The anti-apoptotic activity of XIAP is retained upon mutation of both the caspase 3- and caspase 9-interacting sites.
The X-linked mammalian inhibitor of apoptosis protein (XIAP) has been shown to bind several partners. These partners include caspase 3, caspase 9, DIABLO/Smac, HtrA2/Omi, TAB1, the bone morphogenetic protein receptor, and a presumptive E2 ubiquitin-conjugating enzyme. In addition, we show here that XIAP can bind to itself. To determine which of these interactions are required for it to inhibit apoptosis, we generated point mutant XIAP proteins and correlated their ability to bind other proteins with their ability to inhibit apoptosis. partial differential RING point mutants of XIAP were as competent as their full-length counterparts in inhibiting apoptosis, although impaired in their ability to oligomerize with full-length XIAP. Triple point mutants, unable to bind caspase 9, caspase 3, and DIABLO/HtrA2/Omi, were completely ineffectual in inhibiting apoptosis. However, point mutants that had lost the ability to inhibit caspase 9 and caspase 3 but retained the ability to inhibit DIABLO were still able to inhibit apoptosis, demonstrating that IAP antagonism is required for apoptosis to proceed following UV irradiation.
Silke
John
J
The Walter and Eliza Hall Institute of Medical Research, Victoria 3050, Australia. silke@wehi.edu.au
Hawkins
Christine J
CJ
Ekert
Paul G
PG
Chew
Joanne
J
Day
Catherine L
CL
Pakusch
Miha
M
Verhagen
Anne M
AM
Vaux
David L
DL
D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D017354:Point Mutation; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein; D016335:Zinc Fingers / Q000235:genetics
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; 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; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases