Mitochondrial impairment is a critical event in anthrax lethal toxin-induced cytolysis of murine macrophages.
Numerous early events in anthrax lethal toxin (LT)-mediated cell killing have been described, including uptake of LT and MAPKK cleavage. However, critical downstream events in LT killing remain to be identified. In this study we present evidence that LT causes mitochondrial dysfunction in murine J774A.1 macrophages, as indicated by a continuous drop in both mitochondrial membrane potential and SDH activity. This was further supported by ultrastructural analysis revealing LT-induced swelling of mitochondria. Mitochondrial impairment and cytolysis were controlled by proteasomes in LT-treated macrophages: proteasome inhibitors restored mitochondrial activity and rescued cells from cytolysis, even when added immediately prior to membrane perturbation. Similar to proteasome inhibitors, KCl also efficiently blocked LT-mediated cytolysis, even after late addition. However, KCl did not prevent mitochondrial impairment, though it precluded events linked to LT-induced cytolysis. These events included a precipitous drop in ATP levels and ubiquitinated proteins, revealing that they are epiphenomena in LT killing. Our studies suggest that proteasomes and potassium control LT-induced mitochondrial dysfunction and membrane perturbation, key events in LT killing.
Alileche
Abdelkrim
A
Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Squires
Raynal C
RC
Muehlbauer
Stefan M
SM
Lisanti
Michael P
MP
Brojatsch
Jürgen
J
D000818:Animals; D000881:Anthrax; D000942:Antigens, Bacterial / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000187:drug effects* / Q000473:pathology*; D011189:Potassium Chloride / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011485:Protein Binding; D014176:Protein Biosynthesis; D013385:Succinate Dehydrogenase / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D061988:Proteasome Inhibitors; D025801:Ubiquitin; C030325:anthrax toxin; D011189:Potassium Chloride; D013385:Succinate Dehydrogenase; D046988:Proteasome Endopeptidase Complex