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)

Inhibiting the mitogenic response of vascular endothelial cells may in part mediate the antiangiogenic and anticancer activity of supranutritional selenium supplements. Our previous work had shown that methylseleninic acid (MSeA), a precursor of the critical anticancer methylselenol metabolite pool, was a potent inhibitor of the growth and survival of human umbilical vein endothelial cells (HUVECs). Here we investigated the effects of MSeA on selected protein kinase signaling transduction pathways to characterize their role in methylselenium induction of HUVEC cell cycle arrest and apoptosis. Exposure of asynchronous HUVECs for 30 h to 3-5 microM MSeA led to a profound G(1) arrest, and exposure to higher levels of MSeA not only led to G(1) arrest but also to DNA fragmentation and caspase-mediated cleavage of poly(ADP-ribose)polymerase, both biochemical hallmarks of apoptosis. Immunoblot analyses indicated that G(1) arrest induced by the sublethal doses of MSeA was associated with dose-dependent reductions of the levels of phospho-protein kinase B (also known as AKT or PKB), phospho-extracellular signal regulated kinase (ERK) 1/2, and phospho-Jun NH(2)-terminal kinases 1/2 in the absence of any change in p38 mitogen-activated protein kinase (MAPK) phosphorylation. Apoptosis induced by MSeA was associated with an increased phosphorylation of p38 MAPK in addition to the dephosphorylation of the above kinases. In HUVECs deprived of endothelial cell growth supplement (ECGS) for 48 h, resumption of ECGS stimulation resulted in an approximately 10-fold increase in mitogenic response, as indicated by [(3)H]thymidine incorporation into DNA. The ECGS-stimulated mitogenic response was inhibited in a dose-dependent manner by MSeA exposure with a IC(50) approximately 1 microM and a complete blockage at 3 microM. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K) upstream of AKT, potently inhibited the ECGS-stimulated DNA synthesis (IC(50), approximately 40 nM). Combining MSeA with Wortmannin showed an additive antimitogenic effect. An inhibitor of MAPK/ERK kinase 1, PD98059, also inhibited ECGS-stimulated DNA synthesis (IC(50), approximately 55 microM), but combining PD98059 with MSeA had an effect similar to that when PD98059 was used alone. A time-course experiment indicated that PI3K (AKT and ribosomal protein S6 kinase) activation occurred between 6 and 12 h of ECGS stimulation, and 3 microM MSeA exposure decreased AKT phosphorylation after 12 h of exposure, whereas no inhibitory effect was observed for ERK1/2 phosphorylation throughout the 30-h exposure duration. Additional experiments indicated that MSeA, Wortmannin, or a more specific PI3K inhibitor, LY294002, seemed to target, in the mid- to late-G(1) phase, a common mechanism(s) controlling G(1) progression to S while having no inhibitory effect on DNA synthesis once S-phase had initiated. Taken together, the results support a potent inhibitory activity at achievable serum levels of MSeA on ECGS-stimulated mitogenesis in the mid- to late-G(1) phase, and the target(s) of this inhibitory activity seems to be PI3K or components of this signal pathway. At pharmacological levels of exposure, modulation of ERK1/2 and other protein kinases may be relevant for the proapoptotic action of MSeA.
 ...
PMID:Antimitogenic and proapoptotic activities of methylseleninic acid in vascular endothelial cells and associated effects on PI3K-AKT, ERK, JNK and p38 MAPK signaling. 1158 51

We investigated the role of mitogen-activated protein kinase (MAPK) pathways in hypoxic neuronal injury using primary cultures from murine cerebral cortex. Hypoxia caused the death of approximately 50% of neurons at 16 h and approximately 65% of neurons at 24 h. This was associated with phospho-activation of the MAPK/extracellular signal-regulated kinase (ERK) kinase MEK1/2 and its downstream target ERK1/2, but not p38 MAPK or c-Jun N-terminal kinase (JNK), as detected by western blotting. The MEK1/2 inhibitor, PD98059, increased neuronal death in hypoxic cultures, suggesting that MEK1/2 promotes neuronal survival, whereas the p38 inhibitors, SB202190 and SB203580, had no effect. To identify downstream effects of ERK1/2 that might regulate hypoxic neuronal death, we measured hypoxia-induced phosphorylation of three ERK1/2 targets: the 90-kDa ribosomal protein S6 kinase (RSK), the transcription factor ELK1, and the pro-apoptotic Bcl-2 family protein Bad. We observed increased abundance of inactivated (phospho-)Bad, but no change in phospho-RSK or phospho-ELK1. Moreover, the MEK inhibitor PD98059 reduced phospho-inactivation of Bad in hypoxic cultures. These findings suggest that a cell-survival program involving phospho-activation of MEK1/2 and ERK1/2 and inactivation of Bad is mobilized in hypoxic neurons, and may help to regulate neuronal fate following hypoxic-ischemic injury.
 ...
PMID:MEK and ERK protect hypoxic cortical neurons via phosphorylation of Bad. 1179 50

Previously, we observed that 70-kDa ribosomal protein S6 kinase (p70(s6k)) plays an essential role during the early phase of oocyte maturation in Rana dybowskii. To investigate further the early signal transduction components involved in this process, the possible role of phosphatidylinositol-3 kinase (PI3 kinase) during oocyte maturation was examined. Progesterone-induced oocyte maturation was significantly inhibited by wortmannin and LY294002, specific inhibitors of PI3 kinase. In contrast, protein kinase C activator 12-0-tetradecanoylphorbol-13-acetate-induced oocyte maturation was not inhibited by wortmannin. Protein synthesis was also significantly suppressed by wortmannin treatment during oocyte maturation. Moreover, PI3 kinase inhibitor suppressed progesterone-induced phosphorylation of S6 kinase in a dose-dependent manner. Likewise, PI3 kinase inhibitors significantly inhibited the phosphorylation of mitogen-activated protein (MAP) kinase which was increased during oocyte maturation. Finally, progesterone-induced H1 kinase activity was also inhibited by PI3 kinase inhibitors in a dose-dependent manner. Taken together, these results suggest that PI3 kinase is an initial component of the signal transduction pathway which precedes p70(s6k), MAP kinase, and MPF production during progesterone-induced maturation of amphibian oocyte.
 ...
PMID:Involvement of phosphatidylinositol 3 kinase in the progesterone-induced oocyte maturation in Rana dybowskii. 1203 Jul 77

Although the cellular functions of TSC2 and its protein product, tuberin, are not known, somatic mutations in the TSC2 tumor suppressor gene are associated with tumor development in lymphangioleiomyomatosis (LAM). We found that ribosomal protein S6 (S6), which exerts translational control of protein synthesis and is required for cell growth, is hyperphosphorylated in the smooth muscle-like cell lesions of LAM patients compared with smooth muscle cells from normal human blood vessels and trachea. Smooth muscle (SM) cells derived from these lesions (LAMD-SM) also exhibited S6 hyperphosphorylation, constitutive activation of p70 S6 kinase (p70S6K), and increased basal DNA synthesis. In parallel, TSC2-/- smooth muscle cells (ELT3) and TSC2-/- epithelial cells (ERC15) also exhibited hyperphosphorylation of S6, constitutive activation of p70S6K, and increased basal DNA synthesis. Re-introduction of wild type tuberin into LAMD-SM, ELT3, and ERC15 cells abolished phosphorylation of S6 and significantly inhibited p70S6K activity and DNA synthesis. Rapamycin, an immunosuppressant, inhibited hyperphosphorylation of S6, p70S6K activation, and DNA synthesis in LAMD-SM cells. Interestingly, the basal levels of phosphatidylinositol 3-kinase, Akt/protein kinase B, and p42/p44 MAPK activation were unchanged in LAMD-SM and ELT3 cells relative to levels in normal human tracheal and vascular SM. These data demonstrate that tuberin negatively regulates the activity of S6 and p70S6K specifically, and suggest a potential mechanism for abnormal cell growth in LAM.
 ...
PMID:Tuberin regulates p70 S6 kinase activation and ribosomal protein S6 phosphorylation. A role for the TSC2 tumor suppressor gene in pulmonary lymphangioleiomyomatosis (LAM). 1204

Human vascular smooth muscle cell proliferation and migration contribute to vascular remodeling in pulmonary hypertension and atherosclerosis. The precise mechanisms that regulate structural remodeling of the vessel wall remain unknown. This study tests the hypothesis that phosphatidylinositol 3-kinase (PI3K) activation is both necessary and sufficient to mediate human pulmonary vascular smooth muscle (PVSM) cell proliferation and migration. Microinjection of human PVSM cells with a dominant-negative class IA PI3K inhibited platelet-derived growth factor (PDGF)-induced DNA synthesis by 65% (P < 0.001; chi(2) analysis) compared with cells microinjected with control plasmid, whereas microinjection of cells with a constitutively active class IA PI3K (p110*-CA) was sufficient to induce DNA synthesis (mitotic index of p110*-CA-microinjected cells was 15% vs. 3% in control cells; P < 0.01). Transfection of PVSM cells with p110*-CA was also sufficient to promote human PVSM cell migration. In parallel experiments, stimulation of human PVSM cells with PDGF induced PI3K-dependent activation of Akt, p70 S6 kinase, and ribosomal protein S6 but not mitogen-activated protein kinase. PDGF-induced proliferation and migration was inhibited by LY-294002. These results demonstrate that PI3K signaling is both necessary and sufficient to mediate human PVSM cell proliferation and migration and suggest that the activation of PI3K may play an important role in vascular remodeling.
 ...
PMID:PI3K is required for proliferation and migration of human pulmonary vascular smooth muscle cells. 1211 97

Eukaryotic elongation factor 2 (eEF2) kinase, the enzyme that inactivates eEF2, is controlled by phosphorylation. Previous work showed that stress-activated protein kinase 4 (SAPK4, also called p38delta) inhibits eEF2 kinase in vitro by phosphorylating Ser-359, while ribosomal protein S6 kinases inhibit eEF2 kinase by phosphorylating Ser-366 [Knebel, Morrice and Cohen (2001) EMBO J. 20, 4360-4369; Wang, Li, Williams, Terada, Alessi and Proud (2001) EMBO J. 20, 4370-4379]. In the present study we have examined the effects of the protein synthesis inhibitor anisomycin and tumour necrosis factor-alpha (TNF-alpha) on the phosphorylation of eEF2 kinase. We demonstrate that Ser-359, Ser-366 and two novel sites (Ser-377 and Ser-396) are all phosphorylated in human epithelial KB cells, but only the phosphorylation of Ser-359 and Ser-377 increases in response to these agonists and correlates with the dephosphorylation (activation) of eEF2. Ser-377 is probably a substrate of MAPKAP-K2/K3 (mitogen-activated protein kinase-activated protein kinase 2/kinase 3) in cells, because eEF2 kinase is phosphorylated efficiently by these protein kinases in vitro and phosphorylation of this site, induced by TNF-alpha and low (but not high) concentrations of anisomycin, is prevented by SB 203580, which inhibits SAPK2a/p38, their "upstream" activator. The phosphorylation of Ser-359 induced by high concentrations of anisomycin is probably catalysed by SAPK4/p38delta in cells, because no other stress-activated, proline-directed protein kinase tested phosphorylates this site in vitro and phosphorylation is insensitive to SB 203580. Interestingly, the phosphorylation of Ser-359 induced by TNF-alpha or low concentrations of anisomycin is suppressed by SB 203580, indicating that phosphorylation is also mediated by a novel pathway. Since the phosphorylation of Ser-377 does not inhibit eEF2 kinase in vitro, our results suggest that anisomycin or TNF-alpha inhibit eEF2 kinase via the phosphorylation of Ser-359.
 ...
PMID:Stress-induced regulation of eukaryotic elongation factor 2 kinase by SB 203580-sensitive and -insensitive pathways. 1217

Resveratrol (RV), a polyphenolic substance found in grape skin, is proposed to account in part for the protective effect of red wine in the cardiovascular system. Angiotensin II (Ang II)-induced hypertrophy of vascular smooth muscle cells (VSMCs) is a pivotal step in the development of cardiovascular disease. The aims of this study were to test the hypothesis that RV may alter Ang II-mediated hypertrophic VSMC growth and to identify the putative underlying signaling pathways. We show that RV indeed potently inhibits Ang II-induced [(3)H]leucine incorporation in a concentration-dependent manner (50 microM RV, 71% inhibition). Western blot analysis reveals that phosphorylation of Akt/protein kinase B (PKB) and to a lesser extent the mitogen-activated protein kinase extracellular signal-regulated kinase (ERK) 1/2, both essentially involved in Ang II-mediated hypertrophy, is dose dependently reduced by RV. Consistent with these results, we show that RV attenuates phosphorylation of the p70 ribosomal protein S6 kinase (p70(S6K)), a kinase downstream of the ERK 1/2 as well as the Akt pathway, that is implicated in Ang II-induced protein synthesis. Upstream of Akt/PKB RV seems to mediate its antihypertrophic effect by inhibiting phosphorylation of the phosphatidylinositol 3-kinase (PI(3)K) rather than by activating phosphatases. In summary, we demonstrate for the first time that RV inhibits Ang II-induced VSMC hypertrophy, possibly by interfering mainly with the PI(3)K/Akt and p70(S6K) but also with the ERK 1/2 signaling pathway. Thus, this study delivers important new insight in the molecular pathways that may contribute to the proposed beneficial effects of RV in cardiovascular disease.
 ...
PMID:Resveratrol suppresses angiotensin II-induced Akt/protein kinase B and p70 S6 kinase phosphorylation and subsequent hypertrophy in rat aortic smooth muscle cells. 1223 23

Several protein kinases are involved in the meiotic maturation of frog oocytes in order to activate the maturation-promoting factor (MPF). Among these kinases, the 90 kDa ribosomal protein S6 kinase (p90Rsk or Rsk) is directly phosphorylated and activated by the mitogen-activated protein kinase (MAPK). During Xenopus oocyte maturation, the activation of Rsk closely parallels that of MAPK. Both enzymes are dephosphorylated when the cytostatic factor (CSF) disappears after fertilization. Therefore, Rsk seems to play an essential role in the activation of MPF. To evaluate it in other frog oocytes, we cloned and characterized Rsk cDNA in Rana dybowskii oocytes. The cloned Rana Rsk cDNA had 2,961 bp of nucleotides, which contained a complete single open-reading frame with ATG codon and polyadenylation signal. The deduced amino acid sequence of Rana Rsk is 733 amino acids with 83 kDa. Rana Rsk shows a high homology (about 88%) with Xenopus Rsk. It also had two well-conserved kinase domains with specific phosphorylation sites, which are known to be essential for the activation of Rsk. A Northern analysis showed that Rana Rsk mRNA was strongly expressed in ovary tissue, but weakly in other tissue. Rana Rsk protein is expressed with the pTYB1 vector and purified with the IMPACT-CN system. The purified Rana Rsk cross-reacted with Xenopus, a p90Rsk2 antiserum. Therefore, we examined the phosphorylation of Rana Rsk during Rana oocyte maturation. In P4-treated oocytes, Rana Rsk was phosphorylated about 6-9 h, which correlated well with the germinal vesicle breakdown of Rana oocytes. Therefore, it is likely that Rana Rsk plays an important role in the meiotic maturation of seasonal breeding animals.
 ...
PMID:Cloning of ribosomal protein S6 kinase cDNA and its involvement in meiotic maturation in Rana dybowskii oocytes. 1224 47

Human ribosomal protein S6 kinase includes two protein families: P90RSK and P70S6K, they participate in two different signaling pathways. When the two kinases were inhibited by their antibodies or rapamycin, the proliferation of cells was arrested. However, their analog, the immunosupressant FK-506, can inhibit the proliferation of fibroblast PBL1 without interfering with the activities of P90RSK, P70S6K and MAPK. We take the tactics of "homolog screening" to demonstrate whether there are some novel proteins which can substitute for the known P90RSK and P70S6K or other pathways without interfering with the known P90RSK and P70S6K. With the conserved sequence of mouse p90RSK as a probe, we screened the homologous sequence in NCBI EST database and got three human EST fragments. With the assembled contig as a probe to screen human brain cDNA library, a full-length cDNA of 3833 bp was attained. It contains a completed open reading frame from 165 bp to 2570 bp encoding 802 amino acids. The putative protein has higher homology with other members of p90RSK family. The gene was named RPS6KA5, the accession number in GenBank is AF090421. Northern hybridization showed the gene expressed in 16 human tissues tested, and the gene was localized in 14q31-32.1 by RH mapping. Another novel P70S6K gene has also been cloned. Thus, our initial presumption that there is an analog of known P90RSK and P70S6K in human beings was proved.
 ...
PMID:[Cloning and tissue expressive pattern analysis of the human ribosomal S6 kinase-RPS6KA5 cDNA]. 1254 75

Cholecystokinin (CCK) acting through its G protein-coupled receptor is now known to activate a variety of intracellular signaling mechanisms and thereby regulate a complex array of cellular functions in pancreatic acinar cells. The best studied mechanism is the coupling through heterotrimeric G proteins of the Gq family to activate a phospholipase C leading to an increase in inositol trisphosphate and release of intracellular Ca2+. This pathway along with protein kinase C activation in response to the increase in diacylglycerol stimulates the secretion of digestive enzymes by the process of exocytosis. CCK also activates signaling pathways in acini more related to other processes. The three mitogen activated protein kinase cascades leading to ERKs, JNKs and p38 MAPK are all activated by CCK. CCK activates the ERK cascade by PKC activation of Raf which in turn activates MEK and ERKs. JNKs are activated by a distinct mechanism which requires higher concentrations of CCK. Both ERKs and JNKs are presumed to regulate gene expression. CCK activation of p38 MAPK also plays a role in regulating the actin cytoskeleton through phosphorylation of the small heat shock protein HSP27. The PI3K-PKB-mTOR pathway is activated by CCK and plays a major role in regulating protein synthesis at the translational level. This includes both activation of p70 S6K leading to phosphorylation of ribosomal protein S6 and the phosphorylation of the binding protein for initiation factor 4E leading to formation of the mRNA cap binding complex. Other signaling pathways activated by CCK receptors include NF-kappaB and a variety of tyrosine kinases. Further work is needed to understand how CCK receptors activate most of the above pathways and to better understand the biological events regulated by these diverse signaling pathways.
 ...
PMID:Cholecystokinin activates a variety of intracellular signal transduction mechanisms in rodent pancreatic acinar cells. 1268 72


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>