Apoptosome-independent pathway for apoptosis. Biochemical analysis of APAF-1 defects and biological outcomes.
Induction and execution of apoptosis programs are generally believed to be mediated through a hierarchy of caspase activation. By using two cellular variants obtained from the L1210 cell line (L1210/S and L1210/0), we have shown previously that staurosporine induces apoptotic cell death through both caspase-dependent and caspase-independent pathways. Both pathways normally coexisted in L1210/S cells, whereas L1210/0 cells lacked the ability to activate caspases despite the confirmed presence of both procaspase-3 and -9. Here we show that this defect in caspase activation is not due to mechanisms such as an absence of cytochrome c release, the expression of non-functional caspases, or the presence of an endogenous inhibitor but results from the loss of apoptosis protease activator protein-1 (APAF-1) expression. This absence of APAF-1 protein results from multiple alterations at both genomic and transcriptional levels. However, although this lack of APAF-1 delays the apoptotic program, it does not hamper its execution. Importantly, in these cells, apoptosis develops not only in an APAF-1-independent way but also in the absence of caspase-3 and -9 activation. Altogether these findings provide evidence that apoptosis may occur through alternative signaling pathways independent of APAF-1 expression and totally dissociated from any caspase processing. Therefore, the L1210/0 variant sub-line provides a valuable tool for the elucidation of these pathways.
Belmokhtar
Chafké Ahmed
CA
INSERM U496, Centre G. Hayem, Hôpital Saint-Louis, 1, Avenue Claude Vellefaux, 75010 Paris, France.
Hillion
Josette
J
Dudognon
Charles
C
Fiorentino
Susana
S
Flexor
Maria
M
Lanotte
Michel
M
Ségal-Bendirdjian
Evelyne
E
D000818:Animals; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1; D015139:Blotting, Southern; D015153:Blotting, Western; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D002474:Cell-Free System; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D005091:Exons; D005434:Flow Cytometry; D017353:Gene Deletion; D053804:Granzymes; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D011506:Proteins / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000494:pharmacology; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured
C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D003574:Cytochrome c Group; D011506:Proteins; D012333:RNA, Messenger; D053804:Granzymes; C509214:Gzmb protein, mouse; D012697:Serine Endopeptidases; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D019311:Staurosporine