title: Involvement of proapoptotic molecules Bax and Bak in tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced mitochondrial disruption and apoptosis: differential regulation of cytochrome c and Smac/DIABLO release.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/Apo2L induces apoptosis in a wide variety of cancer and transformed cells. Activation of BID, a "BH3-domain-only" Bcl-2 family member, triggers the oligomerization of proapoptotic family members Bak or Bax, resulting in the release of mitochondrial proteins to cytosol. In this study, we have shown the importance of Bax and Bak in TRAIL-induced apoptosis by studying in murine embryonic fibroblasts (MEFs) from Bax(-/-) and Bak(-/-) animals. TRAIL induced cytochrome c release and apoptosis in wild-type, Bid(-/-), Bax(-/-), or Bak(-/-) MEFs, but not in Bax(-/-) Bak(-/-) double knockout (DKO) MEFs. Bid, which functions upstream of cytochrome c release, was cleaved in all of the knockout cells except in Bid(-/-) MEFs. The release of cytochrome c was correlated with caspase-9 activity. TRAIL increased caspase-3 activity in all of the cells except in DKO cells. TRAIL-induced drop in mitochondrial membrane potential was not observed in DKO MEFs. Unlike cytochrome c release, TRAIL-induced Smac/DIABLO release was blocked in Bid(-/-), Bax(-/-), Bak(-/-), or DKO MEFs, suggesting the differential regulation of these mitochondrial proteins during apoptosis. The apoptotic events downstream of mitochondria were intact in DKO MEFs, because microinjection of cytochrome c, or ectopic expression of mature Smac/DIABLO or pretreatment of Smac N7 peptide completely restored TRAIL sensitivity. In conclusion, the data suggest that Bax and Bak differentially regulate the release of cytochrome c and Smac/DIABLO from mitochondria, and Smac/DIABLO can be used to sensitize cells that are deficient in Bax and Bak genes, or resistant to TRAIL.
authors.affiliation: Department of Pharmaceutical Sciences, University of Maryland, School of Pharmacy, Greenebaum Cancer Center, Baltimore, Maryland 21201-1180, USA.
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Kandasamy
authors.forename: Srinivasa M
authors.initials: SM
authors.lastname: Srinivasula
authors.forename: Emad S
authors.initials: ES
authors.lastname: Alnemri
authors.forename: Craig B
authors.initials: CB
authors.lastname: Thompson
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Korsmeyer
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Bryant
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Srivastava
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000172:deficiency / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D024101:Mitochondrial Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; C494815:Bid protein, mouse; D002352:Carrier Proteins; D003574:Cytochrome c Group; C499605:Diablo protein, mouse; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D020169:Caspases