title: Degradation of DIAP1 by the N-end rule pathway is essential for regulating apoptosis.
abstract: Some members of the inhibitor of apoptosis (IAP) protein family block apoptosis by binding to and neutralizing active caspases. We recently demonstrated that a physical association between IAP and caspases alone is insufficient to regulate caspases in vivo and that an additional level of control is provided by IAP-mediated ubiquitination of both itself and the associated caspases. Here we show that Drosophila IAP 1 (DIAP1) is degraded by the 'N-end rule' pathway and that this process is indispensable for regulating apoptosis. Caspase-mediated cleavage of DIAP1 at position 20 converts the more stable pro-N-degron of DIAP1 into the highly unstable, Asn-bearing, DIAP1 N-degron of the N-end rule degradation pathway. Thus, DIAP1 represents the first known metazoan substrate of the N-end rule pathway that is targeted for degradation through its amino-terminal Asn residue. We demonstrate that the N-end rule pathway is required for regulation of apoptosis induced by Reaper and Hid expression in the Drosophila melanogaster eye. Our data suggest that DIAP1 instability, mediated through caspase activity and subsequent exposure of the N-end rule pathway, is essential for suppression of apoptosis. We suggest that DIAP1 safeguards cell viability through the coordinated mutual destruction of itself and associated active caspases.
authors.affiliation: The Breakthrough Toby Robins Breast Cancer Research Centre, Institute of Cancer Research, Mary-Jean Mitchell Green Building, Chester Beatty Laboratories, Fulham Road, London SW3 6JB, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Ditzel
authors.forename: Rebecca
authors.initials: R
authors.lastname: Wilson
authors.forename: Tencho
authors.initials: T
authors.lastname: Tenev
authors.forename: Anna
authors.initials: A
authors.lastname: Zachariou
authors.forename: Angela
authors.initials: A
authors.lastname: Paul
authors.forename: Emma
authors.initials: E
authors.lastname: Deas
authors.forename: Pascal
authors.initials: P
authors.lastname: Meier
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D001216:Asparagine / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism*; D005123:Eye / Q000166:cytology / Q000378:metabolism*; D005124:Eye Abnormalities / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D051034:Inhibitor of Apoptosis Proteins; D009154:Mutation / Q000235:genetics; D009479:Neuropeptides / Q000378:metabolism; D010641:Phenotype; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics*
chemical_list: C111891:DIAP1 protein, Drosophila; D029721:Drosophila Proteins; C108880:HID protein, Drosophila; D051034:Inhibitor of Apoptosis Proteins; D009479:Neuropeptides; C086973:rpr protein, Drosophila; D001216:Asparagine; D020169:Caspases