Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The epidermal growth factor (EGF) regulates cell proliferation, differentiation, and ion transport using ERK1/2 as a downstream effector. Furthermore, the EGF receptor (EGFR) is involved in signaling by G-protein-coupled receptors, growth hormone, and cytokines via transactivation. It has been suggested that steroids interact with peptide hormones. Previously, we have shown that aldosterone modulates EGF responses in Madin-Darby canine kidney cells (Gekle, M., Freudinger, R., Mildenberger, S., and Silbernagl, S. (2002) Am. J. Physiol. 282, F669-F679). Here, we tested the hypothesis that human EGFR-1 can confer alternative aldosterone responsiveness with respect to ERK1/2 phosphorylation to Chinese hamster ovary cells, which do not express EGFR. Wild-type Chinese hamster ovary cells did not respond to EGF or aldosterone. After transfection of human EGFR-1, the cells responded to EGF, but not to aldosterone. However, when submaximal concentrations of EGF were used, nanomolar concentrations of aldosterone potentiated the action of EGF within minutes, resulting in a leftward shift of the EGF dose-response curve. This was not the case in mock-transfected cells. The EGFR kinase inhibitor tyrphostin AG1478 or the MEK1/2 inhibitor U0126 completely prevented the effect. Furthermore, aldosterone enhanced Tyr phosphorylation of c-Src and EGFR, and an inhibitor of cytosolic tyrosine kinases (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyriociaine) prevented the action of aldosterone. Our data show that aldosterone uses the EGF-EGFR-MEK1/2-ERK1/2 signaling cascade to elicit its alternative effects. In the presence of EGF, aldosterone leads to EGFR transactivation via cytosolic tyrosine kinases of the Src family.
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PMID:Human epidermal growth factor receptor-1 expression renders Chinese hamster ovary cells sensitive to alternative aldosterone signaling. 1224 20

Stimulation of the beta(2)-adrenergic receptor (beta(2)AR) in human embryonic kidney (HEK) 293 cells causes a transient activation of Extracellular Signal-Regulated Kinase (ERK) 1/2. One of the mechanisms proposed for this activation is a PKA-mediated phosphorylation of the beta(2)AR that switches receptor coupling from G(s) to G(i) and triggers internalization of the receptor. To examine these phenomena, we characterized agonist activation of ERK1/2 in HEK293 cells by the endogenous beta(2)AR and in HEK293 cells stably overexpressing either the wild-type beta(2)AR or a substitution mutant beta(2)AR (PKA(-)) that lacks the cyclic AMP-dependent protein kinase (PKA) consensus phosphorylation sites (S261A, S262A and S345A, S346A). As the baseline, we established that epinephrine stimulation of the endogenous beta(2)AR in HEK293 cells (20-30 fmol/mg) caused a rapid and transient activation of ERK1/2 with an EC(50) of 5 to 6 nM. In contrast, the potency of epinephrine stimulation of ERK1/2 in cells stably overexpressing WTbeta(2)AR and PKA(-) (2-4 pmol of beta(2)AR/mg) was increased by over 100-fold relative to HEK293 cells, the EC(50) values being 20 to 60 pM. The nearly identical 100-fold shift in EC(50) for ERK1/2 activation in the PKA(-) and WTbeta(2)AR relative to that in the HEK293 showed that the PKA(-) are fully capable of activating ERK1/2. We also found maximal activation of ERK1/2 in the overexpressing cell lines at concentrations of epinephrine that cause no internalization (i.e., the EC(50) for internalization was 75 nM). Pertussis toxin pretreatment caused only a weak inhibition of epinephrine activation of ERK1/2 in the HEK293 (7-16%) and no inhibition in the PKA(-) cells. Finally we found that the Src family kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (10 microM) caused a >90% inhibition of epinephrine or forskolin activation of ERK1/2 in both cell lines. Our results indicate that the dominant mechanism of beta(2)AR activation of ERK1/2 does not require PKA phosphorylation of the beta(2)AR, receptor internalization or switching from activation of G(s) to G(i) but clearly requires activation of a Src family member that may be downstream of PKA.
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PMID:Beta(2)-adrenergic receptor lacking the cyclic AMP-dependent protein kinase consensus sites fully activates extracellular signal-regulated kinase 1/2 in human embryonic kidney 293 cells: lack of evidence for G(s)/G(i) switching. 1239 Dec 72

4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]- pyrimidine (PP1) was identified as an Src-selective tyrosine kinase inhibitor and has been used extensively to investigate signaling pathways involving Src kinases, including events downstream of the stem cell factor (SCF) receptor c-Kit. While investigating the role of Src kinases in SCF signaling, we found that PP1 completely abrogated the proliferation of M07e cells in response to SCF. PP1 inhibited SCF-induced c-Kit autophosphorylation in intact cells and blocked the activation of mitogen-activated protein kinase and Akt. In vitro kinase assays using immunoprecipitated c-Kit confirmed direct inhibition by PP1. SCF-induced c-Kit phosphorylation was also inhibited by the related inhibitor 4-amino-5- (4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]-pyrimidine (PP2) and by STI571 but not by the Src inhibitor SU6656. PP1 inhibited the activity of mutant constitutively active forms of c-Kit (D814V and D814Y) found in mast cell disorders, and triggered apoptosis in the rat basophilic leukemia cell line RBL-2H3 that expresses mutant c-Kit. In addition, PP1 (and PP2) inhibited the in vitro kinase activity and autophosphorylation in whole cells of p210 Bcr-Abl. PP1 reduced the constitutive activation of signal transducer and activators of transcription 5 and mitogen-activated protein kinase and triggered apoptosis in FDCP1 cells expressing Bcr-Abl. These results have implications for the use of PP1 in investigating intracellular signaling and suggest that PP1 or related compounds may be useful in the treatment of malignant diseases associated with dysregulated c-Kit or Abl tyrosine kinase activity.
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PMID:The Src-selective kinase inhibitor PP1 also inhibits Kit and Bcr-Abl tyrosine kinases. 1247 82

We have recently demonstrated that multiple signalling pathways are involved in thrombin-induced proliferation in rat astrocytes. Thrombin acts by protease-activated receptor-1 (PAR-1) via mitogen-activated protein kinase activity. Signalling includes both Gi/(betagamma subunits)-phosphatidylinositol 3-kinase and a Gq-phospholipase C/Ca2+/protein kinase C (PKC) pathway. In the present study, we investigated the possible protein tyrosine kinases which might be involved in thrombin signalling cascades. We found that, in astrocytes, thrombin can evoke phosphorylation of proline-rich tyrosine kinase (Pyk2) via PAR-1. This process is dependent on the increase in intracellular Ca2+ and PKC activity. Moreover, in response to thrombin stimulation Pyk2 formed a complex with Src tyrosine kinase and adapter protein growth factor receptor-bound protein 2 (Grb2), which could be coprecipitated. Furthermore, both thrombin-induced Pyk2 phosphorylation and extracellular signal-regulated kinase (ERK) 1/2 phosphorylation can be attenuated by Src kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine. From these data we conclude that PAR-1 uses Ca2+- and PKC-dependent Pyk2 to activate Src, thereby leading to ERK1/2 activation, which predominantly recruits Grb2 in rat astrocytes.
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PMID:The role of the Ca2+-sensitive tyrosine kinase Pyk2 and Src in thrombin signalling in rat astrocytes. 1261 35

In the present study, we observed evidence of cross-talk between the cannabinoid receptor CB1 and the orexin 1 receptor (OX1R) using a heterologous system. When the two receptors are co-expressed, we observed a major CB1-dependent enhancement of the orexin A potency to activate the mitogen-activated protein kinase pathway; dose-responses curves indicated a 100-fold increase in the potency of orexin-mediated mitogen-activated protein kinase activation. This effect required a functional CB1 receptor as evidenced by the blockade of the orexin response by the specific CB1 antagonist, N-(piperidino-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-pyrazole-3-carboxamide (SR141716), but also by pertussis toxin, suggesting that this potentiation is Gi-mediated. In contrast to OX1R, the potency of direct activation of CB1 was not affected by co-expression with OX1R. In addition, electron microscopy experiments revealed that CB1 and OX1R are closely apposed at the plasma membrane level; they are close enough to form hetero-oligomers. Altogether, for the first time our data provide evidence that CB1 is able to potentiate an orexigenic receptor. Considering the antiobesity effect of SR141716, these results open new avenues to understand the mechanism by which the molecule may prevent weight gain through functional interaction between CB1 and other receptors involved in the control of appetite.
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PMID:Hypersensitization of the Orexin 1 receptor by the CB1 receptor: evidence for cross-talk blocked by the specific CB1 antagonist, SR141716. 1269 Jan 15

We have studied whether activation of cell adhesion kinase beta (CAKbeta) is involved in stretch-induced signaling pathway in cultured rat vascular smooth muscle cells. Cyclic stretch (1 Hz) induced a rapid (within 1 min) phosphorylation of CAKbeta, whose effect was time and strength dependent. Both Ca(2+) and Na(+) ionophores (A23187 and monensin) stimulated phosphorylation of CAKbeta in a similar fashion to mechanical stretch. The stretch-induced phosphorylation of CAKbeta was inhibited completely by an intracellular Ca(2+) chelator [1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester)] and largely by gadolinium, but only partially by an extracellular Ca(2+) chelator (EGTA). An angiotensin type 1 receptor antagonist (CV11974) abolished the phosphorylation of CAKbeta stimulated by angiotensin II, but not by mechanical stretch. Mechanical stretch rapidly (within 1 min) increased the association of CAKbeta with c-Src, but not pp125(focal adhesion kinase). Stretch-induced phosphorylation of ERK1/2 was inhibited by EGTA and an inhibitor of the Src kinase family [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine], but not by cytochalasin D, to disrupt actin polymerization. 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine or cytochalasin D did not affect stretch-induced phosphorylation of CAKbeta. These data suggest that mechanical stretch stimulates activation of CAKbeta, followed by its association with c-Src, which requires ion influx mainly via stretch-activated nonselective ion channels, thereby leading to activation of the p21(Ras)/ERK1/2 cascade in vascular smooth muscle cells.
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PMID:Activation of cell adhesion kinase beta by mechanical stretch in vascular smooth muscle cells. 1274 90

After a brain insult, ATP is released from injured cells and activates microglia. The microglia that are activated in this way then release a range of bioactive substances, one of which is tumor necrosis factor (TNF). The release of TNF appears to be dependent on the P2X7 receptor. The inhibitors 1,4-diamino-2,3-dicyano-1,4-bis[2-amino-phenylthio]butadiene (U0126), anthra[1,9-cd]pyrazol-6(2H)-one (SP600125), and 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)IH-imidazole (SB203580), which target MEK (mitogen-activated protein kinase kinase), JNK (c-Jun N-terminal kinase), and p38, respectively, all potently suppress the production of TNF in ATP-stimulated microglia, whereas the production of TNF mRNA is strongly inhibited by U0126 and SP600125. SB203580 did not affect the increased levels of TNF mRNA but did prevent TNF mRNA from accumulating in the cytoplasm. The ATP-provoked activation of JNK and p38 [but not extracellular signal-regulated kinase (ERK)] could be inhibited by brilliant blue G, a P2X7 receptor blocker, and by genistein and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, which are general and src-family-specific tyrosine kinase inhibitors, respectively. Most important, we found that treatment of the microglia in neuron-microglia cocultures with the P2X7 agonist 2'-3'-O-(benzoyl-benzoyl) ATP led to significant reductions in glutamate-induced neuronal cell death, and that either TNF-alpha converting enzyme inhibitor or anti-TNF readily suppressed the protective effect implied by this result. Together, these findings indicate that both ERK and JNK are involved in the regulation of TNF mRNA expression, that p38 is involved in the nucleocytoplasmic transport of TNF mRNA, and that a PTK (protein tyrosine kinase), possibly a member of the src family, acts downstream of the P2X7 receptor to activate JNK and p38. Finally, our data suggest that P2X7 receptor-activated microglia protect neurons against glutamate toxicity primarily because they are able to release TNF.
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PMID:Production and release of neuroprotective tumor necrosis factor by P2X7 receptor-activated microglia. 1471 32

Transient stimulation of group I metabotropic glutamate receptors (mGluRs) induces persistent prolonged epileptiform discharges in hippocampal slices via a protein synthesis-dependent process. At present, the signaling process underlying the induction of these epileptiform discharges remains unknown. We examined the possible role of extracellular signal-regulated kinases (ERK1 and ERK2) because these kinases can be activated by group I mGluRs, and their activation may regulate gene expression and alter protein synthesis. The group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG; 50 microm) induced activation of ERK1/2 in hippocampal slices. 2-(2-Diamino-3-methoxyphenyl-4H-1-benzopyran-4-one (PD98059) (50 microm) a specific inhibitor of mitogen-activated protein kinase kinase (MEK), suppressed ERK1/2 activation by DHPG. PD98059 or another MEK inhibitor, 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene (10 microm), also prevented the induction of the prolonged epileptiform discharges by DHPG. In the presence of ionotropic glutamate receptor inhibitors and tetrodotoxin (blockers), DHPG-induced epileptiform discharges were suppressed, whereas ERK1/2 activation persisted. Protein kinase C inhibitors (2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]-3-(1H-indol-3-yl) maleimide, 1 microm; or chelerythrine, 10 microm) did not prevent the generation of DHPG-induced epileptiform discharges, nor did they suppress the activation of ERK1/2 by DHPG in slices pretreated with the blockers. Genistein (30 microm), a broad-spectrum tyrosine kinase inhibitor, suppressed the DHPG-induced epileptiform discharges and the ERK1/2 activation in the presence of blockers. Induction of DHPG-mediated epileptiform discharges was also suppressed by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-D]pyrimidine (10 microm), an Src-family tyrosine kinase inhibitor. The study shows that group I mGluRs activate ERK1/2 through a tyrosine kinase-dependent process and that this activation of ERK1/2 is necessary for the induction of prolonged epileptiform discharges in the hippocampus.
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PMID:Extracellular signal-regulated kinase 1/2 is required for the induction of group I metabotropic glutamate receptor-mediated epileptiform discharges. 1471 40

S32504 [(+)-trans-3,4,4a,5,6,10b-hexahydro-9-carbamoyl-4-propyl-2H-naphth[1,2-b]-1,4-oxazine] displayed marked affinity for cloned, human (h)D(3) receptors (pK(i), 8.1) at which, in total G-protein ([(35)S]GTPgammaS binding, guanosine-5'-O-(3-[(35)S]thio)-triphosphate), Galpha(i3) (antibody capture/scintillation proximity), and mitogen-activated protein kinase (immunoblot) activation procedures, it behaved as an agonist: pEC(50) values, 8.7, 8.6, and 8.5, respectively. These actions were blocked by haloperidol and the selective D(3) receptor antagonist S33084 [(3aR,9bS)-N-[4-(8-cyano-1,3a,4,9b-tetrahydro-3H-benzopyrano[3,4-c]pyrrole-2-yl)-butyl]-(4-phenyl) benzamide)]. S32504 showed lower potency at hD(2S) and hD(2L) receptors in [(35)S]GTPgammaS binding (pEC(50) values, 6.4 and 6.7) and antibody capture/scintillation proximity (hD(2L), pEC(50), 6.6) procedures. However, reflecting signal amplification, it potently stimulated hD(2L) receptor-coupled mitogen-activated protein kinase (pEC(50), 8.6). These actions were blocked by haloperidol and the selective D(2) receptor antagonist L741,626 [4-(4-chlorophenyl)-1-(1H-indol-3-ylmethyl)piperidin-4-ol]. The affinity of S32504 for hD(4) receptors was low (5.3) and negligible for hD(1) and hD(5) receptors (pK(i), <5.0). S32504 showed weak agonist properties at serotonin(1A) ([(35)S]GTPgammaS binding, pEC(50), 5.0) and serotonin(2A) (G(q), pEC(50), 5.2) receptors and low affinity for other (>50) sites. In anesthetized rats, S32504 (0.0025-0.01 mg/kg, i.v.) suppressed electrical activity of ventrotegmental dopaminergic neurons. Correspondingly, S32504 (0.0025-0.63 mg/kg, s.c.) potently reduced dialysis levels (and synthesis) of dopamine in striatum, nucleus accumbens, and frontal cortex of freely moving rats, actions blocked by haloperidol and L741,626 but not by S33084. In contrast, S32504 only weakly inhibited serotonergic transmission and failed to affect noradrenergic transmission. Actions of S32504 were expressed stereospecifically versus its less active enantiomer S32601 [(-)-trans-3,4,4a,5,6,10b-hexahydro-9-carbomoyl-4-propyl-2H-naphth[1,2-b]-1,4-oxazine]. Although the D(3)/D(2) agonist and antiparkinsonian agent ropinirole mimicked the profile of S32504, it was less potent. In conclusion, S32504 is a potent and selective agonist at dopamine D(3) and D(2) receptors.
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PMID:S32504, a novel naphtoxazine agonist at dopamine D3/D2 receptors: I. Cellular, electrophysiological, and neurochemical profile in comparison with ropinirole. 1497 94

1. Neutrophil adhesion regulates a number of processes involved in the pathogenesis of inflammatory diseases including rheumatoid arthritis. Neutrophil destructive potential can be modulated by adhesion, allowing alteration of inflammatory cell behaviour while preserving antimicrobial defences. beta(2)-Integrin-mediated neutrophil adhesion to albumin-coated latex beads (ACLB) allows modulation of integrin clustering and ligation and analysis of the effects of adhesion on neutrophil responses. Tumour necrosis factor-alpha (TNF alpha) enhanced neutrophil binding of different diameter ACLB equally, by almost four-fold, and independently of bead size. Adhesion of neutrophils to ACLB caused a size-dependent generation and release of O(2)(-) and also potentiated TNF alpha-induced O(2)(-) release. 2. Binding of ACLB was not affected by disruption of cytoskeletal integrity with nocodazole or cytochalasin D or following blockade of tyrosine kinase activity. In contrast, tyrosine phosphorylation and an intact cytoskeleton were essential for adhesion- and cytokine-induced O(2)(-) release from neutrophils. Inhibition of adhesion- and cytokine-induced O(2)(-) release by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]pyrimidine (PP2) indicated that a Src-family tyrosine kinase was the principal regulatory pathway mediating this response in neutrophils, a distal role for p38 MAPK was revealed by use of SB203580. 3. Tyrosine phosphorylation of c-Fgr, a Src-family tyrosine kinase, occurred following ACLB adhesion and exposure to TNF alpha, and was susceptible to inhibition by PP2. We suggest that activation of the key regulatory enzyme c-Fgr is achieved following ligation of a critical threshold of integrins following binding of large (>3 microM) ACLB.
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PMID:A critical 'threshold' of beta 2-integrin engagement regulates augmentation of cytokine-mediated superoxide anion release. 1500 1


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