Two distinct Gb3/CD77 signaling pathways leading to apoptosis are triggered by anti-Gb3/CD77 mAb and verotoxin-1.
Globotriasosylceramide (Gb3), a neutral glycosphingolipid, is the B-cell differentiation antigen CD77 and acts as the receptor for most Shiga toxins, including verotoxin-1 (VT-1). We have shown that both anti-Gb3/CD77 mAb and VT-1 induce apoptosis in Burkitt's lymphoma cells. We compared the apoptotic pathways induced by these two molecules by selecting cell lines sensitive to only one of these inducers or to both. In all these cell lines (including the apoptosis-resistant line), VT-1 was transported to the endoplasmic reticulum and inhibited protein synthesis similarly, suggesting that VT-1-induced apoptosis is dissociated from these processes. VT-1 triggered a caspase- and mitochondria-dependent pathway (rapid activation of caspases 8 and 3 associated with a loss of mitochondrial membrane potential (Deltapsim) and the release of cytochrome c from mitochondria). In contrast, the anti-Gb3/CD77 mAb-induced pathway was caspase-independent and only involved partial depolarization of mitochondria. Antioxidant compounds had only marginal effects on VT-1-induced apoptosis but strongly protected cells from anti-Gb3/CD77 mAb-induced apoptosis. VT-1- and anti-Gb3/CD77 mAb-treated cells displayed very different features on electron microscopy. These results clearly indicate that the binding of different ligands to Gb3/CD77 triggers completely different apoptotic pathways.
Tétaud
Cecile
C
Laboratoire Interactions Moléculaires et Cancer, CNRS UMR 8126, Institut Gustave Roussy, 94805 Villejuif cedex, France.
Falguières
Thomas
T
Carlier
Karine
K
Lécluse
Yann
Y
Garibal
Julie
J
Coulaud
Dominique
D
Busson
Pierre
P
Steffensen
Rudi
R
Clausen
Henrik
H
Johannes
Ludger
L
Wiels
Joëlle
J
D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis; D001692:Biological Transport; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008024:Ligands; D008564:Membrane Potentials; D008854:Microscopy, Electron; D022603:Shiga Toxins / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D014281:Trihexosylceramides / Q000378:metabolism*
D000975:Antioxidants; D008024:Ligands; D022603:Shiga Toxins; D014281:Trihexosylceramides; C018549:globotriaosylceramide; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases