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

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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thienopyridine platelet antagonist ticlopidine is associated with development of thrombotic thrombocytopenic purpura (TTP) but the pathophysiology of this link is unclear. Severe deficiency of disintegrin and metalloproteinase with thrombospondin motif-13 (ADAMTS13), described in familial cases and a significant fraction of idiopathic TTP, has been reported in only a few ticlopidine-linked cases. As ticlopidine can disrupt production of extracellular matrix (ECM) components critical to microvascular endothelial cell (MVEC) integrity in vitro, we explored the hypotheses that ticlopidine and ticlopidine-linked TTP plasmas induce MVEC apoptosis in a manner similar to that of idiopathic TTP plasmas, and that ECM components and related mitogen-activated protein kinase (MAPK) signalling cascades may be involved in this process. Replicating the activity of plasmas from patients with idiopathic TTP, plasma from five ticlopidine-linked TTP patients induced apoptosis of primary human dermal, glomerular and hepatic MVEC, but had no effect on pulmonary MVEC or large vessel endothelial cells (EC). Pharmacological levels of ticlopidine initiated apoptosis with similar EC lineage restriction. In parallel, ticlopidine and plasmas from idiopathic and ticlopidine-TTP patients decreased transcripts for the ECM component thrombospondin-1 in MVEC, but not in large vessel EC. These changes were accompanied by prolonged induction of MAPKs extracellular signal-related kinase (ERK)-1/2 and p38 only in TTP susceptible MVEC. Induction of apoptosis by ticlopidine and TTP plasma was abrogated by inhibitors of ERK-1/2 and p38 phosphorylation. In conclusion, MVEC apoptosis related to altered ECM-MVEC interactions may be a key part of the pathology of ticlopidine-linked and idiopathic TTP.
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PMID:Thienopyridine-linked thrombotic microangiopathy: association with endothelial cell apoptosis and activation of MAP kinase signalling cascades. 1468 31

Interleukin (IL)-17 promotes cartilage breakdown by inducing matrix metalloproteinases (MMPs) and aggrecanases (a disintegrin and metalloproteinase with thrombospondin motif, ADAMTS) in arthritic joints. We investigated IL-17 signaling pathways inducing MMP-3, MMP-13 and ADAM-TS4 genes in bovine articular chondrocytes. IL-17 stimulated phosphorylation of extracellular signal-regulated kinase (ERK), protein 38 (p38) and c-Jun N-terminal kinase (JNK). ERK pathway inhibitors, PD98059 and U0126, down-regulated IL-17-induced MMP and ADAM-TS4 gene expression. Protein 38 and JNK pathway inhibitors, SB203580 and SP600125, also reduced induction of these genes. Antioxidants and activating protein-1 transcription factor inhibitors, nordihydroguaiaretic acid and N-acetyl-L-cysteine (NAC) suppressed MMP and ADAM-TS4 genes. Similarly, nuclear factor kappa B (NF-kappaB) pathways inhibitors curcumin and Bay-11-7085 also blocked their induction. Thus MMP-3, MMP-13 and ADAM-TS4 genes are coordinately up-regulated by IL-17 via MAP kinases, activating protein-1 (AP-1) and NF-kappaB mediators, which could be targeted for reducing IL-17-triggered cartilage damage.
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PMID:Interleukin-17 signal transduction pathways implicated in inducing matrix metalloproteinase-3, -13 and aggrecanase-1 genes in articular chondrocytes. 1470 35

The natural hormone 17beta-estradiol (17beta-E2) is known to induce tumor angiogenesis in various target organs by activating positive regulators of angiogenesis. In this study, we show for the first time that in human umbilical vein endothelial cells (HUVECs), 17beta-E2 transiently down-regulates the expression and secretion of a potent negative regulator of angiogenesis, thrombospondin-1 (TSP-1). This inhibitory effect of 17beta-E2 is mediated through nongenomic estrogen receptor (ER)/mitogen-activated protein kinase (MAPK)/extracellular-regulated kinase (ERK) 1/2 and c-Jun NH(2)-terminal kinase (JNK)/stress-activated protein kinase (SAPK) signaling pathways, because this effect can be abolished by a pure ER antagonist (ICI 182,780) and inhibitors of downstream signaling proteins of MAPK signaling cascades, including MAPK kinase 1/2 and ERK1/2 inhibitor and JNK/SAPK inhibitor. To understand the functional role(s) of TSP-1 during estradiol-induced angiogenesis, we examined the growth and migration of endothelial cells in different experimental environments. Using a recombinant protein, we show that increments of TSP-1 protein concentration in culture medium significantly reduce the migration and proliferation of HUVECs stimulated by 17beta-E2. Together, these studies suggest that TSP-1 can be considered an important negative factor in understanding the increased angiogenesis in response to estrogens.
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PMID:Thombospondin-1 disrupts estrogen-induced endothelial cell proliferation and migration and its expression is suppressed by estradiol. 1503 54

We found that thrombospondin-1 (TSP-1) has opposite functions on angiogenesis depending on the nature of the proteolytic fragment released in vivo by the action of proteases. We studied the effect of the 25 and 140 kDa fragments of TSP-1 generated by its proteolytic cleavage on the cascade of mitogen activated protein kinase (MAPK) activation and matrix-metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) function and expression in microvascular endothelium. Post-capillary endothelial cells (CVEC) isolated from bovine heart were used. The 25 kDa fragment enhanced the upregulation of MMP-2 and -9 and reduced TIMP-2 expression leading to CVEC chemoinvasion. Conversely, the 140 kDa fragment blocked MMP-2 and -9 stimulation and doubled TIMP-2 expression, leading to inhibition of endothelial chemoinvasion induced by fibroblast growth factor-2 (FGF-2). MAPK activity (ERK1-2) was induced by TSP-1 and by the 25 kDa fragment, but not by the 140 kDa fragment which, however, promoted MAPK p38 activation. This evidence indicates that fragments originating from TSP-1 switch the pro- or anti-angiogenic phenotype in endothelium by targeting MAPK cascades with opposite functions on MMP/TIMP balance.
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PMID:ERK1-2 and p38 MAPK regulate MMP/TIMP balance and function in response to thrombospondin-1 fragments in the microvascular endothelium. 1505 21

The transforming growth factor (TGF) family of secretory polypeptides comprises signaling proteins involved in numerous physiological processes, including vascular development and vessel wall integrity. Both pro- and anti-angiogenic effects of TGF-beta1 have also been documented. To study the intracellular mechanisms involved in capillary tube morphogenesis, endothelial cell aggregates were cultured in a fibrin matrix. It was found that the pattern of capillary tubes formed in a fibrin matrix was altered in response to TGF-beta1 treatment such that the capillary-like structures displayed a bipolarized pattern. In contrast, in untreated control and fibroblast growth factor-2-treated cells, the pattern of capillary tubes formed was random. TGF-beta1 also downregulated urokinase-type plasminogen activator (uPA) activity while upregulating PA inhibitor (PAI)-1 and thrombospondin (TSP)1 gene expression. To investigate the signaling cascade mediating the phenotypic changes observed, pharmacological inhibitors of p38 MAPK, Sp1 transcription factor, c-Jun NH(2)-terminal kinase (JNK), and the cytokine TNF-alpha were used. The p38 MAPK inhibitor SB203580 reversed the TGF-beta1-dependent inhibition of uPA activity but not its morphogenetic effect. In contrast, the DNA intercalator WP631 and TNF-alpha counteracted the TGF-beta1-induced morphogenetic effect while the JNK inhibitor SP600125 effectively inhibited capillary tube formation. These results indicate that the TGF-beta1-induced capillary tube pattern is independent of the p38 MAPK-activated PAI-1 and TSP1 expression, but the mechanism involves Sp1-dependent transcriptional regulation. The results also raise the possibility that the JNK pathway, which controls convergent extension in Xenopus, may be involved in vessel wall patterning in mammalian systems.
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PMID:Role of TGF-beta1 and JNK signaling in capillary tube patterning. 1520 Nov 40

Glucocorticoid (GC) treatment for the management of autoimmune and inflammatory diseases is associated with decreased bone formation and increased risk for fracture. In MC3T3-E1 cell cultures, 0.1-1 microM dexamethasone (DEX) arrests development of the osteoblast phenotype when administration commences at a commitment stage around the time of confluency. To gain new insights into GC-induced osteoporosis, we performed microarray-based gene expression analysis of GC-arrested MC3T3-E1 cultures, 2.5 days after the administration of DEX. Of the >12 000 transcripts interrogated, 74 were up-regulated and 17 were down-regulated by at least 2.5-fold (P < or = 0.05). Some of these genes, such as Mmp13, Serum/GC-regulated kinase and Tieg, have previously been reported as GC-responsive. Others are shown here for the first time to respond to GCs. DEX strongly repressed Krox20/Egr2 at both the mRNA and the protein level. This is especially significant because mice lacking this transcription factor develop osteoporosis. The data also suggest that the bone morphogenetic protein (BMP) pathway, which is involved in regulating bone mass, and other pathways that influence BMP signaling, are abrogated by GCs: (i) DEX increased the mRNA levels of the BMP antagonists Follistatin and Dan; (ii) DEX increased the levels of p21 Rasgap3 and Ptpn16/MKP-1 mRNAs, negative regulators of the MAP kinase pathway; and (iii) DEX decreased Cox mRNA levels. DEX also increased thrombospondin mRNA levels, which negatively regulate bone mass in vivo, as well as the adipocytic marker Fkbp51. These and other observations disclose novel gene targets, whose regulation by GCs in osteoblasts may shed light on and provide new therapeutic approaches to osteoporosis.
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PMID:Gene expression profiling of glucocorticoid-inhibited osteoblasts. 1529 52

We have shown that inhibition of polyamine biosynthesis with alpha-difluoromethylornithine (DFMO) reduces in vitro invasiveness and metastatic capacity of MDA-MB-435 breast cancer cells. These experiments investigated the mechanisms mediating the anti-invasive properties of DFMO. DFMO did not affect phosphorylation of FAK or Akt, but increased ERK phosphorylation by approximately threefold. To test the biologic significance of this finding, we tested the effect of the MEK inhibitor PD98059 on in vitro invasiveness of MDA-MB-435 breast cancer cells, both in the absence and in the presence of the proinvasive peptide hepatocyte growth factor (HGF) as a chemoattractant. We observed that PD98059 treatment reversed the anti-invasive effect of DFMO under both experimental conditions. Next, we tested the influence of DFMO on the production of the prometastatic peptide osteopontin (OPN) and the anti-metastatic protein thrombospondin-1 (TSP-1). DFMO treatment, while not affecting OPN production, markedly increased the TSP-1 level in the conditioned media. This effect was abolished by putrescine administration, thus indicating the specificity of the DFMO action through the polyamine pathway. PD98059 completely blocked the stimulatory effect of DFMO on TSP-1 production, which supports a mediatory role for activation of the MAPK pathway in the upregulation of this anti-metastatic peptide by DFMO. In summary, our results show that the increase in ERK phosphorylation induced by DFMO plays a critical role in the anti-invasive action of the drug and in its ability to upregulate TSP-1 production.
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PMID:Cellular mechanisms mediating the anti-invasive properties of the ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO) in human breast cancer cells. 1567 71

Insulin-like growth factor binding protein-5 (IGFBP-5) and thrombospondin-1 (TS-1) are both present in extracellular matrix (ECM). Both proteins have been shown to bind to one another with high affinity. The purpose of these studies was to determine how the interaction between IGFBP-5 and TS-1 modulates IGF-I actions in porcine aortic smooth muscle cells (pSMC) in culture. The addition of increasing concentrations of TS-1 to pSMC cultures enhanced the protein synthesis and cell migration responses to IGF-I; whereas the addition of IGFBP-5 alone resulted in minimal changes. In contrast, the addition of IGFBP-5 to cultures that were also exposed to IGF-I and TS-1 resulted in inhibition of protein synthesis. When the cell migration response was assessed, the response to IGF-I plus TS-1 was also significantly inhibited by the addition of IGFBP-5, whereas 1.0 microg/ml of IGFBP-5 alone had no effect on the response to IGF-I. To determine the molecular mechanism by which this inhibition occurred, a mutant form of IGFBP-5 that does not bind to IGF-I was tested. This mutant was equipotent compared to native IGFBP-5 in its ability to inhibit both protein synthesis and cell migration responses to IGF-I plus TS-1 thus excluding the possibility that IGFBP-5 was inhibiting the response to TS-1 and IGF-I by inhibiting IGF-I binding to the IGF-I receptor. To determine if an interaction between TS-1 and IGFBP-5 was the primary determinant of the inhibitory effect of IGFBP-5, an IGFBP-5 mutant that bound poorly to TS-1 was utilized. The addition of 1.0 microg/ml of this mutant did not inhibit the protein synthesis or cell migration responses to IGF-I plus TS-1. To determine the mechanism by which IGFBP-5 binding to TS-1 inhibited cellular responses to TS-1 plus IGF-I, TS-1 binding to integrin associated protein (IAP) was assessed. The addition of IGFBP-5 (1.0 microg/ml) inhibited TS-1-IAP association. In contrast, a mutant form of IGFBP-5 that bound poorly to TS-1 had a minimal effect on TS-1 binding to IAP. Further analysis showed that IGFBP-5 addition altered the ability of TS-1 to modulate the SHPS-1/IAP interaction. When the IGFBP-5 mutant that did not bind to IGF-I was incubated with TS-1 and IGF-I, it inhibited the capacity of TS-1 to enhance the IGF-I receptor phosphorylation and MAP kinase activation in response to IGF-I. In contrast, the IGFBP-5 mutant that did not bind to TS-1 had no effect on IGF-I stimulated IGF-I receptor phosphorylation or MAP kinase activation. These results indicate that IGFBP-5 inhibits the binding of TS-1 to IAP, and this results in an alteration of the ability of TS-1 to modulate the disruption of the IAP/SHPS-1 interaction which leads to attenuation of the ability of TS-1 to enhance cellular responsiveness to IGF-I.
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PMID:Insulin-like growth factor binding protein-5 (IGFBP-5) interacts with thrombospondin-1 to induce negative regulatory effects on IGF-I actions. 1570 Feb 81

Activation of mitogen-activated protein kinase (MAPK) occurs in response to various growth stimulating signals and as a result of activating mutations of the upstream regulators, KRAS and BRAF, which can be found in many types of human cancer. To investigate the roles of MAPK activation in tumors harboring KRAS or BRAF mutations, we inactivated MAPK in ovarian tumor cells using CI-1040, a compound that selectively inhibits MAPK kinase, an upstream regulator of MAPK and thus prevents MAPK activation. Profound growth inhibition and apoptosis were observed in CI-1040-treated tumor cells with mutations in either KRAS or BRAF in comparison with the ovarian cancer cells containing wild-type sequences. Long serial analysis of gene expression identified several differentially expressed genes in CI-1040-treated MPSC1 cells harboring an activating mutation in BRAF (V599L). The most striking changes were down-regulation of cyclin D1, COBRA1, and transglutaminase-2 and up-regulation of tumor necrosis factor-related apoptosis-induced ligand, thrombospondin-1, optineurin, and palladin. These patterns of gene expression were validated in other CI-1040-treated tumor cells based on quantitative PCR. Constitutive expression of cyclin D1 partially reversed the growth inhibitory effect of CI-1040 in MPSC1 cells. Our findings indicate that an activated MAPK pathway is critical in tumor growth and survival of ovarian tumors with KRAS or BRAF mutations and suggest that the CI-1040 induced phenotypes depend on the mutational status of KRAS and BRAF in ovarian tumors.
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PMID:Inactivation of the mitogen-activated protein kinase pathway as a potential target-based therapy in ovarian serous tumors with KRAS or BRAF mutations. 1575 99

Hepatic stellate cells (HSC) cultured on plastic spontaneously transdifferentiate to a myofibroblast-like cell type (MFB). This model system of hepatic fibrogenesis is characterized by phenotypic changes of the cells and increased matrix synthesis. Here, we analyzed if transdifferentiation-dependent induction of ECM components, e.g., collagen type I and thrombospondin-2 (TSP-2), and phenotypic changes are coregulated events and if both processes are mediated via TGF-beta pathway(s). Blocking the TGF-beta-dependent p38 MAPK pathway in HSC with the specific inhibitor SB203580 strongly reduces collagen I and TSP-2 mRNA expression without inhibiting upregulation of the typical MFB-marker, alpha-smooth-muscle actin (alpha-SMA). Similarly, interference with the Smad2/3/4 pathway using dexamethasone also heavily decreased expression of collagen type I and TSP-2 whereas transdifferentiation of HSC to the typical morphology of MFB with loss of fat droplets and increasing alpha-SMA was unchanged. Further, p38 MAPK mediated induction of collagen I and TSP-2 expression by TGF-beta1 was still achieved in the presence of dexamethasone, showing that dexamethasone does not block p38 while it delays Smad2 phosphorylation and antagonizes stimulation of a Smad3/Smad4 dependent TGF-beta reporter construct. Interestingly, in contrast to SB203580 and dexamethasone, overexpression of the TGF-beta antagonist Smad7 reduced ECM expression and simultaneously inhibited morphologic transdifferentiation, indicating that Smad7 fulfills additional features in HSC. In conclusion, our data show that phenotypic changes of transdifferentiating HSC and induction of matrix synthesis are independent processes, the latter being stimulated by both, Smad dependent and MAPK dependent TGF-beta signaling.
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PMID:Transdifferentiation-dependent expression of alpha-SMA in hepatic stellate cells does not involve TGF-beta pathways leading to coinduction of collagen type I and thrombospondin-2. 1590 80


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