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

A 160,000 mol wt precursor of the epidermal growth factor (EGF) receptor has been identified in human A-431 carcinoma cells and skin fibroblasts. The presence of one discrete precursor band indicates the presence of a slow processing step. We have determined that this slow processing step involves the conversion of high mannose N-linked oligosaccharides on the receptor precursor to primarily complex oligosaccharides on the mature form of the receptor. This is shown by 1) the presence of fucose, a characteristic terminal sugar of complex oligosaccharides, in only the mature receptor and by 2) the susceptibility of the precursor to digestion with endoglycosidase H, which cleaves high mannose N-linked oligosaccharides, but not complex oligosaccharides from glycoproteins. The precursor to mature receptor transition half-time is 1.7 h in A-431 cells. This long transition half-time causes an accumulation of approximately 7.2 X 10(5) precursor molecules per cell (approximately 12% of the total population of EGF receptors). The net quantity of mature EGF receptors, but not of receptor precursors, is reduced when EGF is added to the culture medium of A-431 cells. The presence of EGF in the growth medium also decreases electrophoretic migration (as a result of increased phosphate incorporation) of the mature receptor, but not that of the precursor. The EGF-insensitive state of the precursor is most likely due to its intracellular location.
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PMID:Biosynthesis of the epidermal growth factor receptor in cultured human cells. 298 66

An epidermal growth factor (EGF) receptor-interactive monoclonal antibody (151-IgG) that inhibits EGF binding to PC12 rat pheochromocytoma cells and to various other cell types has been produced. The hybridoma clone was obtained by fusing Sp2/O-Ag14 myeloma cells with splenocytes from Balb/C mice which had been immunized with n-octyl glucoside-solubilized protein from isolated PC12 cell plasma membranes. The antibody is an IgG which binds to protein A. 151-IgG did not bind EGF. At 0.5 degrees C 151-IgG was directly competitive for EGF binding to PC12 cells. It also inhibited EGF binding to bovine corneal endothelial cells, rabbit corneal fibroblasts, human foreskin fibroblasts, and normal rat kidney cells, and it slightly enchanced EGF binding to SW 3T3 cells. PC12 cells have the same number of binding sites for 151-IgG as for EGF (approximately 27,000 sites/cell). 151-IgG inhibited the photoactivatable cross-linking of EGF to a protein of Mr 170,000 in PC12 cells. 151-IgG inhibited the EGF-stimulated incorporation of [3H]thymidine into quiescent bovine corneal endothelial cells, rabbit corneal endothelial cells, epithelial normal rat kidney cells, and SW 3T3 cells while it enhanced the EGF-stimulated [3H]thymidine incorporation into quiescent human foreskin fibroblasts. 151-IgG by itself possessed intrinsic EGF-like activity for human fibroblasts but not for the other cells tested. This suggests that there is a difference in EGF receptors and/or processing in these normal cell types.
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PMID:A monoclonal antibody which inhibits epidermal growth factor binding has opposite effects on the biological action of epidermal growth factor in different cells. 298 58

We have studied the synthesis and oligosaccharide processing of the 110,000 dalton form of the epidermal growth factor (EGF) receptor that is secreted into the medium of A-431 cells. Its 90,000 dalton precursor is soluble within the lumen of intracellular membrane vesicles shortly after synthesis, indicating that it lacks a membrane anchor. Analysis of labeled glycopeptides reveals that the glycosylation of the 110,000 dalton, secreted receptor is very similar to that of the 170,000 dalton, plasma membrane receptor. Based on Concanavalin A-Sepharose elution profiles of its glycopeptides, the secreted receptor has both complex and high-mannose N-linked oligosaccharides. Also, like the plasma membrane receptor, the secreted receptor contains N-acetylgalactosamine residues in its complex chains. Not only are major features of oligosaccharide processing of the soluble and membrane-bound forms of the receptor similar, but the kinetics of transport to the cell exterior is the same for each. These data indicate that the glycosylation pattern and kinetics of cellular transport of the EGF receptor are determined by factors other than the sequence of its cytoplasmic and transmembrane domains.
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PMID:Similarities in glycosylation and transport between the secreted and plasma membrane forms of the epidermal growth factor receptor in A-431 cells. 317 Jun 41

In this report, we demonstrate a novel post-translational modification of the epidermal growth factor (EGF) receptor. This modification involves the presence of phosphate, previously thought to exist only on amino acid residues in the EGF receptor, on oligosaccharides of the receptor. We have utilized several independent approaches to determine that mannose phosphate is present on the EGF receptor in A-431 cells. Following metabolic labeling with 32P, immunoisolation of the EGF receptor, and digestion with Pronase radioactivity was determined to be present on high mannose type oligosaccharides by concanavalin A chromatography. Also, after acid hydrolysis of in vivo 32P-labeled EGF receptor, radioactivity was detected that co-migrated with mannose 6-phosphate on two-dimensional thin layer electrophoresis. This radiolabeled material co-eluted with a mannose 6-phosphate standard from a high pressure liquid chromatography anion exchange column. Last, an acid hydrolysate of [3H]mannose-labeled EGF receptor contained two radiolabeled fractions, as analyzed by thin layer electrophoresis, and the radioactivity in one of these fractions was substantially reduced by alkaline phosphatase treatment prior to electrophoresis. These experiments indicate that the mature EGF receptor in A-431 cells contains mannose phosphate. This is a novel modification for membrane receptors and has only been reported previously for lysosomal enzymes and a few secreted proteins.
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PMID:Presence of mannose phosphate on the epidermal growth factor receptor in A-431 cells. 319 17

Newly synthesized enzymes destined for lysosomal localization contain mannose 6-phosphate (Man6-P) residues, allowing interaction with Man6-P receptors (MPRs) and subsequent intracellular targeting to the lysosome. In most cultured cells, lysosomal enzymes are rapidly dephosphorylated after targeting, but in some transformed cell lines, these proteins retain the Man6-P marker. To investigate the significance of this in human malignancy, we examined the persistence of the Man6-P marker in human breast biopsy specimens using MPR derivatives as affinity probes. In one approach, extracts of frozen tissue were standardized to protein content, fractionated by SDS-PAGE, immobilized on nitrocellulose, and probed with iodinated MPR. On average, carcinomas contained 4-fold higher levels of Man6-P glycoproteins than did benign tumors or normal breast samples. In about 15% of the carcinomas, levels of Man6-P glycoproteins were highly elevated (7-10-fold). Multiple Man6-P glycoproteins were detected, suggesting a general alteration in the synthesis or processing of many lysosomal enzymes in carcinomas. In a second approach, sections of formalin-fixed breast biopsy specimens were probed with biotinylated MPR. Malignant cells in 25 of 75 carcinomas exhibited granular cytoplasmic staining in what appears to be intracellular vesicles. Staining was specifically inhibited by Man6-P and was not observed in stromal components or lymphocytes. In addition, Man6-phosphorylated proteins were not detected in the 14 normal or benign biopsy samples examined. Staining appeared to be independent of most prognostic factors examined, including p53, cathepsin D, DNA ploidy, and hormone (estrogen and progesterone) receptor status. However, positive staining was significantly associated with high histological and nuclear grades (P < 0.05) and potentially with c-erbB-2 (P < 0.10), suggesting that elevated levels of Man6-P glycoproteins are associated with the more aggressive tumors.
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PMID:Increased levels of glycoproteins containing mannose 6-phosphate in human breast carcinomas. 761 83

The extracellular domain (621 N-terminal amino acids) of the p170 epidermal growth factor (EGF) receptor has eleven consensus N-linked glycosylation sites. When expressed in Chinese hamster ovary cells this was glycosylated with a combination of high mannose and complex chains. The latter chains were shown by chromatographic separation and mass spectrometric analysis of tryptic digests to be clustered in the EGF-binding domain. Treatment with the endoglycosidase, peptide-N-glycosidase F (PNGase F), reduced the molecular weight from 110 kDa to 75 kDa. Released oligosaccharides were characterised at high sensitivity by high pH anion exchange chromatography with pulsed amperometric detection and gas-liquid chromatography/mass spectrometry. The data were consistent with the complex chains being trisialylated tetra-antennary oligosaccharides fucosylated on the reducing terminal GlcNAc. The large hydrodynamic mass of these oligosaccharides could influence ligand binding, an effect which is likely to vary with the difference in consensus glycosylation sites of proteins related to p170 i.e. p185erbB2/neu, p180erbB3 and p180erbB4.
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PMID:Analysis of the glycosylation patterns of the extracellular domain of the epidermal growth factor receptor expressed in Chinese hamster ovary fibroblasts. 896 17

Breast cancer is associated with increased glucose consumption and can therefore be visualised with the glucose analogue [(18)F]2-deoxy-2-fluoro-D-glucose (FDG) and positron emission tomography (PET). FDG uptake in the primary tumour can vary substantially, and specific tumour characteristics have been demonstrated to determine the degree of glucose metabolism. Factors with a major influence on FDG uptake in breast cancer comprise expression of glucose transporter Glut-1 and hexokinase I, number of viable tumour cells per volume, histological subtype, tumour grading, microvessel density and proliferative activity. Recently, an association between high FDG uptake and a worse prognosis was suggested. Several studies have been performed correlating FDG uptake with a variety of prognostic and molecular biomarkers as well as parameters predicting tumour response to therapy. However, a correlation with important clinical prognostic markers such as axillary lymph node status and size of the primary tumour, expression of oestrogen and progesterone receptors, proto-oncogene c-erbB-2 or VEGF could not be demonstrated. The lack of correlation with important markers of prognosis does not suggest that FDG uptake might be used as a prognostic criterion in breast cancer. Innovative radiotracers for specific imaging of tumoural perfusion ([(15)O]H(2)O), hormone receptor expression ([(18)F]FES), protein synthesis ([(11)C]methionine), proliferation rate ([(18)F]FLT) or bone mineralisation ([(18)F]fluoride) may provide additional information compared with that provided by FDG PET.
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PMID:Biological characterisation of breast cancer by means of PET. 1512 40

Transfection of sense cDNA of N-acetylglucosamyltransferase V (GnTV-S) into human H7721 hepatocarcinoma cells resulted in an increase in the N-acetylglucosaminebeta1,6mannosealpha1,3- branch (GnT-V product) on the N-glycans of epidermal growth factor (EGF) receptor (EGFR), and promotion of its EGF binding and tyrosine autophosphorylation, but showed little effect on the expression of EGFR protein. The phosphorylation at T308, S473 and tyrosine residue(s) and the activity of protein kinase B (Akt/PKB) as well as the phosphorylation of p42/44 mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK) before and after EGF stimulation were concomitantly increased. Conversely, in the antisense GnT-V (GnTV-AS)-transfected H7721 cells, all the results were the reverse of those with GnTV-S-transfected cells. After the cells were treated with 1-deoxymannojirimycin, an inhibitor of N-glycan processing at high mannose, or antibody against the extracellular glycan domain of EGFR, the differences in PKB activity, p42/44 MAPK and MEK phosphorylation among GnTV-S-, GnTV-AS- and mock-transfected cells were significantly attenuated. These findings indicate that the altered expression of GnT-V will change the glycan structure and function of EGFR, which may modify downstream signal transduction.
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PMID:N-acetylglucosaminyltransferase V modifies the signaling pathway of epidermal growth factor receptor. 1524 55