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Biomedical subjects

C Y Pennington

Publications and source records attributed to C Y Pennington.

6 recordsLinked to original sources
PubMed1988

Growth modulation of mouse keratinocytes by transforming growth factors.

The effects of exogenously added transforming growth factor (TGF alpha and TGF beta on the growth of BALB/MK cells were examined. TGF alpha supplanted the epidermal growth factor (EGF) requirement in these cells. In contrast, TGF beta reversibly inhibited the growth of BALB/MK cells by abrogating the stimulatory actions of EGF or TGF alpha. The inhibitory effects of TGF beta appeared to be mediated by events distal to EGF ligand-receptor interactions. Growth inhibition of BALB/MK cells by TGF beta did not result in the induction of differentiation. This finding is different from the growth inhibition of these cells induced by elevated calcium levels (1.5 mM) which was tightly coupled to terminal differentiation. The BALB/MK cells were found to express TGF alpha mRNA, as well as TGF beta mRNA and protein. In addition, TGF alpha, as well as EGF, enhanced TGF alpha gene expression. These studies suggest a role for endogenous TGFs in regulating BALB/MK proliferation. TGF alpha provides a positive growth signal, while TGF beta is a potent inhibitor of growth even in the presence of such positive modulators as TGF alpha and EGF.

Animals↗
PubMed1988

Transforming activity of ras proteins translocated to the plasma membrane by a myristoylation sequence from the src gene product.

Ras p21 proteins exert their biological functions when associated to the inner surface of the plasma membrane. This association is mediated by a lipid molecule which is covalently attached to the protein by a thioester bond through a cysteine at residue 186, at the carboxy end of the molecule. Deletion or substitution of the critical Cys186 residue of the Harvey-ras protein leads to ras-p21 mutants lacking the ability to translocate to the membrane and devoid of transforming activity (Willumsen et al., 1984a, 1984b). We have been able to regenerate both localization to the plasma membrane as well as transforming activity of such mutant ras p21 proteins by fusion of the amino-terminal 15 residues of the v-p60src protein, responsible for the covalent binding of myristic acid and its membrane association. Thus, while translocation to the plasma membrane is necessary for function of the transforming Harvey-ras p21 protein, it appears to be independent of a specific membrane insertion mechanism.

Animals↗
PubMed1987

The human transforming growth factor type alpha coding sequence is not a direct-acting oncogene when overexpressed in NIH 3T3 cells.

A peptide secreted by some tumor cells in vitro imparts anchorage-independent growth to normal rat kidney (NRK) cells and has been termed transforming growth factor type alpha (TGF-alpha). To directly investigate the transforming properties of this factor, the human sequence coding for TGF-alpha was placed under the control of either a metallothionein promoter or a retroviral long terminal repeat. These constructs failed to induce morphological transformation upon transfection of NIH 3T3 cells, whereas viral oncogenes encoding a truncated form of its cognate receptor, the EGF receptor, or another growth factor, sis/platelet-derived growth factor 2, efficiently induced transformed foci. When NIH 3T3 clonal sublines were selected by transfection of TGF-alpha expression vectors in the presence of a dominant selectable marker, they were shown to secrete large amounts of TGF-alpha into the medium, to have downregulated EGF receptors, and to be inhibited in growth by TGF-alpha monoclonal antibody. These results indicated that secreted TGF-alpha interacts with its receptor at a cell surface location. Single cell-derived TGF-alpha-expressing sublines grew to high saturation density in culture. However, when plated as single cells on contact-inhibited monolayers of NIH 3T3 cells, they failed to form colonies, whereas v-sis- and v-erbB-transfected cells formed transformed colonies under the same conditions. Moreover, TGF-alpha-expressing sublines were not tumorigenic in nude mice. These and other results imply that TGF-alpha exerts a growth-promoting effect on the entire NIH 3T3 cell population after secretion into the medium but little, if any, effect on the individual cell synthesizing this factor. It is concluded that the normal coding sequence for TGF-alpha is not a direct-acting oncogene when overexpressed in NIH 3T3 cells.

Base Sequence↗
PubMed1986

Mammalian cell transformation by a murine retrovirus vector containing the avian erythroblastosis virus erbB gene.

A recombinant murine retrovirus vector containing the v-erbB gene of avian erythroblastosis virus was constructed to investigate v-erbB as a transforming gene for mammalian cells. A restriction fragment containing the v-erbB sequences from a molecular clone of avian erythroblastosis virus was inserted into a Moloney murine leukemia virus vector. The construct, designated MuLV/erbB, transformed NIH 3T3 cells at a high efficiency in the DNA transfection assay. Individual MuLV/erbB transfectants grew in soft agar and were tumorigenic. The transfectants contained v-erbB DNA sequences, expressed v-erbB-specific transcripts, and synthesized v-erbB-related glycoproteins. The majority of transfectants produced two major v-erbB gene products of 58 and 66 kilodaltons. However, some transfectants produced much smaller v-erbB-specific proteins. Tunicamycin experiments revealed that the size heterogeneity observed between different transfectants was not due to variations in glycoprotein processing, implying that, in some cases, alterations in the MuLV/erbB genome occurred during the transfection process. These findings indicate that expression of the complete v-erbB gene product is not required for transformation of NIH 3T3 cells. A transmissible murine v-erbB (M-erbB) virus was generated by infection of nonproducer transfectants with amphotrophic murine leukemia virus. Transmission of the rescued M-erbB virus was confirmed by DNA, RNA, and protein analyses. The introduction of a transforming v-erbB gene into mammalian cells by virus infection provides a means of analyzing the mechanism by which this epidermal growth factor receptor-related gene alters the growth and differentiation of cells from various lineages.

Alpharetrovirus↗
PubMed1986

Isolation and oncogenic potential of a novel human src-like gene.

We have isolated cDNA molecules representing the complete coding sequence of a new human gene which is a member of the src family of oncogenes. Nucleotide sequence analysis revealed that this gene, termed slk, encoded a 537-residue protein which was 86% identical to the chicken proto-oncogene product, p60c-src, over a stretch of 191 amino acids at its carboxy terminus. In contrast, only 6% amino acid homology was observed within the amino-terminal 82 amino acid residues of these two proteins. It was possible to activate slk as a transforming gene by substituting approximately two-thirds of the slk coding sequence for an analogous region of the v-fgr onc gene present in Gardner-Rasheed feline sarcoma virus. The resulting hybrid protein molecule expressed in transformed cells demonstrated protein kinase activity with specificity for tyrosine residues.

Amino Acid Sequence↗