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)

The mutant c-erbB-2 gene encoding a protein with Glu instead of Val-659 in the transmembrane domain is able to transform NIH3T3 cells, while the wild type c-erbB-2 unless overexpressed does not. The mutant c-erbB-2 protein shows enhanced tyrosine kinase activity in vitro. Transient expression of this active c-erbB-2 stimulated the 12-O-tetradecanoylphorbol-13-acetate (TPA) response element, serum response element, and cyclic AMP response element. Particularly, stimulation of the TPA response element by active c-erbB-2 was prominent. In contrast, transient expression of wild type c-erbB-2 stimulated none of these elements. Transactivation of the TPA response element was also observed in a cell line that stably expresses active c-erbB-2. The active c-erbB-2-induced transactivation of the TPA response element was partially prevented either by down-regulation of protein kinase C or by the protein kinase C inhibitor H7. These results indicate that protein kinase C is partly involved in oncogenic signalling of the active c-erbB-2 protein that leads to Jun/Fos-mediated transcriptional activation in nuclei.
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PMID:Transactivation of the TPA-responsive element by the oncogenic C-erbB-2 protein is partly mediated by protein kinase C. 167 66

Staurosporine is a potent microbial inhibitor of a number of protein kinases, including protein kinase C, cyclic AMP-dependent kinase, and the tyrosine kinase pp60src. We have used staurosporine to investigate the role of phosphorylation in the regulation of the epidermal growth factor (EGF) receptor in both human epidermal carcinoma A431 cells and mouse Swiss 3T3 fibroblasts. We report here that staurosporine treatment causes enhancement in high affinity EGF binding and a decrease in the phosphorylation state of the unstimulated receptor at a number of residues, including threonine 669. Staurosporine also antagonizes the inhibition of high affinity EGF binding and the increase in phosphorylation state of the unstimulated EGF receptor by phorbol esters and the calcium ionophore A23187. Staurosporine is an effective inhibitor of the EGF-stimulated receptor tyrosine kinase in vitro and thus does not enhance EGF stimulation of EGF receptor autophosphorylation in vivo. These results suggest that phosphorylation plays a major role in the regulation of the high affinity binding state of the EGF receptor in both unstimulated and mitogenically activated cells.
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PMID:Regulation of the epidermal growth factor receptor by growth-modulating agents: effects of staurosporine, a protein kinase inhibitor. 168 32

GCF is a transcriptional regulator that was found to repress transcription of the epidermal growth factor (EGF) receptor and several other genes and is encoded by a 3-kb mRNA (R. Kageyama and I. Pastan, Cell, 59: 815-825, 1989; A. C. Johnson et al., J. Biol. Chem., 267: 1689-1694, 1992). To identify and characterize the GCF gene product at the cellular level, we have developed antibodies against a bacterially expressed GCF fusion protein. GCF antibodies recognize GCF present in extracts from human cells and causes a "supershift" of a protein DNA complex containing a GCF oligonucleotide binding site. The major form of GCF has a molecular weight of approximately M(r) 97,000, identical to that of GCF transiently expressed in CV1 cells by the vaccinia virus system. In addition, other less abundant species with slightly higher and lower apparent molecular weight are specifically recognized, suggesting extensive posttranslational modification. GCF is highly expressed in EGF receptor-negative human cell lines (HUT102, U266, and CA46) and in lower amounts in several EGF receptor-expressing cells (KB, A431, TMK, and HeLa). Cell fractionation studies indicate that GCF is predominantly localized in the nucleus. GCF is a stable protein with a relatively long half-life. In addition, GCF is a phosphoprotein, and the phosphorylated form is found to be associated with the nuclear compartment in both HUT102 and KB cells. Phosphorylation occurs on serine and threonine residues and is stimulated by okadaic acid, phorbol myristate acetate, and cyclic AMP, but not vanadate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Biochemical characterization of human GCF transcription factor in tumor cells. 766 24

It has previously been shown that, in the estrogen-receptor-positive breast-tumor cell lines T47D and ZR75.1, the erbB-2 protein and mRNA content are controlled negatively and positively by, respectively, estrogens and anti-estrogens. Since estrogens have a positive effect on cell proliferation, while anti-estrogens inhibit cell growth, the results suggested that there may be an inverse correlation between growth and erbB-2 expression. We have now examined this matter further. The effect of various growth-modulatory agents including estrogen (E2), progesterone (Pg), retinoic acid (RA), epidermal growth factor (EGF), insulin (Ins), prolactin (Prl), 12-O-tetradecanolyl-phorbol-13-acetate (TPA) and dibutyryl-3':5'-cyclic-AMP (cAMP) on c-erbB-2 promoter activity, RNA and protein expression have been examined. The growth stimulators E2 and EGF both reduced the level of erbB-2 protein. However, while E2 clearly repressed erbB-2 transcription, in the case of EGF, neither mRNA nor transcription were decreased. Of the agents which inhibit the growth of T47D and ZR75.1 cells--Pg, Prl, cAMP, RA and TPA--only Pg and cAMP caused an increase in the erbB-2 protein level. Pg and cAMP positively influenced c-erbB-2 promoter activity and RNA amount. TPA and RA also increased promoter activity but neither erbB-2 mRNA nor protein level was enhanced. The erbB-2 protein expression in cultures of T47D and ZR75.1 cells at different densities was also analyzed. Both the level of erbB-2 protein and c-erbB-2 promoter activity rose markedly in confluent cultures, suggesting a transcriptional mechanism of control. In conclusion, the data suggest that the effects of various agents on erbB-2 expression are complex and cannot be explained simply as reflecting the growth state of the cells.
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PMID:erbB-2 expression in estrogen-receptor-positive breast-tumor cells is regulated by growth-modulatory reagents. 790 79

MDA-MB-231 is a breast epithelial cell line which possesses large amounts of epidermal growth factor (EGF) receptor on its cell surface but does not respond to EGF under standard culture conditions. 8-bromo-cyclic AMP (8Br-cAMP) and cholera-toxin treatments inhibit its growth by increasing its intracellular cAMP level. However, when inhibited in this way, MDA-MB-231 remains unresponsive to EGF. Similar effects--cAMP accumulation and inhibition of cell growth--are produced by forskolin. In addition, this substance specifically blocks MDA-MB-231 cells in G1 phase of the cell cycle. EGF is able to reverse the effect of forskolin on cell proliferation and prevents accumulation of cells in G1 phase without any change of cAMP level. Thus, only when inhibiting cell growth with forskolin does a mitogenic effect of EGF become evident. As cAMP is increased to a similar degree by all three compounds, yet only the effect of forskolin is antagonised by EGF, we suggest that a non-cAMP-mediated effect of forskolin must be considered to explain this effect. In contrast, the mitogenic effect of EGF on the NPM14T4/9 breast epithelial cell line does not change in the presence of forskolin.
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PMID:Evidence for a growth effect of epidermal growth factor on MDA-MB-231 breast cancer cells. 799 25

We have found that the epidermal growth factor (EGF) receptor kinase can utilize the fluorescent ATP derivative, methylanthraniloyl ATP, as a substrate. On the basis of this observation, together with our previous studies that showed that 5'-(p-fluorosulfonylbenzoyl)adenosine (5'-FSBAdo) is a highly specific affinity label for the ATP site of the kinase domain of the EGF receptor, we prepared new derivatives of 5'-FSBAdo, 5'-(p-fluorosulfonyl)-2'(or 3')-(methylanthraniloyl)adenosine (FSBMantAdo), as fluorescent affinity labels for adenine nucleotide binding sites, and in particular for the ATP site of the EGF receptor. The two products were purified by HPLC and were characterized by UV-Vis absorbance spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy, and fluorescence spectroscopy. Incubation of membrane vesicles containing the EGF receptor with either the 2' or 3' derivative resulted in irreversible inhibition of the receptor kinase activity, as assessed by autophosphorylation assays. Preincubation of vesicles with AMP imidodiphosphate (AMPPNP), a hydrolysis-resistant ATP analog, prior to treatment with FSBMantAdo resulted in the protection of the receptor kinase activity' from FSBMantAdo inactivation. Steady state fluorescence spectra (with excitation at 360 nm) revealed a blue shift in the emission maximum of partially purified FSBMantAdo-labeled receptor (426 nm), as compared with the emission maximum of free FSBMantAdo (441 nm) in aqueous solution, suggesting that the receptor-bound label is in a relatively low polarity environment. These studies show that FSBMantAdo is a specific affinity label for the ATP site of the EGF receptor. FSBMantAdo may also prove useful as a fluorescent affinity label for other ATP binding sites.
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PMID:5'-(p-fluorosulfonylbenzoyl)-2'(or 3')-(methylanthraniloyl)adenosine, fluorescent affinity labels for adenine nucleotide binding sites: interaction with the kinase active site of the receptor for epidermal growth factor. 870 25

Earlier reports have indicated that epidermal growth factor (EGF) receptor autophosphorylation, thought to be a key step in receptor transmembrane signaling, can be inactivated with the relatively sulfhydryl-specific reagent N-ethylmaleimide (NEM); however, no Cys residue has been implicated in the catalytic mechanism of the kinase. In an effort to address the mechanism of inhibition by NEM, we have investigated effects of several sulfhydryl-modifying reagents on EGF receptor autophosphorylation and on the kinase activity of the receptor toward an exogenous peptide substrate. Kinase activity is relatively insensitive to iodoacetic acid (IAAcid) and iodoacetamide (IAAmide), though IAAmide-treated receptor displays a higher Km(app) with respect to ATP, relative to untreated receptor. In contrast, even low concentrations of the very specific sulfhydryl reagent p-chloromercuribenzoic acid (PCMB) inactivate the receptor kinase. Pretreatment of the receptor with IAAmide, but not IAAcid, provides substantial protection of the kinase from subsequent treatment with NEM and a degree of protection from subsequent treatment with PCMB. Further, inactivation by NEM, and to a lesser extent PCMB, is inhibited by coincubation of the receptor with the hydrolysis-resistant ATP analog AMP-PNP. The protective effect of IAAmide from inactivation by NEM is also lost when AMP-PNP is present during the IAAmide treatment. Pretreatment of receptor with IAAcid has no effect on subsequent modification by IAAmide. These results, taken together, suggest that NEM, PCMB, and IAAmide, but not IAAcid, modify a Cys residue of the EGF receptor kinase that is inaccessible when nucleotide is bound. Modification of this residue by a bulky reagent (NEM, PCMB) inactivates the kinase by a steric mechanism, while modification with the smaller reagent (IAAmide) results in an active enzyme with altered affinity for ATP. Further, PCMB appears to react with an additional Cys residue (or residues), also resulting in steric inactivation.
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PMID:Effects of sulfhydryl modification reagents on the kinase activity of the epidermal growth factor receptor. 924 24

Markedly increased levels of cyclooxygenase-2 (COX-2) mRNA, protein, and prostaglandin E(2) synthesis were detected in HER-2/neu-transformed human mammary epithelial cells (184B5/HER) compared with its nontransformed partner cell line (184B5). HER-2/neu stimulated COX-2 transcription via the Ras --> Raf --> MAPK pathway. The inductive effects of HER-2/neu were mediated, in part, by enhanced binding of AP-1 (c-Jun, c-Fos, and ATF-2) to the cyclic AMP-response element (-59/-53) of the COX-2 promoter. The potential contribution of the transcription factor PEA3 was also investigated. Elevated levels of PEA3 were detected in 184B5/HER cells. A PEA3 site (-75/-72) was identified juxtaposed to the cyclic AMP-response element. HER-2/neu-mediated activation of the COX-2 promoter was blocked by mutagenizing the PEA3 site or overexpressing antisense to PEA3. To determine whether HER-2/neu status was also a determinant of COX-2 expression in vivo, we compared levels of COX-2 protein in HER-2/neu-positive and -negative human breast cancers. Increased amounts of COX-2 were detected in HER-2/neu-positive tumors. Taken together, these results suggest that closely spaced PEA3 and cyclic AMP-response elements are required for HER-2/neu-mediated induction of COX-2 transcription. The clear relationship between HER-2/neu status and COX-2 expression in human breast tumors suggests that this mechanism is likely to be operative in vivo.
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PMID:Cyclooxygenase-2 is overexpressed in HER-2/neu-positive breast cancer: evidence for involvement of AP-1 and PEA3. 1190 Nov 51

It has been proposed that binding of ligand to the estrogen receptor (ER) releases its association with transcriptional corepressors, allowing the ER to recruit coactivators, which possess histone acetylase activity, and induce transcription of gene promoters containing estrogen response elements. It has also been proposed that the antiestrogen tamoxifen recruits transcriptional corepressors to the AF-2 region of the hormone-binding domain of the ER, thus blocking ER-mediated transcription. The ER cross-talks with a number of mitogenic signaling pathways and second messengers, like the epidermal growth factor receptor, the insulin-like growth factor-I receptor, mitogen-activated protein (MAP) kinase, phosphatidylinositol-3 kinase/Akt, dopamine, and cyclic AMP. Some of these molecules may: (a) support ligand-independent ER transcription; (b) increase the association of ER with coactivators of transcription; and/or (c) reduce the antiestrogen-induced association of ER with corepressors. These events either alone or in combination may result in hormone independence and/or antiestrogen resistance. We have examined whether signaling by HER2/neu (erbB-2) receptor tyrosine kinase, which can induce antiestrogen resistance, can also disrupt the tamoxifen-induced interaction of ER with transcriptional corepressors. Notably, tamoxifen-induced association of ER with the transcriptional corepressors N-CoR or SMRT was reduced in HER2-overexpressing breast tumor cells but not in cells with low HER2 levels. Small molecule inhibitors of the HER2 kinase or MAP extracellular signal-regulated kinase 1/2 or dominant-negative MAP extracellular signal-regulated kinase 1/2 constructs restored the inhibitory effect of tamoxifen on both ER-mediated transcription and tumor cell proliferation. Treatment with both tamoxifen and the small molecule HER1/2 kinase inhibitor AG1478 reduced mitogen-activated protein kinase activity and markedly reduced growth of established MCF-7/HER2 xenografts in athymic nude mice. Similar results have been obtained with ZD1839 ("Iressa"), an epidermal growth factor receptor (HER1) tyrosine kinase inhibitor. Taken together, these data suggest that exogenous inhibitors of the HER-signaling network and other mitogenic pathways can abrogate or delay the emergence of antiestrogen resistance, thus providing an evaluable therapeutic strategy in human breast carcinoma.
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PMID:Inhibition of erbB receptor (HER) tyrosine kinases as a strategy to abrogate antiestrogen resistance in human breast cancer. 1191 37