Interaction of the frog brain kainate receptor expressed in Chinese hamster ovary cells with a GTP-binding protein.

The rapid modulation of ligand-binding affinity (“activation”) is a central property of the integrin family of cell adhesion receptors. The small GTP-binding protein Ras and its downstream effector kinase Raf-1 suppress integrin activation. In this study we explored the relationship between Ras and the closely related small GTP-binding protein R-Ras in modulating the integrin affinity state. We found that R-Ras does not seem to be a direct activator of integrins in Chinese hamster ovary cells. However, we observed that GTP-bound R-Ras strongly antagonizes the Ras/Raf-initiated integrin suppression pathway. Furthermore, this reversal of the Ras/Raf suppressor pathway does not seem to be via a competition between Ras and R-Ras for common downstream effectors or via an inhibition of Ras/Raf-induced MAP kinase activation. Thus, R-Ras and Ras may act in concert to regulate integrin affinity via the activation of distinct downstream effectors.

Download Full-text

Specific role for p85/p110β in GTP-binding-protein-mediated activation of Akt

Biochemical Journal ◽

10.1042/bj20050671 ◽

2005 ◽

Vol 392 (3) ◽

pp. 607-614 ◽

Cited By ~ 37

Author(s):

Hiroshi Kubo ◽

Kaoru Hazeki ◽

Shunsuke Takasuga ◽

Osamu Hazeki

Keyword(s):

Binding Protein ◽

Chinese Hamster Ovary Cells ◽

Point Mutations ◽

Chinese Hamster ◽

Middle Part ◽

Dependent Manner ◽

Gtp Binding Protein ◽

Intact Cells ◽

Ovary Cells ◽

Gtp Binding

We prepared CHO (Chinese hamster ovary) cells expressing both IR (insulin receptor) and A1R (A1 adenosine receptor). Treatment of the cells with insulin or PIA [N6-(2-phenylisopropyl)adenosine], a specific A1R agonist increased Akt activity in the cells in a PI3K- (phosphoinositide 3-kinase) dependent manner. Transfection of p110β into the cells augmented the action of PIA with little effect on insulin. Introduction of a pH1 vector producing shRNA (short hairpin RNA) that targets p110β abolished PIA-induced Akt activation. By contrast, an shRNA probe targeting p110α did not impair the effects of PIA. The effect of PIA in p110α-deficient cells was attenuated effectively by both Δp85 and βARK-CT (β-adrenergic receptor kinase-C-terminal peptide). A Δp85-derived protein possessing point mutations in its two SH2 domains did not impair PIA action. These results suggest that tyrosine-phosphorylated proteins and Gβγ (βγ subunits of GTP-binding protein) are necessary for the specific function of p110β in intact cells. The p110β-middle (middle part of p110β) may play an important role in signal reception from GPCRs (GTP-binding-protein-coupled receptor), because transfection of the middle part impaired PIA sensitivity.

Download Full-text

Overexpression of cold-inducible RNA-binding protein increases interferon-γ production in Chinese-hamster ovary cells

Biotechnology and Applied Biochemistry ◽

10.1042/ba20070032 ◽

2008 ◽

Vol 49 (4) ◽

pp. 247 ◽

Cited By ~ 22

Author(s):

Hong Kiat Tan ◽

May May Lee ◽

Miranda G. S. Yap ◽

Daniel I. C. Wang

Keyword(s):

Chinese Hamster Ovary ◽

Rna Binding ◽

Binding Protein ◽

Chinese Hamster Ovary Cells ◽

Rna Binding Protein ◽

Chinese Hamster ◽

Interferon Γ ◽

Ovary Cells

Download Full-text

[3H]5?-N-Ethylcarboxamidoadenosine selectively labels the low affinity adenosine binding protein, adenotin, on intact chinese hamster ovary cells

Drug Development Research ◽

10.1002/ddr.430290409 ◽

1993 ◽

Vol 29 (4) ◽

pp. 305-309 ◽

Cited By ~ 4

Author(s):

Michael F. Jarvis ◽

Alan Saltzman

Keyword(s):

Chinese Hamster Ovary ◽

Binding Protein ◽

Chinese Hamster Ovary Cells ◽

Chinese Hamster ◽

Ovary Cells ◽

Adenosine Binding Protein

Download Full-text

Polyamine-mediated turnover of ornithine decarboxylase in Chinese-hamster ovary cells

Biochemical Journal ◽

10.1042/bj2360351 ◽

1986 ◽

Vol 236 (2) ◽

pp. 351-357 ◽

Cited By ~ 19

Author(s):

J R Glass ◽

E W Gerner

Keyword(s):

Ornithine Decarboxylase ◽

Chinese Hamster Ovary ◽

Specific Activity ◽

Binding Protein ◽

Chinese Hamster Ovary Cells ◽

Chinese Hamster ◽

Defined Medium ◽

Ovary Cells ◽

Exogenous Substrate ◽

Polyamine Content

We have used Chinese-hamster ovary (CHO) cells maintained in a chemically defined medium to study the regulation of ornithine decarboxylase (ODC) by polyamines. Cells maintained in the defined medium had no detectable putrescine, and approx. 1-3 units of ODC activity/10(6) cells, where 1 unit corresponds to 1 nmol of substrate decarboxylated in 30 min. The defined medium is ornithine-deficient, thus limiting the exogenous substrate for ODC, and subsequently decreasing intracellular polyamine accumulation. Restoration of intracellular putrescine and increased formation of spermidine by addition of exogenous ornithine or putrescine led to a marked decrease in ODC activity, which was paralleled by a decrease in a alpha-DL-difluoromethyl[3,4-3H]ornithine (DFMO)-binding protein of Mr approx. 53,000, which is precipitable with anti-ODC antibody. Calculation of DFMO binding per unit of activity showed no change in the specific activity of the enzyme. We identified [35S]methionine-labelled peptides corresponding to ODC by immunoprecipitation of radiolabeled whole cell proteins. Only one protein was precipitated, of Mr approx. 53 000, which co-migrated with the DFMO-binding protein. Immunoprecipitation of radiolabelled proteins from cells incubated in the presence of exogenous ornithine indicated that the observed activity decrease was not due to an inhibition of ODC protein synthesis. Analysis of immunoprecipitable ODC protein from cells that had been pulse-labelled with [35S]methionine, and then treated for 5 h with 100 microM-ornithine, -putrescine or -spermidine, revealed a distinct disappearance of labelled ODC protein after restoration of intracellular polyamine pools. No detectable turnover of ODC was observed in the absence of exogenous polyamine treatment. These data support the hypothesis that ODC protein, and subsequent activity, is regulated by intracellular polyamine content through mechanisms that influence turnover of the enzyme.

Download Full-text