1
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Eibauer M, Weber MS, Kronenberg-Tenga R, Beales CT, Boujemaa-Paterski R, Turgay Y, Sivagurunathan S, Kraxner J, Köster S, Goldman RD, Medalia O. Vimentin filaments integrate low-complexity domains in a complex helical structure. Nat Struct Mol Biol 2024; 31:939-949. [PMID: 38632361 PMCID: PMC11189308 DOI: 10.1038/s41594-024-01261-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 03/01/2024] [Indexed: 04/19/2024]
Abstract
Intermediate filaments (IFs) are integral components of the cytoskeleton. They provide cells with tissue-specific mechanical properties and are involved in numerous cellular processes. Due to their intricate architecture, a 3D structure of IFs has remained elusive. Here we use cryo-focused ion-beam milling, cryo-electron microscopy and tomography to obtain a 3D structure of vimentin IFs (VIFs). VIFs assemble into a modular, intertwined and flexible helical structure of 40 α-helices in cross-section, organized into five protofibrils. Surprisingly, the intrinsically disordered head domains form a fiber in the lumen of VIFs, while the intrinsically disordered tails form lateral connections between the protofibrils. Our findings demonstrate how protein domains of low sequence complexity can complement well-folded protein domains to construct a biopolymer with striking mechanical strength and stretchability.
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Affiliation(s)
- Matthias Eibauer
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.
| | - Miriam S Weber
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | | | - Charlie T Beales
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | | | - Yagmur Turgay
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
- Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland
| | - Suganya Sivagurunathan
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Julia Kraxner
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany
- MDC Berlin-Buch, Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, University of Göttingen, Göttingen, Germany
| | - Robert D Goldman
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Ohad Medalia
- Department of Biochemistry, University of Zurich, Zurich, Switzerland.
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2
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Abstract
Assembly of intermediate filaments (IFs) is reliant upon amino-terminal head domains. These head domains are of low sequence complexity and are assumed to function in the absence of structural order. Herein, we provide evidence that the head domains of the desmin and neurofilament light (NFL) IF proteins self-associate via the formation of labile but structurally specific cross-β interaction. Disease-causing mutations in the head domains of both proteins cause enhanced cross-β interactions. By assembling desmin and NFL IFs bearing isotopically labeled head domains, we provide evidence of structural order in properly assembled biological filaments. We propose that these observations on IF head domains may be instructive to the function of low complexity domains operative in other aspects of cell biology. Low complexity (LC) head domains 92 and 108 residues in length are, respectively, required for assembly of neurofilament light (NFL) and desmin intermediate filaments (IFs). As studied in isolation, these IF head domains interconvert between states of conformational disorder and labile, β-strand–enriched polymers. Solid-state NMR (ss-NMR) spectroscopic studies of NFL and desmin head domain polymers reveal spectral patterns consistent with structural order. A combination of intein chemistry and segmental isotope labeling allowed preparation of fully assembled NFL and desmin IFs that could also be studied by ss-NMR. Assembled IFs revealed spectra overlapping with those observed for β-strand–enriched polymers formed from the isolated NFL and desmin head domains. Phosphorylation and disease-causing mutations reciprocally alter NFL and desmin head domain self-association yet commonly impede IF assembly. These observations show how facultative structural assembly of LC domains via labile, β-strand–enriched self-interactions may broadly influence cell morphology.
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3
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Intermediate Filaments from Tissue Integrity to Single Molecule Mechanics. Cells 2021; 10:cells10081905. [PMID: 34440673 PMCID: PMC8392029 DOI: 10.3390/cells10081905] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 07/20/2021] [Accepted: 07/22/2021] [Indexed: 12/22/2022] Open
Abstract
Cytoplasmic intermediate filaments (IFs), which together with actin and microtubules form the cytoskeleton, are composed of a large and diverse family of proteins. Efforts to elucidate the molecular mechanisms responsible for IF-associated diseases increasingly point towards a major contribution of IFs to the cell’s ability to adapt, resist and respond to mechanical challenges. From these observations, which echo the impressive resilience of IFs in vitro, we here discuss the role of IFs as master integrators of cell and tissue mechanics. In this review, we summarize our current understanding of the contribution of IFs to cell and tissue mechanics and explain these results in light of recent in vitro studies that have investigated physical properties of single IFs and IF networks. Finally, we highlight how changes in IF gene expression, network assembly dynamics, and post-translational modifications can tune IF properties to adapt cell and tissue mechanics to changing environments.
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4
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MacTaggart B, Kashina A. Posttranslational modifications of the cytoskeleton. Cytoskeleton (Hoboken) 2021; 78:142-173. [PMID: 34152688 DOI: 10.1002/cm.21679] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 06/13/2021] [Accepted: 06/16/2021] [Indexed: 12/12/2022]
Abstract
The cytoskeleton plays important roles in many essential processes at the cellular and organismal levels, including cell migration and motility, cell division, and the establishment and maintenance of cell and tissue architecture. In order to facilitate these varied functions, the main cytoskeletal components-microtubules, actin filaments, and intermediate filaments-must form highly diverse intracellular arrays in different subcellular areas and cell types. The question of how this diversity is conferred has been the focus of research for decades. One key mechanism is the addition of posttranslational modifications (PTMs) to the major cytoskeletal proteins. This posttranslational addition of various chemical groups dramatically increases the complexity of the cytoskeletal proteome and helps facilitate major global and local cytoskeletal functions. Cytoskeletal proteins undergo many PTMs, most of which are not well understood. Recent technological advances in proteomics and cell biology have allowed for the in-depth study of individual PTMs and their functions in the cytoskeleton. Here, we provide an overview of the major PTMs that occur on the main structural components of the three cytoskeletal systems-tubulin, actin, and intermediate filament proteins-and highlight the cellular function of these modifications.
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Affiliation(s)
- Brittany MacTaggart
- School of Veterinary Medicine, Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Anna Kashina
- School of Veterinary Medicine, Department of Biomedical Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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5
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Mariani RA, Paranjpe S, Dobrowolski R, Weber GF. 14-3-3 targets keratin intermediate filaments to mechanically sensitive cell-cell contacts. Mol Biol Cell 2020; 31:930-943. [PMID: 32074004 PMCID: PMC7185971 DOI: 10.1091/mbc.e18-06-0373] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Intermediate filament (IF) cytoskeletal networks simultaneously support mechanical integrity and influence signal transduction pathways. Marked remodeling of the keratin IF network accompanies collective cellular morphogenetic movements that occur during early embryonic development in the frog Xenopus laevis. While this reorganization of keratin is initiated by force transduction on cell–cell contacts mediated by C-cadherin, the mechanism by which keratin filament reorganization occurs remains poorly understood. In this work, we demonstrate that 14-3-3 proteins regulate keratin reorganization dynamics in embryonic mesendoderm cells from Xenopus gastrula. 14-3-3 colocalizes with keratin filaments near cell–cell junctions in migrating mesendoderm. Coimmunoprecipitation, mass spectrometry, and bioinformatic analyses indicate 14-3-3 is associated with Keratin 19 (K19) in the whole embryo and, more specifically, mesendoderm tissue. Inhibition of 14-3-3 results in both the decreased exchange of keratin subunits into filaments and blocks keratin filament recruitment toward cell–cell contacts. Synthetically coupling 14-3-3 to K19 through a unique fusion construct conversely induces the localization of this keratin population to the region of cell–cell contacts. Taken together, these findings indicate that 14-3-3 acts on keratin IFs and is involved in their reorganization to sites of cell adhesion.
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Affiliation(s)
- Richard A Mariani
- Department of Biological Sciences, Rutgers University-Newark, Newark, NJ 07102
| | - Shalaka Paranjpe
- Department of Biological Sciences, Rutgers University-Newark, Newark, NJ 07102
| | - Radek Dobrowolski
- Department of Biological Sciences, Rutgers University-Newark, Newark, NJ 07102.,Department of Biology, University of Indianapolis, Indianapolis, IN 46227
| | - Gregory F Weber
- Department of Biological Sciences, Rutgers University-Newark, Newark, NJ 07102.,Glenn Biggs Institute for Alzheimer's & Neurodegenerative Diseases, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229
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6
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Mónico A, Duarte S, Pajares MA, Pérez-Sala D. Vimentin disruption by lipoxidation and electrophiles: Role of the cysteine residue and filament dynamics. Redox Biol 2019; 23:101098. [PMID: 30658903 PMCID: PMC6859561 DOI: 10.1016/j.redox.2019.101098] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 12/28/2018] [Accepted: 01/05/2019] [Indexed: 12/17/2022] Open
Abstract
The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress, which induce extensive reorganization of the vimentin cytoskeletal network. Here, we have investigated the mechanisms underlying these effects. In vitro, electrophilic lipids, including 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal (HNE), directly bind to vimentin, whereas the oxidant diamide induces disulfide bond formation. Mutation of the single vimentin cysteine residue (Cys328) blunts disulfide formation and reduces lipoxidation by 15d-PGJ2, but not HNE. Preincubation with these agents differentially hinders NaCl-induced filament formation by wild-type vimentin, with effects ranging from delayed elongation and increased filament diameter to severe impairment of assembly or aggregation. Conversely, the morphology of vimentin Cys328Ser filaments is mildly or not affected. Interestingly, preformed vimentin filaments are more resistant to electrophile-induced disruption, although chemical modification is not diminished, showing that vimentin (lip)oxidation prior to assembly is more deleterious. In cells, electrophiles, particularly diamide, induce a fast and drastic disruption of existing filaments, which requires the presence of Cys328. As the cellular vimentin network is under continuous remodeling, we hypothesized that vimentin exchange on filaments would be necessary for diamide-induced disruption. We confirmed that strategies reducing vimentin dynamics, as monitored by FRAP, including cysteine crosslinking and ATP synthesis inhibition, prevent diamide effect. In turn, phosphorylation may promote vimentin disassembly. Indeed, treatment with the phosphatase inhibitor calyculin A to prevent dephosphorylation intensifies electrophile-induced wild-type vimentin filament disruption. However, whereas a phosphorylation-deficient vimentin mutant is only partially protected from disorganization, Cys328Ser vimentin is virtually resistant, even in the presence of calyculin A. Together, these results indicate that modification of Cys328 and vimentin exchange are critical for electrophile-induced network disruption.
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Affiliation(s)
- Andreia Mónico
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Sofia Duarte
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - María A Pajares
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain; Molecular Hepatology Group, Instituto de Investigación Sanitaria del Hospital Universitario La Paz (IdiPAZ), Paseo de la Castellana 261, 28046 Madrid, Spain
| | - Dolores Pérez-Sala
- Department of Structural and Chemical Biology, Centro de Investigaciones Biológicas (CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain.
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7
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Li J, Gao W, Zhang Y, Cheng F, Eriksson JE, Etienne-Manneville S, Jiu Y. Engagement of vimentin intermediate filaments in hypotonic stress. J Cell Biochem 2019; 120:13168-13176. [PMID: 30887571 DOI: 10.1002/jcb.28591] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/01/2019] [Accepted: 02/14/2019] [Indexed: 11/08/2022]
Abstract
Intermediate filaments (IFs) play a key role in the control of cell structure and morphology, cell mechano-responses, migration, proliferation, and apoptosis. However, the mechanisms regulating IFs organization in motile adhesive cells under certain physical/pathological conditions remain to be fully understood. In this study, we found hypo-osmotic-induced stress results in a dramatic but reversible rearrangement of the IF network. Vimentin and nestin IFs are partially depolymerized as they are redistributed throughout the cell cytoplasm after hypo-osmotic shock. This spreading of the IFs requires an intact microtubule network and the motor protein associated transportation. Both nocodazole treatment and depletion of kinesin-1 (KIF5B) block the hypo-osmotic shock-induced rearrangement of IFs showing that the dynamic behavior of IFs largely depends on microtubules and kinesin-dependent transport. Moreover, we show that cell survival rates are dramatically decreased in response to hypo-osmotic shock, which was more severe by vimentin IFs depletion, indicating its contribution to osmotic endurance. Collectively, these results reveal a critical role of vimentin IFs under hypotonic stress and provide evidence that IFs are important for the defense mechanisms during the osmotic challenge.
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Affiliation(s)
- Jian Li
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Wei Gao
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yue Zhang
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Fang Cheng
- School of Pharmaceutical Sciences (Shenzhen), SYSU, China
| | - John E Eriksson
- Cell Biology, Biosciences, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.,Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland
| | - Sandrine Etienne-Manneville
- Institut Pasteur Paris CNRS UMR3691, Cell Polarity, Migration and Cancer Unit, Equipe Labellisée Ligue Contre le Cancer, Paris, France
| | - Yaming Jiu
- CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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8
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Tarbet HJ, Dolat L, Smith TJ, Condon BM, O'Brien ET, Valdivia RH, Boyce M. Site-specific glycosylation regulates the form and function of the intermediate filament cytoskeleton. eLife 2018. [PMID: 29513221 PMCID: PMC5841932 DOI: 10.7554/elife.31807] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intermediate filaments (IF) are a major component of the metazoan cytoskeleton and are essential for normal cell morphology, motility, and signal transduction. Dysregulation of IFs causes a wide range of human diseases, including skin disorders, cardiomyopathies, lipodystrophy, and neuropathy. Despite this pathophysiological significance, how cells regulate IF structure, dynamics, and function remains poorly understood. Here, we show that site-specific modification of the prototypical IF protein vimentin with O-linked β-N-acetylglucosamine (O-GlcNAc) mediates its homotypic protein-protein interactions and is required in human cells for IF morphology and cell migration. In addition, we show that the intracellular pathogen Chlamydia trachomatis, which remodels the host IF cytoskeleton during infection, requires specific vimentin glycosylation sites and O-GlcNAc transferase activity to maintain its replicative niche. Our results provide new insight into the biochemical and cell biological functions of vimentin O-GlcNAcylation, and may have broad implications for our understanding of the regulation of IF proteins in general. Like the body's skeleton, the cytoskeleton gives shape and structure to the inside of a cell. Yet, unlike a skeleton, the cytoskeleton is ever changing. The cytoskeleton consists of many fibers each made from chains of protein molecules. One of these proteins is called vimentin and it forms intermediate filaments in the cytoskeleton. Many different types of cells contain vimentin and a lot of it is found in cancer cells that have spread beyond their original location to other sites in the body. Cells use chemical modifications to regulate cytoskeleton proteins. For example, through a process called glycosylation, cells can reversibly attach a sugar modification called O-GlcNAc to vimentin. O-GlcNAc can be attached to several different parts of vimentin and each location may have a different effect. It is not currently clear how cells control their vimentin filaments or what role O-GlcNAc plays in this process. Using genetic engineering, Tarbet et al. produced human cells in the laboratory with modified vimentin proteins. These altered proteins lacked some of the sites for O-GlcNAc attachment. The goal was to see whether the loss of O-GlcNAc at a specific location would affect fiber formation and cell behavior. The results showed one site where vimentin needs O-GlcNAc to form fibers. Without O-GlcNAc at this site, cells could not migrate towards chemical signals. In addition, in normal human cells, Chlamydia bacteria hijack vimentin and rearrange the filaments to form a cage around themselves for protection. However, the cells lacking O-GlcNAc on vimentin were resistant to infection by Chlamydia bacteria. These findings highlight the importance of O-GlcNAc on vimentin in healthy cells and during infection. Vimentin’s contribution to cell migration may also help to explain its role in the spread of cancer. The importance of O-GlcNAc suggests it could be a new target for therapies. Yet, it also highlights the need for caution due to the delicate balance between the activity of vimentin in healthy and diseased cells. In addition, human cells produce about 70 other vimentin-like proteins and further work will examine if they are also affected by O-GlcNAc.
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Affiliation(s)
- Heather J Tarbet
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - Lee Dolat
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
| | - Timothy J Smith
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - Brett M Condon
- Department of Biochemistry, Duke University School of Medicine, Durham, United States
| | - E Timothy O'Brien
- Department of Biochemistry, Duke University School of Medicine, Durham, United States.,Department of Physics and Astronomy, University of North Carolina, Chapel Hill, United States
| | - Raphael H Valdivia
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
| | - Michael Boyce
- Department of Biochemistry, Duke University School of Medicine, Durham, United States.,Center for Host-Microbial Interactions, Duke University School of Medicine, Durham, United States
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9
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Sanghvi-Shah R, Weber GF. Intermediate Filaments at the Junction of Mechanotransduction, Migration, and Development. Front Cell Dev Biol 2017; 5:81. [PMID: 28959689 PMCID: PMC5603733 DOI: 10.3389/fcell.2017.00081] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 08/30/2017] [Indexed: 01/04/2023] Open
Abstract
Mechanically induced signal transduction has an essential role in development. Cells actively transduce and respond to mechanical signals and their internal architecture must manage the associated forces while also being dynamically responsive. With unique assembly-disassembly dynamics and physical properties, cytoplasmic intermediate filaments play an important role in regulating cell shape and mechanical integrity. While this function has been recognized and appreciated for more than 30 years, continually emerging data also demonstrate important roles of intermediate filaments in cell signal transduction. In this review, with a particular focus on keratins and vimentin, the relationship between the physical state of intermediate filaments and their role in mechanotransduction signaling is illustrated through a survey of current literature. Association with adhesion receptors such as cadherins and integrins provides a critical interface through which intermediate filaments are exposed to forces from a cell's environment. As a consequence, these cytoskeletal networks are posttranslationally modified, remodeled and reorganized with direct impacts on local signal transduction events and cell migratory behaviors important to development. We propose that intermediate filaments provide an opportune platform for cells to both cope with mechanical forces and modulate signal transduction.
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Affiliation(s)
- Rucha Sanghvi-Shah
- Department of Biological Sciences, Rutgers University-NewarkNewark, NJ, United States
| | - Gregory F Weber
- Department of Biological Sciences, Rutgers University-NewarkNewark, NJ, United States
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10
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Abstract
For years intermediate filaments (IF), belonging to the third class of filamentous cytoskeletal proteins alongside microtubules and actin filaments, were thought to be exclusive to metazoan cells. Structurally these eukaryote IFs are very well defined, consisting of globular head and tail domains, which flank the central rod-domain. This central domain is dominated by an α-helical secondary structure predisposed to form the characteristic coiled-coil, parallel homo-dimer. These elementary dimers can further associate, both laterally and longitudinally, generating a variety of filament-networks built from filaments in the range of 10 nm in diameter. The general role of these filaments with their characteristic mechano-elastic properties both in the cytoplasm and in the nucleus of eukaryote cells is to provide mechanical strength and a scaffold supporting diverse shapes and cellular functions.Since 2003, after the first bacterial IF-like protein, crescentin was identified, it has been evident that bacteria also employ filamentous networks, other than those built from bacterial tubulin or actin homologues, in order to support their cell shape, growth and, in some cases, division. Intriguingly, compared to their eukaryote counterparts, the group of bacterial IF-like proteins shows much wider structural diversity. The sizes of both the head and tail domains are markedly reduced and there is great variation in the length of the central rod-domain. Furthermore, bacterial rod-domains often lack the sub-domain organisation of eukaryote IFs that is the defining feature of the IF-family. However, the fascinating display of filamentous assemblies, including rope, striated cables and hexagonal laces together with the conditions required for their formation both in vitro and in vivo strongly resemble that of eukaryote IFs suggesting that these bacterial proteins are deservedly classified as part of the IF-family and that the current definition should be relaxed slightly to allow their inclusion. The lack of extensive head and tail domains may well make the bacterial proteins more amenable for structural characterisation, which will be essential for establishing the mechanism for their association into filaments. What is more, the well-developed tools for bacterial manipulations provide an excellent opportunity of studying the bacterial systems with the prospect of making significant progress in our understanding of the general underlying principles of intermediate filament assemblies.
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Affiliation(s)
- Gabriella H Kelemen
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
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11
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Robert A, Hookway C, Gelfand VI. Intermediate filament dynamics: What we can see now and why it matters. Bioessays 2016; 38:232-43. [PMID: 26763143 DOI: 10.1002/bies.201500142] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The mechanical properties of vertebrate cells are largely defined by the system of intermediate filaments (IF). As part of a dense network, IF polymers are constantly rearranged and relocalized in the cell to fulfill their duty as cells change shape, migrate, or divide. With the development of new imaging technologies, such as photoconvertible proteins and super-resolution microscopy, a new appreciation for the complexity of IF dynamics has emerged. This review highlights new findings about the transport of IF, the remodeling of filaments by a process of severing and re-annealing, and the subunit exchange that occurs between filament precursors and a soluble pool of IF. We will also discuss the unique dynamic features of the keratin IF network. Finally, we will speculate about how the dynamic properties of IF are related to their functions.
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Affiliation(s)
- Amélie Robert
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Caroline Hookway
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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12
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Ridge KM, Shumaker D, Robert A, Hookway C, Gelfand VI, Janmey PA, Lowery J, Guo M, Weitz DA, Kuczmarski E, Goldman RD. Methods for Determining the Cellular Functions of Vimentin Intermediate Filaments. Methods Enzymol 2015; 568:389-426. [PMID: 26795478 DOI: 10.1016/bs.mie.2015.09.036] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The type III intermediate filament protein vimentin was once thought to function mainly as a static structural protein in the cytoskeleton of cells of mesenchymal origin. Now, however, vimentin is known to form a dynamic, flexible network that plays an important role in a number of signaling pathways. Here, we describe various methods that have been developed to investigate the cellular functions of the vimentin protein and intermediate filament network, including chemical disruption, photoactivation and photoconversion, biolayer interferometry, soluble bead binding assay, three-dimensional substrate experiments, collagen gel contraction, optical-tweezer active microrheology, and force spectrum microscopy. Using these techniques, the contributions of vimentin to essential cellular processes can be probed in ever further detail.
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Affiliation(s)
- Karen M Ridge
- Division of Pulmonary and Critical Care Medicine, Chicago, Illinois, USA; Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA; Veterans Administration, Chicago, Illinois, USA.
| | - Dale Shumaker
- Division of Pulmonary and Critical Care Medicine, Chicago, Illinois, USA; Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Amélie Robert
- Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Caroline Hookway
- Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Paul A Janmey
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Departments of Physiology and Physics & Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jason Lowery
- Division of Pulmonary and Critical Care Medicine, Chicago, Illinois, USA
| | - Ming Guo
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
| | - David A Weitz
- School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA; Department of Physics, Harvard University, Cambridge, Massachusetts, USA
| | - Edward Kuczmarski
- Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Robert D Goldman
- Division of Pulmonary and Critical Care Medicine, Chicago, Illinois, USA; Department of Cell and Molecular Biology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
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13
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Schwarz N, Moch M, Windoffer R, Leube RE. Multidimensional Monitoring of Keratin Intermediate Filaments in Cultured Cells and Tissues. Methods Enzymol 2015; 568:59-83. [PMID: 26795467 DOI: 10.1016/bs.mie.2015.07.034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Keratin filaments are a hallmark of epithelial differentiation. Their cell type-specific spatial organization and dynamic properties reflect and support epithelial function. To study this interdependency, imaging of fluorescently tagged keratins is a widely used method by which the temporospatial organization and behavior of the keratin intermediate filament network can be analyzed in living cells. Here, we describe methods that have been adapted and optimized to dissect and quantify keratin intermediate filament network dynamics in vital cultured cells and functional tissues.
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Affiliation(s)
- Nicole Schwarz
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - Marcin Moch
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany
| | - 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.
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14
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Robert A, Rossow MJ, Hookway C, Adam SA, Gelfand VI. Vimentin filament precursors exchange subunits in an ATP-dependent manner. Proc Natl Acad Sci U S A 2015; 112:E3505-14. [PMID: 26109569 PMCID: PMC4500282 DOI: 10.1073/pnas.1505303112] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intermediate filaments (IFs) are a component of the cytoskeleton capable of profound reorganization in response to specific physiological situations, such as differentiation, cell division, and motility. Various mechanisms were proposed to be responsible for this plasticity depending on the type of IF polymer and the biological context. For example, recent studies suggest that mature vimentin IFs (VIFs) undergo rearrangement by severing and reannealing, but direct subunit exchange within the filament plays little role in filament dynamics at steady state. Here, we studied the dynamics of subunit exchange in VIF precursors, called unit-length filaments (ULFs), formed by the lateral association of eight vimentin tetramers. To block vimentin assembly at the ULF stage, we used the Y117L vimentin mutant (vimentin(Y117L)). By tagging vimentin(Y117L) with a photoconvertible protein mEos3.2 and photoconverting ULFs in a limited area of the cytoplasm, we found that ULFs, unlike mature filaments, were highly dynamic. Subunit exchange among ULFs occurred within seconds and was limited by the diffusion of soluble subunits in the cytoplasm rather than by the association and dissociation of subunits from ULFs. Our data demonstrate that cells expressing vimentin(Y117L) contained a large pool of soluble vimentin tetramers that was in rapid equilibrium with ULFs. Furthermore, vimentin exchange in ULFs required ATP, and ATP depletion caused a dramatic reduction of the soluble tetramer pool. We believe that the dynamic exchange of subunits plays a role in the regulation of ULF assembly and the maintenance of a soluble vimentin pool during the reorganization of filament networks.
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Affiliation(s)
- Amélie Robert
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Molly J Rossow
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Caroline Hookway
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Stephen A Adam
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
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15
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Vimentin filament organization and stress sensing depend on its single cysteine residue and zinc binding. Nat Commun 2015; 6:7287. [PMID: 26031447 PMCID: PMC4458873 DOI: 10.1038/ncomms8287] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 04/24/2015] [Indexed: 12/30/2022] Open
Abstract
The vimentin filament network plays a key role in cell architecture and signalling, as well as in epithelial-mesenchymal transition. Vimentin C328 is targeted by various oxidative modifications, but its role in vimentin organization is not known. Here we show that C328 is essential for vimentin network reorganization in response to oxidants and electrophiles, and is required for optimal vimentin performance in network expansion, lysosomal distribution and aggresome formation. C328 may fulfil these roles through interaction with zinc. In vitro, micromolar zinc protects vimentin from iodoacetamide modification and elicits vimentin polymerization into optically detectable structures; in cells, zinc closely associates with vimentin and its depletion causes reversible filament disassembly. Finally, zinc transport-deficient human fibroblasts show increased vimentin solubility and susceptibility to disruption, which are restored by zinc supplementation. These results unveil a critical role of C328 in vimentin organization and open new perspectives for the regulation of intermediate filaments by zinc.
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16
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Bidirectional Interplay between Vimentin Intermediate Filaments and Contractile Actin Stress Fibers. Cell Rep 2015; 11:1511-8. [DOI: 10.1016/j.celrep.2015.05.008] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/21/2015] [Accepted: 05/04/2015] [Indexed: 01/06/2023] Open
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17
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Block J, Schroeder V, Pawelzyk P, Willenbacher N, Köster S. Physical properties of cytoplasmic intermediate filaments. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3053-64. [PMID: 25975455 DOI: 10.1016/j.bbamcr.2015.05.009] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/28/2015] [Accepted: 05/05/2015] [Indexed: 11/29/2022]
Abstract
Intermediate filaments (IFs) constitute a sophisticated filament system in the cytoplasm of eukaryotes. They form bundles and networks with adapted viscoelastic properties and are strongly interconnected with the other filament types, microfilaments and microtubules. IFs are cell type specific and apart from biochemical functions, they act as mechanical entities to provide stability and resilience to cells and tissues. We review the physical properties of these abundant structural proteins including both in vitro studies and cell experiments. IFs are hierarchical structures and their physical properties seem to a large part be encoded in the very specific architecture of the biopolymers. Thus, we begin our review by presenting the assembly mechanism, followed by the mechanical properties of individual filaments, network and structure formation due to electrostatic interactions, and eventually the mechanics of in vitro and cellular networks. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Johanna Block
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Viktor Schroeder
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Göttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Paul Pawelzyk
- Institute of Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Norbert Willenbacher
- Institute of Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Sarah Köster
- Institut für Röntgenphysik, Georg-August-Universität Göttingen, Göttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany.
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18
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Hookway C, Ding L, Davidson MW, Rappoport JZ, Danuser G, Gelfand VI. Microtubule-dependent transport and dynamics of vimentin intermediate filaments. Mol Biol Cell 2015; 26:1675-86. [PMID: 25717187 PMCID: PMC4436779 DOI: 10.1091/mbc.e14-09-1398] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 02/19/2015] [Indexed: 02/05/2023] Open
Abstract
We studied two aspects of vimentin intermediate filament dynamics-transport of filaments and subunit exchange. We observed transport of long filaments in the periphery of cells using live-cell structured illumination microscopy. We studied filament transport elsewhere in cells using a photoconvertible-vimentin probe and total internal reflection microscopy. We found that filaments were rapidly transported along linear tracks in both anterograde and retrograde directions. Filament transport was microtubule dependent but independent of microtubule polymerization and/or an interaction with the plus end-binding protein APC. We also studied subunit exchange in filaments by long-term imaging after photoconversion. We found that converted vimentin remained in small clusters along the length of filaments rather than redistributing uniformly throughout the network, even in cells that divided after photoconversion. These data show that vimentin filaments do not depolymerize into individual subunits; they recompose by severing and reannealing. Together these results show that vimentin filaments are very dynamic and that their transport is required for network maintenance.
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Affiliation(s)
- Caroline Hookway
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Liya Ding
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Michael W Davidson
- National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, Tallahassee, FL 32310
| | - Joshua Z Rappoport
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Gaudenz Danuser
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Vladimir I Gelfand
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
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19
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Nöding B, Herrmann H, Köster S. Direct observation of subunit exchange along mature vimentin intermediate filaments. Biophys J 2014; 107:2923-2931. [PMID: 25517157 PMCID: PMC4269786 DOI: 10.1016/j.bpj.2014.09.050] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 07/25/2014] [Accepted: 09/09/2014] [Indexed: 01/12/2023] Open
Abstract
Actin filaments, microtubules, and intermediate filaments (IFs) are central elements of the metazoan cytoskeleton. At the molecular level, the assembly mechanism for actin filaments and microtubules is fundamentally different from that of IFs. The former two types of filaments assemble from globular proteins. By contrast, IFs assemble from tetrameric complexes of extended, half-staggered, and antiparallel oriented coiled-coils. These tetramers laterally associate into unit-length filaments; subsequent longitudinal annealing of unit-length filaments yields mature IFs. In vitro, IFs form open structures without a fixed number of tetramers per cross-section along the filament. Therefore, a central question for the structural biology of IFs is whether individual subunits can dissociate from assembled filaments and rebind at other sites. Using the fluorescently labeled IF-protein vimentin for assembly, we directly observe and quantitatively determine subunit exchange events between filaments as well as with soluble vimentin pools. Thereby we demonstrate that the cross-sectional polymorphism of donor and acceptor filaments plays an important role. We propose that in segments of donor filaments with more than the standard 32 molecules per cross-section, subunits are not as tightly bound and are predisposed to be released from the filament.
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Affiliation(s)
- Bernd Nöding
- Institute for X-Ray Physics, Georg-August-Universität Göttingen, Göttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
| | - Harald Herrmann
- Division of Molecular Genetics, German Cancer Research Center, Heidelberg, Germany
| | - Sarah Köster
- Institute for X-Ray Physics, Georg-August-Universität Göttingen, Göttingen, Germany; Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany.
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20
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Gruenbaum Y, Aebi U. Intermediate filaments: a dynamic network that controls cell mechanics. F1000PRIME REPORTS 2014; 6:54. [PMID: 25184044 PMCID: PMC4108948 DOI: 10.12703/p6-54] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In humans the superfamily of intermediate filament (IF) proteins is encoded by more than 70 different genes, which are expressed in a cell- and tissue-specific manner. IFs assemble into approximately 10 nm-wide filaments that account for the principal structural elements at the nuclear periphery, nucleoplasm, and cytoplasm. They are also required for organizing the microtubule and microfilament networks. In this review, we focus on the dynamics of IFs and how modifications regulate it. We also discuss the role of nuclear IF organization in determining nuclear mechanics as well as that of cytoplasmic IFs organization in maintaining cell stiffness, formation of lamellipodia, regulation of cell migration, and permitting cell adhesion.
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Affiliation(s)
- Yosef Gruenbaum
- Department of Genetics, Institute of Life Sciences, Hebrew University of JerusalemGivat Ram, Jerusalem 91904Israel
| | - Ueli Aebi
- Biozentrum, University of BaselKlingelbergerstrasse 70, CH-4056 BaselSwitzerland
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21
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Dey P, Togra J, Mitra S. Intermediate filament: structure, function, and applications in cytology. Diagn Cytopathol 2014; 42:628-35. [PMID: 24591257 DOI: 10.1002/dc.23132] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 01/13/2014] [Accepted: 02/16/2014] [Indexed: 11/05/2022]
Abstract
Intermediate filament (IF) constitutes an important cytoskeletal component in nearly all the vertebrate cells. IFs are present both in the cytoplasm and in the nucleus. They play an important role in providing mechanical strength of the cell and tissue, growth and regeneration, cell survival and apoptosis, and finally cell migration. IFs are also expressed differentially in different body tissues. Therefore, judicious use of IF may provide the diagnosis and confirmation of different malignancies. This is particularly helpful in the diagnosis of metastatic malignant tumor from an unknown primary. Expression of IFs particularly cytokeratin and vimentin is also related to prognosis of tumors. In this review, we have discussed the basic structure, dynamics, distribution of IF in cells, and its role in diagnosis of cytology. Possible prognostic roles of IF are also discussed.
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Affiliation(s)
- Pranab Dey
- Department of Cytopathology and Gynecological Pathology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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22
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Vannier C, Pesty A, San-Roman MJ, Schmidt AA. The Bin/amphiphysin/Rvs (BAR) domain protein endophilin B2 interacts with plectin and controls perinuclear cytoskeletal architecture. J Biol Chem 2013; 288:27619-27637. [PMID: 23921385 DOI: 10.1074/jbc.m113.485482] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Proteins of the Bin/amphiphysin/Rvs (BAR) domain superfamily are essential in controlling the shape and dynamics of intracellular membranes. Here, we present evidence for the unconventional function of a member of the endophilin family of BAR and Src homology 3 domain-containing proteins, namely endophilin B2, in the perinuclear organization of intermediate filaments. Using mass spectrometry analysis based on capturing endophilin B2 partners in in situ pre-established complexes in cells, we unravel the interaction of endophilin B2 with plectin 1, a variant of the cytoskeleton linker protein plectin as well as with vimentin. Endophilin B2 directly binds the N-terminal region of plectin 1 via Src homology 3-mediated interaction and vimentin indirectly via plectin-mediated interaction. The relevance of these interactions is strengthened by the selective and drastic reorganization of vimentin around nuclei upon overexpression of endophilin B2 and by the extensive colocalization of both proteins in a meshwork of perinuclear filamentous structures. By generating mutants of the endophilin B2 BAR domain, we show that this phenotype requires the BAR-mediated membrane binding activity of endophilin B2. Plectin 1 or endophilin B2 knockdown using RNA interference disturbed the perinuclear organization of vimentin. Altogether, these data suggest that the endophilin B2-plectin 1 complex functions as a membrane-anchoring device organizing and stabilizing the perinuclear network of vimentin filaments. Finally, we present evidence for the involvement of endophilin B2 and plectin 1 in nuclear positioning in individual cells. This points to the potential importance of the endophilin B2-plectin complex in the biological functions depending on nuclear migration and positioning.
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Affiliation(s)
- Christian Vannier
- From CNRS, UMR7592, Institut Jacques Monod, Université Paris Diderot, Sorbonne Paris Cité, 15 Rue Hélène Brion, F-75205 Paris Cedex 13, France
| | - Arlette Pesty
- From CNRS, UMR7592, Institut Jacques Monod, Université Paris Diderot, Sorbonne Paris Cité, 15 Rue Hélène Brion, F-75205 Paris Cedex 13, France
| | - Mabel Jouve San-Roman
- From CNRS, UMR7592, Institut Jacques Monod, Université Paris Diderot, Sorbonne Paris Cité, 15 Rue Hélène Brion, F-75205 Paris Cedex 13, France
| | - Anne A Schmidt
- From CNRS, UMR7592, Institut Jacques Monod, Université Paris Diderot, Sorbonne Paris Cité, 15 Rue Hélène Brion, F-75205 Paris Cedex 13, France.
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23
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Jacob MD, Audas TE, Uniacke J, Trinkle-Mulcahy L, Lee S. Environmental cues induce a long noncoding RNA-dependent remodeling of the nucleolus. Mol Biol Cell 2013; 24:2943-53. [PMID: 23904269 PMCID: PMC3771955 DOI: 10.1091/mbc.e13-04-0223] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Environmental signals, such heat shock and acidosis, induce a structural and functional remodeling of the nucleolus. This process, which depends on the expression of intergenic long noncoding RNA, reversibly converts the nucleolus from a transcriptionally active ribosome factory into a transcriptionally inert prison for proteins. The nucleolus is a plurifunctional organelle in which structure and function are intimately linked. Its structural plasticity has long been appreciated, particularly in response to transcriptional inhibition and other cellular stresses, although the mechanism and physiological relevance of these phenomena are unclear. Using MCF-7 and other mammalian cell lines, we describe a structural and functional adaptation of the nucleolus, triggered by heat shock or physiological acidosis, that depends on the expression of ribosomal intergenic spacer long noncoding RNA (IGS lncRNA). At the heart of this process is the de novo formation of a large subnucleolar structure, termed the detention center (DC). The DC is a spatially and dynamically distinct region, characterized by an 8-anilino-1-naphthalenesulfonate–positive hydrophobic signature. Its formation is accompanied by redistribution of nucleolar factors and arrest in ribosomal biogenesis. Silencing of regulatory IGS lncRNA prevents the creation of this structure and allows the nucleolus to retain its tripartite organization and transcriptional activity. Signal termination causes a decrease in IGS transcript levels and a return to the active nucleolar conformation. We propose that the induction of IGS lncRNA by environmental signals operates as a molecular switch that regulates the structure and function of the nucleolus.
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Affiliation(s)
- Mathieu D Jacob
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
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24
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Abstract
We have shown previously that neurofilaments and vimentin filaments expressed in nonneuronal cell lines can lengthen by joining ends in a process known as "end-to-end annealing." To test if this also occurs for neurofilaments in neurons, we transfected cultured rat cortical neurons with fluorescent neurofilament fusion proteins and then used photoconversion or photoactivation strategies to create distinct populations of red and green fluorescent filaments. Within several hours we observed the appearance of chimeric filaments consisting of alternating red and green segments, which is indicative of end-to-end annealing of red and green filaments. However, the appearance of these chimeric filaments was accompanied by a gradual fragmentation of the red and green filament segments, which is indicative of severing. Over time we observed a progressive increase in the number of red-green junctions along the filaments accompanied by a progressive decrease in the average length of the alternating red and green fluorescent segments that comprised those filaments, suggesting a dynamic cycle of severing and end-to-end-annealing. Time-lapse imaging of the axonal transport of chimeric filaments demonstrated that the red and green segments moved together, confirming that they were indeed part of the same filament. Moreover, in several instances, we also were able to capture annealing and severing events live in time-lapse movies. We propose that the length of intermediate filaments in cells is regulated by the opposing actions of severing and end-to-end annealing, and we speculate that this regulatory mechanism may influence neurofilament transport within axons.
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25
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Huber F, Schnauß J, Rönicke S, Rauch P, Müller K, Fütterer C, Käs J. Emergent complexity of the cytoskeleton: from single filaments to tissue. ADVANCES IN PHYSICS 2013; 62:1-112. [PMID: 24748680 PMCID: PMC3985726 DOI: 10.1080/00018732.2013.771509] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Revised: 01/11/2013] [Indexed: 05/17/2023]
Abstract
Despite their overwhelming complexity, living cells display a high degree of internal mechanical and functional organization which can largely be attributed to the intracellular biopolymer scaffold, the cytoskeleton. Being a very complex system far from thermodynamic equilibrium, the cytoskeleton's ability to organize is at the same time challenging and fascinating. The extensive amounts of frequently interacting cellular building blocks and their inherent multifunctionality permits highly adaptive behavior and obstructs a purely reductionist approach. Nevertheless (and despite the field's relative novelty), the physics approach has already proved to be extremely successful in revealing very fundamental concepts of cytoskeleton organization and behavior. This review aims at introducing the physics of the cytoskeleton ranging from single biopolymer filaments to multicellular organisms. Throughout this wide range of phenomena, the focus is set on the intertwined nature of the different physical scales (levels of complexity) that give rise to numerous emergent properties by means of self-organization or self-assembly.
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Affiliation(s)
- F. Huber
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - J. Schnauß
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - S. Rönicke
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - P. Rauch
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - K. Müller
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - C. Fütterer
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
| | - J. Käs
- Institute for Experimental Physics I, University of Leipzig, Leipzig, Germany
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26
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Shea TB, Lee S. The discontinuous nature of neurofilament transport accommodates both establishment and repair of the axonal neurofilament array. Cytoskeleton (Hoboken) 2012; 70:67-73. [PMID: 23124969 DOI: 10.1002/cm.21087] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 10/08/2012] [Accepted: 10/11/2012] [Indexed: 12/19/2022]
Abstract
Neurofilaments (NFs) provide structural support to axons. Timely and regional deposition of NFs is essential during axonogenesis, since progressive stabilization of proximal axons is essential to support continued pathfinding of distal axonal regions. NFs undergo short bursts of microtubule-mediated axonal transport interspersed by prolonged pauses. We demonstrate herein that it is this unique "on-off" method of axonal transport, coupled with the ability of NFs to form cation-dependent, phosphomediated lateral associations that allow neurons to mediate the orderly transition from exploratory process to stabilized axon following synaptogenesis. We further demonstrate how this transport method provides for NF maintenance following maturation and encompasses the potential for regeneration.
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Affiliation(s)
- Thomas B Shea
- Department of Biological Sciences, Center for Cellular Neurobiology and Neurodegeneration Research, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, USA.
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27
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Taylor NJ, Wang L, Brown A. Neurofilaments are flexible polymers that often fold and unfold, but they move in a fully extended configuration. Cytoskeleton (Hoboken) 2012; 69:535-44. [PMID: 22693112 DOI: 10.1002/cm.21039] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 05/08/2012] [Accepted: 05/09/2012] [Indexed: 01/29/2023]
Abstract
Time-lapse imaging of neurofilaments in axons of cultured nerve cells has demonstrated that these cytoskeletal polymers move along microtubule tracks in both anterograde and retrograde directions, powered by microtubule motors. The filaments exhibit short bouts of rapid intermittent movement interrupted by prolonged pauses, and the average velocity is slow because they spend most of their time pausing. Here, we show that axonal neurofilaments are also very flexible and frequently exhibit complex and dynamic folding and unfolding behaviors while they are pausing. Remarkably, however, when the filaments move in a sustained manner, we find that they always adopt an unfolded, that is, fully extended configuration, and this applies to movement in both anterograde and retrograde directions. Given the flexibility of neurofilament polymers and the apparent ease with which they can fold back on themselves, the fact that they move in a fully extended configuration suggests that moving neurofilaments may be pulled from their leading end. Thus, we speculate that motors may bind to the leading ends of neurofilaments polymers during both anterograde and retrograde motion.
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Affiliation(s)
- Nicholas J Taylor
- Department of Neuroscience, Wexner Medical Center, Ohio State University, Columbus, Ohio 43210, USA
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28
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Audas TE, Jacob MD, Lee S. The nucleolar detention pathway: A cellular strategy for regulating molecular networks. Cell Cycle 2012; 11:2059-62. [PMID: 22580471 DOI: 10.4161/cc.20140] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Molecular dynamics ensures that proteins and other factors reach their site of action in a timely and efficient manner. This is essential to the formation of molecular complexes, as they require an ever-changing framework of specific interactions to facilitate a model of self-assembly. Therefore, the absence or reduced availability of any key component would significantly impair complex formation and disrupt all downstream molecular networks. Recently, we identified a regulatory mechanism that modulates protein mobility through the inducible expression of a novel family of long noncoding RNA. In response to diverse environmental stimuli, the nucleolar detention pathway (NoDP) captures and immobilizes essential cellular factors within the nucleolus away from their effector molecules. The vast array of putative NoDP targets, including DNA (cytosine-5)-methyltransferase 1 (DNMT1) and the delta catalytic subunit of DNA polymerase (POLD1), suggests that this may be a common and significant regulatory mechanism. Here, we discuss the implications of this new posttranslational strategy for regulating molecular networks.
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Affiliation(s)
- Timothy E Audas
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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29
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Goldman RD, Cleland MM, Murthy SNP, Mahammad S, Kuczmarski ER. Inroads into the structure and function of intermediate filament networks. J Struct Biol 2011; 177:14-23. [PMID: 22120848 DOI: 10.1016/j.jsb.2011.11.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/07/2011] [Accepted: 11/09/2011] [Indexed: 12/20/2022]
Abstract
Although intermediate filaments are one of three major cytoskeletal systems of vertebrate cells, they remain the least understood with respect to their structure and function. This is due in part to the fact that they are encoded by a large gene family which is developmentally regulated in a cell and tissue type specific fashion. This article is in honor of Ueli Aebi. It highlights the studies on IF that have been carried out by our laboratory for more than 40 years. Many of our advances in understanding IF are based on conversations with Ueli which have taken place during adventurous and sometimes dangerous hiking and biking trips throughout the world.
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Affiliation(s)
- Robert D Goldman
- Department of Cell and Molecular Biology, Northwestern University's Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
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30
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D'Angelo F, Tiribuzi R, Armentano I, Kenny JM, Martino S, Orlacchio A. Mechanotransduction: tuning stem cells fate. J Funct Biomater 2011; 2:67-87. [PMID: 24956164 PMCID: PMC4030896 DOI: 10.3390/jfb2020067] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/07/2011] [Accepted: 06/17/2011] [Indexed: 01/10/2023] Open
Abstract
It is a general concern that the success of regenerative medicine-based applications is based on the ability to recapitulate the molecular events that allow stem cells to repair the damaged tissue/organ. To this end biomaterials are designed to display properties that, in a precise and physiological-like fashion, could drive stem cell fate both in vitro and in vivo. The rationale is that stem cells are highly sensitive to forces and that they may convert mechanical stimuli into a chemical response. In this review, we describe novelties on stem cells and biomaterials interactions with more focus on the implication of the mechanical stimulation named mechanotransduction.
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Affiliation(s)
- Francesco D'Angelo
- Department of Experimental Medicine and Biochemical Science, Section of Biochemistry and Molecular Biology, University of Perugia, Via del Giochetto, 06126 Perugia, Italy.
| | - Roberto Tiribuzi
- Department of Experimental Medicine and Biochemical Science, Section of Biochemistry and Molecular Biology, University of Perugia, Via del Giochetto, 06126 Perugia, Italy.
| | - Ilaria Armentano
- Materials Engineering Centre, UdR INSTM, NIPLAB, University of Perugia, Strada di Pentima 4, 05100 Terni, Italy.
| | - Josè Maria Kenny
- Materials Engineering Centre, UdR INSTM, NIPLAB, University of Perugia, Strada di Pentima 4, 05100 Terni, Italy.
| | - Sabata Martino
- Department of Experimental Medicine and Biochemical Science, Section of Biochemistry and Molecular Biology, University of Perugia, Via del Giochetto, 06126 Perugia, Italy.
| | - Aldo Orlacchio
- Department of Experimental Medicine and Biochemical Science, Section of Biochemistry and Molecular Biology, University of Perugia, Via del Giochetto, 06126 Perugia, Italy.
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Kirmse R, Qin Z, Weinert CM, Hoenger A, Buehler MJ, Kreplak L. Plasticity of intermediate filament subunits. PLoS One 2010; 5:e12115. [PMID: 20814582 PMCID: PMC2930322 DOI: 10.1371/journal.pone.0012115] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 07/18/2010] [Indexed: 11/19/2022] Open
Abstract
Intermediate filaments (IFs) assembled in vitro from recombinantly expressed proteins have a diameter of 8–12 nm and can reach several micrometers in length. IFs assemble from a soluble pool of subunits, tetramers in the case of vimentin. Upon salt addition, the subunits form first unit length filaments (ULFs) within seconds and then assembly proceeds further by end-to-end fusion of ULFs and short filaments. So far, IF subunits have mainly been observed by electron microscopy of glycerol sprayed and rotary metal shadowed specimens. Due to the shear forces during spraying the IF subunits appear generally as straight thin rods. In this study, we used atomic force microscopy (AFM), cryo-electron microscopy (cryo-EM) combined with molecular modeling to investigate the conformation of the subunits of vimentin, desmin and keratin K5/K14 IFs in various conditions. Due to their anisotropic shape the subunits are difficult to image at high resolution by cryo-EM. In order to enhance contrast we used a cryo-negative staining approach. The subunits were clearly identified as thin, slightly curved rods. However the staining agent also forced the subunits to aggregate into two-dimensional networks of dot-like structures. To test this conformational change further, we imaged dried unfixed subunits on mica by AFM revealing a mixture of extended and dot-like conformations. The use of divalent ions such as calcium and magnesium, as well as glutaraldehyde exposure favored compact conformations over elongated ones. These experimental results as well as coarse-grained molecular dynamics simulations of a vimentin tetramer highlight the plasticity of IF subunits.
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Affiliation(s)
- Robert Kirmse
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Zhao Qin
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Carl M. Weinert
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Andrea Hoenger
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Markus J. Buehler
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Laurent Kreplak
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail:
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Esue O, Rupprecht L, Sun SX, Wirtz D. Dynamics of the bacterial intermediate filament crescentin in vitro and in vivo. PLoS One 2010; 5:e8855. [PMID: 20140233 PMCID: PMC2816638 DOI: 10.1371/journal.pone.0008855] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 01/04/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Crescentin, the recently discovered bacterial intermediate filament protein, organizes into an extended filamentous structure that spans the length of the bacterium Caulobacter crescentus and plays a critical role in defining its curvature. The mechanism by which crescentin mediates cell curvature and whether crescentin filamentous structures are dynamic and/or polar are not fully understood. METHODOLOGY/PRINCIPAL FINDINGS Using light microscopy, electron microscopy and quantitative rheology, we investigated the mechanics and dynamics of crescentin structures. Live-cell microscopy reveals that crescentin forms structures in vivo that undergo slow remodeling. The exchange of subunits between these structures and a pool of unassembled subunits is slow during the life cycle of the cell however; in vitro assembly and gelation of C. crescentus crescentin structures are rapid. Moreover, crescentin forms filamentous structures that are elastic, solid-like, and, like other intermediate filaments, can recover a significant portion of their network elasticity after shear. The assembly efficiency of crescentin is largely unaffected by monovalent cations (K(+), Na(+)), but is enhanced by divalent cations (Mg(2+), Ca(2+)), suggesting that the assembly kinetics and micromechanics of crescentin depend on the valence of the ions present in solution. CONCLUSIONS/SIGNIFICANCE These results indicate that crescentin forms filamentous structures that are elastic, labile, and stiff, and that their low dissociation rate from established structures controls the slow remodeling of crescentin in C. crescentus.
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Affiliation(s)
- Osigwe Esue
- Department of Pharmaceutical Development, Genentech, South San Francisco, California, United States of America.
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Eriksson JE, Dechat T, Grin B, Helfand B, Mendez M, Pallari HM, Goldman RD. Introducing intermediate filaments: from discovery to disease. J Clin Invest 2009; 119:1763-71. [PMID: 19587451 DOI: 10.1172/jci38339] [Citation(s) in RCA: 301] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
It took more than 100 years before it was established that the proteins that form intermediate filaments (IFs) comprise a unified protein family, the members of which are ubiquitous in virtually all differentiated cells and present both in the cytoplasm and in the nucleus. However, during the past 2 decades, knowledge regarding the functions of these structures has been expanding rapidly. Many disease-related roles of IFs have been revealed. In some cases, the molecular mechanisms underlying these diseases reflect disturbances in the functions traditionally assigned to IFs, i.e., maintenance of structural and mechanical integrity of cells and tissues. However, many disease conditions seem to link to the nonmechanical functions of IFs, many of which have been defined only in the past few years.
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Affiliation(s)
- John E Eriksson
- Department of Biology, Abo Akademi University, Turku, Finland.
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Colakoğlu G, Brown A. Intermediate filaments exchange subunits along their length and elongate by end-to-end annealing. ACTA ACUST UNITED AC 2009; 185:769-77. [PMID: 19468066 PMCID: PMC2711597 DOI: 10.1083/jcb.200809166] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Actin filaments and microtubules lengthen and shorten by addition and loss of subunits at their ends, but it is not known whether this is also true for intermediate filaments. In fact, several studies suggest that in vivo, intermediate filaments may lengthen by end-to-end annealing and that addition and loss of subunits is not confined to the filament ends. To test these hypotheses, we investigated the assembly dynamics of neurofilament and vimentin intermediate filament proteins in cultured cells using cell fusion, photobleaching, and photoactivation strategies in combination with conventional and photoactivatable fluorescent fusion proteins. We show that neurofilaments and vimentin filaments lengthen by end-to-end annealing of assembled filaments. We also show that neurofilaments and vimentin filaments incorporate subunits along their length by intercalation into the filament wall with no preferential addition of subunits to the filament ends, a process which we term intercalary subunit exchange.
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Affiliation(s)
- Gülsen Colakoğlu
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210, USA
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Charbon G, Cabeen MT, Jacobs-Wagner C. Bacterial intermediate filaments: in vivo assembly, organization, and dynamics of crescentin. Genes Dev 2009; 23:1131-44. [PMID: 19417107 DOI: 10.1101/gad.1795509] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Crescentin, which is the founding member of a rapidly growing family of bacterial cytoskeletal proteins, was previously proposed to resemble eukaryotic intermediate filament (IF) proteins based on structural prediction and in vitro polymerization properties. Here, we demonstrate that crescentin also shares in vivo properties of assembly and dynamics with IF proteins by forming stable filamentous structures that continuously incorporate subunits along their length and that grow in a nonpolar fashion. De novo assembly of crescentin is biphasic and involves a cell size-dependent mechanism that controls the length of the structure by favoring lateral insertion of crescentin subunits over bipolar longitudinal extension when the structure ends reach the cell poles. The crescentin structure is stably anchored to the cell envelope, and this cellular organization requires MreB function, identifying a new function for MreB and providing a parallel to the role of actin in IF assembly and organization in metazoan cells. Additionally, analysis of an MreB localization mutant suggests that cell wall insertion during cell elongation normally occurs along two helices of opposite handedness, each counterbalancing the other's torque.
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Affiliation(s)
- Godefroid Charbon
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA
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Wang N, Tytell JD, Ingber DE. Mechanotransduction at a distance: mechanically coupling the extracellular matrix with the nucleus. Nat Rev Mol Cell Biol 2009; 10:75-82. [DOI: 10.1038/nrm2594] [Citation(s) in RCA: 1267] [Impact Index Per Article: 84.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Pittenger JT, Hess JF, Budamagunta MS, Voss JC, FitzGerald PG. Identification of phosphorylation-induced changes in vimentin intermediate filaments by site-directed spin labeling and electron paramagnetic resonance. Biochemistry 2008; 47:10863-70. [PMID: 18803396 PMCID: PMC2656440 DOI: 10.1021/bi801137m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phosphorylation drives the disassembly of the vimentin intermediate filament (IF) cytoskeleton at mitosis. Chromatographic analysis has suggested that phosphorylation produces a soluble vimentin tetramer, but little has been determined about the structural changes that are caused by phosphorylation or the structure of the resulting tetramer. In this study, site-directed spin labeling and electron paramagnetic resonance (SDSL-EPR) were used to examine the structural changes resulting from protein kinase A phosphorylation of vimentin IFs in vitro. EPR spectra suggest that the tetrameric species resulting from phosphorylation is the A11 configuration. EPR spectra also establish that the greatest degree of structural change was found in the linker 2 and the C-terminal half of the rod domain, despite the fact that most phosphorylation occurs in the N-terminal head domain. The phosphorylation-induced changes notably affected the proposed "trigger sequences" located in the linker 2 region, which have been hypothesized to mediate the induction of coiled-coil formation. These data are the first to document specific changes in IF structure resulting from a physiologic regulatory mechanism and provide further evidence, also generated by SDSL-EPR, that the linker regions play a key role in IF structure and regulation of assembly/disassembly.
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Affiliation(s)
- Josh T. Pittenger
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA 95616
| | - John F. Hess
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA 95616
| | - Madhu S. Budamagunta
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA 95616
| | - John C. Voss
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, CA 95616
| | - Paul G. FitzGerald
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA 95616
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Henson FMD, Vincent TA. Alterations in the vimentin cytoskeleton in response to single impact load in an in vitro model of cartilage damage in the rat. BMC Musculoskelet Disord 2008; 9:94. [PMID: 18577232 PMCID: PMC2443134 DOI: 10.1186/1471-2474-9-94] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 06/24/2008] [Indexed: 11/10/2022] Open
Abstract
Background Animal models have provided much information on molecular and cellular changes in joint disease, particularly OA. However there are limitations to in vivo work and single tissue in vitro studies can provide more specific information on individual events. The rat is a commonly used laboratory species but at the current time only in vivo models of rat OA are available to study. The purpose of this study was to investigate the damage that single impact load (SIL) of 0.16J causes in a rat cartilage in vitro model and assess whether this load alters the arrangement of vimentin. Methods Rat cartilage was single impact loaded (200 g from 8 cm) and cultured for up to 48 hours (n = 72 joints). Histological changes were measured using a semi-quantitative modified Mankin score. Immunolocalisation was used to identify changes in vimentin distribution. Results SIL caused damage in 32/36 cartilage samples. Damage included surface fibrillation, fissures, fragmentation, changes in cellularity and loss of proteoglycan. SIL caused a statistically significant increase in modified Mankin score and chondrocyte clusters over time. SIL caused vimentin disassembly (as evidenced by collapse of vimentin around the nucleus). Conclusion This study describes a model of SIL damage to rat cartilage. SIL causes changes in histological/chemical parameters which have been measured using a semi-quantitative modified Mankin score. Single impact load also causes changes in the pattern of vimentin immunoreactivity, indicating vimentin dissassembley. Using a semi-quantitative scoring system the disassembly was shown to be statistically significant in SIL damaged cartilage. The changes described in this paper suggest that this novel single tissue rat model of joint damage is a possible candidate model to replace in vivo models.
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Affiliation(s)
- Frances M D Henson
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 0ES, UK.
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39
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Intermediate filament assembly: dynamics to disease. Trends Cell Biol 2008; 18:28-37. [PMID: 18083519 DOI: 10.1016/j.tcb.2007.11.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 10/31/2007] [Accepted: 11/01/2007] [Indexed: 11/21/2022]
Abstract
Intermediate filament (IF) proteins belong to a large and diverse gene family with broad representation in vertebrate tissues. Although considered the 'toughest' cytoskeletal fibers, studies in cultured cells have revealed that IF can be surprisingly dynamic and highly regulated. This review examines the diversity of IF assembly behaviors, and considers the ideas that IF proteins are co- or post-translationally assembled into oligomeric precursors, which can be delivered to different subcellular compartments by microtubules or actomyosin and associated motor proteins. Their interaction with other cellular elements via IF associated proteins (IFAPs) affects IF dynamics and also results in cellular networks with properties that transcend those of individual components. We end by discussing how mutations leading to defects in IF assembly, network formation or IF-IFAP association compromise in vivo functions of IF as protectors against environmental stress.
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40
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Kim S, Coulombe PA. Intermediate filament scaffolds fulfill mechanical, organizational, and signaling functions in the cytoplasm. Genes Dev 2007; 21:1581-97. [PMID: 17606637 DOI: 10.1101/gad.1552107] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Intermediate filaments (IFs) are cytoskeletal polymers whose protein constituents are encoded by a large family of differentially expressed genes. Owing in part to their properties and intracellular organization, IFs provide crucial structural support in the cytoplasm and nucleus, the perturbation of which causes cell and tissue fragility and accounts for a large number of genetic diseases in humans. A number of additional roles, nonmechanical in nature, have been recently uncovered for IF proteins. These include the regulation of key signaling pathways that control cell survival, cell growth, and vectorial processes including protein targeting in polarized cellular settings. As this discovery process continues to unfold, a rationale for the large size of this family and the context-dependent regulation of its members is finally emerging.
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Affiliation(s)
- Seyun Kim
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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41
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Chou YH, Flitney FW, Chang L, Mendez M, Grin B, Goldman RD. The motility and dynamic properties of intermediate filaments and their constituent proteins. Exp Cell Res 2007; 313:2236-43. [PMID: 17498691 DOI: 10.1016/j.yexcr.2007.04.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Revised: 04/01/2007] [Accepted: 04/05/2007] [Indexed: 12/13/2022]
Abstract
Intermediate filament (IF) proteins exist in multiple structural forms within cells including mature IF, short filaments or 'squiggles', and non-filamentous precursors called particles. These forms are interconvertible and their relative abundance is IF type, cell type- and cell cycle stage-dependent. These structures are often associated with molecular motors, such as kinesin and dynein, and are therefore capable of translocating through the cytoplasm along microtubules. The assembly of mature IF from their precursor particles is also coupled to translation. These dynamic properties of IF provide mechanisms for regulating their reorganization and assembly in response to the functional requirements of cells. The recent findings that IF and their precursors are frequently associated with signaling molecules have revealed new functions for IF beyond their more traditional roles as mechanical integrators of cells and tissues.
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Affiliation(s)
- Ying-Hao Chou
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA
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Kuczmarski ER, Goldman RD. Preparation and Microinjection of x-Rhodamine-Labeled Vimentin. Cold Spring Harb Protoc 2007; 2007:pdb.prot4676. [PMID: 21357022 DOI: 10.1101/pdb.prot4676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTIONIntermediate filaments (IF) are major cytoskeletal systems of vertebrate and many nonvertebrate cells whose expression is cell-type specific and developmentally regulated. This protocol describes the x-rhodamine labeling of one type of IF, vimentin, and a method for microinjection of the labeled vimentin into cultured cells. IF dynamics can then be examined with fluorescence microscopy.
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Pekny M, Wilhelmsson U, Bogestål YR, Pekna M. The role of astrocytes and complement system in neural plasticity. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2007; 82:95-111. [PMID: 17678957 DOI: 10.1016/s0074-7742(07)82005-8] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In neurotrauma, brain ischemia or neurodegenerative diseases, astrocytes become reactive (which is known as reactive gliosis) and this is accompanied by an altered expression of many genes. Two cellular hallmarks of reactive gliosis are hypertrophy of astrocyte processes and the upregulation of the part of the cytoskeleton known as intermediate filaments, which are composed of nestin, vimentin, and GFAP. Our aim has been to better understand the function of reactive astrocytes in CNS diseases. Using mice deficient for astrocyte intermediate filaments (GFAP(-/-)Vim(-/-)), we were able to attenuate reactive gliosis and slow down the healing process after neurotrauma. We demonstrated the key role of reactive astrocytes in neurotrauma-at an early stage after neurotrauma, reactive astrocytes have a neuroprotective effect; at a later stage, they facilitate the formation of posttraumatic glial scars and inhibit CNS regeneration, specifically, they seem to compromise neural graft survival and integration, reduce the extent of synaptic regeneration, inhibit neurogenesis in the old age, and inhibit regeneration of severed CNS axons. We propose that reactive astrocytes are the future target for the therapeutic strategies promoting regeneration and plasticity in the brain and spinal cord in various disease conditions. Through its involvement in inflammation, opsonization, and cytolysis, complement protects against infectious agents. Although most of the complement proteins are synthesized in CNS, the role of the complement system in the normal or ischemic CNS remains unclear. Complement activiation in the CNS has been generally considered as contributing to tissue damage. However, growing body of evidence suggests that complement may be a physiological neuroprotective mechanism as well as it may participate in maintenance and repair of the adult brain.
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Affiliation(s)
- Milos Pekny
- Center for Brain Repair and Rehabilitation, Department of Clinical Neuroscience and Rehabilitation, Institute for Neuroscience and Physiology at Sahlgrenska Academy Göteborg University, 405 30 Göteborg, Sweden
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Norlén L. Stratum corneum keratin structure, function and formation - a comprehensive review. Int J Cosmet Sci 2006; 28:397-425. [DOI: 10.1111/j.1467-2494.2006.00345.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Styers ML, Kowalczyk AP, Faundez V. Architecture of the vimentin cytoskeleton is modified by perturbation of the GTPase ARF1. J Cell Sci 2006; 119:3643-54. [PMID: 16912072 DOI: 10.1242/jcs.03147] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intermediate filaments are required for proper membrane protein trafficking. However, it remains unclear whether perturbations in vesicular membrane transport result in changes in the architecture of the vimentin cytoskeleton. We find that treatment of cells with Brefeldin A, an inhibitor of specific stages of membrane transport, causes changes in the organization of vimentin filaments. These changes arise from movement of pre-existing filaments. Brefeldin A treatment also leads to alterations in the microtubule cytoskeleton. However, this effect is not observed in cells lacking intermediate filaments, indicating that microtubule bundling is downstream of perturbations in the vimentin cytoskeleton. Brefeldin A-induced changes in vimentin architecture are probably mediated through its effects on ADP-ribosylation factor 1 (ARF1). Expression of a dominant-negative mutant of ARF1 induces BFA-like modifications in vimentin morphology. The BFA-dependent changes in vimentin architecture occurred concurrently with the release of the ARF1-regulated adaptor complexes AP-3 and AP-1 from membranes and adaptor redistribution to vimentin networks. These observations indicate that perturbation of the vesicular membrane transport machinery lead to reciprocal changes in the architecture of vimentin networks.
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Affiliation(s)
- Melanie L Styers
- Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University, Atlanta, GA 30322, USA
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Friedland DR, Popper P, Eernisse R, Ringger B, Cioffi JA. Differential expression of cytoskeletal genes in the cochlear nucleus. ACTA ACUST UNITED AC 2006; 288:447-65. [PMID: 16550590 PMCID: PMC2570442 DOI: 10.1002/ar.a.20303] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The relationship between structure and function is clearly illustrated by emerging evidence demonstrating the role of the neuronal cytoskeleton in physiological processes. For example, alterations in axonal caliber, a feature of the cytoskeleton, have been shown to affect reflex arc latencies and are prominent features of several neuropathological disorders. Even in the nonpathologic situation, however, axonal diameter may be a crucial element for the normal function of specialized auditory neurons. To investigate this relationship, we used serial analysis of gene expression and microarray analyses to characterize the expression of cytoskeletal genes in the central auditory system. These data, confirmed by real-time RT-PCR, identified differential expression of intermediate neurofilament transcripts (i.e., Nefh, Nef3, and Nfl) among the subdivisions of the cochlear nucleus. In situ hybridization was used to identify specific classes of neurons within the cochlear nucleus expressing these neurofilament genes. Robust neurofilament expression was seen in bushy cells and cochlear nerve root neurons, suggesting an association between cytoskeletal structure and rapid conduction velocities. Gene expression data were also identified for other classes of cytoskeletal and structural genes important in neuronal function. These results may help to explain some causes of hearing loss in hereditary neuropathies and provide an anatomic basis for understanding normal neuronal function in the central auditory system.
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Affiliation(s)
- David R Friedland
- Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
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47
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Yamaguchi A, Katsu Y, Matsuyama M, Yoshikuni M, Nagahama Y. Phosphorylation of the p34(cdc2) target site on goldfish germinal vesicle lamin B3 before oocyte maturation. Eur J Cell Biol 2006; 85:501-17. [PMID: 16600424 DOI: 10.1016/j.ejcb.2006.02.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2005] [Revised: 02/07/2006] [Accepted: 02/08/2006] [Indexed: 10/24/2022] Open
Abstract
The nuclear membranes surrounding fish and frog oocyte germinal vesicles (GVs) are supported by the lamina, an internal, mesh-like structure that consists of the protein lamin B3. The mechanisms by which lamin B3 is transported into GVs and is assembled to form the nuclear lamina are not well understood. In this study, we developed a heterogeneous microinjection system in which wild-type or mutated goldfish GV lamin B3 (GFLB3) was expressed in Escherichia coli, biotinylated, and microinjected into Xenopus oocytes. The localization of the biotinylated GFLB3 was visualized by fluorescence confocal microscopy. The results of these experiments indicated that the N-terminal domain plays important roles in both nuclear transport and assembly of lamin B3 to form the nuclear lamina. The N-terminal domain includes a major consensus phosphoacceptor site for the p34(cdc2) kinase at amino acid residue Ser-28. To investigate nuclear lamin phosphorylation, we generated a monoclonal antibody (C7B8D) against Ser-28-phosphorylated GFLB3. Two-dimensional (2-D) electrophoresis of GV protein revealed two major spots of lamin B3 with different isoelectric points (5.9 and 6.1). The C7B8D antibody recognized the pI-5.9 spot but not the pI-6.1 spot. The former spot disappeared when the native lamina was incubated with lambda phage protein phosphatase (lambda-PP), indicating that a portion of the lamin protein was already phosphorylated in the goldfish GV-stage oocytes. GFLB3 that had been microinjected into Xenopus oocytes was also phosphorylated in Xenopus GV lamina, as judged by Western blotting with C7B8D. Thus, lamin phosphorylation appears to occur prior to oocyte maturation in vivo in both these species. Taken together, our results suggest that the balance between phosphorylation by interphase lamin kinases and dephosphorylation by phosphatases regulates the conformational changes in the lamin B3 N-terminal head domain that in turn regulates the continual in vivo rearrangement and remodeling of the oocyte lamina.
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Affiliation(s)
- Akihiko Yamaguchi
- Laboratory of Marine Biology, Department of Animal and Marine Bioresource Sciences, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Higashi-Ku, Fukuoka 812-8581, Japan.
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Yang J, Gao J, Adamian M, Wen XH, Pawlyk B, Zhang L, Sanderson MJ, Zuo J, Makino CL, Li T. The ciliary rootlet maintains long-term stability of sensory cilia. Mol Cell Biol 2005; 25:4129-37. [PMID: 15870283 PMCID: PMC1087714 DOI: 10.1128/mcb.25.10.4129-4137.2005] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The striated ciliary rootlet is a prominent cytoskeleton originating from basal bodies of ciliated cells. Although a familiar structure in cell biology, its function has remained unresolved. In this study, we carried out targeted disruption in mice of the gene for rootletin, a component of the rootlet. In the mutant, ciliated cells are devoid of rootlets. Phototransduction and ciliary beating in sensory and motile cilia initially exhibit no apparent functional deficits. However, photoreceptors degenerate over time, and mutant lungs appear prone to pathological changes consistent with insufficient mucociliary clearance. Further analyses revealed a striking fragility at the ciliary base in photoreceptors lacking rootlets. In vitro assays suggest that the rootlet is among the least dynamic of all cytoskeletons and interacts with actin filaments. Thus, a primary function of the rootlet is to provide structural support for the cilium. Inasmuch as photoreceptors elaborate an exceptionally enlarged sensory cilium, they are especially dependent on the rootlet for structural integrity and long-term survival.
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Affiliation(s)
- Jun Yang
- The Berman-Gund Laboratory for the Study of Retinal Degenerations, Howe Laboratory, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA
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Norlén L, Al-Amoudi A. Stratum corneum keratin structure, function, and formation: the cubic rod-packing and membrane templating model. J Invest Dermatol 2004; 123:715-32. [PMID: 15373777 DOI: 10.1111/j.0022-202x.2004.23213.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new model for stratum corneum keratin structure, function, and formation is presented. The structural and functional part of the model, which hereafter is referred to as "the cubic rod-packing model", postulates that stratum corneum keratin intermediate filaments are arranged according to a cubic-like rod-packing symmetry with or without the presence of an intracellular lipid membrane with cubic-like symmetry enveloping each individual filament. The new model could account for (i) the cryo-electron density pattern of the native corneocyte keratin matrix, (ii) the X-ray diffraction patterns, (iii) the swelling behavior, and (iv) the mechanical properties of mammalian stratum corneum. The morphogenetic part of the model, which hereafter is referred to as "the membrane templating model", postulates the presence in cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. The new model could account for (i) the cryo-electron density patterns of the native keratinocyte cytoplasmic space, (ii) the characteristic features of the keratin network formation process, (iii) the dynamic properties of keratin intermediate filaments, (iv) the close lipid association of keratin, (v) the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and (vi) the measured reduction in cell volume and hydration level between the stratum granulosum and stratum corneum. Further, using cryo-transmission electron microscopy on native, fully hydrated, vitreous epidermis we show that the subfilametous keratin electron density pattern consists, both in corneocytes and in viable keratinocytes, of one axial subfilament surrounded by an undetermined number of peripheral subfilaments forming filaments with a diameter of approximately 8 nm.
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Affiliation(s)
- Lars Norlén
- Group of Applied Physics-Biomedical, Department of Physics, University of Geneva, Geneva, Switzerland.
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Abstract
Intermediate filaments, actin-containing microfilaments and microtubules are the three main cytoskeletal systems of vertebrate and many invertebrate cells. Although these systems are composed of distinctly different proteins, they are in constant and intimate communication with one another. Understanding the molecular basis of this cytoskeletal crosstalk is essential for determining the mechanisms that underlie many cell-biological phenomena. Recent studies have revealed that intermediate filaments and their associated proteins are important components in mediating this crosstalk.
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Affiliation(s)
- Lynne Chang
- Feinberg School of Medicine, Northwestern University, Department of Cell and Molecular Biology, 303 East Chicago Avenue, Chicago, Illinois 60611, USA.
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