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)

During development, Glu receptors and N-methyl-D-aspartate receptors in particular initiate a cascade of signal transduction events and gene expression changes primarily involving Ca(2+) ion-mediated signaling induced by activation of either Ca(2+) ion-permeable receptor channels or voltage-sensitive Ca(2+) ion channels. The consecutive activation of major protein kinase signaling pathways, such as Ras-MAPK/ERK and PI3-K-Akt, contributes to regulation of gene expression through the activation of key transcription factors, such as CREB, SRF, MEF-2, NF-kappaB. Metabotropic Glu receptors can also engage these signaling pathways and this may be mediated, in part, by transactivating receptor tyrosine kinases. Indirect effects of Glu receptor stimulation are due to the production and release of neurotrophic factors, such as brain derived neurotrophic factor and also involve glia-neuronal interaction through Glu-induced release of trophic factors from glia. The trophic effect of Glu receptor activation is developmental stage-dependent and may play an important role in determining the selective survival of neurons that made proper connections. During this sensitive developmental period interference with Glu receptor function may lead to widespread neuronal loss. However, NMDA receptor blockade-induced neurodegeneration can also occur in the adult brain. Depending on the stimulus strength, Glu receptors mediate biphasic effects. In addition to synaptic transmission, physiological stimulation of Glu receptors can mediate trophic effects and promote neuronal plasticity. Excessive stimulation is neurotoxic. Attention must, therefore, be paid to these features, when therapeutic manipulation of excitatory amino acid receptors is considered in the clinical setting.
 ...
PMID:Trophic effect of glutamate. 1678 70

Invasion of tumor cells is the primary cause of therapeutic failure in the treatment of malignant gliomas. In an attempt to investigate the properties of the malignant progression of glioma cells, we examined the correlation between cell migration and glial cell-derived neurotrophic factor (GDNF) secretion of two glioma cell lines which differ in their invasive phenotypes. Here, we show that the high-grade C6 cells are more migrative and secrete more GDNF than the low-grade Hs683 cells. GDNF signaling is more highly activated in C6 cells than in Hs683 cells. Treatment of the Hs683 cells with GDNF significantly increased migration comparable to the C6 cells, revealing the autocrine and/or paracrine effect of GDNF on promotion of the glioma cell migration. We then examined the involvement of mitogen-activated protein kinases (MAPKs) including c-Jun N-terminal protein kinase (JNK), extracellular signal-regulated kinases (ERKs) and p38 MAPK in Hs683 cell migration induced by GDNF. A prominent activation of JNK, ERKs and p38 MAPK was observed in the GDNF-treated cells. Functional studies showed that the activation of these MAPKs was critical for Hs683 cell migration induced by GDNF. Our findings revealing molecular mechanisms for the promoting effect of GDNF on glioma cell migration may provide an insight into a better understanding to the malignant progression of human gliomas.
 ...
PMID:Glial cell-derived neurotrophic factor (GDNF) promotes low-grade Hs683 glioma cell migration through JNK, ERK-1/2 and p38 MAPK signaling pathways. 1681 21

During development of the central and peripheral nervous systems, neurite extension mediated via glial-cell-line-derived neurotrophic factor (GDNF) and its receptor RET is critical for neuronal differentiation. In the present study, we investigated the role of the RET substrate Dok-4 in neurite outgrowth induced by the GDNF/RET signaling pathway. In TGW neuroblastoma cells, which endogenously express both RET and Dok-4, depletion of Dok-4 through treatment with small interfering RNA resulted in a marked decrease in GDNF-stimulated neurite outgrowth. By contrast, exogenous expression of wild-type Dok-4 induced sustained p44/42 mitogen-activated protein kinase (ERK1/2) activation and enhanced neurite outgrowth. Expression of Dok-4 mutants in which the tyrosine residues at codons 187, 220 and 270, conserved between Dok-4, -5, and -6, were each replaced with a phenylalanine inhibited sustained ERK1/2 activation and neurite outgrowth. We also found that Dok-4 induced a significant activation of the small G protein Rap1 and that expression of a dominant active Rap1 mutant restored neurite outgrowth in Dok-4-depleted cells. By contrast, expression of a dominant negative Rap1 mutant impaired GDNF-stimulated neurite outgrowth from TGW cells. Finally, we found that neurite formation in cultured rat hippocampal neurons was enhanced by the expression of Dok-4. Together, our results suggest that Dok-4, through activation of the Rap1-ERK1/2 pathway, regulates GDNF-mediated neurite outgrowth during neuronal development.
 ...
PMID:Dok-4 regulates GDNF-dependent neurite outgrowth through downstream activation of Rap1 and mitogen-activated protein kinase. 1682 Apr 12

Parkinson disease is characterized by the selective degeneration of dopaminergic (DA) neurons in substantia nigra. Long term epidemiological studies have implicated exposure to agricultural pesticides as a significant risk factor. Systemic administration of rotenone, a widely used pesticide, causes selective degeneration of nigral DA neurons and Parkinson disease-like symptoms in rats. Our previous study has shown that the microtubule depolymerizing activity of rotenone plays a critical role in its selective toxicity on DA neurons. Rotenone toxicity is mimicked by the microtubule-depolymerizing drug colchicine and attenuated by the microtubule-stabilizing agent taxol. Here we show that nerve growth factor (NGF) significantly reduced rotenone toxicity on TH(+) neurons in midbrain neuronal cultures. The protective effect of NGF was completely abolished by inhibiting the microtubule-associated protein kinase kinase (MEK) and partially reversed by blocking phosphatidylinositol 3-kinase. In addition, NGF decreased colchicine toxicity on TH(+) neurons in a manner dependent on MEK but not phosphatidylinositol 3-kinase. The protective effect of NGF against rotenone toxicity was occluded by the microtubule-stabilizing drug taxol. In a MEK-dependent manner, NGF significantly attenuated rotenone- or colchicine-induced microtubule depolymerization and ensuing accumulation of vesicles in the soma and elevation in protein carbonyls. Moreover, other neurotrophic factors such as brain-derived neurotrophic factor and glia cell line-derived neurotrophic factor also reduced rotenone- or colchicine-induced microtubule depolymerization and death of TH(+) through a MEK-dependent mechanism. Thus, our results suggest that neurotrophic factors activate the microtubule-associated protein kinase pathway to stabilize microtubules, and this action significantly attenuates rotenone toxicity on dopaminergic neurons.
 ...
PMID:Neurotrophic factors stabilize microtubules and protect against rotenone toxicity on dopaminergic neurons. 1688 4

Altered function of gamma-aminobutyric acid type A receptors (GABA(A)Rs) in dentate granule cells of the hippocampus has been associated with temporal lobe epilepsy (TLE) in humans and in animal models of TLE. Such altered receptor function (including increased inhibition by zinc and lack of modulation by benzodiazepines) is related, in part, to changes in the mRNA levels of certain GABA(A)R subunits, including alpha4, and may play a role in epileptogenesis. The majority of GABA(A)Rs that contain alpha4 subunits are extra-synaptic due to lack of the gamma2 subunit and presence of delta. However, it has been hypothesized that seizure activity may result in expression of synaptic receptors with altered properties driven by an increased pool of alpha4 subunits. Results of our previous work suggests that signaling via protein kinase C (PKC) and early growth response factor 3 (Egr3) is the plasticity trigger for aberrant alpha4 subunit gene (GABRA4) expression after status epilepticus. We now report that brain derived neurotrophic factor (BDNF) is the endogenous signal that induces Egr3 expression via a PKC/MAPK-dependent pathway. Taken together with the fact that blockade of tyrosine kinase (Trk) neurotrophin receptors reduces basal GABRA4 promoter activity by 50%, our findings support a role for BDNF as the mediator of Egr3-induced GABRA4 regulation in developing neurons and epilepsy and, moreover, suggest that BDNF may alter inhibitory processing in the brain by regulating the balance between phasic and tonic inhibition.
 ...
PMID:Brain-derived neurotrophic factor (BDNF)-induced synthesis of early growth response factor 3 (Egr3) controls the levels of type A GABA receptor alpha 4 subunits in hippocampal neurons. 1690 9

Neurons in the adult rat dorsal root ganglion (DRG) can be classified into at least three separate subpopulations based on morphologic and phenotypic differences. In this study we have focused on the growth response of these specific subpopulations in vitro with respect to laminin (LN) and growth factor receptor activation. Using a cell selection approach we show that LN-induced neurite growth occurs in the absence of added trophic factors only in heavy-chain neurofilament-positive and calcitonin gene-related peptide-positive DRG neurons [nerve growth factor (NGF)-responsive population]. In contrast, LN alone is not sufficient to stimulate significant neurite growth from lectin Griffonia simplicifolia IB4-positive neurons (IB4+ve), although it is still required to elicit a growth response from these cells in the presence of glial-derived neurotrophic factor (GDNF, e.g. neurite growth occurred only when cells were plated on LN in the presence of GDNF). By using chemical inhibitors we demonstrate that only the phosphatidylinositol 3 kinase (PI 3-K)/Akt pathway is required for neurite growth from the NGF-responsive cell population. However, both the PI 3-K/Akt and MEK/mitogen-activated protein kinase signaling pathways are required for neurite growth from the IB4+ve cell population. Thus, we have identified specific signaling events and environmental requirements associated with neurite growth for different subpopulations of adult DRG neurons, pointing to potential therapeutic targets while identifying an inability for any one treatment alone to repair peripheral nerve damage.
 ...
PMID:Laminin and growth factor receptor activation stimulates differential growth responses in subpopulations of adult DRG neurons. 1693 Mar 99

The focus of our study was to determine the role of G protein-coupled receptor kinases (GRKs) and beta-arrestins in agonist-induced CB1 receptor modulation during cannabinoid tolerance and their dependence from the extracellular signal-regulated kinase (ERK) cascade. In wild-type mice, chronic Delta9-tetrahydrocannabinol (THC) exposure significantly activated specific GRK and beta- arrestin subunits in all the considered brain areas (striatum, cerebellum, hippocampus, and prefrontal cortex), suggesting their involvement in the adaptive processes underlying CB1 receptor downregulation and desensitization. These events were ERK-dependent in the striatum and cerebellum, because they were prevented in the genetic (Ras-GRF1 knockout mice) and pharmacological (SL327-pretreated mice) models of ERK activation inhibition, whereas in the hippocampus and prefrontal cortex, they appeared to be mostly ERK-independent. In the latter areas, ERK activation after chronic THC increased the transcription factors cyclic adenosine monophosphate response element-binding protein and Fos B as well as a downstream protein known as brainderived neurotrophic factor. As a whole, our data suggest that in the striatum and cerebellum, THC-induced ERK activation could represent a key signaling event to initiate homologous desensitization of CB1 receptor, accounting for the development of tolerance to THC-induced hypolocomotion. In the prefrontal cortex and hippocampus, THC-induced alteration in GRKs and beta-arrestins primarily depends on other kinases, whereas ERK activation could be part of the molecular adaptations that underlie the complex behavioral phenotype that defines the addicted state.
 ...
PMID:Changes in the expression of G protein-coupled receptor kinases and beta-arrestins in mouse brain during cannabinoid tolerance: a role for RAS-ERK cascade. 1695 96

Neurotrophic factors are a group of secreted proteins which generally regulate neurite outgrowth and synaptic development. SGP-1 has been reported as a neurotrophic factor, though little is known of its effect on neurite outgrowth, and it is unknown whether SGP-1 affects synaptic development. We report here that SGP-1 is distributed in vesicle-like puncta in somas and dendrites of primary neurons in culture, and that SGP-1 is secreted in culture and is taken up by endocytosis in dendrites. Endogenous extracellular activity of SGP-1 promotes dendritic, but not axonal outgrowth. Furthermore, endogenous activity of SGP-1 increases synaptogenesis in hippocampal neurons as determined by measuring the density and size of synaptophysin puncta and by determining the density of dendritic spines, their surface expression of GluR2 and their immunoreactivity for GluR1. The effect of SGP-1 on the amount of postsynaptic receptors in dendritic spines depends on synaptic activity and apparently on activation of MAPK, as inhibition of either of these abolished the affect. Hence, SGP-1 has neurotrophic effects, increasing dendritic growth and promoting synaptic development in an activity-dependent fashion.
 ...
PMID:SGP-1 increases dendritic and synaptic development dependent on synaptic activity. 1705 25

The RET receptor tyrosine kinase plays a critical role in the development of the enteric nervous system (ENS) and the kidney. Upon glial-cell-line-derived neurotrophic factor (GDNF) stimulation, RET can activate a variety of intracellular signals, including the Ras/mitogen-activated protein kinase, phosphatidylinositol 3-kinase (PI3K)/AKT, and RAC1/JUN NH(2)-terminal kinase (JNK) pathways. We recently demonstrated that the RAC1/JNK pathway is regulated by serine phosphorylation at the juxtamembrane region of RET in a cAMP-dependent manner. To determine the importance of cAMP-dependent modification of the RET signal in vivo, we generated mutant mice in which serine residue 697, a putative protein kinase A (PKA) phosphorylation site, was replaced with alanine (designated S697A mice). Homozygous S697A mutant mice lacked the ENS in the distal colon, resulting from a migration defect of enteric neural crest cells (ENCCs). In vitro organ culture showed an impaired chemoattractant response of the mutant ENCCs to GDNF. JNK activation by GDNF but not ERK, AKT and SRC activation was markedly reduced in neurons derived from the mutant mice. The JNK inhibitor SP600125 and the PKA inhibitor KT5720 suppressed migration of the ENCCs in cultured guts from wild-type mice to comparable degrees. Thus, these findings indicated that cAMP-dependent modification of RET function regulates the JNK signaling responsible for proper migration of the ENCCs in the developing gut.
 ...
PMID:Targeted mutation of serine 697 in the Ret tyrosine kinase causes migration defect of enteric neural crest cells. 1705 Jun 26

We investigated the neuroprotective effect of glial-derived neurotrophic factor (GDNF) upon alcohol-exposed B92 cultures, as well as the role of the cytoskeleton and mitogen-activated protein kinase (MAPK) pathways in this effect. Ethanol (EtOH) was added to cultures, either alone or in combination with 30 ng/ml GDNF. Exposure to EtOH (86 and 172 mM; 60 and 120 min) increased the frequency of apoptotic cells identified by nuclear DNA staining with 4,6-diamidino-2-phenylindole (DAPI). Cultures treated with GDNF showed a decrease in ethanol-induced apoptosis. A jun N-terminal kinase (JNK) pathway is activated by EtOH and their pharmacological inhibition (by SP600125) neutralized ethanol-induced apoptosis, suggesting a role for JNK in EtOH neurotoxicity. Immunocytochemically detected phospho-JNK (p-JNK) showed an unusual filamental expression, and localized together with actin stress fibers. Examination of the cytoskeleton showed that EtOH depolymerized actin filaments, inducing p-JNK dissociation and translocation to the nucleus, which suggests that released p-JNK may contribute to glial cell death after EtOH exposure. Treatment with GDNF, in turn, may neutralize the ethanol-induced cell death pathway. Either a phosphatidylinositol 3-kinase (PI3K)/AKT pathway inhibitor (LY294002) or an inhibitor of the extracellular signal-regulated kinase (ERK) 1, 2 pathways (UO126) failed to neutralize GDNF protective effects. However, the simultaneous use of both inhibitors blocked the protective effect of GDNF, suggesting a role for both signaling cascades in the GDNF protection. These findings provide further insight into the mechanism involved in ethanol-induced apoptosis and the neurotrophic protection of glial cells.
 ...
PMID:Glial-derived neurotrophic factor (GDNF) prevents ethanol (EtOH) induced B92 glial cell death by both PI3K/AKT and MEK/ERK signaling pathways. 1711 37


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