Abstract
Increased interactions between pro-apoptotic BH3-only proteins and anti-apoptotic Bcl-2 family proteins at mitochondria result in tumor initiation, progression and resistance to traditional chemotherapy. Drugs that mimic the BH3 region are expected to release BH3-only proteins from anti-apoptotic proteins, inducing apoptosis in some cancer cells and sensitizing others to chemotherapy. Recently, we applied fluorescence lifetime imaging microscopy and fluorescence resonance energy transfer to measure protein:protein interactions for the Bcl-2 family of proteins in live MCF-7 cells using fluorescent fusion proteins. While the BH3-proteins bound to Bcl-XL and Bcl-2, the BH3 mimetic ABT-737 inhibited binding of only Bad and tBid, but not Bim. We have extended our studies by investigating ABT-263, a clinical drug based on ABT-737. We show that the inhibitory effects and pattern of the two drugs are comparable for both Bcl-XL and Bcl-2. Furthermore, we show that mutation of a conserved residue in the BH3 region in Bad and tBid disrupted their interactions with Bcl-XL and Bcl-2, while the corresponding BimEL mutant showed no decrease in binding to these anti-apoptotic proteins. Therefore, in MCF-7 cells, Bim has unique binding properties compared with other BH3-only proteins that resist displacement from Bcl-XL and Bcl-2 by BH3 mimetics.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Aniline Compounds / pharmacology
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Apoptosis Regulatory Proteins / chemistry
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Apoptosis Regulatory Proteins / metabolism
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Apoptosis* / drug effects
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BH3 Interacting Domain Death Agonist Protein / chemistry
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BH3 Interacting Domain Death Agonist Protein / metabolism
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Bcl-2-Like Protein 11
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Biphenyl Compounds / pharmacology
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Cell Survival / drug effects
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Fluorescence Resonance Energy Transfer / methods*
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Humans
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Luminescent Proteins / metabolism
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MCF-7 Cells
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Membrane Proteins / chemistry
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Membrane Proteins / metabolism
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Microscopy, Fluorescence / methods*
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Molecular Sequence Data
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Mutation / genetics
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Nitrophenols / pharmacology
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Piperazines / pharmacology
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Protein Binding / drug effects
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Proto-Oncogene Proteins / chemistry
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / metabolism*
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Red Fluorescent Protein
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Sulfonamides / pharmacology
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bcl-Associated Death Protein / chemistry
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bcl-Associated Death Protein / metabolism
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bcl-X Protein / metabolism
Substances
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ABT-737
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Aniline Compounds
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Apoptosis Regulatory Proteins
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BCL2L11 protein, human
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BH3 Interacting Domain Death Agonist Protein
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Bcl-2-Like Protein 11
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Biphenyl Compounds
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Luminescent Proteins
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Membrane Proteins
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Nitrophenols
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Piperazines
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Sulfonamides
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bcl-Associated Death Protein
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bcl-X Protein
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navitoclax