Biomedical subjects

W C Dougall

Publications and source records attributed to W C Dougall.

4 recordsLinked to original sources

PubMed1992

Carboxyl-terminal deletion and point mutations decrease the transforming potential of the activated rat neu oncogene product.

The rat neu oncogene encodes a constitutively activated growth factor receptor/transmembrane tyrosine kinase, p185Tneu, that is structurally similar to yet distinct from the epidermal growth factor receptor. To explore the role of the carboxyl-terminal region and of putative autophosphorylation sites in regulating the activity of the rat p185Tneu (T, transforming) protein, we used site-directed mutagenesis to generate a p185Tneu mutant in which a putative tyrosine autophosphorylation site (residue 1253) at the extreme carboxyl terminus was replaced by a phenylalanine residue and a mutant in which the carboxyl-terminal 122 amino acids were deleted. These proteins were expressed in NIH 3T3 cells at comparable levels and exhibited similar autophosphorylation activity, exogenous substrate phosphorylation ability, oligomerization levels, and responsiveness to a partially purified neu-activating factor. However, the mutant p185Tneu proteins displayed a decreased transforming capacity both in vitro and in vivo. This analysis demonstrated that the carboxyl-terminal domain and at least one putative tyrosine autophosphorylation site of p185Tneu play a role in positively regulating the cell growth-regulating properties of the neu protein.

3T3 Cells↗

PubMed1992

Multiple mRNA species generated by alternate polyadenylation from the rat manganese superoxide dismutase gene.

The mitochondrial enzyme, manganese superoxide dismutase (MnSOD) is an integral component of the cell's defense against superoxide-mediated cellular damage. We have isolated and characterized four cDNA clones and the structural gene for rat MnSOD. Northern analyses using MnSOD cDNA probes detected at least five mRNAs in all tissues and cell types examined. Southern and Northern analysis using a 3' non-coding sequence probe, common to all the cDNAs, showed hybridization only to genomic restriction fragments that correspond to our genomic clone and the five MnSOD mRNAs. These data demonstrate that all of the rat MnSOD transcripts are derived from a single functional gene. Primer extension data indicate that transcription initiation is clustered within a few bases. Northern analysis using intron probes demonstrates that all five transcripts are fully processed. Northern analysis using cDNA and genomic probes from sequences progressively 3' to the end of the coding sequence indicates that size heterogeneity in the MnSOD transcripts results from variations in the length of the 3' non-coding sequence. From this data and the location of potential polyadenylation signals near the expected sites of transcript termination, we conclude that the existence of multiple MnSOD mRNA species originate as the result of alternate polyadenylation.

Animals↗

PubMed1991

Manganese superoxide dismutase: a hepatic acute phase protein regulated by interleukin-6 and glucocorticoids.

The superoxide dismutases (SODs) are important metallo-enzymes which scavenge and dismutate the superoxide free radical. They are thought to be the main enzymes in the antioxidant defense system. Identification of stimuli that control transcription of the SOD genes is essential for understanding SOD gene regulation. In this study we show that manganese SOD (MnSOD) mRNA levels are elevated by lipopolysaccharide, a bacterial endotoxin, in rat liver. However, neither lipopolysaccharide nor tumor necrosis factor-alpha had an effect on MnSOD mRNA expression in cultured primary hepatocytes. On the other hand, the inflammatory cytokines, interleukin-1 (IL-1) and IL-6 did increase MnSOD mRNA levels, either 2- or 15-fold, respectively, over a 20-h period in hepatocytes. The IL-6-induced increase in MnSOD mRNA levels was attenuated by dexamethasone, a glucocorticoid, in hepatocytes cultured for less than 16 h. In contrast, in hepatocytes originally cultured for more than 16 h, IL-6 and dexamethasone produced a synergistic increase in MnSOD mRNA levels. The induction of MnSOD expression by IL-6, which is a known inflammatory cytokine, suggests that MnSOD may play a role in the inflammation process. Since inflammation is known to result in oxidative damage to cells, the role of MnSOD may be to protect cells from inflammation-mediated oxidative damage.

Acute-Phase Proteins↗

PubMed1990

Regulation of manganese superoxide dismutase by lipopolysaccharide, interleukin-1, and tumor necrosis factor. Role in the acute inflammatory response.

We have demonstrated a dramatic induction of manganese superoxide dismutase (Mn-SOD) mRNA levels in response to lipopolysaccharide (LPS), interleukin-1, and tumor necrosis factor in pulmonary epithelial cells. These stimuli had no effect on the corresponding mRNA levels for the copper/zinc (Cu/Zn)-SOD. Identical treatments of pulmonary fibroblast cells with LPS showed only minor changes in the Mn-SOD mRNA levels demonstrating a cell type-specific effect for this acute inflammatory mediator. Furthermore, we have shown that hyperoxia has no effect within 24 h on Mn-or Cu/Zn-SOD mRNA levels in either fibroblasts or epithelial cells. The induction of Mn-SOD mRNA levels by LPS is completely inhibited by actinomycin. Treatment of cells with cycloheximide causes an induction equal to that for LPS, whereas co-treatment with cycloheximide and LPS resulted in a "super induction." This data is strongly suggestive of an important role for the Mn-SOD in the acute inflammatory response.

Animals↗