Peer Reviewed

1

Document Type

Article

Publication Date

6-2010

Keywords

Animals, Apoptosis, Carrier Proteins, Cell Membrane Permeability, Cell Proliferation, Cells, Cultured, Cytochromes c, Digitonin, Humans, Luminescent Proteins, Mice, Mitochondria, Mitochondrial Proteins, Neurons, Recombinant Fusion Proteins, X-Linked Inhibitor of Apoptosis Protein

Comments

This article is also available at http://www.nature.com/cddis/index.html

Under the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License, users are free to share (copy, distribute and transmit) and remix (adapt) the contribution under the following conditions (read full legal code):

  • Attribution. Users must attribute the contribution in the manner specified by the author or licensor (but not in any way that suggests that they or their use of the contribution is endorsed by the author or licensor).
  • Noncommercial. Users may not use this work for commercial purposes.
  • Share Alike. If users alter, transform, or build upon this work, they may distribute the resulting work only under the same or similar license to this one.

Abstract

X-linked inhibitor of apoptosis protein (XIAP) is a potent inhibitor of caspases 3, 7 and 9, and mitochondrial Smac (second mitochondria-derived activator of caspase) release during apoptosis inhibits the activity of XIAP. In this study we show that cytosolic XIAP also feeds back to mitochondria to impair Smac release. We constructed a fluorescent XIAP-fusion protein by labelling NH(2)- and COOH-termini with Cerulean fluorescent protein (C-XIAP-C). Immunoprecipitation confirmed that C-XIAP-C retained the ability to interact with Smac and impaired extrinsically and intrinsically activated apoptosis in response to tumour necrosis factor-related apoptosis-inducing ligand/cycloheximide and staurosporine. In C-XIAP-C-expressing cells, cytochrome c release from mitochondria proceeded normally, whereas Smac release was significantly prolonged and incomplete. In addition, physiological expression of native XIAP prolonged or limited Smac release in HCT-116 colon cancer cells and primary mouse cortical neurons. The Smac-binding capacity of XIAP, but not caspase inhibition, was central for mitochondrial Smac retention, as evidenced in experiments using XIAP mutants that cannot bind to Smac or effector caspases. Similarly, the release of a Smac mutant that cannot bind to XIAP was not impaired by C-XIAP-C expression. Full Smac release could however be provoked by rapid cytosolic C-XIAP-C depletion upon digitonin-induced plasma membrane permeabilization. Our findings suggest that although mitochondria may already contain pores sufficient for cytochrome c release, elevated amounts of XIAP can selectively impair and limit the release of Smac.

Disciplines

Physics | Physiology

Citation

Flanagan L, Sebastia J, Tuffy LP, Spring A, Lichawska A, Devocelle M, Prehn JHM, Rehm M. XIAP impairs Smac release from the mitochondria during apoptosis. Cell Death and Disease. 2010;1(6):e.49.

PubMed ID

21364655

DOI Link

10.1038/cddis.2010.26

Share

COinS