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Query: UNIPROT:P04626 (erbB-2)
 5,251 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It was previously demonstrated that the epidermal growth factor (EGF) receptor in human A431 cells undergoes a slow post-translational modification by which it acquires EGF binding capacity (Slieker, L.J., and Lane, M.D. (1985) J. Biol. Chem. 260, 687-690). In this report, the role of glycosylation in the acquisition of ligand binding activity and in the intracellular translocation of the receptor precursor is characterized. Human A431 cells were incubated with [35S]methionine, and 35S-labeled EGF receptors were purified either by immunoprecipitation (total receptor) or by adsorption to an EGF affinity matrix (high affinity, or active receptor). The half-time for receptor activation is approximately 30 min and precedes its acquisition of resistance to endo-beta-N-acetylglucosaminidase H (t 1/2 = 75 min), a medial Golgi event. Activation is blocked by tunicamycin and is markedly slowed (t 1/2 = 120 min) by 1-deoxynojirimycin, an inhibitor of glucosidase I. In the latter case, the oligosaccharide chains are not further processed to complex forms. Treatment of the active high mannose receptor with endo-beta-N-acetylglucosaminidase H generates a fully active aglycoreceptor polypeptide, indicating that core oligosaccharide addition is a prerequisite for activation but that oligosaccharide chains are not intrinsically required for EGF binding. Subcellular fractionation studies showed that the EGF receptor is activated in the endoplasmic reticulum and that translocation from that organelle is extremely slow (t 1/2 = 75 min). Since the latter translocation rate approximates that for the acquisition of the resistance to endoglycosidase H, transit from the endoplasmic reticulum appears to be rate-limiting for the maturation of the receptor. Both tunicamycin and 1-deoxynojirimycin inhibit exit from the endoplasmic reticulum in parallel with their effects on the acquisition of binding activity. Immunoprecipitation of 35S-labeled EGF receptor with antiphosphotyrosine antibody in the presence of ATP suggested that the autophosphorylation activity of the receptor is also acquired post-translationally. The possible correlation of this to EGF binding activity is discussed.
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PMID:Synthesis of epidermal growth factor receptor in human A431 cells. Glycosylation-dependent acquisition of ligand binding activity occurs post-translationally in the endoplasmic reticulum. 349 Apr 80

We have recently reported that a polypeptide mitogen, the embryonal carcinoma-derived growth factor (ECDGF), induces phosphorylation of the epidermal growth factor (EGF) receptor in intact C3H 10T 1/2 mouse fibroblasts with concomittant loss of high affinity EGF binding sites. This phenomenon appears to be mediated through an activation of protein kinase C. Several groups have described an acidic 80,000 dalton protein substrate of protein kinase C. In this paper, we demonstrate that the addition of ECDGF or the phorbol ester TPA to intact C3H 10T 1/2 cells results in the enhanced phosphorylation of this 80 kd protein in vivo. Furthermore, this response is demonstrable in vitro. Thus the addition of ECDGF, the phorbol ester TPA, protein kinase C or phosphoinositidase C to crude membranes prepared from C3H 10T 1/2 cells resulted in the enhanced phosphorylation of this protein. Data obtained by phosphopeptide mapping of the 80 kd protein show that the ECDGF-induced activation of protein kinase C in our membrane preparations is comparable with that obtained in vivo. The availability of an in vitro system in which this response is preserved should now allow a detailed biochemical analysis of the steps between binding of a mitogen to its receptor and the activation of protein kinase C.
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PMID:Embryonal carcinoma-derived growth factor activates protein kinase C in vivo and in vitro. 359 64

The epidermal growth factor (EGF) receptor and other growth factor receptors have been shown to possess tyrosine-specific protein kinase activity. Before the demonstration of kinase activity in growth factor receptors, tyrosine kinases of molecular weight (MW) 60,000 (60K) were found to be encoded by the src oncogene and other oncogenes related to src. Our earlier work on intracellular processing of the EGF receptor, a 170,000-MW polypeptide, provided evidence for proteolytic separation of well defined structural domains, and suggested to us the possibility of separating functional domains by limited proteolysis. The isolation of such kinase domains should facilitate comparison of the receptor/kinase with other well characterized kinases including those of oncogene origin. We report here the identification of a catalytically functional 42K kinase derived proteolytically from the isolated human EGF receptor. This fragment, comparable in size to pp60src, carries the kinase ATP-binding site, and functions catalytically even after detachment from the EGF-binding site and the major autophosphorylation region.
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PMID:42,000-molecular weight EGF receptor has protein kinase activity. 609 Sep 43

Cells transformed by murine sarcoma viruses (MSV) produce and release into their tissue culture media several polypeptide growth stimulating factors. One of these has been partially purified using Bio-Gel P-60 column chromatography followed by DEAE-cellulose chromatography. This growth factor was assigned the name sarcoma growth factor (SGF), and is here shown to require the epidermal growth factor (EGF) receptor in order to function as a growth factor. DEAE-cellulose chromatography yielded a product that was several-fold purer than the material present in the Bio-Gel P-60 column pool II. The biologically active material from the DEAE-cellulose column, when labeled with 125I, showed specific binding to EGF membrane receptors. The specific binding could be prevented with the addition of either unlabeled EGF or SGF. Both radiolabeled SGF and EGF will bind to live or fixed cells. We were able to bind 125I-SGF as well as 125I-EGF to fixed cells and elute the bound material from fixed receptors. The eluted SGF showed a greater than 25-fold increase in specific binding. The biological activities of EGF and SGF could be bound to and eluted from fixed receptors. The eluted SGF showed a greater than 25-fold increase in specific binding. The biological activities of EGF and SGF could be bound to and eluted from fixed cells. A 3T3 clone lacking EGF receptors was unable to respond to either EGF or SGF, whereas it responded well to serum and several other purified growth factors. The SGF isolated using DEAE-cellulose chromatography was unable to compete in a radioimmune assay using 125I-EGF and antibody to purified mouse submaxillary gland EGF; it also was not precipitated by anti-EGF antibody. From these studies it appears that the SGF produced and released by these MSV-transformed cells combines with and requires the EGF receptor in order to exert its biological effects. The peptide, however, is antigenically distinct from mouse submaxillary gland EGF.
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PMID:Sarcoma growth factor (SGF): specific binding to epidermal growth factor (EGF) membrane receptors. 624 30

The Mr = 160,000 epidermal growth factor (EGF) receptor in A431 cells is partially cleaved during membrane isolation to a Mr = 145,000 polypeptide containing both EGF binding and phosphate acceptor sites. We show that the proteolytic degradation of the EGF receptor depends upon the presence of Ca2+ in the medium used to scrape the cells from the substratum. Only the high molecular weight form of the receptor is detected in membranes prepared in the absence of Ca2+. Ca2+-dependent proteolysis occurs rapidly (t1/2 approximately 5 min) following cell scraping. Proteolysis results in a decrease in EGF-dependent phosphorylation of the receptor while retaining EGF binding capacity. In addition, membranes containing the uncleaved form of the receptor reveal a substantial increase in EGF-dependent phosphorylation of proteins with Mr approximately 80, 89, and 185 X 10(3). In the presence of Ca2+, addition of iodoacetic acid to the scraping medium strongly inhibits receptor fragmentation, whereas other inhibitors (phenylmethylsulfonyl fluoride, leupeptin, and pepstatin) have no effect. The results implicate a role for a Ca2+-dependent, SH-sensitive protease in EGF receptor degradation. Prevention of proteolysis yields membrane preparations with highly active EGF-dependent kinase system.
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PMID:Proteolytic cleavage of epidermal growth factor receptor. A Ca2+-dependent, sulfhydryl-sensitive proteolytic system in A431 cells. 628 35

The regulation of protein phosphorylation by Zn2+ ions and by other divalent cations was studied in membrane vesicles from a normal mouse epithelial cell line, MMC-E (Mus musculus castaneous). Four major phosphoacceptor polypeptides were found in these membranes. Micromolar concentrations of Zn2+ ions inhibited the phosphorylation of the epidermal growth factor (EGF) receptor and of threonine residues in a 47,000-dalton polypeptide. In contrast, two polypeptides with molecular weights of 54,000 and 57,000 showed increased phosphorylation, mainly of serine residues, in the p.esence of Zn2+ ions. These results were not obtained using similar concentrations of other divalent cations and were apparently not due to an effect of Zn2+ ions on phosphoprotein phosphatases. Thus, the effects of Zn2+ ions on protein phosphorylation in membrane vesicles are complex and are not restricted to an inhibition of a single protein phosphatase or kinase.
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PMID:Effects of Zn2+ ions on protein phosphorylation in epithelial cell membranes. 630 21

The role of the epidermal growth factor (EGF) receptor system in mediating the biological activities of sarcoma growth factor (SGF) has been assessed by using specific anti-EGF receptor antibodies. There are two classes of anti-EGF receptor antibodies, those that block binding of 125I-labeled EGF (125I-EGF) and those that do not block binding but do interact with a portion of the EGF receptor on the surface of intact cells. Antisera of both types have been assayed for their capacity to affect the biological activities of SGF. The antisera that block 125I-EGF binding to its receptor block the induction of DNA synthesis in human fibroblasts by either EGF or SGF but not by other polypeptide mitogens. Titration of the anti-EGF receptor antiserum indicates the presence of one population of antibody that blocks the site of both EGF and SGF action. Antisera to the EGF receptor that block 125I-EGF binding also inhibited the SGF-dependent anchorage-independent growth of normal cells in soft agar. The antisera to the EGF receptor that does not block 125I-EGF binding or EGF activity did not inhibit any of the biological activities of SGF. The results suggest that occupation of the EGF receptor is required for both the mitogenic and colony-forming activity of SGF.
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PMID:Antibodies to the epidermal growth factor receptor block the biological activities of sarcoma growth factor. 631 May 84

In order to further define the mechanisms by which polypeptide growth factors regulate gene transcription and cellular growth, expression cloning techniques were used to select human epidermal growth factor (EGF) receptor complementary DNA clones. The EGF 3' coding domain shows striking homology to the transforming gene product of avian erythroblastosis virus (v-erbB). Over-expression of EGF receptors in A431 cell lines correlates with increased EGF receptor mRNA levels and amplification (up to 110 times) of the apparently singular EGF receptor gene. There appear to be three cytoplasmic polyadenylated RNA products of EGF receptor gene expression in A431 cells, one of which contains only 5' (EGF binding domain) sequences and is postulated to encode the secreted EGF receptor-related protein.
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PMID:Expression cloning of human EGF receptor complementary DNA: gene amplification and three related messenger RNA products in A431 cells. 632 61

We recently established a new human breast cell line, designated KPL-1, which was derived from the malignant effusion of a patient with breast cancer. This cell line is highly tumorigenic and grows rapidly in female nude mice. Cytogenetic analysis indicated its human origin and revealed a hypertriploid modal number of chromosomes. Electron microscopic examination suggested that the KPL-1 cells are of epithelial origin. Immunohistochemical studies revealed that the cells express cytokeratin, carcinoembryonic antigen and CA 15-3. They also possess a large number of oestrogen receptors but not progesterone receptors. Interestingly, KPL-1 cells seem to grow oestrogen independently in vitro. No amplification of c-erbB-2, c-myc, H-ras and N-ras genes was detected. KPL-1 cells secrete a large amount of tissue polypeptide antigen (TPA). Although the secretion of CA 15-3 seemed to be constant throughout all cell growth phases, TPA secretion increased during the exponential growth phase and decreased during the plateau phase. Serum TPA levels significantly correlated with the volume of KPL-1 tumours transplanted into nude mice. These data suggest that this KPL-1 cell line may be useful for studying oestrogen-independent growth and the kinetics of tumour-associated antigens in vivo as well as in vitro.
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PMID:A new human breast cancer cell line, KPL-1 secretes tumour-associated antigens and grows rapidly in female athymic nude mice. 771 Sep 53

Transforming growth-factor-alpha (TGF-alpha) is a 50-amino-acid polypeptide that binds to the epidermal growth factor (EGF) receptor and stimulates cell growth. It has been suggested that enhanced production of TGF-alpha and EGF receptors by tumour cells promote tumour-cell growth by autocrine mechanisms. In the present study we have investigated the expression of TGF-alpha and EGF receptors in human neuroendocrine tumours, including midgut carcinoid tumours, phaeochromocytomas and medullary thyroid carcinomas. TGF-alpha expression was demonstrated in biopsies of all tumours examined (n = 30) and EGF receptors in a majority of tumours by Northern analysis and/or immunocytochemistry. Expression of TGF-alpha and EGF receptors was also demonstrated in primary cultures of tumour cells. Carcinoid tumours and phaeochromocytomas in culture secreted detectable amounts of TGF-alpha into the culture medium (400-700 pM). The amount of secreted TGF-alpha could be suppressed by octreotide treatment in individual tumours. Administration of exogenous TGF-alpha stimulated carcinoid tumour growth in vitro as determined by the DNA contents of cell cultures. The growth-stimulatory effect of TGF-alpha could be partially blocked by the use of neutralizing anti-EGF receptor monoclonal antibodies (MAbs). In conclusion, several human neuroendocrine tumours express both TGF-alpha and EGF receptors in in vivo and in vitro, suggesting that TGF-alpha may regulate tumour-cell growth by autocrine mechanisms.
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PMID:Expression of transforming growth factor alpha and its receptor in human neuroendocrine tumours. 786 Jan 39


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