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)

The regulation of urokinase plasminogen activator (uPA) expression was investigated in 2 highly metastatic rat mammary adenocarcinoma cell lines, BC1 and MAT 13762. BC1 cells were observed to synthesize, on average, 10 times less uPA enzyme and mRNA than MAT 13762 cells; however this difference was not accounted for by differences in uPA gene copy number/structure or in the rate of uPA gene transcription in the cell lines studied. Moreover, Northern blot analysis of invasive sub-populations derived in vitro from the BC1 cell line revealed levels of uPA expression similar to those of the parent, but a 3-fold elevation in expression of the metalloprotease gene, transin. Further investigation showed that treatment of BC1 cells with either of the protein synthesis inhibitors, cycloheximide or anisomycin, increased the level of both nuclear and cytoplasmic uPA RNA 6- to 18-fold in 4 hr, whilst inducing a maximum 2.6-fold increase in the rate of uPA gene transcription. This increase in uPA gene expression may therefore reflect, in part, an increase in the stability and/or processing of nuclear uPA transcripts. These results suggest that the degree of uPA gene expression does not correlate directly with BC1 tumor-cell invasion in vitro, and that the uPA gene is down-regulated, at least in part, post-transcriptionally in the nucleus of BC1 mammary tumor cells.
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PMID:Post-transcriptional regulation of urokinase plasminogen activator gene expression occurs in the nucleus of BC1 rat mammary tumor cells. 155 91

Degradation of cartilage matrix macromolecules depends on the increase of metalloprotease activity. It has been suggested that interleukin 1 (IL-1) contributes to cartilage break-down by modulating the synthesis of the elements favoring an activation of these metalloenzymes. We analyzed the effect of IL-1 on the synthesis of collagenase, stromelysin, and tissue inhibitor of metalloproteases (TIMP) in human cartilage explants and culture chondrocytes, as well as its effect on the secretion of plasminogen activators (t-PA, u-PA) and inhibitors (PAI-1, PAI-2) in cartilage explants. Messenger RNA levels of collagenase and TIMP were also analyzed following chondrocyte incubation in the presence or absence of IL-1. We demonstrate that IL-1 stimulates the secretion of metalloproteases and t-PA in a dose dependent manner. At a relatively low concentration (5 pg/ml), IL-1 induced collagenase and stromelysin synthesis in parallel with a decline in TIMP secretion. While IL-1 induced collagenase gene expression, no change in the TIMP mRNA level was noted. The increase in t-PA synthesis was accompanied by a decreased PAI-1 level, while the PAI-2 level remained unchanged. u-PA could not be detected in the culture medium. This study gives insight into the ways that the synthesis, activation and inhibition of metalloproteases are modulated by IL-1. These results support the importance of IL-1 in the etiology of cartilage degeneration.
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PMID:In vitro effects of interleukin 1 on the synthesis of metalloproteases, TIMP, plasminogen activators and inhibitors in human articular cartilage. 185 Dec 31

Cultures of transformed fibroblasts actively involved in extracellular matrix degradation have been examined for initial activation of serine and metallo protease cascade systems. Rous sarcoma virus transformed chick embryo fibroblasts (RSVCEF), in contrast to transformed mammalian cells, produce active, two chain urokinase-type plasminogen activator (tcu-PA). Active tcu-PA is found in serum-free, plasmin-free conditioned medium from RSVCEF cultures as determined by two independent methods, immunoprecipitation and differential DFP sensitivity. RSVCEF cultures synthesize and secrete inactive, single chain uPA (scu-PA) which is converted to tcu-PA in a time dependent manner by a catalytic mechanism that appears to involve a functioning uPA receptor on the surface of intact cells. The enzyme activity responsible for this conversion may represent the initiating catalytic event in the PA/plasminogen serine protease cascade system. A 70 kDa prometalloprotease capable of degrading denatured collagen following its activation also is significantly elevated in RSVCEF cultures over that of normal CEF. Trace amounts of the active 62 kDa form of the metalloprotease (gelatinase) is found in the transformed RSVCEF cultures indicating that these cultures produce a natural activator of the prometalloprotease. Plasmin and/or PA do not appear to be the activator of this enzyme as determined by indirect inhibition assays and direct assays employing purified enzymes. The possible central position of pro PA and the 70 kDa prometalloprotease in an interacting, complex protease cascade system involved in extracellular matrix degradation is discussed.
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PMID:Serine protease and metallo protease cascade systems involved in pericellular proteolysis. 196 54

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

Levels of tissue inhibitor of metalloproteases (TIMP) and plasminogen activator (PA)/plasmin were measured and the distribution of PA was studied by immunohistochemical techniques in cartilage and synovium samples from dogs subjected to sectioning of the anterior cruciate ligament of their right knees and sham operation of their left knees (controls). Twenty-three animals were divided into 3 groups and killed at 2, 4, or 8 weeks after surgery. The levels of PA and plasmin were found to be significantly elevated in the osteoarthritic (OA) knee cartilage and synovium at all times after surgery, except for levels of PA in the OA cartilage at 2 weeks. There was a positive correlation between the levels of PA and plasmin in the synovial membrane (r = 0.64, P less than 0.001). In OA knees, the presence of high levels of total and active collagenase was detected in cartilage and in synovium. The levels of these 2 forms of collagenase showed a positive correlation both in cartilage (r = 0.65, P less than 0.001) and in synovium (r = 0.77, P less than 0.001). The levels of TIMP in cartilage from OA and sham operated knees were similar. Although the TIMP level was increased in the OA synovium, it was found only in trace amounts in cartilage. Immunohistochemical studies revealed that both forms of PA, urokinase-type PA and tissue-type PA, and TIMP were present in OA tissues. In the synovium, they were found mainly in monocyte/macrophages, synovial lining cells, and blood vessel cells. In OA cartilage, PA was present only at the superficial level in chondrocytes and in cartilage matrix, whereas TIMP was present in chondrocyte lacunae throughout the full thickness of the cartilage. TIMP was also detected in the superficial level of cartilage from sham operated knees. The results of this study indicate that in OA tissues, there are conditions that favor the synthesis and activation of metalloproteases. PA and plasmin are likely to play an important role in the physiologic activation of metalloproteases, although they are probably not the only system involved in this process. The lack of increased TIMP levels in the OA cartilage, in the presence of increased metalloprotease activity, is also a possible contributing factor in the enzymatic degradation of this tissue.
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PMID:Imbalance between the mechanisms of activation and inhibition of metalloproteases in the early lesions of experimental osteoarthritis. 217 38

Endothelial cells produce and secrete a large number of proteases which are implicated in various disease states. These proteases fall into two classes: serine proteases include plasminogen activators (t-PA) and urokinase (u-PA) and play a major role in fibrinolysis, tissue repair and carcinogenesis; and metalloproteases include collagenases and stromelysine, two enzymes involved in the tissue remodelling that occurs during angiogenesis and tumor growth. The authors have recently identified two other proteases in porcine aortic endothelial cell culture medium. One is an elastase-like enzyme of the metalloprotease group, whereas the other is a new protease whose molecular weight is 85 Kd and whose activity becomes apparent only after exposure of the endothelial cells to platelets. The term Platelet Endothelial Cell Activated Protease accurately describes this enzyme. PECAP degrades casein and fibrinogen. Because PECAP is not inhibited by the usual inhibitors of the various classes of proteases, it remains at present unclassified.
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PMID:[Endothelial cell proteases and their modulation by platelets]. 229 Jun 90

Cultures of neurons from neonatal rat superior cervical, dorsal root, and trigeminal ganglia were grown in the absence of nonneuronal cells in serum-free defined medium. Proteins metabolically labeled with radioactive amino acids and spontaneously released into the culture medium were studied using two-dimensional gel electrophoresis and photofluorography. All three populations of neurons released 12-15 major proteins into the culture medium. Four proteins were released selectively by sympathetic neurons and two proteins were consistently released by both populations of sensory neurons but not by sympathetic neurons. Enzymatic activities are associated with at least two of the released proteins. One is a calcium-dependent metalloprotease, and the other a plasminogen activator. The calcium-dependent metalloprotease has a MW of 62 kDa, requires millimolar calcium for maximum activity, and has a restricted substrate specificity. It degraded native and denatured collagen more readily than casein, albumin, or fibronectin and denatured collagen (gelatin) was a better substrate than native collagen. The plasminogen activator released by neurons has a MW of 51 kDa and is converted to an active 32 kDa form. Its physiochemical properties are similar to urokinase and it was precipitated by a rabbit antiserum produced against human urokinase. A large fraction of both proteases was released by distal processes and/or growth cones suggesting that these proteases could be involved in growth cone functions.
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PMID:Release of plasminogen activator and a calcium-dependent metalloprotease from cultured sympathetic and sensory neurons. 298 45

Results from model tumour systems suggest that either increased levels of certain metalloproteases (MMPs) or decreased levels of their inhibitors correlate with metastatic potential. In this study, levels of two MMPs, i.e. MMP-8 and -9, and their inhibitor tissue inhibitor of metalloprotease type 1 (TIMP-1) were measured by enzyme-linked immunosorbent assay in human breast tumours. Levels of MMP-8 and -9 correlated significantly with each other, but neither MMP correlated with urokinase plasminogen activator. Levels of both MMP-8 and -9 were also significantly related to levels of TIMP-1. In contrast, neither MMP correlated with plasminogen activator inhibitor. No relationship was found between MMP-8, MMP-9 or TIMP-1 and either tumour size or metastasis to axillary nodes. MMP-8 and -9 levels were inversely related to levels of oestrogen receptors. MMP-8 but not MMP-9 levels were also inversely correlated with progesterone receptor levels. It is concluded that the assay for MMP-8 and -9 described here will permit the evaluation of these proteases as prognostic markers in cancer.
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PMID:Assay of matrix metalloproteases types 8 and 9 by ELISA in human breast cancer. 773 94

The invasive nature of human gliomas represents a major factor in preventing their total resection. The exact nature of the underlying mechanisms of tumor cell invasion are still unclear. In this study, we have quantitatively assayed a glioblastoma cell line for its ability to migrate through a polycarbonate filter coated with matrigel which contains a complex of multiple basement membrane components. At 48 h the glioblastoma cell line (U251) showed a rate of invasiveness of 42% and also dependent on the concentration of matrigel. The U251 cell line produced a urokinase type plasminogen activator and a 92-KDa type IV collagenase. Both enzymes were inhibited by the addition of uPA and 92-KDa type IV collagenase antibodies. Those same antibodies reduced the invasion rate of U251 cells from 42% to 12 and 21%, respectively. Similarly, the addition of epsilon-aminocaproic acid (a plasmin inhibitor) or tissue inhibitor of metalloprotease (TIMP2, a collagenase inhibitor) reduced the invasiveness of U251 cells from 42% to 14% and 10%, respectively. Additionally, the other two glioblastoma cell lines (LG11, UWR1) and astrocytes showed a rate of invasiveness at 41%, 61% and 12%, respectively. Finally, the addition of hyaluronic acid to the matrigel, a constituent of brain extracellular matrix, enhanced the rate of invasion. These findings provide evidence for the role of serine proteases and metalloproteases in facilitating the invasion of extracellular matrix components by glioblastoma cell line and suggest a therapeutic role for protease inhibitors in attempting to minimize the invasive propensity of gliomas.
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PMID:Role of plasminogen activator and of 92-KDa type IV collagenase in glioblastoma invasion using an in vitro matrigel model. 796 75

Rous sarcoma virus-transformed chick embryo fibroblasts (RSVCEF) constitute a well-characterized model system for oncogenic transformation, matrix degradation, and cancer invasion. As RSVCEF cultures employ both serine protease and metalloprotease cascades in the process of matrix degradation, they have contributed significantly to understanding the nature and regulation of these molecules involved in invasive cell behavior. RSVCEF produce elevated levels of a matrix metalloprotease-2 (MMP-2) whose hemopexin domain differs from mammalian MMP-2. The majority of MMP-2 produced by RSVCEF is present in a TIMP-free form which enhances its activation, catalytic activity and substrate specificity and therefore its matrix-degrading ability. RSVCEFs also exhibit high levels of urokinase-type plasminogen activator (uPA), which is found in active form in their conditioned medium in complete absence of plasminogen. Recombinantly expressed avian uPA is also in active form, while an active-site mutant of the same maintains its zymogen form, indicating the mechanism of activation of chicken uPA is autocatalytic. A domain and sequence comparison between chicken and human uPA attempts to identify motifs potentially responsible for the zymogen instability of avian uPA and its capability to autoactivate.
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PMID:What structure and function of avian plasminogen activator and matrix metalloproteinase-2 reveal about their counterpart mammalian enzymes, their regulation and their role in tumor invasion. 879 96


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