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Gu W, Chen K, Zhao X, Geng H, Li J, Qin Y, Bai X, Chang YN, Xia S, Zhang J, Ma S, Wu Z, Xing G, Xing G. Highly Dispersed Fullerenols Hamper Osteoclast Ruffled Border Formation by Perturbing Ca 2+ Bundles. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1802549. [PMID: 30334332 DOI: 10.1002/smll.201802549] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 09/29/2018] [Indexed: 06/08/2023]
Abstract
Osteoporosis, a common and serious bone disorder affecting aged people and postmenopausal women, is characterized by osteoclast overactivity. One therapeutic strategy is suppressing the bone resorption function of hyperactive osteoclasts, but there is no effective drug in clinical practice so far. Herein, it is demonstrated that fullerenols suppress the bone resorption of osteoclasts by inhibiting ruffled borders (RBs) formation. The RBs formation, which is supported by well-aligned actin bundles (B-actins), is a critical event for osteoclast bone resorption. To facilitate this function, osteoclast RBs dynamics is regulated by variable microenvironments to bundle F-actins, protrude cell membrane, and so on. B-actin perturbation by fullerenols is determined here, offering an opportunity to regulate osteoclast function by destroying RBs. In vivo, the therapeutic effect of fullerenols on overactive osteoclasts is confirmed in a mouse model of lipopolysaccharide-induced bone erosion. Collectively, the findings suggest that fullerenols adhere to F-actin surfaces and inhibit RBs formation in osteoclasts, mainly through hampering Ca2+ from bundling F-actins, and this is likely due to the stereo-hindrance effect caused by adherent fullerenols.
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Affiliation(s)
- Weihong Gu
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Kui Chen
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoyi Zhao
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, 100049, China
| | - Huan Geng
- Department of Orthopedics, General Hospital of Chinese People's Armed Police Forces, Beijing, 100039, China
| | - Juan Li
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Yanxia Qin
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Xue Bai
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ya-Nan Chang
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Shibo Xia
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jiaxin Zhang
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Sihan Ma
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhonghua Wu
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, 100049, China
| | - Gengyan Xing
- Department of Orthopedics, General Hospital of Chinese People's Armed Police Forces, Beijing, 100039, China
| | - Gengmei Xing
- CAS Key Laboratory for Biomedical Effects of Nanomaterial and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
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Gu W, Bai X, Ren K, Zhao X, Xia S, Zhang J, Qin Y, Lei R, Chen K, Chang YN, Zeng L, Li J, Xing G. Mono-fullerenols modulating cell stiffness by perturbing actin bundling. NANOSCALE 2018; 10:1750-1758. [PMID: 29308471 DOI: 10.1039/c7nr07231g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Understanding what modulates the cell stiffness is important given its potential application as a diagnostic and medical target. Here, we investigated why and how mono-fullerenols affect the cell stiffness. We confirmed the fullerenol-modulation of cell stiffness using atomic force microscopy (AFM) with sphere tips and ascertained that the particles reduce the cell polarity. The structures of b-actin and f-actin were evaluated by inverted fluorescence microscopy, synchrotron radiation small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and AFM. Statistical and quantitative analyses of the SAXS data of fullerenol-treated b-actin and f-actin reveal a transformation from large-size to small-size b-actin and simultaneously to f-actin. The slight increase in f-actin diameter in the treated group suggests that fullerenols attach to the actin surface. We verified the attachment using AFM and high-resolution probes. Collectively, our results suggest that fullerenols hamper the bundling of f-actin to form b-actin by adhering to the surface of f-actin, weakening the bundle-based cell stiffness.
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Affiliation(s)
- Weihong Gu
- CAS Key Laboratory for Biomedical Effects of Nanomaterial & Nanosafety, Institute of High Energy Physics, Chinese Academy of Science (CAS), Beijing 100049, China.
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3
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Mohammadinejad S, Ghamkhari B, Abdolmaleki S. Stability of actin-lysozyme complexes formed in cystic fibrosis disease. SOFT MATTER 2016; 12:6557-6565. [PMID: 27436705 DOI: 10.1039/c6sm00288a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Finding the conditions for destabilizing actin-lysozyme complexes is of biomedical importance in preventing infections in cystic fibrosis. In this manuscript, the effects of different charge-mutants of lysozyme and salt concentration on the stability of actin-lysozyme complexes are studied using Langevin dynamics simulation. A coarse-grained model of F-actin is used in which both its twist and bending rigidities are considered. We observe that the attraction between F-actins is stronger in the presence of wild-type lysozymes relative to the mutated lysozymes of lower charges. By calculating the potential of mean force between F-actins, we conclude that the stability of actin-lysozyme complexes is decreased by reducing the charge of lysozyme mutants. The distributions of different lysozyme charge-mutants show that wild-type (+9e) lysozymes are mostly accumulated in the center of triangles formed by three adjacent F-actins, while lysozyme mutants of charges +7e and +5e occupy the bridging regions between F-actins. Low-charge mutants of lysozyme (+3e) distribute uniformly around F-actins. A rough estimate of the electrostatic energy for these different distributions proves that the distribution in which lysozymes reside in the center of triangles leads to more stable complexes. Also our results in the presence of a salt suggest that at physiological salt concentration of airway, F-actin complexes are not formed by charge-reduced mutants of lysozyme. The findings are interesting because if we can design charge-reduced lysozyme mutants with considerable antibacterial activity, they are not sequestered inside F-actin aggregates and can play their role as antibacterial agents against airway infection.
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Affiliation(s)
- Sarah Mohammadinejad
- Department of Biological Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran.
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Actin bundles cross-linked with α-actinin studied by nanobeam X-ray diffraction. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 45:383-92. [PMID: 26715112 DOI: 10.1007/s00249-015-1107-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 11/24/2015] [Accepted: 12/09/2015] [Indexed: 10/22/2022]
Abstract
We have performed scanning nano-beam small-angle X-ray scattering (nano-SAXS) experiments on in vitro-formed actin filaments cross-linked with [Formula: see text]-actinin. The experimental method combines a high resolution in reciprocal space with a real space resolution as given by the spot-size of the nano-focused X-ray beam, and opens up new opportunities to study local super-molecular structures of actin filaments. In this first proof-of-concept, we show that the local orientation of actin bundles formed by the cross-linking can be visualized by the X-ray darkfield maps. The filament bundles give rise to highly anisotropic diffraction patterns showing distinct streaks perpendicular to the bundle axes. Interestingly, some diffraction patterns exhibit a fine structure in the form of intensity modulations allowing for a more detailed analysis of the order within the bundles. A first empirical quantification of these modulations is included in the present work.
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6
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Gao M, Berghaus M, von der Ecken J, Raunser S, Winter R. Condensation Agents Determine the Temperature-Pressure Stability of F-Actin Bundles. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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7
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Gao M, Berghaus M, von der Ecken J, Raunser S, Winter R. Condensation Agents Determine the Temperature-Pressure Stability of F-Actin Bundles. Angew Chem Int Ed Engl 2015; 54:11088-92. [DOI: 10.1002/anie.201504247] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 06/11/2015] [Indexed: 12/27/2022]
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8
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Janmey PA, Slochower DR, Wang YH, Wen Q, Cēbers A. Polyelectrolyte properties of filamentous biopolymers and their consequences in biological fluids. SOFT MATTER 2014; 10:1439-49. [PMID: 24651463 PMCID: PMC4009494 DOI: 10.1039/c3sm50854d] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Anionic polyelectrolyte filaments are common in biological cells. DNA, RNA, the cytoskeletal filaments F-actin, microtubules, and intermediate filaments, and polysaccharides such as hyaluronan that form the pericellular matrix all have large net negative charge densities distributed over their surfaces. Several filamentous viruses with diameters and stiffnesses similar to those of cytoskeletal polymers also have similar negative charge densities. Extracellular protein filaments such collagen, fibrin and elastin, in contrast, have notably smaller charge densities and do not behave as highly charged polyelectrolytes in solution. This review summarizes data that demonstrate generic counterion-mediated effects on four structurally unrelated biopolymers of similar charge density: F-actin, vimentin, Pf1 virus, and DNA, and explores the possible biological and pathophysiological consequences of the polyelectrolyte properties of biological filaments.
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Affiliation(s)
- Paul A Janmey
- Institute for Medicine and Engineering, University of Pennsylvania, 1010 Vagelos Laboratories, 3340 Smith Walk, Philadelphia, PA 19104, USA
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Borgogna M, Skjåk-Bræk G, Paoletti S, Donati I. On the Initial Binding of Alginate by Calcium Ions. The Tilted Egg-Box Hypothesis. J Phys Chem B 2013; 117:7277-82. [DOI: 10.1021/jp4030766] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Massimiliano Borgogna
- Department of Life Sciences, University of Trieste, via L. Giorgieri, 5, I-34127
Trieste, Italy
| | - Gudmund Skjåk-Bræk
- Department
of Biotechnology, Norwegian University of Science and Technology, NTNU
Sem Sælands vei 6-8, N-7491, Trondheim, Norway
| | - Sergio Paoletti
- Department of Life Sciences, University of Trieste, via L. Giorgieri, 5, I-34127
Trieste, Italy
| | - Ivan Donati
- Department of Life Sciences, University of Trieste, via L. Giorgieri, 5, I-34127
Trieste, Italy
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Varghese A, Rajesh R, Vemparala S. Aggregation of rod-like polyelectrolyte chains in the presence of monovalent counterions. J Chem Phys 2012; 137:234901. [DOI: 10.1063/1.4771920] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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11
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Doyle A, Crosby SR, Burton DR, Lilley F, Murphy MF. Actin bundling and polymerisation properties of eukaryotic elongation factor 1 alpha (eEF1A), histone H2A-H2B and lysozyme in vitro. J Struct Biol 2011; 176:370-8. [PMID: 21964468 DOI: 10.1016/j.jsb.2011.09.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/12/2011] [Accepted: 09/14/2011] [Indexed: 11/28/2022]
Abstract
Elongation factor 1 alpha (eEF1A) is a positively charged protein which has been shown to interact with the actin cytoskeleton. However, to date, a specific actin binding site within the eEF1A sequence has not been identified and the mechanism by which eEF1A interacts with actin remains unresolved. Many protein-protein interactions occur as a consequence of their physicochemical properties and actin bundle formation has been shown to result from non-specific electrostatic interaction with basic proteins. This study investigated interactions between actin, eEF1A and two other positively charged proteins which are not regarded as classic actin binding proteins (namely lysozyme and H2A-H2B) in order to compare their actin organising effects in vitro. For the first time using atomic force microscopy (AFM) we have been able to image the interaction of eEF1A with actin and the subsequent bundling of actin in vitro. Interestingly, we found that eEF1A dramatically increases the rate of polymerisation (45-fold above control levels). We also show for the first time that H2A-H2B has remarkably similar effects upon actin bundling (relative bundle size/number) and polymerisation (35-fold increase above control levels) as eEF1a. The presence of lysozyme resulted in bundles which were distinct from those formed due to eEF1A and H2A-H2B. Lysozyme also increased the rate of actin polymerisation above the control level (by 10-fold). Given the striking similarities between the actin bundling and polymerisation properties of eEF1A and H2A-H2B, our results hint that dimerisation and electrostatic binding may provide clues to the mechanism through which eEF1A-actin bundling occurs.
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Affiliation(s)
- Annette Doyle
- School of Pharmacy & Biomolecular Sciences, Liverpool John Moore University, Liverpool, UK.
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12
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Streichfuss M, Erbs F, Uhrig K, Kurre R, Clemen AEM, Böhm CHJ, Haraszti T, Spatz JP. Measuring forces between two single actin filaments during bundle formation. NANO LETTERS 2011; 11:3676-3680. [PMID: 21838252 DOI: 10.1021/nl201630y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Bundles of filamentous actin are dominant cytoskeletal structures, which play a crucial role in various cellular processes. As yet quantifying the fundamental interaction between two individual actin filaments forming the smallest possible bundle has not been realized. Applying holographic optical tweezers integrated with a microfluidic platform, we were able to measure the forces between two actin filaments during bundle formation. Quantitative analysis yields forces up to 0.2 pN depending on the concentration of bundling agents.
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Affiliation(s)
- Martin Streichfuss
- Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, 70569 Stuttgart, Germany
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13
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Shin H, Grason GM. Structural reorganization of parallel actin bundles by crosslinking proteins: incommensurate states of twist. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:051919. [PMID: 21230512 DOI: 10.1103/physreve.82.051919] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Indexed: 05/30/2023]
Abstract
We construct a coarse-grained model of parallel actin bundles crosslinked by compact globular bundling proteins, such as fascin and espin, necessary components of filopodial and mechanosensory bundles. Consistent with structural observations of bundles, we find that the optimal geometry for crosslinking is overtwisted, requiring a coherent structural change of the helical geometry of the filaments. We study the linker-dependent thermodynamic transition of bundled actin filaments from their native state to the overtwisted state and map out the "twist-state" phase diagram in terms of the availability as well as the flexibility of crosslinker proteins. We predict that the transition from the uncrosslinked to fully crosslinked state is highly sensitive to linker flexibility: flexible crosslinking smoothly distorts the twist state of bundled filaments, while rigidly crosslinked bundles undergo a phase transition, rapidly overtwisting filaments over a narrow range of free crosslinker concentrations. Additionally, we predict a rich spectrum of intermediate structures, composed of alternating domains of sparsely bound (untwisted) and strongly bound (overtwisted) filaments. This model reveals that subtle differences in crosslinking agents themselves modify not only the detailed structure of parallel actin bundles, but also the thermodynamic pathway by which they form.
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Affiliation(s)
- Homin Shin
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
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14
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Lange K. Fundamental role of microvilli in the main functions of differentiated cells: Outline of an universal regulating and signaling system at the cell periphery. J Cell Physiol 2010; 226:896-927. [PMID: 20607764 DOI: 10.1002/jcp.22302] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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15
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Lee DJ, Leikin S, Wynveen A. Fluctuations and interactions of semi-flexible polyelectrolytes in columnar assemblies. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:72202. [PMID: 20352061 PMCID: PMC2844736 DOI: 10.1088/0953-8984/22/7/072202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We have developed a statistical theory for columnar aggregates of semi-flexible polyelectrolytes. The applicability of previous, simplified theories was limited to polyelectrolytes with unrealistically high effective charge and, hence, with strongly suppressed thermal undulations. To avoid this problem, we utilized more consistent approximations for short-range image-charge forces and steric confinement, resulting in new predictions for polyelectrolytes with more practically important, lower effective linear charge densities. In the present paper, we focus on aggregates of wormlike chains with uniform surface charge density, although the same basic ideas may also be applied to structured polyelectrolytes. We find that undulations effectively extend the range of electrostatic interactions between polyelectrolytes upon decreasing aggregate density, in qualitative agreement with previous theories. However, in contrast to previous theories, we demonstrate that steric confinement provides the dominant rather than a negligible contribution at higher aggregate densities and significant quantitative corrections at lower densities, resulting in osmotic pressure isotherms that drastically differ from previous predictions.
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Affiliation(s)
- D J Lee
- Max Planck institute for the physics of complex systems, D-01187, Dresden, Germany.
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16
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Shin H, Purdy Drew KR, Bartles JR, Wong GCL, Grason GM. Cooperativity and frustration in protein-mediated parallel actin bundles. PHYSICAL REVIEW LETTERS 2009; 103:238102. [PMID: 20366178 PMCID: PMC2852194 DOI: 10.1103/physrevlett.103.238102] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Indexed: 05/25/2023]
Abstract
We examine the mechanism of bundling of cytoskeletal actin filaments by two representative bundling proteins, fascin and espin. Small-angle x-ray studies show that increased binding from linkers drives a systematic overtwist of actin filaments from their native state, which occurs in a linker-dependent fashion. Fascin bundles actin into a continuous spectrum of intermediate twist states, while espin only allows for untwisted actin filaments and fully overtwisted bundles. Based on a coarse-grained, statistical model of protein binding, we show that the interplay between binding geometry and the intrinsic flexibility of linkers mediates cooperative binding in the bundle. We attribute the respective continuous (discontinuous) bundling mechanisms of fascin (espin) to difference in the stiffness of linker bonds themselves.
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Affiliation(s)
- Homin Shin
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
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17
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Kohlstedt KL, Vernizzi G, Olvera de la Cruz M. Electrostatics and optimal arrangement of ionic triangular lattices confined to cylindrical fibers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:051503. [PMID: 20364988 DOI: 10.1103/physreve.80.051503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Indexed: 05/29/2023]
Abstract
We study the optimal packing of triangular ionic lattices on the surface of nanofibers. We compute the favored orientation of the lattice with respect to the axis of the cylindrical fiber, and we determine the effects of the surface curvature. Electrostatic interactions prefer chiral arrangements only for special families of lattices that depend on the fiber diameter. However, there are families of lattices that energetically promote achiral configurations. Besides the long-range Coulomb interactions we consider the behavior of short-range elastic forces, represented by interconnected springs between neighboring ions. In this case a different family of achiral lattices is always preferred. We also show that varying the stoichiometric composition of charges, as well as including higher-order curvature effects, does not significantly modify such a scenario.
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Affiliation(s)
- Kevin L Kohlstedt
- Department of Materials Science, Northwestern University, Evanston, Illinois 60208, USA
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18
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Sanders LK, Xian W, Guáqueta C, Strohman MJ, Vrasich CR, Luijten E, Wong GCL. Control of electrostatic interactions between F-actin and genetically modified lysozyme in aqueous media. Proc Natl Acad Sci U S A 2007; 104:15994-9. [PMID: 17911256 PMCID: PMC2042150 DOI: 10.1073/pnas.0705898104] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.
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Affiliation(s)
| | - Wujing Xian
- Departments of *Materials Science and Engineering
| | | | | | | | - Erik Luijten
- Departments of *Materials Science and Engineering
- Physics, and
- The Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801-2920
- To whom correspondence may be addressed at:
Department of Materials Science and Engineering, University of Illinois at Urbana–Champaign, 1304 W. Green Street, Urbana, IL 61801-2920. E-mail: or
| | - Gerard C. L. Wong
- Departments of *Materials Science and Engineering
- Physics, and
- Bioengineering
- The Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana–Champaign, Urbana, IL 61801-2920
- To whom correspondence may be addressed at:
Department of Materials Science and Engineering, University of Illinois at Urbana–Champaign, 1304 W. Green Street, Urbana, IL 61801-2920. E-mail: or
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Abstract
To better understand the mechanism of actin filament (F-actin) bundling by polyamines, we have measured the onset of bundling as a function of polyamine concentration. Samples were centrifuged at low speeds to separate bundles from unbundled actin, and the relative amounts of actin in the pellet and supernatant were determined via gel electrophoresis, yielding a description of the bundling transition as a function of actin and polyamine concentrations. These experiments were carried out for two different polyamines, spermine (tetravalent) and spermidine (trivalent). We found that the threshold concentration of polyamine needed to bundle actin is independent of both actin concentration and Mg2+ concentration over a wide range in Mg2+ concentration. We also find that spermine in F-actin bundles is essentially invisible in solution-phase proton NMR, suggesting that it is bound so tightly to F-actin that it is immobilized.
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Affiliation(s)
- Glenna Z Sowa
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, USA
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20
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The morphology of adsorbed extracellular matrix assemblies is critically dependent on solution calcium concentration. Matrix Biol 2007; 26:156-66. [DOI: 10.1016/j.matbio.2006.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Revised: 10/30/2006] [Accepted: 10/31/2006] [Indexed: 12/31/2022]
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Morin F, Rose F, Martin P, Tarhan MC, Kawakatsu H, Fujita H. Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules. NANOSCALE RESEARCH LETTERS 2007; 2:135-43. [PMID: 21806849 PMCID: PMC3245658 DOI: 10.1007/s11671-007-9044-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Accepted: 02/04/2007] [Indexed: 05/31/2023]
Abstract
Microtubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed.
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Affiliation(s)
- Fabriceolivier Morin
- LIMMS-CNRS/IIS, UMI 2820, University of Tokyo, 4-6-1 Komaba, Tokyo, 153-8505, Japan.
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Purdy KR, Bartles JR, Wong GCL. Structural polymorphism of the actin-espin system: a prototypical system of filaments and linkers in stereocilia. PHYSICAL REVIEW LETTERS 2007; 98:058105. [PMID: 17358907 PMCID: PMC2843914 DOI: 10.1103/physrevlett.98.058105] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Indexed: 05/06/2023]
Abstract
We examine the interaction between cytoskeletal F-actin and espin 3A, a prototypical actin bundling protein found in sensory cell microvilli, including ear cell stereocilia. Espin induces twist distortions in F-actin as well as facilitates bundle formation. Mutations in one of the two F-actin binding sites of espin, which have been implicated in deafness, can tune espin-actin interactions and radically transform the system's phase behavior. These results are compared to recent theoretical work on the general phase behavior linker-rod systems.
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Affiliation(s)
- Kirstin R Purdy
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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