title: A stapled BID BH3 helix directly binds and activates BAX.
abstract: BAX is a multidomain proapoptotic BCL-2 family protein that resides in the cytosol until activated by an incompletely understood trigger mechanism, which facilitates BAX translocation to mitochondria and downstream death events. Whether BAX is activated by direct contact with select BH3-only members of the BCL-2 family is highly debated. Here we detect and quantify a direct binding interaction between BAX and a hydrocarbon-stapled BID BH3 domain, which triggers the functional activation of BAX at nanomolar doses in vitro. Chemical reinforcement of BID BH3 alpha helicity was required to reveal the direct BID BH3-BAX association. We confirm the specificity of this BH3 interaction by characterizing a stapled BAD BH3 peptide that interacts with antiapoptotic BCL-X(L) but does not bind or activate BAX. We further demonstrate that membrane targeting of stapled BID BH3 optimizes its ability to activate BAX, supporting a model in which BID directly engages BAX to trigger mitochondrial apoptosis.
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute and Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA. loren_walensky@dfci.harvard.edu <loren_walensky@dfci.harvard.edu>
authors.forename: Loren D
authors.initials: LD
authors.lastname: Walensky
authors.forename: Kenneth
authors.initials: K
authors.lastname: Pitter
authors.forename: Joel
authors.initials: J
authors.lastname: Morash
authors.forename: Kyoung Joon
authors.initials: KJ
authors.lastname: Oh
authors.forename: Scott
authors.initials: S
authors.lastname: Barbuto
authors.forename: Jill
authors.initials: J
authors.lastname: Fisher
authors.forename: Eric
authors.initials: E
authors.lastname: Smith
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Verdine
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Korsmeyer
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein / Q000737:chemistry / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D019169:Jurkat Cells; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D021381:Protein Transport; D017386:Sequence Homology, Amino Acid; D051028:bcl-2-Associated X Protein / Q000737:chemistry / Q000502:physiology*; D051020:bcl-X Protein / Q000737:chemistry
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494827:Bax protein, mouse; C494815:Bid protein, mouse; D008081:Liposomes; D010455:Peptides; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein