title: Differences in the mechanisms of proapoptotic BH3 proteins binding to Bcl-XL and Bcl-2 quantified in live MCF-7 cells.
abstract: Overexpression of antiapoptotic proteins including Bcl-XL and/or Bcl-2 contributes to tumor initiation, progression, and resistance to therapy by direct interactions with proapoptotic BH3 proteins. Release of BH3 proteins from antiapoptotic proteins kills some cancer cells and sensitizes others to chemotherapy. Binding of Bcl-XL and Bcl-2 to the BH3 proteins Bad, Bid, and the three major isoforms of Bim was measured for fluorescent protein fusions in live cells using fluorescence lifetime imaging microscopy and fluorescence resonance energy transfer. In cells the binding of the proteins at mitochondria is similar to the results from in vitro measurements. However, mutations in the BH3 region of Bim known to inhibit binding to Bcl-XL and Bcl-2 in vitro had much less effect in MCF-7 cells. Moreover, the BH3 mimetic ABT-737 inhibited Bad and Bid but not Bim binding to Bcl-XL and Bcl-2. Thus, the selectivity of ABT-737 also differs markedly from predictions made from in vitro measurements.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Aranovich
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Tony
authors.initials: T
authors.lastname: Collins
authors.forename: Fei
authors.initials: F
authors.lastname: Geng
authors.forename: Sudeepa
authors.initials: S
authors.lastname: Dixit
authors.forename: Brian
authors.initials: B
authors.lastname: Leber
authors.forename: David W
authors.initials: DW
authors.lastname: Andrews
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds / Q000494:pharmacology; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D060066:Protein Interaction Maps; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D051025:bcl-Associated Death Protein / Q000235:genetics / Q000378:metabolism*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C501332:ABT-737; D051017:Apoptosis Regulatory Proteins; C494819:BAD protein, human; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D001426:Bacterial Proteins; D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009596:Nitrophenols; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C054562:yellow fluorescent protein, Bacteria