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Synthesis of protein in intestinal cells exposed to cholera toxin
J W Peterson1, W D Berg, D H Coppenhaver
1Department of Microbiology, University of Texas Medical Branch, Galveston 77550.
Abstract:
The mechanism by which cyclic adenosine monophosphate (AMP), formed by intestinal epithelial cells in response to cholera toxin, ultimately results in alterations in water and electrolyte transport is poorly understood. Several studies have indicated that inhibitors of transcription or translation block much of the transport of ions and water in the intestine and edema formation in tissue elicited by cholera toxin. Data presented in this study confirmed the inhibitory effects of cycloheximide on cholera toxin-induced fluid accumulation in the rabbit intestinal loop model. Neither cycloheximide nor actinomycin D altered the amount of cyclic AMP that accumulated in intestinal cells and Chinese hamster ovary cells exposed to cholera toxin. An increase in [3H]leucine incorporation was readily demonstrable in intestinal epithelial cells from rabbits challenged with Vibrio cholerae. Similarly, intestinal epithelial cells incubated with cholera toxin for 4 hr synthesized substantially more protein than controls as determined by relative incorporation of [35S]methionine. Most of the new protein synthesized in response to cholera toxin was membrane associated and of high molecular weight. The possible significance of the toxin-induced protein relative to cholera pathogenesis was discussed.
Insights
Cholera toxin triggers new protein synthesis in intestinal cells, which is crucial for fluid transport changes. Inhibiting protein synthesis blocks cholera toxin
Area of Science:
- Molecular Biology
- Gastroenterology
- Microbiology
Background:
- The precise mechanism linking cyclic adenosine monophosphate (AMP) to cholera toxin-induced fluid and electrolyte transport alterations in the intestine remains unclear.
- Previous research suggests that inhibiting transcription or translation significantly impacts intestinal ion and water transport, as well as edema formation caused by cholera toxin.
Purpose of the Study:
- To investigate the role of protein synthesis in cholera toxin-induced intestinal fluid accumulation.
- To determine if cycloheximide and actinomycin D affect cyclic AMP levels in response to cholera toxin.
- To characterize the newly synthesized proteins in intestinal epithelial cells following cholera toxin exposure.
Main Methods:
- Utilized a rabbit intestinal loop model to assess the effect of cycloheximide on cholera toxin-induced fluid accumulation.
- Measured cyclic AMP levels in intestinal cells and Chinese hamster ovary cells exposed to cholera toxin, with or without cycloheximide or actinomycin D.
- Quantified protein synthesis by measuring [3H]leucine and [35S]methionine incorporation in intestinal epithelial cells from rabbits challenged with Vibrio cholerae or treated with cholera toxin.
Main Results:
- Cycloheximide effectively inhibited cholera toxin-induced fluid accumulation in the rabbit intestinal loop model.
- Neither cycloheximide nor actinomycin D affected the accumulation of cyclic AMP in intestinal or Chinese hamster ovary cells treated with cholera toxin.
- Significant increases in protein synthesis, particularly of high-molecular-weight, membrane-associated proteins, were observed in intestinal epithelial cells in response to cholera toxin.
Conclusions:
- The inhibitory effect of cycloheximide on cholera toxin-induced fluid transport is not mediated by alterations in cyclic AMP levels.
- Cholera toxin stimulates the synthesis of specific new proteins in intestinal epithelial cells.
- These newly synthesized proteins likely play a significant role in the pathogenesis of cholera by mediating altered water and electrolyte transport.