Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the effects of hydrogen peroxide (H(2)O(2)), a potent naturally occurring oxidant on cell signaling and viability in the pluripotent HT29 intestinal cell line. There was a dose-dependent reduction in cell viability upon exposure to H(2)O(2) as measured by the XTT assay. Features of apoptosis were indicated by the findings of PARP and caspase 3 cleavage, as well as changes in cell morphology using phase contrast and nuclear fragmentation using fluorescence microscopy. There was a dose-dependent increase in the activation of p45-JNK, p42/p44-ERK, and p38-HOG. Surprisingly, oxidant-induced cell injury could be attenuated by preincubation with PD98059 to 50% of untreated control cells (P = 0.002). This and UO126, another MEK inhibitor were ably to reproducibly inhibit p45-JNK activation induced by hydrogen peroxide. Transfection with kinase-inactive constructs of JNK and ERK revealed that the improvement in cell viability was due to inhibition of JNK and not ERK. Transient transfections with AP-1 and NF-kappaB luciferase reporter constructs did not reveal any transcriptional activation due to hydrogen peroxide exposure however, in both cases the basal levels of transcriptional activity were suppressed in the presence of PD98059. It is concluded that JNK mediates H(2)O(2)-induced cellular injury in the HT29 cell line, and additionally, we report for the first time that JNK activation can be inhibited by both PD98059 and UO126 at conventional doses used to inhibit MEK.
Mol Cell Biol Res Commun 2000 Sep
PMID:PD98059 attenuates hydrogen peroxide-induced cell death through inhibition of Jun N-Terminal Kinase in HT29 cells. 1128 30

Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3' kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.
Mol Pharmacol 2001 May
PMID:PI3K inhibitors reverse the suppressive actions of insulin on CYP2E1 expression by activating stress-response pathways in primary rat hepatocytes. 1130 97

Previously, we have reported that insulin induces the expression of the dual-specificity tyrosine phosphatase Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) and that this may represent a negative feedback mechanism to regulate insulin-stimulated MAP kinase activity. In this work, the mechanism of regulation of MKP-1 expression by insulin was examined, particularly the role of the MAP kinase superfamily. Inhibition of the ERK pathway attenuated insulin-stimulated MKP-1 mRNA expression. Expression of dominant negative molecules of the JNK pathway also abolished insulin-stimulated MKP-1 expression. However, inhibition of p38MAPK activity by SB202190 had no effect on insulin-stimulated MKP-1 induction. Simultaneous inhibition of the ERK and JNK pathways abolished the ability of insulin to stimulate MKP-1 expression, however, this combined inhibition was neither additive nor synergistic, suggesting these pathways converge to act on a common final effector. In conclusion, induction of MKP-1 mRNA expression in Hirc B cells by insulin requires activation of both the ERK and JNK pathways, but not p38MAPK.
Mol Cell Biochem 2001 Feb
PMID:Insulin regulates MAP kinase phosphatase-1 induction in Hirc B cells via activation of both extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK). 1133 Aug 28

Mitogen-activated protein kinases (MAPKs) may play crucial roles in the kainic acid (KA)-evoked excitotoxic effect and the regulation of transcription factors (e.g. c-Fos and c-Jun) in hippocampus, but their exact role in the regulation of KA-induced opioid peptides expression has not been well characterized in vivo. Therefore, we examined possible involvement of the phosphorylated form of JNK, as well as CREB, in the regulation of KA-induced proenkephalin and immediate early genes (IEGs) expression in the rat hippocampus. KA increased proenkephalin mRNA expression in rat hippocampus, which was decreased by pre-administration with cycloheximide (CHX, a protein synthesis inhibitor). KA alone increased c-fos as well as c-jun mRNA levels. CHX further enhanced KA-induced c-fos and c-jun mRNA levels. Additionally, KA increased the phosphorylation of JNK, especially JNK1, which was attenuated by CHX. CHX decreased KA-induced c-Fos protein expression. Interestingly, CHX itself increased the phosphorylation of CREB, which was abolished by KA administration. Our results suggest that the phosphorylation of JNK is involved in the up-regulation of the proenkephalin gene expression via c-Fos and c-Jun that is induced by KA in rat hippocampus. However, the phosphorylation of CREB is not associated with the up-regulation of the proenkephalin mRNA level induced by KA in the rat hippocampus.
Mol Cells 2001 Apr 30
PMID:Possible roles of JNK pathway in the regulation of hippocampal proenkephalin and immediate early gene expression induced by kainic acid. 1135 93

c-Jun activation by mitogen-activated protein kinases has been implicated in various cellular signal responses. We investigated how JNK and c-Jun contribute to neuronal differentiation, cell survival, and apoptosis. In differentiated PC12 cells, JNK signaling can induce apoptosis and c-Jun mediates this response. In contrast, we show that in PC12 cells that are not yet differentiated, the AP-1 family member ATF-2 and not c-Jun acts as an executor of apoptosis. In this context c-Jun expression protects against apoptosis and triggers neurite formation. Thus, c-Jun has opposite functions before and after neuronal differentiation. These findings suggest a model in which the balance between ATF-2 and Jun activity in PC12 cells governs the choice between differentiation towards a neuronal fate and an apoptotic program. Further analysis of c-Jun mutants showed that the differentiation response requires functional dimerization and DNA-binding domains and that it is stimulated by phosphorylation in the transactivation domain. In contrast, c-Jun mutants incompetent for DNA binding or dimerization and also mutants lacking JNK binding and phosphorylation sites that cannot elicit neuronal differentiation efficiently protect PC12 cells from apoptosis. Hence, the protective role of c-Jun appears to be mediated by an unconventional mechanism that is separable from its function as a classical AP-1 transcription factor.
Mol Cell Biol 2001 Jul
PMID:Complex functions of AP-1 transcription factors in differentiation and survival of PC12 cells. 1139 Jun 64

We previously described the identification of quail MafA, a novel transcription factor of the Maf bZIP (basic region leucine zipper) family, expressed in the differentiating neuroretina (NR). In the present study, we provide the first evidence that MafA is phosphorylated and that its biological properties strongly rely upon phosphorylation of serines 14 and 65, two residues located in the transcriptional activating domain within a consensus for phosphorylation by mitogen-activated protein kinases and which are conserved among Maf proteins. These residues are phosphorylated by ERK2 but not by p38, JNK, and ERK5 in vitro. However, the contribution of the MEK/ERK pathway to MafA phosphorylation in vivo appears to be moderate, implicating another kinase. The integrity of serine 14 and serine 65 residues is required for transcriptional activity, since their mutation into alanine severely impairs MafA capacity to activate transcription. Furthermore, we show that the MafA S14A/S65A mutant displays reduced capacity to induce expression of QR1, an NR-specific target of Maf proteins. Likewise, the integrity of serines 14 and 65 is essential for the MafA ability to stimulate expression of crystallin genes in NR cells and to induce NR-to-lens transdifferentiation. Thus, the MafA capacity to induce differentiation programs is dependent on its phosphorylation.
Mol Cell Biol 2001 Jul
PMID:Phosphorylation of MafA is essential for its transcriptional and biological properties. 1141 24

CDC25A phosphatase promotes cell cycle progression by activating G(1) cyclin-dependent kinases and has been postulated to be an oncogene because of its ability to cooperate with RAS to transform rodent fibroblasts. In this study, we have identified apoptosis signal-regulating kinase 1 (ASK1) as a CDC25A-interacting protein by yeast two-hybrid screening. ASK1 activates the p38 mitogen-activated protein kinase (MAPK) and c-Jun NH(2)-terminal protein kinase-stress-activated protein kinase (JNK/SAPK) pathways upon various cellular stresses. Coimmunoprecipitation studies demonstrated that CDC25A physically associates with ASK1 in mammalian cells, and immunocytochemistry with confocal laser-scanning microscopy showed that these two proteins colocalize in the cytoplasm. The carboxyl terminus of CDC25A binds to a domain of ASK1 adjacent to its kinase domain and inhibits the kinase activity of ASK1, independent of and without effect on the phosphatase activity of CDC25A. This inhibitory action of CDC25A on ASK1 activity involves diminished homo-oligomerization of ASK1. Increased cellular expression of wild-type or phosphatase-inactive CDC25A from inducible transgenes suppresses oxidant-dependent activation of ASK1, p38, and JNK1 and reduces specific sensitivity to cell death triggered by oxidative stress, but not other apoptotic stimuli. Thus, increased expression of CDC25A, frequently observed in human cancers, could contribute to reduced cellular responsiveness to oxidative stress under mitogenic or oncogenic conditions, while it promotes cell cycle progression. These observations propose a mechanism of oncogenic transformation by the dual function of CDC25A on cell cycle progression and stress responses.
Mol Cell Biol 2001 Jul
PMID:The cell cycle-regulatory CDC25A phosphatase inhibits apoptosis signal-regulating kinase 1. 1141 55

Tolerance in vivo and its in vitro counterpart, anergy, are defined as the state in which helper T lymphocytes are alive but incapable of producing IL-2 and expanding in response to optimal antigenic stimulation. Anergy is induced when the T cell receptor (TCR) is engaged by antigen in the absence of costimulation or IL-2. This leads to unique intracellular signaling events that stand in contrast to those triggered by coligation of the TCR and costimulatory receptors. Specifically, anergy is characterized by lack of activation of lck, ZAP 70, Ras, ERK, JNK, AP-1, and NF-AT. In contrast, anergizing stimuli appear to activate the protein tyrosine kinase fyn, increase intracellular calcium levels, and activate Rap1. Moreover, anergizing TCR signals result in increased intracellular concentrations of the second messenger cAMP. This second messenger upregulates the cyclin-dependent kinase (cdk) inhibitor p27kip1, sequestering cyclin D2-cdk4, and cyclin E/cdk2 complexes and preventing progression of T cells through the G1 restriction point of the cell cycle. In contrast, costimulation through CD28 prevents p27kip1 accumulation by decreasing the levels of intracellular cAMP and promotes p27kip1 down-regulation due to direct degradation of the protein via the ubiquitin-proteasome pathway. Subsequent autocrine action of IL-2 leads to further degradation of p27kip1 and entry into S phase. Understanding the biochemical and molecular basis of T cell anergy will allow the development of new assays to evaluate the immune status of patients in a variety of clinical settings in which tolerance has an important role, including cancer, autoimmune diseases, and organ transplantation. Precise understanding of these biochemical and molecular events is necessary in order to develop novel treatment strategies against cancer. One of the mechanisms by which tumors down-regulate the immune system is through the anergizing inactivation of helper T lymphocytes, resulting in the absence of T cell help to tumor-specific CTLs. Although T-cells specific for tumor associated antigens are detected in cancer patients they often are unresponsive. Reversal of the defects that block the cell cycle progression is mandatory for clonal expansion of tumor specific T cells during the administration of tumor vaccines. Reversal of the anergic state of tumor specific T cells is also critical for the sufficient expansion of such T cells ex vivo for adoptive immunotherapy. On the other hand, understanding the molecular mechanisms of anergy will greatly improve our ability to design novel clinical therapeutic approaches to induce antigen-specific tolerance and prevent graft rejection and graft-versus-host disease. Such treatment approaches will allow transplantation of bone marrow and solid organs between individuals with increasing HLA disparity and therefore expand the donor pool, enable reduction in the need for nonspecific immunosuppression, minimize the toxicity of chemotherapy, and reduce the risk of opportunistic infections.
J Mol Med (Berl) 2001
PMID:Helper T cell anergy: from biochemistry to cancer pathophysiology and therapeutics. 1143 20

Wogonin (Wog), an active component of Scutellaria baicalensis, has antioxidant and anti-inflammatory properties. Monocyte chemotactic protein-1 (MCP-1), a potent chemoattractant for monocytes, plays a crucial role in case of early inflammatory responses, including atherosclerosis. In this study, we investigated the effect of Wog on phorbol ester (PMA)-induced MCP-1 expression in human umbilical vein endothelial cells (ECs). The MCP-1 mRNA levels and MCP-1 release in Wog-treated ECs were measured. Wog inhibited PMA-induced MCP-1 mRNA levels and MCP-1 secretion in a dose-dependent manner. The inhibition of MCP-1 induction by Wog is a transcriptional event, as shown by Wog's significant reduction of both MCP-1 promoter and 4x 12-O-tetradecanoylphorbol-13-acetate response element-luciferase reporter activities. By electrophoretic mobility assay, Wog significantly reduced the AP-1 binding activity induced by PMA. Furthermore, the PMA-induced extracellular signal-regulated kinase 1/2 and c-Jun amino-terminal kinase activities that contributed to AP-1 activity and MCP-1 gene induction were obviously attenuated after pretreating ECs with Wog. The decrease of MCP-1 secretion by Wog pretreatment led to a reduction of monocyte adhesion to ECs. Taken together, our results demonstrate that Wog inhibits MCP-1 induction in ECs; this inhibition is mediated by reducing AP-1 transcriptional activity via the attenuation of ERK1/2 and JNK signal transduction pathways. We conclude that Wog has the potential therapeutic development for use in anti-inflammatory and vascular disorders.
Mol Pharmacol 2001 Sep
PMID:Chinese herbal remedy wogonin inhibits monocyte chemotactic protein-1 gene expression in human endothelial cells. 1150 81

Sphingosine 1 phosphate (S1P), an aminophospholipid, acts extracellularly as a ligand via the specific G protein-coupled receptors of the endothelial differentiation gene (EDG) 1, 3, 5, 6 and 8 receptors family and intracellularly as a second messenger in various cellular types. The aim of this work was to investigate biological activity of S1P in cardiomyocytes with respect to related sphingolipids. S1P was applied for 48 h on rat neonatal cardiomyocytes at 10 nM, 100 nM and 1 microM. S1P induced a concentration-dependent cellular hypertrophy evidenced by an increase in cell size, [3H]-phenylalanine incorporation, protein content and Brain Natriuretic Peptide (BNP) secretion. Among the lipids tested S1P exhibits the lower EC50 (67 nM) followed by dihydro-S1P (107 nM) and sphingosylphosphorylcholine (1.6 microM). The effect of S1P could be related to a stimulation of the EDG1 receptor since we showed that the EDG1 receptor is predominantly expressed at the mRNA and protein levels in rat cardiomyocytes and that specific anti-EDG1 antibodies inhibited the hypertrophic effect induced by S1P. Furthermore the expression level of most other EDG receptors for S1P appeared very low in cardiac myocytes. S1P (100 nM) increased the phosphorylation of p42/44MAPK, p38MAPK, JNK, Akt and p70(S6K), this effect being reversed by inhibitors of their respective phosphorylation which also rescue the hypertrophic phenotype. Finally, S1P stimulated actin stress fibre formation reverted by the Rho inhibitor, the C3 exoenzyme. Altogether, our results show that S1P induces cardiomyocyte hypertrophy mainly via the EDG1 receptor and subsequently via Gi through ERKs, p38 MAPK, JNK, PI3K and via Rho pathway.
J Mol Cell Cardiol 2001 Sep
PMID:EDG1 receptor stimulation leads to cardiac hypertrophy in rat neonatal myocytes. 1154 39


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