XIAP regulates DNA damage-induced apoptosis downstream of caspase-9 cleavage.
The IAP (inhibitor of apoptosis) family of anti-apoptotic proteins regulates programmed cell death. Of the six known human IAP-related proteins, XIAP is the most potent inhibitor. To study the mechanistic effects of XIAP on DNA damage-induced apoptosis, we prepared U-937 cells that stably overexpress XIAP. The results demonstrate that XIAP inhibits apoptosis induced by 1-[beta-d-arabinofuranosyl]cytosine (ara-C) and other genotoxic agents. XIAP had no detectable effect on ara-C-induced release of mitochondrial cytochrome c and attenuated cleavage of procaspase-9. In addition, we show that ara-C induces the association of XIAP with the cleaved fragments of caspase-9 and thereby inhibition of caspase-9 activity. The results also demonstrate that ara-C induces cleavage of procaspase-3 by a caspase-8-dependent mechanism and that XIAP inhibits caspase-3 activity. These results demonstrate that XIAP functions downstream of procaspase-9 cleavage as an inhibitor of both proteolytically processed caspase-9 and -3 in the cellular response to genotoxic stress.
Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA. Rakesh_Datta@dfci.harvard.edu
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Datta
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Oki
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Biedermann
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Ren
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D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D003561:Cytarabine / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D053938:DNA Fragmentation / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D004792:Enzyme Precursors / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D009153:Mutagens / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D020298:U937 Cells; D051636:X-Linked Inhibitor of Apoptosis Protein
D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D004792:Enzyme Precursors; D009153:Mutagens; D010446:Peptide Fragments; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D003561:Cytarabine; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases