Identification of p21 as a target of cycloheximide-mediated facilitation of CD95-mediated apoptosis in human malignant glioma cells.
Human glioma cell lines differ in their requirement for the inhibition of protein synthesis to activate the CD95-dependent killing pathway. CD95 ligand (CD95L) induced mitochondrial cytochrome c release and processing of caspases 3, 7, 8 and 9 in LN-18 cells in the absence of an inhibitor of protein synthesis, cycloheximide (CHX). These biochemical changes were observed in LN-229 cells only in the presence of CHX. The viral caspase inhibitor, cytokine response modifier (crm)-A, inhibited mitochondrial cytochrome c release, caspase processing and cell death under all conditions. Ectopic expression of BCL-X(L) prevented processing of caspase 8 in LN-18 cells but not in LN-229 cells. Thus, caspase 8 activation is amplified through the release of cytochrome c in LN-18 cells but occurs mainly at the receptor in LN-229 cells. In contrast to BCL-2, BCL-X(L), X-linked inhibitor-of-apoptosis protein (XIAP) and FLICE-inhibitory protein (FLIP), the levels of the cyclin-dependent kinase (CDK) inhibitor, p21Waf/Cip1, rapidly decreased in response to CHX. P21 antisense oligonucleotides promoted caspase activation and mitochondrial cytochrome c release and induced strong sensitization to CD95-mediated apoptosis. These data place potentiating effects of CHX (i) to the activation of caspase 8 at the receptor in LN-229 cells as well as (ii) to a down-stream target at least in LN-18 cells, but probably both cell lines, that may be identical with p21Waf/Cip1.
Glaser
T
T
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University of Tübingen, Tübingen, Germany.
Wagenknecht
B
B
Weller
M
M
D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000378:metabolism; D005910:Glioma / Q000473:pathology*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein; D019014:fas Receptor / Q000502:physiology*
D051023:BH3 Interacting Domain Death Agonist Protein; C494812:Bcl2l1 protein, mouse; C494815:Bid protein, mouse; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C493957:Cdkn1a protein, mouse; C506387:Cflar protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D003574:Cytochrome c Group; D047908:Intracellular Signaling Peptides and Proteins; D011500:Protein Synthesis Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D019014:fas Receptor; D003513:Cycloheximide