Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, two rat monoclonal antibodies where developed which bind distinct epitopes on a murine glycoprotein, P112, which is expressed primarily in lung capillary endothelium. In this paper we show that P112 is identical to the endothelial anticoagulant protein, thrombomodulin (TM). Several lines of evidence support this conclusion. First, amino acid analysis of P112 shows a high degree of homology to TM, and both molecules exhibit the same mobility in gel electrophoresis. Second, P112 and TM share reactivity for two different monoclonal antibodies. Third, purified P112, like TM, acts as a cofactor for protein C activation. Finally, two cDNA clones identified with P112 polyclonal antiserum contain sequence identity with the known TM cDNA sequence. Quantitative analysis of TM (P112) expression using a two-site monoclonal antibody assay demonstrates that significantly higher levels of TM are found in lung in comparison with other highly vascularized organs, i.e. the kidney and liver. Quantitative Northern blot data coincides with the two-site assay data and demonstrates that the high level of TM expression in lung is not due to preferential binding of the monoclonal antibodies to lung TM but rather to increased production of TM mRNA in the lung relative to other highly vascularized organs. It is suggested that expression of TM is highest in cells from continuous endothelium.
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PMID:Thrombomodulin is preferentially expressed in Balb/c lung microvessels. 137 3

Previous reports demonstrated that the expression of thrombomodulin (TM) in endothelial cells was modulated by various agents. Although TM was down-regulated by endotoxin or cytokines, up-regulation of TM was accomplished when endothelial cells were stimulated with unphysiologically high concentrations of cyclic AMP derivatives or tumour-promoting phorbol esters. We investigated the expression of TM in human umbilical-vein endothelial cells (HUVECs) by physiological substances that can be released into the bloodstream. Histamine (0.1-10 microM, 1-48 h) increased TM activity, TM antigen in cell lysates and TM mRNA levels, but 5-hydroxytryptamine and bradykinin had no effect. Enhancement of TM activity by histamine was completely blocked by the H1-selective antagonist pyrilamine, whereas the H2-antagonist cimetidine had no effect, showing that histamine up-regulates TM activity via H1-receptors on HUVECs. Enhanced TM activity by histamine and the resultant increase in protein C activation might play a role in a feedback regulation for prevention of vascular thrombosis.
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PMID:Up-regulation of thrombomodulin by activation of histamine H1-receptors in human umbilical-vein endothelial cells in vitro. 164 51

Thrombomodulin (TM), a critical component of the protein C anticoagulant pathway, has previously been localized to endothelial cells (EC), but not smooth muscle cells (SMC) of the blood vessel wall. We demonstrate that cultured rat, bovine, as well as human SMC, but not blood vessel wall smooth muscle tissue, possess significant functional levels of TM and TM mRNA. Cyclic adenosine monophosphate stimulates TM expression in cultured SMC, but not EC, while tumor necrosis factor suppresses TM expression in EC but not cultured SMC. We postulate that following acute or chronic EC injury, luminal SMC can express TM, and are therefore able to protect the damaged blood vessel from thrombosis.
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PMID:Expression of thrombomodulin by smooth muscle cells in culture: different effects of tumor necrosis factor and cyclic adenosine monophosphate on thrombomodulin expression by endothelial cells and smooth muscle cells in culture. 184 62

The expression of thrombomodulin (TM), an antithrombotic factor, was investigated during neutrophilic differentiation of the HL-60 human myeloblastic cell line treated with all-trans retinoic acid (ATRA) or dimethyl sulfoxide (DMSO). Differentiation of the cells into neutrophilic cells progressed in a time- and dose-dependent fashion with ATRA or DMSO, as confirmed by the characteristic appearance of nitroblue tetrazolium (NBT) reduction and phagocytic activities, without induction of nonspecific esterase activity. TM antigen and cofactor activity for thrombin-dependent protein C activation were not detected in untreated HL-60 cells and the cells cultured with DMSO, but were expressed in a time-dependent manner in the cells cultured with ATRA. The level of TM expression in the HL-60 cells was not dose-dependent on ATRA concentrations, but maximum TM expression was obtained at 10(-7) M ATRA. TM expression levels decreased in cells cultured with greater than 10(-6) M ATRA, although the extent of cell differentiation into neutrophilic cells progressed at the higher ATRA concentrations. Since the TM antigen levels in the ATRA-treated cells also paralleled the TM mRNA levels, the data suggests that TM induction in the HL-60 cells cultured with ATRA reflected the levels of TM biosynthesis and was independent of HL-60 differentiation into neutrophilic cells. It was postulated that the appearance of TM with cofactor activity in neutrophilic cells differentiated from leukemic cells may contribute to prevention of vascular thrombosis in differentiation therapy of patients with acute promyelocytic leukemia by ATRA.
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PMID:Thrombomodulin induction by all-trans retinoic acid is independent of HL-60 cells differentiation to neutrophilic cells. 787 35

The vascular endothelium, by virtue of its position at the interface between blood and the vessel wall, is known to play a critical role in the control of thrombosis and fibrinolysis. Thrombomodulin (TM) is a surface receptor that binds thrombin and is a potent activator of the protein C anticoagulant pathway. Although TM expression is known to be regulated by various cytokines, little is known about its response to ever-present biomechanical stimuli. We have explored the role of fluid shear stress, imparted on the luminal surface of the endothelial cell as a result of blood flow, on the expression of TM mRNA and protein in both bovine aortic endothelial (BAE) and bovine smooth muscle (BSM) cells in an in vitro system. We report in the present study that TM expression is regulated by flow. Subjecting BAE cells to fluid shear stress in the physiological range of magnitude of 15 (moderate shear stress) and 36 (elevated shear stress) dynes/cm2 resulted in a mild transient increase followed by a significant decrease in TM mRNA to 37% and 16% of its resting level, respectively, by 9 hours after the onset of flow. In contrast, shear stress at the low magnitude of 4 dynes/cm2 did not affect TM mRNA levels. The sensitivity of TM mRNA expression by flow was found to be specific to endothelium, since it was not observed in BSM cells exposed to steady laminar shear stress of 15 dynes/cm2. Furthermore, unlike BAE cells, BSM cells did not exhibit altered cell shape nor align in the direction of flow after 24 hours of shear stress at 15 dynes/cm2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endothelial expression of thrombomodulin is reversibly regulated by fluid shear stress. 815 32

Thrombomodulin (TM) is an essential cofactor for the physiologic activation of the anticoagulant protein C by thrombin. We have observed that the expression of TM mRNA in response to retinoic acid was markedly increased in human U937 monoblast-like cells, and human MEG01 megakaryocyte-like cells, but not in human umbilical vein cells, murine hemangioma cells, human K562 erythroblast-like cells, and murine HSD fibroblast-like cells. TM activity in U937 cells and MEG01 cells was not detectable in untreated cells, but developed rapidly after treatment with retinoic acid. In endothelial cells there was minimal change in TM activity in response to retinoic acid treatment. We have isolated clones for the genes for murine and human TM and have identified potential retinoic acid response elements in the 5'-flanking region of the human gene. In U937 cells the increase in mRNA levels was associated with increased transcription, and transient transfection studies with reporter plasmids demonstrate functional retinoic acid response elements present in the 5'-flanking region of the gene. Deletion of, and mutations introduced into, the potential retinoic acid response element confirm the functional response in transient transfections.
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PMID:Characterization of thrombomodulin expression in response to retinoic acid and identification of a retinoic acid response element in the human thrombomodulin gene. 820 15

Thrombomodulin (TM) antigen and its cofactor activity for thrombin-dependent protein C activation were not detected in the untreated HL-60 human promyelocytic cell line, but appeared in cells cultured with 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3: 10-1,000 nM) or phorbol 12-myristate 13-acetate (PMA: 0.1-10 nM) accompanied by an increase in TM mRNA levels. The induction of TM increased in parallel with the appearances of both nonspecific esterase activity, a typical marker of monocyte/macrophage lineages, and phagocytic activity. The TM antigen level induced in 1 alpha,25(OH)2D3-treated cells was 8 times higher than that in PMA-treated cells. Trace amounts of TM antigen were induced in neutrophilic cells differentiated from HL-60 by treatment with retinoic acid. These results indicated that different levels of TM were induced in monocytic, macrophagic and neutrophilic cells differentiated from HL-60 cells.
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PMID:Different thrombomodulin induction in monocytic, macrophagic and neutrophilic cells differentiated from HL-60 cells. 838 44

Oxidized low density lipoprotein (LDL), a potent atherogenic lipoprotein, has been shown to cause the alteration of various endothelial functions. We have examined the effect of oxidized LDL on the cofactor activity for thrombin-dependent protein C activation and expression of thrombomodulin (TM), a cell surface antithrombotic glycoprotein, on cultured human umbilical vein endothelial cells. Oxidized LDL prepared by irradiation of LDL with 254-nm ultraviolet light did not directly affect the cofactor activity of isolated TM. Exposure of the cells to oxidized LDL (25-200 microg/ml), but not native LDL and acetylated LDL, reduced TM cofactor activity in parallel with its antigen levels on the cell surface in an oxidation-, concentration- and time-dependent manner. TM mRNA levels were reduced prior to decrease in TM antigen levels and were 50% of the control levels at 3.0 h after treatment of the cells with oxidized LDL. The apparent half-life time (t1/2 = 2.8 h) of TM mRNA in the oxidized LDL-treated cells, however, did not significantly differ from that (t1/2 = 2.6 h) in the control cells when the cells were coincubated with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, a transcriptional inhibitor. Treatment of the cells with bafilomycin A1, an inhibitor for the proton pump of the lysosomes, inhibited intracellular degradation of the LDL and prevented down-regulations of the mRNA and the cell surface TM antigen levels caused by oxidized LDL. The inhibitor molecule in oxidized LDL was shown to be a lipid; organic solvent extracts (300 mg/ml cholesterol, an equivalent concentration with lipids in 200 microg/ml oxidized LDL) of oxidized LDL inhibited expression of TM antigen to nearly the same extent as the oxidized LDL, although water extracts did not affect TM expression on the cells. These results suggested that down-regulation of TM on endothelial cells exposed to oxidized LDL resulted from inhibition of its transcription mediated by lysosomal degradation of oxidized LDL and that a lipid component in the LDL could be an active species. A decrease in TM expression on the surface of endothelial cells may contribute to promote thrombosis in atherosclerotic lesions.
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PMID:Oxidized low density lipoprotein reduces thrombomodulin transcription in cultured human endothelial cells through degradation of the lipoprotein in lysosomes. 862 46

We examined the effects of okadaic acid, a potent specific inhibitor of protein phosphatases 1 and 2A, on the expression of thrombomodulin (TM), a cell surface anti-thrombotic glycoprotein, on cultured human umbilical endothelial cells. Okadaic acid (2.5-10 nM) significantly increased TM antigen levels in parallel with its cofactor activity for thrombin-dependent protein C activation. Incubation of cells with 10 nM okadaic acid for 18 h induced an approximately 240% up-regulation of TM antigen levels that was accompanied by an increase in TM mRNA levels. Co-incubation of cells with okadaic acid and dibutyryl cyclic AMP further increased TM antigen levels. Furthermore, the effect of cAMP on TM expression was augmented by the pretreatment of cells with 10 nM okadaic acid for 18 h. These results provide evidence for the involvement of protein phosphatase in the cellular regulatory mechanisms for TM expression, which is distinct from that by cAMP.
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PMID:Effect of a protein phosphatase inhibitor, okadaic acid, on thrombomodulin expression in cultured human umbilical vein endothelial cells. 905 91

Thrombin's potent effects on astrocytes are mediated by a specific receptor and inhibited by a serpin, protease nexin I (PNI). Thrombomodulin (TM), a membrane protein that forms complexes with thrombin, changing its enzymatic specificity, has not been studied in astrocytes. In primary astrocyte cultures, using Western blotting and immunocytochemistry, we found a 70 kDa TM band and TM localized to the surface with an anti-mouse TM monoclonal antibody. By reverse transcriptase coupled with polymerase chain reaction (RT-PCR), we found the correct sequence for mouse TM mRNA in astrocytes. Finally, we documented calcium-dependent activation of protein C by a thrombin:TM complex with thrombin added to the astrocytes. These results indicate the presence of functionally active TM at the astrocyte surface and add support to a role for thrombin signaling in the nervous system.
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PMID:Novel expression and localization of active thrombomodulin on the surface of mouse brain astrocytes. 906 32


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