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Query: UNIPROT:P06889 (Mol)
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We have previously reported the immunohistochemical localization of transforming growth factor-alpha (TGF alpha) in the intact bovine anterior pituitary gland. Furthermore, we have purified TGF alpha from the conditioned medium of cell cultures derived from the bovine anterior pituitary. We report her the identification of the TGF alpha mRNA from both the intact bovine anterior pituitary gland and the anterior pituitary derived cell cultures. The level of TGF-alpha mRNA in the cell cultures is greater than that present in the intact gland. The TGF-alpha mRNA level increased when the cell cultures were allowed to incubate in their conditioned medium for 3 days, suggesting that a secretory product from the cultured cells is capable of stimulating the accumulation of the TGF-alpha mRNA. 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation of these cells resulted in a 6-fold increase in the level of TGF-alpha secreted into the conditioned medium. TPA appears to stimulate TGF-alpha secretion at the level of gene transcription as TPA treatment also resulted in an increased accumulation of the TGF-alpha mRNA. The epidermal growth factor (EGF) receptor mRNA was examined in these cell cultures and it increased with TPA treatment in an analogous manner to the TGF-alpha mRNA. EGF treatment of the pituitary cells resulted in an increased level of TGF-alpha mRNA which followed the same time course as TPA, maximal stimulation occurred after 8 h of treatment. The magnitude of EGF stimulated TGF-alpha mRNA was not as great as that seen by TPA stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1989 Jun
PMID:Transforming growth factor-alpha expression in the anterior pituitary gland: regulation by epidermal growth factor and phorbol ester in dispersed cells. 278 91

The epidermal growth factor (EGF) receptor is the functional target of the mitogen EGF and the cellular homolog of the avian erythroblastosis virus erbB oncogene product. Regulation of expression of the proto-oncogene encoding the EGF receptor can be elucidated by studying the structure and function of the gene promoter outside the confines of the cell. Previously, we reported the isolation of the human EGF receptor gene promoter. The promoter is highly GC rich, contains no TATA or CAAT box, and has multiple transcription start sites. An S1 nuclease-sensitive site has now been found 80 to 110 base pairs (bp) upstream from the major in vivo transcription initiation site. Two sets of direct repeat sequences were found in this area; both conform to the motif TCCTCCTCC. When deletion mutations were made in this region of the promoter by using either Bal 31 exonuclease or S1 nuclease, we found that in vivo activity dropped three- to fivefold, on the basis of transient-transfection analysis. Examination of nuclear protein binding to normal and mutated promoter DNAs by gel retardation analysis and DNase I footprinting revealed that two specific factors bind to the direct repeat region but cannot bind to the S1 nuclease-mutated promoter. One of the specific factors is the transcription factor Sp1. The results suggest that these nuclear trans-acting factors interact with the S1 nuclease-sensitive region of the EGF receptor gene promoter and either directly or indirectly stimulate transcription.
Mol Cell Biol 1988 Oct
PMID:Modulation of epidermal growth factor receptor proto-oncogene transcription by a promoter site sensitive to S1 nuclease. 284 30

Human prostatic acid phosphatase (PAcP) has been found to have phosphotyrosyl-protein phosphatase activity (H. C. Li, J. Chernoff, L. B. Chen, and A. Kirschonbaun, Eur. J. Biochem. 138:45-51, 1984; M.-F. Lin and G. M. Clinton, Biochem. J. 235:351-357, 1986) and has been suggested to negatively regulate phosphotyrosine levels, at least in part, by inhibition of tyrosine protein kinase activity (M.-F. Lin and G. M. Clinton, Adv. Protein Phosphatases 4:199-228, 1987; M.-F. Lin, C. L. Lee, and G. M. Clinton, Mol. Cell. Biol. 6:4753-4757, 1986). We investigated the molecular interaction of PAcP with a specific tyrosine kinase, the epidermal growth factor (EGF) receptor, from prostate carcinoma cells. Of several proteins phosphorylated in membrane vesicles from prostate carcinoma cells, PAcP selectively dephosphorylated the EGF receptor. The prostate EGF receptor was more efficiently dephosphorylated by PAcP than by another phosphotyrosyl phosphatase, potato acid phosphatase. Further characterization of the interaction of PAcP with the EGF receptor revealed that the optimal rate of dephosphorylation occurred at neutral rather than at acid pH. Thus, the enzyme that we formerly referred to as PAcP we now call prostatic phosphotyrosyl-protein phosphatase. Hydrolysis of phosphate from tyrosine residues in the immunoprecipitated EGF receptor catalyzed by purified prostatic phosphotyrosyl-protein phosphatase caused a 40 to 50% decrease in the receptor tyrosine kinase activity with angiotensin as the substrate. In contrast, autophosphorylation of the receptor was associated with an increase in tyrosine kinase activity.
Mol Cell Biol 1988 Dec
PMID:The epidermal growth factor receptor from prostate cells is dephosphorylated by a prostate-specific phosphotyrosyl phosphatase. 285 98

The neu oncogene was originally identified in cell lines derived from rat neuroectodermal tumors. neu is related to but distinct from the c-erbB gene, which encodes the epidermal growth factor (EGF) receptor. neu encodes a protein, designated p185, that is serologically related to the EGF receptor. Identification of the normal homolog of p185 encoded by the neu proto-oncogene enabled us to compare the product of the neu proto-oncogene with the mutated version specified by the neu oncogene and with the EGF receptor. The normal form of p185 was structurally similar to its transforming counterpart, indicating that activation of the neu oncogene did not cause major structural alterations in the gene product. Both normal and transforming forms of p185 were associated with tyrosine kinase activity, supporting the idea that normal p185 functions as a growth factor receptor. p185 differed both structurally and functionally from the EGF receptor. p185 and the EGF receptor had distinct electrophoretic mobilities when synthesized under normal culture conditions or in the presence of tunicamycin. EGF did not stimulate increased turnover of p185 and did not bind quantitatively to p185. A number of other growth factors failed to stimulate degradation of p185 or tyrosine phosphorylation of p185 and are therefore unlikely to be ligands for p185.
Mol Cell Biol 1986 May
PMID:p185, a product of the neu proto-oncogene, is a receptorlike protein associated with tyrosine kinase activity. 287 63

C-erbB-2 is a human protooncogene homologous with the well-known c-erbB. Genes and gene products of the EGF receptor and c-erbB are known to be closely related and to be closely homologous in their intracellular domain. Inspection of the deduced amino acid sequence suggested that the c-erbB-2 gene encodes a receptor for a yet unidentified growth factor. An immunohistological study was performed by introducing an antibody raised in the rabbit by immunization with a synthetic peptide corresponding to a part of the intracytoplasmic domain of predicted gene product. Specimens from 13 normal human organs, fresh frozen tissue from 41 surgically excised human malignant tumors and eight cell lines maintained in nude mice were studied. Positive staining was found in 4 of the 41 (9.8%) malignant tumors. All of the positive tumors were adenocarcinomas and two adenocarcinoma cell lines were also positive. Amongst the normal human tissues, epithelial cells in stomach, small and large intestine were faintly stained. When the positively stained cell lines were studied by immunoelectronmicroscopy, the reaction was most prominent in the membrane of microvilli, but part of the nuclear membrane, the endoplasmic reticulum and the outer cell membrane were also stained. DNA and mRNA blot assays, as well as our immunoprecipitation test, revealed that immunohistologically positive cell lines bore amplified c-erbB-2 DNA, c-erbB-2 mRNA and 185 kD protein which is supposed to be the gene product, while negative cell lines did not.
Virchows Arch B Cell Pathol Incl Mol Pathol 1987
PMID:Light and electron microscopical demonstration of c- erB-2 gene product-like immunoreactivity in human malignant tumors. 289 5

Treatment of human adenocarcinoma MKN-7 cells with epidermal growth factor (EGF) or phorbol tetradecanoate acetate (TPA) stimulated phosphorylation of the c-erbB-2 gene product. EGF induced a rapid increase in phosphotyrosine followed by relatively gradual increases in phosphoserine and phosphothreonine. On the other hand, the TPA-induced increase in phosphorylations occurred exclusively on serine and threonine residues. Tryptic phosphopeptide mapping analysis suggested that treatments with EGF and TPA induced phosphorylation of many common sites in the c-erbB-2 gene product. However, in contrast to TPA, EGF increased the phosphorylation of the c-erbB-2 protein in cells whose protein kinase C had been down-regulated by long-term pretreatment with TPA, suggesting that EGF and TPA induce phosphorylation by different mechanisms. Since the c-erbB-2 gene product did not show detectable EGF-binding activity, phosphorylation of tyrosine of the c-erbB-2 gene product might be catalyzed directly by the EGF receptor kinase that was activated by EGF.
Mol Cell Biol 1988 Mar
PMID:Tumor promoter and epidermal growth factor stimulate phosphorylation of the c-erbB-2 gene product in MKN-7 human adenocarcinoma cells. 289 79

Compared with normal erbB-2 gp185, mutant erbB-2 proteins generated by mutations either in the transmembrane domain or by NH2-terminal deletion are able to transform NIH 3T3 cells at a 10- to 100-fold greater efficiency. Mutant proteins of both classes show increased tyrosine kinase activity, suggesting that an abnormal level of receptor-associated tyrosine kinase activity is a major determinant of erbB-2 oncogenic potential.
Mol Cell Biol 1988 Dec
PMID:Different structural alterations upregulate in vitro tyrosine kinase activity and transforming potency of the erbB-2 gene. 290 6

A431 cells have an amplification of the epidermal growth factor (EGF) receptor gene, the cellular homolog of the v-erb B oncogene, and overproduce an aberrant 2.9-kilobase RNA that encodes a portion of the EGF receptor. A cDNA (pE15) for the aberrant RNA was cloned, sequenced, and used to analyze genomic DNA blots from A431 and normal cells. These data indicate that the aberrant RNA is created by a gene rearrangement within chromosome 7, resulting in a fusion of the 5' portion of the EGF receptor gene to an unidentified region of genomic DNA. The unidentified sequences are amplified to about the same degree (20- to 30-fold) as the EGF receptor sequences. In situ hybridization to chromosomes from normal cells and A431 cells show that both the EGF receptor gene and the unidentified DNA are localized to the p14-p12 region of chromosome 7. By using cDNA fragments to probe DNA blots from mouse-A431 somatic cell hybrids, the rearranged receptor gene was shown to be associated with translocation chromosome M4.
Mol Cell Biol 1985 07
PMID:Structure and localization of genes encoding aberrant and normal epidermal growth factor receptor RNAs from A431 human carcinoma cells. 299 49

The carbohydrate specificity of the monoclonal antibody EGR/G49, raised against the epidermal growth factor (EGF) receptor of A431 cells, has been investigated by assessing its interactions with glycoproteins and erythrocytes derived from individuals of known blood group ABH, Lewis and secretor types, and by inhibition of binding assays using structurally defined oligosaccharides. The results indicate that this antibody reacts with the difucosylated blood group structures ALeb and ALey: (formula; see text) This antibody differs from the previously described anti-EGF receptor antibody. TL5, which is directed at the terminal blood group A trisaccharide structure and reacts poorly with the ALeb/Ley structures. Since both antibodies were selected for their reactivities with the receptor for EGF, their specificities provide evidence for the presence of both the mono- and difucosylated blood group A structures on the receptor glycoprotein. These antibodies will be invaluable in the studies of the distribution and the roles of blood group related carbohydrate structures in the organisation and function of the EGF and other receptor systems.
Mol Immunol 1985 Jun
PMID:Monoclonal antibody (EGR/G49) reactive with the epidermal growth factor receptor of A431 cells recognizes the blood group ALeb and ALey structures. 299 55

The epidermal growth factor (EGF) receptor, along with several oncogene protein products, possesses tyrosine-specific protein kinase activity. Furthermore, the EGF receptor has structural similarity to the putitive v-erb-B transforming protein. Because of these closely shared characteristics, it is important to elucidate the possible involvement of the EGF receptor in malignant transformation. The epidermal carcinoma cell line A431 exhibits an abnormally high number of EGF receptors, which is associated with the presence of translocation chromosome M4. Recently, A431 cells have been shown to contain amplified sequences for the EGF receptor gene(s) and also to produce a variant mRNA which diverges from the normal EGF receptor mRNA at the 3' end. Here we report, using the human EGF receptor cDNA probe pE7, that the chromosome M4 has a six- to sevenfold amplification of the EGF receptor gene. Furthermore, the presence of M4 in somatic cell hybrids correlates with the production of the variant 2.9-kb mRNA. This aberrant mRNA is apparently generated by an intrachromosomal rearrangement which was detected using as a probe a fragment of the pE15cDNA encoding the variant mRNA.
Somat Cell Mol Genet 1985 Sep
PMID:Translocation chromosome 7 of A431 cells contains amplification and rearrangement of EGF receptor gene responsible for production of variant mRNA. 299 39


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