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)

We have investigated the synthesis and the polarized secretion of plasminogen activators (PAs) in three epithelial cell lines (FRT, derived from rat thyroid; MDCK, from canine kidney, and CaCo-2, from human intestine) grown on filters, in bicameral systems. Confluency and acquisition of functional polarity were assessed by measuring transepithelial resistance and by showing polarized secretion of endogenous proteins. By zymography, before and after immunoprecipitation with specific antibodies, we found that FRT cells synthesized tissue plasminogen activator (tPA) and that tPA activity was mostly confined to the apical cell compartment. MDCK and CaCo-2 cells, instead, synthesized urokinase-type plasminogen activator (uPA). In MDCK cells the uPA activity was found predominantly in the apical cell compartment while in CaCo-2 cells it was mostly basolateral.
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PMID:Polarized secretion of plasminogen activators by epithelial cell monolayers. 148 89

We studied the relationship between differentiation, transformation, and uPA production in a system of rat thyroid cells in vitro. The fully differentiated FRTL5 cells did not produce detectable amounts of uPA, even after stimulation with phorbol esters, potent inducers of uPA expression. All the other cell lines (i.e., FRT, cells which have lost the characteristics of the differentiated thyroid cells; 1-5 G and FRA, transformed cells derived from rat thyroid tumors) produced uPA, the 1-5 G line being the highest producer. Also the FRTL line became positive for uPA production after viral transformation (clone KM4). The lack of uPA expression in FRTL5 cells was not due to the presence of inhibitors and these cells did not produce an inactive molecule, as shown by immunoprecipitation with anti-uPA antibody. However, in FRTL5 cells Northern analysis showed the presence of a small amount of uPA-specific mRNA that increased appreciably after phorbol ester stimulation. In conclusion, in our system uPA expression was a property of undifferentiated and transformed cells; in fully differentiated cells uPA expression was switched off by a still unclear mechanism.
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PMID:Production of urokinase-type plasminogen activator by normal and transformed rat thyroid cells in culture. 254 Oct 4

Alternative splicing of vascular endothelial growth factor (VEGF) mRNA results in three distinct molecular forms of 121 or 165 (V165) amino acids that are released in the conditioned medium of cultured cells and one longer isoform of 189 amino acids (V189) that remains cell-associated. V189 has been expressed in wild type CHO-K1 cells and in glycosaminoglycan-deficient pgsA-745 Chinese hamster ovary (CHO) mutant cells. It could be released from CHO-K1 cell membranes by heparin or a synthetic peptide designed on the sequence encoded by exon 6 but was freely released from CHO mutant cells. In both cases, the immunoreactive V189 was mainly released as a 40-kDa cleaved form, provided that the serine protease urokinase, but not plasmin, was active. Recombinant V189 was purified from insect cells infected with a recombinant baculovirus as a nonmitogenic 50-kDa precursor that binds to the receptor Flt-1 but not to Flk-1. It could be matured by urokinase as a 38-kDa fragment able to bind to Flk-1 and to trigger cell proliferation. V165 and V189, however, could be cleaved by plasmin as 34-kDa fragments that exhibit a decreased mitogenic activity. These findings indicate that the carboxyl-terminal domain of V189 masks its binding domain to Flk-1.
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PMID:Extracellular cleavage of the vascular endothelial growth factor 189-amino acid form by urokinase is required for its mitogenic effect. 914 62

The vascular endothelial growth factor (VEGF) family has recently expanded by the identification and cloning of three additional members, namely VEGF-B, VEGF-C, and VEGF-D. In this study we demonstrate that VEGF-B binds selectively to VEGF receptor-1/Flt-1. This binding can be blocked by excess VEGF, indicating that the interaction sites on the receptor are at least partially overlapping. Mutating the putative VEGF receptor-1/Flt-1 binding determinants Asp63, Asp64, and Glu67 to alanine residues in VEGF-B reduced the affinity to VEGF receptor-1 but did not abolish binding. Mutational analysis of conserved cysteines contributing to VEGF-B dimer formation suggest a structural conservation with VEGF and platelet-derived growth factor. Proteolytic processing of the 60-kDa VEGF-B186 dimer results in a 34-kDa dimer containing the receptor-binding epitopes. The binding of VEGF-B to its receptor on endothelial cells leads to increased expression and activity of urokinase type plasminogen activator and plasminogen activator inhibitor 1, suggesting a role for VEGF-B in the regulation of extracellular matrix degradation, cell adhesion, and migration.
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PMID:Vascular endothelial growth factor B (VEGF-B) binds to VEGF receptor-1 and regulates plasminogen activator activity in endothelial cells. 975 30

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that functions as a transcription factor to mediate ligand-dependent transcriptional regulation. Activation of PPARgamma by the naturally occurring ligand, 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), or members of a new class of oral antidiabetic agents, e.g. BRL49653 and ciglitizone, has been linked to adipocyte differentiation, regulation of glucose homeostasis, inhibition of macrophage and monocyte activation, and inhibition of tumor cell proliferation. Here we report that human umbilical vein endothelial cells (HUVEC) express PPARgamma mRNA and protein. Activation of PPARgamma by the specific ligands 15d-PGJ2, BRL49653, or ciglitizone, dose dependently suppresses HUVEC differentiation into tube-like structures in three-dimensional collagen gels. In contrast, specific PPARalpha and -beta ligands do not affect tube formation although mRNA for these receptors are expressed in HUVEC. PPARgamma ligands also inhibit the proliferative response of HUVEC to exogenous growth factors. Treatment of HUVEC with 15d-PGJ2 also reduced mRNA levels of vascular endothelial cell growth factor receptors 1 (Flt-1) and 2 (Flk/KDR) and urokinase plasminogen activator and increased plasminogen activator inhibitor-1 (PAI-1) mRNA. Finally, administration of 15d-PGJ2 inhibited vascular endothelial cell growth factor-induced angiogenesis in the rat cornea. These observations demonstrate that PPARgamma ligands are potent inhibitors of angiogenesis in vitro and in vivo, and suggest that PPARgamma may be an important molecular target for the development of small-molecule inhibitors of angiogenesis.
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PMID:Peroxisome proliferator-activated receptor gamma ligands are potent inhibitors of angiogenesis in vitro and in vivo. 1008 62

The angiopoietin/Tie receptor system may contribute to angiogenesis and vascular remodeling by mediating interactions of endothelial cells with smooth muscle cells and pericytes. The temporal expression of angiopoietin-1 (Angpo-1), angiopoietin-2 (Angpo-2), Tie-1, and Tie-2 mRNA was studied in a focal cerebral ischemia model in rats. The cDNA fragments obtained from reverse transcription polymerase chain reaction amplification were cloned and used as a probe to detect individual genes. Northern blot analysis showed a delayed increase of a 4.4-kb Angpo-1 transcript for up to 2 weeks after ischemia, eightfold higher than the values of the sham-operated controls. A biphasic expression of a 2.4-kb Angpo-2 transcript was noted, peaking at 24 hours (6.4-fold) and 2 weeks (4.6-fold) after ischemia. The expression of Tie-2 mRNA (4.3 kb), a receptor for Angpo-1, and Tie-1 mRNA (4.3 kb) also increased starting 24 hours after reperfusion and remained elevated for up to 2 weeks after ischemia. The temporal profiles of the expression of these genes were different from those of other angiogenic genes such as basic fibrobast growth factor/fibroblast growth factor receptor and vascular endothelial growth factor/vascular endothelial growth factor receptor and proteolytic enzymes (tissue-type plasminogen activator and urokinase plasminogen activator) and their inhibitors (plasminogen activator inhibitor-1). The expression patterns of these genes could be related to progressive tissue liquefaction and neovascularization after ischemia in this stroke model. Differential expression of these angiogenesis genes suggests the involvement of complex regulatory mechanisms that remain to be characterized.
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PMID:Induction of angiopoietin and Tie receptor mRNA expression after cerebral ischemia-reperfusion. 1069 77

We have previously reported a constitutively activated form of the Flt-1 kinase (BCR-FLTm) molecularly engineered based on the structural backbone of the activated tyrosine kinase BCR-ABL. Here we show that it can induce not only growth stimulation but also tubulogenic differentiation of non-tubulogenic NP31 (non parenchymal) sinusoidal endothelial cells of rat liver in basement membrane matrix. Tubules formed in vitro were accompanied by fenestration structures and allowed circulation when transplanted into syngeneic animals. This biological response was not observed in other activated forms of kinases constructed in a similar fashion, which include Trk (BCR-TRK), KDR (BCR-KDR), and the parental BCR-ABL. Interestingly, formation of fine tubules was accomplished with lower but not higher expression levels of BCR-FLTm. Compared to NP cells in primary culture NP31 is deficient in expression of alpha1 integrin subunit, which was restored by expression of BCR-FLTm that had tubulogenic ability. Matrix-induced tyrosine phosphorylation of an adaptor protein Shc with recruitment of Grb-2 was observed even when tubulogenesis was nearly completed at G1 stage of the cell cycle in 2-3 weeks. Activation of matrix metalloproteinase 2 (MMP-2) and expression of urokinase type plasminogen activator (uPA) was observed with cellular invasion into matrix at the depth of 200-300 microm. Inhibitors for MAP kinase activator MEK1 and for serine proteases showed deleterious effects on the tubulogenesis. We suppose that matrix ligand-induced integrin signals cooperate with a low level of Flt-1 kinase activity to promote tubulogenic behaviors of endothelial cells in this system.
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PMID:An oncogenic form of the Flt-1 kinase has a tubulogenic potential in a sinusoidal endothelial cell line. 1072 21

Expression of urokinase (uPA) and its receptor (uPAR) is associated with increased tumor-cellinvasion and metastasis in several malignancies including breast cancer. An 8-mer peptide derived from the nonreceptor-binding domain of urokinase (A6) has been shown to have antiangiogenic and proapoptotic effects to block the progression of breast cancer in vivo. In the present study, we evaluated the effects of A6 and the antiestrogen tamoxifen (TAM) alone and in combination on estrogen-receptor-positive Mat B-III rat breast cancer cells in vitro and in vivo. Treatment of Mat B-III cells with A6 and TAM resulted in a dose-dependent decrease in tumor-cell invasion through Matrigel; these effects were more marked when A6 and TAM were tested in combination. In addition, treatment of Mat B-III cells with either A6 or TAM resulted in a significant reduction of vascular endothelial growth factor receptor (flk-1) expression and in transforming growth factor beta activity, effects that were significantly higher after combined treatment with A6 and TAM. For in vivo studies, female Fischer rats were inoculated with Mat B-III cells (1 x 10(6)) into the mammary fat pad. These orthotopic tumors were staged to 30-40 mm(3) in volume and then treatment was initiated with A6 (75 mg/kg/day) and TAM (3 mg/kg/day) alone or in combination. Both A6 and TAM caused a significant reduction in tumor volume; however, these antitumor effects were significantly greater in animals receiving both A6 and TAM, which demonstrated a 75% reduction in tumor growth as compared with control animals. The number of macroscopic tumor foci was significantly reduced in A6-treated animals, whereas TAM failed to exhibit any antimetastatic effects. Histological analysis of primary tumors from different groups showed a decrease in new blood-vessel density and increased tumor-cell death in A6- and TAM-treated animals, and these effects were greater in experimental animals receiving A6 and TAM in combination. Collectively, these studies demonstrate that the addition of novel antiangiogenic/antimetastatic agents like A6 to hormone therapy can enhance the antitumor effects of hormone therapy through increased inhibition of angiogenesis and induction of tumor-cell death.
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PMID:An antiangiogenic urokinase-derived peptide combined with tamoxifen decreases tumor growth and metastasis in a syngeneic model of breast cancer. 1218 25

Expression of the tetraspanin CO-029 is associated with poor prognosis in patients with gastrointestinal cancer. In a pancreatic tumor line, overexpression of the rat homologue, D6.1A, induces lethally disseminated intravascular coagulation, suggesting D6.1A engagement in angiogenesis. D6.1A-overexpressing tumor cells induce the greatest amount of angiogenesis in vivo, and tumor cells as well as exosomes derived thereof strikingly increase endothelial cell branching in vitro. Tumor cell-derived D6.1A stimulates angiogenic factor transcription, which includes increased matrix metalloproteinase and urokinase-type plasminogen activator secretion, pronounced vascular endothelial growth factor expression in fibroblasts, vascular endothelial growth factor receptor expression, and strong D6.1A up-regulation in sprouting endothelium. Thus, D6.1A initiates an angiogenic loop that, probably due to the abundance of D6.1A in tumor-derived exosomes, reaches organs distant from the tumor. Most importantly, because of the strong D6.1A up-regulation on sprouting capillaries, angiogenesis could be completely inhibited by a D6.1A-specific antibody, irrespective of whether or not the tumor expresses D6.1A. Tetraspanins have been suggested to be involved in morphogenesis. This is the first report that a tetraspanin, CO-029/D6.1A, promotes tumor growth by its capacity to induce systemic angiogenesis that can effectively, and with high selectivity for sprouting endothelium, be blocked by a D6.1A-specific antibody.
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PMID:Systemic induction of the angiogenesis switch by the tetraspanin D6.1A/CO-029. 1684 54

Ovarian cancer is a highly metastatic disease. Lysophosphatidic acid (LPA) levels are elevated in ascites from ovarian cancer patients, but its potential role in ovarian cancer metastasis has just begun to be revealed. In this work, we show that LPA stimulates invasion of primary ovarian cancer cells, but not ovarian epithelial or borderline ovarian tumor cells, although these benign cells indeed respond to LPA in cell migration. We have found that LPA downregulates tissue inhibitor of metalloproteinases (TIMPs). TIMP2 and TIMP3 play functional role in LPA-induced invasion as negative regulators. G(i) protein, phosphatidylinositol-3 kinase (PI3K), p38 mitogen-activated protein kinase (MAPK), cytosolic phospholipase A(2) and urokinase type plasminogen activator (uPA) are required for LPA-induced cells invasion. TIMP3 may affect two independent downstream targets, vascular endothelial growth factor receptor and p38 MAPK. In vivo, LPA stimulates tumor metastasis in an orthotopic ovarian tumor model, which can be inhibited by a PI3K inhibitor, LY294002. In summary, LPA is likely a key component for promoting ovarian metastasis in vivo. LPA downregulates TIMP3, which may have targets other than metalloproteinases. Our in vivo metastasis mouse model is useful for studying the efficacy of therapeutic regimes of ovarian cancer.
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PMID:Lysophosphatidic acid downregulates tissue inhibitor of metalloproteinases, which are negatively involved in lysophosphatidic acid-induced cell invasion. 1713 Aug 43


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