Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
 10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fragments of the matrix molecule fibronectin (FN) have been shown to modulate tissue remodeling activity by inducing matrix metalloproteinases (MMPs) in synovial fibroblasts. These molecules could contribute to the tissue degradation that occurs during periodontal disease if they also modulate the expression of proteinases in cells of the periodontal ligament (PDL). We tested the hypothesis that FN and specific FN fragments induce the expression of specific proteinases in PDL cells. Using substrate zymograms, reverse zymograms and Western immunoblots, we found that PDL cells constitutively express 72 kDa gelatinase, urokinase-type plasminogen activator (uPA) and at least three inhibitors whose molecular masses correspond to those of the tissue inhibitors of metalloproteinases (TIMPs). A fourth, previously uncharacterized, proteinase inhibitor of approximately 22 kDa was also observed in some cell isolates. PDL cells, when exposed to a 120 kDa proteolytic FN fragment containing the cell-binding domain, were induced to express collagenase and stromelysin and also demonstrated an increased secretion of the serine proteinase uPA. Expression of collagenase increased with increasing concentrations (0.001 microM-1 microM) of the 120 kDa FN fragment. This fragment also induced the expression of a 20 kDa inhibitor, but not of the higher-molecular-mass inhibitors, in PDL cells. The observed alterations in proteinases were associated specifically with the 120 kDa FN fragment, since similar responses were not seen when PDL cells were exposed to either a 60 kDa heparin-binding FN fragment or a 45 kDa collagen/gelatin-binding FN fragment. PDL cells exposed to intact FN did not express the proteinases induced by the 120 kDa fragment but did express 92 kDa gelatinase and the 20 kDa proteinase inhibitor. These data suggest that FN and specific FN fragments can differentially induce the expression of proteinases in PDL cells. Thus, functional regions of FN may modulate many of the functions of PDL cells that contribute to periodontal disease, wound healing and maintenance of extracellular matrix in periodontal tissues.
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PMID:Fibronectin and fibronectin fragments modulate the expression of proteinases and proteinase inhibitors in human periodontal ligament cells. 889 25

Thrombospondin (TSP) is produced by glomerular mesangial cells and one of the extracellular matrix in the mesangium, whereas the physiological role of TSP in mesangial cells is poorly understood. In order to know whether TSP modulates mesangial cell functions, we investigated the effects of TSP on cell adhesion, proliferation, synthesis of extracellular matrix and serine proteinases in cultured human mesangial cells. The substratum of TSP inhibited cell attachment and spreading in a TSP-dose-dependent manner in mesangial cells. Soluble TSP (50 micrograms/ml) also caused the detachment of fully adherent mesangial cells, whereas TSP less than 10 micrograms/ml did not. [3H]-thymidine incorporation into mesangial cells was dose-dependently reduced by TSP. On the other hand, the production of both fibronectin and type IV collagen from mesangial cells was enhanced by TSP. The incubation of mesangial cells with TSP increased the secretion of tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), while plasminogen activator inhibitor-type 1 (PAI-1) decreased. These observations indicate that TSP inhibits cell adhesion and proliferation in cultured human mesangial cells. It is also suggested that TSP influences the metabolism of mesangial matrix by modulating both synthesis and degradation of matrix components. Thus, TSP, may be an important mediator of mesangial cell functions in an autocrine fashion.
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PMID:Thrombospondin modulates adhesion, proliferation and production of extracellular matrix in mesangial cells. 892 89

Fibronectins and plasminogen activators, both tissue and urokinase types, are involved in the physiopathological degradation of the extracellular matrix. Previous reports indicate that fibronectin can be degraded by urokinase without plasminogen. Also, we have shown that tissue-type plasminogen activator can cleave fibronectin, without plasminogen, generating fragments of 30 and 220-250 kDa detectable by immunoblotting analysis. A comparison with urokinase-induced degradation indicates that the cleavage sites are the same for both plasminogen activators. One is close to the carboxyl-terminal, disrupting the fibronectin dimeric structure, and one is near the amino-terminal, generating a 30 kDa fragment. In solution, the activity of tissue-type plasminogen activator was prevalent on the amino-terminal site, while urokinase activity was prevalent on the carboxyl-terminal site. On fibronectin immobilized onto a gelatin coated surface, only the 30 kDa fragment was released when treated with both plasminogen activators. Plasminogen activators also were active on fibronectin assembled into the extracellular matrix of cultured fibroblasts. Urokinase caused the complete disappearance of extracellular matrix fibronectin, together with the release of the 30 and the 220-250 kDa fibronectin fragments, but left a flat morphology, while tissue-type plasminogen activator induced the release of the 30 kDa fragment associated with changes in cellular morphology. The plasminogen-independent fibronectin degradation exerted by tissue-type plasminogen activator and urokinase is 100 times lower than that exerted by plasmin. This may provide a mechanism for localized and limited degradation of fibronectin preventing the generalized proteolysis associated with plasminogen activation.
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PMID:Degradation of human plasma and extracellular matrix fibronectin by tissue type plasminogen activator and urokinase. 893 Jan 38

We constructed vascular endothelial cell monolayer on a fibronectin-coated filter in a Boyden chamber and assessed the ability of 3 LL cells to penetrate through the artificial blood vessel wall. The defense of endothelial cell monolayers against the tumor cell invasion was greatly potentiated by their pretreatment with 5 or 10 micrograms/ml of brefeldin A (BFA) for 1 h (52% or 28% of control invasion). Treatment of the endothelial cell monolayers with BFA resulted in an increase in the release of inhibitory material(s) against urokinase-type plasminogen activator (u-PA) activity of 3 LL cells. Parallel experiments with the cultured endothelial cells and BFA indicated that the fungal metabolite enhanced a rate of accumulation of plasminogen activator inhibitor-1 (PAI-1) antigen, but not of tissue-type plasminogen activator antigen in the medium. The BFA-induced enhancement of PAI-1 antigen release was accompanied with the increased accumulation of the extracellular (membrane/matrix-bound) and intracellular PAI-1 antigen (219% of control at 24 h). These results suggest that BFA can strengthen the defense of vascular endothelium against tumor-cell invasion by enhancing the release and accumulation of PAI-1, which plays a critical role in the regulation of the u-PA-plasmin-collagenase activation cascade.
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PMID:Vascular endothelial cell monolayer formed on membrane filter potentiates the defense against tumor cell invasion by treatment with brefeldin A. 895 Feb 8

Tumor spread may be favored by a reduced production and/or an enhanced degradation of extracellular matrix components (collagen, fibronectin, laminin). Most tumor cell behavior, from growth to spread, may be regulated by cytokines, the exact roles of which, however, are not yet fully understood. We here evaluate the effects of some cytokines (epidermal growth factor, transforming growth factor-beta 1, interleukin-1 alpha, and interleukin-1 beta) on both cell growth and the production of the aminoterminal peptide of type III procollagen, the urokinase plasminogen activator, and the plasminogen activator inhibitor-1 in neoplastic cell lines originating in the pancreas and colon. Cells were stimulated daily with the above cytokines and the aminoterminal peptide of type III procollagen, urokinase plasminogen activator, and plasminogen activator inhibitor-1 were measured in the conditioned media. Epidermal growth factor stimulated cell growth of both cell lines. Transforming growth factor-beta 1 counteracted cell proliferation and stimulated type III procollagen and plasminogen activator inhibitor-1 production only in the colon cancer cell line. Interleukin-1 alpha slightly stimulated cell growth, but inhibited plasminogen activator inhibitor-1 production in both cell lines; interleukin-1 beta did not affect cell growth, but stimulated plasminogen activator inhibitor-1 production by the colon cancer cell line. Our findings suggest that transforming growth factor-beta 1 and interleukin-1 beta may have an antidiffusive effect. These results confirm that cytokine-producing cells have a potential role in stimulating or counteracting tumor growth and spread and also confirm the pivotal role of host-tumor interactions in determining the outcome of a particular neoplasia.
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PMID:Cytokines may influence tumor growth and spread. An in vitro study in two human cancer cell lines. 900 14

An enzyme-linked immunosorbent assay (ELISA) has been developed to measure cellular fibronectin (cFN) in association with human umbilical vein endothelial cells (HUVEC) in culture. The expression of a number of functional domains on the cFN molecule was demonstrated using three specific murine monoclonal antibodies. This system was found to be sensitive, detecting as little as 0.156 microg/ml of cFN, and required only 1.3 x 10(5) cells per well confluent cells per experimental condition. This allowed multiple experiments to be performed on one batch of endothelial cells. cFN was detected on both viable and methanol fixed endothelial cells without significant non-specific antibody binding. The utility of this experimental model was studied by exploring the effect of urokinase activated plasminogen, a potent protease, on the expression of cFN and its functional domains.
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PMID:Detection of fibronectin expression by human endothelial cells using a enzyme-linked immunosorbent assay (ELISA): enzymatic degradation by activated plasminogen. 907 73

Low density lipoprotein receptor-related protein (LRP) mediates the endocytosis of diverse ligands, including urokinase plasminogen activator (uPA) and its receptor, uPAR, which have been implicated in cellular migration. The purpose of this study was to determine whether LRP affects cellular migration. Murine embryonic fibroblasts (MEF) that are LRP-deficient due to targeted gene disruption and exotoxin selection (MEF-2), heterozygous fibroblasts (PEA-10), and wild-type fibroblasts (MEF-1) were compared. When cultures were denuded of cells in a 1-mm-wide strip, all three cell types migrated into the denuded area. The MEF-2 cells migrated nearly twice as rapidly as the MEF-1 cells or PEA-10 cells. The difference in migration velocity was duplicated in culture wells that were precoated with serum or vitronectin and partially duplicated in wells coated with fibronectin but not in wells coated with type I collagen or Matrigel. uPA was detected in MEF-2 conditioned medium (CM) at a concentration of 0.30 +/- 0.02 nM, which was 13-fold higher than the level detected in MEF-1 CM or PEA-10 CM, suggesting one potential mechanism for the enhanced migration of MEF-2 cells. uPAR was also increased on MEF-2 cells by 4-5-fold, as determined by PI-PLC release, and by 2.5-fold, as determined by a uPA/uPAR activity assay. Mannosamine treatment, which down-regulates cell-surface uPAR, decreased MEF-2 migration by 40% without significantly affecting MEF-1 migration. MEF-2 CM, which is uPA-rich, increased the rate of MEF-1 migration, and MEF-1 CM did not. These studies demonstrate alterations in cellular migration and in the activity of the uPA/uPAR system which accompany complete deficiency of LRP expression in fibroblasts. We propose that uPA and uPAR form an autocrine loop for promoting fibroblast migration and that LRP counteracts the activity of this system.
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PMID:Embryonic fibroblasts that are genetically deficient in low density lipoprotein receptor-related protein demonstrate increased activity of the urokinase receptor system and accelerated migration on vitronectin. 916 74

Cell migration involves the integrins, their extracellular matrix ligands, and pericellular proteolytic enzyme systems. We have studied the role of plasminogen activator inhibitor-1 (PAI-1) in cell migration, using human amnion WISH cells and human epidermoid carcinoma HEp-2 cells in an assay measuring migration from microcarrier beads and a modified Boyden-chamber assay. Active, but not latent or reactive center-cleaved, PAI-1 inhibited migration. A PAI-1 mutant without ability to inhibit plasminogen activation was as active as wild-type PAI-1 as a migration inhibitor, showing that inhibition of plasminogen activation was not involved. PAI-1 specifically interfered with intergrin- and vitronectin-mediated migration: Migration onto vitronectin-coated but not onto fibronectin-coated surfaces was inhibited by PAI-1, a cyclic RGD peptide inhibited migration, and both cell lines expressed vitronectin-binding alpha v-integrins. In addition, active PAI-1, but not latent or reactive center-cleaved PAI-1, inhibited vitronectin binding to integrins in an in vitro binding assay, without affecting binding of fibronectin. Monoclonal antibodies against the urokinase receptor, another vitronectin binding protein, did not affect cell migration in the beads assay, while some inhibitory effect was observed in the Boyden-chamber assay. We conclude that PAI-1, independently of its role as a proteinase inhibitor, inhibits cell migration by competing for vitronectin binding to integrins, while the interference of PAI-1 with binding of vitronectin to the urokinase receptor may play a secondary role. These data define a novel function for the serpin PAI-1, enabling it to regulate cell migration over vitronectin-rich extracellular matrix in the body.
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PMID:Plasminogen activator inhibitor-1 represses integrin- and vitronectin-mediated cell migration independently of its function as an inhibitor of plasminogen activation. 916 21

Urokinase plasminogen activator and its receptor are both found at the surface of the cell membrane in many cell types. The plasminogen activator inhibitor type-1 (PAI-1) is often associated with the extracellular matrix. The spatial localization of these three molecules could account for their involvement in cell adhesion and/or migration. We have shown previously that the urokinase receptor mediates mechanical force transmission across the cell surface to the cytoskeleton. Here we investigated whether immobilized plasminogen activator inhibitor type 1 (PAI-1) could regulate cell spreading and cytoskeleton reorganization. Serum deprived human myogenic cells were plated in serum free medium onto bacteriologic dishes precoated with different extracellular matrix ligands (fibronectin, vitronectin, or type 1 collagen) or PAI-1 at increasing concentrations. The number of adherent cells and their projected area were quantitated after 3 hours of plating. PAI-1 promoted cell adhesion and spreading in a dose dependent manner. Addition of antibodies to PAI-1 inhibited the adhesion on PAI-1 coated dishes in a dose dependent way. The PAI-1 mediated cell adhesion required the presence of urokinase at the cell surface. Removal of the glycosylphosphatidylinositol (GPI)-linked proteins abolished cell adhesion on PAI-1 dish, suggesting its dependence on the presence of the urokinase receptor, a GPI-linked receptor. Furthermore, addition of antibodies against alpha v beta3 integrin completely inhibited cell adhesion on PAI-1, suggesting that alpha v beta3 might be the transmembrane molecule that physically connects the complex of PAI-1, urokinase, and urokinase receptor to the cytoskeleton. Visualization of spread cells stained for filamentous actin with confocal microscopy showed a dose-dependent increase of filopodia on PAI-1 coated dishes and cytoskeletal reorganization, suggesting a migratory profile. These data indicate that PAI-1 plays a direct role in dynamic cell adhesion particularly at the leading edge, where increased levels of urokinase plasminogen activator (uPA) and its receptor (uPAR) are localized in migrating cells. Immobilized PAI-1 could therefore serve to bridge the cell surface with the extracellular matrix via the formation of a multimolecular complex that includes alpha v beta3 integrins in myogenic cells.
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PMID:Binding of urokinase to plasminogen activator inhibitor type-1 mediates cell adhesion and spreading. 917 5

1. The efficient repair of gastrointestinal mucosal injuries is essential in the preservation of the epithelial barrier to luminal antigens. Accumulated evidence suggests that epithelial migration plays a major part in this repair by rapidly resealing defects induced by both physiological and pathological insults, a process termed restitution. 2. This migration has been modelled in various ways, most commonly in mechanically wounded monolayers of cell lines or cells in primary culture, and in wounded human or animal tissue. Evidence from these models indicates that migration is a highly complex process, which is likely to involve the tightly controlled spatial and temporal interaction of multiple factors: (i) extracellular molecules such as soluble factors (e.g. growth factors, trefoil peptides, cytokines) and matrix components (e.g. collagen, laminin, fibronectin); (ii) signalling molecules activated by the interaction of these factors with cell surface receptors (e.g. protein kinases, phospholipases, low-molecular-weight GTPases); (iii) factors which regulate adhesion to other cells (e.g. E-cadherin) and to matrix components (e.g. integrins, hyaluronic acid receptors); (iv) factors which regulate detachment from the extracellular matrix (e.g. urokinase-type plasminogen activator, matrix metalloproteinases); and (v) molecules which regulate cytoskeletal function (e.g. Rac), which allows the formation of specialized cellular processes termed lamellipodia. 3. The identification of physiologically relevant factors that stimulate epithelial cell migration, and a better understanding of their mechanism of action, may be beneficial in the development of novel therapeutic approaches in diseases such as inflammatory bowel disease through the pharmacological or dietary enhancement of this migration.
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PMID:Epithelial migration in the colon: filling in the gaps. 930 23


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