title: Cleavage of Bid by executioner caspases mediates feed forward amplification of mitochondrial outer membrane permeabilization during genotoxic stress-induced apoptosis in Jurkat cells.
abstract: The extent to which the BH3-only protein Bid is important for intrinsic (mitochondria-mediated) apoptotic cell death induced by genotoxic stress remains controversial. In the present study, we examine this issue using a panel of gene-manipulated Bax-deficient Jurkat T-lymphocytes. Cells stably depleted of Bid were far less sensitive than control-transfected cells to etoposide-induced apoptosis. In particular, drug-induced Bak activation, cytochrome c release, loss of mitochondrial membrane potential, and caspase activation were all decreased in cells lacking Bid. Reconstitution experiments using recombinant proteins and permeabilized Bid-deficient cells demonstrated that truncated Bid (tBid), but not full-length Bid, potently induced Bak activation and the release of cytochrome c. Further, caspase-8-deficient Jurkat cells efficiently cleaved Bid and were sensitive to drug-induced apoptosis. By comparison, Apaf-1-deficient cells, as well as cells overexpressing full-length X-linked inhibitor of apoptosis protein (XIAP) or the BIR1/BIR2 domains of XIAP, failed to cleave Bid in response to genotoxic stress. These data suggest that tBid plays an important regulatory role in the execution of DNA damage-induced cytochrome c release and apoptosis. However, the fact that cleavage of Bid to tBid is mediated by executioner caspases suggests that a self-amplifying feed forward loop involving caspases, Bid, and mitochondria may help determine irreversible commitment to apoptosis.
authors.affiliation: Department of Pharmacology, Toxicology & Therapeutics and the Kansas University Cancer Center, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors.forename: Shary N
authors.initials: SN
authors.lastname: Shelton
authors.forename: Mary E
authors.initials: ME
authors.lastname: Shawgo
authors.forename: John D
authors.initials: JD
authors.lastname: Robertson
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D002469:Cell Separation; D045304:Cytochromes c / Q000378:metabolism; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D005786:Gene Expression Regulation; D006801:Humans; D019169:Jurkat Cells; D051336:Mitochondrial Membranes / Q000378:metabolism*; D008954:Models, Biological; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D005047:Etoposide; D045304:Cytochromes c; D053181:Caspase 8; D020169:Caspases