1
|
Popgeorgiev N, Gil C, Berthenet K, Bertolin G, Ichim G. Shedding light on mitochondrial outer-membrane permeabilization and membrane potential: State of the art methods and biosensors. Semin Cell Dev Biol 2024; 156:58-65. [PMID: 37438211 DOI: 10.1016/j.semcdb.2023.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 06/21/2023] [Accepted: 07/04/2023] [Indexed: 07/14/2023]
Abstract
Membrane structural integrity is essential for optimal mitochondrial function. These organelles produce the energy needed for all vital processes, provided their outer and inner membranes are intact. This prevents the release of mitochondrial apoptogenic factors into the cytosol and ensures intact mitochondrial membrane potential (ΔΨm) to sustain ATP production. Cell death by apoptosis is generally triggered by outer mitochondrial membrane permeabilization (MOMP), tightly coupled with loss of ΔΨ m. As these two processes are essential for both mitochondrial function and cell death, researchers have devised various techniques to assess them. Here, we discuss current methods and biosensors available for detecting MOMP and measuring ΔΨ m, focusing on their advantages and limitations and discuss what new imaging tools are needed to improve our knowledge of mitochondrial function.
Collapse
Affiliation(s)
- Nikolay Popgeorgiev
- Cancer Cell Death laboratory, part of LabEX DEVweCAN, Cancer Initiation and Tumoral Cell Identity Department, CRCL, U1052 INSERM, UMR CNRS 5286, Centre Léon Bérard, Université Lyon I, Institut Convergence PLAsCAN Lyon, France; Institut Universitaire de France (IUF), Paris, France
| | - Clara Gil
- Cancer Cell Death laboratory, part of LabEX DEVweCAN, Cancer Initiation and Tumoral Cell Identity Department, CRCL, U1052 INSERM, UMR CNRS 5286, Centre Léon Bérard, Université Lyon I, Institut Convergence PLAsCAN Lyon, France
| | - Kevin Berthenet
- Cancer Cell Death laboratory, part of LabEX DEVweCAN, Cancer Initiation and Tumoral Cell Identity Department, CRCL, U1052 INSERM, UMR CNRS 5286, Centre Léon Bérard, Université Lyon I, Institut Convergence PLAsCAN Lyon, France
| | - Giulia Bertolin
- CNRS, Univ Rennes, IGDR (Institute of Genetics and Development of Rennes), Rennes, France.
| | - Gabriel Ichim
- Cancer Cell Death laboratory, part of LabEX DEVweCAN, Cancer Initiation and Tumoral Cell Identity Department, CRCL, U1052 INSERM, UMR CNRS 5286, Centre Léon Bérard, Université Lyon I, Institut Convergence PLAsCAN Lyon, France.
| |
Collapse
|
2
|
Barisch C, Holthuis JCM, Cosentino K. Membrane damage and repair: a thin line between life and death. Biol Chem 2023; 404:467-490. [PMID: 36810295 DOI: 10.1515/hsz-2022-0321] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 02/03/2023] [Indexed: 02/24/2023]
Abstract
Bilayered membranes separate cells from their surroundings and form boundaries between intracellular organelles and the cytosol. Gated transport of solutes across membranes enables cells to establish vital ion gradients and a sophisticated metabolic network. However, an advanced compartmentalization of biochemical reactions makes cells also particularly vulnerable to membrane damage inflicted by pathogens, chemicals, inflammatory responses or mechanical stress. To avoid potentially lethal consequences of membrane injuries, cells continuously monitor the structural integrity of their membranes and readily activate appropriate pathways to plug, patch, engulf or shed the damaged membrane area. Here, we review recent insights into the cellular mechanisms that underly an effective maintenance of membrane integrity. We discuss how cells respond to membrane lesions caused by bacterial toxins and endogenous pore-forming proteins, with a primary focus on the intimate crosstalk between membrane proteins and lipids during wound formation, detection and elimination. We also discuss how a delicate balance between membrane damage and repair determines cell fate upon bacterial infection or activation of pro-inflammatory cell death pathways.
Collapse
Affiliation(s)
- Caroline Barisch
- Molecular Infection Biology Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| | - Joost C M Holthuis
- Molecular Cell Biology Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| | - Katia Cosentino
- Molecular Cell Biophysics Division, Department of Biology and Center of Cellular Nanoanalytics, Osnabrück University, D-49076 Osnabrück, Germany
| |
Collapse
|
3
|
Wolf P, Schoeniger A, Edlich F. Pro-apoptotic complexes of BAX and BAK on the outer mitochondrial membrane. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119317. [PMID: 35752202 DOI: 10.1016/j.bbamcr.2022.119317] [Citation(s) in RCA: 40] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/02/2022] [Accepted: 06/15/2022] [Indexed: 06/15/2023]
Abstract
In multicellular organisms the regulated cell death apoptosis is critically important for both ontogeny and homeostasis. Mitochondria are indispensable for stress-induced apoptosis. The BCL-2 protein family controls mitochondrial apoptosis and initiates cell death through the pro-apoptotic activities of BAX and BAK at the outer mitochondrial membrane (OMM). Cellular survival is ensured by the retrotranslocation of mitochondrial BAX and BAK into the cytosol by anti-apoptotic BCL-2 proteins. BAX/BAK-dependent OMM permeabilization releases the mitochondrial cytochrome c (cyt c), which initiates activation of caspase-9. The caspase cascade leads to cell shrinkage, plasma membrane blebbing, chromatin condensation, and apoptotic body formation. Although it is clear that ultimately complexes of active BAX and BAK commit the cell to apoptosis, the nature of these complexes is still enigmatic. Excessive research has described a range of complexes, varying from a few molecules to several 10,000, in different systems. BAX/BAK complexes potentially form ring-like structures that could expose the inner mitochondrial membrane. It has been suggested that these pores allow the efflux of small proteins and even mitochondrial DNA. Here we summarize the current state of knowledge for mitochondrial BAX/BAK complexes and the interactions between these proteins and the membrane.
Collapse
Affiliation(s)
- Philipp Wolf
- Institute of Biochemistry, Faculty of Veterinary Medicine, University of Leipzig, 04103 Leipzig, Germany
| | - Axel Schoeniger
- Institute of Biochemistry, Faculty of Veterinary Medicine, University of Leipzig, 04103 Leipzig, Germany
| | - Frank Edlich
- Institute of Biochemistry, Faculty of Veterinary Medicine, University of Leipzig, 04103 Leipzig, Germany.
| |
Collapse
|
4
|
Yang Z, Zhang Z, Zhao Y, Ye Q, Li X, Meng L, Long J, Zhang S, Zhang L. Organelle Interaction and Drug Discovery: Towards Correlative Nanoscopy and Molecular Dynamics Simulation. Front Pharmacol 2022; 13:935898. [PMID: 35795548 PMCID: PMC9251060 DOI: 10.3389/fphar.2022.935898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 06/01/2022] [Indexed: 11/23/2022] Open
Abstract
The inter-organelle interactions, including the cytomembrane, endoplasmic reticulum, mitochondrion, lysosome, dictyosome, and nucleus, play the important roles in maintaining the normal function and homeostasis of cells. Organelle dysfunction can lead to a range of diseases (e.g., Alzheimer’s disease (AD), Parkinson’s disease (PD), and cancer), and provide a new perspective for drug discovery. With the development of imaging techniques and functional fluorescent probes, a variety of algorithms and strategies have been developed for the ever-improving estimation of subcellular structures, organelle interaction, and organelle-related drug discovery with accounting for the dynamic structures of organelles, such as the nanoscopy technology and molecular dynamics (MD) simulations. Accordingly, this work summarizes a series of state-of-the-art examples of the recent progress in this rapidly changing field and uncovering the drug screening based on the structures and interactions of organelles. Finally, we propose the future outlook for exciting applications of organelle-related drug discovery, with the cooperation of nanoscopy and MD simulations.
Collapse
Affiliation(s)
- Zhiwei Yang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
- School of Life Science and Technology, Xi’an Jiaotong University, Xi’an, China
- *Correspondence: Zhiwei Yang, ; Lei Zhang,
| | - Zichen Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
| | - Yizhen Zhao
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
| | - Qiushi Ye
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
| | - Xuhua Li
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
| | - Lingjie Meng
- School of Chemistry, Xi’an Jiaotong University, Xi’an, China
- Instrumental Analysis Center, Xi’an Jiaotong University, Xi’an, China
| | - Jiangang Long
- School of Life Science and Technology, Xi’an Jiaotong University, Xi’an, China
| | - Shengli Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
| | - Lei Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi’an Jiaotong University, Xi’an, China
- *Correspondence: Zhiwei Yang, ; Lei Zhang,
| |
Collapse
|
5
|
Gelles JD, Mohammed JN, Chen Y, Sebastian TM, Chipuk JE. A kinetic fluorescence polarization ligand assay for monitoring BAX early activation. CELL REPORTS METHODS 2022; 2:100174. [PMID: 35419554 PMCID: PMC9004659 DOI: 10.1016/j.crmeth.2022.100174] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 12/20/2021] [Accepted: 02/02/2022] [Indexed: 12/23/2022]
Abstract
Developmental, homeostatic, and pharmacological pro-apoptotic signals converge by activating the BCL-2 family member BAX. Studies investigating molecular regulation of BAX are commonly limited to methodologies measuring endpoint phenotypes and do not assess activation of monomeric BAX. Here, we present FLAMBE, a fluorescence polarization ligand assay for monitoring BAX early activation, that measures activation-induced release of a peptide probe in real time. Using complementary parallel and tandem biochemical techniques, we validate, corroborate, and apply FLAMBE to a contemporary repertoire of BAX modulators, characterizing their contributions within the early steps of BAX activation. Additionally, we use FLAMBE to reveal that historically "dead" BAX mutants remain responsive to activation as quasi-functional monomers. We also identify data metrics for comparative analyses and demonstrate that FLAMBE data align with downstream functional observations. Collectively, FLAMBE advances our understanding of BAX activation and fills a methodological void for studying BAX with broad applications in cell biology and therapeutic development. MOTIVATION In vitro BAX activation studies are invaluable platforms for studying cellular and pharmacological modulators of apoptosis. The gold standard for studying BAX function relies on membrane permeabilization assays, which assess the pore-forming activity of oligomeric BAX. However, there are currently no rapid or kinetic assays to interrogate real-time activation of monomeric BAX in solution, thereby limiting any molecular insights that occur upstream of mitochondrial permeabilization. Furthermore, available methods to observe the activation of monomeric BAX suffer from low throughput and static observations. To address this methodological gap, we developed FLAMBE, a kinetic fluorescence polarization-based assay to measure monomeric BAX activation in solution via concomitant displacement of a labeled peptide. This approach maintains the benefits of rapid kinetic data generation in a low-cost microplate format without requiring specialized equipment or large quantities of protein. FLAMBE compliments available experimental strategies and expands the accessibility of investigators to monitor early steps within the BAX activation continuum.
Collapse
Affiliation(s)
- Jesse D. Gelles
- Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Jarvier N. Mohammed
- Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Yiyang Chen
- Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Tara M. Sebastian
- Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Jerry Edward Chipuk
- Laboratory of Mitochondrial Biology in Human Health and Disease, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| |
Collapse
|
6
|
Martens MD, Karch J, Gordon JW. The molecular mosaic of regulated cell death in the cardiovascular system. Biochim Biophys Acta Mol Basis Dis 2021; 1868:166297. [PMID: 34718119 DOI: 10.1016/j.bbadis.2021.166297] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 10/07/2021] [Accepted: 10/22/2021] [Indexed: 12/11/2022]
Abstract
Cell death is now understood to be a highly regulated process that contributes to normal development and tissue homeostasis, alongside its role in the etiology of various pathological conditions. Through detailed molecular analysis, we have come to know that all cells do not always die in the same way, and that there are at least 7 processes involved, including: apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, and autophagy-mediated cell death. These processes act as pieces in the mosaic of cardiomyocyte cell death, which come together depending on context and stimulus. This review details each individual process, as well as highlights how they come together to produce various cardiac pathologies. By knowing how the pieces go together we can aim towards the development of efficacious therapeutics, which will enable us to prevent cardiomyocyte loss in the face of stress, both reducing mortality and improving quality of life.
Collapse
Affiliation(s)
- Matthew D Martens
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Science, University of Manitoba, Winnipeg, Manitoba, Canada; The Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children's Hospital Research Institute of Manitoba, Canada
| | - Jason Karch
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, United States
| | - Joseph W Gordon
- Department of Human Anatomy and Cell Science, Rady Faculty of Health Science, University of Manitoba, Winnipeg, Manitoba, Canada; College of Nursing, Rady Faculty of Health Science, University of Manitoba, Winnipeg, Manitoba, Canada; The Diabetes Research Envisioned and Accomplished in Manitoba (DREAM) Theme of the Children's Hospital Research Institute of Manitoba, Canada.
| |
Collapse
|
7
|
Sperl LE, Rührnößl F, Schiller A, Haslbeck M, Hagn F. High-resolution analysis of the conformational transition of pro-apoptotic Bak at the lipid membrane. EMBO J 2021; 40:e107159. [PMID: 34523144 PMCID: PMC8521305 DOI: 10.15252/embj.2020107159] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 08/09/2021] [Accepted: 08/20/2021] [Indexed: 12/21/2022] Open
Abstract
Permeabilization of the outer mitochondrial membrane by pore-forming Bcl2 proteins is a crucial step for the induction of apoptosis. Despite a large set of data suggesting global conformational changes within pro-apoptotic Bak during pore formation, high-resolution structural details in a membrane environment remain sparse. Here, we used NMR and HDX-MS (Hydrogen deuterium exchange mass spectrometry) in lipid nanodiscs to gain important high-resolution structural insights into the conformational changes of Bak at the membrane that are dependent on a direct activation by BH3-only proteins. Furthermore, we determined the first high-resolution structure of the Bak transmembrane helix. Upon activation, α-helix 1 in the soluble domain of Bak dissociates from the protein and adopts an unfolded and dynamic potentially membrane-bound state. In line with this finding, comparative protein folding experiments with Bak and anti-apoptotic BclxL suggest that α-helix 1 in Bak is a metastable structural element contributing to its pro-apoptotic features. Consequently, mutagenesis experiments aimed at stabilizing α-helix 1 yielded Bak variants with delayed pore-forming activity. These insights will contribute to a better mechanistic understanding of Bak-mediated membrane permeabilization.
Collapse
Affiliation(s)
- Laura E Sperl
- Bavarian NMR Center at the Department of ChemistryTechnical University of MunichGarchingGermany
- Institute of Structural BiologyHelmholtz Zentrum MünchenNeuherbergGermany
| | - Florian Rührnößl
- Center for Functional Protein Assemblies and Department of ChemistryTechnical University of MunichGarchingGermany
| | - Anita Schiller
- Bavarian NMR Center at the Department of ChemistryTechnical University of MunichGarchingGermany
- Institute of Structural BiologyHelmholtz Zentrum MünchenNeuherbergGermany
| | - Martin Haslbeck
- Center for Functional Protein Assemblies and Department of ChemistryTechnical University of MunichGarchingGermany
| | - Franz Hagn
- Bavarian NMR Center at the Department of ChemistryTechnical University of MunichGarchingGermany
- Institute of Structural BiologyHelmholtz Zentrum MünchenNeuherbergGermany
| |
Collapse
|
8
|
Pan X, Zhou Y, Duan X, Cui J, Liu J, Song X, Ma W, Zhang W, Liu Y, Fan Y. The inhibitory effect Polygonum Cillinerve polysaccharide on transmissible gastroenteritis virus of swine. Res Vet Sci 2021; 140:47-55. [PMID: 34399280 DOI: 10.1016/j.rvsc.2021.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 07/17/2021] [Accepted: 08/05/2021] [Indexed: 11/30/2022]
Abstract
Transmissible gastroenteritis virus of swine (TGEV) is one kind of the main pathogens causing viral diarrhea in pig. In this study, the inhibitory effect of Polygonum Cillinerve polysaccharide (PCP) on TGEV was studied. Firstly, MTT method was used to measure the cell viability of PCP. Then Hoechst 33258 fluorescence staining, Annexin V-FITC/PI fluorescence staining, real-time PCR and western blot were used to explore the effect of PCP on inhibiting TGEV. The results showed that PCP could significantly reduce the apoptosis rate induced by TGEV, reduce the expression of ROS, reduce TGEV replication, increase the expression levels of Bcl-2 and Bax genes, increase the expression of Bcl-2 protein, decreased the expression of Cyto c protein, and reduce the amount of cleaved caspase 3. Therefore, PCP had the better inhibitory effect on TGEV, which provided a certain theoretical basis for the prevention and treatment of TGEV.
Collapse
Affiliation(s)
- Xingxue Pan
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Yu Zhou
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Xueqin Duan
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Jing Cui
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Jia Liu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Xiaoping Song
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Wuren Ma
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Weimin Zhang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Yingqiu Liu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Yunpeng Fan
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, PR China.
| |
Collapse
|
9
|
Dudko HV, Urban VA, Davidovskii AI, Veresov VG. Structure-based modeling of turnover of Bcl-2 family proteins bound to voltage-dependent anion channel 2 (VDAC2): Implications for the mechanisms of proapoptotic activation of Bak and Bax in vivo. Comput Biol Chem 2020; 85:107203. [DOI: 10.1016/j.compbiolchem.2020.107203] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/31/2019] [Accepted: 01/13/2020] [Indexed: 12/15/2022]
|
10
|
Kuwana T, King LE, Cosentino K, Suess J, Garcia-Saez AJ, Gilmore AP, Newmeyer DD. Mitochondrial residence of the apoptosis inducer BAX is more important than BAX oligomerization in promoting membrane permeabilization. J Biol Chem 2020; 295:1623-1636. [PMID: 31901077 PMCID: PMC7008371 DOI: 10.1074/jbc.ra119.011635] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 12/27/2019] [Indexed: 12/31/2022] Open
Abstract
Permeabilization of the mitochondrial outer membrane is a key step in the intrinsic apoptosis pathway, triggered by the release of mitochondrial intermembrane space proteins into the cytoplasm. The BCL-2-associated X apoptosis regulator (BAX) protein critically contributes to this process by forming pores in the mitochondrial outer membrane. However, the relative roles of the mitochondrial residence of BAX and its oligomerization in promoting membrane permeabilization are unclear. To this end, using both cell-free and cellular experimental systems, including membrane permeabilization, size-exclusion chromatography-based oligomer, and retrotranslocation assays, along with confocal microscopy analysis, here we studied two BAX C-terminal variants, T182I and G179P. Neither variant formed large oligomers when activated in liposomes. Nevertheless, the G179P variant could permeabilize liposome membranes, suggesting that large BAX oligomers are not essential for the permeabilization. However, when G179P was transduced into BAX/BCL2 agonist killer (BAK) double-knockout mouse embryonic fibroblasts, its location was solely cytoplasmic, and it then failed to mediate cell death. In contrast, T182I was inefficient in both liposome insertion and permeabilization. Yet, when transduced into cells, BAXT182I resided predominantly on mitochondria, because of its slow retrotranslocation and mediated apoptosis as efficiently as WT BAX. We conclude that BAX's mitochondrial residence in vivo, regulated by both targeting and retrotranslocation, is more significant for its pro-apoptotic activity than its ability to insert and to form higher-order oligomers in model membranes. We propose that this finding should be taken into account when developing drugs that modulate BAX activity.
Collapse
Affiliation(s)
- Tomomi Kuwana
- La Jolla Institute for Immunology, La Jolla, California 92037.
| | - Louise E King
- Wellcome Trust Centre for Cell/Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom M13 9PT
| | - Katia Cosentino
- Interfaculty Institute of Biochemistry, University of Tubingen, 72076 Tubingen, Germany
| | | | | | - Andrew P Gilmore
- Wellcome Trust Centre for Cell/Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom M13 9PT
| | | |
Collapse
|
11
|
Elekofehinti OO, Kamdem JP, Saliu TP, Famusiwa CD, Boligon A, Teixeira Rocha JB. Improvement of mitochondrial function by Tapinanthus globifer (A.Rich.) Tiegh. Against hepatotoxic agent in isolated rat's liver mitochondria. JOURNAL OF ETHNOPHARMACOLOGY 2019; 242:112026. [PMID: 31260758 DOI: 10.1016/j.jep.2019.112026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 05/24/2019] [Accepted: 06/07/2019] [Indexed: 06/09/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Disturbed mitochondrial function and energy crisis serve as key mechanisms for the development of liver injury. Hence, targeting cellular mitochondria in liver diseases might serve as a therapeutic option. Tapinanthus globifer (A.Rich.) Tiegh. has been used in traditional medicine in the management of liver disease. However, there is no scientific evidence supporting such use. AIM OF THE STUDY The current investigation was designed to evaluate the protective role of Tapinanthus globifer treatment on the liver mitochondrial function after the induction of hepatotoxicity by the hepatotoxic agent Fe2+in vitro. MATERIALS AND METHODS In this study, isolated mitochondria from rats' liver was incubated with Fe2+ (10 μM) for 1 h in the absence or presence of T. globifer (50, 100 and 200 μg/mL) metanolic extract (MVA). Mitochondrial viability, mitochondrial membrane potential (ΔΨm), mitochondrial swelling (MPTP)., total thiol content, lipid peroxidation (TBARS) and reactive oxygen species (ROS) production were measured. HPLC-DAD was used to identify potential phytochemicals in MVA. RESULTS (MVA) was able to improve mitochondrial dysfunction induced by Fe2+, by attenuating MTT reduction, increased ΔΨm and mitochondrial swelling. Reduced total thiol and non-protein thiol contents which were associated with increased lipid peroxidation and ROS generation in Fe2+-treated mitochondria were significantly improved by MVA co-treatment. HPLC-DAD analysis revealed the presence of gallic acid, catechin, epigallocatechin, caffeic acid, rutin, glycoside flavonoid and quercetin in MVA that can be responsible for its beneficial effect. CONCLUSION MVA phyto-compounds enhance mitochondrial redox signaling and possess mitochondrial function improving potential, thereby, providing scientific basis for its use in traditional medicine.
Collapse
Affiliation(s)
- Olusola Olalekan Elekofehinti
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology, Akure, Ondo State, Nigeria; Biochemical Toxicology Unit, Department of Chemistry, CCNE, Federal University of Santa. Maria, Santa Maria, RS, Brazil.
| | - Jean Paul Kamdem
- Departamento de Ciências Biológicas, Universidade Regional do Cariri, URCA, RuaCel. Antônio Luis, 1161, 63105-000, Crato, Ceará, Brazil
| | - Tolulope Peter Saliu
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology, Akure, Ondo State, Nigeria
| | - Courage Dele Famusiwa
- Bioinformatics and Molecular Biology Unit, Department of Biochemistry, Federal University of Technology, Akure, Ondo State, Nigeria
| | - AlineAugusti Boligon
- Postgraduate Programme in Pharmaceutical Sciences, Federal University of Santa Maria, Campus Camobi, Santa Maria, RS, 97105-900, Brazil
| | - Joao Batista Teixeira Rocha
- Biochemical Toxicology Unit, Department of Chemistry, CCNE, Federal University of Santa. Maria, Santa Maria, RS, Brazil
| |
Collapse
|
12
|
Mitochondria as playmakers of apoptosis, autophagy and senescence. Semin Cell Dev Biol 2019; 98:139-153. [PMID: 31154010 DOI: 10.1016/j.semcdb.2019.05.022] [Citation(s) in RCA: 261] [Impact Index Per Article: 52.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Revised: 05/21/2019] [Accepted: 05/22/2019] [Indexed: 12/16/2022]
Abstract
Mitochondria are the key energy-producing organelles and cellular source of reactive species. They are responsible for managing cell life and death by a balanced homeostasis passing through a network of structures, regulated principally via fission and fusion. Herein we discuss about the most advanced findings considering mitochondria as dynamic biophysical systems playing compelling roles in the regulation of energy metabolism in both physiologic and pathologic processes controlling cell death and survival. Precisely, we focus on the mitochondrial commitment to the onset, maintenance and counteraction of apoptosis, autophagy and senescence in the bioenergetic reprogramming of cancer cells. In this context, looking for a pharmacological manipulation of cell death processes as a successful route for future targeted therapies, there is major biotechnological challenge in underlining the location, function and molecular mechanism of mitochondrial proteins. Based on the critical role of mitochondrial functions for cellular health, a better knowledge of the main molecular players in mitochondria disfunction could be decisive for the therapeutical control of degenerative diseases, including cancer.
Collapse
|
13
|
Phenotypic selection with an intrabody library reveals an anti-apoptotic function of PKM2 requiring Mitofusin-1. PLoS Biol 2019; 17:e2004413. [PMID: 31181072 PMCID: PMC6586363 DOI: 10.1371/journal.pbio.2004413] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 06/20/2019] [Accepted: 05/21/2019] [Indexed: 12/22/2022] Open
Abstract
Bcl-2 family proteins control a decisive apoptotic event: mitochondrial outer membrane permeabilization (MOMP). To discover MOMP-regulating proteins, we expressed a library of intracellular single-chain variable fragments (scFvs) (“intrabodies”) and selected for those rescuing cells from apoptosis induced by BimS (the short isoform of Bim). One anti-apoptotic intrabody, intrabody 5 (IB5), recognized pyruvate kinase M2 (PKM2), which is expressed in cancer cells. PKM2 deletion ablated this clonogenic rescue; thus, IB5 activated a latent cytoprotective function of PKM2. This resulted not from pyruvate kinase activity per se but rather from the formation of an active tetrameric conformation of PKM2. A stably tetrameric PKM2 mutant, K422R, promoted cell survival even in the absence of IB5, and IB5 further increased survival. Mitochondria isolated from IB5-expressing cells were relatively resistant to MOMP in vitro. In cells, IB5 expression up-regulated Mitofusin-1 (Mfn1) and increased mitochondrial length. Importantly, Mfn1 deficiency abrogated IB5’s cytoprotective effect. PKM2’s anti-apoptotic function could help explain its preferential expression in human cancer. Proteins belonging to the Bcl-2 family regulate a common form of cell death known as apoptosis. Typically, these proteins function in apoptosis by controlling the formation of large pores in the mitochondrial outer membrane (MOM). While many proteins that regulate apoptosis have been identified over the years, some may still be unknown. Here, we used an unbiased approach in which we first expressed in cultured tumor cells a library of intracellular single-chain antibodies termed “intrabodies.” We then selected for intrabodies that allowed cells to evade apoptosis. We identified pyruvate kinase isoform M2 (PKM2), a major glycolytic enzyme that has been linked to cancer development, as the specific target of one such anti-apoptotic intrabody. We showed that the PKM2-specific intrabody promoted cell survival not by neutralizing its target but rather by activating an anti-apoptotic function of PKM2. While this cell survival function of PKM2 was not related to changes in the levels of Bcl-2 family proteins or to effects on the enzymatic activity of PKM2, we found that cell survival requires the increased expression of a MOM protein, Mitofusin-1 (Mfn1), known to regulate mitochondrial fusion. We conclude that this cell survival function of PKM2 could contribute to a role in cancer progression for this protein.
Collapse
|
14
|
Contribution of Mitochondrial Ion Channels to Chemo-Resistance in Cancer Cells. Cancers (Basel) 2019; 11:cancers11060761. [PMID: 31159324 PMCID: PMC6627730 DOI: 10.3390/cancers11060761] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 05/16/2019] [Accepted: 05/23/2019] [Indexed: 12/21/2022] Open
Abstract
Mitochondrial ion channels are emerging oncological targets, as modulation of these ion-transporting proteins may impact on mitochondrial membrane potential, efficiency of oxidative phosphorylation and reactive oxygen production. In turn, these factors affect the release of cytochrome c, which is the point of no return during mitochondrial apoptosis. Many of the currently used chemotherapeutics induce programmed cell death causing damage to DNA and subsequent activation of p53-dependent pathways that finally leads to cytochrome c release from the mitochondrial inter-membrane space. The view is emerging, as summarized in the present review, that ion channels located in this organelle may account in several cases for the resistance that cancer cells can develop against classical chemotherapeutics, by preventing drug-induced apoptosis. Thus, pharmacological modulation of these channel activities might be beneficial to fight chemo-resistance of different types of cancer cells.
Collapse
|
15
|
Ader NR, Hoffmann PC, Ganeva I, Borgeaud AC, Wang C, Youle RJ, Kukulski W. Molecular and topological reorganizations in mitochondrial architecture interplay during Bax-mediated steps of apoptosis. eLife 2019; 8:40712. [PMID: 30714902 PMCID: PMC6361589 DOI: 10.7554/elife.40712] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 01/22/2019] [Indexed: 12/25/2022] Open
Abstract
During apoptosis, Bcl-2 proteins such as Bax and Bak mediate the release of pro-apoptotic proteins from the mitochondria by clustering on the outer mitochondrial membrane and thereby permeabilizing it. However, it remains unclear how outer membrane openings form. Here, we combined different correlative microscopy and electron cryo-tomography approaches to visualize the effects of Bax activity on mitochondria in human cells. Our data show that Bax clusters localize near outer membrane ruptures of highly variable size. Bax clusters contain structural elements suggesting a higher order organization of their components. Furthermore, unfolding of inner membrane cristae is coupled to changes in the supramolecular assembly of ATP synthases, particularly pronounced at membrane segments exposed to the cytosol by ruptures. Based on our results, we propose a comprehensive model in which molecular reorganizations of the inner membrane and sequestration of outer membrane components into Bax clusters interplay in the formation of outer membrane ruptures. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
Collapse
Affiliation(s)
- Nicholas R Ader
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.,Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Iva Ganeva
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Alicia C Borgeaud
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Chunxin Wang
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Richard J Youle
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| |
Collapse
|
16
|
Abstract
During apoptosis, mitochondria permeabilize the outer membranes to release apoptogenic proteins from the intermembrane space. This process termed mitochondrial outer membrane permeabilization (MOMP) is regulated by Bcl-2 family proteins. Bax is an effector proapoptotic molecule that permeabilizes the lipid membranes when it is activated by activator BH3-only proteins. We investigated this critical event by developing simple but faithful vesicle systems-outer membrane vesicles (OMVs) and liposomes-to visualize the pores in the membrane by using cryo-electron microscopy (cryo-EM). We have revealed the morphology of the pore, determined the localization of Bax labeled with nanogold and have performed image analysis to help understand the mechanisms of pore formation induced by Bax.
Collapse
Affiliation(s)
- Tomomi Kuwana
- La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA.
| |
Collapse
|
17
|
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.
Collapse
|
18
|
Lai YC, Li CC, Sung TC, Chang CW, Lan YJ, Chiang YW. The role of cardiolipin in promoting the membrane pore-forming activity of BAX oligomers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1861:268-280. [PMID: 29958826 DOI: 10.1016/j.bbamem.2018.06.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 06/17/2018] [Accepted: 06/22/2018] [Indexed: 01/31/2023]
Abstract
BCL-2-associated X (BAX) protein acts as a gatekeeper in regulating mitochondria-dependent apoptosis. Under cellular stress, BAX becomes activated and transforms into a lethal oligomer that causes mitochondrial outer membrane permeabilization (MOMP). Previous studies have identified several structural features of the membrane-associated BAX oligomer; they include the formation of the BH3-in-groove dimer, the collapse of the helical hairpin α5-α6, and the membrane insertion of α9 helix. However, it remains unclear as to the role of lipid environment in determining the conformation and the pore-forming activity of the BAX oligomers. Here we study molecular details of the membrane-associated BAX in various lipid environments using fluorescence and ESR techniques. We identify the inactive versus active forms of membrane-associated BAX, only the latter of which can induce stable and large membrane pores that are sufficient in size to pass apoptogenic factors. We reveal that the presence of CL is crucial to promoting the association between BAX dimers, hence the active oligomers. Without the presence of CL, BAX dimers assemble into an inactive oligomer that lacks the ability to form stable pores in the membrane. This study suggests an important role of CL in determining the formation of active BAX oligomers.
Collapse
Affiliation(s)
- Yei-Chen Lai
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chieh-Chin Li
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Tai-Ching Sung
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chia-Wei Chang
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yu-Jing Lan
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
| |
Collapse
|
19
|
Uren RT, Iyer S, Kluck RM. Pore formation by dimeric Bak and Bax: an unusual pore? Philos Trans R Soc Lond B Biol Sci 2018. [PMID: 28630157 DOI: 10.1098/rstb.2016.0218] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Apoptotic cell death via the mitochondrial pathway occurs in all vertebrate cells and requires the formation of pores in the mitochondrial outer membrane. Two Bcl-2 protein family members, Bak and Bax, form these pores during apoptosis, and how they do so has been investigated for the last two decades. Many of the conformation changes that occur during their transition to pore-forming proteins have now been delineated. Notably, biochemical, biophysical and structural studies indicate that symmetric homodimers are the basic unit of pore formation. Each dimer contains an extended hydrophobic surface that lies on the outer membrane, and is anchored at either end by a transmembrane domain. Membrane-remodelling events such as positive membrane curvature have been reported to accompany apoptotic pore formation, suggesting Bak and Bax form lipidic pores rather than proteinaceous pores. However, it remains unclear how symmetric dimers assemble to porate the membrane. Here, we review how clusters of dimers and their lipid-mediated interactions provide a molecular explanation for the heterogeneous assemblies of Bak and Bax observed during apoptosis.This article is part of the themed issue 'Membrane pores: from structure and assembly, to medicine and technology'.
Collapse
Affiliation(s)
- Rachel T Uren
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Sweta Iyer
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
| | - Ruth M Kluck
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia .,Department of Medical Biology, The University of Melbourne, 1G Royal Parade, Parkville, Victoria 3052, Australia
| |
Collapse
|
20
|
Kalkavan H, Green DR. MOMP, cell suicide as a BCL-2 family business. Cell Death Differ 2018; 25:46-55. [PMID: 29053143 PMCID: PMC5729535 DOI: 10.1038/cdd.2017.179] [Citation(s) in RCA: 406] [Impact Index Per Article: 67.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 09/13/2017] [Accepted: 09/18/2017] [Indexed: 12/11/2022] Open
Abstract
Apoptosis shapes development and differentiation, has a key role in tissue homeostasis, and is deregulated in cancer. In most cases, successful apoptosis is triggered by mitochondrial outer membrane permeabilization (MOMP), which defines the mitochondrial or intrinsic pathway and ultimately leads to caspase activation and protein substrate cleavage. The mitochondrial apoptotic pathway centered on MOMP is controlled by an intricate network of events that determine the balance of the cell fate choice between survival and death. Here we will review how MOMP proceeds and how the main effectors cytochrome c, a heme protein that has a crucial role in respiration, and second mitochondria-derived activator of caspase (SMAC), as well as other intermembrane space proteins, orchestrate caspase activation. Moreover, we discuss recent insights on the interplay of the upstream coordinators and initiators of MOMP, the BCL-2 family. This review highlights how our increasing knowledge on the regulation of critical checkpoints of apoptosis integrates with understanding of cancer development and has begun to translate into therapeutic clinical benefit.
Collapse
Affiliation(s)
- Halime Kalkavan
- Department of Immunology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| | - Douglas R Green
- Department of Immunology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
| |
Collapse
|
21
|
Burke PJ. Mitochondria, Bioenergetics and Apoptosis in Cancer. Trends Cancer 2017; 3:857-870. [PMID: 29198441 PMCID: PMC5957506 DOI: 10.1016/j.trecan.2017.10.006] [Citation(s) in RCA: 269] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 10/12/2017] [Accepted: 10/19/2017] [Indexed: 10/18/2022]
Abstract
Until recently, the dual roles of mitochondria in ATP production (bioenergetics) and apoptosis (cell life/death decision) were thought to be separate. New evidence points to a more intimate link between these two functions, mediated by the remodeling of the mitochondrial ultrastructure during apoptosis. While most of the key molecular players that regulate this process have been identified (primarily membrane proteins), the exact mechanisms by which they function are not yet understood. Because resistance to apoptosis is a hallmark of cancer, and because ultimately all chemotherapies are believed to result directly or indirectly in induction of apoptosis, a better understanding of the biophysical processes involved may lead to new avenues for therapy.
Collapse
Affiliation(s)
- Peter J Burke
- Department of Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA, USA; Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA, USA; Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA.
| |
Collapse
|
22
|
Peña‐Blanco A, García‐Sáez AJ. Bax, Bak and beyond — mitochondrial performance in apoptosis. FEBS J 2017; 285:416-431. [DOI: 10.1111/febs.14186] [Citation(s) in RCA: 340] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/12/2017] [Accepted: 07/26/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Aida Peña‐Blanco
- Interfaculty Institute of Biochemistry Tübingen University Germany
| | - Ana J. García‐Sáez
- Interfaculty Institute of Biochemistry Tübingen University Germany
- Max‐Planck Institute for Intelligent Systems Stuttgart Germany
| |
Collapse
|
23
|
Suhaili SH, Karimian H, Stellato M, Lee TH, Aguilar MI. Mitochondrial outer membrane permeabilization: a focus on the role of mitochondrial membrane structural organization. Biophys Rev 2017; 9:443-457. [PMID: 28823106 DOI: 10.1007/s12551-017-0308-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/31/2017] [Indexed: 12/13/2022] Open
Abstract
Apoptosis is important in regulating cell death turnover and is mediated by the intrinsic and death receptor-based extrinsic pathways which converge at the mitochondrial outer membrane (MOM) leading to mitochondrial outer membrane permeabilization (MOMP). MOMP results in the release of apoptotic proteins that further activate the downstream pathway of apoptosis. Thus, tight regulation of MOMP is crucial in controlling apoptosis, and a lack of control may lead to tissue and organ malformation and the development of cancers. Despite a growing number of studies focusing on the structure and activity of the proteins involved in mediating MOMP, such as the Bcl-2 family proteins, the mechanism of MOMP is not well understood. In particular, the crucial role of the various structural properties and changes in lipid components of the MOM in mediating the recruitment and activation of different Bcl-2 proteins remains poorly understood. Furthermore, the factors that control the changes in mitochondrial membrane integrity from the initiation to the final disruption of MOM have yet to be clearly defined. In this review, we provide an overview of studies that focus on the mitochondrial membrane with a biophysical analysis of the interactions of the Bcl-2 proteins with the mitochondrial membrane.
Collapse
Affiliation(s)
- Siti Haji Suhaili
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC, 3800, Australia
| | - Hamed Karimian
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC, 3800, Australia
| | - Matthew Stellato
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC, 3800, Australia
| | - Tzong-Hsien Lee
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC, 3800, Australia
| | - Marie-Isabel Aguilar
- Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Wellington Rd, Clayton, VIC, 3800, Australia.
| |
Collapse
|
24
|
Rostovtseva TK, Hoogerheide DP, Rovini A, Bezrukov SM. Lipids in Regulation of the Mitochondrial Outer Membrane Permeability, Bioenergetics, and Metabolism. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-55539-3_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
|
25
|
Cosentino K, García-Sáez AJ. Bax and Bak Pores: Are We Closing the Circle? Trends Cell Biol 2016; 27:266-275. [PMID: 27932064 DOI: 10.1016/j.tcb.2016.11.004] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/28/2016] [Accepted: 11/07/2016] [Indexed: 01/19/2023]
Abstract
Bax and its homolog Bak are key regulators of the mitochondrial pathway of apoptosis. On cell stress Bax and Bak accumulate at distinct foci on the mitochondrial surface where they undergo a conformational change, oligomerize, and mediate cytochrome c release, leading to cell death. The molecular mechanisms of Bax and Bak assembly and mitochondrial permeabilization have remained a longstanding question in the field. Recent structural and biophysical studies at several length scales have shed light on key aspects of Bax and Bak function that have shifted how we think this process occurs. These discoveries reveal an unexpected molecular mechanism in which Bax (and likely Bak) dimers assemble into oligomers with an even number of molecules that fully or partially delineate pores of different sizes to permeabilize the mitochondrial outer membrane (MOM) during apoptosis.
Collapse
Affiliation(s)
- Katia Cosentino
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany; Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, Stuttgart, Germany.
| |
Collapse
|
26
|
Mandal T, Shin S, Aluvila S, Chen HC, Grieve C, Choe JY, Cheng EH, Hustedt EJ, Oh KJ. Assembly of Bak homodimers into higher order homooligomers in the mitochondrial apoptotic pore. Sci Rep 2016; 6:30763. [PMID: 27488021 PMCID: PMC4973285 DOI: 10.1038/srep30763] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/08/2016] [Indexed: 11/09/2022] Open
Abstract
In mitochondrial apoptosis, Bak is activated by death signals to form pores of unknown structure on the mitochondrial outer membrane via homooligomerization. Cytochrome c and other apoptotic factors are released from the intermembrane space through these pores, initiating downstream apoptosis events. Using chemical crosslinking and double electron electron resonance (DEER)-derived distance measurements between specific structural elements in Bak, here we clarify how the Bak pore is assembled. We propose that previously described BH3-in-groove homodimers (BGH) are juxtaposed via the 'α3/α5' interface, in which the C-termini of helices α3 and α5 are in close proximity between two neighboring Bak homodimers. This interface is observed concomitantly with the well-known 'α6:α6' interface. We also mapped the contacts between Bak homodimers and the lipid bilayer based on EPR spectroscopy topology studies. Our results suggest a model for the lipidic Bak pore, whereby the mitochondrial targeting C-terminal helix does not change topology to accommodate the lining of the pore lumen by BGH.
Collapse
Affiliation(s)
- Tirtha Mandal
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Seungjin Shin
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Sreevidya Aluvila
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Hui-Chen Chen
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Carter Grieve
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Jun-Yong Choe
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Emily H Cheng
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Eric J Hustedt
- Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Kyoung Joon Oh
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| |
Collapse
|
27
|
Luna-Vargas MPA, Chipuk JE. Physiological and Pharmacological Control of BAK, BAX, and Beyond. Trends Cell Biol 2016; 26:906-917. [PMID: 27498846 DOI: 10.1016/j.tcb.2016.07.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 07/13/2016] [Accepted: 07/14/2016] [Indexed: 01/01/2023]
Abstract
Cellular commitment to the mitochondrial pathway of apoptosis is accomplished when proapoptotic B cell chronic lymphocytic leukemia/lymphoma (BCL)-2 proteins compromise mitochondrial integrity through the process of mitochondrial outer membrane permeabilization (MOMP). For nearly three decades, intensive efforts focused on the identification and interactions of two key proapoptotic BCL-2 proteins: BCL-2 antagonist killer (BAK) and BCL-2-associated X (BAX). Indeed, we now have critical insights into which BCL-2 proteins interact with BAK/BAX to either preserve survival or initiate MOMP. In contrast, while mitochondria are targeted by BAK/BAX, a molecular understanding of how these organelles govern BAK/BAX function remains less clear. Here, we integrate recent mechanistic insights of proapoptotic BCL-2 protein function in the context of mitochondrial environment, and discuss current and potential pharmacological opportunities to control MOMP in disease.
Collapse
Affiliation(s)
- Mark P A Luna-Vargas
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Jerry Edward Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; The Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA; The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
| |
Collapse
|
28
|
Luna-Vargas MP, Chipuk JE. The deadly landscape of pro-apoptotic BCL-2 proteins in the outer mitochondrial membrane. FEBS J 2016; 283:2676-89. [PMID: 26662859 PMCID: PMC4907887 DOI: 10.1111/febs.13624] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/11/2015] [Accepted: 12/08/2015] [Indexed: 01/06/2023]
Abstract
Apoptosis is a biological process that removes damaged, excess or infected cells through a genetically controlled mechanism. This process plays a crucial role in organismal development, immunity and tissue homeostasis, and alterations in apoptosis contribute to human diseases including cancer and auto-immunity. In the past two decades, significant efforts have focused on understanding the function of the BCL-2 proteins, a complex family of pro-survival and pro-apoptotic α-helical proteins that directly control the mitochondrial pathway of apoptosis. Diverse structural investigations of the BCL-2 family members have broadened our mechanistic understanding of their individual functions. However, an often over-looked aspect of the mitochondrial pathway of apoptosis is how the BCL-2 family specifically interacts with and targets the outer mitochondrial membrane to initiate apoptosis. Structural information on the relationship between the BCL-2 family and the outer mitochondrial membrane is missing; likewise, knowledge of the biophysical mechanisms by which the outer mitochondrial membrane affects and effects apoptosis is lacking. In this mini-review, we provide a current overview of the BCL-2 family members and discuss the latest structural insights into BAK/BAX activation and oligomerization in the context of the outer mitochondrial membrane and mitochondrial biology.
Collapse
Affiliation(s)
- Mark P.A. Luna-Vargas
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
| | - Jerry E. Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
| |
Collapse
|
29
|
Pro-apoptotic Bax molecules densely populate the edges of membrane pores. Sci Rep 2016; 6:27299. [PMID: 27255832 PMCID: PMC4891688 DOI: 10.1038/srep27299] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 05/16/2016] [Indexed: 11/28/2022] Open
Abstract
How the pro-apoptotic Bax protein permeabilizes the mitochondrial outer membrane is not fully understood. Previously, using cryo-electron microscopy (cryo-EM), we showed that activated Bax forms large, growing pores. Whether formed in liposomes or in mitochondrial outer membranes, Bax-induced pores exhibit the same morphology, with negative curvature flanking the edges and with no visible protein structure protruding from the membranes. Here we used cryo-EM to show that gold-labeled Bax molecules, after activation by Bid, became localized strictly at pore edges. This argues that Bax acts at short range to deform the membrane. Also, Bax molecules populated the walls of both small and large pores at the same density, implying that Bax is continuously recruited to the pores as they widen. Moreover, because all Bax molecules became oligomerized after membrane insertion, we infer that Bax oligomers are present at pore edges. We suggest that oligomerization may promote pore enlargement.
Collapse
|
30
|
Joshi AS, Fei N, Greenberg ML. Get1p and Get2p are required for maintenance of mitochondrial morphology and normal cardiolipin levels. FEMS Yeast Res 2016; 16:fow019. [PMID: 26926495 DOI: 10.1093/femsyr/fow019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2016] [Indexed: 11/13/2022] Open
Abstract
Cardiolipin (CL) is the signature phospholipid of mitochondrial membranes. CL deficiency leads to defects in mitochondrial function. Using a targeted synthetic lethality screen to identify defects that exacerbate CL deficiency, we determined that deletion of mitochondrial morphology genes in cells lacking CL leads to severe growth defects. We show that ER membrane proteins Get1p and Get2p are required for maintaining normal levels of CL. We propose that these proteins regulate the level of CL by maintaining wild type-like tubular mitochondrial morphology. The genetic interactions observed in this study identify novel physiological modifiers that are required for maintenance of CL levels and mitochondrial morphology.
Collapse
Affiliation(s)
- Amit S Joshi
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Naomi Fei
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Miriam L Greenberg
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| |
Collapse
|
31
|
Bleicken S, Hofhaus G, Ugarte-Uribe B, Schröder R, García-Sáez AJ. cBid, Bax and Bcl-xL exhibit opposite membrane remodeling activities. Cell Death Dis 2016; 7:e2121. [PMID: 26913610 PMCID: PMC4849160 DOI: 10.1038/cddis.2016.34] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/20/2016] [Accepted: 01/25/2016] [Indexed: 12/19/2022]
Abstract
The proteins of the Bcl-2 family have a crucial role in mitochondrial outer membrane permeabilization during apoptosis and in the regulation of mitochondrial dynamics. Current models consider that Bax forms toroidal pores at mitochondria that are responsible for the release of cytochrome c, whereas Bcl-xL inhibits pore formation. However, how Bcl-2 proteins regulate mitochondrial fission and fusion remains poorly understood. By using a systematic analysis at the single vesicle level, we found that cBid, Bax and Bcl-xL are able to remodel membranes in different ways. cBid and Bax induced a reduction in vesicle size likely related to membrane tethering, budding and fission, besides membrane permeabilization. Moreover, they are preferentially located at highly curved membranes. In contrast, Bcl-xL not only counterbalanced pore formation but also membrane budding and fission. Our findings support a mechanism of action by which cBid and Bax induce or stabilize highly curved membranes including non-lamellar structures. This molecular activity reduces the energy for membrane remodeling, which is a necessary step in toroidal pore formation, as well as membrane fission and fusion, and provides a common mechanism that links the two main functions of Bcl-2 proteins.
Collapse
Affiliation(s)
- S Bleicken
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - G Hofhaus
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - B Ugarte-Uribe
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - R Schröder
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - A J García-Sáez
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| |
Collapse
|
32
|
Große L, Wurm CA, Brüser C, Neumann D, Jans DC, Jakobs S. Bax assembles into large ring-like structures remodeling the mitochondrial outer membrane in apoptosis. EMBO J 2016; 35:402-13. [PMID: 26783364 PMCID: PMC4755111 DOI: 10.15252/embj.201592789] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/23/2015] [Accepted: 12/01/2015] [Indexed: 12/05/2022] Open
Abstract
The Bcl-2 family proteins Bax and Bak are essential for the execution of many apoptotic programs. During apoptosis, Bax translocates to the mitochondria and mediates the permeabilization of the outer membrane, thereby facilitating the release of pro-apoptotic proteins. Yet the mechanistic details of the Bax-induced membrane permeabilization have so far remained elusive. Here, we demonstrate that activated Bax molecules, besides forming large and compact clusters, also assemble, potentially with other proteins including Bak, into ring-like structures in the mitochondrial outer membrane. STED nanoscopy indicates that the area enclosed by a Bax ring is devoid of mitochondrial outer membrane proteins such as Tom20, Tom22, and Sam50. This strongly supports the view that the Bax rings surround an opening required for mitochondrial outer membrane permeabilization (MOMP). Even though these Bax assemblies may be necessary for MOMP, we demonstrate that at least in Drp1 knockdown cells, these assemblies are not sufficient for full cytochrome c release. Together, our super-resolution data provide direct evidence in support of large Bax-delineated pores in the mitochondrial outer membrane as being crucial for Bax-mediated MOMP in cells.
Collapse
Affiliation(s)
- Lena Große
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian A Wurm
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian Brüser
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel Neumann
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel C Jans
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Stefan Jakobs
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| |
Collapse
|
33
|
Cardiolipin or MTCH2 can serve as tBID receptors during apoptosis. Cell Death Differ 2016; 23:1165-74. [PMID: 26794447 DOI: 10.1038/cdd.2015.166] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 09/22/2015] [Accepted: 11/26/2015] [Indexed: 01/07/2023] Open
Abstract
During apoptosis, proapoptotic BAX and BAK trigger mitochondrial outer membrane (MOM) permeabilization by a mechanism that is not yet fully understood. BH3-only proteins such as tBID, together with lipids of the MOM, are thought to play a key role in BAX and BAK activation. In particular, cardiolipin (CL) has been shown to stimulate tBID-induced BAX activation in vitro. However, it is still unclear whether this process also relies on CL in the cell, or whether it is more dependent on MTCH2, a proposed receptor for tBID present in the MOM. To address this issue, we deleted both alleles of cardiolipin synthase in human HCT116 cells by homologous recombination, which resulted in a complete absence of CL. The CL-deficient cells were fully viable in glucose but displayed impaired oxidative phosphorylation and an inability to grow in galactose. Using these cells, we found that CL was not required for either tBID-induced BAX activation, or for apoptosis in response to treatment with TRAIL. Downregulation of MTCH2 in HCT116 cells also failed to prevent recruitment of tBID to mitochondria in apoptotic conditions. However, when both CL and MTCH2 were depleted, a significant reduction in tBID recruitment was observed, suggesting that in HCT116 cells, CL and MTCH2 can have redundant functions in this process.
Collapse
|
34
|
Zhang Z, Subramaniam S, Kale J, Liao C, Huang B, Brahmbhatt H, Condon SGF, Lapolla SM, Hays FA, Ding J, He F, Zhang XC, Li J, Senes A, Andrews DW, Lin J. BH3-in-groove dimerization initiates and helix 9 dimerization expands Bax pore assembly in membranes. EMBO J 2015; 35:208-36. [PMID: 26702098 DOI: 10.15252/embj.201591552] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 11/18/2015] [Indexed: 01/08/2023] Open
Abstract
Pro-apoptotic Bax induces mitochondrial outer membrane permeabilization (MOMP) by forming oligomers through a largely undefined process. Using site-specific disulfide crosslinking, compartment-specific chemical labeling, and mutational analysis, we found that activated integral membrane Bax proteins form a BH3-in-groove dimer interface on the MOM surface similar to that observed in crystals. However, after the α5 helix was released into the MOM, the remaining interface with α2, α3, and α4 helices was rearranged. Another dimer interface was formed inside the MOM by two intersected or parallel α9 helices. Combinations of these interfaces generated oligomers in the MOM. Oligomerization was initiated by BH3-in-groove dimerization, without which neither the other dimerizations nor MOMP occurred. In contrast, α9 dimerization occurred downstream and was required for release of large but not small proteins from mitochondria. Moreover, the release of large proteins was facilitated by α9 insertion into the MOM and localization to the pore rim. Therefore, the BH3-in-groove dimerization on the MOM nucleates the assembly of an oligomeric Bax pore that is enlarged by α9 dimerization at the rim.
Collapse
Affiliation(s)
- Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | | | - Justin Kale
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Chenyi Liao
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Bo Huang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Hetal Brahmbhatt
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Samson G F Condon
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Suzanne M Lapolla
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Franklin A Hays
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jingzhen Ding
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Feng He
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xuejun C Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jianing Li
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Alessandro Senes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - David W Andrews
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Jialing Lin
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| |
Collapse
|
35
|
Kim J, Yang Y, Song SS, Na JH, Oh KJ, Jeong C, Yu YG, Shin YK. Beta-amyloid oligomers activate apoptotic BAK pore for cytochrome c release. Biophys J 2015; 107:1601-8. [PMID: 25296312 DOI: 10.1016/j.bpj.2014.07.074] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 07/20/2014] [Accepted: 07/25/2014] [Indexed: 11/18/2022] Open
Abstract
In Alzheimer's disease, cytochrome c-dependent apoptosis is a crucial pathway in neuronal cell death. Although beta-amyloid (Aβ) oligomers are known to be the neurotoxins responsible for neuronal cell death, the underlying mechanisms remain largely elusive. Here, we report that the oligomeric form of synthetic Aβ of 42 amino acids elicits death of HT-22 cells. But, when expression of a bcl-2 family protein BAK is suppressed by siRNA, Aβ oligomer-induced cell death was reduced. Furthermore, significant reduction of cytochrome c release was observed with mitochondria isolated from BAK siRNA-treated HT-22 cells. Our in vitro experiments demonstrate that Aβ oligomers bind to BAK on the membrane and induce apoptotic BAK pores and cytochrome c release. Thus, the results suggest that Aβ oligomers function as apoptotic ligands and hijack the intrinsic apoptotic pathway to cause unintended neuronal cell death.
Collapse
Affiliation(s)
- Jaewook Kim
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Yoosoo Yang
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Seung Soo Song
- Department of Chemistry, Kookmin University, Seoul, Republic of Korea
| | - Jung-Hyun Na
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Department of Chemistry, Kookmin University, Seoul, Republic of Korea
| | - Kyoung Joon Oh
- Department of Biochemistry and Molecular Biology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Cherlhyun Jeong
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Yeon Gyu Yu
- Department of Chemistry, Kookmin University, Seoul, Republic of Korea
| | - Yeon-Kyun Shin
- Biomedical Research Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea; Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa.
| |
Collapse
|
36
|
Siddiqui WA, Ahad A, Ahsan H. The mystery of BCL2 family: Bcl-2 proteins and apoptosis: an update. Arch Toxicol 2015; 89:289-317. [PMID: 25618543 DOI: 10.1007/s00204-014-1448-7] [Citation(s) in RCA: 477] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/23/2014] [Indexed: 01/12/2023]
Abstract
Apoptosis is a critically important biological process that plays an essential role in cell fate and homeostasis. An important component of the apoptotic pathway is the family of proteins commonly known as the B cell lymphoma-2 (Bcl-2). The primary role of Bcl-2 family members is the regulation of apoptosis. Although the structure of Bcl-2 family of proteins was reported nearly 10 years ago, however, it still surprises us with its structural and functional complexity and diversity. A number of studies have demonstrated that Bcl-2 family influences many other cellular processes beyond apoptosis which are generally independent of the regulation of apoptosis, suggesting additional roles for Bcl-2. The disruption of the regulation of apoptosis is a causative event in many diseases. Since the Bcl-2 family of proteins is the key regulator of apoptosis, the abnormalities in its function have been implicated in many diseases including cancer, neurodegenerative disorders, ischemia and autoimmune diseases. In the past few years, our understanding of the mechanism of action of Bcl-2 family of proteins and its implications in various pathological conditions has enhanced significantly. The focus of this review is to summarize the current knowledge on the structure and function of Bcl-2 family of proteins in apoptotic cellular processes. A number of drugs have been developed in the past few years that target different Bcl-2 members. The role of Bcl-2 proteins in the pathogenesis of various diseases and their pharmacological significance as effective molecular therapeutic targets is also discussed.
Collapse
Affiliation(s)
- Waseem Ahmad Siddiqui
- Department of Biochemistry, Faculty of Science, Jamia Hamdard (Hamdard University), New Delhi, 110062, India
| | | | | |
Collapse
|
37
|
Gillies LA, Du H, Peters B, Knudson CM, Newmeyer DD, Kuwana T. Visual and functional demonstration of growing Bax-induced pores in mitochondrial outer membranes. Mol Biol Cell 2014; 26:339-49. [PMID: 25411335 PMCID: PMC4294680 DOI: 10.1091/mbc.e13-11-0638] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We visualized Bax-induced pores in outer membrane vesicles (OMVs) using cryo-electron microscopy and monitored dextran release from these vesicles by flow cytometry. The data argue that Bax promotes mitochondrial outer membrane permeabilization by inducing the formation of large, solitary, and growing pores through a mechanism involving membrane-curvature stress. Bax induces mitochondrial outer membrane permeabilization (MOMP), a critical step in apoptosis in which proteins are released into the cytoplasm. To resolve aspects of the mechanism, we used cryo-electron microscopy (cryo-EM) to visualize Bax-induced pores in purified mitochondrial outer membranes (MOMs). We observed solitary pores that exhibited negative curvature at their edges. Over time, the pores grew to ∼100–160 nm in diameter after 60–90 min, with some pores measuring more than 300 nm. We confirmed these results using flow cytometry, which we used to monitor the release of fluorescent dextrans from isolated MOM vesicles. The dextran molecules were released gradually, in a manner constrained by pore size. However, the release rates were consistent over a range of dextran sizes (10–500 kDa). We concluded that the pores were not static but widened dramatically to release molecules of different sizes. Taken together, the data from cryo-EM and flow cytometry argue that Bax promotes MOMP by inducing the formation of large, growing pores through a mechanism involving membrane-curvature stress.
Collapse
Affiliation(s)
| | - Han Du
- Department of Pathology, University of Iowa, Iowa City, IA 52242
| | | | | | | | | |
Collapse
|
38
|
Gilbert RJ, Serra MD, Froelich CJ, Wallace MI, Anderluh G. Membrane pore formation at protein–lipid interfaces. Trends Biochem Sci 2014; 39:510-6. [DOI: 10.1016/j.tibs.2014.09.002] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/13/2014] [Accepted: 09/15/2014] [Indexed: 11/15/2022]
|
39
|
Activation of mitochondrial protease OMA1 by Bax and Bak promotes cytochrome c release during apoptosis. Proc Natl Acad Sci U S A 2014; 111:14782-7. [PMID: 25275009 DOI: 10.1073/pnas.1417253111] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intrinsic apoptotic stimuli initiate mammalian cells' apoptotic program by first activating the proteins that have only Bcl-2 homology domain 3 (BH3), such as Bcl-2 interacting mediator of cell death (Bim) and truncated BH3 interacting death domain agonist (tBid), which in turn trigger conformational changes in BCL2-associated X (Bax) and BCL2-antagonist/killer (Bak) proteins that enable oligomer formation on the mitochondria, causing cytochrome c and other apoptogenic proteins in the intermembrane space to leak out. Leaked cytochrome c then initiates apoptotic caspase activation through a well-defined biochemical pathway. However, how oligomerized Bax and Bak cause cytochrome c release from mitochondria remains unknown. We report here the establishment of cell lines in which Bim or tBid can be inducibly expressed to initiate apoptosis in a controlled, quantitative manner. We used these cell lines to examine apoptotic events after Bax and Bak oligomerization but before cytochrome c release. The mitochondrial metalloprotease OMA1 was activated in this system in a Bax- and Bak-dependent fashion. Activated OMA1 cleaved the dynamin-like GTPase, optical nerve atrophy 1, an event that is critical for remodeling of mitochondrial cristae. Knockdown or knockout of OMA1 in these cells attenuated cytochrome c release. Thus it is clear that oligomerized Bax and Bak trigger apoptosis by causing both the permeabilization of the mitochondrial outer membrane and activation OMA1.
Collapse
|
40
|
Gillies LA, Kuwana T. Apoptosis regulation at the mitochondrial outer membrane. J Cell Biochem 2014; 115:632-40. [PMID: 24453042 DOI: 10.1002/jcb.24709] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 10/31/2013] [Indexed: 12/20/2022]
Abstract
Mitochondria play a critical role in apoptosis, or programmed cell death, by releasing apoptogenic factors from the intermembrane space. This process, known as mitochondrial outer membrane permeabilization (MOMP), is tightly regulated by the Bcl-2 family proteins. Pro-apoptotic Bcl-2 family members, Bax and Bak, change their conformation when activated by BH3 domain-only proteins in the family and permeabilize the MOM, whereas pro-survival members inhibit permeabilization. The precise nature of the apoptotic pore in the MOM is unknown, but is probably lipidic. Furthermore, it has been realized that there is another layer of MOMP regulation by a protein factor termed the catalyst in the MOM in order for Bax/Bak to achieve efficient and complete membrane permeabilization. Mitochondrial dynamics do not affect MOMP directly, but seem closely coordinated with MOMP for swift protein efflux from mitochondria. This review will present current views on the molecular mechanisms and regulation of MOMP and conclude with recent developments in clinical applications based on the knowledge gleaned from the investigation.
Collapse
|
41
|
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.
Collapse
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.
| |
Collapse
|
42
|
Mignard V, Lalier L, Paris F, Vallette FM. Bioactive lipids and the control of Bax pro-apoptotic activity. Cell Death Dis 2014; 5:e1266. [PMID: 24874738 PMCID: PMC4047880 DOI: 10.1038/cddis.2014.226] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 04/16/2014] [Accepted: 04/18/2014] [Indexed: 12/19/2022]
Abstract
Lipids are key regulators of cell physiology through the control of many aspects of cellular life and survival. In particular, lipids have been implicated at different levels and through many different mechanisms in the cell death program called apoptosis. Here, we discuss the action of lipids in the regulation of the activation and the integration of Bax into the mitochondrial outer membrane, a key pro-apoptotic member of the BCL-2 family. We describe how, during apoptosis, lipids can act simultaneously or in parallel as receptors or ligands for Bax to stimulate or inhibit its pro-death activity.
Collapse
Affiliation(s)
- V Mignard
- Centre de Recherche en Cancérologie Nantes Angers, Nantes, France
- Université de Nantes, Nantes, France
| | - L Lalier
- Centre de Recherche en Cancérologie Nantes Angers, Nantes, France
- Université de Nantes, Nantes, France
- Institut de Cancérologie de l'Ouest, Nantes, France
| | - F Paris
- Centre de Recherche en Cancérologie Nantes Angers, Nantes, France
- Université de Nantes, Nantes, France
- Institut de Cancérologie de l'Ouest, Nantes, France
| | - F M Vallette
- Centre de Recherche en Cancérologie Nantes Angers, Nantes, France
- Université de Nantes, Nantes, France
- Institut de Cancérologie de l'Ouest, Nantes, France
| |
Collapse
|
43
|
Cosentino K, García-Sáez AJ. Mitochondrial alterations in apoptosis. Chem Phys Lipids 2014; 181:62-75. [PMID: 24732580 DOI: 10.1016/j.chemphyslip.2014.04.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 03/20/2014] [Accepted: 04/02/2014] [Indexed: 12/31/2022]
Abstract
Besides their conventional role as energy suppliers for the cell, mitochondria in vertebrates are active regulators of apoptosis. They release apoptotic factors from the intermembrane space into the cytosol through a mechanism that involves the Bcl-2 protein family, mediating permeabilization of the outer mitochondrial membrane. Associated with this event, a number of additional changes affect mitochondria during apoptosis. They include loss of important mitochondrial functions, such as the ability to maintain calcium homeostasis and to generate ATP, as well as mitochondrial fragmentation and cristae remodeling. Moreover, the lipidic component of mitochondrial membranes undergoes important alterations in composition and distribution, which have turned out to be relevant regulatory events for the proteins involved in apoptotic mitochondrial damage.
Collapse
Affiliation(s)
- Katia Cosentino
- German Cancer Research Center, Heidelberg, Germany; Max-Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Ana J García-Sáez
- German Cancer Research Center, Heidelberg, Germany; Max-Planck Institute for Intelligent Systems, Stuttgart, Germany; Interfaculty Institute of Biochemistry (IFIB), University of Tübingen, Tübingen, Germany.
| |
Collapse
|
44
|
Raemy E, Martinou JC. Involvement of cardiolipin in tBID-induced activation of BAX during apoptosis. Chem Phys Lipids 2014; 179:70-4. [DOI: 10.1016/j.chemphyslip.2013.12.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 12/02/2013] [Accepted: 12/04/2013] [Indexed: 02/08/2023]
|
45
|
G.Veresov V, Davidovskii AI. Structural insights into proapoptotic signaling mediated by MTCH2, VDAC2, TOM40 and TOM22. Cell Signal 2014; 26:370-82. [DOI: 10.1016/j.cellsig.2013.11.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 11/14/2013] [Indexed: 01/04/2023]
|
46
|
Aluvila S, Mandal T, Hustedt E, Fajer P, Choe JY, Oh KJ. Organization of the mitochondrial apoptotic BAK pore: oligomerization of the BAK homodimers. J Biol Chem 2013; 289:2537-51. [PMID: 24337568 DOI: 10.1074/jbc.m113.526806] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The multidomain pro-apoptotic Bcl-2 family proteins BAK and BAX are believed to form large oligomeric pores in the mitochondrial outer membrane during apoptosis. Formation of these pores results in the release of apoptotic factors including cytochrome c from the intermembrane space into the cytoplasm, where they initiate the cascade of events that lead to cell death. Using the site-directed spin labeling method of electron paramagnetic resonance (EPR) spectroscopy, we have determined the conformational changes that occur in BAK when the protein targets to the membrane and forms pores. The data showed that helices α1 and α6 disengage from the rest of the domain, leaving helices α2-α5 as a folded unit. Helices α2-α5 were shown to form a dimeric structure, which is structurally homologous to the recently reported BAX "BH3-in-groove homodimer." Furthermore, the EPR data and a chemical cross-linking study demonstrated the existence of a hitherto unknown interface between BAK BH3-in-groove homodimers in the oligomeric BAK. This novel interface involves the C termini of α3 and α5 helices. The results provide further insights into the organization of the BAK oligomeric pores by the BAK homodimers during mitochondrial apoptosis, enabling the proposal of a BAK-induced lipidic pore with the topography of a "worm hole."
Collapse
Affiliation(s)
- Sreevidya Aluvila
- From the Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
| | | | | | | | | | | |
Collapse
|
47
|
The rheostat in the membrane: BCL-2 family proteins and apoptosis. Cell Death Differ 2013; 21:206-15. [PMID: 24162659 DOI: 10.1038/cdd.2013.153] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/22/2013] [Accepted: 09/17/2013] [Indexed: 12/19/2022] Open
Abstract
Apoptosis, a mechanism for programmed cell death, has key roles in human health and disease. Many signals for cellular life and death are regulated by the BCL-2 family proteins and converge at mitochondria, where cell fate is ultimately decided. The BCL-2 family includes both pro-life (e.g. BCL-XL) and pro-death (e.g. BAX, BAK) proteins. Previously, it was thought that a balance between these opposing proteins, like a simple 'rheostat', could control the sensitivity of cells to apoptotic stresses. Later, this rheostat concept had to be extended, when it became clear that BCL-2 family proteins regulate each other through a complex network of bimolecular interactions, some transient and some relatively stable. Now, studies have shown that the apoptotic circuitry is even more sophisticated, in that BCL-2 family interactions are spatially dynamic, even in nonapoptotic cells. For example, BAX and BCL-XL can shuttle between the cytoplasm and the mitochondrial outer membrane (MOM). Upstream signaling pathways can regulate the cytoplasmic-MOM equilibrium of BAX and thereby adjust the sensitivity of cells to apoptotic stimuli. Thus, we can view the MOM as the central locale of a dynamic life-death rheostat. BAX invariably forms extensive homo-oligomers after activation in membranes. However, recent studies, showing that activated BAX monomers determine the kinetics of MOM permeabilization (MOMP), perturb the lipid bilayer and form nanometer size pores, pose questions about the role of the oligomerization. Other lingering questions concern the molecular mechanisms of BAX redistribution between MOM and cytoplasm and the details of BAX/BAK-membrane assemblies. Future studies need to delineate how BCL-2 family proteins regulate MOMP, in concert with auxiliary MOM proteins, in a dynamic membrane environment. Technologies aimed at elucidating the structure and function of the full-length proteins in membranes are needed to illuminate some of these critical issues.
Collapse
|
48
|
Bleicken S, Landeta O, Landajuela A, Basañez G, García-Sáez AJ. Proapoptotic Bax and Bak proteins form stable protein-permeable pores of tunable size. J Biol Chem 2013; 288:33241-52. [PMID: 24100034 DOI: 10.1074/jbc.m113.512087] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The Bcl-2 proapoptotic proteins Bax and Bak mediate the permeabilization of the mitochondrial outer membrane during apoptosis. Current models consider that Bax and Bak form pores at the mitochondrial outer membrane that are responsible for the release of cytochrome c and other larger mitochondrial apoptotic factors (i.e. Smac/DIABLO, AIF, and endoglycosidase G). However, the properties and nature of Bax/Bak apoptotic pores remain enigmatic. Here, we performed a detailed analysis of the membrane permeabilizing activity of Bax and Bak at the single vesicle level. We directly visualized that cBid-activated Bax and BakΔC21 can form membrane pores large enough to release not only cytochrome c, but also allophycocyanine, a protein of 104 kDa. Interestingly, the size of Bax and BakΔC21 pores is not constant, as typically observed in purely proteinaceous channels, but evolves with time and depends on protein concentration. We found that Bax and BakΔC21 formed long-lived pores, whose areas changed with the amount of Bax/BakΔC21 but not with cardiolipin concentration. Altogether, our results demonstrate that Bax and BakΔC21 follow similar mechanisms of membrane permeabilization characterized by the formation of protein-permeable pores of dynamic size, in agreement with the proteolipidic nature of these apoptotic pores.
Collapse
Affiliation(s)
- Stephanie Bleicken
- From the German Cancer Research Center, BioQuant, ImNeuenheimer Feld 267, 69120 Heidelberg, Germany
| | | | | | | | | |
Collapse
|
49
|
Fais F, Tenca C, Ghiotto F, Bruno S. Targeting the Bcl-2 family in B-cell chronic lymphocytic leukemia. Int J Hematol Oncol 2013. [DOI: 10.2217/ijh.13.43] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
SUMMARY B-cell chronic lymphocytic leukemia (CLL) is the most common leukemia in human adults of the western world and no definitive cure is yet available. One key factor in CLL pathogenesis and disease progression is misbalanced Bcl-2 cell death machinery that is shifted towards protection from apoptosis. Thus, strategies to counteract the antiapoptotic action of the Bcl-2 family in CLL cells are being explored. The Bcl-2 family is composed of a growing number of proteins related to Bcl-2 by sequence homology and their interactions regulate the cell’s decision to die. The features of one particular subclass, the BH3-only proteins, are being studied and exploited for the development of therapeutic anticancer approaches that specifically target antiapoptotic Bcl-2 proteins overexpressed in tumors, including CLL. Preclinical and clinical efficacy and toxicity of the most effective among these ‘BH3 mimetics’ are presented, together with a model that accounts for the differential sensitivity of CLL and normal cells to Bcl-2 neutralization.
Collapse
Affiliation(s)
- Franco Fais
- Department of Experimental Medicine (DIMES), University of Genoa, Human Anatomy Section, Via De Toni 14, Genoa 16132, Italy
| | - Claudya Tenca
- Department of Experimental Medicine (DIMES), University of Genoa, Human Anatomy Section, Via De Toni 14, Genoa 16132, Italy
| | - Fabio Ghiotto
- Department of Experimental Medicine (DIMES), University of Genoa, Human Anatomy Section, Via De Toni 14, Genoa 16132, Italy
| | - Silvia Bruno
- Department of Experimental Medicine (DIMES), University of Genoa, Human Anatomy Section, Via De Toni 14, Genoa 16132, Italy
| |
Collapse
|
50
|
Emerging roles of lipids in BCL-2 family-regulated apoptosis. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1542-54. [DOI: 10.1016/j.bbalip.2013.03.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 02/28/2013] [Accepted: 03/02/2013] [Indexed: 01/06/2023]
|