1
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Fox CA, Ryan RO. Studies of the cardiolipin interactome. Prog Lipid Res 2022; 88:101195. [DOI: 10.1016/j.plipres.2022.101195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/28/2022] [Accepted: 09/29/2022] [Indexed: 11/30/2022]
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2
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Cytochrome c Interaction with Cardiolipin Plays a Key Role in Cell Apoptosis: Implications for Human Diseases. Symmetry (Basel) 2022. [DOI: 10.3390/sym14040767] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In the cell cytochrome, c performs different functions depending on the environment in which it acts; therefore, it has been classified as a multifunction protein. When anchored to the outer side of the inner mitochondrial membrane, native cytochrome c acts as a Schweitzer-StennerSchweitzer-Stenner that transfers electrons from cytochrome c reductase to cytochrome c oxidase in the respiratory chain. On the other hand, to interact with cardiolipin (one of the phospholipids making up the mitochondrial membrane) and form the cytochrome c/cardiolipin complex in the apoptotic process, the protein reorganizes its structure into a non-native state characterized by different asymmetry. The formation of the cytochrome c/cardiolipin complex is a fundamental step of the apoptotic pathway, since the structural rearrangement induces peroxidase activity in cytochrome c, the subsequent permeabilization of the membrane, and the release of the free protein into the cytoplasm, where cytochrome c activates the apoptotic process. Apoptosis is closely related to the pathogenesis of neoplastic, neurodegenerative and cardiovascular diseases; in this contest, the biosynthesis and remodeling of cardiolipin are crucial for the regulation of the apoptotic process. Since the role of cytochrome c as a promoter of apoptosis strictly depends on the non-native conformation(s) that the protein acquires when bound to the cardiolipin and such event leads to cytochrome c traslocation into the cytosol, the structural and functional properties of the cytochrome c/cardiolipin complex in cell fate will be the focus of the present review.
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Petit PX, Ardilla-Osorio H, Penalvia L, Nathan E. R. Tafazzin Mutation Affecting Cardiolipin Leads to Increased Mitochondrial Superoxide Anions and Mitophagy Inhibition in Barth Syndrome. Cells 2020; 9:cells9102333. [PMID: 33096711 PMCID: PMC7589545 DOI: 10.3390/cells9102333] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 01/01/2023] Open
Abstract
Tafazzin is a phospholipid transacylase that catalyzes the remodeling of cardiolipin, a mitochondrial phospholipid required for oxidative phosphorylation. Mutations of the tafazzin gene cause Barth syndrome, which is characterized by mitochondrial dysfunction and dilated cardiomyopathy, leading to premature death. However, the molecular mechanisms underlying the cause of mitochondrial dysfunction in Barth syndrome remain poorly understood. We again highlight the fact that the tafazzin deficiency is also linked to defective oxidative phosphorylation associated with oxidative stress. All the mitochondrial events are positioned in a context where mitophagy is a key element in mitochondrial quality control. Here, we investigated the role of tafazzin in mitochondrial homeostasis dysregulation and mitophagy alteration. Using a HeLa cell model of tafazzin deficiency, we show that dysregulation of tafazzin in HeLa cells induces alteration of mitophagy. Our findings provide some additional insights into mitochondrial dysfunction associated with Barth syndrome, but also show that mitophagy inhibition is concomitant with apoptosis dysfunction through the inability of abnormal mitochondrial cardiolipin to assume its role in cytoplasmic signal transduction. Our work raises hope that pharmacological manipulation of the mitophagic pathway together with mitochondrially targeted antioxidants may provide new insights leading to promising treatment for these highly lethal conditions.
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Affiliation(s)
- Patrice X. Petit
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
- Correspondence: or ; Tel.: +33(0)6-78-24-80-87
| | - Hector Ardilla-Osorio
- Laboratoire Cellules Souches et Prions, INSERM-S 1124, Université de Paris—Campus Saint-Germain, 45 rue des Saints Pères, 75006 Paris, France;
| | - Lucile Penalvia
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
| | - Rainey Nathan E.
- SSPIN Saints-Pères Paris Institut de Neurosciences, CNRS UMR 8003, “Mitochondria, Apoptosis and Autophagy Signalling” Université de Paris—Campus Saint-Germain, 45 rue des Saints-Pères, 75006 Paris, France; (L.P.); (R.N.E.)
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Wheel and Deal in the Mitochondrial Inner Membranes: The Tale of Cytochrome c and Cardiolipin. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:6813405. [PMID: 32377304 PMCID: PMC7193304 DOI: 10.1155/2020/6813405] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 02/28/2020] [Indexed: 12/15/2022]
Abstract
Cardiolipin oxidation and degradation by different factors under severe cell stress serve as a trigger for genetically encoded cell death programs. In this context, the interplay between cardiolipin and another mitochondrial factor—cytochrome c—is a key process in the early stages of apoptosis, and it is a matter of intense research. Cytochrome c interacts with lipid membranes by electrostatic interactions, hydrogen bonds, and hydrophobic effects. Experimental conditions (including pH, lipid composition, and post-translational modifications) determine which specific amino acid residues are involved in the interaction and influence the heme iron coordination state. In fact, up to four binding sites (A, C, N, and L), driven by different interactions, have been reported. Nevertheless, key aspects of the mechanism for cardiolipin oxidation by the hemeprotein are well established. First, cytochrome c acts as a pseudoperoxidase, a process orchestrated by tyrosine residues which are crucial for peroxygenase activity and sensitivity towards oxidation caused by protein self-degradation. Second, flexibility of two weakest folding units of the hemeprotein correlates with its peroxidase activity and the stability of the iron coordination sphere. Third, the diversity of the mode of interaction parallels a broad diversity in the specific reaction pathway. Thus, current knowledge has already enabled the design of novel drugs designed to successfully inhibit cardiolipin oxidation.
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El-Hafidi M, Correa F, Zazueta C. Mitochondrial dysfunction in metabolic and cardiovascular diseases associated with cardiolipin remodeling. Biochim Biophys Acta Mol Basis Dis 2020; 1866:165744. [PMID: 32105822 DOI: 10.1016/j.bbadis.2020.165744] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 01/21/2020] [Accepted: 02/20/2020] [Indexed: 02/07/2023]
Abstract
Cardiolipin (CL) is an acidic phospholipid almost exclusively found in the inner mitochondrial membrane, that not only stabilizes the structure and function of individual components of the mitochondrial electron transport chain, but regulates relevant mitochondrial processes, like mitochondrial dynamics and cristae structure maintenance among others. Alterations in CL due to peroxidation, correlates with loss of such mitochondrial activities and disease progression. In this review it is recapitulated the current state of knowledge of the role of cardiolipin remodeling associated with mitochondrial dysfunction in metabolic and cardiovascular diseases.
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Affiliation(s)
- Mohammed El-Hafidi
- Departamento de Biomedicina Cardiovascular, Instituto Nacional de Cardiología I. Ch. 14080, Ciudad de México, México
| | - Francisco Correa
- Departamento de Biomedicina Cardiovascular, Instituto Nacional de Cardiología I. Ch. 14080, Ciudad de México, México
| | - Cecilia Zazueta
- Departamento de Biomedicina Cardiovascular, Instituto Nacional de Cardiología I. Ch. 14080, Ciudad de México, México.
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Flores-Romero H, Ros U, García-Sáez AJ. A lipid perspective on regulated cell death. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2019; 351:197-236. [PMID: 32247580 DOI: 10.1016/bs.ircmb.2019.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Lipids are fundamental to life as structural components of cellular membranes and for signaling. They are also key regulators of different cellular processes such as cell division, proliferation, and death. Regulated cell death (RCD) requires the engagement of lipids and lipid metabolism for the initiation and execution of its killing machinery. The permeabilization of lipid membranes is a hallmark of RCD that involves, for each kind of cell death, a unique lipid profile. While the permeabilization of the mitochondrial outer membrane allows the release of apoptotic factors to the cytosol during apoptosis, permeabilization of the plasma membrane facilitates the release of intracellular content in other nonapoptotic types of RCD like necroptosis and ferroptosis. Lipids and lipid membranes are important accessory molecules required for the activation of protein executors of cell death such as BAX in apoptosis and MLKL in necroptosis. Peroxidation of membrane phospholipids and the subsequent membrane destabilization is a prerequisite to ferroptosis. Here, we discuss how lipids are essential players in apoptosis, the most common form of RCD, and also their role in necroptosis and ferroptosis. Altogether, we aim to highlight the contribution of lipids and membrane dynamics in cell death regulation.
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Affiliation(s)
- Hector Flores-Romero
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Uris Ros
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, Eberhard-Karls-Universität Tübingen, Tübingen, Germany.
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7
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Camilleri A, Ghio S, Caruana M, Weckbecker D, Schmidt F, Kamp F, Leonov A, Ryazanov S, Griesinger C, Giese A, Cauchi RJ, Vassallo N. Tau-induced mitochondrial membrane perturbation is dependent upon cardiolipin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183064. [PMID: 31521630 DOI: 10.1016/j.bbamem.2019.183064] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 08/26/2019] [Accepted: 09/10/2019] [Indexed: 01/14/2023]
Abstract
Misfolding and aggregate formation by the tau protein has been closely related with neurotoxicity in a large group of human neurodegenerative disorders, which includes Alzheimer's disease. Here, we investigate the membrane-active properties of tau oligomers on mitochondrial membranes, using minimalist in vitro model systems. Thus, exposure of isolated mitochondria to oligomeric tau evoked a disruption of mitochondrial membrane integrity, as evidenced by a combination of organelle swelling, efflux of cytochrome c and loss of the mitochondrial membrane potential. Tau-induced mitochondrial dysfunction occurred independently of the mitochondrial permeability transition (mPT) pore complex. Notably, mitochondria were rescued by pre-incubation with 10-N-nonyl acridine orange (NAO), a molecule that specifically binds cardiolipin (CL), the signature phospholipid of mitochondrial membranes. Additionally, NAO prevented direct binding of tau oligomers to isolated mitochondria. At the same time, tau proteins exhibited high affinity to CL-enriched membranes, whilst permeabilisation of lipid vesicles also strongly correlated with CL content. Intriguingly, using single-channel electrophysiology, we could demonstrate the formation of non-selective ion-conducting tau nanopores exhibiting multilevel conductances in mito-mimetic bilayers. Taken together, the data presented here advances a scenario in which toxic cytosolic entities of tau protein would target mitochondrial organelles by associating with their CL-rich membrane domains, leading to membrane poration and compromised mitochondrial structural integrity.
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Affiliation(s)
- Angelique Camilleri
- Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Stephanie Ghio
- Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Mario Caruana
- Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | | | - Felix Schmidt
- Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Munich, Germany
| | - Frits Kamp
- Biomedical Center-BMC, Metabolic Biochemistry, Ludwig-Maximilians-University, Munich, Germany
| | - Andrei Leonov
- MODAG GmbH, Wendelsheim, Germany; Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Sergey Ryazanov
- Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian Griesinger
- Department of NMR Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Armin Giese
- Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Munich, Germany
| | - Ruben J Cauchi
- Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta
| | - Neville Vassallo
- Department of Physiology and Biochemistry, Centre for Molecular Medicine and Biobanking, University of Malta, Msida, Malta.
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Ma ZW, Liu DX. Humanin decreases mitochondrial membrane permeability by inhibiting the membrane association and oligomerization of Bax and Bid proteins. Acta Pharmacol Sin 2018; 39:1012-1021. [PMID: 29265109 DOI: 10.1038/aps.2017.169] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Accepted: 10/18/2017] [Indexed: 12/13/2022] Open
Abstract
Humanin (HN) is a 24-residue peptide identified from the brain of a patient with Alzheimer's disease (AD). HN has been found to protect against neuronal insult caused by Aβ peptides or transfection of familial AD mutant genes. In order to elucidate the molecular mechanisms of HN neuroprotection, we explored the effects of HN on the association of Bax or Bid with lipid bilayers and their oligomerization in the membrane. By using single-molecule fluorescence and Förster resonance energy transfer techniques, we showed that Bax was mainly present as monomers, dimers and tetramers in lipid bilayers, while truncated Bid (tBid) enhanced the membrane association and tetramerization of Bax. HN (100 nmol/L) inhibited the self-association and tBid-activated association of Bax with the bilayers, and significantly decreased the proportion of Bax in tetramers. Furthermore, HN inhibited Bid translocation to lipid bilayers. HN could bind with Bax and Bid either in solution or in the membrane. However, HN could not pull the proteins out of the membrane. Based on these results, we propose that HN binds to Bax and cBid in solution and inhibits their translocation to the membrane. Meanwhile, HN interacts with the membrane-bound Bax and tBid, preventing the recruitment of cytosolic Bax and its oligomerization in the membrane. In this way, HN inhibits Bax pore formation in mitochondrial outer membrane and suppresses cytochrome c release and mitochondria-dependent apoptosis.
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Biguanides sensitize leukemia cells to ABT-737-induced apoptosis by inhibiting mitochondrial electron transport. Oncotarget 2018; 7:51435-51449. [PMID: 27283492 PMCID: PMC5239486 DOI: 10.18632/oncotarget.9843] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/22/2016] [Indexed: 02/04/2023] Open
Abstract
Metformin displays antileukemic effects partly due to activation of AMPK and subsequent inhibition of mTOR signaling. Nevertheless, Metformin also inhibits mitochondrial electron transport at complex I in an AMPK-independent manner, Here we report that Metformin and rotenone inhibit mitochondrial electron transport and increase triglyceride levels in leukemia cell lines, suggesting impairment of fatty acid oxidation (FAO). We also report that, like other FAO inhibitors, both agents and the related biguanide, Phenformin, increase sensitivity to apoptosis induction by the bcl-2 inhibitor ABT-737 supporting the notion that electron transport antagonizes activation of the intrinsic apoptosis pathway in leukemia cells. Both biguanides and rotenone induce superoxide generation in leukemia cells, indicating that oxidative damage may sensitize toABT-737 induced apoptosis. In addition, we demonstrate that Metformin sensitizes leukemia cells to the oligomerization of Bak, suggesting that the observed synergy with ABT-737 is mediated, at least in part, by enhanced outer mitochondrial membrane permeabilization. Notably, Phenformin was at least 10-fold more potent than Metformin in abrogating electron transport and increasing sensitivity to ABT-737, suggesting that this agent may be better suited for targeting hematological malignancies. Taken together, our results suggest that inhibition of mitochondrial metabolism by Metformin or Phenformin is associated with increased leukemia cell susceptibility to induction of intrinsic apoptosis, and provide a rationale for clinical studies exploring the efficacy of combining biguanides with the orally bioavailable derivative of ABT-737, Venetoclax.
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10
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Schlattner U, Tokarska-Schlattner M, Epand RM, Boissan M, Lacombe ML, Kagan VE. NME4/nucleoside diphosphate kinase D in cardiolipin signaling and mitophagy. J Transl Med 2018. [PMID: 29035377 DOI: 10.38/labinvest.2017.113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023] Open
Abstract
Mitophagy is an emerging paradigm for mitochondrial quality control and cell homeostasis. Dysregulation of mitophagy can lead to human pathologies such as neurodegenerative disorders and contributes to the aging process. Complex protein signaling cascades have been described that regulate mitophagy. We have identified a novel lipid signaling pathway that involves the phospholipid cardiolipin (CL). CL is synthesized and normally confined at the inner mitochondrial membrane. However, upon a mitophagic trigger, ie, collapse of the inner membrane potential, CL is rapidly externalized to the mitochondrial surface with the assistance of the hexameric nucleoside diphosphate kinase D (NME4, NDPK-D, or NM23-H4). In addition to its NDP kinase activity, NME4/NDPK-D shows intermembrane phospholipid transfer activity in vitro and in cellular systems, which relies on NME4/NDPK-D interaction with CL, CL-dependent crosslinking of inner and outer mitochondrial membranes by symmetrical, hexameric NME4/NDPK-D, and a putative NME4/NDPK-D-based CL-transfer pathway. CL exposed at the mitochondrial surface then serves as an 'eat me' signal for the mitophagic machinery; it is recognized by the LC3 receptor of autophagosomes, targeting the dysfunctional mitochondrion to lysosomal degradation. Similar NME4-supported CL externalization is likely also involved in apoptosis and inflammatory reactions.
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Affiliation(s)
- Uwe Schlattner
- University Grenoble Alpes, Inserm, Laboratory of Fundamental and Applied Bioenergetics (LBFA) and SFR Environmental and Systems Biology (BEeSy), Grenoble, France
| | - Malgorzata Tokarska-Schlattner
- University Grenoble Alpes, Inserm, Laboratory of Fundamental and Applied Bioenergetics (LBFA) and SFR Environmental and Systems Biology (BEeSy), Grenoble, France
| | - Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
| | - Mathieu Boissan
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, UMRS938, Saint-Antoine Research Center, Paris, France
- Hôpitaux Universitaires Est Parisien-Tenon, Assistance Publique Hôpitaux de Paris, Laboratoire de Biochimie et Hormonologie, Paris, France
| | - Marie-Lise Lacombe
- Sorbonne Universités, UPMC Univ Paris 06, Inserm, UMRS938, Saint-Antoine Research Center, Paris, France
| | - Valerian E Kagan
- Center for Free Radical and Antioxidant Health, Department of Environmental Health, University of Pittsburgh, Pittsburgh, PA, USA
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11
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NME4/nucleoside diphosphate kinase D in cardiolipin signaling and mitophagy. J Transl Med 2018; 98:228-232. [PMID: 29035377 DOI: 10.1038/labinvest.2017.113] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 08/09/2017] [Accepted: 08/10/2017] [Indexed: 01/12/2023] Open
Abstract
Mitophagy is an emerging paradigm for mitochondrial quality control and cell homeostasis. Dysregulation of mitophagy can lead to human pathologies such as neurodegenerative disorders and contributes to the aging process. Complex protein signaling cascades have been described that regulate mitophagy. We have identified a novel lipid signaling pathway that involves the phospholipid cardiolipin (CL). CL is synthesized and normally confined at the inner mitochondrial membrane. However, upon a mitophagic trigger, ie, collapse of the inner membrane potential, CL is rapidly externalized to the mitochondrial surface with the assistance of the hexameric nucleoside diphosphate kinase D (NME4, NDPK-D, or NM23-H4). In addition to its NDP kinase activity, NME4/NDPK-D shows intermembrane phospholipid transfer activity in vitro and in cellular systems, which relies on NME4/NDPK-D interaction with CL, CL-dependent crosslinking of inner and outer mitochondrial membranes by symmetrical, hexameric NME4/NDPK-D, and a putative NME4/NDPK-D-based CL-transfer pathway. CL exposed at the mitochondrial surface then serves as an 'eat me' signal for the mitophagic machinery; it is recognized by the LC3 receptor of autophagosomes, targeting the dysfunctional mitochondrion to lysosomal degradation. Similar NME4-supported CL externalization is likely also involved in apoptosis and inflammatory reactions.
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12
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Bhere D, Tamura K, Wakimoto H, Choi SH, Purow B, Debatisse J, Shah K. microRNA-7 upregulates death receptor 5 and primes resistant brain tumors to caspase-mediated apoptosis. Neuro Oncol 2018; 20:215-224. [PMID: 29016934 PMCID: PMC5777493 DOI: 10.1093/neuonc/nox138] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Background MicroRNAs (miRs) are known to play a pivotal role in tumorigenesis, controlling cell proliferation and apoptosis. In this study, we investigated the potential of miR-7 to prime resistant tumor cells to apoptosis in glioblastoma (GBM). Methods We created constitutive and regulatable miR-7 expression vectors and utilized pharmacological inhibition of caspases and genetic loss of function to study the effect of forced expression of miR-7 on death receptor (DR) pathways in a cohort of GBM with established resistance to tumor necrosis factor apoptosis inducing ligand (TRAIL) and in patient-derived primary GBM stem cell (GSC) lines. We engineered adeno-associated virus (AAV)-miR-7 and stem cell (SC) releasing secretable (S)-TRAIL and utilized real time in vivo imaging and neuropathology to understand the effect of the combined treatment of AAV-miR-7 and SC-S-TRAIL in vitro and in mouse models of GBM from TRAIL-resistant GSC. Results We show that expression of miR-7 in GBM cells results in downregulation of epidermal growth factor receptor and phosphorylated Akt and activation of nuclear factor-kappaB signaling. This leads to an upregulation of DR5, ultimately priming resistant GBM cells to DR-ligand, TRAIL-induced apoptotic cell death. In vivo, a single administration of AAV-miR-7 significantly decreases tumor volumes, upregulates DR5, and enables SC-delivered S-TRAIL to eradicate GBM xenografts generated from patient-derived TRAIL-resistant GSC, significantly improving survival of mice. Conclusions This study identifies the unique role of miR-7 in linking cell proliferation to death pathways that can be targeted simultaneously to effectively eliminate GBM, thus presenting a promising strategy for treating GBM.
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Affiliation(s)
- Deepak Bhere
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Center for Stem Cell Therapeutics and Imaging, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Kaoru Tamura
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Hiroaki Wakimoto
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Center for Stem Cell Therapeutics and Imaging, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Sung Hugh Choi
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Center for Stem Cell Therapeutics and Imaging, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
| | - Benjamin Purow
- Department of Neurology, University of Virginia, Charlottesville, Virginia
| | - Jeremy Debatisse
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Khalid Shah
- Center for Stem Cell Therapeutics and Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts
- Center for Stem Cell Therapeutics and Imaging, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
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Shimasaki K, Watanabe-Takahashi M, Umeda M, Funamoto S, Saito Y, Noguchi N, Kumagai K, Hanada K, Tsukahara F, Maru Y, Shibata N, Naito M, Nishikawa K. Pleckstrin homology domain of p210 BCR-ABL interacts with cardiolipin to regulate its mitochondrial translocation and subsequent mitophagy. Genes Cells 2017; 23:22-34. [PMID: 29205725 DOI: 10.1111/gtc.12544] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 10/30/2017] [Indexed: 02/05/2023]
Abstract
Chronic myeloid leukemia (CML) is caused by the chimeric protein p210 BCR-ABL encoded by a gene on the Philadelphia chromosome. Although the kinase domain of p210 BCR-ABL is an active driver of CML, the pathological role of its pleckstrin homology (PH) domain remains unclear. Here, we carried out phospholipid vesicle-binding assays to show that cardiolipin (CL), a characteristic mitochondrial phospholipid, is a unique ligand of the PH domain. Arg726, a basic amino acid in the ligand-binding region, was crucial for ligand recognition. A subset of wild-type p210 BCR-ABL that was transiently expressed in HEK293 cells was dramatically translocated from the cytosol to mitochondria in response to carbonyl cyanide m-chlorophenylhydrazone (CCCP) treatment, which induces mitochondrial depolarization and subsequent externalization of CL to the organelle's outer membrane, whereas an R726A mutant of the protein was not translocated. Furthermore, only wild-type p210 BCR-ABL, but not the R726A mutant, suppressed CCCP-induced mitophagy and subsequently enhanced reactive oxygen species production. Thus, p210 BCR-ABL can change its intracellular localization via interactions between the PH domain and CL to cope with mitochondrial damage. This suggests that p210 BCR-ABL could have beneficial effects for cancer proliferation, providing new insight into the PH domain's contribution to CML pathogenesis.
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Affiliation(s)
- Kentaro Shimasaki
- Department of Molecular Life Sciences, Graduate School of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
| | - Miho Watanabe-Takahashi
- Department of Molecular Life Sciences, Graduate School of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
| | - Masato Umeda
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Satoru Funamoto
- Department of Neuropathology, Graduate School of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
| | - Yoshiro Saito
- Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
| | - Noriko Noguchi
- Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
| | - Keigo Kumagai
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Fujiko Tsukahara
- Department of Pharmacology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Yoshiro Maru
- Department of Pharmacology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Norihito Shibata
- Division of Molecular Target and Gene Therapy Products, National Institute of Health Sciences, Tokyo, Japan
| | - Mikihiko Naito
- Division of Molecular Target and Gene Therapy Products, National Institute of Health Sciences, Tokyo, Japan
| | - Kiyotaka Nishikawa
- Department of Molecular Life Sciences, Graduate School of Life and Medical Sciences, Doshisha University, Kyotanabe, Kyoto, Japan
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Elliott EI, Sutterwala FS. Initiation and perpetuation of NLRP3 inflammasome activation and assembly. Immunol Rev 2016; 265:35-52. [PMID: 25879282 DOI: 10.1111/imr.12286] [Citation(s) in RCA: 597] [Impact Index Per Article: 74.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The NLRP3 (NOD-like receptor family, pyrin domain containing 3) inflammasome is a multiprotein complex that orchestrates innate immune responses to infection and cell stress through activation of caspase-1 and maturation of inflammatory cytokines pro-interleukin-1β (pro-IL-1β) and pro-IL-18. Activation of the inflammasome during infection can be protective, but unregulated NLRP3 inflammasome activation in response to non-pathogenic endogenous or exogenous stimuli can lead to unintended pathology. NLRP3 associates with mitochondria and mitochondrial molecules, and activation of the NLRP3 inflammasome in response to diverse stimuli requires cation flux, mitochondrial Ca(2+) uptake, and mitochondrial reactive oxygen species accumulation. It remains uncertain whether NLRP3 surveys mitochondrial integrity and senses mitochondrial damage, or whether mitochondria simply serve as a physical platform for inflammasome assembly. The structure of the active, caspase-1-processing NLRP3 inflammasome also requires further clarification, but recent studies describing the prion-like properties of ASC have advanced the understanding of how inflammasome assembly and caspase-1 activation occur while raising new questions regarding the propagation and resolution of NLRP3 inflammasome activation. Here, we review the mechanisms and pathways regulating NLRP3 inflammasome activation, discuss emerging concepts in NLRP3 complex organization, and expose the knowledge gaps hindering a comprehensive understanding of NLRP3 activation.
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Affiliation(s)
- Eric I Elliott
- Inflammation Program, University of Iowa, Iowa City, IA, USA; Interdisciplinary Graduate Program in Molecular and Cellular Biology, University of Iowa, Iowa City, IA, USA; Medical Scientist Training Program, University of Iowa, Iowa City, IA, USA
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15
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Ghio S, Kamp F, Cauchi R, Giese A, Vassallo N. Interaction of α-synuclein with biomembranes in Parkinson's disease--role of cardiolipin. Prog Lipid Res 2015; 61:73-82. [PMID: 26703192 DOI: 10.1016/j.plipres.2015.10.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 10/14/2015] [Accepted: 10/30/2015] [Indexed: 12/15/2022]
Abstract
One of the key molecular events underlying the pathogenesis of Parkinson's disease (PD) is the aberrant misfolding and aggregation of the α-synuclein (αS) protein into higher-order oligomers that play a key role in neuronal dysfunction and degeneration. A wealth of experimental data supports the hypothesis that the neurotoxicity of αS oligomers is intrinsically linked with their ability to interact with, and disrupt, biological membranes; especially those membranes having negatively-charged surfaces and/or lipid packing defects. Consequences of αS-lipid interaction include increased membrane tension, permeation by pore formation, membrane lysis and/or leakage due to the extraction of lipids from the bilayer. Moreover, we assert that the interaction of αS with a liquid-disordering phospholipid uniquely enriched in mitochondrial membranes, namely cardiolipin (1,3-diphosphatidyl-sn-glycerol, CL), helps target the αS oligomeric complexes intracellularly to mitochondria. Binding mediated by CL may thus represent an important pathomechanism by which cytosolic αS could physically associate with mitochondrial membranes and disrupt their integrity. Impaired mitochondrial function culminates in a cellular bioenergetic crisis and apoptotic death. To conclude, we advocate the accelerated discovery of new drugs targeting this pathway in order to restore mitochondrial function in PD.
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Affiliation(s)
- Stephanie Ghio
- Dept. of Physiology and Biochemistry, University of Malta, Msida, Malta
| | - Frits Kamp
- Biomedical Center (BMC), Biochemistry, Ludwig-Maximilians-University & DZNE, 81377 Munich, Germany
| | - Ruben Cauchi
- Dept. of Physiology and Biochemistry, University of Malta, Msida, Malta
| | - Armin Giese
- Zentrum für Neuropathologie und Prionforschung, Ludwig-Maximilians-University, 81377 Munich, Germany
| | - Neville Vassallo
- Dept. of Physiology and Biochemistry, University of Malta, Msida, Malta.
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16
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Bustillo-Zabalbeitia I, Montessuit S, Raemy E, Basañez G, Terrones O, Martinou JC. Specific interaction with cardiolipin triggers functional activation of Dynamin-Related Protein 1. PLoS One 2014; 9:e102738. [PMID: 25036098 PMCID: PMC4103857 DOI: 10.1371/journal.pone.0102738] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 06/23/2014] [Indexed: 11/18/2022] Open
Abstract
Dynamin-Related Protein 1 (Drp1), a large GTPase of the dynamin superfamily, is required for mitochondrial fission in healthy and apoptotic cells. Drp1 activation is a complex process that involves translocation from the cytosol to the mitochondrial outer membrane (MOM) and assembly into rings/spirals at the MOM, leading to membrane constriction/division. Similar to dynamins, Drp1 contains GTPase (G), bundle signaling element (BSE) and stalk domains. However, instead of the lipid-interacting Pleckstrin Homology (PH) domain present in the dynamins, Drp1 contains the so-called B insert or variable domain that has been suggested to play an important role in Drp1 regulation. Different proteins have been implicated in Drp1 recruitment to the MOM, although how MOM-localized Drp1 acquires its fully functional status remains poorly understood. We found that Drp1 can interact with pure lipid bilayers enriched in the mitochondrion-specific phospholipid cardiolipin (CL). Building on our previous study, we now explore the specificity and functional consequences of this interaction. We show that a four lysine module located within the B insert of Drp1 interacts preferentially with CL over other anionic lipids. This interaction dramatically enhances Drp1 oligomerization and assembly-stimulated GTP hydrolysis. Our results add significantly to a growing body of evidence indicating that CL is an important regulator of many essential mitochondrial functions.
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Affiliation(s)
- Itsasne Bustillo-Zabalbeitia
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Sylvie Montessuit
- Department of Cell Biology, University of Geneva, Geneva, Switzerland
| | - Etienne Raemy
- Department of Cell Biology, University of Geneva, Geneva, Switzerland
| | - Gorka Basañez
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
| | - Oihana Terrones
- Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), Bilbao, Spain
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17
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Wang Y, Tjandra N. Structural insights of tBid, the caspase-8-activated Bid, and its BH3 domain. J Biol Chem 2013; 288:35840-51. [PMID: 24158446 DOI: 10.1074/jbc.m113.503680] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Bcl-2 family proteins regulate mitochondria-mediated apoptosis through intricate molecular mechanisms. One of the pro-apoptotic proteins, tBid, can induce apoptosis by promoting Bax activation, Bax homo-oligomerization, and mitochondrial outer membrane permeabilization. Association of tBid on the mitochondrial outer membrane is key to its biological function. Therefore knowing the conformation of tBid on the membrane will be the first step toward understanding its crucial role in triggering apoptosis. Here, we present NMR characterization of the structure and dynamics of human tBid in 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-RAC-(1-glycerol)] micelles. Our data showed that tBid is monomeric with six well defined α-helices in the micelles. Compared with the full-length Bid structure, a longer flexible loop between tBid helix α4 and α5 was observed. Helices in tBid do not pack into a compact-fold but form an extended structure with a C-shape configuration in the micelles. All six tBid helices were shown to interact with LPPG micelles, with helix α6 and α7 being more embedded. Of note, the BH3-containing helix α3, which was previously believed to be exposed above the membrane surface, is also membrane associated, suggesting an "on the membrane" binding mode for tBid interaction with Bax. Our data provided structural details on the membrane-associated state of tBid and the functional implications of its membrane-associated BH3 domain.
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Affiliation(s)
- Yu Wang
- From the Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
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18
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Emerging roles of lipids in BCL-2 family-regulated apoptosis. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1542-54. [DOI: 10.1016/j.bbalip.2013.03.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 02/28/2013] [Accepted: 03/02/2013] [Indexed: 01/06/2023]
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19
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Sawant DA, Tharakan B, Wilson RL, Stagg HW, Hunter FA, Childs EW. Regulation of tumor necrosis factor-α-induced microvascular endothelial cell hyperpermeability by recombinant B-cell lymphoma-extra large. J Surg Res 2013; 184:628-37. [PMID: 23731686 PMCID: PMC3759616 DOI: 10.1016/j.jss.2013.04.079] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/18/2013] [Accepted: 04/30/2013] [Indexed: 11/16/2022]
Abstract
BACKGROUND Tumor necrosis factor-α (TNF-α), a cytotoxic cytokine, induces endothelial cell barrier dysfunction and microvascular hyperpermeability, leading to tissue edema, a hallmark of traumatic injuries. The objective of the present study was to determine whether B-cell lymphoma-extra large (Bcl-xL), an antiapoptotic protein, would regulate and protect against TNF-α-mediated endothelial cell barrier dysfunction and microvascular hyperpermeability. METHODS Rat lung microvascular endothelial cells were grown as monolayers on Transwell membranes, and fluorescein isothiocyanate-bovine albumin flux (5 mg/mL) across the monolayer was measured fluorometrically to indicate changes in monolayer permeability. The rat lung microvascular endothelial cell adherens junctional integrity and actin cytoskeleton was studied using β-catenin immunofluorescence and rhodamine phalloidin dye, respectively. Pretreatment of caspase-8 inhibitor (Z-IETD-FMK, 100 μM) for 1 hour and transfection of Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA (10 μM) for 48 hours were performed to study their respective effects on TNF-α-induced (10 ng/mL; 1-hour treatment) monolayer permeability. Recombinant Bcl-xL protein (2.5 μg/ml) was transfected in rat lung microvascular endothelial cells for 1 hour, and its effect on permeability was demonstrated using a permeability assay. Caspase-3 activity was assayed fluorometrically. RESULTS Z-IETD-FMK pretreatment protected the adherens junctions and decreased TNF-α-induced monolayer hyperpermeability. Bcl-2-homology domain 3-interacting domain death agonist small interfering RNA transfection attenuated the TNF-α-induced increase in monolayer permeability. Recombinant Bcl-xL protein showed protection against TNF-α-induced actin stress fiber formation, an increase in caspase-3 activity, and monolayer hyperpermeability. CONCLUSIONS Our results have demonstrated the protective effects of recombinant Bcl-xL protein against TNF-α-induced endothelial cell adherens junction damage and microvascular endothelial cell hyperpermeability. These findings support the potential for Bcl-xL-based drug development against microvascular hyperpermeability and tissue edema.
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Affiliation(s)
- Devendra A. Sawant
- Department of Surgery, Morehouse School of Medicine, Atlanta, Georgia, USA
| | - Binu Tharakan
- Texas A&M Health Science Center College of Medicine and Scott & White Health Care, Temple, Texas, USA
| | - Rickesha L. Wilson
- Texas A&M Health Science Center College of Medicine and Scott & White Health Care, Temple, Texas, USA
| | - Hayden W. Stagg
- Texas A&M Health Science Center College of Medicine and Scott & White Health Care, Temple, Texas, USA
| | - Felicia A. Hunter
- Department of Surgery, Morehouse School of Medicine, Atlanta, Georgia, USA
| | - Ed W. Childs
- Department of Surgery, Morehouse School of Medicine, Atlanta, Georgia, USA
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20
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Senille V, Lelievre D, Paquet F, Garnier N, Lamb N, Legrand A, Delmas AF, Landon C. The addressing fragment of mitogaligin: first insights into functional and structural properties. Chembiochem 2013; 14:711-20. [PMID: 23532929 DOI: 10.1002/cbic.201200715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Indexed: 11/07/2022]
Abstract
Mitogaligin is a mitochondrion-targeting protein involved in cell death. The sequence of the protein is unrelated to that of any known pro- or antiapoptotic protein. Mitochondrial targeting is controlled by an internal sequence from residues 31 to 53, and although this sequence is essential and sufficient to provoke cell death, the precise mechanism of action at the mitochondrial membrane remains to be elucidated. Here, by focusing on the [31-53] fragment, we first assessed and confirmed its cell cytotoxicity by microinjection. Subsequently, with the aid of membrane models, we evaluated the impact of the membrane environment on the 3D structure of the peptide and on how the peptide is embedded and oriented within membranes. The fragment is well organized, even though it does not contain a canonical secondary structure, and adopts an interfacial location. Structural comparison with other membrane-interacting Trp-rich peptides demonstrated similarities with the antimicrobial peptide tritrpcidin.
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Affiliation(s)
- Violette Senille
- Centre de Biophysique Moléculaire, CNRS UPR4301 affiliated to the University of Orléans, Rue Charles Sadron, 45071 Orléans cedex 2, France
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21
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Caspase-8 binding to cardiolipin in giant unilamellar vesicles provides a functional docking platform for bid. PLoS One 2013; 8:e55250. [PMID: 23418437 PMCID: PMC3572128 DOI: 10.1371/journal.pone.0055250] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 12/21/2012] [Indexed: 12/28/2022] Open
Abstract
Caspase-8 is involved in death receptor-mediated apoptosis in type II cells, the proapoptotic programme of which is triggered by truncated Bid. Indeed, caspase-8 and Bid are the known intermediates of this signalling pathway. Cardiolipin has been shown to provide an anchor and an essential activating platform for caspase-8 at the mitochondrial membrane surface. Destabilisation of this platform alters receptor-mediated apoptosis in diseases such as Barth Syndrome, which is characterised by the presence of immature cardiolipin which does not allow caspase-8 binding. We used a simplified in vitro system that mimics contact sites and/or cardiolipin-enriched microdomains at the outer mitochondrial surface in which the platform consisting of caspase-8, Bid and cardiolipin was reconstituted in giant unilamellar vesicles. We analysed these vesicles by flow cytometry and confirm previous results that demonstrate the requirement for intact mature cardiolipin for caspase-8 activation and Bid binding and cleavage. We also used confocal microscopy to visualise the rupture of the vesicles and their revesiculation at smaller sizes due to alteration of the curvature following caspase-8 and Bid binding. Biophysical approaches, including Laurdan fluorescence and rupture/tension measurements, were used to determine the ability of these three components (cardiolipin, caspase-8 and Bid) to fulfil the minimal requirements for the formation and function of the platform at the mitochondrial membrane. Our results shed light on the active functional role of cardiolipin, bridging the gap between death receptors and mitochondria.
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22
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Patil VA, Greenberg ML. Cardiolipin-mediated cellular signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 991:195-213. [PMID: 23775697 DOI: 10.1007/978-94-007-6331-9_11] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
This review focuses on recent studies showing that cardiolipin (CL), a unique mitochondrial phospholipid, regulates many cellular functions and signaling pathways, both inside and outside the mitochondria. Inside the mitochondria, CL is a critical target of mitochondrial generated reactive oxygen species (ROS) and regulates signaling events related to apoptosis and aging. CL deficiency causes perturbation of signaling pathways outside the mitochondria, including the PKC-Slt2 cell integrity pathway and the high osmolarity glycerol (HOG) pathway, and is a key player in the cross-talk between the mitochondria and the vacuole. Understanding these connections may shed light on the pathology of Barth syndrome, a disorder of CL remodeling.
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Affiliation(s)
- Vinay A Patil
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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23
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PEG-liposomal oxaliplatin induces apoptosis in human colorectal cancer cells via Fas/FasL and caspase-8. Cell Biol Int 2012; 36:289-96. [PMID: 21888623 DOI: 10.1042/cbi20100825] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Since cellular uptake of PEG [poly(ethylene glycol)]-liposomal L-OHP (oxaliplatin) induces bioactive changes in CRC (colorectal cancer), we have investigated its apoptotic effect and anticancer mechanism. Human CRC SW480 cells were treated with PEG-liposomal L-OHP and a caspase-8 inhibitor [Z-IETD-FMK (benzyloxycarbonyl-Ile-Glu-Thr-dl-Asp-fluoromethylketone)]. Apoptosis was measured by FCM (flow cytometry) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. Expression of Fas/FasL and cytochrome c was detected using FCM and an immunofluorescence assay. Expression of caspase-8, Bid, caspase-9, caspase-7 and activated caspase-3 (P17) was examined by Western blot analyses. The results indicated that PEG-liposomal L-OHP (28 μg/ml L-OHP) induced marked apoptosis in SW480 cells compared with 28 μg/ml free L-OHP. The expression levels of Fas, FasL, cytochrome c, caspase-9, caspase-7 and activated caspase-3 proteins were up-regulated, with a corresponding increase in apoptosis; however, expression of caspase-8 and Bid were down-regulated as apoptosis increased. When cells were treated with Z-IETD-FMK, apoptosis was inhibited, but there was little impact on the expression of Fas, FasL, cytochrome c, Bid, caspase-9, caspase-7 and activated caspase-3. These findings indicate that PEG-liposomal L-OHP enhances the anticancer potency of the chemotherapeutic agent; moreover, Fas/FasL and caspase-8 signalling pathways play a key role in mediating PEG-liposomal L-OHP-induced apoptosis.
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24
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Bhat V, Kurouski D, Olenick MB, McDonald CB, Mikles DC, Deegan BJ, Seldeen KL, Lednev IK, Farooq A. Acidic pH promotes oligomerization and membrane insertion of the BclXL apoptotic repressor. Arch Biochem Biophys 2012; 528:32-44. [PMID: 22960132 DOI: 10.1016/j.abb.2012.08.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 08/19/2012] [Accepted: 08/20/2012] [Indexed: 01/03/2023]
Abstract
Solution pH is believed to serve as an intricate regulatory switch in the induction of apoptosis central to embryonic development and cellular homeostasis. Herein, using an array of biophysical techniques, we provide evidence that acidic pH promotes the assembly of BclXL apoptotic repressor into a megadalton oligomer with a plume-like appearance and harboring structural features characteristic of a molten globule. Strikingly, our data reveal that pH tightly modulates not only oligomerization but also ligand binding and membrane insertion of BclXL in a highly subtle manner. Thus, while oligomerization and the accompanying molten globular content of BclXL is least favorable at pH 6, both of these structural features become more pronounced under acidic and alkaline conditions. However, membrane insertion of BclXL appears to be predominantly favored under acidic conditions. In a remarkable contrast, while ligand binding to BclXL optimally occurs at pH 6, it is diminished by an order of magnitude at lower and higher pH. This reciprocal relationship between BclXL oligomerization and ligand binding lends new insights into how pH modulates functional versatility of a key apoptotic regulator and strongly argues that the molten globule may serve as an intermediate primed for membrane insertion in response to apoptotic cues.
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Affiliation(s)
- Vikas Bhat
- Department of Biochemistry and Molecular Biology, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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25
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Zhao K, Zhou H, Zhao X, Wolff DW, Tu Y, Liu H, Wei T, Yang F. Phosphatidic acid mediates the targeting of tBid to induce lysosomal membrane permeabilization and apoptosis. J Lipid Res 2012; 53:2102-2114. [PMID: 22761256 DOI: 10.1194/jlr.m027557] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Upon apoptotic stimuli, lysosomal proteases, including cathepsins and chymotrypsin, are released into cytosol due to lysosomal membrane permeabilization (LMP), where they trigger apoptosis via the lysosomal-mitochondrial pathway of apoptosis. Herein, the mechanism of LMP was investigated. We found that caspase 8-cleaved Bid (tBid) could result in LMP directly. Although Bax or Bak might modestly enhance tBid-triggered LMP, they are not necessary for LMP. To study this further, large unilamellar vesicles (LUVs), model membranes mimicking the lipid constitution of lysosomes, were used to reconstitute the membrane permeabilization process in vitro. We found that phosphatidic acid (PA), one of the major acidic phospholipids found in lysosome membrane, is essential for tBid-induced LMP. PA facilitates the insertion of tBid deeply into lipid bilayers, where it undergoes homo-oligomerization and triggers the formation of highly curved nonbilayer lipid phases. These events induce LMP via pore formation mechanisms because encapsulated fluorescein-conjugated dextran (FD)-20 was released more significantly than FD-70 or FD-250 from LUVs due to its smaller molecular size. On the basis of these data, we proposed tBid-PA interactions in the lysosomal membranes form lipidic pores and result in LMP. We further noted that chymotrypsin-cleaved Bid is more potent than tBid at binding to PA, inserting into the lipid bilayer, and promoting LMP. This amplification mechanism likely contributes to the culmination of apoptotic signaling.
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Affiliation(s)
- Kai Zhao
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China
| | - Hejiang Zhou
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China; Graduate University of Chinese Academy of Sciences, Shijingshan District, Beijing 100049, China
| | - Xingyu Zhao
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China
| | - Dennis W Wolff
- Department of Pharmacology, Creighton University School of Medicine, Omaha, NE 68178; and
| | - Yaping Tu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China; Department of Pharmacology, Creighton University School of Medicine, Omaha, NE 68178; and
| | - Huili Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Centre for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - Taotao Wei
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China.
| | - Fuyu Yang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Chaoyang District, Beijing 100101, China.
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26
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Early decrease in respiration and uncoupling event independent of cytochrome C release in PC12 cells undergoing apoptosis. Int J Cell Biol 2012; 2012:643929. [PMID: 22666257 PMCID: PMC3362053 DOI: 10.1155/2012/643929] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Accepted: 03/09/2012] [Indexed: 11/18/2022] Open
Abstract
Cytochrome c is a key molecule in mitochondria-mediated apoptosis. It also plays a pivotal role in cell respiration. The switch between these two functions occurs at the moment of its release from mitochondria. This process is therefore extremely relevant for the fate of the cell. Since cytochrome c mediates respiration, we studied the changes in respiratory chain activity during the early stages of apoptosis in order to contribute to unravel the mechanisms of cytochrome c release. We found that, during staurosporine (STS)- induced apoptosis in PC12 cells, respiration is affected before the release of cytochrome c, as shown by a decrease in the endogenous uncoupled respiration and an uncoupling event, both occurring independently of cytochrome c release. The decline in the uncoupled respiration occurs also upon Bcl-2 overexpression (which inhibits cytochrome c release), while the uncoupling event is inhibited by Bcl-2. We also observed that the first stage of nuclear condensation during STS-induced apoptosis does not depend on the release of cytochrome c into the cytosol and is a reversibile event. These findings may contribute to understand the mechanisms affecting mitochondria during the early stages of apoptosis and priming them for the release of apoptogenic factors.
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27
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Yin H, Zhu M. Free radical oxidation of cardiolipin: chemical mechanisms, detection and implication in apoptosis, mitochondrial dysfunction and human diseases. Free Radic Res 2012; 46:959-74. [PMID: 22468920 DOI: 10.3109/10715762.2012.676642] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Cardiolipin (CL) is a mitochondria-specific phospholipid and is critical for maintaining the integrity of mitochondrial membrane and mitochondrial function. CL also plays an active role in mitochondria-dependent apoptosis by interacting with cytochrome c (cyt c), tBid and other important Bcl-2 proteins. The unique structure of CL with four linoleic acid side chains in the same molecule and its cellular location make it extremely susceptible to free radical oxidation by reactive oxygen species including free radicals derived from peroxidase activity of cyt c/CL complex, singlet oxygen and hydroxyl radical. The free radical oxidation products of CL have been emerged as important mediators in apoptosis. In this review, we summarize the free radical chemical mechanisms that lead to CL oxidation, recent development in detection of oxidation products of CL by mass spectrometry and the implication of CL oxidation in mitochondria-mediated apoptosis, mitochondrial dysfunction and human diseases.
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Affiliation(s)
- Huiyong Yin
- Laboratory of Lipid Metabolism in Human Nutrition and Related Diseases, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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28
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Wong C, Anderson DJ, Lee EF, Fairlie WD, Ludlam MJC. Direct visualization of Bcl-2 family protein interactions using live cell fluorescent protein redistribution assays. Cell Death Dis 2012; 3:e288. [PMID: 22460384 PMCID: PMC5424096 DOI: 10.1038/cddis.2012.28] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bcl-2 family proteins have important roles in tumor initiation, progression and resistance to therapy. Pro-survival Bcl-2 proteins are regulated by their interactions with pro-death BH3-only proteins making these protein–protein interactions attractive therapeutic targets. Although these interactions have been extensively characterized biochemically, there is a paucity of tools to assess these interactions in cells. Here, we address this limitation by developing quantitative, high throughput microscopy assays to characterize Bcl-2 and BH3-only protein interactions in live cells. We use fluorescent proteins to label the interacting proteins of interest, enabling visualization and quantification of their mitochondria-localized interactions. Using tool compounds, we demonstrate the suitability of our assays to characterize the cellular activity of putative therapeutic molecules that target the interaction between pro-survival Bcl-2 and pro-death BH3-only proteins. In addition to the relevance of our assays for drug discovery, we anticipate that our work will contribute to an improved understanding of the mechanisms that regulate these important protein–protein interactions within the cell.
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Affiliation(s)
- C Wong
- Department of Research Oncology, Genentech, Inc., South San Francisco, CA 90480, USA
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29
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Effects of phospholipids on the functional regulation of tBID in membranes. Mol Cell Biochem 2011; 363:395-408. [PMID: 22189507 DOI: 10.1007/s11010-011-1192-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 12/13/2011] [Indexed: 10/14/2022]
Abstract
The functional interplay between tBID and phospholipids was investigated in this study. The binding of tBID to model membranes was increased by an incorporation of phosphatidylserine (PS) into the liposomes. Using limited proteolysis and mass spectrometry, two peptide regions, which correspond to Ser(100)-Arg(114) and His(89)-Arg(114) in BID, revealed the specific PS-binding site. tBID also decreased the light scattering values of PS-containing liposomes and increased the leakage of fluorescent dye encapsulated in vesicles, which suggest that tBID reduces membrane integrity by fragmentation. The membrane fragmentation by tBID was also observed using confocal and transmission electron microscopy. The activity of tBID paralleled results that were obtained with cardiolipin (CL)-containing membranes. However, other anionic phospholipids had little effect. CL- and PS-induced conformational changes of tBID were observed by circular dichroism and intrinsic fluorescence. CL and PS also stimulated the insertion of BID into lipid monolayers. tBID stimulated the leakage of Ca(2+) from purified microsomes and mitochondria in a protein concentration-dependent manner. In contrast, BID showed significantly reduced effects when compared to tBID in all of the experiments performed. These results suggest that tBID specifically interacts with PS as well as CL and decreases membrane integrity without the aid of other pro-apoptotic proteins.
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Korytowski W, Basova LV, Pilat A, Kernstock RM, Girotti AW. Permeabilization of the mitochondrial outer membrane by Bax/truncated Bid (tBid) proteins as sensitized by cardiolipin hydroperoxide translocation: mechanistic implications for the intrinsic pathway of oxidative apoptosis. J Biol Chem 2011; 286:26334-43. [PMID: 21642428 PMCID: PMC3143596 DOI: 10.1074/jbc.m110.188516] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 05/12/2011] [Indexed: 12/31/2022] Open
Abstract
Cytochrome c (cyt c) release upon oxidation of cardiolipin (CL) in the mitochondrial inner membrane (IM) under oxidative stress occurs early in the intrinsic apoptotic pathway. We postulated that CL oxidation mobilizes not only cyt c but also CL itself in the form of hydroperoxide (CLOOH) species. Relatively hydrophilic CLOOHs could assist in apoptotic signaling by translocating to the outer membrane (OM), thus promoting recruitment of the pro-apoptotic proteins truncated Bid (tBid) and Bax for generation of cyt c-traversable pores. Initial testing of these possibilities showed that CLOOH-containing liposomes were permeabilized more readily by tBid plus Ca(2+) than CL-containing counterparts. Moreover, CLOOH translocated more rapidly from IM-mimetic to OM-mimetic liposomes than CL and permitted more extensive OM permeabilization. We found that tBid bound more avidly to CLOOH-containing membranes than to CL counterparts, and binding increased with increasing CLOOH content. Permeabilization of CLOOH-containing liposomes in the presence of tBid could be triggered by monomeric Bax, consistent with tBid/Bax cooperation in pore formation. Using CL-null mitochondria from a yeast mutant, we found that tBid binding and cyt c release were dramatically enhanced by transfer acquisition of CLOOH. Additionally, we observed a pre-apoptotic IM-to-OM transfer of oxidized CL in cardiomyocytes treated with the Complex III blocker, antimycin A. These findings provide new mechanistic insights into the role of CL oxidation in the intrinsic pathway of oxidative apoptosis.
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Affiliation(s)
- Witold Korytowski
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
- the Institute of Molecular Biology, Jagiellonian University, Krakow 30-387, Poland
| | - Liana V. Basova
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Anna Pilat
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Robert M. Kernstock
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Albert W. Girotti
- From the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
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Martínez-Abundis E, Correa F, Rodríguez E, Soria-Castro E, Rodríguez-Zavala JS, Pacheco-Alvarez D, Zazueta C. A CRAC-like motif in BAX sequence: relationship with protein insertion and pore activity in liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1888-95. [PMID: 21440528 DOI: 10.1016/j.bbamem.2011.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 01/26/2011] [Accepted: 03/21/2011] [Indexed: 02/08/2023]
Abstract
Several proteins that interact with cholesterol have a highly conserved sequence, corresponding to the cholesterol recognition/interaction amino acid consensus. Since cholesterol has been proposed to modulate both oligomerization and insertion of the pro-apoptotic protein BAX, we investigated the existence of such a motif in the BAX sequence. Residues 113 to 119 of the recombinant BAX α5-helix, LFYFASK, correspond with the sequence motif described for the consensus pattern, -L/V-(X)(1-5)-Y-(X)(1-5)-R/K. Functional characterization of the point mutations, K119A, Y115F, and L113A in BAX, was performed in liposomes supplemented with cholesterol, comparing binding, integration, and pore forming activities. Our results show that the mutations Y115F and L113A changed the cholesterol-dependent insertion observed in the wild type protein. In addition, substitutions in the BAX sequence modified the concentration dependency of carboxyfluorescein release in liposomes, although neither pore activity of the wild type or of any of the mutants significantly increased in cholesterol-enriched liposomes. Thus, while it is likely that the putative CRAC motif in BAX accounts for its enhanced insertion in cholesterol-enriched liposomes; the pore forming properties of BAX did not depend on cholesterol content in the membranes, albeit those mutations changed the pore channeling activity of the protein.
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Pasternack RM, Zheng JY, Boustany NN. Detection of mitochondrial fission with orientation-dependent optical Fourier filters. Cytometry A 2011; 79:137-48. [PMID: 21265007 DOI: 10.1002/cyto.a.21011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 10/25/2010] [Accepted: 11/22/2010] [Indexed: 11/08/2022]
Abstract
We utilize a recently developed optical imaging method based on Fourier processing with Gabor-like filters to detect changes in light scattering resulting from alterations in mitochondrial structure in endothelial cells undergoing apoptosis. Imaging based on Gabor filters shows a significant decrease in the orientation of subcellular organelles at 60 to 100 minutes following apoptosis induction and concomitant with mitochondrial fragmentation observed by fluorescence. The optical scatter changes can be detected at low resolution at the whole cell level. At high resolution, we combine fluorescence imaging of the mitochondria with optical Fourier-based imaging to demonstrate that the dynamic decrease in organelle orientation measured by optical Gabor filtering is spatially associated with fluorescent mitochondria and remains largely absent from nonfluorescent subcellular regions. These results provide strong evidence that the optical Gabor responses track mitochondrial fission during apoptosis and can be used to provide label-free, rapid monitoring of this morphological process within single cells.
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Affiliation(s)
- Robert M Pasternack
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854, USA
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Giant unilamellar vesicles (GUVs) as a new tool for analysis of caspase-8/Bid-FL complex binding to cardiolipin and its functional activity. Cell Death Dis 2010; 1:e103. [PMID: 21368876 PMCID: PMC3032292 DOI: 10.1038/cddis.2010.81] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cardiolipin (CL) has recently been shown to be both an anchor and an essential activating platform for caspase-8 on mitochondria. These platforms may be at the mitochondrial contact sites in which truncated Bid (tBid) has been demonstrated to be located. A possible role for CL is to anchor caspase-8 at contact sites (between inner and outer membranes), facilitating its self-activation, Bid-full length (FL) cleavage, tBid generation (and Bax/Bak activation and oligomerization), mitochondrial destabilization and apoptosis. We have developed an in vitro system that mimics the mitochondrial membrane contact site platform. This system involves reconstituting caspase-8, Bid-FL and CL complexes in giant unilamellar vesicles (GUVs). We first validated the system by flow cytometry analysis of light-scattering properties and nonyl acridine orange staining of their CL content. Then, we used flow cytometry analysis to detect the binding of active caspase-8 to CL and the subsequent truncation of bound Bid-FL. The tBid generated interacts with CL and induces GUV breakage and partial re-vesiculation at a smaller size. Our findings suggest an active role for mitochondrial membrane lipids, particularly CL, in binding active caspase-8 and providing a docking site for Bid-FL. This phenomenon was previously only poorly documented and substantially underestimated.
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Dubyak GR. Charge of the mito brigade. Focus on "Changes in mitochondrial surface charge mediate recruitment of signaling molecules during apoptosis". Am J Physiol Cell Physiol 2010; 300:C11-3. [PMID: 21068361 DOI: 10.1152/ajpcell.00454.2010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Lindsay J, Esposti MD, Gilmore AP. Bcl-2 proteins and mitochondria--specificity in membrane targeting for death. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:532-9. [PMID: 21056595 DOI: 10.1016/j.bbamcr.2010.10.017] [Citation(s) in RCA: 215] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 10/22/2010] [Accepted: 10/27/2010] [Indexed: 01/10/2023]
Abstract
The localization and control of Bcl-2 proteins on mitochondria is essential for the intrinsic pathway of apoptosis. Anti-apoptotic Bcl-2 proteins reside on the outer mitochondrial membrane (OMM) and prevent apoptosis by inhibiting the activation of the pro-apoptotic family members Bax and Bak. The Bcl-2 subfamily of BH3-only proteins can either inhibit the anti-apoptotic proteins or directly activate Bax or Bak. How these proteins interact with each other, the mitochondrial surface and within the OMM are complex processes we are only beginning to understand. However, these interactions are fundamental for the transduction of apoptotic signals to mitochondria and the subsequent release of caspase activating factors into the cytosol. In this review we will discuss our knowledge of how Bcl-2 proteins are directed to mitochondria in the first place, a crucial but poorly understood aspect of their regulation. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
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Affiliation(s)
- Jennefer Lindsay
- Wellcome Trust Centre for Cell Matrix Research, Faculty of Life Sciences The University of Manchester, UK.
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