The alpha-5 helix of Bax is sensitive to ubiquitin-dependent degradation

Biochem Biophys Res Commun. 2008 Jun 20;371(1):10-5. doi: 10.1016/j.bbrc.2008.03.122. Epub 2008 Apr 4.

Abstract

The pro-apoptotic protein Bax is instable in many cancer cells but the mechanism of Bax degradation remains unclear. Four different lengths of deductive Bax degradation sensitive (BDS) sequences within BH3-BH1 region, BDS-1 (Bax 67-124), BDS-3 (Bax 74-107), BDS-5 (Bax 67-107), and BDS-7 (Bax 74-124), were tested for the susceptibility to ubiquitin-dependent degradation. Both BDS-1 and BDS-7 which contain the alpha5 helix, a putative pore-forming domain of Bax, are sensitive to proteasome-dependent degradation and ubiquitin-conjugation. The Bax alpha5-deletion mutant (Bax-Deltaalpha5) was stable and also maintained its apoptosis-inducing ability. Deletion of helices alpha1 and part of alpha2 (Bax-Delta1-66) or helices alpha3 and alpha4 (Bax-Deltaalpha3,4) did not affect the sensitivity to degradation. However, Bax-Delta1-66 mutant was not able to induce apoptosis. Thus, we propose that the alpha5 helix of Bax is sensitive to ubiquitin-dependent degradation. Moreover, Bax mutant retains its pro-apoptosis ability when the alpha5 helix is deleted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoptosis* / genetics
  • Cell Line
  • Humans
  • Molecular Sequence Data
  • Mutation
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Structure, Secondary
  • Protein Structure, Tertiary / genetics
  • Sequence Deletion
  • Ubiquitin / metabolism*
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism*

Substances

  • BAX protein, human
  • Ubiquitin
  • bcl-2-Associated X Protein
  • Proteasome Endopeptidase Complex