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Simonyan L, Gonin M, Hanks J, Friedlein J, Dutrec K, Arokium H, Rouchidane Eyitayo A, Doudy TM, Chaignepain S, Manon S, Dejean L. Non-phosphorylatable mutants of Ser184 lead to incomplete activation of Bax. Front Oncol 2023; 12:1068994. [PMID: 36741728 PMCID: PMC9892840 DOI: 10.3389/fonc.2022.1068994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 12/15/2022] [Indexed: 01/20/2023] Open
Abstract
The S184 residue of Bax is the target of several protein kinases regulating cell fate, including AKT. It is well-established that, in cellulo, the substitution of S184 by a non-phosphorylatable residue stimulates both the mitochondrial localization of Bax, cytochrome c release, and apoptosis. However, in in vitro experiments, substituted mutants did not exhibit any increase in their binding capacity to isolated mitochondria or liposomes. Despite exhibiting a significant increase of the 6A7 epitope exposure, substituted mutants remain limited in their ability to form large oligomers, suggesting that they high capacity to promote apoptosis in cells was more related to a high content than to an increased ability to form large pores in the outer mitochondrial membranes.
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Affiliation(s)
- Lilit Simonyan
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France
| | - Mathilde Gonin
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France
| | - James Hanks
- California State University of Fresno, Department of Chemistry and Biochemistry, Fresno, CA, United States
| | - Jordan Friedlein
- California State University of Fresno, Department of Chemistry and Biochemistry, Fresno, CA, United States
| | - Kevin Dutrec
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France
| | - Hubert Arokium
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France
| | - Akandé Rouchidane Eyitayo
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France
| | - Toukounou Megann Doudy
- Université de Bordeaux, CNRS, Centre de Génomique Fonctionnelle Bordeaux (CGFB), Bordeaux, France
| | - Stéphane Chaignepain
- Université de Bordeaux, CNRS, Centre de Génomique Fonctionnelle Bordeaux (CGFB), Bordeaux, France
| | - Stéphen Manon
- Université de Bordeaux, Centre National de la Recherche Scientifique (CNRS), Institut de Biochimie et de Génétique Cellulaires (IBGC), Bordeaux, France,*Correspondence: Stéphen Manon, ; Laurent Dejean,
| | - Laurent Dejean
- California State University of Fresno, Department of Chemistry and Biochemistry, Fresno, CA, United States,*Correspondence: Stéphen Manon, ; Laurent Dejean,
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2
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Rouchidane Eyitayo A, Giraud MF, Daury L, Lambert O, Gonzalez C, Manon S. Cell-free synthesis and reconstitution of Bax in nanodiscs: Comparison between wild-type Bax and a constitutively active mutant. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184075. [PMID: 36273540 DOI: 10.1016/j.bbamem.2022.184075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 10/11/2022] [Accepted: 10/16/2022] [Indexed: 11/06/2022]
Abstract
Bax is a major player in the mitochondrial pathway of apoptosis, by making the Outer Mitochondrial Membrane (OMM) permeable to various apoptogenic factors, including cytochrome c. In order to get further insight into the structure and function of Bax when it is inserted in the OMM, we attempted to reconstitute Bax in nanodiscs. Cell-free protein synthesis in the presence of nanodiscs did not yield Bax-containing nanodiscs, but it provided a simple way to purify full-length Bax without any tag. Purified wild-type Bax (BaxWT) and a constitutively active mutant (BaxP168A) displayed biochemical properties that were in line with previous characterizations following their expression in yeast and human cells followed by their reconstitution into liposomes. Both Bax variants were then reconstituted in nanodiscs. Size exclusion chromatography, dynamic light scattering and transmission electron microscopy showed that nanodiscs formed with BaxP168A were larger than nanodiscs formed with BaxWT. This was consistent with the hypothesis that BaxP168A was reconstituted in nanodiscs as an active oligomer.
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Affiliation(s)
| | - Marie-France Giraud
- IBGC, UMR5095, CNRS, Université de Bordeaux, France; CBMN, UMR5248, CNRS, Université de Bordeaux, France
| | | | | | | | - Stéphen Manon
- IBGC, UMR5095, CNRS, Université de Bordeaux, France.
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3
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Wagner AR, Weindel CG, West KO, Scott HM, Watson RO, Patrick KL. SRSF6 balances mitochondrial-driven innate immune outcomes through alternative splicing of BAX. eLife 2022; 11:e82244. [PMID: 36409059 PMCID: PMC9718523 DOI: 10.7554/elife.82244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 11/20/2022] [Indexed: 11/23/2022] Open
Abstract
To mount a protective response to infection while preventing hyperinflammation, gene expression in innate immune cells must be tightly regulated. Despite the importance of pre-mRNA splicing in shaping the proteome, its role in balancing immune outcomes remains understudied. Transcriptomic analysis of murine macrophage cell lines identified Serine/Arginine Rich Splicing factor 6 (SRSF6) as a gatekeeper of mitochondrial homeostasis. SRSF6-dependent orchestration of mitochondrial health is directed in large part by alternative splicing of the pro-apoptosis pore-forming protein BAX. Loss of SRSF6 promotes accumulation of BAX-κ, a variant that sensitizes macrophages to undergo cell death and triggers upregulation of interferon stimulated genes through cGAS sensing of cytosolic mitochondrial DNA. Upon pathogen sensing, macrophages regulate SRSF6 expression to control the liberation of immunogenic mtDNA and adjust the threshold for entry into programmed cell death. This work defines BAX alternative splicing by SRSF6 as a critical node not only in mitochondrial homeostasis but also in the macrophage's response to pathogens.
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Affiliation(s)
- Allison R Wagner
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
| | - Chi G Weindel
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
| | - Kelsi O West
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
| | - Haley M Scott
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
| | - Robert O Watson
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
| | - Kristin L Patrick
- Department of Microbial Pathogenesis and Immunology, Texas A&M Health, School of MedicineBryanUnited States
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4
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Guedes JP, Baptista V, Santos-Pereira C, Sousa MJ, Manon S, Chaves SR, Côrte-Real M. Acetic acid triggers cytochrome c release in yeast heterologously expressing human Bax. Apoptosis 2022; 27:368-381. [PMID: 35362903 DOI: 10.1007/s10495-022-01717-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/12/2022] [Indexed: 11/29/2022]
Abstract
Proteins of the Bcl-2 protein family, including pro-apoptotic Bax and anti-apoptotic Bcl-xL, are critical for mitochondrial-mediated apoptosis regulation. Since yeast lacks obvious orthologs of Bcl-2 family members, heterologous expression of these proteins has been used to investigate their molecular and functional aspects. Active Bax is involved in the formation of mitochondrial outer membrane pores, through which cytochrome c (cyt c) is released, triggering a cascade of downstream apoptotic events. However, when in its inactive form, Bax is largely cytosolic or weakly bound to mitochondria. Given the central role of Bax in apoptosis, studies aiming to understand its regulation are of paramount importance towards its exploitation as a therapeutic target. So far, studies taking advantage of heterologous expression of human Bax in yeast to unveil regulation of Bax activation have relied on the use of artificial mutated or mitochondrial tagged Bax for its activation, rather than the wild type Bax (Bax α). Here, we found that cell death could be triggered in yeast cells heterologoulsy expressing Bax α with concentrations of acetic acid that are not lethal to wild type cells. This was associated with Bax mitochondrial translocation and cyt c release, closely resembling the natural Bax function in the cellular context. This regulated cell death process was reverted by co-expression with Bcl-xL, but not with Bcl-xLΔC, and in the absence of Rim11p, the yeast ortholog of mammalian GSK3β. This novel system mimics human Bax α regulation by GSK3β and can therefore be used as a platform to uncover novel Bax regulators and explore its therapeutic modulation.
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Affiliation(s)
- Joana P Guedes
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.,Centro de Investigacíon Médica Aplicada (CIMA), Universidad de Navarra, 31008, Pamplona, Spain
| | - Vitória Baptista
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.,Microelectromechanical Systems Research Unit (CMEMS-UMinho), School of Engineering, University of Minho, Campus de Azurém, 4800-058, Guimarães, Portugal.,Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Cátia Santos-Pereira
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.,Centre of Biological Engineering (CEB), Department of Biological Engineering, University of Minho, 4710-057, Braga, Portugal.,LABBELS - Associate Laboratory, Braga, Guimarães, Portugal
| | - Maria João Sousa
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Stéphen Manon
- UMR 5095, CNRS, Université de Bordeaux, Campus Carreire, 1 Rue Camille Saint-Saëns, 33077, Bordeaux, France
| | - Susana R Chaves
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Manuela Côrte-Real
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.
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5
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Bcl-2 Family Members and the Mitochondrial Import Machineries: The Roads to Death. Biomolecules 2022; 12:biom12020162. [PMID: 35204663 PMCID: PMC8961529 DOI: 10.3390/biom12020162] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 01/27/2023] Open
Abstract
The localization of Bcl-2 family members at the mitochondrial outer membrane (MOM) is a crucial step in the implementation of apoptosis. We review evidence showing the role of the components of the mitochondrial import machineries (translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM)) in the mitochondrial localization of Bcl-2 family members and how these machineries regulate the function of pro- and anti-apoptotic proteins in resting cells and in cells committed into apoptosis.
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6
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Contribution of Yeast Studies to the Understanding of BCL-2 Family Intracellular Trafficking. Int J Mol Sci 2021; 22:ijms22084086. [PMID: 33920941 PMCID: PMC8071328 DOI: 10.3390/ijms22084086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/12/2021] [Accepted: 04/13/2021] [Indexed: 12/24/2022] Open
Abstract
BCL-2 family members are major regulators of apoptotic cell death in mammals. They form an intricate regulatory network that ultimately regulates the release of apoptogenic factors from mitochondria to the cytosol. The ectopic expression of mammalian BCL-2 family members in the yeast Saccharomyces cerevisiae, which lacks BCL-2 homologs, has been long established as a useful addition to the available models to study their function and regulation. In yeast, individual proteins can be studied independently from the whole interaction network, thus providing insight into the molecular mechanisms underlying their function in a living context. Furthermore, one can take advantage of the powerful tools available in yeast to probe intracellular trafficking processes such as mitochondrial sorting and interactions/exchanges between mitochondria and other compartments, such as the endoplasmic reticulum that are largely conserved between yeast and mammals. Yeast molecular genetics thus allows the investigation of the role of these processes on the dynamic equilibrium of BCL-2 family members between mitochondria and extramitochondrial compartments. Here we propose a model of dynamic regulation of BCL-2 family member localization, based on available evidence from ectopic expression in yeast.
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7
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Popgeorgiev N, Sa JD, Jabbour L, Banjara S, Nguyen TTM, Akhavan-E-Sabet A, Gadet R, Ralchev N, Manon S, Hinds MG, Osigus HJ, Schierwater B, Humbert PO, Rimokh R, Gillet G, Kvansakul M. Ancient and conserved functional interplay between Bcl-2 family proteins in the mitochondrial pathway of apoptosis. SCIENCE ADVANCES 2020; 6:6/40/eabc4149. [PMID: 32998881 PMCID: PMC7527217 DOI: 10.1126/sciadv.abc4149] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 08/10/2020] [Indexed: 06/10/2023]
Abstract
In metazoans, Bcl-2 family proteins are major regulators of mitochondrially mediated apoptosis; however, their evolution remains poorly understood. Here, we describe the molecular characterization of the four members of the Bcl-2 family in the most primitive metazoan, Trichoplax adhaerens All four trBcl-2 homologs are multimotif Bcl-2 group, with trBcl-2L1 and trBcl-2L2 being highly divergent antiapoptotic Bcl-2 members, whereas trBcl-2L3 and trBcl-2L4 are homologs of proapoptotic Bax and Bak, respectively. trBax expression permeabilizes the mitochondrial outer membrane, while trBak operates as a BH3-only sensitizer repressing antiapoptotic activities of trBcl-2L1 and trBcl-2L2. The crystal structure of a trBcl-2L2:trBak BH3 complex reveals that trBcl-2L2 uses the canonical Bcl-2 ligand binding groove to sequester trBak BH3, indicating that the structural basis for apoptosis control is conserved from T. adhaerens to mammals. Finally, we demonstrate that both trBax and trBak BH3 peptides bind selectively to human Bcl-2 homologs to sensitize cancer cells to chemotherapy treatment.
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Affiliation(s)
- Nikolay Popgeorgiev
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France.
| | - Jaison D Sa
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
| | - Lea Jabbour
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France
| | - Suresh Banjara
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
| | - Trang Thi Minh Nguyen
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France
| | - Aida Akhavan-E-Sabet
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
| | - Rudy Gadet
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France
| | - Nikola Ralchev
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France
| | - Stéphen Manon
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS et Université de Bordeaux, CS61390, 1 Rue Camille Saint-Saëns, 33000 Bordeaux, France
| | - Mark G Hinds
- Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne 3050, Australia
| | - Hans-Jürgen Osigus
- Institute of Animal Ecology, Division of Molecular Evolution, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany
| | - Bernd Schierwater
- Institute of Animal Ecology, Division of Molecular Evolution, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY 10024, USA
| | - Patrick O Humbert
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
| | - Ruth Rimokh
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France
| | - Germain Gillet
- Université de Lyon, Centre de recherche en cancérologie de Lyon, U1052 INSERM, UMR CNRS 5286, Université Lyon I, Centre Léon Bérard, 28 rue Laennec, 69008 Lyon, France.
| | - Marc Kvansakul
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia.
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8
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Flores-Romero H, Ros U, García-Sáez AJ. A lipid perspective on regulated cell death. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2019; 351:197-236. [PMID: 32247580 DOI: 10.1016/bs.ircmb.2019.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lipids are fundamental to life as structural components of cellular membranes and for signaling. They are also key regulators of different cellular processes such as cell division, proliferation, and death. Regulated cell death (RCD) requires the engagement of lipids and lipid metabolism for the initiation and execution of its killing machinery. The permeabilization of lipid membranes is a hallmark of RCD that involves, for each kind of cell death, a unique lipid profile. While the permeabilization of the mitochondrial outer membrane allows the release of apoptotic factors to the cytosol during apoptosis, permeabilization of the plasma membrane facilitates the release of intracellular content in other nonapoptotic types of RCD like necroptosis and ferroptosis. Lipids and lipid membranes are important accessory molecules required for the activation of protein executors of cell death such as BAX in apoptosis and MLKL in necroptosis. Peroxidation of membrane phospholipids and the subsequent membrane destabilization is a prerequisite to ferroptosis. Here, we discuss how lipids are essential players in apoptosis, the most common form of RCD, and also their role in necroptosis and ferroptosis. Altogether, we aim to highlight the contribution of lipids and membrane dynamics in cell death regulation.
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Affiliation(s)
- Hector Flores-Romero
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Uris Ros
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany.
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9
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Maes ME, Grosser JA, Fehrman RL, Schlamp CL, Nickells RW. Completion of BAX recruitment correlates with mitochondrial fission during apoptosis. Sci Rep 2019; 9:16565. [PMID: 31719602 PMCID: PMC6851089 DOI: 10.1038/s41598-019-53049-w] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 10/23/2019] [Indexed: 12/30/2022] Open
Abstract
BAX, a member of the BCL2 gene family, controls the committed step of the intrinsic apoptotic program. Mitochondrial fragmentation is a commonly observed feature of apoptosis, which occurs through the process of mitochondrial fission. BAX has consistently been associated with mitochondrial fission, yet how BAX participates in the process of mitochondrial fragmentation during apoptosis remains to be tested. Time-lapse imaging of BAX recruitment and mitochondrial fragmentation demonstrates that rapid mitochondrial fragmentation during apoptosis occurs after the complete recruitment of BAX to the mitochondrial outer membrane (MOM). The requirement of a fully functioning BAX protein for the fission process was demonstrated further in BAX/BAK-deficient HCT116 cells expressing a P168A mutant of BAX. The mutant performed fusion to restore the mitochondrial network. but was not demonstrably recruited to the MOM after apoptosis induction. Under these conditions, mitochondrial fragmentation was blocked. Additionally, we show that loss of the fission protein, dynamin-like protein 1 (DRP1), does not temporally affect the initiation time or rate of BAX recruitment, but does reduce the final level of BAX recruited to the MOM during the late phase of BAX recruitment. These correlative observations suggest a model where late-stage BAX oligomers play a functional part of the mitochondrial fragmentation machinery in apoptotic cells.
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Affiliation(s)
- M E Maes
- Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI, USA.,Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - J A Grosser
- Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI, USA
| | - R L Fehrman
- Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI, USA
| | - C L Schlamp
- Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI, USA
| | - R W Nickells
- Department of Ophthalmology and Visual Sciences, University of Wisconsin - Madison, Madison, WI, USA.
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10
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The Incomplete Puzzle of the BCL2 Proteins. Cells 2019; 8:cells8101176. [PMID: 31569576 PMCID: PMC6830314 DOI: 10.3390/cells8101176] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 09/25/2019] [Accepted: 09/26/2019] [Indexed: 02/07/2023] Open
Abstract
The proteins of the BCL2 family are key players in multiple cellular processes, chief amongst them being the regulation of mitochondrial integrity and apoptotic cell death. These proteins establish an intricate interaction network that expands both the cytosol and the surface of organelles to dictate the cell fate. The complexity and unpredictability of the BCL2 interactome resides in the large number of family members and of interaction surfaces, as well as on their different behaviours in solution and in the membrane. Although our current structural knowledge of the BCL2 proteins has been proven therapeutically relevant, the precise structure of membrane-bound complexes and the regulatory effect that membrane lipids exert over these proteins remain key questions in the field. Here, we discuss the complexity of BCL2 interactome, the new insights, and the black matter in the field.
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11
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Légiot A, Céré C, Dupoiron T, Kaabouni M, Camougrand N, Manon S. Mitochondria-Associated Membranes (MAMs) are involved in Bax mitochondrial localization and cytochrome c release. MICROBIAL CELL 2019; 6:257-266. [PMID: 31114795 PMCID: PMC6506693 DOI: 10.15698/mic2019.05.678] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The distribution of the pro-apoptotic protein Bax in the outer mi-tochondrial membrane (OMM) is a central point of regulation of apoptosis. It is now widely recognized that parts of the endoplasmic reticulum (ER) are closely associated to the OMM, and are actively involved in different signaling processes. We addressed a possible role of these domains, called Mitochon-dria-Associated Membranes (MAMs) in Bax localization and function, by ex-pressing the human protein in a yeast mutant deleted of MDM34, a ERMES (ER-Mitochondria Encounter Structure) component. By affecting MAMs stabil-ity, the deletion of MDM34 altered Bax mitochondrial localization, and de-creased its capacity to release cytochrome c. Furthermore, the deletion of MDM34 decreased the size of an incompletely released, MAMs-associated pool of cytochrome c.
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Affiliation(s)
- Alexandre Légiot
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Claire Céré
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Thibaud Dupoiron
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Mohamed Kaabouni
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Nadine Camougrand
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Stéphen Manon
- Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS & Université de Bordeaux, Campus Carreire, CS61390, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
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12
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Topology of active, membrane-embedded Bax in the context of a toroidal pore. Cell Death Differ 2018; 25:1717-1731. [PMID: 30185826 DOI: 10.1038/s41418-018-0184-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 04/20/2018] [Accepted: 05/21/2018] [Indexed: 01/18/2023] Open
Abstract
Bax is a Bcl-2 protein critical for apoptosis induction. In healthy cells, Bax is mostly a monomeric, cytosolic protein, while upon apoptosis initiation it inserts into the outer mitochondrial membrane, oligomerizes, and forms pores that release proapoptotic factors like Cytochrome c into the cytosol. The structures of active Bax and its homolog Bak are only partially understood and the topology of the proteins with respect to the membrane bilayer is controversially described in the literature. Here, we systematically review and examine the protein-membrane, protein-water, and protein-protein contacts of the nine helices of active Bax and Bak, and add a new set of topology data obtained by fluorescence and EPR methods. We conclude based on the consistent part of the datasets that the core/dimerization domain of Bax (Bak) is water exposed with only helices 4 and 5 in membrane contact, whereas the piercing/latch domain is in peripheral membrane contact, with helix 9 being transmembrane. Among the available structural models, those considering the dimerization/core domain at the rim of a toroidal pore are the most plausible to describe the active state of the proteins, although the structural flexibility of the piercing/latch domain does not allow unambiguous discrimination between the existing models.
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13
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Hou D, Che Z, Chen P, Zhang W, Chu Y, Yang D, Liu J. Suppression of AURKA alleviates p27 inhibition on Bax cleavage and induces more intensive apoptosis in gastric cancer. Cell Death Dis 2018; 9:781. [PMID: 30013101 PMCID: PMC6048174 DOI: 10.1038/s41419-018-0823-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 05/03/2018] [Accepted: 05/31/2018] [Indexed: 12/13/2022]
Abstract
Bax is a key molecule in mitochondria-apoptosis pathway, however it is not always an efficient apoptosis inducer in chemotherapeutic agents-treated cancer cells. Here, we found that specific inhibition of AURKA by MLN8237-induced calpain-mediated Bax cleavage at N-terminal 33th asparagine (c-Bax) to promote apoptosis. The c-Bax, as Bax, could also efficiently located to mitochondria but c-Bax is a stronger apoptosis inducer than Bax. Morever, c-Bax-induced apoptosis could not be blocked by the canonical Bax inhibitor, Bcl-2. Further study found p27 was degraded and subsequently Bax was transformed to c-Bax through calpain. Also, p27 efficiently inhibited Bax cleavage and p27 knockdown sensitized apoptosis through Bax cleavage when cancer cells were treated with MLN8237. It is also demonstrated that the anti-apoptotic role of p27 lies its cytoplasmic localization. Finally, we found that the positive correlation between AURKA and p27 in advanced gastric cancer patients. In conclusion, we found that MNL8237 suppressed cell growth by regulating calpain-dependent Bax cleavage and p27 dysregulation in gastric cancer cells.
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Affiliation(s)
- Daisen Hou
- Department of Digestive Diseases of Huashan Hospital and Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Zhihui Che
- Department of Digestive Diseases, National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Ping Chen
- Department of Digestive Diseases of Huashan Hospital and Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Wenli Zhang
- Department of Digestive Diseases, National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Yiwei Chu
- Institute of Biomedical Sciences and Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Dongqin Yang
- Department of Digestive Diseases, National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China.
| | - Jie Liu
- Department of Digestive Diseases of Huashan Hospital and Institute of Biomedical Sciences, Fudan University, Shanghai, China. .,Department of Digestive Diseases, National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China.
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14
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Mañas A, Chen W, Nelson A, Yao Q, Xiang J. BaxΔ2 sensitizes colorectal cancer cells to proteasome inhibitor-induced cell death. Biochem Biophys Res Commun 2018; 496:18-24. [PMID: 29291406 PMCID: PMC6022363 DOI: 10.1016/j.bbrc.2017.12.156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 12/26/2017] [Indexed: 12/23/2022]
Abstract
Proteasome inhibitors, such as bortezomib and carfilzomib, are FDA approved for the treatment of hemopoietic cancers, but recent studies have shown their great potential for treatment of solid tumors. BaxΔ2, a unique proapoptotic Bax isoform, promotes non-mitochondrial cell death and sensitizes cancer cells to chemotherapy. However, endogenous BaxΔ2 proteins are unstable and susceptible to proteasomal degradation. Here, we screened a panel of proteasome inhibitors in colorectal cancer cells with different Bax statuses. We found that all proteasome inhibitors tested were able to block BaxΔ2 degradation without affecting the level of Baxα or Bcl-2 proteins. Among the inhibitors tested, only bortezomib and carfilzomib were able to induce differential cell death corresponding to the distinct Bax statuses. BaxΔ2-positive cells had a significantly higher level of cell death at low nanomolar concentrations than Baxα-positive or Bax-negative cells. Furthermore, bortezomib-induced cell death in BaxΔ2-positive cells was predominantly dependent on the caspase 8/3 pathway, consistent with our previous studies. These results imply that BaxΔ2 can selectively sensitize cancer cells to proteasome inhibitors, enhancing their potential to treat colon cancer and other solid tumors.
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Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Wenjing Chen
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
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15
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N-terminal acetylation modulates Bax targeting to mitochondria. Int J Biochem Cell Biol 2017; 95:35-42. [PMID: 29233735 DOI: 10.1016/j.biocel.2017.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 11/28/2017] [Accepted: 12/06/2017] [Indexed: 01/13/2023]
Abstract
The pro-apoptotic Bax protein is the main effector of mitochondrial permeabilization during apoptosis. Bax is controlled at several levels, including post-translational modifications such as phosphorylation and S-palmitoylation. However, little is known about the contribution of other protein modifications to Bax activity. Here, we used heterologous expression of human Bax in yeast to study the involvement of N-terminal acetylation by yNaa20p (yNatB) on Bax function. We found that human Bax is N-terminal (Nt-)acetylated by yNaa20p and that Nt-acetylation of Bax is essential to maintain Bax in an inactive conformation in the cytosol of yeast and Mouse Embryonic Fibroblast (MEF) cells. Bax accumulates in the mitochondria of yeast naa20Δ and Naa25-/- MEF cells, but does not promote cytochrome c release, suggesting that an additional step is required for full activation of Bax. Altogether, our results show that Bax N-terminal acetylation by NatB is involved in its mitochondrial targeting.
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16
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Mañas A, Wang S, Nelson A, Li J, Zhao Y, Zhang H, Davis A, Xie B, Maltsev N, Xiang J. The functional domains for Bax∆2 aggregate-mediated caspase 8-dependent cell death. Exp Cell Res 2017; 359:342-355. [PMID: 28807790 PMCID: PMC5718386 DOI: 10.1016/j.yexcr.2017.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/07/2017] [Accepted: 08/08/2017] [Indexed: 01/09/2023]
Abstract
Bax∆2 is a functional pro-apoptotic Bax isoform having alterations in its N-terminus, but sharing the rest of its sequence with Baxα. Bax∆2 is unable to target mitochondria due to the loss of helix α1. Instead, it forms cytosolic aggregates and activates caspase 8. However, the functional domain(s) responsible for BaxΔ2 behavior have remained elusive. Here we show that disruption of helix α1 makes Baxα mimic the behavior of Bax∆2. However, the other alterations in the Bax∆2 N-terminus have no significant impact on aggregation or cell death. We found that the hallmark BH3 domain is necessary but not sufficient for aggregation-mediated cell death. We also noted that the core region shared by Baxα and Bax∆2 is required for the formation of large aggregates, which is essential for BaxΔ2 cytotoxicity. However, aggregation by itself is unable to trigger cell death without the C-terminus. Interestingly, the C-terminal helical conformation, not its primary sequence, appears to be critical for caspase 8 recruitment and activation. As Bax∆2 shares core and C-terminal sequences with most Bax isoforms, our results not only reveal a structural basis for Bax∆2-induced cell death, but also imply an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members.
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Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sheng Wang
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jiajun Li
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Yu Zhao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aislinn Davis
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Bingqing Xie
- Department of Computer Science, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Natalia Maltsev
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
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17
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Karageorgis A, Claron M, Jugé R, Aspord C, Thoreau F, Leloup C, Kucharczak J, Plumas J, Henry M, Hurbin A, Verdié P, Martinez J, Subra G, Dumy P, Boturyn D, Aouacheria A, Coll JL. Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model. Mol Ther 2017; 25:534-546. [PMID: 28153100 DOI: 10.1016/j.ymthe.2016.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 01/03/2023] Open
Abstract
Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin αvβ3, which is a well-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5 μM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]4-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.
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Affiliation(s)
- Anastassia Karageorgis
- INSERM U1209, Institut Albert Bonniot, 38706 La Tronche, France; Université Grenoble Alpes, 38000 Grenoble, France
| | - Michaël Claron
- Université Grenoble Alpes, 38000 Grenoble, France; CNRS UMR 5250, ICMG FR2607, 38000 Grenoble, France
| | - Romain Jugé
- Molecular Biology of the Cell Laboratory (LBMC), Ecole Normale Supérieure de Lyon, UMR 5239 CNRS - UCBL - ENS Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
| | - Caroline Aspord
- Université Grenoble Alpes, 38000 Grenoble, France; EMR EFS-UGA-INSERM U1209- CNRS, Immunobiology and Immunotherapy of Chronic Diseases, 38706 La Tronche, France; EFS Rhone-Alpes, R&D Laboratory, 38701 La Tronche, France
| | - Fabien Thoreau
- INSERM U1209, Institut Albert Bonniot, 38706 La Tronche, France; Université Grenoble Alpes, 38000 Grenoble, France; CNRS UMR 5250, ICMG FR2607, 38000 Grenoble, France
| | - Claire Leloup
- Université Grenoble Alpes, 38000 Grenoble, France; EMR EFS-UGA-INSERM U1209- CNRS, Immunobiology and Immunotherapy of Chronic Diseases, 38706 La Tronche, France; EFS Rhone-Alpes, R&D Laboratory, 38701 La Tronche, France
| | - Jérôme Kucharczak
- Molecular Biology of the Cell Laboratory (LBMC), Ecole Normale Supérieure de Lyon, UMR 5239 CNRS - UCBL - ENS Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France
| | - Joël Plumas
- Université Grenoble Alpes, 38000 Grenoble, France; EMR EFS-UGA-INSERM U1209- CNRS, Immunobiology and Immunotherapy of Chronic Diseases, 38706 La Tronche, France; EFS Rhone-Alpes, R&D Laboratory, 38701 La Tronche, France
| | - Maxime Henry
- INSERM U1209, Institut Albert Bonniot, 38706 La Tronche, France; Université Grenoble Alpes, 38000 Grenoble, France
| | - Amandine Hurbin
- INSERM U1209, Institut Albert Bonniot, 38706 La Tronche, France; Université Grenoble Alpes, 38000 Grenoble, France
| | - Pascal Verdié
- CNRS UMR 5247, Institut des Biomolécules Max Mousseron IBMM, 34095 Montpellier, France
| | - Jean Martinez
- CNRS UMR 5247, Institut des Biomolécules Max Mousseron IBMM, 34095 Montpellier, France
| | - Gilles Subra
- CNRS UMR 5247, Institut des Biomolécules Max Mousseron IBMM, 34095 Montpellier, France
| | - Pascal Dumy
- CNRS UMR 5250, ICMG FR2607, 38000 Grenoble, France; CNRS UMR 5247, Institut des Biomolécules Max Mousseron IBMM, 34095 Montpellier, France
| | - Didier Boturyn
- Université Grenoble Alpes, 38000 Grenoble, France; CNRS UMR 5250, ICMG FR2607, 38000 Grenoble, France
| | - Abdel Aouacheria
- Molecular Biology of the Cell Laboratory (LBMC), Ecole Normale Supérieure de Lyon, UMR 5239 CNRS - UCBL - ENS Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; Institut des Sciences de l'Evolution de Montpellier (ISEM), UMR 5554, Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, 34095 Montpellier, France.
| | - Jean-Luc Coll
- INSERM U1209, Institut Albert Bonniot, 38706 La Tronche, France; Université Grenoble Alpes, 38000 Grenoble, France.
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18
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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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19
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Gupta R, Ghosh S. JNK3 phosphorylates Bax protein and induces ability to form pore on bilayer lipid membrane. BIOCHIMIE OPEN 2017; 4:41-46. [PMID: 29450140 PMCID: PMC5801821 DOI: 10.1016/j.biopen.2017.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/01/2017] [Indexed: 11/15/2022]
Abstract
Bax is a pro-apoptotic cytosolic protein. In this work native (unphosphorylated) and JNK3 phosphorylated Bax proteins are studied on artificial bilayer membranes for pore formation. Phosphorylated Bax formed pore on the bilayer lipid membrane whereas native one does not. In cells undergoing apoptosis the pore formed by the phosphorylated Bax could be important in cytochrome c release from the mitochondrial intermembrane space to the cytosol. The low conductance (1.5 nS) of the open state of the phosphorylated Bax pore corresponds to pore diameter of 0.9 nm which is small to release cytochrome c (∼3.4 nm). We hypothesized that JNK3 phosphorylated Bax protein can form bigger pores after forming complexes with other mitochondrial proteins like VDAC, t-Bid etc. to release cytochrome c.
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Affiliation(s)
- Rajeev Gupta
- Department of Physiology, All India Institute of Medical Sciences, India
| | - Subhendu Ghosh
- Department of Biophysics, University of Delhi South Campus, India
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20
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Conformational Heterogeneity of Bax Helix 9 Dimer for Apoptotic Pore Formation. Sci Rep 2016; 6:29502. [PMID: 27381287 PMCID: PMC4933972 DOI: 10.1038/srep29502] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 06/20/2016] [Indexed: 11/27/2022] Open
Abstract
Helix α9 of Bax protein can dimerize in the mitochondrial outer membrane (MOM) and lead to apoptotic pores. However, it remains unclear how different conformations of the dimer contribute to the pore formation on the molecular level. Thus we have investigated various conformational states of the α9 dimer in a MOM model — using computer simulations supplemented with site-specific mutagenesis and crosslinking of the α9 helices. Our data not only confirmed the critical membrane environment for the α9 stability and dimerization, but also revealed the distinct lipid-binding preference of the dimer in different conformational states. In our proposed pathway, a crucial iso-parallel dimer that mediates the conformational transition was discovered computationally and validated experimentally. The corroborating evidence from simulations and experiments suggests that, helix α9 assists Bax activation via the dimer heterogeneity and interactions with specific MOM lipids, which eventually facilitate proteolipidic pore formation in apoptosis regulation.
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21
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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: 69] [Impact Index Per Article: 8.6] [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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22
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Liu Z, Ding Y, Ye N, Wild C, Chen H, Zhou J. Direct Activation of Bax Protein for Cancer Therapy. Med Res Rev 2015; 36:313-41. [PMID: 26395559 DOI: 10.1002/med.21379] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 08/18/2015] [Accepted: 08/22/2015] [Indexed: 12/13/2022]
Abstract
Bax, a central cell death regulator, is an indispensable gateway to mitochondrial dysfunction and a major proapoptotic member of the B-cell lymphoma 2 (Bcl-2) family proteins that control apoptosis in normal and cancer cells. Dysfunction of apoptosis renders the cancer cell resistant to treatment as well as promotes tumorigenesis. Bax activation induces mitochondrial membrane permeabilization, thereby leading to the release of apoptotic factor cytochrome c and consequently cancer cell death. A number of drugs in clinical use are known to indirectly activate Bax. Intriguingly, recent efforts demonstrate that Bax can serve as a promising direct target for small-molecule drug discovery. Several direct Bax activators have been identified to hold promise for cancer therapy with the advantages of specificity and the potential of overcoming chemo- and radioresistance. Further investigation of this new class of drug candidates will be needed to advance them into the clinic as a novel means to treat cancer.
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Affiliation(s)
- Zhiqing Liu
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
| | - Ye Ding
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
| | - Na Ye
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
| | - Christopher Wild
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
| | - Haiying Chen
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
| | - Jia Zhou
- Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555
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23
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Renault TT, Teijido O, Missire F, Ganesan YT, Velours G, Arokium H, Beaumatin F, Llanos R, Athané A, Camougrand N, Priault M, Antonsson B, Dejean LM, Manon S. Bcl-xL stimulates Bax relocation to mitochondria and primes cells to ABT-737. Int J Biochem Cell Biol 2015; 64:136-46. [DOI: 10.1016/j.biocel.2015.03.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 03/29/2015] [Accepted: 03/30/2015] [Indexed: 12/26/2022]
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24
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Identification of 12/15-lipoxygenase as a regulator of axon degeneration through high-content screening. J Neurosci 2015; 35:2927-41. [PMID: 25698732 DOI: 10.1523/jneurosci.2936-14.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Axon degeneration is a programed process that takes place during development, in response to neuronal injury, and as a component of neurodegenerative disease pathology, yet the molecular mechanisms that drive this process remain poorly defined. In this study, we have developed a semi-automated, 384-well format axon degeneration assay in rat dorsal root ganglion (DRG) neurons using a trophic factor withdrawal paradigm. Using this setup, we have screened a library of known drugs and bioactives to identify several previously unappreciated regulators of axon degeneration, including lipoxygenases. Multiple structurally distinct lipoxygenase inhibitors as well as mouse DRG neurons lacking expression of 12/15-lipoxygenase display protection of axons in this context. Retinal ganglion cell axons from 12/15-lipoxygenase-null mice were similarly protected from degeneration following nerve crush injury. Through additional mechanistic studies, we demonstrate that lipoxygenases act cell autonomously within neurons to regulate degeneration, and are required for mitochondrial permeabilization and caspase activation in the axon. These findings suggest that these enzymes may represent an attractive target for treatment of neuropathies and provide a potential mechanism for the neuroprotection observed in various settings following lipoxygenase inhibitor treatment.
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25
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Chi X, Kale J, Leber B, Andrews DW. Regulating cell death at, on, and in membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2100-13. [PMID: 24927885 DOI: 10.1016/j.bbamcr.2014.06.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 05/29/2014] [Accepted: 06/03/2014] [Indexed: 11/17/2022]
Abstract
Bcl-2 family proteins are central regulators of apoptosis. Various family members are located in the cytoplasm, endoplasmic reticulum, and mitochondrial outer membrane in healthy cells. However during apoptosis most of the interactions between family members that determine the fate of the cell occur at the membranes of intracellular organelles. It has become evident that interactions with membranes play an active role in the regulation of Bcl-2 family protein interactions. Here we provide an overview of various models proposed to explain how the Bcl-2 family regulates apoptosis and discuss how membrane binding affects the structure and function of each of the three categories of Bcl-2 proteins (pro-apoptotic, pore-forming, and anti-apoptotic). We also examine how the Bcl-2 family regulates other aspects of mitochondrial and ER physiology relevant to cell death.
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Affiliation(s)
- Xiaoke Chi
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Justin Kale
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Brian Leber
- Department of Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - David W Andrews
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Biological Sciences, Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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26
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Evaluation of Bax and Bak gene mutations and expression in breast cancer. BIOMED RESEARCH INTERNATIONAL 2014; 2014:249372. [PMID: 24672785 PMCID: PMC3933335 DOI: 10.1155/2014/249372] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 11/11/2013] [Indexed: 02/07/2023]
Abstract
Genetic analyses have provided evidence to suggest that Bax and Bak are the essential genes for apoptosis in mammalians cells. This study aimed to search for biomarkers in breast cancer to be used as prognostic markers for the disease. The Bak and Bax genes expressions were analyzed in 23 breast cancer patients by RT-PCR technique. SSCP technique was used to detect the mobility of the abnormal fragment in Bak exon 4. PCR for Bax promoter was digested with Tau 1 restriction enzyme to identify a single polymorphism G(-248)A. The expression of Bak gene is related to several clinical factors of breast cancer. The analysis of Bax RNA showed 4 isoforms of Bax with different distributions in the normal and tumor tissues. These isoforms were Bax α, d, δ, and ζ. Exon 4 had a normal pattern in all cases of breast cancer. There was a statistically significant difference in the frequency distribution of the G(-248)A genotypes in the breast cancer tissues with grade 3+high, T2 stage, lobular +other, and PR −ve subgroups. In this study, Bak expression seems to lead to development of breast cancer and affects the disease progression. Also, Bax d and Bax δ could be used as risk factor and biomarker for breast cancer with the distribution of G284A.
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27
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Renault TT, Chipuk JE. Death upon a kiss: mitochondrial outer membrane composition and organelle communication govern sensitivity to BAK/BAX-dependent apoptosis. ACTA ACUST UNITED AC 2013; 21:114-23. [PMID: 24269152 DOI: 10.1016/j.chembiol.2013.10.009] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 10/03/2013] [Accepted: 10/21/2013] [Indexed: 01/24/2023]
Abstract
For stressed cells to induce the mitochondrial pathway of apoptosis, a cohort of pro-apoptotic BCL-2 proteins must collaborate with the outer mitochondrial membrane to permeabilize it. BAK and BAX are the two pro-apoptotic BCL-2 family members that are required for mitochondrial outer membrane permeabilization. While biochemical and structural insights of BAK/BAX function have expanded in recent years, very little is known about the role of the outer mitochondrial membrane in regulating BAK/BAX activity. In this review, we will highlight the impact of mitochondrial composition (both protein and lipid) and mitochondrial interactions with cellular organelles on BAK/BAX function and cellular commitment to apoptosis. A better understanding of how BAK/BAX and mitochondrial biology are mechanistically linked will likely reveal novel insights into homeostatic and pathological mechanisms associated with apoptosis.
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Affiliation(s)
- Thibaud T Renault
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA
| | - Jerry E Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA.
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28
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Rego A, Trindade D, Chaves SR, Manon S, Costa V, Sousa MJ, Côrte-Real M. The yeast model system as a tool towards the understanding of apoptosis regulation by sphingolipids. FEMS Yeast Res 2013; 14:160-78. [DOI: 10.1111/1567-1364.12096] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/02/2013] [Accepted: 09/06/2013] [Indexed: 11/30/2022] Open
Affiliation(s)
- António Rego
- Departamento de Biologia; Centro de Biologia Molecular e Ambiental; Universidade do Minho; Braga Portugal
- Instituto de Biologia Molecular e Celular; Universidade do Porto; Porto Portugal
| | - Dário Trindade
- Departamento de Biologia; Centro de Biologia Molecular e Ambiental; Universidade do Minho; Braga Portugal
- CNRS; UMR5095; Université de Bordeaux 2; Bordeaux France
| | - Susana R. Chaves
- Departamento de Biologia; Centro de Biologia Molecular e Ambiental; Universidade do Minho; Braga Portugal
| | - Stéphen Manon
- CNRS; UMR5095; Université de Bordeaux 2; Bordeaux France
| | - Vítor Costa
- Instituto de Biologia Molecular e Celular; Universidade do Porto; Porto Portugal
- Departamento de Biologia Molecular; Instituto de Ciências Biomédicas Abel Salazar; Universidade do Porto; Porto Portugal
| | - Maria João Sousa
- Departamento de Biologia; Centro de Biologia Molecular e Ambiental; Universidade do Minho; Braga Portugal
| | - Manuela Côrte-Real
- Departamento de Biologia; Centro de Biologia Molecular e Ambiental; Universidade do Minho; Braga Portugal
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Haferkamp B, Zhang H, Lin Y, Yeap X, Bunce A, Sharpe J, Xiang J. BaxΔ2 is a novel bax isoform unique to microsatellite unstable tumors. J Biol Chem 2012; 287:34722-9. [PMID: 22910913 PMCID: PMC3464575 DOI: 10.1074/jbc.m112.374785] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The pro-death Bcl-2 family protein and tumor suppressor Bax is frequently mutated in tumors with microsatellite instability (MSI). The mutation often results in a "Bax negative" phenotype and therefore is generally thought to be beneficial to the development of the tumor. Here, we report the identification of a novel Bax isoform, BaxΔ2, which is unique to microsatellite unstable tumors. BaxΔ2 is generated by a unique combination of a microsatellite deletion in Bax exon 3 and alternative splicing of Bax exon 2. Consistently, BaxΔ2 is only detected in MSI cell lines and primary tumors. BaxΔ2 is a potent cell death inducer but does not directly target mitochondria. In addition, BaxΔ2 sensitizes certain MSI tumor cells to a subset of chemotherapeutic agents, such as adriamycin. Thus, our data provide evidence that mutation and alternative splicing of tumor suppressors such as Bax are not always beneficial to tumor development but can be detrimental instead.
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Affiliation(s)
- Bonnie Haferkamp
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Honghong Zhang
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Yuting Lin
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Xinyi Yeap
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Alex Bunce
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
| | | | - Jialing Xiang
- From the Illinois Institute of Technology, Chicago, Illinois 60616 and
- To whom correspondence should be addressed: Dept. of Biological and Chemical Sciences, Illinois Institute of Technology, 3101 South Dearborn St., Chicago, IL 60616. Tel.: 312-567-3491; Fax: 312-567-3494; E-mail:
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Interaction of the full-length Bax protein with biomimetic mitochondrial liposomes: A small-angle neutron scattering and fluorescence study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:384-401. [DOI: 10.1016/j.bbamem.2011.10.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 09/15/2011] [Accepted: 10/07/2011] [Indexed: 12/13/2022]
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31
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Renault TT, Grandier-Vazeille X, Arokium H, Velours G, Camougrand N, Priault M, Teijido O, Dejean LM, Manon S. The cytosolic domain of human Tom22 modulates human Bax mitochondrial translocation and conformation in yeast. FEBS Lett 2011; 586:116-21. [DOI: 10.1016/j.febslet.2011.12.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 11/15/2011] [Accepted: 12/01/2011] [Indexed: 10/14/2022]
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32
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BAX unleashed: the biochemical transformation of an inactive cytosolic monomer into a toxic mitochondrial pore. Trends Biochem Sci 2011; 36:642-52. [PMID: 21978892 DOI: 10.1016/j.tibs.2011.08.009] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/26/2011] [Accepted: 08/31/2011] [Indexed: 02/07/2023]
Abstract
BAX, the BCL-2-associated X protein, is a cardinal proapoptotic member of the BCL-2 family, which regulates the critical balance between cellular life and death. Because so many medical conditions can be categorized as diseases of either too many or too few cells, dissecting the biochemistry of BCL-2 family proteins and developing pharmacological strategies to target them have become high priority scientific objectives. Here, we focus on BAX, a latent, cytosolic and monomeric protein that transforms into a lethal mitochondrial oligomer in response to cellular stress. New insights into the structural location of BAX's 'on switch', and the multi-step conformational changes that ensue upon BAX activation, are providing fresh opportunities to modulate BAX for potential benefit in human diseases characterized by pathologic cell survival or unwanted cellular demise.
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Abstract
The pro-apoptototic protein Bax (Bcl-2 Associated protein X) plays a central role in the mitochondria-dependent apoptotic pathway. In healthy mammalian cells, Bax is essentially cytosolic and inactive. Following a death signal, the protein is translocated to the outer mitochondrial membrane, where it promotes a permeabilization that favors the release of different apoptogenic factors, such as cytochrome c. The regulation of Bax translocation is associated to conformational changes that are under the control of different factors. The evidences showing the involvement of different Bax domains in its mitochondrial localization are presented. The interactions between Bax and its different partners are described in relation to their ability to promote (or prevent) Bax conformational changes leading to mitochondrial addressing and to the acquisition of the capacity to permeabilize the outer mitochondrial membrane.
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Affiliation(s)
- Thibaud T Renault
- CNRS, Institut de Biochimie et de Génétique Cellulaires, UMR5095, F-33000 Bordeaux, France
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34
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Valero JG, Sancey L, Kucharczak J, Guillemin Y, Gimenez D, Prudent J, Gillet G, Salgado J, Coll JL, Aouacheria A. Bax-derived membrane-active peptides act as potent and direct inducers of apoptosis in cancer cells. J Cell Sci 2011; 124:556-64. [PMID: 21245196 PMCID: PMC3428271 DOI: 10.1242/jcs.076745] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although many cancer cells are primed for apoptosis, they usually develop resistance to cell death at several levels. Permeabilization of the outer mitochondrial membrane, which is mediated by proapoptotic Bcl-2 family members such as Bax, is considered as a point of no return for initiating apoptotic cell death. This crucial role has placed Bcl-2 family proteins as recurrent targets for anticancer drug development. Here, we propose and demonstrate a new concept based on minimal active versions of Bax to induce cell death independently of endogenous Bcl-2 proteins. We show that membrane-active segments of Bax can directly induce the release of mitochondria-residing apoptogenic factors and commit tumor cells promptly and irreversibly to caspase-dependent apoptosis. On this basis, we designed a peptide encompassing part of the Bax pore-forming domain, which can target mitochondria, induce cytochrome c release and trigger caspase-dependent apoptosis. Moreover, this Bax-derived 'poropeptide' produced effective tumor regression after peritumoral injection in a nude mouse xenograft model. Thus, peptides derived from proteins that form pores in the mitochondrial outer membrane represent novel templates for anticancer agents.
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Affiliation(s)
- Juan Garcia Valero
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Lucie Sancey
- Institut d'oncologie/développement Albert Bonniot de Grenoble
INSERM : U823CHU GrenobleEFSUniversité Joseph Fourier - Grenoble IInstitut Albert Bonniot, BP170, 38042 Grenoble Cedex 9,FR
| | - Jérôme Kucharczak
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Yannis Guillemin
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Diana Gimenez
- Instituto de Ciencia Molecular
Universidad de ValenciaPolígono La Coma, s/n, 46980 Paterna, Valencia,ES
| | - Julien Prudent
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Germain Gillet
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Jesús Salgado
- Instituto de Ciencia Molecular
Universidad de ValenciaPolígono La Coma, s/n, 46980 Paterna, Valencia,ES
- Departamento de Bioquímica y Biología Molecular
Universidad de ValenciaC/ Doctor Moliner, 50, 46100 Burjassot, Valencia,ES
| | - Jean-Luc Coll
- Institut d'oncologie/développement Albert Bonniot de Grenoble
INSERM : U823CHU GrenobleEFSUniversité Joseph Fourier - Grenoble IInstitut Albert Bonniot, BP170, 38042 Grenoble Cedex 9,FR
| | - Abdel Aouacheria
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
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Westphal D, Dewson G, Czabotar PE, Kluck RM. Molecular biology of Bax and Bak activation and action. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:521-31. [PMID: 21195116 DOI: 10.1016/j.bbamcr.2010.12.019] [Citation(s) in RCA: 378] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 12/17/2010] [Accepted: 12/19/2010] [Indexed: 12/26/2022]
Abstract
Bax and Bak are two nuclear-encoded proteins present in higher eukaryotes that are able to pierce the mitochondrial outer membrane to mediate cell death by apoptosis. Thus, organelles recruited by nucleated cells to supply energy can be recruited by Bax and Bak to kill cells. The two proteins lie in wait in healthy cells where they adopt a globular α-helical structure, seemingly as monomers. Following a variety of stress signals, they convert into pore-forming proteins by changing conformation and assembling into oligomeric complexes in the mitochondrial outer membrane. Proteins from the mitochondrial intermembrane space then empty into the cytosol to activate proteases that dismantle the cell. The arrangement of Bax and Bak in membrane-bound complexes, and how the complexes porate the membrane, is far from being understood. However, recent data indicate that they first form symmetric BH3:groove dimers which can be linked via an interface between the α6-helices to form high order oligomers. Here, we review how Bax and Bak change conformation and oligomerize, as well as how oligomers might form a pore. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
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Ghibelli L, Diederich M. Multistep and multitask Bax activation. Mitochondrion 2010; 10:604-13. [PMID: 20709625 DOI: 10.1016/j.mito.2010.08.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 07/27/2010] [Accepted: 08/04/2010] [Indexed: 12/18/2022]
Abstract
Bax is a pro-apoptotic protein allowing apoptosis to occur through the intrinsic, damage-induced pathway, and amplifying that one occurring via the extrinsic, receptor mediated pathway. Bax is present in viable cells and activated by pro-apoptotic stimuli. Activation implies structural changes, consisting of exposure of the N terminus and hydrophobic domains; changes in localization, consisting in migration from cytosol to mitochondria and endoplasmic reticulum membranes; changes in the aggregation status, from monomer to dimer and multimer. Bax has multiple critical domains, namely the N terminus exposed after activation; two hydrophobic stretches exposed for membrane anchorage; two reactive cysteines allowing multimerization; the BH3 domain for interactions with the Bcl-2 family members; alpha helix 1 for t-Bid interaction. Bax has also multiple functions: it releases different mitochondrial factors such as cytochrome c, SMAC/diablo; it regulates mitochondrial fission, the mitochondrial permeability transition pore; it promotes Ca(2+) leakage through ER membrane. Altogether, Bax activation is a complex multi-step phenomenon. Here, we analyze these events as logically separable or alternative steps, attempting to assess their role, timing and reciprocal relation.
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Affiliation(s)
- Lina Ghibelli
- Dipartimento di Biologia, Universita' di Roma Tor Vergata, Via della Ricerca Scientifica, I-00133 Rome, Italy.
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37
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Zhang Z, Zhu W, Lapolla SM, Miao Y, Shao Y, Falcone M, Boreham D, McFarlane N, Ding J, Johnson AE, Zhang XC, Andrews DW, Lin J. Bax forms an oligomer via separate, yet interdependent, surfaces. J Biol Chem 2010; 285:17614-27. [PMID: 20382739 DOI: 10.1074/jbc.m110.113456] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Interactions of Bcl-2 family proteins regulate permeability of the mitochondrial outer membrane and apoptosis. In particular, Bax forms an oligomer that permeabilizes the membrane. To map the interface of the Bax oligomer we used Triton X-100 as a membrane surrogate and performed site-specific photocross-linking. Bax-specific adducts were formed through photo-reactive probes at multiple sites that can be grouped into two surfaces. The first surface overlaps with the BH1-3 groove formed by Bcl-2 Homology motif 1, 2, and 3; the second surface is a rear pocket located on the opposite side of the protein from the BH1-3 groove. Further cross-linking experiments using Bax BH3 peptides and mutants demonstrated that the two surfaces interact with their counterparts in neighboring proteins to form two separated interfaces and that interaction at the BH1-3 groove primes the rear pocket for further interaction. Therefore, Bax oligomerization proceeds through a series of interactions that occur at separate, yet allosterically, coupled interfaces.
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Affiliation(s)
- Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73126, USA
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Wang Z, Havasi A, Gall J, Bonegio R, Li Z, Mao H, Schwartz JH, Borkan SC. GSK3beta promotes apoptosis after renal ischemic injury. J Am Soc Nephrol 2010; 21:284-94. [PMID: 20093356 DOI: 10.1681/asn.2009080828] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The mechanism by which the serine-threonine kinase glycogen synthase kinase-3beta (GSK3beta) affects survival of renal epithelial cells after acute stress is unknown. Using in vitro and in vivo models, we tested the hypothesis that GSK3beta promotes Bax-mediated apoptosis, contributing to tubular injury and organ dysfunction after acute renal ischemia. Exposure of renal epithelial cells to metabolic stress activated GSK3beta, Bax, and caspase 3 and induced apoptosis. Expression of a constitutively active GSK3beta mutant activated Bax and decreased cell survival after metabolic stress. In contrast, pharmacologic inhibition (4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione [TDZD-8]) or RNA interference-mediated knockdown of GSK3beta promoted cell survival. Furthermore, RNA interference-mediated knockdown of Bax abrogated the cell death induced by constitutively active GSK3beta. In a cell-free assay, TDZD-8 inhibited the phosphorylation of a peptide containing the Bax serine(163) site targeted by stress-activated GSK3beta. In rats, TDZD-8 inhibited ischemia-induced activation of GSK3beta, Bax, and caspase 3; ameliorated tubular and epithelial cell damage; and significantly protected renal function. Taken together, GSK3beta-mediated Bax activation induces apoptosis and tubular damage that contribute to acute ischemic kidney injury.
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Affiliation(s)
- Zhiyong Wang
- Evans Biomedical Research Center, Renal Section, Room 546, 650 Albany Street, Boston, MA 02118-2518, USA
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39
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The Bax carboxy-terminal hydrophobic helix does not determine organelle-specific targeting but is essential for maintaining Bax in an inactive state and for stable mitochondrial membrane insertion. Apoptosis 2009; 15:14-27. [DOI: 10.1007/s10495-009-0410-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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40
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Abstract
Bid, a pro-apoptotic member of the Bcl-2 family, was initially discovered through binding to both pro-apoptotic Bax and anti-apoptotic Bcl-2. During apoptosis, Bid can be cleaved not only by caspase-8 during death receptor apoptotic signaling, but also by other caspases, granzyme B, calpains and cathepsins. Protease-cleaved Bid migrates to mitochondria where it induces permeabilization of the outer mitochondrial membrane that is dependent on the pro-apoptotic proteins Bax and/or Bak, and thus Bid acts as a sentinel for protease-mediated death signals. Although sequence analysis suggests that Bid belongs to the BH3-only subgroup of the Bcl-2 family, structural and phylogenetic analysis suggests that Bid may be more related to multi-BH region proteins such as pro-apoptotic Bax. Analysis of membrane binding by protease-cleaved Bid reveals mechanistic similarities with the membrane binding of Bax. For both proteins, membrane binding is characterized by relief of N-terminal inhibition of sequences promoting migration to membranes, insertion into the bilayer of the central hydrophobic hairpin helices and exposure of the BH3 region. These findings implicate Bid as a BH3-only protein that is both structurally and functionally related to multi-BH region Bcl-2 family proteins such as Bax.
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41
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Gallenne T, Gautier F, Oliver L, Hervouet E, Noël B, Hickman JA, Geneste O, Cartron PF, Vallette FM, Manon S, Juin P. Bax activation by the BH3-only protein Puma promotes cell dependence on antiapoptotic Bcl-2 family members. ACTA ACUST UNITED AC 2009; 185:279-90. [PMID: 19380879 PMCID: PMC2700382 DOI: 10.1083/jcb.200809153] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is still unclear whether the BH3-only protein Puma (p53 up-regulated modulator of apoptosis) can prime cells to death and render antiapoptotic BH3-binding Bcl-2 homologues necessary for survival through its ability to directly interact with proapoptotic Bax and activate it. In this study, we provide further evidence, using cell-free assays, that the BH3 domain of Puma binds Bax at an activation site that comprises the first helix of Bax. We also show that, in yeast, Puma interacts with Bax and triggers its killing activity when Bcl-2 homologues are absent but not when Bcl-xL is expressed. Finally, endogenous Puma is involved in the apoptotic response of human colorectal cancer cells to the Bcl-2/Bcl-xL inhibitor ABT-737, even in conditions where the expression of Mcl-1 is down-regulated. Thus, Puma is competent to trigger Bax activity by itself, thereby promoting cellular dependence on prosurvival Bcl-2 family members.
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Affiliation(s)
- Tristan Gallenne
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 892, Département de Recherche en Cancérologie, F-44035 Nantes, Cedex 01, France
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42
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The fowlpox virus BCL-2 homologue, FPV039, interacts with activated Bax and a discrete subset of BH3-only proteins to inhibit apoptosis. J Virol 2009; 83:7085-98. [PMID: 19439472 DOI: 10.1128/jvi.00437-09] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apoptosis is a potent immune barrier against viral infection, and many viruses, including poxviruses, encode proteins to overcome this defense. Interestingly, the avipoxviruses, which include fowlpox and canarypox virus, are the only poxviruses known to encode proteins with obvious Bcl-2 sequence homology. We previously characterized the fowlpox virus protein FPV039 as a Bcl-2-like antiapoptotic protein that inhibits apoptosis by interacting with and inactivating the proapoptotic cellular protein Bak. However, both Bak and Bax can independently trigger cell death. Thus, to effectively inhibit apoptosis, a number of viruses also inhibit Bax. Here we show that FPV039 inhibited apoptosis induced by Bax overexpression and prevented both the conformational activation of Bax and the subsequent formation of Bax oligomers at the mitochondria, two critical steps in the induction of apoptosis. Additionally, FPV039 interacted with activated Bax in the context of Bax overexpression and virus infection. Importantly, the ability of FPV039 to interact with active Bax and inhibit Bax activity was dependent on the structurally conserved BH3 domain of FPV039, even though this domain possesses little sequence homology to other BH3 domains. FPV039 also inhibited apoptosis induced by the BH3-only proteins, upstream activators of Bak and Bax, despite interacting detectably with only two: BimL and Bik. Collectively, our data suggest that FPV039 inhibits apoptosis by sequestering and inactivating multiple proapoptotic Bcl-2 proteins, including certain BH3-only proteins and both of the critical "gatekeepers" of apoptosis, Bak and Bax.
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Huang F, Nie C, Yang Y, Yue W, Ren Y, Shang Y, Wang X, Jin H, Xu C, Chen Q. Selenite induces redox-dependent Bax activation and apoptosis in colorectal cancer cells. Free Radic Biol Med 2009; 46:1186-96. [PMID: 19439215 DOI: 10.1016/j.freeradbiomed.2009.01.026] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 01/21/2009] [Accepted: 01/22/2009] [Indexed: 12/29/2022]
Abstract
Emerging evidence suggests that selenium has chemotherapeutic potential by inducing cancer cell apoptosis with minimal side effects to normal cells. However, the mechanism by which selenium induces apoptosis is not well understood. We have investigated the role of Bax, a Bcl-2 family protein and a critical regulator of the mitochondrial apoptotic pathway, in selenite-induced apoptosis in colorectal cancer cells. We found that supranutritional doses of selenite could induce typical apoptosis in colorectal cancer cells in vitro and in xenograft tumors. Selenite triggers a conformational change in Bax, as detected by the 6A7 antibody, and leads to Bax translocation into the mitochondria, where Bax forms oligomers to mediate cytochrome c release. Importantly, we show that the two conserved cysteine residues of Bax seem to be critical for sensing the intracellular ROS to initiate Bax conformational changes and subsequent apoptosis. Our results show for the first time that selenite can activate the apoptotic machinery through redox-dependent activation of Bax and further suggest that selenite could be useful in cancer therapy.
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Affiliation(s)
- Fang Huang
- National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China
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Fu NY, Sukumaran SK, Kerk SY, Yu VC. Baxbeta: a constitutively active human Bax isoform that is under tight regulatory control by the proteasomal degradation mechanism. Mol Cell 2009; 33:15-29. [PMID: 19150424 DOI: 10.1016/j.molcel.2008.11.025] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 10/23/2008] [Accepted: 11/27/2008] [Indexed: 01/01/2023]
Abstract
Although mRNAs of multiple isoforms of Bax, which encodes a central regulator of apoptosis signaling, have been reported, only Baxalpha protein has been well documented and studied. Baxalpha exists in latent form and is activated upon apoptosis induction through conformational changes. Here we demonstrate that Baxbeta protein is ubiquitously present among human cells, but its activity is restricted through stringent regulation by proteasomal degradation. In contrast to Baxalpha, native Baxbeta spontaneously integrates into mitochondrial membrane and is highly potent in inducing cytochrome c release from mitochondria. Remarkably, Baxbeta protein is upregulated by apoptotic stimuli via inhibition of its ubiquitination process, and stable expression of Baxbeta in HCT116-Bax(-/-) cells restores their sensitivity to multiple stimuli. Baxbeta associates with and promotes Baxalpha activation. Moreover, selective knockdown of Baxbeta desensitizes HCT116-Bax(+/-) cells to Bax-dependent apoptosis signaling. These observations underscore the plasticity of human Bax in serving its role as a "gatekeeper" for apoptosis.
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Affiliation(s)
- Nai Yang Fu
- Institute of Molecular and Cell Biology, Agency for Science, Technology, and Research, 61 Biopolis Drive, Singapore 138673, Republic of Singapore
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Billen LP, Kokoski CL, Lovell JF, Leber B, Andrews DW. Bcl-XL inhibits membrane permeabilization by competing with Bax. PLoS Biol 2008; 6:e147. [PMID: 18547146 PMCID: PMC2422857 DOI: 10.1371/journal.pbio.0060147] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 05/02/2008] [Indexed: 11/23/2022] Open
Abstract
Although Bcl-XL and Bax are structurally similar, activated Bax forms large oligomers that permeabilize the outer mitochondrial membrane, thereby committing cells to apoptosis, whereas Bcl-XL inhibits this process. Two different models of Bcl-XL function have been proposed. In one, Bcl-XL binds to an activator, thereby preventing Bax activation. In the other, Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, as all three proteins are present simultaneously. We examined the mechanism of Bax activation by tBid and its inhibition by Bcl-XL using full-length recombinant proteins and measuring permeabilization of liposomes and mitochondria in vitro. Our results demonstrate that Bcl-XL and Bax are functionally similar. Neither protein bound to membranes alone. However, the addition of tBid recruited molar excesses of either protein to membranes, indicating that tBid activates both pro- and antiapoptotic members of the Bcl-2 family. Bcl-XL competes with Bax for the activation of soluble, monomeric Bax through interaction with membranes, tBid, or t-Bid-activated Bax, thereby inhibiting Bax binding to membranes, oligomerization, and membrane permeabilization. Experiments in which individual interactions were abolished by mutagenesis indicate that both Bcl-XL–tBid and Bcl-XL–Bax binding contribute to the antiapoptotic function of Bcl-XL. By out-competing Bax for the interactions leading to membrane permeabilization, Bcl-XL ties up both tBid and Bax in nonproductive interactions and inhibits Bax binding to membranes. We propose that because Bcl-XL does not oligomerize it functions like a dominant-negative Bax in the membrane permeabilization process. During development and under stress, cells can become committed to die via programmed cell death (apoptosis). In most cases, the permeabilization of the outer mitochondrial membrane is a key component of this commitment. The membrane permeablization step is both positively and negatively regulated by members of the Bcl-2 family of proteins. One member of this protein family with only a BH3 region, such as tBid, activates another family member, Bax, causing it to form large complexes that generate membrane-spanning pores, hence making the membrane permeable. Antiapoptotic members of the Bcl-2 family, such as Bcl-XL, are structurally similar to Bax but inhibit the membrane permeabilization process by an unknown mechanism. Two mutually exclusive models have been proposed to explain how the Bcl-2 family is operating: one states that Bcl-XL binds to tBid, thereby preventing Bax activation, while the second suggests that Bcl-XL binds directly to activated Bax. It has been difficult to sort out which interaction is important in cells, where multiple members of all three protein families are present simultaneously. Here, we describe an in vitro system containing the three recombinant proteins and the use of mutagenesis to selectively remove individual interactions. We show that Bcl-XL inhibits Bax by competing with it for binding to membranes, tBid, and activated Bax. Because Bcl-XL does not form pores, it inhibits apoptosis by acting as if it is a dominant-negative version of Bax. Bcl-XL and Bax are structurally similar members of the Bcl-2 family of cell-death-related proteins, and they compete for binding to membranes, as well as to Bcl-2 family member tBid and activated Bax. Unlike Bax, Bcl-XL is unable to oligomerize and form pores in membranes, so it inhibits membrane permeabilization--a key step during commitment to apoptosis--by functioning like a dominant-negative Bax.
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Affiliation(s)
- Lieven P Billen
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Candis L Kokoski
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Jonathan F Lovell
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Brian Leber
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - David W Andrews
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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Cottet S, Schorderet DF. Triggering of Bcl-2-related pathway is associated with apoptosis of photoreceptors in Rpe65-/- mouse model of Leber's congenital amaurosis. Apoptosis 2008; 13:329-42. [PMID: 18274907 DOI: 10.1007/s10495-008-0180-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mutations in RPE65 protein is characterized by the loss of photoreceptors, although the molecular pathways triggering retinal cell death remain largely unresolved. The role of the Bcl-2 family of proteins in retinal degeneration is still controversial. However, alteration in Bcl-2-related proteins has been observed in several models of retinal injury. In particular, Bax has been suggested to play a crucial role in apoptotic pathways in murine glaucoma model as well as in retinal detachment-associated cell death. We demonstrated that Bcl-2-related signaling pathway is involved in Rpe65-dependent apoptosis of photoreceptors during development of the disease. Pro-apoptotic Bax alpha and beta isoforms were upregulated in diseased retina. This was associated with a progressive reduction of anti-apoptotic Bcl-2, reflecting imbalanced Bcl-2/Bax ratio as the disease progresses. Moreover, specific translocation of Bax beta from cytosol to mitochondria was observed in Rpe65-deficient retina. This correlated with the initiation of photoreceptor cell loss at 4 months of age, and further increased during disease development. Altogether, these data suggest that Bcl-2-apoptotic pathway plays a crucial role in Leber's congenital amaurosis disease. They further highlight a new regulatory mechanism of Bax-dependent apoptosis based on regulated expression and activation of specific isoforms of this protein.
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Affiliation(s)
- Sandra Cottet
- Institute for Research in Ophthalmology (IRO), Avenue Grand-Champsec 64, 1950, Sion 4, Switzerland.
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Christenson E, Merlin S, Saito M, Schlesinger P. Cholesterol effects on BAX pore activation. J Mol Biol 2008; 381:1168-83. [PMID: 18590739 DOI: 10.1016/j.jmb.2008.06.037] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 06/11/2008] [Accepted: 06/13/2008] [Indexed: 01/29/2023]
Abstract
The importance of BCL-2 family proteins in the control of cell death has been clearly established. One of the key members of this family, BAX, has soluble, membrane-bound, and membrane-integrated forms that are central to the regulation of apoptosis. Using purified monomeric human BAX, defined liposomes, and isolated human mitochondria, we have characterized the soluble to membrane transition and pore formation by this protein. For the purified protein, activation, but not oligomerization, is required for membrane binding. The transition to the membrane environment includes a binding step that is reversible and distinct from the membrane integration step. Oligomerization and pore activation occur after the membrane integration. In cells, BAX targets several intracellular membranes but notably does not target the plasma membrane while initiating apoptosis. When cholesterol was added to either the liposome bilayer or mitochondrial membranes, we observed increased binding but markedly reduced integration of BAX into both membranes. This cholesterol inhibition of membrane integration accounts for the reduction of BAX pore activation in liposomes and mitochondrial membranes. Our results indicate that the presence of cholesterol in membranes inhibits the pore-forming activity of BAX by reducing the ability of BAX to transition from a membrane-associated protein to a membrane-integral protein.
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Affiliation(s)
- Eric Christenson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Abstract
INTRODUCTION Osteoblasts depend on a constant supply of prosurvival signals from their microenvironment. When trophic factors become limited by injury or disease, cells undergo apoptosis. This study establishes the regulation and function of Bim, Bak, and Bax in this response. MATERIALS AND METHODS MBA-15.4 murine osteoblasts and primary human bone marrow stromal cells (hBMSCs) were subjected to growth factor depletion by serum starvation (1% FCS or serum withdrawal). Protein phosphorylation, activation, or expression was quantified by Western blotting and gene expression by real-time PCR. Regulation of apoptosis in response to serum depletion was determined using siRNA specific for Bim, Bak, or Bax, followed by TUNEL staining. Statistical significance was determined by one-way ANOVA after multiple experimental repeats. RESULTS Serum depletion strongly induced expression of the proapoptotic protein Bim in both hBMSC and MBA-15.4 osteoblasts. Detailed analysis of the mouse line showed that both mRNA and protein levels rose from 2 h to peak between 16 and 24 h, in conjunction with activation of caspase 3 and rising levels of apoptosis. Both actinomycin D and cycloheximide prevented this increase in Bim, indicating transcriptional regulation. Serum deprivation caused immediate and sustained decreases in phosphorylation of prosurvival kinases, ERK and PKB, preceding upregulation of Bim. Pathway inhibitors, U0126 or LY294002, strongly increased both Bim mRNA and protein, confirming that both kinases regulate Bim. These inhibitors also induced osteoblast apoptosis within 24-72 h. JC-1 tracer detected mitochondrial potential disruption after serum deprivation, indicating involvement of the intrinsic pathway. Moreover, activation-associated conformational changes were detected in the channel-formers, Bax and Bak. Selective knockdown of Bim or Bak by siRNA protected osteoblasts from serum depletion-induced apoptosis by 50%, whereas knockdown of Bax alone or Bak and Bax together reduced apoptosis by 90%. CONCLUSIONS Our data indicate that Bim, Bak, and Bax actively mediate osteoblast apoptosis induced by trophic factor withdrawal. The complex upstream regulation of Bim may provide targets for therapeutic enhancement of osteoblast viability.
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Valentijn AJ, Upton JP, Bates N, Gilmore AP. Bax targeting to mitochondria occurs via both tail anchor-dependent and -independent mechanisms. Cell Death Differ 2008; 15:1243-54. [PMID: 18437166 DOI: 10.1038/cdd.2008.39] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Bax is a member of the Bcl-2 family that, together with Bak, is required for permeabilisation of the outer mitochondrial membrane (OMM). Bax differs from Bak in that it is predominantly cytosolic in healthy cells and only associates with the OMM after an apoptotic signal. How Bax is targeted to the OMM is still a matter of debate, with both a C-terminal tail anchor and an N-terminal pre-sequence being implicated. We now show definitively that Bax does not contain an N-terminal import sequence, but does have a C-terminal anchor. The isolated N terminus of Bax cannot target a heterologous protein to the OMM, whereas the C terminus can. Furthermore, if the C terminus is blocked, Bax fails to target to mitochondria upon receipt of an apoptotic stimulus. Zebra fish Bax, which shows a high degree of amino-acid homology with mammalian Bax within the C terminus, but not in the N terminus, can rescue the defective cell-death phenotype of Bax/Bak-deficient cells. Interestingly, we find that Bax mutants, which themselves cannot target mitochondria or induce apoptosis, are recruited to clusters of activated wild-type Bax on the OMM of apoptotic cells. This appears to be an amplification of Bax activation during cell death that is independent of the normal tail anchor-mediated targeting.
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Affiliation(s)
- A J Valentijn
- Wellcome Trust Centre for Cell Matrix Research, Faculty of Life Sciences, The University of Manchester, Manchester, UK
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Susini L, Besse S, Duflaut D, Lespagnol A, Beekman C, Fiucci G, Atkinson AR, Busso D, Poussin P, Marine JC, Martinou JC, Cavarelli J, Moras D, Amson R, Telerman A. TCTP protects from apoptotic cell death by antagonizing bax function. Cell Death Differ 2008; 15:1211-20. [PMID: 18274553 DOI: 10.1038/cdd.2008.18] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Translationally controlled tumor protein (TCTP) is a potential target for cancer therapy. It functions as a growth regulating protein implicated in the TSC1-TSC2 -mTOR pathway or a guanine nucleotide dissociation inhibitor for the elongation factors EF1A and EF1Bbeta. Accumulating evidence indicates that TCTP also functions as an antiapoptotic protein, through a hitherto unknown mechanism. In keeping with this, we show here that loss of tctp expression in mice leads to increased spontaneous apoptosis during embryogenesis and causes lethality between E6.5 and E9.5. To gain further mechanistic insights into this apoptotic function, we solved and refined the crystal structure of human TCTP at 2.0 A resolution. We found a structural similarity between the H2-H3 helices of TCTP and the H5-H6 helices of Bax, which have been previously implicated in regulating the mitochondrial membrane permeability during apoptosis. By site-directed mutagenesis we establish the relevance of the H2-H3 helices in TCTP's antiapoptotic function. Finally, we show that TCTP antagonizes apoptosis by inserting into the mitochondrial membrane and inhibiting Bax dimerization. Together, these data therefore further confirm the antiapoptotic role of TCTP in vivo and provide new mechanistic insights into this key function of TCTP.
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Affiliation(s)
- L Susini
- Molecular Engines Laboratories, 20 rue Bouvier, Paris, France
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