title: ARTS binds to a distinct domain in XIAP-BIR3 and promotes apoptosis by a mechanism that is different from other IAP-antagonists.
abstract: ARTS (Sept4_i2), is a pro-apoptotic protein localized at the mitochondria of living cells. In response to apoptotic signals, ARTS rapidly translocates to the cytosol where it binds and antagonizes XIAP to promote caspase activation. However, the mechanism of interaction between these two proteins and how it is regulated remained to be explored. In this study, we show that ARTS and XIAP bind directly to each other, as recombinant ARTS and XIAP proteins co-immunoprecipitate together. We also show that over expression of ARTS alone is sufficient to induce a strong down-regulation of XIAP protein levels and that this reduction occurs through the ubiquitin proteasome system (UPS). Using various deletion and mutation constructs of XIAP we show that ARTS specifically binds to the BIR3 domain in XIAP. Moreover, we found that ARTS binds to different sequences in BIR3 than other IAP antagonists such as SMAC/Diablo. Computational analysis comparing the location of the putative ARTS interface in BIR3 with the known interfaces of SMAC/Diablo and caspase 9 support our results indicating that ARTS interacts with residues in BIR3 that are different from those involved in binding SMAC/Diablo and caspase 9. We therefore suggest that ARTS binds and antagonizes XIAP in a way which is distinct from other IAP-antagonists to promote apoptosis.
authors.affiliation: Cell Death Research Laboratory, Department of Biology, University of Haifa, Mount Carmel, Israel.
authors.forename: Bavat
authors.initials: B
authors.lastname: Bornstein
authors.forename: Yossi
authors.initials: Y
authors.lastname: Gottfried
authors.forename: Natalia
authors.initials: N
authors.lastname: Edison
authors.forename: Anna
authors.initials: A
authors.lastname: Shekhtman
authors.forename: Tali
authors.initials: T
authors.lastname: Lev
authors.forename: Fabian
authors.initials: F
authors.lastname: Glaser
authors.forename: Sarit
authors.initials: S
authors.lastname: Larisch
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011994:Recombinant Proteins / Q000378:metabolism; D058112:Septins / Q000378:metabolism*; D017384:Sequence Deletion; D013379:Substrate Specificity; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C499605:Diablo protein, mouse; D024101:Mitochondrial Proteins; D011994:Recombinant Proteins; D025801:Ubiquitin; D051636:X-Linked Inhibitor of Apoptosis Protein; C506434:Casp9 protein, mouse; D053453:Caspase 9; D046988:Proteasome Endopeptidase Complex; C115474:Sept4 protein, mouse; D058112:Septins