C2-ceramide signaling in glioma cells: synergistic enhancement of CD95-mediated, caspase-dependent apoptosis.
Most human malignant glioma cell lines are susceptible to CD95 ligand (CD95L)-induced apoptosis. Here, we report that glioma cells are also susceptible to the cytotoxic effects of exogenous C2-ceramide. This form of cell death exhibits some morphological features of apoptosis as assessed by electron microscopy, but is unaffected by the broad spectrum caspase inhibitor, zVAD-fmk. Further, CD95L-induced apoptosis is synergistically enhanced by coexposure of the glioma cells to CD95L and C2-ceramide. CD95L-induced caspase 3-like activity, cytochrome c release and cleavage of caspases 3, 8, 9 and poly(ADP-ribose)polymerase (PARP) increase substantially after cotreatment with CD95L and C2-ceramide compared with CD95L treatment alone. None of these events occur in response to cytotoxic concentrations of C2-ceramide alone. C2-ceramide does not alter CD95 expression. Gene transfer-mediated enhancement of CD95 expression results not only in increased susceptibility to CD95L, but also in increased sensitivity to C2-ceramide. We conclude that (i) synergistic induction of apoptosis by C2-ceramide and CD95L depend on a cross-talk between the two signal transduction pathways and that (ii) C2-ceramide, independently of its sensitizing effects on CD95-dependent caspase activation, is also capable of triggering an apoptotic signaling cascade that is unaffected by zVAD-fmk-mediated caspase inhibition, but promoted by high levels of CD95 expression.
Wagenknecht
B
B
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University of Tübingen, Tübingen, Germany.
Roth
W
W
Gulbins
E
E
Wolburg
H
H
Weller
M
M
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein; D006801:Humans; D015151:Immunoblotting; D008562:Membrane Glycoproteins / Q000378:metabolism; D008854:Microscopy, Electron; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009457:Neuroglia / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; C064769:N-acetylsphingosine; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D013110:Sphingosine