51
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Adams JM, Cory S. The BCL-2 arbiters of apoptosis and their growing role as cancer targets. Cell Death Differ 2017; 25:27-36. [PMID: 29099483 PMCID: PMC5729526 DOI: 10.1038/cdd.2017.161] [Citation(s) in RCA: 375] [Impact Index Per Article: 53.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/30/2017] [Accepted: 08/31/2017] [Indexed: 02/08/2023] Open
Abstract
Impaired apoptosis plays a central role in cancer development and limits the efficacy of conventional cytotoxic therapies. Deepening understanding of how opposing factions of the BCL-2 protein family switch on apoptosis and of their structures has driven development of a new class of cancer drugs that targets various pro-survival members by mimicking their natural inhibitors, the BH3-only proteins. These ‘BH3 mimetic’ drugs seem destined to become powerful new weapons in the arsenal against cancer. Successful clinical trials of venetoclax/ABT-199, a specific inhibitor of BCL-2, have led to its approval for a refractory form of chronic lymphocytic leukaemia and to scores of on-going trials for other malignancies. Furthermore, encouraging preclinical studies of BH3 mimetics that target other BCL-2 pro-survival members, particularly MCL-1, offer promise for cancers resistant to venetoclax. This review sketches the impact of the BCL-2 family on cancer development and therapy, describes how interactions of family members trigger apoptosis and discusses the potential of BH3 mimetic drugs to advance cancer therapy.
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Affiliation(s)
- Jerry M Adams
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.,Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
| | - Suzanne Cory
- The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.,Department of Medical Biology, University of Melbourne, Parkville, VIC 3052, Australia
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52
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Peña‐Blanco A, García‐Sáez AJ. Bax, Bak and beyond — mitochondrial performance in apoptosis. FEBS J 2017; 285:416-431. [DOI: 10.1111/febs.14186] [Citation(s) in RCA: 340] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/12/2017] [Accepted: 07/26/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Aida Peña‐Blanco
- Interfaculty Institute of Biochemistry Tübingen University Germany
| | - Ana J. García‐Sáez
- Interfaculty Institute of Biochemistry Tübingen University Germany
- Max‐Planck Institute for Intelligent Systems Stuttgart Germany
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53
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Dingeldein APG, Pokorná Š, Lidman M, Sparrman T, Šachl R, Hof M, Gröbner G. Apoptotic Bax at Oxidatively Stressed Mitochondrial Membranes: Lipid Dynamics and Permeabilization. Biophys J 2017; 112:2147-2158. [PMID: 28538152 DOI: 10.1016/j.bpj.2017.04.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/23/2017] [Accepted: 04/05/2017] [Indexed: 12/20/2022] Open
Abstract
Mitochondria are crucial compartments of eukaryotic cells because they function as the cellular power plant and play a central role in the early stages of programmed cell death (apoptosis). To avoid undesired cell death, this apoptotic pathway is tightly regulated by members of the Bcl-2 protein family, which interact on the external surface of the mitochondria, i.e., the mitochondrial outer membrane (MOM), and modulate its permeability to apoptotic factors, controlling their release into the cytosol. A growing body of evidence suggests that the MOM lipids play active roles in this permeabilization process. In particular, oxidized phospholipids (OxPls) formed under intracellular stress seem to directly induce apoptotic activity at the MOM. Here we show that the process of MOM pore formation is sensitive to the type of OxPls species that are generated. We created MOM-mimicking liposome systems, which resemble the cellular situation before apoptosis and upon triggering of oxidative stress conditions. These vesicles were studied using 31P solid-state magic-angle-spinning nuclear magnetic resonance spectroscopy and differential scanning calorimetry, together with dye leakage assays. Direct polarization and cross-polarization nuclear magnetic resonance experiments enabled us to probe the heterogeneity of these membranes and their associated molecular dynamics. The addition of apoptotic Bax protein to OxPls-containing vesicles drastically changed the membranes' dynamic behavior, almost completely negating the previously observed effect of temperature on the lipids' molecular dynamics and inducing an ordering effect that led to more cooperative membrane melting. Our results support the hypothesis that the mitochondrion-specific lipid cardiolipin functions as a first contact site for Bax during its translocation to the MOM in the onset of apoptosis. In addition, dye leakage assays revealed that different OxPls species in the MOM-mimicking vesicles can have opposing effects on Bax pore formation.
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Affiliation(s)
| | - Šárka Pokorná
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Lidman
- Department of Chemistry, Umeå University, Umeå, Sweden
| | | | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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54
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BAK α6 permits activation by BH3-only proteins and homooligomerization via the canonical hydrophobic groove. Proc Natl Acad Sci U S A 2017; 114:7629-7634. [PMID: 28673969 DOI: 10.1073/pnas.1702453114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
BAK and BAX are the essential effectors of apoptosis because without them a cell is resistant to most apoptotic stimuli. BAK and BAX undergo conformation changes to homooligomerize then permeabilize the mitochondrial outer membrane during apoptosis. How BCL-2 homology 3 (BH3)-only proteins bind to activate BAK and BAX is unclear. We report that BH3-only proteins bind inactive full-length BAK at mitochondria and then dissociate following exposure of the BAK BH3 and BH4 domains before BAK homodimerization. Using a functional obstructive labeling approach, we show that activation of BAK involves important interactions of BH3-only proteins with both the canonical hydrophobic binding groove (α2-5) and α6 at the rear of BAK, with interaction at α6 promoting an open groove to receive a BH3-only protein. Once activated, how BAK homodimers multimerize to form the putative apoptotic pore is unknown. Obstructive labeling of BAK beyond the BH3 domain and hydrophobic groove did not inhibit multimerization and mitochondrial damage, indicating that critical protein-protein interfaces in BAK self-association are limited to the α2-5 homodimerization domain.
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55
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Identification and expression analysis of alternatively spliced new transcript isoform of Bax gene in mouse. Gene 2017; 621:21-31. [DOI: 10.1016/j.gene.2017.04.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 04/07/2017] [Accepted: 04/12/2017] [Indexed: 12/29/2022]
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56
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Zhang M, Zheng J, Nussinov R, Ma B. Release of Cytochrome C from Bax Pores at the Mitochondrial Membrane. Sci Rep 2017; 7:2635. [PMID: 28572603 PMCID: PMC5453941 DOI: 10.1038/s41598-017-02825-7] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 04/19/2017] [Indexed: 12/12/2022] Open
Abstract
How cytochrome C is released from the mitochondria to the cytosol via Bax oligomeric pores, a process which is required for apoptosis, is still a mystery. Based on experimentally measured residue-residue distances, we recently solved the first atomic model for Bax oligomeric pores at the membranes using computational approaches. Here, we investigate the mechanism at the microsecond time- and nanometer space- scale using MD simulations. Our free energy landscape depicts a low barrier for the permeation of cytochrome C into the Bax C-terminal mouth, with the pathway proceeding to the inner cavity and exiting via the N-terminal mouth. Release is guided by organized charged/hydrophilic surfaces. The hydrophilicity and negative charge of the pore surface gradually increase along the release pathway from the pore entry to the exit opening. Rather than inert passing of the cytochrome C through a rigid pore, the flexible pore may selectively aid the cytochrome C passage. Once the Bax pore is formed in the membrane, with a low energy barrier, the release of cytochrome C may be readily achieved through energy fluctuations. Collectively, our work provides mechanistic insight in atomic detail into the release of cytochrome C through Bax oligomeric pores.
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Affiliation(s)
- Mingzhen Zhang
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio, 44325, USA
| | - Jie Zheng
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio, 44325, USA
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD, 21702, USA
- Sackler Inst. of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD, 21702, USA.
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57
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Simonyan L, Légiot A, Lascu I, Durand G, Giraud MF, Gonzalez C, Manon S. The substitution of Proline 168 favors Bax oligomerization and stimulates its interaction with LUVs and mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1144-1155. [DOI: 10.1016/j.bbamem.2017.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 02/28/2017] [Accepted: 03/14/2017] [Indexed: 12/23/2022]
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58
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Birkinshaw RW, Czabotar PE. The BCL-2 family of proteins and mitochondrial outer membrane permeabilisation. Semin Cell Dev Biol 2017; 72:152-162. [PMID: 28396106 DOI: 10.1016/j.semcdb.2017.04.001] [Citation(s) in RCA: 168] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 03/03/2017] [Accepted: 04/06/2017] [Indexed: 01/24/2023]
Abstract
Apoptosis is a form of programmed cell death critical for the development and homeostasis of multicellular organisms. A key event within the mitochondrial pathway to apoptosis is the permeabilisation of the mitochondrial outer membrane (MOM), a point of no return in apoptotic progression. This event is governed by a complex interplay of interactions between BCL-2 family members. Here we discuss the roles of opposing factions within the family. We focus on the structural details of these interactions, how they promote or prevent apoptosis and recent developments towards understanding the conformational changes of BAK and BAX that lead to MOM permeabilisation. These interactions and structural insights are of particular interest for drug discovery, as highlighted by the development of therapeutics that target pro-survival family members and restore apoptosis in cancer cells.
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Affiliation(s)
- Richard W Birkinshaw
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Peter E Czabotar
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia; Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia.
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59
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Uren RT, O'Hely M, Iyer S, Bartolo R, Shi MX, Brouwer JM, Alsop AE, Dewson G, Kluck RM. Disordered clusters of Bak dimers rupture mitochondria during apoptosis. eLife 2017; 6. [PMID: 28182867 PMCID: PMC5302884 DOI: 10.7554/elife.19944] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 01/08/2017] [Indexed: 11/13/2022] Open
Abstract
During apoptosis, Bak and Bax undergo major conformational change and form symmetric dimers that coalesce to perforate the mitochondrial outer membrane via an unknown mechanism. We have employed cysteine labelling and linkage analysis to the full length of Bak in mitochondria. This comprehensive survey showed that in each Bak dimer the N-termini are fully solvent-exposed and mobile, the core is highly structured, and the C-termini are flexible but restrained by their contact with the membrane. Dimer-dimer interactions were more labile than the BH3:groove interaction within dimers, suggesting there is no extensive protein interface between dimers. In addition, linkage in the mobile Bak N-terminus (V61C) specifically quantified association between dimers, allowing mathematical simulations of dimer arrangement. Together, our data show that Bak dimers form disordered clusters to generate lipidic pores. These findings provide a molecular explanation for the observed structural heterogeneity of the apoptotic pore. DOI:http://dx.doi.org/10.7554/eLife.19944.001 A healthy organism must carefully remove unwanted, diseased or damaged cells. These unwanted cells can bring about their own death in a controlled process known as apoptosis. Maintaining an appropriate level of apoptosis is crucial to good health: excessive cell death can contribute to neurodegenerative disorders, whereas too little can result in cancer. All cells contain powerhouses called mitochondria, which produce energy. Mitochondria are the scene of a critical ‘point of no return’ in apoptosis. When a cell receives a death signal, a ‘killer’ protein known as Bak punches holes (or pores) in the membrane of the mitochondria. These pores allow toxic molecules to leak out from the mitochondria into the interior of the cell, where they trigger a series of events that dismantles the cell from the inside out. To create the pores, Bak undergoes extensive shape changes that allow the proteins to form dimers that then cluster and perforate the membrane. To investigate how Bak clusters assemble on the mitochondrial membrane, Uren et al. used cultured cells and biochemical techniques to show where the Bak dimers contacted each other before and after the pore formed; these findings were complemented with mathematical modelling. The results show that during apoptosis, Bak dimers contact each other at several different places (rather than at one or two places) to assemble into disorderly, ever-changing clusters. Based on these observations, Uren et al. suggest that the enlarging clusters stress the membrane and cause pores to form. The next step is to investigate whether physical forces that act within the mitochondrial membrane could drive the clustering of Bak proteins. This knowledge could ultimately enable us to learn how to manipulate apoptosis in cells, potentially as part of treatments for the diseases in which this cell death process occurs inappropriately. DOI:http://dx.doi.org/10.7554/eLife.19944.002
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Affiliation(s)
- Rachel T Uren
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Martin O'Hely
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Sweta Iyer
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Ray Bartolo
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
| | - Melissa X Shi
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Jason M Brouwer
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Amber E Alsop
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Grant Dewson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
| | - Ruth M Kluck
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria, Australia
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60
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Garenne D, Renault TT, Manon S. Bax mitochondrial relocation is linked to its phosphorylation and its interaction with Bcl-xL. MICROBIAL CELL 2016; 3:597-605. [PMID: 28357332 PMCID: PMC5348979 DOI: 10.15698/mic2016.12.547] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The heterologous expression of Bax, and other Bcl-2 family members, in the yeast Saccharomyces cerevisiae, has proved to be a valuable reporter system to investigate the molecular mechanisms underlying their interaction with mitochondria. By combining the co-expression of Bax and Bcl-xL mutants with analyzes of their localization and interaction in mitochondria and post-mitochondrial supernatants, we showed that the ability of Bax and Bcl-xL to interact is dependent both on Bax phosphorylation - mimicked by a substitution S184D - and by Bax and Bcl-xL localization. This, and previous data, provide the molecular basis for a model of dynamic equilibrium for Bax localization and activation, regulated both by phosphorylation and Bcl-xL.
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Affiliation(s)
- David Garenne
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France. ; Present address: INRA, UMR1332, 71 Avenue Edouard Bourlaud, 33882 Villenave d'Ornon, France
| | - Thibaud T Renault
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France. ; Present address: Department of Regulation in Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
| | - Stéphen Manon
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France
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61
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Cosentino K, García-Sáez AJ. Bax and Bak Pores: Are We Closing the Circle? Trends Cell Biol 2016; 27:266-275. [PMID: 27932064 DOI: 10.1016/j.tcb.2016.11.004] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/28/2016] [Accepted: 11/07/2016] [Indexed: 01/19/2023]
Abstract
Bax and its homolog Bak are key regulators of the mitochondrial pathway of apoptosis. On cell stress Bax and Bak accumulate at distinct foci on the mitochondrial surface where they undergo a conformational change, oligomerize, and mediate cytochrome c release, leading to cell death. The molecular mechanisms of Bax and Bak assembly and mitochondrial permeabilization have remained a longstanding question in the field. Recent structural and biophysical studies at several length scales have shed light on key aspects of Bax and Bak function that have shifted how we think this process occurs. These discoveries reveal an unexpected molecular mechanism in which Bax (and likely Bak) dimers assemble into oligomers with an even number of molecules that fully or partially delineate pores of different sizes to permeabilize the mitochondrial outer membrane (MOM) during apoptosis.
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Affiliation(s)
- Katia Cosentino
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany; Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, Stuttgart, Germany.
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62
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Abstract
The BCL2-selective BH3 mimetic venetoclax was recently approved for the treatment of relapsed, chromosome 17p-deleted chronic lymphocytic leukemia (CLL) and is undergoing extensive testing, alone and in combination, in lymphomas, acute leukemias, and solid tumors. Here we summarize recent advances in understanding of the biology of BCL2 family members that shed light on the action of BH3 mimetics, review preclinical and clinical studies leading to the regulatory approval of venetoclax, and discuss future investigation of this new class of antineoplastic agent.
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Affiliation(s)
- Haiming Dai
- Division of Oncology Research , Mayo Clinic, Rochester, MN, 55905, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, 55905, USA.,Center for Medical Physics and Technology, Hefei Institute of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China
| | - X Wei Meng
- Division of Oncology Research , Mayo Clinic, Rochester, MN, 55905, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, 55905, USA
| | - Scott H Kaufmann
- Division of Oncology Research , Mayo Clinic, Rochester, MN, 55905, USA.,Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, Rochester, MN, 55905, USA
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63
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Barbado MV, Medrano M, Caballero-Velázquez T, Álvarez-Laderas I, Sánchez-Abarca LI, García-Guerrero E, Martín-Sánchez J, Rosado IV, Piruat JI, Gonzalez-Naranjo P, Campillo NE, Páez JA, Pérez-Simón JA. Cannabinoid derivatives exert a potent anti-myeloma activity both in vitro and in vivo. Int J Cancer 2016; 140:674-685. [PMID: 27778331 DOI: 10.1002/ijc.30483] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 09/17/2016] [Accepted: 10/13/2016] [Indexed: 01/02/2023]
Abstract
Although hematopoietic and immune system show high levels of the cannabinoid receptor CB2, the potential effect of cannabinoids on hematologic malignancies has been poorly determined. Here we have investigated their anti-tumor effect in multiple myeloma (MM). We demonstrate that cannabinoids induce a selective apoptosis in MM cell lines and in primary plasma cells of MM patients, while sparing normal cells from healthy donors, including hematopoietic stem cells. This effect was mediated by caspase activation, mainly caspase-2, and was partially prevented by a pan-caspase inhibitor. Their pro-apoptotic effect was correlated with an increased expression of Bax and Bak, a decrease of Bcl-xL and Mcl-1, a biphasic response of Akt/PKB and an increase in the levels of ceramide in MM cells. Inhibition of ceramide synthesis partially prevented apoptosis, indicating that these sphingolipids play a key role in the pro-apoptotic effect of cannabinoids in MM cells. Remarkably, blockage of the CB2 receptor also inhibited cannabinoid-induced apoptosis. Cannabinoid derivative WIN-55 enhanced the anti-myeloma activity of dexamethasone and melphalan overcoming resistance to melphalan in vitro. Finally, administration of cannabinoid WIN-55 to plasmacytoma-bearing mice significantly suppressed tumor growth in vivo. Together, our data suggest that cannabinoids may be considered as potential therapeutic agents in the treatment of MM.
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Affiliation(s)
- M Victoria Barbado
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Mayte Medrano
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Teresa Caballero-Velázquez
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Isabel Álvarez-Laderas
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Luis Ignacio Sánchez-Abarca
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Estefania García-Guerrero
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Jesús Martín-Sánchez
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - Iván Valle Rosado
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | - José Ignacio Piruat
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
| | | | | | | | - José Antonio Pérez-Simón
- Department of Hematology, Institute of Biomedicine of Sevilla (IBIS/CSIC), University Hospital Virgen del Rocío, Universidad de Sevilla, Spain
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64
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Zhang M, Zheng J, Nussinov R, Ma B. Oncogenic Mutations Differentially Affect Bax Monomer, Dimer, and Oligomeric Pore Formation in the Membrane. Sci Rep 2016; 6:33340. [PMID: 27630059 PMCID: PMC5024136 DOI: 10.1038/srep33340] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 08/25/2016] [Indexed: 12/20/2022] Open
Abstract
Dysfunction of Bax, a pro-apoptotic regulator of cellular metabolism is implicated in neurodegenerative diseases and cancer. We have constructed the first atomistic models of the Bax oligomeric pore consisting with experimental residue-residue distances. The models are stable, capturing well double electron-electron resonance (DEER) spectroscopy measurements and provide structural details in line with the DEER data. Comparison with the latest experimental results revealed that our models agree well with both Bax and Bak pores, pointed to a converged structural arrangement for Bax and Bak pore formation. Using multi-scale molecular dynamics simulations, we probed mutational effects on Bax transformation from monomer → dimer → membrane pore formation at atomic resolution. We observe that two cancer-related mutations, G40E and S118I, allosterically destabilize the monomer and stabilize an off-pathway swapped dimer, preventing productive pore formation. This observation suggests a mechanism whereby the mutations may work mainly by over-stabilizing the monomer → dimer transformation toward an unproductive off-pathway swapped-dimer state. Our observations point to misfolded Bax states, shedding light on the molecular mechanism of Bax mutation-elicited cancer. Most importantly, the structure of the Bax pore facilitates future study of releases cytochrome C in atomic detail.
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Affiliation(s)
- Mingzhen Zhang
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio 44325
| | - Jie Zheng
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio 44325
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD 21702, USA
- Sackler Inst. of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD 21702, USA
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65
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Mandal T, Shin S, Aluvila S, Chen HC, Grieve C, Choe JY, Cheng EH, Hustedt EJ, Oh KJ. Assembly of Bak homodimers into higher order homooligomers in the mitochondrial apoptotic pore. Sci Rep 2016; 6:30763. [PMID: 27488021 PMCID: PMC4973285 DOI: 10.1038/srep30763] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/08/2016] [Indexed: 11/09/2022] Open
Abstract
In mitochondrial apoptosis, Bak is activated by death signals to form pores of unknown structure on the mitochondrial outer membrane via homooligomerization. Cytochrome c and other apoptotic factors are released from the intermembrane space through these pores, initiating downstream apoptosis events. Using chemical crosslinking and double electron electron resonance (DEER)-derived distance measurements between specific structural elements in Bak, here we clarify how the Bak pore is assembled. We propose that previously described BH3-in-groove homodimers (BGH) are juxtaposed via the 'α3/α5' interface, in which the C-termini of helices α3 and α5 are in close proximity between two neighboring Bak homodimers. This interface is observed concomitantly with the well-known 'α6:α6' interface. We also mapped the contacts between Bak homodimers and the lipid bilayer based on EPR spectroscopy topology studies. Our results suggest a model for the lipidic Bak pore, whereby the mitochondrial targeting C-terminal helix does not change topology to accommodate the lining of the pore lumen by BGH.
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Affiliation(s)
- Tirtha Mandal
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Seungjin Shin
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Sreevidya Aluvila
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Hui-Chen Chen
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Carter Grieve
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Jun-Yong Choe
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Emily H Cheng
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Eric J Hustedt
- Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Kyoung Joon Oh
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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66
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Targeting BCL-2-like Proteins to Kill Cancer Cells. Trends Cancer 2016; 2:443-460. [PMID: 28741496 DOI: 10.1016/j.trecan.2016.07.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/06/2016] [Accepted: 07/07/2016] [Indexed: 02/01/2023]
Abstract
Mutations that impair apoptosis contribute to cancer development and reduce the effectiveness of conventional anti-cancer therapies. These insights and understanding of how the B cell lymphoma (BCL)-2 protein family governs apoptosis have galvanized the search for a new class of cancer drugs that target its pro-survival members by mimicking their natural antagonists, the BCL-2 homology (BH)3-only proteins. Successful initial clinical trials of the BH3 mimetic venetoclax/ABT-199, specific for BCL-2, have led to its recent licensing for refractory chronic lymphocytic leukemia and to multiple ongoing trials for other malignancies. Moreover, preclinical studies herald the potential of emerging BH3 mimetics targeting other BCL-2 pro-survival members, particularly myeloid cell leukemia (MCL)-1, for multiple cancer types. Thus, BH3 mimetics seem destined to become powerful new weapons in the arsenal against cancer. This review sketches the discovery of the BCL-2 family and its impact on cancer development and therapy; describes how interactions of family members trigger apoptosis; outlines the development of BH3 mimetic drugs; and discusses their potential to advance cancer therapy.
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67
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Luna-Vargas MP, Chipuk JE. The deadly landscape of pro-apoptotic BCL-2 proteins in the outer mitochondrial membrane. FEBS J 2016; 283:2676-89. [PMID: 26662859 PMCID: PMC4907887 DOI: 10.1111/febs.13624] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/11/2015] [Accepted: 12/08/2015] [Indexed: 01/06/2023]
Abstract
Apoptosis is a biological process that removes damaged, excess or infected cells through a genetically controlled mechanism. This process plays a crucial role in organismal development, immunity and tissue homeostasis, and alterations in apoptosis contribute to human diseases including cancer and auto-immunity. In the past two decades, significant efforts have focused on understanding the function of the BCL-2 proteins, a complex family of pro-survival and pro-apoptotic α-helical proteins that directly control the mitochondrial pathway of apoptosis. Diverse structural investigations of the BCL-2 family members have broadened our mechanistic understanding of their individual functions. However, an often over-looked aspect of the mitochondrial pathway of apoptosis is how the BCL-2 family specifically interacts with and targets the outer mitochondrial membrane to initiate apoptosis. Structural information on the relationship between the BCL-2 family and the outer mitochondrial membrane is missing; likewise, knowledge of the biophysical mechanisms by which the outer mitochondrial membrane affects and effects apoptosis is lacking. In this mini-review, we provide a current overview of the BCL-2 family members and discuss the latest structural insights into BAK/BAX activation and oligomerization in the context of the outer mitochondrial membrane and mitochondrial biology.
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Affiliation(s)
- Mark P.A. Luna-Vargas
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
| | - Jerry E. Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
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68
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Pro-apoptotic Bax molecules densely populate the edges of membrane pores. Sci Rep 2016; 6:27299. [PMID: 27255832 PMCID: PMC4891688 DOI: 10.1038/srep27299] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 05/16/2016] [Indexed: 11/28/2022] Open
Abstract
How the pro-apoptotic Bax protein permeabilizes the mitochondrial outer membrane is not fully understood. Previously, using cryo-electron microscopy (cryo-EM), we showed that activated Bax forms large, growing pores. Whether formed in liposomes or in mitochondrial outer membranes, Bax-induced pores exhibit the same morphology, with negative curvature flanking the edges and with no visible protein structure protruding from the membranes. Here we used cryo-EM to show that gold-labeled Bax molecules, after activation by Bid, became localized strictly at pore edges. This argues that Bax acts at short range to deform the membrane. Also, Bax molecules populated the walls of both small and large pores at the same density, implying that Bax is continuously recruited to the pores as they widen. Moreover, because all Bax molecules became oligomerized after membrane insertion, we infer that Bax oligomers are present at pore edges. We suggest that oligomerization may promote pore enlargement.
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69
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Iyer S, Anwari K, Alsop AE, Yuen WS, Huang DCS, Carroll J, Smith NA, Smith BJ, Dewson G, Kluck RM. Identification of an activation site in Bak and mitochondrial Bax triggered by antibodies. Nat Commun 2016; 7:11734. [PMID: 27217060 PMCID: PMC4890306 DOI: 10.1038/ncomms11734] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 04/25/2016] [Indexed: 12/31/2022] Open
Abstract
During apoptosis, Bak and Bax are activated by BH3-only proteins binding to the α2–α5 hydrophobic groove; Bax is also activated via a rear pocket. Here we report that antibodies can directly activate Bak and mitochondrial Bax by binding to the α1–α2 loop. A monoclonal antibody (clone 7D10) binds close to α1 in non-activated Bak to induce conformational change, oligomerization, and cytochrome c release. Anti-FLAG antibodies also activate Bak containing a FLAG epitope close to α1. An antibody (clone 3C10) to the Bax α1–α2 loop activates mitochondrial Bax, but blocks translocation of cytosolic Bax. Tethers within Bak show that 7D10 binding directly extricates α1; a structural model of the 7D10 Fab bound to Bak reveals the formation of a cavity under α1. Our identification of the α1–α2 loop as an activation site in Bak paves the way to develop intrabodies or small molecules that directly and selectively regulate these proteins. During apoptosis, Bak and Bax are activated by BH3-only proteins binding to a specific hydrophobic groove. Here, the authors show that antibodies can also activate Bak and mitochondrial Bax by binding to the α1-α2 loop, thus identifying a potential clinical target.
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Affiliation(s)
- Sweta Iyer
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
| | - Khatira Anwari
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
| | - Amber E Alsop
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
| | - Wai Shan Yuen
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
| | - David C S Huang
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
| | - John Carroll
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria 3800, Australia
| | - Nicholas A Smith
- Department of Chemistry and Physics, La Trobe Institute for Molecular Sciences, La Trobe University, Victoria 3086, Australia
| | - Brian J Smith
- Department of Chemistry and Physics, La Trobe Institute for Molecular Sciences, La Trobe University, Victoria 3086, Australia
| | - Grant Dewson
- Cell Signalling and Cell Death Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
| | - Ruth M Kluck
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Victoria 3052, Australia
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70
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Pushing the size limit of de novo structure ensemble prediction guided by sparse SDSL-EPR restraints to 200 residues: The monomeric and homodimeric forms of BAX. J Struct Biol 2016; 195:62-71. [PMID: 27129417 DOI: 10.1016/j.jsb.2016.04.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 04/25/2016] [Accepted: 04/26/2016] [Indexed: 01/24/2023]
Abstract
Structure determination remains a challenge for many biologically important proteins. In particular, proteins that adopt multiple conformations often evade crystallization in all biologically relevant states. Although computational de novo protein folding approaches often sample biologically relevant conformations, the selection of the most accurate model for different functional states remains a formidable challenge, in particular, for proteins with more than about 150 residues. Electron paramagnetic resonance (EPR) spectroscopy can obtain limited structural information for proteins in well-defined biological states and thereby assist in selecting biologically relevant conformations. The present study demonstrates that de novo folding methods are able to accurately sample the folds of 192-residue long soluble monomeric Bcl-2-associated X protein (BAX). The tertiary structures of the monomeric and homodimeric forms of BAX were predicted using the primary structure as well as 25 and 11 EPR distance restraints, respectively. The predicted models were subsequently compared to respective NMR/X-ray structures of BAX. EPR restraints improve the protein-size normalized root-mean-square-deviation (RMSD100) of the most accurate models with respect to the NMR/crystal structure from 5.9Å to 3.9Å and from 5.7Å to 3.3Å, respectively. Additionally, the model discrimination is improved, which is demonstrated by an improvement of the enrichment from 5% to 15% and from 13% to 21%, respectively.
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71
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Renault TT, Dejean LM, Manon S. A brewing understanding of the regulation of Bax function by Bcl-xL and Bcl-2. Mech Ageing Dev 2016; 161:201-210. [PMID: 27112371 DOI: 10.1016/j.mad.2016.04.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 04/19/2016] [Accepted: 04/22/2016] [Indexed: 12/17/2022]
Abstract
Bcl-2 family members form a network of protein-protein interactions that regulate apoptosis through permeabilization of the mitochondrial outer membrane. Deciphering this intricate network requires streamlined experimental models, including the heterologous expression in yeast. This approach had previously enabled researchers to identify domains and residues that underlie the conformational changes driving the translocation, the insertion and the oligomerization of the pro-apoptotic protein Bax at the level of the mitochondrial outer membrane. Recent studies that combine experiments in yeast and in mammalian cells have shown the unexpected effect of the anti-apoptotic protein Bcl-xL on the priming of Bax. As demonstrated with the BH3-mimetic molecule ABT-737, this property of Bcl-xL, and of Bcl-2, is crucial to elaborate about how apoptosis could be reactivated in tumoral cells.
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Affiliation(s)
- Thibaud T Renault
- Helmholtz Center for Infection Research, Junior Research Group Infection Biology of Salmonella, Inhoffenstraße 7, 38124 Braunschweig, Germany; Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
| | - Laurent M Dejean
- California State University of Fresno, Department of Chemistry, 2555 E. San Ramon Ave M/S SB70, Fresno, CA 93740-8034, USA
| | - Stéphen Manon
- CNRS, UMR5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France; Université de Bordeaux, 146 Rue Léo Saignat, 33076 Bordeaux, France.
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72
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Lidman M, Pokorná Š, Dingeldein APG, Sparrman T, Wallgren M, Šachl R, Hof M, Gröbner G. The oxidized phospholipid PazePC promotes permeabilization of mitochondrial membranes by Bax. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1288-97. [PMID: 26947183 DOI: 10.1016/j.bbamem.2016.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 02/24/2016] [Accepted: 03/02/2016] [Indexed: 12/25/2022]
Abstract
Mitochondria play a crucial role in programmed cell death via the intrinsic apoptotic pathway, which is tightly regulated by the B-cell CLL/lymphoma-2 (Bcl-2) protein family. Intracellular oxidative stress causes the translocation of Bax, a pro-apoptotic family member, to the mitochondrial outer membrane (MOM) where it induces membrane permeabilization. Oxidized phospholipids (OxPls) generated in the MOM during oxidative stress directly affect the onset and progression of mitochondria-mediated apoptosis. Here we use MOM-mimicking lipid vesicles doped with varying concentrations of 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC), an OxPl species known to significantly enhance Bax-membrane association, to investigate three key aspects of Bax's action at the MOM: 1) induction of Bax pores in membranes without additional mediator proteins, 2) existence of a threshold OxPl concentration required for Bax-membrane action and 3) mechanism by which PazePC disturbs membrane organization to facilitate Bax penetration. Fluorescence leakage studies revealed that Bax-induced leakage, especially its rate, increased with the vesicles' PazePC content without any detectable threshold neither for OxPl nor Bax. Moreover, the leakage rate correlated with the Bax to lipid ratio and the PazePC content. Solid state NMR studies and calorimetric experiments on the lipid vesicles confirmed that OxPl incorporation disrupted the membrane's organization, enabling Bax to penetrate into the membrane. In addition, 15N cross polarization (CP) and insensitive nuclei enhanced by polarization transfer (INEPT) MAS NMR experiments using uniformly (15)N-labeled Bax revealed dynamically restricted helical segments of Bax embedded in the membrane, while highly flexible protein segments were located outside or at the membrane surface.
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Affiliation(s)
- Martin Lidman
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden
| | - Šárka Pokorná
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic; Department of Biochemistry, Charles University, Hlavova 8, 128 40 Prague 2, Czech Republic
| | | | - Tobias Sparrman
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden
| | - Marcus Wallgren
- Department of Medical Chemistry and Biophysics, University of Umeå, SE-901 87 Umeå, Sweden
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Gerhard Gröbner
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden.
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73
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Bleicken S, Hofhaus G, Ugarte-Uribe B, Schröder R, García-Sáez AJ. cBid, Bax and Bcl-xL exhibit opposite membrane remodeling activities. Cell Death Dis 2016; 7:e2121. [PMID: 26913610 PMCID: PMC4849160 DOI: 10.1038/cddis.2016.34] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/20/2016] [Accepted: 01/25/2016] [Indexed: 12/19/2022]
Abstract
The proteins of the Bcl-2 family have a crucial role in mitochondrial outer membrane permeabilization during apoptosis and in the regulation of mitochondrial dynamics. Current models consider that Bax forms toroidal pores at mitochondria that are responsible for the release of cytochrome c, whereas Bcl-xL inhibits pore formation. However, how Bcl-2 proteins regulate mitochondrial fission and fusion remains poorly understood. By using a systematic analysis at the single vesicle level, we found that cBid, Bax and Bcl-xL are able to remodel membranes in different ways. cBid and Bax induced a reduction in vesicle size likely related to membrane tethering, budding and fission, besides membrane permeabilization. Moreover, they are preferentially located at highly curved membranes. In contrast, Bcl-xL not only counterbalanced pore formation but also membrane budding and fission. Our findings support a mechanism of action by which cBid and Bax induce or stabilize highly curved membranes including non-lamellar structures. This molecular activity reduces the energy for membrane remodeling, which is a necessary step in toroidal pore formation, as well as membrane fission and fusion, and provides a common mechanism that links the two main functions of Bcl-2 proteins.
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Affiliation(s)
- S Bleicken
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - G Hofhaus
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - B Ugarte-Uribe
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - R Schröder
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - A J García-Sáez
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
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74
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Dai H, Ding H, Meng XW, Peterson KL, Schneider PA, Karp JE, Kaufmann SH. Constitutive BAK activation as a determinant of drug sensitivity in malignant lymphohematopoietic cells. Genes Dev 2016; 29:2140-52. [PMID: 26494789 PMCID: PMC4617978 DOI: 10.1101/gad.267997.115] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mitochondrial outer membrane permeabilization (MOMP), a key step in the intrinsic apoptotic pathway, is incompletely understood. Current models emphasize the role of BH3-only BCL2 family members in BAX and BAK activation. Here we demonstrate concentration-dependent BAK autoactivation under cell-free conditions and provide evidence that this autoactivation plays a key role in regulating the intrinsic apoptotic pathway in intact cells. In particular, we show that up to 80% of BAK (but not BAX) in lymphohematopoietic cell lines is oligomerized and bound to anti-apoptotic BCL2 family members in the absence of exogenous death stimuli. The extent of this constitutive BAK oligomerization is diminished by BAK knockdown and unaffected by BIM or PUMA down-regulation. Further analysis indicates that sensitivity of cells to BH3 mimetics reflects the identity of the anti-apoptotic proteins to which BAK is constitutively bound, with extensive BCLXL•BAK complexes predicting navitoclax sensitivity, and extensive MCL1•BAK complexes predicting A1210477 sensitivity. Moreover, high BAK expression correlates with sensitivity of clinical acute myelogenous leukemia to chemotherapy, whereas low BAK levels correlate with resistance and relapse. Collectively, these results inform current understanding of MOMP and provide new insight into the ability of BH3 mimetics to induce apoptosis without directly activating BAX or BAK.
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Affiliation(s)
- Haiming Dai
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota 55905, USA; Center for Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Science, Hefei 230031, China
| | - Husheng Ding
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - X Wei Meng
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Kevin L Peterson
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Paula A Schneider
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA
| | - Judith E Karp
- Sidney Kimmel Cancer Center at Johns Hopkins, Baltimore, Maryland 21287, USA
| | - Scott H Kaufmann
- Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota 55905, USA
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75
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Zhang Z, Subramaniam S, Kale J, Liao C, Huang B, Brahmbhatt H, Condon SGF, Lapolla SM, Hays FA, Ding J, He F, Zhang XC, Li J, Senes A, Andrews DW, Lin J. BH3-in-groove dimerization initiates and helix 9 dimerization expands Bax pore assembly in membranes. EMBO J 2015; 35:208-36. [PMID: 26702098 DOI: 10.15252/embj.201591552] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 11/18/2015] [Indexed: 01/08/2023] Open
Abstract
Pro-apoptotic Bax induces mitochondrial outer membrane permeabilization (MOMP) by forming oligomers through a largely undefined process. Using site-specific disulfide crosslinking, compartment-specific chemical labeling, and mutational analysis, we found that activated integral membrane Bax proteins form a BH3-in-groove dimer interface on the MOM surface similar to that observed in crystals. However, after the α5 helix was released into the MOM, the remaining interface with α2, α3, and α4 helices was rearranged. Another dimer interface was formed inside the MOM by two intersected or parallel α9 helices. Combinations of these interfaces generated oligomers in the MOM. Oligomerization was initiated by BH3-in-groove dimerization, without which neither the other dimerizations nor MOMP occurred. In contrast, α9 dimerization occurred downstream and was required for release of large but not small proteins from mitochondria. Moreover, the release of large proteins was facilitated by α9 insertion into the MOM and localization to the pore rim. Therefore, the BH3-in-groove dimerization on the MOM nucleates the assembly of an oligomeric Bax pore that is enlarged by α9 dimerization at the rim.
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Affiliation(s)
- Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | | | - Justin Kale
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Chenyi Liao
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Bo Huang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Hetal Brahmbhatt
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Samson G F Condon
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Suzanne M Lapolla
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Franklin A Hays
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jingzhen Ding
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Feng He
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xuejun C Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jianing Li
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Alessandro Senes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - David W Andrews
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Jialing Lin
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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76
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Gilbert RJC. Protein-lipid interactions and non-lamellar lipidic structures in membrane pore formation and membrane fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:487-99. [PMID: 26654785 DOI: 10.1016/j.bbamem.2015.11.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 10/23/2015] [Accepted: 11/30/2015] [Indexed: 12/27/2022]
Abstract
Pore-forming proteins and peptides act on their targeted lipid bilayer membranes to increase permeability. This approach to the modulation of biological function is relevant to a great number of living processes, including; infection, parasitism, immunity, apoptosis, development and neurodegeneration. While some pore-forming proteins/peptides assemble into rings of subunits to generate discrete, well-defined pore-forming structures, an increasing number is recognised to form pores via mechanisms which co-opt membrane lipids themselves. Among these, membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) family proteins, Bax/colicin family proteins and actinoporins are especially prominent and among the mechanisms believed to apply are the formation of non-lamellar (semi-toroidal or toroidal) lipidic structures. In this review I focus on the ways in which lipids contribute to pore formation and contrast this with the ways in which lipids are co-opted also in membrane fusion and fission events. A variety of mechanisms for pore formation that involve lipids exists, but they consistently result in stable hybrid proteolipidic structures. These structures are stabilised by mechanisms in which pore-forming proteins modify the innate capacity of lipid membranes to respond to their environment, changing shape and/or phase and binding individual lipid molecules directly. In contrast, and despite the diversity in fusion protein types, mechanisms for membrane fusion are rather similar to each other, mapping out a pathway from pairs of separated compartments to fully confluent fused membranes. Fusion proteins generate metastable structures along the way which, like long-lived proteolipidic pore-forming complexes, rely on the basic physical properties of lipid bilayers. Membrane fission involves similar intermediates, in the reverse order. I conclude by considering the possibility that at least some pore-forming and fusion proteins are evolutionarily related homologues. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- Robert J C Gilbert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
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77
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Gutiérrez-Venegas G, Guadarrama-Solís A, Muñoz-Seca C, Arreguín-Cano JA. Hydrogen peroxide-induced apoptosis in human gingival fibroblasts. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2015; 8:15563-15572. [PMID: 26884825 PMCID: PMC4730038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 08/23/2015] [Indexed: 06/05/2023]
Abstract
In the process of bleaching vital, discolored teeth, low concentrations of hydrogen peroxide (H2O2) are effective alternatives to heat-activated 30% H2O2. However, interest has been expressed in the assessment of pathological effects of long-term exposure to bleaching agents such as irritation and ulceration of the gingival or other soft tissues. The aim of the present study was to determine the effect of hydrogen peroxide on apoptosis in human gingival fibroblasts (HGF). Cytochrome c, Bcl-2, Bax, Bid and caspase-3 protein expression were detected by Western blotting. HGF cell apoptosis induced by H2O2 was both dose and time dependent. The addition of H2O2 resulted in the release of cytochrome c to the cytosol, and an increase of Caspase-3 cleavage. Data suggest that oxidative stress-induced apoptosis in HGF is intrinsic pathway involved the release of apoptotic signal from mitochondria.
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Affiliation(s)
- Gloria Gutiérrez-Venegas
- Laboratorio de Bioquímica de la División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México, Ciudad Universitaria D.F., México
| | - Adriana Guadarrama-Solís
- Laboratorio de Bioquímica de la División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México, Ciudad Universitaria D.F., México
| | - Carmen Muñoz-Seca
- Laboratorio de Bioquímica de la División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México, Ciudad Universitaria D.F., México
| | - Juan Antonio Arreguín-Cano
- Laboratorio de Bioquímica de la División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de México, Ciudad Universitaria D.F., México
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78
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Sung TC, Li CY, Lai YC, Hung CL, Shih O, Yeh YQ, Jeng US, Chiang YW. Solution Structure of Apoptotic BAX Oligomer: Oligomerization Likely Precedes Membrane Insertion. Structure 2015; 23:1878-1888. [PMID: 26299946 DOI: 10.1016/j.str.2015.07.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/06/2015] [Accepted: 07/28/2015] [Indexed: 12/23/2022]
Abstract
Proapoptotic BAX protein is largely cytosolic in healthy cells, but it oligomerizes and translocates to mitochondria upon receiving apoptotic stimuli. A long-standing challenge has been the inability to capture any structural information beyond the onset of activation. Here, we present solution structures of an activated BAX oligomer by means of spectroscopic and scattering methods, providing details about the monomer-monomer interfaces in the oligomer and how the oligomer is assembled from homodimers. We show that this soluble oligomer undergoes a direct conversion into membrane-inserted oligomer, which has the ability of inducing apoptosis and structurally resembles a membrane-embedded oligomer formed from BAX monomers in lipid environment. Structural differences between the soluble and the membrane-inserted oligomers are manifested in the C-terminal helices. Our data suggest an alternative pathway of apoptosis in which BAX oligomer formation occurs prior to membrane insertion.
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Affiliation(s)
- Tai-Ching Sung
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Ching-Yu Li
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yei-Chen Lai
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chien-Lun Hung
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Orion Shih
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yi-Qi Yeh
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - U-Ser Jeng
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
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79
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Gahl RF, Tekle E, Zhu GA, Taraska JW, Tjandra N. Acquiring snapshots of the orientation of trans-membrane protein domains using a hybrid FRET pair. FEBS Lett 2015; 589:885-9. [PMID: 25747388 DOI: 10.1016/j.febslet.2015.02.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/14/2015] [Accepted: 02/21/2015] [Indexed: 01/24/2023]
Abstract
One challenge in studying the function of membrane-embedded proteins is determining the orientation of key domains in the context of the changing and dynamic membrane environment. We describe a confocal microscopy setup that utilizes external electric field pulses to direct dipicrylamine (DPA) to a membrane leaflet. The detection of FRET between DPA and a fluorescent probe attributes it to the inner or outer leaflet of a membrane. By utilizing short acquisition times and confocal imaging, this attribution could be made even in changing membrane environments. Our setup adds versatility to the study of the biological activity of membrane-embedded proteins.
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Affiliation(s)
- Robert F Gahl
- Biochemistry and Biophysics Center, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20892, USA
| | - Ephrem Tekle
- Biochemistry and Biophysics Center, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20892, USA
| | - Gefei Alex Zhu
- Biochemistry and Biophysics Center, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20892, USA
| | - Justin W Taraska
- Biochemistry and Biophysics Center, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20892, USA
| | - Nico Tjandra
- Biochemistry and Biophysics Center, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, Bethesda, MD 20892, USA.
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80
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Abstract
As mitochondria are the powerhouses of the cell, their damage during the cell suicide process of apoptosis is essentially responsible for cellular demise in most cells. A key family of proteins, the B-cell lymphoma-2 (BCL-2) family, determines the integrity of mitochondria in the face of apoptotic insult. A comprehensive understanding of the molecular details of how apoptosis is initiated and how it culminates is essential if apoptosis is to fulfil its undoubted potential as a therapeutic target to treat diseases ranging from cancer to neurodegenerative conditions. Recent advances have provided significant insight into the control of this fundamental process while prompting a re-evaluation of what was considered dogma in the field. Emerging evidence also points to a potential overarching control network that governs not only apoptosis but other fundamental mitochondrial processes, including mitochondrial fission/fusion and quality control.
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Affiliation(s)
- Mark Xiang Li
- Walter and Eliza Hall Institute of Medical Research1G Royal Parade, Parkville, Melbourne, Victoria 3052Australia
- Department of Medical Biology, University of MelbourneParkville, Victoria 3050Australia
| | - Grant Dewson
- Walter and Eliza Hall Institute of Medical Research1G Royal Parade, Parkville, Melbourne, Victoria 3052Australia
- Department of Medical Biology, University of MelbourneParkville, Victoria 3050Australia
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81
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Correia C, Lee SH, Meng XW, Vincelette ND, Knorr KLB, Ding H, Nowakowski GS, Dai H, Kaufmann SH. Emerging understanding of Bcl-2 biology: Implications for neoplastic progression and treatment. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1658-71. [PMID: 25827952 DOI: 10.1016/j.bbamcr.2015.03.012] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/20/2015] [Accepted: 03/22/2015] [Indexed: 02/07/2023]
Abstract
Bcl-2, the founding member of a family of apoptotic regulators, was initially identified as the protein product of a gene that is translocated and overexpressed in greater than 85% of follicular lymphomas (FLs). Thirty years later we now understand that anti-apoptotic Bcl-2 family members modulate the intrinsic apoptotic pathway by binding and neutralizing the mitochondrial permeabilizers Bax and Bak as well as a variety of pro-apoptotic proteins, including the cellular stress sensors Bim, Bid, Puma, Bad, Bmf and Noxa. Despite extensive investigation of all of these proteins, important questions remain. For example, how Bax and Bak breach the outer mitochondrial membrane remains poorly understood. Likewise, how the functions of anti-apoptotic Bcl-2 family members such as eponymous Bcl-2 are affected by phosphorylation or cancer-associated mutations has been incompletely defined. Finally, whether Bcl-2 family members can be successfully targeted for therapeutic advantage is only now being investigated in the clinic. Here we review recent advances in understanding Bcl-2 family biology and biochemistry that begin to address these questions.
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Affiliation(s)
- Cristina Correia
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Sun-Hee Lee
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - X Wei Meng
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Nicole D Vincelette
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Katherine L B Knorr
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Husheng Ding
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA
| | - Grzegorz S Nowakowski
- Division of Hematology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Haiming Dai
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA.
| | - Scott H Kaufmann
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA; Division of Hematology, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA.
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82
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Iyer S, Bell F, Westphal D, Anwari K, Gulbis J, Smith BJ, Dewson G, Kluck RM. Bak apoptotic pores involve a flexible C-terminal region and juxtaposition of the C-terminal transmembrane domains. Cell Death Differ 2015; 22:1665-75. [PMID: 25744027 DOI: 10.1038/cdd.2015.15] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Revised: 01/07/2015] [Accepted: 01/21/2015] [Indexed: 12/22/2022] Open
Abstract
Bak and Bax mediate apoptotic cell death by oligomerizing and forming a pore in the mitochondrial outer membrane. Both proteins anchor to the outer membrane via a C-terminal transmembrane domain, although its topology within the apoptotic pore is not known. Cysteine-scanning mutagenesis and hydrophilic labeling confirmed that in healthy mitochondria the Bak α9 segment traverses the outer membrane, with 11 central residues shielded from labeling. After pore formation those residues remained shielded, indicating that α9 does not line a pore. Bak (and Bax) activation allowed linkage of α9 to neighboring α9 segments, identifying an α9:α9 interface in Bak (and Bax) oligomers. Although the linkage pattern along α9 indicated a preferred packing surface, there was no evidence of a dimerization motif. Rather, the interface was invoked in part by Bak conformation change and in part by BH3:groove dimerization. The α9:α9 interaction may constitute a secondary interface in Bak oligomers, as it could link BH3:groove dimers to high-order oligomers. Moreover, as high-order oligomers were generated when α9:α9 linkage in the membrane was combined with α6:α6 linkage on the membrane surface, the α6-α9 region in oligomerized Bak is flexible. These findings provide the first view of Bak carboxy terminus (C terminus) membrane topology within the apoptotic pore.
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Affiliation(s)
- S Iyer
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - F Bell
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia
| | - D Westphal
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - K Anwari
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - J Gulbis
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - B J Smith
- Department of Chemistry and Physics, La Trobe Institute for Molecular Sciences, La Trobe University, Melbourne, Victoria 3086, Australia
| | - G Dewson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - R M Kluck
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3010, Australia
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83
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Lalaoui N, Lindqvist LM, Sandow JJ, Ekert PG. The molecular relationships between apoptosis, autophagy and necroptosis. Semin Cell Dev Biol 2015; 39:63-9. [PMID: 25736836 DOI: 10.1016/j.semcdb.2015.02.003] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 01/30/2015] [Accepted: 02/02/2015] [Indexed: 02/08/2023]
Abstract
Cells are constantly subjected to a vast range of potentially lethal insults, which may activate specific molecular pathways that have evolved to kill the cell. Cell death pathways are defined partly by their morphology, and more specifically by the molecules that regulate and enact them. As these pathways become more thoroughly characterized, interesting molecular links between them have emerged, some still controversial and others hinting at the physiological and pathophysiological roles these death pathways play. We describe specific molecular programs controlling cell death, with a focus on some of the distinct features of the pathways and the molecular links between them.
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Affiliation(s)
- Najoua Lalaoui
- Division of Cell Signalling and Cell Death, Walter and Eliza Hall Institute, 1G Royal Parade, Parkville, Victoria 3050, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
| | - Lisa M Lindqvist
- Division of Cell Signalling and Cell Death, Walter and Eliza Hall Institute, 1G Royal Parade, Parkville, Victoria 3050, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
| | - Jarrod J Sandow
- Division of Cell Signalling and Cell Death, Walter and Eliza Hall Institute, 1G Royal Parade, Parkville, Victoria 3050, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia.
| | - Paul G Ekert
- Division of Cell Signalling and Cell Death, Walter and Eliza Hall Institute, 1G Royal Parade, Parkville, Victoria 3050, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia; Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Rd, Parkville, Victoria 3052, Australia; Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Flemington Rd, Parkville, Victoria 3052, Australia.
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84
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Chan CH, Tsai CJ, Chiang YW. Side-Chain Packing Interactions Stabilize an Intermediate of BAX Protein against Chemical and Thermal Denaturation. J Phys Chem B 2014; 119:54-64. [DOI: 10.1021/jp5091334] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Chun-Hui Chan
- Department of Chemistry and
Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chia-Jung Tsai
- Department of Chemistry and
Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry and
Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan
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85
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Landeta O, Valero JG, Flores-Romero H, Bustillo-Zabalbeitia I, Landajuela A, Garcia-Porras M, Terrones O, Basañez G. Lipid-dependent bimodal MCL1 membrane activity. ACS Chem Biol 2014; 9:2852-63. [PMID: 25314294 DOI: 10.1021/cb500592e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Increasing evidence indicates that the mitochondrial lipid membrane environment directly modulates the BCL2 family protein function, but the underlying mechanisms are still poorly understood. Here, we used minimalistic reconstituted systems to examine the influence of mitochondrial lipids on MCL1 activity and conformation. Site-directed mutagenesis and fluorescence spectroscopic analyses revealed that the BCL2 homology region of MCL1 (MCL1ΔNΔC) inhibits permeabilization of MOM-like membranes exclusively via canonical BH3-into-groove interactions with both cBID-like activators and BAX-like effectors. Contrary to currently popular models, MCL1ΔNΔC did not require becoming embedded into the membrane to inhibit membrane permeabilization, and interaction with cBID was more productive for MCL1ΔNΔC inhibitory activity than interaction with BAX. We also report that membranes rich in cardiolipin (CL), but not phosphatidylinositol (PI), trigger a profound conformational change in MCL1ΔNΔC leading to membrane integration and unleashment of an intrinsic lipidic pore-forming activity of the molecule. Cholesterol (CHOL) reduces both the conformational change and the lipidic pore-forming activity of MCL1ΔNΔC in CL-rich membranes, but it does not affect the interaction of MCL1ΔNΔC with proapoptotic partners in MOM-like liposomes. In addition, we identified MCL1α5 as the minimal domain of the protein responsible for its membrane-permeabilizing function both in model membranes and at the mitochondrial level. Our results provide novel mechanistic insight into MCL1 function in the context of a membrane milieu and add significantly to a growing body of evidence supporting an active role of mitochondrial membrane lipids in BCL2 protein function.
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Affiliation(s)
- Olatz Landeta
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Juan Garcia Valero
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Hector Flores-Romero
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Itsasne Bustillo-Zabalbeitia
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Ane Landajuela
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Miguel Garcia-Porras
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Oihana Terrones
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Gorka Basañez
- Unidad de Biofisica, Centro Mixto Consejo Superior de Investigaciones Científicas (CSIC)-Euskal Herriko Unibertsitatea/Universidad del Pais Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
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86
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Abstract
In this issue, Bleicken et al. (2014) use double electron-electron resonance (DEER) spectroscopy to propose a new model for the active form of Bax at membranes that differs significantly from those previously proposed.
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Affiliation(s)
- David W Andrews
- Sunnybrook Research Institute and Department of Biochemistry, University of Toronto, Toronto, ON M4N 3M5, Canada.
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