title: Killing of rat basophilic leukemia cells by lethal toxin from Clostridium sordellii: critical role of phosphatidylinositide 3'-OH kinase/Akt signaling.
abstract: Clostridium sordellii lethal toxin (TcsL) belongs to the family of clostridial glucosylating toxins. TcsL exhibits glucosyltransferase activity to inactivate Rho and Ras proteins. On cultured cells, TcsL causes actin reorganization ("cytopathic effect") and apoptotic cell death ("cytotoxic effect"). This study is based on the concept that the cytotoxic effects of TcsL depend on the glucosylation of critical substrate proteins rather than on the glucosyltransferase activity per se. The cytotoxic effects of TcsL depend on the glucosyltransferase activity of TcsL, as neither chemically inactivated TcsL nor a glucosyltransferase-deficient mutant version of TcsL caused it. The TcsL homologous toxin B from Clostridium difficile serotype F strain 1470 (TcdBF) also failed to cause cytotoxic effects. Correlation of the toxins' respective protein substrate specificities highlighted (H/K/N)Ras as critical substrate proteins for the cytotoxic effects. (H/K/N)Ras are critical upstream regulators of phosphatidylinositide 3'-OH kinase (PI3K)/Akt survival signaling. Tauroursodeoxycholic acid (TUDCA) classified to activate PI3K/Akt signaling downstream of apoptosis-inducing stimuli prevented the cytotoxic effects of TcsL. In conclusion, (H/K/N)Ras glucosylation and subsequent inhibition of PI3K/Akt signaling are critical for the cytotoxic effects of TcsL.
authors.affiliation: Institut für Toxikologie, Medizinische Hochschule Hannover, D-30625 Hannover, Germany.
authors.forename: Stefanie C
authors.initials: SC
authors.lastname: Dreger
authors.forename: Florian
authors.initials: F
authors.lastname: Schulz
authors.forename: Johannes
authors.initials: J
authors.lastname: Huelsenbeck
authors.forename: Ralf
authors.initials: R
authors.lastname: Gerhard
authors.forename: Fred
authors.initials: F
authors.lastname: Hofmann
authors.forename: Ingo
authors.initials: I
authors.lastname: Just
authors.forename: Harald
authors.initials: H
authors.lastname: Genth
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006031:Glycosylation / Q000187:drug effects; D016695:Glycosyltransferases / Q000378:metabolism; D015471:Leukemia, Basophilic, Acute / Q000201:enzymology / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology
chemical_list: D001427:Bacterial Toxins; D053148:Caspase 3; D016695:Glycosyltransferases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D013655:Taurochenodeoxycholic Acid; C488583:Clostridium difficile lethal toxin B; C072292:lethal toxin LT, Clostridium sordellii; C031655:ursodoxicoltaurine