title: Essential roles of the Bcl-2 family of proteins in caspase-2-induced apoptosis.
abstract: Caspase-2 is an initiating caspase required for stress-induced apoptosis in various human cancer cells. Recent studies suggest that it can mediate the death function of tumor suppressor p53 and is activated by a multimeric protein complex, PIDDosome. However, it is not clear how caspase-2 exerts its apoptotic function in cells and whether its enzymatic activity is required for the apoptotic function. In this study, we used both in vitro mitochondrial cytochrome c release assays and cell culture apoptosis analyses to investigate the mechanism by which caspase-2 induces apoptosis. We show that active caspase-2, but neither a catalytically mutated caspase-2 nor active caspase-2 with its inhibitor, can cause cytochrome c release. Caspase-2 failed to induce cytochrome c release from mitochondria with Bid(-/-) background, and the release could be restored by addition of the wild-type Bid protein, but not by Bid with the caspase-2 cleavage site mutated. Caspase-2 was not able to induce cytochrome c release from Bax(-/-)Bak(-/-) mitochondria either. In cultured cells, gene deletion of Bax/Bak or Bid abrogated apoptosis induced by overexpression of caspase-2. Collectively, these results indicate that proteolytic activation of Bid and the subsequent induction of the mitochondrial apoptotic pathway through Bax/Bak is essential for apoptosis triggered by caspase-2.
authors.affiliation: Cell Biology Program, Memorial Sloan-Kettering Cancer Center, Cornell University Weill Graduate School of Medical Sciences, New York, New York 10021, USA.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Gao
authors.forename: Yufang
authors.initials: Y
authors.lastname: Shao
authors.forename: Xuejun
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D053143:Caspase 2; D020169:Caspases / Q000096:biosynthesis* / Q000378:metabolism; D002384:Catalysis; D002460:Cell Line; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D003580:Cytochromes / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D034622:RNA Interference; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D003580:Cytochromes; D018076:DNA, Complementary; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D053143:Caspase 2; D020169:Caspases