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Relationship between intermediate filaments and microfilaments in cultured fibroblasts: Evidence for common foci during cell spreading (1986)

Green, Kathleen J. ; Talian, John C. ; Goldman, Robert D.

New York, NY : Wiley-Blackwell

Cell Motility and the Cytoskeleton 6 (1986), S. 406-418

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ISSN: 0886-1544

Keywords: Intermediate filaments ; microfilaments fibroblast cell spreading ; focal center ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Spreading and fully spread chick embryo fibroblasts (CEF) were examined by double-label fluorescence microscopy using the actin-specific probe rhodamine-phalloidin and an antibody directed against CEF intermediate filaments (IF). During midspreading, a striking relationship became discernible: statistical analysis showed that approximately half of the cell population exhibited one or more phase-dense, phalloidin-binding nodules that appeared to act as foci from which IF diverged. Coincidence between actin-containing structures and IF was not limited to these centers; IF could also frequently be seen running in close parallel arrays with stress fibers.Ultrastructural analysis confirmed the presence of non-membrane-bound out-pocketings along the length of stress fibers from which 10-nm IF diverged. These structures varied in size and shape, and displayed a dense, fine fibrillar appearance. IF and microfilaments (MF) were distinguished by size and by decoration of MF with myosin subfragment-1. Other IF-MF interactions were seen in cells of all stages: IF were observed to loop through stress fibers, most frequently at the cell margins. In colchicine-treated cells, IF became redistributed into cables that often ran parallel and appeared to merge with stress fibers. Cytochalasin D-treated CEF exhibited loose aggregates of actin-containing material that appeared to be associated with IF.These results suggest the possibility of an interaction between actin-containing structures and IF, particularly during cell spreading in cultured fibroblasts.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/cm.970060406

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Evidence for an interaction between the cell surface and intermediate filaments in cultured fibroblasts (1986)

Green, Kathleen J. ; Goldman, Robert D.

New York, NY : Wiley-Blackwell

Cell Motility and the Cytoskeleton 6 (1986), S. 389-405

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ISSN: 0886-1544

Keywords: cell membrane complex ; extracellular matrix ; fibronectin ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Intermediate filaments (IF) were found in close proximity to the plasma membrane in substrate attached baby hamster kidney cells (BHK-21) and chick embryo fibroblasts (CEF) as well as cells removed from their substrate in the absence of trypsin. However, in cells removed with trypsin, it appeared that IF had retracted away from the membrane. In cells with abundant extracellular matrix (ECM), colchicine induced massive cables of IF, which appeared to interact with specialized areas of the inner plasma membrane. In cells lysed to extract most microfilaments and cytoplasmic constituents, the intact IF network which remained was closely associated with the ECM. From these ultrastructural observations it was concluded that IF interact in some way with a “cell membrane complex” defined as comprising the plasma membrane and molecules attached to its inner and outer surfaces.In order to investigate the possibility that components of the membrane complex may co-isolate with IF, native intermediate filaments (NIF) were prepared. In addition to the structural subunits and other associated polypeptides, a ∼220 kd species which reacted specifically with antibodies directed against the ECM protein fibronectin (FN) was observed; 220 kd was still present after NIF were isolated under pH conditions where FN is more soluble, suggesting that its presence was not simply due to the coprecipitation of two insoluble proteins. Immunofluorescence and immunogold localization confirmed that FN is a component of the cell membrane complex with which IF appeared to interact.

Additional Material: 10 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/cm.970060405

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Fractionation of desmosomes and comparison of the polypeptide composition of desmosomes prepared from two bovine epithelial tissues (1988)

Jones, Stephanie M. ; Jones, Jonathan C. R. ; Goldman, Robert D.

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 36 (1988), S. 223-236

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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.

Additional Material: 9 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jcb.240360304

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