title: BH3 domains of BH3-only proteins differentially regulate Bax-mediated mitochondrial membrane permeabilization both directly and indirectly.
abstract: Using a Bax-dependent membrane-permeabilization assay, we show that peptides corresponding to the BH3 domains of Bcl-2 family "BH3-only" proteins have dual functions. Several BH3 peptides relieved the inhibition of Bax caused by the antiapoptotic Bcl-x(L) and/or Mcl-1 proteins, some displaying a specificity for either Bcl-x(L) or Mcl-1. Besides having this derepression function, the Bid and Bim peptides activated Bax directly and were the only BH3 peptides tested that could potently induce cytochrome c release from mitochondria in cultured cells. Furthermore, Bax activator molecules (cleaved Bid protein and the Bim BH3 peptide) synergistically induced cytochrome c release when introduced into cells along with derepressor BH3 peptides. These observations support a unified model of BH3 domain function, encompassing both positive and negative regulation of other Bcl-2 family members. In this model, the simple inhibition of antiapoptotic functions is insufficient to induce apoptosis unless a direct activator of Bax or Bak is present.
authors.affiliation: La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, CA 92121, USA. t-kuwana@uiowa.edu
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kuwana
authors.forename: Lisa
authors.initials: L
authors.lastname: Bouchier-Hayes
authors.forename: Jerry E
authors.initials: JE
authors.lastname: Chipuk
authors.forename: Christine
authors.initials: C
authors.lastname: Bonzon
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Sullivan
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Green
authors.forename: Donald D
authors.initials: DD
authors.lastname: Newmeyer
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism*; D010539:Permeability; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D051017:Apoptosis Regulatory Proteins; 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; D002352:Carrier Proteins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D045304:Cytochromes c