Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endocytosis of tissue-type plasminogen activator (t-PA) by different types of rat liver cells was studied in immunocytochemically labelled cryosections as well as in biochemical experiments. For morphological localization of the ligand in different endocytic compartments involved in its catabolism, rat livers were fixed at various times (1-24 min) after injection of t-PA. Late-endosomal and lysosomal compartments were identified by double-labelling the sections with antibodies to the lysosomal proteins glycoprotein Igp 120 and cathepsin D. In liver t-PA was localized in sinusoidal endothelial cells (EC), parenchymal cells (PC) and to some extent in Kupffer cells (KC), indicating that it is internalized and degraded in all three cell types. In specimens fixed 6 min after injection PC, EC and KC were found to contribute to 69, 24 and 7% respectively of total t-PA endocytosed. The transfer from late endosomes to lysosomes was found to be faster in EC than in PC. The morphological findings were supported by studies of the endocytic mechanisms employing isolated perfused livers and primary hepatocytes. The presence of monensin, an inhibitor of lysosomal protein degradation, reduced the amount of t-PA degraded to about 50% of the control values. The catalytic site seems not to be required for the catabolism of t-PA in hepatic cells. The inhibition of t-PA by D-phenylalanyl-L-prolylarginyl-chloromethane did not influence receptor recognition and catabolic processing, as determined in morphological studies using labelled cryosections, in binding studies employing liver cell membranes and primary hepatocytes, as well as in liver-perfusion experiments.
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PMID:Endocytosis and intracellular processing of tissue-type plasminogen activator by rat liver cells in vivo. 155 69

We studied the effects of transforming growth factor-beta (TGF-beta), tissue plasminogen activator (tPA), and their combination in cats subjected to splanchnic artery occlusion (SAO) with reperfusion. Untreated anesthetized cats subjected to total occlusion of the celiac, superior, and inferior mesenteric arteries for 120 min, followed by reperfusion, uniformly died within 120 min after reperfusion. The mean survival time was 75 +/- 8 min. Plasma amino-nitrogen concentrations and cathepsin D and myocardial depressant factor (MDF) activities were markedly elevated following reperfusion. Superior mesenteric artery (SMA) rings isolated from cats subjected to SAO with reperfusion exhibited a significant loss of vasorelaxation to the endothelium-dependent dilators acetylcholine and A-23187. Administration of tPA (1 mg/kg) intravenously just before reperfusion did not prolong survival time (81 +/- 10 min) nor did it influence any biochemical or cardiovascular responses following reperfusion or ameliorate the depressed endothelium-dependent relaxation of SMA rings. In contrast, TGF-beta (50 micrograms/cat) ameliorated the SAO postreperfusion state in terms of survival rate and plasma MDF activity, and protected against depressed endothelium-dependent relaxation of SMA rings. TGF-beta alone slightly increased the survival time to 102 +/- 11 min. However, combined treatment with tPA (1 mg/kg) and TGF-beta (50 micrograms/cat) preserved endothelium-dependent relaxation and prevented increases in plasma amino-nitrogen more prominently than TGF-beta given alone and significantly increased the survival time to 118 +/- 3 min (p less than 0.01). These results indicate that TGF-beta exerts beneficial effects in SAO followed by reperfusion in cats, and tPA has an augmenting action on some of the beneficial effects of TGF-beta. These findings suggest that TGF-beta alone or in combination with tPA may be potentially useful therapeutic regimens in splanchnic ischemia shock by preserving splanchnic parenchymal and endothelial cells.
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PMID:Beneficial effects of transforming growth factor-beta and tissue plasminogen activator in splanchnic artery occlusion and reperfusion in cats. 171 97

Cathepsin D (CD, EC 3.4.23.5) is a lysosomal protease induced by estrogen in certain estrogen receptor (ER)-positive breast cancer cell lines but produced constitutively by ER-negative cell lines. Our aims in this investigation were to study the distribution of CD in human breast cancers and to relate its concentrations to various biochemical, histological, and clinical characteristics. The concentrations of CD were significantly higher in breast carcinomas than in either normal breast tissues or benign breast tumors. In primary carcinomas, CD concentrations did not correlate with the concentrations of ER or with the estrogen-inducible protease t-PA. However, CD concentrations did correlate weakly but significantly with both UK-PA antigen and UK-PA activity. Also, CD concentrations did not correlate with either tumor stage or axillary node status but did correlate significantly with tumor grade. Patients with cancers containing high concentrations of CD had a significantly shorter overall survival than did patients with low concentrations of the enzyme.
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PMID:Cathepsin D concentration in breast cancer cytosols: correlation with biochemical, histological, and clinical findings. 189 58

A highly active angiotensin-producing enzyme (enzyme II) was obtained from dog serum by acid treatment and fractionation to remove angiotensinase and converting enzyme, separate an inhibitor, and convert an inactive precursor (proenzyme II) to enzyme II. Proenzyme II was found to be converted to enzyme II by an endogenous activating enzyme identified as plasmin. Conversion was also caused by the interaction of bacterial streptokinase with human proactivator, by trypsin, and by an activator formed from liver tissue extract and dog serum. Neither plasma kallikrein nor the labile, human extrinsic tissue-type plasminogen activator induced activation. The inhibitor, which normally blocks the activation of proenzyme II, was unusually stable against high temperatures and extremes of pH, and it was not identical to any of the six known protease inhibitors of serum. Enzyme II was not identical to other angiotensin-producing enzymes such as enzyme I, renin, cathepsin D, pepsin, plasmin, tonin, or cathepsin G. Enzyme II reacted maximally at pH 4.7 and produced up to 2250 ng of angiotensin I/ml serum/hr from the substrate of dog serum (i.e., amounts 3200-fold higher than that produced by endogenous renin of normal dog serum). Since at pH 7.2, angiotensin I formation is still about 30 times higher than that of renin, enzyme II may be physiologically active under some conditions.
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PMID:Angiotensin-producing serum enzyme II. Formation by inhibitor removal and proenzyme activation. 390 15

Proteolytic modification of circulating insulin-like growth factor binding protein-3 (IGFBP-3) has been described in a number of conditions. Using Western ligand blotting and SDS-PAGE analysis of fragmentation patterns of 125I-labelled IGFBP-3 and 125-labelled IGFBP-1, we have examined conditioned media from cultured human cell lines for the presence of proteolytic activity and compared this with the action of circulating proteases and with characterized enzymes including cathepsin D, kallikrein, plasmin and tissue plasminogen activator. 125I-Labelled IGFBP-3 was incubated with serum from pregnant women, patients following heart surgery and patients with cancer of the breast, lung or head/neck. Following separation of the preincubated samples by SDS-PAGE, a distinct pattern of degradation fragments was observed which was similar in all cases. This proteolytic activity was inhibited in the presence of EDTA, phenanthroline and 4(-2-aminoethyl)-benzenesulphonylfluoride, HCl. These proteases had no detectable effect on IGFBP-1. Serum-free conditioned medium from a human dermal fibroblast cell line, a rabdomyosarcoma, a cervical, a bladder, a chorio- and two-tongue squamous cell carcinoma cell lines all contained proteolytic activity which fragmented IGFBP-3. The pattern of fragments was similar in all cell lines but different from that produced by the circulating proteases. Six out of nine cell lines produced protease(s) which degraded IGFBP-1 in addition to IGFBP-3. Whilst all the characterized enzymes tested also fragmented IGFBP-3 and plasmin cleaved IGFBP-1, none of these acted in the same way as either circulating or cell line-derived proteolytic activity. The activity associated with the characterized enzymes and cell lines was inhibited in the presence of serum from normal healthy subjects. These results demonstrate that the serum of pregnant women, post-operative patients and patients with cancer contain circulating proteases which cause fragmentation of IGFBP-3 but have little effect on IGFBP-1. Cell-derived proteases were shown to act on IGFBP-3 and IGFBP-1 in a number of instances but are not active in the presence of circulating inhibitors. These proteases may play an important role in regulating the availability of IGFs to normal and neoplastic tissues.
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PMID:Proteolytic modification of insulin-like growth factor-binding proteins: comparison of conditioned media from human cell lines, circulating proteases and characterized enzymes. 750 92

Plasminogen activator inhibitor-1 (PAI-1) is the most important inhibitor of tissue-type plasminogen activator (t-PA) in plasma and plays a major role in the regulation of fibrinolysis. Plasma t-PA/PAI-1 complexes are cleared via a receptor-dependent mechanism in hepatocytes, while the fate of complexes formed in the extracellular matrix and in thrombi is less well understood. In this study, the degradation of t-PA/PAI-1 complexes by monocytes was examined. THP-1 monocytoid cells and freshly isolated human monocytes internalize and degrade [125I]t-PA/PAI-1 complexes at rates of 11.4 +/- 5.9 (mean +/- S.D.) and 44.6 +/- 6.3 ng/10(6) cells/h, respectively. Degradation is blocked by receptor-associated protein (RAP), indicating a member of the low density lipoprotein (LDL) receptor family is involved in the uptake/degradation of t-PA/PAI-1 complexes by monocytes. Degradation of t-PA/PAI-1 complexes is also inhibited by chloroquine and by pepstatin A, suggesting that a lysosomal aspartyl protease is likely involved. SDS-PAGE and Western blotting demonstrated that the purified lysosomal aspartyl protease, cathepsin D, is capable of digesting t-PA (t1/2 15 min), active PAI-1 (t1/2 2 h), and t-PA/PAI-1 complex (t1/2 30 min). Cathepsin D sequentially cleaves PAI-1 after hydrophobic amino acids, yielding lower molecular weight fragments. PAI-1 conformation influences the degradative efficiency of cathepsin D, with vitronectin-bound PAI-1 and latent PAI-1 exhibiting resistance to proteolysis and > 10-fold prolongation in t1/2. These data provide evidence that t-PA/PAI-1 complexes are internalized by human monocytes via a member of the low density lipoprotein (LDL) receptor family, and identifies cathepsin D-like aspartyl protease activity as largely responsible for the degradation of these complexes. Furthermore, vitronectin-bound PAI-1 and latent PAI-1 are relatively resistant to degradation by cathepsin D, which may be of importance in complex physiological environments.
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PMID:Cathepsin D-like aspartyl protease activity mediates the degradation of tissue-type plasminogen activator/plasminogen activator inhibitor-1 complexes in human monocytes. 766 1

All the malignant tumors possess the same characteristic to form distant secondary tumors or metastasis. The acquisition of the metastatic potential takes place in random accumulation of different genetic and cellular changes. Their combination allows one or several tumor cells to achieve the whole metastatic process. The metastatic process involves numerous interactions between the tumor cells and the host cells of the tumor cells and the extracellular matrix. The attachment of the metastatic cells to the extracellular matrix specific glycoproteins involves cell surface receptors as integrins, sialyled residues or CD44. On the other hand, other adhesive molecules (Cadherins) display inhibitory action on the metastatic process. The enzymatic lysis is carried out by glycolytic enzymes and proteases: metalloproteases (inhibitors TIMP1 et TIMP2), serine proteases (tPA, uPA-inhibitors: PAI1 and PAI2). Cathepsin D or Heparanases. Several enzymes may be necessary for the degradation of the basal membrane. The crossing of both basal membrane and stroma can be made on account of the cell motility. Some factors can modify this property as AMF (Autocrin Motility Factor) or ATX (Autotoxin) but the molecular mechanisms involved in the migration are not yet completely understood. The last stage is relative to the cells proliferation in the site organ; it depends on autocrine (CSF1, IL2, Bombesine...) or some paracrine growth factors. However, the formation of metastasis is possible only in the site organ attaching the cells.
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PMID:[The metastatic process]. 770 63

The effect of structure of the estrogen ligand on the accumulation of tPA mRNA and the activity of extracellular fibrinolytic enzyme has been examined in cultures of MCF-7 cells. Estradiol(E2)-stimulated fibrinolytic activity was preceded by an increase in actinomycin D sensitive tPA mRNA synthesis which peaked at 18 h. Ten A- and D-ring structural analogs of E2 affected tPA mRNA accumulation and extracellular fibrinolytic activity. Only in the case of two A-ring isomers (2- and 4-hydroxyestratrien-17 beta-ol) was the decreased effect of the ligand's structural change on tPA mRNA accumulation and fibrinolysis not explained by a comparable decline in affinity of the ligand for estrogen receptor. Both of these analogs functioned as antiestrogens. The stimulatory capacity of androstanediols on the tPA gene required that the 3-hydroxyl group be positioned in the beta-configuration. Absence of the 17 beta-hydroxy group was beneficial to the maximum accumulation of tPA mRNA. As has been reported for other estrogen responsive genes (progesterone receptor, cathepsin D and pS2), regulation by estrogens is not related directly to the affinity of the ligand for ER, but this activity may be determined by the location of the electronegative isopotential above the A-ring of estrogenic ligands.
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PMID:Induction of tissue plasminogen activator mRNA and activity by structurally altered estrogens. 774 7

Fibroblastoid synovial lining cells isolated from rheumatoid and other chronic inflammatory synovial tissue exhibit distinctive and sustained alterations in serial culture not commonly found in similarly cultured cells from osteoarthritic synovium. These are demonstrable using a multi-gene dot blot assay by labelling reverse transcribed fibroblast cDNA which is hybridized to plasmids containing relevant target gene inserts. Cultured synovial fibroblastoid cells from patients with chronic inflammatory synovitis expressed significantly higher levels of stromelysin, vimentin and TIMP-1 mRNA and lower levels of c-myc compared to cells isolated from osteoarthritis synovium although with considerable variation. Early fetal synovial lining cells were similar to cells from osteoarthritis synovium but vimentin expression was higher. Marked differences in patterns of gene expression between cell lines persisted through 10 serial passages over 6-8 months. In whole synovia, the average level of mRNA for stromelysin, vimentin, IL-4, IL-6, TIMP-1, cathepsin D, gelatinase, TGF alpha, c-fms and DR beta were preferentially expressed in inflammatory tissue while c-myc expression was higher in osteoarthritis synovium. Inflammatory synovium also expressed TNF alpha, IL-1 alpha, IL-1 beta, IL-2, c-sis, tissue plasminogen activator, CSF-1, and GM-CSF. This pattern resembles, in part, that found in cultured inflammatory fibroblasts but, in addition, gene products apparently reflecting the presence of activated monocytes and lymphocytes were detected. These results provide evidence that profiles of certain gene activation in cells from patients with inflammatory synovitis differ from those with non-inflammatory disease and suggest that the fibroblastoid cells are responsible for a considerable proportion of the altered phenotypic expression pattern in whole tissue. Furthermore, this modulated pattern of gene activation appears to be an intrinsic pro-inflammatory characteristic of the fibroblastoid cells initiated in response to chronic inflammation and persists for a prolonged period in the absence of other inflammatory cells.
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PMID:Sustained and distinctive patterns of gene activation in synovial fibroblasts and whole synovial tissue obtained from inflammatory synovitis. 809 Nov 28

Extravasation and intravasation of tumor cells in solid malignant tumors is controlled by 3 steps: 1) attachment to and interaction of tumor cells with components of the basement membrane and the extracellular matrix, 2) local proteolysis, and 3) tumor cell migration. Evidence has accumulated that different types of tumor-associated proteases, their inhibitors and receptors are involved in tumor invasion and metastasis. Four different classes of proteases are known to be correlated with the malignant phenotype: 1) Matrix metalloproteases; including collagenases, gelatinases and stromelysins. 2) Cysteine proteases; including cathepsins B and L. 3) Aspartyl protease cathepsin D. 4) Serine proteases; including plasmin and tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). A strong independent prognostic value (relapse-free and/or overall survival) has especially been demonstrated for uPA and its inhibitor PAI-1 in patients with cancer of the breast, ovary, stomach, esophagus, colon, lung, and kidney thus predicting the course of the cancer disease. The strong correlation between elevated uPA and/or PAI-1 values in primary cancer tissues and the malignant phenotype of cancer cells has prompted to explore new tumor biology-oriented concepts in order to suppress uPA or uPA receptor (CD87) expression or to abrogate interaction of uPA with CD87. Various very different approaches to interfere with the expression or reactivity of uPA or CD87 at the gene or protein level were successfully tested including antisense oligonucleotides, antibodies, inhibitors and recombinant or synthetic uPA and CD87 analogues.
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PMID:Urokinase-type plasminogen activator (uPA) and its receptor (CD87): a new target in tumor invasion and metastasis. 855 77


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