Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The neu (c-erbB-2) proto-oncogene encodes a tyrosine kinase receptor that is overexpressed in 20 to 30% of human breast tumors. Herein, cyclin D1 protein levels were increased in mammary tumors induced by overexpression of wild-type Neu or activating mutants of Neu in transgenic mice and in MCF7 cells overexpressing transforming Neu. Analyses of 12 Neu mutants in MCF7 cells indicated important roles for specific C-terminal autophosphorylation sites and the extracellular domain in cyclin D1 promoter activation. Induction of cyclin D1 by NeuT involved Ras, Rac, Rho, extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38, but not phosphatidylinositol 3-kinase. NeuT induction of the cyclin D1 promoter required the E2F and Sp1 DNA binding sites and was inhibited by dominant negative E2F-1 or DP-1. Neu-induced transformation was inhibited by a cyclin D1 antisense or dominant negative E2F-1 construct in Rat-1 cells. Growth of NeuT-transformed mammary adenocarcinoma cells in nude mice was blocked by the cyclin D1 antisense construct. These results demonstrate that E2F-1 mediates a Neu-signaling cascade to cyclin D1 and identify cyclin D1 as a critical downstream target of neu-induced transformation.
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PMID:Cyclin D1 is required for transformation by activated Neu and is induced through an E2F-dependent signaling pathway. 1061 Dec 46

Protein tyrosine phosphorylation is an integral part of cytokine-induced proliferation and differentiation of hematopoietic cells. The authors previously reported cloning and characterization of the receptor tyrosine kinase Tif, also termed Tyro3. Using the yeast 2-hybrid technology, they recently identified that the p85 subunit of phosphatidylinositol 3-kinase (PI3 kinase) interacted with the cytoplasmic domain of Tyro3. On treatment with epidermal growth factor (EGF), NIH3T3 cells expressed EGFR/Tyro3 (a fusion receptor with the extracellular domain from epidermal growth factor receptor and the transmembrane and cytoplasmic domains from Tyro3), and EGFR/Tyro3 was rapidly phosphorylated on tyrosine residues. The interaction between Tyro3 and p85 was also confirmed by glutathione S-transferase (GST) pull-down experiments. Co-immunoprecipitation followed by Western blot analysis revealed that PI3 kinase was associated with and phosphorylated by the activated Tyro3. Tyro3-associated PI3 kinase exhibited an enhanced kinase activity. In addition, EGF treatment of EGFR/Tyro3-expressing cells led to enhanced phosphorylation of Akt, a downstream component of PI3 kinase. Treatment of NIH3T3 cells expressing a full length of rat Tyro-3, but not NIH3T3 cells, with protein S also resulted in phosphorylation of Akt. Soft agar colony assays showed that the addition of EGF to EGFR/Tyro3-transfected cells, but not to the parental NIH3T3 cells, resulted in a concentration-dependent increase in the formation of anchorage-independent colonies. Tyro3-mediated transformation of NIH3T3 cells was significantly blocked by wortmannin, a PI3 kinase-specific inhibitor. Results of these combined studies strongly suggested that the oncogenic transforming ability of Tyro3 was mediated at least in part by the PI3 kinase pathway. (Blood. 2000;95:633-638)
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PMID:Transforming activity of receptor tyrosine kinase tyro3 is mediated, at least in part, by the PI3 kinase-signaling pathway. 1062 73

Trigeminal neurinoma cells were used to characterize the involvement of ERK, JNK, p38 and phosphatidylinositol 3-kinase (PI3-K)/Akt signaling pathways in the induction of apoptosis. Activation of JNK by anisomycin, the inhibition of ERK activation by PD098059 or a blockage of the PI3-K/Akt pathway by wortmannin or LY294002 alone, was not sufficient for the induction of apoptosis. Apoptosis was rapidly induced when the activation of JNK was coupled with the inhibition of PI3-K/Akt, and the induction was further enhanced by a concurrent inhibition of ERK activation. The p38 inhibitor, PD169316, reduced the activities of ERK and Akt. Rapid induction of apoptosis occurred when the inhibition of p38 was coupled with JNK activation, and a concurrent inhibition of PI3-K/Akt potentiated the induction. Apoptosis was also induced without JNK activation, though at a slower rate, by a combined treatment with PD169316 and LY294002. A concomitant inhibition of ERK and Akt activation induced apoptosis without JNK activation, although with a considerable delay of its onset. These results suggest that ERK, JNK, p38 and PI3-K/Akt signaling pathways interact to form an integrated network, and the induction of apoptosis requires coordinated changes in these signaling pathways.
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PMID:Changes in the mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt signaling associated with the induction of apoptosis. 1062 25

The Gab1 protein is tyrosine phosphorylated in response to various growth factors and serves as a docking protein that recruits a number of downstream signaling proteins, including phosphatidylinositol 3-kinase (PI-3 kinase). To determine the role of Gab1 in signaling via the epidermal growth factor (EGF) receptor (EGFR) we tested the ability of Gab1 to associate with and modulate signaling by this receptor. We show that Gab1 associates with the EGFR in vivo and in vitro via pTyr sites 1068 and 1086 in the carboxy-terminal tail of the receptor and that overexpression of Gab1 potentiates EGF-induced activation of the mitogen-activated protein kinase and Jun kinase signaling pathways. A mutant of Gab1 unable to bind the p85 subunit of PI-3 kinase is defective in potentiating EGFR signaling, confirming a role for PI-3 kinase as a downstream effector of Gab1. Inhibition of PI-3 kinase by a dominant-interfering mutant of p85 or by Wortmannin treatment similarly impairs Gab1-induced enhancement of signaling via the EGFR. The PH domain of Gab1 was shown to bind specifically to phosphatidylinositol 3,4,5-triphosphate [PtdIns(3,4,5)P3], a product of PI-3 kinase, and is required for activation of Gab1-mediated enhancement of EGFR signaling. Moreover, the PH domain mediates Gab1 translocation to the plasma membrane in response to EGF and is required for efficient tyrosine phosphorylation of Gab1 upon EGF stimulation. In addition, overexpression of Gab1 PH domain blocks Gab1 potentiation of EGFR signaling. Finally, expression of the gene for the lipid phosphatase PTEN, which dephosphorylates PtdIns(3,4, 5)P3, inhibits EGF signaling and translocation of Gab1 to the plasma membrane. These results reveal a novel positive feedback loop, modulated by PTEN, in which PI-3 kinase functions as both an upstream regulator and a downstream effector of Gab1 in signaling via the EGFR.
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PMID:A novel positive feedback loop mediated by the docking protein Gab1 and phosphatidylinositol 3-kinase in epidermal growth factor receptor signaling. 1064 29

Insulin-like growth factor I (IGF-I) is an important mediator of breast cancer cell growth, although the signaling pathways important for IGF-I-mediated effects in breast cancer cells are still being elucidated. We had demonstrated previously that increased intracellular cAMP in MCF-7 breast cancer cells inhibited cell growth and IGF-I-induced gene expression, as determined using a reporter gene assay. This effect of cAMP on IGF-I signaling was independent of IGF-I-induced activation of the mitogen-activated protein kinases extracellular signal-regulated kinases 1 and 2 (ERK1 and -2). To determine whether this effect of cAMP may be mediated via another mitogen-activated protein kinase, the ability of IGF-I to activate the c-Jun N-terminal kinases (JNKs) was investigated. Treatment of MCF-7 cells with 100 ng/ml IGF-I increased the level of phosphorylated JNK, as determined by Western blot analysis. JNK phosphorylation was not evident until 15 min after treatment with IGF-I, and peak levels of phosphorylation were present at 30-60 min. This was in contrast to ERK phosphorylation, which was present within 7.5 min of IGF-I treatment. Determination of JNK activity using an immune complex assay demonstrated a 3.3- and 3.5-fold increase in JNK1 and -2 activity, respectively, 30 min after treatment with 100 ng/ml IGF-I. The use of PD98059, which inhibits activation of ERK1 and -2, and LY 294002, an inhibitor of phosphatidylinositol 3-kinase, demonstrated that IGF-I-induced activation of JNK1 is independent of ERK and phosphatidylinositol 3-kinase activation. In contrast, increasing intracellular cAMP with forskolin resulted in abrogation of IGF-I-induced JNK activity. In summary, these data demonstrate that IGF-I activates the JNKs in MCF-7 breast cancer cells and, taken together with the results of our previous study, suggest that JNK may contribute to IGF-I-mediated gene expression and, possibly, cell growth in MCF-7 breast cancer cells.
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PMID:Insulin-like growth factor I activates c-Jun N-terminal kinase in MCF-7 breast cancer cells. 1065 Sep 34

The RET gene codes for a receptor tyrosine kinase that plays a crucial role during the development of both the enteric nervous system and the kidney. Germ line missense mutations at one of six codons specifying extracytoplasmic cysteines are responsible for two related cancer disorders as follows: multiple endocrine neoplasia type2A (MEN2A) and familial medullary thyroid carcinoma (FMTC). MEN2A and FMTC mutations result in a constitutive catalytic activity and as a consequence convert RET into a dominantly acting transforming gene. Although it has been shown that RET-MEN2 mutants activate several transduction pathways, their respective contribution to the neoplastic phenotype remains poorly understood. Over the past few years, it has become increasingly clear that the transforming ability of several viral and cellular oncoproteins depends on their capacity to activate phosphatidylinositol 3-kinase (PI3K). We now report that RET carrying a representative MEN2A mutation at Cys-634 (termed RET-MEN2A) activates PI3K and its downstream effector, the serine/threonine kinase AKT/protein kinase B. Previous studies have demonstrated that mutation of Tyr-1062, which is the intracellular docking site for Shc and Enigma on RET, abolishes the RET-MEN2A transforming activity. We provide evidence that mutation of Tyr-1062 abrogates the binding of the p85 regulatory subunit of PI3K to RET-MEN2A and the subsequent stimulation of the PI3K/AKT pathway. Furthermore, infection of rat fibroblasts with a retrovirus expressing a dominant-interfering form of PI3K suppresses RET-MEN2A-dependent transformation, whereas overexpression of AKT enhances the RET-MEN2A oncogenic potential. In summary, these data are consistent with the notion that RET-mediated cell-transforming effect is critically dependent on the activation of the PI3K/AKT pathway.
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PMID:Transforming ability of MEN2A-RET requires activation of the phosphatidylinositol 3-kinase/AKT signaling pathway. 1065 52

An important aspect of multi-step tumorigenesis is the mutational activation of genes of the RAS family, particularly in sporadic cancers of the pancreas, colon, lung and myeloid system. RAS genes encode small GTP-binding proteins that affect gene expression in a global way by acting as major switches in signal transduction processes, coupling extracellular signals with transcription factors. Oncogenic forms of RAS are locked in their active state and transduce signals essential for transformation, angiogenesis, invasion and metastasis via downstream pathways involving the RAF/MEK/ERK cascade of cytoplasmic kinases, the small GTP-binding proteins RAC and RHO, phosphatidylinositol 3-kinase and others. We have used subtractive suppression hybridization (SSH), a PCR-based cDNA subtraction technique, to contrast differential gene expression profiles in immortalized, non-tumorigenic rat embryo fibroblasts and in HRAS- transformed cells. Sequence and expression analysis of more than 1,200 subtracted cDNA fragments revealed transcriptional stimulation or repression of 104 ESTs, 45 novel sequences and 244 known genes in HRAS- transformed cells compared with normal cells. Furthermore, we identified common and distinct targets in cells transformed by mutant HRAS, KRAS and NRAS, as well as 61 putative target genes controlled by the RAF/MEK/ERK pathway in reverted cells treated with the MEK-specific inhibitor PD 98059.
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PMID:A genome-wide survey of RAS transformation targets. 1065 59

This study was initiated to identify signaling proteins used by the receptors for vascular endothelial cell growth factor KDR/Flk1, and Flt1. Two-hybrid cloning and immunoprecipitation from human umbilical vein endothelial cells (HUVEC) showed that KDR binds to and promotes the tyrosine phosphorylation of phospholipase Cgamma (PLCgamma). Neither placental growth factor, which activates Flt1, epidermal growth factor (EGF), or fibroblast growth factor (FGF) induced tyrosine phosphorylation of PLCgamma, indicating that KDR is uniquely important to PLCgamma activation in HUVEC. By signaling through KDR, VEGF promoted the tyrosine phosphorylation of focal adhesion kinase, induced activation of Akt, protein kinase Cepsilon (PKCepsilon), mitogen-activated protein kinase (MAPK), and promoted thymidine incorporation into DNA. VEGF activates PLCgamma, PKCepsilon, and phosphatidylinositol 3-kinase independently of one another. MEK, PLCgamma, and to a lesser extent PKC, are in the pathway through which KDR activates MAPK. PLCgamma or PKC inhibitors did not affect FGF- or EGF-mediated MAPK activation. MAPK/ERK kinase inhibition diminished VEGF-, FGF-, and EGF-promoted thymidine incorporation into DNA. However, blockade of PKC diminished thymidine incorporation into DNA induced by VEGF but not FGF or EGF. Signaling through KDR/Flk1 activates signaling pathways not utilized by other mitogens to induce proliferation of HUVEC.
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PMID:Utilization of distinct signaling pathways by receptors for vascular endothelial cell growth factor and other mitogens in the induction of endothelial cell proliferation. 1067 53

A protein that binds the intracellular domain of KDR (KDR-IC), a receptor for vascular endothelial cell growth factor (VEGF), was identified by two-hybrid screening. Two-hybrid mapping showed that the VEGF receptor-associated protein (VRAP) interacted with tyrosine 951 in the kinase insert domain of KDR. Northern blot analysis identified multiple VRAP transcripts in peripheral leukocytes, spleen, thymus, heart, lung, and human umbilical vein endothelial cells (HUVEC). The predominant VRAP mRNA encodes a 389-amino acid protein that contains an SH2 domain and a C-terminal proline-rich motif. In HUVEC, VEGF promotes association of VRAP with KDR. Phospholipase C gamma and phosphatidylinositol 3-kinase, effector proteins that are downstream of KDR and important to VEGF-induced endothelial cell survival and proliferative responses, associate constitutively with VRAP. These observations identify VRAP as an adaptor that recruits cytoplasmic signaling proteins to KDR, which plays an important role in normal and pathological angiogenesis.
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PMID:VRAP is an adaptor protein that binds KDR, a receptor for vascular endothelial cell growth factor. 1069 92

Binding of platelet-derived growth factor receptor (PDGF) to its receptor (PDGFR) activates its receptor tyrosine kinase which autophosphorylates tyrosine residues. The p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase) binds to specific phosphotyrosines on PDGFR-beta and through the associated p110 catalytic subunit of PI 3-kinase catalyzes the formation of lipids that are involved in intracellular signaling. We examined if GM1 affects interactions between PDGFR-beta and specific proteins involved in PDGFR-mediated signaling. U-1242 MG cells were studied under different growth conditions using immunoprecipitation and Western Blot analysis. PDGF-stimulated the association of PDGFR-beta with p85, ras GTPase-activating protein and PLC gamma. GM1 decreased these associations in parallel with decreased tyrosine phosphorylation of PDGFR. PDGF augmented the activity of PI 3-kinase associated with PDGFR-beta, and this was attenuated by GM1. However, GM1 did not alter SH2 domains of p85. GM1 probably inhibits PDGF-induced signaling proteins with PDGFR-beta by inhibiting phosphorylation of specific tyrosines on the receptor which bind to SH2-domains on signaling proteins.
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PMID:GM1 inhibits early signaling events mediated by PDGF receptor in cultured human glioma cells. 1069 3


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