201
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Ramachandran G, Udgaonkar JB. Mechanistic studies unravel the complexity inherent in tau aggregation leading to Alzheimer's disease and the tauopathies. Biochemistry 2013; 52:4107-26. [PMID: 23721410 DOI: 10.1021/bi400209z] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The aggregation of the protein tau into amyloid fibrils is known to be involved in the causation of the neurodegenerative tauopathies and the progression of cognitive decline in Alzheimer's disease. This review surveys the mechanism of tau aggregation with special emphasis on the information obtained from biochemical and biophysical studies. First, tau is described from a structure-function perspective. Subsequently, the connection of tau to neurodegeneration is explained, and a description of the tau amyloid fibril is provided. Lastly, studies of the mechanism of tau fibril formation are reviewed, and the physiological significance of these studies with reference to how they can clarify many aspects of disease progression is described. The aim of this review is to underscore how mechanistic studies reveal the complexity of the tau fibril formation pathway and the plethora of species populated on or off the pathway of aggregation, and how this information can be beneficial in the design of inhibitors or drugs that ameliorate neurodegeneration.
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Affiliation(s)
- Gayathri Ramachandran
- National Centre for Biological Sciences, Tata Institute of Fundamental Research , Bangalore 560065, India
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202
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Abstract
PURPOSE OF REVIEW Intraneuronal lesions consisting of abnormal tau protein are seen to develop from the beginning until the end-phase of the pathological process underlying Alzheimer's disease. This review highlights the earliest phase of this process. RECENT FINDINGS Development of abnormal tau frequently begins during childhood or puberty in nuclei of the lower brainstem sending diffuse projections to the cerebral cortex. Nonfibrillar abnormal tau material first occurs in the proximal axon of projection neurons in the locus coeruleus. Subsequently, a similar material (pretangle material) fills the somatodendritic compartment. In contrast with the pretangle material in cell bodies and dendrites, the nonfibrillar material in the axon normally does not convert into stable fibrillary inclusions. SUMMARY Projection neurons (not only those of the locus coeruleus) are sturdy and can survive for a lifetime despite the existence of Alzheimer-related abnormal tau. Currently, little understood mechanisms most probably exist that enable neurons to fulfill their general functions even when severe tau pathology is present. The proclivity of predisposed neuronal types to develop abnormal tau may be intrinsic to the human brain. However, the tempo of disease progression reveals considerable individual differences, thereby offering opportunities to study conditions that may modify disease progression.
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203
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Yao J, Gao X, Sun W, Yao T, Shi S, Ji L. Molecular Hairpin: A Possible Model for Inhibition of Tau Aggregation by Tannic Acid. Biochemistry 2013; 52:1893-902. [DOI: 10.1021/bi400240c] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Junliang Yao
- Department of Chemistry, Tongji University, Shanghai 200092, China
| | - Xing Gao
- Department of Chemistry, Tongji University, Shanghai 200092, China
| | - Wenliang Sun
- Department of Chemistry, Tongji University, Shanghai 200092, China
| | - Tianming Yao
- Department of Chemistry, Tongji University, Shanghai 200092, China
| | - Shuo Shi
- Department of Chemistry, Tongji University, Shanghai 200092, China
| | - Liangnian Ji
- MOE Laboratory of Bioinorganic
and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, China
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204
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Camero S, Benítez MJ, Jiménez JS. Anomalous Protein–DNA Interactions Behind Neurological Disorders. PROTEIN-NUCLEIC ACIDS INTERACTIONS 2013; 91:37-63. [DOI: 10.1016/b978-0-12-411637-5.00002-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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205
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The fuzzy coat of pathological human Tau fibrils is a two-layered polyelectrolyte brush. Proc Natl Acad Sci U S A 2012; 110:E313-21. [PMID: 23269837 DOI: 10.1073/pnas.1212100110] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structure and properties of amyloid-like Tau fibrils accumulating in neurodegenerative diseases have been debated for decades. Although the core of Tau fibrils assembles from short β-strands, the properties of the much longer unstructured Tau domains protruding from the fibril core remain largely obscure. Applying immunogold transmission EM, and force-volume atomic force microscopy (AFM), we imaged human Tau fibrils at high resolution and simultaneously mapped their mechanical and adhesive properties. Tau fibrils showed a ≈ 16-nm-thick fuzzy coat that resembles a two-layered polyelectrolyte brush, which is formed by the unstructured short C-terminal and long N-terminal Tau domains. The mechanical and adhesive properties of the fuzzy coat are modulated by electrolytes and pH, and thus by the cellular environment. These unique properties of the fuzzy coat help in understanding how Tau fibrils disturb cellular interactions and accumulate in neurofibrillary tangles.
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206
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Gallat FX, Laganowsky A, Wood K, Gabel F, van Eijck L, Wuttke J, Moulin M, Härtlein M, Eisenberg D, Colletier JP, Zaccai G, Weik M. Dynamical coupling of intrinsically disordered proteins and their hydration water: comparison with folded soluble and membrane proteins. Biophys J 2012; 103:129-36. [PMID: 22828339 DOI: 10.1016/j.bpj.2012.05.027] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 05/03/2012] [Accepted: 05/18/2012] [Indexed: 11/16/2022] Open
Abstract
Hydration water is vital for various macromolecular biological activities, such as specific ligand recognition, enzyme activity, response to receptor binding, and energy transduction. Without hydration water, proteins would not fold correctly and would lack the conformational flexibility that animates their three-dimensional structures. Motions in globular, soluble proteins are thought to be governed to a certain extent by hydration-water dynamics, yet it is not known whether this relationship holds true for other protein classes in general and whether, in turn, the structural nature of a protein also influences water motions. Here, we provide insight into the coupling between hydration-water dynamics and atomic motions in intrinsically disordered proteins (IDP), a largely unexplored class of proteins that, in contrast to folded proteins, lack a well-defined three-dimensional structure. We investigated the human IDP tau, which is involved in the pathogenic processes accompanying Alzheimer disease. Combining neutron scattering and protein perdeuteration, we found similar atomic mean-square displacements over a large temperature range for the tau protein and its hydration water, indicating intimate coupling between them. This is in contrast to the behavior of folded proteins of similar molecular weight, such as the globular, soluble maltose-binding protein and the membrane protein bacteriorhodopsin, which display moderate to weak coupling, respectively. The extracted mean square displacements also reveal a greater motional flexibility of IDP compared with globular, folded proteins and more restricted water motions on the IDP surface. The results provide evidence that protein and hydration-water motions mutually affect and shape each other, and that there is a gradient of coupling across different protein classes that may play a functional role in macromolecular activity in a cellular context.
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Affiliation(s)
- F-X Gallat
- Comissariat à l'Energie Atomique, Institut de Biologie Structurale, Grenoble, France
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207
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Wu JW, Herman M, Liu L, Simoes S, Acker CM, Figueroa H, Steinberg JI, Margittai M, Kayed R, Zurzolo C, Di Paolo G, Duff KE. Small misfolded Tau species are internalized via bulk endocytosis and anterogradely and retrogradely transported in neurons. J Biol Chem 2012. [PMID: 23188818 DOI: 10.1074/jbc.m112.394528] [Citation(s) in RCA: 378] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The accumulation of Tau into aggregates is associated with key pathological events in frontotemporal lobe degeneration (FTD-Tau) and Alzheimer disease (AD). Recent data have shown that misfolded Tau can be internalized by cells in vitro (Frost, B., Jacks, R. L., and Diamond, M. I. (2009) J. Biol. Chem. 284, 12845-12852) and propagate pathology in vivo (Clavaguera, F., Bolmont, T., Crowther, R. A., Abramowski, D., Frank, S., Probst, A., Fraser, G., Stalder, A. K., Beibel, M., Staufenbiel, M., Jucker, M., Goedert, M., and Tolnay, M. (2009) Nat. Cell Biol. 11, 909-913; Lasagna-Reeves, C. A., Castillo-Carranza, D. L., Sengupta, U., Guerrero-Munoz, M. J., Kiritoshi, T., Neugebauer, V., Jackson, G. R., and Kayed, R. (2012) Sci. Rep. 2, 700). Here we show that recombinant Tau misfolds into low molecular weight (LMW) aggregates prior to assembly into fibrils, and both extracellular LMW Tau aggregates and short fibrils, but not monomers, long fibrils, nor long filaments purified from brain extract are taken up by neurons. Remarkably, misfolded Tau can be internalized at the somatodendritic compartment, or the axon terminals and it can be transported anterogradely, retrogradely, and can enhance tauopathy in vivo. The internalized Tau aggregates co-localize with dextran, a bulk-endocytosis marker, and with the endolysosomal compartments. Our findings demonstrate that exogenous Tau can be taken up by cells, uptake depends on both the conformation and size of the Tau aggregates and once inside cells, Tau can be transported. These data provide support for observations that tauopathy can spread trans-synaptically in vivo, via cell-to-cell transfer.
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Affiliation(s)
- Jessica W Wu
- Department of Pathology and Cell Biology, Taub Institute for Alzheimer's Disease Research, Columbia University, New York, New York 10032, USA
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208
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Flach K, Hilbrich I, Schiffmann A, Gärtner U, Krüger M, Leonhardt M, Waschipky H, Wick L, Arendt T, Holzer M. Tau oligomers impair artificial membrane integrity and cellular viability. J Biol Chem 2012; 287:43223-33. [PMID: 23129775 DOI: 10.1074/jbc.m112.396176] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The microtubule-associated protein Tau is mainly expressed in neurons, where it binds and stabilizes microtubules. In Alzheimer disease and other tauopathies, Tau protein has a reduced affinity toward microtubules. As a consequence, Tau protein detaches from microtubules and eventually aggregates into β-sheet-containing filaments. The fibrillization of monomeric Tau to filaments is a multistep process that involves the formation of various aggregates, including spherical and protofibrillar oligomers. Previous concepts, primarily developed for Aβ and α-synuclein, propose these oligomeric intermediates as the primary cytotoxic species mediating their deleterious effects through membrane permeabilization. In the present study, we thus analyzed whether this concept can also be applied to Tau protein. To this end, viability and membrane integrity were assessed on SH-SY5Y neuroblastoma cells and artificial phospholipid vesicles, treated with Tau monomers, Tau aggregation intermediates, or Tau fibrils. Our findings suggest that oligomeric Tau aggregation intermediates are the most toxic compounds of Tau fibrillogenesis, which effectively decrease cell viability and increase phospholipid vesicle leakage. Our data integrate Tau protein into the class of amyloidogenic proteins and enforce the hypothesis of a common toxicity-mediating mechanism for amyloidogenic proteins.
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Affiliation(s)
- Katharina Flach
- Department of Molecular and Cellular Mechanisms of Neurodegeneration, Paul Flechsig Institute of Brain Research, Faculty of Medicine, Jahnallee 59, University of Leipzig, 04109 Leipzig, Germany
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209
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Combs B, Gamblin TC. FTDP-17 tau mutations induce distinct effects on aggregation and microtubule interactions. Biochemistry 2012; 51:8597-607. [PMID: 23043292 DOI: 10.1021/bi3010818] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
FTDP-17 mutations in the tau gene lead to early onset frontotemporal dementias characterized by the pathological aggregation of the microtubule-associated protein tau. Tau aggregation is closely correlated with the progression and severity of localized atrophy of certain regions in the brain. These mutations are primarily located in or near the microtubule-binding repeat regions of tau and can have vastly different effects on the protein. Some mutations have been linked to effects such as increased levels of aggregation, hyperphosphorylation, defects in mRNA splicing, and weakened interaction with microtubules. Given the differential effects of the mutations, it may not be surprising that the pathology associated with FTDP-17 can vary widely as well. Despite this variety, several of the mutations are commonly used interchangeably as aggregation inducers for in vitro and in vivo models of tauopathies. We generated recombinant forms of 12 FTDP-17 mutations chosen for their predicted effects on the charge, hydrophobicity, and secondary structure of the protein. We then examined the effects that the mutations had on the properties of in vitro aggregation of the protein and its ability to stabilize microtubule assembly. The group of mutations induced very different effects on the total amount of aggregation, the kinetics of aggregation, and filament morphology. Several of the mutations inhibited the microtubule stabilization ability of tau, while others had very little effect compared to wild-type tau. These results indicate that the mechanisms of disease progression may differ among FTDP-17 mutations and that the effects of the varying mutations may not be equal in all model systems.
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Affiliation(s)
- Benjamin Combs
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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210
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Elbaum-Garfinkle S, Rhoades E. Identification of an aggregation-prone structure of tau. J Am Chem Soc 2012; 134:16607-13. [PMID: 22998648 DOI: 10.1021/ja305206m] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The aggregation and deposition of normally soluble proteins is the hallmark of several devastating neurodegenerative disorders. For proteins such as tau in Alzheimer's disease and α-synuclein in Parkinson's disease, aggregation involves a transition from an intrinsically disordered monomer to a highly structured fiber. While understanding the role of these proteins in neurodegeneration requires elucidation of the structural basis of self-association, the conformational heterogeneity of disordered proteins makes their structural characterization inherently challenging. Here we use single molecule Förster resonance energy transfer to measure the conformational ensemble of tau in the absence and presence of heparin to identify critical conformational changes relevant to the initiation of aggregation. We find that different domains of tau display distinct conformational properties that are strongly correlated with their degree of disorder and that may relate to their roles in aggregation. Moreover, we observe that heparin binding induces a distinct two-state structural transition in tau characterized by a loss of long-range contacts and a concomitant compaction of the microtubule binding domain. Our results describe a conformational intermediate of tau that precedes the formation of aggregates and could serve as a target for tau-focused therapeutics.
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Affiliation(s)
- Shana Elbaum-Garfinkle
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, Connecticut 06520-8114, USA
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211
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Ciasca G, Campi G, Battisti A, Rea G, Rodio M, Papi M, Pernot P, Tenenbaum A, Bianconi A. Continuous thermal collapse of the intrinsically disordered protein tau is driven by its entropic flexible domain. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:13405-13410. [PMID: 22891813 DOI: 10.1021/la302628y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The tau protein belongs to the category of Intrinsically Disordered Proteins (IDP), which in their native state lack a folded structure and fluctuate between many conformations. In its physiological state, tau helps nucleating and stabilizing the microtubules' (MTs) surfaces in the axons of the neurons. Tau is mainly composed by two domains: (i) the binding domain that tightly bounds the MT surfaces and (ii) the projection domain that exerts a long-range entropic repulsive force and thus provides the proper spacing between adjacent MTs. Tau is also involved in the genesis and in the development of the Alzheimer disease when it detaches from MT surfaces and aggregates in paired helical filaments. Unfortunately, the molecular mechanisms behind these phenomena are still unclear. Temperature variation, rarely considered in biological studies, is here used to provide structural information on tau correlated to its role as an entropic spacer between adjacent MTs surfaces. In this paper, by means of small-angle X-ray scattering and molecular dynamics simulation, we demonstrate that tau undergoes a counterintuitive collapse phenomenon with increasing temperature. A detailed analysis of our results, performed by the Ensemble Optimization Method, shows that the thermal collapse is coupled to the occurrence of a transient long-range contact between a region encompassing the end of the proline-rich domain P2 and the first part of the repeats domain, and the region of the N-terminal domain entailing residues 80-150. Interestingly these two regions involved in the tau temperature collapse belong to the flexible projection domain that acts as an entropic bristle and regulates the MTs' architecture. Our results show that temperature is an important parameter that influences the dynamics of the tau projection domain, and hence its entropic behavior.
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212
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Abstract
Atomic force microscopy (AFM) has been used in numerous studies to visualize and analyze the structure and conformation of biological samples, from single molecules to biopolymers to cells. The possibility to analyze native samples without fixation, staining and in physiological buffer conditions, combined with the sub-nanometer resolution, makes AFM a versatile tool for the analysis of protein aggregation and amyloid structures. Here, we describe the application of AFM to study fibrillar Tau protein aggregates.
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213
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Bozkurt O, Haman Bayari S, Severcan M, Krafft C, Popp J, Severcan F. Structural alterations in rat liver proteins due to streptozotocin-induced diabetes and the recovery effect of selenium: fourier transform infrared microspectroscopy and neural network study. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:076023. [PMID: 22894506 DOI: 10.1117/1.jbo.17.7.076023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The relation between protein structural alterations and tissue dysfunction is a major concern as protein fibrillation and/or aggregation due to structural alterations has been reported in many disease states. In the current study, Fourier transform infrared microspectroscopic imaging has been used to investigate diabetes-induced changes on protein secondary structure and macromolecular content in streptozotocin-induced diabetic rat liver. Protein secondary structural alterations were predicted using neural network approach utilizing the amide I region. Moreover, the role of selenium in the recovery of diabetes-induced alterations on macromolecular content and protein secondary structure was also studied. The results revealed that diabetes induced a decrease in lipid to protein and glycogen to protein ratios in diabetic livers. Significant alterations in protein secondary structure were observed with a decrease in α-helical and an increase in β-sheet content. Both doses of selenium restored diabetes-induced changes in lipid to protein and glycogen to protein ratios. However, low-dose selenium supplementation was not sufficient to recover the effects of diabetes on protein secondary structure, while a higher dose of selenium fully restored diabetes-induced alterations in protein structure.
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Affiliation(s)
- Ozlem Bozkurt
- Middle East Technical University, Department of Biological Sciences, 06800 Ankara, Turkey
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214
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Villemagne VL, Furumoto S, Fodero-Tavoletti M, Harada R, Mulligan RS, Kudo Y, Masters CL, Yanai K, Rowe CC, Okamura N. The challenges of tau imaging. FUTURE NEUROLOGY 2012. [DOI: 10.2217/fnl.12.34] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In vivo imaging of tau pathology will provide new insights into tau deposition in the human brain, thus facilitating research into causes, diagnosis and treatment of major dementias, such as Alzheimer’s disease, or some variants of frontotemporal lobar degeneration, in which tau plays a role. Tau imaging poses several challenges, some related to the singularities of tau aggregation, and others related to radiotracer design. Several groups around the world are working on the development of imaging agents that will allow the in vivo assessment of tau deposition in aging and in neurodegeneration. Development of a tau imaging tracer will enable researchers to noninvasively examine the degree and extent of tau pathology in the brain, quantify changes in tau deposition over time, evaluate its relation to cognition and assess the efficacy of anti-tau therapy.
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Affiliation(s)
- Victor L Villemagne
- Department of Nuclear Medicine & Centre for PET, Austin Health, 145 Studley Road, Heidelberg, VIC 3084, Melbourne, Australia
| | - Shozo Furumoto
- Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan
| | | | - Ryuichi Harada
- Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan
| | - Rachel S Mulligan
- Department of Nuclear Medicine & Centre for PET, Austin Health, 145 Studley Road, Heidelberg, VIC 3084, Melbourne, Australia
| | - Yukitsuka Kudo
- Innovation of New Biomedical Engineering Center, Tohoku University, Sendai, Japan
| | | | - Kazuhiko Yanai
- Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan
| | - Chistopher C Rowe
- Department of Nuclear Medicine & Centre for PET, Austin Health, 145 Studley Road, Heidelberg, VIC 3084, Melbourne, Australia
| | - Nobuyuki Okamura
- Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan
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215
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Battisti A, Ciasca G, Grottesi A, Bianconi A, Tenenbaum A. Temporary secondary structures in tau, an intrinsically disordered protein. MOLECULAR SIMULATION 2012. [DOI: 10.1080/08927022.2011.633347] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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216
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Structure and pathology of tau protein in Alzheimer disease. Int J Alzheimers Dis 2012; 2012:731526. [PMID: 22690349 PMCID: PMC3368361 DOI: 10.1155/2012/731526] [Citation(s) in RCA: 203] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/28/2012] [Accepted: 03/29/2012] [Indexed: 12/17/2022] Open
Abstract
Alzheimer's disease (AD) is the most common type of dementia. In connection with the global trend of prolonging human life and the increasing number of elderly in the population, the AD becomes one of the most serious health and socioeconomic problems of the present. Tau protein promotes assembly and stabilizes microtubules, which contributes to the proper function of neuron. Alterations in the amount or the structure of tau protein can affect its role as a stabilizer of microtubules as well as some of the processes in which it is implicated. The molecular mechanisms governing tau aggregation are mainly represented by several posttranslational modifications that alter its structure and conformational state. Hence, abnormal phosphorylation and truncation of tau protein have gained attention as key mechanisms that become tau protein in a pathological entity. Evidences about the clinicopathological significance of phosphorylated and truncated tau have been documented during the progression of AD as well as their capacity to exert cytotoxicity when expressed in cell and animal models. This paper describes the normal structure and function of tau protein and its major alterations during its pathological aggregation in AD.
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217
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Voss K, Combs B, Patterson KR, Binder LI, Gamblin TC. Hsp70 alters tau function and aggregation in an isoform specific manner. Biochemistry 2012; 51:888-98. [PMID: 22236337 DOI: 10.1021/bi2018078] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tauopathies are characterized by abnormal aggregation of the microtubule associated protein tau. This aggregation is thought to occur when tau undergoes shifts from its native conformation to one that exposes hydrophobic areas on separate monomers, allowing contact and subsequent association into oligomers and filaments. Molecular chaperones normally function by binding to exposed hydrophobic stretches on proteins and assisting in their refolding. Chaperones of the heat shock protein 70 (Hsp70) family have been implicated in the prevention of abnormal tau aggregation in adult neurons. Tau exists as six alternatively spliced isoforms, and all six isoforms appear capable of forming the pathological aggregates seen in Alzheimer's disease. Because tau isoforms differ in primary sequence, we sought to determine whether Hsp70 would differentially affect the aggregation and microtubule assembly characteristics of the various tau isoforms. We found that Hsp70 inhibits tau aggregation directly and not through inducer-mediated effects. We also determined that Hsp70 inhibits the aggregation of each individual tau isoform and was more effective at inhibiting the three repeat isoforms. Finally, all tau isoforms robustly induced microtubule formation while in the presence of Hsp70. The results presented herein indicate that Hsp70 affects tau isoform dysfunction while having very little impact on the normal function of tau to mediate microtubule assembly. This indicates that targeting Hsp70 to tau may provide a therapeutic approach for the treatment of tauopathies that avoids disruption of normal tau function.
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Affiliation(s)
- Kellen Voss
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, United States
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218
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Abstract
Tauopathies are age-related neurodegenerative diseases that are characterized by the presence of aggregates of abnormally phosphorylated tau. As tau was originally discovered as a microtubule-associated protein, it has been hypothesized that neurodegeneration results from a loss of the ability of tau to associate with microtubules. However, tau has been found to have other functions aside from the promotion and stabilization of microtubule assembly. It is conceivable that such functions may be affected by the abnormal phosphorylation of tau and might have consequences for neuronal function or viability. This chapter provides an overview of tau structure, functions, and its involvement in neurodegenerative diseases.
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219
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Truncation of tau at E391 promotes early pathologic changes in transgenic mice. J Neuropathol Exp Neurol 2011; 70:1006-19. [PMID: 22002427 DOI: 10.1097/nen.0b013e31823557fb] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Proteolytic cleavage of tau at glutamic acid 391 (E391) is linked to the pathogenesis of Alzheimer disease (AD). This C-terminal-truncated tau species exists in neurofibrillary tangles and abnormal neurites in the brains of AD patients and may potentiate tau polymerization. We generated a mouse model that expresses human tau truncated at E391 to begin to elucidate the role of this C-terminal-truncated tau species in the development of tau pathology. Our results show that truncated but otherwise wild-type human tau is sufficient to drive pretangle pathologic changes in tau, including accumulation of insoluble tau, somatodendritic redistribution, formation of pathologic conformations, and dual phosphorylation of tau at sites associated with AD pathology. In addition, these mice exhibit atypical neuritic tau immunoreactivity, including abnormal neuritic processes and dystrophic neurites. These results suggest that changes in tau proteolysis can initiate tauopathy.
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220
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Moore CL, Huang MH, Robbennolt SA, Voss KR, Combs B, Gamblin TC, Goux WJ. Secondary nucleating sequences affect kinetics and thermodynamics of tau aggregation. Biochemistry 2011; 50:10876-86. [PMID: 22085312 DOI: 10.1021/bi2014745] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tau protein was scanned for highly amyloidogenic sequences in amphiphilic motifs (X)(n)Z, Z(X)(n)Z (n ≥ 2), or (XZ)(n) (n ≥ 2), where X is a hydrophobic residue and Z is a charged or polar residue. N-Acetyl peptides homologous to these sequences were used to study aggregation. Transmission electron microscopy (TEM) showed seven peptides, in addition to well-known primary nucleating sequences Ac(275)VQIINK (AcPHF6*) and Ac(306)VQIVYK (AcPHF6), formed fibers, tubes, ribbons, or rolled sheets. Of the peptides shown by TEM to form amyloid, Ac(10)VME, AcPHF6*, Ac(375)KLTFR, and Ac(393)VYK were found to enhance the fraction of β-structure of AcPHF6 formed at equilibrium, and Ac(375)KLTFR was found to inhibit AcPHF6 and AcPHF6* aggregation kinetics in a dose-dependent manner, consistent with its participation in a hybrid steric zipper model. Single site mutants were generated which transformed predicted amyloidogenic sequences in tau into non-amyloidogenic ones. A M11K mutant had fewer filaments and showed a decrease in aggregation kinetics and an increased lag time compared to wild-type tau, while a F378K mutant showed significantly more filaments. Our results infer that sequences throughout tau, in addition to PHF6 and PHF6*, can seed amyloid formation or affect aggregation kinetics or thermodynamics.
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Affiliation(s)
- Christopher L Moore
- Department of Chemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
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221
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Chaudhary N, Singh S, Nagaraj R. Aggregation properties of a short peptide that mediates amyloid fibril formation in model proteins unrelated to disease. J Biosci 2011; 36:679-89. [DOI: 10.1007/s12038-011-9104-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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222
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Landahl EC, Antipova O, Bongaarts A, Barrea R, Berry R, Binder LI, Irving T, Orgel J, Vana L, Rice SE. X-ray diffraction from intact tau aggregates in human brain tissue. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT 2011; 649:184-187. [PMID: 21876609 PMCID: PMC3162212 DOI: 10.1016/j.nima.2011.01.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We describe an instrument to record x-ray diffraction patterns from diseased regions of human brain tissue by combining an in-line visible light fluorescence microscope with an x-ray diffraction microprobe. We use thiazine red fluorescence to specifically label and detect the filamentous tau protein pathology associated with Pick's disease, as several labs have done previously. We demonstrate that thiazine red-enhanced regions within the tissue show periodic structure in x-ray diffraction that is not observed in healthy tissue. One observed periodicity (4.2 Å) is characteristic of cross-beta sheet structure, consistent with previous results from powder diffraction studies performed on purified, dried tau protein.
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Affiliation(s)
- Eric C Landahl
- DePaul University, Department of Physics, 2219 N. Kenmore Ave., Chicago, IL 60614
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223
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Plumley JA, Dannenberg JJ. Comparison of β-sheets of capped polyalanine with those of the tau-amyloid structures VQIVYK and VQIINK. A density functional theory study. J Phys Chem B 2011; 115:10560-6. [PMID: 21797271 DOI: 10.1021/jp205388q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We present ONIOM calculations using B3LYP/d95(d,p) as the high and AM1 as the low level on parallel β-sheets containing from two to ten strands of Ac-VQIVYK-NHMe and Ac-VQIINK-NHMe, as well as both parallel and antiparallel Ac-AAAAAA-NHMe. We find that the first two sequences form more stable sheets due to the additional H-bonding between the Q's in the side chains of both and the N's in the side chain of Ac-VQIINK-NHMe. However, the H-bonds in the amyloid chains are significantly weakened by attractive strain, which prevents all the interstrand H-bonds from achieving their optimal geometries simultaneously and requires high distortion energies for the individual strands in the sheets. The antiparallel Ac-AAAAAA-NHMe's are generally more stable and more cooperative than the parallel sheets, principally due to the higher distortion energies of the latter.
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Affiliation(s)
- Joshua A Plumley
- Department of Chemistry, City University of New York-Hunter College and Graduate School, 695 Park Avenue, New York, New York 10065, United States
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224
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Abstract
While the microtubule-binding capacity of the protein tau has been known for many years, new functions of tau in signaling and cytoskeletal organization have recently emerged. In this review, we highlight these functions and the potential roles of tau in neurodegenerative disease. We also discuss the therapeutic potential of drugs targeting various aspects of tau biology.
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Affiliation(s)
- Meaghan Morris
- Gladstone Institute of Neurological Disease, San Francisco, CA 94158, USA
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225
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Miller Y, Ma B, Nussinov R. Synergistic interactions between repeats in tau protein and Aβ amyloids may be responsible for accelerated aggregation via polymorphic states. Biochemistry 2011; 50:5172-81. [PMID: 21506544 PMCID: PMC3109766 DOI: 10.1021/bi200400u] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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Amyloid plaques and neurofibrillary tangles simultaneously accumulate in Alzheimer’s disease (AD). It is known that Aβ and tau exist together in the mitochondria; however, the interactions between Aβ oligomers and tau are controversial. Moreover, it is still unclear which specific domains in the tau protein can interact with Aβ oligomers and what could be the effect of these interactions. Herein, we examine three different Aβ–tau oligomeric complexes. These complexes present interactions of Aβ with three domains in the tau protein; all contain high β-structure propensity in their R2, R3, and R4 repeats. Our results show that, among these, Aβ oligomers are likely to interact with the R2 domain to form a stable complex with better alignment in the turn region and the β-structure domain. We therefore propose that the R2 domain can interact with soluble Aβ oligomers and consequently promote aggregation. EM and AFM images and dimensions revealed highly polymorphic tau aggregates. We suggest that the polymorphic tau and Aβ–tau aggregates may be largely due to repeat sequences which are prone to variable turn locations along the tau repeats.
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Affiliation(s)
- Yifat Miller
- Center for Cancer Research Nanobiology Program NCI-Frederick, Frederick, MD 21702, USA
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226
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Wegmann S, Schöler J, Bippes CA, Mandelkow E, Muller DJ. Competing interactions stabilize pro- and anti-aggregant conformations of human Tau. J Biol Chem 2011; 286:20512-24. [PMID: 21498513 DOI: 10.1074/jbc.m111.237875] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Aggregation of Tau into amyloid-like fibrils is a key process in neurodegenerative diseases such as Alzheimer. To understand how natively disordered Tau stabilizes conformations that favor pathological aggregation, we applied single-molecule force spectroscopy. Intramolecular interactions that fold polypeptide stretches of ~19 and ~42 amino acids in the functionally important repeat domain of full-length human Tau (hTau40) support aggregation. In contrast, the unstructured N terminus randomly folds long polypeptide stretches >100 amino acids that prevent aggregation. The pro-aggregant mutant hTau40ΔK280 observed in frontotemporal dementia favored the folding of short polypeptide stretches and suppressed the folding of long ones. This trend was reversed in the anti-aggregant mutant hTau40ΔK280/PP. The aggregation inducer heparin introduced strong interactions in hTau40 and hTau40ΔK280 that stabilized aggregation-prone conformations. We show that the conformation and aggregation of Tau are regulated through a complex balance of different intra- and intermolecular interactions.
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Affiliation(s)
- Susanne Wegmann
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland
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227
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Liu C, Sawaya MR, Cheng PN, Zheng J, Nowick JS, Eisenberg D. Characteristics of amyloid-related oligomers revealed by crystal structures of macrocyclic β-sheet mimics. J Am Chem Soc 2011; 133:6736-44. [PMID: 21473620 DOI: 10.1021/ja200222n] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Protein amyloid oligomers have been strongly linked to amyloid diseases and can be intermediates to amyloid fibers. β-Sheets have been identified in amyloid oligomers. However, because of their transient and highly polymorphic properties, the details of their self-association remain elusive. Here we explore oligomer structure using a model system: macrocyclic peptides. Key amyloidogenic sequences from Aβ and tau were incorporated into macrocycles, thereby restraining them to β-strands, but limiting the growth of the oligomers so they may crystallize and cannot fibrillate. We determined the atomic structures for four such oligomers, and all four reveal tetrameric interfaces in which β-sheet dimers pair together by highly complementary, dry interfaces, analogous to steric zippers found in fibers, suggesting a common structure for amyloid oligomers and fibers. In amyloid fibers, the axes of the paired sheets are either parallel or antiparallel, whereas the oligomeric interfaces display a variety of sheet-to-sheet pairing angles, offering a structural explanation for the heterogeneity of amyloid oligomers.
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Affiliation(s)
- Cong Liu
- UCLA-DOE Institute for Genomics and Proteomics, University of California, Los Angeles, California 90095, USA
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228
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Ultrastructural alterations of Alzheimer's disease paired helical filaments by grape seed-derived polyphenols. Neurobiol Aging 2010; 33:1427-39. [PMID: 21196065 DOI: 10.1016/j.neurobiolaging.2010.11.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 09/20/2010] [Accepted: 11/02/2010] [Indexed: 11/21/2022]
Abstract
Abnormal folding of the microtubule-associated protein tau leads to aggregation of tau into paired helical filaments (PHFs) and neurofibrillary tangles, the major hallmark of Alzheimer's disease (AD). We have recently shown that grape seed polyphenol extract (GSPE) reduces tau pathology in the TMHT mouse model of tauopathy (Wang et al., 2010). In the present studies we assessed the impact of GSPE exposure on the ultrastructure of PHFs isolated from Alzheimer's disease brain. Transmission electron microscopy revealed that GSPE induced profound dose- and time-dependent alterations in the morphology of PHFs with partial disintegration of filaments. Filaments showed ∼2-fold enlargement in width and displayed numerous protrusions and splayed ends consistent with unfolding of tau and diminished structural stability. In addition, GSPE induced a reduction in immunogold labeling with antibodies against the C-terminal half (12E8, PHF-1) and the middle region of tau (AT8, Tau5, pSer214 tau, and AT180) but not the C-terminal end (Tau46). In comparison, labeling of N-terminus (Alz50) was enhanced. It is unlikely that alterations in immunogold labeling were due to biochemical alterations, e.g., protein phosphatase or proteolytic activities potentially stimulated by GSPE, because western blotting studies have shown the preservation of full length polypeptides of tau and their phospho-epitopes in GSPE-treated samples. The GSPE mechanism may include a noncovalent interaction of polyphenols with proline residues in the proline-rich domain of tau, with Pin1 sites at P213 and P232 most seriously affected as judged by suppression of labeling. Collectively, our results suggest that GSPE has a significant potential for therapeutic development by neutralizing phospho-epitopes and disrupting fibrillary conformation leading to disintegration of PHFs.
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229
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Zhao JH, Liu HL, Chuang CK, Liu KT, Tsai WB, Ho Y. Molecular dynamics simulations to investigate the stability and aggregation behaviour of the amyloid-forming peptide VQIVYK from tau protein. MOLECULAR SIMULATION 2010. [DOI: 10.1080/08927022.2010.499147] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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230
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Pasinetti GM, Ho L. Role of grape seed polyphenols in Alzheimer's disease neuropathology. NUTRITION AND DIETARY SUPPLEMENTS 2010; 2010:97-103. [PMID: 23730149 DOI: 10.2147/nds.s6898] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Alzheimer's disease (AD) is an age-related neurodegenerative condition characterized by a progressive decline in cognitive function. AD affects approximately five million people in the US, creating a devastating financial burden on health care costs and an emotional burden on caregivers. To date, there is no cure for AD, so researchers are continually exploring novel avenues for the prevention and treatment of this condition. In this article, we present some findings from our laboratory and those of others on the potential benefits of a grape seed polyphenolic extract (GSPE) for the prevention and treatment of AD, including its chemical composition, bioactivity, bioavailability, safety, and tolerability, and the mechanisms by which it interferes with AD pathogenesis. Findings presented in this review article support the development of GSPE as a preventative and/or therapeutic agent in AD.
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Affiliation(s)
- Giulio Maria Pasinetti
- Department of Neurology, Mount Sinai School of Medicine, New York ; Geriatric Research, education and Clinical Center, James J Peters veteran Affairs Medical Center, Bronx, New York, USA
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231
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Wegmann S, Jung YJ, Chinnathambi S, Mandelkow EM, Mandelkow E, Muller DJ. Human Tau isoforms assemble into ribbon-like fibrils that display polymorphic structure and stability. J Biol Chem 2010; 285:27302-27313. [PMID: 20566652 DOI: 10.1074/jbc.m110.145318] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fibrous aggregates of Tau protein are characteristic features of Alzheimer disease. We applied high resolution atomic force and EM microscopy to study fibrils assembled from different human Tau isoforms and domains. All fibrils reveal structural polymorphism; the "thin twisted" and "thin smooth" fibrils resemble flat ribbons (cross-section approximately 10 x 15 nm) with diverse twist periodicities. "Thick fibrils" show periodicities of approximately 65-70 nm and thicknesses of approximately 9-18 nm such as routinely reported for "paired helical filaments" but structurally resemble heavily twisted ribbons. Therefore, thin and thick fibrils assembled from different human Tau isoforms challenge current structural models of paired helical filaments. Furthermore, all Tau fibrils reveal axial subperiodicities of approximately 17-19 nm and, upon exposure to mechanical stress or hydrophobic surfaces, disassemble into uniform fragments that remain connected by thin thread-like structures ( approximately 2 nm). This hydrophobically induced disassembly is inhibited at enhanced electrolyte concentrations, indicating that the fragments resemble structural building blocks and the fibril integrity depends largely on hydrophobic and electrostatic interactions. Because full-length Tau and repeat domain constructs assemble into fibrils of similar thickness, the "fuzzy coat" of Tau protein termini surrounding the fibril axis is nearly invisible for atomic force microscopy and EM, presumably because of its high flexibility.
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Affiliation(s)
- Susanne Wegmann
- Department of Biosystems Science and Engineering, ETH Zürich, CH-4058 Basel, Switzerland
| | - Yu Jin Jung
- Biotechnology Center, University of Technology, 01307 Dresden, Germany
| | - Subashchandrabose Chinnathambi
- Max-Planck-Unit for Structural Molecular Biology, c/o DESY, 22607 Hamburg, Germany and the German Center for Neurodegenerative Diseases, c/o CAESAR, 53175 Bonn, Germany
| | - Eva-Maria Mandelkow
- Max-Planck-Unit for Structural Molecular Biology, c/o DESY, 22607 Hamburg, Germany and the German Center for Neurodegenerative Diseases, c/o CAESAR, 53175 Bonn, Germany
| | - Eckhard Mandelkow
- Max-Planck-Unit for Structural Molecular Biology, c/o DESY, 22607 Hamburg, Germany and the German Center for Neurodegenerative Diseases, c/o CAESAR, 53175 Bonn, Germany.
| | - Daniel J Muller
- Department of Biosystems Science and Engineering, ETH Zürich, CH-4058 Basel, Switzerland.
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232
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Curcumin labeling of neuronal fibrillar tau inclusions in human brain samples. J Neuropathol Exp Neurol 2010; 69:405-14. [PMID: 20448485 DOI: 10.1097/nen.0b013e3181d709eb] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The study aimed to characterize curcumin (CCM) (fluorescent yellow curry pigment) labeling of neuronal fibrillar tau inclusions (FTIs) in representative cases of 3 main tauopathies: Alzheimer disease (AD), progressive supranuclear palsy, and Pick disease. After identification of FTIs in hematoxylin and eosin-stained brain sections, sequential labeling and signal colocalization image analysis were used to compare CCM with thioflavine S (ThS), monoclonal antibody AT8 immunofluorescence, and Gallyas silver staining by visualizing the same FTIs. Curcumin preference for specific tau isoforms was tested with 3-repeat tau and 4-repeat tau isoform-specific immunofluorescence. Curcumin proved highly comparable to ThS and Gallyas staining in its detection of FTIs. When comparing CCM with AT8, ThS, and Gallyas staining in AD and progressive supranuclear palsy, 3 types of neuronal tau deposits were observed: nonfibrillar intracellular material labeled only with AT8, fibrillar intracellular inclusions labeled by all the methods, and fibrillar extracellular FTIs labeled with CCM, ThS, and Gallyas staining but not with AT8. Although CCM labeling overlapped with both 3-repeat tau and 4-repeat tau in AD, it did not label 3-repeat tau FTIs in Pick disease probably because of their different ultrastructural characteristics. In summary, CCM fluorescence reliably detected neuronal FTIs in AD and progressive supranuclear palsy and surpassed AT8 immunolabeling in visualizing later stages of FTIs, including ghost tangles. These results provide the basis for potential future applications of CCM binding of tau aggregates in diagnostic pathology and in vivo.
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233
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Sugiyama T, Miyashiro D, Takao D, Iwamoto H, Sugimoto Y, Wakabayashi K, Kamimura S. Quick shear-flow alignment of biological filaments for X-ray fiber diffraction facilitated by methylcellulose. Biophys J 2010; 97:3132-8. [PMID: 20006950 DOI: 10.1016/j.bpj.2009.09.041] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 09/20/2009] [Accepted: 09/23/2009] [Indexed: 11/25/2022] Open
Abstract
X-ray fiber diffraction is one of the most useful methods for examining the structural details of live biological filaments under physiological conditions. To investigate biologically active or labile materials, it is crucial to finish fiber alignment within seconds before diffraction analysis. However, the conventional methods, e.g., magnetic field alignment and low-speed centrifugations, are time-consuming and not very useful for such purposes. Here, we introduce a new alignment method using a rheometer with two parallel disks, which was applied to observe fiber diffractions of axonemes, tobacco mosaic tobamovirus, and microtubules. We found that fibers were aligned within 5 s by giving high shear flow (1000-5000 s(-1)) to the medium and that methylcellulose contained in the medium (approximately 1%) was essential to the accomplishment of uniform orientation with a small angular deviation (<5 degrees). The new alignment method enabled us to execute structure analyses of axonemes by small-angle x-ray diffraction. Since this method was also useful for the quick alignment of purified microtubules, as well as tobacco mosaic tobamovirus, we expect that we can apply it to the structural analysis of many other biological filaments.
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Affiliation(s)
- Takaaki Sugiyama
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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234
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Bulic B, Pickhardt M, Mandelkow EM, Mandelkow E. Tau protein and tau aggregation inhibitors. Neuropharmacology 2010; 59:276-89. [PMID: 20149808 DOI: 10.1016/j.neuropharm.2010.01.016] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 01/20/2010] [Accepted: 01/26/2010] [Indexed: 12/13/2022]
Abstract
Alzheimer disease is characterized by pathological aggregation of two proteins, tau and Abeta-amyloid, both of which are considered to be toxic to neurons. In this review we summarize recent advances on small molecule inhibitors of protein aggregation with emphasis on tau, with activities mediated by the direct interference of self-assembly. The inhibitors can be clustered in several compound classes according to their chemical structure, with subsequent description of the structure-activity relationships, showing that hydrophobic interactions are prevailing. The description is extended to the pharmacological profile of the compounds in order to evaluate their drug-likeness, with special attention to toxicity and bioavailability. The collected data indicate that following the improvements of the in vitro inhibitory potencies, the consideration of the in vivo pharmacokinetics is an absolute prerequisite for the development of compounds suitable for a transfer from bench to bedside.
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Affiliation(s)
- Bruno Bulic
- Center for Advanced European Studies and Research, Bonn, Germany.
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235
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Mo ZY, Zhu YZ, Zhu HL, Fan JB, Chen J, Liang Y. Low micromolar zinc accelerates the fibrillization of human tau via bridging of Cys-291 and Cys-322. J Biol Chem 2009; 284:34648-57. [PMID: 19826005 DOI: 10.1074/jbc.m109.058883] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A hallmark of a group of neurodegenerative diseases such as Alzheimer disease is the formation of neurofibrillary tangles, which are principally composed of bundles of filaments formed by microtubule-associated protein Tau. Clarifying how natively unstructured Tau protein forms abnormal aggregates is of central importance for elucidating the etiology of these diseases. There is considerable evidence showing that zinc, as an essential element that is highly concentrated in brain, is linked to the development or progression of these diseases. Herein, by using recombinant human Tau fragment Tau(244-372) and its mutants, we have investigated the effect of zinc on the aggregation of Tau. Low micromolar concentrations of Zn(2+) dramatically accelerate fibril formation of wild-type Tau(244-372) under reducing conditions, compared with no Zn(2+). Higher concentrations of Zn(2+), however, induce wild-type Tau(244-372) to form granular aggregates in reducing conditions. Moreover, these non-fibrillar aggregates assemble into mature Tau filaments when Zn(2+) has been chelated by EDTA. Unlike wild-type Tau(244-372), low micromolar concentrations of Zn(2+) have no obvious effects on fibrillization kinetics of single mutants C291A and C322A and double mutant C291A/C322A under reducing conditions. The results from isothermal titration calorimetry show that one Zn(2+) binds to one Tau molecule via tetrahedral coordination to Cys-291 and Cys-322 as well as two histidines, with moderate, micromolar affinity. Our data demonstrate that low micromolar zinc accelerates the fibrillization of human Tau protein via bridging Cys-291 and Cys-322 in physiological reducing conditions, providing clues to understanding the relationship between zinc dyshomeostasis and the etiology of neurodegenerative diseases.
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Affiliation(s)
- Zhong-Ying Mo
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China
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236
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Mao X, Ma X, Liu L, Niu L, Yang Y, Wang C. Structural characteristics of the beta-sheet-like human and rat islet amyloid polypeptides as determined by scanning tunneling microscopy. J Struct Biol 2009; 167:209-15. [DOI: 10.1016/j.jsb.2009.05.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 05/13/2009] [Accepted: 05/15/2009] [Indexed: 10/20/2022]
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237
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Congdon EE, Figueroa YH, Wang L, Toneva G, Chang E, Kuret J, Conrad C, Duff KE. Inhibition of tau polymerization with a cyanine dye in two distinct model systems. J Biol Chem 2009; 284:20830-9. [PMID: 19478088 PMCID: PMC2742848 DOI: 10.1074/jbc.m109.016089] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 05/22/2009] [Indexed: 01/02/2023] Open
Abstract
In a host of neurodegenerative diseases Tau, a microtubule-associated protein, aggregates into insoluble lesions within neurons. Previous studies have utilized cyanine dyes as Tau aggregation inhibitors in vitro. Herein we utilize cyanine dye 3,3'-diethyl-9-methyl-thiacarbocyanine iodide (C11) to modulate Tau polymerization in two model systems, an organotypic slice culture model derived from Tau transgenic mice and a split green fluorescent protein complementation assay in Tau-expressing cells. In slice cultures, submicromolar concentrations (0.001 microm) of C11 produced a significant reduction of aggregated Tau and a corresponding increase in unpolymerized Tau. In contrast, treatment with a 1 microm dose promoted aggregation of Tau. These results were recapitulated in the complementation assay where administration of 1 microm C11 produced a significant increase in polymerized Tau relative to control, whereas treatment of cells with 0.01 microm C11 resulted in a marked reduction of aggregated Tau. In the organotypic slice cultures, modulation of Tau aggregation was independent of changes in phosphorylation at disease and microtubule binding relevant epitopes for both dosing regimes. Furthermore, treatment with 0.001 microm C11 resulted in a decrease in both total filament mass and number. There was no evidence of apoptosis or loss of synaptic integrity at either dose, however, whereas submicromolar concentrations of C11 did not interfere with microtubule binding, higher doses resulted in a decrease in the levels of microtubule-bound Tau. Overall, a cyanine dye can dissociate aggregated Tau in an ex vivo model of tauopathy with little toxicity and exploration of the use of these type of dyes as therapeutic agents is warranted.
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Affiliation(s)
- Erin E. Congdon
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
| | - Yvette H. Figueroa
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
| | - Lili Wang
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
| | - Galina Toneva
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
| | | | - Jeff Kuret
- Department of Cellular and Molecular Biology, Ohio State University, Columbus, Ohio 43210
| | - Christopher Conrad
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
| | - Karen E. Duff
- From the Department of Pathology, Taub Institute, Columbia University and Department of Integrative Neuroscience, New York State Psychiatric Institute, New York, New York 10032 and
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238
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Barrio JR, Satyamurthy N, Huang SC, Petrič A, Small GW, Kepe V. Dissecting molecular mechanisms in the living brain of dementia patients. Acc Chem Res 2009; 42:842-50. [PMID: 19281227 DOI: 10.1021/ar800189x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Understanding the molecular mechanisms associated with the development of dementia is essential for designing successful interventions. Dementia, like cancer and cardiovascular disease, requires early detection to potentially arrest or prevent further disease progression. By the time a neurologist begins to manage clinical symptoms, the disease has often damaged the brain significantly. Because successful treatment is the logical goal, detecting the disease when brain damage is still limited is of the essence. The role of chemistry in this discovery process is critical. With the advent of molecular imaging, the understanding of molecular mechanisms in human neurodegenerative diseases has exploded. Traditionally, knowledge of enzyme and neurotransmitter function in humans has been extrapolated from animal studies, but now we can acquire data directly from both healthy and diseased human subjects. In this Account, we describe the use of molecular imaging probes to elucidate the biochemical and cellular bases of dementia (e.g., Alzheimer's disease) and the application of these discoveries to the design of successful therapeutic interventions. Molecular imaging permits observation and evaluation of the basic molecular mechanisms of disease progression in the living brains of patients. 2-Deoxy-2-[(18)F]fluoro-d-glucose is used to assess the effect of Alzheimer's disease progression on neuronal circuits projecting from and to the temporal lobe (one of the earliest metabolic signs of the disease). Recently, we have developed imaging probes for detection of amyloid neuropathology (both tau and beta-amyloid peptide deposits) and neuronal losses. These probes allow us to visualize the development of pathology in the living brain of dementia patients and its consequences, such as losses of critical neurons associated with memory deficits and other neuropsychiatric impairments. Because inflammatory processes are tightly connected to the brain degenerative processes, inflammation is now emerging as an important target for new molecular imaging probes. The combination of molecular probes targeting various processes of dementia is a useful tool for detailed monitoring of disease mechanism, progression, and diagnosis, as well as for the development of rational strategies for promising therapeutic interventions.
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Affiliation(s)
| | | | | | - Andrej Petrič
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerèeva 5, 1000 Ljubljana, Slovenia
| | - Gary W. Small
- Department of Psychiatry and Biobehavioral Sciences, and Semel Institute for Neuroscience and Human Behavior
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239
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Bulic B, Pickhardt M, Schmidt B, Mandelkow EM, Waldmann H, Mandelkow E. Development of tau aggregation inhibitors for Alzheimer's disease. Angew Chem Int Ed Engl 2009; 48:1740-52. [PMID: 19189357 DOI: 10.1002/anie.200802621] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A variety of human diseases are suspected to be directly linked to protein misfolding. Highly organized protein aggregates, called amyloid fibrils, and aggregation intermediates are observed; these are considered to be mediators of cellular toxicity and thus attract a great deal of attention from investigators. Neurodegenerative pathologies such as Alzheimer's disease account for a major part of these protein misfolding diseases. The last decade has witnessed a renaissance of interest in inhibitors of tau aggregation as potential disease-modifying drugs for Alzheimer's disease and other "tauopathies". The recent report of a phase II clinical trial with the tau aggregation inhibitor MTC could hold promise for the validation of the concept. This Review summarizes the available data concerning small-molecule inhibitors of tau aggregation from a medicinal chemistry point of view.
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Affiliation(s)
- Bruno Bulic
- Max-Planck-Institute for Molecular Physiology, Dortmund, Germany.
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240
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Bulic B, Pickhardt M, Schmidt B, Mandelkow EM, Waldmann H, Mandelkow E. Entwicklung von Inhibitoren der Tau-Aggregation bei Morbus Alzheimer. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200802621] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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241
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Effect of phosphorylation on interaction of human tau protein with 14-3-3ζ. Biochem Biophys Res Commun 2009; 379:990-4. [DOI: 10.1016/j.bbrc.2008.12.164] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 12/30/2008] [Indexed: 11/19/2022]
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242
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Bravo R, Arimon M, Valle-Delgado JJ, García R, Durany N, Castel S, Cruz M, Ventura S, Fernàndez-Busquets X. Sulfated Polysaccharides Promote the Assembly of Amyloid β1–42 Peptide into Stable Fibrils of Reduced Cytotoxicity. J Biol Chem 2008; 283:32471-83. [DOI: 10.1074/jbc.m709870200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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243
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Ding H, Johnson GVW. New application of beta-galactosidase complementation to monitor tau self-association. J Neurochem 2008; 106:1545-51. [PMID: 18498442 DOI: 10.1111/j.1471-4159.2008.05496.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neurofibrillary tangles composed of hyperphosphorylated and aberrantly cleaved microtubule-associated protein tau are a major neuropathological hallmark of Alzheimer's disease. Recent studies suggest that the predominant neurotoxic effect of pathologically processed tau is mediated by intermediate tau multimers rather than the mature tau tangles, thus underscoring the importance of studying tau self-association preceding tangle formation. However, experimental approaches for such studies are limited. Here, we describe a modification of the beta-galactosidase (beta-gal) complementation assay, which provides a simple, sensitive and quantitative system to monitor pre-tangle tau-tau interactions in a cell model. Full-length tau (T4) and tau truncated at D421 (C3, to mimic caspase-cleaved tau) were fused to one of a pair of weakly complementing beta-gal mutants (Deltaalpha and Deltaomega) and expressed in human embryonic kidney cells. The tau-tau interactions and the subsequent juxtapositioning of Deltaalpha and Deltaomega led to beta-gal complementation and an increase in beta-gal activity which was detected by histochemical staining and quantified by chemiluminescent assays. After cross-linking with disuccinimidyl suberate, tau formed high molecular weight complexes which were detected on denaturing acrylamide gels, further confirming the close proximity among self-associated tau molecules. The self-association of C3 appeared to be less efficient than that of T4. Furthermore, treatment with lithium decreased beta-gal complementation of both T4 and C3 indicating that the interaction of these proteins was attenuated. Overall, this study suggests that beta-gal complementation assay can be a useful tool to monitor tau self-association.
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Affiliation(s)
- Huiping Ding
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama, USA
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244
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Andronesi OC, Bergen MV, Biernat J, Seidel K, Griesinger C, Mandelkow E, Baldus M. Characterization of Alzheimer’s-like Paired Helical Filaments from the Core Domain of Tau Protein Using Solid-State NMR Spectroscopy. J Am Chem Soc 2008; 130:5922-8. [DOI: 10.1021/ja7100517] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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245
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Perrodou E, Chica C, Poch O, Gibson TJ, Thompson JD. A new protein linear motif benchmark for multiple sequence alignment software. BMC Bioinformatics 2008; 9:213. [PMID: 18439277 PMCID: PMC2374782 DOI: 10.1186/1471-2105-9-213] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Accepted: 04/25/2008] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Linear motifs (LMs) are abundant short regulatory sites used for modulating the functions of many eukaryotic proteins. They play important roles in post-translational modification, cell compartment targeting, docking sites for regulatory complex assembly and protein processing and cleavage. Methods for LM detection are now being developed that are strongly dependent on scores for motif conservation in homologous proteins. However, most LMs are found in natively disordered polypeptide segments that evolve rapidly, unhindered by structural constraints on the sequence. These regions of modular proteins are difficult to align using classical multiple sequence alignment programs that are specifically optimised to align the globular domains. As a consequence, poor motif alignment quality is hindering efforts to detect new LMs. RESULTS We have developed a new benchmark, as part of the BAliBASE suite, designed to assess the ability of standard multiple alignment methods to detect and align LMs. The reference alignments are organised into different test sets representing real alignment problems and contain examples of experimentally verified functional motifs, extracted from the Eukaryotic Linear Motif (ELM) database. The benchmark has been used to evaluate and compare a number of multiple alignment programs. With distantly related proteins, the worst alignment program correctly aligns 48% of LMs compared to 73% for the best program. However, the performance of all the programs is adversely affected by the introduction of other sequences containing false positive motifs. The ranking of the alignment programs based on LM alignment quality is similar to that observed when considering full-length protein alignments, however little correlation was observed between LM and overall alignment quality for individual alignment test cases. CONCLUSION We have shown that none of the programs currently available is capable of reliably aligning LMs in distantly related sequences and we have highlighted a number of specific problems. The results of the tests suggest possible ways to improve program accuracy for difficult, divergent sequences.
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Affiliation(s)
- Emmanuel Perrodou
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Department of Structural Biology and Genomics, F-67400 Illkirch, France.
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246
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Jiang LF, Yao TM, Zhu ZL, Wang C, Ji LN. Impacts of Cd(II) on the conformation and self-aggregation of Alzheimer's tau fragment corresponding to the third repeat of microtubule-binding domain. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1774:1414-21. [PMID: 17920001 DOI: 10.1016/j.bbapap.2007.08.014] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 08/10/2007] [Accepted: 08/15/2007] [Indexed: 11/26/2022]
Abstract
Environmental exposure to some heavy metals such as cadmium appears to be a risk factor for Alzheimer's disease (AD), however, definite mechanism of their toxicity in AD remains to be elucidated. Previous studies largely focused on the metal ions binding to beta-amyloid, however, very few papers concerned the interaction between tau and metal ions. For the first time, we investigated the impacts of Cd(II) on the conformation and self-aggregation of Alzheimer's tau peptide R3, corresponding to the third repeat of microtubule-binding domain. The initial state of R3 was proven to be dimeric linked by intermolecular disulfide bond, in the non-reducing buffer (Tris-HCl buffer pH7.5, containing no reducing reagent). In this paper, we show that Cd(II) can accelerate heparin-induced aggregation of R3 or independently induce the aggregation of R3, as monitored by ThS fluorescence. In the presence of Cd(II), the resulting R3 filaments became much smaller, as revealed by electron microscopy. Binding to the Cd(II) ion, the dimeric R3 partially lost its random coil, and converted to alpha-helix structure, as revealed by CD and Raman spectrum. Stoichiometric analysis of CD signal against the ratio of [Cd(II)]/[R3] suggested that the coordination intermediate consisted of two R3 dimers binding to a central cadmium ion. As the seed, the coordination intermediate could extensively accelerate the self-aggregation of R3 via promoting the nucleation step. On the other hand, gain in alpha-helix structure on the peptide chain, by coordinating with Cd(II), could be a critical role to promote self-aggregation, as revealed by Raman spectrum. These results provide a further insight into the mechanism of tau filament formation and emphasize the possible involvement of Cd(II) in the pathogenesis of AD.
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Affiliation(s)
- Ling-Feng Jiang
- Department of Chemistry, Tongji University, Shanghai 200092, China
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247
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Abstract
Tau is a microtubule-associated protein involved in microtubule assembly and stabilization. Filamentous deposits made of tau constitute a major defining characteristic of several neurodegenerative diseases known as tauopathies including Alzheimer's disease. The involvement of tau in neurodegeneration has been clarified by the identification of genetic mutations in the tau gene in cases with familial frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Although the mechanism through which tau mutations lead to neuronal death is still unresolved, it is clear that tau mutations lead to formation of tau filaments that have a different morphology, contain different types of tau isoforms and produce distinct tau deposits. The range of tau pathology identified in FTDP-17 recapitulates the tau pathology present in sporadic tauopathies and indicates that tau dysfunction plays a major role also in these diseases.
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Affiliation(s)
- Laura Gasparini
- Cambridge Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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248
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Chun W, Johnson GVW. Activation of Glycogen Synthase Kinase 3β Promotes the Intermolecular Association of Tau. J Biol Chem 2007; 282:23410-7. [PMID: 17565981 DOI: 10.1074/jbc.m703706200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tau is hyperphosphorylated and undergoes proteolysis in Alzheimer disease brain. Caspase-cleaved tau efficiently forms fibrillary structures in vitro and in situ. Glycogen synthase kinase 3beta (GSK3beta) phosphorylates tau and induces the aggregation of caspase-cleaved tau in situ. Given the hypothesis that increased association of tau precedes the formation of fibrillar structures, we generated a cell model to quantitate the extent of tau association in situ using fluorescence resonance energy transfer (FRET) microscopy. The cyan and yellow fluorescent proteins were attached to full-length (T4) and caspase-cleaved (T4C3) tau at either the N or C termini, and a pair of cyan and yellow fluorescent protein-tagged tau were co-transfected into human embryonic kidney cells. The FRET efficiency was examined in the presence of a constitutively active or a kinase-dead GSK3beta. Active GSK3beta significantly increased FRET efficiency with both T4 and T4C3, indicating that GSK3beta activation resulted in an increase in the self-association of both T4 and T4C3, but interestingly only T4 is efficiently phosphorylated by GSK3beta. There was no significant difference in FRET efficiency between T4 and T4C3, although only T4C3 in the presence of active GSK3beta leads to the formation of Sarkosyl-insoluble inclusions. These FRET studies demonstrate that GSK3beta facilitates the association of T4 and T4C3, and the presence of caspase-cleaved tau is necessary for the evolution of tau oligomers into Sarkosyl-insoluble inclusions even though it is not extensively phosphorylated. These data imply that increased association of tau should not be regarded as a direct indicator of the formation of insoluble tau aggregates.
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Affiliation(s)
- Wanjoo Chun
- Department of Psychiatry, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35294, USA
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249
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Ubhi KK, Shaibah H, Newman TA, Shepherd D, Mudher A. A comparison of the neuronal dysfunction caused by Drosophila tau and human tau in a Drosophila model of tauopathies. INVERTEBRATE NEUROSCIENCE 2007; 7:165-71. [PMID: 17636367 DOI: 10.1007/s10158-007-0052-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Accepted: 06/25/2007] [Indexed: 02/07/2023]
Abstract
Hyperphosphorylation and aggregation of tau into tangles is a feature of disorders such as Alzheimer's disease and other Tauopathies. To model these disorders in Drosophila melanogaster, human tau has been over-expressed and a variety of phenotypes have been observed including neurotoxicity, disrupted neuronal and synaptic function and locomotor impairments. Neuronal dysfunction has been seen prior to neuronal death and in the absence of tangle formation. The Drosophila tau protein shares a large degree of homology with human tau but differs in the crucial microtubule binding domains. Although like human tau Drosophila tau can induce neurotoxicity, little is known about its ability to disrupt neuronal function. In this study we demonstrate that like human tau, over-expression of Drosophila tau results in disrupted axonal transport, altered neuromuscular junction morphology and locomotor impairments. This indicates that like human tau, over-expression of Drosophila tau compromises neuronal function despite significant differences in microtubule binding regions.
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Affiliation(s)
- Kiren K Ubhi
- Department of Neuroscience, University of Southampton, School of Biological Sciences, Bassett Crescent East, Southampton, SO16 7PX, UK
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250
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Andrews JM, Roberts CJ. A Lumry-Eyring nucleated polymerization model of protein aggregation kinetics: 1. Aggregation with pre-equilibrated unfolding. J Phys Chem B 2007; 111:7897-913. [PMID: 17571872 DOI: 10.1021/jp070212j] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A mathematical model is presented of the kinetics of non-native protein aggregation that combines Lumry-Eyring and nucleated polymerization (LENP) descriptions. The LENP model is solved for cases in which aggregation rates are slow compared to folding-unfolding equilibration and is shown to be a generalization of a number of previously proposed nucleation-and-growth models for non-native and native protein aggregation. The model solutions exhibit a number of qualitative kinetic regimes. Each regime has a characteristic set of experimental signatures that are related to the relative rates of growth and nucleation as well as to the threshold size at which aggregates condense to form higher-order structures or other phases. Approximate model solutions provide practical rate equations that can be regressed against typical experimental kinetic data to obtain mechanistic parameters characterizing the aggregation pathway. In all kinetic regimes, it is found that observed rate coefficients (kobs) or half-lives (t50) obtained from extent-of-reaction measurements are convolutions of more than one stage in the pathway unless purely seeded growth occurs. Despite this convolution, the combination of apparent reaction order (time domain) and the scaling of kobs or t50 with initial protein concentration provides a means to determine a value for the dominant nucleus size in each case. Additional information, such as equilibrium unfolding thermodynamics and the limiting aggregate size distribution, are required to further deconvolute kobs into intrinsic contributions from nucleation, growth, and conformational changes. The model and analysis are expected to be generally applicable to a wide range of proteins and polypeptides that form non-native aggregates.
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Affiliation(s)
- Jennifer M Andrews
- Department of Chemical Engineering, 150 Academy Street, Colburn Laboratory, University of Delaware, Newark, Delaware 19716, USA
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