BCL-2 selectively interacts with the BID-induced open conformer of BAK, inhibiting BAK auto-oligomerization

J Biol Chem. 2003 Jul 4;278(27):25039-45. doi: 10.1074/jbc.M302930200. Epub 2003 Apr 29.

Abstract

Caspase-8 cleaves BID to tBID, which targets mitochondria and induces oligomerization of BAX and BAK within the outer membrane, resulting in release of cytochrome c from the organelle. Here, we have initiated these steps in isolated mitochondria derived from control and BCL-2-overexpressing cells using synthetic BH3 peptides and subsequently analyzed the BCL members by chemical cross-linking. The results show that the BH3 domain of BID interacts with and induces an "open" conformation of BAK, exposing the BAK N terminus. This open (activated) conformer of BAK potently induces oligomerization of non-activated ("closed") conformers, causing a cascade of BAK auto-oligomerization. Induction of the open conformation of BAK occurs even in the presence of excess BCL-2, but BCL-2 selectively interacts with this open conformer and blocks BAK oligomerization and cytochrome c release, dependent on the ratio of BID BH3 and BCL-2. This mechanism of inhibition by BCL-2 also occurs in intact cells stimulated with Fas or expressing tBID. Although BID BH3 interacts with both BCL-2 and BAK, the results indicate that when BCL-2 is in excess it can sequester the BID BH3-induced activated conformer of BAK, effectively blocking downstream events. This model suggests that the primary mechanism for BCL-2 blockade targets activated BAK rather than sequestering tBID.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoptosis
  • BH3 Interacting Domain Death Agonist Protein
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Dimerization
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Protein Binding
  • Protein Conformation
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • bcl-2 Homologous Antagonist-Killer Protein

Substances

  • BH3 Interacting Domain Death Agonist Protein
  • Carrier Proteins
  • Membrane Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2 Homologous Antagonist-Killer Protein