The serine protease Omi/HtrA2 is released from mitochondria during apoptosis. Omi interacts with caspase-inhibitor XIAP and induces enhanced caspase activity

Cell Death Differ. 2002 Jan;9(1):20-6. doi: 10.1038/sj.cdd.4400970.


Proteome analysis of supernatant of isolated mitochondria exposed to recombinant tBid, a proapoptotic Bcl-2 member, revealed the presence of the serine protease Omi, also called HtrA2. This release was prevented in mitochondria derived from Bcl-2-transgenic mice. Release of Omi under apoptotic conditions was confirmed in vivo in livers from mice injected with agonistic anti-Fas antibodies and was prevented in livers from Bcl-2 transgenic mice. Omi release also occurs in apoptotic dying but not in necrotic dying fibrosarcoma L929 cells, treated with anti-Fas antibodies and TNF, respectively. The amino acid sequence reveals the presence of an XIAP interaction motif at the N-terminus of mature Omi. We demonstrate an interaction between endogeneous Omi and recombinant XIAP. Furthermore we show that endogenous Omi is involved in enhanced activation of caspases in cytosolic extracts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Apoptosis / physiology*
  • BH3 Interacting Domain Death Agonist Protein
  • Carrier Proteins / pharmacology
  • Caspases / metabolism*
  • Cells, Cultured
  • Cytosol / metabolism
  • Enzyme Activation
  • High-Temperature Requirement A Serine Peptidase 2
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Mitochondria / metabolism*
  • Mitochondrial Proteins
  • Molecular Sequence Data
  • Proteins / metabolism*
  • Serine Endopeptidases / metabolism*
  • Translocation, Genetic / drug effects
  • X-Linked Inhibitor of Apoptosis Protein


  • BH3 Interacting Domain Death Agonist Protein
  • Bid protein, mouse
  • Carrier Proteins
  • Mitochondrial Proteins
  • Proteins
  • X-Linked Inhibitor of Apoptosis Protein
  • Serine Endopeptidases
  • High-Temperature Requirement A Serine Peptidase 2
  • Htra2 protein, mouse
  • Caspases