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)

Staphylococcal enterotoxin B (SEB) is a bacterial enterotoxin able to simultaneously bind to class II molecules on APCs and to selected V beta regions (including V beta 8) of the TCR complex. Administration of SEB to adult BALB/c mice results in clonal activation of T cells bearing V beta 8 receptors, leading to an excessive release of proinflammatory cytokines. This initial immune response is followed by a long-lasting state of V beta 8-specific unresponsiveness, thought to benefit both the host (as it contributes to the down-regulation of the inflammatory response) and the bacterium (through ligand-specific T cell anergy). However, it is not clear how this type of restricted unresponsiveness can effectively impair the generation of an antibacterial response. To gain insight into the mechanism by which Gram-positive bacteria subvert the host immune response, we have investigated the immune competence of SEB-treated mice 48 h following SEB administration. We demonstrate in this report that in vivo, SEB induces a transient but profound state of unresponsiveness affecting both T and Ag-presenting cell functions. Although in vivo activation by SEB appears to be V beta-restricted under our experimental conditions, SEB-treated mice displayed an early (lasting 48 to 72 h postinjection) and V beta-unrestricted unresponsive state characterized by the inability to produce IL-2 in response to polyclonal TCR mitogens including third party bacterial superantigens (staphylococcal enterotoxin A and toxic shock syndrome toxin 1, SEA and TSST-1, respectively), Abs to non-SEB reactive V beta regions (V beta 6), anti-CD3 epsilon Abs, and a lectin (Con A). Spleen cell populations from SEB-treated mice also displayed defective APC functions, possibly related to a selective decrease in splenic dendritic cells numbers. Taken together, these observations indicate that SEB induces an early and transient state of immunodeficiency in vivo, representing a potential mechanism for escaping host immune surveillance.
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PMID:Staphylococcal enterotoxin B induces an early and transient state of immunosuppression characterized by V beta-unrestricted T cell unresponsiveness and defective antigen-presenting cell functions. 905 96

Thrombomodulin (TM), recognized as an essential vessel wall cofactor of the antithrombotic mechanism, is also expressed by a wide range of tumor cells. Tumor cell lines subcloned from four patients with malignant melanoma displayed a negative correlation between TM expression and cell proliferation in vitro and in vivo. Overexpression of wild-type TM decreased cell proliferation in vitro and tumor growth in vivo. TM mutants with altered protein C activation capacity lead to a similar effect. In contrast, transfection of melanoma cells with mutant TM constructs, in which a portion of the cytoplasmic or lectin domain was deleted, abrogated the antiproliferative effect associated with overexpression of wild-type TM. Experiments performed with either peptide agonists/antagonists of the thrombin receptor, with hirudin, or with inhibitors of thrombin-TM interaction did not alter the growth inhibitory effect of TM overexpression. These data suggest that TM exerts an effect on cell proliferation independent of thrombin and the thrombin receptor, possibly related to the binding of novel ligands to determinants in the lectin domain which might trigger signal transduction pathways dependent on the cytoplasmic domain.
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PMID:Thrombomodulin modulates growth of tumor cells independent of its anticoagulant activity. 952 72

Thrombomodulin is a cofactor protein on vascular endothelial cells that inhibits the procoagulant functions of thrombin and enhances thrombin-catalyzed activation of anticoagulant protein C. Thrombomodulin also accelerates the proteolytic activation of a plasma procarboxypeptidase referred to as thrombin-activable fibrinolysis inhibitor (TAFI). In this study, we describe structures on recombinant membrane-bound thrombomodulin that are required for human TAFI activation. Deletion of the N-terminal lectin-like domain and epidermal growth factor (EGF)-like domains 1 and 2 had no effect on TAFI or protein C activation, whereas deletions including EGF-like domain 3 selectively abolished thrombomodulin cofactor activity for TAFI activation. Provided that thrombomodulin EGF-like domain 3 was present, TAFI competitively inhibited protein C activation catalyzed by the thrombin-thrombomodulin complex. A thrombomodulin construct lacking EGF-like domain 3 functioned normally as a cofactor for protein C activation but was insensitive to inhibition by TAFI. Thus, the anticoagulant and antifibrinolytic cofactor activities of thrombomodulin have distinct structural requirements: protein C binding to the thrombin-thrombomodulin complex requires EGF-like domain 4, whereas TAFI binding also requires EGF-like domain 3.
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PMID:Activation of thrombin-activable fibrinolysis inhibitor requires epidermal growth factor-like domain 3 of thrombomodulin and is inhibited competitively by protein C. 957 59

Thrombomodulin (TM), in addition to its significance in the protein C anticoagulant pathway and cardiovascular diseases, has recently been shown to play important roles in normal embryonic development, several inflammatory conditions, as well as in tumor biology and in the pathogenesis of chronic radiation toxicity. We cloned and sequenced the cDNA encoding the complete TM protein from the Sprague-Dawley rat. The cDNA sequence consisted of a 78-bp 5' non-coding region and a 1731-bp open reading frame encoding 577 amino acids. Comparison of the deduced amino acid sequences showed Sprague-Dawley rat TM to be 87% homologous with mouse and 70.3% with human TM. In addition to the previously described highly conserved region in the lectin-like domain, another region was found which possessed significant homology among the species and may be involved in regulating cell surface expression of TM. Primers and fluorogenic probe for 5' exonuclease-based real time RT-PCR detection (TaqMan PCR) were constructed based on the cDNA sequence information and used to determine steady-state TM mRNA levels in lung, intestine, kidney, brain, and liver. The highest TM mRNA levels were found in lung and the lowest in liver. Immunohistochemistry confirmed that TM was mainly localized on the endothelium of blood vessels and lymphatics. The alveolar capillaries of lung showed the strongest immunoreactivity, whereas the endothelium of hepatic sinusoids and cerebral cortex were virtually negative.
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PMID:cDNA cloning and sequencing, gene expression, and immunolocalization of thrombomodulin in the Sprague-Dawley rat. 1023 Oct 31

Increased levels of the acute phase protein C-reactive protein (CRP) in plasma may indicate severe acute abdominal disease, risk of serious postoperative complications or malignancy; serial measurements may indicate postoperative complications, relapse of intra-abdominal sepsis and complications during acute pancreatitis. The increase in CRP is an unspecific acute phase reaction, however, and low levels do not exclude these conditions. These facts are important obstacles to the clinical routine use of CRP measurements. The aim of this study was to look for possible biochemical microheterogeneity of CRP in single plasma samples from various large groups of patients to overcome these problems. Two-hundred-and-twelve patients with acute abdominal diseases, 274 patients with various forms and stages of cancer and 134 patients operated on due to benign diseases, were studied. The biochemical studies included SDS-PAGE, native PAGE and gel filtration for molecular weight determinations, isoelectric focusing and crossed immuno-electrophoresis for electrophoretic mobility studies and Concavalin A and ACA 34 as intermediary gels for possible lectin binding or complexation. Western blot analysis was also used to identify CRP. In summary, however, these more elaborate biochemical methods could not disclose any microheterogneity of CRP in plasma and thus did not add any diagnostic information to the crude levels.
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PMID:No microheterogenous changes of plasma C-reactive protein found in man during various diseases. 1046 68

The structure and function of snake venom proteases are briefly reviewed by putting the focus on their effects on hemostasis and thrombosis and comparing with their mammalian counterparts. Up to date, more than 150 different proteases have been isolated and about one third of them structurally characterized. Those proteases are classified into serine proteases and metalloproteinases. A number of the serine proteases show fibrin(ogen)olytic (thrombin-like) activities, which are not susceptible to hirudin or heparin and perhaps to most endogenous serine protease inhibitors, and form abnormal fibrin clots. Some of them have kininogenase (kallikrein-like) activity releasing hypotensive bradykinin. A few venom serine proteases specifically activate coagulation factor V, protein C, plasminogen or platelets. The venom metalloproteinases, belonging to the metzincin family, generally show fibrin(ogen)olytic and extracellular matrix-degrading (hemorrhagic) activities. A few venom metalloproteinases show a unique substrate specificity toward coagulation factor X, platelet membrane receptors or von Willebrand factor. A number of the metalloproteinases have chimeric structures composed of several domains such as proteinase, disintegrin-like, Cys-rich and lectin-like domains. The disintegrin-like domain seems to facilitate the action of those metalloproteinases by interacting with platelet receptors. A more detailed analysis of snake venom proteases should find their usefulness for the medical and pharmacological applications in the field of thrombosis and hemostasis.
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PMID:Snake venom proteases affecting hemostasis and thrombosis. 1070 55

To examine the role of early carbohydrate recognition/trimming reactions in targeting endoplasmic reticulum (ER)-retained, misfolded glycoproteins for ER-associated degradation (ERAD), we have stably expressed the cog thyroglobulin (Tg) mutant cDNA in Chinese hamster ovary cells. We found that inhibitors of ER mannosidase I (but not other glycosidases) acutely suppressed Cog Tg degradation and also perturbed the ERAD process for Tg reduced with dithiothreitol as well as for gamma-carboxylation-deficient protein C expressed in warfarin-treated baby hamster kidney cells. Kifunensine inhibition of ER mannosidase I also suppressed ERAD in castanospermine-treated cells; thus, suppression of ERAD does not require lectin-like binding of ER chaperones calnexin and calreticulin to monoglucosylated oligosaccharides. Notably, the undegraded protein fraction remained completely microsome-associated. In pulse-chase studies, kifunensine-sensitive degradation was still inhibitable even 1 h after Tg synthesis. Intriguingly, chronic treatment with kifunensine caused a 3-fold accumulation of Cog Tg in Chinese hamster ovary cells and did not lead to significant induction of the ER unfolded protein response. We hypothesize that, in a manner not requiring lectin-like activity of calnexin/calreticulin, the recognition or processing of a specific branched N-linked mannose structure enhances the efficiency of glycoprotein retrotranslocation from the ER lumen.
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PMID:Endoplasmic reticulum (ER)-associated degradation of misfolded N-linked glycoproteins is suppressed upon inhibition of ER mannosidase I. 1098 71

Thrombomodulin (TM) is a vascular endothelial cell (EC) receptor that is a cofactor for thrombin-mediated activation of the anticoagulant protein C. The extracellular NH(2)-terminal domain of TM has homology to C-type lectins that are involved in immune regulation. Using transgenic mice that lack this structure (TM(LeD/LeD)), we show that the lectin-like domain of TM interferes with polymorphonuclear leukocyte (PMN) adhesion to ECs by intercellular adhesion molecule 1-dependent and -independent pathways through the suppression of extracellular signal-regulated kinase (ERK)(1/2) activation. TM(LeD/LeD) mice have reduced survival after endotoxin exposure, accumulate more PMNs in their lungs, and develop larger infarcts after myocardial ischemia/reperfusion. The recombinant lectin-like domain of TM suppresses PMN adhesion to ECs, diminishes cytokine-induced increase in nuclear factor kappaB and activation of ERK(1/2), and rescues ECs from serum starvation, findings that may explain why plasma levels of soluble TM are inversely correlated with cardiovascular disease. These data suggest that TM has antiinflammatory properties in addition to its role in coagulation and fibrinolysis.
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PMID:The lectin-like domain of thrombomodulin confers protection from neutrophil-mediated tissue damage by suppressing adhesion molecule expression via nuclear factor kappaB and mitogen-activated protein kinase pathways. 1220 72

Thrombomodulin (TM), a component of the protein C anticoagulant pathway, is critical for the maintenance of vascular thromboresistance. To facilitate the study of in vivo TM regulation, we cloned and sequenced the cDNA encoding full-length rabbit TM. Translation of the open reading frame predicts a 580 amino acid protein that contains a 19 amino acid signal peptide, one lectin-like and six EGF-like extracellular domains, a 23 amino acid transmembrane domain and a 36 amino acid cytoplasmic domain. In addition, there are three potential N-linked and six O-linked glycosylation sites. Comparison of the predicted rabbit TM protein with those of human, mouse and rat reveals 67-72% primary sequence conservation with identical domain homology. TM gene expression was quantified in rabbit cardiovascular tissue by real-time PCR using primers and probe based on the derived cDNA sequence and found to correlate with protein expression as determined by Western blot analysis.
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PMID:cDNA cloning of rabbit thrombomodulin and characterization of gene expression in cardiovascular tissue. 1501 48

As part of a general project aimed at elucidating the initiation of mucin-type O-glycosylation in helminth parasites, we have characterized a novel ppGalNAc-T (UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase) from the cestode Echinococcus granulosus (Eg-ppGalNAc-T1). A full-length cDNA was isolated from a library of the tissue-dwelling larval stage of the parasite, and found to code for a 654-amino-acid protein containing all the structural features of ppGalNAc-Ts. Functional characterization of a recombinant protein lacking the transmembrane domain showed maximal activity at 28 degrees C, in the range 6.5-7.5 pH units and in the presence of Cu2+. In addition, it transferred GalNAc to a broad range of substrate peptides, derived from human mucins and O-glycosylated parasite proteins, including acceptors containing only serine or only threonine residues. Interestingly, the C-terminal region of Eg-ppGalNAc-T1 bears a highly unusual lectin domain, considerably longer than the one from other members of the family, and including only one of the three ricin B repeats generally present in ppGalNAc-Ts. Furthermore, a search for conserved domains within the protein C-terminus identified a fragment showing similarity to a recently defined domain, specialized in the binding of organic phosphates (CYTH). The role of the lectin domain in the determination of the substrate specificity of these enzymes suggests that Eg-ppGalNAc-T1 would be involved in the glycosylation of a special type of substrate. Analysis of the tissue distribution by in situ hybridization and immunohistochemistry revealed that this transferase is expressed in the hydatid cyst wall and the subtegumental region of larval worms. Therefore it could participate in the biosynthesis of O-glycosylated parasite proteins exposed at the interface between E. granulosus and its hosts.
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PMID:Characterization of a UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase with an unusual lectin domain from the platyhelminth parasite Echinococcus granulosus. 1514 32


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