title: Caspase activation by granzyme B is indirect, and caspase autoprocessing requires the release of proapoptotic mitochondrial factors.
abstract: Apoptosis in response to granzyme B involves activation of caspase-dependent target cell death pathways. Herein, we show that granzyme B initiates caspase processing but cannot fully process procaspase-3 in intact Jurkat T leukemia or NT2 neuronal cells. Rather, the release from mitochondria of proapoptotic mediators cytochrome c, Smac/Diablo, and HtrA2/Omi facilitates full activation of caspases that results from autoprocessing. Bcl-2 overexpression in mitochondria suppresses the release of these proapoptotic molecules, resulting in cell survival despite partial procaspase processing by granzyme B. We propose that binding of inhibitor of apoptosis (IAP) proteins to partially processed procaspases inhibits cell death unless mitochondrial disruption also occurs in response to granzyme B or activated BH3-domain proteins such as truncated Bid.
authors.affiliation: Cancer Immunology Program, Peter MacCallum Cancer Institute, Locked Bag 1, A'Beckett Street, 8006, Melbourne, Australia.
authors.forename: Vivien R
authors.initials: VR
authors.lastname: Sutton
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Wowk
authors.forename: Michael
authors.initials: M
authors.lastname: Cancilla
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Trapani
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D015870:Gene Expression; D019254:Genes, bcl-2; D053804:Granzymes; D000074923:High-Temperature Requirement A Serine Peptidase 2; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D008954:Models, Biological; D011506:Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D003574:Cytochrome c Group; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C509213:GZMB protein, human; D053804:Granzymes; D012697:Serine Endopeptidases; C000615914:HTRA2 protein, human; D000074923:High-Temperature Requirement A Serine Peptidase 2; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases