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

The type-III deletion variant of the epidermal growth factor receptor (EGFRvIII) is frequently found in glioblastomas and other malignant human tumours. Although EGFRvIII confers ligand-independent oncogenic transformation of cell lines, the mechanism by which it promotes aberrant cellular proliferation is unknown. Using cell lines expressing comparable numbers of either wild-type receptor (EGFRwt) or EGFRvIII, we compared several parameters of receptor activation: dimerization, tyrosine phosphorylation and activation of intracellular signalling proteins. Like activated EGFRwt, EGFRvIII was phosphorylated and bound constitutively to the Shc adapter protein. Indeed, EGFRvIII-associated Shc had a higher phosphotyrosine content than Shc associated with stimulated EGFRwt. EGFRwt dimerized in response to either EGF or transforming growth factor alpha. Higher cross-linker concentrations and incubation at higher temperatures (37 degrees C) allowed detection of EGFRwt dimers even in the absence of exogenous ligand. In contrast, EGFRvIII failed to dimerize under any conditions studied. Moreover, neither mitogen-activated protein kinase nor phospholipase Cgamma were phosphorylated in EGFRvIII-expressing cells. We conclude that the deletion of 267 amino acids from the 621-amino-acid N-terminal domain of EGFR does not result simply in a constitutively activated receptor, but alters the spectrum of signalling cascades utilized. Furthermore the ligand-independent transforming activity of EGFRvIII is independent of receptor dimerization.
 ...
PMID:Receptor dimerization is not a factor in the signalling activity of a transforming variant epidermal growth factor receptor (EGFRvIII). 921 Apr 10

We found that natural (long-chain) ceramide 1-phosphate can be dispersed into aqueous solution when dissolved in an appropriate mixture of methanol/dodecane (49:1, v/v). This solvent mixture facilitates the interaction of this phosphosphingolipid with cells. Under these conditions, incubation of EGFR T17 fibroblasts with natural ceramide 1-phosphate caused a potent stimulation of DNA synthesis. This effect was accompanied by an increase in the levels of proliferating-cell nuclear antigen. Concentrations of natural ceramide 1-phosphate that stimulated the synthesis of DNA did not inhibit adenylate cyclase activity, nor did they stimulate phospholipase D. Natural ceramide 1-phosphate did not alter the cellular phosphorylation state of tyrosine residues or of mitogen-activated protein kinase. Furthermore, natural ceramide 1-phosphate failed to induce the expression of the proto-oncogenes c-myc and c-fos. Both the stimulation of DNA synthesis and the induction of proliferating-cell nuclear antigen by natural ceramide 1-phosphate were inhibited by natural ceramides. This work suggests that the use of methanol and dodecane to deliver natural ceramide 1-phosphate to cells may be useful for elucidation of the biological function(s) and mechanism(s) of action of ceramide 1-phosphate.
 ...
PMID:Stimulation of DNA synthesis by natural ceramide 1-phosphate. 923 Jan 25

Prostate carcinoma (PCA) is the most commonly diagnosed malignancy in American men. Our knowledge of PCA growth regulation lags behind that of other cancers, such as breast and colon carcinomas. Among receptor tyrosine kinases, the ErbB family is most frequently implicated in neoplasia. We report here the expression of ErbB family kinases and their ligands in PCA cell lines and a xenograft. While ErbB1/EGFR, ErbB2/NEU, and ErbB3 were always observed in a distinct pattern, ErbB4 was not observed. Interestingly, while TGF-alpha was expressed in the majority of PCA lines, the ligand Neu Differentiation Factor/Heregulin (NDF) was expressed only in an immortalized, non-transformed prostate epithelial line. Concomitantly, there was a significant difference in biological response to these ligands. NDF inhibited LNCaP growth and induced an epithelial-like morphological change, in contrast to TGF-alpha, which accelerated cell growth. We also performed the first comprehensive analysis of NDF signaling in a prostate line. LNCaP stimulated with NDF demonstrated crosstalk between ErbB3 and ErbB2 which did not involve ErbB1. NDF also turned on several cascades, including those of PI3-K, ERK/MAPK, mHOG/p38 and JNK/SAPK, but not those of PLCgamma or the STAT family. This signaling pattern is distinct from that of TGF-alpha. The activation of mHOG by ErbB2 or ErbB3 has not been reported, and may contribute to the unusual phenotype. PI3-K activation is characterized by the formation of a striking 'activation complex' with multiple tyrosine-phosphorylated species, including ErbB3. Our studies provide a framework in which to dissect the growth and differentiation signals of prostate cancer cells.
 ...
PMID:ErbB kinases and NDF signaling in human prostate cancer cells. 940 Sep 97

Malignant human gliomas are the most common forms of primary tumors in the central nerve system. Due to their location and invasive nature, treatment so far has been mainly palliative. Thus, understanding the molecular detail of tumor transformation and progression is crucial for developing effective therapeutic strategy for this fetal tumor. Among the genetic alternations found in these tumors, p53 inactivation and PDGF/PDGFR activation represent the early events, and the loss of chromosome 10 and gene amplification and rearrangement of EGFR represent the late events. Studies with both glioma cell lines and primary tumor tissues have strongly suggested that TGF-alpha and EGFR function as an important autocrine loop in supporting proliferation of human glioma, especially in high grade glioma, since elevated TGF-alpha expression is also found in these high grade tumors. Furthermore, down regulation of the expression of TGF-alpha by antisense constructs has been shown to inhibit several types of human tumor cell growth including glioma. Other means of therapeutic approaches using this autocrine loop as a target also include the use of monoclonal antibodies and their cytotoxic conjugated. Considerable understanding of the EGFR-mediated signal transduction pathways has become available recently, which including GRB2/mSOS1 mediated MAP kinase activation; JAK/STATs pathway; PLC-gamma pathway. However, much work still needs to be done before a specific component of these pathways can be applied for effective control of tumor growth in the clinic.
 ...
PMID:The autocrine loop of TGF-alpha/EGFR and brain tumors. 944 27

Interleukin-6 (IL-6) is a cytokine that was initially recognized as a regulator of immune and inflammatory responses, but it also regulates the growth of many tumour cells, including prostrate carcinoma. Overexpression of the growth-factor receptors ErbB2/neu and ErbB3 has been implicated in the neoplastic transformation of prostate carcinoma. Here we show that treatment of the prostate cancer cell line LNCaP with IL-6 induces tyrosine phosphorylation of ErbB2 and ErbB3, but not ErbB1/EGFR. We also show that ErbB2 forms a complex with the gp130 subunit of the IL-6 receptor in an IL-6-dependent manner. This association is important because the inhibition of ErbB2 activity results in abrogation of IL-6-induced MAPK activation. Thus ErbB2 is a critical component of IL-6 signalling through the MAP kinase pathway. These data show how a cytokine receptor can diversify its signalling pathways by engaging with a growth-factor receptor kinase.
 ...
PMID:Requirement of ErbB2 for signalling by interleukin-6 in prostate carcinoma cells. 959 Jun 94

Lipid metabolism can play an important role in the development and progression of human cancers. We have used Syrian hamster embryo (SHE) fibroblasts as a model system to study how lipid metabolites can alter cell proliferation and apoptosis. For example, the linoleic acid metabolite 13(S)-HpODE enhances EGF-dependent growth by inhibiting de-phosphorylation of the EGFR which leads to activation of the MAP kinase pathway. In contrast, the arachidonic acid metabolite, PGE2, inhibits EGF-dependent mitogenesis and the expression of the proto-oncogenes c-myc, c-jun, and jun-B. In this study, we have investigated the mechanism by which PGE2 attenuates these responses by studying the EGF signaling cascade in SHE cells. PGE2 pretreatment caused a concentration-dependent decrease in EGF-dependent phosphorylation of MAP kinase and a corresponding inhibition of EGF-stimulated MAP kinase activity. Pretreatment of the SHE cells with PGE2 had little effect on the magnitude of EGF-dependent receptor auto-phosphorylation and the phosphorylation of GAP suggesting a down-stream target. Treatment of cells with forskolin and EGF causes similar inhibition of MAP kinase phosphorylation as observed with PGE2 and EGF. Since PGE2 elevates cAMP in these cells, it may act by altering cAMP accumulation. Raf-1 activity can be inhibited by a cAMP-dependent process. Raf-1 activity, measured by phosphorylation of Mek-1, was attenuated by the addition of PGE2. To determine if inhibition of Raf-1 activity causes inhibition of the MAP kinase pathway, cells were concomitantly incubated with PGE2 and EGF. Inhibition of MAP kinase phosphorylation was observed. From these data, we propose that in SHE cells PGE2 increases cAMP levels, which in turn causes inhibition of Raf-1 activity. The MAP kinase pathway is thus downregulated which decreases mitogenesis and proto-oncogene expression. This study demonstrates that an arachidonic acid metabolite can modulate phosphorylation and activity of key signal transduction proteins in a growth factor mitogenic pathway.
 ...
PMID:Inhibition of EGF-dependent mitogenesis by prostaglandin E2 in Syrian hamster embryo fibroblasts. 965

A new conditional Egfr allele was used to dissect the roles of the receptor in eye development and to test two published models. EGFR function is necessary for morphogenetic furrow initiation, is not required for establishment of the founder R8 cell in each ommatidium, but is necessary to maintain its differentiated state. EGFR is required subsequently for recruitment of all other neuronal cells. The initial EGFR-dependent MAP kinase activation occurs in the furrow, but the active kinase (dp-ERK) is observed only in the cytoplasm for over 2 hours. Similarly, SEVENLESS-dependent activation results in cytoplasmic appearance of dp-ERK for 6 hours. These results suggest an additional regulated step in this pathway and we discuss models for this.
 ...
PMID:Dissecting the roles of the Drosophila EGF receptor in eye development and MAP kinase activation. 972 95

Transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) are members of the EGF family of growth factors. They have a common receptor, the EGF receptor. This belongs to the tyrosine kinase group of receptors called the ErbB receptor family. Other members are ErbB-2, ErbB-3, and ErbB-4. Binding of either ligand to the receptor elicits an increase in tyrosine kinase activity, resulting in the autophosphorylation of the receptor followed by a phosphorylation cascade of other tyrosine kinase substrates including mitogen-activated protein kinase (MAPK). TGF-alpha and EGF have been shown to stimulate cell division in the olfactory epithelium in vitro and may regulate cell division in vivo. To investigate whether exogenous TGF-alpha or EGF has a functional effect on the olfactory mucosa in vivo, 12.5-50 micrograms of each growth factor was administered to rats via the carotid artery. After 2 min, olfactory mucosa and liver samples were collected, homogenized, and immunoprecipitated with antibodies to the ErbB receptors. The immunoprecipitates were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblotting. Using phosphotyrosine antibody, the receptors were probed for phosphorylation. Activation of MAPK was also investigated using MAPK antibody. Exogenous TGF-alpha activated EGFR, ErbB-2 and MAPK, whereas EGF activated only the EGFR. TGF-alpha was a more potent activator of EGFR than EGF. Neither ligand had an effect on ErbB-3 and ErbB-4 receptors. These effects were absent in the control animals which received the same solution without the growth factor. These results are consistent with the notion that binding of TGF-alpha to EGFR may play a role in olfactory cell division in vivo.
 ...
PMID:Differential activation of ErbB receptors in the rat olfactory mucosa by transforming growth factor-alpha and epidermal growth factor in vivo. 980 67

During late stages of breast cancer progression, tumors frequently acquire steroid hormone resistance with concurrent amplification of growth factor receptors; this alteration predicts a poor prognosis. We show here that following treatment with the progestin, R5020, breast cancer cells undergo a "biochemical shift" in the regulation of epidermal growth factor (EGF)-stimulated signaling pathways: R5020 potentiates the effects of EGF by up-regulating EGFR, c-ErbB2 and c-ErbB3 receptors, and by enhancing EGF-stimulated tyrosine phosphorylation of signaling molecules known to associate with activated type I receptors. Independently of EGF, R5020 increases Stat5 protein levels, association of Stat5 with phosphotyrosine-containing proteins, and tyrosine phosphorylation of JAK2 and Shc. Furthermore, progestins "prime" breast cancer cells for growth signals by potentiating EGF-stimulated p42/p44 mitogen-activated protein kinase (MAPK), p38 MAP kinase, and JNK activities. Although the levels of cyclin D1, cyclin E, and p21(WAF1), are up-regulated by R5020 alone, they are synergistically up-regulated by EGF in the presence of R5020. Up-regulation of cell cycle proteins by EGF is blocked by inhibition of p42/p44 MAPK only in the presence of R5020, supporting a shift in the regulation of these cell cycle mediators from MAPK-independent to MAPK-dependent pathways. In summary, progesterone selectively increases the sensitivity of key kinase cascades to growth factors, thereby priming cells for stimulation by latent growth signals. These data support a model in which breast cancer cell growth switches from steroid hormone to growth factor dependence.
 ...
PMID:Convergence of progesterone and epidermal growth factor signaling in breast cancer. Potentiation of mitogen-activated protein kinase pathways. 981 39


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