Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04626 (erbB-2)
 5,251 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have isolated from KB cells stimulated with interleukin-1 (IL-1) a protein kinase that phosphorylates a peptide (T669) based on the sequence around T669 of the epidermal growth factor (EGF) receptor. The enzyme, which had an apparent molecular mass of 45 kDa on gel-filtration chromatography, was purified 170,000-fold from cytosolic extracts by sequential chromatography on Mono Q, Mono S, phenyl-Sepharose, Superose 12, ATP-Sepharose and Mono Q. The enzyme activity co-chromatographed at the last step with a 45 kDa protein band that stained for phosphotyrosine. This peak fraction also contained some actin and a 60 kDa protein that stained weakly for phosphotyrosine. The T669 peptide is a substrate for mitogen-activated protein (MAP) kinase. Amounts of IL-1-induced T669 kinase and activated recombinant p42 MAP kinase having equal activity on T669 peptide were compared on commonly used MAP kinase substrates. T669 kinase was two or three orders of magnitude less active on myelin basic protein or microtubule-associated protein-2 than was MAP kinase. The IL-1-induced T669 kinase did not react with antiserum to p42/p44 MAP kinase. It was inactivated by treatment with protein phosphatase 2A or protein phosphotyrosine phosphatase 1B, so it may be regulated by dual phosphorylation in similar fashion to MAP kinase. The dephosphorylated enzyme was not re-activated by MAP kinase kinase. This novel enzyme could lie on a kinase cascade induced by IL-1. It may be responsible for phosphorylating T669 of the EGF receptor.
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PMID:Interleukin-1 activates a novel protein kinase that phosphorylates the epidermal-growth-factor receptor peptide T669. 794 18

Pulmonary epithelial cells are important in lung growth, development, and injury. H441 pulmonary adenocarcinoma cells may be a useful model for studying pulmonary epithelial cell growth factor responses in vitro. Isolated pulmonary epithelial type II cells proliferate in response to transforming growth factor (TGF)-alpha via the epidermal growth factor (EGF) receptor. Type II cells also proliferate in response to hepatocyte growth factor (HGF). In the present study, H441 cell responses to these growth factors were examined, and compared to type II cells. Both the EGF-R and the c-met proto-oncogene receptor, to which HGF binds, were immunoprecipitated from H441 cells. In H441 cells, addition of TGF-alpha resulted in phosphorylation of the EGF receptor and increased cell number and tritiated thymidine incorporation. Incubation with HGF resulted in phosphorylation of its c-met proto-oncogene receptor in type II and H441 cells, and also increased cell number and tritiated thymidine incorporation. Both HGF and TGF-alpha stimulated phosphorylation of the intracellular signaling molecules p42 and p44 mitogen activated protein kinases in H441 cells. H441 cells exhibited responses to mitogenic growth factors similar to type II cells and may be useful as a model for type II cell growth factor responses and signal transduction.
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PMID:H441 pulmonary epithelial cell mitogenic effects and signaling pathways in response to HGF and TGF-alpha. 945 67

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.
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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

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.
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PMID:Ras, but not Src, transformation of RIE-1 epithelial cells is dependent on activation of the mitogen-activated protein kinase cascade. 963 33

The activation of growth factor receptors and receptors coupled to heterotrimeric guanine nucleotide-binding proteins (G-proteins) can increase mitogen-activated protein (MAP) kinase activity in many cells. Previously, we demonstrated that the activation of G-protein-coupled P2Y2 receptors by extracellular ATP and UTP stimulated MAP (p42 ERK2) kinase by a mechanism that was dependent on the elevation of [Ca2+]i and the activation of related adhesion focal tyrosine kinase (RAFTK) (also called PYK2, CAKbeta, and CADTK) and protein kinase C (PKC). Here, we examine further the signaling cascade between the P2Y2 receptor and MAP kinase. MAP kinase was transiently activated by exposure of PC12 cells to UTP. UTP, ionomycin, and phorbol ester (phorbol 12-myristate 13-acetate) increased MAP kinase activity and also promoted the tyrosine phosphorylation of RAFTK, the epidermal growth factor (EGF) receptor, SHC, and p120(cbl). Down-regulation of PKC and inhibition of the elevation of [Ca2+]i, conditions that block the activation of MAP kinase, also blocked the increases in the tyrosine phosphorylation of RAFTK and the EGF receptor. AG1478, a tyrphostin selective for the EGF receptor, reduced the activation of MAP kinase, the tyrosine phosphorylation of SHC, the association of Grb2 with SHC, and the tyrosine phosphorylation of the EGF receptor and p120(cbl) but did not block the tyrosine phosphorylation of RAFTK. The similar effects of UTP, ionomycin, and phorbol 12-myristate 13-acetate (PMA) on these signaling proteins demonstrate that the two signaling molecules from phosphatidylinositol 4,5-bisphosphate hydrolysis ([Ca2+]i, from inositol 1,4,5-trisphosphate production, and diacylglycerol) can individually initiate the activation of MAP kinase in an EGF receptor-dependent manner. These results demonstrate that the P2Y2 receptor-mediated transactivation of the EGF receptor occurs at a point downstream of RAFTK and indicate that the EGF receptor is required for P2Y2 receptor-mediated MAP kinase activation. Although P2Y2 and EGF receptors may both activate a similar multiprotein signaling cascade immediately upstream of MAP kinase, the P2Y2 receptor appears to uniquely utilize [Ca2+]i, PKC, and, subsequently, RAFTK.
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PMID:Related adhesion focal tyrosine kinase and the epidermal growth factor receptor mediate the stimulation of mitogen-activated protein kinase by the G-protein-coupled P2Y2 receptor. Phorbol ester or [Ca2+]i elevation can substitute for receptor activation. 972 39

There is convincing evidence that mitogen-activated protein kinase (MAPK) activation is coupled to both receptor tyrosine kinase and G protein-coupled receptors. The presence of the epidermal growth factor (EGF) receptor and the GnRH receptor on the surface of GGH(3)1' cells makes this cell line a good model for the assessment of MAPK activation by receptor tyrosine kinases and G protein-coupled receptors. In this study, to assess the activated and total (i.e. activated plus inactivated) MAPK, the phosphorylation state of p44 and p42 MAPKs was examined using antisera that distinguish phospho-p44/42 MAPK (Thr202/Tyr204) from p44/42 MAPK (phosphorylation state independent). The data show that both EGF (200 ng/ml) and Buserelin (a GnRH agonist; 10 ng/ml) provoke rapid activation of MAPK (within 5 and 15 min, respectively) after binding to their receptors. The role of protein kinase A (PKA) and protein kinase C (PKC) signal transduction pathways in mediating MAPK activation was also assessed. Both phorbol ester (phorbol 12-myristate 13-acetate; 10 ng/ml) and (Bu)2cAMP (1 mM) trigger the phosphorylation of MAPK, suggesting potential roles for PKC and PKA signaling events in MAPK activation in GGH(3)1' cells. Treatment of PKC-depleted cells with Buserelin activated MAPK, suggesting involvement of PKC-independent signal transduction pathways in MAPK activation in response to GnRH. Similarly, treatment of PKC-depleted cells with forskolin (50 microM) or cholera toxin (100 ng/ml) stimulated MAPK activation, whereas pertussis toxin (100 ng/ml) had no measurable effect. To further assess the role of PKA in response to EGF and Buserelin, cells were treated with EGF (200 ng/ml) for 3 min or with Buserelin (10 ng/ml) for 10 min after pretreatment with 3-isobutyl-1-methylxanthine (0.5 mM), forskolin (50 microM), or (Bu)2cAMP (1 mM) for 15 min. The results show that MAPK can be activated in a PKA-dependent manner in GGH(3)1' cells. Consistent with previous reports, the current data support the view that MAPK activation can be achieved via both PKC- and PKA-dependent signaling pathways triggered by the GnRH receptor that couples to G(q/11) and Gs alpha-subunit proteins. In contrast, G(i/o)alpha does not appear to participate in MAPK activation in GGH(3)1' cells.
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PMID:The role of protein kinases A and C pathways in the regulation of mitogen-activated protein kinase activation in response to gonadotropin-releasing hormone receptor activation. 1021 77

Activation of the ras oncogene is an important step in carcinogenesis. Human MCF-10A mammary epithelial cells were transformed with a point-mutated form of the Ha-ras oncogene. Epidermal growth factor receptor (EGFR) phosphorylation levels were chronically elevated after EGF induction and the EGFR ligand-driven internalization rate was slower in Ha-ras transformed MCF-10A cells. Additionally, basal levels of p42/44 mitogen-activated protein kinase (MAPK) expression and enzyme activity were significantly higher in Ha-ras transformed cells, localized predominantly in the nucleus. The anti-EGFR monoclonal antibody (MAb) 225 and the EGFR tyrosine kinase inhibitor PD153035 blocked anchorage-independent growth of Ha-ras transformed cells in soft agar and were more effective when used in combination. The MEK inhibitor PD98059 and anti-erbB-2 MAb L26 also suppressed colony formation of Ha-ras transformed cells in soft agar. Therefore, Ha-ras transformation leads to an augmentation in signaling through the EGFR as a result of an increase in ligand-dependent phosphorylation, a decrease in its internalization and an up-regulation in basal p44/42 MAPK levels. These effects may contribute to uncontrolled growth of Ha-ras-transformed human mammary epithelial cells.
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PMID:RAS transformation causes sustained activation of epidermal growth factor receptor and elevation of mitogen-activated protein kinase in human mammary epithelial cells. 1096 38

Cells derived from the inner medullary collecting duct undergo in vitro branching tubulogenesis to both the c-met receptor ligand hepatocyte growth factor (HGF) as well as epidermal growth factor (EGF) receptor ligands. In contrast, many other cultured renal epithelial cells respond in this manner only to HGF, suggesting that these two receptors may use independent signaling pathways during morphogenesis. We have therefore compared the signaling pathways for mIMCD-3 cell morphogenesis in response to EGF and HGF. Inhibition of the p42/44 mitogen-activated protein kinase (MAPK) pathway with the mitogen-activated protein kinase kinase (MKK1) inhibitor PD98059 (50 microm) markedly inhibits HGF-induced cell migration with only partial inhibition of EGF-induced cell motility. Similarly, HGF-dependent, but not EGF-dependent, branching morphogenesis was more greatly inhibited by the MKK1 inhibitor. Examination of EGF-stimulated cells demonstrated that extracellular-regulated kinase 5 (ERK5) was activated in response to EGF but not HGF, and that activation of ERK5 was only 60% inhibited by 50 microm PD98059. In contrast, the MKK inhibitor U0126 markedly inhibited both ERK1/2 and ERK5 activation and completely prevented HGF- and EGF-dependent migration and branching process formation. Expression of dominant negative ERK5 (dnBMK1) likewise inhibited EGF-dependent branching process formation, but did not affect HGF-dependent branching process formation. Our results indicate that activation of the ERK1/ERK2 signaling pathway is critical for HGF-induced cell motility/morphogenesis in mIMCD-3 cells, whereas ERK5 appears to be required for EGF-dependent morphogenesis.
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PMID:Differential MAPK pathways utilized for HGF- and EGF-dependent renal epithelial morphogenesis. 1111 51

Overexpression of the HER2 (neu/c-erbB-2) oncogene frequently coincides with an aggressive clinical course of certain human adenocarcinomas. Expression and secretion of aberrant HER2 splice variants has been reported in various cell lines and tissues and can interfere with the oncogenic HER2 activity. Here we demonstrate, using two different approaches, that expression of a truncated 100 kDa HER2 variant which encodes the extracellular domain of HER2 (HER-ECD) inhibits growth factor-mediated tumour cell proliferation. A HER2-ECD cDNA encoding the truncated variant was overexpressed in MCF7 breast cancer cells. HER2-ECD overexpression decreased spontaneous proliferation of MCF7 cells as well as heregulin-mediated soft agar colony formation. Concomitantly, heregulin-induced phosphorylation of HER4 as well as downstream activation of p44/p42 MAP-kinases was decreased. To confirm these data, ribozymes were targeted to the 3'-untranslated region of the 2.3 kb HER2-ECD mRNA which is spontaneously expressed in MKN7 gastric cancer cells. HER2-ECD-targeted ribozymes downregulated HER2-ECD expression and enhanced EGF-mediated soft agar colony formation of MKN7 cells. In parallel, EGF-induced activation of p44/p42 MAP-kinases and activation of c-Fos expression were increased in ribozyme-transfected MKN7 cells. Finally, in RT-PCR we found a trend towards a progressive loss of 2.3 kb HER2-ECD mRNA expression in more advanced gastric tumours. These data show that the HER2-ECD variant inhibits growth factor-mediated tumour cell proliferation suggesting an important role during the progression of human cancer.
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PMID:Expression of a truncated 100 kDa HER2 splice variant acts as an endogenous inhibitor of tumour cell proliferation. 1136 Jan 94

Mouse capillary endothelial cells (1G11 cell line) embedded in type I collagen gels undergo in vitro angiogenesis. Cells rapidly reorganize and form capillary-like structures when stimulated with serum. Transforming growth factor beta1 (TGF-beta1) alone can substitute for serum and induce cell survival and tubular network formation. This TGF-beta1-mediated angiogenic activity depends on phosphatidylinositol 3-kinase (PI3K) and p42/p44 mitogen-activated protein kinase (MAPK) signaling. We showed that specific inhibitors of either pathway (wortmannin, LY-294002, and PD-98059) all suppressed TGF-beta1-induced angiogenesis mainly by compromising cell survival. We established that TGF-beta1 stimulated the expression of TGF-alpha mRNA and protein, the tyrosine phosphorylation of a 170-kDa membrane protein representing the epidermal growth factor (EGF) receptor, and the delayed activation of PI3K/Akt and p42/p44 MAPK. Moreover, we showed that all these TGF-beta1-mediated signaling events, including tubular network formation, were suppressed by incubating TGF-beta1-stimulated endothelial cells with a soluble form of an EGF receptor (ErbB-1) or tyrphostin AG1478, a specific blocker of EGF receptor tyrosine kinase. Finally, addition of TGF-alpha alone poorly stimulated angiogenesis; however, by reducing cell death, it strongly potentiated the action of TGF-beta1. We therefore propose that TGF-beta1 promotes angiogenesis at least in part via the autocrine secretion of TGF-alpha, a cell survival growth factor, activating PI3K/Akt and p42/p44 MAPK.
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PMID:Transforming growth factor beta1 (TGF-beta1) promotes endothelial cell survival during in vitro angiogenesis via an autocrine mechanism implicating TGF-alpha signaling. 1158 5


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