title: 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.affiliation: Drug Discovery Department, Moffitt Cancer Center, University of South Florida, Tampa, Florida 33612, USA.
authors.forename: Aslamuzzaman
authors.initials: A
authors.lastname: Kazi
authors.forename: Jiazhi
authors.initials: J
authors.lastname: Sun
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Doi
authors.forename: Shen-Shu
authors.initials: SS
authors.lastname: Sung
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Hang
authors.initials: H
authors.lastname: Yin
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Rodriguez
authors.forename: Jorge
authors.initials: J
authors.lastname: Becerril
authors.forename: Norbert
authors.initials: N
authors.lastname: Berndt
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hamilton
authors.forename: Hong-Gang
authors.initials: HG
authors.lastname: Wang
authors.forename: Saïd M
authors.initials: SM
authors.lastname: Sebti
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010446:Peptide Fragments / Q000494:pharmacology*; D010797:Phthalimides / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D061988:Proteasome Inhibitors; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*; D051025:bcl-Associated Death Protein / Q000235:genetics / Q000378:metabolism*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C494819:BAD protein, human; C494772:BAK1 protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C474007:Bax protein (53-86); D000072224:Bcl-2-Like Protein 11; D004151:Dipeptides; D008565:Membrane Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010446:Peptide Fragments; D010797:Phthalimides; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D045304:Cytochromes c; C118004:CEP 1612; C505407:CASP3 protein, human; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex