Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.73 (urokinase-type plasminogen activator)
10,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor cells traverse basement membranes (BM) during the stages of the metastatic process. Penetration of the BM may involve proteolysis by enzymes directly or indirectly associated with tumor cells. This study evaluated the role of the serine proteases urokinase (plasminogen activator), plasmin, and another regulatory protease, alpha-thrombin, in the degradation of the BM. Homogeneously pure enzyme preparations were incubated with isolated components of BM and with whole human amnion BM. The BM components consisted of acid-extracted type IV collagen, pepsin fragments of collagen type IV, laminin, and fibronectin. Collagen type V (alpha A alpha B) associated with the peri-BM zone was also studied. The purity of the enzymes was verified by gel electrophoresis and inhibitor studies. Digestion of the BM components was performed at 25 degrees using matched activity for the different enzymes. Urokinase failed to significantly degrade fibronectin or any of the other BM components. Under the same 25 degrees (native) conditions, plasmin and thrombin cleaved fibronectin and laminin into multiple specific fragments but did not produce a major cleavage of acid-extracted type IV collagen, pepsinized type IV collagen, or alpha A alpha B (type V) collagade fibronectin or any of the other BM components. Under the same 25 degrees (native) conditions, plasmin and thrombin cleaved fibronectin and laminin into multiple specific fragments but did not produce a major cleavage of acid-extracted type IV collagen, pepsinized type IV collagen, or alpha A alpha B (type V) collagade fibronectin or any of the other BM components. Under the same 25 degrees (native) conditions, plasmin and thrombin cleaved fibronectin and laminin into multiple specific fragments but did not produce a major cleavage of acid-extracted type IV collagen, pepsinized type IV collagen, or alpha A alpha B (type V) collagen. alpha-Thrombn selectively degraded only the m.w. 400,000 chain of laminin, whereas plasmin degraded both the laminin chains. Digestion of laminin by the serine proteases was time and concentration dependent, as verified by a new degradation assay using [14C]laminin. A variety of normal and neoplastic cells were tested for the presence of laminin-degrading proteases. macrophages, polymorphonuclear leukocytes, and metastatic tumor cells contained a significant laminin-degarding activity. The activity was enhanced by the addition of plasminogen. Type V collagen was cleaved by thrombin and plasmin at 35 degrees but not at temperatures below 33 degrees. Following treatment of whole-amnion BM with any of these enzymes, electron microscopy demonstrated preservation of the lamina densa. Immunohistology studies indicated that laminin, but not type IV collagen, was removed from the whole BM by plasmin treatment. The results suggest that these BM components are poor substrates for plasminogen activators and that plasmin alone is not sufficient to completely degrade the whole BM...
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PMID:Effect of plasminogen activator (urokinase), plasmin, and thrombin on glycoprotein and collagenous components of basement membrane. 645 54

In WEHI-3B murine leukemic cells, plasminogen activator and plasminogen binding sites are associated with the cell membrane. The putative receptor for the zymogen exhibits low affinity for the ligand (dissociation constant of 0.38 microM and a high binding capacity (40,000 sites per cell). Plasminogen also binds in a cooperative fashion to type I collagen with an affinity which is higher than that displayed by cells. Collagen-bound plasminogen can be activated by cells preincubated with plasminogen in a manner that cells develop the capacity to adhere to type I collagen. The activation of collagen-bound plasminogen by cellular urokinase-like plasminogen activator (u-PA) was 60% more efficient than the activation of the soluble (not bound) form of plasminogen. These results suggest that in the invasive phenomena, WEHI cells operate as carriers of plasminogen from plasma to tissue. In addition, collagen can serve as a reservoir of zymogen in the extracellular matrix milieu through direct binding to plasminogen and at the same time allow more efficient plasminogen activation.
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PMID:Surface-associated plasminogen activation in leukemic cells: interaction with extracellular matrix. 781 13

Recent studies have shown that serine protease inhibitors can be regulated in their activity, specificity, and location by glycoprotein or extracellular matrix (ECM) co-factors. Protease nexin-1 (PN-1) is a member of the serpin superfamily of serine protease inhibitors which can rapidly inhibit thrombin, urokinase, and plasmin. PN-1 binds tightly to and is regulated by the ECM. This interaction accelerates the inhibition of thrombin by PN-1 and blocks urokinase and plasmin inhibition by PN-1. Previous work showed that heparan sulfate proteoglycan is largely responsible for the acceleration of thrombin inhibition by PN-1. Our current studies were directed at identifying ECM component(s) that decreased the ability of PN-1 to inhibit urokinase and plasmin. These studies showed that collagen type IV decreased the formation of SDS-stable complexes between urokinase or plasmin and PN-1 without affecting formation of complexes between thrombin and PN-1. The second order rate constant for inhibition of urokinase by PN-1 was markedly decreased with increasing collagen type IV, whereas the second order rate constant for inhibition of thrombin by PN-1 was unaffected by addition of collagen type IV. Other ECM components (collagen type I, vitronectin, fibronectin, and heat-denatured collagen type IV) did not affect complex formation or the rate of inhibition of proteases by PN-1, indicating that these effects were specific to collagen type IV. Binding of PN-1 to immobilized collagen type IV was demonstrated using an enzyme-linked immunosorbent assay; the concentration of PN-1 necessary to obtain 50% saturation of the immobilized collagen type IV binding sites was approximately 15 nM. Collagen type IV was also copurified with PN-1 from fibroblast-conditioned medium. These results demonstrate a novel regulation of serpin specificity in which an ECM co-factor decreased the inhibition of certain proteases by the serpin without affecting the inhibition of its target protease.
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PMID:Regulation of protease nexin-1 target protease specificity by collagen type IV. 800 28

Hepatocytes were grown in chemically defined hepatocyte growth medium (HGM) containing hepatocyte growth factor (HGF) and epidermal growth factor (EGF) on collagen-coated polystyrene beads in roller bottle cultures, forming clusters of beads, and proliferating hepatocytes and nonparenchymal cells, including fenestrated endothelium-forming vascular structures. Desmin-positive cells surrounded hepatocytes. Collagen types I and III were deposited in a diffuse manner whereas collagen type IV surrounded the clusters of the epithelial cells, forming a basement membrane. When the mixed cell clusters were implanted in Matrigel (Collaborative Research, Bedford, MA), hepatocytes grew in three dimensions, forming plates and ducts. Many single, long plates of hepatocytes were seen, suggesting progressive linear assembly guided by hepatocyte specific structural parameters. HGF, EGF, and transforming growth factor-alpha (TGF-alpha) enhance these phenomena. HGF plus EGF elicited maximal response. TGF-beta1 suppressed formation of the ducts and plates. Within three months in Matrigel, the cultures established monolayers composed of plates, ducts, and a well-delineated canalicular network. The mixed cultures expressed albumin, A1AT, AFP, transferrin, and CYPIIB1. Following implantation of the cell clusters in Matrigel, there was decreased expression of c-met, urokinase, urokinase receptor, and TGF-beta1. Electron microscopy showed differentiated hepatocytes with nearly normal ultrastructure. The proliferating cell nuclear antigen (PCNA) labeling index was high (more than 80%) whereas the Bromo-deoxyaridine labeling index of ongoing DNA synthesis varied from 10% to 15%. These results show that the mixed cultures of proliferating hepatocytes and nonparenchymal cells can reproduce the hallmark structures of hepatic histological architecture while maintaining differentiation and the capacity to proliferate. (HEPATOLOGY 1999;29:90-100.)
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PMID:Morphogenetic events in mixed cultures of rat hepatocytes and nonparenchymal cells maintained in biological matrices in the presence of hepatocyte growth factor and epidermal growth factor. 986 82

Collagen breakdown and apoptotic cell death within the apex of the preovulatory ovine follicle are hallmarks of impending ovarian rupture. An integrative mechanism is proposed whereby gonadotrophic stimulation of urokinase-type plasminogen activator secretion by the follicular-contiguous ovarian surface epithelium elicits a localized increase in tissue plasmin, which activates collagenolysis and tumour necrosis factor alpha-induced cell death within the formative ovulatory stigma.
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PMID:Plasmin-tumour necrosis factor interaction in the ovulatory process. 1069 67

Collagen breakdown and cellular death (apoptosis and inflammatory necrosis) within the apex of preovulatory ovine follicles are hallmarks of impending ovarian rupture. An integrative mechanism is presented whereby gonadotropic stimulation of urokinase-type plasminogen activator secretion by ovarian surface epithelial cells bordering the preovulatory follicle elicits a localized increase in tissue plasmin, which activates latent collagenases and secretion of tumor necrosis factor-alpha (TNF-alpha) from thecal endothelium. TNF-alpha potentiates collagenolysis (via matrix metalloproteinase gene expression) and (at elevated concentrations) mediates epithelial/vascular dissolution. Incidental damage to DNA of ovarian surface epithelial cells circumjacent to the ruptured follicle is a putative etiological factor in ovarian cancer.
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PMID:Proteolytic and cellular death mechanisms in ovulatory ovarian rupture. 1081 Feb 5

The cardiac extracellular matrix consists of a three-dimensional structural network of interstitial collagens to which other matrix components are attached. The main physiological functions of this network are to retain tissue integrity and cardiac pump function. Collagen deposition is controlled and can be modulated by hormonal factors, growth factors, cytokines, regulatory proteins and/or hemodynamic factors. Increased collagen deposition is a prerequisite to prevent dilatation of the infarcted area. Excessive accumulation of collagen leads to ventricular diastolic and systolic dysfunction and ultimately contributes to heart failure. An appropriate balance of extracellular matrix synthesis and degradation is required for normal morphogenesis and maintenance of tissue architecture. A disbalance in the extracellular matrix turnover either by decreased matrix synthesis and/or increased degradation leads to less than normal extracellular matrix in the myocardium which in its turn may lead to cardiac dilatation or even rupture. Extracellular matrix degrading enzymes expressed after myocardial infarction belong to the families of serine and matrix metalloproteinases (MMPs) and are secreted as latent proenzymes that have to be activated. It is crucial to keep the activity of these enzymes under tight control by either influencing the synthesis, activation or inhibition by tissue inhibitors of MMPs (TIMPs) or alpha2-macroglobulin. First studies using MMP inhibitors in experimental models of myocardial infarction seem to give attenuation of ventricular geometry but not always improvement of cardiac function. A central role in the activation of MMPs plays the plasminogen-plasmin system. Invasion of inflammatory cells and hitherto the rest of the wound healing cascade is inhibited in plasminogen or uPA deficient mice, most likely by the inhibition of MMP activity. Regulating the balance of extracellular matrix remodeling either by extracellular matrix synthesis or degradation might be one of the possible prevention mechanisms for heart failure. But also regeneration of the vascular and cardiomyocyte network might be potential new treatments for people with heart failure.
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PMID:Integration of concepts: cardiac extracellular matrix remodeling after myocardial infarction. 1255 43

The deposition of fibrin is an integral part of the tissue repair process, but its persistence is also associated with a number of fibrotic conditions. This study addressed the hypothesis that reduced fibrinolysis and fibrin persistence are associated with an enhanced accumulation of collagen and the development of skin fibrosis. Decreased fibrinolysis was confirmed in fibrin gel cultures that contained human dermal fibroblasts plus the specific plasmin inhibitor alpha(2)-antiplasmin or dermal fibroblasts isolated from plasminogen activator (PA)-deficient mice. Collagen accumulation was significantly increased in the presence of inhibitor and in tPA-deficient, but not uPA-deficient, fibroblasts compared with controls. These findings were also confirmed using a skin fibrosis model in which multiple injections of fibrin were given subcutaneously to PA-deficient mice. Injection sites from tPA-deficient mice displayed significantly increased collagen levels compared with uPA-deficient mice and wild-type controls. Up-regulation of fibroblast procollagen gene expression and reduced activation of pro-MMP-1 appeared to mediate the increase in collagen by human dermal fibroblasts in the presence of alpha2-antiplasmin. These findings suggest that persistent fibrin is associated with enhanced collagen accumulation that may result in the development of fibrotic skin disorders in which reduced fibrinolysis is a feature.
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PMID:Fibrin-induced skin fibrosis in mice deficient in tissue plasminogen activator. 1612 52

Early deep venous thrombosis (DVT) resolution is associated with neutrophil (PMN) influx. This study examined the role of PMNs in thrombus neovascularization and vein wall injury after DVT. A rat model of DVT by inferior vena cava (IVC) ligation was performed with control serum or rabbit anti-rat PMN serum administered perioperatively with sacrifice at 2 and 7 days. At 2 days, neutropenic rats had 1.6-fold larger thrombi (P = .04) and 1.4-fold higher femoral venous pressures by water manometry (P = .008) but no difference in thrombus neovascularization was observed. By 7 days, DVT sizes were similar, but vein wall injury persisted in the neutropenic rats with a 2.0-fold increase in vein wall stiffness by microtensiometry (P < .05), as well as a 1.2-fold increased thickness (P = .04). Collagen and profibrotic growth factors were significantly increased in neutropenic IVC at 7 days (all P < .05). Vein wall and intrathrombus uPA byWestern immunoblotting, and intrathrombus MMP-9 gelatinase activity were significantly less in neutropenic rats than controls (P < .001). Conversely, MMP-2 was significantly elevated in neutropenic IVC at 2 days after DVT. However, neutropenia induced 24 hours after DVT formation resulted in no significant increase in vein wall stiffness or collagen levels at 7 days, despite 1.4-fold larger thrombi (P < .05). These data suggest a critical early role for PMN in post DVT vein wall remodeling.
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PMID:Neutrophils modulate post-thrombotic vein wall remodeling but not thrombus neovascularization. 1649 89

The topical application of a mixture of sugar and povidone--iodine (PI) has been reported to accelerate the healing of cutaneous wounds and ulcers by promoting re-epithelialization and granulation tissue formation as well as having an anti-microbial effect. To clarify the mechanisms accounting for the efficacy of a 70% sugar and 3% PI paste (U-PASTAtrade mark) (SP), various keratinocytes and fibroblasts functions, including proliferation, collagen synthesis, integrin expression, and cytokine and proteinase secretions in the presence of SP were investigated. Cultured human keratinocytes and fibroblasts were treated with various concentrations of SP, SU and PI. The secretion of urokinase-type plasminogen activator (u-PA), transforming growth factor (TGF)-alpha and interleukin-1alpha from keratinocytes, was detected by ELISA. Collagen synthesis of fibroblasts was examined by means of detecting proline uptake. Furthermore, integrin expressions of these cells were analyzed using a flow cytometer. SP and PI increased intra-cellular u-PA of keratinocytes and stimulated the secretion of u-PA and TGF-alpha. Sugar accelerated the extra-cellular u-PA level only. Both SP and sugar increased the collagen synthesis of fibroblasts. SP and PI also remarkably induced the expressions of extra-cellular matrix receptor integrins, alpha1, alpha2, alpha3, alpha4, alpha5 and beta1, on the surface of keratinocytes and fibroblasts. SP, the mixture of sugar and PI, is likely to act on wounds not only as an antibiotic agent, but also as a modulator for keratinocytes and fibroblasts.
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PMID:Mixture of sugar and povidone--iodine stimulates wound healing by activating keratinocytes and fibroblast functions. 1686 30


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