title: Apoptosis-inducing factor is a target for ubiquitination through interaction with XIAP.
abstract: X-linked inhibitor of apoptosis (XIAP) is an inhibitor of apoptotic cell death that protects cells by caspase-dependent and independent mechanisms. In a screen for molecules that participate with XIAP in regulating cellular activities, we identified apoptosis-inducing factor (AIF) as an XIAP binding protein. Baculoviral IAP repeat 2 of XIAP is sufficient for the XIAP/AIF interaction, which is disrupted by Smac/DIABLO. In healthy cells, mature human AIF lacks only the first 54 amino acids, differing significantly from the apoptotic form, which lacks the first 102 amino-terminal residues. Fluorescence complementation and immunoprecipitation experiments revealed that XIAP interacts with both AIF forms. AIF was found to be a target of XIAP-mediated ubiquitination under both normal and apoptotic conditions, and an E3 ubiquitin ligase-deficient XIAP variant displayed a more robust interaction with AIF. Expression of either XIAP or AIF attenuated both basal and antimycin A-stimulated levels of reactive oxygen species (ROS), and when XIAP and AIF were expressed in combination, a cumulative decrease in ROS was observed. These results identify AIF as a new XIAP binding partner and indicate a role for XIAP in regulating cellular ROS.
authors.affiliation: BSRB, Room 2057, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Wilkinson
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Wilkinson
authors.forename: Stefanie
authors.initials: S
authors.lastname: Galbán
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Csomos
authors.forename: Colin S
authors.initials: CS
authors.lastname: Duckett
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D051033:Apoptosis Inducing Factor / Q000737:chemistry / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D017353:Gene Deletion; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D054875:Ubiquitination; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051033:Apoptosis Inducing Factor; D051636:X-Linked Inhibitor of Apoptosis Protein; D020169:Caspases