title: Involvement of caspase-2 and caspase-9 in endoplasmic reticulum stress-induced apoptosis: a role for the IAPs.
abstract: Dysregulation of apoptosis is involved in a wide spectrum of disease ranging from proliferative to degenerative disorders. An emerging area of study in apoptosis is the critical contribution of the endoplasmic reticulum (ER) in both mitochondrial and ER specific apoptosis pathways. Here we show that brefeldin A and tunicamycin-mediated ER stress lead to caspase-dependent apoptosis involving caspase-2. Confocal microscopy and subcellular fractionation indicate that caspase-2 is localized to the ER, and following ER stress, the processing of caspase-2 and -9 is an early event preceding the activation of caspase-3 and -7 and the cleavage of the caspase substrate poly(ADP-ribose) polymerase (PARP). Inhibition and silencing of either caspase-2 or caspase-9 suppress ER stress-induced apoptosis, as demonstrated by annexin V binding. Similarly, transduction with an adenovirus encoding either Inhibitors of Apoptosis (IAP) protein HIAP1/c-IAP2 or HIAP2/c-IAP1 also suppresses ER stress-induced apoptosis. However, among HIAP1, HIAP2 and XIAP, only HIAP2 binds and inhibits caspase-2. Our results thus indicate a novel mechanism by which HIAP2 can regulate ER-initiated apoptosis by modulating the activity of caspase-2.
authors.affiliation: Apoptosis Research Centre, Children's Hospital of Eastern Ontario Research Institute II, Ottawa, Ontario, Canada K1H 8L1.
authors.forename: Herman H
authors.initials: HH
authors.lastname: Cheung
authors.forename: N
authors.initials: N
authors.lastname: Lynn Kelly
authors.forename: Peter
authors.initials: P
authors.lastname: Liston
authors.forename: Robert G
authors.initials: RG
authors.lastname: Korneluk
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites / Q000235:genetics; D020126:Brefeldin A / Q000494:pharmacology; D053143:Caspase 2; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D024161:Collagen Type XI / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D014162:Transfection; D014415:Tunicamycin / Q000494:pharmacology; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C499319:COL11A2 protein, human; D061945:Caspase Inhibitors; D024161:Collagen Type XI; D000091342:Endoplasmic Reticulum Chaperone BiP; D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; D051034:Inhibitor of Apoptosis Proteins; D018832:Molecular Chaperones; D009842:Oligopeptides; D034741:RNA, Small Interfering; D051636:X-Linked Inhibitor of Apoptosis Protein; C427308:benzoylcarbonyl-valyl-aspartyl-valyl-alanyl-aspartyl-fluoromethyl ketone; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; D014415:Tunicamycin; D020126:Brefeldin A; C506433:CASP9 protein, human; D053143:Caspase 2; D053453:Caspase 9; D020169:Caspases