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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 181-194 
    ISSN: 0886-1544
    Keywords: desmosomes ; keratinocytes ; tumor cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In cultured human keratinocytes (NHEK) maintained in medium containing low levels of Ca2+ (0.04 mM) desmoplakin is a component of certain electron-dense bodies in the cytoplasm. These bodies are associated with bundles of intermediate filaments. Upon elevation of the level of Ca2+ in the culture medium to 1.2 mM, desmoplakin first appears at sites of cell - cell contact in association with bundles of intermediate filaments. Subsequently, desmoplakin becomes incorporated into desmosomes in a manner comparable to that seen in mouse keratinocytes (Jones and Goldman: Journal of Cell Biology 101:506-517, 1985). NHEK cells maintained for 24 hr at Ca2+ concentrations between 0.04 mM and 0.18 mM were processed for immunofluorescence, immunoelectron, and conventional electron microscopical analysis. In NHEK cells grown at Ca2+ concentrations of 0.11 mM, desmoplakin appears to be localized in electron-dense bodies associated with intermediate filaments at sites of cell - cell contact in the absence of formed desmosomes. At a Ca2+ concentration of 0.13 mM desmoplakin is arrayed like beads on a “string” of intermediate filaments at areas of cell - cell association. At 0.15 mM, desmosome formation occurs, and desmoplakin is associated with the desmosomal plaque. In basal cell carcinoma cells desmoplakin is not restricted to desmosomes but also occurs in certain electron-dense bodies morphologically similar to those seen in NHEK maintained in low levels of Ca2+ and during early stages of desmosome assembly. We discuss the possibility of “cycling” of desmoplakin through these bodies in proliferative cells.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 560-569 
    ISSN: 0886-1544
    Keywords: hemidesmosome ; desmosome ; cell junction ; autoantibodies ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although the mammalian epidermal basal cell hemidesmosome bears some superficial resemblance to one half of a desmosome at the ultrastructural level, examination of the structure of the electron-dense submembranous plaques of the hemidesmosome and desmosome reveals that they differ with respect to their overall morphology and dimensions. Based on these findings, we wondered whether components of the desmosome are present in the hemidesmosome. In order to determine this we prepared a number of stratified squamous epithelial tissues for indirect immunofluorescence using antibody preparations directed against known desmosome components including desmoplakin and certain glycoproteins. These antibody preparations do not show reaction with hemidesmosomes by indirect immunofluorescence criteria. We have also utilized bullous pemphigoid (BP) autoantibodies that have been shown to recognize hemidesmosomes in mammalian skin cells [Mutasim et al., J. Invest. Derm., 84:47-53, 1985]. Double label indirect immunofluorescence observations of neonatal mouse skin prepared using desmoplakin antibodies and BP autoantibodies reveal that hemidesmosomes that are stained by the BP autoantibodies are not recognized by the desmoplakin antibodies. We confirmed these findings at the ultrastructural level by indirect immunogold localization of desmoplakin antibodies and BP autoantibodies. Therefore, the hemidesmosome does not appear to be one half of a desmosome and may possess a very different molecular organization relative to the desmosome. We raise the possibility that the variability between the hemidesmosome and desmosome that we detect at the morphological and immunological level may reflect the functional differences of these two types of junctions.
    Additional Material: 8 Ill.
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  • 3
    ISSN: 0886-1544
    Keywords: intermediate filament ; desmosomes ; epidermal keratinocytes ; nuclear envelope ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have shown, by indirect immunofluorescence microscopy using an antiserum against the mouse keratin subunit K2 and by electron microscopy, that transformed (PAM) and primary (PME) mouse epidermal cells possess extensive net works of IF bundles. Following trypsinization and replating of PAM cells, IF bundles are seen to move as a continuous net work from a perinuclear zone into the peripheral cytoplasmic regions. In PAM cells lysed in high-ionic-strength solutions containing Triton ×-100 and DNAase-1, IF bundles appear to be closely associated with nuclear envelope remnants and, in some cases, appear to be attached to nuclear pore complexes. PME cells cultivated in low Ca2+-containing medium possess perinuclear birefringent arrays of IF bundles. Within 2 hours of switching the cells to normal Ca2+ levels, the PME IF bundle network moves towards and establishes contact with the cell surface as desmosomes form. Live cells observed by phase contrast and fixed cells observed by immunofluorescence microscopy demonstrate that desmosomes can be distinguished as dark bands separating neighboring cells. There is little difference between the major proteins seen in SDS-polyacrylamide gel profiles of isolated IF bundle net works from PME cells before and after the Ca2+ switch. Therefore, a reorganization of relatively insoluble membrane-associated protein following the Ca2+ switch may be involved in desmosome formation. The isolated IF networks from PAM cells differ in protein composition compared to the PME IF networks. This may be related to the greatly reduced number of desmosomes in PAM cells. The IF bundle system in epidermal cells appears to be involved in shape formation, shape maintenance, the establishment of desmosomes, nuclear centration, and cell-cell contact.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 36 (1988), S. 223-236 
    ISSN: 0730-2312
    Keywords: desmosomes ; bovine epithelial tissue ; fractionation ; polypeptide composition ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Desmosomes isolated from bovine tongue mucosa or muzzle epidermis appeared identical by ultrastructural analyses but had some differences in their polypeptide compositions as determined by SDS-PAGE. These preparations were extracted in 9 M urea, 10 mM Tris-HCl (pH 9), and 25 mM B-mercaptoethanol and then centrifuged at 240,000g for 30 min. The urea-soluble and insoluble fractions were analyzed by SDS-PAGE. The urea soluble fractions of both tongue and muzzle desmosomes were enriched in polypeptides of 240, 210, 81, and 75 kDa and also polypeptides (40 to 70 kDa) that were keratin-like, as determined by immunoblotting analyses with keratin antisera. The urea insoluble fraction of tongue desmosomes contained glycoproteins of 165, 160, 140, 110, and 100 kDa, while this fraction from muzzle contained glycoproteins of 165, 115, and 105 kDa. Ultrastructural examinations of insoluble pellets obtained from urea extracted tongue and muzzle desmosomes showed that most of the components at the cytoplasmic faces of the desmosomes were removed, while the membrane regions of the desmosomes resisted the treatment. The urea soluble proteins were dialyzed against 10 mM Tris-HCl (pH 7.6), and the resulting preparation was pelleted by centrifugation and examined by electron microscopy. Ultrastructural examination of this material revealed that it had assembled into a fibrillar meshwork, similar to the fibrillar region adjacent to the submembranous plaque of isolated desmosomes. Thus, treatment of isolated desmosomes with 9 M urea allowed the fractionation of membrane-associated desmosomal proteins from cytoplasmic desmosomal proteins. A comparison of these fractions from tongue and muzzle indicated that the polypeptide compositions of the desmosomes varied between tissues, especially with respect to the fractions enriched in either glycoproteins or keratin.
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  • 5
  • 6
    Publication Date: 1988-03-01
    Print ISSN: 0730-2312
    Electronic ISSN: 1097-4644
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Published by Wiley
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  • 7
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