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)

Abnormal mesangial extracellular matrix remodeling by mesangial cells (MCs) is the hallmark of progressive glomerulonephritis (GN). We recently showed, using a type I collagen gel contraction assay, that alpha 1 beta 1 integrin-dependent MC adhesion and migration are necessary cell behaviors for collagen matrix remodeling. To further determine the mechanism of alpha 1 beta 1 integrin-mediated collagen remodeling, we studied the signaling pathways of MCs that participate in the regulation of collagen gel contraction. Immunoprecipitation and phosphotyrosine detection revealed that gel contraction is associated with the enhanced activity and phosphorylation of ERK1/2 by MCs. The tyrosine kinase inhibitors herbimycin and genistein inhibited collagen gel contraction dose dependently. Furthermore, targeting ERK1/2 activity with a MEK inhibitor, PD98059, and antisense ERK1/2 hindered gel contraction in a dose-dependent manner. Similar inhibitory effects on gel contraction and ERK1/2 phosphorylation were observed when MC-mediated gel contraction was performed in the presence of function-blocking anti-alpha1 or anti-beta1 integrin antibodies. However, cell adhesion and migration assays indicated that PD98059 and antisense ERK1/2 blocked alpha 1 beta 1 integrin-dependent MC migration, but did not interfere with collagen adhesion, although there was a marked decrease in ERK1/2 phosphorylation and ERK1/2 protein expression in cell adhesion on type I collagen. None of the above could affect membrane expression of alpha 1 beta 1 integrin. These results suggested that ERK1/2 activation is critical for the alpha 1 beta 1 integrin-dependent MC migration necessary for collagen matrix reorganization. We therefore conclude that ERK1/2 may serve as a possible target for pharmacological inhibition of pathological collagen matrix formation in GN.
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PMID:Requirement for tyrosine kinase-ERK1/2 signaling in alpha 1 beta 1 integrin-mediated collagen matrix remodeling by rat mesangial cells. 1147 53

Parathyroid hormone (PTH)-related peptide (PTHrP) can modulate the proliferation and differentiation of a number of cell types including osteoblasts. PTHrP can activate a G protein-coupled PTH/PTHrP receptor, which can interface with several second-messenger systems. In the current study, we have examined the signaling pathways involved in stimulated type I collagen and alkaline phosphatase expression in the human osteoblast-derived osteosarcoma cells, MG-63. By use of Northern blotting and histochemical analysis, maximum induction of these two markers of osteoblast differentiation occurred after 8 h of treatment with 100 nM PTHrP-(1-34). Chemical inhibitors of adenylate cyclase (H-89) or of protein kinase C (chelerythrine chloride) each diminished PTHrP-mediated type I collagen and alkaline phosphatase stimulation in a dose-dependent manner. These effects of PTHrP could also be blocked by inhibiting the Ras-mitogen-activated protein kinase (MAPK) pathway with a Ras farnesylation inhibitor, B1086, or with a MAPK inhibitor, PD-98059. Transient transfection of MG-63 cells with a mutant form of Galpha, which can sequester betagamma-subunits, showed significant downregulation of PTHrP-stimulated type I collagen expression, as did inhibition of phosphatidylinositol 3-kinase (PI 3-kinase) by wortmannin. Consequently, the betagamma-PI 3-kinase pathway may be involved in PTHrP stimulation of Ras. Collectively, these results demonstrate that, acting via its G protein-coupled receptor, PTHrP can induce indexes of osteoblast differentiation by utilizing multiple, perhaps parallel, signaling pathways.
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PMID:Induction of osteoblast differentiation indexes by PTHrP in MG-63 cells involves multiple signaling pathways. 1150 Mar 4

Activation of hepatic stellate cells (HSC) has been identified as a critical step in hepatic fibrogenesis and is regulated by several factors including cytokines and oxidative stress. However, the molecular mechanism for HSC inactivation is not well understood. We investigated an N-acetyl-L-cysteine (NAC)-mediated signaling pathway involved in HSC inactivation. NAC, which acting through its reducing activity, induced cell arrest at G1 via the mitogen-activated protein kinase (MAPK) kinase (MEK)/MAPK pathway in a Ras-independent manner. The sustained activation of this extracellular signal-regulated kinase induced the expression of p21(Cip1/WAF1), a cell cycle-dependent kinase inhibitor, and mediated cell growth arrest through the Sp1 transcription activator-dependent mechanism. These effects of NAC were all reversed by treatment of HSC with MEK inhibitor PD98059 followed by culturing HSC on type I collagen-coated flasks. The collagen-mediated suppression of NAC-induced arrest may be due to an overriding of the cell cycle arrest through an acceleration of integrin-induced cell growth. NAC action is actually dependent on modulating the redox states of cysteine residues of target proteins such as Raf-1, MEK, and ERK. In conclusion, an understanding of the NAC signaling pathway in HSC should provide the theoretical basis for clinical approaches using antioxidant therapies in liver fibrosis.
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PMID:N-acetylcysteine induces cell cycle arrest in hepatic stellate cells through its reducing activity. 1150 53

Mouse capillary endothelial cells (1G11 cell line) embedded in type I collagen gels undergo in vitro angiogenesis. Cells rapidly reorganize and form capillary-like structures when stimulated with serum. Transforming growth factor beta1 (TGF-beta1) alone can substitute for serum and induce cell survival and tubular network formation. This TGF-beta1-mediated angiogenic activity depends on phosphatidylinositol 3-kinase (PI3K) and p42/p44 mitogen-activated protein kinase (MAPK) signaling. We showed that specific inhibitors of either pathway (wortmannin, LY-294002, and PD-98059) all suppressed TGF-beta1-induced angiogenesis mainly by compromising cell survival. We established that TGF-beta1 stimulated the expression of TGF-alpha mRNA and protein, the tyrosine phosphorylation of a 170-kDa membrane protein representing the epidermal growth factor (EGF) receptor, and the delayed activation of PI3K/Akt and p42/p44 MAPK. Moreover, we showed that all these TGF-beta1-mediated signaling events, including tubular network formation, were suppressed by incubating TGF-beta1-stimulated endothelial cells with a soluble form of an EGF receptor (ErbB-1) or tyrphostin AG1478, a specific blocker of EGF receptor tyrosine kinase. Finally, addition of TGF-alpha alone poorly stimulated angiogenesis; however, by reducing cell death, it strongly potentiated the action of TGF-beta1. We therefore propose that TGF-beta1 promotes angiogenesis at least in part via the autocrine secretion of TGF-alpha, a cell survival growth factor, activating PI3K/Akt and p42/p44 MAPK.
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PMID:Transforming growth factor beta1 (TGF-beta1) promotes endothelial cell survival during in vitro angiogenesis via an autocrine mechanism implicating TGF-alpha signaling. 1158 5

After liver injury, hepatic stellate cells (HSCs) undergo a process of activation with expression of smooth muscle alpha-actin (alpha-SMA), an increased proliferation rate, and a dramatic increase in synthesis of type I collagen. The intracellular signaling mechanisms of activation and perpetuation of the activated phenotype in HSCs are largely unknown. In this study the role of the stress-activated protein kinases, c-Jun N-terminal kinase (JNK) and p38, were evaluated in primary cultures of rat HSCs. The effect of JNK was assessed by using an adenovirus expressing a dominant negative form of transforming growth factor beta (TGF-beta)-activated kinase 1 (TAK1) (Ad5dnTAK1) and a new selective pharmacologic inhibitor SP600125. The effect of p38 was assessed with the selective pharmacologic inhibitor SB203580. These kinases were inhibited starting either in quiescent HSCs (culture day 1) or in activated HSCs (culture day 5). Although blocking TAK1/JNK and p38 decreased the expression of alpha-SMA protein in early stages of HSC activation, no effect was observed when TAK1/JNK or p38 were inhibited in activated HSCs. JNK inhibition increased and p38 inhibition decreased collagen alpha1(I) mRNA level as measured by RNase protection assays, with maximal effects observed in early stages of HSC activation. Furthermore, TAK1/JNK inhibition decreased HSC proliferation, whereas p38 inhibition led to an increased proliferation rate of HSCs, independently of its activation status. These results show novel roles for the TAK1/JNK pathway and p38 during HSC activation in culture. Despite similar activators of TAK1/JNK and p38, their functions in HSCs are distinct and opposed.
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PMID:TAK1/JNK and p38 have opposite effects on rat hepatic stellate cells. 1167 66

Signals from bone morphogenetic protein receptors (BMPRs) and cell adhesion to type I collagen are both important for osteoblastic differentiation and functions. BMP signals are mediated mostly by Smad and collagen signals are transduced by integrins to activate focal adhesion kinase (FAK) and its downstream molecules. This study was undertaken to clarify how extracellular matrix collagen signals converge with BMP actions. We show that integrin activation by collagen was involved in BMP signals because disruption of either collagen synthesis or collagen-alpha2beta1-integrin binding inhibited the stimulatory effect of BMP-2 on osteoblastic MC3T3-E1 cells. Downstream signals of collagen-integrin might be FAK-Ras-extracellular signal-regulated kinase (ERK) in osteoblastic cells. We further show that Ras-ERK signals enhanced the transcriptional activity of Smad1 in response to BMP in these cells transiently transfected with expression plasmids for a constitutively active mutant RasV12, a dominant negative mutant RasN17, and an ERK phosphatase CL100. Ras-ERK signals did not augment the transcriptional activity of Smad3 in response to transforming growth factor beta (TGF-beta) receptor activation but that of Smad1 in response to BMPR activation as examined in COS-1 cells. These observations suggest that the Ras-ERK pathway downstream of integrin-FAK is involved in Smad1 signals activated by BMP and provide a possible mechanism for cooperation between intracellular signals activated by integrin and BMPRs in osteoblastic cells.
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PMID:Stimulation of Smad1 transcriptional activity by Ras-extracellular signal-regulated kinase pathway: a possible mechanism for collagen-dependent osteoblastic differentiation. 1181 54

Transforming growth factor beta (TGF-beta) activates Ras/MAPK signaling in many cell types. Because TGF-beta and BMP-2 exert similar effects, we examined if this signaling is stimulated by both factors and analyzed the relationship between this signaling and the Smads in osteoblasts. BMP-2 and TGF-beta stimulated Ras, MAPK, and AP-1 activities. The DNA binding activities of c-Fos, FosB/Delta FosB, Fra-1, Fra-2, and JunB were up-regulated whereas JunD activity was decreased. c-Fos, FosB/Delta FosB, and JunB were associated with Smad4. The stimulation of AP-1 by BMP-2 and TGF-beta was dependent on Smad signaling, and anti-Smad4 antibody interfered with AP-1 activity. Thus, BMP-2 and TGF-beta activate both Ras/MAPK/AP-1 and Smad signaling in osteoblasts with Smads modulating AP-1 activity. To determine the roles of MAPK in BMP-2 and TGF-beta function, we analyzed the effect of ERK and p38 inhibitors on the regulation of bone matrix protein expression and JunB and JunD levels by these two factors. ERK and p38 mediated TGF-beta suppression of osteocalcin and JunD as well as stimulation of JunB. p38 was essential in BMP-2 up-regulation of type I collagen, fibronectin, osteopontin, osteocalcin, and alkaline phosphatase activity whereas ERK mediated BMP-2 stimulation of fibronectin and osteopontin. Thus, ERK and p38 differentially mediate TGF-beta and BMP-2 function in osteoblasts.
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PMID:Signal transductions induced by bone morphogenetic protein-2 and transforming growth factor-beta in normal human osteoblastic cells. 1185 97

Recent studies suggest that prostaglandin E may have the ability to suppress cytokine responsiveness. We examined the effects of prostaglandin E administration on several parameters of the acute and chronic hepatic injury induced by bile duct ligation. Enisoprost, a prostaglandin E(1) analog was found to suppress early hepatic and Ito cell type I collagen gene expression without diminishing the induction of the fibrogenic cytokine, transforming growth factor beta. Overall hepatic inflammation and cell proliferation were not altered, suggesting that prostaglandin E acts distal to the initial injurious event(s). During the later phases, drug administration reduced total collagen accumulation as well as type I collagen periductular infiltration associated with early nodule formation. Ito cell mitogenesis occurs during liver injury and fibrogenesis in vivo coincident with the de novo expression of Ito cell platelet-derived growth factor beta (PDGFbeta) receptor messenger RNA. PDGF-induced mitogenesis was studied in cultured rat hepatic Ito cells which resemble the myofibroblast associated with liver injury. Pretreatment with prostaglandin E markedly suppressed the PDGF response in a dose-dependent fashion. The PDGF-induced cascade was studied plus minus PGE to determine the level of regulation which induced the observed suppression. PGE caused no apparent diminution in the abundance of the surface PDGFbeta receptor nor its subsequent activation and tyrosine phosphorylation following PDGF stimulation. The cytoplasmic "secondary messengers" mitogen-activated protein kinase pp42--44 and raf kinase appeared to be comparably induced and therefore unaffected by PGE. Raf perinuclear translocation was also intact, and comparable degrees of nuclear egr, fos, and jun expression occurred. Because other studies have suggested that many of these features of the PDGF cascade may be causally and sequentially linked, the data collectively suggest that the dominant PGE mitogenic suppressive effect resides at a Raf-MAP parallel pathway or at a nuclear level distal to the induction of these early growth response genes.
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PMID:Prostaglandin E Suppresses Hepatic Fibrosis: Section I. The In Vivo Approach; Section II. The In Vitro Approach. 1185 47

Although protein kinase C (PKC) activation is required for endothelial cell (EC) growth, migration, adhesion, and vessel formation, the role of individual PKC isoenzymes in these events is not defined. Because PKCalpha has been previously linked with enhanced EC migration and response to angiogenic growth factors, we characterized a specific phosphorothioate-modified 21-mer antisense PKCalpha (AS-PKCalpha). AS-PKCalpha (500 nmol/L) prevented the expression of PKCalpha protein by 90% in human ECs and did not reduce the expression of any other PKC isoenzyme. AS-PKCalpha reduced human EC migration by 64% compared with its control oligonucleotide in a "scratch" wounding assay, and AS-PKCalpha reduced human EC adhesion to the extracellular matrix protein vitronectin by 18%. Phosphorylation of mitogen-activated protein kinase (extracellular signal-regulated kinase 1/2) induced by vascular endothelial growth factor was inhibited by 30% in human ECs transfected with AS-PKCalpha. Compared with control, AS-PKCalpha also reduced the number of EC tubes formed in a 3D type I collagen gel assay by 37.5%. Finally, using an osmotic minipump, we infused AS-PKCalpha into mice in which myocardial infarction was induced by coronary ligation and found that the oligonucleotide was primarily taken up by intramyocardial blood vessels. Compared with the results with control oligonucleotide, AS-PKCalpha oligonucleotide inhibited the number of anti-PKCalpha-stained blood vessels by 48% and reduced the total vessel number by 72% as well. In conclusion, the expression of PKCalpha is required for full EC migration, adhesion to vitronectin, vascular endothelial growth factor-induced extracellular signal-regulated kinase activation, and tube formation and is likely to be of importance in myocardial angiogenesis in vivo after ischemia.
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PMID:Inhibition of protein kinase Calpha prevents endothelial cell migration and vascular tube formation in vitro and myocardial neovascularization in vivo. 1190 26

The constitutive shedding of BP180 (collagen XVII) from human keratinocytes in culture was totally prevented by batimastat (5 microM), a wide spectrum matrix metalloprotease (MMP) inhibitor. However, keratinocytes did not express active MMP and generation of active Gelatinase A (MMP-2) and Gelatinase B (MMP-9) at the cell plasma membrane by increasing the ceramide content of keratinocytes did not influence BP180 processing to a 120 kDa species. A disintegrin and metalloprotease (ADAM) is probably involved in such a shedding event since release of 120 kDa polypeptide was inhibited by Decanoyl-Arg-Val-Lys-Arg CH2Cl (30 microM), a specific furin convertase inhibitor; culturing cells on to several matrix substrata i.e. type I collagen, type IV collagen, laminin-1 or laminin-5 had no effect on BP180 processing. Overall our data indicated that the metalloprotease-mediated shedding of BP180 from keratinocytes in culture is insensitive either to agents which activate MAP kinase pathway (ceramide) or to cell-matrix interactions.
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PMID:The metalloprotease-directed shedding of BP 180 (collagen XVII) from human keratinocytes in culture is unaffected by ceramide and cell-matrix interaction. 1197 64


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