FKHRL1-mediated expression of Noxa and Bim induces apoptosis via the mitochondria in neuroblastoma cells.
Protein kinase-B (PKB) and its target, the forkhead transcription factor like 1 (FKHRL1)/FoxO3a, have been suggested as regulators of neurotrophin-mediated cell survival in neuronal cells. We analyzed human neuroblastoma cells and found that FKHRL1 was phosphorylated, suggesting its inactivation. To study FKHRL1 function, we infected SH-EP and NB15 cells with a 4OH-tamoxifen-regulated FKHRL1(A3)ER(tm) transgene. Activation of FKHRL1 promoted cytochrome-c release and caspase-dependent apoptosis. FKHRL1 induced TRAIL and the BH3-only proteins Noxa and Bim, implicating both extrinsic and intrinsic death pathways. However, expression of dnFADD did not inhibit FKHRL1-induced cell death, whereas Bcl2 protected against apoptosis. This excluded the death-receptor pathway and suggested that cell death decision is regulated by Bcl2-rheostat. Importantly, RNAi knockdown of Noxa or Bim decreased apoptosis, indicating that Noxa and Bim cooperate to mediate FKHRL1-induced cell death. We conclude that Noxa and Bim establish a connection between FKHRL1 and mitochondria, and that both BH3-only proteins are critically involved in FKHRL1-induced apoptosis in neuroblastoma.
Obexer
P
P
Tyrolean Cancer Research Institute, Innsbruck, Austria. Petra.Obexer@uibk.ac.at
Geiger
K
K
Ambros
P F
PF
Meister
B
B
Ausserlechner
M J
MJ
D064413:3-Phosphoinositide-Dependent Protein Kinases; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism / Q000502:physiology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D009447:Neuroblastoma / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D013629:Tamoxifen / Q000032:analysis / Q000494:pharmacology; D014161:Transduction, Genetic; D019014:fas Receptor / Q000378:metabolism / Q000502:physiology
D064413:3-Phosphoinositide-Dependent Protein Kinases; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D020169:Caspases; D053200:Fas-Associated Death Domain Protein; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D008565:Membrane Proteins; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D013629:Tamoxifen; D019014:fas Receptor; C000606775:BCL2L11 protein, human; C474007:Bax protein (53-86); C505533:FADD protein, human; C491901:FAS protein, human; C499517:FOXO3 protein, human; C498702:PMAIP1 protein, human