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Inhibition of the activity of pseudomonas toxin by methylamine
Abstract:
Methylamine at a concentration of 20 mM protected mouse LM cell fibroblasts from the action of pseudomonas toxin. Nearly total protection was observed when cells were pretreated with amine before the addition to toxin and amine, when amine and toxin were added simultaneously, or when amine was added up to 30 min after toxin binding. Later addition of methylamine afforded partial protection of the monolayers. Using electron microscopy, we observed that toxin initially bound diffusely to the cell surface but rapidly moved to coated pits and was internalized after cells were warmed to 37 C. Methylamine blocked the clustering of toxin into coated-pit areas of the membrane but did not alter the overall level of toxin internalization. It is suggested that pseudomonas toxin enters mammalian cells by receptor-mediated endocytosis and that methylamine alters the entry process. In those instances in which partial protection was seen when methylamine was added after toxin internalization, the primary amine may be functioning by inactivation of lysosomal processing of the toxin.
Insights
Methylamine protects mouse cells from Pseudomonas toxin by blocking its entry into coated pits. This amine treatment alters toxin internalization, suggesting a novel mechanism for cellular protection against bacterial toxins.
Area of Science:
- Cell biology
- Toxicology
- Biochemistry
Background:
- Pseudomonas toxin is a potent cytotoxin that affects mammalian cells.
- Understanding the mechanism of toxin entry is crucial for developing protective strategies.
Purpose of the Study:
- To investigate the protective effect of methylamine against Pseudomonas toxin.
- To elucidate the mechanism by which methylamine confers protection.
Main Methods:
- Mouse LM cell fibroblasts were treated with methylamine and Pseudomonas toxin.
- Electron microscopy was used to visualize toxin binding and internalization.
- The effect of methylamine on toxin clustering and entry into coated pits was analyzed.
Main Results:
- Methylamine (20 mM) provided significant protection to mouse cells from Pseudomonas toxin.
- Protection was observed when methylamine was added before, during, or up to 30 minutes after toxin binding.
- Methylamine inhibited toxin clustering into coated pits but did not affect overall toxin internalization.
- Later addition of methylamine resulted in partial protection, potentially via lysosomal inactivation.
Conclusions:
- Pseudomonas toxin enters mammalian cells via receptor-mediated endocytosis.
- Methylamine interferes with the initial steps of toxin entry by preventing clustering into coated pits.
- Methylamine may offer protection by altering the endocytic pathway or inactivating the toxin intracellularly.