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 epithelial lining of the airways is subject to injury through several processes, including infections, bronchiolitis, and fume exposures. Because airway fibrin deposition influences the course of local injury, we examined how two inflammatory cytokines influenced fibrin formation and clearance in human tracheal epithelial cells (TEC). TEC were treated with transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha). TNF-alpha increased release of tissue factor (TF)-related procoagulant activity that, through generation of factor Xa, promotes assembly of the prothrombinase complex at the cell surface. Fibrinolytic activity was plasminogen dependent and due to both urokinase (uPA) and tissue plasminogen activator (tPA). The cells expressed plasminogen activator inhibitor 1 (PAI-1), but relatively little PAI-2. Depression of fibrinolysis by TGF-beta correlated with increased PAI-1. Conversely, TNF-alpha increased plasminogen activator (PA) activity due to increased uPA. Fibrinolytic activity was inhibited by actinomycin D and cyclohexamide, but changes in mRNAs for uPA, tPA, PAI-1, and TF by either cytokine were not appreciable. PAI-2 mRNA was not found. The data indicate that TGF-beta decreases the fibrinolytic capacity of TEC, suggesting that this cytokine promotes fibrin retention. TNF-alpha increases expression of both procoagulant and fibrinolytic activities; this differential regulation could favor both pericellular fibrin formation and dissolution.
 ...
PMID:Effects of TGF-beta and TNF-alpha on procoagulant and fibrinolytic pathways of human tracheal epithelial cells. 781 Jun 74

Heparin and heparan sulfate, exhibiting wide biological interactions, are constituted of block structures. A defined pentasaccharide motif was found responsible for the enhancement of the rate of inactivation of factor Xa by antithrombin III. Heparin also interacts with other serine proteinase inhibitors as protease nexin I, and thus possibly modulates extracellular matrix proteolysis by serine proteinases in the pericellular environment. Human neutrophil elastase (HNE) activity is inhibited by heparin with Ki = 75 pM. This strong interaction is electrostatic, involving HNE/arginine residues disposed in a "cluster shoe" arrangement on the surface of the molecule and mainly OSO3- groups of heparin. HNE-heparin interactions also interfere with HNE associations with its natural inhibitors: it decreases the rate of association of HNE with alpha 1 proteinase inhibitor (alpha 1 P(i)) by 3 orders of magnitude, while increasing kass between HNE and mucus bronchial inhibitor (MBI) by > 10 fold. In vivo experiments demonstrated that heparin fragments lacking anticoagulant activity were able to nearly completely abolish emphysematous lesions induced in mice by a single intratracheal administration of 200 micrograms HNE. Long chain unsaturated fatty acids peptide conjugates were described as competitive HNE inhibitors (Hornebeck W. et al. 1985). We synthesized N-oleoyl heparin derivative (3 oleoyl groups/one molecule of heparin); such a lipophilic glycosaminoglycan (LipoGAG), although acting as an elastin protecting agent, possessed lower HNE inhibitory capacity as compared with heparin. In contrast, however, it was able to inhibit other serine proteinases such as urokinase, plasmin, porcine pancreatic apha-chymotrypsin and elastase. Such Lipo GAG's can be therefore useful to control matrix metalloproteinases (MMPs) during tissue remodeling or tumor invasion.
 ...
PMID:Heparin and its derivatives modulate serine proteinases (SERPS) serine proteinase inhibitors (SERPINS) balance. Physiopathological relevance. 789 38

Because fibrin is commonly observed within arthritic joints, studies were undertaken to determine whether purified coagulation and fibrinolytic proteases degrade cartilage in vitro and to seek evidence for the activation of coagulation in arthritic joints through measurements of the levels of inhibitor-enzyme complexes and several other proteins associated with coagulation and fibrinolysis. The concentrations of 13 plasma proteins and complexes of thrombin and Factor Xa with antithrombin III were measured in synovial fluids recovered at the time of knee replacement surgery. All zymogens necessary to constitute the coagulation cascade were present. Thrombin and the combination of prothrombin plus prothrombinase induced proteoglycan release from both normal and arthritic cartilages. Factor Xa and plasmin induced release from diseased cartilage only, and urokinase, tissue plasminogen activator, and activated protein C were without effect at the levels used. At saturating levels of thrombin (> or = 2.0 microM) 80% of the proteoglycan content of normal cartilage was released within 24 h. Thrombin, which is cationic, reversibly binds cartilage with Kd = 7.0 +/- 1.0 microM and Bmax = 820 +/- 70 ng/mg of human cartilage. Levels of thrombin-antithrombin III complexes in synovial fluids and arthritis were 4-fold higher in osteo (OA) and 43-fold higher in rheumatoid (RA) than in controls (0.98 nM). Factor Xa-antithrombin III complex levels were threefold lower in OA and fivefold higher in RA than in controls (0.24 nM). These elevated levels of enzyme-inhibitor complexes imply a history of activation of coagulation within the joint, especially in RA. Since thrombin degrades cartilage in vitro and had been generated in vivo, as inferred by the existence of thrombin-antithrombin III complexes, intraarticular activation of coagulation may both contribute to the pathology of arthritis and comprise a target for therapy and diagnosis.
 ...
PMID:Studies of thrombin-induced proteoglycan release in the degradation of human and bovine cartilage. 804 Mar

Thrombolytic therapy paradoxically induces the formation of fibrinopeptide A, fibrin degradation products and thrombin-antithrombin complexes, indicating thrombin generation. Part of the mechanism of this thrombin generation under the influence of thrombolytic agents was unraveled in this study. We measured thrombin with a chromogenic substrate at several time intervals after recalcification of citrated plasma which had been preincubated with urokinase, streptokinase, recombinant tissue plasminogen activator (rt-PA) or recombinant single-chain urokinase-type plasminogen activator (rscu-PA). Thrombin generation induced by the addition of thromboplastin together with calcium (extrinsic pathway) was greatly accelerated in the presence of streptokinase (from about 7 to 2 min), and to a lesser extent in the presence of urokinase, rt-PA or rscu-PA. Similar effects were seen after the addition of calcium to the plasma containing the thrombolytic agent and preincubated with partial thromboplastin (intrinsic pathway). Hirudin quenched the conversion of the chromogenic substrate completely, confirming that thrombin was the active enzyme. Aprotinine did not affect the results, and the effect of streptokinase was also observed in plasminogen-depleted plasma. We conclude that streptokinase, and to a lesser extent other thrombolytic agents, activate the prothrombinase complex directly or indirectly through a calcium-dependent mechanism, independently of plasminogen, with a resulting acceleration of thrombin generation.
 ...
PMID:Thrombin generation induced by the intrinsic or extrinsic coagulation pathway is accelerated by streptokinase, independently of plasminogen. 816 24

A Limulus intracellular coagulation inhibitor, designated LICI, was isolated from hemocytes of the Japanese horseshoe crab (Tachypleus tridentatus), using three steps of chromatography, including dextran sulfate-Sepharose CL-6B, Sephacryl S-200, and Mono S. LICI is a single-chain glycoprotein with an apparent M(r) = 48,000 estimated by SDS-polyacrylamide gel electrophoresis. It blocks the amidolytic activities of Limulus lipopolysaccharide-sensitive serine protease, factor C, by forming a covalent 1:1 complex with the protease. The second-order rate constant for inhibition of factor C was 2.5 x 10(6) M-1 s-1 at 37 degrees C. LICI also inhibited human alpha-thrombin, rat salivary kallikrein, bovine plasmin, and trypsin but not Limulus clotting enzyme, Limulus factor B, bovine factor Xa, human factor XIa, human tissue plasminogen activator, human urokinase, chymotrypsin, elastase, and papain. Glycosaminoglycans such as heparin and heparan sulfate had no effect on the inhibitory activity. A cDNA coding for LICI was isolated from a hemocyte cDNA library. The open reading frame of the 1,257-base pair cDNA codes for the mature protein of 394 amino acids, of which 223 residues were confirmed by amino acid sequence analysis. LICI shows significant sequence identities to members of the serpin superfamily, such as human plasminogen activator inhibitor type 2 (40%) and human monocyte/neutrophil elastase inhibitor (39%). LICI contains a putative reactive site, -Arg-Ser-, at the corresponding position present in several inhibitors of the serpin superfamily. The subcellular localization, determined using an anti-LICI polyclonal antibody, indicated that LICI colocates with the Limulus serine protease zymogens in large granules in the hemocyte.
 ...
PMID:A Limulus intracellular coagulation inhibitor with characteristics of the serpin superfamily. Purification, characterization, and cDNA cloning. 827 48

The use of first generation plasminogen activators, urokinase, streptokinase and tissue plasminogen activator has revolutionized thrombolytic therapy for myocardial infarction and ischaemia, and potentially stroke. However, thrombolytic therapy employing these activators is limited by reocclusion of the very arteries being opened, which follows in a small but significant number of patients. The development of second generation plasminogen activators, e.g. staphylokinase and anisoylated plasminogen streptokinase activator complex, has not alleviated the problems encountered with classical plasminogen activators. It is now widely recognized that aberrant platelet aggregation induced primarily by thrombin, rather than plasmin, is one of the major causes of recurrent thrombosis following pharmacologic thrombolysis. Agents that (a) inhibit enzymatic and/or coagulant activity of thrombin, (b) block binding of thrombin to its receptor, and (c) interfere with the generation of thrombin by the prothrombinase complex may compromise haemostasis resulting in haemorrhage. We recently demonstrated that thrombin-induced platelet aggregation is accompanied by cleavage of aggregin, a putative ADP-receptor on the platelet surface, and that these events are indirectly mediated by intracellularly activated calpain expressed on the surface. In this review, we discuss the known mechanisms of thrombin-induced platelet aggregation and suggest relative advantages of potential pharmacological agents, being developed in our laboratory, over those that have been previously developed and tested. These inhibitors selectively prevent aggregation of platelets induced by thrombin by inhibiting calpain expressed on the surface. Moreover, one of these inhibitors which blocks thrombin-induced platelet aggregation does not interfere with other platelet responses mediated by thrombin or platelet aggregation induced by other agonists, such as, ADP, collagen, phorbol myristate acetate and thromboxane A2 mimetics. This selectivity could reduce the chances of perturbing the formation of a haemostatic plug.
 ...
PMID:Reocclusion after thrombolytic therapy: strategies for inhibiting thrombin-induced platelet aggregation. 832 74

Both human and bovine prothrombin fragment 2 (the second kringle) have been cocrystallized separately with human PPACK (D-Phe-Pro-Arg)-thrombin, and the structures of these noncovalent complexes have been determined and refined (R = 0.155 and 0.157, respectively) at 3.3-A resolution using X-ray crystallographic methods. The kringles interact with thrombin at a site that has previously been proposed to be the heparin binding region. The latter is a highly electropositive surface near the C-terminal helix of thrombin abundant in arginine and lysine residues. These form salt bridges with acidic side chains of kringle 2. Somewhat unexpectedly, the negative groups of the kringle correspond to an enlarged anionic center of the lysine binding site of lysine binding kringles such as plasminogens K1 and K4 and TPA K2. The anionic motif is DGDEE in prothrombin kringle 2. The corresponding cationic center of the lysine binding site region has an unfavorable Arg70Asp substitution, but Lys35 is conserved. However, the folding of fragment 2 is different from that of prothrombin kringle 1 and other kringles: the second outer loop possesses a distorted two-turn helix, and the hairpin beta-turn of the second inner loop pivots at Val64 and Asp70 by 60 degrees. Lys35 is located on a turn of the helix, which causes it to project into solvent space in the fragment 2-thrombin complex, thereby devastating any vestige of the cationic center of the lysine binding site. Since fragment 2 has not been reported to bind lysine, it most likely has a different inherent folding conformation for the second outer loop, as has also been observed to be the case with TPA K2 and the urokinase kringle. The movement of the Val64-Asp70 beta-turn is most likely a conformational change accompanying complexation, which reveals a new heretofore unsuspected flexibility in kringles. The fragment 2-thrombin complex is only the second cassette module-catalytic domain structure to be determined for a multidomain blood protein and only the third domain-domain interaction to be described among such proteins, the others being factor Xa without a Gla domain and Ca2+ prothrombin fragment 1 with a Gla domain and a kringle.
 ...
PMID:Structures of the noncovalent complexes of human and bovine prothrombin fragment 2 with human PPACK-thrombin. 838 13

A recent report described a thrombin inhibitory activity in the soluble fraction of human placenta and the cytosolic fraction of K562 cells. Isolation and characterization of the functionally inactive 35-38-kDa placental form of this protein revealed that it was a novel serine proteinase inhibitor (Coughlin, P. B., Tetaz, T., and Salem, H. H. (1993) J. Biol. Chem. 268, 9541-9547). In the present study, we observed a 67-kDa sodium dodecyl sulfate (SDS)-stable complex when 125I-thrombin was incubated with the cytosolic fraction of a monkey kidney epithelial cell line, BSC-1. This complex was not observed in either the particulate cell fraction extracted with 0.2% Triton X-100 or medium conditioned by cells, suggesting that the thrombin-complexing factor is confined to the cytoplasm. The cytoplasmic antithrombin activity was purified to apparent homogeneity from the cytosol of BSC-1 cells previously pulsed with [35S]methionine by a combination of heparin-agarose chromatography, Mono Q fast protein liquid chromatography, and anhydrotrypsin-Affi-Gel 10 affinity chromatography. Analysis of the affinity-purified preparation by SDS-polyacrylamide gel electrophoresis and fluorography revealed a single protein with an apparent molecular mass of 38 kDa. The purified 38-kDa protein inhibited the amidolytic activities of thrombin, trypsin, urokinase, and factor Xa but not that of elastase. Incubation of the 38-kDa protein with excess thrombin identified approximately 60% of the labeled 38-kDa protein in an SDS-stable 67-kDa complex. The purified 38-kDa inhibitor was cleaved with cyanogen bromide and the isolated peptides subjected to microsequencing. Amino acid sequence obtained for a region within this protein exhibited significant homology with human antithrombin III and plasminogen activator inhibitors 1 and 2. This homologous peptide contained the full complement of residues designated as highly conserved in helix F of the greater serine proteinase inhibitor superfamily. In addition, an internal sequence of GGGGDIHQGF was found in the monkey cytoplasmic inhibitor, which is identical to that reported for an internal sequence of the human placental inhibitor. These findings confirm the existence of a novel cytoplasmic serine proteinase inhibitor in mammalian cells and provide additional details of its molecular properties. The physiological function of this novel serine proteinase inhibitor in cytoplasm is unknown.
 ...
PMID:Isolation and characterization of an intracellular serine proteinase inhibitor from a monkey kidney epithelial cell line. 840 7

The myxoma and malignant rabbit fibroma poxviruses are lethal tumorigenic viruses of rabbits whose virulence is modulated by the production of a virus-encoded secreted serine proteinase inhibitor, SERP-1. This viral protein was detected in medium harvested from myxoma and malignant rabbit fibroma virus-infected cells, and its inhibitory profile has been characterized by gel and kinetic analysis. SERP-1 forms complexes with and inhibits the human fibrinolytic enzymes plasmin, urokinase, and two-chain tissue-type plasminogen activator (association rate constants 3.4 x 10(4), 4.3 x 10(4), and 3.6 x 10(4) M-1 s-1 respectively). It is also able to inhibit C1S, the first enzyme in the complement cascade with an association rate constant which was unaffected by the addition of heparin (1.3 x 10(3) M-1 s-1). SERP-1 acts as a substrate for and is cleaved by thrombin, porcine trypsin, human neutrophil elastase, porcine pancreatic elastase, thermolysin, subtilisin, bovine alpha-chymotrypsin, and factor Xa. Incubation with kallikrein and cathepsin G had no effect. The structure of SERP-1 has been modeled on other members of the serpin family which revealed the characteristic serpin architecture apart from the absence of the D-helix. Structural analysis and kinetic assays demonstrate that the absence of this region does not prevent inhibitory activity and furthermore allow the identification of cysteine residues involved in internal and intermolecular disulfide bonding.
 ...
PMID:Inhibition of plasmin, urokinase, tissue plasminogen activator, and C1S by a myxoma virus serine proteinase inhibitor. 841 56

In a previous report, we described the molecular cloning, expression, and partial characterization of a second human tissue factor pathway inhibitor (TFPI), which we designated as TFPI-2 [Sprecher, C. A., et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 3353-3357]. Recombinant TFPI-2 inhibited the amidolytic activity of trypsin as well as that of factor VIIa in complex with tissue factor. TFPI-2 recently has been shown to be identical to placental protein 5 (PP5), a glycoprotein originally isolated from placenta that exhibits serine protease inhibitory activity. In the present study, we have examined TFPI-2/PP5 for its ability to inhibit a number of serine proteases involved in blood coagulation and fibrinolysis, inasmuch as TFPI-2/PP5 prolonged the coagulation time of human plasma induced by either tissue factor or contact activation in a dose-dependent manner. In addition to its ability to inhibit the amidolytic and proteolytic activities of the factor VIIa-tissue factor complex, TFPI-2/PP5 strongly inhibited the amidolytic activities of human factor XIa, human plasma kallikrein, and human plasmin with Ki values of 15, 25, and 3 nM, respectively. TFPI-2/PP5 was also a weak inhibitor of the activation of factor X by a complex of human factor IXa and poly(lysine) with an apparent Ki of 410 nM. Heparin markedly enhanced the ability of TFPI-2/PP5 to inhibit factor VIIa-tissue factor both in the solution phase and on cell surfaces. In addition, heparin augmented the inhibition of human factor Xa amidolytic activity at relatively high levels (10-100 nM) of TFPI-2/PP5. No significant inhibition of glandular kallikrein, urinary plasminogen activator, tissue plasminogen activator, human activated protein C, human factor Xa, human thrombin, or leukocyte elastase was observed when these proteases were incubated with TFPI-2 in the absence of heparin.
 ...
PMID:Inhibitory properties of a novel human Kunitz-type protease inhibitor homologous to tissue factor pathway inhibitor. 855 84


<< Previous 1 2 3 4 5 6 7 8 9 Next >>