Related Experiment Videos
Receptor-mediated entry of Pseudomonas toxin: methylamine blocks clustering step
Abstract:
Clustering of ligands into coated regions of the plasma membrane is an early step in receptor-mediated endocytosis. The association of Pseudomonas exotoxin A (PE) with mouse LM fibroblasts was visualized by using biotinyl-PE and avidingold. Movement of PE into coated regions occurred within 30 s of warming monolayers to 37 degrees C. This clustering was stopped by the primary amines methylamine and ammonium chloride but was not altered by the tertiary amine chloroquine. Toxin internalization was rapid, with a half-time of approximately 5 min. Although primary amines stopped clustering, they did not alter the rate of toxin internalization; they did alter the route followed after entry. We have shown previously that methylamine protects cells from the lethal action of PE. Here we suggest that methylamine protects, at least in part, by blocking clustering, and that receptor-mediated endocytosis is required for efficient expression of PE toxicity.
Insights
Pseudomonas exotoxin A (PE) clustering on cell membranes is blocked by primary amines, suggesting this clustering is essential for PE toxicity. This finding impacts understanding of toxin entry and cell protection strategies.
Area of Science:
- Cell Biology
- Molecular Biology
- Toxicology
Background:
- Receptor-mediated endocytosis is a key cellular process for internalizing molecules.
- Pseudomonas exotoxin A (PE) utilizes this pathway for cellular entry and toxicity.
Purpose of the Study:
- To investigate the early steps of Pseudomonas exotoxin A (PE) binding and internalization.
- To determine the role of ligand clustering in receptor-mediated endocytosis of PE.
- To explore the protective mechanisms of primary amines against PE toxicity.
Main Methods:
- Visualizing the association of biotinylated PE with mouse LM fibroblasts using avidin-gold conjugates.
- Observing the movement of PE into coated membrane regions upon warming cells to 37°C.
- Assessing the effect of primary amines (methylamine, ammonium chloride) and a tertiary amine (chloroquine) on PE clustering and internalization.
Main Results:
- PE rapidly clustered into coated membrane regions within 30 seconds of warming cells.
- Primary amines, but not chloroquine, effectively blocked PE clustering.
- While primary amines did not alter the rate of PE internalization, they did change its intracellular route.
- PE internalization occurred rapidly, with a half-time of approximately 5 minutes.
Conclusions:
- Ligand clustering into coated membrane regions is an early, critical step in receptor-mediated endocytosis of PE.
- Primary amines protect cells from PE toxicity, at least partially, by inhibiting this essential clustering process.
- Receptor-mediated endocytosis is required for the efficient toxic effects of PE.