1
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Piccinini A, Kohlbrecher J, Moussaoui D, Winter A, Prévost S. Effect of cardiolipin on the lamellarity and elongation of liposomes hydrated in PBS. J Colloid Interface Sci 2024; 669:844-855. [PMID: 38749223 DOI: 10.1016/j.jcis.2024.04.211] [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: 12/20/2023] [Revised: 03/25/2024] [Accepted: 04/29/2024] [Indexed: 05/27/2024]
Abstract
Lamellarity and shape are important factors in the formation of vesicles and determine their role in biological systems and pharmaceutical applications. Cardiolipin (CL) is a major lipid in many biological membranes and exerts a great influence on their structural organization due to its particular structure and physico-chemical properties. Here, we used small-angle X-ray and neutron scattering to study the effects of CL with different acyl chain lengths and saturations (CL14:0, CL18:1, CL18:2) on vesicle morphology and lamellarity in membrane models containing mixtures of phosphatidylcholine and phosphatidylethanolamine with different acyl chain lengths and saturations (C14:0 and C 18:1). Measurements were performed in the presence of Phosphate Buffer Saline (PBS), at 37°C, to better reflect physiological conditions, which resulted in strong effects on vesicle morphology, depending on the type and amount of CL used. The presence of small quantities of CL (from 2.5%) reduced inter-membrane correlations and increased perturbation of the membrane, an effect which is enhanced in the presence of matched shorter saturated acyl chains, and mainly unilamellar vesicles (ULV) are formed. In extruded vesicles, employed for SANS experiments, flattened vesicles are observed partly due to the hypertonic effect of PBS, but also influenced by the type of CL added. Our experimental data from SAXS and SANS revealed a strong dependence on CL content in shaping the membrane microstructure, with an apparent optimum in the PC:CL mixture in terms of promoting reduced correlations, preferred curvature and elongation. However, the use of PBS caused distinct differences from previously published studies in water in terms of vesicle shape, and highlights the need to investigate vesicle formation under physiological conditions in order to be able to draw conclusions about membrane formation in biological systems.
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Affiliation(s)
- Alice Piccinini
- Institut Laue-Langevin - The European Neutron Source, 38042 Grenoble, France; School of Life Sciences, Keele University, ST55BG Staffordshire, United Kingdom; Dept. of Medical Biotechnology and Translational Medicine Università degli Studi di Milano, 20054 Milan, Italy
| | | | | | - Anja Winter
- School of Life Sciences, Keele University, ST55BG Staffordshire, United Kingdom.
| | - Sylvain Prévost
- Institut Laue-Langevin - The European Neutron Source, 38042 Grenoble, France
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2
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Peng X, Yang Y, Hou R, Zhang L, Shen C, Yang X, Luo Z, Yin Z, Cao Y. MTCH2 in Metabolic Diseases, Neurodegenerative Diseases, Cancers, Embryonic Development and Reproduction. Drug Des Devel Ther 2024; 18:2203-2213. [PMID: 38882047 PMCID: PMC11180440 DOI: 10.2147/dddt.s460448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 05/21/2024] [Indexed: 06/18/2024] Open
Abstract
Mitochondrial carrier homolog 2 (MTCH2) is a member of the solute carrier 25 family, located on the outer mitochondrial membrane. MTCH2 was first identified in 2000. The development in MTCH2 research is rapidly increasing. The most well-known role of MTCH2 is linking to the pro-apoptosis BID to facilitate mitochondrial apoptosis. Genetic variants in MTCH2 have been investigated for their association with metabolic and neurodegenerative diseases, however, no intervention or therapeutic suggestions were provided. Recent studies revealed the physiological and pathological function of MTCH2 in metabolic diseases, neurodegenerative diseases, cancers, embryonic development and reproduction via regulating mitochondrial apoptosis, metabolic shift between glycolysis and oxidative phosphorylation, mitochondrial fusion/fission, epithelial-mesenchymal transition, etc. This review endeavors to assess a total of 131 published articles to summarise the structure and physiological/pathological role of MTCH2, which has not previously been conducted. This review concludes that MTCH2 plays a crucial role in metabolic diseases, neurodegenerative diseases, cancers, embryonic development and reproduction, and the predominant molecular mechanism is regulation of mitochondrial function. This review gives a comprehensive state of current knowledgement on MTCH2, which will promote the therapeutic research of MTCH2.
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Affiliation(s)
- Xiaoqing Peng
- School of Pharmacy, Anhui Medical University, Hefei, People’s Republic of China
- Inflammation and Immune Mediated Diseases Laboratory of Anhui Province, Anhui Institute of Innovative Drugs, Hefei, Anhui, People’s Republic of China
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
- The Key National Health Commission Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, People’s Republic of China
| | - Yuanyuan Yang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
- The Key National Health Commission Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, People’s Republic of China
| | - Ruirui Hou
- School of Pharmacy, Anhui Medical University, Hefei, People’s Republic of China
| | - Longbiao Zhang
- School of Pharmacy, Anhui Medical University, Hefei, People’s Republic of China
| | - Can Shen
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
| | - Xiaoyan Yang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
| | - Zhigang Luo
- Department of Cardiology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
| | - Zongzhi Yin
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
- The Key National Health Commission Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, People’s Republic of China
| | - Yunxia Cao
- Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, People’s Republic of China
- The Key National Health Commission Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, People’s Republic of China
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3
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Zheng X, Chu B. The biology of mitochondrial carrier homolog 2. Mitochondrion 2024; 75:101837. [PMID: 38158152 DOI: 10.1016/j.mito.2023.101837] [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: 08/08/2023] [Revised: 12/24/2023] [Accepted: 12/26/2023] [Indexed: 01/03/2024]
Abstract
The mitochondrial carrier system is in charge of small molecule transport between the mitochondria and the cytoplasm as well as being an integral portion of the core mitochondrial function. One member of the mitochondrial carrier family of proteins, mitochondrial carrier homolog 2 (MTCH2), is characterized as a critical mitochondrial outer membrane protein insertase participating in mitochondrial homeostasis. Accumulating evidence demonstrate that MTCH2 is integrally linked to cell death and mitochondrial metabolism, and its genetic alterations cause a variety of disease phenotypes, ranging from obesity, Alzheimer's disease, and tumor. To provide a comprehensive insight into the current understanding of MTCH2, we present a detailed description of the physiopathological functions of MTCH2, ranging from apoptosis, mitochondrial dynamics, and metabolic homeostasis regulation. Moreover, we summarized the impact of MTCH2 in human diseases, and highlighted tumors, to assess the role of MTCH2 mutations or variable expression on pathogenesis and target therapeutic options.
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Affiliation(s)
- Xiaohe Zheng
- Department of Pathology, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai 317000, China
| | - Binxiang Chu
- Department of Orthopedic, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai 317000, China.
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4
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King LE, Hohorst L, García-Sáez AJ. Expanding roles of BCL-2 proteins in apoptosis execution and beyond. J Cell Sci 2023; 136:jcs260790. [PMID: 37994778 DOI: 10.1242/jcs.260790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023] Open
Abstract
The proteins of the BCL-2 family are known as key regulators of apoptosis, with interactions between family members determining permeabilisation of the mitochondrial outer membrane (MOM) and subsequent cell death. However, the exact mechanism through which they form the apoptotic pore responsible for MOM permeabilisation (MOMP), the structure and specific components of this pore, and what roles BCL-2 proteins play outside of directly regulating MOMP are incompletely understood. Owing to the link between apoptosis dysregulation and disease, the BCL-2 proteins are important targets for drug development. With the development and clinical use of drugs targeting BCL-2 proteins showing success in multiple haematological malignancies, enhancing the efficacy of these drugs, or indeed developing novel drugs targeting BCL-2 proteins is of great interest to treat cancer patients who have developed resistance or who suffer other disease types. Here, we review our current understanding of the molecular mechanism of MOMP, with a particular focus on recently discovered roles of BCL-2 proteins in apoptosis and beyond, and discuss what implications these functions might have in both healthy tissues and disease.
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Affiliation(s)
- Louise E King
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne 50931, Germany
| | - Lisa Hohorst
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne 50931, Germany
| | - Ana J García-Sáez
- Institute for Genetics, CECAD Research Center, University of Cologne, Cologne 50931, Germany
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5
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Lim D, Choe SH, Jin S, Lee S, Kim Y, Shin HC, Choi JS, Oh DB, Kim SJ, Seo J, Ku B. Structural basis for proapoptotic activation of Bak by the noncanonical BH3-only protein Pxt1. PLoS Biol 2023; 21:e3002156. [PMID: 37315086 DOI: 10.1371/journal.pbio.3002156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 05/10/2023] [Indexed: 06/16/2023] Open
Abstract
Bak is a critical executor of apoptosis belonging to the Bcl-2 protein family. Bak contains a hydrophobic groove where the BH3 domain of proapoptotic Bcl-2 family members can be accommodated, which initiates its activation. Once activated, Bak undergoes a conformational change to oligomerize, which leads to mitochondrial destabilization and the release of cytochrome c into the cytosol and eventual apoptotic cell death. In this study, we investigated the molecular aspects and functional consequences of the interaction between Bak and peroxisomal testis-specific 1 (Pxt1), a noncanonical BH3-only protein exclusively expressed in the testis. Together with various biochemical approaches, this interaction was verified and analyzed at the atomic level by determining the crystal structure of the Bak-Pxt1 BH3 complex. In-depth biochemical and cellular analyses demonstrated that Pxt1 functions as a Bak-activating proapoptotic factor, and its BH3 domain, which mediates direct intermolecular interaction with Bak, plays a critical role in triggering apoptosis. Therefore, this study provides a molecular basis for the Pxt1-mediated novel pathway for the activation of apoptosis and expands our understanding of the cell death signaling coordinated by diverse BH3 domain-containing proteins.
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Affiliation(s)
- Dahwan Lim
- Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Critical Diseases Diagnostics Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Department of Biochemistry, Chungnam National University, Daejeon, Korea
| | - So-Hui Choe
- Aging Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
| | - Sein Jin
- Aging Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
| | - Seulgi Lee
- Department of Biochemistry, Chungnam National University, Daejeon, Korea
| | - Younjin Kim
- Department of Biochemistry, Chungnam National University, Daejeon, Korea
| | - Ho-Chul Shin
- Critical Diseases Diagnostics Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
| | - Joon Sig Choi
- Department of Biochemistry, Chungnam National University, Daejeon, Korea
| | - Doo-Byoung Oh
- Aging Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon, Korea
| | - Seung Jun Kim
- Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Critical Diseases Diagnostics Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Department of Proteome Structural Biology, KRIBB School of Bioscience, University of Science and Technology, Daejeon, Korea
| | - Jinho Seo
- Aging Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon, Korea
| | - Bonsu Ku
- Disease Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, Korea
- Department of Proteome Structural Biology, KRIBB School of Bioscience, University of Science and Technology, Daejeon, Korea
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6
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Clifton LA, Wacklin-Knecht HP, Ådén J, Mushtaq AU, Sparrman T, Gröbner G. Creation of distinctive Bax-lipid complexes at mitochondrial membrane surfaces drives pore formation to initiate apoptosis. SCIENCE ADVANCES 2023; 9:eadg7940. [PMID: 37267355 PMCID: PMC10413641 DOI: 10.1126/sciadv.adg7940] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 04/28/2023] [Indexed: 06/04/2023]
Abstract
Apotosis is an essential process tightly regulated by the Bcl-2 protein family where proapoptotic Bax triggers cell death by perforating the mitochondrial outer membrane. Although intensively studied, the molecular mechanism by which these proteins create apoptotic pores remains elusive. Here, we show that Bax creates pores by extracting lipids from outer mitochondrial membrane mimics by formation of Bax/lipid clusters that are deposited on the membrane surface. Time-resolved neutron reflectometry and Fourier transform infrared spectroscopy revealed two kinetically distinct phases in the pore formation process, both of which were critically dependent on cardiolipin levels. The initially fast adsorption of Bax on the mitochondrial membrane surface is followed by a slower formation of pores and Bax-lipid clusters on the membrane surface. Our findings provide a robust molecular understanding of mitochondrial membrane perforation by cell-killing Bax protein and illuminate the initial phases of programmed cellular death.
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Affiliation(s)
- Luke A. Clifton
- ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 OQX, UK
| | - Hanna P. Wacklin-Knecht
- European Spallation Source ERIC, ESS, P.O. Box 176, SE-22100 Lund, Sweden
- Department of Chemistry, Division of Physical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden
| | - Jörgen Ådén
- Department of Chemistry, University of Umeå, SE-90187 Umeå, Sweden
| | - Ameeq Ul Mushtaq
- Department of Chemistry, University of Umeå, SE-90187 Umeå, Sweden
| | - Tobias Sparrman
- Department of Chemistry, University of Umeå, SE-90187 Umeå, Sweden
| | - Gerhard Gröbner
- Department of Chemistry, University of Umeå, SE-90187 Umeå, Sweden
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7
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Means RE, Katz SG. Balancing life and death: BCL-2 family members at diverse ER-mitochondrial contact sites. FEBS J 2022; 289:7075-7112. [PMID: 34668625 DOI: 10.1111/febs.16241] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 10/11/2021] [Accepted: 10/19/2021] [Indexed: 01/13/2023]
Abstract
The outer mitochondrial membrane is a busy place. One essential activity for cellular survival is the regulation of membrane integrity by the BCL-2 family of proteins. Another critical facet of the outer mitochondrial membrane is its close approximation with the endoplasmic reticulum. These mitochondrial-associated membranes (MAMs) occupy a significant fraction of the mitochondrial surface and serve as key signaling hubs for multiple cellular processes. Each of these pathways may be considered as forming their own specialized MAM subtype. Interestingly, like membrane permeabilization, most of these pathways play critical roles in regulating cellular survival and death. Recently, the pro-apoptotic BCL-2 family member BOK has been found within MAMs where it plays important roles in their structure and function. This has led to a greater appreciation that multiple BCL-2 family proteins, which are known to participate in numerous functions throughout the cell, also have roles within MAMs. In this review, we evaluate several MAM subsets, their role in cellular homeostasis, and the contribution of BCL-2 family members to their functions.
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Affiliation(s)
- Robert E Means
- Department of Pathology, Yale University School of Medicine, New Haven, CT, USA
| | - Samuel G Katz
- Department of Pathology, Yale University School of Medicine, New Haven, CT, USA
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8
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Rose M, Kurylowicz M, Mahmood M, Winkel S, Moran-Mirabal JM, Fradin C. Direct Measurement of the Affinity between tBid and Bax in a Mitochondria-Like Membrane. Int J Mol Sci 2021; 22:8240. [PMID: 34361006 PMCID: PMC8348223 DOI: 10.3390/ijms22158240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/19/2021] [Accepted: 07/22/2021] [Indexed: 01/05/2023] Open
Abstract
The execution step in apoptosis is the permeabilization of the outer mitochondrial membrane, controlled by Bcl-2 family proteins. The physical interactions between the different proteins in this family and their relative abundance literally determine the fate of the cells. These interactions, however, are difficult to quantify, as they occur in a lipid membrane and involve proteins with multiple conformations and stoichiometries which can exist both in soluble and membrane. Here we focus on the interaction between two core Bcl-2 family members, the executor pore-forming protein Bax and the truncated form of the activator protein Bid (tBid), which we imaged at the single particle level in a mitochondria-like planar supported lipid bilayer. We inferred the conformation of the proteins from their mobility, and detected their transient interactions using a novel single particle cross-correlation analysis. We show that both tBid and Bax have at least two different conformations at the membrane, and that their affinity for one another increases by one order of magnitude (with a 2D-KD decreasing from ≃1.6μm-2 to ≃0.1μm-2) when they pass from their loosely membrane-associated to their transmembrane form. We conclude by proposing an updated molecular model for the activation of Bax by tBid.
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Affiliation(s)
- Markus Rose
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (M.R.); (M.K.); (M.M.); (S.W.)
| | - Martin Kurylowicz
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (M.R.); (M.K.); (M.M.); (S.W.)
| | - Mohammad Mahmood
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (M.R.); (M.K.); (M.M.); (S.W.)
| | - Sheldon Winkel
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (M.R.); (M.K.); (M.M.); (S.W.)
| | - Jose M. Moran-Mirabal
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON L8S 4M1, Canada;
| | - Cécile Fradin
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (M.R.); (M.K.); (M.M.); (S.W.)
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4K1, Canada
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9
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Dadsena S, King LE, García-Sáez AJ. Apoptosis regulation at the mitochondria membrane level. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183716. [PMID: 34343535 DOI: 10.1016/j.bbamem.2021.183716] [Citation(s) in RCA: 74] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/26/2021] [Accepted: 07/27/2021] [Indexed: 02/05/2023]
Abstract
Mitochondrial outer membrane permeabilization (MOMP) is a key checkpoint in apoptosis that activates the caspase cascade and irreversibly causes the majority of cells to die. The proteins of the Bcl-2 family are master regulators of apoptosis that form a complex interaction network within the mitochondrial membrane that determines the induction of MOMP. This culminates in the activation of the effector members Bax and Bak, which permeabilize the mitochondrial outer membrane to mediate MOMP. Although the key role of Bax and Bak has been established, many questions remain unresolved regarding molecular mechanisms that control the apoptotic pore. In this review, we discuss the recent progress in our understanding of the regulation of Bax/Bak activity within the mitochondrial membrane.
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Affiliation(s)
- Shashank Dadsena
- Institute for Genetics, CECAD Research Center, University of Cologne, Germany
| | - Louise E King
- Institute for Genetics, CECAD Research Center, University of Cologne, Germany
| | - Ana J García-Sáez
- Institute for Genetics, CECAD Research Center, University of Cologne, Germany.
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10
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Lv F, Qi F, Zhang Z, Wen M, Kale J, Piai A, Du L, Wang S, Zhou L, Yang Y, Wu B, Liu Z, Del Rosario J, Pogmore J, Chou JJ, Andrews DW, Lin J, OuYang B. An amphipathic Bax core dimer forms part of the apoptotic pore wall in the mitochondrial␣membrane. EMBO J 2021; 40:e106438. [PMID: 34101209 PMCID: PMC8280806 DOI: 10.15252/embj.2020106438] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 04/17/2021] [Accepted: 04/27/2021] [Indexed: 02/01/2023] Open
Abstract
Bax proteins form pores in the mitochondrial outer membrane to initiate apoptosis. This might involve their embedding in the cytosolic leaflet of the lipid bilayer, thus generating tension to induce a lipid pore with radially arranged lipids forming the wall. Alternatively, Bax proteins might comprise part of the pore wall. However, there is no unambiguous structural evidence for either hypothesis. Using NMR, we determined a high-resolution structure of the Bax core region, revealing a dimer with the nonpolar surface covering the lipid bilayer edge and the polar surface exposed to water. The dimer tilts from the bilayer normal, not only maximizing nonpolar interactions with lipid tails but also creating polar interactions between charged residues and lipid heads. Structure-guided mutations demonstrate the importance of both types of protein-lipid interactions in Bax pore assembly and core dimer configuration. Therefore, the Bax core dimer forms part of the proteolipid pore wall to permeabilize mitochondria.
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Affiliation(s)
- Fujiao Lv
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Fei Qi
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Maorong Wen
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Justin Kale
- Biological Sciences, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada
| | - Alessandro Piai
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Lingyu Du
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Shuqing Wang
- School of Pharmacy, Tianjin Medical University, Tianjin, China
| | - Liujuan Zhou
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yaqing Yang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Bin Wu
- National Facility for Protein Science in Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Zhijun Liu
- National Facility for Protein Science in Shanghai, Chinese Academy of Sciences, Shanghai, China
| | - Juan Del Rosario
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Justin Pogmore
- Biological Sciences, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - David W Andrews
- Biological Sciences, Sunnybrook Research Institute, University of Toronto, Toronto, ON, Canada
| | - Jialing Lin
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.,Stephenson Cancer Center, Oklahoma City, OK, USA
| | - Bo OuYang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
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11
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Wyżewski Z, Świtlik W, Mielcarska MB, Gregorczyk-Zboroch KP. The Role of Bcl-xL Protein in Viral Infections. Int J Mol Sci 2021; 22:ijms22041956. [PMID: 33669408 PMCID: PMC7920434 DOI: 10.3390/ijms22041956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/13/2021] [Accepted: 02/14/2021] [Indexed: 02/06/2023] Open
Abstract
Bcl-xL represents a family of proteins responsible for the regulation of the intrinsic apoptosis pathway. Due to its anti-apoptotic activity, Bcl-xL co-determines the viability of various virally infected cells. Their survival may determine the effectiveness of viral replication and spread, dynamics of systemic infection, and viral pathogenesis. In this paper, we have reviewed the role of Bcl-xL in the context of host infection by eight different RNA and DNA viruses: hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), influenza A virus (IAV), Epstein-Barr virus (EBV), human T-lymphotropic virus type-1 (HTLV-1), Maraba virus (MRBV), Schmallenberg virus (SBV) and coronavirus (CoV). We have described an influence of viral infection on the intracellular level of Bcl-xL and discussed the impact of Bcl-xL-dependent cell survival control on infection-accompanying pathogenic events such as tissue damage or oncogenesis. We have also presented anti-viral treatment strategies based on the pharmacological regulation of Bcl-xL expression or activity.
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Affiliation(s)
- Zbigniew Wyżewski
- Institute of Biological Sciences, Cardinal Stefan Wyszyński University in Warsaw, 01-815 Warsaw, Poland
- Correspondence: ; Tel.: +48 728-208-338
| | - Weronika Świtlik
- Department of Biochemistry and Microbiology, Institute of Biology, Warsaw University of Life Sciences-SGGW, 02-787 Warsaw, Poland;
| | - Matylda Barbara Mielcarska
- Institute of Veterinary Medicine, Warsaw University of Life Sciences, 02-787 Warsaw, Poland; (M.B.M.); (K.P.G.-Z.)
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12
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Vasquez-Montes V, Ladokhin AS. Expanding MPEx Hydropathy Analysis to Account for Electrostatic Contributions to Protein Interactions with Anionic Membranes. J Membr Biol 2021; 254:109-117. [PMID: 33564913 DOI: 10.1007/s00232-021-00170-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 01/05/2021] [Indexed: 12/21/2022]
Abstract
Hydropathy plots are a crucial tool to guide experimental design, as they generate predictions of protein-membrane interactions and their bilayer topology. The predictions are based on experimentally determined hydrophobicity scales, which provide an estimate for the propensity and stability of these interactions. A significant improvement to the accuracy of hydropathy analyses was provided by the development of the popular Wimley-White interfacial and octanol hydrophobicity scales. These scales have been previously incorporated into the freely available MPEx (Membrane Protein Explorer) online application. Here, we introduce a substantial update to MPEx that allows for the consideration of electrostatic contributions to the bilayer partitioning free energy. This component originates from the Coulombic attraction or repulsion of charges between proteins and membranes. Its inclusion in hydropathy calculations increases the accuracy of hydropathy plot predictions and extends their use to more complex systems (i.e., anionic membranes). We illustrate the application of this analysis to studies on the membrane selectivity of antimicrobial peptides, the membrane partitioning of ion-channel gating modifiers, and the amyloid proteins α-synuclein and Tau, as well as pH-dependent bilayer interactions of diphtheria toxin and apoptotic inhibitor Bcl-xL.
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Affiliation(s)
- Victor Vasquez-Montes
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, 66160, USA.
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13
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Kobeissy H, Hage-Sleiman R, Dakdouk Z, Kozhaya L, Dbaibo G. Crosstalk between Noxa, Bcl-2, and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia. Mol Cell Biochem 2020; 475:215-226. [PMID: 32767230 DOI: 10.1007/s11010-020-03874-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 08/01/2020] [Indexed: 02/06/2023]
Abstract
Ionizing radiation induces apoptosis in human Molt-4 leukemia cells in a p53-dependent manner. The tumor suppressor p53 stimulates various downstream targets that presumably trigger, individually or in concert, de novo ceramide synthesis and intrinsic apoptosis via mitochondrial outer membrane permeabilization (MOMP). Among these targets, BH3-only protein Noxa was found to be promptly activated by p53 prior to ceramide accumulation and apoptosis in response to irradiation. To evaluate the relation between Noxa and ceramide in irradiation-induced apoptosis, Noxa was silenced in Molt-4 cells and apoptosis, p53 expression, and ceramide accumulation were assessed in response to irradiation. In the absence of Noxa, irradiation of Molt-4 cells still induced apoptosis in a p53-dependent manner however ceramide levels decreased significantly although they remained higher than untreated control. Upon irradiation, Noxa was found to translocate to the mitochondria where endogenous ceramide accumulation was observed. In contrast, overexpression of Bcl-2, another mitochondrial protein, in Molt-4 cells abolished the endogenous ceramide accumulation and apoptosis. In irradiation-induced, p53-dependent pathways of apoptosis, the pro-apoptotic Noxa represents one of several, yet to be identified, pathways simultaneously triggered by p53 to produce mitochondrial ceramide accumulation and apoptosis. In contrast, Bcl-2 functions as a broader inhibitor of both ceramide accumulation and apoptosis. Altogether, these results indicate that members of the Bcl-2 family differentially regulate ceramide accumulation and reveal the existence of crosstalk between Bcl-2 family members and ceramide in mediating p53-dependent apoptosis in Molt-4 human T-cell leukemia.
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Affiliation(s)
- Hadile Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Rouba Hage-Sleiman
- Department of Biology, Faculty of Sciences, Lebanese University, Hadath, Lebanon.
| | - Zeinab Dakdouk
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Lina Kozhaya
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Ghassan Dbaibo
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Beirut, Lebanon. .,Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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14
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Lipid asymmetry of a model mitochondrial outer membrane affects Bax-dependent permeabilization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183241. [DOI: 10.1016/j.bbamem.2020.183241] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/16/2020] [Accepted: 02/12/2020] [Indexed: 11/24/2022]
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15
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Abstract
For over three decades, a mainstay and goal of clinical oncology has been the development of therapies promoting the effective elimination of cancer cells by apoptosis. This programmed cell death process is mediated by several signalling pathways (referred to as intrinsic and extrinsic) triggered by multiple factors, including cellular stress, DNA damage and immune surveillance. The interaction of apoptosis pathways with other signalling mechanisms can also affect cell death. The clinical translation of effective pro-apoptotic agents involves drug discovery studies (addressing the bioavailability, stability, tumour penetration, toxicity profile in non-malignant tissues, drug interactions and off-target effects) as well as an understanding of tumour biology (including heterogeneity and evolution of resistant clones). While tumour cell death can result in response to therapy, the selection, growth and dissemination of resistant cells can ultimately be fatal. In this Review, we present the main apoptosis pathways and other signalling pathways that interact with them, and discuss actionable molecular targets, therapeutic agents in clinical translation and known mechanisms of resistance to these agents.
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Affiliation(s)
| | - Wafik S El-Deiry
- The Warren Alpert Medical School, Brown University, Providence, RI, USA.
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16
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Alfaifi MY, Shati AA, Alshehri MA, Elbehairi SEI, Fahmy UA, Alshehri OY. Atorvastatin-TPGS-PLGA Nanoparticles Cytotoxicity Augmentation Against Liver Cancer HepG2 cells. INT J PHARMACOL 2020. [DOI: 10.3923/ijp.2020.79.86] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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17
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Ralph SJ, Nozuhur S, ALHulais RA, Rodríguez‐Enríquez S, Moreno‐Sánchez R. Repurposing drugs as pro‐oxidant redox modifiers to eliminate cancer stem cells and improve the treatment of advanced stage cancers. Med Res Rev 2019; 39:2397-2426. [DOI: 10.1002/med.21589] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 03/20/2019] [Accepted: 03/31/2019] [Indexed: 01/10/2023]
Affiliation(s)
- Stephen J. Ralph
- School of Medical ScienceGriffith University Southport Australia
| | - Sam Nozuhur
- School of Medical ScienceGriffith University Southport Australia
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18
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Vasquez-Montes V, Vargas-Uribe M, Pandey NK, Rodnin MV, Langen R, Ladokhin AS. Lipid-modulation of membrane insertion and refolding of the apoptotic inhibitor Bcl-xL. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:691-700. [PMID: 31004798 DOI: 10.1016/j.bbapap.2019.04.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 04/16/2019] [Indexed: 02/07/2023]
Abstract
Bcl-xL is a member of the Bcl-2 family of apoptotic regulators, responsible for inhibiting the permeabilization of the mitochondrial outer membrane, and a promising anti-cancer target. Bcl-xL exists in the following conformations, each believed to play a role in the inhibition of apoptosis: (a) a soluble folded conformation, (b) a membrane-anchored (by its C-terminal α8 helix) form, which retains the same fold as in solution and (c) refolded membrane-inserted conformations, for which no structural data are available. Previous studies established that in the cell Bcl-xL exists in a dynamic equilibrium between soluble and membranous states, however, no direct evidence exists in support of either anchored or inserted conformation of the membranous state in vivo. In this in vitro study, we employed a combination of fluorescence and EPR spectroscopy to characterize structural features of the bilayer-inserted conformation of Bcl-xL and the lipid modulation of its membrane insertion transition. Our results indicate that the core hydrophobic helix α6 inserts into the bilayer without adopting a transmembrane orientation. This insertion disrupts the packing of Bcl-xL and releases the regulatory N-terminal BH4 domain (α1) from the rest of the protein structure. Our data demonstrate that both insertion and refolding of Bcl-xL are modulated by lipid composition, which brings the apparent pKa of insertion to the threshold of physiological pH. We hypothesize that conformational rearrangements associated with the bilayer insertion of Bcl-xL result in its switching to a so-called non-canonical mode of apoptotic inhibition. Presented results suggest that the alteration in lipid composition before and during apoptosis can serve as an additional factor regulating the permeabilization of the mitochondrial outer membrane.
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Affiliation(s)
- Victor Vasquez-Montes
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Mauricio Vargas-Uribe
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Nitin K Pandey
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Mykola V Rodnin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Ralf Langen
- Zilkha Neurogenetic Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Alexey S Ladokhin
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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Bax to the future - A novel, high-yielding approach for purification and expression of full-length Bax protein for structural studies. Protein Expr Purif 2019; 158:20-26. [PMID: 30738180 DOI: 10.1016/j.pep.2019.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 01/18/2019] [Accepted: 02/05/2019] [Indexed: 01/27/2023]
Abstract
Mitochondria-mediated apoptosis (programmed cell death) involves a sophisticated signaling and regulatory network that is regulated by the Bcl-2 protein family. Members of this family have either pro- or anti-apoptotic functions. An important pro-apoptotic member of this family is the cytosolic Bax. This protein is crucial for the onset of apoptosis by perforating the mitochondrial outer membrane (MOM). This process can be seen as point of no return, since disintegration of the MOM leads to the release of apotogenic factors such as cytochrome c into the cytosol triggering the activation of caspases and subsequent apoptotic steps. Bax is able to interact with the MOM with both its termini, making it inherently difficult to express in E. coli. In this study, we present a novel approach to express and purify full-length Bax with significantly increased yields, when compared to the commonly applied strategy. Using a double fusion approach with an N-terminal GST-tag and a C-terminal Intein-CBD-tag, we were able to render both Bax termini inactive and prevent disruptive interactions from occurring during gene expression. By deploying an Intein-CBD-tag at the C-terminus we were further able to avoid the introduction of any artificial residues, hence ensuring the native like activity of the membrane-penetrating C-terminus of Bax. Further, by engineering a His6-tag to the C-terminus of the CBD-tag we greatly improved the robustness of the purification procedure. We report yields for pure, full-length Bax protein that are increased by an order of magnitude, when compared to commonly used Bax expression protocols.
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Dingeldein A, Sparrman T, Gröbner G. Oxidatively stressed mitochondria-mimicking membranes: A molecular insight into their organization during apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:2644-2654. [DOI: 10.1016/j.bbamem.2018.10.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 09/24/2018] [Accepted: 10/03/2018] [Indexed: 12/14/2022]
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21
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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.
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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.
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22
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NADPH Oxidase Signaling Pathway Mediates Mesenchymal Stem Cell-Induced Inhibition of Hepatic Stellate Cell Activation. Stem Cells Int 2018; 2018:1239143. [PMID: 29861737 PMCID: PMC5971305 DOI: 10.1155/2018/1239143] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/28/2018] [Indexed: 12/16/2022] Open
Abstract
Background Bone marrow-derived mesenchymal stem cells (BMSCs) have blossomed into an effective approach with great potential for the treatment of liver fibrosis. The aim of this study was to investigate the underlying antifibrosis mechanisms by which the BMSC inhibit activated hepatic stellate cells (HSCs) in vivo and in vitro. Methods To study the effect of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) on activated HSCs, we used HSCs and the coculture systems to evaluate the inhibition of activated HSCs from the aspects of the apoptosis of activated HSCs. In addition, activation of NADPH oxidase pathway and the changes in liver histopathology were tested by using the carbon tetrachloride- (CCl4-) induced liver fibrosis in mice. Results Introduction of hBM-MSCs significantly inhibited the proliferation of activated HSCs by inducing the apoptosis process of activated HSCs. The effect of hBM-MSCs reduced the signaling pathway of NADPH oxidase in activated HSCs. Besides, the signaling pathway of NADPH oxidase mediated hBM-MSC upregulation of the expression of the peroxisome proliferator-activated receptor γ and downregulation of the expression of α1(I) collagen and alpha-smooth muscle actin (α-SMA) in activated HSCs. Moreover, the hBM-MSC-induced decrease in the signaling pathway of NADPH oxidase was accompanied by the decrease of the activated HSC number and liver fibrosis in a mouse model of CCl4-induced liver fibrosis. Conclusion The hBM-MSCs act as a promising drug source against liver fibrosis development with respect to hepatopathy as a therapeutic target.
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23
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Hantusch A, Das KK, García-Sáez AJ, Brunner T, Rehm M. Bax retrotranslocation potentiates Bcl-x L's antiapoptotic activity and is essential for switch-like transitions between MOMP competency and resistance. Cell Death Dis 2018; 9:430. [PMID: 29567940 PMCID: PMC5864878 DOI: 10.1038/s41419-018-0464-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 01/25/2018] [Accepted: 02/05/2018] [Indexed: 12/26/2022]
Abstract
The rapid, typically all-or-none process of mitochondrial outer membrane permeabilization (MOMP) constitutes a primary cell death decision that is controlled by the Bcl-2 family interactome. However, how strict all-or-none MOMP decisions are governed by and emanate from the dynamic interplay of pro- and antiapoptotic Bcl-2 family members remains incompletely understood. In particular, it is unclear to which extent the shuttling of Bcl-2 family species between lipid and aqueous phases contributes to regulating MOMP sensitivity. Here, we studied the interplay of tBid, Bax, and Bcl-xL, using a combined approach of deterministic mathematical modeling and retrospective as well as prospective experimental testing of model predictions. Systems modeling of the tBid–Bax interplay and their fluxes between cytosol and mitochondrial membranes reproduced experimental data on tBid-triggered Bax activation and oligomerization highly accurately. Extending these studies to analyze the cell-protective role of Bcl-xL strikingly revealed that the activity of Bcl-xL to retrotranslocate activated Bax from membranes back into the cytosol is essential to reproduce or correctly predict experimental outcomes. These included the potency of Bcl-xL in suppressing Bax oligomerization, its role in limiting Bax membrane recruitment, the resistance threshold to low concentrations of MOMP triggers as well as a response potentiaton arising from combinations of tBid and sensitizer BH3-only peptides. Importantly, retrotranslocation activity of Bcl-xL is necessary to strictly separate conditions of MOMP competency and resistance. Our results therefore identify Bax retrotranslocation by Bcl-xL as an indispensable component of the molecular switch by which Bcl-2 family members govern cellular death decisions.
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Affiliation(s)
- Annika Hantusch
- Department of Biology, Chair of Biochemical Pharmacology, University of Konstanz, 78457, Konstanz, Germany.,Konstanz Research School Chemical Biology, University of Konstanz, 78457, Konstanz, Germany
| | - Kushal K Das
- Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Str. 4, 72076, Tübingen, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Str. 4, 72076, Tübingen, Germany
| | - Thomas Brunner
- Department of Biology, Chair of Biochemical Pharmacology, University of Konstanz, 78457, Konstanz, Germany.,Konstanz Research School Chemical Biology, University of Konstanz, 78457, Konstanz, Germany
| | - Markus Rehm
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland. .,Centre for Systems Medicine, Royal College of Surgeons in Ireland, Dublin 2, Ireland. .,Institute of Cell Biology and Immunology, University of Stuttgart, 70569, Stuttgart, Germany. .,Stuttgart Research Center Systems Biology, University of Stuttgart, 70569, Stuttgart, Germany.
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24
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Why should neuroscientists worry about iron? The emerging role of ferroptosis in the pathophysiology of neuroprogressive diseases. Behav Brain Res 2017; 341:154-175. [PMID: 29289598 DOI: 10.1016/j.bbr.2017.12.036] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 12/23/2017] [Accepted: 12/27/2017] [Indexed: 12/12/2022]
Abstract
Ferroptosis is a unique form of programmed death, characterised by cytosolic accumulation of iron, lipid hydroperoxides and their metabolites, and effected by the fatal peroxidation of polyunsaturated fatty acids in the plasma membrane. It is a major driver of cell death in neurodegenerative neurological diseases. Moreover, cascades underpinning ferroptosis could be active drivers of neuropathology in major psychiatric disorders. Oxidative and nitrosative stress can adversely affect mechanisms and proteins governing cellular iron homeostasis, such as the iron regulatory protein/iron response element system, and can ultimately be a source of abnormally high levels of iron and a source of lethal levels of lipid membrane peroxidation. Furthermore, neuroinflammation leads to the upregulation of divalent metal transporter1 on the surface of astrocytes, microglia and neurones, making them highly sensitive to iron overload in the presence of high levels of non-transferrin-bound iron, thereby affording such levels a dominant role in respect of the induction of iron-mediated neuropathology. Mechanisms governing systemic and cellular iron homeostasis, and the related roles of ferritin and mitochondria are detailed, as are mechanisms explaining the negative regulation of ferroptosis by glutathione, glutathione peroxidase 4, the cysteine/glutamate antiporter system, heat shock protein 27 and nuclear factor erythroid 2-related factor 2. The potential role of DJ-1 inactivation in the precipitation of ferroptosis and the assessment of lipid peroxidation are described. Finally, a rational approach to therapy is considered, with a discussion on the roles of coenzyme Q10, iron chelation therapy, in the form of deferiprone, deferoxamine (desferrioxamine) and deferasirox, and N-acetylcysteine.
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25
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BCL-2 family proteins: changing partners in the dance towards death. Cell Death Differ 2017; 25:65-80. [PMID: 29149100 PMCID: PMC5729540 DOI: 10.1038/cdd.2017.186] [Citation(s) in RCA: 916] [Impact Index Per Article: 130.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/17/2017] [Accepted: 09/19/2017] [Indexed: 02/06/2023] Open
Abstract
The BCL-2 family of proteins controls cell death primarily by direct binding interactions that regulate mitochondrial outer membrane permeabilization (MOMP) leading to the irreversible release of intermembrane space proteins, subsequent caspase activation and apoptosis. The affinities and relative abundance of the BCL-2 family proteins dictate the predominate interactions between anti-apoptotic and pro-apoptotic BCL-2 family proteins that regulate MOMP. We highlight the core mechanisms of BCL-2 family regulation of MOMP with an emphasis on how the interactions between the BCL-2 family proteins govern cell fate. We address the critical importance of both the concentration and affinities of BCL-2 family proteins and show how differences in either can greatly change the outcome. Further, we explain the importance of using full-length BCL-2 family proteins (versus truncated versions or peptides) to parse out the core mechanisms of MOMP regulation by the BCL-2 family. Finally, we discuss how post-translational modifications and differing intracellular localizations alter the mechanisms of apoptosis regulation by BCL-2 family proteins. Successful therapeutic intervention of MOMP regulation in human disease requires an understanding of the factors that mediate the major binding interactions between BCL-2 family proteins in cells.
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26
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Musatov A, Sedlák E. Role of cardiolipin in stability of integral membrane proteins. Biochimie 2017; 142:102-111. [PMID: 28842204 DOI: 10.1016/j.biochi.2017.08.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 08/21/2017] [Indexed: 01/13/2023]
Abstract
Cardiolipin (CL) is a unique phospholipid with a dimeric structure having four acyl chains and two phosphate groups found almost exclusively in certain membranes of bacteria and of mitochondria of eukaryotes. CL interacts with numerous proteins and has been implicated in function and stabilization of several integral membrane proteins (IMPs). While both functional and stabilization roles of CL in IMPs has been generally acknowledged, there are, in fact, only limited number of quantitative analysis that support this function of CL. This is likely caused by relatively complex determination of parameters characterizing stability of IMPs and particularly intricate assessment of role of specific phospholipids such as CL in IMPs stability. This review aims to summarize quantitative findings regarding stabilization role of CL in IMPs reported up to now.
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Affiliation(s)
- Andrej Musatov
- Department of Biophysics, Institute of Experimental Physics Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia.
| | - Erik Sedlák
- Centre for Interdisciplinary Biosciences, P.J. Šafárik University, Jesenná 5, 040 01 Košice, Slovakia.
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27
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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.
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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.
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28
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Dingeldein APG, Pokorná Š, Lidman M, Sparrman T, Šachl R, Hof M, Gröbner G. Apoptotic Bax at Oxidatively Stressed Mitochondrial Membranes: Lipid Dynamics and Permeabilization. Biophys J 2017; 112:2147-2158. [PMID: 28538152 DOI: 10.1016/j.bpj.2017.04.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/23/2017] [Accepted: 04/05/2017] [Indexed: 12/20/2022] Open
Abstract
Mitochondria are crucial compartments of eukaryotic cells because they function as the cellular power plant and play a central role in the early stages of programmed cell death (apoptosis). To avoid undesired cell death, this apoptotic pathway is tightly regulated by members of the Bcl-2 protein family, which interact on the external surface of the mitochondria, i.e., the mitochondrial outer membrane (MOM), and modulate its permeability to apoptotic factors, controlling their release into the cytosol. A growing body of evidence suggests that the MOM lipids play active roles in this permeabilization process. In particular, oxidized phospholipids (OxPls) formed under intracellular stress seem to directly induce apoptotic activity at the MOM. Here we show that the process of MOM pore formation is sensitive to the type of OxPls species that are generated. We created MOM-mimicking liposome systems, which resemble the cellular situation before apoptosis and upon triggering of oxidative stress conditions. These vesicles were studied using 31P solid-state magic-angle-spinning nuclear magnetic resonance spectroscopy and differential scanning calorimetry, together with dye leakage assays. Direct polarization and cross-polarization nuclear magnetic resonance experiments enabled us to probe the heterogeneity of these membranes and their associated molecular dynamics. The addition of apoptotic Bax protein to OxPls-containing vesicles drastically changed the membranes' dynamic behavior, almost completely negating the previously observed effect of temperature on the lipids' molecular dynamics and inducing an ordering effect that led to more cooperative membrane melting. Our results support the hypothesis that the mitochondrion-specific lipid cardiolipin functions as a first contact site for Bax during its translocation to the MOM in the onset of apoptosis. In addition, dye leakage assays revealed that different OxPls species in the MOM-mimicking vesicles can have opposing effects on Bax pore formation.
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Affiliation(s)
| | - Šárka Pokorná
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Lidman
- Department of Chemistry, Umeå University, Umeå, Sweden
| | | | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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He SH, Liu HG, Zhou YF, Yue QF. Liquiritin (LT) exhibits suppressive effects against the growth of human cervical cancer cells through activating Caspase-3 in vitro and xenograft mice in vivo. Biomed Pharmacother 2017; 92:215-228. [DOI: 10.1016/j.biopha.2017.05.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 04/28/2017] [Accepted: 05/05/2017] [Indexed: 01/09/2023] Open
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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]
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31
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Fernández-Marrero Y, Bleicken S, Das KK, Bachmann D, Kaufmann T, Garcia-Saez AJ. The membrane activity of BOK involves formation of large, stable toroidal pores and is promoted by cBID. FEBS J 2017; 284:711-724. [PMID: 28064468 DOI: 10.1111/febs.14008] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 12/19/2016] [Accepted: 01/06/2017] [Indexed: 12/27/2022]
Abstract
The BCL-2 family members are key regulators of the intrinsic apoptotic pathway, which is defined by permeabilization of the mitochondrial outer membrane by members of the BAX-like subfamily. BOK is classified as a BAX-like protein; however, its (patho-)physiological role remains largely unclear. We therefore assessed the membrane permeabilization potential of C-terminally truncated recombinant BOK, BOK∆C . We show that BOK∆C can permeabilize liposomes mimicking the composition of mitochondrial outer membrane, but not of endoplasmic reticulum, forming large and stable pores over time. Importantly, pore formation was enhanced by the presence of cBID and refractory to the addition of antiapoptotic BCL-XL . However, isolated mitochondria from Bax-/- Bak-/- cells were resistant to BOK-induced cytochrome c release, even in the presence of cBID. Taken together, we show that BOK∆C can permeabilize liposomes, and cooperate with cBID, but its role in directly mediating mitochondrial permeabilization is unclear and may underlie a yet to be determined negative regulation.
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Affiliation(s)
| | | | - Kushal Kumar Das
- Interfaculty Institute of Biochemistry, University of Tübingen, Germany
| | | | | | - Ana J Garcia-Saez
- Interfaculty Institute of Biochemistry, University of Tübingen, Germany
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32
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Sarosiek KA, Fraser C, Muthalagu N, Bhola PD, Chang W, McBrayer SK, Cantlon A, Fisch S, Golomb-Mello G, Ryan JA, Deng J, Jian B, Corbett C, Goldenberg M, Madsen JR, Liao R, Walsh D, Sedivy J, Murphy DJ, Carrasco DR, Robinson S, Moslehi J, Letai A. Developmental Regulation of Mitochondrial Apoptosis by c-Myc Governs Age- and Tissue-Specific Sensitivity to Cancer Therapeutics. Cancer Cell 2017; 31:142-156. [PMID: 28017613 PMCID: PMC5363285 DOI: 10.1016/j.ccell.2016.11.011] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 09/13/2016] [Accepted: 11/17/2016] [Indexed: 01/20/2023]
Abstract
It is not understood why healthy tissues can exhibit varying levels of sensitivity to the same toxic stimuli. Using BH3 profiling, we find that mitochondria of many adult somatic tissues, including brain, heart, and kidneys, are profoundly refractory to pro-apoptotic signaling, leading to cellular resistance to cytotoxic chemotherapies and ionizing radiation. In contrast, mitochondria from these tissues in young mice and humans are primed for apoptosis, predisposing them to undergo cell death in response to genotoxic damage. While expression of the apoptotic protein machinery is nearly absent by adulthood, in young tissues its expression is driven by c-Myc, linking developmental growth to cell death. These differences may explain why pediatric cancer patients have a higher risk of developing treatment-associated toxicities.
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Affiliation(s)
- Kristopher A Sarosiek
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Cameron Fraser
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA
| | | | - Patrick D Bhola
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Weiting Chang
- Harvard Medical School, Boston, MA 02115, USA; Division of Genetics and Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Samuel K McBrayer
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Adam Cantlon
- Harvard Medical School, Boston, MA 02115, USA; Division of Genetics and Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Sudeshna Fisch
- Harvard Medical School, Boston, MA 02115, USA; Division of Genetics and Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Gail Golomb-Mello
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Jeremy A Ryan
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Jing Deng
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Brian Jian
- Department of Neurosurgery, Kaiser Permanente, Sacramento, CA 95815, USA
| | - Chris Corbett
- Department of Neurosurgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Marti Goldenberg
- Department of Neurosurgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Joseph R Madsen
- Harvard Medical School, Boston, MA 02115, USA; Department of Neurosurgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Ronglih Liao
- Harvard Medical School, Boston, MA 02115, USA; Division of Genetics and Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Dominic Walsh
- Harvard Medical School, Boston, MA 02115, USA; Division of Genetics and Division of Cardiovascular Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - John Sedivy
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Daniel J Murphy
- Cancer Research UK Beatson Institute, Glasgow G61 1BD, Scotland; Institute of Cancer Sciences, University of Glasgow, Glasgow G61 1BD, Scotland
| | - Daniel Ruben Carrasco
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA
| | - Shenandoah Robinson
- Harvard Medical School, Boston, MA 02115, USA; Department of Neurosurgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Javid Moslehi
- Division of Cardiovascular Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Division of Hematology-Oncology, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Cardio-Oncology Program, Department of Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Anthony Letai
- Department of Medical Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Mayer 430, Boston, MA 02115, USA; Harvard Medical School, Boston, MA 02115, USA.
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Pro-apoptotic cBid and Bax exhibit distinct membrane remodeling activities: An AFM study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:17-27. [PMID: 27755971 DOI: 10.1016/j.bbamem.2016.10.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 09/16/2016] [Accepted: 10/13/2016] [Indexed: 11/22/2022]
Abstract
Bcl-2 proteins are key regulators of the mitochondrial outer membrane (MOM) permeabilization that mediates apoptosis. During apoptosis, Bid is cleaved (cBid) and translocates to the MOM, where it activates Bax. Bax then oligomerizes and induces MOM permeabilization. However, little is known about how these proteins affect membrane organization aside from pore formation. In previous studies, we have shown that both cBid and Bax are able to remodel membranes and stabilize curvature. Here, we dissected the independent effects of Bax and cBid on supported lipid structures mimicking the mitochondrial composition by means of atomic force spectroscopy. We show that cBid did not permeabilize the membrane but lowered the membrane breakthrough force. On the other hand, Bax effects were dependent on its oligomeric state. Monomeric Bax did not affect the membrane properties. In contrast, oligomeric Bax lowered the breakthrough force of the membrane, which in the context of pore formation, implies a lowering of the line tension at the edge of the pore.
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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.
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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.
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Abstract
Apoptosis is a form of programmed cell death that is critical for basic human development and physiology. One of the more important surprises in cell biology in the last two decades is the extent to which mitochondria represent a physical point of convergence for many apoptosis-inducing signals in mammalian cells. Mitochondria not only adjudicate the decision of whether or not to commit to cell death, but also release toxic proteins culminating in widespread proteolysis, nucleolysis, and cell engulfment. Interactions among BCL-2 family proteins at the mitochondrial outer membrane control the release of these toxic proteins and, by extension, control cellular commitment to apoptosis. This pathway is particularly relevant to cancer treatment, as most cancer chemotherapies trigger mitochondrial-mediated apoptosis. In this Review, we discuss recent advances in the BCL-2 family interactions, their control by upstream factors, and how the mitochondria itself alters these interactions. We also highlight recent clinical insights into mitochondrial-mediated apoptosis and novel cancer therapies that exploit this pathway.
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Affiliation(s)
- Patrick D Bhola
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Anthony Letai
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
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36
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Conformational Heterogeneity of Bax Helix 9 Dimer for Apoptotic Pore Formation. Sci Rep 2016; 6:29502. [PMID: 27381287 PMCID: PMC4933972 DOI: 10.1038/srep29502] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 06/20/2016] [Indexed: 11/27/2022] Open
Abstract
Helix α9 of Bax protein can dimerize in the mitochondrial outer membrane (MOM) and lead to apoptotic pores. However, it remains unclear how different conformations of the dimer contribute to the pore formation on the molecular level. Thus we have investigated various conformational states of the α9 dimer in a MOM model — using computer simulations supplemented with site-specific mutagenesis and crosslinking of the α9 helices. Our data not only confirmed the critical membrane environment for the α9 stability and dimerization, but also revealed the distinct lipid-binding preference of the dimer in different conformational states. In our proposed pathway, a crucial iso-parallel dimer that mediates the conformational transition was discovered computationally and validated experimentally. The corroborating evidence from simulations and experiments suggests that, helix α9 assists Bax activation via the dimer heterogeneity and interactions with specific MOM lipids, which eventually facilitate proteolipidic pore formation in apoptosis regulation.
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Tajeddine N. How do reactive oxygen species and calcium trigger mitochondrial membrane permeabilisation? Biochim Biophys Acta Gen Subj 2016; 1860:1079-88. [DOI: 10.1016/j.bbagen.2016.02.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 02/16/2016] [Accepted: 02/22/2016] [Indexed: 10/22/2022]
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Sathappa M, Alder NN. The ionization properties of cardiolipin and its variants in model bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1362-72. [PMID: 26965987 DOI: 10.1016/j.bbamem.2016.03.007] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/25/2016] [Accepted: 03/03/2016] [Indexed: 01/01/2023]
Abstract
The anionic phospholipid cardiolipin has an unusual dimeric structure with a two-phosphate headgroup and four acyl chains. Cardiolipin is present in energy-transducing membranes that maintain electrochemical gradients, including most bacterial plasma membranes and the mitochondrial inner membrane, where it mediates respiratory complex assembly and activation, among many other roles. Dysfunctional biogenesis of cardiolipin is implicated in the pathogenesis of several diseases including Barth syndrome. Because cardiolipin is a dominant anionic lipid in energy-conserving membranes, its headgroup is a major contributor to surface charge density and the bilayer electrostatic profile. However, the proton dissociation behavior of its headgroup remains controversial. In one model, the pKa values of the phosphates differ by several units and the headgroup exists as a monoanion at physiological pH. In another model, both phosphates ionize as strong acids with low pKa values and the headgroup exists in dianionic form at physiological pH. Using independent electrokinetic and spectroscopic approaches, coupled with analysis using Gouy-Chapman-Stern formalism, we have analyzed the ionization properties of cardiolipin within biologically relevant lipid bilayer model systems. We show that both phosphates of the cardiolipin headgroup show strong ionization behavior with low pKa values. Moreover, cardiolipin variants lacking structural features proposed to be required to maintain disparate pKa values--namely the secondary hydroxyl on the central glycerol or a full complement of four acyl chains--were shown to have ionization behavior identical to intact cardiolipin. Hence, these results indicate that within the physiological pH range, the cardiolipin headgroup is fully ionized as a dianion. We discuss the implications of these results with respect to the role of cardiolipin in defining membrane surface potential, activating respiratory complexes, and modulating membrane curvature.
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Affiliation(s)
- Murugappan Sathappa
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, United States
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, United States.
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Lidman M, Pokorná Š, Dingeldein APG, Sparrman T, Wallgren M, Šachl R, Hof M, Gröbner G. The oxidized phospholipid PazePC promotes permeabilization of mitochondrial membranes by Bax. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1288-97. [PMID: 26947183 DOI: 10.1016/j.bbamem.2016.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 02/24/2016] [Accepted: 03/02/2016] [Indexed: 12/25/2022]
Abstract
Mitochondria play a crucial role in programmed cell death via the intrinsic apoptotic pathway, which is tightly regulated by the B-cell CLL/lymphoma-2 (Bcl-2) protein family. Intracellular oxidative stress causes the translocation of Bax, a pro-apoptotic family member, to the mitochondrial outer membrane (MOM) where it induces membrane permeabilization. Oxidized phospholipids (OxPls) generated in the MOM during oxidative stress directly affect the onset and progression of mitochondria-mediated apoptosis. Here we use MOM-mimicking lipid vesicles doped with varying concentrations of 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC), an OxPl species known to significantly enhance Bax-membrane association, to investigate three key aspects of Bax's action at the MOM: 1) induction of Bax pores in membranes without additional mediator proteins, 2) existence of a threshold OxPl concentration required for Bax-membrane action and 3) mechanism by which PazePC disturbs membrane organization to facilitate Bax penetration. Fluorescence leakage studies revealed that Bax-induced leakage, especially its rate, increased with the vesicles' PazePC content without any detectable threshold neither for OxPl nor Bax. Moreover, the leakage rate correlated with the Bax to lipid ratio and the PazePC content. Solid state NMR studies and calorimetric experiments on the lipid vesicles confirmed that OxPl incorporation disrupted the membrane's organization, enabling Bax to penetrate into the membrane. In addition, 15N cross polarization (CP) and insensitive nuclei enhanced by polarization transfer (INEPT) MAS NMR experiments using uniformly (15)N-labeled Bax revealed dynamically restricted helical segments of Bax embedded in the membrane, while highly flexible protein segments were located outside or at the membrane surface.
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Affiliation(s)
- Martin Lidman
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden
| | - Šárka Pokorná
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic; Department of Biochemistry, Charles University, Hlavova 8, 128 40 Prague 2, Czech Republic
| | | | - Tobias Sparrman
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden
| | - Marcus Wallgren
- Department of Medical Chemistry and Biophysics, University of Umeå, SE-901 87 Umeå, Sweden
| | - Radek Šachl
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Martin Hof
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v. v. i., Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Gerhard Gröbner
- Department of Chemistry, University of Umeå, SE-901 87 Umeå, Sweden.
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Bleicken S, Hofhaus G, Ugarte-Uribe B, Schröder R, García-Sáez AJ. cBid, Bax and Bcl-xL exhibit opposite membrane remodeling activities. Cell Death Dis 2016; 7:e2121. [PMID: 26913610 PMCID: PMC4849160 DOI: 10.1038/cddis.2016.34] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 01/20/2016] [Accepted: 01/25/2016] [Indexed: 12/19/2022]
Abstract
The proteins of the Bcl-2 family have a crucial role in mitochondrial outer membrane permeabilization during apoptosis and in the regulation of mitochondrial dynamics. Current models consider that Bax forms toroidal pores at mitochondria that are responsible for the release of cytochrome c, whereas Bcl-xL inhibits pore formation. However, how Bcl-2 proteins regulate mitochondrial fission and fusion remains poorly understood. By using a systematic analysis at the single vesicle level, we found that cBid, Bax and Bcl-xL are able to remodel membranes in different ways. cBid and Bax induced a reduction in vesicle size likely related to membrane tethering, budding and fission, besides membrane permeabilization. Moreover, they are preferentially located at highly curved membranes. In contrast, Bcl-xL not only counterbalanced pore formation but also membrane budding and fission. Our findings support a mechanism of action by which cBid and Bax induce or stabilize highly curved membranes including non-lamellar structures. This molecular activity reduces the energy for membrane remodeling, which is a necessary step in toroidal pore formation, as well as membrane fission and fusion, and provides a common mechanism that links the two main functions of Bcl-2 proteins.
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Affiliation(s)
- S Bleicken
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - G Hofhaus
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - B Ugarte-Uribe
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
| | - R Schröder
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, Heidelberg, 69120, Germany
| | - A J García-Sáez
- Membrane Biophysics, Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, Stuttgart 70569, Germany.,German Cancer Research Center, Im Neuenheimer Feld 267, Heidelberg 69120, Germany.,Membrane Biophysics, Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, Tübingen 72076, Germany
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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.
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Zhang Z, Subramaniam S, Kale J, Liao C, Huang B, Brahmbhatt H, Condon SGF, Lapolla SM, Hays FA, Ding J, He F, Zhang XC, Li J, Senes A, Andrews DW, Lin J. BH3-in-groove dimerization initiates and helix 9 dimerization expands Bax pore assembly in membranes. EMBO J 2015; 35:208-36. [PMID: 26702098 DOI: 10.15252/embj.201591552] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 11/18/2015] [Indexed: 01/08/2023] Open
Abstract
Pro-apoptotic Bax induces mitochondrial outer membrane permeabilization (MOMP) by forming oligomers through a largely undefined process. Using site-specific disulfide crosslinking, compartment-specific chemical labeling, and mutational analysis, we found that activated integral membrane Bax proteins form a BH3-in-groove dimer interface on the MOM surface similar to that observed in crystals. However, after the α5 helix was released into the MOM, the remaining interface with α2, α3, and α4 helices was rearranged. Another dimer interface was formed inside the MOM by two intersected or parallel α9 helices. Combinations of these interfaces generated oligomers in the MOM. Oligomerization was initiated by BH3-in-groove dimerization, without which neither the other dimerizations nor MOMP occurred. In contrast, α9 dimerization occurred downstream and was required for release of large but not small proteins from mitochondria. Moreover, the release of large proteins was facilitated by α9 insertion into the MOM and localization to the pore rim. Therefore, the BH3-in-groove dimerization on the MOM nucleates the assembly of an oligomeric Bax pore that is enlarged by α9 dimerization at the rim.
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Affiliation(s)
- Zhi Zhang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | | | - Justin Kale
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Chenyi Liao
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Bo Huang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Hetal Brahmbhatt
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Samson G F Condon
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Suzanne M Lapolla
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Franklin A Hays
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jingzhen Ding
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Feng He
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xuejun C Zhang
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jianing Li
- Department of Chemistry, University of Vermont, Burlington, VT, USA
| | - Alessandro Senes
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - David W Andrews
- Biological Sciences, Sunnybrook Research Institute, Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Jialing Lin
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA Peggy and Charles Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
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Wang Y, Wang R, Wang Y, Peng R, Wu Y, Yuan Y. Ginkgo biloba extract mitigates liver fibrosis and apoptosis by regulating p38 MAPK, NF-κB/IκBα, and Bcl-2/Bax signaling. DRUG DESIGN DEVELOPMENT AND THERAPY 2015; 9:6303-17. [PMID: 26664050 PMCID: PMC4671772 DOI: 10.2147/dddt.s93732] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Background Liver fibrosis is the consequence of diverse liver injuries and can eventually develop into liver cirrhosis. Ginkgo biloba extract (GBE) is an extract from dried ginkgo leaves that has many pharmacological effects because of its various ingredients and has been shown to be hepatoprotective. Purpose and methods Aimed to investigate the underlying protective mechanisms of GBE on carbon tetrachloride (CCl4)-induced liver fibrosis in rats. Male Sprague Dawley rats were randomly divided into four groups: control group (C), model group (M), low-dose group (L), and high-dose group (H). Liver fibrosis was induced by CCl4 groups M, L, and H: group C was administered saline. In addition, GBE at different doses was used to treat groups L and H. Results The results of hematoxylin and eosin staining, Masson’s trichrome staining, a liver function index, and a liver fibrosis index showed that GBE application noticeably mitigated fibrosis and improved the function of the liver. The western blotting and immunohistochemistry analyses indicated that GBE reduced liver fibrosis not only by inhibiting p38 MAPK and NF-κBp65 via inhibition of IκBα degradation but also by inhibiting hepatocyte apoptosis via downregulation of Bax, upregulation of Bcl-2, and subsequent inhibition of caspase-3 activation. Inflammation-associated factors and hepatic stellate cell (HSC)-activation markers further demonstrated that GBE could effectively inhibit HSC activation and inflammation as a result of its regulation of p38 MAPK and nuclear factor-kappa B/IκBα signaling. Conclusion Our findings indicated a novel role for GBE in the treatment of liver fibrosis. The potential mechanisms may be associated with the following signaling pathways: 1) the p38 MAPK and nuclear factor-kappa B/IκBα signaling pathways (inhibiting inflammation and HSCs activation) and 2) the Bcl-2/Bax signaling pathway (inhibiting the apoptosis of hepatocytes).
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Affiliation(s)
- Yuanyuan Wang
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Rong Wang
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Yujie Wang
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Ruqin Peng
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Yan Wu
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Yongfang Yuan
- Department of Pharmacy, Shanghai 9th People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
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Effect of Cholesterol on the Structure of a Five-Component Mitochondria-Like Phospholipid Membrane. MEMBRANES 2015; 5:664-84. [PMID: 26529029 PMCID: PMC4704005 DOI: 10.3390/membranes5040664] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 10/16/2015] [Indexed: 12/23/2022]
Abstract
Cellular membranes have a complex phospholipid composition that varies greatly depending on the organism, cell type and function. In spite of this complexity, most structural data available for phospholipid bilayers concern model systems containing only one or two different phospholipids. Here, we examine the effect of cholesterol on the structure of a complex membrane reflecting the lipid composition of mitochondrial membranes, with five different types of headgroups (phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS) and cardiolipin (CL)) and a variety of hydrocarbon tails. This particular system was chosen because elevated cholesterol contents in mitochondrial membranes have been linked to a breaking down of Bax-mediated membrane permeabilization and resistance to cancer treatments. High resolution electron density profiles were determined by X-ray reflectivity, while the area per phospholipid chain, Apc, and the chain order parameter, SX-ray, were determined by wide-angle X-ray scattering (WAXS). We show that chain order increases upon the addition of cholesterol, resulting in both a thickening of the lipid bilayer and a reduction in the average surface area per phospholipid chain. This effect, well known as cholesterol’s condensation effect, is similar, but not as pronounced as for single-component phospholipid membranes. We conclude by discussing the relevance of these findings for the insertion of the pro-apoptotic protein Bax in mitochondrial membranes with elevated cholesterol content.
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Zheng JH, Viacava Follis A, Kriwacki RW, Moldoveanu T. Discoveries and controversies in BCL-2 protein-mediated apoptosis. FEBS J 2015; 283:2690-700. [DOI: 10.1111/febs.13527] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Revised: 08/30/2015] [Accepted: 09/23/2015] [Indexed: 01/20/2023]
Affiliation(s)
- Janet H. Zheng
- Department of Structural Biology; St Jude Children's Research Hospital; Memphis TN USA
| | - Ariele Viacava Follis
- Department of Structural Biology; St Jude Children's Research Hospital; Memphis TN USA
| | - Richard W. Kriwacki
- Department of Structural Biology; St Jude Children's Research Hospital; Memphis TN USA
| | - Tudor Moldoveanu
- Department of Structural Biology; St Jude Children's Research Hospital; Memphis TN USA
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