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)

One of the major actions of interleukin-6 (IL-6) is the transcriptional activation of acute-phase plasma proteins (APP) genes in liver cells. Signaling by the IL-6 receptor is mediated through the signal transducing subunit gp130 and involves the activation of Janus-associated kinases (JAKs), signal transducer and activator of transcription 3 (STAT3), and mitogen-activated protein (MAP) kinase. Functional analysis of gp130 in rat hepatoma cells by using transduced chimeric G-CSFR-gp130 receptor constructs demonstrates that SHP-2, the Src homology 2 (SH2) domain-containing protein tyrosine phosphatase, acts as a negative regulator of the JAK/STAT signaling in part by downregulating JAK activity, thereby indirectly moderating the induction of STAT3-dependent APP genes. This study shows that in hepatoma cells, the recruitment and tyrosine phosphorylation of SHP-2, but not SHC, is the primary signaling event associated with the activation of MAP kinases (ERK1/2) by gp130. Overexpression of truncated SHP-2 that lacks Grb2-interacting sites, but not the full-length catalytically inactive SHP-2, reduces ERK activation by IL-6, confirming the signal-mediating role of SHP-2. Activation of ERK1/2 is correlated with induction of the immediate-early response genes. Stimulation of the c-fos, c-jun, and egr-1 genes is essentially absent in cells expressing gp130 with a Y759F mutation, which is unable to recruit SHP-2. Interestingly, both JAK/STAT and SHP-2 pathways regulate the induction of the junB gene. Moreover, disengagement of SHP-2 from gp130 signaling not only enhances APP gene induction but also further reduces cell proliferation, in part correlated with the attenuated expression of immediate-early response genes. These results suggest that IL-6 regulation of APP genes is affected by SHP-2 in two ways: SHP-2 acts as a phosphatase on the JAK/STAT pathway and serves as linker to the MAP kinase pathway, which in turn moderates APP production.
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PMID:Dual signaling role of the protein tyrosine phosphatase SHP-2 in regulating expression of acute-phase plasma proteins by interleukin-6 cytokine receptors in hepatic cells. 1040 24

Reactive gliosis is the most prominent response to diverse forms of central nervous system (CNS) injury. The signaling events that mediate this characteristic response to neural injury are under intense investigation. Several studies have demonstrated the activation of phosphoproteins within the mitogen-activated protein kinase (MAPK) and Janus kinase (JAK) pathways following neural insult. These signaling pathways may be involved or responsible for the glial response following injury, by virtue of their ability to phosphorylate and dynamically regulate the activity of various transcription factors. This study sought to delineate, in vivo, the relative contribution of MAPK- and JAK-signaling components to reactive gliosis as measured by induction of glial-fibrillary acidic protein (GFAP), following chemical-induced neural damage. At time points (6, 24, and 48 h) following methamphetamine (METH, 10 mg/kg x 4, s.c.) administration, female C57BL/6J mice were sacrificed by focused microwave irradiation, a technique that preserves steady-state phosphorylation. Striatal (target) and nontarget (hippocampus) homogenates were assayed for METH-induced changes in markers of dopamine (DA) neuron integrity as well as differences in the levels of activated phosphoproteins. GFAP upregulation occurred as early as 6 h, reaching a threefold induction 48 h following METH exposure. Neurotoxicant-induced reductions in striatal levels of DA and tyrosine hydroxylase (TH) paralleled the temporal profile of GFAP induction. Blots of striatal homogenates, probed with phosphorylation-state specific antibodies, demonstrated significant changes in activated forms of extracellular-regulated kinase 1/2 (ERK 1/2), c-jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), MAPK/ERK kinase (MEK1/2), 70-kDa ribosomal S6 kinase (p70 S6), cAMP responsive element binding protein (CREB), and signal transducer and activator of transcription 3 (STAT3). MAPK-related phosphoproteins exhibited an activation profile that peaked at 6 h, remained significantly increased at 24, and fell to baseline levels 48 h following neurotoxicant treatment. The ribosomal S6 kinase was enhanced over 60% for all time points examined. Immunoreactivity profiles for the transcription factors CREB and STAT3 indicated maximal increases in phosphorylation occurring at 24 h, and measuring greater than 2- or 17-fold, respectively. Specific signaling events were found to occur with a time course suggestive of their involvement in the gliotic response. The toxicant-induced activation of these growth-associated signaling cascades suggests that these pathways could be obligatory for the triggering and/or persistence of reactive gliosis and may therefore serve as potential targets for modulation of glial response to neural damage.
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PMID:Protein phosphorylation cascades associated with methamphetamine-induced glial activation. 1108 25

Previously, we have demonstrated that oxidative stress or Ras/ERK activation leads to the transcriptional repression of alpha-subunit of epithelial Na(+) channel (ENaC) in lung and salivary epithelial cells. Here, we further investigated the coordinated molecular mechanisms by which alpha-ENaC expression is regulated. Using both stable and transient transfection assays, we demonstrate that the overexpression of high mobility group protein I-C (HMGI-C), a Ras/ERK-inducible HMG-I family member, represses glucocorticoid receptor (GR)/dexamethasone (Dex)-stimulated alpha-ENaC/reporter activity in salivary epithelial cells. Northern analyses further confirm that the expression of endogenous alpha-ENaC gene in salivary Pa-4 cells is suppressed by an ectopic HMGI-C overexpression. Through yeast two-hybrid screening and co-immunoprecipitation assays from eukaryotic cells, we also discovered the interaction between HMGI-C and PIAS3 (protein inhibitor of activated STAT3 (signal transducer and activator of transcription 3)). A low level of ectopically expressed PIAS3 cooperatively inhibits GR/Dex-dependent alpha-ENaC transcription in the presence of HMGI-C. Reciprocally, HMGI-C expression also coordinately enhances PIAS3-mediated repression of STAT3-dependent transactivation. Moreover, overexpression of antisense HMGI-C construct is capable of reversing the repression mediated by Ras V12 on GR- and STAT3-dependent transcriptional activation. Together, our results demonstrate that Ras/ERK-mediated induction of HMGI-C is required to effectively repress GR/Dex-stimulated transcription of alpha-ENaC gene and STAT3-mediated transactivation. These findings delineate a network of inhibitory signaling pathways that converge on HMGI-C.PIAS3 complex, causally associating Ras/ERK activation with the repression of both GR and STAT3 signaling pathways in salivary epithelial cells.
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PMID:Requirement for high mobility group protein HMGI-C interaction with STAT3 inhibitor PIAS3 in repression of alpha-subunit of epithelial Na+ channel (alpha-ENaC) transcription by Ras activation in salivary epithelial cells. 1139 Mar 95

Self-renewal and the maintenance of pluripotency of mouse embryonal stem (ES) cells in vitro requires exogenous leukemia inhibitory factor (LIF). Mouse ES cells can be cultured and kept undifferentiated in the absence of embryonal feeder-cell layers when exogenous LIF concentrations are maintained above a threshold concentration. An important downstream target of LIF signal transduction in mouse ES cells is the transcription factor signal transducer and activator of transcription 3 (STAT3). In contrast to mouse ES cells, human ES cells are unresponsive to LIF and depend on feeder cells for undifferentiated growth. Here, we investigated the activation patterns of LIF-downstream effectors in mouse and human embryonal carcinoma (EC) cells. We report that LIF induces both ERK-1 as well as STAT3 activation in mouse P19 EC cells. LIF enhances the proliferation rate of P19 EC cells, which depends on ERK activity but does not require activation of STAT3. In contrast, LIF does not activate STAT3, ERK, or the gp130 receptor in human N tera-2/D1 EC cells, although all receptor components are expressed. The negative feedback protein suppressor of cytokine signaling 1 (SOCS-1) is constitutively expressed in N tera-2/D1 EC cells, suggesting that LIF signal transduction is inhibited by elevated levels of SOCS-1 expression.
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PMID:LIF-induced STAT3 signaling in murine versus human embryonal carcinoma (EC) cells. 1185 63

The MMP, matrilysin (MMP-7), has been shown to be overexpressed in prostate cancer cells and to increase prostate cancer cell invasion. Prostate stromal fibroblasts secrete factor(s), including fibroblast growth factor-1 (FGF-1) that induces promatrilysin expression in LNCaP cells. In the present study, we investigated the signal transduction pathway involved in the FGF-1-induced expression of promatrilysin. FGF-1 treatment significantly increased the activation of extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2). This induction was time-dependent and was sustained until 24 hours after treatment. Treating the cells with MEK1/2 inhibitor (PD98059) eliminated ERK activation completely and blocked FGF-1-mediated induction of promatrilysin expression. Transient transfection studies with human matrilysin promoter resulted in a four- to five-fold increase in reporter luciferase enzyme activity that was blocked by the MEK1/2 inhibitor (PD98059). Serine phosphorylation of signal transducer and activator of transcription 3 (STAT3) was observed after FGF-1 treatment and pretreatment with 20 microM PD98059-abolished STAT3 phosphorylation. Transient transfection with dominant negative STAT3 inhibited FGF-1-induced transactivation of the matrilysin promoter indicating that STAT3 plays an important role in FGF1-induced matrilysin expression. We propose that the FGF-1-induced signaling pathway that leads to promatrilysin expression is ERK-dependent and leads to phosphorylation of Ser-727 on STAT3, phosphorylated STAT3, then binds and transactivates the matrilysin promoter. Our results demonstrate that ERK-MAP kinase and transcription factor STAT3 are important components of FGF-1-mediated signaling, which induce promatrilysin expression in LNCaP cells.
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PMID:Fibroblast growth factor-1 induced promatrilysin expression through the activation of extracellular-regulated kinases and STAT3. 1192 92

Growth-related oncogene protein-alpha (GRO-alpha) is a member of the C-X-C chemokine family with a wide variety of biological activities. We studied the production of GRO-alpha by human umbilical vein endothelial cells (HUVEC) in response to the stimulation with soluble form of interleukin-6 receptor alpha (sIL-6R). sIL-6R stimulated HUVEC to express GRO-alpha mRNA and secrete GRO-alpha protein in concentration-and time-dependent manners. The sIL-6R-induced GRO-alpha expression was inhibited by the pretreatment of the cells with AG490, a janus kinase 2 (JAK2) inhibitor, or with U0126, a MAP kinase-ERK kinase (MEK) inhibitor. sIL-6R also induced the phosphorylation of both Src homology 2-protein tyrosine phosphatase-2 (SHP-2), signal transducer and activator of transcription 3 (STAT3) and MEK. AG490 pretreatment inhibited the MEK phosphorylation but did not affect the STAT3 phosphorylation. We conclude that sIL-6R induces GRO-alpha expression in HUVEC through the activation of JAK2 and MEK.
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PMID:Production of growth related oncogene protein-alpha in human umbilical vein endothelial cells stimulated with soluble interleukin-6 receptor-alpha: role of signal transducers, janus kinase 2 and mitogen-activated kinase kinase. 1200

Granulocyte colony-stimulating factor (G-CSF) is the major regulator of neutrophil production. Studies in cell lines have established that conserved tyrosines Tyr704, Tyr729, Tyr744, Tyr764 within the cytoplasmic domain of G-CSF receptor (G-CSF-R) contribute significantly to G-CSF-induced proliferation, differentiation, and cell survival. However, it is unclear whether these tyrosines are equally important under more physiologic conditions. Here, we investigated how individual G-CSF-R tyrosines affect G-CSF responses of primary myeloid progenitors. We generated G-CSF-R-deficient mice and transduced their bone marrow cells with tyrosine "null" mutant (m0), single tyrosine "add-back" mutants, or wild-type (WT) receptors. G-CSF-induced responses were determined in primary colony assays, serial replatings, and suspension cultures. We show that removal of all tyrosines had no major influence on primary colony growth. However, adding back Tyr764 strongly enhanced proliferative responses, which was reverted by inhibition of ERK activity. Tyr729, which we found to be associated with the suppressor of cytokine signaling, SOCS3, had a negative effect on colony formation. After repetitive replatings, the clonogenic capacities of cells expressing m0 gradually dropped compared with WT. The presence of Tyr729, but also Tyr704 and Tyr744, both involved in activation of signal transducer and activator of transcription 3 (STAT3), further reduced replating efficiencies. Conversely, Tyr764 greatly elevated the clonogenic abilities of myeloid progenitors, resulting in a more than 10(4)-fold increase of colony-forming cells over m0 after the fifth replating. These findings suggest that tyrosines in the cytoplasmic domain of G-CSF-R, although dispensable for G-CSF-induced colony growth, recruit signaling mechanisms that regulate the maintenance and outgrowth of myeloid progenitor cells.
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PMID:Signaling mechanisms coupled to tyrosines in the granulocyte colony-stimulating factor receptor orchestrate G-CSF-induced expansion of myeloid progenitor cells. 1246 31

Overexpressed epidermal growth receptor factor receptors (EGFRs) are thought to contribute to the malignant phenotype of human glioblastomas (GBMs), but the mechanism is not well understood. We found that SKMG-3 cells, a rare GBM cell line that maintains EGFR gene amplification in vitro, produced high levels of EGFR protein. The cells also expressed the related receptors HER2/neu and HER4, but not HER3. Immunoblots and tryptic phosphopeptide maps showed that the SKMG-3 EGFRs were intact and functional and that a subset of these receptors were spontaneously autophosphorylated. EGF treatment stimulated phosphorylation of the EGFRs as well as the downstream effectors Erk, AKT1, stat3 and c-Cbl. Under minimal growth conditions, the unstimulated SKMG-3 cells contained constitutively phosphorylated Erk and AKTI but no detectable stat3 DNA-binding complexes. The EGFR kinase inhibitor PD158780 reduced the constitutive phosphorylation of the receptor and Erk but not that of AKT1. In contrast, inhibition of phosphatidylinositol-3-kinase (PI3K) blocked the constitutive phosphorylation of Erk and AKT-1 but not the EGFR. We conclude that the SKMG-3 cells represent the subset of GBMs with amplified EGFR genes that overexpress intact receptors. The results also suggest that in some GBMs, signals from overexpressed EGFRs contribute to the constitutive phosphorylation of Erk, but these signals may not required for the constitutive activation of PI3K or AKT1.
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PMID:Spontaneous activation and signaling by overexpressed epidermal growth factor receptors in glioblastoma cells. 1253 15

Thyroid papillary carcinomas are characterized by RET/PTC (rearranged in transformation/papillary thyroid carcinoma) rearrangements that result in fusion of the tyrosine kinase domain of the RET receptor to the N-terminal sequences encoded by heterologous genes. This thyroid-specific rearrangement causes aberrant expression of RET/PTC and results in constitutive ligand-independent activation of RET kinase. However, it is unclear how RET/PTC activates the specific signaling pathways for cellular transformation. In this study, we show that RET/PTC associates with signal transducer and activator of transcription 3 (STAT3) and activates it by the specific phosphorylation of the tyrosine 705 residue. Activation of STAT3 requires the intrinsic kinase activity of RET/PTC; Janus tyrosine kinase and c-Src kinase are not involved in the RET/PTC-mediated activation of STAT3. RET/PTC-induced activation of STAT3 induces the STAT3-responsive genes, vascular endothelial growth factor, cyclin D1, and intercellular adhesion molecule 1. In addition, RET/PTC-mediated cellular transformation and proliferation of transformed cells require tyrosine 705 phosphorylation of STAT3 in NIH3T3 cells. We conclude that STAT3 activation by the RET/PTC tyrosine kinase is one of the critical signaling pathways for the regulation of specific genes, such as cyclin D1, vascular endothelial growth factor, and intercellular adhesion molecule 1, and for cellular transformation.
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PMID:Activation of signal transducer and activator of transcription 3 by oncogenic RET/PTC (rearranged in transformation/papillary thyroid carcinoma) tyrosine kinase: roles in specific gene regulation and cellular transformation. 1263 86

Signal transducer and activator of transcription 3 (STAT3), normally activated by Janus kinase (JAK) in response to cytokine stimulation, has been shown to have oncogenic potential. In addition to JAK, recent data suggest that STAT3 can also be activated by other proteins such as the aberrant fusion protein, NPM-ALK, which is expressed in a subset of systemic anaplastic large cell lymphoma (ALCL). In this study, we investigated the possible role of JAK in activating STAT3 in ALCL using two ALK-positive ALCL cell lines, Karpas 299 and SU-DHL-1. At the steady state, JAK3 showed detectable tyrosine phosphorylation by immunoprecipitation. Treatment with AG490, a JAK inhibitor, decreased but did not completely abrogate tyrosine phosphorylation of JAK3 and STAT3 in a concentration-dependent manner. Similar results were obtained using two other inhibitors of JAK3, WHI-P131 and WHI-P154. These biochemical changes were associated with apoptosis in both cell lines that was coupled with activation of caspase 3 and decreased bcl-xL and bcl-2. Cell cycle analysis revealed a decrease in the S phase, which may be attributed to cyclin D3 downregulation and p21(waf1) upregulation. Importantly, the tyrosine kinase activity of NPM-ALK, as assessed by an in vitro assay, decreased with increasing concentrations of AG490. Our findings highlight the importance of JAK3 in activating STAT3 in ALCL, and that NPM-ALK-mediated activation of STAT3 is influenced by the functional status of JAK3.
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PMID:Inhibition of JAK3 induces apoptosis and decreases anaplastic lymphoma kinase activity in anaplastic large cell lymphoma. 1293 99


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