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)

Malignant tumors are generally characterized by extensive local tissue invasion and destruction of ECM which may be due to increased constitutive expression and activity of secreted proteases. Moreover, a large number of diverse protease activities may be constitutively over-expressed in a simultaneous or co-ordinated fashion, thereby significantly increasing cellular invasive potential of the cells. To explore this relationship, we have measured steady-state levels of mRNA coding for urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), transin and tissue-specific inhibitor of metalloproteinases (TIMP); as well as gelatinolytic, caseinolytic and plasminogen activator activities secreted by SPI, a non-metastatic mouse mammary carcinoma cell line and 4 metastatic sublines derived from it. mRNA encoding metalloproteinase transin was increased 15- to 20-fold, while TIMP transcripts were decreased 3-fold in the metastatic sublines compared to parental SPI tumor cells. Metastatic sublines secreted higher levels of gelatinase (i.e., 92 kDa and 64 kDa) as well as proteases with caseinolytic activity (i.e., 115 kDa and 57 kDa) when compared with SPI cells. Moreover, these enzymes were identified as neutral metalloproteinases. Although the amount of uPA mRNA appeared to be the same in SPI and the metastatic sublines, the latter secreted 1.5-3 times more uPA activity into the culture supernatants. Metastatic competence in the SPI tumor model is therefore associated with increased secretion of several metalloproteinase activities and uPA, as well as decreased TIMP expression, consistent with a more invasive phenotype.
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PMID:Constitutive expression and secretion of proteases in non-metastatic SP1 mammary carcinoma cells and its metastatic sublines. 204

Extracellular matrix metalloproteases are secreted by the resident cells of the tissue in a proenzyme form, and their extracellular activity is regulated at the level of gene expression, proenzyme activation, and interaction with inhibitors. To understand the molecular mechanisms that control the activity of ECM metalloproteases and their effect on the cellular phenotype, we have established cell lines in which the transcription of the protease genes is repressed. We also have undertaken a detailed study of the pathway of extracellular activation of interstitial procollagenase. Stable transfection of three human tumor cell lines--H-ras-transformed bronchial epithelial cells TBE-1, fibrosarcoma cells HT1080, and melanoma cells A2058--with the adenovirus E1A gene dramatically repressed the expression of the secreted proteases, type IV and interstitial collagenases, and urokinase-type plasminogen activator. Concomitantly, E1A-expressing cells showed reduced metastatic activity in vivo and reduced ability to traverse a reconstituted basement membrane in vitro. Monospecific anti-type IV collagenase antibody inhibited the invasive activity of parental tumor cell lines in the in vitro system, suggesting a possible causal relationship between the effect of E1A on the expression of secreted proteases and the reduced metastatic potential of the E1A-expressing transformants. We have also studied the mechanism of regulation of metalloprotease activity at the level of extracellular activation by investigating the cascade of proteolytic events that results in the activation of interstitial procollagenase. Cocultivation of the major cellular components of skin, dermal fibroblasts, and epidermal keratinocytes induces activation of interstitial procollagenase and prostromelysin in the presence of plasminogen. This activation occurs through a uPA-plasmin-dependent pathway in which plasmin catalyzes the first step in activation of both collagenase and stromelysin by amino-terminal processing. Activated stromelysin can in turn convert plasmin-activated collagenase into a fully active enzyme by removal of approximately 15 amino acid residues from the carboxyl end of the enzyme. This second step of activation results in a 5-8-fold further increase in specific activity of collagenase. This cascade of proteolytic events may constitute a major physiologic pathway of collagenase activation.
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PMID:Secreted proteases. Regulation of their activity and their possible role in metastasis. 215 52

In the course of studies on the regulation of plasminogen activator-mediated extracellular matrix degradation in muscle we found the presence of a factor, a cellular inhibitor of serine proteases having features similar to the serpin protease nexin I (PNI). This factor was present in the medium and at maximum concentration following fusion of skeletal muscle cells in culture. The ability of the PNI homologue in mouse muscle to inhibit ECM degradation by urokinase in myoblast medium was compared to that of human PNI purified from human fibroblasts. Stable (to SDS) 1:1 molar ratio complex formation between PNI and proteases, the proposed means by which these enzymes are regulated and removed, was also detected. Cell surface receptors for protease:PNI complexes, the specific binding sites for inactive complex internalization, were found on multinucleated myotubes, while little or no receptor activity was detected on myoblasts. These data suggest that developmental regulation of a) increased PNI proteolytic inhibitory activity expression and b) the appearance of protease:inhibitor complex receptors on muscle cell surfaces during myogenesis may constitute important regulatory features of muscle surface proteolytic activity. They complement previous studies of proteoglycan metabolism in muscle, which itself contains molecules capable of regulating the activity of myotube surface proteases.
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PMID:Plasminogen activators and their inhibitors in the neuromuscular system: II. Serpins and serpin: protease complex receptors increase during in vitro myogenesis. 216 58

8701-BC cells, derived from a primary carcinoma of the breast, constitutively express mRNA for urokinase-type plasminogen activator (uPA). In this paper, we demonstrated the presence of uPA in the conditioned medium, and of uPA-receptor (uPAR) on the cell surface of 8701-BC cells, which therefore have the potential for an autocrine mechanism of uPA-mediated stimulation. We examined whether exogenous addition of either intact uPA, or its amino-terminal fragment (uPA-ATF), which lacks catalytic activity but retains the uPAR binding site and a growth factor-like domain, or immunoneutralisation of endogenous uPA-uPAR interactions could exert any effect on the proliferative and invasive behaviour of 8701-BC cells. The data demonstrate that, while uPA promotes growth and invasion of 8701-BC cells, its effect reversed by blocking uPA-uPAR interactions, uPA-ATF not only fails to impart growth factor-like signals, but also restrains cell invasion in vitro. In the light of these and other data, an active participation of ATF in the complex cell-ECM network of interactions underlying cancer progression can be postulated. In addition, it appears worth considering the possibility of testing the effect of this uPA fragment in vivo for the therapy of breast (and possibly other) human invasive carcinomas.
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PMID:In vitro anti-proliferative and anti-invasive role of aminoterminal fragment of urokinase-type plasminogen activator on 8701-BC breast cancer cells. 869 76

Malignant human melanoma cells produce many matrix-degrading enzymes, including plasminogen activators and matrix metalloproteinases. These enzymes have substrate specificity for different components of ECM and most of them have been demonstrated to contribute to melanoma cell-mediated dissolution of matrices and to melanoma cell invasion. The degradation of complex matrices in vitro requires the cooperation of proteases with specificity for glycoproteins and collagens. The contribution of proteases to spontaneous melanoma metastasis was studied by overexpressing specific protease inhibitors in human melanoma cells. Overexpression of PAI-2 inhibited the spread of distant metastasis indicating a role for uPA/plasmin in melanoma invasion. Overexpression of TIMP-2, in contrast, reduced the growth rate of subcutaneous tumors, but did not inhibit metastasis, indicating that MMP activities promote melanoma growth in the skin and may not be required for metastatic dissemination. Thus, uPA and MMP activities are involved in different processes, but they both contribute to melanoma malignancy.
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PMID:Different roles for plasminogen activators and metalloproteinases in melanoma metastasis. 881 95

The cell surface urokinase-type plasminogen activator receptor (uPAR) has been shown to be a key molecule in regulating plasminogen-mediated extracellular proteolysis. To investigate the role of uPAR in invasion of brain tumors, human glioblastoma cell line SNB19 was stably transfected with a vector capable of expressing an antisense transcript complementary to the 300 base pair of the 5' end of the uPAR mRNA. Parental and stably transfected (vector, sense, and antisense) cell lines were analysed for uPAR mRNA transcript by Northern blot analysis, and receptor protein levels were measured by radioreceptor assays and Western blotting. Significant reduction of uPAR sites was observed in the antisense transfected cell lines. The levels of uPAR mRNA were significantly decreased in antisense clones compared to control, vector and sense clones. The invasive potential of the cell lines in vitro was measured by Matrigel invasion assay and migration of cells from spheroids to monolayers. The antisense transfected cells showed a markedly lower level of invasion and migration than the controls. The antisense clones were more adhesive to the ECM components compared to parental, vector and sense clones. All transfected (vector, sense and antisense) clones and parental cells produced similar levels of uPA activity without any significant difference however, MMP-2 activity was decreased in antisense clones compared to controls. These results demonstrate that uPAR expression is critical for the invasiveness of human gliomas and down regulation of uPAR expression may be a feasible approach to decrease invasiveness.
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PMID:In vitro inhibition of human glioblastoma cell line invasiveness by antisense uPA receptor. 917 95

The multifunctionality of adhesion receptor ligands as well as the promiscuous nature of vascular integrins and nonintegrin-dependent adhesive interactions allow ligand-receptor binding of variable strength. The cooperation with pericellular proteolysis cascades is required for vascular remodelling during angiogenesis, atherogenesis or inflammatory processes. In particular, integrin-dependent cell contact, spreading and (trans-)migration can be modulated by ECM-associated PAI-1 and uPA-receptor driven reactions that are intimately linked to the invasive potential of cells. Recently, mechanisms of molecular crosstalk between these receptor systems have been recognized: (a) uPA-receptor may directly interact with beta 1- and beta 2-integrins on circulating blood cells; (b) av beta 3-integrin-directly binds to a matrix metalloproteinase; (c) uPA and PAI-1 balance the high affinity binding of vitronectin to uPA-receptor; (d) vitronectin-dependent cell adhesion and migration involving alpha v-integrins or uPA-receptor are blocked by active PAI-1 independent of its role as protease inhibitor. These results are compatible with vascular injury studies in uPA- and PAI-1 knock-out mice and provide new targets for the treatment of diseases associated with imbalanced vascular remodelling.
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PMID:Molecular crosstalk between adhesion receptors and proteolytic cascades in vascular remodelling. 919 34

Monocyte-derived foam cells figure prominently in rupture-prone regions of atherosclerotic plaque. As urokinase/urokinase-receptor (u-PA/u-PAR) is the trigger of a proteolytic cascade responsible for ECM degradation, we have examined the effect of atherogenic lipoproteins on monocyte surface expression of u-PAR and u-PA. Peripheral blood monocytes, isolated from 10 healthy volunteers, were incubated with 10 to 200 microg/ml of native or oxidised (ox-) atherogenous lipoproteins for 18 h and cell surface expression of u-PA and u-PAR was analysed by flow cytometry. Both LDL and Lp(a) induced a dose-dependent increase in u-PA (1.6-fold increase with 200 microg/ml of ox-LDL) and u-PAR [1.7-fold increase with 200 microg/ml of ox-Lp(a)]. There is a great variability of the response among the donors, some of them remaining non-responders (absence of increase of u-PA or u-PAR) even at 200 microg/ml of lipoproteins. In positive responders, enhanced u-PA/u-PAR is associated with a significant increase of plasmin generation ( .9-fold increase with 200 microg/ml of ox-LDL), as determined by an amidolytic assay. Furthermore, monocyte adhesion to vitronectin and fibrinogen was significantly enhanced by the lipoproteins [respectively 2-fold and 1.7-fold increase with 200 microg/ml of ox-Lp(a)], due to the increase of micro-PAR and ICAM-1, which are receptors for vitronectin and fibrinogen. These data suggest that atherogenous lipoproteins could contribute to the development of atheromatous plaque by increasing monocyte adhesion and trigger plaque weakening by inducing ECM degradation.
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PMID:Increased expression of u-PA and u-PAR on monocytes by LDL and Lp(a) lipoproteins--consequences for plasmin generation and monocyte adhesion. 1023 46

Tumor progression and metastasis may result in part from the selection of cell clones competent for survival, invasion and growth at secondary sites and characterized by loss of growth inhibitory responses, acquisition of increased adhesiveness and enhanced motility and protease expression. Transforming growth factor-beta1 (TGF-beta1) is produced by osteoblasts (OB) in a latent form and is activated by proteases in a cell-dependent manner. We show here that OB conditioned medium (OB CM) modulates Matrigel invasion of a bone metastatic prostate cancer cell line (PC3) and that this effect is blocked by antibody against TGF-beta1 and by uPA/plasmin inhibitors, suggesting that TGF-beta1 can modulate OB-mediated cell recruitment and that PC3 cells can activate TGF-beta1. TGF-beta1 induces uPA and PAI-1 secretion and promotes binding of uPA at the external plasma membrane with increased membrane-associated plasmin activity. Matrix metalloprotease-9 (MMP-9) is induced both in the medium and in the membrane associated form. Moreover, the balance between proteolytic activity and inhibition is crucial in the metastatic event. Indeed, the increment of PAI-1 could have an important regulatory role on the extracellular proteolysis and might explain the decrease of net PA and gelatinolytic activities measured in the medium. In addition, PAI-1 plays a regulative role localizing matrix degradation in some specific sites, such as areas of cell-to-cell or cell-to-ECM contacts. In conclusion, TGF-beta1 enhances PC3 Matrigel invasion by a uPA/plasmin-dependent mechanism, also involving the MMP-9, and thus may play a central role in malignant prostate tumor progression as a result of stimulating bone matrix invasion.
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PMID:Osteoblast-derived TGF-beta1 modulates matrix degrading protease expression and activity in prostate cancer cells. 1065 34

Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of both tissue- and urokinase-type plasminogen activators (t-PA, u-PA). PAI-1 also regulates the attachment of cells to the adhesive glycoprotein vitronectin (VN). PAI-1 gene expression has been observed in various cell types, and many regulatory factors have been identified to play a role in PAI-1 gene transcription. The complete picture of how the PAI-1 gene is expressed when cells adhere to a culture plate has not been fully elucidated. We found that in anchorage-dependent cells, PAI-1 gene was up-regulated when cells were beginning to attach to a culture dish and was down-regulated when cells had attached completely. The PAI-1 gene expression was induced only in adhered cells but not in non-adhered cells. The regulation of PAI-1 protein was also found in both culture medium and cell lysate when cells were attached to a culture dish. Our experiment indicates that vitronectin and fibronectin, as components of ECM, may be the factors involved in the regulation of PAI-1 gene expression. PAI-1, as an inhibitor of the interaction between vitronectin and integrin alphavbeta3, may also be a regulator of its own expression.
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PMID:Cell adhesion regulates the plasminogen activator inhibitor-1 gene expression in anchorage-dependent cells. 1182 81


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