1
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Devarakonda SS, Basha S, Pithakumar A, L B T, Mukunda DC, Rodrigues J, K A, Biswas S, Pai AR, Belurkar S, Mahato KK. Molecular mechanisms of neurofilament alterations and its application in assessing neurodegenerative disorders. Ageing Res Rev 2024; 102:102566. [PMID: 39481763 DOI: 10.1016/j.arr.2024.102566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2024] [Revised: 10/04/2024] [Accepted: 10/24/2024] [Indexed: 11/02/2024]
Abstract
Neurofilaments are intermediate filaments present in neurons. These provide structural support and maintain the size and shape of the neurons. Dysregulation, mutation, and aggregation of neurofilaments raise the levels of these proteins in the blood and cerebrospinal fluid (CSF), which are characteristic features of axonal damage and certain rare neurological diseases, such as Giant Axonal Neuropathy and Charcot-Mare-Tooth disease. Understanding the structure, dynamics, and function of neurofilaments has been greatly enhanced by a diverse range of biochemical and preclinical investigations conducted over more than four decades. Recently, there has been a resurgence of interest in post-translational modifications of neurofilaments, such as phosphorylation, aggregation, mutation, oxidation, etc. Over the past twenty years, several rare disorders have been studied from structural alterations of neurofilaments. These disorders are monitored by fluid biomarkers such as neurofilament light chains. Currently, there are many tools, such as Enzyme-Linked Immunosorbent Assay, Electrochemiluminescence Assay, Single-Molecule Array, Western/immunoblotting, etc., in use to assess the neurofilament proteins in Blood and CSF. However, all these techniques utilize expensive, non-specific, or antibody-based methods, which make them unsuitable for routine screening of neurodegenerative disorders. This provides room to search for newer sensitive, cost-effective, point-of-care tools for rapid screening of the disease. For a long time, the molecular mechanisms of neurofilaments have been poorly understood due to insufficient research attempts, and a deeper understanding of them remains elusive. Therefore, this review aims to highlight the available literature on molecular mechanisms of neurofilaments and the function of neurofilaments in axonal transport, axonal conduction, axonal growth, and neurofilament aggregation, respectively. Further, this review discusses the role of neurofilaments as potential biomarkers for the identification of several neurodegenerative diseases in clinical laboratory practice.
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Affiliation(s)
| | - Shaik Basha
- Department of Biophysics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Anjana Pithakumar
- Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Thoshna L B
- Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | | | - Jackson Rodrigues
- Department of Biophysics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Ameera K
- Department of Biophysics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Shimul Biswas
- Department of Biophysics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Aparna Ramakrishna Pai
- Department of Neurology, Kasturba Medical College-Manipal, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Sushma Belurkar
- Department of Pathology, Kasturba Medical College-Manipal, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India
| | - Krishna Kishore Mahato
- Department of Biophysics, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal - 576104, Karnataka, India.
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2
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Abstract
Aβ plaques are one of the two lesions in the brain that define the neuropathological diagnosis of Alzheimer's disease. Plaques are highly diverse structures; many of them include massed, fibrillar polymers of the Aβ protein referred to as Aβ-amyloid, but some lack the defining features of amyloid. Cellular elements in 'classical' plaques include abnormal neuronal processes and reactive glial cells, but these are not present in all plaques. Plaques have been given various names since their discovery in 1892, including senile plaques, amyloid plaques, and neuritic plaques. However, with the identification in the 1980s of Aβ as the obligatory and universal component of plaques, the term 'Aβ plaques' has become a unifying term for these heterogeneous formations. Tauopathy, the second essential lesion of the Alzheimer's disease diagnostic dyad, is downstream of Aβ-proteopathy, but it is critically important for the manifestation of dementia. The etiologic link between Aβ-proteopathy and tauopathy in Alzheimer's disease remains largely undefined. Aβ plaques develop and propagate via the misfolding, self-assembly and spread of Aβ by the prion-like mechanism of seeded protein aggregation. Partially overlapping sets of risk factors and sequelae, including inflammation, genetic variations, and various environmental triggers have been linked to plaque development and idiopathic Alzheimer's disease, but no single factor has emerged as a requisite cause. The value of Aβ plaques per se as therapeutic targets is uncertain; although some plaques are sites of focal gliosis and inflammation, the complexity of inflammatory biology presents challenges to glia-directed intervention. Small, soluble, oligomeric assemblies of Aβ are enriched in the vicinity of plaques, and these probably contribute to the toxic impact of Aβ aggregation on the brain. Measures designed to reduce the production or seeded self-assembly of Aβ can impede the formation of Aβ plaques and oligomers, along with their accompanying abnormalities; given the apparent long timecourse of the emergence, maturation and proliferation of Aβ plaques in humans, such therapies are likely to be most effective when begun early in the pathogenic process, before significant damage has been done to the brain. Since their discovery in the late 19th century, Aβ plaques have, time and again, illuminated fundamental mechanisms driving neurodegeneration, and they should remain at the forefront of efforts to understand, and therefore treat, Alzheimer's disease.
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Affiliation(s)
- Lary C. Walker
- Department of Neurology and Yerkes National Primate Research Center, Emory University
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3
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Li D, Cho YK. High specificity of widely used phospho-tau antibodies validated using a quantitative whole-cell based assay. J Neurochem 2019; 152:122-135. [PMID: 31325178 DOI: 10.1111/jnc.14830] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 06/25/2019] [Accepted: 07/11/2019] [Indexed: 02/04/2023]
Abstract
Antibodies raised against defined phosphorylation sites of the microtubule-associated protein tau are widely used in scientific research and being applied in clinical assays. However, recent studies have revealed an alarming degree of non-specific binding found in these antibodies. In order to quantify and compare the specificity phospho-tau antibodies and other post-translational modification site-specific antibodies in general, a measure of specificity is urgently needed. Here, we report a robust flow cytometry assay using human embryonic kidney cells that enables the determination of a specificity parameter termed Φ, which measures the fraction of non-specific signal in antibody binding. We validate our assay using anti-tau antibodies with known specificity profiles, and apply it to measure the specificity of seven widely used phospho-tau antibodies (AT270, AT8, AT100, AT180, PHF-6, TG-3, and PHF-1) among others. We successfully determined the Φ values for all antibodies except AT100, which did not show detectable binding in our assay. Our results show that antibodies AT8, AT180, PHF-6, TG-3, and PHF-1 have Φ values near 1, which indicates no detectable non-specific binding. AT270 showed Φ value around 0.8, meaning that approximately 20% of the binding signal originates from non-specific binding. Further analyses using immunocytochemistry and western blotting confirmed the presence of non-specific binding of AT270 to non-tau proteins found in human embryonic kidney cells and the mouse hippocampus. We anticipate that the quantitative approach and parameter introduced here will be widely adopted as a standard for reporting the specificity for phospho-tau antibodies, and potentially for post-translational modification targeting antibodies in general. Cover Image for this issue: doi: 10.1111/jnc.14727.
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Affiliation(s)
- Dan Li
- Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut, USA
| | - Yong Ku Cho
- Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut, USA.,Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, USA.,Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, USA.,Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, Connecticut, USA
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4
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Li D, Cho YK. High specificity of widely used phospho-tau antibodies validated using a quantitative whole-cell based assay. J Neurochem 2019. [PMID: 31325178 DOI: 10.1111/jnc.14727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Antibodies raised against defined phosphorylation sites of the microtubule-associated protein tau are widely used in scientific research and being applied in clinical assays. However, recent studies have revealed an alarming degree of non-specific binding found in these antibodies. In order to quantify and compare the specificity phospho-tau antibodies and other post-translational modification site-specific antibodies in general, a measure of specificity is urgently needed. Here, we report a robust flow cytometry assay using human embryonic kidney cells that enables the determination of a specificity parameter termed Φ, which measures the fraction of non-specific signal in antibody binding. We validate our assay using anti-tau antibodies with known specificity profiles, and apply it to measure the specificity of seven widely used phospho-tau antibodies (AT270, AT8, AT100, AT180, PHF-6, TG-3, and PHF-1) among others. We successfully determined the Φ values for all antibodies except AT100, which did not show detectable binding in our assay. Our results show that antibodies AT8, AT180, PHF-6, TG-3, and PHF-1 have Φ values near 1, which indicates no detectable non-specific binding. AT270 showed Φ value around 0.8, meaning that approximately 20% of the binding signal originates from non-specific binding. Further analyses using immunocytochemistry and western blotting confirmed the presence of non-specific binding of AT270 to non-tau proteins found in human embryonic kidney cells and the mouse hippocampus. We anticipate that the quantitative approach and parameter introduced here will be widely adopted as a standard for reporting the specificity for phospho-tau antibodies, and potentially for post-translational modification targeting antibodies in general. Cover Image for this issue: doi: 10.1111/jnc.14727.
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Affiliation(s)
- Dan Li
- Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut, USA
| | - Yong Ku Cho
- Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut, USA.,Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, USA.,Institute for Systems Genomics, University of Connecticut, Storrs, Connecticut, USA.,Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, Connecticut, USA
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5
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Didonna A, Opal P. The role of neurofilament aggregation in neurodegeneration: lessons from rare inherited neurological disorders. Mol Neurodegener 2019; 14:19. [PMID: 31097008 PMCID: PMC6524292 DOI: 10.1186/s13024-019-0318-4] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 04/26/2019] [Indexed: 12/13/2022] Open
Abstract
Many neurodegenerative disorders, including Parkinson's, Alzheimer's, and amyotrophic lateral sclerosis, are well known to involve the accumulation of disease-specific proteins. Less well known are the accumulations of another set of proteins, neuronal intermediate filaments (NFs), which have been observed in these diseases for decades. NFs belong to the family of cytoskeletal intermediate filament proteins (IFs) that give cells their shape; they determine axonal caliber, which controls signal conduction; and they regulate the transport of synaptic vesicles and modulate synaptic plasticity by binding to neurotransmitter receptors. In the last two decades, a number of rare disorders caused by mutations in genes that encode NFs or regulate their metabolism have been discovered. These less prevalent disorders are providing novel insights into the role of NF aggregation in the more common neurological disorders.
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Affiliation(s)
- Alessandro Didonna
- Department of Neurology and Weill Institute for Neurosciences, University of California at San Francisco, San Francisco, CA, 94158, USA
| | - Puneet Opal
- Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA. .,Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, 60611, USA.
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6
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Phosphorylation of different tau sites during progression of Alzheimer's disease. Acta Neuropathol Commun 2018; 6:52. [PMID: 29958544 PMCID: PMC6027763 DOI: 10.1186/s40478-018-0557-6] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 06/19/2018] [Indexed: 11/21/2022] Open
Abstract
Alzheimer’s disease is characterized by accumulation of amyloid plaques and tau aggregates in several cortical brain regions. Tau phosphorylation causes formation of neurofibrillary tangles and neuropil threads. Phosphorylation at tau Ser202/Thr205 is well characterized since labeling of this site is used to assign Braak stage based on occurrence of neurofibrillary tangles. Only little is known about the spatial and temporal phosphorylation profile of other phosphorylated tau (ptau) sites. Here, we investigate total tau and ptau at residues Tyr18, Ser199, Ser202/Thr205, Thr231, Ser262, Ser396, Ser422 as well as amyloid-β plaques in human brain tissue of AD patients and controls. Allo- and isocortical brain regions were evaluated applying rater-independent automated quantification based on digital image analysis. We found that the level of ptau at several residues, like Ser199, Ser202/Thr205, and Ser422 was similar in healthy controls and Braak stages I to IV but was increased in Braak stage V/VI throughout the entire isocortex and transentorhinal cortex. Quantification of ThioS-stained plaques showed a similar pattern. Only tau phosphorylation at Tyr18 and Thr231 was already significantly increased in the transentorhinal region at Braak stage III/IV and hence showed a progressive increase with increasing Braak stages. Additionally, the increase in phosphorylation relative to controls was highest at Tyr18, Thr231 and Ser199. By contrast, Ser396 tau and Ser262 tau showed only a weak phosphorylation in all analyzed brain regions and only minor progression. Our results suggest that the ptau burden in the isocortex is comparable between all analyzed ptau sites when using a quantitative approach while levels of ptau at Tyr18 or Thr231 in the transentorhinal region are different between all Braak stages. Hence these sites could be crucial in the pathogenesis of AD already at early stages and therefore represent putative novel therapeutic targets.
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Gorantla NV, Shkumatov AV, Chinnathambi S. Conformational Dynamics of Intracellular Tau Protein Revealed by CD and SAXS. Methods Mol Biol 2017; 1523:3-20. [PMID: 27975241 DOI: 10.1007/978-1-4939-6598-4_1] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A native conformation of a protein is essential for its biological role. In certain conditions, some proteins show non-native conformations, leading to aggregation, which in turn may produce severe pathologies. Such physiological conditions are classified as protein misfolding diseases. Alzheimer's disease (AD) is the most common form of dementia. Extracellular senile plaques formed by Amyloid β and intracellular aggregates formed by microtubule-associated protein Tau (MAPT) are the hallmarks of AD. Physiological role of MAPT is to maintain the integrity and stability of microtubules, however it tends to self-aggregate forming intracellular paired helical filaments (PHFs) during AD. MAPT is also subjected to various post-translational modifications such as phosphorylation, glycosylation, truncation, and acetylation. Being natively unfolded, MAPT is prone to full characterization at atomic level. Small-angle X-ray scattering (SAXS) is often applied in combination with other biophysical methods, like nuclear magnetic resonance (NMR), circular dichroism (CD), fluorescence spectroscopy, analytical ultracentrifugation (AUC), or dynamic light scattering (DLS) to characterize natively unfolded systems. Here we describe the practical aspects of MAPT characterization by SAXS and CD in detail as well as outline the inferred structural and functional implications.
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Affiliation(s)
- Nalini Vijay Gorantla
- Neurobiology Group, Division of Biochemical Sciences, National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, 411008, Pune, Maharashtra, India.,Academy of Scientific and Innovative Research (AcSIR), 10025, New Delhi, India
| | | | - Subashchandrabose Chinnathambi
- Neurobiology Group, Division of Biochemical Sciences, National Chemical Laboratory (CSIR-NCL), Dr. Homi Bhabha Road, 411008, Pune, Maharashtra, India. .,Academy of Scientific and Innovative Research (AcSIR), 10025, New Delhi, India.
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8
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Qi H, Prabakaran S, Cantrelle FX, Chambraud B, Gunawardena J, Lippens G, Landrieu I. Characterization of Neuronal Tau Protein as a Target of Extracellular Signal-regulated Kinase. J Biol Chem 2016; 291:7742-53. [PMID: 26858248 DOI: 10.1074/jbc.m115.700914] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Indexed: 01/16/2023] Open
Abstract
Tau neuronal protein has a central role in neurodegeneration and is implicated in Alzheimer disease development. Abnormal phosphorylation of Tau impairs its interaction with other proteins and is associated with its dysregulation in pathological conditions. Molecular mechanisms leading to hyperphosphorylation of Tau in pathological conditions are unknown. Here, we characterize phosphorylation of Tau by extracellular-regulated kinase (ERK2), a mitogen-activated kinase (MAPK) that responds to extracellular signals. Analysis ofin vitrophosphorylated Tau by activated recombinant ERK2 with nuclear magnetic resonance spectroscopy (NMR) reveals phosphorylation of 15 Ser/Thr sites.In vitrophosphorylation of Tau using rat brain extract and subsequent NMR analysis identifies the same sites. Phosphorylation with rat brain extract is known to transform Tau into an Alzheimer disease-like state. Our results indicate that phosphorylation of Tau by ERK2 alone is sufficient to produce the same characteristics. We further investigate the mechanism of ERK2 phosphorylation of Tau. Kinases are known to recognize their protein substrates not only by their specificity for a targeted Ser or Thr phosphorylation site but also by binding to linear-peptide motifs called docking sites. We identify two main ERK2 docking sites in Tau sequence using NMR. Our results suggest that ERK2 dysregulation in Alzheimer disease could lead to abnormal phosphorylation of Tau resulting in the pathology of the disease.
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Affiliation(s)
- Haoling Qi
- From Lille University, CNRS UMR8576, F-59000 Lille, France
| | - Sudhakaran Prabakaran
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, and
| | | | | | - Jeremy Gunawardena
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, and
| | - Guy Lippens
- From Lille University, CNRS UMR8576, F-59000 Lille, France
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9
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Goto H, Tanaka H, Kasahara K, Inagaki M. Phospho-Specific Antibody Probes of Intermediate Filament Proteins. Methods Enzymol 2016; 568:85-111. [DOI: 10.1016/bs.mie.2015.07.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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10
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Du LY, Chang LYL, Ardiles AO, Tapia-Rojas C, Araya J, Inestrosa NC, Palacios AG, Acosta ML. Alzheimer's Disease-Related Protein Expression in the Retina of Octodon degus. PLoS One 2015; 10:e0135499. [PMID: 26267479 PMCID: PMC4534194 DOI: 10.1371/journal.pone.0135499] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 07/22/2015] [Indexed: 01/06/2023] Open
Abstract
New studies show that the retina also undergoes pathological changes during the development of Alzheimer's disease (AD). While transgenic mouse models used in these previous studies have offered insight into this phenomenon, they do not model human sporadic AD, which is the most common form. Recently, the Octodon degus has been established as a sporadic model of AD. Degus display age-related cognitive impairment associated with Aβ aggregates and phosphorylated tau in the brain. Our aim for this study was to examine the expression of AD-related proteins in young, adult and old degus retina using enzyme-linked or fluorescence immunohistochemistry and to quantify the expression using slot blot and western blot assays. Aβ4G8 and Aβ6E10 detected Aβ peptides in some of the young animals but the expression was higher in the adults. Aβ peptides were observed in the inner and outer segment of the photoreceptors, the nerve fiber layer (NFL) and ganglion cell layer (GCL). Expression was higher in the central retinal region than in the retinal periphery. Using an anti-oligomer antibody we detected Aβ oligomer expression in the young, adult and old retina. Immunohistochemical labeling showed small discrete labeling of oligomers in the GCL that did not resemble plaques. Congo red staining did not result in green birefringence in any of the animals analyzed except for one old (84 months) animal. We also investigated expression of tau and phosphorylated tau. Expression was seen at all ages studied and in adults it was more consistently observed in the NFL-GCL. Hyperphosphorylated tau detected with AT8 antibody was significantly higher in the adult retina and it was localized to the GCL. We confirm for the first time that Aβ peptides and phosphorylated tau are expressed in the retina of degus. This is consistent with the proposal that AD biomarkers are present in the eye.
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Affiliation(s)
- Lucia Y. Du
- School of Optometry and Vision Science, The University of Auckland, Auckland, New Zealand
| | - Lily Y-L. Chang
- School of Optometry and Vision Science, The University of Auckland, Auckland, New Zealand
| | - Alvaro O. Ardiles
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Cheril Tapia-Rojas
- Center for Aging and Regeneration (CARE), Department of Cell and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Joaquin Araya
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Nibaldo C. Inestrosa
- Center for Aging and Regeneration (CARE), Department of Cell and Molecular Biology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Adrian G. Palacios
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Monica L. Acosta
- School of Optometry and Vision Science, The University of Auckland, Auckland, New Zealand
- New Zealand National Eye Centre, The University of Auckland, Auckland, New Zealand
- * E-mail:
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11
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Kimura T, Ishiguro K, Hisanaga SI. Physiological and pathological phosphorylation of tau by Cdk5. Front Mol Neurosci 2014; 7:65. [PMID: 25076872 PMCID: PMC4097945 DOI: 10.3389/fnmol.2014.00065] [Citation(s) in RCA: 181] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 06/26/2014] [Indexed: 11/13/2022] Open
Abstract
Hyperphosphorylation of microtubule-associated protein tau is one of the major pathological events in Alzheimer’s disease (AD) and other related neurodegenerative diseases, including frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17). Mutations in the tau gene MAPT are a cause of FTDP-17, and the mutated tau proteins are hyperphosphorylated in patient brains. Thus, it is important to determine the molecular mechanism of hyperphosphorylation of tau to understand the pathology of these diseases collectively called tauopathy. Tau is phosphorylated at many sites via several protein kinases, and a characteristic is phosphorylation at Ser/Thr residues in Ser/Thr-Pro sequences, which are targeted by proline-directed protein kinases such as ERK, GSK3β, and Cdk5. Among these kinases, Cdk5 is particularly interesting because it could be abnormally activated in AD. Cdk5 is a member of the cyclin-dependent kinases (Cdks), but in contrast to the major Cdks, which promote cell cycle progression in proliferating cells, Cdk5 is activated in post-mitotic neurons via the neuron-specific activator p35. Cdk5-p35 plays a critical role in brain development and physiological synaptic activity. In contrast, in disease brains, Cdk5 is thought to be hyperactivated by p25, which is the N-terminal truncated form of p35 and is generated by cleavage with calpain. Several reports have indicated that tau is hyperphosphorylated by Cdk5-p25. However, normal and abnormal phosphorylation of tau by Cdk5 is still not completely understood. In this article, we summarize the physiological and pathological phosphorylation of tau via Cdk5.
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Affiliation(s)
- Taeko Kimura
- Laboratory of Molecular Neuroscience, Department of Biological Sciences, Tokyo Metropolitan University Hachioji, Japan
| | - Koichi Ishiguro
- Department of Neurology, Graduate School of Medicine, Juntendo University Bunkyo, Japan
| | - Shin-Ichi Hisanaga
- Laboratory of Molecular Neuroscience, Department of Biological Sciences, Tokyo Metropolitan University Hachioji, Japan
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C-terminal region of MAP7 domain containing protein 3 (MAP7D3) promotes microtubule polymerization by binding at the C-terminal tail of tubulin. PLoS One 2014; 9:e99539. [PMID: 24927501 PMCID: PMC4057234 DOI: 10.1371/journal.pone.0099539] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 05/16/2014] [Indexed: 12/24/2022] Open
Abstract
MAP7 domain containing protein 3 (MAP7D3), a newly identified microtubule associated protein, has been shown to promote microtubule assembly and stability. Its microtubule binding region has been reported to consist of two coiled coil motifs located at the N-terminus. It possesses a MAP7 domain near the C-terminus and belongs to the microtubule associated protein 7 (MAP7) family. The MAP7 domain of MAP7 protein has been shown to bind to kinesin-1; however, the role of MAP7 domain in MAP7D3 remains unknown. Based on the bioinformatics analysis of MAP7D3, we hypothesized that the MAP7 domain of MAP7D3 may have microtubule binding activity. Indeed, we found that MAP7 domain of MAP7D3 bound to microtubules as well as enhanced the assembly of microtubules in vitro. Interestingly, a longer fragment MDCT that contained the MAP7 domain (MD) with the C-terminal tail (CT) of the protein promoted microtubule polymerization to a greater extent than MD and CT individually. MDCT stabilized microtubules against dilution induced disassembly. MDCT bound to reconstituted microtubules with an apparent dissociation constant of 3.0±0.5 µM. An immunostaining experiment showed that MDCT localized along the length of the preassembled microtubules. Competition experiments with tau indicated that MDCT shares its binding site on microtubules with tau. Further, we present evidence indicating that MDCT binds to the C-terminal tail of tubulin. In addition, MDCT could bind to tubulin in HeLa cell extract. Here, we report a microtubule binding region in the C-terminal region of MAP7D3 that may have a role in regulating microtubule assembly dynamics.
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Crutcher KA, Anderton BH, Barger SW, Ohm TG, Snow AD. Cellular and molecular pathology in alzheimer's disease. Hippocampus 2013. [DOI: 10.1002/hipo.1993.4500030730] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Keith A. Crutcher
- Department of Neurosurgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, U.S.A
| | | | - Steven W. Barger
- Department of Anatomy and Neurobiology, University of Kentucky Medical Center, Lexington, Kentucky, U.S.A
| | - Thomas G. Ohm
- Zentrum der Morphologie, J. W. Goethe‐Universität, Frankfurt, Germany
| | - Alan D. Snow
- Department of Neuropathology, University of Washington, Seattle, Washington, U.S.A
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14
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Affiliation(s)
- Brian H. Anderton
- Department of Neuroscience, Institute of Psychiatry, University of London, London, U.K
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15
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Mandelkow EM, Mandelkow E. Biochemistry and cell biology of tau protein in neurofibrillary degeneration. Cold Spring Harb Perspect Med 2013; 2:a006247. [PMID: 22762014 DOI: 10.1101/cshperspect.a006247] [Citation(s) in RCA: 549] [Impact Index Per Article: 45.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Tau represents the subunit protein of one of the major hallmarks of Alzheimer disease (AD), the neurofibrillary tangles, and is therefore of major interest as an indicator of disease mechanisms. Many of the unusual properties of Tau can be explained by its nature as a natively unfolded protein. Examples are the large number of structural conformations and biochemical modifications (phosphorylation, proteolysis, glycosylation, and others), the multitude of interaction partners (mainly microtubules, but also other cytoskeletal proteins, kinases, and phosphatases, motor proteins, chaperones, and membrane proteins). The pathological aggregation of Tau is counterintuitive, given its high solubility, but can be rationalized by short hydrophobic motifs forming β structures. The aggregation of Tau is toxic in cell and animal models, but can be reversed by suppressing expression or by aggregation inhibitors. This review summarizes some of the structural, biochemical, and cell biological properties of Tau and Tau fibers. Further aspects of Tau as a diagnostic marker and therapeutic target, its involvement in other Tau-based diseases, and its histopathology are covered by other chapters in this volume.
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Affiliation(s)
- Eva-Maria Mandelkow
- Max-Planck Unit for Structural Molecular Biology, c/o DESY, 22607 Hamburg, Germany; DZNE, German Center for Neurodegenerative Diseases, and CAESAR Research Center, 53175 Bonn, Germany.
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16
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Shukla V, Zheng YL, Mishra SK, Amin ND, Steiner J, Grant P, Kesavapany S, Pant HC. A truncated peptide from p35, a Cdk5 activator, prevents Alzheimer's disease phenotypes in model mice. FASEB J 2012; 27:174-86. [PMID: 23038754 DOI: 10.1096/fj.12-217497] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Alzheimer's disease (AD), one of the leading neurodegenerative disorders of older adults, which causes major socioeconomic burdens globally, lacks effective therapeutics without significant side effects. Besides the hallmark pathology of amyloid plaques and neurofibrillary tangles (NFTs), it has been reported that cyclin-dependent kinase 5 (Cdk5), a critical neuronal kinase, is hyperactivated in AD brains and is, in part, responsible for the above pathology. Here we show that a modified truncated 24-aa peptide (TFP5), derived from the Cdk5 activator p35, penetrates the blood-brain barrier after intraperitoneal injections, inhibits abnormal Cdk5 hyperactivity, and significantly rescues AD pathology (up to 70-80%) in 5XFAD AD model mice. The mutant mice, injected with TFP5 exhibit behavioral rescue, whereas no rescue was observed in mutant mice injected with either saline or scrambled peptide. However, TFP5 does not inhibit cell cycle Cdks or normal Cdk5/p35 activity, and thereby has no toxic side effects (even at 200 mg/kg), a common problem in most current therapeutics for AD. In addition, treated mice displayed decreased inflammation, amyloid plaques, NFTs, cell death, and an extended life by 2 mo. These results suggest TFP5 as a potential therapeutic, toxicity-free candidate for AD.
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Affiliation(s)
- Varsha Shukla
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
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17
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Jeganathan S, Chinnathambi S, Mandelkow EM, Mandelkow E. Conformations of microtubule-associated protein Tau mapped by fluorescence resonance energy transfer. Methods Mol Biol 2012; 849:85-99. [PMID: 22528085 DOI: 10.1007/978-1-61779-551-0_7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
The microtubule-associated protein Tau plays a physiological role of stabilizing neuronal microtubules by binding to their lateral surface. Tau belongs to the category of natively unfolded protein as it shows typical features of random coil, as analyzed by various biophysical techniques. In cells, it is subjected to several posttranslational modifications (e.g., phosphorylation, cleavage, ubiquitination, and glycosylation). In neurodegenerative diseases, Tau forms insoluble aggregates called paired helical filaments (PHFs). We have applied fluorescence resonance energy transfer (FRET) to examine the conformations of soluble Tau. We created a series of Tau mutants, each carrying one tryptophan and one cysteine (labeled by IEADANS). This made it possible to measure the distance between these FRET pairs placed in different domains of Tau. This approach enables one to analyze the global folding of soluble Tau and its alteration upon phosphorylation and denaturation.
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18
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Novel diffusion barrier for axonal retention of Tau in neurons and its failure in neurodegeneration. EMBO J 2011; 30:4825-37. [PMID: 22009197 DOI: 10.1038/emboj.2011.376] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 09/21/2011] [Indexed: 12/12/2022] Open
Abstract
Missorting of Tau from axons to the somatodendritic compartment of neurons is a hallmark of Alzheimer's disease, but the mechanisms underlying normal sorting and pathological failure are poorly understood. Here, we used several Tau constructs labelled with photoconvertible Dendra2 to analyse its mobility in polarized neurons. This revealed a novel mechanism of sorting-a retrograde barrier in the axon initial segment (AIS) operating as cellular rectifier. It allows anterograde flow of axonal Tau but prevents retrograde flow back into soma and dendrites. The barrier requires binding of Tau to microtubules but does not require F-actin and thus is distinct from the sorting of membrane-associated proteins at the AIS. The barrier breaks down when Tau is phosphorylated in its repeat domain and detached from microtubules, for example, by the kinase MARK/Par1. These observations link the pathological hallmarks of Tau missorting and hyperphosphorylation in neurodegenerative diseases.
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19
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García-Sierra F, Jarero-Basulto JJ, Kristofikova Z, Majer E, Binder LI, Ripova D. Ubiquitin is associated with early truncation of tau protein at aspartic acid(421) during the maturation of neurofibrillary tangles in Alzheimer's disease. Brain Pathol 2011; 22:240-50. [PMID: 21919991 DOI: 10.1111/j.1750-3639.2011.00525.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Pathological processing of tau protein during the formation and maturation of neurofibrillary tangles (NFTs) includes abnormal phosphorylation, conformational changes and truncation of the C-terminus at aspartic-acid(421) (apoptotic product) and glutamic-acid(391) residues. Abnormal phosphorylation and misfolding may serve as recognition signals for ubiquitin-targeting and proteosomal processing. For this reason, we sought to determine whether ubiquitin-targeting of tau is associated with particular tau modifications that herald specific stages of NFTs maturation in the hippocampus of Alzheimer's disease cases. Using multiple tau antibodies, we found that 30% of the total load of NFTs is ubiquitin-associated. As reported previously ubiquitin immunoreactivity was associated with markers of phosphorylated tau in certain NFTs; however, a strong association was also found between ubiquitin and the earliest known truncation event at aspartic-acid(421) . These findings indicate that tau protein in the NFTs may be dually subjected to both apoptotic and proteosomal processing. By contrast ubiquitin immunoreactivity was poorly associated with truncation of tau at glutamic-acid(391) , suggesting that this proteolytic event may be independent of proteosomal activity. It would appear, therefore, that ubiquitin targeting of tau protein occurs at NFTs in the early and intermediate stages of the maturation.
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Affiliation(s)
- Francisco García-Sierra
- Department of Cell Biology, Center of Research and Advanced Studies of the National Polytechnic Institute, Mexico City, Mexico.
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20
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Rojo LE, Alzate-Morales J, Saavedra IN, Davies P, Maccioni RB. Selective interaction of lansoprazole and astemizole with tau polymers: potential new clinical use in diagnosis of Alzheimer's disease. J Alzheimers Dis 2010; 19:573-89. [PMID: 20110603 DOI: 10.3233/jad-2010-1262] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We describe the interactions of two benzimidazole derivatives, astemizole (AST) and lansoprazole (LNS), with anomalous aggregates of tau protein (neurofibrillary tangles). Interestingly, these compounds, with important medical applications in the treatment of allergies and gastrointestinal disorders respectively, specifically bind to aggregated variants of tau protein and to paired helical filaments isolated from brains of Alzheimer's disease (AD) patients. These ligands appear to be a powerful tool to tag brain-isolated tau-aggregates and heparin-induced polymers of recombinant tau. The interactions of AST and LNS with tau aggregates were assessed by classical radioligand assays, surface plasmon resonance, and bioinformatic approaches. The affinity of AST and LNS for tau aggregates was comparatively higher than that for amyloid-beta polymers according to our data. This is relevant since senile plaques are also abundant but are not pathognomonic in AD patients. Immunochemical studies on paired helical filaments from brains of AD patients and surface plasmon resonance studies confirm these findings. The capacity of these drugs to penetrate the blood-brain barrier was evaluated: i) in vitro by parallel artificial membrane permeability assay followed by experimental Log P determinations; and ii) in vivo by pharmacokinetic studies comparing distribution profiles in blood and brain of mice using HPLC/UV. Importantly, our studies indicate that the brain/blood concentration ratios for these compounds were suitable for their use as PET radiotracers. Since neurofibrillary tangles are positively correlated with cognitive impairment, we concluded that LNS and AST have a great potential in PET neuroimaing for in vivo early detection of AD and in reducing the formation of neurofibrillary tangles.
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Affiliation(s)
- Leonel E Rojo
- International Center for Biomedicine (ICC), Faculty of Sciences, University of Chile, Santiago, Chile
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21
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Increased expression of cdk5/p25 in N2a cells leads to hyperphosphorylation and impaired axonal transport of neurofilament proteins. Life Sci 2010; 86:532-7. [DOI: 10.1016/j.lfs.2010.02.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/02/2010] [Accepted: 02/06/2010] [Indexed: 11/21/2022]
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22
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Higuero AM, Sánchez-Ruiloba L, Doglio LE, Portillo F, Abad-Rodríguez J, Dotti CG, Iglesias T. Kidins220/ARMS modulates the activity of microtubule-regulating proteins and controls neuronal polarity and development. J Biol Chem 2009; 285:1343-57. [PMID: 19903810 DOI: 10.1074/jbc.m109.024703] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
In order for neurons to perform their function, they must establish a highly polarized morphology characterized, in most of the cases, by a single axon and multiple dendrites. Herein we find that the evolutionarily conserved protein Kidins220 (kinase D-interacting substrate of 220-kDa), also known as ARMS (ankyrin repeat-rich membrane spanning), a downstream effector of protein kinase D and neurotrophin and ephrin receptors, regulates the establishment of neuronal polarity and development of dendrites. Kidins220/ARMS gain and loss of function experiments render severe phenotypic changes in the processes extended by hippocampal neurons in culture. Although Kidins220/ARMS early overexpression hinders neuronal development, its down-regulation by RNA interference results in the appearance of multiple longer axon-like extensions as well as aberrant dendritic arbors. We also find that Kidins220/ARMS interacts with tubulin and microtubule-regulating molecules whose role in neuronal morphogenesis is well established (microtubule-associated proteins 1b, 1a, and 2 and two members of the stathmin family). Importantly, neurons where Kidins220/ARMS has been knocked down register changes in the phosphorylation activity of MAP1b and stathmins. Altogether, our results indicate that Kidins220/ARMS is a key modulator of the activity of microtubule-regulating proteins known to actively regulate neuronal morphogenesis and suggest a mechanism by which it contributes to control neuronal development.
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Affiliation(s)
- Alonso M Higuero
- Instituto de Investigaciones Biomédicas de Madrid Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28029, Spain
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23
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Salajegheh M, Pinkus JL, Nazareno R, Amato AA, Parker KC, Greenberg SA. Nature of “Tau” immunoreactivity in normal myonuclei and inclusion body myositis. Muscle Nerve 2009; 40:520-8. [DOI: 10.1002/mus.21471] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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24
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Leuba G, Vernay A, Zimmermann V, Saini K, Kraftsik R, Savioz A. Differential damage in the frontal cortex with aging, sporadic and familial Alzheimer's disease. Brain Res Bull 2009; 80:196-202. [PMID: 19559767 DOI: 10.1016/j.brainresbull.2009.06.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 06/17/2009] [Accepted: 06/18/2009] [Indexed: 11/19/2022]
Abstract
In order to understand relationships between executive and structural deficits in the frontal cortex of patients within normal aging or Alzheimer's disease, we studied frontal pathological changes in young and old controls compared to cases with sporadic (AD) or familial Alzheimer's disease (FAD). We performed a semi-automatic computer assisted analysis of the distribution of beta-amyloid (Abeta) deposits revealed by Abeta immunostaining as well as of neurofibrillary tangles (NFT) revealed by Gallyas silver staining in Brodman areas 10 (frontal polar), 12 (ventro-infero-median) and 24 (anterior cingular), using tissue samples from 5 FAD, 6 sporadic AD and 10 control brains. We also performed densitometric measurements of glial fibrillary acidic protein, principal compound of intermediate filaments of astrocytes, and of phosphorylated neurofilament H and M epitopes in areas 10 and 24. All regions studied seem almost completely spared in normal old controls, with only the oldest ones exhibiting a weak percentage of beta-amyloid deposit and hardly any NFT. On the contrary, all AD and FAD cases were severely damaged as shown by statistically significant increased percentages of beta-amyloid deposit, as well as by a high number of NFT. FAD cases (all from the same family) had statistically more beta-amyloid and GFAP than sporadic AD cases in both areas 10 and 24 and statistically more NFT only in area 24. The correlation between the percentage of beta-amyloid and the number of NFT was significant only for area 24. Altogether, these data suggest that the frontal cortex can be spared by AD type lesions in normal aging, but is severely damaged in sporadic and still more in familial Alzheimer's disease. The frontal regions appear to be differentially vulnerable, with area 12 having the less amyloid burden, area 24 the less NFT and area 10 having both more amyloid and more NFT. This pattern of damage in frontal regions may represent a strong neuroanatomical support for the deterioration of attention and cognitive capacities as well as for the presence of emotional and behavioral troubles in AD patients.
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Affiliation(s)
- Geneviève Leuba
- Department of Psychiatry, CHUV, Center for Psychiatric Neuroscience, Lausanne, Switzerland.
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25
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Ni MH, Wu CC, Chan WH, Chien KY, Yu JS. GSK-3 mediates the okadaic acid-induced modification of collapsin response mediator protein-2 in human SK-N-SH neuroblastoma cells. J Cell Biochem 2008; 103:1833-48. [PMID: 17902168 DOI: 10.1002/jcb.21575] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Collapsin response mediator protein-2 (CRMP-2), a phosphoprotein involved in axonal outgrowth and microtubule dynamics, is aberrantly phosphorylated in Alzheimer's disease (AD) brain. Alteration of glycogen synthase kinase-3 (GSK-3) activity is associated with the pathogenesis of AD. Here, we show that CRMP-2 is one of the major substrates for GSK-3 in pig brain extracts. Both GSK-3alpha and 3beta phosphorylate purified pig brain CRMP-2 and significantly alter its mobility in SDS-gels, resembling the CRMP-2 modification observed in AD brain. Interestingly, this modification can be detected in SK-N-SH neuroblastoma cells treated with a phosphatase inhibitor, okadaic acid (OA), and GSK-3 inhibitors completely block this OA-induced event. Knockdown of both GSK-3alpha and 3beta, but not either kinase alone, impairs OA-induced modification of CRMP-2. Mutation of Ser-518 or Ser-522 of CRMP-2, which are highly phosphorylated in AD brain, to Ala blocks the OA-induced modification of CRMP-2 in SK-N-SH cells. Ser-522 prephosphorylated by Cdk5 is required for subsequent GSK-3alpha-mediated phosphorylation of CRMP-2 in vitro. Collectively, our results demonstrate for the first time that OA can induce phosphorylation of CRMP-2 in SK-N-SH cells at sites aberrantly phosphorylated in AD brain, and both GSK-3alpha and 3beta and Ser-522 kinase(s) are involved in this process.
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Affiliation(s)
- Mei-Hui Ni
- Graduate Institute of Basic Medical Sciences, Medical College of Chang Gung University, Tao-Yuan, Taiwan, Republic of China
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26
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Jeganathan S, Hascher A, Chinnathambi S, Biernat J, Mandelkow EM, Mandelkow E. Proline-directed pseudo-phosphorylation at AT8 and PHF1 epitopes induces a compaction of the paperclip folding of Tau and generates a pathological (MC-1) conformation. J Biol Chem 2008; 283:32066-76. [PMID: 18725412 DOI: 10.1074/jbc.m805300200] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tau, a neuronal microtubule-associated protein that aggregates in Alzheimer disease is a natively unfolded protein. In solution, Tau adopts a "paperclip" conformation, whereby the N- and C-terminal domains approach each other and the repeat domain ( Jeganathan, S., von Bergen, M., Brutlach, H., Steinhoff, H. J., and Mandelkow, E. (2006) Biochemistry 45, 2283-2293 ). In AD, Tau is in a hyperphosphorylated state. The consequences for microtubule binding or aggregation are a matter of debate. We therefore tested whether phosphorylation alters the conformation of Tau. To avoid the ambiguities of heterogeneous phosphorylation we cloned "pseudo-phosphorylation" mutants of Tau where combinations of Ser or Thr residues were converted into Glu. These mutations were combined with FRET pairs inserted in different locations to allow distance measurements. The results show that the paperclip conformation becomes tighter or looser, depending on the pseudo-phosphorylation state. In particular, pseudo-phosphorylation at the epitope of the diagnostic antibody AT8* (S199E + S202E + T205E) moves the N-terminal domain away from the C-terminal domain. Pseudo-phosphorylation at the PHF1 epitope (S396E + S404E) moves the C-terminal domain away from the repeat domain. In both cases the paperclip conformation is opened up. By contrast, the combination of AT8* and PHF1 sites leads to compaction of the paperclip, such that the N-terminus approaches the repeat domain. The compaction becomes even stronger by combining pseudo-phosphorylated AT8*, AT100, and PHF1 epitopes. This is accompanied by a strong increase in the reaction with conformation-dependent antibody MC1, suggesting the generation of a pathological conformation characteristic for Tau in AD. Furthermore, the compact paperclip conformation enhances the aggregation to paired helical filaments but has little influence on microtubule interactions. The data provide a framework for the global folding of Tau dependent on proline-directed phosphorylation in the domains flanking the repeats and the consequences for pathological properties of Tau.
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Affiliation(s)
- Sadasivam Jeganathan
- Max Planck Unit for Structural Molecular Biology, Notkestrasse 85, D-22607 Hamburg, Germany
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27
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Deng Y, Li B, Liu F, Iqbal K, Grundke-Iqbal I, Brandt R, Gong CX. Regulation between O-GlcNAcylation and phosphorylation of neurofilament-M and their dysregulation in Alzheimer disease. FASEB J 2007; 22:138-45. [PMID: 17687114 PMCID: PMC2262915 DOI: 10.1096/fj.07-8309com] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The medium subunit of neurofilament (NF-M) is extensively modified by phosphate and O-linked beta-N-acetylglucosamine (O-GlcNAc). Phosphorylation of NF-M plays a critical role in regulating its translocation, filament formation, and function. However, the regulation of NF-M phosphorylation and the role of NF-M O-GlcNAcylation (a modification by which GlcNAc is attached to the serine/threonine residues of a protein via an O-linked glycosidic bond) are largely unknown. Here, we demonstrate that O-GlcNAcylation and phosphorylation of NF-M regulate each other reciprocally in cultured neuroblastoma cells and in metabolically active rat brain slices. In animal models of fasting rats, which mimicked the decreased glucose uptake/metabolism observed in brains of individuals with Alzheimer disease (AD), we found a decrease in O-GlcNAcylation and increase in phosphorylation of NF-M. We also observed decreased O-GlcNAcylation and an increased phosphorylation of NF-M in AD brain. These results suggest that O-GlcNAcylation and phosphorylation of NF-M are regulated reciprocally and that the hyperphosphorylation and accumulation of NF-M in AD brain might be caused by impaired brain glucose uptake/metabolism via down-regulation of NF-M O-GlcNAcylation.
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Affiliation(s)
- Yanqiu Deng
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
| | - Bin Li
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
| | - Fei Liu
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
| | - Khalid Iqbal
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
| | - Inge Grundke-Iqbal
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
| | - Roland Brandt
- Department of Neurobiology, University of Osnabruck, Osnabruck, Germany
| | - Cheng-Xin Gong
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA and
- Correspondence: Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Rd., Staten Island, NY 10314, USA. E-mail:
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28
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Plattner F, Angelo M, Giese KP. The roles of cyclin-dependent kinase 5 and glycogen synthase kinase 3 in tau hyperphosphorylation. J Biol Chem 2006; 281:25457-65. [PMID: 16803897 DOI: 10.1074/jbc.m603469200] [Citation(s) in RCA: 276] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperphosphorylation of the microtubule-associated protein tau is a characteristic feature of neurodegenerative tauopathies including Alzheimer disease. Over-activation of proline-directed kinases, such as cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3 (GSK3), has been implicated in the aberrant phosphorylation of tau at proline-directed sites. In this study we tested the roles of Cdk5 and GSK3 in tau hyperphosphorylation in vivo using transgenic mice with p25-induced Cdk5 over-activation. We found that over-activation of Cdk5 in young transgenic animals does not induce tau hyperphosphorylation at sites recognized by the antibodies AT8, AT100, PHF-1, and TG3. In fact, we observed that Cdk5 over-activation leads to inhibition of GSK3. However, in old transgenic animals the inhibition of GSK3 is lost and results in increased GSK3 activity, which coincides with tau hyperphosphorylation at the AT8 and PHF-1 sites. Pharmacological inhibition of GSK3 in old transgenic mice by chronic treatment with lithium leads to a reduction of the age-dependent increase in tau hyperphosphorylation. Furthermore, we found that Cdk5, GSK3, and PP2A co-immunoprecipitate, suggesting a functional association of these molecules. Together, these results reveal the role of GSK3 as a key mediator of tau hyperphosphorylation, whereas Cdk5 acts as a modulator of tau hyperphosphorylation via the inhibitory regulation of GSK3. Furthermore, these findings suggest that disruption of regulation of GSK3 activity underlies tau hyperphosphorylation in neurodegenerative tauopathies. Hence, GSK3 may be a prime target for therapeutic intervention in tauopathies including Alzheimer disease.
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Affiliation(s)
- Florian Plattner
- Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, United Kingdom.
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29
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Trivedi N, Marsh P, Goold RG, Wood-Kaczmar A, Gordon-Weeks PR. Glycogen synthase kinase-3beta phosphorylation of MAP1B at Ser1260 and Thr1265 is spatially restricted to growing axons. J Cell Sci 2005; 118:993-1005. [PMID: 15731007 DOI: 10.1242/jcs.01697] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent experiments show that the microtubule-associated protein (MAP) 1B is a major phosphorylation substrate for the serine/threonine kinase glycogen synthase kinase-3beta (GSK-3beta) in differentiating neurons. GSK-3beta phosphorylation of MAP1B appears to act as a molecular switch regulating the control that MAP1B exerts on microtubule dynamics in growing axons and growth cones. Maintaining a population of dynamically unstable microtubules in growth cones is important for axon growth and growth cone pathfinding. We have mapped two GSK-3beta phosphorylation sites on mouse MAP1B to Ser1260 and Thr1265 using site-directed point mutagenesis of recombinant MAP1B proteins, in vitro kinase assays and phospho-specific antibodies. We raised phospho-specific polyclonal antibodies to these two sites and used them to show that MAP1B is phosphorylated by GSK-3beta at Ser1260 and Thr1265 in vivo. We also showed that in the developing nervous system of rat embryos, the expression of GSK-3beta phosphorylated MAP1B is spatially restricted to growing axons, in a gradient that is highest distally, despite the expression of MAP1B and GSK-3beta throughout the entire neuron. This suggests that there is a mechanism that spatially regulates the GSK-3beta phosphorylation of MAP1B in differentiating neurons. Heterologous cell transfection experiments with full-length MAP1B, in which either phosphorylation site was separately mutated to a valine or, in a double mutant, in which both sites were mutated, showed that these GSK-3beta phosphorylation sites contribute to the regulation of microtubule dynamics by MAP1B.
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Affiliation(s)
- Niraj Trivedi
- The MRC Centre for Developmental Neurobiology, New Hunts House, Guy's Campus, King's College London, London SE1 1UL, UK
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30
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Liao L, Cheng D, Wang J, Duong DM, Losik TG, Gearing M, Rees HD, Lah JJ, Levey AI, Peng J. Proteomic Characterization of Postmortem Amyloid Plaques Isolated by Laser Capture Microdissection. J Biol Chem 2004; 279:37061-8. [PMID: 15220353 DOI: 10.1074/jbc.m403672200] [Citation(s) in RCA: 235] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The presence of amyloid plaques in the brain is one of the pathological hallmarks of Alzheimer's disease (AD). We report here a comprehensive proteomic analysis of senile plaques from postmortem AD brain tissues. Senile plaques labeled with thioflavin-S were procured by laser capture microdissection, and their protein components were analyzed by liquid chromatography coupled with tandem mass spectrometry. We identified a total of 488 proteins co-isolated with the plaques, and we found multiple phosphorylation sites on the neurofilament intermediate chain, implicating the complexity and diversity of cellular processes involved in the plaque formation. More significantly, we identified 26 proteins enriched in the plaques of two AD cases by quantitative comparison with surrounding non-plaque tissues. The localization of several proteins in the plaques was further confirmed by the approach of immunohistochemistry. In addition to previously identified plaque constituents, we discovered novel association of dynein heavy chain with the plaques in human postmortem brain and in a double transgenic AD mouse model, suggesting that neuronal transport may play a role in neuritic degeneration. Overall, our results revealed for the first time the sub-proteome of amyloid plaques that is important for further studies on disease biomarker identification and molecular mechanisms of AD pathogenesis.
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Affiliation(s)
- Lujian Liao
- Department of Human Genetics, Center for Neurodegenerative Disease, Enory University School of Medicine, Atlanta, GA 30322, USA
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31
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Gong CX, Liu F, Wu G, Rossie S, Wegiel J, Li L, Grundke-Iqbal I, Iqbal K. Dephosphorylation of microtubule-associated protein tau by protein phosphatase 5. J Neurochem 2004; 88:298-310. [PMID: 14690518 DOI: 10.1111/j.1471-4159.2004.02147.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Protein phosphatase 5 (PP5) is a 58-kDa novel phosphoseryl/phosphothreonyl protein phosphatase. It is ubiquitously expressed in all mammalian tissues examined, with a high level in the brain, but little is known about its physiological substrates. We found that this phosphatase dephosphorylated recombinant tau phosphorylated with cAMP-dependent protein kinase and glycogen synthase kinase-3beta, as well as abnormally hyperphosphorylated tau isolated from brains of patients with Alzheimer's disease. The specific activity of PP5 toward tau was comparable to those reported with other protein substrates examined to date. The PP5 activity toward tau was stimulated by arachidonic acid by 30- to 45-fold. Immunostaining demonstrated that PP5 was primarily cytoplasmic in PC12 cells and in neurons of postmortem human brain tissue. A small pool of PP5 associated with microtubules. Expression of active PP5 in PC12 cells resulted in reduced phosphorylation of tau, suggesting that PP5 can also dephosphorylate tau in cells. These results suggest that PP5 plays a role in the dephosphorylation of tau and might be involved in the molecular pathogenesis of Alzheimer's disease.
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Affiliation(s)
- Cheng-Xin Gong
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York 10314, USA.
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32
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Li L, von Bergen M, Mandelkow EM, Mandelkow E. Structure, stability, and aggregation of paired helical filaments from tau protein and FTDP-17 mutants probed by tryptophan scanning mutagenesis. J Biol Chem 2002; 277:41390-400. [PMID: 12198126 DOI: 10.1074/jbc.m206334200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
By using tryptophan scanning mutagenesis, we observed the kinetics and structure of the polymerization of tau into paired helical filaments (PHFs) independently of exogenous reporter dyes. The fluorescence exhibits pronounced blue shifts due to burial of the residue inside PHFs, depending on Trp position. The effect is greatest near the center of the repeat domain, showing that the packing is tightest near the beta-structure inducing hexapeptide motifs. The tryptophan response allows measurement of PHF stability made by different tau isoforms and mutants. Unexpectedly, the stability of PHFs is quite low (denaturation half-points approximately 1.0 m GdnHCl), implying that incipient aggregation should be reversible and that the observed high stability of Alzheimer PHFs is due to other factors. The stability increases with the number of repeats and with tau mutants promoting beta-structure, arguing for a gain of toxic function in frontotemporal dementias. Fluorescence resonance energy transfer (FRET) was used to analyze the distances of Tyr(310) to tryptophans in different positions. The degree of FRET in the soluble protein was position-dependent, with highest signals within the second and third repeats but low or no signals further away. In PHFs most mutants showed FRET, indicating that tight packing results from assembly of tau into PHFs.
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Affiliation(s)
- Li Li
- Max-Planck-Unit for Structural Molecular Biology Notkestrasse 85, 22607 Hamburg, Germany
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Abstract
PURPOSE OF THE REVIEW This review focuses on the recent additions to the literature in the clinical and genetic aspects of progressive supranuclear palsy. RECENT FINDINGS Clinical features of progressive supranuclear palsy are reasonably well established and known to be quite characteristic. Recent epidemiological studies suggest that the disorder is more common than previously considered and that it is frequently misdiagnosed. New laboratory and novel imaging techniques are being tested and cerebrospinal fluid levels of tau protein have been found helpful in diagnosis. Pathological and biochemical studies in progressive supranuclear palsy brains have shown the predominance of hyperphosphorylated tau isoforms which contain the sequence encoded by exon 10 (4R) aggregated into filaments. Familial tauopathies linked to tau gene mutations showing clinical and neuropathological overlap with sporadic progressive supranuclear palsy have been described. Despite recent discoveries of the strong genetic association of sporadic progressive supranuclear palsy with tau gene polymorphisms, a specific risk allele for developing the palsy has not yet been identified yet. SUMMARY Recent clinical studies and clinicopathological correlations are contributing significantly to the delineation of the clinical features of progressive supranuclear palsy. These features and the appropriate use of laboratory tests allow for an earlier identification of the disease and a more accurate premortem diagnosis. However, no specific biological markers for the disorder are available yet, and consequently diagnosis in the early stages or when some of the characteristic signs and symptoms are missing, remains a major challenge. Despite the recent advances in the understanding of genetic factors involved in progressive supranuclear palsy, the cause of the disease still remains unknown. Biochemical studies in brains from progressive supranuclear palsy patients provide a potential helpful instrument to improve the characterization of this disorder.
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Affiliation(s)
- Pau Pastor
- Parkinson's disease and Movement Disorders Unit, Neurology Service, Clinical Institute for Nervous System Disorders, University Hospital Clinic, August Pi i Sunyer Institute for Biomedical Investigation, Villaroel 170, 08036 Barcelona, Spain
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Town T, Zolton J, Shaffner R, Schnell B, Crescentini R, Wu Y, Zeng J, DelleDonne A, Obregon D, Tan J, Mullan M. p35/Cdk5 pathway mediates soluble amyloid-beta peptide-induced tau phosphorylation in vitro. J Neurosci Res 2002; 69:362-72. [PMID: 12125077 DOI: 10.1002/jnr.10299] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alzheimer's disease (AD) is pathologically characterized by deposition of amyloid-beta peptides (Abeta) as senile plaques and by the occurrence of neurofibrillary tangles (NFTs) composed primarily of hyperphosphorylated tau protein. Activation of cyclin-dependent kinase 5 (Cdk5) via its potent activator p25 has recently been shown to promote phosphorylation of tau at AD-specific phosphoepitopes, and increased cleavage of p35 to p25 has been demonstrated in AD patients, suggesting that Cdk5 may represent a pathogenic tau protein kinase. We were interested in the potential effect of soluble forms of Abeta on Cdk5-mediated AD-like tau phosphorylation, insofar as previous studies of human biopsies and aged canine and primate brains have shown that dystrophic neurites appear before the formation of neuritic plaques. We transfected N2a cells with a p35 vector (N2a/p35 cells) and, after differentiation, challenged these cells with Abeta(1-42) peptide in soluble form (sAbeta(1-42)). Results show that sAbeta(1-42) at relatively low levels (1-5 microM) dose-dependently increases tau phosphorylation at AD-specific phosphoepitopes in differentiated N2a/p35 cells compared with controls, an effect that is blocked by antisense oligonucleotides against p35. sAbeta(1-42)-induced tau phosphorylation is concomitant with an increase in both p25 to p35 ratio and Cdk5 activity (but not protein levels). Additionally, blockade of L-type calcium channels or inhibition of calpain completely abolishes this effect. Taken together, these data indicate that sAbeta is a potent activator of the p25/Cdk5 pathway, resulting in promotion of AD-like tau phosphorylation in vitro.
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Affiliation(s)
- Terrence Town
- The Roskamp Institute, Department of Psychiatry, University of South Florida, Tampa 33613, USA
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Holzer M, Rödel L, Seeger G, Gärtner U, Narz F, Janke C, Heumann R, Arendt T. Activation of mitogen-activated protein kinase cascade and phosphorylation of cytoskeletal proteins after neurone-specific activation of p21ras. II. Cytoskeletal proteins and dendritic morphology. Neuroscience 2002; 105:1041-54. [PMID: 11530241 DOI: 10.1016/s0306-4522(01)00246-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present study, we analysed changes in the expression, subcellular distribution and phosphorylation state of the microtubule-associated protein tau and other cytoskeletal proteins after neurone-specific activation of the mitogen-activated protein kinase (MAPK) in the CNS in vivo. We used transgenic mice with a neurone-specific expression of activated ras protein (p21H-ras(Val12), synapsin I promoter) that is associated with an augmented activity of the MAPK. Chronic activation of MAPK cascade influenced tau protein phosphorylation, localisation and dendritic morphology. While the amount of tau protein was elevated by 9%, phospho-epitopes detected by the monoclonal antibodies AT270, 12E8 and SMI34 were increased by about 21%, 40% and 59% respectively. Steady-state levels of tau mRNA were not affected. Thus, the increase in tau protein was most likely due to stabilisation of tau protein by augmented phosphorylation. While in wild-type animals tau protein was preferentially localised in axons, a prominent immunoreactivity was found in the somatodendritic compartment of transgenic mice. This subcellular translocation typically seen in pyramidal neurones was associated with an increase in the dendritic calibre by about 30% and is paralleled by an increase in tubulin of 19%. We were unable to obtain any morphological indication of neurodegenerative processes in these animals. We suggest that the moderate increase in tau protein and phosphorylation may be part of the neuroprotective mechanism. However, further studies on aged transgenic mice will be necessary to establish potential effects on neuronal viability.
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Affiliation(s)
- M Holzer
- Paul Flechsig Institute of Brain Research, Department of Neuroanatomy, University of Leipzig, Germany
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36
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Torack RM, Miller JW, Roth KA. Deafferentation-induced abnormal neurofilament phosphorylation in red nucleus neurones. Neuropathol Appl Neurobiol 2001; 27:444-50. [PMID: 11903927 DOI: 10.1046/j.1365-2990.2001.00355.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hippocampal deafferentation has been proposed as a pathogenetic mechanism for neurofibrillary tangle (NFT) formation in human mesolimbocortical dementia. We previously developed a rodent model of hippocampal deafferentation involving bilateral destructive lesions of the ventrotegmental area (VTA), septum of the medial forebrain and entorhinal cortex combined with pharmacological inhibition of serotonin 5-HT2 and dopamine D1 receptors. Unexpectedly, we observed an alteration in phosphorylated neurofilament protein immunoreactivity and argyrophilia in magnocellular neurones of the red nucleus. Here, we determined the neuroanatomical, pharmacological and temporal requirements for this effect on red nucleus neurones. We found that abnormal phosphorylation and argyrophilia were critically dependent on bilateral destruction of the VTA and antagonism of 5-HT2 receptors. Although extensive neurofilament hyperphosphorylation and argyrophilia were observed in red nucleus magnocellular neurones within nine days of treatment, no NFTs were formed and these effects were transitory. Resolution of these cytoskeletal abnormalities was accompanied by increased expression of the calcium binding protein, parvalbumin, suggesting that alterations in intraneuronal calcium levels may modify the deafferentation response.
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Affiliation(s)
- R M Torack
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO 63110, USA
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Takao M, Ghetti B, Murrell JR, Unverzagt FW, Giaccone G, Tagliavini F, Bugiani O, Piccardo P, Hulette CM, Crain BJ, Farlow MR, Heyman A. Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures. J Neuropathol Exp Neurol 2001; 60:1137-52. [PMID: 11764087 DOI: 10.1093/jnen/60.12.1137] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.
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Affiliation(s)
- M Takao
- Indiana Alzheimer Disease Center, Indiana University School of Medicine, Indianapolis 46202, USA
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Wang J, Tung YC, Wang Y, Li XT, Iqbal K, Grundke-Iqbal I. Hyperphosphorylation and accumulation of neurofilament proteins in Alzheimer disease brain and in okadaic acid-treated SY5Y cells. FEBS Lett 2001; 507:81-7. [PMID: 11682063 DOI: 10.1016/s0014-5793(01)02944-1] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the role of neurofilament (NF) proteins in Alzheimer disease (AD) neurofibrillary degeneration. The levels and degree of phosphorylation of NF proteins in AD neocortex were determined by Western blots developed with a panel of phosphorylation-dependent NF antibodies. Levels of all three NF subunits and the degree of phosphorylation of NF-H and NF-M were significantly increased in AD as compared to Huntington disease brains used as control tissue. The increase in the levels of NF-H and NF-M was 1.7- and 1.5-fold (P<0.01) as determined by monoclonal antibody SMI33, and was 1.6-fold (P<0.01) in NF-L using antibody NR4. The phosphorylation of NF-H and NF-M in AD was increased respectively at the SMI31 epitope by 1.6- and 1.9-fold (P<0.05) and at the SMI33 epitope by 2.7- and 1.3-fold (P<0.01 and P<0.05). Essentially similar effects were observed in SY5Y human neuroblastoma cells when treated with okadaic acid, an inhibitor of protein phosphatase (PP)-2A and -1. This is the first biochemical evidence which unambiguously demonstrates the hyperphosphorylation and the accumulation of NF subunits in AD brain, and shows that the inhibition of PP-2A/PP-1 activities can lead to the hyperphosphorylation of NF-H and NF-M subunits.
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Affiliation(s)
- J Wang
- Pathophysiology Department, Tongji Medical College, Hubei, Wuhan, PR China.
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Stumptner C, Fuchsbichler A, Lehner M, Zatloukal K, Denk H. Sequence of events in the assembly of Mallory body components in mouse liver: clues to the pathogenesis and significance of Mallory body formation. J Hepatol 2001; 34:665-75. [PMID: 11434612 DOI: 10.1016/s0168-8278(00)00099-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
BACKGROUND/AIMS Chronic intoxication of mice with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or griseofulvin (GF) results in appearance of Mallory bodies (MBs) and alterations of the keratin cytoskeleton, which are reversible upon drug withdrawal but recur after readministration within 2-3 days. METHODS DDC- or GF-treated and recovered mice were reintoxicated with the original drugs but also colchicine and lumicolchicine. Cytoskeletal alterations of hepatocytes and MB formation were monitored by immunofluorescence microscopy using keratin, MB-specific antibodies, antibodies to phosphoepitopes and to HSP70. Keratin 8/18 mRNA expression and protein levels were determined by competitive reverse transcription-polymerase chain reaction, in situ-hybridization and western blotting. RESULTS Duration of pretreatment was important for the efficiency of MB triggering. Rapid increase of keratin 8/18 mRNA and proteins was found in all reintoxicated mice concomitant with MB formation, whereby keratin 8 prevailed over keratin 18. Keratins and a protein with heat shock characteristics (M(M) 120-1 antigen) were the earliest detectable MB components, whereas ubiquitination and phosphorylation followed later. CONCLUSIONS Overproduction of keratins is a major but not the only step responsible for MB formation. Additional components (e.g. M(M) 120-1 antigen) and excess of keratin 8 over keratin 18 are essential.
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Affiliation(s)
- C Stumptner
- Department of Pathology, University of Graz, School of Medicine, Austria
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40
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Shanavas A, Papasozomenos SC. tau kinases in the rat heat shock model: possible implications for Alzheimer disease. Proc Natl Acad Sci U S A 2000; 97:14139-44. [PMID: 11121021 PMCID: PMC18884 DOI: 10.1073/pnas.97.26.14139] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have previously shown, by using the phosphate-dependent anti-tau antibodies Tau-1 and PHF-1, that heat shock induces rapid dephosphorylation of tau followed by hyperphosphorylation in female rats. In this study, we analyzed in forebrain homogenates from female Sprague-Dawley rats the activities of extracellular signal regulated kinase 1/2 (ERK1/2), c-Jun NH(2)-terminal kinase (JNK), glycogen synthase kinase-3beta (GSK-3beta), cyclin-dependent kinase 5 (Cdk5), cAMP-dependent protein kinase A (PKA), and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) at 0 (n = 5), 3 (n = 4), 6 (n = 5), and 12 (n = 5) h after heat shock and in non-heat-shocked controls (n = 5). Immunoprecipitation kinase assays at 0 h showed suppression of the activities of all kinases except of GSK-3beta, which showed increased activity. At 3-6 h, the activities of ERK1/2, JNK, Cdk5, and GSK-3beta toward selective substrates were increased; however, only JNK, Cdk5, and GSK-3beta but not ERK1/2 were overactivated toward purified bovine tau. At 3-6 h, kinase assays specific for PKA and CaMKII showed no increased activity toward either tau or selective substrates. All of eight anti-tau antibodies tested showed dephosphorylation at 0 h and hyperphosphorylation at 3-6 h, except for 12E8, which showed hyperphosphorylation also at 0 h. Immunoblot analysis using activity-dependent antibodies against ERK1/2, JNK, and GSK-3beta confirmed the above data. Increased activation and inhibition of kinases after heat shock were statistically significant in comparison with controls. Because tau is hyperphosphorylated in Alzheimer disease these findings suggest that JNK, GSK-3beta, and Cdk5 may play a role in its pathogenesis.
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Affiliation(s)
- A Shanavas
- Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, Houston, TX 77030, USA
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41
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Goode BL, Chau M, Denis PE, Feinstein SC. Structural and functional differences between 3-repeat and 4-repeat tau isoforms. Implications for normal tau function and the onset of neurodegenetative disease. J Biol Chem 2000; 275:38182-9. [PMID: 10984497 DOI: 10.1074/jbc.m007489200] [Citation(s) in RCA: 173] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tau, MAP2, and MAP4 are members of a microtubule-associated protein (MAP) family that are each expressed as "3-repeat" and "4-repeat" isoforms. These isoforms arise from tightly controlled tissue-specific and/or developmentally regulated alternative splicing of a 31-amino acid long "inter-repeat:repeat module," raising the possibility that different MAP isoforms may possess some distinct functional capabilities. Consistent with this hypothesis, regulatory mutations in the human tau gene that disrupt the normal balance between 3-repeat and 4-repeat tau isoform expression lead to a collection of neurodegenerative diseases known as FTDP-17 (fronto-temporal dementias and Parkinsonism linked to chromosome 17), which are characterized by the formation of pathological tau filaments and neuronal cell death. Unfortunately, very little is known regarding structural and functional differences between the isoforms. In our previous analyses, we focused on 4-repeat tau structure and function. Here, we investigate 3-repeat tau, generating a series of truncations, amino acid substitutions, and internal deletions and examining the functional consequences. 3-Repeat tau possesses a "core microtubule binding domain" composed of its first two repeats and the intervening inter-repeat. This observation is in marked contrast to the widely held notion that tau possesses multiple independent tubulin-binding sites aligned in sequence along the length of the protein. In addition, we observed that the carboxyl-terminal sequences downstream of the repeat region make a strong but indirect contribution to microtubule binding activity in 3-repeat tau, which is in contrast to the negligible effect of these same sequences in 4-repeat tau. Taken together with previous work, these data suggest that 3-repeat and 4-repeat tau assume complex and distinct structures that are regulated differentially, which in turn suggests that they may possess isoform-specific functional capabilities. The relevance of isoform-specific structure and function to normal tau action and the onset of neurodegenerative disease are discussed.
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Affiliation(s)
- B L Goode
- Neuroscience Research Institute and Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, California 93106, USA
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42
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Mukaetova-Ladinska EB, Garcia-Siera F, Hurt J, Gertz HJ, Xuereb JH, Hills R, Brayne C, Huppert FA, Paykel ES, McGee M, Jakes R, Honer WG, Harrington CR, Wischik CM. Staging of cytoskeletal and beta-amyloid changes in human isocortex reveals biphasic synaptic protein response during progression of Alzheimer's disease. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 157:623-36. [PMID: 10934165 PMCID: PMC1850134 DOI: 10.1016/s0002-9440(10)64573-7] [Citation(s) in RCA: 153] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/09/2000] [Indexed: 11/28/2022]
Abstract
We have examined the relationships between dementia, loss of synaptic proteins, changes in the cytoskeleton, and deposition of beta-amyloid plaques in the neocortex in a clinicopathologically staged epidemiological cohort using a combination of biochemical and morphometric techniques. We report that loss of synaptic proteins is a late-stage phenomenon, occurring only at Braak stages 5 and 6, or at moderate to severe clinical grades of dementia. Loss of synaptic proteins was seen only after the emergence of the full spectrum of tau and beta-amyloid pathology in the neocortex at stage 4, but not in the presence of beta-amyloid plaques alone. Contrary to previous studies, we report increases in the levels of synaptophysin, syntaxin, and SNAP-25 at stage 3 and of alpha-synuclein and MAP2 at stage 4. Minimal and mild clinical grades of dementia were associated with either unchanged or elevated levels of synaptic proteins in the neocortex. Progressive aggregation of paired helical filament (PHF)-tau protein could be detected biochemically from stage 2 onwards, and this was earliest change relative to the normal aging background defined by Braak stage 1 that we were able to detect in the neocortex. These results are consistent with the possibility that failure of axonal transport associated with early aggregation of tau protein elicits a transient adaptive synaptic response to partial de-afferentation that may be mediated by trophic factors. This early abnormality in cytoskeletal function may contribute directly to the earliest clinically detectable stages of dementia.
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Friedhoff P, von Bergen M, Mandelkow EM, Mandelkow E. Structure of tau protein and assembly into paired helical filaments. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1502:122-32. [PMID: 10899437 DOI: 10.1016/s0925-4439(00)00038-7] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Over the past few years the systematic investigation of paired helical filament assembly from tau protein in vitro has become feasible. We review our current understanding of the structure and conformations of tau protein and how this affects tau's assembly into the pathological paired helical filaments in Alzheimer's disease.
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Affiliation(s)
- P Friedhoff
- Max-Planck-Unit for Structural Molecular Biology, Hamburg, Germany
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44
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Wilczynski GM, Engel WK, Askanas V. Association of active extracellular signal-regulated protein kinase with paired helical filaments of inclusion-body myositis muscle suggests its role in inclusion-body myositis tau phosphorylation. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 156:1835-40. [PMID: 10854206 PMCID: PMC1850072 DOI: 10.1016/s0002-9440(10)65056-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/16/2000] [Indexed: 11/19/2022]
Abstract
The possible role of extracellular signal-regulated kinase (ERK) in the pathogenesis of inclusion-body myositis (IBM) was investigated by immunostaining the active phosphorylated form of ERK in muscle biopsies of six IBM and 14 control patients. Between 80% and 90% of IBM vacuolated muscle fibers contained well-defined ERK-immunoreactive inclusions, which were co-localized by light microscopy, with phosphorylated tau in 70 to 80% of those fibers. Immunoelectronmicroscopy colocalized ERK to small amorphous tufts adjacent to the muscle fiber paired-helical filaments. Strong ERK immunoreactivity was also present at the postsynaptic domain of all human neuromuscular junctions. Our study suggests 1) that ERK, a signal transducer, might play a role in IBM pathogenesis, including participation in the pathological phosphorylation of IBM tau; and 2) that signal transduction abnormalities may be a component of the IBM pathogenic cascade. Our novel immunolocalization of ERK at the postsynaptic domain of human neuromuscular junctions supports a role in transcription of junctional-protein genes. The ERK localized in nonjunctional regions of IBM fibers may underlie the known pathological up-regulation of junctional proteins there.
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Affiliation(s)
- G M Wilczynski
- Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, Los Angeles, CA 90017-1912, USA
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45
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Torreilles F, Roquet F, Granier C, Pau B, Mourton-Gilles C. Binding specificity of monoclonal antibody AD2: influence of the phosphorylation state of tau. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 78:181-5. [PMID: 10891598 DOI: 10.1016/s0169-328x(00)00073-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Using recombinant human tau protein phosphorylated by a brain extract and the glycogen synthase kinase-3beta in the absence or the presence of heparin, we showed that phosphorylation-dependent antibody AD2 recognition only requires phosphorylated Ser-396. By the Spot multiple peptide synthesis method, we showed that Tyr-394, Ser(P)-396 and Pro-397 are critical for AD2 binding. A decrease in the binding of AD2 was observed with increasing phosphorylation of residues in the vicinity of Ser(P)-396.
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Affiliation(s)
- F Torreilles
- CNRS UMR 5094 Institut de Biotechnologie en Immunoanalyse et Pharmacologie UFR Pharmacie, 15 Av. Charles Flahault, 34060 Montpellier Cedex 2, France
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46
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Affiliation(s)
- H Denk
- Department of Pathology, University of Graz School of Medicine, Austria.
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47
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Abstract
The changes in tau that are associated with the early formation of tangles in aging and in preclinical and very mild Alzheimer's Disease (AD) were studied with two antibodies against AD-specific tau: PHF-1, which recognizes a phosphorylated epitope at Ser396 through 404, and MC-1, which recognizes a folded, conformational epitope that includes amino acids at both 7 through 9 and 312 through 342. Both antibodies demonstrated cells with diffuse or granular staining (diffuse tangles) and cells with fibrillar staining (fibrillar tangles). The fibrillar tangles corresponded to classical tangles and increase exponentially with age and severity of AD. The diffuse tangles seemed to represent an earlier form of tangles; their density peaked around preclinical AD, and then decreased in more severe stages of AD. MC-1 consistently stained more diffuse tangles than PHF-1, suggesting that the conformational change in tau precedes phosphorylation at the PHF-1 epitope during paired helical filament formation.
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Affiliation(s)
- N V Uboga
- Department of Anatomy and Neurobiology and Alzheimer's Disease Research Center, Washington University School of Medicine, 660 S. Eudid Avenue, St. Louis, MO 63110, USA
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48
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Kim D, Su J, Cotman CW. Sequence of neurodegeneration and accumulation of phosphorylated tau in cultured neurons after okadaic acid treatment. Brain Res 1999; 839:253-62. [PMID: 10519048 DOI: 10.1016/s0006-8993(99)01724-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Within neurofibrillary tangles and dystrophic neurites of Alzheimer's disease (AD), the cytoskeletal protein tau is abnormally hyperphosphorylated. In the present study, we examined the effect of okadaic acid (OA), a protein phosphatase inhibitor, in rat cultured neurons. Low concentrations of OA induce degeneration of neurites, rounding of cell bodies, detachment from the substratum, and eventual neuronal death. During OA-induced degeneration, SMI-31 immunoreactivity became punctate in neurites at 6 h after OA treatment, and over time, accumulated in cell bodies and dystrophic neurites. Hyperphosphorylation of tau and marked loss of MAP-2-positive dendrites occurred after 6 h of treatment with OA. Thereafter, AT-8 and PHF-1 immunoreactivity accumulated in cell bodies and subsequently appeared in distal axon-like neurites. These results demonstrate that OA treatment induced hyperphosphorylation of tau and preferential dendritic damage, with subsequent accumulation of phosphorylated tau in cell bodies and dystrophic axon-like neurites. OA-induced neurodegeneration may provide a useful model to study AD.
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Affiliation(s)
- D Kim
- Department of Psychobiology, University of California, Irvine 92697-4540, USA.
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Stumptner C, Heid H, Fuchsbichler A, Hauser H, Mischinger HJ, Zatloukal K, Denk H. Analysis of intracytoplasmic hyaline bodies in a hepatocellular carcinoma. Demonstration of p62 as major constituent. THE AMERICAN JOURNAL OF PATHOLOGY 1999; 154:1701-10. [PMID: 10362795 PMCID: PMC1866621 DOI: 10.1016/s0002-9440(10)65426-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intracytoplasmic hyaline bodies (IHBs) resemble inclusions in hepatocellular carcinoma cells, which so far have escaped further characterization. A relationship to Mallory bodies was suggested on the basis of light microscopy and filamentous ultrastructure. A hepatocellular carcinoma containing numerous IHBs was studied. Our studies revealed immunoreactivity of IHBs with the monoclonal antibodies SMI 31 and MPM-2, which recognize hyperphosphorylated epitopes present on paired helical filaments in Alzheimer's disease brains (SMI 31) or on diverse proteins hyperphosphorylated by mitotic kinases in the M-phase of the cell cycle (MPM-2). One- and two-dimensional gel electrophoresis of tumor extracts followed by immunoblotting with SMI 31 and MPM-2 antibodies revealed a major immunoreactive protein with an apparent molecular weight between 62 and 65 kd, which was resolved into several highly acidic (pH 4.5) protein components in two-dimensional gels. This protein was undetectable in non-neoplastic liver tissue. Sequence analysis identified the SMI 31 and MPM-2 immunoreactive material as p62, indicating that p62 is a major constituent of IHBs. p62 is an only recently discovered protein that is a phosphotyrosine-independent ligand of the SH2 domain of p56(lck), a member of the c-src family of cytoplasmic kinases. Moreover, p62 binds ubiquitin and may act as an adapter linking ubiquitinated species to other proteins. These features suggest a role of p62 in signal transduction and possibly also carcinogenesis. IHBs observed in the hepatocellular carcinoma cells presented are the first indications of a role of p62 in disease.
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Affiliation(s)
- C Stumptner
- Departments of Pathology* and Surgery,double dagger University of Graz School of Medicine, Graz, Austria
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Biernat J, Mandelkow EM. The development of cell processes induced by tau protein requires phosphorylation of serine 262 and 356 in the repeat domain and is inhibited by phosphorylation in the proline-rich domains. Mol Biol Cell 1999; 10:727-40. [PMID: 10069814 PMCID: PMC25198 DOI: 10.1091/mbc.10.3.727] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/1998] [Accepted: 01/04/1999] [Indexed: 11/11/2022] Open
Abstract
The differentiation of neurons and the outgrowth of neurites depends on microtubule-associated proteins such as tau protein. To study this process, we have used the model of Sf9 cells, which allows efficient transfection with microtubule-associated proteins (via baculovirus vectors) and observation of the resulting neurite-like extensions. We compared the phosphorylation of tau23 (the embryonic form of human tau) with mutants in which critical phosphorylation sites were deleted by mutating Ser or Thr residues into Ala. One can broadly distinguish two types of sites, the KXGS motifs in the repeats (which regulate the affinity of tau to microtubules) and the SP or TP motifs in the domains flanking the repeats (which contain epitopes for antibodies diagnostic of Alzheimer's disease). Here we report that both types of sites can be phosphorylated by endogenous kinases of Sf9 cells, and that the phosphorylation pattern of the transfected tau is very similar to that of neurons, showing that Sf9 cells can be regarded as an approximate model for the neuronal balance between kinases and phosphatases. We show that mutations in the repeat domain and in the flanking domains have opposite effects. Mutations of KXGS motifs in the repeats (Ser262, 324, and 356) strongly inhibit the outgrowth of cell extensions induced by tau, even though this type of phosphorylation accounts for only a minor fraction of the total phosphate. This argues that the temporary detachment of tau from microtubules (by phosphorylation at KXGS motifs) is a necessary condition for establishing cell polarity at a critical point in space or time. Conversely, the phosphorylation at SP or TP motifs represents the majority of phosphate (>80%); mutations in these motifs cause an increase in cell extensions, indicating that this type of phosphorylation retards the differentiation of the cells.
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Affiliation(s)
- J Biernat
- Max-Planck-Unit for Structural Molecular Biology, D-22603 Hamburg, Germany
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