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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phorbol ester-sensitive EL4 murine thymoma cells respond to phorbol 12-myristate 13-acetate with activation of ERK mitogen-activated protein kinases, synthesis of interleukin-2, and death, whereas phorbol ester-resistant variants of this cell line do not exhibit these responses. Additional aspects of the resistant phenotype were examined, using a newly-established resistant cell line. Phorbol ester induced morphological changes, ERK activation, calcium-dependent activation of the c-Jun N-terminal kinase (JNK), interleukin-2 synthesis, and growth inhibition in sensitive but not resistant cells. A series of protein kinase C activators caused membrane translocation of protein kinase C's (PKCs) alpha, eta, and theta in both cell lines. While PKC eta was expressed at higher levels in sensitive than in resistant cells, overexpression of PKC eta did not restore phorbol ester-induced ERK activation to resistant cells. In sensitive cells, PKC activators had similar effects on cell viability and ERK activation, but differed in their abilities to induce JNK activation and interleukin-2 synthesis. PD 098059, an inhibitor of the mitogen activated protein (MAP)/ERK kinase kinase MEK, partially inhibited ERK activation and completely blocked phorbol ester-induced cell death in sensitive cells. Thus MEK and/or ERK activation, but not JNK activation or interleukin-2 synthesis, appears to be required for phorbol ester-induced toxicity. Alterations in phorbol ester response pathways, rather than altered expression of PKC isoforms, appear to confer phorbol ester resistance to EL4 cells.
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PMID:Effects of protein kinase C activators on phorbol ester-sensitive and -resistant EL4 thymoma cells. 932 80

Morphine sulfate causes immunomodulatory and immunosuppressive effects in human. In this study, the signaling pathway involved in these morphine effects was studied. Addition of morphine sulfate to human CEMx174 lymphocytic cells resulted in increased expression of mitogen-activated protein kinase cascade proteins. Morphine enhanced the cellular levels of ERK1 (44 kDa), ERK2 (42 kDa), a 54-kDa ERK, MEK1 (45 kDa), and MEKK (78 kDa). A time-dependent increase in the activated (Thr and Tyr dually phosphorylated) state of ERK1 and ERK2 was also observed. Naloxone, a morphine antagonist, reversed the observed morphine effects, implicating a micro opioid receptor-mediated process. These findings suggest that mitogen-activated protein kinases are important intermediates in signal transduction pathways initiated by morphine receptors in immune cells.
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PMID:Induction and activation of mitogen-activated protein kinases of human lymphocytes as one of the signaling pathways of the immunomodulatory effects of morphine sulfate. 934 Nov 10

The adverse effects of lipopolysaccharide (LPS) are mediated primarily by tumor necrosis factor alpha (TNF-alpha). TNF-alpha production by LPS-stimulated macrophages is regulated at the levels of both transcription and translation. It has previously been shown that several mitogen-activated protein kinases (MAPKs) are activated in response to LPS. We set out to determine which MAPK signaling pathways are activated in our system and which MAPK pathways are required for TNF-alpha gene transcription or TNF-alpha mRNA translation. We confirm activation of the MAPK family members extracellular-signal-regulated kinases 1 and 2 (ERK1 and ERK2), p38, and Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), as well as activation of the immediate upstream MAPK activators MAPK/ERK kinases 1 and 4 (MEK1 and MEK4). We demonstrate that LPS also activates MEK2, MEK3, and MEK6. Furthermore, we demonstrate that dexamethasone, which inhibits the production of cytokines, including TNF-alpha, significantly inhibits LPS induction of JNK/SAPK activity but not that of p38, ERK1 and ERK2, or MEK3, MEK4, or MEK6. Dexamethasone also blocks the sorbitol but not anisomycin stimulation of JNK/SAPK activity. A kinase-defective mutant of SAPKbeta, SAPKbeta K-A, blocked translation of TNF-alpha, as determined by using a TNF-alpha translational reporting system. Finally, overexpression of wild-type SAPKbeta was able to overcome the dexamethasone-induced block of TNF-alpha translation. These data confirm that three MAPK family members and their upstream activators are stimulated by LPS and demonstrate that JNK/SAPK is required for LPS-induced translation of TNF-alpha mRNA. A novel mechanism by which dexamethasone inhibits translation of TNF-alpha is also revealed.
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PMID:Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) is required for lipopolysaccharide stimulation of tumor necrosis factor alpha (TNF-alpha) translation: glucocorticoids inhibit TNF-alpha translation by blocking JNK/SAPK. 934 88

Recent studies have indicated that serine phosphorylation regulates the activities of STAT1 and STAT3. However, the kinase(s) responsible and the role of serine phosphorylation in STAT function remain unresolved. In the present studies, we examined the growth factor-dependent serine phosphorylation of STAT1 and STAT3. We provide in vitro and in vivo evidence that the ERK family of mitogen-activated protein (MAP) kinases, but not JNK or p38, specifically phosphorylate STAT3 at serine 727 in response to growth factors. Evidence for additional mitogen-regulated serine phosphorylation is also provided. STAT1 is a relatively poor substrate for all MAP kinases tested both in vitro and in vivo. STAT3 serine phosphorylation, not its tyrosine phosphorylation, results in retarded mobility of the STAT3 protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Importantly, serine 727 phosphorylation negatively modulates STAT3 tyrosine phosphorylation, which is required for dimer formation, nuclear translocation, and the DNA binding activity of this transcriptional regulator. Interestingly, the cytokine interleukin-6 also stimulates STAT3 serine phosphorylation, but in contrast to growth factors, this occurs by an ERK-independent process.
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PMID:STAT3 serine phosphorylation by ERK-dependent and -independent pathways negatively modulates its tyrosine phosphorylation. 934 14

Members of the epidermal growth-factor-receptor tyrosine-kinase (EGFR) family play important roles both in normal growth regulation/cell differentiation and in the genesis and progression of human neoplasia. In the present study, we analysed distinct heregulin (HRG) signals mediated by the HRG receptors HER3 and HER4. In overexpression cell systems, we demonstrate that HRG-induced transformation by "kinase-impaired" HER3 is dependent on coexpression of kinase active HER2. In cells coexpressing HER2 and HER4, however, both kinases significantly contribute to the HRG-induced mitogenic stimulus. In addition, we show that HER3 is no substrate of HRG-activated HER4. Analysis of EGFR crosstalk in a panel of human carcinoma cell lines revealed mainly HRG-induced activation of HER2/HER3, whereas HER4 activation is also detectable to various extents. Evidence for HRG-induced activation of HER3 and/or HER4 indicates relevance of cell-specific expression patterns of these high- and low-affinity HRG receptors in the modulation of a ligand-induced stimulus. Specific signal modulation and definition can be demonstrated further by distinct time courses of mitogen-activated protein (MAP) kinase (MAPK) activation, which are induced by distinct HRG isotypes via differential binding to HER2/HER3 versus HER2/HER4. In concert, these mechanisms of signal modulation may be decisive for the diverse biological activities of HRG in different cell types.
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PMID:Distinct characteristics of heregulin signals mediated by HER3 or HER4. 936 20

The transcription factor Elk-1 is a component of ternary complex factor and regulates gene expression in response to a wide variety of extracellular stimuli. Phosphorylation of the C-terminal domain of Elk-1, especially at serine 383, is important for its transactivation activity. Recently mitogen-activated protein kinases, such as extracellular signal-regulated kinase, stress-activated protein kinase, and p38 mitogen-activated protein kinase have been demonstrated to be Elk-1 kinases. However, negative regulators of Elk-1, such as protein phosphatases, still remain to be identified. Here we report that COS cell lysates were able to dephosphorylate an extracellular signal-regulated kinase-phosphorylated glutathione S-transferase-Elkc fusion protein, including serine 383. The phosphatase activity was inhibited by cyclosporin A (a calcineurin inhibitor) but not by okadaic acid (a PP1 and PP2A inhibitor). Purified calcineurin also could efficiently dephosphorylate glutathione S-transferase-Elkc in vitro. Pretreatment of COS cells with cyclosporin A significantly enhanced epidermal growth factor-induced serine 383 Elk-1 phosphorylation whereas ionomycin inhibited the Elk-1 phosphorylation. These data provide both in vitro and in vivo evidence that calcineurin is the major Elk-1 phosphatase and plays a critical role in Elk-1 regulation. The identification of calcineurin as the major Elk-1 phosphatase may provide a mechanism for Elk-1 regulation by Ca2+ signals as well as a possible biochemical basis for the neurotoxicity and nephrotoxicity of the immunosuppressant drug cyclosporin A.
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PMID:The calcium/calmodulin-dependent protein phosphatase calcineurin is the major Elk-1 phosphatase. 936 95

The small GTPase RhoB is immediate-early inducible by DNA damaging treatments and thus part of the early response of eukaryotic cells to genotoxic stress. To investigate the regulation of this cellular response, we isolated the gene for rhoB from a mouse genomic library. Sequence analysis of the rhoB gene showed that its coding region does not contain introns. The promoter region of rhoB harbors regulatory elements such as TATA, CAAT, and Sp1 boxes but not consensus sequences for AP-1, Elk-1, or c-Jun/ATF-2. The rhoB promoter was activated by UV irradiation, but not by 12-O-tetradecanoylphorbol-13-acetate treatment. rhoB promoter deletion constructs revealed a fragment of 0.17 kilobases in size which was sufficient in eliciting the UV response. This minimal promoter fragment contains TATA and CAAT boxes but no other known regulatory elements. Neither MEK inhibitor PD98059 nor p38 kinase inhibitor SB203580 blocked stimulation of rhoB by UVC (UV light, 254 nm) which indicates that ERK or p38 mitogen-activated protein (MAP) kinase are not involved in the UV induction of rhoB. Also, phosphatidylinositol 3-kinase inhibitor wortmannin, which blocks UV stimulation of both JNK and p38 MAP kinase, did not inhibit rhoB activation. Furthermore, activation of JNK by interleukin-1beta did not affect rhoB expression. These data indicate that JNK is not involved in the regulation of rhoB. Overexpression of wild-type Rac as well as the Rho guanine-dissociation inhibitor caused activation of rhoB. Wild-type RhoB inhibited both basal and UV-stimulated rhoB promoter activity, indicating a negative regulatory feedback by RhoB itself. The data provide evidence both for a signal transduction pathway independent of JNK, ERK, and p38 MAP kinase to be involved in the induction of rhoB by genotoxic stress, and furthermore, indicate autoregulation of rhoB.
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PMID:rhoB encoding a UV-inducible Ras-related small GTP-binding protein is regulated by GTPases of the Rho family and independent of JNK, ERK, and p38 MAP kinase. 938 98

UVC irradiation activates mitogen-activated protein kinases (MAPKs), including ERK, JNK, and P38. This study examined the role of protein kinase C (PKC) in the regulation of UVC-stimulated MAPKs activation. Either the depletion of PKC by prolonged treatment of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) or the inhibition of PKC by a selective PKC inhibitor, UCN-01-ME, attenuated UVC-activation of ERK1/2, keeping the activation of JNK1/2 intact. However, K252a, a non-selective PKC inhibitor, inhibited the activation of both ERK1/2 and JNK1/2 by UVC. In three isoforms of PKC (alpha, delta, epsilon) examined, PKC epsilon shows the most evident translocation, a temporal association with cell membrane, upon the UVC irradiation of NIH 3T3 cells. These results suggest that PKC is acting in the UVC-dependent activation of ERK1/2, and PKC epsilon is one of the PKC isozymes playing such a role.
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PMID:Involvement of protein kinase C in the activation of extracellular signal-regulated kinase 1/2 by UVC irradiation. 938 66

The observation that mitogen-activated protein (MAP) kinases ERK1 and ERK2 are constitutively activated in a number of oncogene-transformed cell lines has led to the hypothesis that prolonged activation of these enzymes is required for the transformation process. To investigate this question, we have examined the regulation of the ERK pathway in Rat1 fibroblasts transformed with activated c-Raf-1 (Raf22W), v-Ha-Ras, and v-Src. Expression of these oncoproteins had no effect on the enzymatic activity of ERK1 and ERK2 in either serum-starved or exponentially growing cells. Moreover, the stimulatory effect of serum on ERK1/ERK2 activity was substantially reduced or abrogated in these cells; this impairment was associated with a strong attenuation of c-fos gene induction. In contrast, expression of Raf22w, v-Ha-Ras, or v-Src resulted in the constitutive activation of the upstream kinases MEK1 and MEK2. Treatment of the cells with vanadate completely restored the activation of ERK1/ERK2 in oncogene-transformed cells, suggesting the involvement of a vanadate-sensitive tyrosine phosphatase. Northern blot analysis of VH1-like dual-specificity MAP kinase phosphatases did not reveal any significant difference in the mRNA expression pattern of these genes between parental and transformed Rat1 cells. Phosphoamino acid analysis indicated that ERK1 is phosphorylated on threonine, but not on tyrosine, in oncogene-transformed cells and that vanadate treatment restores tyrosine phosphorylation. We conclude from these results that ERK1/ERK2 activity is repressed by a single-specificity tyrosine phosphatase in oncogene-transformed rat fibroblasts.
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PMID:Repression of mitogen-activated protein kinases ERK1/ERK2 activity by a protein tyrosine phosphatase in rat fibroblasts transformed by upstream oncoproteins. 939 54

Vascular endothelial growth factor A (here referred to as VEGF) is an endothelium-specific growth factor that binds to two distinct receptor tyrosine kinases, designated Flt-1 and KDR/Flk-1. VEGF stimulates autophosphorylation of both receptors, but little is known about their signal transduction properties. In this study, we used porcine aortic endothelial (PAE) cells overexpressing KDR (PAE/KDR) to evaluate the interaction of KDR with intracellular proteins and compared them with Flt-1-expressing PAE cells (PAE/Flt-1). VEGF-induced stimulation of KDR results in the association and phosphorylation of the 46-, 52-, and 66-kDa isoforms of Shc and the induction of Shc-Grb2 complex formation. In a similar fashion, KDR associates with Grb2 and Nck in a ligand-dependent fashion, suggesting Shc, Grb2, and Nck as potential candidates involved in the regulation of endothelial function. Another strong candidate is mitogen-activated protein (MAP) kinase, which is strongly activated in response to VEGF stimulation as demonstrated by phosphorylation of the specific substrate myelin basic protein. Inhibition of MAP kinase activation by PD98059, a specific MAP kinase kinase inhibitor, results in inhibition of VEGF-induced proliferation of PAE/KDR cells. In contrast, VEGF-induced stimulation of Flt-1 does not activate MAP kinase in PAE/Flt-1 cells. In this study we provide the first two examples of molecules potentially capable of functionally counteracting the endothelial response to VEGF, namely SHP-1 and SHP-2. These two SH2 protein-tyrosine phosphatases physically associate with KDR secondary to VEGF stimulation, raising the interesting possibility that both molecules participate in the generation and/or modulation of VEGF-induced signals. Taken together, our results substantially broaden the spectrum of KDR-associating molecules, indicating that endothelial function and angiogenesis are regulated by a diverse network of signal transduction cascades.
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PMID:The vascular endothelial growth factor receptor KDR activates multiple signal transduction pathways in porcine aortic endothelial cells. 940 64


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