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)

G-protein-coupled receptors (GPCRs) are a large group of integral membrane receptors that transmit signals from a diverse array of external stimuli, including neurotransmitters, hormones, phospholipids, photons, odorants and taste ligands. In response to ligand binding, the GPCRs initiate diverse downstream signaling pathways through four groups of G proteins and other interacting proteins. Key components in GPCR-induced intracellular signaling are four groups of mitogen-activated protein kinase (MAPK) cascades: extracellular signal-related kinase (ERK), Jun N-terminal kinase (JNK), p38MAPK and big MAPK (BMK). The hallmark of MAPK signaling is the stimulation-dependent nuclear translocation of the involved kinases, which regulate gene expression and the cytoplasmic acute response to mitogenic, stress-related, apoptotic and survival stimuli. A special type of GPCR is the gonadotropin-releasing hormone (GnRH) receptor, which uses primarily the Gq protein for its downstream signaling. GnRH activates all four MAPK cascades by a PKC-dependent mechanism. Common signaling molecules, including the tyrosine kinase c-SRC and the small GTPases CDC42, RAC and RAS, are implicated in various aspects of the GnRH-MAPK pathways. Thus, the activation of MAPK cascades by GnRH opens a new vista in the understanding of the transcriptional regulation of genes encoding gonadotropins. However, additional studies on cell lines and whole animals are required to understand GnRH signaling in the context of other hormones during the reproductive cycle of mouse and human.
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PMID:Activation of MAPK cascades by G-protein-coupled receptors: the case of gonadotropin-releasing hormone receptor. 1070 49

PTK787/ZK 222584 (1-[4-chloroanilino]-4-[4-pyridylmethyl] phthalazine succinate) is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, active in the submicromolar range. It also inhibits other class III kinases, such as the platelet-derived growth factor (PDGF) receptor beta tyrosine kinase, c-Kit, and c-Fms, but at higher concentrations. It is not active against kinases from other receptor families, such as epidermal growth factor receptor, fibroblast growth factor receptor-1, c-Met, and Tie-2, or intracellular kinases such as c-Src, c-Abl, and protein kinase C-alpha. PTK787/ZK 222584 inhibits VEGF-induced autophosphorylation of kinase insert domain-containing receptor (KDR), endothelial cell proliferation, migration, and survival in the nanomolar range in cell-based assays. In concentrations up to 1 microM, PTK787/ZK 222584 does not have any cytotoxic or antiproliferative effect on cells that do not express VEGF receptors. After oral dosing (50 mg/kg) to mice, plasma concentrations of PTK787/ZK 222584 remain above 1 microM for more than 8 h. PTK787/ZK 222584 induces dose-dependent inhibition of VEGF and PDGF-induced angiogenesis in a growth factor implant model, as well as a tumor cell-driven angiogenesis model after once-daily oral dosing (25-100 mg/kg). In the same dose range, it also inhibits the growth of several human carcinomas, grown s.c. in nude mice, as well as a murine renal carcinoma and its metastases in a syngeneic, orthotopic model. Histological examination of tumors revealed inhibition of microvessel formation in the interior of the tumor. PTK787/ZK 222584 is very well tolerated and does not impair wound healing. It also does not have any significant effects on circulating blood cells or bone marrow leukocytes as a single agent or impair hematopoetic recovery after concomitant cytotoxic anti-cancer agent challenge. This novel compound has therapeutic potential for the treatment of solid tumors and other diseases where angiogenesis plays an important role.
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PMID:PTK787/ZK 222584, a novel and potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, impairs vascular endothelial growth factor-induced responses and tumor growth after oral administration. 1078 82

H/K-ATPase preparations (the G1 membrane) from pig stomach contain both kinases and phosphatases and show reversible phosphorylation of Tyr(7), Tyr(10), and Ser(27) residues of the alpha-chain of H/K-ATPase. The Tyr-kinase is sensitive to genistein and quercetin and recognized by anti-c-Src antibody. The Ser-kinase is dependent on Ca(2)(+) (K(0.5) = 0.9 microM), sensitive to a PKC inhibitor, and recognized by antibodies against PKCalpha and PKCbetaII. The addition of 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS) caused a dramatic increase in the phosphorylation of added synthetic copolymer substrates and permitted the phosphorylation of maltose-binding proteins fused with the N-terminal domain of alpha-chains. The phosphotyrosine phosphatase was inhibited by vanadate. The phosphoserine phosphatase was inhibited by okadaic acid and by inhibitor-2. The presence of protein phosphatase-1 was immunologically detected. Column chromatographic separation of CHAPS-solubilized G1 membrane and others indicate the apparent molecular weight of the Src-kinase to be approximately 60 kDa, the PKCalpha and/or PKCbII to be approximately 80 kDa, the Tyr-phosphatase to be 200 kDa, and PP-1 to be approximately 35 kDa. These data show that these membrane-bound enzyme systems are in sufficiently close proximity to be responsible for reversible phosphorylation of Tyr(7), Tyr(10), and Ser(27) of the catalytic subunit of membrane H/K-ATPase in parietal cells, the physiological role of which is unknown.
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PMID:Membrane enzyme systems responsible for the Ca(2+)-dependent phosphorylation of Ser(27), the independent phosphorylation of Tyr(10) and Tyr(7), and the dephosphorylation of these phosphorylated residues in the alpha-chain of H/K-ATPase. 1078 91

Fluorescence polarization (FP) has been used to develop high throughput screening (HTS) assays for nuclear receptor-ligand displacement and kinase inhibition. FP is a solution-based, homogeneous technique requiring no immobilization or separation of reaction components. The FP-based estrogen receptor (ER) assay is based on the competition of fluorescein-labeled estradiol and estrogen-like compounds for binding to ER. These studies determined the Kd for this interaction to be 3 nM for ERalpha and 2 nM for ERbeta; IC50 values for 17beta-estradiol, tamoxifen, 4-OH-tamoxifen, and diethylstibestrol were determined to be 5.6, 189, 26, and 3.5 nM, respectively. In a screen of 50 lead compounds from a transcriptional activation screen, 21 compounds had IC50 values below 10 microM, with one having an almost 100-fold higher affinity for ERbeta over ERalpha. These data show that an FP-based competitive binding assay can be used to screen diverse compounds with a broad range of binding affinities for ERs. The FP-based protein-tyrosine kinase (PTK) assay uses fluorescein-labeled phosphopeptides bound to anti-phosphotyrosine antibodies. Phosphopeptides generated by a kinase compete for this binding. In c-Src kinase reactions, polarization decreased with time as reaction products displaced the fluorescein-labeled phosphopeptide from the anti-phosphotyrosine antibodies. The experimentally determined IC50 of AG 1478 was 400 pM, while Genistein did not inhibit the epidermal growth factor receptor at similar concentrations. Like the FP-based PTK assay, the protein kinase C (PKC) assay utilizes competition. PKC isoforms had different turnover rates for the peptide substrate. The IC50 for staurosporine was less than 10 nM for all PKC isoforms. Tyrosine phosphatase assays use direct binding rather than competition. Increasing concentrations of T-cell protein-tyrosine phosphatase (TC PTP) increased the rate of dephosphorylation. This change in polarization was dependent on TC PTP and was inhibited by 50 microM Na3VO4. The IC50 of Na3VO4 was 4 nM for TC PTP. These data demonstrate that a FP-based assay can detect kinase and phosphatase activity. Homogeneous, fluorescent techniques such as FP are now methods of choice for screening many types of drug targets. New HTS instrumentation and assay methods like these make FP a technology easily incorporated into HTS.
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PMID:Development of high throughput screening assays using fluorescence polarization: nuclear receptor-ligand-binding and kinase/phosphatase assays. 1080 7

Upon exposure to elevated growth temperatures, mammalian cells exhibit a variety of cellular responses, such as the expression of heat-shock proteins (HSPs) and the activation of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). In this study, we show that heat shock transiently induces morphological change (cell elongation) and polymerization of actin, but not of microtubules, in human erythroleukaemic K562 cells. Pretreatment with actinomycin D or cycloheximide did not prevent the heat shock-induced cell elongation and actin reorganization, indicating that gene transcription and protein synthesis are not required for this phenomenon. The alterations in cell morphology and actin structure in response to heat shock were specifically inhibited by genistein, a tyrosine kinase inhibitor, but not by other kinase inhibitors, including tyrosine kinase inhibitors (herbimycin and tyrphostin) and protein kinase C inhibitors (staurosporine and H7). The activities of genistein-sensitive tyrosine kinase (GTK) and c-Src were enhanced by heat-shock treatment. In addition, a 75 kDa protein was highly phosphorylated in its tyrosine residues(s) by heat shock, and the phosphorylation was prevented by genistein pretreatment. Genistein also inhibited the heat-shock-induced SAPK/JNK activation and HSP expression. In contrast, while colchicine, a microtubule-disrupting agent, was able to induce actin polymerization and SAPK/JNK activation, these events were not inhibited by genistein. These results suggest that the heat-shock-induced actin polymerization, HSP expression, and SAPK/JNK activation may be mediated by the specific signal pathway involving GTK(s), while colchicine-induced actin polymerization and SAPK/JNK activation is regulated in a different manner.
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PMID:Heat shock-induced actin polymerization, SAPK/JNK activation, and heat-shock protein expression are mediated by genistein-sensitive tyrosine kinase(s) in K562 cells. 1087 92

c-src is a nonreceptor tyrosine protein kinase that is highly concentrated in synaptic regions, including synaptic vesicles and growth cones. Here, we report that the mRNA signal of pp60c-src is widely distributed in the rat brain with particularly high concentrations in the hippocampus. After spatial maze learning, up-regulation of c-src mRNA was observed in the CA3 region of the hippocampus, which was accompanied by increases in pp60c-src protein in hippocampal synaptosomal preparations. Training also triggered an increase in c-src protein tyrosine kinase activity that was correlated with its tyrosine dephosphorylation in the synaptic membrane fraction. After training, pp60c-src from hippocampus showed enhanced interactions with synaptic proteins such as synapsin I, synaptophysin, and the type 2 N-methyl-d-aspartate receptor, as well as the cytoskeletal protein actin. The association of pp60c-src with insulin receptor in the synaptic membrane fraction, however, was temporally decreased after training. Furthermore, in vitro results showed that Ca(2+) and protein kinase C might be involved in the regulation of protein-protein interactions of pp60c-src. These results suggest, therefore, that pp60c-src participates in the regulation of hippocampal synaptic activity during learning and memory.
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PMID:Nonreceptor tyrosine protein kinase pp60c-src in spatial learning: synapse-specific changes in its gene expression, tyrosine phosphorylation, and protein-protein interactions. 1088 33

The activation of extracellular signal-regulated kinases 1/2 (ERK1/2) was assessed in isolated rat mesenteric resistance arteries (200-micrometer diameter) in a pressure myograph and stimulated for 5 minutes by angiotensin II (Ang II, 0.1 micromol/L) with a pressure of 70 mm Hg. ERK1/2 activity was measured by using an in-gel assay, and ERK1/2 phosphorylation was measured by Western blot analysis with use of a phospho-specific ERK1/2 antibody. Ang II (0.1 micromol/L) induced contraction (28% of phenylephrine contraction, 10 micromol/L). ERK kinase inhibitor PD98059 (10 micromol/L) attenuated this contraction by 36% but not that to phenylephrine or K(+) (60 mmol/L). In unpressurized arteries, Ang II increased ERK1/2 activity by 26%, and pressure (70 mm Hg) itself increased ERK1/2 activity by 72%. Ang II and pressure together acted synergistically, increasing ERK1/2 activity by 264%. Thus, in pressurized vessels, Ang II (0.1 micromol/L) increased ERK1/2 activity by 112%, calculated as [(364/172)-1]x100, which was confirmed by a measured 72% increase in ERK1/2 phosphorylation. Ang II type 1 receptor blockade by candesartan (10 micromol/L) abolished the Ang II-induced increase in ERK1/2 activity, but Ang II type 2 receptor blockade (PD123319, 10 micromol/L) did not. The Ang II-induced increase in ERK1/2 activity was inhibited by protein kinase C inhibitors Ro-31-8220 (1 micromol/L) and Go-6976 (300 nmol/L) and tyrosine kinase inhibitors genistein (1 micromol/L, general) and herbimycin A (1 micromol/L, c-Src family). The present findings show for the first time in intact resistance arteries that ERK1/2 activation is rapidly regulated by Ang II, is synergistic with pressure, and is involved in contraction. The ERK1/2 signaling pathway apparently includes upstream protein kinase C and c-Src.
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PMID:Angiotensin II stimulates extracellular signal-regulated kinase activity in intact pressurized rat mesenteric resistance arteries. 1104 Feb 45

-The anti-inflammatory effects of salicylate are well known, but the intracellular mechanisms underlying those effects remain to be clarified and are not explained solely by an influence on cyclooxygenase activity. In the present study, we have used cardiac fibroblasts stimulated by either angiotensin II (Ang II) or platelet-derived growth factor (PDGF) to demonstrate an inhibitory effect of salicylate on the phosphorylation of the nonreceptor tyrosine kinases, proline-rich tyrosine kinase 2 (PYK2) and c-Src, by immunoprecipitation and immunoblotting methods. This inhibition was dose dependent, with a clear effect observed at concentrations between 5 and 20 mmol/L salicylate. Intracellular Ca(2+) chelation and protein kinase C (PKC) inhibition reduced Ang II and PDGF-induced PYK2 and c-Src phosphorylation. Salicylate significantly inhibited the phosphorylation of both of the tyrosine kinases activated by either ionophore A23187 or thapsigargin treatment, which led to an elevation of cytosolic Ca(2+). Activation of PKC by phorbol ester phosphorylated both PYK2 and Src, and this effect also was attenuated by salicylate. In contrast, salicylate had no effect on either the transactivation of the epidermal growth factor receptor by Ang II or the phosphorylation of phospholipase C-gamma by PDGF. These studies indicate a novel site of action for salicylate on PYK2 and c-Src phosphorylation and suggest that this inhibitory effect on these important signaling intermediates may be through a Ca(2+)- and PKC-dependent mechanism.
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PMID:Salicylate Inhibits Phosphorylation of the Nonreceptor Tyrosine Kinases, Proline-Rich Tyrosine Kinase 2 and c-Src. 1120 70

The aim of this study was to determine whether internalisation of the angiotensin II (Ang II) AT(1A) receptor (AT(1A)R) was a prerequisite for Ang II-induced activation of the extracellular signal-regulated kinases, ERK-1/2. The human embryonic kidney (HEK293) cell line stably transfected with either the wild-type rat AT(1A)R or an internalisation-deficient C-terminal truncated mutant of the AT(1A)R (AT(1A)T318R) was used as a model for these studies. Inhibition of AT(1A)R internalisation by treatment with an inhibitor of clathrin-mediated endocytosis, Concanavalin A (Con A), did not inhibit Ang II-induced ERK-1/2 activation. Furthermore, cells transfected with the internalisation-deficient AT(1A)T318R mutant readily activated ERK-1/2 in response to Ang II. Ang II activated ERK-1/2 via two distinct signalling pathways in HEK-AT(1A)R cells. Approximately half of Ang II-induced ERK-1/2 activation was protein kinase C (PKC)-dependent, and the remainder was calcium- and c-Src-dependent and involved transactivation of the epidermal growth factor receptor (EGFR). In summary, Ang II-induced activation of ERK-1/2 occurs via two distinct pathways in HEK293 cells, neither of which requires AT(1A)R internalisation.
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PMID:The mechanism of angiotensin II-induced extracellular signal-regulated kinase-1/2 activation is independent of angiotensin AT(1A) receptor internalisation. 1130 44

The tumor-promoting phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate) cooperates with c-Src overexpression to transform rat fibroblasts. TPA transforms c-Src-overexpressing cells by depleting the delta isoform of protein kinase C (PKCdelta). Tamoxifen, which has both estrogen-mimetic and estrogen-antagonist properties, has been widely used to improve the prognosis of breast cancer patients. However, with extended use, there is an increased risk for endometrial and other cancers that can be observed within 10 years of treatment. We report here that tamoxifen, similar to TPA, cooperates with c-Src overexpression to transform 3Y1 rat fibroblasts. Tamoxifen induced both DNA synthesis and anchorage-independent cell proliferation in c-Src-overexpressing, but not in parental, 3Y1 rat fibroblasts. Tamoxifen also induced an association between c-Src and PKCdelta that resulted in the tyrosine phosphorylation and down-regulation of PKCdelta. These phenotypes were not induced by estrogen, indicating that the effect of tamoxifen was in addition to any estrogen-mimetic effects. Thus, in addition to the hyperplasia-inducing capability of an estrogen-mimetic, tamoxifen has an additional tumor-promoting capability similar to that of TPA. The dual tumor-promoting capability of both estrogen- and TPA-mimetic properties for tamoxifen may contribute to the increased incidence of endometrial cancers observed in the relatively short exposure period of <10 years.
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PMID:Novel tumor-promoting property of tamoxifen. 1133 Dec 47


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