiko Akiyama
- Department of Neuropathology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Toshio Kawamata
- Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, Kobe, Japan
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9
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Braak H, Del Tredici K. The preclinical phase of the pathological process underlying sporadic Alzheimer’s disease. Brain 2015; 138:2814-33. [DOI: 10.1093/brain/awv236] [Citation(s) in RCA: 293] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/21/2015] [Indexed: 12/13/2022] Open
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Jacob MS, Duffy CJ. Might cortical hyper-responsiveness in aging contribute to Alzheimer's disease? PLoS One 2014; 9:e105962. [PMID: 25208332 PMCID: PMC4160186 DOI: 10.1371/journal.pone.0105962] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 07/25/2014] [Indexed: 01/23/2023] Open
Abstract
Our goal is to understand the neural basis of functional impairment in aging and Alzheimer's disease (AD) to be able to characterize clinically significant decline and assess therapeutic efficacy. We used frequency-tagged ERPs to word and motion stimuli to study the effects of stimulus conditions and selective attention. ERPs to word or motion increase when a task-irrelevant 2nd stimulus is added, but decrease when the task is moved to that 2nd stimulus. Spectral analyses show task effects on response power without 2nd stimulus effects. However, phase coherence shows both 2nd stimulus and task effects. Thus, power and coherence are dissociably modulated by stimulus and task effects. Task-dependent phase coherence successively declines in aging and AD. In contrast, task-dependent spectral power increases in aging, only to decrease in AD. We hypothesize that age-related declines in signal coherence, associated with increased power generation, stresses neurons and contributes to the loss of response power and the development of functional impairment in AD.
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Affiliation(s)
- Michael S. Jacob
- Department of Neurology and the Center for Visual Science, The University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Psychiatry, The University of California San Francisco Medical Center, San Francisco, California, United States of America
| | - Charles J. Duffy
- Department of Neurology and the Center for Visual Science, The University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
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The Beta-amyloid protein of Alzheimer's disease: communication breakdown by modifying the neuronal cytoskeleton. Int J Alzheimers Dis 2013; 2013:910502. [PMID: 24416616 PMCID: PMC3876695 DOI: 10.1155/2013/910502] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 11/07/2013] [Indexed: 01/28/2023] Open
Abstract
Alzheimer's disease (AD) is one of the most prevalent severe neurological disorders afflicting our aged population. Cognitive decline, a major symptom exhibited by AD patients, is associated with neuritic dystrophy, a degenerative growth state of neurites. The molecular mechanisms governing neuritic dystrophy remain unclear. Mounting evidence indicates that the AD-causative agent, β-amyloid protein (Aβ), induces neuritic dystrophy. Indeed, neuritic dystrophy is commonly found decorating Aβ-rich amyloid plaques (APs) in the AD brain. Furthermore, disruption and degeneration of the neuronal microtubule system in neurons forming dystrophic neurites may occur as a consequence of Aβ-mediated downstream signaling. This review defines potential molecular pathways, which may be modulated subsequent to Aβ-dependent interactions with the neuronal membrane as a consequence of increasing amyloid burden in the brain.
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Paraffin sections of 70-100 μm: a novel technique and its benefits for studying the nervous system. J Neurosci Methods 2013; 215:241-4. [PMID: 23537935 DOI: 10.1016/j.jneumeth.2013.03.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 11/20/2022]
Abstract
This technical communication provides a protocol for processing paraffin-embedded tissue blocks from the nervous system sectioned at 70-100 μm. Staining is performed on free-floating sections. Unlike 4-15 μm thick paraffin sections, this technique permits (1) the accurate recognition of specific cell types and cytoarchitectonic units (subcortical nuclei and cortical layers) and, owing to the superimposition of large numbers of biological structures, (2) the accurate assessment of pathological changes, e.g., those associated with synucleinopathies, tauopathies, and TDP-43 proteinopathies.
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Incorporation of cofilin into rods depends on disulfide intermolecular bonds: implications for actin regulation and neurodegenerative disease. J Neurosci 2012; 32:6670-81. [PMID: 22573689 DOI: 10.1523/jneurosci.6020-11.2012] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Rod-shaped aggregates ("rods"), containing equimolar actin and the actin dynamizing protein cofilin, appear in neurons following a wide variety of potentially oxidative stress: simulated microischemia, cofilin overexpression, and exposure to peroxide, excess glutamate, or the dimer/trimer forms of amyloid-β peptide (Aβd/t), the most synaptotoxic Aβ species. These rods are initially reversible and neuroprotective, but if they persist in neurites, the synapses degenerate without neurons dying. Herein we report evidence that rod formation depends on the generation of intermolecular disulfide bonds in cofilin. Of four Cys-to-Ala cofilin mutations expressed in rat E18 hippocampal neurons, only the mutant incapable of forming intermolecular bonds (CC39,147AA) has significantly reduced ability to incorporate into rods. Rod regions show unusually high oxidation levels. Rods, isolated from stressed neurons, contain dithiothreitol-sensitive multimeric forms of cofilin, predominantly dimer. Oligomerization of cofilin in cells represents one more mechanism for regulating the actin dynamizing activity of cofilin and probably underlies synaptic loss.
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β-Secretases, Alzheimer's Disease, and Down Syndrome. Curr Gerontol Geriatr Res 2012; 2012:362839. [PMID: 22481915 PMCID: PMC3299320 DOI: 10.1155/2012/362839] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 12/05/2011] [Indexed: 01/01/2023] Open
Abstract
Individuals with Down Syndrome (DS), or trisomy 21, develop Alzheimer's disease (AD) pathology by approximately 40 years of age. Chromosome 21 harbors several genes implicated in AD, including the amyloid precursor protein and one homologue of the β-site APP cleaving enzyme, BACE2. Processing of the amyloid precursor protein by β-secretase (BACE) is the rate-limiting step in the production of the pathogenic Aβ peptide. Increased amounts of APP in the DS brain result in increased amounts of Aβ and extracellular plaque formation beginning early in life. BACE dysregulation potentially represents an overlapping biological mechanism with sporadic AD and a common therapeutic target. As the lifespan for those with DS continues to increase, age-related concerns such as obesity, depression, and AD are of growing concern. The ability to prevent or delay the progression of neurodegenerative diseases will promote healthy aging and improve quality of life for those with DS.
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Whiteman IT, Minamide LS, Goh DL, Bamburg JR, Goldsbury C. Rapid changes in phospho-MAP/tau epitopes during neuronal stress: cofilin-actin rods primarily recruit microtubule binding domain epitopes. PLoS One 2011; 6:e20878. [PMID: 21738590 PMCID: PMC3125162 DOI: 10.1371/journal.pone.0020878] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 05/11/2011] [Indexed: 11/18/2022] Open
Abstract
Abnormal mitochondrial function is a widely reported contributor to neurodegenerative disease including Alzheimer's disease (AD), however, a mechanistic link between mitochondrial dysfunction and the initiation of neuropathology remains elusive. In AD, one of the earliest hallmark pathologies is neuropil threads comprising accumulated hyperphosphorylated microtubule-associated protein (MAP) tau in neurites. Rod-like aggregates of actin and its associated protein cofilin (AC rods) also occur in AD. Using a series of antibodies--AT270, AT8, AT100, S214, AT180, 12E8, S396, S404 and S422--raised against different phosphoepitopes on tau, we characterize the pattern of expression and re-distribution in neurites of these phosphoepitope labels during mitochondrial inhibition. Employing chick primary neuron cultures, we demonstrate that epitopes recognized by the monoclonal antibody 12E8, are the only species rapidly recruited into AC rods. These results were recapitulated with the actin depolymerizing drug Latrunculin B, which induces AC rods and a concomitant increase in the 12E8 signal measured on Western blot. This suggests that AC rods may be one way in which MAP redistribution and phosphorylation is influenced in neurons during mitochondrial stress and potentially in the early pathogenesis of AD.
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Affiliation(s)
- Ineka T. Whiteman
- The Brain and Mind Research Institute, University of Sydney, Sydney, Australia
- Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Laurie S. Minamide
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - De Lian Goh
- The Brain and Mind Research Institute, University of Sydney, Sydney, Australia
- Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - James R. Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Claire Goldsbury
- The Brain and Mind Research Institute, University of Sydney, Sydney, Australia
- Bosch Institute, School of Medical Sciences, University of Sydney, Sydney, Australia
- * E-mail:
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Davis RC, Marsden IT, Maloney MT, Minamide LS, Podlisny M, Selkoe DJ, Bamburg JR. Amyloid beta dimers/trimers potently induce cofilin-actin rods that are inhibited by maintaining cofilin-phosphorylation. Mol Neurodegener 2011; 6:10. [PMID: 21261978 PMCID: PMC3037337 DOI: 10.1186/1750-1326-6-10] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 01/24/2011] [Indexed: 11/10/2022] Open
Abstract
Background Previously we reported 1 μM synthetic human amyloid beta1-42 oligomers induced cofilin dephosphorylation (activation) and formation of cofilin-actin rods within rat hippocampal neurons primarily localized to the dentate gyrus. Results Here we demonstrate that a gel filtration fraction of 7PA2 cell-secreted SDS-stable human Aβ dimers and trimers (Aβd/t) induces maximal neuronal rod response at ~250 pM. This is 4,000-fold more active than traditionally prepared human Aβ oligomers, which contain SDS-stable trimers and tetramers, but are devoid of dimers. When incubated under tyrosine oxidizing conditions, synthetic human but not rodent Aβ1-42, the latter lacking tyrosine, acquires a marked increase (620 fold for EC50) in rod-inducing activity. Gel filtration of this preparation yielded two fractions containing SDS-stable dimers, trimers and tetramers. One, eluting at a similar volume to 7PA2 Aβd/t, had maximum activity at ~5 nM, whereas the other, eluting at the void volume (high-n state), lacked rod inducing activity at the same concentration. Fractions from 7PA2 medium containing Aβ monomers are not active, suggesting oxidized SDS-stable Aβ1-42 dimers in a low-n state are the most active rod-inducing species. Aβd/t-induced rods are predominantly localized to the dentate gyrus and mossy fiber tract, reach significance over controls within 2 h of treatment, and are reversible, disappearing by 24 h after Aβd/t washout. Overexpression of cofilin phosphatases increase rod formation when expressed alone and exacerbate rod formation when coupled with Aβd/t, whereas overexpression of a cofilin kinase inhibits Aβd/t-induced rod formation. Conclusions Together these data support a mechanism by which Aβd/t alters the actin cytoskeleton via effects on cofilin in neurons critical to learning and memory.
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Affiliation(s)
- Richard C Davis
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA.
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Davis RC, Maloney MT, Minamide LS, Flynn KC, Stonebraker MA, Bamburg JR. Mapping cofilin-actin rods in stressed hippocampal slices and the role of cdc42 in amyloid-beta-induced rods. J Alzheimers Dis 2010; 18:35-50. [PMID: 19542631 DOI: 10.3233/jad-2009-1122] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dissociated hippocampal neurons exposed to a variety of degenerative stimuli form neuritic cofilin-actin rods. Here we report on stimulus driven regional rod formation in organotypic hippocampal slices. Ultrastructural analysis of rods formed in slices demonstrates mitochondria and vesicles become entrapped within some rods. We developed a template for combining and mapping data from multiple slices, enabling statistical analysis for the identification of vulnerable sub-regions. Amyloid-beta (Abeta) induces rods predominantly in the dentate gyrus region, and Abeta-induced rods are reversible following washout. Rods that persist 24 h following transient (30 min) ATP-depletion are broadly distributed, whereas rods formed in response to excitotoxic glutamate localize within and nearby the pyramidal neurons. Time-lapse imaging of cofilin-GFP-expressing neurons within slices shows neuronal rod formation begins rapidly and peaks by 10 min of anoxia. In approximately 50% of responding neurons, Abeta-induced rod formation acts via cdc42, an upstream regulator of cofilin. These new observations support a role for cofilin-actin rods in stress-induced disruption of cargo transport and synaptic function within hippocampal neurons and suggest both cdc42-dependent and independent pathways modulate cofilin activity downstream from Abeta.
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Affiliation(s)
- Richard C Davis
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.,Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA
| | - Michael T Maloney
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.,Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Laurie S Minamide
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Kevin C Flynn
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.,Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA.,Max Planck Institute of Neurobiology, Martinsreid, Munich, Germany
| | - Matthew A Stonebraker
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - James R Bamburg
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA.,Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA
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Muresan V, Muresan Z. Is abnormal axonal transport a cause, a contributing factor or a consequence of the neuronal pathology in Alzheimer's disease? FUTURE NEUROLOGY 2009; 4:761-773. [PMID: 20076770 DOI: 10.2217/fnl.09.54] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Axonal transport, the process by which membrane-bound organelles and soluble protein complexes are transported into and out of axons, ensures proper function of the neuron, including that of the synapse. As such, abnormalities in axonal transport could lead to neuronal pathology and disease. Similar to many neurodegenerative diseases, axonal transport is deficient in Alzheimer's disease (AD), a neurodegenerative brain disorder that affects old-age humans and is characterized by the deterioration of cognitive function and progressive memory loss. It was proposed that the synaptic pathology and neuronal degeneration that develops in AD could be caused by an abnormal axonal transport, and that the mutated proteins that cause early-onset AD, as well as the genetic variants that confer predisposition to late-onset AD might somehow impede axonal transport. This paper analyzes the data that support or contradict this hypothesis. Together, they indicate that, although abnormalities in axonal transport are part of the disease, additional studies are required to clearly establish to what extent deficient axonal transport is the cause or the effect of the neuronal pathology in AD, and to identify mechanisms that lead to its perturbation.
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Affiliation(s)
- Virgil Muresan
- University of Medicine & Dentistry of New Jersey, New Jersey Medical School, Department of Pharmacology & Physiology, 185 South Orange Avenue, MSB, I-683 Newark, NJ 07103, USA, Tel.: +1 973 972 2392, ,
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19
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Activated actin-depolymerizing factor/cofilin sequesters phosphorylated microtubule-associated protein during the assembly of alzheimer-like neuritic cytoskeletal striations. J Neurosci 2009; 29:12994-3005. [PMID: 19828813 DOI: 10.1523/jneurosci.3531-09.2009] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In Alzheimer's disease (AD), rod-like cofilin aggregates (cofilin-actin rods) and thread-like inclusions containing phosphorylated microtubule-associated protein (pMAP) tau form in the brain (neuropil threads), and the extent of their presence correlates with cognitive decline and disease progression. The assembly mechanism of these respective pathological lesions and the relationship between them is poorly understood, yet vital to understanding the causes of sporadic AD. We demonstrate that, during mitochondrial inhibition, activated actin-depolymerizing factor (ADF)/cofilin assemble into rods along processes of cultured primary neurons that recruit pMAP/tau and mimic neuropil threads. Fluorescence resonance energy transfer analysis revealed colocalization of cofilin-GFP (green fluorescent protein) and pMAP in rods, suggesting their close proximity within a cytoskeletal inclusion complex. The relationship between pMAP and cofilin-actin rods was further investigated using actin-modifying drugs and small interfering RNA knockdown of ADF/cofilin in primary neurons. The results suggest that activation of ADF/cofilin and generation of cofilin-actin rods is required for the subsequent recruitment of pMAP into the inclusions. Additionally, we were able to induce the formation of pMAP-positive ADF/cofilin rods by exposing cells to exogenous amyloid-beta (Abeta) peptides. These results reveal a common pathway for pMAP and cofilin accumulation in neuronal processes. The requirement of activated ADF/cofilin for the sequestration of pMAP suggests that neuropil thread structures in the AD brain may be initiated by elevated cofilin activation and F-actin bundling that can be caused by oxidative stress, mitochondrial dysfunction, or Abeta peptides, all suspected initiators of synaptic loss and neurodegeneration in AD.
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20
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Bamburg JR, Bloom GS. Cytoskeletal pathologies of Alzheimer disease. CELL MOTILITY AND THE CYTOSKELETON 2009; 66:635-49. [PMID: 19479823 PMCID: PMC2754410 DOI: 10.1002/cm.20388] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The histopathological hallmarks of Alzheimer disease are the extracellular amyloid plaques, composed principally of the amyloid beta peptide, and the intracellular neurofibrillary tangles, composed of paired helical filaments of the microtubule-associated protein, tau. Other histopathological structures involving actin and the actin-binding protein, cofilin, have more recently been recognized. Here we review new findings about these cytoskeletal pathologies, and, emphasize how plaques, tangles, the actin-containing inclusions and their respective building blocks may contribute to Alzheimer pathogenesis and the primary behavioral symptoms of the disease. Cell Motil. Cytoskeleton, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- James R Bamburg
- Department of Biochemistry and Molecular Biology, Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, USA.
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21
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Yoon SY, Choi JE, Yoon JH, Huh JW, Kim DH. BACE inhibitor reduces APP-beta-C-terminal fragment accumulation in axonal swellings of okadaic acid-induced neurodegeneration. Neurobiol Dis 2006; 22:435-44. [PMID: 16480887 DOI: 10.1016/j.nbd.2005.12.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 11/15/2005] [Accepted: 12/12/2005] [Indexed: 11/19/2022] Open
Abstract
Emerging evidence suggests that not only beta-amyloid but also other amyloid precursor protein (APP) fragments, such as the beta-C-terminal fragment (betaCTF), might be involved in Alzheimer's disease (AD). Treatment of neurons with okadaic acid (OA), a protein phosphatase-2A inhibitor, has been used to induce tau phosphorylation and neuronal death to create a research model of AD. In this study, we analyzed axonopathy and APP regulation in cultured rat neurons treated with OA. After OA treatment, the neurons presented with axonal swellings filled with vesicles, microtubule fragments, and transport molecules such as kinesin and synapsin-I. Western blotting showed that intracellular APP levels were increased and immunocytochemistry using antibodies against the APP C-terminus showed that APP accumulated in the axonal swellings. This APP C-terminus immunoreactivity disappeared when neurons were cotreated with a beta-secretase inhibitor, but not with alpha- or gamma-secretase inhibitors, indicating that the accumulation was primarily composed of APP-betaCTF. These findings provide the first evidence that APP-betaCTF can accumulate in the axons of OA-treated neurons, and may suggest that APP-betaCTF is involved in the pathogenesis of AD.
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Affiliation(s)
- Seung Yong Yoon
- Department of Anatomy and Cell Biology, University of Ulsan College of Medicine, Seoul, South Korea
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22
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Abstract
Oxidative stress has been implicated in the pathogenesis of a number of human neurodegenerative disorders of the central nervous system (CNS), including Alzheimer's disease (AD). To better understand the pathological effects of oxidative stress on CNS neurons we used a primary human brain cell culture model of hydrogen peroxide-induced oxidative stress. Neuronal and astrocytic morphology was visualised by immunofluorescence with antibodies to the neuron-specific microtubule component beta-tubulin III and against glial fibrillary acidic protein (GFAP), respectively. After exposure to 40 mM H(2)O(2) for 60-90 min, axonal swelling was observed, which developed into axonal beading after 48 h. No beading was observed in GFAP-positive astrocytes. Despite the concentration of H(2)O(2) used, neurons remained attached to the substratum and showed no signs of apoptosis. This was attributed to the neuroprotective effect of the B-27 medium supplement, which contained antioxidants. The axonal swelling and beading was consistent with a disruption of microtubules by oxidative stress and subsequent hold-up of axonal transport.
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Affiliation(s)
- Ben Roediger
- Neuroscience Unit, School of Biological Sciences A08, University of Sydney, 2006, Sydney, NSW, Australia
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23
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Götz J, Chen F, van Dorpe J, Nitsch RM. Formation of neurofibrillary tangles in P301l tau transgenic mice induced by Abeta 42 fibrils. Science 2001; 293:1491-5. [PMID: 11520988 DOI: 10.1126/science.1062097] [Citation(s) in RCA: 1079] [Impact Index Per Article: 46.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
beta-Amyloid plaques and neurofibrillary tangles (NFTs) are the defining neuropathological hallmarks of Alzheimer's disease, but their pathophysiological relation is unclear. Injection of beta-amyloid Abeta42 fibrils into the brains of P301L mutant tau transgenic mice caused fivefold increases in the numbers of NFTs in cell bodies within the amygdala from where neurons project to the injection sites. Gallyas silver impregnation identified NFTs that contained tau phosphorylated at serine 212/threonine 214 and serine 422. NFTs were composed of twisted filaments and occurred in 6-month-old mice as early as 18 days after Abeta42 injections. Our data support the hypothesis that Abeta42 fibrils can accelerate NFT formation in vivo.
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Affiliation(s)
- J Götz
- Division of Psychiatry Research, University of Zürich, August Forel Strasse 1, 8008 Zürich, Switzerland.
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24
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Minamide LS, Striegl AM, Boyle JA, Meberg PJ, Bamburg JR. Neurodegenerative stimuli induce persistent ADF/cofilin-actin rods that disrupt distal neurite function. Nat Cell Biol 2000; 2:628-36. [PMID: 10980704 DOI: 10.1038/35023579] [Citation(s) in RCA: 285] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inclusions containing actin-depolymerizing factor (ADF) and cofilin, abundant proteins in adult human brain, are prominent in hippocampal and cortical neurites of the post-mortem brains of Alzheimer's patients, especially in neurites contacting amyloid deposits. The origin and role of these inclusions in neurodegeneration are, however, unknown. Here we show that mediators of neurodegeneration induce the rapid formation of transient or persistent rod-like inclusions containing ADF/cofilin and actin in axons and dendrites of cultured hippocampal neurons. Rods form spontaneously within neurons overexpressing active ADF/cofilin, suggesting that the activation (by dephosphorylation) of ADF/cofilin that occurs in response to neurodegenerative stimuli is sufficient to induce rod formation. Persistent rods that span the diameter of the neurite disrupt microtubules and cause degeneration of the distal neurite without killing the neuron. These findings suggest a common pathway that can lead to loss of synapses.
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Affiliation(s)
- L S Minamide
- Department of Biochemistry and Molecular Biology, and the Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado 80523-1870, USA
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25
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Hall GF, Chu B, Lee G, Yao J. Human tau filaments induce microtubule and synapse loss in an in vivo model of neurofibrillary degenerative disease. J Cell Sci 2000; 113 ( Pt 8):1373-87. [PMID: 10725221 DOI: 10.1242/jcs.113.8.1373] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The intracellular accumulation of tau protein and its aggregation into filamentous deposits is the intracellular hallmark of neurofibrillary degenerative diseases such as Alzheimer's Disease and familial tauopathies in which tau is now thought to play a critical pathogenic role. Until very recently, the lack of a cellular model in which human tau filaments can be experimentally generated has prevented direct investigation of the causes and consequences of tau filament formation in vivo. In this study, we show that human tau filaments formed in lamprey central neurons (ABCs) that chronically overexpress human tau resemble the ‘straight filaments’ seen in Alzheimer's Disease and other neurofibrillary conditions, and are distinguishable from neurofilaments by their ultrastructure, distribution and intracellular behavior. We also show that tau filament formation in ABCs is associated with a distinctive pattern of dendritic degeneration that closely resembles the cytopathology of human neurofibrillary degenerative disease. This pattern includes localized cytoskeletal disruption and aggregation of membranous organelles, distal dendritic beading, and the progressive loss of dendritic microtubules and synapses. These results suggest that tau filament formation may be responsible for many key cytopathological features of neurofibrillary degeneration, possibly via the loss of microtubule based intracellular transport.
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Affiliation(s)
- G F Hall
- Department of Biological Sciences, University of Massachusetts, Lowell, Massachusetts 01854, USA.
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