Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombin is primarily known for its role in homeostasis and thrombosis. However, this enzyme also plays important roles in wound healing and pathologic situations such as inflammation and tumorigenesis. Among the molecules stimulated by thrombin in these latter processes are the stress response proteins, chemokines. Chemokines are also known for their roles in inflammatory responses and tumor development. These correlative observations strongly suggest that chemokines may be mediators of some of thrombin's functions in these processes. Elucidation of the molecular mechanisms of stimulation of chemokines by thrombin may help to unravel the ways in which their expression can be modulated. Up-regulation of the chemokine 9E3/cCAF by thrombin occurs via its proteolytically activated receptor with subsequent transactivation of the epidermal growth factor receptor tyrosine kinase. This study shows that stimulation by thrombin very rapidly activates this chemokine at the transcriptional level, that 2 Elk1 binding elements located between -534 and -483 bp of the promoter are major thrombin response elements, that activation occurs via the Elk1 transcription factor, and that the latter is directly activated by MEK1/ERK2. The common occurrence of Elk1 binding domains in the promoters of immediate early response genes suggests that it may be characteristically involved in gene activation by stress-inducing agents. (Blood. 2000;96:3696-3706)
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PMID:Novel nuclear target for thrombin: activation of the Elk1 transcription factor leads to chemokine gene expression. 1109 49

On endothelial cells, thrombin binds to thrombomodulin (TM), an integral membrane-bound glycoprotein, and to protease-activated receptors (PARs). Thrombin binding to TM modulates endothelial cell and smooth muscle cell proliferation mediated through PAR1. We studied the phosphorylation and nuclear translocation of extracellular signal-regulated kinases (ERKs) 1 and 2 in human umbilical vein endothelial cells activated by thrombin. Thrombin and thrombin receptor-activating peptide (TRAP)-induced DNA synthesis were significantly inhibited by PD98059, an inhibitor of ERK phosphorylation. Immunoblots of phosphorylated ERKs (pERKs) and immunocytochemical studies of pERK localization revealed differences in the signal generated by thrombin and TRAP. After a short activation (15 minutes), the phosphorylation and the intracellular localization of pERKs were the same with the 2 agonists. After 4 hours, however, pERKs were visualized in the nuclei of thrombin-activated cells but barely detectable in TRAP-activated cells. Moreover, after 4 hours, the pERKs were visualized in the nuclei of cells stimulated by TRAP in the presence of a thrombin mutant that bound to TM, whereas they were around the nuclei in cells stimulated by thrombin in the presence of a monoclonal antibody preventing thrombin binding to TM. The results demonstrate that ERKs are involved in human umbilical vein endothelial cell DNA synthesis mediated by PAR agonists, that the duration of pERK nuclear retention is in inverse ratio to the mitogenic response, and that in addition to its role in the regulation of blood coagulation, TM acts as a thrombin receptor that modulates the duration of pERK nuclear retention and cell proliferation in response to thrombin.
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PMID:Thrombomodulin prolongs thrombin-induced extracellular signal-regulated kinase phosphorylation and nuclear retention in endothelial cells. 1130 85

The elevated level of thrombin has been detected in the airway fluids of asthmatic patients. However, the implication of thrombin in the pathogenesis of bronchial hyperreactivity was not completely understood. Therefore, in this study we investigated the effect of thrombin on cell proliferation and p42/p44 mitogen-activated protein kinase (MAPK) activation in human tracheal smooth muscle cells (TSMCs). Thrombin stimulated [3H]thymidine incorporation and p42/p44 MAPK phosphorylation in a time- and concentration-dependent manner in TSMCs. Pretreatment of TSMCs with pertussis toxin (PTX) significantly inhibited [3H]thymidine incorporation and phosphorylation of MAPK induced by thrombin. These responses were attenuated by tyrosine kinase inhibitors genistein and herbimycin A, phosphatidyl inositide (PI)-phospholipase C (PLC) inhibitor U73122, protein kinase C (PKC) inhibitor GF109203X, removal of Ca(2+) by addition of BAPTA/AM plus EGTA, and PI 3-kinase inhibitors wortmannin and LY294002. In addition, thrombin-induced [3H]-thymidine incorporation and p42/p44 MAPK phosphorylation was completely inhibited by PD98059 (an inhibitor of MEK1/2), indicating that activation of MEK1/2 was required for these responses. Furthermore, overexpression of dominant negative mutants, RasN17 and Raf-301, significantly suppressed p42/p44 MAPK activation induced by thrombin and PDGF-BB, indicating that Ras and Raf may be required for activation of these kinases. These results conclude that the mitogenic effect of thrombin was mediated through the activation of Ras/Raf/MEK/MAPK pathway. Thrombin-mediated MAPK activation was modulated by PI-PLC, Ca(2+), PKC, tyrosine kinase, and PI 3-kinase associated with cell proliferation in cultured human TSMCs.
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PMID:Mechanisms of thrombin-induced MAPK activation associated with cell proliferation in human cultured tracheal smooth muscle cells. 1130 43

Thrombin is a potent mitogen for vascular smooth muscle cells (VSMC) and has been implicated its pathogenic role in vascular remodelling. However, the signalling pathways by which thrombin mediates its mitogenic response are not fully understood. We have previously reported that thrombin activates p38 mitogen-activated protein kinase (p38 MAPK) by a tyrosine kinase-dependent mechanism, and that p38 MAPK has a role in thrombin-induced mitogenic response in rat VSMC. In the present study, we examine the involvement of epidermal growth factor (EGF) receptor in thrombin-induced p38 MAPK activation. We found that thrombin induced EGF receptor tyrosine phosphorylation (transactivation) in A10 cells, a clonal VSMC cell line. A selective inhibitor of EGF receptor kinase (AG1478) inhibited the p38 MAPK activation in a dose-dependent manner, whereas it had no effect on the response to platelet-derived growth factor (PDGF). EGF receptor phosphorylation induced by thrombin was inhibited by BAPTA-AM and GF109203X, which suggest a requirement for intracellular Ca(2+) increase and protein kinase C. We next examined the effect of AG1478 on thrombin-induced DNA synthesis. AG1478 inhibited thrombin-induced DNA synthesis in a dose-dependent manner. In contrast, PDGF-induced DNA synthesis was not affected by AG1478. In conclusion, these data suggest that the EGF receptor transactivation and subsequent p38 MAPK activation is required for thrombin-induced proliferation of VSMC.
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PMID:Thrombin-induced p38 mitogen-activated protein kinase activation is mediated by epidermal growth factor receptor transactivation pathway. 1130 36

Activation of the mitogen-activated protein kinase (MAPK) cascade is a well documented mechanism for the G-protein-coupled receptors. Here, we have analysed the requirements for ERKs and p38 MAPK activation by thrombin in Jurkat T cells. We show that thrombin-mediated ERKs activation requires both PTK and PKC activities, whereas p38 MAPK activation is dependent only on PTKs. Thrombin-induced ERK and p38 MAPK activation was more pronounced in p56Lck deficient cells indicating that this PTK exerts a negative control on MAPK activity. Accordingly, overexpression of p50 Csk a kinase that inactivates p56Lck induced constitutive activation of ERKs. Requirement for a Src kinase was evidenced by expression of a constitutively active form of p59Fyn in Jurkat cells. Besides its effect on tyrosine phosphorylation events, thrombin also triggered a rapid and robust redistribution of PKCepsilon and delta from the cytosol to the membrane. Expression of constitutively active and dominant negative PKCepsilon demonstrates the pivotal role of this PKC isoform in ERKs activation by thrombin. These data are consistent with a model where thrombin induces ERK activation via both PKC-dependent and independent pathways, whereas p38 MAPK activation requires only PTKs. The PKC-independent pathway requires Src kinases other than p56Lck more likely p59Fyn, while the PKC-dependent mechanism depends on PKCepsilon
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PMID:Differential requirements for ERK1/2 and P38 MAPK activation by thrombin in T cells. Role of P59Fyn and PKCepsilon. 1136 Jan 80

Thrombin is a potent mitogen for vascular smooth muscle cells. However, the signaling pathways by which thrombin mediates its mitogenic response are not fully understood. The ERK (extracellular signal-regulated protein kinase) and JNK (c-Jun N-terminal kinase) members of the mitogen-activated protein kinase (MAPK) family are reported to be activated by thrombin. We have investigated the response to thrombin of another member of the MAPK family, p38 MAPK, which has been suggested to be activated by both stress and inflammatory stimuli in vascular smooth muscle cells. We found that thrombin induced time- and dose-dependent activation of p38 MAPK. Maximal stimulation of p38 MAPK was observed after a 10-min incubation with 1 unit ml(-1) thrombin. GF109203X, a protein kinase C inhibitor, and prolonged treatment with phorbol 12-myristate 13-acetate partially inhibited p38 MAPK activation. A tyrosine kinase inhibitor, genistein, also inhibited p38 MAPK activation in a dose-dependent manner. p38 MAPK activation was inhibited by overexpression of betaARK1ct (beta-adrenergic receptor kinase I C-terminal peptide). p38 MAPK activation was also inhibited by expression of dominant-negative Ras, not by dominant-negative Rac. We next examined the effect of a p38 MAPK inhibitor, SB203580, on thrombin-induced proliferation. SB203580 inhibited thrombin-induced DNA synthesis in a dose-dependent manner. These results suggest that thrombin activates p38 MAPK in a manner dependent on Gbetagamma, protein kinase C, a tyrosine kinase, and Ras, that p38 MAPK has a role in thrombin-induced mitogenic response in the cells.
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PMID:Thrombin activates p38 mitogen-activated protein kinase in vascular smooth muscle cells. 1138 1

The stimulation of platelet-derived growth factor (PDGF) receptors shifts vascular smooth muscle (VSM) cells toward a more proliferative phenotype. Thrombin activates the same signaling cascades in VSM cells, namely the Ras/Raf/MEK/ERK and the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathways. Nonetheless, thrombin was not mitogenic, but rather increased the expression of the smooth muscle-specific myosin heavy chain (SM-MHC) indicative of an in vitro re-differentiation of VSM cells. A more detailed analysis of the temporal pattern and relative signal intensities revealed marked differences. The strong and biphasic phosphorylation of ERK1/2 in response to thrombin correlated with its ability to increase the activity of the SM-MHC promoter whereas Akt was only partially and transiently phosphorylated. By contrast, PDGF, a potent mitogen in VSM cells, induced a short-lived ERK1/2 phosphorylation but a complete and sustained phosphorylation of Akt. The phosphorylated form of Akt physically interacted with Raf. Moreover, Akt phosphorylated Raf at Ser(259), resulting in a reduced Raf kinase activity and a termination of MEK and ERK1/2 phosphorylation. Disruption of the PI 3-kinase signaling prevented the PDGF-induced Akt and Raf-Ser(259) phosphorylation. Under these conditions, PDGF elicited a more sustained MEK and ERK phosphorylation and increased SM-MHC promoter activity. Consistently, in cells that express dominant negative Akt, PDGF increased SM-MHC promoter activity. Furthermore, expression of constitutively active Akt blocked the thrombin-stimulated SM-MHC promoter activity. Thus, we present evidence that the balance and cross-regulation between the PI 3-kinase/Akt and Ras/Raf/MEK signaling cascades determine the temporal pattern of ERK1/2 phosphorylation and may thereby guide the phenotypic modulation of vascular smooth muscle cells.
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PMID:Regulation of Raf by Akt controls growth and differentiation in vascular smooth muscle cells. 1144 34

Thrombin, the terminal serine protease in the coagulation cascade, is a proinflammatory molecule in vivo and induces endothelial activation in vitro. The cellular signaling mechanisms involved in this function are unknown. The role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in thrombin-induced chemokine production was studied. Phosphorylation of both p38 MAPK and its substrate, ATF-2, was observed in human umbilical vein endothelial cells (HUVECs) stimulated with thrombin, with a maximum after 5 minutes of stimulation. Using the selective p38 MAPK inhibitor SB203580, there was a significant decrease in thrombin-induced interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) protein production and messenger RNA steady-state levels. In addition, SB203580 decreased IL-8 and MCP-1 production induced by the thrombin receptor-1 agonist peptide (TRAP), suggesting functional links between the thrombin G protein-coupled receptor and the p38 MAPK pathway. Furthermore, endothelial activation in the presence of SB203580 decreased the chemotactic activity of thrombin-stimulated HUVEC supernatant on neutrophils and monocytic cells. In contrast, the p42/p44 MAPK pathway did not appear to be involved in thrombin- or TRAP-induced endothelial chemokine production, because there was no reduction in the presence of the p42/p44-specific inhibitor PD98059. These results demonstrate that the p38 rather than p42/44 MAPK signaling pathway plays an important role in thrombin-induced endothelial proinflammatory activation and suggest that inhibition of p38 MAPK may be an interesting target for anti-inflammatory strategies in vascular diseases combining thrombosis and inflammation. (Blood. 2001;98:667-673)
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PMID:The p38 mitogen-activated protein kinase pathway plays a critical role in thrombin-induced endothelial chemokine production and leukocyte recruitment. 1146 65

The inhibitory gamma subunits of the retinal rod and cone photoreceptor type 6 retinal cyclic guanosine monophosphate phosphodiesterase (PDEgamma) are expressed in non-retinal tissues. Here, we show that PDEgamma interacts with the G-protein-coupled receptor kinase 2 signaling system to regulate the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase in human embryonic kidney 293 cells. This is based upon several lines of evidence. First, the transfection of cells with an antisense rod PDEgamma plasmid construct, which reduced endogenous rod PDEgamma expression, ablated the epidermal growth factor- and thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase. Second, the transfection of cells with recombinant rod or cone PDEgamma and/or G-protein-coupled receptor kinase 2 increased the stimulation of p42/p44 mitogen-activated protein kinase by epidermal growth factor or thrombin. In contrast, a G-protein-coupled receptor kinase 2 phosphorylation-resistant rod PDEgamma mutant failed to increase the epidermal growth factor- or thrombin-dependent stimulation of p42/p44 mitogen-activated protein kinase and, in fact, functioned as a dominant negative. Thrombin also stimulated the association of endogenous rod PDEgamma with dynamin II, which was increased in cells transfected with rod PDEgamma or G-protein-coupled receptor kinase 2. Dynamin II plays a critical role in regulating endocytosis of receptor signal complexes required for activation of p42/p44 mitogen-activated protein kinase. Therefore, PDEgamma may have an important role in promoting endocytosis of receptor signal complexes leading to the activation of p42/p44 mitogen-activated protein kinase. We conclude that PDEgamma is an entirely novel intermediate regulating mitogenic signaling from both receptor tyrosine kinase and G-protein-coupled receptors in human embryonic kidney 293 cells.
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PMID:The inhibitory gamma subunit of the type 6 retinal cyclic guanosine monophosphate phosphodiesterase is a novel intermediate regulating p42/p44 mitogen-activated protein kinase signaling in human embryonic kidney 293 cells. 1150 44

An imbalance of nitric oxide and endothelin plays an important role in cardiovascular disease. Thrombin exerts profound effects on endothelial function. The present study investigated the molecular mechanisms by which thrombin regulates endothelial nitric oxide synthase (eNOS) and endothelin-converting enzyme (ECE)-1 expression in human endothelial cells. Incubation of human umbilical vein endothelial cells with thrombin (0.01 to 4 U/mL) for 15 to 24 hours markedly downregulated eNOS and increased ECE-1 protein level in a dose-dependent manner. Thrombin also decreased eNOS mRNA and increased ECE-1 mRNA level. In mRNA stability assay, thrombin shortened the half-life of eNOS mRNA but not that of ECE-1 mRNA. Activation of protease-activated receptor 1 by the agonist (SFLLRN, 10 to 100 micromol/L) had no effect on eNOS expression but increased ECE-1 level as thrombin. Thrombin activated Rho A and extracellular signal-regulated kinase (ERK)1 and ERK2. Inhibition of Rho A by C3 exoenzyme (20 microgram/mL) and ROCK by Y-27632 (10 micromol/L) prevented the downregulation of eNOS expression by thrombin. Y-27632 also prevented the reduction in NOS activity induced by prolonged incubation with thrombin. On the other hand, inhibition of ERK1 and ERK2 activation by PD98059 (50 micromol/L) prevented the upregulation of ECE-1 expression by thrombin as well as the increase in ECE activity and ET-1 accumulation in the medium. Treatment of rat aorta with thrombin overnight impaired endothelium-dependent relaxations but not endothelium-independent relaxations. Thus, thrombin suppresses eNOS and upregulates ECE-1 expression via Rho/ROCK and ERK pathway, respectively. These effects of thrombin may be important for endothelial dysfunction in cardiovascular disease, particularly during acute coronary episodes.
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PMID:Thrombin suppresses endothelial nitric oxide synthase and upregulates endothelin-converting enzyme-1 expression by distinct pathways: role of Rho/ROCK and mitogen-activated protein kinase. 1157 23


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