Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.12.2 (MEK)
 18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of dopamine and L-DOPA on survival were examined in differentiated PC12 cells. Addition of dopamine to the culture medium at 3-30 microM prevented cell death induced by depletion of serum and nerve growth factor (NGF). At 100 microM, dopamine induced cell death. The cell-protective effect of dopamine was not affected by nomifensine, an inhibitor of dopamine uptake, or pargyline, an inhibitor of monoamine oxidase, suggesting that dopamine is working outside the cell. The cell-protective effect of dopamine was blunted by SCH-23390, a D(1) antagonist, but not sulpiride, a D(2) antagonist, indicating that the cell protective effect of dopamine is mediated by D(1) receptors in PC12 cells. L-DOPA also protected PC12 cells from cell death induced by depletion of serum and NGF at low concentrations and showed toxicity at high concentration. The effect of L-DOPA was unchanged after inhibition of conversion of L-DOPA to dopamine by m-hydroxybenzylhydrazine (NSD-1015), an inhibitor of DOPA decarboxylase, suggesting that L-DOPA itself is working for cell protection. Intracellular Ca(2+) concentration and mitogen-activated protein (MAP) kinase activity were increased by both dopamine and L-DOPA. The effects of dopamine and L-DOPA on cell survival were blunted by nicardipine, a Ca(2+) channel blocker, and PD-98059, an inhibitor of MAP kinase kinase (MEK). These results taken together raised the possibility that dopamine and L-DOPA protect PC12 cells from cell death at low concentrations by activating MAP kinase activity via elevation of intracellular Ca(2+) concentration.
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PMID:Effects of dopamine and L-DOPA on survival of PC12 cells. 1100 93

Nerve growth factor stimulated axonal outgrowth from explanted mouse dorsal root ganglia is dependent on mitogen activated protein kinase. PD98059 ([2-(2'amino-3'-methoxyphenyl)-oxanaphthalen-4-one]) blocks mitogen activated protein kinase by inhibiting its immediate upstream activator, mitogen activated protein kinase kinase (also known as MEK). Here we used PD98059 to study the role of mitogen activated protein kinase in the axonal outgrowth of adult dorsal root ganglia explants. Whereas PD98059 at 50 microM left spontaneous axonal outgrowth unaffected, it markedly inhibited nerve growth factor stimulated axon growth when assessed after two days in culture. A mitogen activated protein kinase assay and immunoblotting using antibodies discriminating between activated and inactivated kinase, both confirmed that PD98059 reduced the amount of activated enzyme in nerve growth factor stimulated preparations, while the total amounts of the kinase remained unchanged. Immunohistochemistry revealed the presence of neuronal mitogen activated protein kinase kinase and mitogen activated protein kinase itself. The latter enzyme was found to be activated in the growing axons, as seen by whole-mount labelling. At the ganglionic level activated mitogen activated protein kinase was preferentially detected in satellite cells. The results show that nerve growth factor stimulated axonal outgrowth in vitro from adult mouse dorsal root ganglia utilizes the mitogen activated protein kinase pathway.
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PMID:Mitogen activated protein kinase inhibition by PD98059 blocks nerve growth factor stimulated axonal outgrowth from adult mouse dorsal root ganglia in vitro. 1100 78

We investigated neurotrophic effects of interleukin 3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) on cultured sympathetic neurons obtained from mouse superior cervical ganglia. After 1 day of culture with physiological concentrations of mouse recombinant IL-3 and GM-CSF, the numbers of process-bearing neurons were increased. Maximum responses were elicited by 10 U/ml IL-3 and 1 U/ml GM-CSF, which were equivalent to the action of a submaximal dose (5 ng/ml) of nerve growth factor (NGF). The effects of IL-3 and GM-CSF were completely blocked by their corresponding antibodies, but not by anti-NGF, indicting their action is specific and completely independent of NGF. IL-3 and, to a lesser extent, GM-CSF were also able to protect NGF-differentiated neurons from apoptotic cell death caused by NGF withdrawal. The mitogen-activated protein (MAP) kinase signal transduction pathway is known to be involved in action of IL-3 and GM-CSF on hemopoietic cells, and thus we examined the participation of this pathway in the neurotrophic activities of IL-3 and GM-CSF. IL-3 and GM-CSF stimulation of the differentiated neurons was found to result in a rapid elevation of MAP kinase activity, and PD98059, an inhibitor of MAP kinase kinase activity, blocked both the neuritogenic and neuroprotective effects of IL-3 and GM-CSF. Immunocytochemical studies showed that IL-3 and GM-CSF receptors were present on the differentiated neurons. Thus, IL-3 and GM-CSF appear to be able to stimulate sympathetic nerve growth, via specific cytokine receptors on neurons, which lead to activation of the MAP kinase pathway that then mediates the observed neurotrophic effects.
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PMID:Neurotrophic action of interleukin 3 and granulocyte-macrophage colony-stimulating factor on murine sympathetic neurons. 1112 79

Rat pheochromocytoma PC12 cells have been widely used as a cell system for study of growth factor-stimulated cell functions. We report here that nerve growth factor (NGF) stimulated both chemotaxis (directional migration) and chemokinesis (random migration) of PC12 cells. Treatment with a MEK1/2-specific inhibitor (PD98059) or expression of a dominant negative variant of Ras differentially inhibited NGF-stimulated chemotaxis but not chemokinesis of PC12 cells. Priming of PC12 cells with NGF resulted in reduced extracellular signal-regulated kinase (ERK) activation and loss of chemotactic, but not chemokinetic, response. In addition, NGF stimulation of ERK is known to involve an early transient phase of activation followed by a late sustained phase of activation; in contrast, epidermal growth factor (EGF) elicits only early transient ERK activation. We observed that like NGF, EGF also stimulated both chemotaxis and chemokinesis, and treatment with PD98059 abolished the EGF-stimulated chemotaxis. Therefore, the early transient phase of ERK activation functioned in signaling chemotaxis; the late sustained phase of ERK activation did not seem to have an essential role. In addition, our results suggested that chemotactic signaling required a threshold level of ERK activation; at below threshold level of ERK activation, chemotaxis would not occur.
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PMID:A differential role of extracellular signal-regulated kinase in stimulated PC12 pheochromocytoma cell movement. 1116 24

Rat pheochromocytoma PC12 cells undergo neuronal differentiation in response to nerve growth factor (NGF). The differentiation involves protein kinase cascades that include the kinases MEK and ERK, as well as activation of the transcription factors c-Jun and c-Fos. We show here, that exposure of PC12 cells to mannosylerythritol lipid (MEL), a yeast extracellular glycolipid, enhances the activity of acetylcholinesterase and interrupts the cell cycle at the G1 phase, with resulting outgrowth of neurites and partial cellular differentiation. Treatment with MEL stimulates the phosphorylation of ERK to a similar extent as treatment with NGF, although, the appearance of phosphorylated ERK is somewhat delayed. Both the MEL-induced outgrowth of neurites and the increase in the activity of acetylcholinesterase are prevented by PD98059, a specific inhibitor of MEK. Northern blotting analysis of c-jun transcripts and analysis of transcription in PC12 cells of a c-jun/CAT reporter construct demonstrated a significant increase in the rate of transcription of the c-jun gene upon treatment with MEL. The sequence elements required for the MEL-mediated activation of transcription of the c-jun gene are located between nucleotides -126 and -79 in the 5' flanking region. Our results suggest that MEL induces characteristics of neuronal differentiation in PC12 cells, with transactivation of the c-jun gene, via an ERK-related signal cascade that is partially overlapping the pathways activated in response to NGF. These results might provide the groundwork for the use of microbial extracellular glycolipids as novel reagents for the treatment of cancer cells.
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PMID:Mannosylerythritol lipid induces characteristics of neuronal differentiation in PC12 cells through an ERK-related signal cascade. 1116 72

Although the neurotoxicity of lead exposure is well documented, the cellular and molecular mechanisms underlying lead neurotoxicity have not been well defined. We have investigated the effect of lead on nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells and the role in this process of extracellular signal regulated protein kinase (ERK), a key component of NGF-induced differentiation. We found that exposure of cells to lead acetate (0.1-100 microM) resulted in enhanced NGF-induced neurite outgrowth. Lead exposure also promoted formation of multiple neurites per cell in NGF-treated cells. However, lead alone did not cause neurite outgrowth. Lead also enhanced NGF-induced ERK phosphorylation and activation, but lead alone did not stimulate ERK. The MAP kinase kinase (MEK) inhibitor, PD98059, significantly decreased the effect of lead on NGF-induced neurite outgrowth and ERK activation. These findings indicate that exposure of cells to low, toxic levels of lead amplifies growth factor-induced neurite outgrowth by means of an ERK-dependent signaling pathway.
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PMID:Lead enhances NGF-induced neurite outgrowth in PC12 cells by potentiating ERK/MAPK activation. 1123 54

Treatment of PC12 cells with nerve growth factor induces their differentiation into sympathetic neuron-like cells and the concomitant expression of the neural cell adhesion molecule L1, a member of the Ig superfamily. To investigate the mechanism of L1-stimulated neurite outgrowth in PC12 cells, substrate-immobilized fusion proteins containing different extracellular domains of L1 were assayed for their neuritogenic activity. Surprisingly, domain Ig2 of L1, which was previously found to contain both homophilic binding and neuritogenic activities, failed to promote neurite outgrowth. In contrast, L1-Ig6 stimulated neurite outgrowth from PC12 cells. Despite this, homotypic binding of PC12 cells was significantly inhibited by antibodies against L1-Ig2, indicating that L1-L1 binding contributed to the intercellular adhesiveness of PC12 cells, but L1-stimulated neurite outgrowth depends on heterophilic interactions. Thus, PC12 cells provide a valuable model for the study of these two distinct functions of L1. Mutagenesis of L1-Ig6 highlighted the importance of the Arg-Gly-Asp motif in this domain for neuritogenesis. Inhibition studies using cyclic Arg-Gly-Asp-containing peptide and anti-integrin antibodies suggested the involvement of alphavbeta3 integrin. Furthermore, neurite outgrowth stimulated by L1-Ig6 was inhibited by lavendustin A and the MEK inhibitor PD98059, suggesting a signaling pathway that involves tyrosine kinase activation and the mitogen-activated protein kinase cascade.
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PMID:PC12 cells utilize the homophilic binding site of L1 for cell-cell adhesion but L1-alphavbeta3 interaction for neurite outgrowth. 1123 39

Neuronal apoptotic death induced by nerve growth factor (NGF) deprivation is reported to be in part mediated through a pathway that includes Rac1 and Cdc42, mitogen-activated protein kinase kinases 4 and 7 (MKK4 and -7), c-Jun N-terminal kinases (JNKs), and c-Jun. However, additional components of the pathway remain to be defined. We show here that members of the mixed-lineage kinase (MLK) family (including MLK1, MLK2, MLK3, and dual leucine zipper kinase [DLK]) are expressed in neuronal cells and are likely to act between Rac1/Cdc42 and MKK4 and -7 in death signaling. Overexpression of MLKs effectively induces apoptotic death of cultured neuronal PC12 cells and sympathetic neurons, while expression of dominant-negative forms of MLKs suppresses death evoked by NGF deprivation or expression of activated forms of Rac1 and Cdc42. CEP-1347 (KT7515), which blocks neuronal death caused by NGF deprivation and a variety of additional apoptotic stimuli and which selectively inhibits the activities of MLKs, effectively protects neuronal PC12 cells from death induced by overexpression of MLK family members. In addition, NGF deprivation or UV irradiation leads to an increase in both level and phosphorylation of endogenous DLK. These observations support a role for MLKs in the neuronal death mechanism. With respect to ordering the death pathway, dominant-negative forms of MKK4 and -7 and c-Jun are protective against death induced by MLK overexpression, placing MLKs upstream of these kinases. Additional findings place the MLKs upstream of mitochondrial cytochrome c release and caspase activation.
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PMID:The MLK family mediates c-Jun N-terminal kinase activation in neuronal apoptosis. 1141 47

We have studied the role of MAP kinase pathways in neuronal nitric oxide synthase (nNOS) induction during the differentiation of PC12 cells. In nerve growth factor (NGF)-treated PC12 cells, we find nNOS induced at RNA and protein levels, resulting in increased NOS activity. We note that neither nNOS mRNA, nNOS protein nor NOS activity is induced by NGF treatment in cells that have been infected with a dominant negative Ras adenovirus. We have also used drugs that block MAP kinase pathways and assessed their ability to inhibit nNOS induction. Even though U0126 and PD98059 are both MEK inhibitors, we find that U0126, but not PD98059, blocks induction of nNOS protein and NOS activity in NGF-treated PC12 cells. Also, the p38 kinase inhibitor, SB203580, does not block nNOS induction in our clone of PC12 cells. Since the JNK pathway is not activated in NGF-treated PC12 cells, we conclude that the Ras-ERK pathway and not the p38 or JNK pathway is required for nNOS induction in NGF-treated PC12 cells. We find that U0126 is much more effective than PD98059 in blocking the Ras-ERK pathway, thereby explaining the discrepancy in nNOS inhibition. We conclude that the Ras-ERK pathway is required for nNOS induction.
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PMID:The Ras-ERK pathway is required for the induction of neuronal nitric oxide synthase in differentiating PC12 cells. 1148 66

A1 adenosine receptors (A1ARs) are expressed in the brain during critical periods of neurogenesis and neuronal differentiation. To examine influences of A1AR activation on neuronal development we studied the effects of A1AR activation on process growth in PC12 cells expressing A1ARs and in primary cultures of cortical and hippocampal neurons. In PC12 cells, we found that A1AR activation potently inhibited nerve growth factor (NGF)-induced neurite growth and induced stress fiber formation. A1ARs action was not mediated by inhibition of p44/42 MAP kinase activity, as inhibition of MEK/MAP kinase had no effects on A1AR action. When Rho kinase activity was blocked, A1AR agonists no longer inhibited neurite growth and stress fiber formation was blocked. In neurons, A1AR activation also inhibited process growth, and A1AR action was also mediated by Rho kinase. These data show that A1AR activation inhibits neurite growth and that the inhibitory effects of A1AR are dependent on Rho kinase.
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PMID:A1 adenosine receptor activation inhibits neurite process formation by Rho kinase-mediated pathways. 1156 36


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