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Brouwer JM, Westphal D, Dewson G, Robin AY, Uren RT, Bartolo R, Thompson GV, Colman PM, Kluck RM, Czabotar PE. Bak core and latch domains separate during activation, and freed core domains form symmetric homodimers. Mol Cell 2014; 55:938-946. [PMID: 25175025 DOI: 10.1016/j.molcel.2014.07.016] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Revised: 07/08/2014] [Accepted: 07/24/2014] [Indexed: 01/11/2023]
Abstract
Apoptotic stimuli activate and oligomerize the proapoptotic proteins Bak and Bax, resulting in mitochondrial outer-membrane permeabilization and subsequent cell death. This activation can occur when certain BH3-only proteins interact directly with Bak and Bax. Recently published crystal structures reveal that Bax separates into core and latch domains in response to BH3 peptides. The distinguishing characteristics of BH3 peptides capable of directly activating Bax were also elucidated. Here we identify specific BH3 peptides capable of "unlatching" Bak and describe structural insights into Bak activation and oligomerization. Crystal structures and crosslinking experiments demonstrate that Bak undergoes a conformational change similar to that of Bax upon activation. A structure of the Bak core domain dimer provides a high-resolution image of this key intermediate in the pore-forming oligomer. Our results confirm an analogous mechanism for activation and dimerization of Bak and Bax in response to certain BH3 peptides.
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Affiliation(s)
- Jason M Brouwer
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Dana Westphal
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Grant Dewson
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Adeline Y Robin
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Rachel T Uren
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Ray Bartolo
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Geoff V Thompson
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Peter M Colman
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia
| | - Ruth M Kluck
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia.
| | - Peter E Czabotar
- Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Melbourne, Victoria 3052, Australia.
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Yao S, Westphal D, Babon JJ, Thompson GV, Robin AY, Adams JM, Colman PM, Czabotar PE. NMR studies of interactions between Bax and BH3 domain-containing peptides in the absence and presence of CHAPS. Arch Biochem Biophys 2014; 545:33-43. [PMID: 24434006 DOI: 10.1016/j.abb.2014.01.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 12/26/2013] [Accepted: 01/06/2014] [Indexed: 01/27/2023]
Abstract
Activation and oligomerisation of Bax, a key pro-apoptotic Bcl-2 family protein, are key steps in the mitochondrial pathway to apoptosis. The signals for apoptosis are conveyed by the distantly related BH3-only proteins, which use their short BH3 domain, an amphipathic α-helix, to interact with other Bcl-2 family members. Here we report an NMR study of interactions between BaxΔC and BH3 domain-containing peptides in the absence and presence of CHAPS, a zwitterionic detergent. We find for the first time that CHAPS interacts weakly with BaxΔC (fast exchange on the NMR chemical shift timescale), at concentrations below micelle formation and with an estimated Kd in the tens of mM. Direct and relatively strong-interactions (slow exchange on the NMR chemical shift timescale) were also observed for BaxΔC with BaxBH3 (estimated Kd of circa 150μM) or BimBH3 in the absence of CHAPS. The interaction with either peptide alone induced widespread chemical shift perturbations to BaxΔC in solution which implies that BaxΔC might have undergone significant conformation change upon binding the BH3 peptide. However, BaxΔC remained monomeric upon binding either CHAPS or a BH3 peptide alone, but the presence of both provoked it to form a dimer.
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Affiliation(s)
- Shenggen Yao
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia; Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
| | - Dana Westphal
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia
| | - Jeffrey J Babon
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia
| | - Geoff V Thompson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Adeline Y Robin
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia
| | - Jerry M Adams
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia
| | - Peter M Colman
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia
| | - Peter E Czabotar
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, The University of Melbourne, Victoria 3010, Australia.
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Czabotar PE, Lee EF, Thompson GV, Wardak AZ, Fairlie WD, Colman PM. Mutation to Bax beyond the BH3 domain disrupts interactions with pro-survival proteins and promotes apoptosis. J Biol Chem 2011; 286:7123-31. [PMID: 21199865 PMCID: PMC3044969 DOI: 10.1074/jbc.m110.161281] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 12/15/2010] [Indexed: 11/06/2022] Open
Abstract
Pro-survival members of the Bcl-2 family of proteins restrain the pro-apoptotic activity of Bax, either directly through interactions with Bax or indirectly by sequestration of activator BH3-only proteins, or both. Mutations in Bax that promote apoptosis can provide insight into how Bax is regulated. Here, we describe crystal structures of the pro-survival proteins Mcl-1 and Bcl-x(L) in complex with a 34-mer peptide from Bax that encompasses its BH3 domain. These structures reveal canonical interactions between four signature hydrophobic amino acids from the BaxBH3 domain and the BH3-binding groove of the pro-survival proteins. In both structures, Met-74 from the Bax peptide engages with the BH3-binding groove in a fifth hydrophobic interaction. Various Bax Met-74 mutants disrupt interactions between Bax and all pro-survival proteins, but these Bax mutants retain pro-apoptotic activity. Bax/Bak-deficient mouse embryonic fibroblast cells reconstituted with several Bax Met-74 mutants are more sensitive to the BH3 mimetic compound ABT-737 as compared with cells expressing wild-type Bax. Furthermore, the cells expressing Bax Met-74 mutants are less viable in colony assays even in the absence of an external apoptotic stimulus. These results support a model in which direct restraint of Bax by pro-survival Bcl-2 proteins is a barrier to apoptosis.
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Affiliation(s)
- Peter E. Czabotar
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
| | - Erinna F. Lee
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
| | - Geoff V. Thompson
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
| | - Ahmad Z. Wardak
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
| | - W. Douglas Fairlie
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
- Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Peter M. Colman
- From the Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia and
- Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia
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