Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently demonstrated that, in rat aortic smooth muscle cells, alpha-thrombin stimulated Stat3/SIF-A (signal transducers and activators of transcription 3/sis-inducing factor-A) activity [G. J. Bhat et al. (1997) Hypertension 29(Pt. 2), 356-360]. In the present study, we observed that exposure of CCL39 cells (a Chinese hamster lung fibroblast cell line) to alpha-thrombin resulted in a time-dependent decrease in basal SIF-A activity. We hypothesized that the decrease in basal SIF-A was due to the initiation of an inhibitory pathway, following alpha-thrombin exposure. To test this hypothesis, we determined if alpha-thrombin would inhibit Stat3 and SIF-A activation by interleukin-6 (IL-6), leukemia inhibitory factor (LIF), and ciliary neurotrophic factor (CNTF). In support of this hypothesis, alpha-thrombin inhibited the Stat3/SIF-A response induced by all the above cytokines. The inhibition by alpha-thrombin was concentration dependent, was sensitive to hirudin, and was mimicked by the thrombin receptor agonist peptide. The inhibition did not require the activation of phorbol 12-myristate 13-acetate-sensitive isoforms of protein kinase C and was reversed by pretreatment with the mitogen-activated protein kinase kinase 1 (MAPKK1 or MEK1) inhibitor PD98059. Inhibitory cross talk between alpha-thrombin and IL-6 was also observed in MRC-5 cells, a fibroblast cell line derived from human lung tissue. Thus, we identify a novel alpha-thrombin inhibitory pathway which, acting through a MAPKK1-dependent mechanism, blocks IL-6-, LIF-, and CNTF-induced Stat3/SIF-A activation. This inhibitory cross talk may provide an important regulatory function to modulate gene transcription by these cytokines, during immune and inflammatory responses.
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PMID:alpha-Thrombin inhibits signal transducers and activators of transcription 3 signaling by interleukin-6, leukemia inhibitory factor, and ciliary neurotrophic factor in CCL39 cells. 947 6

In vitro megakaryocytic differentiation of the pluripotent K562 human leukemia cell line is induced by PMA. Treatment of K562 cells with PMA results in growth arrest, polyploidy, morphological changes, and increased cell-cell and cell-substrate adhesion. These PMA-induced changes in K562 cells are preceded by a rapid rise in the activity of MEK (MAP kinase/extracellular regulated kinases) that leads to a sustained activation of ERK2 (extracellular regulated kinase; MAPK). Blockade of MEK1 activation by PD098059, a recently described specific MEK inhibitor [D. T. Dudley et al. (1995). Proc. Natl. Acad. Sci. USA 92, 7686-7689], reverses both the growth arrest and the morphological changes of K562 cells induced by PMA treatment. These changes are not associated with a disruption of PMA-induced down-regulation of BCR-ABL kinase or early integrin signaling events but are associated with a block of the cell-surface expression of the gpIIb/IIIa (CD41) integrin, a cell marker of megakaryocytic differentiation. These results demonstrate that the PMA-induced signaling cascade initiated by protein kinase C activation requires the activity of the MEK/ERK signaling complex to regulate cell cycle arrest, thus regulating the program that leads to the cell-surface expression of markers associated with megakaryocytic differentiation.
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PMID:A role for the MEK/MAPK pathway in PMA-induced cell cycle arrest: modulation of megakaryocytic differentiation of K562 cells. 947 49

We examined the possibility that the alpha6A and alpha6B cytoplasmic domain variants of the alpha6beta1 integrin differentially activate p42 and p44 mitogen-activated protein (MAP) kinases. P388D1 macrophages that express equivalent surface levels of either the alpha6Abeta1 or alpha6Bbeta1 integrin were used to examine this issue. Adhesion to laminin-1 mediated by the alpha6Abeta1 integrin triggered activation of a substantial fraction of total p42 and p44 MAP kinases as assessed using a mobility shift assay, immunoblot analysis with a phosphospecific MAP kinase antibody, and an immune complex kinase assay. In contrast, ligation of the alpha6Bbeta1 integrin did not trigger significant MAP kinase activation. These data were confirmed by antibody clustering of the alpha6beta1 integrins. Both the alpha6Abeta1 and alpha6Bbeta1 integrins were capable of activating the p70 ribosomal S6 kinase and this activation, unlike MAP kinase activation, is dependent on phosphoinositide 3-OH kinase. Activation of MAP kinase by alpha6beta1 requires both Ras and protein kinase C activity. A functional correlate for differential activation of MAP kinase was provided by the findings that the alpha6Abeta1 transfectants migrated significantly better on laminin than the alpha6Bbeta1 transfectants and this migration was dependent on MAP kinase activity based on the use of the MAP kinase kinase (MEK1) inhibitor PD98059. Our findings demonstrate that the alpha6beta1 integrin can activate MAP kinase, that this activation is regulated by the cytoplasmic domain of the alpha6 subunit, and that it relates to alpha6beta1-mediated migration.
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PMID:Regulation of mitogen-activated protein kinase activation by the cytoplasmic domain of the alpha6 integrin subunit. 948 28

We have previously demonstrated that hydrogen peroxide (H2O2) treatment of bovine tracheal myocytes increases the activity of extracellular signal-regulated kinases (ERK), serine/threonine kinases of the mitogen-activated protein (MAP) kinase superfamily thought to play a key role in the transduction of mitogenic signals to the cell nucleus. Moreover, H2O2-induced ERK activation was partially reduced by pretreatment with phorbol 12,13-dibutyrate, which depletes protein kinase C (PKC). In this study, we further examined the signaling intermediates responsible for ERK activation by H2O2 in airway smooth muscle, focusing on MAP kinase/ERK kinase (MEK), a dual-function kinase which is required and sufficient for ERK activation in bovine tracheal myocytes; Raf-1, a serine/threonine kinase known to activate MEK; and PKC. Pretreatment of cells with inhibitors of MEK (PD98059), Raf-1 (forskolin), and PKC (chelerythrine) each reduced H2O2-induced ERK activity. In addition, H2O2 treatment significantly increased both MEK1 and Raf-1 activity. No activation of MEK2 was detected. Together these data suggest that H2O2 may stimulate ERK via successive activation of PKC, Raf-1, and MEK1.
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PMID:Hydrogen peroxide activates extracellular signal-regulated kinase via protein kinase C, Raf-1, and MEK1. 953 45

Leukemia cells respond to toxic stimuli by undergoing a form of programmed cell death known as apoptosis. However, the signaling events responsible for the execution of this form of death are poorly understood. Mitogen-activated protein kinase (MAPK) signaling cascades are involved in the cellular response to extracellular stimuli. Specifically, extracellular signal-regulated kinases (ERKs) have been associated with proliferation and differentiation, whereas the c-Jun N-terminal kinase/stress-activated protein kinases (JNK/SAPKs) have been implicated in cell arrest and death. We report the use of 12-O-tetradecanoylphorbol-13-acetate (TPA) in the inhibition of apoptosis in HL-60 cells stimulated with the JNK/SAPK activator anisomycin. This anti-apoptotic effect was accompanied by a sustained increase in ERK activity. Furthermore, the use of protein kinase C (PKC) inhibitors suggested that PKC was involved in the induction of ERK activity and in the inhibition of apoptosis by TPA since the inhibition of apoptosis was attenuated when cells were pretreated with PKC inhibitors. Lastly, we observed that the use of the MEK1 inhibitor PD98059 inhibited TPA-mediated ERK activity and abrogated the anti-apoptotic effects of TPA. However, apoptotic inhibition was not solely ERK-dependent since cells lacking JNK/SAPK stimulation did not undergo apoptosis. Therefore, we conclude that TPA inhibits the induction of apoptosis in anisomycin-treated HL-60 cells through an ERK-dependent pathway and that this effect can be reversed by the attenuation of ERK activity accompanied with the stimulation of JNK/SAPK activity.
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PMID:Extracellular signal-regulated kinase (ERK) activity is required for TPA-mediated inhibition of drug-induced apoptosis. 953 20

The pathway supporting the conditioned stimulus (CS) is one site of plasticity that has been studied extensively in conditioned Hermissenda. Several signal transduction pathways have been implicated in classical conditioning of this preparation, although the major emphasis has been on protein kinase C. Here we provide evidence for the activation and phosphorylation of a mitogen-activated protein kinase (MAPK) pathway by one-trial and multi-trial conditioning. A one-trial in vitro conditioning procedure consisting of light (CS) paired with the application of 5-HT results in the increased incorporation of 32PO4 into proteins detected with two-dimensional gel electrophoresis. Two of the phosphoproteins have molecular weights of 44 and 42 kDa, consistent with extracellular signal-regulated protein kinases (ERK1 and ERK2). Phosphorylation of the 44 and 42 kDa proteins by one-trial conditioning was inhibited by pretreatment with PD098059, A MEK1 (ERK-Activating kinase) inhibitor. Assays of ERK activity with brain myelin basic protein as a substrate revealed greater ERK activity for the group that received one-trial conditioning compared with an unpaired control group. Western blot analysis of phosphorylated ERK using antibodies recognizing the dually phosphorylated forms of ERK1 and ERK2 showed an increase in phosphorylation after one-trial conditioning compared with unpaired controls. The increased phosphorylation of ERK after one-trial conditioning was blocked by pretreatment with PD098059. Hermissenda that received 10 or 15 conditioning trials showed significant behavioral suppression compared with pseudo-random controls. After conditioning and behavioral testing, the conditioned animals showed significantly greater phosphorylation of ERK compared with the pseudo-random controls. These results show that the ERK-MAPK signaling pathway is activated in Pavlovian conditioning of Hermissenda.
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PMID:Phosphorylation of mitogen-activated protein kinase by one-trial and multi-trial classical conditioning. 954 55

The involvement of serine/threonine protein phosphatases in signaling pathways that control the expression of the cyclooxygenase-2 (COX-2) gene in human chondrocytes was examined. Okadaic acid (OKA), an inhibitor of protein phosphatases 1 (PP-1) and 2A (PP-2A), induced a delayed, time-dependent increase in the rate of COX-2 gene transcription (runoff assay) resulting in increased steady-state mRNA levels and enzyme synthesis. The latter response was dose dependent over a narrow range of 1-30 nmol/L with declining expression and synthesis of COX-2 at higher concentrations due to cell toxicity. The delayed increase in COX-2 mRNA expression was accompanied by the induction of the proto-oncogenes c-jun, junB, junD, and c-fos (but not FosB or Fra-1). Increased phosphorylation of CREB-1/ATF-1 transcription factors was observed beginning at 4 h and reached a zenith at 8 h. Gel-shift analysis confirmed the up-regulation of AP-1 and CRE nuclear binding proteins, though there was little or no OKA-induced nuclear protein binding to SP-1, AP-2, NF-kappaB or NF-IL-6 regulatory elements. OKA-induced nuclear protein binding to 32P-CRE oligonucleotides was abrogated by a pharmacological inhibitor of protein kinase A (PKA), KT-5720; the latter compound also inhibited OKA-induced COX-2 enzyme synthesis. Calphostin C (CalC), an inhibitor of PKC isoenzymes, had little effect in this regard. Inhibition of 12P-CRE binding was also observed in the presence of an antibody to CREB-binding protein (265-kDa CBP), an integrator and coactivator of cAMP-responsive genes. The binding to 32P-CRE was unaffected in the presence of excess radioinert AP-1 and COX-2 NF-IL-6 oligonucleotides, although a COX-2 CRE-oligo competed very efficiently. 32P-AP-1 consensus sequence binding was unaffected by incubation of chondrocytes with KT-5720 or CalC, but was dramatically diminished by excess radioinert AP-1 and CRE-COX-2 oligos. Supershift analysis in the presence of antibodies to c-Jun, c-Fos, JunD, and JunB suggested that AP-1 complexes were composed of c-Fos, JunB, and possibly c-Jun. OKA has no effect on total cellular PKC activity but caused a delayed time-dependent increase in total PKA activity and synthesis. OKA suppressed the activity of the MAP kinases, ERK1/2 in a time-dependent fashion, suggesting that the Raf-1/MEKK1/MEK1/ERK1,2 cascade was compromised by OKA treatment. By contrast, OKA caused a dramatic increase in SAPK/JNK expression and activity, indicative of an activation of MEKK1/JNKK/SAPK/JNK pathway. OKA stimulated a dose-dependent activation of CAT activity using transfected promoter-CAT constructs harboring the regulatory elements AP-1 (c-jun promoter) and CRE (CRE-tkCAT). We conclude that in primary phenotypically stable human chondrocytes, COX-2 gene expression may be controlled by critical phosphatases that interact with phosphorylation dependent (e.g., MAP kinases:AP-1, PKA:CREB/ATF) signaling pathways. AP-1 and CREB/ATF families of transcription factors may be important substrates for PP-1/PP-2A in human chondrocytes.
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PMID:Transcriptional induction of cyclooxygenase-2 gene by okadaic acid inhibition of phosphatase activity in human chondrocytes: co-stimulation of AP-1 and CRE nuclear binding proteins. 962 Jan 67

The signaling of ligands operating via heterotrimeric G proteins is mediated by a complex network that involves sequential phosphorylation events. Signaling by the G protein-coupled receptor GnRH was shown to include elevation of Ca2+ and activation of phospholipases, protein kinase C (PKC) and extra-cellular signal-regulated kinase (ERK). In this study, GnRH was shown to activate Jun N-Terminal Kinase (JNK)/SAPK in alpha T3-1 cells in a PKC- and tyrosine kinase-dependent manner. GnRH as well as tumor-promoting agent (TPA) also increased c-Src activity, which peaked at 2 min after GnRH stimulation and was sensitive both to PKC and to tyrosine kinase inhibitors. Coexpression of Csk, which serves as a Src-dominant interfering kinase, and constitutively active forms of Src, together with JNK, confirmed the involvement of c-Src downstream of PKC in the GnRH-JNK pathway. Coexpression of dominant negative and constitutively active forms of CDC42, Rac1, Ras, MEKK1, and MEK1 with JNK indicated that JNK activation by GnRH and TPA is mediated by CDC42 and MEKK1. Ras and MEK1, which are involved in a related mitogen-activated protein kinase (MAPK) pathway, did not affect JNK activation in alpha T3-1 cells. Taken together, our results suggest that GnRH stimulation of JNK activity is mediated by a unique pathway that includes sequential activation of PKC, c-Src, CDC42, and probably also MEKK1.
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PMID:Stimulation of Jun N-terminal kinase (JNK) by gonadotropin-releasing hormone in pituitary alpha T3-1 cell line is mediated by protein kinase C, c-Src, and CDC42. 962 57

The RBCK1 protein was recently identified as a protein kinase C-interacting protein with a new type of RBCC (RING-B-Box-Coiled-coil) region, possessing both DNA-binding and transcriptional activities unlike other proteins in the RBCC protein family (Tokunaga et al. Biochem. Biophys. Res. Commun. 244, 353-359, 1998). To identify protein motifs in the RBCC region of RBCK1 essential for the transcriptional activity, RBCK1 mutant proteins have been constructed and analyzed by using the GAL4 chimeric transcription regulator system. We have found that both of the RING-finger and the B-Box motifs are indispensable for the transcriptional activity of RBCK1. This is the first observation that these protein motifs of the RBCC protein family play a crucial role in transcriptional activation. In addition, we have examined the effect of co-expression of several protein kinases on the transcriptional activity of RBCK1. Protein kinase A (PKA) was found to enhance the activity by about eightfold, whereas both ERK (extracellular signal-regulated kinase) activator kinase 1 (MEK1) and MEK kinase 1 (MEKK1) significantly repressed the activity. Because RBCC proteins are presumed to act as a proto-oncoprotein, these results suggest that the RBCK1 protein is involved in the intracellular signaling cascades along with PKA, MEK1, and MEKK1 and mediates cell growth and differentiation.
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PMID:Transcriptional activity of RBCK1 protein (RBCC protein interacting with PKC 1): requirement of RING-finger and B-Box motifs and regulation by protein kinases. 964 38

By using high throughput screening of microbial broths, we have identified a compound, designated Ro 09-2210, which is able to block anti-CD3 induced peripheral blood T cell activation with an IC50 = 40 nM. Ro 09-2210 was also able to block antigen-induced IL-2 secretion with an IC50 = 30 nM, but was considerably less potent at blocking Ca2+ flux stimulated by anti-CD3 treatment. To determine the mechanism of action of Ro 09-2210, we set up a transient expression system in Jurkat T cells using a variety of reporter gene constructs and showed effective inhibition of phorbol ester/ionomycin-induced NF-AT activation and anti-CD3 induced NF-AT with IC50 = 7.7 and 10 nM, respectively. Ro 09-2210 was also able to inhibit phorbol ester/ionomycin-induced activation of AP1 with IC50 = <10 nM. We further showed that Ro 09-2210 was unable to inhibit c-jun induced expression of AP1-dependent reporter constructs (IC50 > 500 nM), but was able to potently inhibit ras-induced AP1 activation (IC50 = 20 nM). This suggested that Ro 09-2210 was inhibiting an activator of AP-1 which was upstream of c-jun and downstream of ras signaling. To investigate further, we then purified a number of different kinases, including PKC, PhK, ZAP-70, ERK, and MEK 1 (a MKK), and showed that Ro 09-2210 was a selective inhibitor of MEK1 in vitro (IC50 = 59 nM).
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PMID:Ro 09-2210 exhibits potent anti-proliferative effects on activated T cells by selectively blocking MKK activity. 964 41


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