title: Cell-specific inositol 1,4,5 trisphosphate 3-kinase mediates epithelial cell apoptosis in response to oxidative stress in Drosophila.
abstract: Organismal stress responses to oxidative stress are relevant to ageing and disease and involve key cell-/tissue-specific signal transduction mechanisms. Using Drosophila, an established in vivo model for stress studies, we show that cell-specific inositol phosphate signalling specifically via inositol 1,4,5 trisphosphate 3-kinase (InsP(3) 3-K, IP(3)K), negatively regulates organismal responses to oxidative stress. We demonstrate that the Drosophila Malpighian tubule (equivalent to vertebrate kidney and liver) is a key epithelial sensor for organismal oxidative stress responses: precise targeting of either gain-of-function constructs of Drosophila IP(3)Ks (IP(3)K-1 and IP(3)K-2), or loss-of-function (RNAi) constructs to only one cell type in tubule reversibly modulates survival of stress-challenged adult flies. In vivo, targeted IP(3)K-1 directly increases H(2)O(2) production, pro-apoptotic caspase-9 activity and mitochondrial membrane potential. The mitochondrial calcium load in tubule principal cells-assessed by luminescent and fluorescent genetically-encoded mitochondrial calcium reporters-is significantly increased by IP(3)K-1 under oxidative stress conditions, leading to apoptosis. The Drosophila orthologues of human apoptotic bcl-2 genes include debcl and buffy. Oxidative stress challenge does not modulate gene expression of either debcl or buffy in tubules; and altered debcl expression does not influence survival rates under oxidative stress challenge. Finally, targeted over-expression of either debcl or buffy to tubule principal cells does not impact on tubule caspase-9 activity. Thus, IP(3)K-1 modulates epithelial cell apoptosis without involvement of bcl-2-type proteins.
authors.affiliation: University of Glasgow, UK.
authors.forename: Selim
authors.initials: S
authors.lastname: Terhzaz
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Finlayson
authors.forename: Laura
authors.initials: L
authors.lastname: Stirrat
authors.forename: JingLi
authors.initials: J
authors.lastname: Yang
authors.forename: Herve
authors.initials: H
authors.lastname: Tricoire
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Woods
authors.forename: Julian A T
authors.initials: JA
authors.lastname: Dow
authors.forename: Shireen-A
authors.initials: SA
authors.lastname: Davies
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000201:enzymology*; D004847:Epithelial Cells / Q000166:cytology* / Q000201:enzymology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008317:Malpighian Tubules / Q000166:cytology / Q000201:enzymology; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000201:enzymology; D009928:Organ Specificity; D018384:Oxidative Stress; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016019:Survival Analysis
chemical_list: D051017:Apoptosis Regulatory Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D006861:Hydrogen Peroxide; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D053453:Caspase 9; D002118:Calcium