title: Inactivation of Drosophila Apaf-1 related killer suppresses formation of polyglutamine aggregates and blocks polyglutamine pathogenesis.
abstract: Huntington's disease (HD) is caused by expansion of a polyglutamine tract near the N-terminal of huntingtin. Mutant huntingtin forms aggregates in striatum and cortex, where extensive cell death occurs. We used a Drosophila polyglutamine peptide model to assess the role of specific cell death regulators in polyglutamine-induced cell death. Here, we report that polyglutamine-induced cell death was dramatically suppressed in flies lacking Dark, the fly homolog of human Apaf-1, a key regulator of apoptosis. Dark appeared to play a role in the accumulation of polyglutamine-containing aggregates. Suppression of cell death, caspase activation and aggregate formation were also observed when mutant huntingtin exon 1 was expressed in homozygous dark mutant animals. Expanded polyglutamine induced a marked increase in expression of Dark, and Dark was observed to colocalize with ubiquitinated protein aggregates. Apaf-1 also was found to colocalize with huntingtin-containing aggregates in a murine model and HD brain, suggesting a common role for Dark/Apaf-1 in polyglutamine pathogenesis in invertebrates, mice and man. These findings suggest that limiting Apaf-1 activity may alleviate both pathological protein aggregation and neuronal cell death in HD.
authors.affiliation: Neurogenetics Program, Department of Neurology, Neuropsychiatric Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Tzu-Kang
authors.initials: TK
authors.lastname: Sang
authors.forename: Chenjian
authors.initials: C
authors.lastname: Li
authors.forename: Wencheng
authors.initials: W
authors.lastname: Liu
authors.forename: Antony
authors.initials: A
authors.lastname: Rodriguez
authors.forename: John M
authors.initials: JM
authors.lastname: Abrams
authors.forename: S Lawrence
authors.initials: SL
authors.lastname: Zipursky
authors.forename: George R
authors.initials: GR
authors.lastname: Jackson
mesh_terms: D000818:Animals; D053477:Apoptotic Protease-Activating Factor 1; D001921:Brain / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005091:Exons; D005123:Eye / Q000294:innervation / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron; D009154:Mutation; D009410:Nerve Degeneration / Q000378:metabolism / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C506592:APAF1 protein, human; C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D029721:Drosophila Proteins; C086055:HTT protein, human; C506812:Htt protein, mouse; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D011506:Proteins; C400550:dark protein, Drosophila; C097188:polyglutamine; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases