Lethal toxin from Clostridium sordellii induces apoptotic cell death by disruption of mitochondrial homeostasis in HL-60 cells.
Lethal toxin (LT) from Clostridium sordellii (strain IP82) inactivates in glucosylating the small GTPases Ras, Rap, Ral and Rac. In the present study we show that LT-IP82 induces cell death via an intrinsic apoptotic pathway in the myeloid cell-line HL-60. LT-IP82 was found to disrupt mitochondrial homeostasis as characterized by a decrease in mitochondrial transmembrane potential and cardiolipin alterations, associated with the release of cytochrome c in the cytosol. Time-course studies of caspase activation revealed that caspase-9 and caspase-3 were activated before caspase-8. Moreover, although LT-IP82-induced cell death was abrogated by caspase-inhibitors, these inhibitors did not suppress mitochondrial alterations, indicating that caspase activation occurs downstream of mitochondria. Protection of mitochondria by Bcl-2 overexpression prevented mitochondrial changes as well as apoptosis induction. Furthermore, evidence is provided that LT-IP82-induced apoptosis is not a consequence of cortical actin disorganization, suggesting that Rac inactivation does not initiate the apoptotic process. Cell exposure to LT-IP82 leads to a co-localization of the toxin with a mitochondrial marker within 2 h. Therefore, we suggest that LT-IP82 could act at the mitochondrion level independently of its enzymatic effect on small GTPases.
Petit
Patrice
P
Institut Cochin, Inserm U567, Department of Developmental Genetic and Molecular PathologyICGM, 24 rue du Faubourg Saint-Jacques, 75014 Paris, France.
Bréard
Jacqueline
J
Montalescot
Valérie
V
El Hadj
Noomen Ben
NB
Levade
Thierry
T
Popoff
Michel
M
Geny
Blandine
B
D000199:Actins / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001427:Bacterial Toxins / Q000494:pharmacology*; D015415:Biomarkers; D002308:Cardiolipins / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003013:Clostridium / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018922:HL-60 Cells; D006706:Homeostasis; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D013997:Time Factors
D000199:Actins; D000590:Amino Acid Chloromethyl Ketones; D001427:Bacterial Toxins; D015415:Biomarkers; D002308:Cardiolipins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C072292:lethal toxin LT, Clostridium sordellii; D045304:Cytochromes c; D005964:Glucosyltransferases; D013108:Sphingomyelin Phosphodiesterase; D020169:Caspases