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)

Maspin is a novel serine protease inhibitor with tumor suppressive activity, inhibiting tumor invasion and metastasis. To date, the underlying molecular mechanism of maspin remains elusive. Recombinant maspin has been shown to specifically inhibit cell surface-associated urokinase-type plasminogen activator (uPA) and fibrinogen-bound tissue-type plasminogen activator. However, the role of endogenous maspin in plasminogen activation is totally unknown. To address this issue, we generated stable maspin-expressing transfectants using prostate carcinoma cells DU145 as the parental cell line. We report here that endogenous maspin exerts pleiotropic inhibitory effects on the pericellular uPA system. Maspin expression led to a significantly reduced level of cell surface-bound uPA and uPA receptor proteins without altering the steady-state levels of the respective mRNAs. Treatment with receptor-associated protein (RAP), a specific inhibitor of low-density lipoprotein receptor-related protein, lead to a significantly increased level of secreted uPA and cell surface uPAR in maspin transfectants but not in the mock control cells. A combination of enzymatic and molecular analyses revealed that maspin inhibits the cell surface-mediated plasminogen activation by forming an SDS-resistant complex with cell surface-bound uPA. In addition, maspin expression led to a dramatic reduction in the release of active uPA, both high molecular weight and the low molecular weight, into the conditioned culture medium. Consistently, the conditioned medium of maspin transfectant clones had a significantly reduced activity in converting plasminogen to plasmin. The inhibitory effect of maspin on pericellular uPA correlates with significantly decreased cell invasion potential and motility in vitro. The maspin-neutralizing antibody (Abs4A) reversed the subdued invasive potential of maspin transfectant cells in a dose-dependent manner. In summary, this study provides the first evidence that endogenous maspin is a potent inhibitor of pericellular uPA. Furthermore, our results support a current hypothesis that maspin blocks tumor invasion and motility by inhibiting localized pericellular proteolysis.
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PMID:Pleiotrophic inhibition of pericellular urokinase-type plasminogen activator system by endogenous tumor suppressive maspin. 1175 84

The urokinase-type plasminogen activator (uPA) system is a dynamic complex in which the membrane receptor uPAR binds uPA that binds the plasminogen activator inhibitor (PAI)-1 localized in the extracellular matrix, resulting in endocytosis of the whole complex by the low-density lipoprotein receptor-related protein (LRP). High expression of PAI-1 is paradoxically associated with marked tumor spreading and poor prognosis. We previously reported a nonproteolytic role of the [uPAR:uPA:PAI-1:LRP] complex operative in cell migration. Here we explored whether matrix PAI-1 could be used as a migration support by human breast cancer cells. We showed that the uPA system and LRP are localized at filopodia of invasive cells, and that formation/internalization of the [uPAR:uPA:PAI-1:LRP] complex is required for attachment and migration of cancer cells on plastic and on a PAI-1 coat. PAI-1 increased both filopodia formation and migration of cancer cells suggesting a chemokine-like activity. Migration velocity, expression of the uPA system, use of the [uPAR:uPA:PAI-1:LRP] complex to migrate, and promigratory effects of PAI-1 paralleled cancer cell invasiveness. Phenotyping and functional analysis of invasive cancer cell subclones indicated that different cell subpopulations may use different strategies to migrate depending on both the environment and their expression of the uPA system, some of them taking advantage of abundant available PAI-1.
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PMID:Promigratory effect of plasminogen activator inhibitor-1 on invasive breast cancer cell populations. 1178 17

Plasminogen activator inhibitor 1 (PAI-1) inhibits plasminogen activators (u-PA and t-PA) by forming stable complexes endocytosed via a low-density lipoprotein receptor superfamily member-dependent mechanism. PAI-1 circulates actively in plasma and latently in platelets but is also secreted and deposited into the matrix by several cells, where it participates in tissue repair processes.
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PMID:Plasminogen activator inhibitor 1: physiological and pathophysiological roles. 1190 93

Urokinase plasminogen activator (uPA) is a multifunctional protein that has been implicated in several physiological and pathological processes involving cell adhesion and migration in addition to fibrinolysis. In a previous study we found that two-chain urokinase plasminogen activator (tcuPA) stimulates phenylephrine-induced vasoconstriction of isolated rat aortic rings. In the present paper we report that uPA(-/-) mice have a significantly lower mean arterial blood pressure than do wild type mice and that aortic rings from uPA(-/-) mice show an attenuated contractile response to phenylephrine. In contrast, the blood pressure of urokinase receptor knockout (uPAR(-/-)) mice and the response of their isolated aortic rings to phenylephrine were normal, indicating that the effect of uPA on vascular contraction is independent of uPAR. Addition of mouse and human uPA almost completely reversed both the impaired vascular contractility and the lower arterial blood pressure in vivo. The in vitro and in vivo effects of infused uPA on aortic contractility and the restoration of normal blood pressure in uPA(-/-) mice were prevented by antibody to low-density lipoprotein receptor-related protein/alpha(2)-macroglobulin receptor (LRP). A modified form of uPA that lacks the kringle failed to restore the blood pressure in uPA(-/-) mice, notwithstanding having a longer half-life in the circulation. Ligands that regulate the interaction of uPA with LRP, such as PAI-1 or the PAI-1-derived peptide (EEIIMD), abolished the vasoactivity of tcuPA in vitro and in vivo. These studies identify a novel signal transducing cellular receptor pathway involved in the regulation of vascular contractility.
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PMID:Binding of urokinase to low density lipoprotein-related receptor (LRP) regulates vascular smooth muscle cell contraction. 1217 38

We recently reported that human recombinant melanotransferrin (p97) presents a high transport rate across the blood-brain barrier that might involve the low-density lipoprotein receptor-related protein (LRP). We now report new interactions between p97 and another LRP ligand, the urokinase plasminogen activator (uPA) complex. By using biospecific interaction analysis, both pro-uPA and plasminogen are shown to interact with immobilized p97. Moreover, the activation of plasminogen by pro-uPA is increased by soluble p97. Because the uPA system plays a crucial role in cell migration, both in cancer and in angiogenesis, we also measured the impact of both endogenous membrane-bound and exogenous p97 on cell migration. The monoclonal antibody L235 (which recognizes a conformational epitope on p97) inhibited the migration of human microvascular endothelial cells (HMECs-1) and of human melanoma SK-MEL-28 cells, indicating that endogenous membrane-bound p97 could be associated with this process. In addition, low concentrations of exogenous p97 (10 and 100 nM) inhibited HMEC-1 and SK-MEL28 cell migration by more than 50%. These results indicate that membrane-bound and soluble p97 affect the migration capacity of endothelial and melanoma cells and suggest that p97 could be involved in the regulation of plasminogen activation by interacting with pro-uPA and plasminogen.
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PMID:Regulation of plasminogen activation: a role for melanotransferrin (p97) in cell migration. 1275 Jan 56

We have previously demonstrated that human recombinant soluble melanotransferrin (hr-sMTf) interacts with the single-chain zymogen pro urokinase-type plasminogen activator (scu-PA) and plasminogen. In the present work, the impact of exogenous hr-sMTf on endothelial cells (EC) migration and morphogenic differentiation into capillary-like structures (tubulogenesis) was assessed. hr-sMTF at 10 nM inhibited by 50% the migration and tubulogenesis of human microvessel EC (HMEC-1). In addition, in hr-sMTf-treated HMEC-1, the expression of both urokinase-type plasminogen activator receptor (u-PAR) and low-density lipoprotein receptor-related protein (LRP) are down-regulated. However, fluorescence-activated cell sorting analysis revealed a 25% increase in cell surface u-PAR in hr-sMTf-treated HMEC-1, whereas the binding of the urokinase-type plasminogen activator (u-PA)*plasminogen activator inhibitor-1 (PAI-1) complex is decreased. This reduced u-PA-PAI-1 binding is correlated with a strong inhibition of the HMEC-1 plasminolytic activity, indicating that exogenous hr-sMTf treatment alters the internalization and recycling processes of free and active u-PAR at the cellular surface. Overall, these results demonstrate that exogenous hr-sMTf affects plasminogen activation at the cell surface, thus leading to the inhibition of EC movement and tubulogenesis. These results are the first to consider the potential use of hr-sMTf as a possible therapeutic agent in angiogenesis-related pathologies.
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PMID:Inhibition of endothelial cell movement and tubulogenesis by human recombinant soluble melanotransferrin: involvement of the u-PAR/LRP plasminolytic system. 1584 38

The low-density lipoprotein receptor-related protein-1 (LRP-1) is a multifunctional receptor that undergoes constitutive endocytosis and recycling. To identify LRP-1 in lipid rafts, we biotin-labeled cells using a membrane-impermeable reagent and prepared Triton X-100 fractions. Raft-associated proteins were identified in streptavidin affinity-precipitates of the Triton X-100-insoluble fraction. PDGF beta-receptor was identified exclusively in lipid rafts, whereas transferrin receptor was excluded. LRP-1 distributed partially into rafts in murine embryonic fibroblasts (MEFs) and HT 1080 cells, but not in smooth muscle cells and CHO cells. LRP-1 partitioning into rafts was not altered by ligands, including alpha2-macroglobulin, platelet-derived growth factor-BB, and receptor-associated protein (RAP). To examine LRP-1 trafficking between membrane microdomains, we developed a novel method based on biotinylation and detergent fractionation. Association of LRP-1 with rafts was transient; by 15 min, nearly all of the LRP-1 that was initially raft-associated exited this compartment. LRP-1 in the Triton X-100-soluble fraction, which excludes lipid rafts, demonstrated complex kinetics, with phases reflecting import from rafts, endocytosis, and recycling. Potassium depletion blocked LRP-1 endocytosis but did not inhibit trafficking of LRP-1 from rafts into detergent-soluble microdomains. Our data support a model in which LRP-1 transiently associates with rafts but does not form a stable pool. Fluid movement of LRP-1 between microdomains may facilitate its function in promoting the endocytosis of other plasma membrane proteins, such as the urokinase receptor, which localizes in lipid rafts.
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PMID:The low-density lipoprotein receptor-related protein-1 associates transiently with lipid rafts. 1614 55

Low-density lipoprotein receptor family members (LRs) play a key role in the catabolism of many membrane-associated proteins, such as complexes between proteinases and their receptors, in addition to being involved in lipoprotein metabolism as suspected by the hitherto well-established functions of low-density lipoprotein receptor, in a variety of tissues. Recent studies using receptor-deficient or -overexpressing animals and cells have suggested that certain LRs are important regulators of the migration (and proliferation) of vascular smooth muscle cells (SMCs). LR expression is markedly induced in intimal or medial SMCs during the formation of atherosclerotic lesions. Because LRs can modulate the activity of the urokinase-type plasminogen activator (uPA) receptor and possibly of the platelet-derived growth factor (PDGF) receptor, LRs may influence the migration of SMCs through functional modulation of these membrane receptors. Therefore, SMC migration may be regulated by time-restricted expression of LRs. In agreement with the concept of functional interaction between LRs and membrane signaling receptors, a negative regulator of uPA receptor protein catabolism, LR11, has been identified. Statins modulate the PDGF-induced migration of intimal SMCs via the LR11/uPA receptor cascade. Selective modification of the LRs/uPA receptor/PDGF receptor systems in SMCs may be important for suppression of atherosclerotic plaque formation as well as for preventing intimal thickening after angioplasty.
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PMID:Modulation of smooth muscle cell migration by members of the low-density lipoprotein receptor family. 1657 89

It is well documented that tumor suppressive maspin inhibits tumor cell invasion and extracellular matrix remodeling. Maspin is a cytosolic, cell surface-associated, and secreted protein in the serine protease inhibitor superfamily. Although several molecules have been identified as candidate intracellular maspin targets, the extracellular maspin target(s) remains elusive. Although maspin does not directly inhibit urokinase-type plasminogen activator (uPA) activity, we have shown evidence that maspin may block the pericellular proteolysis mediated by cell surface-associated uPA. In the current study, maspin significantly inhibited the Ca2+ reduction-induced detachment of DU145 cells. This maspin effect was associated with increased and sustained levels of mature focal adhesion contacts (FAC). We noted that maspin (a) colocalized with uPA and uPA receptor (uPAR), (b) enhanced the interaction between uPAR and low-density lipoprotein receptor related protein, and (c) induced rapid internalization of uPA and uPAR. The maspin effects on surface-associated uPA and uPAR required the interaction between uPA and uPAR. Further biochemical and biophysical analyses revealed that maspin specifically bound to pro-uPA with a deduced K(d) of 270 nmol/L and inhibited the plasmin-mediated pro-uPA cleavage. Interestingly, substitution of maspin p1' site Arg340 in the reactive site loop (RSL) with alanine not only abolished the binding to pro-uPA but also diminished the maspin effects on pro-uPA cleavage and cell detachment. These data show an important role of maspin RSL in regulating the uPA/uPAR-dependent cell detachment. Together, our data led to a new hypothesis that maspin may stabilize mature FACs by quenching localized uPA/uPAR complex before uPA activation.
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PMID:Maspin retards cell detachment via a novel interaction with the urokinase-type plasminogen activator/urokinase-type plasminogen activator receptor system. 1661 39

Complete resection of malignant glioblastomas is usually impossible because of diffuse and widespread invasion of tumor cells, and complementary approaches need to be developed in order to improve the efficacy of current treatments. Consumption of fruits and berries has been associated with decreased risk of developing cancer and there is great interest in the use of molecules from dietary origin to improve anticancer therapies. In this work, we report that the aglycons of the most abundant anthocyanins in fruits, cyanidin (Cy), delphinidin (Dp), and petunidin (Pt), act as potent inhibitors of glioblastoma cell migration. Dp clearly exhibited the highest inhibitory potency, this effect being related to the ortho-dihydroxyphenyl structure on the B-ring and the presence of a free hydroxyl group at position 3. Dp decreases the expression of both urokinase-type plasminogen activator receptor (uPAR) and the low-density lipoprotein receptor-related protein (LRP), acting at the transcriptional levels. In addition, Dp upregulated urokinase-type plasminogen activator (uPA) and downregulated the plasminogen activator inhibitor-1 (PAI-1) but decreased, in a concentration-dependent manner, the uPA-dependent conversion of plasminogen to plasmin, indicating that the upregulation of uPA observed with these compounds was not associated with induction of the plasminolytic activity. Overall, these results demonstrate that Dp, Pt, and Cy affect plasminogen activation, thus leading to the inhibition of glioblastoma cell migration and therefore they may be helpful for the development of new strategies for cancer prevention and therapy.
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PMID:Anthocyanidins inhibit migration of glioblastoma cells: structure-activity relationship and involvement of the plasminolytic system. 1682 70


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