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Okumura H, Itoh SG. Molecular dynamics simulations of amyloid-β(16-22) peptide aggregation at air-water interfaces. J Chem Phys 2021; 152:095101. [PMID: 33480728 DOI: 10.1063/1.5131848] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Oligomers of amyloid-β (Aβ) peptides are known to be related to Alzheimer's disease, and their formation is accelerated at hydrophilic-hydrophobic interfaces, such as the cell membrane surface and air-water interface. Here, we report molecular dynamics simulations of aggregation of Aβ(16-22) peptides at air-water interfaces. First, 100 randomly distributed Aβ(16-22) peptides moved to the interface. The high concentration of peptides then accelerated their aggregation and formation of antiparallel β-sheets. Two layers of oligomers were observed near the interface. In the first layer from the interface, the oligomer with less β-bridges exposed the hydrophobic residues to the air. The second layer consisted of oligomers with more β-bridges that protruded into water. They are more soluble in water because the hydrophobic residues are covered by N- and C-terminal hydrophilic residues that are aligned well along the oligomer edge. These results indicate that amyloid protofibril formation mainly occurs in the second layer.
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Affiliation(s)
- Hisashi Okumura
- Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Satoru G Itoh
- Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
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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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Lee H, Lee H, Lee M. Studies of Small Molecule Dyes that Interact with Pyrene-labeled Amyloid Fragments. B KOREAN CHEM SOC 2014. [DOI: 10.5012/bkcs.2014.35.11.3369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Xu W, Zhang C, Morozova-Roche L, Zhang JZH, Mu Y. pH-dependent conformational ensemble and polymorphism of amyloid-β core fragment. J Phys Chem B 2013; 117:8392-9. [PMID: 23786168 DOI: 10.1021/jp404034x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Characterization of amyloid oligomeric species is important due to its possible responsibility for the toxicity of amyloid proteins, whereas it is difficult to detect by current spectroscopic techniques. The pH-dependent tetramerization and fibrillation of the central hydrophobic segment of Alzheimer amyloid β-peptide (Aβ(12-24)) were respectively explored by all-atom replica exchange molecular dynamics simulations and by fluorescence and atomic force microscopy measurements. Our combined study shows that more β-sheet structures in the early event of tetramerization is linked directly to the high propensity to form amyloid fibrils in the consequent fibrillation. Both tetramerization and fibrillation are strongly regulated by pH. At pH 5.0, Aβ(12-24) has two opposite terminal charges. The electrostatic attraction between the side-chains of His13/His14 and Glu22/Asp23 thus acts as a "pattern keeper", resulting in high propensity of amyloid formation. These results suggest that pH effects most likely by affecting the ionization properties of the Aβ(12-24) peptide. Specifically, the pH-dependent equilibrium conformational distribution of different aggregate species are well-investigated in detail. Our findings also give hints to other experimental findings that the kinetics and morphologies of Aβ fibril formation are strongly pH-dependent.
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Affiliation(s)
- Weixin Xu
- State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062, China
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Li Y, Ji C, Xu W, Zhang JZH. Dynamical stability and assembly cooperativity of β-sheet amyloid oligomers--effect of polarization. J Phys Chem B 2012; 116:13368-73. [PMID: 23101885 DOI: 10.1021/jp3086599] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The soluble intermediate oligomers of amyloidogenic proteins are suspected to be more cytotoxic than the mature fibrils in neurodegenerative disorders. Here, the dynamic stability and assembly cooperativity of a model oligomer of human islet amyloid polypeptide (hIAPP) segments were explored by means of all-atom molecular dynamics (MD) simulations under different force fields including AMBER99SB, OPLS, and polarized protein-specific charge (PPC) model. Simulation results show that the dynamic stability of β-sheet oligomers is seriously impacted by electrostatic polarization. Without inclusion of polarization (simulation under standard AMBER and OPLS force field), the β-sheet oligomers are dynamically unstable during MD simulation. For comparison, simulation results under PPC give significantly more stable dynamical structures of the oligomers. Furthermore, calculation of electrostatic interaction energy between the neighboring β strands with an approximate polarizable method produces energetic evidence for cooperative assembly of β-strand oligomers. This result supports a picture of downhill-like cooperative assembly of β strands during fibrillation process. The present study demonstrates the critical role of polarization in dynamic stability and assembly cooperativity of β-sheet-rich amyloid oligomers.
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Affiliation(s)
- Yang Li
- State Key Laboratory of Precision Spectroscopy and Department of Physics, Institute of Theoretical and Computational Science, East China Normal University, Shanghai, China
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Saracino GAA, Cigognini D, Silva D, Caprini A, Gelain F. Nanomaterials design and tests for neural tissue engineering. Chem Soc Rev 2012; 42:225-62. [PMID: 22990473 DOI: 10.1039/c2cs35065c] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nanostructured scaffolds recently showed great promise in tissue engineering: nanomaterials can be tailored at the molecular level and scaffold morphology may more closely resemble features of extracellular matrix components in terms of porosity, framing and biofunctionalities. As a consequence, both biomechanical properties of scaffold microenvironments and biomaterial-protein interactions can be tuned, allowing for improved transplanted cell engraftment and better controlled diffusion of drugs. Easier said than done, a nanotech-based regenerative approach encompasses different fields of know-how, ranging from in silico simulations, nanomaterial synthesis and characterization at the nano-, micro- and mesoscales to random library screening methods (e.g. phage display), in vitro cellular-based experiments and validation in animal models of the target injury. All of these steps of the "assembly line" of nanostructured scaffolds are tightly interconnected both in their standard analysis techniques and in their most recent breakthroughs: indeed their efforts have to jointly provide the deepest possible analyses of the diverse facets of the challenging field of neural tissue engineering. The purpose of this review is therefore to provide a critical overview of the recent advances in and drawbacks and potential of each mentioned field, contributing to the realization of effective nanotech-based therapies for the regeneration of peripheral nerve transections, spinal cord injuries and brain traumatic injuries. Far from being the ultimate overview of such a number of topics, the reader will acknowledge the intrinsic complexity of the goal of nanotech tissue engineering for a conscious approach to the development of a regenerative therapy and, by deciphering the thread connecting all steps of the research, will gain the necessary view of its tremendous potential if each piece of stone is correctly placed to work synergically in this impressive mosaic.
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Affiliation(s)
- Gloria A A Saracino
- Center for Nanomedicine and Tissue Engineering, A.O. Ospedale Niguarda Cà Granda, Milan, 20162, Italy
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Masters CL, Selkoe DJ. Biochemistry of amyloid β-protein and amyloid deposits in Alzheimer disease. Cold Spring Harb Perspect Med 2012; 2:a006262. [PMID: 22675658 PMCID: PMC3367542 DOI: 10.1101/cshperspect.a006262] [Citation(s) in RCA: 395] [Impact Index Per Article: 32.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Progressive cerebral deposition of the amyloid β-protein (Aβ) in brain regions serving memory and cognition is an invariant and defining feature of Alzheimer disease. A highly similar but less robust process accompanies brain aging in many nondemented humans, lower primates, and some other mammals. The discovery of Aβ as the subunit of the amyloid fibrils in meningocerebral blood vessels and parenchymal plaques has led to innumerable studies of its biochemistry and potential cytotoxic properties. Here we will review the discovery of Aβ, numerous aspects of its complex biochemistry, and current attempts to understand how a range of Aβ assemblies, including soluble oligomers and insoluble fibrils, may precipitate and promote neuronal and glial alterations that underlie the development of dementia. Although the role of Aβ as a key molecular factor in the etiology of Alzheimer disease remains controversial, clinical trials of amyloid-lowering agents, reviewed elsewhere in this book, are poised to resolve the question of its pathogenic primacy.
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Affiliation(s)
- Colin L Masters
- The Mental Health Research Institute, The University of Melbourne, Parkville 3010, Australia.
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Xu W, Zhang C, Derreumaux P, Gräslund A, Morozova-Roche L, Mu Y. Intrinsic determinants of Aβ(12-24) pH-dependent self-assembly revealed by combined computational and experimental studies. PLoS One 2011; 6:e24329. [PMID: 21957446 PMCID: PMC3177821 DOI: 10.1371/journal.pone.0024329] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 08/04/2011] [Indexed: 11/19/2022] Open
Abstract
The propensity of amyloid- (A) peptide to self-assemble into highly ordered amyloid structures lies at the core of their accumulation in the brain during Alzheimer's disease. By using all-atom explicit solvent replica exchange molecular dynamics simulations, we elucidated at the atomic level the intrinsic determinants of the pH-dependent dimerization of the central hydrophobic segment A and related these with the propensity to form amyloid fibrils measured by experimental tools such as atomic force microscopy and fluorescence. The process of A dimerization was evaluated in terms of free energy landscape, side-chain two-dimensional contact probability maps, -sheet registries, potential mean force as a function of inter-chain distances, secondary structure development and radial solvation distributions. We showed that dimerization is a key event in A amyloid formation; it is highly prompted in the order of pH 5.02.98.4 and determines further amyloid growth. The dimerization is governed by a dynamic interplay of hydrophobic, electrostatic and solvation interactions permitting some variability of -sheets at each pH. These results provide atomistic insight into the complex process of molecular recognition detrimental for amyloid growth and pave the way for better understanding of the molecular basis of amyloid diseases.
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Affiliation(s)
- Weixin Xu
- State Key Laboratory of Precision Spectroscopy, Institute of Theoretical and Computational Science, East China Normal University, Shanghai, China
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Ce Zhang
- Departments of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique, UPR9080 CNRS, Institut de Biologie Physico-Chimique, Paris, France
| | - Astrid Gräslund
- Department of Biophysics, Stockholm University, Stockholm, Sweden
| | - Ludmilla Morozova-Roche
- Departments of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
- * E-mail: (LM); (YM)
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (LM); (YM)
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Effect of atom- and group-based truncations on biomolecules simulated with reaction-field electrostatics. J Mol Model 2011; 17:2883-93. [PMID: 21311933 DOI: 10.1007/s00894-011-0975-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 01/17/2011] [Indexed: 10/18/2022]
Abstract
The performance of the reaction-field method of electrostatics is tested in molecular dynamics simulations of protein human interleukin-4 and a short DNA fragment in explicit solvent. Two truncation schemes are considered: one based on the position of atomic charges in water molecules and the other on the position of groups of charges. The group-based truncation leads to the melting of the DNA double helix. In contrast, the atom-based truncation maintains the helical structure intact. Similarly for the protein, the group-based truncation leads to an unfolding at pH 2 while the atom-based truncation produces stable trajectories at low and normal pH, in agreement with experiment. Artificial repulsion between charged residues associated with the group-based truncation is identified as the microscopic reason behind unfolding of the protein. Implications of different truncation schemes in reaction-field simulations of biomolecules are discussed.
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Cao Z, Liu L, Wang J. Effects of pH and Temperature on the Structural and Thermodynamic Character of a-syn12 Peptide in Aqueous Solution. J Biomol Struct Dyn 2010; 28:343-53. [DOI: 10.1080/07391102.2010.10507364] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Wallace JA, Shen JK. Probing the strand orientation and registry alignment in the propagation of amyloid fibrils. Biochemistry 2010; 49:5290-8. [PMID: 20491446 DOI: 10.1021/bi100137y] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Detailed knowledge of the structure and growth mechanism of amyloid fibrils is important for understanding the disease process. Recently, solid-state NMR and other spectroscopic data have revealed the equilibrium organization of the tertiary structure of fibrils formed by various segments of beta-amyloid peptides. A three-step "dock-and-lock" mechanism for fibril growth has been proposed on the basis of the kinetic data. Here we use all-atom replica-exchange molecular dynamics simulations in generalized-Born implicit solvent to probe the mechanism of tertiary structure propagation in fibrils of Abeta(16-22) modeled as an oligomer consisting of two beta-sheets each having four strands. The data show that following association with the oligomer, but before being fully locked onto the existing beta-sheet, the added monomer predominantly samples states with the antiparallel strand orientation, but both in- and one-residue shifted backbone hydrogen bond alignments. The in-register state, which is the experimentally observed equilibrium alignment, is marginally more stable than the registry-shifted one. These results suggest that, following the fast docking step, the added monomer dynamically slides in the backbone registry, and stabilization of the preferential alignment must occur in the second locking step as the monomer becomes fully integrated with the fibril. We also delineate the electrostatic and hydrophobic effects in directing the registry alignment during monomer addition. Surprisingly, the in-register alignment provides both increased cross-strand electrostatic attraction and hydrophobic surface burial. Finally, our data support the notion that side chain hydrophobic burial is a major driving force for beta-sheet assembly.
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Affiliation(s)
- Jason A Wallace
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA
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