Involvement of caspase 1 and its activator Ipaf upstream of mitochondrial events in apoptosis

FEBS J. 2006 Jun;273(12):2766-78. doi: 10.1111/j.1742-4658.2006.05293.x.

Abstract

PTP-S2/TC45 is a nuclear protein tyrosine phosphatase that activates p53 and induces caspase 1-dependent apoptosis. We analyzed the role of ICE protease-activating factor (Ipaf), an activator of caspase 1 in p53-dependent apoptosis. We also determined the sequence of events that lead to apoptosis upon caspase 1 activation by Ipaf. PTP-S2 expression induced Ipaf mRNA in MCF-7 cells which was dependent on p53. PTP-S2-induced apoptosis was inhibited by a dominant-negative mutant of Ipaf and also by an Ipaf-directed short-hairpin RNA. Doxorubicin-induced apoptosis was potentiated by the expression of caspase 1 (but not by a catalytic mutant of caspase 1) and required endogenous Ipaf. Doxorubicin treatment of MCF-7 cells resulted in activation of exogenous caspase 1, which was partly dependent on endogenous Ipaf. An activated form of Ipaf induced caspase 1-dependent apoptosis that was inhibited by Bcl2 and also by a dominant inhibitor of caspase 9 (caspase 9s). Caspase 1-dependent apoptosis induced by doxorubicin was also inhibited by Bcl2 and caspase 9s, but caspase 1 activation by activated Ipaf was not inhibited by Bcl2. Mitochondrial membrane permeabilization was induced by caspase 1 and activated Ipaf, which was inhibited by Bcl2, but not by caspase 9s. Expression of caspase 1 with activated Ipaf resulted in the activation of Bax at mitochondria. Our results suggest that Ipaf is involved in PTP-S2-induced apoptosis and that caspase 1, when activated by Ipaf, causes release of mitochondrial proteins (cytochrome c and Omi) through Bax activation, thereby functioning as an initiator caspase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / antagonists & inhibitors
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / physiology*
  • Apoptosis* / drug effects
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins / antagonists & inhibitors
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / physiology*
  • Caspase 1 / genetics
  • Caspase 1 / metabolism*
  • Caspase 9
  • Caspases / genetics
  • Caspases / metabolism
  • Caspases / pharmacology
  • Cell Membrane Permeability
  • Doxorubicin / metabolism
  • Doxorubicin / pharmacology
  • Enzyme Activation / drug effects
  • Fluorescent Antibody Technique
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Mice
  • Mitochondria / genetics
  • Mitochondria / metabolism*
  • Protein Tyrosine Phosphatase, Non-Receptor Type 2
  • Protein Tyrosine Phosphatases / metabolism
  • Protein Tyrosine Phosphatases / pharmacology
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / pharmacology
  • Signal Transduction
  • Transcriptional Activation
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins
  • NLRC4 protein, human
  • Proto-Oncogene Proteins c-bcl-2
  • Tumor Suppressor Protein p53
  • caspase 9s, human
  • Doxorubicin
  • PTPN2 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 2
  • Protein Tyrosine Phosphatases
  • Ptpn2 protein, mouse
  • CASP9 protein, human
  • Casp9 protein, mouse
  • Caspase 9
  • Caspases
  • Caspase 1