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Pretti E, Shell MS. Mapping the configurational landscape and aggregation phase behavior of the tau protein fragment PHF6. Proc Natl Acad Sci U S A 2023; 120:e2309995120. [PMID: 37983502 PMCID: PMC10691331 DOI: 10.1073/pnas.2309995120] [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] [Received: 06/13/2023] [Accepted: 10/17/2023] [Indexed: 11/22/2023] Open
Abstract
The PHF6 (Val-Gln-Ile-Val-Tyr-Lys) motif, found in all isoforms of the microtubule-associated protein tau, forms an integral part of ordered cores of amyloid fibrils formed in tauopathies and is thought to play a fundamental role in tau aggregation. Because PHF6 as an isolated hexapeptide assembles into ordered fibrils on its own, it is investigated as a minimal model for insight into the initial stages of aggregation of larger tau fragments. Even for this small peptide, however, the large length and time scales associated with fibrillization pose challenges for simulation studies of its dynamic assembly, equilibrium configurational landscape, and phase behavior. Here, we develop an accurate, bottom-up coarse-grained model of PHF6 for large-scale simulations of its aggregation, which we use to uncover molecular interactions and thermodynamic driving forces governing its assembly. The model, not trained on any explicit information about fibrillar structure, predicts coexistence of formed fibrils with monomers in solution, and we calculate a putative equilibrium phase diagram in concentration-temperature space. We also characterize the configurational and free energetic landscape of PHF6 oligomers. Importantly, we demonstrate with a model of heparin that this widely studied cofactor enhances the aggregation propensity of PHF6 by ordering monomers during nucleation and remaining associated with growing fibrils, consistent with experimentally characterized heparin-tau interactions. Overall, this effort provides detailed molecular insight into PHF6 aggregation thermodynamics and pathways and, furthermore, demonstrates the potential of modern multiscale modeling techniques to produce predictive models of amyloidogenic peptides simultaneously capturing sequence-specific effects and emergent aggregate structures.
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Affiliation(s)
- Evan Pretti
- Department of Chemical Engineering, University of California, Santa Barbara, CA93106-5080
| | - M. Scott Shell
- Department of Chemical Engineering, University of California, Santa Barbara, CA93106-5080
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2
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Pal S, Roy R, Paul S. Deciphering the Role of ATP on PHF6 Aggregation. J Phys Chem B 2022; 126:4761-4775. [PMID: 35759245 DOI: 10.1021/acs.jpcb.2c01768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aggregation of Tau protein, which are involved in Alzheimer's disease, are associated with the self-assembly of the hexapeptide sequence, paired helical filament 6 (PHF6) from repeat 3 of Tau. In order to treat Alzheimer's disease and other such tauopathies, one of the therapeutic strategies is to inhibit aggregation of Tau and its nucleating segments. Therefore, we have studied the effect of adenosine triphosphate (ATP) on the aggregation of PHF6. ATP has, interestingly, demonstrated its ability to inhibit and dissolve protein aggregates. Using classical molecular dynamics simulations, we observed that the hydrophobic core of PHF6 segment displays extended β-sheet conformation, which stabilizes PHF6 aggregates. However, the distribution of ATP around the vicinity of the peptides enables PHF6 to remain discrete and attain random coil conformers. The interpeptide interactions are substituted by PHF6-ATP interactions through hydrogen bonding and hydrophobic interactions (including π-π stacking). Furthermore, the adenosine moiety of ATP contributes more than the triphosphate chain toward PHF6-ATP interaction. Ultimately, this work establishes the inhibitory activity of ATP against Tau aggregation; hence, the therapeutic effect of ATP should be explored further in regard to the effective treatment of Alzheimer's disease.
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Affiliation(s)
- Saikat Pal
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
| | - Rituparna Roy
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
| | - Sandip Paul
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
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Choi RH, Kim H. Density functional theory study of the dimer structure of amyloidogenic active sequence
VQIVYK. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Ryu Ho Choi
- Department of Applied Chemistry Kumoh National Institute of Technology Gumi Republic of Korea
| | - Ho‐Tae Kim
- Department of Applied Chemistry Kumoh National Institute of Technology Gumi Republic of Korea
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4
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Chatterjee P, Le T, Bui HTD, Cho MK, Ham S. Atomic Level Investigations of Early Aggregation of Tau43 in Water I. Conformational Propensity of Monomeric Tau43. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Prathit Chatterjee
- Department of Chemistry The Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa‐ro 47‐Gil 100, Yongsan‐Ku Seoul 04310 Korea
| | - Thi‐Diem Le
- Department of Chemistry The Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa‐ro 47‐Gil 100, Yongsan‐Ku Seoul 04310 Korea
| | - Huong T. D. Bui
- Department of Chemistry The Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa‐ro 47‐Gil 100, Yongsan‐Ku Seoul 04310 Korea
| | - Myung Keun Cho
- Department of Chemistry The Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa‐ro 47‐Gil 100, Yongsan‐Ku Seoul 04310 Korea
- Department of Chemistry College of Natural Sciences, Seoul National University, Gwanak‐ro 1, Gwanak‐ku Seoul 08826 Korea
| | - Sihyun Ham
- Department of Chemistry The Research Institute of Natural Sciences, Sookmyung Women's University, Cheongpa‐ro 47‐Gil 100, Yongsan‐Ku Seoul 04310 Korea
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5
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Li Y, Peng X. Comparison of the force fields on monomeric and fibrillar PHF6 of tau protein. Biophys Chem 2021; 277:106631. [PMID: 34116358 DOI: 10.1016/j.bpc.2021.106631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/18/2021] [Accepted: 06/01/2021] [Indexed: 11/19/2022]
Abstract
The hexapeptide 306VQIVYK311 (PHF6) plays an important role in the aggregation of Tau protein, which is a hallmark of the Alzheimer's disease (AD). In this article, we systematically compare the effects of eight popular all-atom force fields on the monomeric and fibrillar PHF6 in the molecular dynamics (MD) simulations, which could be helpful in the computer-aided drug design against PHF6. We show that the fibrillar PHF6 prefers β-strand-like structures in all the force fields while the monomer has different structural preferences depending on the force fields. The interactions for stabilizing the fibril are further investigated. In the end, according to the interactions revealed by NMR and the stability of the fibril in the literature, we benchmark the force fields.
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Affiliation(s)
- Yanchun Li
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China
| | - Xubiao Peng
- Center for Quantum Technology Research, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, China; Beijing Academy of Quantum Information Sciences, Beijing 100193, China.
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6
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Yang J, Agnihotri MV, Huseby CJ, Kuret J, Singer SJ. A theoretical study of polymorphism in VQIVYK fibrils. Biophys J 2021; 120:1396-1416. [PMID: 33571490 DOI: 10.1016/j.bpj.2021.01.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 01/07/2021] [Accepted: 01/11/2021] [Indexed: 02/06/2023] Open
Abstract
The VQIVYK fragment from the Tau protein, also known as PHF6, is essential for aggregation of Tau into neurofibrillary lesions associated with neurodegenerative diseases. VQIVYK itself forms amyloid fibrils composed of paired β-sheets. Therefore, the full Tau protein and VQIVYK fibrils have been intensively investigated. A central issue in these studies is polymorphism, the ability of a protein to fold into more than one structure. Using all-atom molecular simulations, we generate five stable polymorphs of VQIVYK fibrils, establish their relative free energy with umbrella sampling methods, and identify the side chain interactions that provide stability. The two most stable polymorphs, which have nearly equal free energy, are formed by interdigitation of the mostly hydrophobic VIY "face" sides of the β-sheets. Another stable polymorph is formed by interdigitation of the QVK "back" sides. When we turn to examine structures from cryo-electron microscopy experiments on Tau filaments taken from diseased patients or generated in vitro, we find that the pattern of side chain interactions found in the two most stable face-to-face as well as the back-to-back polymorphs are recapitulated in amyloid structures of the full protein. Thus, our studies suggest that the interactions stabilizing PHF6 fibrils explain the amyloidogenicity of the VQIVYK motif within the full Tau protein and provide justification for the use of VQIVYK fibrils as a test bed for the design of molecules that identify or inhibit amyloid structures.
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Affiliation(s)
- Jaehoon Yang
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio
| | - Mithila V Agnihotri
- Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, Ohio
| | - Carol J Huseby
- Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, Ohio
| | - Jeff Kuret
- Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, Ohio; Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, Ohio.
| | - Sherwin J Singer
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio; Interdisciplinary Biophysics Graduate Program, The Ohio State University, Columbus, Ohio.
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Choi RH, Kim HT. Analysis of oligomeric complexes of the amyloid-forming FYLLYY peptide by collision-induced dissociation with electrospray ionization mass spectrometry. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2020; 26:361-368. [PMID: 32915641 DOI: 10.1177/1469066720958373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The monomeric and oligomeric structures of the "FYLLYY" β2 microglobulin (β2m) active sequence, formed in (DMSO/CH3CN) solution, were investigated using electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Dissociation of dimer and trimer ions was investigated by tandem mass spectrometry using collision induced dissociation (CID). The covalent bond fragmentation patterns were observed in the 21+ and 32+ MS/MS spectra (21+ = [dimer+H]1+ and 32+ = [trimer + 2H]2+). A π-π stacking geometry for the FYLLYY 21+ complex and partial parallel β-sheet geometry for the 32+ complex are proposed to be stable structures. The observed covalent bond fragment ions in the MS/MS spectra of the 32+ complex are considered to have originated from the partial parallel β-sheet moiety. The FYLLYY → AALLGY (or FYLLAA) substituted sequence was also investigated by CID-MS/MS. Our MS/MS analysis suggests that the π-π stacking interaction structures are important in dimer binding rather than the structures of a complete parallel or anti-parallel β-sheet 21+ complex.
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Affiliation(s)
- Ryu Ho Choi
- Department of Applied Chemistry, Kumoh National Institute of Technology, Gumi, Republic of Korea
| | - Ho-Tae Kim
- Department of Applied Chemistry, Kumoh National Institute of Technology, Gumi, Republic of Korea
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Viswanathan GK, Shwartz D, Losev Y, Arad E, Shemesh C, Pichinuk E, Engel H, Raveh A, Jelinek R, Cooper I, Gosselet F, Gazit E, Segal D. Purpurin modulates Tau-derived VQIVYK fibrillization and ameliorates Alzheimer's disease-like symptoms in animal model. Cell Mol Life Sci 2020; 77:2795-2813. [PMID: 31562564 PMCID: PMC11104911 DOI: 10.1007/s00018-019-03312-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 08/11/2019] [Accepted: 09/19/2019] [Indexed: 01/20/2023]
Abstract
Neurofibrillary tangles of the Tau protein and plaques of the amyloid β peptide are hallmarks of Alzheimer's disease (AD), which is characterized by the conversion of monomeric proteins/peptides into misfolded β-sheet rich fibrils. Halting the fibrillation process and disrupting the existing aggregates are key challenges for AD drug development. Previously, we performed in vitro high-throughput screening for the identification of potent inhibitors of Tau aggregation using a proxy model, a highly aggregation-prone hexapeptide fragment 306VQIVYK311 (termed PHF6) derived from Tau. Here we have characterized a hit molecule from that screen as a modulator of Tau aggregation using in vitro, in silico, and in vivo techniques. This molecule, an anthraquinone derivative named Purpurin, inhibited ~ 50% of PHF6 fibrillization in vitro at equimolar concentration and disassembled pre-formed PHF6 fibrils. In silico studies showed that Purpurin interacted with key residues of PHF6, which are responsible for maintaining its β-sheets conformation. Isothermal titration calorimetry and surface plasmon resonance experiments with PHF6 and full-length Tau (FL-Tau), respectively, indicated that Purpurin interacted with PHF6 predominantly via hydrophobic contacts and displayed a dose-dependent complexation with FL-Tau. Purpurin was non-toxic when fed to Drosophila and it significantly ameliorated the AD-related neurotoxic symptoms of transgenic flies expressing WT-FL human Tau (hTau) plausibly by inhibiting Tau accumulation and reducing Tau phosphorylation. Purpurin also reduced hTau accumulation in cell culture overexpressing hTau. Importantly, Purpurin efficiently crossed an in vitro human blood-brain barrier model. Our findings suggest that Purpurin could be a potential lead molecule for AD therapeutics.
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Affiliation(s)
- Guru Krishnakumar Viswanathan
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Dana Shwartz
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Yelena Losev
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Elad Arad
- Ilse Katz Institute (IKI) for Nanoscale Science and Technology, Ben Gurion University of the Negev, 8410501, Beer Sheva, Israel
- Department of Chemistry, Ben Gurion University of the Negev, 8410501, Beer Sheva, Israel
| | - Chen Shemesh
- The Joseph Sagol Neuroscience Center, Sheba Medical Center, Tel Hashomer, 52621, Ramat Gan, Israel
| | - Edward Pichinuk
- Blavatnik Center for Drug Discovery, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Hamutal Engel
- Blavatnik Center for Drug Discovery, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Avi Raveh
- Blavatnik Center for Drug Discovery, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Raz Jelinek
- Ilse Katz Institute (IKI) for Nanoscale Science and Technology, Ben Gurion University of the Negev, 8410501, Beer Sheva, Israel
- Department of Chemistry, Ben Gurion University of the Negev, 8410501, Beer Sheva, Israel
| | - Itzik Cooper
- The Joseph Sagol Neuroscience Center, Sheba Medical Center, Tel Hashomer, 52621, Ramat Gan, Israel
- Interdisciplinary Center Herzliya, Herzliya, Israel
| | - Fabien Gosselet
- Blood-Brain Barrier Laboratory (LBHE), Université d'Artois, Lens, France
| | - Ehud Gazit
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, Tel-Aviv University, 69978, Tel Aviv, Israel
- Blavatnik Center for Drug Discovery, Tel-Aviv University, 69978, Tel Aviv, Israel
| | - Daniel Segal
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, Tel-Aviv University, 69978, Tel Aviv, Israel.
- The Interdisciplinary Sagol School of Neurosciences, Tel-Aviv University, 69978, Tel Aviv, Israel.
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Moreno-Castillo E, Álvarez-Ginarte YM, Valdés-Tresanco ME, Montero-Cabrera LA, Moreno E, Valiente PA. Understanding the disrupting mechanism of the Tau aggregation motif " 306 VQIVYK 311 " by phenylthiazolyl-hydrazides inhibitors. J Mol Recognit 2020; 33:e2848. [PMID: 32227525 DOI: 10.1002/jmr.2848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/09/2020] [Accepted: 03/10/2020] [Indexed: 12/23/2022]
Abstract
Alzheimer's disease is a progressive neurodegenerative disorder characterized by the abnormal processing of the Tau and the amyloid precursor proteins. The unusual aggregation of Tau is based on the formation of intermolecular β-sheets through two motifs: 275 VQIINK280 and 306 VQIVYK311 . Phenylthiazolyl-hydrazides (PTHs) are capable of inhibiting/disassembling Tau aggregates. However, the disaggregation mechanism of Tau oligomers by PTHs is still unknown. In this work, we studied the disruption of the oligomeric form of the Tau motif 306 VQIVYK311 by PTHs through molecular docking, molecular dynamics, and free energy calculations. We predicted hydrophobic interactions as the major driving forces for the stabilization of Tau oligomer, with V306 and I308 being the major contributors. Nonpolar component of the binding free energy is essential to stabilize Tau-PTH complexes. PTHs disrupted mainly the van der Waals interactions between the monomers, leading to oligomer destabilization. Destabilization of full Tau filament by PTHs and emodin was not observed in the sampled 20 ns; however, in all cases, the nonpolar component of the binding free energy is essential for the formation of Tau filament-PTH and Tau filament-emodin. These results provide useful clues for the design of more effective Tau-aggregation inhibitors.
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Affiliation(s)
| | | | | | | | - Ernesto Moreno
- Faculty of Basic Sciences, Universidad de Medellín, Medellín, Colombia
| | - Pedro A Valiente
- Center of Protein Studies, Faculty of Biology, University of Havana, La Habana, Cuba
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Haj E, Losev Y, Guru KrishnaKumar V, Pichinuk E, Engel H, Raveh A, Gazit E, Segal D. Integrating in vitro and in silico approaches to evaluate the "dual functionality" of palmatine chloride in inhibiting and disassembling Tau-derived VQIVYK peptide fibrils. Biochim Biophys Acta Gen Subj 2018; 1862:1565-1575. [PMID: 29634991 DOI: 10.1016/j.bbagen.2018.04.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 03/20/2018] [Accepted: 04/03/2018] [Indexed: 01/02/2023]
Abstract
BACKGROUND Alzheimer's disease (AD) is the most common neurodegenerative disorder which is characterized by the deposits of intra-cellular tau protein and extra-cellular amyloid-β (Aβ) peptides in the human brain. Understanding the mechanism of protein aggregation and finding compounds that are capable of inhibiting its aggregation is considered to be highly important for disease therapy. METHODS We used an in vitro High-Throughput Screening for the identification of potent inhibitors of tau aggregation using a proxy model; a highly aggregation-prone hexapeptide fragment 306VQIVYK311 derived from tau. Using ThS fluorescence assay we screened a library of 2401 FDA approved, bio-active and natural compounds in attempt to find molecules which can efficiently modulate tau aggregation. RESULTS Among the screened compounds, palmatine chloride (PC) alkaloid was able to dramatically reduce the aggregation propensity of PHF6 at sub-molar concentrations. PC was also able to disassemble preformed aggregates of PHF6 and reduce the amyloid content in a dose-dependent manner. Insights obtained from MD simulation showed that PC interacted with the key residues of PHF6 responsible for β-sheet formation, which could likely be the mechanism of inhibition and disassembly. Furthermore, PC could effectively inhibit the aggregation of full-length tau and disassemble preformed aggregates. CONCLUSIONS We found that PC possesses "dual functionality" towards PHF6 and full-length tau, i.e. inhibit their aggregation and disassemble pre-formed fibrils. GENERAL SIGNIFICANCE The "dual functionality" of PC is valuable as a disease modifying strategy for AD, and other tauopathies, by inhibiting their progress and reducing the effect of fibrils already present in the brain.
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Affiliation(s)
- Esraa Haj
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Yelena Losev
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel
| | - V Guru KrishnaKumar
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel; Department of Biological Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, Gujarat 382355, India
| | - Edward Pichinuk
- BLAVATNIK CENTER for Drug Discovery, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Hamutal Engel
- BLAVATNIK CENTER for Drug Discovery, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Avi Raveh
- BLAVATNIK CENTER for Drug Discovery, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Ehud Gazit
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel; BLAVATNIK CENTER for Drug Discovery, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Daniel Segal
- Department of Molecular Microbiology and Biotechnology, School of Molecular Cell Biology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel; The Interdisciplinary Sagol School of Neurosciences, Tel-Aviv University, Tel Aviv 69978, Israel.
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11
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Smit FX, Luiken JA, Bolhuis PG. Primary Fibril Nucleation of Aggregation Prone Tau Fragments PHF6 and PHF6. J Phys Chem B 2016; 121:3250-3261. [PMID: 27776213 DOI: 10.1021/acs.jpcb.6b07045] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We performed replica exchange molecular dynamics and forward flux sampling simulations of hexapeptide VQIINK and VQIVYK systems, also known as, respectively, fragments PHF6* and PHF6 from the tau protein. Being a part of the microtubule binding region, these fragments are known to be aggregation prone, and at least one of them is a prerequisite for fibril formation of the tau protein. Using a coarse-grained force field, we establish the phase behavior of both fragments, and investigate the nucleation kinetics for the conversion into a β-sheet fibril. As the conversion is, in principle, a reversible process, we predict the rate constants for both the fibril formation and melting, and examine the corresponding mechanisms. Our simulations indicate that, while both fragments form disordered aggregates, only PHF6 is able to form β-sheet fibrils. This observation provides a possible explanation for the lack of available steric zipper crystal structures for PHF6*.
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Affiliation(s)
- Florent X Smit
- van't Hoff Institute for Molecular Sciences, University of Amsterdam , PO Box 94157, 1090 GD Amsterdam, The Netherlands
| | - Jurriaan A Luiken
- van't Hoff Institute for Molecular Sciences, University of Amsterdam , PO Box 94157, 1090 GD Amsterdam, The Netherlands
| | - Peter G Bolhuis
- van't Hoff Institute for Molecular Sciences, University of Amsterdam , PO Box 94157, 1090 GD Amsterdam, The Netherlands
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12
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Abstract
The paired helical filaments (PHF) formed by the intrinsically disordered human protein tau are one of the pathological hallmarks of Alzheimer disease. PHF are fibers of amyloid nature that are composed of a rigid core and an unstructured fuzzy coat. The mechanisms of fiber formation, in particular the role that hydration water might play, remain poorly understood. We combined protein deuteration, neutron scattering, and all-atom molecular dynamics simulations to study the dynamics of hydration water at the surface of fibers formed by the full-length human protein htau40. In comparison with monomeric tau, hydration water on the surface of tau fibers is more mobile, as evidenced by an increased fraction of translationally diffusing water molecules, a higher diffusion coefficient, and increased mean-squared displacements in neutron scattering experiments. Fibers formed by the hexapeptide (306)VQIVYK(311) were taken as a model for the tau fiber core and studied by molecular dynamics simulations, revealing that hydration water dynamics around the core domain is significantly reduced after fiber formation. Thus, an increase in water dynamics around the fuzzy coat is proposed to be at the origin of the experimentally observed increase in hydration water dynamics around the entire tau fiber. The observed increase in hydration water dynamics is suggested to promote fiber formation through entropic effects. Detection of the enhanced hydration water mobility around tau fibers is conjectured to potentially contribute to the early diagnosis of Alzheimer patients by diffusion MRI.
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13
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Nath A, Sammalkorpi M, DeWitt DC, Trexler AJ, Elbaum-Garfinkle S, O'Hern CS, Rhoades E. The conformational ensembles of α-synuclein and tau: combining single-molecule FRET and simulations. Biophys J 2013. [PMID: 23199922 DOI: 10.1016/j.bpj.2012.09.032] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are increasingly recognized for their important roles in a range of biological contexts, both in normal physiological function and in a variety of devastating human diseases. However, their structural characterization by traditional biophysical methods, for the purposes of understanding their function and dysfunction, has proved challenging. Here, we investigate the model IDPs α-Synuclein (αS) and tau, that are involved in major neurodegenerative conditions including Parkinson's and Alzheimer's diseases, using excluded volume Monte Carlo simulations constrained by pairwise distance distributions from single-molecule fluorescence measurements. Using this, to our knowledge, novel approach we find that a relatively small number of intermolecular distance constraints are sufficient to accurately determine the dimensions and polymer conformational statistics of αS and tau in solution. Moreover, this method can detect local changes in αS and tau conformations that correlate with enhanced aggregation. Constrained Monte Carlo simulations produce ensembles that are in excellent agreement both with experimental measurements on αS and tau and with all-atom, explicit solvent molecular dynamics simulations of αS, with much lower configurational sampling requirements and computational expense.
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Affiliation(s)
- Abhinav Nath
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA.
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