1
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Venkatramani A, Ashtam A, Panda D. EB1 Increases the Dynamics of Tau Droplets and Inhibits Tau Aggregation: Implications in Tauopathies. ACS Chem Neurosci 2024; 15:1219-1233. [PMID: 38445984 DOI: 10.1021/acschemneuro.3c00815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024] Open
Abstract
EB1, a microtubule plus end-tracking protein (+TIP), regulates microtubule dynamics. Recent evidence indicates cross-talk between EB proteins and tau, a microtubule-associated neuronal protein that is important for the growth and stability of microtubules. We investigated the interaction between tau and EB1 and the effect of binding of EB1 on tau function and aggregation. EB1 colocalized with tau in SH-SY5Y cells and coimmunoprecipitated with tau. Further, purified EB1 impaired the ability of adult tau to induce tubulin polymerization in vitro. EB1 bound to tau with a dissociation constant of 2.5 ± 0.7 μM. EB1 reduced heparin-induced tau aggregation with a half-maximal inhibitory concentration of 4.3 ± 0.2 μM, and increased the dynamics of tau in phase-separated droplets. The fluorescence recovery rate in tau droplets increased from 0.02 ± 0.01 to 0.07 ± 0.03 s-1, while the half-time of recovery decreased from 44.5 ± 14 to 13.5 ± 6 s in the presence of 8 μM EB1, suggesting a delay in the transition of tau from the soluble to aggregated form in tau liquid-liquid phase separation. EB1 decreased the rate of aggregation and increased the critical concentration of tau aggregation. Dynamic light scattering, atomic force microscopy, dot blot assays, and SDS-PAGE analysis showed that EB1 inhibited the formation of oligomers and higher-order aggregates of tau. The data suggest a novel role for EB1 as a regulator of tau function and aggregation, and the findings indicated the role of the EB family proteins in neuronal function and neurodegeneration.
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Affiliation(s)
- Anuradha Venkatramani
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Anvesh Ashtam
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Dulal Panda
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
- National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160062, India
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2
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Malyshka D, Jimenez-Harrison D, Kuret J. Sedimentation and Laser Light Scattering Methods for Quantifying Synthetic Tau Aggregation Propensity. Methods Mol Biol 2024; 2754:117-129. [PMID: 38512664 DOI: 10.1007/978-1-0716-3629-9_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Tau aggregation assays detect and quantify the conversion of soluble tau monomers into species having filamentous or oligomeric structure. Assays for filamentous aggregates in cross-β-sheet conformation leverage optical, biochemical, or biophysical methods, each with their own advantages and throughput capacity. Here we provide protocols for two medium-throughput assays based on sedimentation and laser light scattering and compare their performance, their utility for characterizing tau aggregation dynamics, and their limitations relative to other approaches. Additionally, a protocol for transmission electron microscopy analysis is updated so as to be compatible with the truncated tau variants that have emerged as powerful tools for interrogating the structural basis of tau polymorphism. Together these methods contribute to a rich tool kit for interrogating tau aggregation kinetics and propensity over a wide range of experimental conditions.
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Affiliation(s)
- Dmitry Malyshka
- Medical Scientist Training Program, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Daniela Jimenez-Harrison
- Medical Scientist Training Program, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Jeff Kuret
- Department of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, OH, USA.
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3
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Jiang L, Ding X, Wang W, Yang X, Li T, Lei P. Head-to-Head Comparison of Different Blood Collecting Tubes for Quantification of Alzheimer’s Disease Biomarkers in Plasma. Biomolecules 2022; 12:biom12091194. [PMID: 36139033 PMCID: PMC9496121 DOI: 10.3390/biom12091194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Revised: 08/24/2022] [Accepted: 08/26/2022] [Indexed: 12/01/2022] Open
Abstract
To examine whether the type of blood collection tubes affects the quantification of plasma biomarkers for Alzheimer’s disease analyzed with a single-molecule array (Simoa), we recruited a healthy cohort (n = 34, 11 males, mean age = 28.7 ± 7.55) and collected plasma in the following tubes: dipotassium ethylenediaminetetraacetic acid (K2-EDTA), heparin lithium (Li-Hep), and heparin sodium (Na-Hep). Plasma tau, phosphorylated tau 181 (p-tau181), amyloid β (1–40) (Aβ40), and amyloid β (1–42) (Aβ42) were quantified using Simoa. We compared the value of plasma analytes, as well as the effects of sex on the measurements. We found that plasma collected in Li-Hep and Na-Hep tubes yielded significantly higher tau and p-tau181 levels compared to plasma collected in K2-EDTA tubes from the same person, but there was no difference in the measured values of the Aβ40, Aβ42, and Aβ42/40 ratio. Therefore, the type of blood collecting tubes should be considered when planning studies that measure plasma tau.
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Affiliation(s)
- Lijun Jiang
- Mental Health Center and Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xulong Ding
- Mental Health Center and Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
- Dushu Lake Hospital Affiliated to Soochow University, Medical Center of Soochow University, Suzhou Dushu Lake Hospital, Suzhou 215125, China
| | - Wenxiao Wang
- Deyang Mental Health Center, Deyang 618099, China
| | - Xiaobin Yang
- Deyang Mental Health Center, Deyang 618099, China
| | - Tao Li
- Mental Health Center and Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
- Department of Neurobiology, Affiliated Mental Health Center & Hangzhou Seventh People’s Hospital, Zhejiang University School of Medicine, Hangzhou 310063, China
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Science and Brain-machine Integration, School of Brain Science and Brain Medicine, Zhejiang University, Hangzhou 310012, China
- Correspondence: (T.L.); (P.L.)
| | - Peng Lei
- Mental Health Center and Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
- Correspondence: (T.L.); (P.L.)
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4
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Alzheimer’s Disease and Tau Self-Assembly: In the Search of the Missing Link. Int J Mol Sci 2022; 23:ijms23084192. [PMID: 35457009 PMCID: PMC9032712 DOI: 10.3390/ijms23084192] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 03/30/2022] [Accepted: 03/31/2022] [Indexed: 11/17/2022] Open
Abstract
Alzheimer’s disease (AD) is a multifactorial neurodegenerative disease characterized by progressive cognitive impairment, apathy, and neuropsychiatric disorders. Two main pathological hallmarks have been described: neurofibrillary tangles, consisting of tau oligomers (hyperphosphorylated tau) and Aβ plaques. The influence of protein kinases and phosphatases on the hyperphosphorylation of tau is already known. Hyperphosphorylated tau undergoes conformational changes that promote its self-assembly. However, the process involving these mechanisms is yet to be elucidated. In vitro recombinant tau can be aggregated by the action of polyanions, such as heparin, arachidonic acid, and more recently, the action of polyphosphates. However, how that process occurs in vivo is yet to be understood. In this review, searching the most accurate and updated literature on the matter, we focus on the precise molecular events linking tau modifications, its misfolding and the initiation of its pathological self-assembly. Among these, we can identify challenges regarding tau phosphorylation, the link between tau heteroarylations and the onset of its self-assembly, as well as the possible metabolic pathways involving natural polyphosphates, that may play a role in tau self-assembly.
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5
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Buawangpong N, Pinyopornpanish K, Siri-Angkul N, Chattipakorn N, Chattipakorn SC. The role of trimethylamine-N-Oxide in the development of Alzheimer's disease. J Cell Physiol 2021; 237:1661-1685. [PMID: 34812510 DOI: 10.1002/jcp.30646] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 11/07/2021] [Accepted: 11/09/2021] [Indexed: 02/06/2023]
Abstract
Alzheimer's disease is associated with multiple risk factors and is the most common type of dementia. Trimethylamine-N-oxide (TMAO), a gut microbiota metabolite derived from dietary choline and carnitine, has recently been identified as a potential risk factor of Alzheimer's disease. It has been demonstrated that TMAO is associated with Alzheimer's disease through various pathophysiological pathways. As a result of molecular crowding effects, TMAO causes the aggregation of the two proteins, amyloid-beta peptide and tau protein. The aggregation of these proteins is the main pathology associated with Alzheimer's disease. In addition, it has been found that TMAO can activate astrocytes, and inflammatory response. Besides molecular investigation, animal and human studies have also supported the existence of a functional relationship between TMAO and cognitive decline. This article comprehensively summarizes the relationship between TMAO and Alzheimer's disease including emerging evidence from in vitro, in vivo, and clinical studies. We hope that this knowledge will improve the prevention and treatment of Alzheimer's disease in the near future.
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Affiliation(s)
- Nida Buawangpong
- Department of Family Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | | | - Natthapat Siri-Angkul
- Department of Physiology, Cardiac Electrophysiology Unit, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University Chiang Mai, Chiang Mai, Thailand
| | - Nipon Chattipakorn
- Neurophysiology Unit, Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Department of Physiology, Cardiac Electrophysiology Unit, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University Chiang Mai, Chiang Mai, Thailand
| | - Siriporn C Chattipakorn
- Neurophysiology Unit, Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.,Center of Excellence in Cardiac Electrophysiology Research, Chiang Mai University Chiang Mai, Chiang Mai, Thailand.,Department of Oral Biology and Diagnostic Sciences, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand
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6
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Calfio C, Gonzalez A, Singh SK, Rojo LE, Maccioni RB. The Emerging Role of Nutraceuticals and Phytochemicals in the Prevention and Treatment of Alzheimer's Disease. J Alzheimers Dis 2021; 77:33-51. [PMID: 32651325 DOI: 10.3233/jad-200443] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
One of the major challenges of medical sciences has been finding a reliable compound for the pharmacological treatment of Alzheimer's disease (AD). As most of the drugs directed to a variety of targets have failed in finding a medical solution, natural products from Ayurvedic medicine or nutraceutical compounds emerge as a viable preventive therapeutics' pathway. Considering that AD is a multifactorial disease, nutraceutical compounds offer the advantage of a multitarget approach, tagging different molecular sites in the human brain, as compared with the single-target activity of most of the drugs used for AD treatment. We review in-depth important medicinal plants that have been already investigated for therapeutic uses against AD, focusing on a diversity of pharmacological actions. These targets include inhibition of acetylcholinesterase, β-amyloid senile plaques, oxidation products, inflammatory pathways, specific brain receptors, etc., and pharmacological actions so diverse as anti-inflammatory, memory enhancement, nootropic effects, glutamate excitotoxicity, anti-depressants, and antioxidants. In addition, we also discuss the activity of nutraceutical compounds and phytopharmaceuticals formulae, mainly directed to tau protein aggregates mechanisms of action. These include compounds such as curcumin, resveratrol, epigallocatechin-3-gallate, morin, delphinidins, quercetin, luteolin, oleocanthal, and meganatural-az and other phytochemicals such as huperzine A, limonoids, azaphilones, and aged garlic extract. Finally, we revise the nutraceutical formulae BrainUp-10 composed of Andean shilajit and B-complex vitamins, with memory enhancement activity and the control of neuropsychiatric distress in AD patients. This integrated view on nutraceutical opens a new pathway for future investigations and clinical trials that are likely to render some results based on medical evidence.
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Affiliation(s)
- Camila Calfio
- Laboratory of Neurosciences and Functional Medicine, International Center for Biomedicine (ICC) and Faculty of Sciences, University of Chile, Santiago, Chile
| | - Andrea Gonzalez
- Laboratory of Neurosciences and Functional Medicine, International Center for Biomedicine (ICC) and Faculty of Sciences, University of Chile, Santiago, Chile
| | - Sandeep Kumar Singh
- Indian Scientific Education and Technology Foundation, Lucknow, India.,Centre of Biomedical Research (CBMR), Lucknow, India
| | - Leonel E Rojo
- Department of Biology, University of Santiago, Santiago, Chile
| | - Ricardo B Maccioni
- Laboratory of Neurosciences and Functional Medicine, International Center for Biomedicine (ICC) and Faculty of Sciences, University of Chile, Santiago, Chile.,Department of Neurology, Faculty of Medicine, University of Chile, Santiago, Chile
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7
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Medina L, González-Lizárraga F, Dominguez-Meijide A, Ploper D, Parrales V, Sequeira S, Cima-Omori MS, Zweckstetter M, Del Bel E, Michel PP, Outeiro TF, Raisman-Vozari R, Chehín R, Socias SB. Doxycycline Interferes With Tau Aggregation and Reduces Its Neuronal Toxicity. Front Aging Neurosci 2021; 13:635760. [PMID: 33828477 PMCID: PMC8020845 DOI: 10.3389/fnagi.2021.635760] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 02/22/2021] [Indexed: 01/15/2023] Open
Abstract
Tauopathies are neurodegenerative disorders with increasing incidence and still without cure. The extensive time required for development and approval of novel therapeutics highlights the need for testing and repurposing known safe molecules. Since doxycycline impacts α-synuclein aggregation and toxicity, herein we tested its effect on tau. We found that doxycycline reduces amyloid aggregation of the 2N4R and K18 isoforms of tau protein in a dose-dependent manner. Furthermore, in a cell free system doxycycline also prevents tau seeding and in cell culture reduces toxicity of tau aggregates. Overall, our results expand the spectrum of action of doxycycline against aggregation-prone proteins, opening novel perspectives for its repurposing as a disease-modifying drug for tauopathies.
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Affiliation(s)
- Luciana Medina
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
| | - Florencia González-Lizárraga
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
| | - Antonio Dominguez-Meijide
- Department of Experimental Neurodegeneration, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Goettingen, Goettingen, Germany.,Laboratory of Neuroanatomy and Experimental Neurology, Department of Morphological Sciences, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), Instituto de Investigación Sanitaria de Santiago de Compostela (IDIS), University of Santiago de Compostela, Santiago de Compostela, Spain.,Networking Research Center on Neurodegenerative Diseases (CIBERNED), Madrid, Spain
| | - Diego Ploper
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
| | - Valeria Parrales
- Sorbonne Université, Paris Brain Institute -ICM, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Assistance Publique - Hôpitaux de Paris (APHP), Hôpital de la Pitié Salpêtrière, Paris, France
| | - Sabrina Sequeira
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
| | - Maria-Sol Cima-Omori
- German Center for Neurodegenerative Diseases Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Göttingen, Germany
| | - Markus Zweckstetter
- German Center for Neurodegenerative Diseases Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Göttingen, Germany.,Department for NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Elaine Del Bel
- Physiology- Dental School of Ribeirão Preto, University of São Paulo, São Paulo, Brazil
| | - Patrick P Michel
- Sorbonne Université, Paris Brain Institute -ICM, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Assistance Publique - Hôpitaux de Paris (APHP), Hôpital de la Pitié Salpêtrière, Paris, France
| | - Tiago Fleming Outeiro
- Department of Experimental Neurodegeneration, Center for Biostructural Imaging of Neurodegeneration, University Medical Center Goettingen, Goettingen, Germany.,Max Planck Institute for Experimental Medicine, Goettingen, Germany.,Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Rita Raisman-Vozari
- Sorbonne Université, Paris Brain Institute -ICM, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS), Assistance Publique - Hôpitaux de Paris (APHP), Hôpital de la Pitié Salpêtrière, Paris, France
| | - Rosana Chehín
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
| | - Sergio B Socias
- Instituto de Investigación en Medicina Molecular y Celular Aplicada (IMMCA) (UNT-CONICET-SIPROSA), Tucumán, Argentina
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8
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Kaur J, Giri A, Bhattacharya M. The protein-surfactant stoichiometry governs the conformational switching and amyloid nucleation kinetics of tau K18. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2020; 49:425-434. [PMID: 32691116 DOI: 10.1007/s00249-020-01447-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 06/07/2020] [Accepted: 07/02/2020] [Indexed: 06/11/2023]
Abstract
Amyloids are pathological hallmarks of a number of debilitating neurodegenerative diseases. Understanding the molecular mechanism of protein amyloid assembly with an emphasis on structural characterization of early, key prefibrillar species is important for targeted drug design and clinical interventions. Tau is an intrinsically disordered, microtubule-binding protein which is also implicated in various neurodegenerative disorders such as frontotemporal dementia, Down's syndrome, Alzheimer's disease, etc. Earlier reports have demonstrated that tau aggregation in vitro is triggered by anionic inducers, presumably due to charge compensation which facilitates intermolecular association between the tau polypeptide chains. However, the molecular mechanism of tau amyloid aggregation, involving the structural characterization of amyloidogenic intermediates formed especially during early key steps, remains elusive. In this work, we have employed a spectroscopic toolbox to elucidate the mechanism of anionic surfactant-induced disorder-to-order amyloid transition of a tau segment. This study revealed that the amyloid assembly is mediated via binding-induced conformational switching into an early partially helical amyloid-competent intermediate. Additionally, protein and inducer concentration-dependent studies indicated that at the higher protein and/or inducer concentrations, competing off-pathway intermediates dampen the amyloid assembly which implies that the stoichiometry of protein and inducer plays a key regulatory role in the amyloid nucleation and fibril elongation kinetics.
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Affiliation(s)
- Jaspreet Kaur
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Thapar Technology Campus, Bhadson Road, Patiala, Punjab, 147004, India
| | - Anjali Giri
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Thapar Technology Campus, Bhadson Road, Patiala, Punjab, 147004, India
| | - Mily Bhattacharya
- School of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Thapar Technology Campus, Bhadson Road, Patiala, Punjab, 147004, India.
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9
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Huseby CJ, Bundschuh R, Kuret J. The role of annealing and fragmentation in human tau aggregation dynamics. J Biol Chem 2019; 294:4728-4737. [PMID: 30745358 DOI: 10.1074/jbc.ra118.006943] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 01/25/2019] [Indexed: 11/06/2022] Open
Abstract
Alzheimer's disease pathogenesis is associated with the conversion of monomeric tau protein into filamentous aggregates. Because both toxicity and prion-like spread of pathogenic tau depend in part on aggregate size, the processes that underlie filament formation and size distribution are of special importance. Here, using a combination of biophysical and computational approaches, we investigated the fibrillation dynamics of the human tau isoform 2N4R. We found that tau filaments engage in a previously uncharacterized secondary process involving end-to-end annealing and that rationalization of empirical aggregation data composed of total protomer concentrations and fibril length distributions requires inclusion of this process along with filament fragmentation. We noted that annealing of 2N4R tau filaments is robust, with an intrinsic association rate constant of a magnitude similar to that mediating monomer addition and consistent with diffusion-mediated protein-protein interactions in the absence of long-range attractive forces. In contrast, secondary nucleation on the surface of tau filaments did not detectably contribute to tau aggregation dynamics. These results indicate that tau filament ends engage in a range of homotypic interactions involving monomers, oligomers, and filaments. They further indicate that, in the case of tau protein, fibril annealing and fragmentation along with primary nucleation and elongation are the major processes controlling filament size distribution.
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Affiliation(s)
| | - Ralf Bundschuh
- From the Interdisciplinary Biophysics Graduate Program.,Departments of Physics, Internal Medicine, and Chemistry and Biochemistry, and
| | - Jeff Kuret
- From the Interdisciplinary Biophysics Graduate Program, .,Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio 43210
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10
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Rauch JN, Olson SH, Gestwicki JE. Interactions between Microtubule-Associated Protein Tau (MAPT) and Small Molecules. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a024034. [PMID: 27940599 DOI: 10.1101/cshperspect.a024034] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Tau aggregation is linked to multiple neurodegenerative disorders that are collectively termed tauopathies. Small molecules are powerful probes of the aggregation process, helping to reveal the key steps and serving as diagnostics and reporters. Moreover, some of these small molecules may have potential as therapeutics. This review details how small molecules and chemical biology have helped to elucidate the mechanisms of tau aggregation and how they are being used to detect and prevent tau aggregation. In addition, we comment on how new insights into tau prions are changing the approach to small molecule discovery.
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Affiliation(s)
- Jennifer N Rauch
- Institute for Neurodegenerative Diseases, Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, California 94158
| | - Steven H Olson
- Institute for Neurodegenerative Diseases, Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, California 94158
| | - Jason E Gestwicki
- Institute for Neurodegenerative Diseases, Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, California 94158
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11
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Jangholi A, Ashrafi-Kooshk MR, Arab SS, Riazi G, Mokhtari F, Poorebrahim M, Mahdiuni H, Kurganov BI, Moosavi-Movahedi AA, Khodarahmi R. Appraisal of role of the polyanionic inducer length on amyloid formation by 412-residue 1N4R Tau protein: A comparative study. Arch Biochem Biophys 2016; 609:1-19. [DOI: 10.1016/j.abb.2016.09.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 09/08/2016] [Accepted: 09/12/2016] [Indexed: 10/21/2022]
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12
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Tiernan CT, Combs B, Cox K, Morfini G, Brady ST, Counts SE, Kanaan NM. Pseudophosphorylation of tau at S422 enhances SDS-stable dimer formation and impairs both anterograde and retrograde fast axonal transport. Exp Neurol 2016; 283:318-29. [PMID: 27373205 PMCID: PMC4992631 DOI: 10.1016/j.expneurol.2016.06.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/22/2016] [Accepted: 06/28/2016] [Indexed: 12/17/2022]
Abstract
In Alzheimer's disease (AD), tau undergoes numerous modifications, including increased phosphorylation at serine-422 (pS422). In the human brain, pS422 tau protein is found in prodromal AD, correlates well with cognitive decline and neuropil thread pathology, and appears associated with increased oligomer formation and exposure of the N-terminal phosphatase-activating domain (PAD). However, whether S422 phosphorylation contributes to toxic mechanisms associated with disease-related forms of tau remains unknown. Here, we report that S422-pseudophosphorylated tau (S422E) lengthens the nucleation phase of aggregation without altering the extent of aggregation or the types of aggregates formed. When compared to unmodified tau aggregates, the S422E modification significantly increased the amount of SDS-stable tau dimers, despite similar levels of immunoreactivity with an oligomer-selective antibody (TOC1) and another antibody that reports PAD exposure (TNT1). Vesicle motility assays in isolated squid axoplasm further revealed that S422E tau monomers inhibited anterograde, kinesin-1 dependent fast axonal transport (FAT). Unexpectedly, and unlike unmodified tau aggregates, which selectively inhibit anterograde FAT, aggregates composed of S422E tau were found to inhibit both anterograde and retrograde FAT. Highlighting the relevance of these findings to human disease, pS422 tau was found to colocalize with tau oligomers and with a fraction of tau showing increased PAD exposure in the human AD brain. This study identifies novel effects of pS422 on tau biochemical properties, including prolonged nucleation and enhanced dimer formation, which correlate with a distinct inhibitory effect on FAT. Taken together, these findings identify a novel mechanistic basis by which pS422 confers upon tau a toxic effect that may directly contribute to axonal dysfunction in AD and other tauopathies.
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Affiliation(s)
- Chelsea T Tiernan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Benjamin Combs
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Kristine Cox
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Gerardo Morfini
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, IL 60612, USA
| | - Scott T Brady
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, IL 60612, USA
| | - Scott E Counts
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Department of Family Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA; Hauenstein Neuroscience Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI 49503, USA
| | - Nicholas M Kanaan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA; Hauenstein Neuroscience Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI 49503, USA.
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13
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Mitra G, Gupta S, Poddar A, Bhattacharyya B. MAP2c prevents arachidonic acid-induced fibril formation of tau: Role of chaperone activity and phosphorylation. Biophys Chem 2015; 205:16-23. [DOI: 10.1016/j.bpc.2015.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/02/2015] [Accepted: 06/02/2015] [Indexed: 01/16/2023]
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14
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Kashchiev D. Protein fibrillation due to elongation and fragmentation of initially appeared fibrils: a simple kinetic model. J Chem Phys 2014; 139:105103. [PMID: 24050370 DOI: 10.1063/1.4819496] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The assembly of various proteins into fibrillar aggregates is an important phenomenon with wide implications ranging from human disease to nanoscience. Employing a new model, we analyze the kinetics of protein fibrillation in the case when the process occurs by elongation of initially appeared fibrils which multiply solely by fragmentation, because fibril nucleation is negligible. Owing to its simplicity, our model leads to mathematically friendly and physically clear formulas for the time dependence of the fibrillation degree and for a number of experimental observables such as the maximum fibrillation rate, the fibrillation lag time, and the half-fibrillation time. These formulas provide a mechanistic insight into the kinetics of fragmentation-affected fibrillation of proteins. We confront theory with experiment and find that our model allows a good global description of a large dataset [W.-F. Xue, S. W. Homans, and S. E. Radford, Proc. Natl. Acad. Sci. U.S.A. 105, 8926 (2008)] for the fibrillation kinetics of beta-2 microglobulin. Our analysis leads to new methods for experimental determination of the fibril solubility, elongation rate constant, and nucleation rate from data for the time course of protein fibrillation.
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Affiliation(s)
- Dimo Kashchiev
- Institute of Physical Chemistry, Bulgarian Academy of Sciences, ul. Acad. G. Bonchev 11, Sofia 1113, Bulgaria
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15
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Gendreau KL, Hall GF. Tangles, Toxicity, and Tau Secretion in AD - New Approaches to a Vexing Problem. Front Neurol 2013; 4:160. [PMID: 24151487 PMCID: PMC3801151 DOI: 10.3389/fneur.2013.00160] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/26/2013] [Indexed: 12/14/2022] Open
Abstract
When the microtubule (MT)-associated protein tau is not bound to axonal MTs, it becomes hyperphosphorylated and vulnerable to proteolytic cleavage and other changes typically seen in the hallmark tau deposits (neurofibrillary tangles) of tau-associated neurodegenerative diseases (tauopathies). Neurofibrillary tangle formation is preceded by tau oligomerization and accompanied by covalent crosslinking and cytotoxicity, making tangle cytopathogenesis a natural central focus of studies directed at understanding the role of tau in neurodegenerative disease. Recent studies suggest that the formation of tau oligomers may be more closely related to tau neurotoxicity than the presence of the tangles themselves. It has also become increasingly clear that tau pathobiology involves a wide variety of other cellular abnormalities including a disruption of autophagy, vesicle trafficking mechanisms, axoplasmic transport, neuronal polarity, and even the secretion of tau, which is normally a cytosolic protein, to the extracellular space. In this review, we discuss tau misprocessing, toxicity and secretion in the context of normal tau functions in developing and mature neurons. We also compare tau cytopathology to that of other aggregation-prone proteins involved in neurodegeneration (alpha synuclein, prion protein, and APP). Finally, we consider potential mechanisms of intra- and interneuronal tau lesion spreading, an area of particular recent interest.
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Affiliation(s)
- Kerry L Gendreau
- Department of Biological Sciences, University of Massachusetts Lowell , Lowell, MA , USA
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16
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Xu LR, Liu XL, Chen J, Liang Y. Protein disulfide isomerase interacts with tau protein and inhibits its fibrillization. PLoS One 2013; 8:e76657. [PMID: 24098548 PMCID: PMC3788760 DOI: 10.1371/journal.pone.0076657] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 08/30/2013] [Indexed: 01/20/2023] Open
Abstract
Background Tau protein is implicated in the pathogenesis of neurodegenerative disorders such as tauopathies including Alzheimer disease, and Tau fibrillization is thought to be related to neuronal toxicity. Physiological inhibitors of Tau fibrillization hold promise for developing new strategies for treatment of Alzheimer disease. Because protein disulfide isomerase (PDI) is both an enzyme and a chaperone, and implicated in neuroprotection against Alzheimer disease, we want to know whether PDI can prevent Tau fibrillization. In this study, we have investigated the interaction between PDI and Tau protein and the effect of PDI on Tau fibrillization. Methodology/Principal Findings As evidenced by co-immunoprecipitation and confocal laser scanning microscopy, human PDI interacts and co-locates with some endogenous human Tau on the endoplasmic reticulum of undifferentiated SH-SY5Y neuroblastoma cells. The results from isothermal titration calorimetry show that one full-length human PDI binds to one full-length human Tau (or human Tau fragment Tau244–372) monomer with moderate, micromolar affinity at physiological pH and near physiological ionic strength. As revealed by thioflavin T binding assays, Sarkosyl-insoluble SDS-PAGE, and transmission electron microscopy, full-length human PDI remarkably inhibits both steps of nucleation and elongation of Tau244–372 fibrillization in a concentration-dependent manner. Furthermore, we find that two molecules of the a-domain of human PDI interact with one Tau244–372 molecule with sub-micromolar affinity, and inhibit both steps of nucleation and elongation of Tau244–372 fibrillization more strongly than full-length human PDI. Conclusions/Significance We demonstrate for the first time that human PDI binds to Tau protein mainly through its thioredoxin-like catalytic domain a, forming a 1∶1 complex and preventing Tau misfolding. Our findings suggest that PDI could act as a physiological inhibitor of Tau fibrillization, and have applications for developing novel strategies for treatment and early diagnosis of Alzheimer disease.
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Affiliation(s)
- Li-Rong Xu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiao-Ling Liu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jie Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yi Liang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
- * E-mail:
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17
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Abstract
In Alzheimer disease (AD) and other tauopathies, microtubule-associated protein tau becomes hyperphosphorylated, undergoes conformational changes, aggregates, eventually becoming neurofibrillary tangles (NFTs). As accumulating evidence suggests that NFTs themselves may not be toxic, attention is now turning toward the role of intermediate tau oligomers in AD pathophysiology. Sarkosyl extraction is a standard protocol for investigating insoluble tau aggregates in brains. There is a growing consensus that sarkosyl-insoluble tau correlates with the pathological features of tauopathy. While sarkosyl-insoluble tau from tauopathy brains has been well characterized as a pool of filamentous tau, other dimers, multimers, and granules of tau are much less well understood. There are protocols for identifying these tau oligomers. In this mini review, we discuss the characteristics of tau oligomers isolated via different methods and materials.
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Affiliation(s)
- Yan Ren
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, College of Medicine, University of Florida , Gainesville, FL , USA
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18
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Barré P, Eliezer D. Structural transitions in tau k18 on micelle binding suggest a hierarchy in the efficacy of individual microtubule-binding repeats in filament nucleation. Protein Sci 2013; 22:1037-48. [PMID: 23740819 DOI: 10.1002/pro.2290] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/21/2013] [Accepted: 05/22/2013] [Indexed: 12/31/2022]
Abstract
The protein tau is found in an aggregated filamentous state in the intraneuronal paired helical filament deposits characteristic of Alzheimer's disease and other related dementias and mutations in tau protein and mRNA cause frontotemproal dementia. Tau isoforms include a microtubule-binding domain containing either three or four imperfect tandem microtubule binding repeats that also form the core of tau filaments and contain hexapaptide motifs that are critical for tau aggregation. The tau microtubule-binding domain can also engage in direct interactions with detergents, fatty acids, or membranes, which can greatly facilitate tau aggregation and may also mediate some tau functions. Here, we show that the alternatively spliced second microtubule-binding repeat exhibits significantly different structural characteristics compared with the other three repeats in the context of the intact repeat domain. Most notably, the PHF6* hexapeptide motif located at the N-terminus of repeat 2 has a lower propensity to form strand-like structure than the corresponding PHF6 motif in repeat 3, and unlike PHF6 converts to partially helical structure in the micelle-bound state. Interestingly, the behavior of the Module-B motif, located at the beginning of repeat 4, resembles that of PHF6* rather than PHF6. Our observations, combined with previous results showing that PHF6* and Module-B are both less effective than PHF6 in nucleating tau aggregation, suggest a hierarchy in the efficacy of these motifs in nucleating tau aggregation that originates in differences in their intrinsic propensities for extended strand-like structure and the resistance of these propensities to changes in tau's environment.
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Affiliation(s)
- Patrick Barré
- Department of Biochemistry, Program in Structural Biology, Weill Cornell Medical College, New York, 10065, USA
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19
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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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20
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Nath A, Rhoades E. A flash in the pan: dissecting dynamic amyloid intermediates using fluorescence. FEBS Lett 2013; 587:1096-105. [PMID: 23458258 DOI: 10.1016/j.febslet.2013.02.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 02/21/2013] [Accepted: 02/22/2013] [Indexed: 12/15/2022]
Abstract
Several widespread and severe degenerative diseases are characterized by the deposition of amyloid protein aggregates in affected tissues. While there is great interest in the complete description of the aggregation pathway of the proteins involved, a molecular level understanding is hindered by the complexity of the self-assembly process. In particular, the early stages of aggregation, where dynamic, heterogeneous and often toxic intermediates are populated, are resistant to high-resolution structural characterization. Fluorescence spectroscopy is a powerful and versatile tool for such analysis. In this review, we survey its application to provide residue-specific information about amyloid intermediate states for three selected proteins: IAPP, α-synuclein, and tau.
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Affiliation(s)
- Abhinav Nath
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT, USA
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21
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Cisek K, Jensen JR, Honson NS, Schafer KN, Cooper GL, Kuret J. Ligand electronic properties modulate tau filament binding site density. Biophys Chem 2012; 170:25-33. [PMID: 23072817 DOI: 10.1016/j.bpc.2012.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 09/05/2012] [Accepted: 09/06/2012] [Indexed: 10/27/2022]
Abstract
Small molecules that bind tau-bearing neurofibrillary lesions are being sought for premortem diagnosis, staging, and treatment of Alzheimer's disease and other tauopathic neurodegenerative diseases. The utility of these agents will depend on both their binding affinity and binding site density (B(max)). Previously we identified polarizability as a descriptor of protein aggregate binding affinity. To examine its contribution to binding site density, we investigated the ability of two closely related benzothiazole derivatives ((E)-2-[[4-(dimethylamino)phenyl]azo]-6-methoxybenzothiazole) and ((E)-2-[2-[4-(dimethylamino)phenyl]ethenyl]-6-methoxybenzothiazole) that differed in polarizability to displace probes of high (Thioflavin S) and low (radiolabeled (E,E)-1-iodo-2,5-bis(3-hydroxycarbonyl-4-methoxy)styrylbenzene; IMSB) density sites. Consistent with their site densities, Thioflavin S completely displaced radiolabeled IMSB, but IMSB was incapable of displacing Thioflavin S. Although both benzothiazoles displaced the low B(max) IMSB probe, only the highly polarizable analog displaced near saturating concentrations of the Thioflavin S probe. Quantum calculations showed that high polarizability reflected extensive pi-electron delocalization fostered by the presence of electron donating and accepting groups. These data suggest that electron delocalization promotes ligand binding at a subset of sites on tau aggregates that are present at high density, and that optimizing this aspect of ligand structure can yield tau-directed agents with superior diagnostic and therapeutic performance.
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Affiliation(s)
- Katryna Cisek
- Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, Columbus, OH 43210, USA
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22
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Ramachandran G, Udgaonkar JB. Evidence for the Existence of a Secondary Pathway for Fibril Growth during the Aggregation of Tau. J Mol Biol 2012; 421:296-314. [DOI: 10.1016/j.jmb.2012.01.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/02/2012] [Accepted: 01/05/2012] [Indexed: 12/21/2022]
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23
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Ramachandran G, Udgaonkar JB. Understanding the kinetic roles of the inducer heparin and of rod-like protofibrils during amyloid fibril formation by Tau protein. J Biol Chem 2011; 286:38948-59. [PMID: 21931162 DOI: 10.1074/jbc.m111.271874] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aggregation of the natively disordered protein, Tau, to form lesions called neurofibrillary tangles is a characteristic feature of several neurodegenerative tauopathies. The polyanion, heparin, is commonly used as an inducer in studies of Tau aggregation in vitro, but there is surprisingly no comprehensive model describing, quantitatively, all aspects of the heparin-induced aggregation reaction. In this study, rate constants and extents of fibril formation by the four repeat domain of Tau (Tau4RD) have been reproducibly determined over a full range of heparin and protein concentrations. The kinetic role of heparin in the nucleation-dependent fibril formation reaction is shown to be limited to participation in the initial rate-limiting steps; a single heparin molecule binds two Tau4RD molecules, forming an aggregation-competent protein dimer, which then serves as a building block for further fibril growth. Importantly, the minimal kinetic model that is proposed can quantitatively account for the characteristic bell-shaped dependence of the aggregation kinetics on the stoichiometry of protein to heparin. Very importantly, this study also identifies for the first time short and thin, rod-like protofibrils that are populated transiently, early during the time course of fibril formation. The identification of these protofibrils as bona fide off-pathway species has implications for the development of therapies for tauopathies based on driving fibril formation as a means of protecting the cell from smaller, putatively toxic aggregates.
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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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24
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Elbaum-Garfinkle S, Ramlall T, Rhoades E. The role of the lipid bilayer in tau aggregation. Biophys J 2010; 98:2722-30. [PMID: 20513417 PMCID: PMC2877329 DOI: 10.1016/j.bpj.2010.03.013] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/12/2010] [Accepted: 03/02/2010] [Indexed: 11/22/2022] Open
Abstract
Tau is a microtubule associated protein whose aggregation is implicated in a number of neurodegenerative diseases. We investigate the mechanism by which anionic lipid vesicles induce aggregation of tau in vitro using K18, a fragment of tau corresponding to the four repeats of the microtubule binding domain. Our results show that aggregation occurs when the amount of K18 bound to the lipid bilayer exceeds a critical surface density. The ratio of protein/lipid at the critical aggregation concentration is pH-dependent, as is the binding affinity. At low pH, where the protein binds with high affinity, the critical surface density is independent both of total lipid concentration as well as the fraction of anionic lipid present in the bilayer. Furthermore, the aggregates consist of both protein and vesicles and bind the beta-sheet specific dye, Thioflavin T, in the manner characteristic of pathological aggregates. Our results suggest that the lipid bilayer facilitates protein-protein interactions both by screening charges on the protein and by increasing the local protein concentration, resulting in rapid aggregation. Because anionic lipids are abundant in cellular membranes, these findings contribute to understanding tau-lipid bilayer interactions that may be relevant to disease pathology.
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Key Words
- al488, alexa fluor 488
- cac, critical aggregation concentration
- fcs, fluorescence correlation spectroscopy
- luvs, large unilamellar vesicles
- nft, neurofibrillary tangle
- pc, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine
- phfs, paired helical filaments
- ps, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine
- tht, thioflavin t
- rhod-pe, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-n-(lissamine rhodamine b sulfonyl)
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Affiliation(s)
- Shana Elbaum-Garfinkle
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | - Trudy Ramlall
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York
| | - Elizabeth Rhoades
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
- Department of Physics, Yale University, New Haven, Connecticut
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25
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Zhu HL, Fernández C, Fan JB, Shewmaker F, Chen J, Minton AP, Liang Y. Quantitative characterization of heparin binding to Tau protein: implication for inducer-mediated Tau filament formation. J Biol Chem 2009; 285:3592-3599. [PMID: 19959468 DOI: 10.1074/jbc.m109.035691] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurofibrillary tangles, principally composed of bundles of filaments formed by the microtubule-associated protein Tau, are a hallmark of a group of neurodegenerative diseases such as Alzheimer disease. Polyanionic cofactors such as heparin can induce Tau filament formation in vitro. Here we quantitatively characterize the interaction between recombinant human Tau fragment Tau(244-372) and heparin (average molecular mass = 7 kDa) as well as heparin-induced fibril formation by using static light scattering, isothermal titration calorimetry, turbidity assays, and transmission electron microscopy. Our data clearly show that at physiological pH, heparin 7K, and human Tau(244-372) form a tight 1:1 complex with an equilibrium association constant exceeding 10(6) m(-1) under reducing conditions, triggering Tau fibrillization. In the absence of dithiothreitol, heparin shows a moderate binding affinity (10(5) m(-1)) to Tau(244-372), similarly triggering Tau fibrillization. Further fibrillization kinetics analyses show that the lag time appears to be approximately invariant up to a molar ratio of 2:1 and then increases at larger ratios of heparin/Tau. The maximum slope representing the apparent rate constant for fibril growth increases sharply with substoichiometric ratios of heparin/Tau and then decreases to some extent with ratios of >1:1. The retarding effect of heparin in excess is attributed to the large increase in ionic strength of the medium arising from free heparin. Together, these results suggest that the formation of the 1:1 complex of Tau monomer and heparin plays an important role in the inducer-mediated Tau filament formation, providing clues to understanding the pathogenesis of neurodegenerative diseases.
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Affiliation(s)
- Hai-Li Zhu
- From the State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China and
| | - Cristina Fernández
- the Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Jun-Bao Fan
- From the State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China and
| | - Frank Shewmaker
- the Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Jie Chen
- From the State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China and
| | - Allen P Minton
- the Laboratory of Biochemistry and Genetics, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Yi Liang
- From the State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China and.
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26
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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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27
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Voss K, Gamblin TC. GSK-3beta phosphorylation of functionally distinct tau isoforms has differential, but mild effects. Mol Neurodegener 2009; 4:18. [PMID: 19409104 PMCID: PMC2683827 DOI: 10.1186/1750-1326-4-18] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Accepted: 05/02/2009] [Indexed: 12/30/2022] Open
Abstract
Background Tau protein exists as six different isoforms that differ by the inclusion or exclusion of exons 2, 3 and 10. Exon 10 encodes a microtubule binding repeat, thereby resulting in three isoforms with three microtubule binding repeats (3R) and three isoforms that have four microtubule binding repeats (4R). In normal adult brain, the relative amounts of 3R tau and 4R tau are approximately equal. These relative protein levels are preserved in Alzheimer's disease, although in other neurodegenerative tauopathies such as progressive supranuclear palsy, corticobasal degeneration and Pick's disease, the ratio of 3R:4R is frequently altered. Because tau isoforms are not equally involved in these diseases, it is possible that they either have inherently unique characteristics owing to their primary structures or that post-translational modification, such as phosphorylation, differentially affects their properties. Results We have determined the effects of phosphorylation by a kinase widely believed to be involved in neurodegenerative processes, glycogen synthase kinase-3β (GSK-3β), on the microtubule binding and inducer-initiated polymerization of these isoforms in vitro. We have found that each isoform has a unique microtubule binding and polymerization profile that is altered by GSK-3β. GSK-3β phosphorylation had differential effects on the isoforms although there were similarities between isoforms and the effects were generally mild. Conclusion These results indicate that tau phosphorylation by a single kinase can have isoform specific outcomes. The mild nature of these changes, however, makes it unlikely that differential effects of GSK-3β phosphorylation on the isoforms are causative in neurodegenerative disease. Instead, the inherent differences in the isoform interactions themselves and local conditions in the diseased cells are likely the major determinant of isoform involvement in various neurodegenerative disorders.
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Affiliation(s)
- Kellen Voss
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA.
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28
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Abstract
Tau aggregates into neurofibrillary tangles in Alzheimer's disease and tauopathies. There is ongoing debate about whether tau aggregation is toxic and which form of tau is toxic. Based on recent studies showing that mature tau tangles can be dissociated from neuronal loss and cognitive deficits, it can be hypothesized that the intermediate pre-fibrillar tau aggregate is the predominant neurotoxic tau species. The toxicity of tau aggregation includes loss of physiological functions of native tau and gain of pathological functions of pre-fibrillar tau species. Mature tau tangles per se might be relatively inert or even represent failed cytoprotective efforts of protein quality control machineries in response to accumulating toxic tau species. Further studies on the mechanisms of tau aggregation, the structure of intermediate tau forms and their toxicity are needed to settle this debate.
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Affiliation(s)
- Huiping Ding
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, USA
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29
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Peterson DW, Zhou H, Dahlquist FW, Lew J. A soluble oligomer of tau associated with fiber formation analyzed by NMR. Biochemistry 2008; 47:7393-404. [PMID: 18558718 DOI: 10.1021/bi702466a] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Alzheimer's disease (AD) is characterized by the intracellular accumulation of the neurofibrillary tangles comprised mainly of the microtubule-associated protein, tau. A critical aspect of understanding tangle formation is to understand the transition of soluble monomeric tau into mature fibrils by characterizing the structure of intermediates along the aggregation pathway. We have carried out multidimensional NMR studies on a C-terminal fragment of human tau (tau (187)) to gain structural insight into the aggregation process. To specifically monitor intermolecular interaction between tau molecules in solution, we combined (15)N- and (14)N-labeled tau, the latter of which was modified with a paramagnetic nitroxide spin label (MTSL). Paramagnetic relaxation enhancement (PRE) of (15)N-tau by interaction with MTSL- (14)N-tau allowed identification of low molecular weight oligomers of tau (187) that formed in response to heparin-induced aggregation. Two regions, VQIINK (280) and VQIVYK (311), were exclusively broadened by MTSL located at varied positions in the tau molecule. We propose that soluble oligomers of tau (187) are generated via intermolecular interactions at these motifs triggered by heparin addition. However, the associated line broadening at these motifs cannot be due to interaction between tau (187) and heparin directly. Instead, these specific interactions necessarily occur between tau molecules and are intermolecular in nature. Our data support the idea that VQIINK (280) and VQIVYK (311) are the major, if not sole, critical regions that directly mediate intermolecular contact between tau molecules during the early phases of aggregation.
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Affiliation(s)
- Dylan W Peterson
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA
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30
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Panyukov YV, Nemykh MA, Dobrov EN, Drachev VA. Surfactant-induced amorphous aggregation of tobacco mosaic virus coat protein: a physical methods approach. Macromol Biosci 2008; 8:199-209. [PMID: 17886326 DOI: 10.1002/mabi.200700145] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The interactions of non-ionic surfactant Triton X-100 and the coat protein of tobacco mosaic virus, which is an established model for both ordered and non-ordered protein aggregation, were studied using turbidimetry, differential scanning calorimetry, isothermal titration calorimetry, and dynamic light scattering. It was found that at the critical aggregation concentration (equal to critical micelle concentration) of 138 x 10(-6) M, Triton X-100 induces partial denaturation of tobacco mosaic virus coat protein molecules followed by protein amorphous aggregation. Protein aggregation has profound ionic strength dependence and proceeds due to hydrophobic sticking of surfactant-protein complexes (start aggregates) with initial radii of 46 nm. It has been suggested that the anionic surfactant sodium dodecyl sulfate forms mixed micelles with Triton X-100 and therefore reverses protein amorphous aggregation with release of protein molecules from the amorphous aggregates. A stoichiometric ratio of 5 was found for Triton X-100-sodium dodecyl sulfate interactions.
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Affiliation(s)
- Yuliy V Panyukov
- A.N. Belozersky Institute of Physico-Chemical Biology and Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow 119992, Russia.
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Honson NS, Jensen JR, Darby MV, Kuret J. Potent inhibition of tau fibrillization with a multivalent ligand. Biochem Biophys Res Commun 2007; 363:229-34. [PMID: 17854770 PMCID: PMC2048976 DOI: 10.1016/j.bbrc.2007.08.166] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 08/28/2007] [Indexed: 11/23/2022]
Abstract
Small-molecule inhibitors of tau fibrillization are under investigation as tools for interrogating the tau aggregation pathway and as potential therapeutic agents for Alzheimer's disease. Established inhibitors include thiacarbocyanine dyes, which can inhibit recombinant tau fibrillization in the presence of anionic surfactant aggregation inducers. In an effort to increase inhibitory potency, a cyclic bis-thiacarbocyanine molecule containing two thiacarbocyanine moieties was synthesized and characterized with respect to tau fibrillization inhibitory activity by electron microscopy and ligand aggregation state by absorbance spectroscopy. Results showed that the inhibitory activity of the bis-thiacarbocyanine was qualitatively similar to a monomeric cyanine dye, but was more potent with 50% inhibition achieved at approximately 80nM concentration. At all concentrations tested in aqueous solution, the bis-thiacarbocyanine collapsed to form a closed clamshell structure. However, the presence of tau protein selectively stabilized the open conformation. These results suggest that the inhibitory activity of bis-thiacarbocyanine results from multivalency, and reveal a route to more potent tau aggregation inhibitors.
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Affiliation(s)
- Nicolette S. Honson
- Center for Molecular Neurobiology, Department of Molecular & Cellular Biochemistry, College of Medicine
| | - Jordan R. Jensen
- Center for Molecular Neurobiology, Department of Molecular & Cellular Biochemistry, College of Medicine
| | - Michael V. Darby
- College of Pharmacy; The Ohio State University, Columbus, OH 43210
| | - Jeff Kuret
- Center for Molecular Neurobiology, Department of Molecular & Cellular Biochemistry, College of Medicine
- *Corresponding Author: Jeff Kuret, Ph.D., Center for Molecular Neurobiology, 1060 Carmack Rd., Columbus, OH 43210, Fax: 614-292-5379, Email address: (J. Kuret)
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Honson NS, Johnson RL, Huang W, Inglese J, Austin CP, Kuret J. Differentiating Alzheimer disease-associated aggregates with small molecules. Neurobiol Dis 2007; 28:251-60. [PMID: 17761424 PMCID: PMC2194600 DOI: 10.1016/j.nbd.2007.07.018] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Accepted: 07/11/2007] [Indexed: 11/28/2022] Open
Abstract
Alzheimer disease is diagnosed postmortem by the density and spatial distribution of beta-amyloid plaques and tau-bearing neurofibrillary tangles. The major protein component of each lesion adopts cross-beta-sheet conformation capable of binding small molecules with submicromolar affinity. In many cases, however, Alzheimer pathology overlaps with Lewy body disease, characterized by the accumulation of a third cross-beta-sheet forming protein, alpha-synuclein. To determine the feasibility of distinguishing tau aggregates from beta-amyloid and alpha-synuclein aggregates with small molecule probes, a library containing 72,455 small molecules was screened for antagonists of tau-aggregate-mediated changes in Thioflavin S fluorescence, followed by secondary screens to distinguish the relative affinity for each substrate protein. Results showed that >10-fold binding selectivity among substrates could be achieved, with molecules selective for tau aggregates containing at least three aromatic or rigid moieties connected by two rotatable bonds.
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Affiliation(s)
- Nicolette S. Honson
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
| | | | - Wenwei Huang
- NIH Chemical Genomics Center, Rockville, MD 20850
| | | | | | - Jeff Kuret
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
- * Corresponding Author: Jeff Kuret, Ph.D., Center for Molecular Neurobiology, 1060 Carmack Rd., Columbus, OH 43210, , Tel: (614) 688-5899, Fax: (614) 292-5379
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Mamikonyan G, Necula M, Mkrtichyan M, Ghochikyan A, Petrushina I, Movsesyan N, Mina E, Kiyatkin A, Glabe CG, Cribbs DH, Agadjanyan MG. Anti-A beta 1-11 antibody binds to different beta-amyloid species, inhibits fibril formation, and disaggregates preformed fibrils but not the most toxic oligomers. J Biol Chem 2007; 282:22376-86. [PMID: 17545160 PMCID: PMC2435219 DOI: 10.1074/jbc.m700088200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Different strategies proposed as therapy for Alzheimer disease (AD) have aimed to reduce the level of toxic forms of A beta peptide in the brain. Here, we directly analyze the therapeutic utility of the polyclonal anti-A beta(1-11) antibody induced in 3xTg-AD mice vaccinated with the second generation prototype epitope vaccine. Substoichiometric concentrations of purified anti-A beta(1-11) antibody prevented aggregation of A beta(42) and induced disaggregation of preformed A beta(42) fibrils down to nonfilamentous and nontoxic species. Anti-A beta(1-11) antibody delayed A beta(42) oligomer formation but ultimately appeared to stabilize nonfibrillar conformations, including oligomer-like assemblies. The reduced oligomer-mediated cytotoxicity observed upon preincubation of A beta oligomers with the anti-A beta(1-11) antibody in the absence of oligomer disaggregation suggests a possible oligomer rearrangement in the presence of the antibody. These in vitro observations suggest that preventive vaccination may protect from AD or may delay the onset of the disease, whereas therapeutic vaccination cannot disrupt the toxic oligomers and may only minimally alleviate preexisting AD pathology.
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Affiliation(s)
- Grigor Mamikonyan
- Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647
| | - Mihaela Necula
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - Mikayel Mkrtichyan
- Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647
| | - Anahit Ghochikyan
- Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647
| | - Irina Petrushina
- Institute for Brain Aging and Dementia, University of California, Irvine, California 92697
| | - Nina Movsesyan
- Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647
| | - Erene Mina
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - Anatoly Kiyatkin
- Department of Pathology, Thomas Jefferson University, Philadelphia, Pennsylvania 19115
| | - Charles G. Glabe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - David H. Cribbs
- Institute for Brain Aging and Dementia, University of California, Irvine, California 92697
| | - Michael G. Agadjanyan
- Department of Immunology, The Institute for Molecular Medicine, Huntington Beach, California 92647
- Institute for Brain Aging and Dementia, University of California, Irvine, California 92697
- To whom correspondence should be addressed: The Institute for Molecular Medicine, 16371 Gothard St., H, Huntington Beach, CA 92647-3652. Tel.: 714-596-7821; Fax: 714-596-3791; E-mail:
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Congdon EE, Necula M, Blackstone RD, Kuret J. Potency of a tau fibrillization inhibitor is influenced by its aggregation state. Arch Biochem Biophys 2007; 465:127-35. [PMID: 17559794 PMCID: PMC2048980 DOI: 10.1016/j.abb.2007.05.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 05/07/2007] [Accepted: 05/08/2007] [Indexed: 11/17/2022]
Abstract
Tau fibrillization is a potential therapeutic target for Alzheimer's and other neurodegenerative diseases. Several small-molecule inhibitors of tau aggregation have been developed for this purpose. One of them, 3,3'-bis(beta-hydroxyethyl)-9-ethyl-5,5'-dimethoxythiacarbocyanine iodide (N744), is a cationic thiacarbocyanine dye that inhibits recombinant tau filament formation when present at submicromolar concentrations. To prepare dosing regimens for testing N744 activity in biological models, its full concentration-effect relationship in the range 0.01-60muM was examined in vitro by electron microscopy and laser light scattering methods. Results revealed that N744 concentration dependence was biphasic, with fibrillization inhibitory activity appearing at submicromolar concentration, but with relief of inhibition and increases in fibrillization apparent above 10muM. Therefore, fibrillization was inhibited 50% only over a narrow concentration range, which was further reduced by filament stabilizing modifications such as tau pseudophosphorylation. N744 inhibitory activity also was paralleled by changes in its aggregation state, with dimer predominating at inhibitory concentrations and large dye aggregates appearing at high concentrations. Ligand dimerization was promoted by the presence of tau protein, which lowered the equilibrium dissociation constant for dimerization more than an order of magnitude relative to controls. The results suggest that ligand aggregation may play an important role in both inhibitory and disinhibitory phases of the concentration-effect curve, and may lead to complex dose-response relationships in model systems.
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Affiliation(s)
- Erin E. Congdon
- Neuroscience Graduate Studies Program, The Ohio State University, Columbus, OH 43210
| | - Mihaela Necula
- Biophysics Program, The Ohio State University, Columbus, OH 43210
| | - Robert D. Blackstone
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
| | - Jeff Kuret
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
- *Corresponding Author: Jeff Kuret, Ph.D., Center for Molecular Neurobiology 1060 Carmack Rd. Columbus, OH 43210, TEL: (614) 688-5899, FAX: (614) 292-5379,
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35
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Necula M, Kayed R, Milton S, Glabe CG. Small Molecule Inhibitors of Aggregation Indicate That Amyloid β Oligomerization and Fibrillization Pathways Are Independent and Distinct. J Biol Chem 2007; 282:10311-24. [PMID: 17284452 DOI: 10.1074/jbc.m608207200] [Citation(s) in RCA: 533] [Impact Index Per Article: 31.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alzheimer disease is characterized by the abnormal aggregation of amyloid beta peptide into extracellular fibrillar deposits known as amyloid plaques. Soluble oligomers have been observed at early time points preceding fibril formation, and these oligomers have been implicated as the primary pathological species rather than the mature fibrils. A significant issue that remains to be resolved is whether amyloid oligomers are an obligate intermediate on the pathway to fibril formation or represent an alternate assembly pathway that may or may not lead to fiber formation. To determine whether amyloid beta oligomers are obligate intermediates in the fibrillization pathway, we characterized the mechanism of action of amyloid beta aggregation inhibitors in terms of oligomer and fibril formation. Based on their effects, the small molecules segregated into three distinct classes: compounds that inhibit oligomerization but not fibrillization, compounds that inhibit fibrillization but not oligomerization, and compounds that inhibit both. Several compounds selectively inhibited oligomerization at substoichiometric concentrations relative to amyloid beta monomer, with some active in the low nanomolar range. These results indicate that oligomers are not an obligate intermediate in the fibril formation pathway. In addition, these data suggest that small molecule inhibitors are useful for clarifying the mechanisms underlying protein aggregation and may represent potential therapeutic agents that target fundamental disease mechanisms.
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Affiliation(s)
- Mihaela Necula
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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36
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Johansson AS, Garlind A, Berglind-Dehlin F, Karlsson G, Edwards K, Gellerfors P, Ekholm-Pettersson F, Palmblad J, Lannfelt L. Docosahexaenoic acid stabilizes soluble amyloid-β protofibrils and sustains amyloid-β-induced neurotoxicity in vitro. FEBS J 2007; 274:990-1000. [PMID: 17227385 DOI: 10.1111/j.1742-4658.2007.05647.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Enrichment of diet and culture media with the polyunsaturated fatty acid docosahexaenoic acid has been found to reduce the amyloid burden in mice and lower amyloid-beta (Abeta) levels in both mice and cultured cells. However, the direct interaction of polyunsaturated fatty acids, such as docosahexaenoic acid, with Abeta, and their effect on Abeta aggregation has not been explored in detail. Therefore, we have investigated the effect of docosahexaenoic acid, arachidonic acid and the saturated fatty acid arachidic acid on monomer oligomerization into protofibrils and protofibril fibrillization into fibrils in vitro, using size exclusion chromatography. The polyunsaturated fatty acids docosahexaenoic acid and arachidonic acid at micellar concentrations stabilized soluble Abeta42 wild-type protofibrils, thereby hindering their conversion to insoluble fibrils. As a consequence, docosahexaenoic acid sustained amyloid-beta-induced toxicity in PC12 cells over time, whereas Abeta without docosahexaenoic acid stabilization resulted in reduced toxicity, as Abeta formed fibrils. Arachidic acid had no effect on Abeta aggregation, and neither of the fatty acids had any protofibril-stabilizing effect on Abeta42 harboring the Arctic mutation (AbetaE22G). Consequently, AbetaArctic-induced toxicity could not be sustained using docosahexaenoic acid. These results provide new insights into the toxicity of different Abeta aggregates and how endogenous lipids can affect Abeta aggregation.
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Affiliation(s)
- Ann-Sofi Johansson
- Department of Public Health and Caring Sciences, Uppsala University, Rudbeck Laboratory, Sweden.
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37
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Mizushima F, Minoura K, Tomoo K, Sumida M, Taniguchi T, Ishida T. Fluorescence-coupled CD conformational monitoring of filament formation of tau microtubule-binding repeat domain. Biochem Biophys Res Commun 2006; 343:712-8. [PMID: 16563344 DOI: 10.1016/j.bbrc.2006.02.185] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 02/28/2006] [Indexed: 10/24/2022]
Abstract
To clarify the contribution of the three- or four-repeated peptide moiety in tau microtubule-binding domain (MBD) to paired helical filament (PHF) formation, conformational transition accompanied by heparin-induced filament formation was investigated stepwise for four repeat peptides (R1-R4), one three-repeated R1-R3-R4 peptide (3RMBD), and one four-repeated R1-R2-R3-R4 peptide (4RMBD) using a combination of thioflavin S fluorescence and circular dichroism (CD) measurements in a neutral buffer (pH 7.6). The comparison of the fluorescence profile of each repeat peptide with those of 3RMBD and 4RMBD showed the synergistic contribution of R1-R4 to PHF formation of MBD. The CD spectrum measured as a function of filament formation time indicates that: (i) two conformational transitions occur for the filament formations of R3 (from the random structure to the beta-sheet structure) and 3RMBD (from the random structure to the alpha-helix structure), (ii) the filament formations of R2 and 4RMBD proceed via the synchronized conformational transitions of the alpha-helix and random structures, and (iii) the filament formation of 4RMBD is dependent on the aggregation behavior of R2. These data are useful for elucidating the MBD conformational transition in tau PHF formation.
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Affiliation(s)
- Fumie Mizushima
- Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
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38
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Yin H, Kuret J. C-terminal truncation modulates both nucleation and extension phases of τ fibrillization. FEBS Lett 2005; 580:211-5. [PMID: 16364303 DOI: 10.1016/j.febslet.2005.11.077] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 11/30/2005] [Indexed: 11/16/2022]
Abstract
Proteolytic post-translational modification has been proposed as an early stage event in the aggregation of tau protein and formation of neurofibrillary lesions in Alzheimer's disease. Caspases and other proteases cleave tau in vivo at discrete locations including Asp421 and Glu391. Both cleavage products are prone to aggregation relative to wild-type, full-length tau protein. To determine the mechanism underlying this effect, the fibrillization of tau truncated after Asp421 and Glu391 residues was characterized in a full-length four-repeat tau background using quantitative electron microscopy methods under homogeneous nucleation conditions. Both C-terminal truncations decreased critical concentration relative to full-length tau, resulting in more filament mass at reaction plateau. Moreover, truncation directly augmented the efficiency of the nucleation reaction. The results suggest the mechanism through which C-terminal proteolysis can modulate tau filament accumulation depending on whether it precedes or follows nucleation.
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Affiliation(s)
- Haishan Yin
- Ohio State Biochemistry Program, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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39
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Necula M, Kuret J. A static laser light scattering assay for surfactant-induced tau fibrillization. Anal Biochem 2005; 333:205-15. [PMID: 15450794 DOI: 10.1016/j.ab.2004.05.044] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Indexed: 11/22/2022]
Abstract
Static light scattering is an important solution-based method for assaying spontaneous protein aggregation reactions. But the reliability of the measurements when conducted in the presence of fibrillization inducers has been questioned. Here the utility of static laser light scattering for quantitative assay of anionic micelle-induced protein fibrillization was characterized using tau protein, the major component of neurofibrillary lesions of Alzheimer's disease. Both inducer micellization and tau fibrillization made significant contributions to light scattering intensity. The intensity arising solely from micellization was quantified using proteins that promoted inducer micellization but could not fibrillize, such as mixed histones and assembly-incompetent mutant htau40(I277P/I308P). When corrected for micellization, reaction progress curves for wild-type tau fibrillization were sigmoidal and correlated well with measurements of total filament length made by transmission electron microscopy. The utility of the improved laser light scattering assay was demonstrated by quantifying the effect of inducer concentration on tau assembly kinetics using a three-parameter Gompertz growth function. Results showed that alkyl sulfate detergent accelerated tau nucleation as reflected by shorter lag times and modulated pre-nuclear equilibria to yield more filament mass at reaction equilibrium.
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Affiliation(s)
- Mihaela Necula
- Biophysics Program,The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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40
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Abstract
The increasing use of recombinantly expressed therapeutic proteins in the pharmaceutical industry has highlighted issues such as their stability during long-term storage and means of efficacious delivery that avoid adverse immunogenic side effects. Controlled chemical modifications, such as substitutions, acylation and PEGylation, have fulfilled some but not all of their promises, while hydrogels and lipid-based formulations could well be developed into generic delivery systems. Strategies to curb the aggregation and misfolding of proteins during storage are likely to benefit from the recent surge of interest in protein fibrillation. This might in turn lead to generally accepted guidelines and tests to avoid unforeseen adverse effects in drug delivery.
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Affiliation(s)
- Sven Frokjaer
- Department of Pharmaceutics, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100 Copenhagen O, Denmark
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41
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Kuret J, Chirita CN, Congdon EE, Kannanayakal T, Li G, Necula M, Yin H, Zhong Q. Pathways of tau fibrillization. Biochim Biophys Acta Mol Basis Dis 2005; 1739:167-78. [PMID: 15615636 DOI: 10.1016/j.bbadis.2004.06.016] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Accepted: 06/02/2004] [Indexed: 11/22/2022]
Abstract
New methods for analyzing tau fibrillization have yielded insights into the biochemical transitions involved in the process. Here we review the parallels between the sequential progression of tau fibrillization observed macroscopically in Alzheimer's disease (AD) lesions and the pathway of tau aggregation observed in vitro with purified tau preparations. In addition, pharmacological agents for further dissection of fibrillization mechanism and lesion formation are discussed.
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Affiliation(s)
- Jeff Kuret
- Center for Molecular Neurobiology, Department of Molecular and Cellular Biochemistry, Ohio St. University College of Medicine and Public Health, 1060 Carmack Rd., Columbus, OH 43210, USA.
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42
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Necula M, Kuret J. Site-specific pseudophosphorylation modulates the rate of tau filament dissociation. FEBS Lett 2005; 579:1453-7. [PMID: 15733856 DOI: 10.1016/j.febslet.2005.01.047] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 01/10/2005] [Accepted: 01/25/2005] [Indexed: 01/22/2023]
Abstract
Hyperphosphorylation of tau is of fundamental importance for neurofibrillary lesion development in Alzheimer's disease, but the mechanisms through which it acts are not clear. Experiments with pseudophosphorylation mutants of full-length tau protein indicate that incorporation of negative charge into specific sites can modulate the aggregation reaction, and that this occurs by altering the critical concentration of assembly. Here, the kinetic origin of this effect was determined using quantitative electron microscopy methods and pseudophosphorylation mutant T212E in a full-length four-repeat tau background. On the basis of disaggregation rates, decreases in critical concentration resulted primarily from decreases in the dissociation rate constant. The results suggest a mechanism through which site-specific posttranslational modifications can modulate filament accumulation at low free intracellular tau concentrations.
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Affiliation(s)
- Mihaela Necula
- Biophysics Program, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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43
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Kuret J, Congdon EE, Li G, Yin H, Yu X, Zhong Q. Evaluating triggers and enhancers of tau fibrillization. Microsc Res Tech 2005; 67:141-55. [PMID: 16103995 DOI: 10.1002/jemt.20187] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alzheimer's disease is characterized in part by the aggregation of tau protein into filamentous inclusions. Because tau filaments form in brain regions associated with memory retention, and because their appearance correlates well with the degree of dementia, they have emerged as robust markers of disease progression. Yet the discovery that mutations in tau protein can lead directly to filament and tangle formation in humans, and that filament formation is linked to neurodegeneration in model biological systems, suggests that tau aggregation may also contribute directly to degeneration in affected neurons. In this context, the mechanism of tau filament formation and its modulation by mutation and posttranslational modification is of fundamental importance. Here, recent progress on the molecular mechanisms underlying tau aggregation deduced from in vivo and in vitro experimentation is reviewed and a model rationalizing the effect of posttranslational and other structural modifications on assembly kinetics and thermodynamics is presented. We hypothesize that tau aggregation can be described as a heterogeneous nucleation reaction, where exogenous effectors, tau gene mutations, or other modifications that stabilize assembly-competent conformations of tau act to trigger the fibrillization reaction. In contrast, those that modulate postnuclear equilibria can enhance fibrillization by increasing the free energy difference between polymers and unincorporated monomers, resulting in stabilization of filaments at low bulk protein concentrations.
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Affiliation(s)
- Jeff Kuret
- Department of Molecular and Cellular Biochemistry and Center for Molecular Neurobiology, The Ohio State University College of Medicine and Public Health, Columbus, Ohio 43210, USA.
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44
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Oakley MT, Garibaldi JM, Hirst JD. Lattice models of peptide aggregation: Evaluation of conformational search algorithms. J Comput Chem 2005; 26:1638-46. [PMID: 16170797 DOI: 10.1002/jcc.20306] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We present a series of conformational search calculations on the aggregation of short peptide fragments that form fibrils similar to those seen in many protein mis-folding diseases. The proteins were represented by a face-centered cubic lattice model with the conformational energies calculated using the Miyazawa-Jernigan potential. The searches were performed using algorithms based on the Metropolis Monte Carlo method, including simulated annealing and replica exchange. We also present the results of searches using the tabu search method, an algorithm that has been used for many optimization problems, but has rarely been used in protein conformational searches. The replica exchange algorithm consistently found more stable structures then the other algorithms, and was particularly effective for the octamers and larger systems.
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Affiliation(s)
- Mark T Oakley
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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45
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Gamblin TC. Potential structure/function relationships of predicted secondary structural elements of tau. Biochim Biophys Acta Mol Basis Dis 2005; 1739:140-9. [PMID: 15615633 DOI: 10.1016/j.bbadis.2004.08.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2004] [Accepted: 08/30/2004] [Indexed: 01/14/2023]
Abstract
The microtubule-associated protein tau is believed to be a natively unfolded molecule with virtually no secondary structure. However, this protein self-associates into filamentous forms in various neurodegenerative diseases. Since these filamentous forms show a remarkable degree of higher order due to their regular widths and periodicity, it is widely speculated that tau does contain secondary structures that come together to form tertiary and quaternary structures in the filamentous form. The purpose of this review is to use the primary sequence of tau along with predictive methods in an effort to identify potential secondary structural elements that could be involved in its normal and pathological functions. Although there are few predicted structural elements in the tau molecule, these analyses should lead to a better understanding of the structure/function relationships that regulate the behavior of tau.
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Affiliation(s)
- T Chris Gamblin
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave. Lawrence, KS 66045, USA.
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46
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Hall GF, Yao J. Modeling tauopathy: a range of complementary approaches. Biochim Biophys Acta Mol Basis Dis 2004; 1739:224-39. [PMID: 15615641 DOI: 10.1016/j.bbadis.2004.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Accepted: 10/05/2004] [Indexed: 11/24/2022]
Abstract
The large group of neurodegenerative diseases which feature abnormal metabolism and accumulation of tau protein (tauopathies) characteristically produce a multiplicity of cellular and systemic abnormalities in human patients. Understanding the complex pathogenetic mechanisms by which abnormalities in tau lead to systemic neurofibrillary degenerative disease requires the construction and use of model experimental systems in which the behavior of human tau can be analyzed under controlled conditions. In this paper, we survey the ways in which in vitro, cellular and whole-animal models of human tauopathy are being used to add to our knowledge of the pathogenetic mechanisms underlying these conditions. In particular, we focus on the complementary advantages and limitations of various approaches to constructing tauopathy models presently in use with respect to those of murine transgenic tauopathy models.
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Affiliation(s)
- Garth F Hall
- Department of Biological Sciences, University of Massachusetts, Lowell, Massachusetts 01854, USA.
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Liu M, Ni J, Kosik KS, Yeh LA. Development of a Fluorescent High Throughput Assay for Tau Aggregation. Assay Drug Dev Technol 2004; 2:609-19. [PMID: 15674019 DOI: 10.1089/adt.2004.2.609] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A high throughput assay for measuring tau aggregation using fluorescent resonance energy transfer (FRET) is described. Full-length recombinant tau labeled with Cy3 or Cy5 dye is used as ligand, and the induction of aggregation is accomplished by the addition of arachidonic acid. In the presence of this fatty acid, tau aggregation is measured by FRET in a 384-well format. The nature of tau aggregation is further characterized by competition with unlabeled tau and cross-linking experiments. It is concluded that the FRET observed under the experimental condition is due to the accumulation of tau dimers and tetramers. A model for tau aggregation is presented. The performance of this assay in a high throughput format is demonstrated and can be used to identify inhibitors of tau aggregation.
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Affiliation(s)
- Min Liu
- Laboratory for Drug Discovery in Neurodegeneration, Brigham and Women's Hospital and Harvard Medical School, Cambridge, MA, USA
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von Bergen M, Barghorn S, Biernat J, Mandelkow EM, Mandelkow E. Tau aggregation is driven by a transition from random coil to beta sheet structure. Biochim Biophys Acta Mol Basis Dis 2004; 1739:158-66. [PMID: 15615635 DOI: 10.1016/j.bbadis.2004.09.010] [Citation(s) in RCA: 267] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Revised: 09/23/2004] [Accepted: 09/23/2004] [Indexed: 11/28/2022]
Abstract
The abnormal aggregation of the microtubule associated protein tau into paired helical filaments (PHFs) is one the hallmarks of Alzheimer's disease. The soluble protein is one of the longest natively unfolded proteins, lacking significant amounts of secondary structure over a sequence of 441 amino acids in the longest isoform. Furthermore, the unfolded character is consistent with some notable features of the protein like stability towards heat and acid treatment. It is still unclear how these characteristics support the physiological function of binding to and stabilization of microtubules. We review here some recent studies on how an unfolded protein such as tau can adopt beta-structure, which then leads to the highly ordered morphology of the PHFs. The core sequence for both microtubule binding and PHF formation is the microtubule binding domain containing three or four repeats. This region alone is sufficient for PHF formation and mostly unfolded in the soluble state. A search for sequence motifs within this region crucial for PHF building revealed two hexapeptides in the second and the third repeat. Some of the genetically linked cases of FTDP-17 show missense mutations in or adjacent to these hexapeptide motifs. Proteins containing the P301L and the DeltaK280 mutations exhibit accelerated aggregation. The importance of the two hexapeptides stems from their capacity to undergo a conformational change from a random coil to a beta sheet structure. The increase of beta sheet structure is a typical feature of an amyloidogenic protein and is the basis of other characteristics like a decreased sensitivity towards proteolytic degradation and Congo red binding. PHFs aggregated in vitro and in vivo contain beta-sheet structure, as judged by circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction.
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Affiliation(s)
- Martin von Bergen
- Max-Planck-Unit for Structural Molecular Biology, Notkestrasse 85, D-22607 Hamburg, Germany
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Necula M, Kuret J. Pseudophosphorylation and Glycation of Tau Protein Enhance but Do Not Trigger Fibrillization in Vitro. J Biol Chem 2004; 279:49694-703. [PMID: 15364924 DOI: 10.1074/jbc.m405527200] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alzheimer's disease is defined in part by the intraneuronal aggregation of tau protein into filamentous lesions. The pathway is accompanied by posttranslational modifications including phosphorylation and glycation, each of which has been shown to promote tau fibrillization in vitro when present at high stoichiometry. To clarify the site-specific impact of posttranslational modification on tau fibrillization, the ability of recombinant full-length four repeat tau protein (htau40) and 11 pseudophosphorylation mutants to fibrillize in the presence of anionic inducer was assayed in vitro using transmission electron microscopy and laser light scattering assays. Tau glycated with d-glucose was examined as well. Both glycated tau and pseudophosphorylation mutants S199E, T212E, S214E, double mutant T212E/S214E, and triple mutant S199E/S202E/T205E yielded increased filament mass at equilibrium relative to wild-type tau. Increases in filament mass correlated strongly with decreases in critical concentration, indicating that both pseudophosphorylation and glycation promoted fibrillization by shifting equilibrium toward the fibrillized state. Analysis of reaction time courses further revealed that increases in filament mass were not associated with reduced lag times, indicating that these posttranslational modifications did not promote filament nucleation. The results suggest that site-specific posttranslational modifications can stabilize filaments once they nucleate, and thereby support their accumulation at low intracellular tau concentrations.
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Affiliation(s)
- Mihaela Necula
- Biophysics Program, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
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Terwel D, Lasrado R, Snauwaert J, Vandeweert E, Van Haesendonck C, Borghgraef P, Van Leuven F. Changed conformation of mutant Tau-P301L underlies the moribund tauopathy, absent in progressive, nonlethal axonopathy of Tau-4R/2N transgenic mice. J Biol Chem 2004; 280:3963-73. [PMID: 15509565 DOI: 10.1074/jbc.m409876200] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein tau-3R/4R isoform ratio and phosphorylation regulates binding to microtubules and, when disturbed by aging or mutations, results in diverse tauopathies and in neurodegeneration. The underlying mechanisms were studied here in three transgenic mouse strains with identical genetic background, all expressing the tau-4R/2N isoform driven specifically in neurons by the thy1 gene promoter. Two strains, expressing human tau-4R/2N or mutant tau-4R/2N-P301L at similar, moderate levels, developed very different phenotypes. Tau-4R/2N mice became motor-impaired already around age 6-8 weeks, accompanied by axonopathy (dilatations, spheroids), but no tau aggregates, and surviving normally. In contrast, tau-P301L mice developed neurofibrillary tangles from age 6 months, without axonal dilatations and, despite only minor motor problems, all succumbing before the age of 13 months. The third strain, obtained by tau knock-out/knock-in (tau-KOKI), expressed normal levels of wild-type human tau-4R/2N replacing all mouse tau isoforms. Tau-KOKI mice survived normally with minor motor problems late in life and without any obvious pathology. Biochemically, a fraction of neuronal tau in aging tau-P301L mice was hyperphosphorylated concomitant with conformational changes and aggregation, but overall, tau-4R/2N was actually more phosphorylated than tau-P301L. Significantly, tau with changed conformation and with hyperphosphorylation colocalized in the same neurons in aging tau-P301L mice. Taken together, we conclude that excessive binding of tau-4R/2N as opposed to reduced binding of tau-P301L to microtubules is responsible for the development of axonopathy and tauopathy, respectively, in tau-4R/2N and tau-P301L mice and that the conformational change of tau-P301L is a major determinant in triggering the tauopathy.
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Affiliation(s)
- Dick Terwel
- Experimental Genetics Group, Department of Human Genetics, KU Leuven, B-3000 Leuven, Belgium
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