The BH3 alpha-helical mimic BH3-M6 disrupts Bcl-X(L), Bcl-2, and MCL-1 protein-protein interactions with Bax, Bak, Bad, or Bim and induces apoptosis in a Bax- and Bim-dependent manner.

Abstract

A critical hallmark of cancer cell survival is evasion of apoptosis. This is commonly due to overexpression of anti-apoptotic proteins such as Bcl-2, Bcl-X(L), and Mcl-1, which bind to the BH3 α-helical domain of pro-apoptotic proteins such as Bax, Bak, Bad, and Bim, and inhibit their function. We designed a BH3 α-helical mimetic BH3-M6 that binds to Bcl-X(L) and Mcl-1 and prevents their binding to fluorescently labeled Bak- or Bim-BH3 peptides in vitro. Using several approaches, we demonstrate that BH3-M6 is a pan-Bcl-2 antagonist that inhibits the binding of Bcl-X(L), Bcl-2, and Mcl-1 to multi-domain Bax or Bak, or BH3-only Bim or Bad in cell-free systems and in intact human cancer cells, freeing up pro-apoptotic proteins to induce apoptosis. BH3-M6 disruption of these protein-protein interactions is associated with cytochrome c release from mitochondria, caspase-3 activation and PARP cleavage. Using caspase inhibitors and Bax and Bak siRNAs, we demonstrate that BH3-M6-induced apoptosis is caspase- and Bax-, but not Bak-dependent. Furthermore, BH3-M6 disrupts Bcl-X(L)/Bim, Bcl-2/Bim, and Mcl-1/Bim protein-protein interactions and frees up Bim to induce apoptosis in human cancer cells that depend for tumor survival on the neutralization of Bim with Bcl-X(L), Bcl-2, or Mcl-1. Finally, BH3-M6 sensitizes cells to apoptosis induced by the proteasome inhibitor CEP-1612.

• Authors: Aslamuzzaman Kazi, Jiazhi Sun, Kenichiro Doi, Shen-Shu Sung, Yoshinori Takahashi, Hang Yin, Johanna M Rodriguez, Jorge Becerril, Norbert Berndt, Andrew D Hamilton, Hong-Gang Wang, Saïd M Sebti
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 286 Issue 11 Pg. 9382-92 (Mar 18 2011) ISSN: 1083-351X [Electronic] United States
• PMID: 21148306 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Apoptosis Regulatory Proteins
• BAD protein, human
• BAK1 protein, human
• BAX protein, human
• BCL2L1 protein, human
• BCL2L11 protein, human
• BH3 Interacting Domain Death Agonist Protein
• BID protein, human
• Bax protein (53-86)
• Bcl-2-Like Protein 11
• Dipeptides
• Membrane Proteins
• Myeloid Cell Leukemia Sequence 1 Protein
• Peptide Fragments
• Phthalimides
• Protease Inhibitors
• Proteasome Inhibitors
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-bcl-2
• bcl-2 Homologous Antagonist-Killer Protein
• bcl-2-Associated X Protein
• bcl-Associated Death Protein
• bcl-X Protein
• Cytochromes c
• CEP 1612
• CASP3 protein, human
• Caspase 3
• Proteasome Endopeptidase Complex

Topics

• Animals
• Apoptosis (drug effects, physiology)
• Apoptosis Regulatory Proteins (genetics, metabolism)
• BH3 Interacting Domain Death Agonist Protein (genetics, metabolism)
• Bcl-2-Like Protein 11
• Caspase 3 (genetics, metabolism)
• Cell Line, Tumor
• Cytochromes c (genetics, metabolism)
• Dipeptides (pharmacology)
• HEK293 Cells
• Humans
• Membrane Proteins (genetics, metabolism)
• Mitochondria
• Myeloid Cell Leukemia Sequence 1 Protein
• Peptide Fragments (pharmacology)
• Phthalimides (pharmacology)
• Protease Inhibitors (pharmacology)
• Proteasome Endopeptidase Complex (genetics, metabolism)
• Proteasome Inhibitors
• Protein Structure, Tertiary
• Proto-Oncogene Proteins (genetics, metabolism, pharmacology)
• Proto-Oncogene Proteins c-bcl-2 (genetics, metabolism)
• bcl-2 Homologous Antagonist-Killer Protein (genetics, metabolism)
• bcl-2-Associated X Protein (genetics, metabolism)
• bcl-Associated Death Protein (genetics, metabolism)
• bcl-X Protein (genetics, metabolism)