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  • CELL  (33)
  • 1
    Keywords: BIOLOGY ; ARCHITECTURE ; cytoskeleton ; PROTEIN ; CELL ; MICROSCOPY ; intermediate filament ; AMINO-ACID-SEQUENCE ; CROSS-LINKING ; review ; DESMIN ; ROD DOMAIN ; HUMAN VIMENTIN ; KERATIN FILAMENTS ; RAY SOLUTION SCATTERING ; SWITZERLAND ; COILED-COIL
    Type of Publication: Book chapter
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  • 2
    Keywords: CELLS ; EXPRESSION ; IN-VITRO ; CELL ; human ; IN-VIVO ; VITRO ; VIVO ; NETWORK ; GENE ; PROTEIN ; PROTEINS ; TIME ; INFECTION ; RAT ; CONTRAST ; STAGE ; DISRUPTION ; MUTATION ; MUTATIONS ; MUSCLE ; ASSEMBLY PROPERTIES ; SERIES ; GREEN FLUORESCENT PROTEIN ; ORGANIZATION ; ADENOVIRUS ; ALPHA-B-CRYSTALLIN ; DILATED CARDIOMYOPATHY ; EPIDERMOLYSIS-BULLOSA SIMPLEX ; INTERMEDIATE-FILAMENT PROTEINS ; MICE LACKING DESMIN ; MUSCULAR-DYSTROPHY ; SKELETAL MYOPATHY ; SMOOTH-MUSCLE ; Z-DISCS
    Abstract: Mutations in desmin have been associated with a subset of human myopathies. Symptoms typically appear in the second to third decades of life, but in the most severe cases can manifest themselves earlier. How desmin mutations lead to aberrant muscle function, however, remains poorly defined. We created a series of four mutations in rat desmin and tested their in vitro filament assembly properties. RDM-G, a chimera between desmin and green fluorescent protein, formed protofilament-like structures in vitro. RDM-1 and RDM-2 blocked in vitro assembly at the unit-length filament stage, while RDM-3 had more subtle effects on assembly. When expressed in cultured rat neonatal cardiac myocytes via adenovirus infection, these mutant proteins disrupted the endogenous desmin filament to an extent that correlated with their defects in in vitro assembly properties. Disruption of the desmin network by RDM-1 was also associated with disruption of plectin, myosin, and a-actinin organization in a significant percentage of infected cells. In contrast, expression of RDM-2, which is similar to previously characterized human mutant desmins, took longer to disrupt desmin and plectin organization and had no significant effect on myosin or alpha-actinin organization over the 5-day time course of our studies. RDM-3 had the mildest effect on in vitro assembly and no discernable effect on either desmin, plectin, myosin, or a-actinin organization in vivo. These results indicate that mutations in desmin have both direct and indirect effects on the cytoarchitecture of cardiac myocytes
    Type of Publication: Journal article published
    PubMed ID: 12529857
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  • 3
    Keywords: CELL ; Germany ; human ; DISEASE ; DISEASES ; DISTINCT ; GENE ; PROTEIN ; PROTEINS ; INTERMEDIATE-SIZED FILAMENTS ; IMPACT ; BIOLOGY ; NUMBER ; MUTATION ; MUTATIONS ; US ; cytoskeleton ; intermediate filaments ; vimentin ; DE-NOVO ; ALPHA-B-CRYSTALLIN ; MICE LACKING DESMIN ; HUMAN-DISEASE ; ARCHITECTURE ; intermediate filament ; CHICKEN SKELETAL-MUSCLE ; desmin-related myopathy ; desminopathy ; filament assembly ; HEAD DOMAIN ; IMMUNOCYTOCHEMICAL ANALYSIS ; MYOFIBRILLAR MYOPATHY ; RESTRICTIVE CARDIOMYOPATHY ; VERTEBRATE SMOOTH-MUSCLE
    Abstract: Desmin, the major intermediate filament (IF) protein of muscle, is evolutionarily highly conserved from shark to man. Recently, an increasing number of mutations of the desmin gene has been described to be associated with human diseases such as certain skeletal and cardiac myopathies. These diseases are histologically characterised by intracellular aggregates containing desmin and various associated proteins. Although there is progress regarding our knowledge on the cellular function of desmin within the cytoskeleton, the impact of each distinct mutation is currently not understood at all. In order to get insight into how such mutations affect filament assembly and their integration into the cytoskeleton we need to establish IF structure at atomic detail. Recent progress in determining the dimer structure of the desmin-related IF-protein vimentin allows us to assess how such mutations may affect desmin filament architecture. (C) 2004 Elsevier Inc. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 15477095
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  • 4
    Keywords: EXPRESSION ; CELL ; Germany ; IN-VIVO ; MECHANISM ; mechanisms ; cytoskeleton ; MICROTUBULES ; intermediate filaments ; INTERMEDIATE-FILAMENTS ; LIVING CELLS ; REVEALS ; ATOMIC-FORCE MICROSCOPY ; intermediate filament ; MOLECULAR-MECHANISM ; HUMAN HAIR KERATINS ; HUMAN VIMENTIN ; NUCLEAR LAMINA ; PROTEIN-FOLDING MOTIF ; TAIL DOMAIN
    Type of Publication: Journal article published
    PubMed ID: 15501448
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  • 5
    Keywords: brain ; ENVIRONMENT ; CELLS ; IN-VITRO ; CELL ; human ; IN-VIVO ; MICROSCOPY ; MODEL ; VITRO ; VIVO ; NETWORKS ; PROTEIN ; PROTEINS ; TISSUE ; murine ; REDUCTION ; RAT ; SKIN ; IDENTIFICATION ; MUTATION ; FIBER ; MUTATIONS ; LENGTH ; intermediate filaments ; INTERMEDIATE-FILAMENTS ; keratin ; vimentin ; LIVING CELLS ; ATOMIC-FORCE MICROSCOPY ; BEHAVIOR ; INSIGHTS ; intermediate filament ; SINGLE ; RECOMBINANT ; PROTOCOL ; DESMIN ; SWITZERLAND ; LEVEL ; INTERMEDIATE ; PERSISTENCE ; function ; AFM ; ALPHA-KERATIN FIBERS ; HAGFISH SLIME THREADS ; MECHANICAL-BEHAVIOR ; neurofilament ; stretching ; EUKARYOTIC CELLS ; NEUROFILAMENTS
    Abstract: Intermediate filaments (IFs) are structural elements of eukaryotic cells with distinct mechanical properties. Tissue integrity is severely impaired, in particular in skin and muscle, when IFs are either absent or malfunctioning due to mutations. Our knowledge on the mechanical properties of IFs is mainly based on tensile testing of macroscopic fibers and on the rheology of IF networks. At the single filament level, the only piece of data available is a measure of the persistence length of vimentin IFs. Here, we have employed an atomic force microscopy (AFM) based protocol to directly probe the mechanical properties of single cytoplasmic IFs when adsorbed to a solid support in physiological buffer environment. Three IF types were studied in vitro: recombinant murine desmin, recombinant human keratin K5/K14 and neurofilaments isolated from rat brains, which are composed of the neurofilament triplet proteins NF-L, NF-M and NF-H. Depending on the experimental conditions, the AFM tip was used to laterally displace or to stretch single IFs on the support they had been adsorbed to. Upon applying force, IFs were stretched on average 2.6-fold. The maximum stretching that we encountered was 3.6-fold. A large reduction of the apparent filament diameter was observed concomitantly. The observed mechanical properties therefore suggest that IFs may indeed function as mechanical shock absorbers in vivo.
    Type of Publication: Journal article published
    PubMed ID: 16257415
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  • 6
    Keywords: CELL ; RNA ; STAGE ; NUCLEUS ; ORGANIZATION ; nuclear envelope ; CHROMOSOMES ; LIFE ; RNA processing ; nuclear dynamics ; nuclear structure and disease
    Type of Publication: Journal article published
    PubMed ID: 17068488
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  • 7
    Keywords: CELLS ; IN-VITRO ; CELL ; human ; MICROSCOPY ; MODEL ; MODELS ; PATHWAY ; VITRO ; DISEASE ; DISTINCT ; PROTEIN ; PROTEINS ; mechanisms ; DYNAMICS ; polymorphism ; OLIGOMERS ; cytoskeleton ; intermediate filaments ; INTERMEDIATE-FILAMENTS ; vimentin ; REVEALS ; DIMER ; electron microscopy ; intermediate filament ; ELECTRON-MICROSCOPY ; assembly ; PH ; HUMAN VIMENTIN ; analytical ultracentrifugation ; KERATIN FILAMENTS ; BIOLOGICAL MACROMOLECULES ; DIMERS ; AXES ; ADJACENT ; FILAMENTS ; 3D structure
    Abstract: intermediate filaments (IF's), along with microtubules, microfilaments, and associated cross-bridging proteins, constitute the cytoskeleton of metazoan cells. While crystallographic data on the dimer representing the elementary IF "building block" have recently become available, little structural detail is known about both the mature IF architecture and its assembly pathway. Here, we have applied solution small-angle x-ray scattering to investigate the in vitro assembly of a 53-kDa human IF protein vimentin at pH 8.4 by systematically varying the ionic strength conditions, and complemented these experiments by electron microscopy and analytical ultracentrifugation. While a vimentin solution in 5 mM Tris(.)HCl (pH 8.4) contains predominantly tetramers, addition of 20 mM NaCl induces further lateral assembly evidenced by the shift of the sedimentation coeficient and yields a distinct octameric intermediate. Four octamers eventually associate into unit-length filaments (ULFs) that anneal longitudinally. Based on the small-angle x-ray scattering experiments supplemented by crystallographic data and additional structural constraints, 3D molecular models of the vimentin tetramer, octamer, and ULF were constructed. Within each of the three oligomers, the adjacent dimers are aligned exclusively in an approximately half-staggered antiparallel A(11) mode with a distance of 3.2-3.4 nm between their axes. The ULF appears to be a dynamic and a relatively loosely packed structure with a roughly even mass distribution over its cross-section
    Type of Publication: Journal article published
    PubMed ID: 17050693
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  • 8
    Keywords: CELLS ; IN-VITRO ; CELL ; COMBINATION ; PROTEIN ; PROTEINS ; DIFFERENTIATION ; TISSUE ; COMPLEX ; COMPLEXES ; FAMILY ; primary ; DOMAIN ; TISSUES ; BIOLOGY ; MEMBER ; MEMBERS ; polymorphism ; ELEMENT ; PATTERNS ; ELEMENTS ; NUCLEUS ; CRYSTAL-STRUCTURE ; MUSCLE ; STABILITY ; tomography ; intermediate filaments ; INTERMEDIATE-FILAMENTS ; Jun ; keratin ; vimentin ; epidermis ; DIMER ; ATOMIC-STRUCTURE ; intermediate filament ; molecular ; ONCOLOGY ; PROGRAM ; review ; RE ; FAMILIES ; PATTERN ; ELECTRON-MICROSCOPY ; assembly ; COILED-COIL ; EPIDERMAL KERATIN FILAMENTS ; ROD DOMAIN ; analysis ; methods ; LONG ; USA ; FILAMENTS ; STEM ; modeling ; X-RAY ; SHAPE ; cryo-electron tomography ; FIBROUS PROTEINS ; HELICAL COILED COILS ; IV ALPHA-INTERNEXIN ; PLASTICITY ; small-angle X-ray scattering ; TRICHOCYTE KERATIN
    Abstract: Intermediate filaments (IFs) represent one of the prominent cytoskeletal elements of metazoan cells. Their constituent proteins are coded by a multigene family, whose members are expressed in complex patterns that are controlled by developmental programs of differentiation. Hence, IF proteins found in epidermis differ significantly from those in muscle or neuronal tissues. Due to their fibrous nature, which stems from a fairly conserved central alpha-helical coiled-coil rod domain, IF proteins have long resisted crystallization and thus determination of their atomic structure. Since they represent the primary structural elements that determine the shape of the nucleus and the cell more generally, a major challenge is to arrive at a more rational understanding of how their nanomechanical properties effect the stability and plasticity of cells and tissues. Here, we review recent structural results of the coiled-coil dimer, assembly intermediates and growing filaments that have been obtained by a hybrid methods approach involving a rigorous combination of X-ray crystallography, small angle X-ray scattering, cryo-electron tomography, computational analysis and molecular modeling. (c) 2007 Elsevier Inc. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 17521629
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  • 9
    Keywords: CELLS ; IN-VITRO ; CELL ; VITRO ; NETWORK ; NETWORKS ; PROTEIN ; PROTEINS ; MECHANISM ; DOMAIN ; BIOLOGY ; VARIANTS ; ACID ; STRESS ; LENGTH ; cytoskeleton ; vimentin ; AMINO-ACIDS ; ATOMIC-FORCE MICROSCOPY ; BEHAVIOR ; DOMAINS ; ORIGIN ; VARIANT ; SCIENCE ; F-ACTIN ; PERSISTENCE ; ELASTICITY ; amino acids ; VISCOELASTIC PROPERTIES ; rheology ; BIOPOLYMER NETWORKS ; ACTIN SOLUTIONS ; cell mechanics ; DEFICIENT CELLS ; FLUORESCENT INDICATOR MAG-INDO-1
    Abstract: Intermediate filament networks in the cytoplasm and nucleus are critical for the mechanical integrity of metazoan cells. However, the mechanism of crosslinking in these networks and the origins of their mechanical properties are not understood. Here, we study the elastic behavior of in vitro networks of the intermediate filament protein vimentin. Rheological experiments reveal that vimentin networks stiffen with increasing concentrations of Ca2+ and Mg2+, showing that divalent cations act as crosslinkers. We quantitatively describe the elastic response of vimentin networks over five decades of applied stress using a theory that treats the divalent cations as crosslinkers: at low stress, the behavior is entropic in origin, and increasing stress pulls out thermal fluctuations from single filaments, giving rise to a nonlinear response; at high stress, enthalpic stretching of individual filaments significantly modifies the nonlinearity. We investigate the elastic properties of networks formed by a series of protein variants with stepwise tail truncations and find that the last 11 amino acids of the C-terminal tail domain mediate crosslinking by divalent ions. We determined the single-filament persistence length, l(P) approximate to 0.5 mu m, and Young's modulus, Y approximate to 9 MPa; both are consistent with literature values. Our results provide insight into a crosslinking mechanism for vimentin networks and suggest that divalent ions may help regulate the cytoskeletal structure and mechanical properties of cells. (C) 2010 Elsevier Ltd. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 20447406
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  • 10
    Keywords: CELL ; MODEL ; MODELS ; intermediate filaments ; DNA-REPLICATION ; BUILDING-BLOCKS ; chromatin,coiled coils,filament assembly,lamina,lamina-associated proteins,laminopathy,nuclear membr ; DREIFUSS MUSCULAR-DYSTROPHY ; HUMAN-DISEASE ; lamin ; LEM DOMAIN ; MEMBRANE PROTEIN ; PARTIAL LIPODYSTROPHY ; PORE COMPLEXES ; RETINOBLASTOMA GENE-PRODUCT ; TRANSCRIPTIONAL REPRESSION
    Type of Publication: Journal article published
    PubMed ID: 14504651
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