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Internalization and processing of Bacillus anthracis lethal toxin by toxin-sensitive and -resistant cells
Y Singh1, S H Leppla, R Bhatnagar
1United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21701-5011.
The Journal of Biological Chemistry
|July 5, 1989
Summary
Anthrax lethal toxin selectively lyses certain macrophages. Resistance in other cell types suggests a lack of intracellular target or defective lethal factor (LF) processing, potentially requiring protective antigen post-endocytosis.
Area of Science:
- Cell Biology
- Immunology
- Microbiology
Background:
- Anthrax lethal toxin, composed of protective antigen and lethal factor (LF), exhibits differential cytotoxicity.
- Macrophages, particularly the J774A.1 cell line, are sensitive to lethal toxin, while others like IC-21 are resistant.
Purpose of the Study:
- To elucidate the molecular basis for differential sensitivity to anthrax lethal toxin in various cell types.
- To investigate the specific steps in the intoxication pathway responsible for resistance.
Main Methods:
- Comparative analysis of protective antigen binding and activation in sensitive and resistant cells.
- Introduction of lethal factor (LF) into cells via osmotic lysis of pinocytic vesicles to assess translocation and intracellular activity.
Main Results:
- No differences observed in protective antigen receptor binding or activation between sensitive and resistant cells.
- Lethal factor (LF) introduction via osmotic lysis lysed only J774A.1 cells, indicating intracellular resistance mechanisms in IC-21 and L6 myoblasts.
- Reduced LF potency in J774A.1 cells suggests protective antigen's role beyond initial endocytosis.
Conclusions:
- Cellular resistance to anthrax lethal toxin is likely due to the absence of an intracellular LF target or impaired LF activation.
- Protective antigen may play a role in LF activity after cellular uptake, contributing to toxin potency.