title: A Krebs Cycle Component Limits Caspase Activation Rate through Mitochondrial Surface Restriction of CRL Activation.
abstract: How cells avoid excessive caspase activity and unwanted cell death during apoptotic caspase-mediated removal of large cellular structures is poorly understood. We investigate caspase-mediated extrusion of spermatid cytoplasmic contents in Drosophila during spermatid individualization. We show that a Krebs cycle component, the ATP-specific form of the succinyl-CoA synthetase β subunit (A-Sβ), binds to and activates the Cullin-3-based ubiquitin ligase (CRL3) complex required for caspase activation in spermatids. In vitro and in vivo evidence suggests that this interaction occurs on the mitochondrial surface, thereby limiting the source of CRL3 complex activation to the vicinity of this organelle and reducing the potential rate of caspase activation by at least 60%. Domain swapping between A-Sβ and the GTP-specific SCSβ (G-Sβ), which functions redundantly in the Krebs cycle, show that the metabolic and structural roles of A-Sβ in spermatids can be uncoupled, highlighting a moonlighting function of this Krebs cycle component in CRL activation.
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Aram
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Tslil
authors.initials: T
authors.lastname: Braun
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Carmel
authors.initials: C
authors.lastname: Braverman
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yosef
authors.initials: Y
authors.lastname: Kaplan
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Liat
authors.initials: L
authors.lastname: Ravid
authors.affiliation: Electron Microscopy Unit, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Smadar
authors.initials: S
authors.lastname: Levin-Zaidman
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel. Electronic address: eli.arama@weizmann.ac.il.
authors.forename: Eli
authors.initials: E
authors.lastname: Arama
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D020169:Caspases / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology*; D044842:Cullin Proteins / Q000378:metabolism*; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D008297:Male; D008840:Microfilament Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D013087:Spermatids / Q000254:growth & development / Q000378:metabolism*; D013389:Succinate-CoA Ligases / Q000378:metabolism
chemical_list: C503647:Cul3 protein, Drosophila; D044842:Cullin Proteins; D029721:Drosophila Proteins; D008840:Microfilament Proteins; D020033:Protein Isoforms; C080353:kel protein, Drosophila; D020169:Caspases; D013389:Succinate-CoA Ligases
keywords: CRL3; Drosophila; Klhl10; SCS; caspase; cell remodeling; partial cellular destruction; spermatids; succinyl coenzyme A synthetase