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)

Betacellulin is a member of the epidermal growth factor (EGF) family. These soluble proteins are ligands for one or more of the four receptor tyrosine kinases encoded by the erbB gene family (erbB-1/epidermal growth factor receptor (EGFR), neu/erbB-2/HER2, erbB-3/HER3 and erbB-4/HER4). While evidence suggests that betacellulin is a ligand for the EGFR, the ability of betacellulin to regulate other erbB family receptors has not been analysed. Previously we engineered derivatives of the mouse Ba/F3 hematopoietic cell line to ectopically express erbB family receptors, singly and in pairwise combinations. We have stimulated this panel of cell lines with betacellulin and two other EGF family members, EGF itself and neuregulin-beta (NRG-beta). In the cell lines expressing a single erbB family receptor, betacellulin not only stimulated EGFR tyrosine phosphorylation, but it activated erbB-4 as well. Furthermore, in the double recombinant Ba/F3 derivatives, betacellulin stimulated a complex pattern of receptor phosphorylation distinct from the patterns activated by NRG-beta and EGF. Moreover, betacellulin stimulated a complex pattern of interleukin-3 independence in the Ba/F3 derivatives distinct from those activated by NRG-beta and EGF. These data identify a novel receptor for betacellulin and establish that different EGF family ligands activate distinct patterns of receptor phosphorylation and coupling to cellular signaling pathways.
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PMID:Betacellulin activates the epidermal growth factor receptor and erbB-4, and induces cellular response patterns distinct from those stimulated by epidermal growth factor or neuregulin-beta. 857 Feb 11

Cripto-1 (CR-1), a recently discovered protein of the epidermal growth factor (EGF) family, was found to interact with a high affinity, saturable binding site(s) on HC-11 mouse mammary epithelial cells and on several different human breast cancer cell lines. This receptor exhibits specificity for CR-1, since other EGF-related peptides including EGF, transforming growth factor alpha, heparin-binding EGF-like growth factor, amphiregulin, epiregulin, betacellulin, or heregulin beta1 that bind to either the EGF receptor or to other type 1 receptor tyrosine kinases such as erb B-3 or erb B-4 fail to compete for binding. Conversely, CR-1 was found not to directly bind to or to activate the tyrosine kinases associated with the EGFR, erb B-2, erb B-3, or erb B-4 either alone or in various pairwise combinations which have been ectopically expressed in Ba/F3 mouse pro-B lymphocyte cells. However, exogenous CR-1 could induce an increase in the tyrosine phosphorylation of 185- and 120-kDa proteins and a rapid (within 3-5 min) increase in the tyrosine phosphorylation of the SH2-containing adaptor proteins p66, p52, and p46 Shc in mouse mammary HC-11 epithelial cells and in human MDA-MB-453 and SKBr-3 breast cancer cells. CR-1 was also found to promote an increase in the association of the adaptor Grb2-guanine nucleotide exchange factor-mouse son of sevenless (mSOS) signaling complex with tyrosine-phosphorylated Shc in HC-11 cells. Finally, CR-1 was able to increase p42(erk-2) mitogen-activated protein kinase (MAPK) activity in HC-11 cells within 5-10 min of treatment. These data demonstrate that CR-1 can function through a receptor which activates intracellular components in the ras/raf/MEK/MAPK pathway.
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PMID:Cripto enhances the tyrosine phosphorylation of Shc and activates mitogen-activated protein kinase (MAPK) in mammary epithelial cells. 901 73

Much attention has recently focused upon hepatocyte growth factor (HGF) as a potential regulator of epithelial branching morphogenesis. However, since neither the HGF nor c-met "knockout" mice show abnormal kidney branching morphogenesis, we sought to analyze the relative importance of HGF in in vitro branching morphogenesis compared with other factors secreted by the embryonic kidney. Exploiting an assay that employs kidney epithelial cells (murine inner medullary collecting duct, mIMCD3) seeded in collagen cocultured with the embryonic kidney, we found that a tyrosine kinase inhibitor that is highly specific for the epidermal growth factor (EGF) receptor (EGFR), tyrphostin AG1478, inhibited mIMCD3 cell process formation (an early step in branching tubulogenesis) by 40%, whereas high concentrations of neutralizing anti-HGF antibodies had a lesser effect (20% inhibition), suggesting that EGFR ligands account for a larger fraction of branching morphogens secreted by the embryonic kidney than HGF. In addition, when an embryonic epithelial cell line derived from c-met (-/-) mice was cocultured with the embryonic kidney, these c-met (-/-) cells underwent process formation. EGFR ligands but not HGF were able to induce branching tubulogenesis in these cells. All EGFR ligands tested, including EGF, transforming growth factor-alpha, heparin-binding EGF, betacellulin, and amphiregulin, induced mIMCD3 cell tubulogenesis. EGFR ligands caused upregulation of urokinase, urokinase receptor, and matrix metalloprotease-1, and tubulogenesis could be inhibited by the metalloprotease inhibitor 1,10-phenanthroline. Our results support the notion that multiple parallel and potentially redundant growth factor-dependent pathways regulate branching tubulogenesis.
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PMID:EGF receptor ligands are a large fraction of in vitro branching morphogens secreted by embryonic kidney. 932 21

Betacellulin (BTC) is a member of the EGF ligand family that directly binds to both EGFR and HER4 and induces the growth of certain epithelial cell types. Fusion proteins composed of the terminal 48 or 50 amino acids of mature betacellulin and a binding defective form of Pseudomonas exotoxin (BTC-TX48 and BTC-TX50, respectively), have been produced. BTC-TX50 induced tyrosine phosphorylation of both EGFR and HER4, whereas BTC-TX48 induced phosphorylation of HER4 but to a much lesser extent EGFR, indicating that the presence of two additional amino acid residues, Arg62 and Lys63, contribute to full kinase activity. BTC-TX50 was up to 300-fold more active at inhibiting protein synthesis than BTC-TX48 on cell lines expressing EGFR, most likely due to the >tenfold higher affinity of BTC-TX50. MDA-MB-453 breast carcinoma cells which express HER4 but not EGFR, were not sensitive to either BTC-TX form. These data indicate that despite the ability of BTC-TX to bind and phosphorylate HER4, it was only cytotoxic to cells expressing EGFR. The inability of BTC-TX to kill cells was likely due to its failure to internalize through HER4.
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PMID:Betacellulin-Pseudomonas toxin fusion proteins bind but are not cytotoxic to cells expressing HER4; correlation of EGFR for cytotoxic activity. 952 63

We present a novel 96-well assay which we have applied to a structure-function study of epidermal growth factor receptor dimerization. The basis of the assay lies in the increased probability of EGFRs being captured as dimers by a bivalent antibody when they are immobilized in the presence of a cognate ligand. Once immobilized, the antibody acts as a tether, retaining the receptor in its dimeric state with a resultant 5-7-fold increase in binding of a radiolabeled ligand probe. When the assay was applied to members of the EGF ligand family, murine EGF, transforming growth factor alpha, and heparin-binding EGF-like growth factor were comparable with human EGF (EC50 = 2nM); betacellulin, which has a broader receptor specificity, was slightly less effective. In contrast, amphiregulin (AR1-84), which has a truncated C-tail and lacks a conserved leucine residue, was ineffective unless used at >1 microM. We further probed the involvement of the C-tail and the conserved leucine residue in receptor dimerization by comparing the activities of two genetically modified EGFs (the chimera mEGF/TGFalpha44-50 and the EGF point mutant L47A) and a C-terminally extended form of AR (AR1-90) with those of two other unrelated EGF mutants (I23T and L15A). The potency of these ligands was in the order EGF > I23T > mEGF/TGFalpha44-50 > L47A = L15A >> AR1-90 > AR1-84. Although AR was much worse than predicted from its affinity, this defect could be partially rectified by co-localization of the immobilizing antibody with heparin. Thus, it seems likely that AR cannot dimerize the EGFR unless other accessory molecules are present to stabilize its functional association with the EGFR.
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PMID:Structure-function studies of ligand-induced epidermal growth factor receptor dimerization. 953 6

The ErbB-1 receptor tyrosine kinase binds to six different growth factors, whose prototype is the epidermal growth factor (EGF). Two homologous epithelial receptors, ErbB-3 and ErbB-4, bind all isoforms of another family of growth factors, the Neu differentiation factors (NDFs/neuregulins). The fourth member of the ErbB family, ErbB-2, acts as the preferred heterodimeric partner of ligand-occupied complexes of the three other ErbB proteins. Here we report that at high concentrations, EGF can induce cell growth and differentiation in the absence of ErbB-1. This function is shared by betacellulin, but not by three other ligands, including the transforming growth factor alpha (TGFalpha). The functional receptor was identified as a heterodimer between ErbB-3 and ErbB-2, a previously identified oncogenic complex. When singly expressed, neither ErbB-3 nor ErbB-2 can mediate signaling by EGF. In addition, when co-expressed, blocking either receptor by using site-specific antibodies inhibited EGF and betacellulin activities, indicating strict cooperativity between ErbB-3 and ErbB-2. Through analysis of chimeras between EGF and TGFalpha, we identified the middle portion of EGF (loop B) as the site that enables activation of ErbB-2/ErbB-3. In conclusion, cooperative and promiscuous binding of stroma-derived growth factors by the epithelium-expressed ErbB-2/ErbB-3 heterodimer may be significant to cancer development. The mechanistic implications of our results for a model that attributes receptor dimerization to ligand bivalency, as well as to a recently proposed mechanism of secondary dimerization, are discussed.
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PMID:The oncogenic ErbB-2/ErbB-3 heterodimer is a surrogate receptor of the epidermal growth factor and betacellulin. 954 26

The human epidermal growth factor receptor (HER or ErbB) family consists of four distinct members, including the epidermal growth factor (EGF) receptor (EGFR, HER1, or ErbB1), ErbB2 (HER2 or neu), ErbB3 (HER3), and ErbB4 (HER4). Activation of these receptors plays an important role in the regulation of cell proliferation, differentiation, and survival in several different tissues. Binding of a specific ligand to one of the ErbB receptors triggers the formation of specific receptor homo- and heterodimers, with ErbB2 being the preferred signaling partner. We analyzed the levels of various ErbB receptor messenger RNAs in a series of nontransformed cell lines by real time quantitative RT-PCR. The cell lines chosen were derived from a variety of tissues, including pancreas, lung, heart, and nervous system. Further, we measured biological responses in these cell lines upon treatment with EGF, betacellulin, and two types of neuregulins, heregulin and sensory and motor neuron-derived factor. All cell lines examined expressed detectable levels of ErbB2. High levels of expression of ErbB3 were correlated with responsiveness to heregulin and sensory and motor neuron-derived factor, whereas high levels of EGFR expression were correlated with responsiveness to EGF and betacellulin. Moreover, the sensitivity of a cell line to ErbB ligands was also correlated with the levels of expression of the appropriate ErbB receptors in that cell line. These results are consistent with our hypothesis that appropriate biological responsiveness to ErbB ligands is determined by the levels of expression of specific ErbB receptor combinations within a given tissue.
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PMID:Biological response to ErbB ligands in nontransformed cell lines correlates with a specific pattern of receptor expression. 983 11

The epidermal growth factor (EGF)-receptor (EGFR) family includes four homologous transmembrane receptor protein tyrosine kinases, EGFR, ErbB-2, ErbB-3, and ErbB-4. This receptor family plays a pivotal role in regulating cell proliferation, differentiation, and transformation. Ligand-induced activation of these receptors results in formation of homo- and heterodimers, which undergo transphosphorylation and transactivation. The aim of this study was to characterize the role of EGFR family members in signaling EGF-induced human airway smooth muscle (HASM) cell proliferation. Here, we show that EGF stimulates activation of EGFR and transactivation of ErbB-2 in quiescent HASM cells. Phosphatidylinositol (PI) 3-kinase, a critical signaling enzyme that modulates HASM cell growth, is preferentially associated with ErbB-2, and EGF-stimulated transactivation of ErbB-2 induces PI 3-kinase activation. ErbB-3 and ErbB-4 are present in HASM cells; however, EGF has no effect on their activation. Betacellulin, a ligand for EGFR, ErbB-3, and ErbB-4, induced DNA synthesis of HASM cells and stimulated signaling through the activation of EGFR and ErbB-2 but not of ErbB-3 and ErbB-4. Heregulin, a specific ligand for ErbB-3 and ErbB-4, did not effect DNA synthesis and did not activate its specific receptors. These data suggest that EGF imparts signals that involve activation of ErbB-2 and are associated with ErbB-2 PI 3-kinase activation. Despite the mRNA and protein expression of all members of the EGFR family, ligand-stimulated signaling induced activation of EGFR and ErbB-2 but not of ErbB-3 and ErbB-4.
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PMID:EGF activates ErbB-2 and stimulates phosphatidylinositol 3-kinase in human airway smooth muscle cells. 995 Aug 86

The epidermal growth factor receptor (EGFR, c-erbB1) plays a pivotal role in maintenance and repair of epithelial tissues; however, little is known about coexpression of c-erbB receptors and their ligands in human bronchial epithelium. We therefore analyzed the expression of these molecules in cultured bronchial epithelial cells and normal bronchial mucosa, using reverse transcription-polymerase chain reaction (RT- PCR), flow cytometry, and immunohistochemistry. Messenger RNA (mRNA) encoding EGFR, c-erbB2, and c-erbB3, but not c-erbB4, was detected in primary cultures of human bronchial epithelial cells, as well as in the human bronchial epithelial-derived cell lines H292 and 16HBE 14o-. Transcripts encoding epidermal growth factor (EGF), heparin binding epidermal growth factor (HB-EGF), transforming growth factor-alpha (TGF-alpha), and amphiregulin (AR) were also detected, and expression of the three receptors and four ligands was confirmed by immunocytochemical staining of the cultured cells. Immunohistochemical analysis of resin- or paraffin-embedded sections from surgical specimens of bronchial mucosa revealed strong membrane staining for EGFR within the bronchial epithelium; this was particularly evident between basal cells and the basal aspect of columnar cells. The patterns of staining for c-erbB2 and c-erbB3 in the bronchial epithelium were similar to those for EGFR. Immunostaining for EGF, TGF-alpha, AR, HB- EGF, and betacellulin (BTC) was intense in the submucosal glands; with the exception of BTC, EGFR ligand immunoreactivity was also observed in the bronchial epithelium, where it paralleled EGFR staining. Colocalization of c-erbB receptors and ligands demonstrates the potential for productive c-erbB receptor interactions in bronchial epithelium. Further study of these interactions may help to define their role in maintenance and repair of the bronchial epithelium.
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PMID:Expression of c-erbB receptors and ligands in human bronchial mucosa. 1022 61

Head and neck squamous cell carcinomas (HNSCCs) are characterized by a marked propensity for local invasion and dissemination to cervical lymph nodes, with distant metastases developing in 30-40% of cases. Overexpression of the epidermal growth factor receptor (EGFR/c-erbB-1) and/or its ligands and high levels of certain matrix metalloproteinases (MMPs) have been associated with poor prognosis. The aim of this study was to examine the effects of EGFR ligands on gelatinase expression and invasion in HNSCC cell lines. We tested epidermal growth factor (EGF), transforming growth factor alpha, betacellulin, heparin-binding EGF, and amphiregulin and measured expression of gelatinases MMP-9 and MMP-2 in an established squamous carcinoma cell line (Detroit-562) and in two cell lines newly derived from patients with head and neck cancers (SIHN-005A and SIHN-006). Incubation of the cell lines with EGF-like ligands up-regulated MMP-9 (but not MMP-2) expression as measured by semiquantitative reverse transcription-PCR in a dose-dependent manner, with the effects being most marked in cells with high EGFR levels and undetectable in cells with low levels. Maximum stimulation was obtained in a concentration range of 10-100 nM. In addition, we confirmed by zymography that gelatinolytic activity consistent with MMP-9 (Mr 92,000) was up-regulated in parallel with increases in gene expression. Betacellulin (which binds both to EGFR and c-erbB-4 receptors) consistently increased MMP-9 expression and activation to a significantly greater degree than the other four ligands when tested at equimolar concentrations. In parallel with MMP-9 up-regulation, all EGF-like ligands increased tumor cell invasion through Matrigel in in vitro Transwell assays. These activities were independent of ligand effects on cell proliferation. Antagonist (ICR62) or agonist (ICR9) anti-EGFR monoclonal antibodies, respectively, inhibited or potentiated MMP-9 activity and tumor cell invasion induced by all ligands. Furthermore, a monoclonal antibody that neutralizes MMP-9 activity (Abl) also inhibited ligand-induced invasion of HNSCC. We confirmed that tumor cell lines used in these studies (and a larger series not reported here) generally expressed multiple c-erbB receptors and ligands. These results indicate that autocrine or paracrine signaling through EGFR potentiates the invasive potential of HNSCC via the selective up-regulation and activation of MMP-9. Furthermore, ligands such as betacellulin (which is commonly expressed in HNSCC), which can bind to and activate other c-erbB receptors, may be especially potent in this regard.
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PMID:Epidermal growth factor-like ligands differentially up-regulate matrix metalloproteinase 9 in head and neck squamous carcinoma cells. 1070 34


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