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)

Mitogen-activated protein kinases (MAPKs) have been implicated as regulators of cellular differentiation. The biological effect of MAPK signaling in the nucleus is achieved by signal-responsive transcription factors. Here, we have investigated the connection of MAPKs, transcription factor AP-1, and alpha2beta1 integrin expression in K562 cells undergoing differentiation along the megakaryocytic pathway. We report that three distinct MAPKs, ERK, JNK, and p38, are activated during the TPA-induced megakaryocytic differentiation. Activation of MAPK pathways is followed by acquisition of the AP-1 DNA-binding and transactivation capacities. AP-1 DNA-binding activity consists primarily of JunD, c-Fos, and Fra-1, and is accompanied with the increased expression and phosphorylation of these subunits. While inhibition of JNK mainly prevents expression and phosphorylation of JunD and c-Jun, inhibition of the ERK pathway suppresses both phosphorylation and expression of Jun proteins, and expression of c-Fos and Fra-1. Furthermore, only the activity of the ERK pathway is essential for the differentiation response, as determined by expression of alpha2beta1 (CD49b) integrin. The importance of AP-1 as a mediator ERK signaling during differentiation is demonstrated by the findings that expression of c-fos siRNA and dominant negative AP-1/c-Jun(bZIP) downregulate the TPA- and ERK-induced expression of alpha2beta1 integrin mRNAs and proteins. Conversely, coexpression of JunD or c-Jun and c-Fos can induce alpha2beta1 integrin expression independently of upstream signals. Taken together, the results show that AP-1 is a nuclear target of the ERK-pathway and mediates alpha2beta1 integrin expression during megakaryocytic differentiation of K562 cells.
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PMID:AP-1 regulates alpha2beta1 integrin expression by ERK-dependent signals during megakaryocytic differentiation of K562 cells. 1570 84

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.
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PMID:Simvastatin inhibits MMP-9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP-9 mRNA levels. 1572 60

We generated A21-13 cells expressing p14(ARF) in the presence of doxycycline in order to examine the stability of p14(ARF) protein. The effects of proteasome inhibitor MG132 on p14(ARF) protein stabilization were detectable using our experimental procedure. Introduction of mutant p53 did not affect MG132-mediated p14(ARF) protein stabilization. We found that phorbol ester TPA (12-o-tetradecanoyl-phorbol 13-acetate) stabilized p14(ARF) protein and that p53 status had no effect on TPA-mediated stabilization. TPA-mediated stabilization was abolished by staurosporine but not by lovastatin or U0126. We further investigated which isoforms of PKC were involved in TPA-mediated p14(ARF) stabilization using short-interference RNA. Knockdown of PKCalpha, but not PKCdelta, attenuated TPA-mediated p14(ARF) stabilization. These findings suggest that PKCalpha is involved in TPA-mediated stabilization of p14(ARF) protein, and this effect of TPA was not affected by the Ras/MAPK pathway or p53 status. Our results are indicative of a novel role of PKC in p14(ARF) protein stability.
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PMID:PKCalpha is involved in phorbol ester TPA-mediated stabilization of p14ARF. 1582 86

Annexin A6 is a calcium-dependent membrane-binding protein that interacts with signalling proteins, including the GTPase-activating protein p120GAP, one of the most important inactivators of Ras. Since we have demonstrated that annexin A6 inhibits EGF- and TPA-induced Ras signalling, we investigated whether modulation of Ras activity by annexin A6 was mediated via altered subcellular localization of p120GAP. First, we exploited our observation that high-density lipoproteins (HDL) can activate the Ras/MAP kinase pathway. Expression of annexin A6 caused a significant reduction in HDL-induced activation of Ras and Raf-1. Annexin A6 promoted membrane binding of p120GAP in vitro, and plasma membrane targeting of p120GAP in living cells, both in a Ca(2+)-dependent manner, which is consistent with annexin A6 promoting the Ca(2+)-dependent assembly of p120GAP-Ras at the plasma membrane. We then extended these studies to other cell types and stimuli. Expression of annexin A6 in A431 cells reduced, while RNAi-mediated suppression of annexin A6 in HeLa cells enhanced EGF-induced Ras and Erk activation. Importantly, the enhancement of Ras activation following RNAi-mediated reduction in p120GAP levels was more marked in annexin A6-expressing A431 cells than controls, indicating that the effect of annexin A6 on Ras was mediated via p120GAP. Finally, we demonstrated that annexin A6 promotes plasma membrane targeting of p120GAP in A431 cells in response to a variety of stimuli, resulting in colocalization with H-Ras. These findings demonstrate an important role for annexin A6 in regulating plasma membrane localization of p120GAP and hence Ras activity.
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PMID:Annexin A6 stimulates the membrane recruitment of p120GAP to modulate Ras and Raf-1 activity. 1594 Feb 62

ped/pea-15 is a cytosolic protein performing a broad antiapoptotic function. We show that, upon DMBA/TPA-induced skin carcinogenesis, transgenic mice overexpressing ped/pea-15 (Tg(ped/pea-15)) display early development of papillomas and a four-fold increase in papilloma number compared to the nontransgenic littermates (P<0.001). The malignant conversion frequency was 24% for the Tg(ped/pea-15) mice and only 5% in controls (P<0.01). The isolated application of TPA, but not that of DMBA, was sufficient to reversibly upregulate ped/pea-15 in both untransformed skin and cultured keratinocytes. ped/pea-15 protein levels were also increased in DMBA/TPA-induced papillomas of both Tg(ped/pea-15) and control mice. Isolated TPA applications induced Caspase-3 activation and apoptosis in nontransformed mouse epidermal tissues. The induction of both Caspase-3 and apoptosis by TPA were four-fold inhibited in the skin of the Tg(ped/pea-15) compared to the nontransgenic mice, accompanied by a similarly sized reduction in TPA-induced JNK and p38 stimulation and by constitutive induction of cytoplasmic ERK activity in the transgenics. ped/pea-15 expression was stably increased in cell lines from DMBA/TPA-induced skin papillomas and carcinomas, paralleled by protection from TPA apoptosis. In the A5 spindle carcinoma cell line, antisense inhibition of ped/pea-15 expression simultaneously rescued sensitivity to TPA-induced Caspase-3 function and apoptosis. The antisense also reduced A5 cell ability to grow in semisolid media by 65% (P<0.001) and increased by three-fold tumor latency time (P<0.01). Thus, the expression levels of ped/pea-15 control Caspase-3 function and epidermal cell apoptosis in vivo and determine susceptibility to skin tumor development.
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PMID:Raised expression of the antiapoptotic protein ped/pea-15 increases susceptibility to chemically induced skin tumor development. 1604 59

Increased serine/threonine phosphorylation of insulin receptor substrate-1 (IRS-1) is associated with cellular insulin resistance. We have recently identified serine 318 (Ser318) as a novel protein kinase C-zeta (PKC-zeta)-dependent phosphorylation site within IRS-1. As other kinases may phosphorylate at this serine residue as well, we aimed to identify such kinases in the present study. In C2C12 myotubes, exposure to insulin or phorbol ester markedly increased Ser318 phosphorylation. In contrast, high glucose, tumor necrosis factor-alpha, and free fatty acids did not provoke Ser318 phosphorylation. JNK and the PI 3-kinase/mTOR pathway were found to be implicated in insulin-induced Ser318 phosphorylation, but not in TPA-stimulated phosphorylation that was, at least partly, mediated by classical or novel PKC. In conclusion, with JNK and the PI 3-kinase/mTOR pathway as mediators of insulin-induced Ser318 phosphorylation, we have identified kinases that have previously been reported to play key roles in phosphorylation of other serine residues in IRS-1.
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PMID:Insulin-induced stimulation of JNK and the PI 3-kinase/mTOR pathway leads to phosphorylation of serine 318 of IRS-1 in C2C12 myotubes. 1609 31

Protein kinase C-delta (PKC-delta) becomes activated in pancreatic acini in response to cholecystokinin (CCK) and plays a pivotal role in the exocrine pancreatic secretion. Rottlerin, a polyphenolic compound, has been widely used as a potent and specific PKC-delta inhibitor. However, some recent studies showed that rottlerin was not effective in inhibiting PKCdelta activity in vitro and that may display unspecific effects. The aims of this work were to investigate the specificity of rottlerin as an inhibitor of PKC-delta activity in intact cells and to elucidate the biochemical causes of its unspecificity. Preincubation of pancreatic acini with rottlerin (6 microM) inhibited CCK-stimulated translocation, tyrosine phosphorylation (TyrP) and activation of PKC-delta in pancreatic acini in a time-dependent manner. Rottlerin inhibited amylase secretion stimulated by both PKC-dependent pathways (CCK, bombesin, carbachol, TPA) and also by PKC-independent pathways (secretin, VIP, cAMP analogue). CCK-stimulation of MAPK activation and p125(FAK) TyrP which are mediated by PKC-dependent and -independent pathways were also inhibited by rottlerin. Moreover, rottlerin rapidly depleted ATP content in pancreatic acini in a similar way as the mitochondrial uncouplers CCCP and FCCP. All studied inhibitory effects of rottlerin in pancreatic acini were mimicked by FCCP (agonists-stimulated amylase secretion, p125(FAK) TyrP, MAPK activation and PKC-delta TyrP and translocation). Finally, rottlerin as well as FCCP display a potent inhibitory effect on the activation of other PKC isoforms present in pancreatic acini. Our results suggest that rottlerin effects in pancreatic acini are not due to a specific PKC-delta blockade, but likely due to its negative effect on acini energy resulting in ATP depletion. Therefore, to study the role of PKC-delta in cellular processes using rottlerin it is essential to keep in mind that may deplete ATP levels and inhibit different PKC isoforms. Our results give reasons for a more careful choice of rottlerin for PKC-delta investigation.
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PMID:Rottlerin inhibits stimulated enzymatic secretion and several intracellular signaling transduction pathways in pancreatic acinar cells by a non-PKC-delta-dependent mechanism. 1636 65

We generated extracellular signal-regulated kinase 1/2 (ERK1/2) mutants by introducing a single amino-acid substitution in subdomain V of the catalytic domain and then examined the susceptibility of these mutants to PP1 derivatives originally designed as Src inhibitors. Substituting smaller amino acids (alanine [Ala (A)] or glycine [Gly (G)]) for glutamine [Gln (Q)] in subdomain V drastically increased the susceptibility of ERK1/2 to 1-naphthyl PP1 (1NA-PP1). Wild-type ERK1/2 was resistant to 1NA-PP1 inhibition. ERK1(Q122A) and ERK2(Q103A) were inhibited by 1NA-PP1 at IC(50) values of 1.7 +/- 0.13 and 2.1 +/- 0.18 microM, respectively. ERK1(Q122G) and ERK2(Q103G) were inhibited by 1NA-PP1 with IC(50) values of 3.6 +/- 0.26 and 18 +/- 2.2 microM, respectively. Other derivatives of PP1 (1-naphthylmethyl PP1 and 2-naphthylmethyl PP1) did not significantly inhibit ERK1/2 and its various mutants. In addition, these ERK1/2 mutants were activated by TPA when they were expressed in mammalian cells. These results suggest that the Gln residue of subdomain V is important in determining the susceptibility of ERK1/2 to 1NA-PP1 without significant changes in their enzymatic characteristics.
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PMID:A single amino-acid change in ERK1/2 makes the enzyme susceptible to PP1 derivatives. 1643 Dec 18

Proapoptotic nuclear receptor family member Nur77 translocates from the nucleus to the mitochondria, where it interacts with Bcl-2 to trigger apoptosis. Nur77 translocation is induced by certain apoptotic stimuli, including the synthetic retinoid-related 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN)/CD437 class. In this study, we investigated the molecular mechanism by which AHPN/CD437 analog (E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces Nur77 nuclear export. Our results demonstrate that 3-Cl-AHPC effectively activated Jun N-terminal kinase (JNK), which phosphorylates Nur77. Inhibition of JNK activation by a JNK inhibitor suppressed 3-Cl-AHPC-induced Nur77 nuclear export and apoptosis. In addition, several JNK upstream activators, including the phorbol ester TPA, anisomycin and MAPK kinase kinase-1 (MEKK1), phosphorylated Nur77 and induced its nuclear export. However, Nur77 phosphorylation by JNK, although essential, was not sufficient for inducing Nur77 nuclear export. Induction of Nur77 nuclear export by MEKK1 required a prolonged MEKK1 activation and was attenuated by Akt activation. Expression of constitutively active Akt prevented MEKK1-induced Nur77 nuclear export. Conversely, transfection of dominant-negative Akt or treatment with a phosphatidylinositol 3-kinase (PI3-K) inhibitor accelerated MEKK1-induced Nur77 nuclear export. Furthermore, mutation of an Akt phosphorylation residue Ser351 in Nur77 abolished the effect of Akt or the PI3-K inhibitor. Together, our results demonstrate that both activation of JNK and inhibition of Akt play a role in translocation of Nur77 from the nucleus to the cytoplasm.
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PMID:Regulation of Nur77 nuclear export by c-Jun N-terminal kinase and Akt. 1643 70

The present study investigated the effect of the medicinal plant Salviae miltiorrhizae radix (SMR) on dopaminergic neurotransmission in comparison with amphetamine. The effect of SM (0.1 g/ml) on K(+) (20 mM)-stimulated dopamine (DA) release from rat striatal slices was compared with amphetamine (10(-4) M). Amphetamine and SMR significantly increased K(+)-stimulated DA release (P<0.001) from rat striatal slices when compared with K(+)-stimulated alone. On the other hand, to examine whether in vitro SMR treatment induces DA release in PC12 cells, the role of protein kinases has been investigated in the induction of the SMR-mediated events by using inhibitors of protein kinase C (PKC), mitogen activated protein kinase (MAP kinase) or protein kinase A (PKA). PKC inhibitors chelerythrine (50 and 100 nM), Ro31-8220 (100 nM) and the MAP kinase inhibitor, PD98059 (20 microM) inhibited the ability of SMR to elicit the SMR-stimulated DA release. The direct-acting PKC activator, 12-O-tetradecanoyl phorbol 13-acetate (TPA, 100 nM) mimicked the ability of SMR to elicit DA release. On the contrary, a selective PKA inhibitor, 50 microM Rp-8-Br-cAMP, blocked the development of SMR-stimulated DA release. The results demonstrated that SMR may stimulate DA release and that SMR-induced increases in MAP kinase and PKC are important for induction of the enhancement in transporter-mediated DA release and PKA was also required for the enhancement in SMR-stimulated DA release. SMR treatment (0.1-10 microg/ml) to the hydrogen peroxide (H(2)O(2))-treated PC12 cells activated the enzyme activities such as catalase, superoxide dismutase and glutathione peroxidase, and decreased the malondialdehyde level, indicating that SMR has also protective effects against free radical-induced cell toxicity. Therefore, the mechanism by which SMR induces the enhancement in SMR-stimulated DA release is apparent. It remains to be determined whether the effect of SMR on DA function is important in its therapeutic use in the treatment of drug addiction.
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PMID:Salviae Miltiorrhizae BGE Radix increases rat striatal K(+)-stimulated dopamine release and activates the dopamine release with protection against hydrogen peroxide-induced injury in rat pheochromocytoma PC12 cells. 1700 10


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