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)

PD 089828, a novel protein tyrosine kinase inhibitor of a new structural class, the 6-aryl-pyrido-[2,3-d]pyrimidines, was identified by screening a compound library with assays that measured protein tyrosine kinase activity. PD 089828 was found to inhibit human full-length fibroblast growth factor (FGF) receptor-1 (FGFR-1), platelet-derived growth factor (PDGF) receptor beta subunit (PDGFR-beta), Src nonreceptor tyrosine kinase (c-Src) and epidermal growth factor (EGF) receptor (EGFR) tyrosine kinases with half-maximal inhibitory potencies (IC50 values) of 0.15 +/- 0.02 (n = 4), 0.18 +/- 0.04 (n = 3), 1.76 +/- 0.28 (n = 4) and 5.47 +/- 0.78 (n = 6) microM, respectively. PD 089828 was further characterized as an ATP competitive inhibitor of the growth factor receptor tyrosine kinases (FGFR-1, PDGFR-beta and EGFR) but a noncompetitive inhibitor of c-Src tyrosine kinase with respect to ATP. In addition, PD 089828 inhibited PDGF- and EGF-stimulated receptor autophosphorylation in vascular SMC (VSMC) and basic FGF-mediated tyrosine phosphorylation in A121 cells with IC50 values similar to the potencies observed for inhibition of receptor tyrosine kinase activity. The inhibition of PDGF receptor autophosphorylation in VSMC by PD 089828 occurred rapidly, with maximal effects reached within 5 min of drug exposure. Inhibition after single exposure was long lasting but also rapidly reversible, occurring within 5 min after drug removal. The PDGF-induced association of downstream signaling proteins, including phosphoinositide-3-kinase (PI-3K), growth factor receptor binding protein-2 (GRB2), SH-2 domain and collagen like (Shc) and phospholipase Cgamma (PLCgamma), with VSMC PDGF receptors was also blocked as a result of the inhibition of PDGF-stimulated receptor autophosphorylation by PD 089828. PD 089828 also inhibited the PDGF-induced tyrosine phosphorylation of the 44- and 42-kDa mitogen-activated protein kinase isoforms. Moreover, the effects of PD 089828 were demonstrated in functional assays in which PDGF-stimulated DNA synthesis, PDGF-directed migration and serum-stimulated growth of VSMC were all inhibited to the same extent as PDGF receptor autophosphorylation (IC50 = 0.8, 4.5 and 1.8 microM, respectively). These results highlight the biological characteristics of PD 089828 as a novel, broadly active protein tyrosine kinase inhibitor with long-lasting but reversible cellular effects. The potential therapeutic use of these broadly acting, nonselective inhibitors as antiproliferative and antimigratory agents could extend to such diseases as cancer, atherosclerosis and restenosis in which redundancies in growth-signaling pathways are known to exist.
 ...
PMID:Inhibition of growth factor-mediated tyrosine phosphorylation in vascular smooth muscle by PD 089828, a new synthetic protein tyrosine kinase inhibitor. 919 Aug 82

To determine whether p185HER2 overexpression per se triggers p185HER2 cellular signaling or whether an extracellular signal is required, we transfected PC12 cells with the human erbB-2 proto-oncogene, and established a cell line that overexpresses p185HER2. PC12-HER2 cells, maintained in suspension culture or plated on a collagen layer, showed the same morphology and growth rate as PC12 and PC12 mock-transfected control cells. When treated with monoclonal antibody (MAb) MGr6 or other anti-p185HER2 MAbs, PC12-HER2 cells specifically underwent neuronal differentiation comparable to that induced by nerve growth factor (NGF), and the differentiation-inducing effect of the MAb was dramatically enhanced by the addition of a second anti-mouse IgG. MAb-induced cell differentiation correlated with p185HER2 phosphorylation, recruitment of Shc and Grb-2 transducer molecules into complexes, and MAPK phosphorylation. These data indicate the requirement for a specific binding-induced activation of the overexpressed p185HER2 receptor in inducing PC12 cell differentiation. PC12-HER2 cells represent a suitable system for selection of p185HER2-activating ligands (peptides, phage-displayed peptides or proteins) or specific inhibitors of its tyrosine kinase activity.
 ...
PMID:Binding-induced activation of overexpressed p185HER2 is essential in triggering neuronal differentiation of PC12 cells. 936 Nov 87

The effects of activating the Gq protein-coupled cholecystokinin (CCK) receptor on different proteins/signaling molecules in the mitogen-activated protein kinase (MAPK) cascade in pancreatic acinar cells were analyzed and compared with the effects of activating the tyrosine kinase-coupled epidermal growth factor (EGF) receptor. Both EGF and CCK octapeptide rapidly increased the activity of the MAPKs [extracellular signal-regulated kinase (ERK) 1 and ERK2], reaching a maximum within 2.5 min when 3.9- and 8.5-fold increases, respectively, were observed. The EGF-induced increase of MAPK activity was transient, with only a slight elevation after 30 min, whereas CCK-stimulated MAPK remained at a high level of activation to 60 min. The protein kinase C inhibitor GF-109203X abolished the activation by phorbol ester and inhibited the effect of CCK by 78% but had no effect on EGF-activated MAPK activity. EGF and CCK activated both forms of MAPK kinase (MEK), with CCK having a much larger effect, activating MEK1 by 6-fold and MEK2 by 10-fold, whereas EGF activated both MEKs by only 2-fold. Immunoblotting revealed three different forms of Raf in pancreatic acinar cells. Of the total basal Raf kinase activity, 3.7% was Raf-A, 89.0% was Raf-B, and 7.3% was c-Raf-1. All three forms of Raf were stimulated to a greater extent by CCK than by EGF, which was especially evident for Raf-A and c-Raf-1. The effect of CCK in activating Rafs was at least partially mimicked by stimulation with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. EGF significantly increased GTP-bound Ras by 183 and 164% at 2.5 and 10 min, respectively; CCK and TPA had no measurable effect. Our study suggests that CCK and EGF activate the MAPK cascade by distinct mechanisms in pancreatic acinar cells.
 ...
PMID:Cholecystokinin and EGF activate a MAPK cascade by different mechanisms in rat pancreatic acinar cells. 937 31

The epidermal growth factor (EGF) receptor mediates the effects of both EGF and transforming growth factor alpha (TGFalpha). Recent data suggested that EGF acts as a partial agonist/antagonist in hepatocytes, TGFalpha exerting a larger maximal stimulation of DNA synthesis than EGF. To further study the mechanisms involved in mediating the different effects of EGF and TGFalpha, we have examined receptor binding of the two growth factors and their action on the p42/p44 mitogen-activated protein (MAP) kinase activity in hepatocytes. Single-ligand concentration curves and competition experiments showed that the binding affinity to a common population of surface binding sites was about 20-fold lower for TGFalpha than for EGF. MAP kinase activity responded to EGF and TGFalpha with different kinetics. While the two agents produced almost identical acute (5 min) stimulation (peak about fivefold), TGFalpha produced a more sustained MAP kinase activity than EGF. The difference between EGF and TGFalpha was still detectable 24 h after growth factor addition. The results show that in hepatocytes a lower receptor affinity of TGFalpha, as compared to EGF, is associated with a more sustained activation of the MAP kinase and a greater efficacy in the stimulation of DNA synthesis. This suggests that differential interaction of these two agents with the EGF receptor results in differences in the downstream events elicited at a given level of receptor occupancy. The data also are compatible with a role of a prolonged MAP kinase activity in the mitogenic effects of EGF and TGFalpha.
 ...
PMID:Response to transforming growth factor alpha (TGFalpha) and epidermal growth factor (EGF) in hepatocytes: lower EGF receptor affinity of TGFalpha is associated with more sustained activation of p42/p44 mitogen-activated protein kinase and greater efficacy in stimulation of DNA synthesis. 949 76

We have recently reported that angiotensin II (Ang II)-induced mitogen-activated protein kinase (MAPK) activation is mainly mediated by Ca2+-dependent activation of a protein tyrosine kinase through Gq-coupled Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMC). In the present study, we found Ang II rapidly induced the tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and its association with Shc and Grb2. These reactions were inhibited by the EGF receptor kinase inhibitor, AG1478. The Ang II-induced phosphorylation of the EGF receptor was mimicked by a Ca2+ ionophore and completely inhibited by an intracellular Ca2+ chelator. Thus, AG1478 abolished the MAPK activation induced by Ang II, a Ca2+ ionophore as well as EGF but not by a phorbol ester or platelet-derived growth factor-BB in the VSMC. Moreover, Ang II induced association of EGF receptor with catalytically active c-Src. This reaction was not affected by AG1478. These data indicate that Ang II induces Ca2+-dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.
 ...
PMID:Calcium-dependent epidermal growth factor receptor transactivation mediates the angiotensin II-induced mitogen-activated protein kinase activation in vascular smooth muscle cells. 953 70

The interruption of signaling cascades in intact cells through the introduction of nonpermeant compounds inferred by in vitro studies to specifically inhibit epidermal growth factor (EGF) receptor (EGF-R) function is described. Two nonpermeant [(alkylamino)methyl]acrylophenone derivatives, [(dimethylamino)methyl] acrylo-para-[(benzoylsulfonyl)-oxy]phenone and [(dimethylamino)-methyl]acrylo-para-[(hydroxy-benzoylsulfonyl++ +)-oxy]phenone, were introduced by in situ electroporation into mouse or rat fibroblasts growing on indium-tin oxide-coated glass. Cells were subsequently stimulated with growth factors and assessed for activation of a downstream target, the extracellular signal-regulated kinase (ERK1/2), by probing with specific antibodies. Electrodes and slides were configured to provide non-electroporated control cells side by side with the electroporated ones, both growing on the same type of indium-tin oxide-coated glass surface. Using this set-up, these compounds could inhibit EGF- but not platelet-derived growth factor (PDGF)-mediated ERK1/2 activation in vivo. These results demonstrate the potential of the in situ electroporation approach for the study of tyrosine kinase action using selective but nonpermeant inhibitors that would otherwise be ineffective in intact cells.
 ...
PMID:Inhibition of epidermal growth factor-mediated ERK1/2 activation by in situ electroporation of nonpermeant [(alkylamino)methyl]acrylophenone derivatives. 953 6

The receptor kinase activity associated with the epidermal growth factor (EGF) receptor and platelet-derived growth factor (PDGF) receptor plays an important role in ligand-induced signaling events. The effect of specific, synthetic chemical inhibitors of PDGF- and EGF-mediated receptor tyrosine autophosphorylation on receptor signaling were examined in NIH 3T3 cells overexpressing PDGF or EGF receptors. Specific inhibition of ligand-dependent receptor autophosphorylation, PI3K activation, mitogen-activated protein kinase (MAPK) activation, cyclin E-associated kinase activity and cell proliferation was measured after treatment of cells with these inhibitors. A synthetic PDGF receptor kinase inhibitor exhibited specific inhibitory properties when tested for PDGF-induced receptor autophosphorylation, MAPK activity, PI3K activation, entry into S phase and cyclin E-associated kinase activity. A synthetic EGF receptor kinase inhibitor showed selective inhibitor properties when tested for EGF-induced receptor autophosphorylation, MAPK activation, PI3K activation, entry into S phase and cyclin E-associated kinase activity. In both cases, these compounds were found to be effective as inducers of growth arrest and accumulation of cells in the G1 phase of the cell cycle after ligand treatment. However, at high concentrations, the EGF receptor kinase inhibitor was observed to exhibit some nonspecific effects as demonstrated by attenuation of PDGF-induced receptor autophosphorylation and cell cycle progression. This demonstrates that it is critical to use the lowest concentration of such an inhibitor that will alter the response under investigation, to have confidence that the conclusions derived from the use of such inhibitor are valid. We conclude that these experimental parameters signify useful end points to measure the relative selectivity of tyrosine kinase inhibitors that affect receptor-mediated signal transduction.
 ...
PMID:Inhibition of platelet-derived growth factor and epidermal growth factor receptor signaling events after treatment of cells with specific synthetic inhibitors of tyrosine kinase phosphorylation. 958 Jun 35

In C3H/10T1/2 murine fibroblasts, overexpression of both c-Src and the human epidermal growth factor (EGF) receptor 1 (HER1) is required for detection of stable complexes between the two molecules and results in hyperactivation of the receptor and synergistic increases in tumor formation in nude mice, as compared with cells that overexpress only one of the pair. Elevated levels or activities of c-Src and HER1 also occur in a subset of later-stage breast cancers, suggesting that interactions between these two molecules could contribute to a more aggressive clinical course. To determine whether stable complexes between c-Src and HER1 occur in human breast cancers under the same conditions as in murine fibroblasts and whether the appearance of such complexes correlates with enhanced signaling through the EGF receptor and increased tumor growth, human breast tumor cell lines and tumor tissues were analyzed for a number of c-Src/HER1-mediated signaling events and tumorigenicity. In a panel of 14 cell lines, 10 overexpressed c-Src, and of these, five contained elevated levels of HER1 and exhibited an EGF-dependent association between HER1 and c-Src. This association was also present in a HER1/c-Src-overexpressing tumor sample from a breast cancer patient. Further analysis of signaling events revealed that phosphorylation of the HER1 substrate, Shc, and its downstream effector, mitogen-activated protein kinase, was increased in EGF-stimulated MDA-MB-468, MDA-MB-231, and BT-549 cells (which overexpress both c-Src and HER1) as compared with MCF7 and ZR-75-1 cells (which only overexpress c-Src). Furthermore, MDA-MB-468 and MDA-MB-231 cells displayed increased tumorigenicity in nude mice. These results support the hypothesis that c-Src/HER1 interactions contribute to tumor progression in certain late-stage breast tumor cells.
 ...
PMID:Characterization of human epidermal growth factor receptor and c-Src interactions in human breast tumor cells. 958 56

Recent evidence indicates that the epidermal growth factor (EGF) receptor mediates a branch of lysophosphatidic acid (LPA)-induced signal transduction pathways that activate mitogen-activated protein (MAP) kinase. However, it is unclear whether the intrinsic tyrosine kinase activity of EGF receptor is involved. We previously showed that reactive oxygen species (ROS) were involved in the LPA-stimulated MAP kinase pathway. Here, we identify tyrosine phosphorylation of EGF receptor as an LPA signaling step that requires ROS. To evaluate the role of the tyrosine kinase activity of EGF receptor in the LPA-stimulated MAP kinase pathway, we examined the effects of an EGF receptor-specific tyrosine kinase inhibitor, PD158780. PD158780 potently inhibited the LPA-stimulated MAP kinase kinase 1/2 (MKK1/2) activation and EGF receptor tyrosine phosphorylation in HeLa cells, while it had no detectable effect on c-Src kinase activity. PD158780 also inhibited LPA-induced MKK1/2 activation and DNA synthesis in NIH 3T3 cells. Furthermore, we compared LPA-stimulated MKK1/2 and MAP kinase activation, transcriptional activity of the c-fos promoter, and DNA synthesis in B82L cells, which lack endogenous EGF receptor, and B82L cells expressing kinase-defective or wild-type human EGF receptor. Results obtained from analysis of these cell lines suggest that the EGF receptor tyrosine kinase contributes to the LPA-stimulated MAP kinase activation, c-fos transcription, and mitogenesis.
 ...
PMID:Role of tyrosine kinase activity of epidermal growth factor receptor in the lysophosphatidic acid-stimulated mitogen-activated protein kinase pathway. 960 60

Src transformation of NIH3T3 mouse fibroblasts has been shown to be dependent on Ras function. Since we recently showed that the signaling pathways that mediate Ras transformation of RIE-1 rat intestinal epithelial cells are distinct from those that cause Ras transformation of fibroblasts, we utilized three approaches to determine if Src transformation of RIE-1 cells is dependent on Ras. First, although both Ras and Src cause upregulation of an epidermal growth factor (EGF) receptor-dependent autocrine growth loop, only Ras transformation required this activity. Second, whereas both Src and Ras caused upregulation of the p42 and p44 mitogen-activated protein kinases (MAPKs), only Ras transformation was blocked by the inhibition of MAPK activation by treatment with the PD 98059 MEK inhibitor. Third, treatment with the farnesyltransferase inhibitor FTI-277 blocked Ras, but not Src, transformation. Taken together, these observations suggest that Src transformation of RIE-1 cells is not dependent on Ras. Finally, we determined that Ras activation of Raf-independent pathways alone is sufficient to cause growth transformation of RIE-1 cells. Thus, both Ras and Src cause transformation of RIE-1 cells via pathways distinct from those required to cause transformation of NIH3T3 cells.
 ...
PMID:Ras, but not Src, transformation of RIE-1 epithelial cells is dependent on activation of the mitogen-activated protein kinase cascade. 963 33


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