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:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several signaling pathways have been implicated in mediating TGF-beta1-induced extracellular matrix production and fibrosis. We have shown recently that induction of biglycan (BGN) expression by TGF-beta1 depended on a functional Smad pathway (Chen, W.-B., Lenschow, W., Tiede, K., Fischer, J. W., Kalthoff, H., and Ungefroren, H. (2002) J. Biol. Chem. 277, 36118-36128). Here, we present evidence that the ability of TGF-beta 1 to induce BGN mRNA, in addition to Smads, requires p38 MAPK signaling, because 1) pharmacological inhibitors of p38 dose-dependently inhibited the TGF-beta effect without significantly affecting the transcriptional activity of a constitutively active mutant of the TGF-beta type I receptor or Smad2 phosphorylation at concentrations up to 10 microm, 2) the up-regulation of BGN mRNA was preceded by a delayed increase in the phosphorylation of p38 and its upstream activator MKK6 in TGF-beta 1-treated PANC-1 cells, 3) inhibition of the p38 pathway by stable retroviral transduction with a dominant negative mutant of either p38 or MKK6 reduced TGF-beta 1-induced BGN mRNA expression, and 4) overexpression of wild-type p38 or MKK6, but not MKK3, augmented the TGF-beta 1 effect on BGN mRNA. We further demonstrate that the (delayed) p38 activation by TGF-beta 1 is downstream of Smads and requires a functional Smad pathway, because blocking TGF-beta-induced p38 activity with SB202190 had no effect on Smad2 phosphorylation, but blocking Smad signaling by forced expression of Smad7 abolished TGF-beta1 induction of p38 activation and, as shown earlier, BGN mRNA expression; finally, re-expression of Smad4 in Smad4-null CFPAC-1 cells restored TGF-beta-induced p38 phosphorylation and, as demonstrated previously, BGN mRNA accumulation. These results clearly show that TGF-beta induction of BGN expression in pancreatic cells requires activation of MKK6-p38 MAPK signaling downstream of Smad signaling and provide a mechanistic clue to the up-regulation of BGN seen in inflammatory response-related fibrosis and desmoplasia.
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PMID:Regulation of biglycan gene expression by transforming growth factor-beta requires MKK6-p38 mitogen-activated protein Kinase signaling downstream of Smad signaling. 1253 52

Neutrophil elastase (NE) plays an important role in emphysema, a pulmonary disease associated with excessive elastolysis and ineffective repair of interstitial elastin. Besides its direct elastolytic activity, NE releases soluble epidermal growth factor receptor (EGFR) ligands and initiates EGFR/MEK/ERK signaling to downregulate tropoelastin mRNA in neonatal rat lung fibroblasts (DiCamillo SJ, Carreras I, Panchenko MV, Stone PJ, Nugent MA, Foster JA, and Panchenko MP. J Biol Chem 277: 18938-18946, 2002). We now report that NE downregulates tropoelastin mRNA in the rat fetal lung fibroblast line RFL-6. The tropoelastin mRNA downregulation is preceded by release of EGF-like and TGF-alpha-like polypeptides and requires EGFR/MEK/ERK signaling, because it is prevented by the EGFR inhibitor AG1478 and the MEK/ERK uncoupler U0126. Tropoelastin expression in RFL-6 fibroblasts is governed by autocrine TGF-beta signaling, because TGF-beta type I receptor kinase inhibitor or TGF-beta neutralizing antibody dramatically decreases tropoelastin mRNA and protein levels. Half-life of tropoelastin mRNA in RFL-6 cells is >24 h, but it is decreased to approximately 8 h by addition of TGF-beta neutralizing antibody, EGF, TGF-alpha, or NE. Tropoelastin mRNA destabilization by NE, EGF, or TGF-alpha is abolished by AG1478 or U0126. EGF-dependent tropoelastin mRNA downregulation is reversed upon ligand withdrawal, whereas chronic EGF treatment leads to persistent downregulation of tropoelastin mRNA and protein levels and decreases insoluble elastin deposition. We conclude that NE-initiated EGFR/MEK/ERK signaling cascade overrides the autocrine TGF-beta signaling on tropoelastin mRNA stability and, therefore, decreases the elastogenic response in RFL-6 fibroblasts. We hypothesize that persistent EGFR/MEK/ERK signaling could impede the TGF-beta-induced elastogenesis/elastin repair in the chronically inflamed, elastase/anti-elastase imbalanced lung in emphysema.
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PMID:Neutrophil elastase-initiated EGFR/MEK/ERK signaling counteracts stabilizing effect of autocrine TGF-beta on tropoelastin mRNA in lung fibroblasts. 1647 61

The molecular genetic profiles that characterize pancreatic ductal neoplasia have taken shape recently with the help of immunohistochemistry and the establishment of the nomenclature describing pancreatic ductal tumorigenesis. K-ras mutations frequently occur early, changes in the expression and genetic integrity of the p16 gene appear in intermediate lesions, and the inactivation of the p53, DPC4, and BRCA2 genes occur late in the neoplastic progression. Tumor-suppressor genes inactivated in pancreatic cancer such as ALK5, TGFBR2, MKK4, and STK11/LKB1 have been identified, although their roles in tumor progression are not yet well defined. Additional discoveries in this tumor system may be on the horizon, will further refine the molecular genetic profiles for the disease, and should suggest some clinical uses for this fund of knowledge.
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PMID:Molecular genetics of ductal pancreatic neoplasia. 1703 Nov 13

Transforming growth factor beta 1 (TGF-beta1) is a potent tumor suppressor but, paradoxically, TGF-beta1 enhances tumor growth and metastasis in the late stages of cancer progression. This study investigated the role of TGF-beta type I receptor, ALK5, and three mitogen-activated protein kinases (MAPKs) in metastasis by breast cancer cell line MDA-MB-231. We show that autocrine TGF-beta signaling in MDA-MB-231 cells is required for tumor cell invasion and tumor angiogenesis. Expression of kinase-inactive ALK5 reduces tumor invasion and formation of new blood vessels within the tumor orthotopic xenografts in severe combined immunodeficiency (SCID) mice. In contrast, constitutively active ALK5-T204D enhances tumor invasion and angiogenesis by stimulating expression of matrix metalloproteinase MMP-9/gelatinase-B. Ablation of MMP-9 in ALK5-T204D cells by RNA interference (RNAi) reduces tumor invasion and tumor growth. Importantly, RNAi-MMP-9 reduces tumor neovasculature and increases tumor cell death. Induction of MMP-9 by TGF-beta-ALK5 signaling requires MEK-ERK but not JNK, p38 MAPK or Smad4. Dominant-negative MEK blocks and constitutively active MEK1 enhances MMP-9 expression. However, all three MAPK cascades (ERK, JNK and p38 MAPK) are required for TGF-beta-mediated cell migration. Collectively, our results show that TGF-beta-ALK5-MAPK signaling in tumor cells promotes tumor angiogenesis and MMP-9 is an important component of this program.
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PMID:ALK5 promotes tumor angiogenesis by upregulating matrix metalloproteinase-9 in tumor cells. 1707 48

Mesenchymal stem cells (MSCs) can differentiate into diverse cell types including adipogenic, osteogenic, chondrogenic and myogenic lineages. In the present study, we demonstrated for the first time that sphingosylphosphorylcholine (SPC) induces differentiation of human adipose-tissue-derived mesenchymal stem cells (hATSCs) to smooth-muscle-like cell types. SPC increased the expression levels of several smooth-muscle-specific genes, such as those for alpha-smooth-muscle actin (alpha-SMA), h1-calponin and SM22alpha, as effectively as transforming growth factor beta (TGF-beta1) and TGF-beta3. SPC elicited delayed phosphorylation of Smad2 after 24 hours exposure, in contrast to rapid phosphorylation of Smad2 induced by TGF-beta treatment for 10 minutes. Pretreatment of the cells with pertussis toxin or U0126, an MEK inhibitor, markedly attenuated the SPC-induced expression of beta-SMA and delayed phosphorylation of Smad2, suggesting that the Gi/o-ERK pathway is involved in the increased expression of alpha-SMA through induction of delayed Smad2 activation. In addition, SPC increased secretion of TGF-beta1 through an ERK-dependent pathway, and the SPC-induced expression of alpha-SMA and delayed phosphorylation of Smad2 were blocked by SB-431542, a TGF-beta type I receptor kinase inhibitor, or anti-TGF-beta1 neutralizing antibody. Silencing of Smad2 expression with small interfering RNA (siRNA) abrogated the SPC-induced expression of alpha-SMA. These results suggest that SPC-stimulated secretion of TGF-beta1 plays a crucial role in SPC-induced smooth muscle cell (SMC) differentiation through a Smad2-dependent pathway. Both SPC and TGF-beta increased the expression levels of serum-response factor (SRF) and myocardin, transcription factors involved in smooth muscle differentiation. siRNA-mediated depletion of SRF or myocardin abolished the alpha-SMA expression induced by SPC or TGF-beta. These results suggest that SPC induces differentiation of hATSCs to smooth-muscle-like cell types through G(i/o)-ERK-dependent autocrine secretion of TGF-beta, which activates a Smad2-SRF/myocardin-dependent pathway.
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PMID:Sphingosylphosphorylcholine induces differentiation of human mesenchymal stem cells into smooth-muscle-like cells through a TGF-beta-dependent mechanism. 1710 65

Sphingosylphosphorylcholine (SPC) has been reported to stimulate the expression of fibronectin (FN), which plays a key role in cell recruitment and adhesion during wound healing. In a previous study, we reported that SPC induces differentiation of human adipose tissue-derived mesenchymal stem cells (hATSCs) to smooth muscle-like cell types through ERK-dependent autocrine secretion of TGF-beta1 and delayed activation of the TGF-beta1-Smad pathway. In the present study, we demonstrated that SPC dose- and time-dependently increased the expression of FN in hATSCs. Pretreatment of the cells with U0126, an MEK inhibitor, markedly attenuated the SPC-induced expression of FN and delayed phosphorylation of Smad2, suggesting that ERK is involved in the SPC induction of FN expression through activation of Smad2. In addition, the SPC-induced expression of FN and delayed activation of Smad2 were abrogated by SB-431542, a TGF-beta type I receptor kinase inhibitor, or anti-TGF-beta1 neutralizing antibody. Furthermore, the SPC-induced expression of FN was abrogated by adenoviral expression of Smad7, an inhibitory Smad, or short interference RNA (siRNA)-mediated depletion of endogenous Smad2 expression, suggesting that SPC induces the expression of FN through ERK-dependent activation of the TGF-beta1-Smad2 crosstalk pathway. Adhesion of U937 monocytic cells to hATSCs was enhanced by pretreatment of hATSCs with SPC or TGF-beta1 for 4 days, and the peptide GRGDSP (an antagonist of fibronectin receptors) blocked the adhesion of U937 cells to the hATSCs. These results led us to suggest that SPC-induced FN expression plays a pivotal role in the wound healing by stimulating adhesion and recruitment of leukocytes.
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PMID:Sphingosylphosphorylcholine stimulates expression of fibronectin through TGF-beta1-Smad-dependent mechanism in human mesenchymal stem cells. 1748 39

Angiotensin II (Ang II) is involved in the development of cardiovascular disease and vascular remodeling. In this study, we demonstrate that treatment of human adipose tissue-derived mesenchymal stem cells (hADSCs) with Ang II increased the expression of smooth muscle-specific genes, including alpha-smooth muscle actin (alpha-SMA), calponin, h-caldesmon, and smooth muscle myosin heavy chain (SM-MHC), and also elicited the secretion of transforming growth factor-beta1 (TGF-beta1) and delayed phosphorylation of Smad2. The Ang II-induced expression of alpha-SMA and delayed phosphorylation of Smad2 were blocked by pretreatment of the cells with a TGF-beta type I receptor kinase inhibitor, SB-431542, small interference RNA-mediated depletion of endogenous Smad2, and adenoviral expression of Smad7. Furthermore, the Ang II-induced TGF-beta1 secretion, alpha-SMA expression, and delayed phosphorylation of Smad2 in hADSCs were abrogated by the MEK inhibitor U0126, suggesting a pivotal role of MEK/ERK pathway in the Ang II-induced activation of TGF-beta1-Smad2 signaling pathway. The smooth muscle-like cells which were differentiated from hADSCs by Ang II treatment exhibited contraction in response to 60mM KCl. These results suggest that Ang II induces differentiation of hADSCs to contractile smooth muscle-like cells through ERK-dependent activation of the autocrine TGF-beta1-Smad2 crosstalk pathway.
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PMID:Angiotensin II-induced differentiation of adipose tissue-derived mesenchymal stem cells to smooth muscle-like cells. 1857 60

Phenotypic expression of alpha-smooth muscle actin (alpha-SMA), a smooth muscle marker, has been implicated in vascular diseases, fibrosis, wound healing, and tissue remodeling. Bradykinin (BK), a vasoactive peptide produced during tissue injury, plays a key role in inflammatory and vascular responses associated with tissue injury. In the present study, we demonstrated for the first time that BK treatment increased alpha-SMA expression in human adipose tissue-derived mesenchymal stem cells (hADSCs). This BK-induced alpha-SMA expression was abrogated by small interfering RNA (siRNA)-mediated depletion of endogenous myocardin, a transcription factor involved in smooth muscle differentiation. BK also increased the intracellular calcium concentration ([Ca(2+)](i)), a response that was completely blocked by treatment with a BK B2 receptor-specific antagonist (HOE 140), suggesting that the BK B2 receptor was participating in BK-induced cellular responses. In addition, BK induced the secretion of transforming growth factor-beta1 (TGF-beta1) and autocrine activation of Smad2. Pretreatment with a TGF-beta type I receptor kinase inhibitor (SB-431542), small interfering RNA-mediated depletion of endogenous Smad2, or adenoviral expression of Smad7 (an inhibitory Smad isoform) all blocked BK-induced alpha-SMA expression and Smad2 phosphorylation. Furthermore, a MEK-specific inhibitor (U0126) abrogated BK-induced TGF-beta1 secretion, Smad2 phosphorylation, and alpha-SMA expression. These results suggest that BK induced expression of alpha-SMA in hADSCs through ERK-dependent activation of the autocrine TGF-beta1-Smad2 crosstalk pathway.
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PMID:Bradykinin-induced expression of alpha-smooth muscle actin in human mesenchymal stem cells. 1865 27

Transforming growth factor-beta (TGF-beta) plays a key role in scleroderma pathogenesis. The transcription factor early growth response-1 (Egr-1) mediates the stimulation of collagen transcription elicited by TGF-beta and is necessary for the development of pulmonary fibrosis in mice. Here, we report that TGF-beta causes a time- and dose-dependent increase in Egr-1 protein and mRNA levels and enhanced transcription of the Egr-1 gene via serum response elements in normal fibroblasts. The ability of TGF-beta to stimulate Egr-1 was preserved in Smad3-null mice and in explanted Smad3-null fibroblasts. The response was blocked by a specific mitogen-activated protein kinase kinase 1 (MEK1) inhibitor but not by an ALK5 kinase inhibitor. Furthermore, MEK1 was phosphorylated by TGF-beta, which was sufficient to drive Egr-1 transactivation. Stimulation by TGF-beta enhanced the transcriptional activity of Elk-1 via the MEK-extracellular signal-regulated kinase 1/2 pathway. Bleomycin-induced scleroderma in the mouse was accompanied by increased Egr-1 accumulation in lesional fibroblasts. Furthermore, biopsies of lesional skin and lung from patients with scleroderma showed increased Egr-1 levels, which were highest in early diffuse disease. Moreover, both Egr-1 mRNA and protein were elevated in explanted scleroderma skin fibroblasts in vitro. Together, these findings define a Smad-independent TGF-beta signal transduction mechanism that underlies the stimulation of Egr-1, demonstrate for the first time sustained Egr-1 up-regulation in fibrotic lesions and suggests that Egr-1 has a role in the induction and progression of fibrosis.
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PMID:Smad-independent transforming growth factor-beta regulation of early growth response-1 and sustained expression in fibrosis: implications for scleroderma. 1877 33

Among the broad variety of compounds generated via oxidative reactions in low-density lipoproteins (LDL) and subsequently found in the atherosclerotic plaque are aldehydes that are still esterified to the parent lipid, termed core aldehydes. The most represented cholesterol core aldehyde in LDL is 9-oxononanoyl cholesterol (9-ONC), an oxidation product of cholesteryl linoleate. 9-ONC, at a concentration detectable in biological material, markedly up-regulates mRNA expression and protein level of both the pro-fibrogenic and pro-apoptotic cytokine transforming growth factor beta1 (TGF-beta1) and the TGF-beta receptor type I (TbetaRI) in human U937 promonocytic cells. We also observed increased membrane presentation of TGF-beta receptor type II (TbetaRII). Experiments employing the TbetaRI inhibitor SB431542, or the TGFbeta antagonist DANFc chimera, have shown that the effect on TbetaRI is directly induced by 9-ONC, while TbetaRII up-regulation seems stimulated by its specific ligand, i.e. TGFbeta1, over-secreted meanwhile by treated cells. Increased levels of the cytokine and of its specific receptors in 9-ONC-treated cells clearly occurs through stimulation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), as demonstrated by ERK1/2 knockdown experiments using mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MEK1 and MEK2) siRNAs, or PD98059, a selective MEK1/2 inhibitor. 9-ONC might thus sustain further vascular remodeling due to atherosclerosis, not simply by stimulating synthesis of the pro-fibrogenic cytokine TGF-beta1 in vascular cells, but also and chiefly by enhancing the TGF-beta1 autocrine loop, because of the marked up-regulation of the cytokine's specific receptors TbetaRI and TbetaRII.
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PMID:The core-aldehyde 9-oxononanoyl cholesterol increases the level of transforming growth factor beta1-specific receptors on promonocytic U937 cell membranes. 1930 74


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