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Mattiello S, Guzzini A, Del Giudice A, Santulli C, Antonini M, Lupidi G, Gunnella R. Physico-Chemical Characterization of Keratin from Wool and Chicken Feathers Extracted Using Refined Chemical Methods. Polymers (Basel) 2022; 15:181. [PMID: 36616532 PMCID: PMC9824254 DOI: 10.3390/polym15010181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 12/19/2022] [Accepted: 12/27/2022] [Indexed: 12/31/2022] Open
Abstract
In this work, the characteristic structure of keratin extracted from two different kinds of industrial waste, namely sheep wool and chicken feathers, using the sulfitolysis method to allow film deposition, has been investigated. The structural and microscopic properties have been studied by means of scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), and infrared (IR) spectroscopy. Following this, small-angle X-ray scattering (SAXS) analysis for intermediate filaments has been performed. The results indicate that the assembly character of the fiber can be obtained by using the most suitable extraction method, to respond to hydration, thermal, and redox agents. The amorphous part of the fiber and medium range structure is variously affected by the competition between polar bonds (reversible hydrogen bonds) and disulfide bonds (DB), the covalent irreversible ones, and has been investigated by using fine structural methods such as Raman and SAXS, which have depicted in detail the intermediate filaments of keratin from the two different animal origins. The preservation of the secondary structure of the protein obtained does offer a potential for further application of the waste-obtained keratin in polymer films and, possibly, biocomposites.
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Affiliation(s)
- Sara Mattiello
- Physics Section, School of Science and Technology, Università di Camerino, via Madonna delle Carceri, 62032 Camerino, Italy
| | - Alessandro Guzzini
- School of Bioscience and Veterinary Medicine, Università di Camerino, via Gentile III da Varano, 62032 Camerino, Italy
| | - Alessandra Del Giudice
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Carlo Santulli
- Geology Section, School of Science and Technology, Università di Camerino, via Gentile III da Varano 7, 62032 Camerino, Italy
| | - Marco Antonini
- ENEA—SSPT BIOAG PROBIO Via Gentile III da Varano, 62032 Camerino, Italy
| | - Giulio Lupidi
- School of Bioscience and Veterinary Medicine, Università di Camerino, via Gentile III da Varano, 62032 Camerino, Italy
| | - Roberto Gunnella
- Physics Section, School of Science and Technology, Università di Camerino, via Madonna delle Carceri, 62032 Camerino, Italy
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2
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Multiscale mechanics and temporal evolution of vimentin intermediate filament networks. Proc Natl Acad Sci U S A 2021; 118:2102026118. [PMID: 34187892 DOI: 10.1073/pnas.2102026118] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytoskeleton, an intricate network of protein filaments, motor proteins, and cross-linkers, largely determines the mechanical properties of cells. Among the three filamentous components, F-actin, microtubules, and intermediate filaments (IFs), the IF network is by far the most extensible and resilient to stress. We present a multiscale approach to disentangle the three main contributions to vimentin IF network mechanics-single-filament mechanics, filament length, and interactions between filaments-including their temporal evolution. Combining particle tracking, quadruple optical trapping, and computational modeling, we derive quantitative information on the strength and kinetics of filament interactions. Specifically, we find that hydrophobic contributions to network mechanics enter mostly via filament-elongation kinetics, whereas electrostatics have a direct influence on filament-filament interactions.
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3
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Elbalasy I, Mollenkopf P, Tutmarc C, Herrmann H, Schnauß J. Keratins determine network stress responsiveness in reconstituted actin-keratin filament systems. SOFT MATTER 2021; 17:3954-3962. [PMID: 33724291 DOI: 10.1039/d0sm02261f] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The cytoskeleton is a major determinant of cell mechanics, and alterations in the central mechanical aspects of cells are observed during many pathological situations. Therefore, it is essential to investigate the interplay between the main filament systems of the cytoskeleton in the form of composite networks. Here, we investigate the role of keratin intermediate filaments (IFs) in network strength by studying in vitro reconstituted actin and keratin 8/18 composite filament networks via bulk shear rheology. We co-polymerized these structural proteins in varying ratios and recorded how their relative content affects the overall mechanical response of the various composites. For relatively small deformations, we found that all composites exhibited an intermediate linear viscoelastic behaviour compared to that of the pure networks. In stark contrast, when larger deformations were imposed the composites displayed increasing strain stiffening behaviour with increasing keratin content. The extent of strain stiffening is much more pronounced than in corresponding experiments performed with vimentin IF as a composite network partner for actin. Our results provide new insights into the mechanical interplay between actin and keratin filaments in which keratin provides reinforcement to actin. This interplay may contribute to the overall integrity of cells. Hence, the high keratin 8/18 content of mechanically stressed simple epithelial cell layers, as found in the lung and the intestine, provides an explanation for their exceptional stability.
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Affiliation(s)
- Iman Elbalasy
- Peter-Debye Institute for Soft Matter Physics, Leipzig University, 04103 Leipzig, Germany
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4
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Denz M, Marschall M, Herrmann H, Köster S. Ion type and valency differentially drive vimentin tetramers into intermediate filaments or higher order assemblies. SOFT MATTER 2021; 17:870-878. [PMID: 33237065 DOI: 10.1039/d0sm01659d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Vimentin intermediate filaments, together with actin filaments and microtubules, constitute the cytoskeleton in cells of mesenchymal origin. The mechanical properties of the filaments themselves are encoded in their molecular architecture and depend on their ionic environment. It is thus of great interest to disentangle the influence of both the ion type and their concentration on vimentin assembly. We combine small angle X-ray scattering and fluorescence microscopy and show that vimentin in the presence of the monovalent ions, K+ and Na+, assembles into "standard filaments" with a radius of about 6 nm and 32 monomers per cross-section. In contrast, di- and multivalent ions, independent of type and valency, lead to the formation of thicker filaments associating over time into higher order structures. Hence, our results may indeed be of relevance for living cells, as local ion concentrations in the cytoplasm during certain physiological activities may differ considerably from average intracellular concentrations.
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Affiliation(s)
- Manuela Denz
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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5
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Haimov E, Windoffer R, Leube RE, Urbakh M, Kozlov MM. Model for Bundling of Keratin Intermediate Filaments. Biophys J 2020; 119:65-74. [PMID: 32533940 PMCID: PMC7335914 DOI: 10.1016/j.bpj.2020.05.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 01/19/2023] Open
Abstract
Keratin intermediate filaments form dynamic intracellular networks, which span the entire cytoplasm and provide mechanical strength to the cell. The mechanical resilience of the keratin intermediate filament network itself is determined by filament bundling. The bundling process can be reproduced in artificial conditions in the absence of any specific cross-linking proteins, which suggests that it is driven by generic physical forces acting between filaments. Here, we suggest a detailed model for bundling of keratin intermediate filaments based on interfilament electrostatic and hydrophobic interactions. It predicts that the process is limited by an optimal bundle thickness, which is determined by the electric charge of the filaments, the number of hydrophobic residues in the constituent keratin polypeptides, and the extent to which the electrolyte ions are excluded from the bundle interior. We evaluate the kinetics of the bundling process by considering the energy barrier a filament has to overcome for joining a bundle.
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Affiliation(s)
- Ehud Haimov
- School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv, Israel
| | - Reinhard Windoffer
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Rudolf E Leube
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Michael Urbakh
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv, Israel.
| | - Michael M Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
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6
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Lorenz C, Forsting J, Schepers AV, Kraxner J, Bauch S, Witt H, Klumpp S, Köster S. Lateral Subunit Coupling Determines Intermediate Filament Mechanics. PHYSICAL REVIEW LETTERS 2019; 123:188102. [PMID: 31763918 DOI: 10.1103/physrevlett.123.188102] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Indexed: 05/27/2023]
Abstract
The cytoskeleton is a composite network of three types of protein filaments, among which intermediate filaments (IFs) are the most extensible ones. Two very important IFs are keratin and vimentin, which have similar molecular architectures but different mechanical behaviors. Here we compare the mechanical response of single keratin and vimentin filaments using optical tweezers. We show that the mechanics of vimentin strongly depends on the ionic strength of the buffer and that its force-strain curve suggests a high degree of cooperativity between subunits. Indeed, a computational model indicates that in contrast to keratin, vimentin is characterized by strong lateral subunit coupling of its charged monomers during unfolding of α helices. We conclude that cells can tune their mechanics by differential use of keratin versus vimentin.
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Affiliation(s)
- Charlotta Lorenz
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Johanna Forsting
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Anna V Schepers
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Julia Kraxner
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Susanne Bauch
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Hannes Witt
- Institute for Organic and Biomolecular Chemistry, University of Göttingen, Tammanstraße 2, 37077 Göttingen, Germany
- Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 7, 37077 Göttingen
| | - Stefan Klumpp
- Institute for Dynamics of Complex Systems, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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7
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Brennich ME, Vainio U, Wedig T, Bauch S, Herrmann H, Köster S. Mutation-induced alterations of intra-filament subunit organization in vimentin filaments revealed by SAXS. SOFT MATTER 2019; 15:1999-2008. [PMID: 30719518 DOI: 10.1039/c8sm02281j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Vimentin intermediate filaments constitute a distinct filament system in mesenchymal cells that is instrumental for cellular mechanics and migration. In vitro, the rod-like monomers assemble in a multi-step, salt-dependent manner into micrometer long biopolymers. To disclose the underlying mechanisms further, we employed small angle X-ray scattering on two recombinant vimentin variants, whose assembly departs at strategic points from the normal assembly route: (i) vimentin with a tyrosine to leucine change at position 117; (ii) vimentin missing the non-α-helical carboxyl-terminal domain. Y117L vimentin assembles into unit-length filaments (ULFs) only, whereas ΔT vimentin assembles into filaments containing a higher number of tetramers per cross section than normal vimentin filaments. We show that the shape and inner structure of these mutant filaments is significantly altered. ULFs assembled from Y117L vimentin contain more, less tightly bundled vimentin tetramers, and ΔT vimentin filaments preserve the number density despite the higher number of tetramers per filament cross-section.
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Affiliation(s)
- Martha E Brennich
- Institute for X-ray Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
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8
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Bernhardt M, Nicolas JD, Osterhoff M, Mittelstädt H, Reuss M, Harke B, Wittmeier A, Sprung M, Köster S, Salditt T. Correlative microscopy approach for biology using X-ray holography, X-ray scanning diffraction and STED microscopy. Nat Commun 2018; 9:3641. [PMID: 30194418 PMCID: PMC6128893 DOI: 10.1038/s41467-018-05885-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 07/30/2018] [Indexed: 12/31/2022] Open
Abstract
We present a correlative microscopy approach for biology based on holographic X-ray imaging, X-ray scanning diffraction, and stimulated emission depletion (STED) microscopy. All modalities are combined into the same synchrotron endstation. In this way, labeled and unlabeled structures in cells are visualized in a complementary manner. We map out the fluorescently labeled actin cytoskeleton in heart tissue cells and superimpose the data with phase maps from X-ray holography. Furthermore, an array of local far-field diffraction patterns is recorded in the regime of small-angle X-ray scattering (scanning SAXS), which can be interpreted in terms of biomolecular shape and spatial correlations of all contributing scattering constituents. We find that principal directions of anisotropic diffraction patterns coincide to a certain degree with the actin fiber directions and that actin stands out in the phase maps from holographic recordings. In situ STED recordings are proposed to formulate models for diffraction data based on co-localization constraints.
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Affiliation(s)
- M Bernhardt
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - J-D Nicolas
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - M Osterhoff
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - H Mittelstädt
- Abberior Instruments, Hans-Adolf-Krebs-Weg 1, D-37077, Göttingen, Germany
| | - M Reuss
- Abberior Instruments, Hans-Adolf-Krebs-Weg 1, D-37077, Göttingen, Germany
| | - B Harke
- Abberior Instruments, Hans-Adolf-Krebs-Weg 1, D-37077, Göttingen, Germany
| | - A Wittmeier
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - M Sprung
- Deutsches Elektronen-Synchrotron (DESY), Notkestraße 47c, D-22607, Hamburg, Germany
| | - S Köster
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany
| | - T Salditt
- Institut für Röntgenphysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077, Göttingen, Germany.
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9
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Deek J, Maan R, Loiseau E, Bausch AR. Reconstitution of composite actin and keratin networks in vesicles. SOFT MATTER 2018; 14:1897-1902. [PMID: 29464258 DOI: 10.1039/c7sm00819h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Although cytoskeletal networks are interpenetrating and interacting in living cells, very little is understood as to the effect their interaction has on their properties. Here, as a step towards elucidating the synergistic cellular role of these structural proteins, we investigate isolated keratin and actin composites and show how the in vitro network formation of keratin influences the properties of actin networks and vice versa. By encapsulating purified composite networks into vesicles and separating the time scales of network formation we are able to demonstrate that the actin network stabilizes keratin networks by providing an elastic resistance to their collapse in vitro.
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Affiliation(s)
- J Deek
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
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10
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Nicolas JD, Bernhardt M, Krenkel M, Richter C, Luther S, Salditt T. Combined scanning X-ray diffraction and holographic imaging of cardiomyocytes. J Appl Crystallogr 2017. [DOI: 10.1107/s1600576717003351] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
This article presents scanning small-angle X-ray scattering (SAXS) experiments on the actomyosin assemblies in freeze-dried neo-natal rat cardiac muscle cells. By scanning the cells through a sub-micrometre focused beam, the local structure and filament orientation can be probed and quantified. To this end, SAXS data were recorded and analyzed directly in reciprocal space to generate maps of different structural parameters (scanning SAXS). The scanning SAXS experiments were complemented by full-field holographic imaging of the projected electron density, following a slight rearrangement of the instrumental setup. It is shown that X-ray holography is ideally suited to complete missing scattering data at low momentum transfer in the structure factor, extending the covered range of spatial frequencies by two orders of magnitude. Regions of interest for scanning can be easily selected on the basis of the electron density maps. Finally, the combination of scanning SAXS and holography allows for a direct verification of possible radiation-induced structural changes in the cell.
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11
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Deek J, Hecht F, Rossetti L, Wißmiller K, Bausch AR. Mechanics of soft epithelial keratin networks depend on modular filament assembly kinetics. Acta Biomater 2016; 43:218-229. [PMID: 27403885 DOI: 10.1016/j.actbio.2016.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 06/04/2016] [Accepted: 07/09/2016] [Indexed: 11/15/2022]
Abstract
UNLABELLED Structural adaptability is a pivotal requirement of cytoskeletal structures, enabling their reorganization to meet the cellular needs. Shear stress, for instance, results in large morphological network changes of the human soft epithelial keratin pair K8:K18, and is accompanied by an increase in keratin phosphorylation levels. Yet the mechanisms responsible for the disruption of the network structure in vivo remain poorly understood. To understand the effect of the stress-related site-specific phosphorylation of the K8:K18 pair, we created phosphomimicry mutants - K8(S431E), K8(S73E), K18(S52E) - in vitro, and investigated the various steps of keratin assembly from monomer to network structure using fluorescence and electron microscopy, and using rheology characterized their network mechanical properties. We find that the addition of a charged group produces networks with depleted intra-connectivity, which translates to a mechanically weaker and more deformable network. This large variation in network structure is achieved by the formation of shorter mutant filaments, which exhibit differing assembly kinetics and a manifestly reduced capacity to form the extended structures characteristic of the wild-type system. The similarity in outcome for all the phosphomimicry mutants explored points to a more general mechanism of structural modulation of intermediate filaments via phosphorylation. Understanding the role of kinetic effects in the construction of these cytoskeletal biopolymer networks is critical to elucidating their structure-function properties, providing new insight for the design of keratin-inspired biomaterials. STATEMENT OF SIGNIFICANCE Structural remodeling of cytoskeletal networks accompanies many cellular processes. Interestingly, levels of phosphorylation of the human soft epithelial keratin pair K8:K18 increase during their stress-related structural remodeling. Our multi-scale study sheds light on the poorly understood mechanism with which site-specific phosphorylation induces disruption of the keratin network structure in vivo. We show how phosphorylation reduces keratin filament length, an effect that propagates through to the mesoscopic structure, resulting in the formation of connectivity-depleted and mechanically weaker networks. We determine that the intrinsically-set filament-to-filament attractions that drive bundle assembly give rise to the structural variability by enabling the formation of kinetically-arrested structures. Overall, our results shed light on how self-assembled intermediate filament structures can be tailored to exhibit different structural functionalities.
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Affiliation(s)
- Joanna Deek
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Fabian Hecht
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Leone Rossetti
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Katharina Wißmiller
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany
| | - Andreas R Bausch
- Lehrstuhl für Zellbiophysik E27, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
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12
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Lateral association and elongation of vimentin intermediate filament proteins: A time-resolved light-scattering study. Proc Natl Acad Sci U S A 2016; 113:11152-11157. [PMID: 27655889 DOI: 10.1073/pnas.1606372113] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vimentin intermediate filaments (IFs) are part of a family of proteins that constitute one of the three filament systems in the cytoskeleton, a major contributor to cell mechanics. One property that distinguishes IFs from the other cytoskeletal filament types, actin filaments and microtubules, is their highly hierarchical assembly pathway, where a lateral association step is followed by elongation. Here we present an innovative technique to follow the elongation reaction in solution and in situ by time-resolved static and dynamic light scattering, thereby precisely capturing the relevant time and length scales of seconds to minutes and 60-600 nm, respectively. We apply a quantitative model to our data and succeed in consistently describing the entire set of data, including particle mass, radius of gyration, and hydrodynamic radius during longitudinal association.
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13
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Martin I, Moch M, Neckernuss T, Paschke S, Herrmann H, Marti O. Both monovalent cations and plectin are potent modulators of mechanical properties of keratin K8/K18 networks. SOFT MATTER 2016; 12:6964-6974. [PMID: 27489177 DOI: 10.1039/c6sm00977h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Intermediate filament (IF) networks are a major contributor to cell rigidity and thus serve as vital elements to preserve the integrity of entire cell layers. Keratin K8 and K18 IFs are the basic constituents of the cytoskeleton of epithelial cells. The mechanical properties of K8/K18 networks depend on the structural arrangements of individual filaments within the network. This paper investigates the architecture of these networks in vitro under the influence of the monovalent cation potassium and that of the cytolinker protein plectin. Whereas increasing amounts of potassium ions lead to filament bundling, plectin interlinks filaments at filament intersection points but does not lead to bundle formation. The mechanics of the resulting networks are investigated by microrheology with assembled K8/K18 networks. It is shown that bundling induced by potassium ions significantly stiffens the network. Furthermore, our measurements reveal an increase in plectin-mediated keratin network rigidity as soon as an amount corresponding to more than 20% of the plectin present in cells is added to the keratin IF networks. In parallel, we investigated the influence of plectin on cell rigidity in detergent-extracted epithelial vulva carcinoma derived A431 cells in situ. These cytoskeletons, containing mostly IFs, actin filaments and associated proteins, exhibit a significantly decreased stiffness, when plectin is downregulated to ≈10% of the normal value. Therefore, we assume that plectin, via the formation of IF-IF connections and crosslinking of IFs to actin filaments, is an important contributor to cell stiffness.
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Affiliation(s)
- I Martin
- Institute of Experimental Physics, Ulm University, 89081 Ulm, Germany.
| | - M Moch
- Department of Internal Medicine I, Ulm University, 89081 Ulm, Germany and Institute of Molecular and Cellular Anatomy, RWTH Aachen University, 52057 Aachen, Germany
| | - T Neckernuss
- Institute of Experimental Physics, Ulm University, 89081 Ulm, Germany.
| | - S Paschke
- Department of General and Visceral Surgery, Ulm University, 89081 Ulm, Germany
| | - H Herrmann
- Division Molecular Genetics, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany and Institute of Neuropathology, University Hospital Erlangen, 91054 Erlangen, Germany
| | - O Marti
- Institute of Experimental Physics, Ulm University, 89081 Ulm, Germany.
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14
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Paust T, Neckernuss T, Mertens LK, Martin I, Beil M, Walther P, Schimmel T, Marti O. Active multi-point microrheology of cytoskeletal networks. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:484-491. [PMID: 27335739 PMCID: PMC4901545 DOI: 10.3762/bjnano.7.42] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 03/10/2016] [Indexed: 06/06/2023]
Abstract
Active microrheology is a valuable tool to determine viscoelastic properties of polymer networks. Observing the response of the beads to the excitation of a reference leads to dynamic and morphological information of the material. In this work we present an expansion of the well-known active two-point microrheology. By measuring the response of multiple particles in a viscoelastic medium in response to the excitation of a reference particle, we are able to determine the force propagation in the polymer network. For this purpose a lock-in technique is established that allows for extraction of the periodical motion of embedded beads. To exert a sinusoidal motion onto the reference bead an optical tweezers setup in combination with a microscope is used to investigate the motion of the response beads. From the lock-in data the so called transfer tensor can be calculated, which is a direct measure for the ability of the network to transmit mechanical forces. We also take a closer look at the influence of noise on lock-in measurements and state some simple rules for improving the signal-to-noise ratio.
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Affiliation(s)
- Tobias Paust
- Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Tobias Neckernuss
- Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Lina Katinka Mertens
- Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Ines Martin
- Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Michael Beil
- Department of Internal Medicine I, Ulm University, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Paul Walther
- Central Electron Microscopy Facility, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Thomas Schimmel
- Institute of Applied Physics and Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany
| | - Othmar Marti
- Institute of Experimental Physics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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15
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Hémonnot CYJ, Reinhardt J, Saldanha O, Patommel J, Graceffa R, Weinhausen B, Burghammer M, Schroer CG, Köster S. X-rays Reveal the Internal Structure of Keratin Bundles in Whole Cells. ACS NANO 2016; 10:3553-3561. [PMID: 26905642 DOI: 10.1021/acsnano.5b07871] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In recent years, X-ray imaging of biological cells has emerged as a complementary alternative to fluorescence and electron microscopy. Different techniques were established and successfully applied to macromolecular assemblies and structures in cells. However, while the resolution is reaching the nanometer scale, the dose is increasing. It is essential to develop strategies to overcome or reduce radiation damage. Here we approach this intrinsic problem by combing two different X-ray techniques, namely ptychography and nanodiffraction, in one experiment and on the same sample. We acquire low dose ptychography overview images of whole cells at a resolution of 65 nm. We subsequently record high-resolution nanodiffraction data from regions of interest. By comparing images from the two modalities, we can exclude strong effects of radiation damage on the specimen. From the diffraction data we retrieve quantitative structural information from intracellular bundles of keratin intermediate filaments such as a filament radius of 5 nm, hexagonal geometric arrangement with an interfilament distance of 14 nm and bundle diameters on the order of 70 nm. Thus, we present an appealing combined approach to answer a broad range of questions in soft-matter physics, biophysics and biology.
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Affiliation(s)
- Clément Y J Hémonnot
- Institute for X-ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Juliane Reinhardt
- Deutsches Elektronen-Synchrotron , Notkestrasse 85, 22607 Hamburg, Germany
| | - Oliva Saldanha
- Institute for X-ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Jens Patommel
- Institute of Structural Physics, Technische Universität Dresden , Zellescher Weg 16, 01069 Dresden, Germany
| | - Rita Graceffa
- Institute for X-ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Britta Weinhausen
- European Synchrotron Radiation Facility , 71, Avenue des Martyrs, 38043 Grenoble, France
| | - Manfred Burghammer
- European Synchrotron Radiation Facility , 71, Avenue des Martyrs, 38043 Grenoble, France
- Department of Analytical Chemistry, Ghent University , Krijgslaan 281, 9000 Ghent, Belgium
| | - Christian G Schroer
- Deutsches Elektronen-Synchrotron , Notkestrasse 85, 22607 Hamburg, Germany
- Institute for Nanostructure and Solid State Physics, Department of Physics, University of Hamburg , Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Sarah Köster
- Institute for X-ray Physics, University of Göttingen , Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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