5 results on '"Laminin ultrastructure"'
Search Results
2. Cross-linking of laminin-nidogen complexes by tissue transglutaminase. A novel mechanism for basement membrane stabilization.
- Author
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Aeschlimann D and Paulsson M
- Subjects
- Animals, Blotting, Western, Cadaverine analogs & derivatives, Cadaverine metabolism, Electrophoresis, Polyacrylamide Gel, Fibronectins metabolism, Fluorescent Antibody Technique, Fluorescent Dyes, Guinea Pigs, Kidney metabolism, Laminin ultrastructure, Liver enzymology, Liver metabolism, Membrane Proteins ultrastructure, Microscopy, Electron, Myocardium metabolism, Putrescine metabolism, Basement Membrane metabolism, Laminin metabolism, Membrane Glycoproteins, Membrane Proteins metabolism, Transglutaminases metabolism
- Abstract
The laminin-nidogen complex, a major component of basement membranes, incorporates [3H]putrescine and monodansylcadaverine in the presence of guinea pig liver transglutaminase. Label was detected in nidogen in the isolated, as well as in the complexed form, but not in laminin. The incorporation proceeds in a time-dependent manner at a rate similar to that achieved with N,N-dimethylcasein, a well characterized transglutaminase substrate. Saturation of incorporation site(s), as well as comparison with the incorporation level in reference proteins, indicated the presence of one high affinity amine acceptor site in nidogen. Electron microscopy of the reaction products showed that the laminin-nidogen complexes become stabilized in a head-to-head arrangement, characteristic of Ca(2+)-induced self-aggregation. Indirect immunofluorescence and detection of transglutaminase activity on unfixed cryosections revealed an extracellular distribution of tissue transglutaminase. Intensive staining was observed in collagen-rich connective tissue. Codistribution with nidogen was not a ubiquitous feature, but was observed in many locations. more...
- Published
- 1991
Catalog
3. Molecular architecture of basement membranes.
- Author
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Yurchenco PD and Schittny JC
- Subjects
- Animals, Basement Membrane ultrastructure, Calcium physiology, Collagen ultrastructure, Glycoproteins ultrastructure, Glycosaminoglycans physiology, Laminin ultrastructure, Macromolecular Substances, Microscopy, Electron, Proteoglycans physiology, Proteoglycans ultrastructure, Basement Membrane physiology, Extracellular Matrix ultrastructure, Membrane Glycoproteins
- Abstract
Basement membranes are specialized extracellular matrices with support, sieving, and cell regulatory functions. The molecular architectures of these matrices are created through specific binding interactions between unique glycoprotein and proteoglycan protomers. Type IV collagen chains, using NH2-terminal, COOH-terminal, and lateral association, form a covalently stabilized polygonal framework. Laminin, a four-armed glycoprotein, self-assembles through terminal-domain interactions to form a second polymer network, Entactin/nidogen, a dumbbell-shaped sulfated glycoprotein, binds laminin near its center and interacts with type IV collagen, bridging the two. A large heparan sulfate proteoglycan, important for charge-dependent molecular sieving, is firmly anchored in the basement membrane and can bind itself through a core-protein interaction to form dimers and oligomers and bind laminin and type IV collagen through its glycosaminoglycan chains. Heterogeneity of structure and function occur in different tissues, in development, and in response to different physiological needs. The molecular architecture of these matrices may be regulated during or after primary assembly through variations in compositions, isoform substitutions, and the modifying influence of exogenous macromolecules such as heparin and heparan sulfate. more...
- Published
- 1990
- Full Text
- View/download PDF
4. Dissection of laminin by cathepsin G into its long-arm and short-arm structures and localization of regions involved in calcium dependent stabilization and self-association.
- Author
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Bruch M, Landwehr R, and Engel J
- Subjects
- Animals, Cathepsin G, Humans, Laminin ultrastructure, Leukocyte Elastase, Membrane Proteins metabolism, Mice, Molecular Weight, Pancreatic Elastase pharmacology, Peptide Fragments metabolism, Protein Conformation, Serine Endopeptidases, Calcium metabolism, Cathepsins pharmacology, Laminin metabolism, Membrane Glycoproteins
- Abstract
Native laminin-nidogen complex isolated from mouse Engelbreth-Holm-Swarm tumor was treated with purified cathepsin G or leucocyte elastase, two neutral serine proteases which play a role in inflammatory processes accompanied by degradation of basement membranes. Both enzymes were found to be more active than porcine pancreatic elastase. In the absence of Ca2+, laminin fragments produced by leucocyte elastase resembled those formed by the pancreatic enzyme but at physiological concentrations of Ca2+ cleavage by cathepsin G was much more selective. Initially laminin (900 kDa) was cleaved at two major sites only with similar rates leading to three fragments. Fragment C1-4 (about 550 kDa) comprises the intact three short arms of the molecule and fragment C8-9 (about 350 kDa) contains the entire triple-coiled region by which its three chains are assembled and the major part of the terminal globular domain of the long arm. The remaining C-terminal region of this domain was recovered as fragment C3 of about 50 kDa. Stabilization against proteolytic attack was restricted to the region of fragment C1-4 and only this fragment exhibited strong Ca2+ dependent self-association similar to that of intact laminin or of its complex with nidogen. The associative properties of fragment C1-4 were dramatically diminished upon removal of the tip of one of the short arms comprising fragment 4. In addition, this provides a clear assignment of the important laminin function to a distinct domain in one of its short arms. The new fragment C8-9 may be employed for exploring the properties and possible functions of the upper long-arm region which so far has not been available as a fragment. more...
- Published
- 1989
- Full Text
- View/download PDF
5. Domains of laminin with growth-factor activity.
- Author
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Panayotou G, End P, Aumailley M, Timpl R, and Engel J
- Subjects
- Amino Acid Sequence, Animals, Cell Adhesion, Cell Division drug effects, Cells, Cultured cytology, Epidermal Growth Factor pharmacology, Extracellular Matrix physiology, Laminin ultrastructure, Membrane Proteins pharmacology, Mice, Peptide Fragments pharmacology, Solubility, Structure-Activity Relationship, Time Factors, Growth Substances physiology, Laminin physiology, Membrane Glycoproteins
- Abstract
Laminin and fragments (1, 1-4) containing the inner rod-like segments from its short arms, which consist of cysteine-rich, "EGF-like" repeats, stimulated thymidine incorporation in cultured cells possessing EGF receptors but had no effect on a cell line lacking this receptor. The response was comparable to that of EGF concerning effective concentrations, magnitude, time dependence, and synergistic enhancement by insulin. Other fragments (4 and 8) were inactive. Laminin and its active fragments could not compete with the binding of EGF to cells. There was no correlation between growth promotion and attachment of cells to a high affinity binding site present on laminin fragment 8. The data indicate that mitogenic effects induced by laminin and EGF proceed in some steps via related pathways and that different domains of laminin are involved in growth promotion and in adhesion and spreading of cells. more...
- Published
- 1989
- Full Text
- View/download PDF
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