title: Caspase-8-mediated cleavage of Bid and protein phosphatase 2A-mediated activation of Bax are necessary for Verotoxin-1-induced apoptosis in Burkitt's lymphoma cells.
abstract: Verotoxin (VT-1) is a cytotoxin, produced by Shigella dysenteriae type 1 or by Shiga toxin-producing Escherichia coli, which binds specifically to globotriaosylceramide (Gb3). This glycosphingolipid is a B cell differentiation antigen (Gb3/CD77) strongly expressed on Burkitt's lymphoma cells. We have previously shown that, in these cells, VT-1 induces apoptosis via a caspase- and mitochondria-dependent pathway. In this report, we provide new insights into this signal transduction pathway. First, we demonstrate that VT-1-induced apoptosis requires degradation of the caspase-8 inhibitory molecule c-FLIPL and that this degradation occurs through the ubiquitin-proteasome pathway. Furthermore, we show that mitochondrial activation is mainly due to i) cleavage and activation of the pro-apoptotic Bcl-2 family member Bid by caspase-8 and ii) Bax relocalization to mitochondrial membranes which lead to cytochrome c release. However, tBid is not involved in Bax relocalization, and relocalization is most likely controlled by the extent of Bax phosphorylation: in non-treated BL cells, p38 MAPK participates in the retention of Bax in the cytoplasm in an inactive form whereas in VT-1 treated cells, protein phosphatase 2A is activated and induces Bax relocalization to mitochondria.
authors.affiliation: UMR 8126 CNRS, Université Paris-Sud 11, Institut Gustave Roussy, 94805 Villejuif cedex, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Garibal
authors.forename: Emilie
authors.initials: E
authors.lastname: Hollville
authors.forename: Benjamin
authors.initials: B
authors.lastname: Renouf
authors.forename: Cécile
authors.initials: C
authors.lastname: Tétaud
authors.forename: Joëlle
authors.initials: J
authors.lastname: Wiels
mesh_terms: D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D002051:Burkitt Lymphoma / Q000378:metabolism*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism*; D002460:Cell Line; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D022622:Shiga Toxin 1 / Q000494:pharmacology*; D012762:Shigella dysenteriae / Q000378:metabolism; D015398:Signal Transduction; D014281:Trihexosylceramides / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D022622:Shiga Toxin 1; D014281:Trihexosylceramides; D025801:Ubiquitin; D051028:bcl-2-Associated X Protein; C018549:globotriaosylceramide; D045304:Cytochromes c; D048051:p38 Mitogen-Activated Protein Kinases; D054648:Protein Phosphatase 2; D053181:Caspase 8; D046988:Proteasome Endopeptidase Complex