Differentiation-dependent sensitivity to apoptogenic factors in PC12 cells.
We have investigated the role of the mitochondrial pathway during cell death following serum and nerve growth factor (NGF)/dibutyryl cyclic AMP (Bt(2)cAMP) withdrawal in undifferentiated or NGF/Bt(2)cAMP-differentiated PC12 cells, respectively. Holocytochrome c, Smac/DIABLO, and Omi/HtrA2 are released rapidly following trophic factor deprivation in PC12 cells. Bcl-2 and Akt inhibited this release. The protection, however, persisted longer in differentiated PC12 cells. In differentiated, but not undifferentiated cells, Bcl-2 and Akt also inhibited apoptosis downstream of holocytochrome c release. Thus, undifferentiated PC12 cells showed marked sensitivity to induction of apoptosis by microinjected cytochrome c even in the presence of NGF, Bcl-2, or Akt. In contrast, in differentiated cells these factors suppressed cell death. Consistent with these observations, in vitro processing of procaspase 9 in response to cytochrome c was observed in extracts from undifferentiated but not differentiated cells expressing Akt or Bcl-2. Endogenous caspase 9 was cleaved during cell death, whereas dominant negative caspase 9 inhibited cell death. The results from determining the role of inhibitors of apoptosis (IAPs) suggest that acquisition of inhibition by IAPs is part of the differentiation program. Ubiquitin-DeltaN-AVPI Smac/DIABLO induced cell death in differentiated cells only. c-IAP-2 is unregulated in differentiated cells, whereas X-linked IAP levels decreased in these cells coincident with cell death. Moreover, expressing X-linked IAP rendered undifferentiated cells resistant to microinjected cytochrome c. Overall, the inhibitory regulation, of cell death at the level of release of mitochondrial apoptogenic factors and at post-mitochondrial activation of caspase 9 observed in differentiated PC12 cells, is reduced or absent in the undifferentiated counterparts.
Vyas
Sheela
S
INSERM U497, Ecole Normale Supérieure, 46, rue d'Ulm, Paris 75005, France. vyas@wotan.ens.fr
Juin
Philippe
P
Hancock
David
D
Suzuki
Yasuyuki
Y
Takahashi
Ryosuke
R
Triller
Antoine
A
Evan
Gerard
G
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D016895:Culture Media, Serum-Free; D045304:Cytochromes c / Q000378:metabolism / Q000494:pharmacology; D004789:Enzyme Activation; D019254:Genes, bcl-2; D015750:Genes, gag; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D051058:Oncogene Protein v-akt; D016716:PC12 Cells; D051381:Rats; D015682:Retroviridae Proteins, Oncogenic / Q000235:genetics; D014162:Transfection
D016895:Culture Media, Serum-Free; D015682:Retroviridae Proteins, Oncogenic; D045304:Cytochromes c; D020932:Nerve Growth Factor; D051058:Oncogene Protein v-akt; C506433:CASP9 protein, human; C506434:Casp9 protein, mouse; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases