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Chlamydia trachomatis inhibits apoptosis in infected cells by targeting the pro-apoptotic proteins Bax and Bak. Cell Death Differ 2022; 29:2046-2059. [PMID: 35397654 PMCID: PMC9525694 DOI: 10.1038/s41418-022-00995-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 03/24/2022] [Accepted: 03/24/2022] [Indexed: 11/08/2022] Open
Abstract
AbstractApoptosis acts in defense against microbial infection, and many infectious agents have developed strategies to inhibit host cell apoptosis. The human pathogen Chlamydia trachomatis (Ctr) is an obligate intracellular bacterium that strongly inhibits mitochondrial apoptosis of its human host cell but there is no agreement how the bacteria achieve this. We here provide a molecular analysis of chlamydial apoptosis-inhibition in infected human cells and demonstrate that the block of apoptosis occurs during the activation of the effectors of mitochondrial apoptosis, Bak and Bax. We use small-molecule Bcl-2-family inhibitors and gene targeting to show that previous models cannot explain the anti-apoptotic effect of chlamydial infection. Although the anti-apoptotic Bcl-2-family protein Mcl-1 was strongly upregulated upon infection, Mcl-1-deficient cells and cells where Mcl-1 was pharmacologically inactivated were still protected. Ctr-infection could inhibit both Bax- and Bak-induced apoptosis. Apoptotic Bax-oligomerization and association with the outer mitochondrial membrane was reduced upon chlamydial infection. Infection further inhibited apoptosis induced conformational changes of Bak, as evidenced by changes to protease sensitivity, oligomerization and release from the mitochondrial porin VDAC2. Mitochondria isolated from Ctr-infected cells were protected against the pro-apoptotic Bcl-2-family proteins Bim and tBid but this protection was lost upon protease digestion. However, the protective effect of Ctr-infection was reduced in cells lacking the Bax/Bak-regulator VDAC2. We further found that OmpA, a porin of the outer membrane of Ctr, associated upon experimental expression with mitochondria and inhibited apoptosis, phenocopying the effect of the infection. These results identify a novel way of apoptosis inhibition, involving only the most downstream modulator of mitochondrial apoptosis and suggest that Chlamydia has a protein dedicated to the inhibition of apoptosis to secure its survival in human cells.
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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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Morgenstern M, Peikert CD, Lübbert P, Suppanz I, Klemm C, Alka O, Steiert C, Naumenko N, Schendzielorz A, Melchionda L, Mühlhäuser WWD, Knapp B, Busch JD, Stiller SB, Dannenmaier S, Lindau C, Licheva M, Eickhorst C, Galbusera R, Zerbes RM, Ryan MT, Kraft C, Kozjak-Pavlovic V, Drepper F, Dennerlein S, Oeljeklaus S, Pfanner N, Wiedemann N, Warscheid B. Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context. Cell Metab 2021; 33:2464-2483.e18. [PMID: 34800366 PMCID: PMC8664129 DOI: 10.1016/j.cmet.2021.11.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 09/01/2021] [Accepted: 11/01/2021] [Indexed: 12/18/2022]
Abstract
Mitochondria are key organelles for cellular energetics, metabolism, signaling, and quality control and have been linked to various diseases. Different views exist on the composition of the human mitochondrial proteome. We classified >8,000 proteins in mitochondrial preparations of human cells and defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP). We identified interactors of translocases, respiratory chain, and ATP synthase assembly factors. The abundance of MitoCoP proteins covers six orders of magnitude and amounts to 7% of the cellular proteome with the chaperones HSP60-HSP10 being the most abundant mitochondrial proteins. MitoCoP dynamics spans three orders of magnitudes, with half-lives from hours to months, and suggests a rapid regulation of biosynthesis and assembly processes. 460 MitoCoP genes are linked to human diseases with a strong prevalence for the central nervous system and metabolism. MitoCoP will provide a high-confidence resource for placing dynamics, functions, and dysfunctions of mitochondria into the cellular context.
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Affiliation(s)
- Marcel Morgenstern
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christian D Peikert
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Philipp Lübbert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Ida Suppanz
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Cinzia Klemm
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Oliver Alka
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Conny Steiert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Nataliia Naumenko
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Alexander Schendzielorz
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Laura Melchionda
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Wignand W D Mühlhäuser
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Bettina Knapp
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Jakob D Busch
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Sebastian B Stiller
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Stefan Dannenmaier
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Caroline Lindau
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Mariya Licheva
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Christopher Eickhorst
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg, Germany
| | - Riccardo Galbusera
- Neurologic Clinic and Policlinic, Departments of Medicine, Clinical Research and Biomedical Engineering, University Hospital Basel and University of Basel, Basel, Switzerland
| | - Ralf M Zerbes
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Michael T Ryan
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, 3800 Melbourne, VIC, Australia
| | - Claudine Kraft
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Vera Kozjak-Pavlovic
- Department of Microbiology, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Friedel Drepper
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Sven Dennerlein
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Silke Oeljeklaus
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Nikolaus Pfanner
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Nils Wiedemann
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
| | - Bettina Warscheid
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; CIBSS Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany.
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AREL1 E3 ubiquitin ligase inhibits TNF-induced necroptosis via the ubiquitination of MTX2. Exp Ther Med 2021; 22:1195. [PMID: 34584540 PMCID: PMC8422393 DOI: 10.3892/etm.2021.10629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
Previously, we reported on a novel anti-apoptotic E3 ubiquitin ligase, apoptosis-resistant E3 ubiquitin protein ligase 1 (AREL1), that ubiquitinates inhibitors of apoptosis proteins antagonists. The present study demonstrated that AREL1 ubiquitinated Metaxin 2 (MTX2), which was involved in TNF-induced necroptosis. MTX2 has been identified as a protein that belongs to the Metaxin family. It interacts with another Metaxin protein, Metaxin 1 (MTX1), which is localized in the outer membrane of mitochondria, and is involved in TNF-induced necroptosis. This study found that AREL1 interacted with MTX2, but not MTX1, while the amino-terminal domain of MTX2 interacted with MTX1, AREL1 interacted with the carboxyl-terminal domain of MTX2. Furthermore, AREL1 expression led to a decrease in the protein expression of MTX2, but not MTX1. However, a mutant form of AREL1, AREL1C790A, which is deficient for E3 activity, did not cause MTX2 degradation. Moreover, the protein levels of MTX2 were increased by AREL1 knockdown. Therefore, these results implied that AREL1 ubiquitinates and promotes the degradation of MTX2. The expression of MTX2, together with MTX1, enhanced TNF-induced necroptosis. However, AREL1 inhibited necroptosis even in cells expressing Metaxin proteins. Therefore, these results suggested that the inhibition of AREL1-dependent ubiquitination of MTX2 could be beneficial to sensitize tumor cells to TNF-induced necroptosis.
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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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Kreimendahl S, Rassow J. The Mitochondrial Outer Membrane Protein Tom70-Mediator in Protein Traffic, Membrane Contact Sites and Innate Immunity. Int J Mol Sci 2020; 21:E7262. [PMID: 33019591 PMCID: PMC7583919 DOI: 10.3390/ijms21197262] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 09/25/2020] [Accepted: 09/28/2020] [Indexed: 02/08/2023] Open
Abstract
Tom70 is a versatile adaptor protein of 70 kDa anchored in the outer membrane of mitochondria in metazoa, fungi and amoeba. The tertiary structure was resolved for the Tom70 of yeast, showing 26 α-helices, most of them participating in the formation of 11 tetratricopeptide repeat (TPR) motifs. Tom70 serves as a docking site for cytosolic chaperone proteins and co-chaperones and is thereby involved in the uptake of newly synthesized chaperone-bound proteins in mitochondrial biogenesis. In yeast, Tom70 additionally mediates ER-mitochondria contacts via binding to sterol transporter Lam6/Ltc1. In mammalian cells, TOM70 promotes endoplasmic reticulum (ER) to mitochondria Ca2+ transfer by association with the inositol-1,4,5-triphosphate receptor type 3 (IP3R3). TOM70 is specifically targeted by the Bcl-2-related protein MCL-1 that acts as an anti-apoptotic protein in macrophages infected by intracellular pathogens, but also in many cancer cells. By participating in the recruitment of PINK1 and the E3 ubiquitin ligase Parkin, TOM70 can be implicated in the development of Parkinson's disease. TOM70 acts as receptor of the mitochondrial antiviral-signaling protein (MAVS) and thereby participates in the corresponding system of innate immunity against viral infections. The protein encoded by Orf9b in the genome of SARS-CoV-2 binds to TOM70, probably compromising the synthesis of type I interferons.
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Affiliation(s)
| | - Joachim Rassow
- Institute for Biochemistry and Pathobiochemistry, Ruhr-University Bochum, 44801 Bochum, Germany;
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CRISPR/Cas9 Knockout of Bak Mediates Bax Translocation to Mitochondria in response to TNF α/CHX-induced Apoptosis. BIOMED RESEARCH INTERNATIONAL 2019; 2019:9071297. [PMID: 31637258 PMCID: PMC6766168 DOI: 10.1155/2019/9071297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 07/07/2019] [Accepted: 08/04/2019] [Indexed: 02/06/2023]
Abstract
TNFα/CHX-induced apoptosis is dependent on caspase-8 activation and regulated by Bcl-2. However, the specific participants and precise mechanisms underlying this apoptotic pathway are poorly understood. The proapoptotic proteins Bak and Bax—members of the Bcl-2 family—are essential for the functioning of the mitochondrial apoptotic pathway. In this study, we used the CRISPR/Cas9 system to knockout Bak in the human SH-SY5Y cell line and determined the effects of this knockout on TNFα/CHX-induced apoptosis. Our data showed that overexpression of Bcl-2 dramatically prevented TNFα/CHX-induced apoptosis, and then pro-apoptotic protein Bak was downregulated and became more resistant to TNFα/CHX-induced apoptosis, because both TNFα/CHX-induced PARP cleavage and caspase activation were blocked in BAK−/− cells or using specific siRNA, whereas Bax was dispensable in TNFα/CHX-induced apoptosis, as evidenced using specific siRNA. Bax translocated from the cytosol into the mitochondria in response to TNFα/CHX, and CRISPR/Cas9 knockout of Bak significantly decreased this translocation. These results indicate that TNFα/CHX-induced apoptosis does not occur in Bak−/− cells, suggesting that TNFα/CHX-induced apoptosis is Bak-dependent but Bax-independent.
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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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9
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Parvin N, Carrie C, Pabst I, Läßer A, Laha D, Paul MV, Geigenberger P, Heermann R, Jung K, Vothknecht UC, Chigri F. TOM9.2 Is a Calmodulin-Binding Protein Critical for TOM Complex Assembly but Not for Mitochondrial Protein Import in Arabidopsis thaliana. MOLECULAR PLANT 2017; 10:575-589. [PMID: 28062321 DOI: 10.1016/j.molp.2016.12.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/18/2016] [Accepted: 12/22/2016] [Indexed: 05/24/2023]
Abstract
The translocon on the outer membrane of mitochondria (TOM) facilitates the import of nuclear-encoded proteins. The principal machinery of mitochondrial protein transport seems conserved in eukaryotes; however, divergence in the composition and structure of TOM components has been observed between mammals, yeast, and plants. TOM9, the plant homolog of yeast Tom22, is significantly smaller due to a truncation in the cytosolic receptor domain, and its precise function is not understood. Here we provide evidence showing that TOM9.2 from Arabidopsis thaliana is involved in the formation of mature TOM complex, most likely by influencing the assembly of the pore-forming subunit TOM40. Dexamethasone-induced RNAi gene silencing of TOM9.2 results in a severe reduction in the mature TOM complex, and the assembly of newly imported TOM40 into the complex is impaired. Nevertheless, mutant plants are fully viable and no obvious downstream effects of the loss of TOM complex, i.e., on mitochondrial import capacity, were observed. Furthermore, we found that TOM9.2 can bind calmodulin (CaM) in vitro and that CaM impairs the assembly of TOM complex in the isolated wild-type mitochondria, suggesting a regulatory role of TOM9.2 and a possible integration of TOM assembly into the cellular calcium signaling network.
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Affiliation(s)
- Nargis Parvin
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Chris Carrie
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Isabelle Pabst
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Antonia Läßer
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Debabrata Laha
- Center for Plant Molecular Biology, Plant Physiology, University of Tuebingen, Auf der Morgenstelle 32, 72076 Tuebingen, Germany
| | - Melanie V Paul
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Peter Geigenberger
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Ralf Heermann
- Department Biology I, Microbiology, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany
| | - Kirsten Jung
- Department Biology I, Microbiology, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany; Department of Biology, Center for Integrated Protein Science (Munich), Ludwig-Maximilians-University Munich, 81377 Munich, Germany
| | - Ute C Vothknecht
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany; Department of Biology, Center for Integrated Protein Science (Munich), Ludwig-Maximilians-University Munich, 81377 Munich, Germany.
| | - Fatima Chigri
- Department Biology I, Botany, Ludwig-Maximilians-University Munich, Großhaderner Straße 2-4, 82152 Martinsried, Germany; Department of Biology, Center for Integrated Protein Science (Munich), Ludwig-Maximilians-University Munich, 81377 Munich, Germany.
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Madamba SM, Damri KN, Dejean LM, Peixoto PM. Mitochondrial Ion Channels in Cancer Transformation. Front Oncol 2015; 5:120. [PMID: 26090338 PMCID: PMC4455240 DOI: 10.3389/fonc.2015.00120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Accepted: 05/15/2015] [Indexed: 11/13/2022] Open
Abstract
Cancer transformation involves reprograming of mitochondrial function to avert cell death mechanisms, monopolize energy metabolism, accelerate mitotic proliferation, and promote metastasis. Mitochondrial ion channels have emerged as promising therapeutic targets because of their connection to metabolic and apoptotic functions. This mini review discusses how mitochondrial channels may be associated with cancer transformation and expands on the possible involvement of mitochondrial protein import complexes in pathophysiological process.
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Affiliation(s)
- Stephen M. Madamba
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
- City University of New York Graduate Center, New York, NY, USA
| | - Kevin N. Damri
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
| | - Laurent M. Dejean
- Department of Chemistry, College of Science and Mathematics, California State University Fresno, Fresno, CA, USA
| | - Pablo M. Peixoto
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
- City University of New York Graduate Center, New York, NY, USA
- Department of Basic Sciences, New York University College of Dentistry, New York, NY, USA
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Asmarinah A, Paradowska-Dogan A, Kodariah R, Tanuhardja B, Waliszewski P, Mochtar CA, Weidner W, Hinsch E, HINSCH ELVIRA. Expression of the Bcl-2 family genes and complexes involved in the mitochondrial transport in prostate cancer cells. Int J Oncol 2014; 45:1489-96. [PMID: 25177836 DOI: 10.3892/ijo.2014.2576] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 06/19/2014] [Indexed: 01/20/2023] Open
Abstract
Alteration of molecular pathways triggering apoptosis gives raise to various pathological tissue processes, such as tumorigenesis. The mitochondrial pathway is regulated by both the genes of the Bcl-2 family and the genes encoding mitochondrial transport molecules. Those proteins allow a release of cyctochrome c through the outer mitochondrial membrane. This release activates the caspase cascade resulting in death of cells. There are at least two main transport systems associated with the family of Bcl-2 proteins that are involved in transport of molecules through the outer mitochondrial membrane, i.e., the voltage dependent anion channels (VDACs) and translocases of the outer mitochondrial membrane proteins (TOMs). We investigated the expression of genes of the Bcl-2 family, i.e., pro-apoptotic Bak and Bid, and anti-apoptotic Bcl-2; VDAC gene, i.e., VDAC1, VDAC2 and VDAC3; and TOMM genes, i.e., TOMM20, TOMM22 and TOMM40. This study was performed at the mRNA and the protein level. Fourteen paraffin embedded prostate cancer tissues and five normal prostate tissues were analyzed by the quantitative PCR array and immunohistochemistry. We found a significant increase in both mRNA expression of the anti-apoptotic Bcl-2 gene and VDAC1 gene in prostate cancer tissue in comparison with their normal counterparts. Translation of the anti-apoptotic Bcl-2 and VDAC1 genes in prostate cancer tissue was slightly increased. We observed no significant differences in the mRNA expression of the pro-apoptotic Bak and Bid genes, VDAC2 or VDAC3 genes or the three TOMM genes in these tissues. The pro-apoptotic Bax protein was downtranslated significantly in secretory cells of prostate cancer as compared to normal prostate. We suggest that this protein is a good candidate as biomarker for prostate cancer.
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Cartron PF, Petit E, Bellot G, Oliver L, Vallette FM. Metaxins 1 and 2, two proteins of the mitochondrial protein sorting and assembly machinery, are essential for Bak activation during TNF alpha triggered apoptosis. Cell Signal 2014; 26:1928-34. [DOI: 10.1016/j.cellsig.2014.04.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 04/27/2014] [Indexed: 10/25/2022]
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Bax targets mitochondria by distinct mechanisms before or during apoptotic cell death: a requirement for VDAC2 or Bak for efficient Bax apoptotic function. Cell Death Differ 2014; 21:1925-35. [PMID: 25146925 DOI: 10.1038/cdd.2014.119] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Revised: 06/24/2014] [Accepted: 07/13/2014] [Indexed: 01/15/2023] Open
Abstract
In non-apoptotic cells, Bak constitutively resides in the mitochondrial outer membrane. In contrast, Bax is in a dynamic equilibrium between the cytosol and mitochondria, and is commonly predominant in the cytosol. In response to an apoptotic stimulus, Bax and Bak change conformation, leading to Bax accumulation at mitochondria and Bak/Bax oligomerization to form a pore in the mitochondrial outer membrane that is responsible for cell death. Using blue native-PAGE to investigate how Bax oligomerizes in the mitochondrial outer membrane, we observed that, like Bak, a proportion of Bax that constitutively resides at mitochondria associates with voltage-dependent anion channel (VDAC)2 prior to an apoptotic stimulus. During apoptosis, Bax dissociates from VDAC2 and homo-oligomerizes to form high molecular weight oligomers. In cells that lack VDAC2, constitutive mitochondrial localization of Bax and Bak was impaired, suggesting that VDAC2 has a role in Bax and Bak import to, or stability at, the mitochondrial outer membrane. However, following an apoptotic stimulus, Bak and Bax retained the ability to accumulate at VDAC2-deficient mitochondria and to mediate cell death. Silencing of Bak in VDAC2-deficient cells indicated that Bax required either VDAC2 or Bak in order to translocate to and oligomerize at the mitochondrial outer membrane to efficiently mediate apoptosis. In contrast, efficient Bak homo-oligomerization at the mitochondrial outer membrane and its pro-apoptotic function required neither VDAC2 nor Bax. Even a C-terminal mutant of Bax (S184L) that localizes to mitochondria did not constitutively target mitochondria deficient in VDAC2, but was recruited to mitochondria following an apoptotic stimulus dependent on Bak or upon over-expression of Bcl-xL. Together, our data suggest that Bax localizes to the mitochondrial outer membrane via alternate mechanisms, either constitutively via an interaction with VDAC2 or after activation via interaction with Bcl-2 family proteins.
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Functions of the C-terminal domains of apoptosis-related proteins of the Bcl-2 family. Chem Phys Lipids 2014; 183:77-90. [PMID: 24892727 DOI: 10.1016/j.chemphyslip.2014.05.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 05/12/2014] [Accepted: 05/13/2014] [Indexed: 02/06/2023]
Abstract
Bcl-2 family proteins are involved in cell homeostasis, where they regulate cell death. Some of these proteins are pro-apoptotic and others pro-survival. Moreover, many of them share a similar domain composition with several of the so-called BH domains, although some only have a BH3 domain. A C-terminal domain is present in all the multi-BH domain proteins and in some of the BH3-only ones. This C-terminal domain is hydrophobic or amphipathic, for which reason it was thought when they were discovered that they were membrane anchors. Although this is indeed one of their functions, it has since been observed that they may also serve as regulators of the function of some members of this family, such as Bax. They may also serve to recognize the target membrane of some of these proteins, which only after an apoptotic signal, are incorporated into a membrane. It has been shown that peptides that imitate the sequence of C-terminal domains can form pores and may serve as a model to design cytotoxic molecules.
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15
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Jiang X, Li X, Huang H, Jiang F, Lin Z, He H, Chen Y, Yue F, Zou J, He Y, You P, Wang W, Yang W, Zhao H, Lai Y, Wang F, Zhong W, Liu L. Elevated levels of mitochondrion-associated autophagy inhibitor LRPPRC are associated with poor prognosis in patients with prostate cancer. Cancer 2014; 120:1228-36. [PMID: 24390809 DOI: 10.1002/cncr.28551] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 11/22/2013] [Accepted: 12/02/2013] [Indexed: 12/31/2022]
Abstract
BACKGROUND Autophagy has recently been found to play important roles in tumorigenesis and leucine-rich pentatricopeptide repeat motif-containing protein (LRPPRC) has been identified as an inhibitor that suppresses autophagy and mitophagy and maintains mitochondrial activity. The authors hypothesized that LRPPRC levels can be used as a biomarker for the diagnosis and prognosis of prostate cancer. METHODS Immunochemistry analysis was performed to evaluate the levels of LRPPRC in 112 samples collected from patients with prostate adenocarcinoma (PCa) and 38 samples from patients with benign prostatic hyperplasia (BPH) who were enrolled in hospitals in Guangzhou City, China and were followed for 10 years. RESULTS Significantly higher levels of LRPPRC were found in PCa samples compared with BPH samples. Greater than 75% of patients with PCa demonstrated high levels of LRPPRC whereas only 10% of patients with BPH were found to have similar levels of LRPPRC. The levels of LRPPRC were found to be positively correlated with tumor grade, metastasis, and serum prostate-specific antigen level, but were negatively correlated with hormone therapy sensitivity after 2 years of surgery and overall survival. The association between high levels of LRPPRC and late-stage PCa or hormone therapy insensitivity was confirmed in tissue samples collected from prostate-specific phosphatase and tensin homolog (PTEN)(-/-) mice or hormone-dependent and hormone-independent PCa cell lines. CONCLUSIONS LRPPRC levels may be used as an independent biomarker for patients with PCa at a late stage with poor prognosis.
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Affiliation(s)
- Xianhan Jiang
- Department, of Urology, The Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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16
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Ma S, Hockings C, Anwari K, Kratina T, Fennell S, Lazarou M, Ryan MT, Kluck RM, Dewson G. Assembly of the Bak apoptotic pore: a critical role for the Bak protein α6 helix in the multimerization of homodimers during apoptosis. J Biol Chem 2013; 288:26027-26038. [PMID: 23893415 DOI: 10.1074/jbc.m113.490094] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bak and Bax are the essential effectors of the intrinsic pathway of apoptosis. Following an apoptotic stimulus, both undergo significant changes in conformation that facilitates their self-association to form pores in the mitochondrial outer membrane. However, the molecular structures of Bak and Bax oligomeric pores remain elusive. To characterize how Bak forms pores during apoptosis, we investigated its oligomerization under native conditions using blue native PAGE. We report that, in a healthy cell, inactive Bak is either monomeric or in a large complex involving VDAC2. Following an apoptotic stimulus, activated Bak forms BH3:groove homodimers that represent the basic stable oligomeric unit. These dimers multimerize to higher-order oligomers via a labile interface independent of both the BH3 domain and groove. Linkage of the α6:α6 interface is sufficient to stabilize higher-order Bak oligomers on native PAGE, suggesting an important role in the Bak oligomeric pore. Mutagenesis of the α6 helix disrupted apoptotic function because a chimera of Bak with the α6 derived from Bcl-2 could be activated by truncated Bid (tBid) and could form BH3:groove homodimers but could not form high molecular weight oligomers or mediate cell death. An α6 peptide could block Bak function but did so upstream of dimerization, potentially implicating α6 as a site for activation by BH3-only proteins. Our examination of native Bak oligomers indicates that the Bak apoptotic pore forms by the multimerization of BH3:groove homodimers and reveals that Bak α6 is not only important for Bak oligomerization and function but may also be involved in how Bak is activated by BH3-only proteins.
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Affiliation(s)
- Stephen Ma
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia
| | - Colin Hockings
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia
| | - Khatira Anwari
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia
| | - Tobias Kratina
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia
| | - Stephanie Fennell
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia
| | - Michael Lazarou
- the Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Michael T Ryan
- the Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Australia
| | - Ruth M Kluck
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia
| | - Grant Dewson
- From the Walter and Eliza Hall Institute of Medical Research, Melbourne 3052, Australia,; the Department of Medical Biology, University of Melbourne, Melbourne 3010, Australia,.
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Feng L, Zhang D, Fan C, Ma C, Yang W, Meng Y, Wu W, Guan S, Jiang B, Yang M, Liu X, Guo D. ER stress-mediated apoptosis induced by celastrol in cancer cells and important role of glycogen synthase kinase-3β in the signal network. Cell Death Dis 2013; 4:e715. [PMID: 23846217 PMCID: PMC3730400 DOI: 10.1038/cddis.2013.222] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 05/03/2013] [Accepted: 05/06/2013] [Indexed: 01/13/2023]
Abstract
HeLa cells treated with celastrol, a natural compound with inhibitive effect on proteasome, exhibited increase in apoptotic rate and characteristics of apoptosis. To clarify the signal network activated by celastrol to induce apoptosis, both the direct target proteins and undirect target proteins of celastrol were searched in the present study. Proteasome catalytic subunit β1 was predicted by computational analysis to be a possible direct target of celastrol and confirmed by checking direct effect of celastrol on the activity of recombinant human proteasome subunit β1 in vitro. Undirect target-related proteins of celastrol were searched using proteomic studies including two-dimensional electrophoresis (2-DE) analysis and iTRAQ-based LC-MS analysis. Possible target-related proteins of celastrol such as endoplasmic reticulum protein 29 (ERP29) and mitochondrial import receptor Tom22 (TOM22) were found by 2-DE analysis of total cellular protein expression profiles. Further study showed that celastrol induced ER stress and ER stress inhibitor could ameliorate cell death induced by celastrol. Celastrol induced translocation of Bax into the mitochondria, which might be related to the upregulation of BH-3-only proteins such as BIM and the increase in the expression level of TOM22. To further search possible target-related proteins of celastrol in ER and ER-related fractions, iTRAQ-based LC-MS method was use to analyze protein expression profiles of ER/microsomal vesicles-riched fraction of cells with or without celastrol treatment. Based on possible target-related proteins found in both 2-DE analysis and iTRAQ-based LC-MS analysis, protein–protein interaction (PPI) network was established using bioinformatic analysis. The important role of glycogen synthase kinase-3β (GSK3β) in the signal cascades of celastrol was suggested. Pretreatment of LiCL, an inhibitor of GSK3β, could significantly ameliorate apoptosis induced by celastrol. On the basis of the results of the present study, possible signal network of celastrol activated by celastrol leading to apoptosis was predicted.
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Affiliation(s)
- L Feng
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, PR China
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18
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Programming cancer cells for high expression levels of Mcl1. EMBO Rep 2013; 14:328-36. [PMID: 23478333 DOI: 10.1038/embor.2013.20] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 02/11/2013] [Indexed: 01/21/2023] Open
Abstract
The Bcl2 pro-survival protein family has long been recognized for its important contributions to cancer. At elevated levels relative to pro-apoptotic effector members, the survival proteins prevent cancer cells from initiating apoptosis in the face of many intrinsic tumour-suppressing pathways and extrinsic therapeutic treatments aimed at controlling tumorigenesis. Recent studies, including genome-wide analyses, have begun to focus attention on a particularly enigmatic member of the family-myeloid cell leukaemia 1 (Mcl1). For reasons that are not clear, Mcl1 in cancer cells is turned over rapidly, eliminated primarily through the ubiquitin-proteasome pathway. Moreover, the mechanistic aspects of this constitutive membrane-associated protein have not been fully elucidated. As the pro-cancer activity of Mcl1 requires elevated expression levels of the protein, the cancer genome adapts to ensure either high levels of synthesis or evasion of degradation, or both. Here, we focus on the complex strategies at play and their therapeutic implications.
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McNally MA, Soane L, Roelofs BA, Hartman AL, Hardwick JM. The N-terminal helix of Bcl-xL targets mitochondria. Mitochondrion 2013; 13:119-24. [PMID: 23333404 DOI: 10.1016/j.mito.2013.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Revised: 12/16/2012] [Accepted: 01/07/2013] [Indexed: 11/26/2022]
Abstract
Anti- and pro-apoptotic Bcl-2 family members regulate the mitochondrial phase of apoptotic cell death. The mitochondrial targeting mechanisms of Bcl-2 family proteins are tightly regulated. Known outer mitochondrial membrane targeting sequences include the C-terminal tail and central helical hairpin. Bcl-xL also localizes to the inner mitochondrial membrane, but these targeting sequences are unknown. Here we investigate the possibility that the N-terminus of Bcl-xL also contains mitochondrial targeting information. Amino acid residues 1-28 of Bcl-xL fused to EGFP are sufficient to target mitochondria. Although positive charges and helical propensity are required for targeting, similar to import sequences the N-terminus is not sufficient for efficient mitochondrial import.
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Affiliation(s)
- Melanie A McNally
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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20
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Sam50 functions in mitochondrial intermembrane space bridging and biogenesis of respiratory complexes. Mol Cell Biol 2012; 32:1173-88. [PMID: 22252321 DOI: 10.1128/mcb.06388-11] [Citation(s) in RCA: 157] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitochondria possess an outer membrane (OMM) and an inner membrane (IMM), which folds into invaginations called cristae. Lipid composition, membrane potential, and proteins in the IMM influence organization of cristae. Here we show an essential role of the OMM protein Sam50 in the maintenance of the structure of cristae. Sam50 is a part of the sorting and assembly machinery (SAM) necessary for the assembly of β-barrel proteins in the OMM. We provide evidence that the SAM components exist in a large protein complex together with the IMM proteins mitofilin and CHCHD3, which we term the mitochondrial intermembrane space bridging (MIB) complex. Interactions between OMM and IMM components of the MIB complex are crucial for the preservation of cristae. After destabilization of the MIB complex, we observed deficiency in the assembly of respiratory chain complexes. Long-term depletion of Sam50 influences the amounts of proteins from all large respiratory complexes that contain mitochondrially encoded subunits, pointing to a connection between the structural integrity of cristae, assembly of respiratory complexes, and/or the maintenance of mitochondrial DNA (mtDNA).
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21
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Abstract
Apoptosis is a process of programmed cell death that serves as a major mechanism for the precise regulation of cell numbers, and as a defense mechanism to remove unwanted and potentially dangerous cells. Studies in nematode, Drosophila and mammals have shown that, although regulation of the cell death machinery is somehow different from one species to another, it is controlled by homologous proteins and involves mitochondria. In mammals, activation of caspases (cysteine proteases that are the main executioners of apoptosis) is under the tight control of the Bcl-2 family proteins, named in reference to the first discovered mammalian cell death regulator. These proteins mainly act by regulating the release of caspases activators from mitochondria. Although for a long time the absence of mitochondrial changes was considered as a hallmark of apoptosis, mitochondria appear today as the central executioner of apoptosis. In this chapter, we present the current view on the mitochondrial pathway of apoptosis with a particular attention to new aspects of the regulation of the Bcl-2 proteins family control of mitochondrial membrane permeabilization: the mechanisms implicated in their mitochondrial targeting and activation during apoptosis, the function(s) of the oncosuppressive protein p53 at the mitochondria and the role of the processes of mitochondrial fusion and fission.
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22
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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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23
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Lin S, Perera M, Nguyen T, Datskovskiy D, Miles M, Colombini M. Bax forms two types of channels, one of which is voltage-gated. Biophys J 2011; 101:2163-9. [PMID: 22067154 PMCID: PMC3207152 DOI: 10.1016/j.bpj.2011.09.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 09/18/2011] [Accepted: 09/20/2011] [Indexed: 01/23/2023] Open
Abstract
When activated, the proapoptotic protein Bax permeabilizes the mitochondrial outer membrane, allowing the release of proteins into the cytosol and thus initiating the execution phase of apoptosis. When activated Bax was reconstituted into phospholipid membranes, we discovered a new, to our knowledge, property of Bax channels: voltage gating. We also found that the same Bax sample under the same experimental conditions could give rise to two radically different channels: Type A, which is small, well behaved, homogeneous, and voltage-gated, and Type B, which is large, noisy, and voltage-independent. One Type B channel can be converted irreversibly into a population of Type A channels by the addition of La(3+). This conversion process appears to involve a two-dimensional budding mechanism. The existence of these two types of Bax channels suggests a process for controlling the degree of mitochondrial outer membrane permeabilization.
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Affiliation(s)
| | | | | | | | | | - Marco Colombini
- Department of Biology, University of Maryland, College Park, Maryland
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24
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Dewson G, Ma S, Frederick P, Hockings C, Tan I, Kratina T, Kluck RM. Bax dimerizes via a symmetric BH3:groove interface during apoptosis. Cell Death Differ 2011; 19:661-70. [PMID: 22015607 DOI: 10.1038/cdd.2011.138] [Citation(s) in RCA: 145] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
During apoptotic cell death, Bax and Bak change conformation and homo-oligomerize to permeabilize mitochondria. We recently reported that Bak homodimerizes via an interaction between the BH3 domain and hydrophobic surface groove, that this BH3:groove interaction is symmetric, and that symmetric dimers can be linked via the α6-helices to form the high order oligomers thought responsible for pore formation. We now show that Bax also dimerizes via a BH3:groove interaction after apoptotic signaling in cells and in mitochondrial fractions. BH3:groove dimers of Bax were symmetric as dimers but not higher order oligomers could be linked by cysteine residues placed in both the BH3 and groove. The BH3:groove interaction was evident in the majority of mitochondrial Bax after apoptotic signaling, and correlated strongly with cytochrome c release, supporting its central role in Bax function. A second interface between the Bax α6-helices was implicated by cysteine linkage studies, and could link dimers to higher order oligomers. We also found that a population of Bax:Bak heterodimers generated during apoptosis formed via a BH3:groove interaction, further demonstrating that Bax and Bak oligomerize via similar mechanisms. These findings highlight the importance of BH3:groove interactions in apoptosis regulation by the Bcl-2 protein family.
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Affiliation(s)
- G Dewson
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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25
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Singh V, Mueller U, Freyschmidt-Paul P, Zöller M. Delayed type hypersensitivity-induced myeloid-derived suppressor cells regulate autoreactive T cells. Eur J Immunol 2011; 41:2871-82. [PMID: 21728175 DOI: 10.1002/eji.201141696] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2011] [Revised: 06/05/2011] [Accepted: 06/27/2011] [Indexed: 12/15/2022]
Abstract
Mild but efficient treatments of autoimmune diseases are urgently required. One such therapy, long-term maintenance of chronic delayed type hypersensitivity, has been described for alopecia areata (AA), a hair follicle-affecting autoimmune disease. The molecular mechanisms underlying the therapeutic efficacy are unknown, but may involve myeloid-derived suppressor cells (MDSCs). AA-affected mice were treated with squaric acid dibutyl ester (SADBE). The immunoreactivity of SADBE-treated AA lymphocytes and of AA lymphocytes co-cultured with SADBE-induced MDSCs was analyzed. The curative effect of SADBE was abolished by all-transretinoic acid, which drives MDSCs into differentiation, confirming a central role for MDSCs in therapeutic SADBE treatment. SADBE and SADBE-induced MDSCs strongly interfered with sustained autoreactive T-cell proliferation in response to AA skin lysate (autoantigen), which was accompanied by weak ζ-chain down-regulation and strongly impaired Lck activation. In contrast, activation of the mitochondrial apoptosis pathway and blockade of the anti-apoptotic PI3K/Akt pathway by SADBE-induced MDSCs did not require T-cell receptor engagement. Apoptosis induction correlated with high TNF-α expression in SADBE-induced MDSCs and elevated TNFRI levels in AA lymphocytes. SADBE-induced MDSCs interfere with persisting autoreactive T-cell proliferation and promote apoptosis of these T cells, which qualifies MDSCs induced and maintained by chronic delayed type hypersensitivity reactions as promising therapeutics in organ-related autoimmune diseases.
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Affiliation(s)
- Vibhuti Singh
- Department of Tumor Cell Biology, University Hospital of Surgery, Heidelberg, Germany
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26
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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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27
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Dukanovic J, Rapaport D. Multiple pathways in the integration of proteins into the mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:971-80. [DOI: 10.1016/j.bbamem.2010.06.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 06/22/2010] [Accepted: 06/23/2010] [Indexed: 11/25/2022]
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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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29
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Lazarou M, Stojanovski D, Frazier AE, Kotevski A, Dewson G, Craigen WJ, Kluck RM, Vaux DL, Ryan MT. Inhibition of Bak activation by VDAC2 is dependent on the Bak transmembrane anchor. J Biol Chem 2010; 285:36876-83. [PMID: 20851889 DOI: 10.1074/jbc.m110.159301] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bax and Bak are pro-apoptotic factors that are required for cell death by the mitochondrial or intrinsic pathway. Bax is found in an inactive state in the cytosol and upon activation is targeted to the mitochondrial outer membrane where it releases cytochrome c and other factors that cause caspase activation. Although Bak functions in the same way as Bax, it is constitutively localized to the mitochondrial outer membrane. In the membrane, Bak activation is inhibited by the voltage-dependent anion channel isoform 2 (VDAC2) by an unknown mechanism. Using blue native gel electrophoresis, we show that in healthy cells endogenous inactive Bak exists in a 400-kDa complex that is dependent on the presence of VDAC2. Activation of Bak is concomitant with its release from the 400-kDa complex and the formation of lower molecular weight species. Furthermore, substitution of the Bak transmembrane anchor with that of the mitochondrial outer membrane tail-anchored protein hFis1 prevents association of Bak with the VDAC2 complex and increases the sensitivity of cells to an apoptotic stimulus. Our results suggest that VDAC2 interacts with the hydrophobic tail of Bak to sequester it in an inactive state in the mitochondrial outer membrane, thereby raising the stimulation threshold necessary for permeabilization of the mitochondrial outer membrane and cell death.
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Affiliation(s)
- Michael Lazarou
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne 3086, Australia
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30
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Abstract
Mitochondria are the cells' powerhouse, but also their suicidal weapon store. Dozens of lethal signal transduction pathways converge on mitochondria to cause the permeabilization of the mitochondrial outer membrane, leading to the cytosolic release of pro-apoptotic proteins and to the impairment of the bioenergetic functions of mitochondria. The mitochondrial metabolism of cancer cells is deregulated owing to the use of glycolytic intermediates, which are normally destined for oxidative phosphorylation, in anabolic reactions. Activation of the cell death machinery in cancer cells by inhibiting tumour-specific alterations of the mitochondrial metabolism or by stimulating mitochondrial membrane permeabilization could therefore be promising therapeutic approaches.
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Affiliation(s)
- Simone Fulda
- University Children's Hospital, Ulm University, Eythstrasse 24, D-89075 Ulm, Germany.
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31
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Van Herreweghe F, Festjens N, Declercq W, Vandenabeele P. Tumor necrosis factor-mediated cell death: to break or to burst, that's the question. Cell Mol Life Sci 2010; 67:1567-79. [PMID: 20198502 PMCID: PMC11115929 DOI: 10.1007/s00018-010-0283-0] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 01/20/2010] [Indexed: 02/06/2023]
Abstract
In this review, we discuss the signal-transduction pathways of three major cellular responses induced by tumor necrosis factor (TNF): cell survival through NF-kappaB activation, apoptosis, and necrosis. Recruitment and activation of caspases plays a crucial role in the initiation and execution of TNF-induced apoptosis. However, experimental inhibition of caspases reveals an alternative cell death pathway, namely necrosis, also called necroptosis, suggesting that caspases actively suppress the latter outcome. TNF-induced necrotic cell death crucially depends on the kinase activity of receptor interacting protein serine-threonine kinase 1 (RIP1) and RIP3. It was recently demonstrated that ubiquitination of RIP1 determines whether it will function as a pro-survival or pro-cell death molecule. Deeper insight into the mechanisms that control the molecular switches between cell survival and cell death will help us to understand why TNF can exert so many different biological functions in the etiology and pathogenesis of human diseases.
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Affiliation(s)
- Franky Van Herreweghe
- Unit For Molecular Signalling and Cell Death, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Ghent (Zwijnaarde), Belgium
- Unit for Molecular Signalling and Cell Death, Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Ghent, Belgium
| | - Nele Festjens
- Unit for Molecular Glycobiology, Department for Molecular Biomedical Research, VIB, Ghent University, Technologiepark 927, 9052 Ghent, Belgium
- Laboratory for Protein Biochemistry and Biomolecular Engineering, Department of Biochemistry and Microbiology, Ghent University, Ledeganckstraat 35, 9052 Ghent, Belgium
| | - Wim Declercq
- Unit For Molecular Signalling and Cell Death, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Ghent (Zwijnaarde), Belgium
- Unit for Molecular Signalling and Cell Death, Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Ghent, Belgium
| | - Peter Vandenabeele
- Unit For Molecular Signalling and Cell Death, Department for Molecular Biomedical Research, VIB, Technologiepark 927, 9052 Ghent (Zwijnaarde), Belgium
- Unit for Molecular Signalling and Cell Death, Department of Biomedical Molecular Biology, Ghent University, Technologiepark 927, 9052 Ghent, Belgium
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32
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Abstract
The release of pro-apoptotic proteins from the mitochondria is a key event in cell death signaling that is regulated by Bcl-2 family proteins. For example, cleavage of the BH3-only protein, Bid, by multiple proteases leads to the formation of truncated Bid that, in turn, promotes the insertion/oligomerization of Bax into the mitochondrial outer membrane, resulting in pore formation and the release of proteins residing in the intermembrane space. Bax, a monomeric protein in the cytosol is targeted to the mitochondria by a yet unknown mechanism. Several proteins of the outer mitochondrial membrane have been proposed to act as receptors for Bax, among them the voltage-dependent anion channel, VDAC, and the mitochondrial protein translocase of the outer membrane, the TOM complex. Alternatively, the unique mitochondrial phospholipid, cardiolipin, has been ascribed a similar function. Here, we review recent work on the mechanisms of activation and the targeting of Bax to the mitochondria and discuss the advantages and limitations of the methods used to study this process.
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