Cell-specific Inositol 1,4,5 Trisphosphate 3-kinase Mediates Epithelial Cell Apoptosis in Response to Oxidative Stress in Drosophila

Cell Signal. 2010 May;22(5):737-48. doi: 10.1016/j.cellsig.2009.12.009. Epub 2010 Jan 11.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis*
  • Calcium / metabolism
  • Caspase 9 / metabolism
  • Drosophila melanogaster / cytology*
  • Drosophila melanogaster / enzymology*
  • Epithelial Cells / cytology*
  • Epithelial Cells / enzymology*
  • Hydrogen Peroxide / metabolism
  • Malpighian Tubules / cytology
  • Malpighian Tubules / enzymology
  • Membrane Potential, Mitochondrial
  • Mitochondria / enzymology
  • Organ Specificity
  • Oxidative Stress*
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Survival Analysis

Substances

  • Apoptosis Regulatory Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Hydrogen Peroxide
  • Phosphotransferases (Alcohol Group Acceptor)
  • Inositol 1,4,5-trisphosphate 3-kinase
  • Caspase 9
  • Calcium