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)

We have previously found that epidermal growth factor (EGF) mediates growth through the Jun N-terminal kinase/stress-activated kinase (JNK/SAPK) pathway in A549 human lung carcinoma cells. As observed here, EGF treatment also greatly enhances the tumorigenicity of A549 cells, suggesting an important role for JNK in cancer cell growth (F. Bost, R. McKay, N. Dean, and D. Mercola, J. Biol. Chem. 272:33422-33429, 1997). Several isoforms families of JNK, JNK1, JNK2, and JNK3, have been isolated; they arise from alternative splicing of three different genes and have distinct substrate binding properties. Here we have used specific phosphorothioate oligonucleotides targeted against the two major isoforms, JNK1 and JNK2, to discriminate their roles in EGF-induced transformation. Multiple antisense sequences have been screened, and two high-affinity and specific candidates have been identified. Antisense JNK1 eliminated steady-state mRNA and JNK1 protein expression with a 50% effective concentration (EC50) of <0.1 microM but did not alter JNK2 mRNA or protein levels. Conversely, antisense JNK2 specifically eliminated JNK2 steady-state mRNA and protein expression with an EC50 of 0.1 microM. Antisense JNK1 and antisense JNK2 inhibited by 40 and 70%, respectively, EGF-induced total JNK activity, whereas sense and scrambled-sequence control oligonucleotides had no effect. The elimination of mRNA, protein, and JNK activities lasted 48 and 72 h following a single Lipofectin treatment with antisense JNK1 and JNK2, respectively, indicating sufficient duration for examining the impact of specific elimination on the phenotype. Direct proliferation assays demonstrated that antisense JNK2 inhibited EGF-induced doubling of growth as well as the combination of active antisense oligonucleotides did. EGF treatment also induced colony formation in soft agar. This effect was completely inhibited by antisense JNK2 and combined-antisense treatment but not altered by antisense JNK1 alone. These results show that EGF doubles the proliferation (growth in soft agar as well as tumorigenicity in athymic mice) of A549 lung carcinoma cells and that the JNK2 isoform but not JNK1 is utilized for mediating the effects of EGF. This study represents the first demonstration of a cellular phenotype regulated by a JNK isoform family, JNK2.
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PMID:The Jun kinase 2 isoform is preferentially required for epidermal growth factor-induced transformation of human A549 lung carcinoma cells. 1002 81

POU domain proteins have been implicated as key regulators during development and lymphocyte activation. The POU domain protein T-cell factor beta1 (TCFbeta1), which binds octamer and octamer-related sequences, is a potent transactivator. In this study, we showed that TCFbeta1 is phosphorylated following activation via the T-cell receptor or by stress-induced signals. Phosphorylation of TCFbeta1 occurred predominantly at serine and threonine residues. Signals which upregulate Jun kinase (JNK)/stress-activated protein kinase activity also lead to association of JNK with TCFbeta1. JNK associates with the activation domain of TCFbeta1 and phosphorylates its DNA binding domain. The phosphorylation of recombinant TCFbeta1 by recombinant JNK enhances the ability of TCFbeta1 to bind to a consensus octamer motif. Consistent with this conclusion, TCFbeta1 upregulates reporter gene transcription in an activation- and JNK-dependent manner. In addition, inhibition of JNK activity by catalytically inactive MEKK (in which methionine was substituted for the lysine at position 432) also inhibits the ability of TCFbeta1 to drive inducible transcription from the interleukin-2 promoter. These results suggest that stress-induced signals and T-cell activation induce JNK, which then acts on multiple cis sequences by modulating distinct transactivators like c-Jun and TCFbeta1. This demonstrates a coupling between the JNK activation pathway and POU domain proteins and implicates TCFbeta1 as a physiological target in the JNK signal transduction pathway leading to coordinated biological responses.
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PMID:Jun kinase phosphorylates and regulates the DNA binding activity of an octamer binding protein, T-cell factor beta1. 1002 89

The effectiveness of chemotherapy for human cancers is limited by pharmacokinetic parameters such as variation in metabolism and is determined by the cellular response. In this work, we aimed to gain a more holistic understanding of the molecular basis of glioma response to the DNA-alkylating agent 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) by using a systematic approach: we investigated the expression of 588 genes with various cellular functions in a BCNU-resistant glioblastoma cell line and a BCNU-sensitive subline before and after treatment with BCNU. Our gene expression profiling revealed major differences in gene expression between these two cell lines, especially after treatment with BCNU. One striking example was that BCNU decreased the expression of six DNA-repair genes in sensitive but not in resistant cells. In sensitive cells, BCNU treatment resulted in the induction of two MAP kinase genes; this finding suggests that the specific response to BCNU in sensitive cells may involve the Jun kinase signal transduction pathway. After BCNU treatment, marked induction of tumor necrosis factor was detected only in sensitive cells, suggesting that tumor necrosis factor is a mediator of BCNU-induced cell death. Bcl-2 family members were not altered by BCNU in sensitive cells, suggesting that BCNU-induced cell death may be independent of the bcl-2 pathway. Results of the present study demonstrate that gene expression profiling may facilitate identification of cellular pathways associated with specific responses to chemotherapeutic agents and contribute to an understanding of the molecular basis of drug action.
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PMID:Characterization of cellular pathways involved in glioblastoma response to the chemotherapeutic agent 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU) by gene expression profiling. 1002 10

The role of cbl-b in signaling by the epidermal growth factor receptor (EGFR) was studied and compared with c-cbl. We demonstrate in vivo, that cbl-b, like c-cbl, is phosphorylated and recruited to the EGFR upon EGF stimulation and both cbl proteins can bind to the Grb2 adaptor protein. To investigate the functional role of cbl proteins in EGFR signaling, we transfected cbl-b or c-cbl into 32D cells overexpressing the EGFR (32D/EGFR). This cell line is absolutely dependent on exogenous IL-3 or EGF for sustained growth. 32D/EGFR cells overexpressing cbl-b showed markedly inhibited growth in EGF compared to c-cbl transfectants and vector controls. This growth inhibition by cbl-b was the result of a dramatic increase in the number of cells undergoing apoptosis. Consistent with this finding, cbl-b overexpression markedly decreased the amplitude and duration of AKT activation upon EGF stimulation compared to either vector controls or c-cbl overexpressing cells. In addition, the duration of EGF mediated MAP kinase and Jun kinase activation in cells overexpressing cbl-b is shortened. These data demonstrate that cbl-b inhibits EGF-induced cell growth and that cbl-b and c-cbl have distinct roles in EGF mediated signaling.
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PMID:cbl-b inhibits epidermal growth factor receptor signaling. 1008 40

Costimulation of TCR/CD3 and CD28 receptors leads to activation of the Jun kinase (JNK) cascade, which plays a key role in T cell activation, including activation of the IL-2 promoter. We demonstrate that the JNK cascade plays a central role in the activation of the CD28 response element (CD28RE) in the IL-2 promoter. This response element is linked to an activating protein-1 (AP-1) site, which functions synergistically with the CD28RE. The role of the JNK cascade in the activation of this composite element is twofold: 1) activation of the AP-1 site through transcriptional activation of c-Jun, and 2) activation of the CD28RE through selective cross-talk with I kappa B kinase-beta (IKK beta). Dominant-negative versions of JNK kinase, c-Jun, and IKK beta interfered In CD3- plus CD28-induced CD28RE/AP-1 luciferase activity in Jurkat cells. In contrast, the dominant-active JNK kinase kinase, MEKK1, induced CD28RE/AP-1 luciferase activity, in parallel with induction of c-Jun and c-Rel binding to this combined promoter site. Dominant-active MEKK1 also induced transfected IKK beta, but not IKK alpha, activity. In contrast to the JNK cascade, the extracellular signal-regulated kinase (ERK) cascade did not exert an affect on the CD28RE/AP-1 site, but did contribute to activation of the distal NF-AT/AP-1 site.
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PMID:The Jun kinase cascade is responsible for activating the CD28 response element of the IL-2 promoter: proof of cross-talk with the I kappa B kinase cascade. 1009 68

Differential expression and localization of c-Jun N-terminal kinases (JNKs) in the human brain may reflect transduction of a variety of extracellular stimuli to selective cellular responses. Of the three JNKs, JNK1 and 2 are widely distributed in tissues and JNK3 is predominantly restricted to brain where it is expressed in neurons. Although there is considerable molecular conservation among all three JNKs, we distinguished expression of each by in situ hybridization, immunoblot analysis with a panel of antibodies, and stress-activation using c-Jun as substrate. In the human central nervous system (CNS), there are at least 10 isoforms: JNK3alpha1 and JNK1alpha1 were the major JNK isoforms expressed; JNK2 was not detected. On immunoblots of brain homogenates, antibody selectivity identified JNK3alpha1 as a 45-kDa protein, JNK1alpha1, a slightly lower band at 44 kDa, and a 50-kDa band of unknown specificity. Recombinant human JNK3alpha1, transfected either into CHO, COS-1, or Neuro2A (N2A) cells, was strongly expressed as a 45-kDa protein in each. Transfected JNK3alpha1, and endogenous JNK1, each immunoprecipitated from N2A cells, phosphorylated recombinant forms of human c-Jun. Kinase activity of each JNK was modestly stimulated in N2A cells by anisomycin but not by ceramide, UV irradiation, or heat shock. Endogenous JNK activation, especially at a low level, may reflect a chronic and cumulative stress process that contributes to hyperphosphorylation of cytoskeletal proteins such as those found in Alzheimer's disease (AD), and ultimately, induction of apoptosis.
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PMID:Human c-Jun N-terminal kinase expression and activation in the nervous system. 1010 Dec 27

The p53 tumor suppressor protein is a transcription factor that plays a key role in the process of apoptosis and the cell's defense against tumor development. Activation of p53 occurs, at least in part, by phosphorylation of its protein. Very recently it has been reported that UV induced a functional activation of p53 via phosphorylation at serine 389. Here, we report that the UV-induced phosphorylation of p53 at serine 389 is mediated by p38 kinase. UVC-induced phosphorylation of p53 at serine 389 was markedly impaired by either pretreatment of cells with p38 kinase inhibitor, SB202190, or stable expression of a dominant negative mutant of p38 kinase. In contrast, there was no inhibition observed in cells treated with specific MEK1 inhibitor, PD98059, or with stable expression of a dominant negative mutant of ERK2 or JNK1. Most importantly, p38 kinase could be co-immunoprecipitated with p53 by using antibodies against p53. Incubation of active p38 kinase with p53 protein caused the phosphorylation of p53 protein at serine 389 in vitro, while no phosphorylation of p53 at serine 389 was observed when p53 was incubated with activated JNK2 or ERK2. Furthermore, pretreatment of cells with SB202190 blocked the p53 DNA binding activity and p53-dependent transcription. These results strongly suggest that the p38 kinase is at least one of the most important mediators of p53 phosphorylation at serine 389 induced by UVC radiation.
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PMID:p38 kinase mediates UV-induced phosphorylation of p53 protein at serine 389. 1021 89

To investigate the protection mechanism of Bcl-2 against tumour necrosis factor (TNF)-mediated cell death, the bcl2 gene was transfected into the L929 cells and stably expressed. Two clones having different sensitivity among bcl2-transfected L929 clones had been isolated, and termed clone R1 and R2. It was observed that activation of manganese superoxide dismutase (MnSOD) and suppression of Jun kinase of clone R1 and R2 were correlated with protection from TNF cytotoxicity. Upon treatment with TNF, clone R1 and R2 were more resistant than control L929 cells against TNF cytotoxicity and the protective effect of clone R1 was stronger than clone R2. However, in case of TNF plus actinomycin D treatment, clone R1 was still resistant against TNF cytotoxicity, whereas clone R2 became more sensitive than control L929 cells. The JNK activities of clone R1 and R2 were suppressed upon TNF treatment and in case of TNF plus actinomycin D treatment, clone R2 showed a marked increase in JNK activities and had higher activity than control L929 cells. The specific activities of MnSOD of clone R1 and R2 upon TNF treatment were 70 U/ml and 33 U/ml, respectively, while the MnSOD activity was not detectable in control L929 cells. When TNF and actinomycin D were treated simultaneously, MnSOD activity was not detectable in control L929 cells and bcl2 -transfected L929 cells (clone R1, R2). Consistent with these results, both clone R1 and R2 showed higher levels of MnSOD mRNA expression than control L929 cells after TNF treatment. These data suggest that suppression of Jun kinase and increase of MnSOD may be involved in inhibitory action of Bcl-2 against TNF, and the balance between MnSOD and JNK signalling pathway may be an important factor for the protection of bcl2-transfected L929 cells from TNF cytotoxicity.
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PMID:Increase of MnSOD expression and decrease of JNK activity determine the TNF sensitivity in bcl2-transfected L929 cells. 1032 66

Fas ligation in the presence of cycloheximide induced Jun N-terminal kinase 1 (JNK1) and JNK2 phosphorylation, caspase activation and cell death in the IL-3-dependent cell line BAF3. Fas-mediated apoptosis was prevented by expression of dominant negative FADD but not inhibited by IL-3. To investigate the role of JNK activation in this process, we examined cells over-expressing a JNK-specific phosphatase M3/6. M3/6 prevented Fas stimulation of JNK, but did not affect Fas-mediated caspase activation or cell death, demonstrating that JNK activation is not required for these processes.
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PMID:JNK activation is not required for Fas-mediated apoptosis. 1039 81

Extracellular signals activate mitogen-activated protein kinase (MAPK) cascades to execute complex cellular programs, like proliferation, differentiation and apoptosis. In mammalian cells, three MAPK families have been characterized: extracellular signal-regulated kinase (ERK), which is activated by growth factors, peptide hormones and neurotransmitters, and Jun kinase (JNK) and p38 MAPK, which are activated by cellular stress stimulus as well as growth factors. This review describes the family of 90 kDa ribosomal S6 kinases (RSK; also known as p90rsk or MAPK-activated protein kinase-1, MAPKAP-K1), which were among the first substrates of ERK to be discovered and which has proven to be a ubiquitous and versatile mediator of ERK signal transduction. RSK is composed of two functional kinase domains that are activated in a sequential manner by a series of phosphorylations. Recently, a family of RSK-related kinases that are activated by ERK as well as p38 MAPK were discovered and named mitogen- and stress-activated protein kinases (MSK). A number of cellular functions of RSK have been proposed. (1) Regulation of gene expression via association and phosphorylation of transcriptional regulators including c-Fos, estrogen receptor, NFkappaB/IkappaB alpha, cAMP-response element-binding protein (CREB) and CREB-binding protein; (2) RSK is implicated in cell cycle regulation in Xenopus laevis oocytes by inactivation of the Myt1 protein kinase leading to activation of the cyclin-dependent kinase p34cdc2; (3) RSK may regulate protein synthesis by phosphorylation of polyribosomal proteins and glycogen synthase kinase-3; and (4) RSK phosphorylates the Ras GTP/GDP-exchange factor, Sos leading to feedback inhibition of the Ras-ERK pathway.
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PMID:Role and regulation of 90 kDa ribosomal S6 kinase (RSK) in signal transduction. 1041 21


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