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Biomedical subjects

M D Waterfield

Publications and source records attributed to M D Waterfield.

At least 145 records · Page 8Linked to original sources
PubMed1988

Expression of the human EGF receptor with ligand-stimulatable kinase activity in insect cells using a baculovirus vector.

The mechanism by which the binding of epidermal growth factor (EGF) to specific cell surface receptors induces a range of biological responses remains poorly understood. An important part of the study of signal transduction in this system involves the production of sufficient native and mutant EGF receptor species for X-ray crystallographic and spectroscopic analysis. Baculovirus vectors containing the cDNA encoding the human EGF receptor protein have here been utilized to infect insect cells. This results in expression of a 155-kb transmembrane protein which is recognized by four antibodies against different regions of the human EGF receptor. Studies with tunicamycin, monensen and endoglycosidase H show the difference in size between the recombinant and the native receptor is due to alterations in glycocsylation. Studies of [125I] EGF binding shows a Kd of 2 X 10(-9) M in intact infected insect cells which falls to 2 X 10(-7) M upon detergent solubilization. The recombinant protein exhibits an EGF-stimulated tyrosine protein kinase activity and an analysis of tryptic peptides shows that the phosphate acceptor sites are similar to those of the EGF receptor isolated from A431 cells. These observations indicate that functional EGF receptor can be expressed in insect cells, and furthermore, this system can be used for large-scale production.

Animals↗
PubMed1988

Loss of three major auto phosphorylation sites in the EGF receptor does not block the mitogenic action of EGF.

The EGF receptor cDNA has been transfected into receptor-negative Chinese hamster ovary (CHO) cells. A mutant cell line (CHO 11) was isolated that expresses a receptor of lower molecular weight than the EGF receptor from A431 cells (150,000 daltons compared to 170,000 daltons) and which appeared as a doublet on SDS-PAGE. By digestion of the receptor with endoglycosidase F it was shown that an altered pattern of glycosylation could not account for the smaller size of the protein, although it could explain the appearance of the CHO 11 receptor as a doublet protein. A deletion was located to the transfected cDNA and shown to involve the removal of coding sequences for the most C-terminal 20,000 daltons of the EGF receptor, which contains the three major autophosphorylation sites. Despite the loss of these sites the EGF receptor from CHO 11 cells binds EGF, demonstrates protein tyrosine kinase activity in response to EGF, and transduces a mitogenic signal. The CHO 11 receptor protein is still autophosphorylated on alternative tyrosine residues. We conclude that phosphorylation of the three tyrosines (P1, P2, and P3) in the C-terminal domain of the receptor is not required for signal transduction by the EGF receptor in these cells.

Animals↗
PubMed1987

On the tertiary structure of the extracellular domains of the epidermal growth factor and insulin receptors.

Alignment of the sequences, the identification of conserved residue patterns and secondary structure predictions indicate that the extra-cellular regions of the human and Drosophila epidermal growth factor (EGF), c-erb-B2 and human insulin receptors each contain two large, homologous domains (L) which are probably comprised of at least four short alpha-helices followed by turns of conserved length and beta-strands. In the human and Drosophila EGF and c-erb-B2 receptors these homologous domains are each followed by a series of smaller cystine-rich domains (S) to give a gene-duplicated structure of L1S11S12S13L2S21S22S23. In the human insulin receptor, the second series of cystine domains is replaced by a different sequence. These duplicated structures are probably organised as a pseudo-symmetrical dimer. There are two 'hyper-variable' regions, one at the end of the large domains and one in the cystine-rich sequences, which are candidates for hormone or growth-factor binding.

Amino Acid Sequence↗
PubMed1987

The isolation and characterisation of cDNA and genomic clones for human lecithin: cholesterol acyltransferase.

The protein sequencing of tryptic peptides from purified human lecithin: cholesterol acyltransferase (LCAT) identified sufficient amino-acid sequence to construct a corresponding mixed oligonucleotide probe. This was used to screen an adult human cDNA liver library, from which incomplete cDNA clones were isolated. The DNA sequence of these clones allows the prediction of the entire amino-acid sequence of the mature LCAT enzyme. The mature protein consists of 416 amino acids and contains several marked stretches of hydrophobic residues and four potential glycosylation sites. The cDNA probe detects LCAT mRNA sequences approx. 1500 bases long in human liver, but not intestine, RNA. The cDNA probe was used to isolate LCAT genomic recombinants from a human genomic library. Southern blotting data, and restriction site mapping, suggest that there is a single human LCAT structural gene between 4.3 and 5.5 kb in size.

Amino Acid Sequence↗
PubMed1987

Expression of the c-erbB-2 protein in normal and transformed cells.

Two synthetic peptides from the predicted sequence of the human c-erbB-2 protein were synthesized and used to raise antisera in rabbits. The sequences chosen were identical to those in the homologous rat c-neu protein. The antibodies produced reacted with the immunizing peptides in ELISA but showed little or no cross-reaction with the partly homologous peptides found in equivalent positions in the human EGF receptor. Both antipeptide antibodies, and a monoclonal antibody (MAb) specific for the rat neu protein, immunoprecipitated a 185-kDa protein from 35S-methionine-labelled lysates prepared from a rat cell line known to express high levels of the c-neu protein. The antipeptide antibodies also recognized a protein of the same size in Western blots. In addition, both antipeptide antibodies immunoprecipitated a 190-kDa protein from labelled cell lysates prepared from human and monkey cells. Antibodies to one of the peptides, which showed no detectable cross-reaction with human, rat or monkey EGF receptor, were used to examine the expression of the c-erbB-2 protein on a variety of cultured cell types. Eleven transformed, I non-established and 2 immortalized cell types were examined by immunoprecipitation for their level of expression of the c-erbB-2 protein and of the EGF receptor. The numbers of EGF receptors varied widely between different cell lines, whereas the level of the c-erbB-2 protein, which was found on all of the cell types examined, was more constant. The number of c-erbB-2 molecules present was estimated by autoradiography to be about 100,000 per cell. The antibodies were then used to examine the location and level of expression of the human c-erbB-2 and rat c-neu proteins in normal tissues. Immunohistochemical staining showed that the c-erbB-2 protein was highly expressed in rat kidney proximal tubules and loop of Henle. The c-erbB-2 protein was also present on normal human epithelial cells but in some cases with a different distribution to that of the EGF receptor.

Amino Acid Sequence↗
PubMed1987

Epidermal growth factor receptors in lung tumours.

Immunocytochemical analysis of epidermal growth factor (EGF) receptor expression was carried out on frozen sections of 109 primary lung tumours resected at the Brompton Hospital from February 1984 to May 1985. Tumours with detectable levels of this proto-oncogene protein were significantly more frequent among squamous cell carcinomas than among other types of lung tumour. No truncated EGF receptors were detected in the tumours using two monoclonal antibodies (Mabs) directed against different portions of the receptor (EGFR1 and F4). Mab F4 is the first antibody to the EGF receptor to show reactivity in paraffin sections. Southern blot analysis of a subset of the tumours detected amplification of the EGF receptor gene in squamous cell carcinomas but not in adenocarcinomas. The one carcinosarcoma examined had a re-arranged and amplified EGF receptor gene. Measurement of EGF receptor expression in lung tumours can be of diagnostic value and may prove to be useful in the development of antibody-directed therapy.

Adenocarcinoma↗
PubMed1987

Evaluation of epidermal growth factor receptors in bladder tumours.

Epidermal growth factor (EGF) receptor expression in 31 primary human bladder tumours was quantitated using both structural and functional assays and the EGF receptor gene in the same tumours was analyzed by Southern blot analysis. Immunocytochemical studies using the EGFR1 monoclonal antibody (Mab) showed a significant correlation between EGF receptor levels and the stage and grade of the tumours. Autophosphorylation assays employed to evaluate the receptor's tyrosine kinase activity gave results which in general were consistent with the immunocytochemical data. Using internally controlled immunocytochemical studies with two Mabs and Southern blot analysis of DNA isolated from the tumours, no evidence was obtained for the production of truncated receptors similar to those encoded by the v-erb-B oncogene. Gene amplification was not found in any of the superficial tumours, but one invasive tumour with high EGF receptor expression had an 8-10 fold amplification of the EGF receptor gene. The EGF receptor isolated from this tumour showed a normal pattern of tyrosine phosphorylation at all three major autophosphorylation sites. Our detailed study is consistent with the correlation previously found between EGF receptor expression and stage and grade of bladder tumours, and suggests that at this level of analysis EGF receptors in bladder tumours are not abnormal in structure or size, autophosphorylation activity, or gene structure.

Carcinoma, Transitional Cell↗
PubMed1986

Platelet-derived growth factors as possible mediators of vascular proliferation in the sporadic haemolytic uraemic syndrome.

Mitogenic activity was measured in matched plasma and serum samples from 17 children with typical epidemic haemolytic uraemic syndrome (HUS), 13 with atypical sporadic HUS, 7 with other renal diseases, and 8 normal children. The serum mitogenic activity of the normal children (median 18.35, range 15-35 U/ml) greatly exceeded that of plasma (median 5.4, range 1.04-11.9 U/ml). Patients with atypical sporadic HUS had raised plasma mitogenic activity (median 9.35, range 0-35 U/ml, p less than 0.01). Both plasma and serum from children with the typical epidemic form of HUS had low or undetectable mitogenic activity (median for plasma 1.0, range 0-5.9 U/ml, p less than 0.001; median for serum 1.85, range 0-23.8 U/ml, p less than 0.005). These low concentrations in typical epidemic HUS were associated with the presence of an inhibitor of cell growth. The results suggest that there is intravascular release of platelet mitogens in atypical sporadic HUS and that these mitogens may therefore be mediators of the vascular proliferative lesions.

Adolescent↗
PubMed1986

The complete primary structure of protein kinase C--the major phorbol ester receptor.

Protein kinase C, the major phorbol ester receptor, was purified from bovine brain and through the use of oligonucleotide probes based on partial amino acid sequence, complementary DNA clones were derived from bovine brain complementary DNA libraries. Thus, the complete amino acid sequence of bovine protein kinase C was determined, revealing a domain structure. At the amino terminal is a cysteine-rich domain with an internal duplication; a putative calcium-binding domain follows, and there is at the carboxyl terminal a domain that shows substantial homology, but not identity, to sequences of other protein kinase.

Amino Acid Sequence↗
PubMed1986

Multiple, distinct forms of bovine and human protein kinase C suggest diversity in cellular signaling pathways.

A new family of protein kinase C-related genes has been identified in bovine, human, and rat genomes. The alpha-, beta-, and gamma-type protein kinase sequences are highly homologous, include a kinase domain, and potential calcium-binding sites, and they contain interspersed variable regions. The corresponding genes are located on distinct human chromosomes; the possibility of even greater genetic complexity of this gene family is suggested by Northern and Southern hybridization analyses.

Animals↗
PubMed1986

Antibodies to the ATP-binding site of the human epidermal growth factor (EGF) receptor as specific inhibitors of EGF-stimulated protein-tyrosine kinase activity.

A region of the primary amino acid sequence of the epidermal growth factor receptor (EGF) protein-tyrosine kinase, which is involved in ATP binding, was identified using chemical modification and immunological techniques. EGF receptor was 14C-labelled with the ATP analogue 5'-p-fluorosulphonylbenzoyladenosine and from a tryptic digest a single radiolabelled peptide was isolated. The amino acid sequence was determined to be residues 716-724 and hence lysine residue 721 is located within the ATP-binding site. Antisera were elicited in rabbits to a synthetic peptide identical to residues 716-727 of the EGF receptor and the homologous sequence in v-erb B transforming protein from avian erythroblastosis virus. The affinity-purified antibodies precipitated human ECF receptor from A431 cells and placenta, and the v-erb B protein from erythroblasts. The antibodies inhibited EGF-stimulated receptor protein-tyrosine kinase autophosphorylation and phosphorylation of an exogenous peptide substrate containing tyrosine. The antibodies did not immunoprecipitate the transforming proteins pp60v-src or P120gag-abl or cAMP-dependent protein kinase, proteins which have homologous but not identical sequences surrounding the lysine residue within the ATP-binding site, nor did they react with the platelet-derived growth factor receptor. The antibodies had no effect on the kinase activity of purified v-abl protein in solution. The antibodies may therefore be a specific inhibitor of the tyrosine kinase of the EGF receptor.

Adenosine↗
PubMed1986

Structural and functional features of a cell surface phosphoglycoprotein associated with tumorigenic phenotype in human fibroblast x HeLa cell hybrids.

Monoclonal antibodies have been raised against a dimeric cell surface antigen (p75/150) which is specifically associated with the tumorigenic phenotype in human fibroblast X HeLa hybrids. During biosynthesis, a precursor molecule (p70/140), was associated with microsomal membranes in vivo but possessed no detectable cytoplasmic domains. At this stage, each p70 monomer contained 3 "high-mannose" type N-linked glycans which were subsequently processed into endoglycosidase H-insensitive complex oligosaccharides on the mature cell surface forms. Cleavage of this cell surface form with endoglycosidase F yielded non-N-glycosylated polypeptides of Mr = 60,000/120,000. All the monoclonal antibodies identified similar non-N-glycosylated polypeptides in cells grown in the presence of tunicamycin. p75/150 could be weakly labeled with [3H]palmitic or myristic acid. In vivo, p75/150 was found to be phosphorylated on serine residues. Immunoprecipitates of p75/150 from HeLa or tumorigenic hybrid cell lysates exhibited protein kinase activity in vitro, which phosphorylated p75/150 itself, also on serine residues. We were unable to detect this kinase activity in normal fibroblasts and in the nontumorigenic hybrid cells. Furthermore, we were unable to detect p75/150 or its precursors by either cell surface labeling, metabolic labeling, or Western blotting in nontumorigenic cell hybrids; p75/150 thus represents a tumor-specific marker in this system. Tryptic peptides of highly purified p75/150 have been generated, but their amino acid sequences did not reveal any significant homology with previously described proteins.

Amino Acid Sequence↗
PubMed1986

Megakaryoblastic transformation of myelofibrosis with expression of the c-sis oncogene.

We describe a case of primary myelofibrosis which terminated in an acute megakaryoblastic leukaemia with massive marrow fibrosis and osteosclerosis. The megakaryocyte lineage of the terminal phase was confirmed by ultrastructural and surface marker studies of the blast cells. The leukaemic phase was associated with the presence of large numbers of progressively more immature megakaryocyte progenitors in the peripheral blood. The expression of c-sis mRNA in these blast cells was significantly higher than in normal mononuclear cells. Activation of the c-sis protooncogene leading to increased production of platelet-derived growth factor could be related to the progressive fibrosis observed.

Adult↗