Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vasodilator effects of thrombin depend on activation of proteinase-activated receptor (PAR)-1 and the subsequent release of endothelin (ET)-1, which stimulates the generation of nitric oxide and PGs. We recently showed that thrombin released matrix metalloproteinase-2 (MMP-2) from rat arteries. We have now studied the significance of this release for the vasodilator effects of thrombin. Thrombin (>/=100 pmol), but not a PAR-1-activating peptide (TFLLR-NH(2)), produced a long-lasting (>10 min) vasorelaxation of rat mesenteric arteries, as detected by a microperfusion bioassay. Thrombin induced a simultaneous release of vascular MMP-2 into arterial perfusates, as revealed by zymography. Interestingly, the vasodilator effects of thrombin were inhibited by a tissue inhibitor of MMP-2 (TIMP-2, 10 pmol). Moreover, infusion of exogenous MMP-2 (5 pmol) resulted in vasorelaxation. These vasodilatory effects of thrombin and MMP-2 were significantly (P < 0.05) inhibited by endothelium denudation and by PD-142893 (2 nmol), an antagonist of ET receptors. Furthermore, both thrombin and MMP-2 constricted endothelium-denuded arteries. These results show that the vasodilator effects of thrombin may depend, in part, on a release of vascular MMP-2 and downstream activation of ETs. Thus MMP-2-dependent signaling may complement the PAR-1-dependent pathway of vasodilator action of thrombin.
 ...
PMID:Role of matrix metalloproteinase-2 in thrombin-induced vasorelaxation of rat mesenteric arteries. 1077 24

Gelatinase A, a member of the matrix metalloproteinase (MMP) family, plays an important role during angiogenesis. It is constitutively expressed by human endothelial cells as a latent enzyme and requires activation. Thrombin is the only described physiological inducer of gelatinase A in human endothelial cells. In this study, we investigated the mechanisms of gelatinase A activation by another physiological inducer, collagen. Endothelial cells were cultured on various ECM components for 24 h and the conditioned media were assessed for gelatinase A activity using gelatin zymography. The results demonstrated that type I collagen matrix specifically activates gelatinase A after 24 h in human umbilical vein and 48 h in neonatal foreskin endothelial cells. In contrast, thrombin activated gelatinase A after only 2 h. Activation by collagen was sustained over long periods of time in culture (96 h). Unlike thrombin-induced activation, collagen required active membrane type 1-MMP (MT1-MMP) on the endothelial cell surface to activate gelatinase A. In addition, collagen-induced activation of gelatinase A was inhibited by antibodies to the integrin receptor, alpha(2)beta(1), but not alpha(3)beta(1). Our findings, that collagen can provide long-term activation of gelatinase A are likely to be relevant to endothelial cell invasion during angiogenesis.
 ...
PMID:Three-dimensional collagen matrices induce delayed but sustained activation of gelatinase A in human endothelial cells via MT1-MMP. 1078 59

Endothelial cells expose receptors for vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) at the abluminal, basal surface that work as basic regulators of tumor-induced angiogenesis. Their specific localization makes them susceptible to the activity of tumor-released stimulatory factors, like VEGF/VPF, which induce proliferation of the endothelial cell toward the extracellular matrix. At the same time, VEGF/VPF stimulates endothelial cells to expose tissue factor (TF), the high-affinity transmembrane receptor and cofactor for cellular initiation of the plasma coagulation protease cascades through the extrinsic pathway, so generating thrombin. Thrombin exerts a number of activities: it forms an extracellular fibrin barrier from the VEGF/VPF-dependent fibrinogen extravasation; it activates progelatinase-A (pro-MMP-2), which destroys the basal membrane, allowing proliferation of endothelial cells (ECs) in the novel tumoral fibrin matrix; finally, it induces EC proliferation, potentiating the VEGF effect. Another important factor exposed at the abluminal endothelial cell surface is membrane type 1 matrix metalloproteinase (MT1-MMP), a membrane-bound metalloproteinase, which also activates progelatinase-A, allowing an alternative pathway to that of thrombin to destroy the basal membrane. In addition, we will see that MT1-MMP is also engaged in a direct, cell-associated fibrinolytic activity, essential for tubulogenesis of the novel outsprouting capillary.
 ...
PMID:Molecular polarity in endothelial cells and tumor-induced angiogenesis. 1106 39

Recently accumulated large bodies of evidence have strongly implicated proteolytic enzymes released by subgingival plaque bacteria in the pathogenicity of periodontal disease. With regard to proteolytic power, however, the contribution from different microbial species considered as periodontal pathogens is not equal. Two of these bacteria, P. gingivalis and T. denticola, have developed an elaborate proteolytic systems composed of several surface-located or secreted enzymes, which apparently serve a role to provide bacteria with nutrients in the form of small peptides and amino acids. Of these two species, proteinases of P. gingivalis are the most intensively studied, and during the last decade an impressive array of information has been accumulated with respect to the biochemical characterization of purified proteinases and structure of the genes encoding them, the regulation of expression and the effects of these enzymes on host systems. In addition, studies on proteinase-deficient isogenic mutants has shed light on both their housekeeping functions and potential role(s) in the pathogenicity of periodontitis. Among several proteinases produced by P. gingivalis, the cysteine proteinases, referred to as gingipains, are clearly in the spotlight. They are the subject of several recent reviews and generally considered as the major virulence factors of this periodontal pathogen (59, 105, 139, 182, 183, 186, 281, 284, 286, 289). Gingipains seem to be key players in subverting host defense systems with, significantly, the complement and neutrophils being the main target. In addition, through uncontrolled activation of kallikrein/kinin pathway and coagulation cascade they contribute to local generation of bradykinin and thrombin, two synergistically working pro-inflammatory reagents with a strongly, although indirectly, stimulatory effect on bone resorption. Furthermore, the ability to interact with the cytokine networking systems has the potential to dysregulate the local inflammatory reaction. Finally, gingipains have a strong effect on mechanisms controlling host matrix metalloproteinase activity at the level of gene expression and zymogen activation (Fig. 10). Collectively, at the periodontal lesion site, the non-restrained action of gingipains, supported by other proteinases locally produced by subgingival plaque bacteria, would dysregulate most mechanisms controlling inflammatory reaction. Although successful in limiting infection to the periodontium, the ultimate effect of uncontrolled inflammatory processes would be the destruction of periodontal connective tissue, certainly the hallmark of periodontitis.
 ...
PMID:Role of bacterial proteinases in matrix destruction and modulation of host responses. 1127 66

The activation of the matrix metalloproteinase progelatinase A (MMP-2) has been of keen interest because an increase in MMP-2 activity has been implicated in disease states such as cancer and atherosclerosis. Activation of MMP-2 occurs on the surface of specific cell types in two steps. In the first step, primary cleavage of MMP-2 by a membrane-type matrix metalloproteinase generates an intermediate. A secondary cleavage and activation of the intermediate is thought to occur autocatalytically. Previous studies have shown that thrombin can also activate progelatinase A in the presence of endothelial cells. We show that this cell-dependent mechanism of MMP-2 activation also occurs with THP-1 cells and involves binding of thrombin to thrombomodulin present on the cell surface and generation of the anti-coagulant protein, activated protein C. We demonstrate that activated protein C is directly responsible for activation and cleavage of the gelatinase A intermediate. This work contributes new mechanistic insights into the activation of MMP-2 and provides a novel link between matrix metalloproteinase activation and anti-coagulation.
 ...
PMID:Thrombin-thrombomodulin activation of protein C facilitates the activation of progelatinase A. 1129 49

Osteopontin (OPN) is a secreted phosphoprotein shown to function in wound healing, inflammation, and tumor progression. Expression of OPN is often co-localized with members of the matrix metalloproteinase (MMP) family. We report that OPN is a novel substrate for two MMPs, MMP-3 (stromelysin-1) and MMP-7 (matrilysin). Three cleavage sites were identified for MMP-3 in human OPN, and two of those sites were also cleaved by MMP-7. These include hydrolysis of the human Gly166-Leu167, Ala201-Tyr202 (MMP-3 only), and Asp210-Leu211 peptide bonds. Only the N-terminal Gly-Leu cleavage site is conserved in rat OPN (Gly151-Leu152). These sites are distinct from previously reported cleavage sites in OPN for the proteases thrombin or enterokinase. We found evidence for the predicted MMP cleavage fragments of OPN in vitro in tumor cell lines, and in vivo in remodeling tissues such as the postpartum uterus, where OPN and MMPs are co-expressed. Furthermore, cleavage of OPN by MMP-3 or MMP-7 potentiated the function of OPN as an adhesive and migratory stimulus in vitro through cell surface integrins. We predict that interaction of MMPs with OPN at tumor and wound healing sites in vivo may be a mechanism of regulation of OPN bioactivity.
 ...
PMID:Osteopontin, a novel substrate for matrix metalloproteinase-3 (stromelysin-1) and matrix metalloproteinase-7 (matrilysin). 1137 93

Thrombin, a critical enzyme in the coagulation cascade, has also been associated with angiogenesis and activation of the zymogen form of matrix metalloproteinase-2 (MMP-2 or gelatinase-A). We show that thrombin activated pro-MMP-2 in a dose- and time-dependent manner in cultured human umbilical-vein endothelial cells (HUVECs) to generate a catalytically active 63 kDa protein that accumulated as the predominant form in the conditioned medium. This 63 kDa thrombin-activated MMP-2 is distinct from the 62 kDa species found following concanavalin A or PMA stimulated pro-MMP-2 activation. Hirudin and leupeptin blocked thrombin-induced pro-MMP-2 activation, demonstrating that the proteolytic activity of thrombin is essential. However, activation was also dependent upon membrane-type-MMP (MT-MMP) action, since it was blocked by EDTA, o-phenanthroline, hydroxamate metalloproteinase inhibitors, tissue inhibitor of metalloproteinase-2 (TIMP-2) and TIMP-4, but not TIMP-1. Thrombin inefficiently cleaved recombinant 72 kDa pro-MMP-2, but efficiently cleaved the 64 kDa MT-MMP-processed intermediate form in the presence of cells. Thrombin also rapidly (within 1 h) increased cellular MT-MMP activity, and at longer time points (>6 h) it increased expression of MT1-MMP mRNA and protein. Thus signalling via proteinase-activated receptors (PARs) may play a role in thrombin-induced MMP-2 activation, though this does not appear to involve PAR1, PAR2, or PAR4 in HUVECs. These results indicate that in HUVECs the activation of pro-MMP-2 by thrombin involves increased MT-MMP activity and preferential cleavage of the MT-MMP-processed 64 kDa MMP-2 form in the presence of cells. The integration of these proteinase systems in the vascular endothelium may be important during thrombogenesis and tissue remodelling associated with neovascularization.
 ...
PMID:Activation of pro-(matrix metalloproteinase-2) (pro-MMP-2) by thrombin is membrane-type-MMP-dependent in human umbilical vein endothelial cells and generates a distinct 63 kDa active species. 1141 41

Protease-activated receptor 1 (PAR-1) is a G-coupled membrane protein. In this study, we analyzed the expression of PAR-1 in oral squamous cell carcinomas (SCCs). PAR-1 was expressed in oral SCCs, but the level of PAR-1 protein was lower in non-metastatic cells than in metastatic cells. Thrombin stimulated the growth of metastatic cells, and both thrombin and thrombin receptor activation peptide (TRP) enhanced the adhesion of these cells to fibronectin, but had no effect on non-metastatic cells. Thrombin and TRP also induced matrix metalloproteinase (MMP)-2 and MMP-9 activities in metastatic cells. These results suggest that PAR-1 may contribute to the growth and invasive potential of oral SCC.
 ...
PMID:Expression of protease-activated receptor 1 in oral squamous cell carcinoma. 1143 Nov 6

Endothelial cell invasion is an essential event during angiogenesis (formation of new blood vessels). The process involves the degradation of the basement membrane and the underlying interstitium. The matrix metalloproteinase (MMP) family is considered to be primarily responsible for matrix degradation. Two members of the family, gelatinase A and B play an important role in angiogenesis. This review outlines recent findings on their regulation in human endothelial cells. Latent gelatinase B is secreted from endothelial cells. This enzyme can also accumulate in the cytosol as an active enzyme, free of TIMP-1. In contrast, latent gelatinase A is constitutively secreted from the cells. Unlike other MMPs, gelatinase A activation occurs on the cell membrane and is mediated by MT1-MMP. A number of physiological activators have recently been described. These include thrombin and activated protein C, both of which activate gelatinase A independent of the MT1-MMP pathway. These new findings may lead to therapeutic interventions for the treatment of angiogenic-dependent diseases such as cancer and arthritis.
 ...
PMID:Human endothelial gelatinases and angiogenesis. 1147 Feb 30

Circulating monocytes adhere to platelets and matrix proteins at sites of vascular injury, where engagement of specific surface tethering molecules mediates outside-in signaling and synthesis of gene products by the leukocytes. Here we demonstrate that interaction of isolated human monocytes with collagen induces matrix metalloproteinase-9 (MMP-9; gelatinase B) synthesis by monocytes, a process that is greatly enhanced in the presence of platelets. MMP-9 is a potent matrix degrading enzyme implicated in atherosclerotic plaque rupture, aneurysm formation, and other vascular syndromes. Synthesis of MMP-9 by monocytes is tightly regulated and synergistically increased following adhesion to collagen and platelets. Adhesion to control matrix proteins alone did not result in MMP-9 protein production and, similarly, adhesion of monocytes to platelets activated with thrombin in suspension was not sufficient to induce MMP-9 synthesis in the absence of monocyte adhesion to collagen. Interruption of intercellular contact between platelets and monocytes dramatically inhibited MMP-9 synthesis. These observations demonstrate that discrete adhesion-dependent signaling pathways govern MMP-9 synthesis by monocytes. The synthesis of MMP-9 by monocytes may be critical in vascular syndromes and other pathological processes that are dependent on dysregulated cell-cell and cell-matrix interactions.
 ...
PMID:Differential regulation of matrix metalloproteinase-9 by monocytes adherent to collagen and platelets. 1155 38


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