51
|
Majd S, Power JHT, Koblar SA, Grantham HJM. The impact of tau hyperphosphorylation at Ser 262 on memory and learning after global brain ischaemia in a rat model of reversible cardiac arrest. IBRO Rep 2016; 2:1-13. [PMID: 30135928 PMCID: PMC6084925 DOI: 10.1016/j.ibror.2016.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 12/12/2016] [Accepted: 12/21/2016] [Indexed: 01/12/2023] Open
Abstract
An increase in phosphorylated tau (p-tau) is associated with Alzheimer's disease (AD), and brain hypoxia. Investigation of the association of residue-specific tau hyperphosphorylation and changes in cognition, leads to greater understanding of its potential role in the pathology of memory impairment. The aims of this study are to investigate the involvement of the main metabolic kinases, Liver Kinase B1 (LKB1) and Adenosine Monophosphate Kinase Protein Kinase (AMPK), in tau phosphorylation-derived memory impairment, and to study the potential contribution of the other tau kinases and phosphatases including Glycogen Synthase Kinase (GSK-3β), Protein kinase A (PKA) and Protein Phosphatase 2A (PP2A). Spatial memory and learning were tested in a rat global brain ischemic model of reversible cardiac arrest (CA). The phosphorylation levels of LKB1, AMPK, GSK-3β, PP2A, PKA and tau-specific phosphorylation were assessed in rats, subjected to ischaemia/reperfusion and in clinically diagnosed AD and normal human brains. LKB1 and AMPK phosphorylation increased 4 weeks after CA as did AMPK related p-tau (Ser262). The animals showed unchanged levels of GSK-3β specific p-tau (Ser202/Thr205), phospho-PP2A (Tyr307), total GSK-3β, PP2A, phospho-cAMP response element-binding protein (CREB) which is an indicator of PKA activity, and no memory deficits. AD brains had hyperphosphorylated tau in all the residues of Ser262, Ser202 and Thr205, with increased phosphorylation of both AMPK (Thr172) and GSK-3β (Ser9), and reduced PP2A levels. Our data suggests a crucial role for a combined activation of tau kinases and phosphatases in adversely affecting memory and that hyperphosphorylation of tau in more than one specific site may be required to create memory deficits. Short-term brain ischaemia causes AMPK activation and tau phosphorylation at its AMPK-sensitive site (Ser262). Activation of GSK-3β, PP2A and PKA are remained unchanged in short-term brain ischaemia/reperfusion. In clinical cases of AD, activation of AMPK, GSK-3β, PP2A and multiple site hyperphosphorylation of tau are observed. Hyperphosphorylation of tau (Ser262) alone without involving the other tau kinases/phosphatase does not affect memory.
Collapse
Affiliation(s)
- Shohreh Majd
- Neuronal Injury and Repair Laboratory, Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, Australia
| | - John H T Power
- Department of Human Physiology, School of Medicine, Flinders University, Adelaide, Australia
| | - Simon A Koblar
- School of Medicine, The Queen Elizabeth Hospital (TQEH) Campus, University of Adelaide, Australia
| | - Hugh J M Grantham
- Neuronal Injury and Repair Laboratory, Centre for Neuroscience, School of Medicine, Flinders University, Adelaide, Australia
| |
Collapse
|
52
|
Frenkel-Pinter M, Tal S, Scherzer-Attali R, Abu-Hussien M, Alyagor I, Eisenbaum T, Gazit E, Segal D. Naphthoquinone-Tryptophan Hybrid Inhibits Aggregation of the Tau-Derived Peptide PHF6 and Reduces Neurotoxicity. J Alzheimers Dis 2016; 51:165-78. [PMID: 26836184 DOI: 10.3233/jad-150927] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Tauopathies, such as Alzheimer's disease (AD), are a group of disorders characterized neuropathologically by intracellular toxic accumulations of abnormal protein aggregates formed by misfolding of the microtubule-associated protein tau. Since protein self-assembly appears to be an initial key step in the pathology of this group of diseases, intervening in this process can be both a prophylactic measure and a means for modifying the course of the disease for therapeutic purposes. We and others have shown that aromatic small molecules can be effective inhibitors of aggregation of various protein assemblies, by binding to the aromatic core in aggregation-prone motifs and preventing their self-assembly. Specifically, we have designed a series of small aromatic naphthoquinone-tryptophan hybrid molecules as candidate aggregation inhibitors of β -sheet based assembly and demonstrated their efficacy toward inhibiting aggregation of the amyloid-β peptide, another culprit of AD, as well as of various other aggregative proteins involved in other protein misfolding diseases. Here we tested whether a leading naphthoquinone-tryptophan hybrid molecule, namely NQTrp, can be repurposed as an inhibitor of the aggregation of the tau protein in vitro and in vivo. We show that the molecule inhibits the in vitro assembly of PHF6, the aggregation-prone fragment of tau protein, reduces hyperphosphorylated tau deposits and ameliorates tauopathy-related behavioral defect in an established transgenic Drosophila model expressing human tau. We suggest that NQTrp, or optimized versions of it, could act as novel disease modifying drugs for AD and other tauopathies.
Collapse
|
53
|
Sandhu P, Naeem MM, Lu C, Kumarathasan P, Gomes J, Basak A. Ser 422 phosphorylation blocks human Tau cleavage by caspase-3: Biochemical implications to Alzheimer's Disease. Bioorg Med Chem Lett 2016; 27:642-652. [PMID: 27989667 DOI: 10.1016/j.bmcl.2016.11.087] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 11/29/2016] [Accepted: 11/29/2016] [Indexed: 12/16/2022]
Abstract
Proteolytic truncation of microtubule associated human (h) Tau protein by caspase-3 at the carboxy (C) terminus has been linked to the pathogenesis of Alzheimer's Disease (AD). This cleavage likely occurs between Asp421↓Ser422 leading to the formation of 421-mer truncated Tau protein which has been found to be present as aggregate in high level after phosphorylation in mortal AD brain tissue compared to normal. At least 50 phosphorylation sites involving Ser, Thr and Tyr residues have been identified or proposed in hTau and a selected number of them have been implicated in hTau aggregation following latter's proteolytic truncation. Interestingly, it is further noted that Ser422 residue present in the P1' position of hTau caspase-3 cleavage region is a potential phosphorylation site. So we became interested to examine in vitro the effect of phospho-Ser422 residue on hTau cleavage by caspase-3 which is a crucial upstream event associated with hTau self-assembly leading to AD pathogenesis. The goal of this project is to study in vitro the caspase-3 cleavage site of hTau protein and to examine the kinetics of this cleavage following Ser422 phosphorylation and treatment with caspase-3 inhibitors. This is achieved by designing peptides from the sequence of hTau protein containing the proposed caspase-3 cleavage region. Peptides were designed from 441-mer major human Tau protein sequence that encompasses the proposed caspase-3 cleavage site [Asp421↓Ser422]. Corresponding phospho-, dextro-Ser422 and dextro-Asp421 analogs were also designed. Peptides were synthesized by solid phase chemistry, purified and fully characterized by mass spectrometry. These were then incubated with recombinant caspase-3 enzyme under identical condition for digestion and analyzed for cleavage by mass spectrometry and RP-HPLC chromatograms. Our results indicated that while the control peptide is efficiently cleaved by caspase-3 at Asp421↓Ser422 site producing the expected N- and C-terminal fragment peptides, the corresponding phospho-Ser422 peptide remained completely resistant to the cleavage. Substitution of Asp421 by its dextro isoform also blocks peptide cleavage by caspase-3. However substitution of Ser422 by its dextro isoform in the peptide did not affect the cleavage significantly. The above results were further confirmed by caspase-3 digestion experiment in the presence of varying amounts of caspase-3 inhibitor (Ac-DQVD-aldehyde) which was found to block this cleavage in a highly effective manner. Our results highlighted the crucial significance of Ser422 phosphorylation and suggest that the kinase associated with this Ser-phosphorylation may protect Tau from aggregation. Thus specific promoters/activators of this kinase may find useful therapeutic benefits in arresting Tau truncation by caspase-3 and the progression of AD. In addition our data demonstrated that Tau-peptides where Ser422 or Asp421 are substituted by their respective dextro isomers, exhibit different cleavage kinetics by caspase-3 and this may have important implications in therapeutic intervention of Tau aggregation and associated AD.
Collapse
Affiliation(s)
- Priya Sandhu
- Interdisciplinary School of Health Sciences, Faculty of Health Science, U Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
| | - Mansur Mohammad Naeem
- Interdisciplinary School of Health Sciences, Faculty of Health Science, U Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
| | - Chunyu Lu
- Interdisciplinary School of Health Sciences, Faculty of Health Science, U Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
| | - Premkumari Kumarathasan
- Environmental Health Science and Research Bureau, Environmental and Radiation Health Sciences Directorate, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada
| | - James Gomes
- Interdisciplinary School of Health Sciences, Faculty of Health Science, U Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
| | - Ajoy Basak
- Interdisciplinary School of Health Sciences, Faculty of Health Science, U Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada; Chronic Disease Program, Ottawa Hospital Research Institute, 725 Parkdale Ave., Ottawa, ON K1Y 4E9, Canada.
| |
Collapse
|
54
|
Frenkel-Pinter M, Tal S, Scherzer-Attali R, Abu-Hussien M, Alyagor I, Eisenbaum T, Gazit E, Segal D. Cl-NQTrp Alleviates Tauopathy Symptoms in a Model Organism through the Inhibition of Tau Aggregation-Engendered Toxicity. NEURODEGENER DIS 2016; 17:73-82. [PMID: 27760426 DOI: 10.1159/000448518] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/19/2016] [Indexed: 11/19/2022] Open
Abstract
Alzheimer's disease (AD) is the most abundant tauopathy and is characterized by Aβ-derived plaques and tau-derived tangles, resulting from the unfolding of the corresponding monomeric subunits into ordered β-sheet oligomers and fibrils. Intervening in the toxic aggregation process is a promising therapeutic approach, but, to date, a disease-modifying therapy is neither available for AD nor for other tauopathies. Along these lines, we have previously demonstrated that a small naphthoquinone-tryptophan hybrid, termed NQTrp, is an effective modulator of tauopathy in vitro and in vivo. However, NQTrp is difficult to synthesize and is not very stable. Therefore, we tested whether a more stable and easier-to-synthesize modified version of NQTrp, containing a Cl ion, namely Cl-NQTrp, is also an effective inhibitor of tau aggregation in vitro and in vivo. Cl-NQTrp was previously shown to efficiently inhibit the aggregation of various amyloidogenic proteins and peptides. We demonstrate that Cl-NQTrp inhibits the in vitro assembly of PHF6, the aggregation-prone fragment of tau, and alleviates tauopathy symptoms in a transgenic Drosophila model through the inhibition of tau aggregation-engendered toxicity. These results suggest that Cl-NQTrp could be a unique potential therapeutic for AD since it targets aggregation of both Aβ and tau.
Collapse
Affiliation(s)
- Moran Frenkel-Pinter
- Department of Molecular Microbiology and Biotechnology, Interdisciplinary Sagol School of Neurosciences, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | | | | | | | | | | | | | | |
Collapse
|
55
|
Nam SC. Role of Tau, a microtubule associated protein, in Drosophila photoreceptor morphogenesis. Genesis 2016; 54:553-561. [PMID: 27579500 DOI: 10.1002/dvg.22966] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 08/28/2016] [Accepted: 08/29/2016] [Indexed: 11/08/2022]
Abstract
Cell polarity genes have important functions in photoreceptor morphogenesis. Based on recent discovery of stabilized microtubule cytoskeleton in developing photoreceptors and its role in photoreceptor cell polarity, microtubule associated proteins might have important roles in controlling cell polarity proteins' localizations in developing photoreceptors. Here, Tau, a microtubule associated protein, was analyzed to find its potential role in photoreceptor cell polarity. Tau colocalizes with acetylated/stabilized microtubules in developing pupal photoreceptors. Although it is known that tau mutant photoreceptor has no defects in early eye differentiation and development, it shows dramatic disruptions of cell polarity proteins, adherens junctions, and the stable microtubules in developing pupal photoreceptors. This role of Tau in cell polarity proteins' localization in photoreceptor cells during the photoreceptor morphogenesis was further supported by Tau's overexpression studies. Tau overexpression caused dramatic expansions of apical membrane domains where the polarity proteins localize in the developing pupal photoreceptors. It is also found that Tau's role in photoreceptor cell polarity depends on Par-1 kinase. Furthermore, a strong genetic interaction between tau and crumbs was found. It is found that Tau has a crucial role in cell polarity protein localization during pupal photoreceptor morphogenesis stage, but not in early eye development including eye cell differentiation.
Collapse
Affiliation(s)
- Sang-Chul Nam
- Department of Biology, Texas A&M International University, Laredo, TX, 78041
| |
Collapse
|
56
|
Tau phosphorylation at Alzheimer's disease-related Ser356 contributes to tau stabilization when PAR-1/MARK activity is elevated. Biochem Biophys Res Commun 2016; 478:929-34. [PMID: 27520376 DOI: 10.1016/j.bbrc.2016.08.053] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 08/08/2016] [Indexed: 02/08/2023]
Abstract
Abnormal phosphorylation of the microtubule-associated protein tau is observed in many neurodegenerative diseases, including Alzheimer's disease (AD). AD-related phosphorylation of two tau residues, Ser262 and Ser356, by PAR-1/MARK stabilizes tau in the initial phase of mismetabolism, leading to subsequent phosphorylation events, accumulation, and toxicity. However, the relative contribution of phosphorylation at each of these sites to tau stabilization has not yet been elucidated. In a Drosophila model of human tau toxicity, we found that tau was phosphorylated at Ser262, but not at Ser356, and that blocking Ser262 phosphorylation decreased total tau levels. By contrast, when PAR-1 was co-overexpressed with tau, tau was hyperphosphorylated at both Ser262 and Ser356. Under these conditions, the protein levels of tau were significantly elevated, and prevention of tau phosphorylation at both residues was necessary to completely suppress this elevation. These results suggest that tau phosphorylation at Ser262 plays the predominant role in tau stabilization when PAR-1/MARK activity is normal, whereas Ser356 phosphorylation begins to contribute to this process when PAR-1/MARK activity is abnormally elevated, as in diseased brains.
Collapse
|
57
|
Bodea L, Eckert A, Ittner LM, Piguet O, Götz J. Tau physiology and pathomechanisms in frontotemporal lobar degeneration. J Neurochem 2016; 138 Suppl 1:71-94. [PMID: 27306859 PMCID: PMC5094566 DOI: 10.1111/jnc.13600] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 01/31/2016] [Accepted: 02/24/2016] [Indexed: 12/27/2022]
Abstract
Frontotemporal lobar degeneration (FTLD) has been associated with toxic intracellular aggregates of hyperphosphorylated tau (FTLD-tau). Moreover, genetic studies identified mutations in the MAPT gene encoding tau in familial cases of the disease. In this review, we cover a range of aspects of tau function, both in the healthy and diseased brain, discussing several in vitro and in vivo models. Tau structure and function in the healthy brain is presented, accentuating its distinct compartmentalization in neurons and its role in microtubule stabilization and axonal transport. Furthermore, tau-driven pathology is discussed, introducing current concepts and the underlying experimental evidence. Different aspects of pathological tau phosphorylation, the protein's genomic and domain organization as well as its spreading in disease, together with MAPT-associated mutations and their respective models are presented. Dysfunction related to other post-transcriptional modifications and their effect on normal neuronal functions such as cell cycle, epigenetics and synapse dynamics are also discussed, providing a mechanistic explanation for the observations made in FTLD-tau cases, with the possibility for therapeutic intervention. In this review, we cover aspects of tau function, both in the healthy and diseased brain, referring to different in vitro and in vivo models. In healthy neurons, tau is compartmentalized, with higher concentrations found in the distal part of the axon. Cargo molecules are sensitive to this gradient. A disturbed tau distribution, as found in frontotemporal lobar degeneration (FTLD-tau), has severe consequences for cellular physiology: tau accumulates in the neuronal soma and dendrites, leading among others to microtubule depolymerization and impaired axonal transport. Tau forms insoluble aggregates that sequester additional molecules stalling cellular physiology. Neuronal communication is gradually lost as toxic tau accumulates in dendritic spines with subsequent degeneration of synapses and synaptic loss. Thus, by providing a mechanistic explanation for the observations made in FTLD-tau cases, arises a possibility for therapeutic interventions. This article is part of the Frontotemporal Dementia special issue.
Collapse
Affiliation(s)
- Liviu‐Gabriel Bodea
- Clem Jones Centre for Ageing Dementia ResearchQueensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Anne Eckert
- Neurobiology LaboratoryPsychiatric University Clinics BaselUniversity of BaselBaselSwitzerland
| | - Lars Matthias Ittner
- Dementia Research UnitSchool of Medical SciencesFaculty of MedicineUniversity of New South WalesSydneyNSWAustralia
| | | | - Jürgen Götz
- Clem Jones Centre for Ageing Dementia ResearchQueensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| |
Collapse
|
58
|
Chouhan AK, Guo C, Hsieh YC, Ye H, Senturk M, Zuo Z, Li Y, Chatterjee S, Botas J, Jackson GR, Bellen HJ, Shulman JM. Uncoupling neuronal death and dysfunction in Drosophila models of neurodegenerative disease. Acta Neuropathol Commun 2016; 4:62. [PMID: 27338814 PMCID: PMC4918017 DOI: 10.1186/s40478-016-0333-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 06/07/2016] [Indexed: 02/04/2023] Open
Abstract
Common neurodegenerative proteinopathies, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are characterized by the misfolding and aggregation of toxic protein species, including the amyloid beta (Aß) peptide, microtubule-associated protein Tau (Tau), and alpha-synuclein (αSyn) protein. These factors also show toxicity in Drosophila; however, potential limitations of prior studies include poor discrimination between effects on the adult versus developing nervous system and neuronal versus glial cell types. In addition, variable expression paradigms and outcomes hinder systematic comparison of toxicity profiles. Using standardized conditions and medium-throughput assays, we express human Tau, Aß or αSyn selectively in neurons of the adult Drosophila retina and monitor age-dependent changes in both structure and function, based on tissue histology and recordings of the electroretinogram (ERG), respectively. We find that each protein causes a unique profile of neurodegenerative pathology, demonstrating distinct and separable impacts on neuronal death and dysfunction. Strikingly, expression of Tau leads to progressive loss of ERG responses whereas retinal architecture and neuronal numbers are largely preserved. By contrast, Aß induces modest, age-dependent neuronal loss without degrading the retinal ERG. αSyn expression, using a codon-optimized transgene, is characterized by marked retinal vacuolar change, progressive photoreceptor cell death, and delayed-onset but modest ERG changes. Lastly, to address potential mechanisms, we perform transmission electron microscopy (TEM) to reveal potential degenerative changes at the ultrastructural level. Surprisingly, Tau and αSyn each cause prominent but distinct synaptotoxic profiles, including disorganization or enlargement of photoreceptor terminals, respectively. Our findings highlight variable and dynamic properties of neurodegeneration triggered by these disease-relevant proteins in vivo, and suggest that Drosophila may be useful for revealing determinants of neuronal dysfunction that precede cell loss, including synaptic changes, in the adult nervous system.
Collapse
|
59
|
Ando K, Maruko-Otake A, Ohtake Y, Hayashishita M, Sekiya M, Iijima KM. Stabilization of Microtubule-Unbound Tau via Tau Phosphorylation at Ser262/356 by Par-1/MARK Contributes to Augmentation of AD-Related Phosphorylation and Aβ42-Induced Tau Toxicity. PLoS Genet 2016; 12:e1005917. [PMID: 27023670 PMCID: PMC4811436 DOI: 10.1371/journal.pgen.1005917] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/15/2016] [Indexed: 12/31/2022] Open
Abstract
Abnormal accumulation of the microtubule-interacting protein tau is associated with neurodegenerative diseases including Alzheimer’s disease (AD). β-amyloid (Aβ) lies upstream of abnormal tau behavior, including detachment from microtubules, phosphorylation at several disease-specific sites, and self-aggregation into toxic tau species in AD brains. To prevent the cascade of events leading to neurodegeneration in AD, it is essential to elucidate the mechanisms underlying the initial events of tau mismetabolism. Currently, however, these mechanisms remain unclear. In this study, using transgenic Drosophila co-expressing human tau and Aβ, we found that tau phosphorylation at AD-related Ser262/356 stabilized microtubule-unbound tau in the early phase of tau mismetabolism, leading to neurodegeneration. Aβ increased the level of tau detached from microtubules, independent of the phosphorylation status at GSK3-targeted SP/TP sites. Such mislocalized tau proteins, especially the less phosphorylated species, were stabilized by phosphorylation at Ser262/356 via PAR-1/MARK. Levels of Ser262 phosphorylation were increased by Aβ42, and blocking this stabilization of tau suppressed Aβ42-mediated augmentation of tau toxicity and an increase in the levels of tau phosphorylation at the SP/TP site Thr231, suggesting that this process may be involved in AD pathogenesis. In contrast to PAR-1/MARK, blocking tau phosphorylation at SP/TP sites by knockdown of Sgg/GSK3 did not reduce tau levels, suppress tau mislocalization to the cytosol, or diminish Aβ-mediated augmentation of tau toxicity. These results suggest that stabilization of microtubule-unbound tau by phosphorylation at Ser262/356 via the PAR-1/MARK may act in the initial steps of tau mismetabolism in AD pathogenesis, and that such tau species may represent a potential therapeutic target for AD. Alzheimer’s disease (AD) is the most common cause of dementia resulting from progressive neuron loss. Two proteins, β-amyloid (Aβ) and tau, accumulate in AD brains and are involved in AD pathogenesis. In healthy neurons, tau binds to microtubules to regulate its stability; in AD brains, however, tau is detached from microtubules and phosphorylated at multiple sites. Such abnormal tau behavior, which is likely to be triggered by Aβ, results in generation of pathological tau species that mediate neuron loss. However, the detailed mechanisms underlying this event remain incompletely understood. Using transgenic flies expressing human tau and Aβ as a model system, we found that tau phosphorylation at specific AD-related sites stabilized microtubule-unbound tau in the early phase of tau mismetabolism to generate toxic tau species. Moreover, this process is critical for Aβ to promote subsequent tau phosphorylation and neurodegeneration. Our results reveal a critical step in the initiation of tau mismetabolism, and this process may represent a potential therapeutic target for AD.
Collapse
Affiliation(s)
- Kanae Ando
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
- * E-mail: (KA); (KMI)
| | - Akiko Maruko-Otake
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Yosuke Ohtake
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, Pennsylvania, United States of America
| | - Motoki Hayashishita
- Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Michiko Sekiya
- Department of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | - Koichi M. Iijima
- Department of Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
- * E-mail: (KA); (KMI)
| |
Collapse
|
60
|
Hannan SB, Dräger NM, Rasse TM, Voigt A, Jahn TR. Cellular and molecular modifier pathways in tauopathies: the big picture from screening invertebrate models. J Neurochem 2016; 137:12-25. [PMID: 26756400 DOI: 10.1111/jnc.13532] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/14/2015] [Accepted: 01/04/2016] [Indexed: 12/16/2022]
Abstract
Abnormal tau accumulations were observed and documented in post-mortem brains of patients affected by Alzheimer's disease (AD) long before the identification of mutations in the Microtubule-associated protein tau (MAPT) gene, encoding the tau protein, in a different neurodegenerative disease called Frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17). The discovery of mutations in the MAPT gene associated with FTDP-17 highlighted that dysfunctions in tau alone are sufficient to cause neurodegeneration. Invertebrate models have been diligently utilized in investigating tauopathies, contributing to the understanding of cellular and molecular pathways involved in disease etiology. An important discovery came with the demonstration that over-expression of human tau in Drosophila leads to premature mortality and neuronal dysfunction including neurodegeneration, recapitulating some key neuropathological features of the human disease. The simplicity of handling invertebrate models combined with the availability of a diverse range of experimental resources make these models, in particular Drosophila a powerful invertebrate screening tool. Consequently, several large-scale screens have been performed using Drosophila, to identify modifiers of tau toxicity. The screens have revealed not only common cellular and molecular pathways, but in some instances the same modifier has been independently identified in two or more screens suggesting a possible role for these modifiers in regulating tau toxicity. The purpose of this review is to discuss the genetic modifier screens on tauopathies performed in Drosophila and C. elegans models, and to highlight the common cellular and molecular pathways that have emerged from these studies. Here, we summarize results of tau toxicity screens providing mechanistic insights into pathological alterations in tauopathies. Key pathways or modifiers that have been identified are associated with a broad range of processes including, but not limited to, phosphorylation, cytoskeleton organization, axonal transport, regulation of cellular proteostasis, transcription, RNA metabolism, cell cycle regulation, and apoptosis. We discuss the utility and application of invertebrate models in elucidating the cellular and molecular functions of novel and uncharacterized disease modifiers identified in large-scale screens as well as for investigating the function of genes identified as risk factors in genome-wide association studies from human patients in the post-genomic era. In this review, we combined and summarized several large-scale modifier screens performed in invertebrate models to identify modifiers of tau toxicity. A summary of the screens show that diverse cellular processes are implicated in the modification of tau toxicity. Kinases and phosphatases are the most predominant class of modifiers followed by components required for cellular proteostasis and axonal transport and cytoskeleton elements.
Collapse
Affiliation(s)
- Shabab B Hannan
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center, Heidelberg, Germany.,Graduate School of Cellular and Molecular Neuroscience, Graduate Training Center of Neuroscience, University of Tübingen, Tübingen, Germany
| | - Nina M Dräger
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center, Heidelberg, Germany
| | - Tobias M Rasse
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center, Heidelberg, Germany
| | - Aaron Voigt
- Department of Neurology at University Clinic Aachen, RWTH Aachen, Germany
| | - Thomas R Jahn
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center, Heidelberg, Germany
| |
Collapse
|
61
|
Bougé AL, Parmentier ML. Tau excess impairs mitosis and kinesin-5 function, leading to aneuploidy and cell death. Dis Model Mech 2016; 9:307-19. [PMID: 26822478 PMCID: PMC4833329 DOI: 10.1242/dmm.022558] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 01/21/2016] [Indexed: 12/31/2022] Open
Abstract
In neurodegenerative diseases such as Alzheimer's disease (AD), cell cycle defects and associated aneuploidy have been described. However, the importance of these defects in the physiopathology of AD and the underlying mechanistic processes are largely unknown, in particular with respect to the microtubule (MT)-binding protein Tau, which is found in excess in the brain and cerebrospinal fluid of affected individuals. Although it has long been known that Tau is phosphorylated during mitosis to generate a lower affinity for MTs, there is, to our knowledge, no indication that an excess of this protein could affect mitosis. Here, we studied the effect of an excess of human Tau (hTau) protein on cell mitosis in vivo. Using the Drosophila developing wing disc epithelium as a model, we show that an excess of hTau induces a mitotic arrest, with the presence of monopolar spindles. This mitotic defect leads to aneuploidy and apoptotic cell death. We studied the mechanism of action of hTau and found that the MT-binding domain of hTau is responsible for these defects. We also demonstrate that the effects of hTau occur via the inhibition of the function of the kinesin Klp61F, the Drosophila homologue of kinesin-5 (also called Eg5 or KIF11). We finally show that this deleterious effect of hTau is also found in other Drosophila cell types (neuroblasts) and tissues (the developing eye disc), as well as in human HeLa cells. By demonstrating that MT-bound Tau inhibits the Eg5 kinesin and cell mitosis, our work provides a new framework to consider the role of Tau in neurodegenerative diseases. Drosophila Collection: We show that Tau, a microtubule-binding protein involved in many neurodegenerative diseases, impairs mitosis when in excess. We show that this occurs via the inhibition of the kinesin-5 mitotic motor.
Collapse
Affiliation(s)
- Anne-Laure Bougé
- Department of Neurosciences, Institut de Génomique Fonctionnelle, CNRS-UMR5203, INSERM-U1191, Université Montpellier, 141 Rue de la Cardonille, Montpellier F-34094, Cedex 5, France
| | - Marie-Laure Parmentier
- Department of Neurosciences, Institut de Génomique Fonctionnelle, CNRS-UMR5203, INSERM-U1191, Université Montpellier, 141 Rue de la Cardonille, Montpellier F-34094, Cedex 5, France
| |
Collapse
|
62
|
Gilley J, Ando K, Seereeram A, Rodríguez-Martín T, Pooler AM, Sturdee L, Anderton BH, Brion JP, Hanger DP, Coleman MP. Mislocalization of neuronal tau in the absence of tangle pathology in phosphomutant tau knockin mice. Neurobiol Aging 2015; 39:1-18. [PMID: 26923397 DOI: 10.1016/j.neurobiolaging.2015.11.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 11/25/2015] [Accepted: 11/28/2015] [Indexed: 01/22/2023]
Abstract
Hyperphosphorylation and fibrillar aggregation of the microtubule-associated protein tau are key features of Alzheimer's disease and other tauopathies. To investigate the involvement of tau phosphorylation in the pathological process, we generated a pair of complementary phosphomutant tau knockin mouse lines. One exclusively expresses phosphomimetic tau with 18 glutamate substitutions at serine and/or threonine residues in the proline-rich and first microtubule-binding domains to model hyperphosphorylation, whereas its phosphodefective counterpart has matched alanine substitutions. Consistent with expected effects of genuine phosphorylation, association of the phosphomimetic tau with microtubules and neuronal membranes is severely disrupted in vivo, whereas the phosphodefective mutations have more limited or no effect. Surprisingly, however, age-related mislocalization of tau is evident in both lines, although redistribution appears more widespread and more pronounced in the phosphomimetic tau knockin. Despite these changes, we found no biochemical or immunohistological evidence of pathological tau aggregation in mice of either line up to at least 2 years of age. These findings raise important questions about the role of tau phosphorylation in driving pathology in human tauopathies.
Collapse
Affiliation(s)
- Jonathan Gilley
- Signalling Programme, The Babraham Institute, Cambridge, UK.
| | - Kunie Ando
- Laboratory of Histology, Neuroanatomy and Neuropathology, Faculty of Medicine, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussells, Belgium
| | - Anjan Seereeram
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Teresa Rodríguez-Martín
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Amy M Pooler
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Laura Sturdee
- Signalling Programme, The Babraham Institute, Cambridge, UK
| | - Brian H Anderton
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | - Jean-Pierre Brion
- Laboratory of Histology, Neuroanatomy and Neuropathology, Faculty of Medicine, ULB Neuroscience Institute, Université Libre de Bruxelles, Brussells, Belgium
| | - Diane P Hanger
- Department of Basic and Clinical Neuroscience (PO37), Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
| | | |
Collapse
|
63
|
Cowan CM, Quraishe S, Hands S, Sealey M, Mahajan S, Allan DW, Mudher A. Rescue from tau-induced neuronal dysfunction produces insoluble tau oligomers. Sci Rep 2015; 5:17191. [PMID: 26608845 PMCID: PMC4660438 DOI: 10.1038/srep17191] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 10/12/2015] [Indexed: 12/18/2022] Open
Abstract
Aggregation of highly phosphorylated tau is a hallmark of Alzheimer’s
disease and other tauopathies. Nevertheless, animal models demonstrate that
tau-mediated dysfunction/toxicity may not require large tau aggregates but instead
may be caused by soluble hyper-phosphorylated tau or by small tau oligomers.
Challenging this widely held view, we use multiple techniques to show that insoluble
tau oligomers form in conditions where tau-mediated dysfunction is rescued in
vivo. This shows that tau oligomers are not necessarily always toxic.
Furthermore, their formation correlates with increased tau levels, caused
intriguingly, by either pharmacological or genetic inhibition of tau kinase
glycogen-synthase-kinase-3beta (GSK-3β). Moreover, contrary to common
belief, these tau oligomers were neither highly phosphorylated, and nor did they
contain beta-pleated sheet structure. This may explain their lack of toxicity. Our
study makes the novel observation that tau also forms non-toxic insoluble oligomers
in vivo in addition to toxic oligomers, which have been reported by
others. Whether these are inert or actively protective remains to be established.
Nevertheless, this has wide implications for emerging therapeutic strategies such as
those that target dissolution of tau oligomers as they may be ineffective or even
counterproductive unless they act on the relevant toxic oligomeric tau species.
Collapse
Affiliation(s)
- Catherine M Cowan
- Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Shmma Quraishe
- Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Sarah Hands
- Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Megan Sealey
- Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Sumeet Mahajan
- Institute of Life Sciences and Department of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
| | - Douglas W Allan
- Department of Cellular and Physiological Sciences, Life Science Institute, University of British Columbia, Vancouver, V6T 1Z3, Canada
| | - Amritpal Mudher
- Centre for Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| |
Collapse
|
64
|
Lin Q, Cao YP, Gao J. Common Polymorphisms in the GSK3β Gene May Contribute to the Pathogenesis of Alzheimer Disease: A Meta-Analysis. J Geriatr Psychiatry Neurol 2015; 28:83-93. [PMID: 25351705 DOI: 10.1177/0891988714554712] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 08/26/2014] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Although it is well known that GSK3β participates in the proliferation and survival of various tumor cells, its role in diseases of the central nervous system has been sparsely documented. In the past few years, studies regarding the relationship between GSK3β rs334558 T>C and rs6438552 C>T polymorphisms and Alzheimer disease (AD) risk have yielded contradictory results. As such, this meta-analysis seeks to satisfy the need to further investigate this relationship. METHODS In this research, published studies regarding the association of GSK3β rs6438552 and rs334558 mutation with AD risk was systematically assessed. Studies were retrieved from MEDLINE, Science Citation Index, the Cochrane Library, PubMed, Embase, CINAHL, Current Contents Index, Chinese Biomedical, Chinese Journal Full-Text, and Weipu Journal. Pooled odds ratios and 95% confidence intervals were calculated for allele contrast and homozygous, heterozygous, dominant, and recessive genetic model comparisons. RESULTS It was found that GSK3β rs334558 T>C and rs6438552 C>T polymorphisms were correlated with susceptibility to AD under 4 genetic models (all P<.05). In country-stratified subgroups, the results showed increased risk of developing AD in rs334558 T>C polymorphism among Chinese and Spain populations in majority groups. GSK3β rs6438552 C>T polymorphism was correlated with increased the risk of developing AD only in Australian populations. CONCLUSION Our findings suggest that there exists a significant association between GSK3β rs334558 T>C polymorphism and increased susceptibility of AD. Moreover, future updated studies with stratified case-control population are warranted for validation studies.
Collapse
Affiliation(s)
- Qiao Lin
- Department of Neurology, The Fourth Affiliated Hospital of China Medical University, Shenyang, PR China
| | - Yun-Peng Cao
- Department of Neurology, the First Hospital of China Medical University, Shenyang, PR China
| | - Jie Gao
- Department of Anatomy, the First Hospital of China Medical University, Shenyang, PR China
| |
Collapse
|
65
|
Modeling the complex pathology of Alzheimer's disease in Drosophila. Exp Neurol 2015; 274:58-71. [PMID: 26024860 DOI: 10.1016/j.expneurol.2015.05.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Revised: 05/13/2015] [Accepted: 05/17/2015] [Indexed: 12/18/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of dementia and the most common neurodegenerative disorder. AD is mostly a sporadic disorder and its main risk factor is age, but mutations in three genes that promote the accumulation of the amyloid-β (Aβ42) peptide revealed the critical role of amyloid precursor protein (APP) processing in AD. Neurofibrillary tangles enriched in tau are the other pathological hallmark of AD, but the lack of causative tau mutations still puzzles researchers. Here, we describe the contribution of a powerful invertebrate model, the fruit fly Drosophila melanogaster, to uncover the function and pathogenesis of human APP, Aβ42, and tau. APP and tau participate in many complex cellular processes, although their main function is microtubule stabilization and the to-and-fro transport of axonal vesicles. Additionally, expression of secreted Aβ42 induces prominent neuronal death in Drosophila, a critical feature of AD, making this model a popular choice for identifying intrinsic and extrinsic factors mediating Aβ42 neurotoxicity. Overall, Drosophila has made significant contributions to better understand the complex pathology of AD, although additional insight can be expected from combining multiple transgenes, performing genome-wide loss-of-function screens, and testing anti-tau therapies alone or in combination with Aβ42.
Collapse
|
66
|
Quantitative interaction proteomics of neurodegenerative disease proteins. Cell Rep 2015; 11:1134-46. [PMID: 25959826 PMCID: PMC9014711 DOI: 10.1016/j.celrep.2015.04.030] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 03/27/2015] [Accepted: 04/14/2015] [Indexed: 11/20/2022] Open
Abstract
Several proteins have been linked to neurodegenerative disorders (NDDs), but their molecular function is not completely understood. Here, we used quantitative interaction proteomics to identify binding partners of Amyloid beta precursor protein (APP) and Presenilin-1 (PSEN1) for Alzheimer’s disease (AD), Huntingtin (HTT) for Huntington’s disease, Parkin (PARK2) for Parkinson’s disease, and Ataxin-1 (ATXN1) for spinocerebellar ataxia type 1. Our network reveals common signatures of protein degradation and misfolding and recapitulates known biology. Toxicity modifier screens and comparison to genome-wide association studies show that interaction partners are significantly linked to disease phenotypes in vivo. Direct comparison of wild-type proteins and disease-associated variants identified binders involved in pathogenesis, highlighting the value of differential interactome mapping. Finally, we show that the mitochondrial protein LRPPRC interacts preferentially with an early-onset AD variant of APP. This interaction appears to induce mitochondrial dysfunction, which is an early phenotype of AD. Hosp et al. show that quantitative interaction proteomics of neurodegenerative disease proteins captures interactions relevant to pathogenesis. Differential interactome mapping reveals preferential binding of the mitochondrial protein LRPPRC with an early-onset Alzheimer’s disease (AD) variant of APP, potentially contributing to mitochondrial dysfunction observed in AD.
Collapse
|
67
|
Sun M, Chen L. Studying tauopathies in Drosophila: A fruitful model. Exp Neurol 2015; 274:52-7. [PMID: 25862286 DOI: 10.1016/j.expneurol.2015.03.029] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 03/06/2015] [Accepted: 03/31/2015] [Indexed: 11/26/2022]
Abstract
Tauopathies are a group of neurodegenerative disorders that include hereditary frontotemporal dementias (FTDs) such as FTD with parkinsonism linked to chromosome 17 (FTDP-17), as well as sporadic variants of FTDs like progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and Pick's disease. These diverse diseases all have in common the presence of abnormally phosphorylated tau aggregates. In this review, we will summarize key features of transgenic Drosophila models of tauopathies and a number of insights into disease mechanisms as well as therapeutic implications gained from the fruit fly models.
Collapse
Affiliation(s)
- Mingkuan Sun
- Department of Pathology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA; The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Science, Southeast University, Nanjing 210009, China
| | - Liam Chen
- Department of Pathology, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
68
|
Dujardin S, Colin M, Buée L. Invited review: Animal models of tauopathies and their implications for research/translation into the clinic. Neuropathol Appl Neurobiol 2015; 41:59-80. [DOI: 10.1111/nan.12200] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 11/23/2014] [Indexed: 02/01/2023]
Affiliation(s)
- Simon Dujardin
- Inserm, UMR1172 Jean-Pierre Aubert Research Centre; Lille France
- Faculté de Médecine; Université de Lille; France
- Memory Clinic; CHRU; Lille France
| | - Morvane Colin
- Inserm, UMR1172 Jean-Pierre Aubert Research Centre; Lille France
- Faculté de Médecine; Université de Lille; France
- Memory Clinic; CHRU; Lille France
| | - Luc Buée
- Inserm, UMR1172 Jean-Pierre Aubert Research Centre; Lille France
- Faculté de Médecine; Université de Lille; France
- Memory Clinic; CHRU; Lille France
| |
Collapse
|
69
|
Ali Y, Ruan K, Grace Zhai R. Drosophila Models of Tauopathy. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00054-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
|
70
|
Papanikolopoulou K, Skoulakis EMC. Temporally distinct phosphorylations differentiate Tau-dependent learning deficits and premature mortality in Drosophila. Hum Mol Genet 2014; 24:2065-77. [PMID: 25524708 DOI: 10.1093/hmg/ddu726] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Abnormally phosphorylated Tau protein, the major component of neurofibrillary tangles, is critical in the pathogenesis of Alzheimer's disease and related Tauopathies. We used Drosophila to examine the role of key disease-associated phosphorylation sites on Tau-mediated neurotoxicity. We present evidence that the late-appearing phosphorylation on Ser(238) rather than hyperphosphorylation per se is essential for Tau toxicity underlying premature mortality in adult flies. This site is also occupied at the time of neurodegeneration onset in a mouse Tauopathy model and in damaged brain areas of confirmed Tauopathy patients, suggesting a similar critical role on Tau toxicity in humans. In contrast, occupation of Ser(262) is necessary for Tau-dependent learning deficits in adult Drosophila. Significantly, occupation of Ser(262) precedes and is required for Ser(238) phosphorylation, and these temporally distinct phosphorylations likely reflect conformational changes. Because sequential occupation of Ser(262) and Ser(238) is required for the progression from Tau-mediated learning deficits to premature mortality in Drosophila, they may also play similar roles in the escalating symptom severity in Tauopathy patients, congruent with their presence in damaged regions of their brains.
Collapse
Affiliation(s)
- Katerina Papanikolopoulou
- Division of Neuroscience, Biomedical Sciences Research Centre 'Alexander Fleming', Vari 16672, Greece
| | - Efthimios M C Skoulakis
- Division of Neuroscience, Biomedical Sciences Research Centre 'Alexander Fleming', Vari 16672, Greece
| |
Collapse
|
71
|
Huang Y, Wu Z, Cao Y, Lang M, Lu B, Zhou B. Zinc binding directly regulates tau toxicity independent of tau hyperphosphorylation. Cell Rep 2014; 8:831-42. [PMID: 25066125 PMCID: PMC4306234 DOI: 10.1016/j.celrep.2014.06.047] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 05/20/2014] [Accepted: 06/24/2014] [Indexed: 01/13/2023] Open
Abstract
Tau hyperphosphorylation is thought to underlie tauopathy. Working in a Drosophila tauopathy model expressing a human Tau mutant (hTauR406W, or Tau*), we show that zinc contributes to the development of Tau toxicity through two independent actions: by increasing Tau phosphorylation and, more significantly, by directly binding to Tau. Elimination of zinc binding through amino acid substitution of Cys residues has a minimal effect on phosphorylation levels yet essentially eliminates Tau toxicity. The toxicity of the zinc-binding-deficient mutant Tau* (Tau*C2A) and overexpression of native Drosophila Tau, also lacking the corresponding zinc-binding Cys residues, are largely impervious to zinc concentration. Importantly, restoration of zinc-binding ability to Tau* by introduction of a zinc-binding residue (His) into the original Cys positions restores zinc-responsive toxicities in proportion to zinc-binding affinities. These results indicate zinc binding is a substantial contributor to tauopathy and have implications for therapy development.
Collapse
Affiliation(s)
- Yunpeng Huang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhihao Wu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Yu Cao
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Minglin Lang
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Bingwei Lu
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Bing Zhou
- State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
| |
Collapse
|
72
|
Bolkan BJ, Kretzschmar D. Loss of Tau results in defects in photoreceptor development and progressive neuronal degeneration in Drosophila. Dev Neurobiol 2014; 74:1210-25. [PMID: 24909306 DOI: 10.1002/dneu.22199] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 05/28/2014] [Accepted: 06/04/2014] [Indexed: 12/20/2022]
Abstract
Accumulations of Tau, a microtubule-associated protein (MAP), into neurofibrillary tangles is a hallmark of Alzheimer's disease and other tauopathies. However, the mechanisms leading to this pathology are still unclear: the aggregates themselves could be toxic or the sequestration of Tau into tangles might prevent Tau from fulfilling its normal functions, thereby inducing a loss of function defect. Surprisingly, the consequences of losing normal Tau expression in vivo are still not well understood, in part due to the fact that Tau knockout mice show only subtle phenotypes, presumably due to the fact that mammals express several MAPs with partially overlapping functions. In contrast, flies express fewer MAP, with Tau being the only member of the Tau/MAP2/MAP4 family. Therefore, we used Drosophila to address the physiological consequences caused by the loss of Tau. Reducing the levels of fly Tau (dTau) ubiquitously resulted in developmental lethality, whereas deleting Tau specifically in neurons or the eye caused progressive neurodegeneration. Similarly, chromosomal mutations affecting dTau also caused progressive degeneration in both the eye and brain. Although photoreceptor cells initially developed normally in dTau knockdown animals, they subsequently degenerated during late pupal stages whereas weaker dTau alleles caused an age-dependent defect in rhabdomere structure. Expression of wild type human Tau partially rescued the neurodegenerative phenotype caused by the loss of endogenous dTau, suggesting that the functions of Tau proteins are functionally conserved from flies to humans.
Collapse
Affiliation(s)
- Bonnie J Bolkan
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon, 97239
| | | |
Collapse
|
73
|
Beharry C, Cohen LS, Di J, Ibrahim K, Briffa-Mirabella S, Alonso ADC. Tau-induced neurodegeneration: mechanisms and targets. Neurosci Bull 2014; 30:346-58. [PMID: 24733656 DOI: 10.1007/s12264-013-1414-z] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 01/03/2014] [Indexed: 11/28/2022] Open
Abstract
The accumulation of hyperphosphorylated tau is a common feature of several dementias. Tau is one of the brain microtubule-associated proteins. Here we discuss tau's functions in microtubule assembly and stabilization and with regard to its interactions with other proteins. We describe and analyze important post-translational modifications: hyperphosphorylation, ubiquitination, glycation, glycosylation, nitration, polyamination, proteolysis, acetylation, and methylation. We discuss how these post-translational modifications can alter tau's biological function. We analyze the role of mitochondrial health in neurodegeneration. We propose that microtubules could be a therapeutic target and review different approaches. Finally, we consider whether tau accumulation or its conformational change is related to tau-induced neurodegeneration, and propose a mechanism of neurodegeneration.
Collapse
Affiliation(s)
- Cindy Beharry
- Department of Biology and Center for Developmental Neuroscience, College of Staten Island, Graduate Center, The City University of New York, Staten Island, NY, 10314, USA
| | | | | | | | | | | |
Collapse
|
74
|
Lund H, Gustafsson E, Svensson A, Nilsson M, Berg M, Sunnemark D, von Euler G. MARK4 and MARK3 associate with early tau phosphorylation in Alzheimer's disease granulovacuolar degeneration bodies. Acta Neuropathol Commun 2014; 2:22. [PMID: 24533944 PMCID: PMC4046661 DOI: 10.1186/2051-5960-2-22] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 02/11/2014] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND The progression of Alzheimer's disease (AD) is associated with an increase of phosphorylated tau in the brain. One of the earliest phosphorylated sites on tau is Ser262 that is preferentially phosphorylated by microtubule affinity regulating kinase (MARK), of which four isoforms exist. Herein we investigated the expression of MARK1-4 in the hippocampus of non-demented elderly (NDE) and AD cases. RESULTS In situ hybridization revealed a uniform, neuronal distribution of all four isoform mRNAs in NDE and AD. Immunohistochemical analyses using isoform-selective antibodies demonstrated that MARK4 in a phosphorylated form colocalizes with p-tau Ser262 in granulovacuolar degeneration bodies (GVDs) that progressively accumulate in AD. In contrast MARK4 is largely absent in the neuronal cytoplasm. MARK3 was localized to a subset of the GVD-containing neurons and also had a weak general cytoplasmic neuronal staining in both NDE and AD. These results suggest that in AD, phosphorylated MARK3 and MARK4 are sequestered and proteolysed in GVDs. MARK1 and MARK2 were absent in GVDs and exhibited relatively uniform neuronal expressions with no apparent differences between NDE and AD. CONCLUSION We found that the phosphorylated and fragmented forms of MARK4 and to some extent MARK3 are present in GVDs in AD, and that this expression is highly correlated with phosphorylation of tau at Ser262. This may represent a cellular defense mechanism to remove activated MARK and p-tau Ser262 from the cytosol, thereby reducing the phosphorylating effect on tau Ser262 that appears to be a critical step for subsequent neurodegeneration.
Collapse
|
75
|
Povellato G, Tuxworth RI, Hanger DP, Tear G. Modification of the Drosophila model of in vivo Tau toxicity reveals protective phosphorylation by GSK3β. Biol Open 2014; 3:1-11. [PMID: 24429107 PMCID: PMC3892155 DOI: 10.1242/bio.20136692] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/29/2013] [Indexed: 01/17/2023] Open
Abstract
Hyperphosphorylation of the microtubule associated protein, Tau, is the hallmark of a group of neurodegenerative disorders known as the tauopathies which includes Alzheimer's disease. Precisely how and why Tau phosphorylation is increased in disease is not fully understood, nor how individual sites modify Tau function. Several groups have used the Drosophila visual system as an in vivo model to examine how the toxicity of Tau varies with phosphorylation status. This system relies on overexpression of Tau from transgenes but is susceptible to position effects altering expression and activity of the transgenes. We have refined the system by eliminating position effects through the use of site-specific integration. By standardising Tau expression levels we have been able to compare directly the toxicity of different isoforms of Tau and Tau point mutants that abolish important phosphorylation events. We have also examined the importance of human kinases in modulating Tau toxicity in vivo. We were able to confirm that human GSK3β phosphorylates Tau and increases toxicity but, unexpectedly, we identified that preventing phosphorylation of Ser404 is a protective event. When phosphorylation at this site is prevented, Tau toxicity in the Drosophila visual system is increased in the presence of GSK3β. Our data suggest that not all phosphorylation events on Tau are associated with toxicity.
Collapse
Affiliation(s)
- Giulia Povellato
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UK
| | - Richard I. Tuxworth
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UK
- School of Clinical and Experimental Medicine, University of Birmingham, The Medical School, Birmingham B15 2TT, UK
| | - Diane P. Hanger
- Department of Neuroscience, King's College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
| | - Guy Tear
- MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Hospital Campus, London SE1 1UL, UK
| |
Collapse
|
76
|
Roy B, Jackson GR. Interactions between Tau and α-synuclein augment neurotoxicity in a Drosophila model of Parkinson's disease. Hum Mol Genet 2014; 23:3008-23. [PMID: 24430504 DOI: 10.1093/hmg/ddu011] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Clinical and pathological studies have suggested considerable overlap between tauopathies and synucleinopathies. Several genome-wide association studies have identified alpha-Synuclein (SNCA) and Tau (MAPT) polymorphisms as common risk factors for sporadic Parkinson's disease (PD). However, the mechanisms by which subtle variations in the expression of wild-type SNCA and MAPT influence risk for PD and the underlying cellular events that effect neurotoxicity remain unclear. To examine causes of neurotoxicity associated with the α-Syn/Tau interaction, we used the fruit fly as a model. We utilized misexpression paradigms in three different tissues to probe the α-Syn/Tau interaction: the retina, dopaminergic neurons and the larval neuromuscular junction. Misexpression of Tau and α-Syn enhanced a rough eye phenotype and loss of dopaminergic neurons in fly tauopathy and synucleinopathy models, respectively. Our findings suggest that interactions between α-Syn and Tau at the cellular level cause disruption of cytoskeletal organization, axonal transport defects and aberrant synaptic organization that contribute to neuronal dysfunction and death associated with sporadic PD. α-Syn did not alter levels of Tau phosphorylated at the AT8 epitope. However, α-Syn and Tau colocalized in ubiquitin-positive aggregates in eye imaginal discs. The presence of Tau also led to an increase in urea soluble α-Syn. Our findings have important implications in understanding the cellular and molecular mechanisms underlying α-Syn/Tau-mediated synaptic dysfunction, which likely arise in the early asymptomatic phase of sporadic PD.
Collapse
Affiliation(s)
- Bidisha Roy
- Mitchell Center for Neurodegenerative Diseases
| | | |
Collapse
|
77
|
Prüßing K, Voigt A, Schulz JB. Drosophila melanogaster as a model organism for Alzheimer's disease. Mol Neurodegener 2013; 8:35. [PMID: 24267573 PMCID: PMC4222597 DOI: 10.1186/1750-1326-8-35] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 11/13/2013] [Indexed: 02/05/2023] Open
Abstract
Drosophila melanogaster provides an important resource for in vivo modifier screens of neurodegenerative diseases. To study the underlying pathogenesis of Alzheimer’s disease, fly models that address Tau or amyloid toxicity have been developed. Overexpression of human wild-type or mutant Tau causes age-dependent neurodegeneration, axonal transport defects and early death. Large-scale screens utilizing a neurodegenerative phenotype induced by eye-specific overexpression of human Tau have identified several kinases and phosphatases, apoptotic regulators and cytoskeleton proteins as determinants of Tau toxicity in vivo. The APP ortholog of Drosophila (dAPPl) shares the characteristic domains with vertebrate APP family members, but does not contain the human Aβ42 domain. To circumvent this drawback, researches have developed strategies by either direct secretion of human Aβ42 or triple transgenic flies expressing human APP, β-secretase and Drosophila γ-secretase presenilin (dPsn). Here, we provide a brief overview of how fly models of AD have contributed to our knowledge of the pathomechanisms of disease.
Collapse
Affiliation(s)
- Katja Prüßing
- Department of Neurology, University Medical Center, RWTH Aachen, Pauwelsstrasse 30, D-52074 Aachen, Germany.
| | | | | |
Collapse
|
78
|
Schwalbe M, Biernat J, Bibow S, Ozenne V, Jensen MR, Kadavath H, Blackledge M, Mandelkow E, Zweckstetter M. Phosphorylation of human Tau protein by microtubule affinity-regulating kinase 2. Biochemistry 2013; 52:9068-79. [PMID: 24251416 DOI: 10.1021/bi401266n] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Tau protein plays an important role in neuronal physiology and Alzheimer's neurodegeneration. Its abilities to aggregate abnormally, to bind to microtubules (MTs), and to promote MT assembly are all influenced by phosphorylation. Phosphorylation of serine residues in the KXGS motifs of Tau's repeat domain, crucial for MT interactions and aggregation, is facilitated most efficiently by microtubule-associated protein/microtubule affinity-regulating kinases (MARKs). Here we applied high-resolution nuclear magnetic resonance analysis to study the kinetics of phosphorylation of Tau by MARK2 and its impact on the structure and microtubule binding of Tau. We demonstrate that MARK2 binds to the N-terminal tail of Tau and selectively phosphorylates three major and five minor serine residues in the repeat domain and C-terminal tail. Structural changes induced by phosphorylation of Tau by MARK2 are highly localized in the proximity of the phosphorylation site and do not affect the global conformation, in contrast to phosphorylation in the proline-rich region. Furthermore, single-residue analysis of binding of Tau to MTs provides support for a model in which Tau's hot spots of MT interaction bind independently of each other and are differentially affected by phosphorylation.
Collapse
Affiliation(s)
- Martin Schwalbe
- German Center for Neurodegenerative Diseases (DZNE) , 37077 Göttingen, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
79
|
Agholme L, Nath S, Domert J, Marcusson J, Kågedal K, Hallbeck M. Proteasome inhibition induces stress kinase dependent transport deficits--implications for Alzheimer's disease. Mol Cell Neurosci 2013; 58:29-39. [PMID: 24270002 DOI: 10.1016/j.mcn.2013.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 10/10/2013] [Accepted: 11/14/2013] [Indexed: 01/21/2023] Open
Abstract
Alzheimer's disease (AD) is characterized by accumulation of two misfolded and aggregated proteins, β-amyloid and hyperphosphorylated tau. Both cellular systems responsible for clearance of misfolded and aggregated proteins, the lysosomal and the proteasomal, have been shown to be malfunctioning in the aged brain and more so in patients with neurodegenerative diseases, including AD. This malfunction could be contributing to β-amyloid and tau accumulation, eventually aggregating in plaques and tangles. We have investigated the impact of decreased proteasome activity on tau phosphorylation as well as on microtubule stability and transport. To do this, we used our recently developed neuronal model where human SH-SY5Y cells obtain neuronal morphology and function through differentiation. We found that exposure to low doses of the proteasome inhibitor MG-115 caused tau phosphorylation, microtubule destabilization and disturbed neuritic transport. Furthermore, reduced proteasome activity activated several proteins implicated in tau phosphorylation and AD pathology, including c-Jun N-terminal kinase, c-Jun and extracellular signal-regulated protein kinase (ERK) 1/2. Restoration of the microtubule transport was achieved by inhibiting ERK 1/2 activation, and simultaneous inhibition of both ERK 1/2 and c-Jun reversed the proteasome inhibition-induced tau phosphorylation. Taken together, this study suggests that a decrease in proteasome activity can, through activation of c-Jun and ERK 1/2, result in several events related to neurodegenerative diseases. Restoration of proteasome activity or modulation of ERK 1/2 and c-Jun function can open new treatment possibilities against neurodegenerative diseases such as AD.
Collapse
Affiliation(s)
- Lotta Agholme
- Experimental Pathology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Sangeeta Nath
- Experimental Pathology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Jakob Domert
- Experimental Pathology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Jan Marcusson
- Geriatric, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Katarina Kågedal
- Experimental Pathology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden
| | - Martin Hallbeck
- Experimental Pathology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden; Department of Clinical Pathology, County Council of Östergötland, Linköping, Sweden.
| |
Collapse
|
80
|
Lenz S, Karsten P, Schulz JB, Voigt A. Drosophila as a screening tool to study human neurodegenerative diseases. J Neurochem 2013; 127:453-60. [PMID: 24028575 DOI: 10.1111/jnc.12446] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 08/22/2013] [Accepted: 09/03/2013] [Indexed: 11/28/2022]
Abstract
In an aging society, research involving neurodegenerative disorders is of paramount importance. Over the past few years, research on Alzheimer's and Parkinson's diseases has made tremendous progress. Experimental studies, however, rely mostly on transgenic animal models, preferentially using mice. Although experiments on mice have enormous advantages, they also have some inherent limitations, some of which can be overcome by the use of Drosophila melanogaster as an experimental animal. Among the major advantages of using the fly is its small genome, which can also be modified very easily. The fact that its genome lends itself to diverse alterations (e. g. mutagenesis, transposons) has made the fly a useful organism to perform large-scale and genome-wide screening approaches. This has opened up an entirely new field of experimental research aiming to elucidate genetic interactions and screen for modifiers of disease processes in vivo. Here, we provide a brief overview of how flies can be used to analyze molecular mechanisms underlying human neurodegenerative diseases.
Collapse
Affiliation(s)
- Sarah Lenz
- Department of Neurology, University Medical Center, RWTH Aachen, Aachen, Germany
| | | | | | | |
Collapse
|
81
|
Choksi DK, Roy B, Chatterjee S, Yusuff T, Bakhoum MF, Sengupta U, Ambegaokar S, Kayed R, Jackson GR. TDP-43 Phosphorylation by casein kinase Iε promotes oligomerization and enhances toxicity in vivo. Hum Mol Genet 2013; 23:1025-35. [PMID: 24105464 DOI: 10.1093/hmg/ddt498] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Dominant mutations in transactive response DNA-binding protein-43 (TDP-43) cause amyotrophic lateral sclerosis. TDP-43 inclusions occur in neurons, glia and muscle in this disease and in sporadic and inherited forms of frontotemporal lobar degeneration. Cytoplasmic localization, cleavage, aggregation and phosphorylation of TDP-43 at the Ser409/410 epitope have been associated with disease pathogenesis. TDP-43 aggregation is not a common feature of mouse models of TDP-43 proteinopathy, and TDP-43 is generally not thought to acquire an amyloid conformation or form fibrils. A number of putative TDP-43 kinases have been identified, but whether any of these functions to regulate TDP-43 phosphorylation or toxicity in vivo is not known. Here, we demonstrate that human TDP-43(Q331K) undergoes cytoplasmic localization and aggregates when misexpressed in Drosophila when compared with wild-type and M337V forms. Coexpression of Q331K with doubletime (DBT), the fly homolog of casein kinase Iε (CKIε), enhances toxicity. There is at best modest basal phosphorylation of misexpressed human TDP-43 in Drosophila, but coexpression with DBT increases Ser409/410 phosphorylation of all TDP-43 isoforms tested. Phosphorylation of TDP-43 in the fly is specific for DBT, as it is not observed using the validated tau kinases GSK-3β, PAR-1/MARK2 or CDK5. Coexpression of DBT with TDP-43(Q331K) enhances the formation of high-molecular weight oligomeric species coincident with enhanced toxicity, and treatment of recombinant oligomeric TDP-43 with rat CKI strongly enhances its toxicity in mammalian cell culture. These data identify CKIε as a potent TDP-43 kinase in vivo and implicate oligomeric species as the toxic entities in TDP-43 proteinopathies.
Collapse
|
82
|
Chronic noise exposure and Alzheimer disease: Is there an etiological association? Med Hypotheses 2013; 81:623-6. [DOI: 10.1016/j.mehy.2013.07.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 06/27/2013] [Accepted: 07/05/2013] [Indexed: 11/19/2022]
|
83
|
Impact of N-tau on adult hippocampal neurogenesis, anxiety, and memory. Neurobiol Aging 2013; 34:2551-63. [PMID: 23769395 DOI: 10.1016/j.neurobiolaging.2013.05.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Revised: 04/11/2013] [Accepted: 05/08/2013] [Indexed: 01/12/2023]
Abstract
Different pathological tau species are involved in memory loss in Alzheimer's disease, the most common cause of dementia among older people. However, little is known about how tau pathology directly affects adult hippocampal neurogenesis, a unique form of structural plasticity implicated in hippocampus-dependent spatial learning and mood-related behavior. To this aim, we generated a transgenic mouse model conditionally expressing a pathological tau fragment (26-230 aa of the longest human tau isoform, or N-tau) in nestin-positive stem/progenitor cells. We found that N-tau reduced the proliferation of progenitor cells in the adult dentate gyrus, reduced cell survival and increased cell death by a caspase-3-independent mechanism, and recruited microglia. Although the number of terminally differentiated neurons was reduced, these showed an increased dendritic arborization and spine density. This resulted in an increase of anxiety-related behavior and an impairment of episodic-like memory, whereas less complex forms of spatial learning remained unaltered. Understanding how pathological tau species directly affect neurogenesis is important for developing potential therapeutic strategies to direct neurogenic instructive cues for hippocampal function repair.
Collapse
|
84
|
Mairet-Coello G, Courchet J, Pieraut S, Courchet V, Maximov A, Polleux F. The CAMKK2-AMPK kinase pathway mediates the synaptotoxic effects of Aβ oligomers through Tau phosphorylation. Neuron 2013; 78:94-108. [PMID: 23583109 DOI: 10.1016/j.neuron.2013.02.003] [Citation(s) in RCA: 266] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2013] [Indexed: 12/25/2022]
Abstract
Amyloid-β 1-42 (Aβ42) oligomers are synaptotoxic for excitatory cortical and hippocampal neurons and might play a role in early stages of Alzheimer's disease (AD) progression. Recent results suggested that Aβ42 oligomers trigger activation of AMP-activated kinase (AMPK), and its activation is increased in the brain of patients with AD. We show that increased intracellular calcium [Ca²⁺](i) induced by NMDA receptor activation or membrane depolarization activates AMPK in a CAMKK2-dependent manner. CAMKK2 or AMPK overactivation is sufficient to induce dendritic spine loss. Conversely, inhibiting their activity protects hippocampal neurons against synaptotoxic effects of Aβ42 oligomers in vitro and against the loss of dendritic spines observed in the human APP(SWE,IND)-expressing transgenic mouse model in vivo. AMPK phosphorylates Tau on KxGS motif S262, and expression of Tau S262A inhibits the synaptotoxic effects of Aβ42 oligomers. Our results identify a CAMKK2-AMPK-Tau pathway as a critical mediator of the synaptotoxic effects of Aβ42 oligomers.
Collapse
Affiliation(s)
- Georges Mairet-Coello
- Department of Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | | | | | | | | | |
Collapse
|
85
|
Abstract
AbstractRecent investigations into the etiology and pathogenesis of Alzheimer’s disease (AD) in the past few years have expanded to include previously unexplored and/or disconnected aspects of AD and related conditions at both the cellular and systemic levels of organization. These include how AD-associated abnormalities affect the cell cycle and neuronal differentiation state and how they recruit signal transduction, membrane trafficking and protein transcytosis mechanisms to produce a neurotoxic syndrome capable of spreading itself throughout the brain. The recent expansion of AD research into intercellular and new aspects of cellular degenerative mechanisms is causing a systemic re-evaluation of AD pathogenesis, including the roles played by well-studied elements, such as the generation of Aβ and tau protein aggregates. It is also changing our view of neurodegenerative diseases as a whole. Here we propose a conceptual framework to account for some of the emerging aspects of the role of tau in AD pathogenesis.
Collapse
|
86
|
Newman T, Sinadinos C, Johnston A, Sealey M, Mudher A. Using Drosophila models of neurodegenerative diseases for drug discovery. Expert Opin Drug Discov 2012; 6:129-40. [PMID: 22647132 DOI: 10.1517/17460441.2011.549124] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and Huntington's disease are increasing in prevalence as our aging population increases in size. Despite this, currently there are no disease-modifying drugs available for the treatment of these conditions. Drosophila melanogaster is a highly tractable model organism that has been successfully used to emulate various aspects of these diseases in vivo. These Drosophila models have not been fully exploited in drug discovery and design strategies. AREAS COVERED This review explores how Drosophila models can be used to facilitate drug discovery. Specifically, we review their uses as a physiologically-relevant medium to high-throughput screening tool for the identification of therapeutic compounds and discuss how they can aid drug discovery by highlighting disease mechanisms that may serve as druggable targets in the future. The reader will appreciate how the various attributes of Drosophila make it an unsurpassed model organism and how Drosophila models of neurodegeneration can contribute to drug discovery in a variety of ways. EXPERT OPINION Drosophila models of human neurodegenerative diseases can make a significant contribution to the unmet need of disease-modifying therapeutic intervention for the treatment of these increasingly common neurodegenerative conditions.
Collapse
Affiliation(s)
- Tracey Newman
- University of Southampton, School of Medicine, Life Science Building 85, Southampton, SO17 1BJ, UK +44 2380 597642 ;
| | | | | | | | | |
Collapse
|
87
|
Cui B, Zhu L, She X, Wu M, Ma Q, Wang T, Zhang N, Xu C, Chen X, An G, Liu H. Chronic noise exposure causes persistence of tau hyperphosphorylation and formation of NFT tau in the rat hippocampus and prefrontal cortex. Exp Neurol 2012; 238:122-9. [PMID: 22971273 DOI: 10.1016/j.expneurol.2012.08.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 08/05/2012] [Accepted: 08/28/2012] [Indexed: 10/27/2022]
Abstract
The non-auditory effects of noise exposure on the central nervous system have been established both epidemiologically and experimentally. Chronic noise exposure (CNE) has been associated with tau hyperphosphorylation and Alzheimer's disease (AD)-like pathological changes. However, experimental evidence for these associations remains limited. The aim of the current study was to explore the effects of CNE [100 dB sound pressure level (SPL) white noise, 4 h/d×14 d] on tau phosphorylation in the rat hippocampus and the prefrontal cortex. Forty-eight male Wistar rats were randomly assigned to two groups: a noise-exposed group and a control group. The levels of radioimmunoprecipitation assay (RIPA)-soluble and RIPA-insoluble phosphorylated tau at Ser202, Ser396, Ser404, and Ser422 in the hippocampus and the prefrontal cortex were measured at different time points (days 0, 3, 7, and 14) after the end of the last noise exposure. Exposure to white noise for 14 consecutive days significantly increased the levels of tau phosphorylation at Ser202, Ser396, Ser404, and Ser422, the sites typically phosphorylated in AD brains, in the hippocampus and the prefrontal cortex. Tau hyperphosphorylation persisted for 7 to 14 d after the cessation of noise exposure. These alterations were also concomitant with the generation of pathological neurofibrillary tangle (NFT) tau 3, 7 and 14 d after the end of the stimulus. Furthermore, lasting increases in proteins involved in hyperphosphorylation, namely glycogen synthase kinase 3β (GSK3β) and protein phosphatase 2A (PP2A), were found to occur in close correspondence with increase in tau hyperphosphorylation. The results of this study show that CNE leads to long-lasting increases in non-NFT hyperphosphorylated tau and delayed formation of misfolded NFT tau in the hippocampus and the prefrontal cortex. Our results also provide evidence for the involvement of GSK3β and PP2A in these processes.
Collapse
Affiliation(s)
- Bo Cui
- Department of Occupational Hygiene, Institute of Health and Environmental Medicine, Academy of Military Medical Sciences, Tianjin, China.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
88
|
Rincon-Limas DE, Jensen K, Fernandez-Funez P. Drosophila models of proteinopathies: the little fly that could. Curr Pharm Des 2012; 18:1108-22. [PMID: 22288402 PMCID: PMC3290773 DOI: 10.2174/138161212799315894] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Accepted: 12/19/2011] [Indexed: 02/08/2023]
Abstract
Alzheimer’s, Parkinson’s, and Huntington’s disease are complex neurodegenerative conditions with high prevalence characterized by protein misfolding and deposition in the brain. Considerable progress has been made in the last two decades in identifying the genes and proteins responsible for several human ‘proteinopathies’. A wide variety of wild type and mutant proteins associated with neurodegenerative conditions are structurally unstable, misfolded, and acquire conformations rich in ß-sheets (ß-state). These conformers form highly toxic self-assemblies that kill the neurons in stereotypical patterns. Unfortunately, the detailed understanding of the molecular and cellular perturbations caused by these proteins has not produced a single disease-modifying therapy. More than a decade ago, several groups demonstrated that human proteinopathies reproduce critical features of the disease in transgenic flies, including protein misfolding, aggregation, and neurotoxicity. These initial reports led to an explosion of research that has contributed to a better understanding of the molecular mechanisms regulating conformational dynamics and neurotoxic cascades. To remain relevant in this competitive environment, Drosophila models will need to expand their flexible, innovative, and multidisciplinary approaches to find new discoveries and translational applications.
Collapse
Affiliation(s)
- Diego E Rincon-Limas
- Department of Neurology, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0236, USA.
| | | | | |
Collapse
|
89
|
Chadwick L, Gentle L, Strachan J, Layfield R. Review: unchained maladie - a reassessment of the role of Ubb(+1) -capped polyubiquitin chains in Alzheimer's disease. Neuropathol Appl Neurobiol 2012; 38:118-31. [PMID: 22082077 DOI: 10.1111/j.1365-2990.2011.01236.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Molecular misreading allows the formation of mutant proteins in the absence of gene mutations. A mechanism has been proposed by which a frameshift mutant of the ubiquitin protein, Ubb(+1) , which accumulates in an age-dependent manner as a result of molecular misreading, contributes to neuropathology in Alzheimer's disease (Lam et al. 2000). Specifically, in the Ubb(+1) -mediated proteasome inhibition hypothesis Ubb(+1) 'caps' unanchored (that is, nonsubstrate linked) polyubiquitin chains, which then act as dominant inhibitors of the 26S proteasome. A review of subsequent literature indicates that this original hypothesis is broadly supported, and offers new insights into the mechanisms accounting for the age-dependent accumulation of Ubb(+1) , and how Ubb(+1) -mediated proteasome inhibition may contribute to Alzheimer's disease. Further, recent studies have highlighted a physiological role for free endogenous unanchored polyubiquitin chains in the direct activation of certain protein kinases. This raises the possibility that Ubb(+1) -capped unanchored polyubiquitin chains could also exert harmful effects through the aberrant activation of tau or other ubiquitin-dependent kinases, neuronal NF-κB activity or NF-κB-mediated neuroinflammatory processes.
Collapse
Affiliation(s)
- L Chadwick
- School of Biomedical Sciences, University of Nottingham, UK
| | | | | | | |
Collapse
|
90
|
Drosophila models of tauopathies: what have we learned? Int J Alzheimers Dis 2012; 2012:970980. [PMID: 22701808 PMCID: PMC3373119 DOI: 10.1155/2012/970980] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 04/08/2012] [Indexed: 01/10/2023] Open
Abstract
Aggregates of the microtubule-associated protein Tau are neuropathological hallmark lesions in Alzheimer's disease (AD) and related primary tauopathies. In addition, Tau is genetically implicated in a number of human neurodegenerative disorders including frontotemporal dementia (FTD) and Parkinson's disease (PD). The exact mechanism by which Tau exerts its neurotoxicity is incompletely understood. Here, we give an overview of how studies using the genetic model organism Drosophila over the past decade have contributed to the molecular understanding of Tau neurotoxicity. We compare the different available readouts for Tau neurotoxicity in flies and review the molecular pathways in which Tau has been implicated. Finally, we emphasize that the integration of genome-wide approaches in human or mice with high-throughput genetic validation in Drosophila is a fruitful approach.
Collapse
|
91
|
Tau Phosphorylation by GSK3 in Different Conditions. Int J Alzheimers Dis 2012; 2012:578373. [PMID: 22675648 PMCID: PMC3362846 DOI: 10.1155/2012/578373] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 03/15/2012] [Indexed: 11/18/2022] Open
Abstract
Almost a 20% of the residues of tau protein are phosphorylatable amino acids: serine, threonine, and tyrosine. In this paper we comment on the consequences for tau of being a phosphoprotein. We will focus on serine/threonine phosphorylation. It will be discussed that, depending on the modified residue in tau molecule, phosphorylation could be protective, in processes like hibernation, or toxic like in development of those diseases known as tauopathies, which are characterized by an hyperphosphorylation and aggregation of tau.
Collapse
|
92
|
Lasagna-Reeves CA, Castillo-Carranza DL, Sengupta U, Sarmiento J, Troncoso J, Jackson GR, Kayed R. Identification of oligomers at early stages of tau aggregation in Alzheimer's disease. FASEB J 2012; 26:1946-59. [PMID: 22253473 DOI: 10.1096/fj.11-199851] [Citation(s) in RCA: 361] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Neurofibrillary tangles (NFTs) are a pathological hallmark of Alzheimer's disease (AD); however, the relationship between NFTs and disease progression remains controversial. Analyses of tau animal models suggest that phenotypes coincide with accumulation of soluble aggregated tau species but not the accumulation of NFTs. The pathological role of prefilamentous tau aggregates, e.g., tau oligomeric intermediates, is poorly understood, in part because of methodological challenges. Here, we engineered a novel tau oligomer-specific antibody, T22, and used it to elucidate the temporal course and biochemical features of oligomers during NFT development in AD brain. We found that tau oligomers in human AD brain samples were 4-fold higher than those in the controls. We also revealed the role of oligomeric tau conformers in pretangles, neuritic plaques, and neuropil threads in the frontal cortex tissue from AD brains; this analysis uncovers a consistent code that governs tau oligomerization with regard to degree of neuronal cytopathology. These data are the first to characterize the role of tau oligomers in the natural history of NFTs, and they highlight the suitability of tau oligomers as therapeutic targets in AD and related tauopathies.
Collapse
Affiliation(s)
- Cristian A Lasagna-Reeves
- University of Texas Medical Branch, 301 University Blvd., Medical Research Building, Room 10.138C, Galveston, TX, USA
| | | | | | | | | | | | | |
Collapse
|
93
|
Cui B, Wu M, She X, Liu H. Impulse noise exposure in rats causes cognitive deficits and changes in hippocampal neurotransmitter signaling and tau phosphorylation. Brain Res 2012; 1427:35-43. [DOI: 10.1016/j.brainres.2011.08.035] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 08/04/2011] [Accepted: 08/13/2011] [Indexed: 10/17/2022]
|
94
|
Cowan CM, Sealey MA, Quraishe S, Targett MT, Marcellus K, Allan D, Mudher A. Modelling tauopathies in Drosophila: insights from the fruit fly. Int J Alzheimers Dis 2011; 2011:598157. [PMID: 22254145 PMCID: PMC3255107 DOI: 10.4061/2011/598157] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 11/02/2011] [Indexed: 01/04/2023] Open
Abstract
Drosophila melanogaster is an experimentally tractable model organism that has been used successfully to model aspects of many human neurodegenerative diseases. Drosophila models of tauopathy have provided valuable insights into tau-mediated mechanisms of neuronal dysfunction and death. Here we review the findings from Drosophila models of tauopathy reported over the past ten years and discuss how they have furthered our understanding of the pathogenesis of tauopathies. We also discuss the multitude of technical advantages that Drosophila offers, which make it highly attractive as a model for such studies.
Collapse
Affiliation(s)
- Catherine M Cowan
- Centre for Biological Sciences, University of Southampton, University Road, Southampton SO17 3JD, UK
| | | | | | | | | | | | | |
Collapse
|
95
|
Cheung ZH, Ip NY. Cdk5: a multifaceted kinase in neurodegenerative diseases. Trends Cell Biol 2011; 22:169-75. [PMID: 22189166 DOI: 10.1016/j.tcb.2011.11.003] [Citation(s) in RCA: 184] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 11/09/2011] [Accepted: 11/14/2011] [Indexed: 10/14/2022]
Abstract
Since the identification of cyclin-dependent kinase-5 (Cdk5) as a tau kinase and member of the Cdk family almost 20 years ago, deregulation of Cdk5 activity has been linked to an array of neurodegenerative diseases. As knowledge on the etiopathological mechanisms of these diseases evolved through the years, Cdk5 has also been implicated in additional cellular events that are affected under these pathological conditions. From the role of Cdk5 in the regulation of synaptic functions to its involvement in autophagy deregulation, significant insights have been obtained regarding the role of Cdk5 as a key regulator of neurodegeneration. Here, we summarize recent findings on the involvement of Cdk5 in the pathophysiological mechanisms underlying various neurodegenerative diseases.
Collapse
Affiliation(s)
- Zelda H Cheung
- Division of Life Science, Molecular Neuroscience Center and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
| | | |
Collapse
|
96
|
Yoshida H, Goedert M. Phosphorylation of microtubule-associated protein tau by AMPK-related kinases. J Neurochem 2011; 120:165-76. [DOI: 10.1111/j.1471-4159.2011.07523.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
97
|
Ali YO, Ruan K, Zhai RG. NMNAT suppresses tau-induced neurodegeneration by promoting clearance of hyperphosphorylated tau oligomers in a Drosophila model of tauopathy. Hum Mol Genet 2011; 21:237-50. [PMID: 21965302 DOI: 10.1093/hmg/ddr449] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Tauopathies, including Alzheimer's disease, are a group of neurodegenerative diseases characterized by abnormal tau hyperphosphorylation that leads to formation of neurofibrillary tangles. Drosophila models of tauopathy display prominent features of the human disease including compromised lifespan, impairments of learning, memory and locomotor functions and age-dependent neurodegeneration visible as vacuolization. Here, we use a Drosophila model of frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), in order to study the neuroprotective capacity of a recently identified neuronal maintenance factor, nicotinamide mononucleotide (NAD) adenylyl transferase (NMNAT), a protein that has both NAD synthase and chaperone function. NMNAT is essential for maintaining neuronal integrity under normal conditions and has been shown to protect against several neurodegenerative conditions. However, its protective role in tauopathy has not been examined. Here, we show that overexpression of NMNAT significantly suppresses both behavioral and morphological deficits associated with tauopathy by means of reducing the levels of hyperphosphorylated tau oligomers. Importantly, the protective activity of NMNAT protein is independent of its NAD synthesis activity, indicating a role for direct protein-protein interaction. Next, we show that NMNAT interacts with phosphorylated tau in vivo and promotes the ubiquitination and clearance of toxic tau species. Consequently, apoptosis activation was significantly reduced in brains overexpressing NMNAT, and neurodegeneration was suppressed. Our report on the molecular basis of NMNAT-mediated neuroprotection in tauopathies opens future investigation of this factor in other protein foldopathies.
Collapse
Affiliation(s)
- Yousuf O Ali
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA
| | | | | |
Collapse
|
98
|
Ambegaokar SS, Jackson GR. Functional genomic screen and network analysis reveal novel modifiers of tauopathy dissociated from tau phosphorylation. Hum Mol Genet 2011; 20:4947-77. [PMID: 21949350 PMCID: PMC3221533 DOI: 10.1093/hmg/ddr432] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A functional genetic screen using loss-of-function and gain-of-function alleles was performed to identify modifiers of tau-induced neurotoxicity using the 2N/4R (full-length) isoform of wild-type human tau expressed in the fly retina. We previously reported eye pigment mutations, which create dysfunctional lysosomes, as potent modifiers; here, we report 37 additional genes identified from ∼1900 genes screened, including the kinases shaggy/GSK-3beta, par-1/MARK, CamKI and Mekk1. Tau acts synergistically with Mekk1 and p38 to down-regulate extracellular regulated kinase activity, with a corresponding decrease in AT8 immunoreactivity (pS202/T205), suggesting that tau can participate in signaling pathways to regulate its own kinases. Modifiers showed poor correlation with tau phosphorylation (using the AT8, 12E8 and AT270 epitopes); moreover, tested suppressors of wild-type tau were equally effective in suppressing toxicity of a phosphorylation-resistant S11A tau construct, demonstrating that changes in tau phosphorylation state are not required to suppress or enhance its toxicity. Genes related to autophagy, the cell cycle, RNA-associated proteins and chromatin-binding proteins constitute a large percentage of identified modifiers. Other functional categories identified include mitochondrial proteins, lipid trafficking, Golgi proteins, kinesins and dynein and the Hsp70/Hsp90-organizing protein (Hop). Network analysis uncovered several other genes highly associated with the functional modifiers, including genes related to the PI3K, Notch, BMP/TGF-β and Hedgehog pathways, and nuclear trafficking. Activity of GSK-3β is strongly upregulated due to TDP-43 expression, and reduced GSK-3β dosage is also a common suppressor of Aβ42 and TDP-43 toxicity. These findings suggest therapeutic targets other than mitigation of tau phosphorylation.
Collapse
Affiliation(s)
- Surendra S Ambegaokar
- Department of Neurology, University of Texas Medical Branch, 301 University Blvd., MRB 10.138, Galveston, TX 77555, USA
| | | |
Collapse
|
99
|
Pritchard SM, Dolan PJ, Vitkus A, Johnson GVW. The toxicity of tau in Alzheimer disease: turnover, targets and potential therapeutics. J Cell Mol Med 2011; 15:1621-35. [PMID: 21348938 PMCID: PMC4373356 DOI: 10.1111/j.1582-4934.2011.01273.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 02/08/2011] [Indexed: 11/28/2022] Open
Abstract
It has been almost 25 years since the initial discovery that tau was the primary component of the neurofibrillary tangles (NFTs) in Alzheimer disease (AD) brain. Although AD is defined by both β-amyloid (Aβ) pathology (Aβ plaques) and tau pathology (NFTs), whether or not tau played a critical role in disease pathogenesis was a subject of discussion for many years. However, given the increasing evidence that pathological forms of tau can compromise neuronal function and that tau is likely an important mediator of Aβ toxicity, there is a growing awareness that tau is a central player in AD pathogenesis. In this review we begin with a brief history of tau, then provide an overview of pathological forms of tau, followed by a discussion of the differential degradation of tau by either the proteasome or autophagy and possible mechanisms by which pathological forms of tau may exert their toxicity. We conclude by discussing possible avenues for therapeutic intervention based on these emerging themes of tau's role in AD.
Collapse
Affiliation(s)
- Susanne M Pritchard
- Gail V.W. JOHNSON, Ph.D., Department of Anesthesiology, 601 Elmwood Ave., Box 604, Rm. 4–6314, University of Rochester, Rochester, NY 14642, USA. Tel.: 585-276-3740 Fax: 585-276-2418 E-mail:
| | | | - Alisa Vitkus
- Department of Anesthesiology and the Interdepartmental Graduate Program in Neuroscience, University of RochesterRochester, NY, USA
| | - Gail VW Johnson
- Department of Anesthesiology and the Interdepartmental Graduate Program in Neuroscience, University of RochesterRochester, NY, USA
| |
Collapse
|
100
|
Hanger DP, Noble W. Functional implications of glycogen synthase kinase-3-mediated tau phosphorylation. Int J Alzheimers Dis 2011; 2011:352805. [PMID: 21776376 PMCID: PMC3139124 DOI: 10.4061/2011/352805] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 05/06/2011] [Indexed: 11/29/2022] Open
Abstract
Tau is primarily a neuronal microtubule-associated protein that has functions related to the stabilisation of microtubules. Phosphorylation of tau is an important dynamic and regulatory element involved in the binding of tau to tubulin. Thus, highly phosphorylated tau is more likely to be present in the cytosolic compartment of neurons, whereas reduced phosphate burden allows tau to bind to and stabilise the microtubule cytoskeleton. Highly phosphorylated forms of tau are deposited in the brain in a range of neurodegenerative disorders including Alzheimer's disease, progressive supranuclear palsy, and frontotemporal lobar degeneration associated with Pick bodies. A key candidate kinase for both physiological and pathological tau phosphorylation is glycogen synthase kinase-3 (GSK-3). Multiple phosphorylation sites have been identified on tau exposed to GSK-3 in vitro and in cells. In this review, we highlight recent data suggesting a role for GSK-3 activity on physiological tau function and on tau dysfunction in neurodegenerative disease.
Collapse
Affiliation(s)
- Diane P Hanger
- Department of Neuroscience (P037), MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
| | | |
Collapse
|