XIAP Inhibition of caspase-3 Preserves Its Association With the Apaf-1 Apoptosome and Prevents CD95- And Bax-induced Apoptosis

Cell Death Differ. 2002 Sep;9(9):881-92. doi: 10.1038/sj.cdd.4401069.

Abstract

Ligation of death receptors or formation of the Apaf-1 apoptosome results in the activation of caspases and execution of apoptosis. We recently demonstrated that X-linked inhibitor-of-apoptosis protein (XIAP) associates with the apoptosome in vitro. By utilizing XIAP mutants, we now report that XIAP binds to the 'native' apoptosome complex via a specific interaction with the small p12 subunit of processed caspase-9. Indeed, we provide the first direct evidence that XIAP can simultaneously bind active caspases-9 and -3 within the same complex and that inhibition of caspase-3 by the Linker-BIR2 domain prevents disruption of BIR3-caspase-9 interactions. Recent studies suggest that inhibition of caspase-3 is dispensable for its anti-apoptotic effects. However, we clearly demonstrate that inhibition of caspase-3 is required to inhibit CD95 (Fas/Apo-1)-mediated apoptosis, whereas inhibition of either caspase-9 or caspase-3 prevents Bax-induced cell death. Finally, we illustrate for the first time that XIAP mutants, which are incapable of binding to caspases-9 and -3 are completely devoid of anti-apoptotic activity. Thus, XIAP's capacity to maintain inhibition of caspase-9 within the Apaf-1 apoptosome is influenced by its ability to simultaneously inhibit active caspase-3, and depending upon the apoptotic stimulus, inhibition of caspase-9 or 3 is essential for XIAP's anti-apoptotic activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins
  • Apoptotic Protease-Activating Factor 1
  • Binding Sites / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Carrier Proteins / metabolism
  • Caspase 3
  • Caspase 9
  • Caspases / metabolism*
  • Cells, Cultured
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism
  • Enzyme Inhibitors / pharmacology
  • Eukaryotic Cells / cytology
  • Eukaryotic Cells / drug effects
  • Eukaryotic Cells / enzymology*
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Mitochondrial Proteins / metabolism
  • Models, Biological
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism
  • Mutation / genetics
  • Proteasome Endopeptidase Complex
  • Proteins / genetics*
  • Proteins / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2*
  • Signal Transduction / genetics
  • X-Linked Inhibitor of Apoptosis Protein
  • bcl-2-Associated X Protein
  • fas Receptor / metabolism*

Substances

  • APAF1 protein, human
  • Apoptosis Regulatory Proteins
  • Apoptotic Protease-Activating Factor 1
  • BAX protein, human
  • Caenorhabditis elegans Proteins
  • Carrier Proteins
  • DIABLO protein, human
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Mitochondrial Proteins
  • Multienzyme Complexes
  • Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • bcl-2-Associated X Protein
  • bir-2 protein, C elegans
  • fas Receptor
  • CASP3 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 9
  • Caspases
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex