title: Metabolic regulation of Drosophila apoptosis through inhibitory phosphorylation of Dronc.
abstract: Apoptosis ensures tissue homeostasis in response to developmental cues or cellular damage. Recently reported genome-wide RNAi screens have suggested that several metabolic regulators can modulate caspase activation in Drosophila. Here, we establish a previously unrecognized link between metabolism and Drosophila apoptosis by showing that cellular NADPH levels modulate the initiator caspase Dronc through its phosphorylation at S130. Depletion of NADPH removed this inhibitory phosphorylation, resulting in the activation of Dronc and subsequent cell death. Conversely, upregulation of NADPH prevented Dronc-mediated apoptosis upon DIAP1 RNAi or cycloheximide treatment. Furthermore, this CaMKII-mediated phosphorylation of Dronc hindered Dronc activation, but not its catalytic activity. Blockade of NADPH production aggravated the death-inducing activity of Dronc in specific neurons, but not in the photoreceptor cells of the eyes of transgenic flies; similarly, non-phosphorylatable Dronc was more potent than wild type in triggering specific neuronal apoptosis. Our observations reveal a novel regulatory circuitry in Drosophila apoptosis, and, as NADPH levels are elevated in cancer cells, also provide a genetic model to understand aberrations in cancer cell apoptosis resulting from metabolic alterations.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Chih-Sheng
authors.initials: CS
authors.lastname: Yang
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thomenius
authors.forename: Eugene C
authors.initials: EC
authors.lastname: Gan
authors.forename: Wanli
authors.initials: W
authors.lastname: Tang
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Freel
authors.forename: Thomas J S
authors.initials: TJ
authors.lastname: Merritt
authors.forename: Leta K
authors.initials: LK
authors.lastname: Nutt
authors.forename: Sally
authors.initials: S
authors.lastname: Kornbluth
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism*; D002470:Cell Survival; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D004789:Enzyme Activation; D047468:Immunoprecipitation; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: C111891:DIAP1 protein, Drosophila; D029721:Drosophila Proteins; D051034:Inhibitor of Apoptosis Proteins; D008293:Malates; D034741:RNA, Small Interfering; C400550:dark protein, Drosophila; D009249:NADP; C030298:malic acid; D020169:Caspases; C118731:dronc protein, Drosophila