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Cholera toxin effects on cell growth accompanied by selective alterations in metabolite uptake and modification of
Abstract:
Exposure of Chinese hamster ovary cells to cholera toxin at or below mug levels causes a marked morphological changes and increased adhesion and orientation of the cells. Such changes are paralleled by alterations in surface proteins as indicated by the cholera toxin-mediated modifications detectable by lactoperoxidase-catalyzed radioiodination of outer proteins. Mild tryptic treatment of cells prelabeled with [3H]glucosamine revealed a different kinetics of release of external glycoproteins in cells exposed to the toxin. An alteration in a specific glycoprotein species in cholera toxin-treated cells became evident by polyacrylamide gel electrophoresis followed by fluorography of 3H-labeled cellular glycoproteins. The effects of cholera toxin on surface proteins and growth of the cells occurred in the absence of a modification in amino acid uptake or incorporation of precursors into protein. However, thymidine uptake and glucosamine incorporation were inversely affected to toxin treatment. Some of the effects of the toxin appeared to be antagonized by colchicine.
Insights
Cholera toxin alters Chinese hamster ovary cell surface proteins and growth, affecting glycoprotein release and thymidine uptake. Colchicine partially counteracted these toxin-induced effects.
Area of Science:
- Cell Biology
- Biochemistry
- Toxicology
Background:
- Cholera toxin is known to affect cellular processes.
- Understanding its impact on cell surface dynamics is crucial.
Purpose of the Study:
- To investigate the effects of cholera toxin on Chinese hamster ovary (CHO) cell morphology, adhesion, and surface protein alterations.
- To elucidate the specific changes in cell surface glycoproteins and their incorporation kinetics.
Main Methods:
- Exposure of CHO cells to varying concentrations of cholera toxin.
- Lactoperoxidase-catalyzed radioiodination to detect surface protein modifications.
- Tryptic digestion and [3H]glucosamine labeling to analyze glycoprotein release kinetics.
- Polyacrylamide gel electrophoresis and fluorography for glycoprotein analysis.
- Measurement of amino acid, thymidine, and glucosamine uptake/incorporation.
Main Results:
- Cholera toxin induced significant morphological changes, increased cell adhesion, and altered surface protein profiles.
- Differential kinetics of external glycoprotein release were observed in toxin-treated cells.
- A specific glycoprotein species was altered in cholera toxin-exposed cells.
- Thymidine uptake and glucosamine incorporation were inversely affected by toxin treatment, while amino acid uptake remained unchanged.
- Colchicine demonstrated an antagonistic effect on some cholera toxin-induced cellular changes.
Conclusions:
- Cholera toxin profoundly impacts CHO cell surface protein composition and cellular metabolism.
- The observed alterations in glycoproteins and metabolic pathways highlight the toxin's complex cellular mechanisms.
- Colchicine may modulate specific cholera toxin-mediated cellular responses.