scholarly journals Multiple regulation of ornithine decarboxylase in enzyme-overproducing cells

1993 ◽  
Vol 289 (2) ◽  
pp. 581-586 ◽  
Author(s):  
T Kameji ◽  
S Hayashi ◽  
K Hoshino ◽  
Y Kakinuma ◽  
K Igarashi
Keyword(s):  
Cell Line ◽  
Ornithine Decarboxylase ◽  
Synthesis Rate ◽  
Translational Efficiency ◽  
Irreversible Inhibitor ◽  
Variant Cell ◽  
Mrna Content ◽  
The Stability ◽  
Variant Cell Line ◽  
Fm3a Cells

We have isolated from mouse FM3A cells a variant cell line, termed EXOD-1, that overproduces ornithine decarboxylase (ODC). The cells were resistant to alpha-difluoromethylornithine, an irreversible inhibitor of the enzyme, and produced the enzyme protein to the extent of approx. 3-6% of total cytosolic protein. The rate of ODC synthesis in this cell line accounted for 25-50% of the rate of total protein synthesis. The amounts of the ODC gene and its mRNA in the variant cells were both about 60 times as much as those in wild-type FM3A cells. Upon removal of the inhibitor, the growth of the ODC-overproducing cells was stimulated approx. 2-fold. Under these conditions, the rate of ODC synthesis increased about 4-fold on day 1 and then decreased to near the original level by day 3. The amount of ODC mRNA increased about 1.7-fold on day 1 and 2.5-fold on day 3. No correlation was observed between changes in ODC synthesis rate and in ODC mRNA content, suggesting a translational repression of ODC mRNA due to accumulation of polyamines. In fact, the cellular contents of putrescine and spermidine markedly increased and that of spermine inversely decreased during the same period. Pulse-chase experiments showed that the accumulation of putrescine and spermidine also elicited a rapid degradation of ODC. Excess amounts of newly synthesized putrescine and cadaverine were excreted into the medium, whereas spermidine, spermine and acetylated polyamines were undetectable there. We conclude that ODC regulation upon removal of the inhibitor is dependent on at least three steps, namely the level of mRNA, the translational efficiency of mRNA and the stability of the enzyme, the last two of which are involved in cellular polyamines.

Predominant expression of σ and ε globin genes in human leukemia K-562(S6) variant cell line

1983 ◽  
Vol 39 (4) ◽  
pp. 415-416 ◽  
Author(s):  
R. Gambari ◽  
G. Raschellà ◽  
R. Biagini ◽  
M. Tripodi ◽  
M. G. Farace ◽  
...  
Keyword(s):  
Cell Line ◽  
Human Leukemia ◽  
Globin Genes ◽  
Variant Cell ◽  
Variant Cell Line ◽  
Predominant Expression

A Swiss 3T3 variant cell line resistant to the effects of tumor promoters cannot be transformed by src

1990 ◽  
Vol 10 (8) ◽  
pp. 4155-4162
Author(s):  
M Nori ◽  
L K Shawver ◽  
M J Weber
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cell Line ◽  
Inhibitory Effect ◽  
Tumor Promoters ◽  
Kinase C ◽  
Growth Inhibitory ◽  
Variant Cell ◽  
Swiss 3T3 ◽  
Variant Cell Line

To study the relationship between oncogenesis by v-src and normal cellular signalling pathways, we determined the effects of v-src on 3T3-TNR9 cells, a Swiss 3T3 variant which does not respond mitogenically to tumor promoters such as 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We found that src was unable to transform these variant cells, whether the oncogene was introduced by infection with a murine retrovirus vector or by transfection with plasmid DNA. 3T3-TNR9 cells were not inherently resistant to transformation, since infection with similar recombinant retroviruses containing either v-ras or v-abl did induce transformation. Further analysis of Swiss 3T3 and 3T3-TNR9 cell populations infected with the v-src-containing retrovirus revealed that although the amount of v-src DNA in each was approximately the same, the level of the v-src message and protein and the overall level of phosphotyrosine expressed in the infected variants was much less than in infected parental cells. Cotransfection experiments using separate v-src and neo plasmids revealed a decrease in the number of G418-resistant colonies when transfections of TNR9 cells occurred in the presence of the src-containing plasmid, suggesting a growth inhibitory effect of v-src on 3T3-TNR9 cells, as has also been found for TPA itself. Since v-src cannot transform this variant cell line, which does not respond mitogenically to the protein kinase C agonist TPA, we suggest that src makes use of the protein kinase C pathway as part of its signalling activities.

Maintained PC1 and PC2 Expression in the AtT-20 Variant Cell Line 6T3 Lacking Regulated Secretion and POMC: Restored POMC Expression and Regulated Secretion after cAMP Treatment

1995 ◽  
Vol 14 (2) ◽  
pp. 175-188 ◽  
Author(s):  
ROBERT DAY ◽  
SUZANNE BENJANNET ◽  
LINDA MATSUUCHI ◽  
REGIS B. KELLY ◽  
MIECZYSLAW MARCINKIEWICZ ◽  
...  
Keyword(s):  
Cell Line ◽  
Regulated Secretion ◽  
Variant Cell ◽  
Variant Cell Line

scholarly journals Temperature-sensitive transport of glycoproteins to the surface of a variant mouse lymphoma cell line.

1988 ◽  
Vol 8 (2) ◽  
pp. 833-842 ◽  
Author(s):  
M Nori ◽  
M R Stallcup
Keyword(s):  
Cell Surface ◽  
Cell Line ◽  
Lymphoma Cell ◽  
Response To Treatment ◽  
Temperature Sensitive ◽  
Lymphoma Cell Line ◽  
Wild Type ◽  
Variant Cell ◽  
Variant Cell Line ◽  
Mouse Lymphoma

The expression of mouse mammary tumor virus (MMTV) glycoproteins on the surface of stably infected mouse lymphoma cell line W7MG1 is dramatically increased by glucocorticoid hormones. A variant cell line, W7M.TS1, was selected from W7MG1 for its lack of expression of MMTV glycoproteins on the cell surface in response to treatment with glucocorticoid. Hormonal stimulation of MMTV RNA levels and hormone-induced cytolysis occurred normally in the variant cells. Furthermore, the rates of production of the precursor and mature forms of MMTV glycoproteins in the presence of glucocorticoid were similar in variant and wild-type cells. However, the accumulation of MMTV glycoproteins on the cell surface after hormone treatment was delayed by about 8 h in the variant relative to wild-type cells. The steady-state level of a constitutively expressed cellular protein, T200, on the variant cell surface was comparable to that on wild-type cells. However, in pulse-chase experiments, the appearance of newly synthesized T200 on the cell surface was delayed in the variant compared with wild-type cells. Another glucocorticoid hormone response, removal of H-2 class I antigens from the cell surface, was also delayed in the variant relative to wild-type cells, suggesting that turnover or internalization of cell surface glycoproteins may also be affected in the variant. The defects in the variant cell line were observed at 37 degrees C, but not at 31 degrees C; the variant cells grew normally at both temperatures. This variant phenotype defines a new genetic entity that is important for transport of glycoproteins between internal microsomal compartments and the cell surface.

scholarly journals Human myeloma cells acquire resistance to difluoromethylornithine by amplification of ornithine decarboxylase gene

1987 ◽  
Vol 242 (1) ◽  
pp. 199-203 ◽  
Author(s):  
P Leinonen ◽  
L Alhonen-Hongisto ◽  
R Laine ◽  
O A Jänne ◽  
J Jänne
Keyword(s):  
Effective Dose ◽  
Ornithine Decarboxylase ◽  
Polyacrylamide Gel Electrophoresis ◽  
Fold Increase ◽  
Synthesis Rate ◽  
Irreversible Inhibitor ◽  
Myeloma Cells ◽  
Cultured Human Cells ◽  
Enzyme Molecules ◽  
Dose Dependent

Stepwise increments of the concentration of 2-difluoromethylornithine (DFMO), a mechanism-based irreversible inhibitor of mammalian ornithine decarboxylase (ODC), resulted in a selection of cultured human IgG-myeloma cells (Sultan cell line) capable of growing in the presence of up to 3 mM-DFMO. This capacity was associated with 10-fold increase in ODC activity in the dialysed extracts of drug-resistant myeloma cells, markedly enhanced synthesis rate for ODC enzyme molecules, as revealed by a 20 min [35S]methionine labelling of cellular proteins, followed by specific immunoprecipitation and SDS/polyacrylamide-gel electrophoresis, dose-dependently increased expression of ODC mRNA in resistant cells (effective dose causing 50% inhibition), dose-dependent amplification of ODC gene sequences in a 9-kilobase-pairs EcoRI genomic DNA fragment, and (v) a 10-fold increase in the ED50 (effective dose causing 50% inhibition) for the anti-proliferative action of DFMO in these myeloma cells. These results represent one of the few gene amplifications described in cultured human cells.

scholarly journals An HL-60 Variant Cell Line Defective in Cholesterol Synthesis.

1995 ◽  
Vol 20 (1) ◽  
pp. 13-21
Author(s):  
Motokatsu Tsuyuki ◽  
Koichiro Yoshihara
Keyword(s):  
Cell Line ◽  
Cholesterol Synthesis ◽  
Variant Cell ◽  
Variant Cell Line
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