Calcium is required for the expression of anthrax lethal toxin activity in the macrophagelike cell line J774A.1.
AUTOR(ES)
Bhatnagar, R
RESUMO
Anthrax lethal toxin, which consists of two separate proteins, protective antigen (Mr, 82,700) and lethal factor (Mr, approximately 83,000), is cytotoxic to the macrophagelike cell line J774A.1. Removal of calcium from the culture medium protected cells against the action of lethal toxin. Calcium depletion during the binding phase of intoxication afforded only partial protection. Further analysis showed that calcium removal caused some inhibition of protective antigen binding but that it had minimal effect on proteolytic conversion of protective antigen to the active 63-kilodalton fragment and that it had no effect on lethal factor binding. Cells to which lethal toxin had bound in the presence of calcium were protected when transferred to calcium-depleted culture medium, indicating a role for calcium at a postbinding stage. When ammonium chloride is present with lethal toxin, toxin accumulates in intracellular vesicles. Calcium-free medium protected these cells upon removal of the amine block, suggesting that calcium is also required at a step after internalization of lethal toxin. Calcium channel blockers inhibited 45Ca2+ uptake and protected cells against cytotoxicity. Calmodulin inhibitors also protected against the action of lethal toxin, suggesting involvement of calmodulin at a step during intoxication. We conclude that calcium is required at several steps in the intoxication of cells by anthrax lethal toxin.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=313848Documentos Relacionados
- Biochemical and physiological changes induced by anthrax lethal toxin in J774 macrophage-like cells.
- Differential expression of inward and outward potassium currents in the macrophage-like cell line J774.1.
- Protein synthesis is required for expression of anthrax lethal toxin cytotoxicity.
- Proteasome Activity Is Required for Anthrax Lethal Toxin To Kill Macrophages
- Characterization of a calmodulin-binding protein that is deficient in trifluoperazine-resistant variants of the macrophage-like cell line J774.