Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Fibrinogen molecules are comprised of two sets of disulfide-bridged Aalpha-, Bbeta-, and gamma-chains. Each molecule contains two outer D domains connected to a central E domain by a coiled-coil segment. Fibrin is formed after thrombin cleavage of fibrinopeptide A (FPA) from fibrinogen Aalpha-chains, thus initiating fibrin polymerization. Double-stranded fibrils form through end-to-middle domain (D:E) associations, and concomitant lateral fibril associations and branching create a clot network. Fibrin assembly facilitates intermolecular antiparallel C-terminal alignment of gamma-chain pairs, which are then covalently 'cross-linked' by factor XIII ('plasma protransglutaminase') or XIIIa to form 'gamma-dimers'. In addition to its primary role of providing scaffolding for the intravascular thrombus and also accounting for important clot viscoelastic properties, fibrin(ogen) participates in other biologic functions involving unique binding sites, some of which become exposed as a consequence of fibrin formation. This review provides details about fibrinogen and fibrin structure, and correlates this information with biological functions that include: (i) suppression of plasma factor XIII-mediated cross-linking activity in blood by binding the factor XIII A2B2 complex. (ii) Non-substrate thrombin binding to fibrin, termed antithrombin I (AT-I), which down-regulates thrombin generation in clotting blood. (iii) Tissue-type plasminogen activator (tPA)-stimulated plasminogen activation by fibrin that results from formation of a ternary tPA-plasminogen-fibrin complex. Binding of inhibitors such as alpha2-antiplasmin, plasminogen activator inhibitor-2, lipoprotein(a), or histidine-rich glycoprotein, impairs plasminogen activation. (iv) Enhanced interactions with the extracellular matrix by binding of fibronectin to fibrin(ogen). (v) Molecular and cellular interactions of fibrin beta15-42. This sequence binds to heparin and mediates platelet and endothelial cell spreading, fibroblast proliferation, and capillary tube formation. Interactions between beta15-42 and vascular endothelial (VE)-cadherin, an endothelial cell receptor, also promote capillary tube formation and angiogenesis. These activities are enhanced by binding of growth factors like fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF), and cytokines like interleukin (IL)-1. (vi) Fibrinogen binding to the platelet alpha(IIb)beta3 receptor, which is important for incorporating platelets into a developing thrombus. (vii) Leukocyte binding to fibrin(ogen) via integrin alpha(M)beta2 (Mac-1), which is a high affinity receptor on stimulated monocytes and neutrophils.
...
PMID:Fibrinogen and fibrin structure and functions. 1610 57

Thrombin, a serine protease that plays a pivotal role in blood coagulation, wound healing, and angiogenesis, has also been implicated in the mitogenesis of various cell types. Previously, we showed that thrombin and the thrombin receptor agonist peptide (TRAP-14; SFLLRNPNDKYEPF) for protease-activated receptor 1 (PAR1) induce vascular endothelial growth factor (VEGF) secretion in PC-12 cells. In this study, we show that thrombin and TRAP-14 also stimulate VEGF secretion in the human NB-1 neuroblastoma cells. In these cells, we further show that thrombin-induced VEGF secretion was blocked by cycloheximide and actinomycin D, indicating that de novo protein synthesis is essential for this process. Reduced thrombin-induced VEGF secretion upon treatment with LY294002, calphostin C, or BAPTA, further suggests that the process is dependent on phosphatidyl-inositol-3-kinase, protein kinase C, and calcium. However, the complete loss of thrombin-induced VEGF production upon treatment with argatroban, a derivative of arginine and a potent anticoagulant/antithrombin agent, supports the notion that argatroban serves as a useful therapeutic tool for thrombin-associated pathologic conditions. Here, it appears that argatroban may be effective in controlling disorders linked to thrombin-induced VEGF production in neuronal cells.
...
PMID:Inhibition of thrombin-induced vascular endothelial growth factor production in human neuroblastoma (NB-1) cells by argatroban. 1629 85

The aim of this study was to examine our hypothesis that platelets of patients with breast cancer were functionally altered compared to healthy controls. The results have shown that the platelets from women with early breast cancer released significantly more vascular endothelial growth factor (VEGF) when stimulated with thrombin, tissue factor, clotting, or over a period of time. Similarly, release of thrombospondin (TSP) with thrombin and tissue factor was higher, but failed to reach a significant level. Thus, the observed differences in platelet response support our hypothesis, but warrant further work to determine the reason underlying the observed difference and potential clinical relevance of our findings.
...
PMID:Alteration in platelet function in patients with early breast cancer. 1630 84

For many years, fibrin sealants were associated with bone substitutes to promote bone healing. However, the osteoblastic response to fibrin sealant components remains poorly documented. In this study, MC3T3-E1 osteoblastic cells were cultured on biphasic calcium phosphate ceramic (MBCP) coated with Tissucol components (thrombin and fibrinogen). Analysis of osteoblastic differentiation markers by RT-PCR revealed that MBCP coated with Tissucol stimulated mRNA levels for osteocalcin and alkaline phosphatase (ALP). Of all the components of Tissucol, thrombin has been reported to affect osteoblastic behavior. Our results demonstrated that low thrombin concentrations (0.5-5 U/ml) stimulated mRNA levels for ALP, whereas high thrombin concentrations (50-100 U/ml) decreased mRNA levels for ALP and PTH/PTHrP receptor and also increased mRNA level for the osteoclastogenesis inhibitor OPG. As thrombin stimulated angiogenesis, we then wondered whether thrombin could influence the expression of angiogenic factors. Low thrombin concentrations were shown to up-regulate mRNA levels for VEGF-B and VEGF-R1, suggesting an autocrine/paracrine role for VEGF-B. Higher thrombin concentrations also up-regulated mRNA for VEGF-A and neuropilin-1. In conclusion, the association of MBCP with thrombin and fibrinogen appears to be a convenient scaffold for bone cell differentiation. Thrombin could also acts at the cellular level by increasing the angiogenic potential of osteoblasts as well as their responsiveness to thrombin and VEGF.
...
PMID:The modulation of gene expression in osteoblasts by thrombin coated on biphasic calcium phosphate ceramic. 1643 94

Interleukin 8 (IL-8) and vascular endothelial growth factor (VEGF) are two cytokines promoting prostate tumor growth and angiogenesis. The main coagulation protease thrombin may modulate the malignant phenotype of prostate cancer cells via its cellular receptor(s). We aimed to investigate the effects of thrombin on IL-8 and VEGF expression in DU 145 prostate cancer cells. Thrombin induced the expression and secretion of IL-8 and VEGF, with more pronounced effects on IL-8. Target-specific siRNA-induced protease-activated receptor 1 (PAR-1) knockdown completely neutralized thrombin-enhanced cytokine secretion, demonstrating the essential role of PAR-1. Inhibitors of either extracellular signal-regulating kinase (ERK) or phosphatidylinositol 3-kinase (PI3K) partly reversed the thrombin-induced cytokine expression, suggesting that both ERK and PI3K kinase pathways may be involved in IL-8 and VEGF expression. The results suggest that the thrombin/PAR-1 system upregulates cytokines in prostate cancer cells which in turn may contribute to the progression of prostate cancer.
...
PMID:Thrombin/thrombin receptor (PAR-1)-mediated induction of IL-8 and VEGF expression in prostate cancer cells. 1653 Jul 25

Glomerular endothelial cells (GEnC) are specialized cells with important roles in physiological filtration and glomerular disease. Despite their unique features, GEnC have been little studied because of difficulty in maintaining them in cell culture. We have addressed this problem by generation of conditionally immortalized (ci) human GEnC using technology with which we have previously produced ci podocytes. Primary culture GEnC were transduced with temperature-sensitive simian virus 40 large tumour antigen and telomerase using retroviral vectors. Cells were selected, cloned, and then characterized by light and electron microscopy (EM), response to vascular endothelial growth factor (VEGF), and tumour necrosis factor (TNF)alpha, expression of endothelial markers by focused gene array, immunofluorescence and Western blotting, and formation and behaviour of monolayers. CiGEnC proliferated at the permissive temperature (33 degrees C) and became growth arrested at the non-permissive temperature (37 degrees C). CiGEnC retained morphological features of early-passage primary culture GEnC up to at least p41, confirming successful immortalization. EM demonstrated fenestrations, increased in number by VEGF. mRNA analysis confirmed expression of the endothelial markers platelet endothelial cell adhesion molecule 1, intercellular adhesion molecule 2, VEGF receptor 2, and von Willebrand factor, validated by immunofluorescence and Western blotting. CiGEnC also expressed Tie2, and TNFalpha upregulated E-selectin. CiGEnC formed monolayers with barrier properties responsive to cyclic adenosine 3',5' monophosphate (cAMP) and thrombin. CiGEnC retain the markers and behaviour of primary culture GEnC. They express fenestrations which are upregulated in response to VEGF. These cells are a unique resource for further study of GEnC and their roles in glomerular filtration, glomerular disease, and response to glomerular injury.
...
PMID:Conditionally immortalized human glomerular endothelial cells expressing fenestrations in response to VEGF. 1655 32

The mechanism of thrombin-induced angiogenesis is poorly understood. Using a gene chip array to investigate the pro-malignant phenotype of thrombin-stimulated cells, we observed that thrombin markedly up-regulates growth-regulated oncogene-alpha (GRO-alpha) in several tumor cell lines as well as endothelial cells by mRNA and protein analysis. Thrombin enhanced the secretion of GRO-alpha from tumor cells 25- to 64-fold. GRO-alpha is a CXC chemokine with tumor-associated angiogenic as well as oncogenic activation following ligation of its CXCR2 receptor. GRO-alpha enhanced angiogenesis in the chick chorioallantoic membrane assay 2.2-fold, providing direct evidence for GRO-alpha as an angiogenic growth factor. Anti-GRO-alpha antibody completely inhibited the 2.7-fold thrombin-induced up-regulation of angiogenesis, as well as the 1.5-fold thrombin-induced up-regulation of both endothelial cell cord formation in Matrigel and growth in vitro. Thrombin as well as its PAR-1 receptor activation peptide [thrombin receptor activation peptide (TRAP)] as well as GRO-alpha all markedly increased vascular regulatory proteins and growth factors: matrix metalloproteinase (MMP)-1, MMP-2, vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2), CD31, and receptors KDR and CXCR2 in human umbilical vein endothelial cells. All of the thrombin/TRAP gene up-regulations were completely inhibited by anti-GRO-alpha antibody and unaffected by irrelevant antibody. Similar inhibition of gene up-regulation as well as thrombin-induced chemotaxis was noted with small interfering RNA (shRNA) GRO-alpha KD 4T1 breast tumor and B16F10 melanoma cells. In vivo tumor growth studies in wild-type mice with shRNA GRO-alpha KD cells revealed 2- to 4-fold impaired tumor growth, metastasis, and angiogenesis, which was not affected by endogenous thrombin. Thus, thrombin-induced angiogenesis requires the up-regulation of GRO-alpha. Thrombin up-regulation of GRO-alpha in tumor cells as well as endothelial cells contributes to tumor angiogenesis.
...
PMID:Growth-regulated oncogene is pivotal in thrombin-induced angiogenesis. 1661 33

Activation and dysfunction of the endothelium underlie many vascular disorders including atherosclerosis, tumor growth, and inflammation. We recently reported that thrombin and vascular endothelial growth factor, but not tumor necrosis factor-alpha, results in dramatic up-regulation of Down syndrome critical region (DSCR)-1 gene in endothelial cells, a negative feedback regulator of calcineurin-NFAT signaling. Constitutive expression of DSCR-1 in activated endothelial cells markedly impaired NFAT nuclear localization, proliferation, tube formation, and tumor growth. The goal of the present study was to elucidate the relative roles of NFAT/DSCR-1 and NF-kappaB/I-kappaB in mediating thrombin-responsive gene expression in endothelial cells. DNA microarrays of thrombin-treated human umbilical vein endothelial cells overexpressing DSCR-1 or constitutive active IkappaBalpha revealed genes that were dependent on NFAT and/or NF-kappaB activity. Vascular cell adhesion molecule-1 was inhibited both by DSCR-1 and I-kappaB at the level of mRNA, protein, promoter activity, and function (monocyte adhesion). Using a combination of transient transfections, electrophoretic mobility shift assays, and chromatin immunoprecipitation, thrombin was shown to induce time-dependent coordinate binding of RelA and NFATc to a tandem NF-kappaB element in the upstream promoter region of vascular cell adhesion molecule-1. Together, these findings suggest that thrombin-mediated activation of endothelial cells involves an interplay between NFAT and NF-kappaB signaling pathways and their negative feedback inhibitors, DSCR-1 and I-kappaB, respectively. As natural brakes in the inflammatory process, DSCR-1 and I-kappaB may lend themselves to therapeutic manipulation in vasculopathic disease states.
...
PMID:Thrombin-induced autoinhibitory factor, Down syndrome critical region-1, attenuates NFAT-dependent vascular cell adhesion molecule-1 expression and inflammation in the endothelium. 1662 81

Oligodendrocyte precursor cells recognized with the NG2 antibody respond rapidly to CNS injuries with hypertrophy and upregulation of the NG2 chondroitin sulfate proteoglycan within 24 h. These cells participate in glial scar formation, remaining around the injury site for several weeks. After injury, reactive oligodendrocyte precursor cells increase their production of several chondroitin sulfate proteoglycans, including NG2: this cell type thus represents a component of the inhibitory environment that prevents regeneration of axons in the injured CNS. This study analyzes factors that activate oligodendrocyte precursor cells. Both microglia and astrocytes become reactive around motor neurons following peripheral nerve lesions. We show that oligodendrocyte precursor cells do not hypertrophy or increase NG2 levels after these lesions. Those lesions that cause an oligodendrocyte precursor cell reaction generally open the blood-brain barrier. We therefore opened the blood-brain barrier with microinjections of vascular endothelial growth factor or lipopolysaccharide to the rat and mouse brain, and examined oligodendrocyte precursor cell reactivity after 24 h. Both treatments led to increases in NG2 and hypertrophy of oligodendrocyte precursor cells. Of directly injected blood components serum and thrombin were without effect, while platelets and macrophages activated oligodendrocyte precursor cells. We tested the effects of a range of injury-related cytokines, of which tumor necrosis factor alpha; interleukin-1; transforming growth factor beta; interferon gamma had effects on oligodendrocyte precursor cells. Oligodendrocyte precursor cell chemokines, and mitogens did not increase NG2 levels.
...
PMID:The injury response of oligodendrocyte precursor cells is induced by platelets, macrophages and inflammation-associated cytokines. 1663 14

Protease-activated receptor 2 (PAR2) is a G-protein coupled receptor that is cleaved and activated by serine proteases including the coagulation protease factor VIIa (FVIIa). There is evidence that PAR2 function contributes to angiogenesis, but the mechanisms involved are poorly defined. Here we show that PAR2 activation in human breast cancer cells leads to the upregulation of vascular endothelial growth factor (VEGF). Activation of PAR2 with agonist peptide (AP), trypsin or FVIIa results in a robust increase of VEGF message and protein. Incubation of cells with PAR1-AP, PAR3-AP, PAR4-AP, or thrombin has only a modest effect on VEGF production. Cleavage blocking antibodies show that FVIIa-mediated VEGF production is PAR2 mediated. Mitogen-activated protein kinase (MAPK) pathway inhibitors U0126 and SB203580 inhibit PAR2-mediated VEGF production. Incubation of cells with PAR2-AP leads to significant extracellular regulated kinase1/2 (ERK1/2) and p38 MAPK phosphorylation and activation. Collectively, these data suggest that PAR2 signaling through MAPK pathways leads to the production of proangiogenic VEGF in breast cancer cells.
...
PMID:Protease-activated receptor-2 regulates vascular endothelial growth factor expression in MDA-MB-231 cells via MAPK pathways. 1665 Aug 17


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---