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Effect of energy inhibitors on cell surface diphtheria toxin receptor numbers
Abstract:
The effects of various metabolic inhibitors on cell-surface receptors for diphtheria toxin were studied. Incubation of Vero cells at 37 degrees C with fluoride, azide, salicylate, and, to a lesser degree, with deoxyglucose resulted in an apparent loss of receptors for the toxin. With some drugs the loss was rapid (half-time approximately 8-9 min) while with others considerably longer time periods were required (half-time greater than or equal to 40 min). The loss of toxin receptors could also be induced by the drugs at 4 degrees C. Washing out the drugs and incubating the cells at 37 degrees C led to a complete restoration of receptors to control numbers. Restoration did not occur if cells were incubated at 4 degrees C. The regain of binding capacity was not dependent on RNA or protein synthesis. It is suggested that metabolic inhibitors may block a continuous process required to maintain toxin receptors in a functional state at the cell surface.
Insights
Metabolic inhibitors like fluoride and azide reduce diphtheria toxin receptors on cells. Receptor levels fully recovered when cells were warmed, indicating a reversible process not requiring new protein or RNA synthesis.
Area of Science:
- Cell Biology
- Toxicology
- Molecular Biology
Background:
- Diphtheria toxin utilizes cell-surface receptors for entry.
- The dynamic nature of cell-surface receptors is crucial for cellular processes.
Purpose of the Study:
- To investigate the impact of metabolic inhibitors on diphtheria toxin receptor expression.
- To elucidate the reversibility and underlying mechanisms of receptor modulation.
Main Methods:
- Vero cells were incubated with various metabolic inhibitors (fluoride, azide, salicylate, deoxyglucose) at different temperatures (37°C and 4°C).
- Diphtheria toxin receptor levels were assessed following inhibitor treatment and subsequent washout.
- Receptor recovery was evaluated under different temperature conditions and in the presence/absence of RNA/protein synthesis inhibitors.
Main Results:
- Metabolic inhibitors, particularly fluoride and azide, caused a rapid or gradual loss of diphtheria toxin receptors.
- Receptor loss was observed at both 37°C and 4°C.
- Warming cells to 37°C after inhibitor removal fully restored receptor numbers, while incubation at 4°C prevented recovery.
- Receptor restoration occurred independently of new RNA or protein synthesis.
Conclusions:
- Metabolic inhibitors reversibly affect diphtheria toxin receptor levels on Vero cells.
- A continuous cellular process, dependent on temperature but not de novo synthesis, is essential for maintaining functional toxin receptors.
- These findings suggest metabolic inhibitors interfere with a dynamic mechanism regulating receptor stability or recycling at the cell surface.