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Rouchidane Eyitayo A, Giraud MF, Daury L, Lambert O, Gonzalez C, Manon S. Cell-free synthesis and reconstitution of Bax in nanodiscs: Comparison between wild-type Bax and a constitutively active mutant. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184075. [PMID: 36273540 DOI: 10.1016/j.bbamem.2022.184075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 10/11/2022] [Accepted: 10/16/2022] [Indexed: 11/06/2022]
Abstract
Bax is a major player in the mitochondrial pathway of apoptosis, by making the Outer Mitochondrial Membrane (OMM) permeable to various apoptogenic factors, including cytochrome c. In order to get further insight into the structure and function of Bax when it is inserted in the OMM, we attempted to reconstitute Bax in nanodiscs. Cell-free protein synthesis in the presence of nanodiscs did not yield Bax-containing nanodiscs, but it provided a simple way to purify full-length Bax without any tag. Purified wild-type Bax (BaxWT) and a constitutively active mutant (BaxP168A) displayed biochemical properties that were in line with previous characterizations following their expression in yeast and human cells followed by their reconstitution into liposomes. Both Bax variants were then reconstituted in nanodiscs. Size exclusion chromatography, dynamic light scattering and transmission electron microscopy showed that nanodiscs formed with BaxP168A were larger than nanodiscs formed with BaxWT. This was consistent with the hypothesis that BaxP168A was reconstituted in nanodiscs as an active oligomer.
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Affiliation(s)
| | - Marie-France Giraud
- IBGC, UMR5095, CNRS, Université de Bordeaux, France; CBMN, UMR5248, CNRS, Université de Bordeaux, France
| | | | | | | | - Stéphen Manon
- IBGC, UMR5095, CNRS, Université de Bordeaux, France.
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Marwarha G, Røsand Ø, Slagsvold KH, Høydal MA. GSK3β Inhibition Is the Molecular Pivot That Underlies the Mir-210-Induced Attenuation of Intrinsic Apoptosis Cascade during Hypoxia. Int J Mol Sci 2022; 23:ijms23169375. [PMID: 36012628 PMCID: PMC9409400 DOI: 10.3390/ijms23169375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/09/2022] [Accepted: 08/17/2022] [Indexed: 11/16/2022] Open
Abstract
Apoptotic cell death is a deleterious consequence of hypoxia-induced cellular stress. The master hypoxamiR, microRNA-210 (miR-210), is considered the primary driver of the cellular response to hypoxia stress. We have recently demonstrated that miR-210 attenuates hypoxia-induced apoptotic cell death. In this paper, we unveil that the miR-210-induced inhibition of the serine/threonine kinase Glycogen Synthase Kinase 3 beta (GSK3β) in AC-16 cardiomyocytes subjected to hypoxia stress underlies the salutary protective response of miR-210 in mitigating the hypoxia-induced apoptotic cell death. Using transient overexpression vectors to augment miR-210 expression concomitant with the ectopic expression of the constitutive active GSK3β S9A mutant (ca-GSK3β S9A), we exhaustively performed biochemical and molecular assays to determine the status of the hypoxia-induced intrinsic apoptosis cascade. Caspase-3 activity analysis coupled with DNA fragmentation assays cogently demonstrate that the inhibition of GSK3β kinase activity underlies the miR-210-induced attenuation in the hypoxia-driven apoptotic cell death. Further elucidation and delineation of the upstream cellular events unveiled an indispensable role of the inhibition of GSK3β kinase activity in mediating the miR-210-induced mitigation of the hypoxia-driven BAX and BAK insertion into the outer mitochondria membrane (OMM) and the ensuing Cytochrome C release into the cytosol. Our study is the first to unveil that the inhibition of GSK3β kinase activity is indispensable in mediating the miR-210-orchestrated protective cellular response to hypoxia-induced apoptotic cell death.
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Affiliation(s)
- Gurdeep Marwarha
- Group of Molecular and Cellular Cardiology, Department of Circulation and Medical Imaging, Faculty of Medicine and Health, Norwegian University of Science and Technology (NTNU), 7034 Trondheim, Norway
| | - Øystein Røsand
- Group of Molecular and Cellular Cardiology, Department of Circulation and Medical Imaging, Faculty of Medicine and Health, Norwegian University of Science and Technology (NTNU), 7034 Trondheim, Norway
| | - Katrine Hordnes Slagsvold
- Group of Molecular and Cellular Cardiology, Department of Circulation and Medical Imaging, Faculty of Medicine and Health, Norwegian University of Science and Technology (NTNU), 7034 Trondheim, Norway
- Department of Cardiothoracic Surgery, St. Olavs University Hospital, 7030 Trondheim, Norway
| | - Morten Andre Høydal
- Group of Molecular and Cellular Cardiology, Department of Circulation and Medical Imaging, Faculty of Medicine and Health, Norwegian University of Science and Technology (NTNU), 7034 Trondheim, Norway
- Correspondence: ; Tel.: +47-48134843
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Hakiminia B, Alikiaii B, Khorvash F, Mousavi S. Oxidative stress and mitochondrial dysfunction following traumatic brain injury: From mechanistic view to targeted therapeutic opportunities. Fundam Clin Pharmacol 2022; 36:612-662. [PMID: 35118714 DOI: 10.1111/fcp.12767] [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: 08/05/2021] [Revised: 01/15/2022] [Accepted: 02/02/2022] [Indexed: 02/07/2023]
Abstract
Traumatic brain injury (TBI) is one of the most prevalent causes of permanent physical and cognitive disabilities. TBI pathology results from primary insults and a multi-mechanistic biochemical process, termed as secondary brain injury. Currently, there are no pharmacological agents for definitive treatment of patients with TBI. This article is presented with the purpose of reviewing molecular mechanisms of TBI pathology, as well as potential strategies and agents against pathological pathways. In this review article, materials were obtained by searching PubMed, Scopus, Elsevier, Web of Science, and Google Scholar. This search was considered without time limitation. Evidence indicates that oxidative stress and mitochondrial dysfunction are two key mediators of the secondary injury cascade in TBI pathology. TBI-induced oxidative damage results in the structural and functional impairments of cellular and subcellular components, such as mitochondria. Impairments of mitochondrial electron transfer chain and mitochondrial membrane potential result in a vicious cycle of free radical formation and cell apoptosis. The results of some preclinical and clinical studies, evaluating mitochondria-targeted therapies, such as mitochondria-targeted antioxidants and compounds with pleiotropic effects after TBI, are promising. As a proposed strategy in recent years, mitochondria-targeted multipotential therapy is a new hope, waiting to be confirmed. Moreover, based on the available findings, biologics, such as stem cell-based therapy and transplantation of mitochondria are novel potential strategies for the treatment of TBI; however, more studies are needed to clearly confirm the safety and efficacy of these strategies.
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Affiliation(s)
- Bahareh Hakiminia
- Department of Clinical Pharmacy and Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Babak Alikiaii
- Department of Anesthesiology and Intensive Care, Alzahra Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Fariborz Khorvash
- Department of Neurology, Alzahra Hospital, Isfahan University of Medical Sciences, Isfahan, Iran
| | - Sarah Mousavi
- Department of Clinical Pharmacy and Pharmacy Practice, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran
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4
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Hypoxic preconditioning in renal ischaemia-reperfusion injury: a review in pre-clinical models. Clin Sci (Lond) 2021; 135:2607-2618. [PMID: 34878507 DOI: 10.1042/cs20210615] [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: 06/09/2021] [Revised: 10/14/2021] [Accepted: 10/29/2021] [Indexed: 12/17/2022]
Abstract
Ischaemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and chronic kidney disease, which consists of cellular damage and renal dysfunction. AKI is a major complication that is of particular concern after cardiac surgery and to a lesser degree following organ transplantation in the immediate post-transplantation period, leading to delayed graft function. Because effective therapies are still unavailable, several recent studies have explored the potential benefit of hypoxic preconditioning (HPC) on IRI. HPC refers to the acquisition of increased organ tolerance to subsequent ischaemic or severe hypoxic injury, and experimental evidences suggest a potential benefit of HPC. There are three experimental forms of HPC, and, for better clarity, we named them as follows: physical HPC, HPC via treated-cell administration and stabilised hypoxia-inducible factor (HIF)-1α HPC, or mimicked HPC. The purpose of this review is to present the latest developments in the literature on HPC in the context of renal IRI in pre-clinical models. The data we compiled suggest that preconditional activation of hypoxia pathways protects against renal IRI, suggesting that HPC could be used in the treatment of renal IRI in transplantation.
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Huang CL, Chao CC, Lee YC, Lu MK, Cheng JJ, Yang YC, Wang VC, Chang WC, Huang NK. Paraquat Induces Cell Death Through Impairing Mitochondrial Membrane Permeability. Mol Neurobiol 2015; 53:2169-88. [DOI: 10.1007/s12035-015-9198-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 04/22/2015] [Indexed: 12/20/2022]
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6
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Gillies LA, Du H, Peters B, Knudson CM, Newmeyer DD, Kuwana T. Visual and functional demonstration of growing Bax-induced pores in mitochondrial outer membranes. Mol Biol Cell 2014; 26:339-49. [PMID: 25411335 PMCID: PMC4294680 DOI: 10.1091/mbc.e13-11-0638] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We visualized Bax-induced pores in outer membrane vesicles (OMVs) using cryo-electron microscopy and monitored dextran release from these vesicles by flow cytometry. The data argue that Bax promotes mitochondrial outer membrane permeabilization by inducing the formation of large, solitary, and growing pores through a mechanism involving membrane-curvature stress. Bax induces mitochondrial outer membrane permeabilization (MOMP), a critical step in apoptosis in which proteins are released into the cytoplasm. To resolve aspects of the mechanism, we used cryo-electron microscopy (cryo-EM) to visualize Bax-induced pores in purified mitochondrial outer membranes (MOMs). We observed solitary pores that exhibited negative curvature at their edges. Over time, the pores grew to ∼100–160 nm in diameter after 60–90 min, with some pores measuring more than 300 nm. We confirmed these results using flow cytometry, which we used to monitor the release of fluorescent dextrans from isolated MOM vesicles. The dextran molecules were released gradually, in a manner constrained by pore size. However, the release rates were consistent over a range of dextran sizes (10–500 kDa). We concluded that the pores were not static but widened dramatically to release molecules of different sizes. Taken together, the data from cryo-EM and flow cytometry argue that Bax promotes MOMP by inducing the formation of large, growing pores through a mechanism involving membrane-curvature stress.
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Affiliation(s)
| | - Han Du
- Department of Pathology, University of Iowa, Iowa City, IA 52242
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7
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Gillies LA, Kuwana T. Apoptosis regulation at the mitochondrial outer membrane. J Cell Biochem 2014; 115:632-40. [PMID: 24453042 DOI: 10.1002/jcb.24709] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 10/31/2013] [Indexed: 12/20/2022]
Abstract
Mitochondria play a critical role in apoptosis, or programmed cell death, by releasing apoptogenic factors from the intermembrane space. This process, known as mitochondrial outer membrane permeabilization (MOMP), is tightly regulated by the Bcl-2 family proteins. Pro-apoptotic Bcl-2 family members, Bax and Bak, change their conformation when activated by BH3 domain-only proteins in the family and permeabilize the MOM, whereas pro-survival members inhibit permeabilization. The precise nature of the apoptotic pore in the MOM is unknown, but is probably lipidic. Furthermore, it has been realized that there is another layer of MOMP regulation by a protein factor termed the catalyst in the MOM in order for Bax/Bak to achieve efficient and complete membrane permeabilization. Mitochondrial dynamics do not affect MOMP directly, but seem closely coordinated with MOMP for swift protein efflux from mitochondria. This review will present current views on the molecular mechanisms and regulation of MOMP and conclude with recent developments in clinical applications based on the knowledge gleaned from the investigation.
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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Cheng G, Kong RH, Zhang LM, Zhang JN. Mitochondria in traumatic brain injury and mitochondrial-targeted multipotential therapeutic strategies. Br J Pharmacol 2013; 167:699-719. [PMID: 23003569 DOI: 10.1111/j.1476-5381.2012.02025.x] [Citation(s) in RCA: 215] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Traumatic brain injury (TBI) is a major health and socioeconomic problem throughout the world. It is a complicated pathological process that consists of primary insults and a secondary insult characterized by a set of biochemical cascades. The imbalance between a higher energy demand for repair of cell damage and decreased energy production led by mitochondrial dysfunction aggravates cell damage. At the cellular level, the main cause of the secondary deleterious cascades is cell damage that is centred in the mitochondria. Excitotoxicity, Ca(2+) overload, reactive oxygen species (ROS), Bcl-2 family, caspases and apoptosis inducing factor (AIF) are the main participants in mitochondria-centred cell damage following TBI. Some preclinical and clinical results of mitochondria-targeted therapy show promise. Mitochondria- targeted multipotential therapeutic strategies offer new hope for the successful treatment of TBI and other acute brain injuries.
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Affiliation(s)
- Gang Cheng
- Neurosurgical Department, PLA Navy General Hospital, Beijing, China
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10
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Kinnally KW, Martinez-Caballero S, Dejean LM. Detection of the mitochondrial apoptosis-induced channel (MAC) and its regulation by Bcl-2 family proteins. ACTA ACUST UNITED AC 2011; Chapter 2:Unit2.12. [PMID: 20941703 DOI: 10.1002/0471140856.tx0212s30] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Apoptosis is a phenomenon fundamental to higher eukaryotes that is integral to such diverse cellular processes as tissue homeostasis, organogenesis, and response to toxins. The release from mitochondria of apoptotic factors such as cytochrome c is a key step during apoptosis of most cells. Cytochrome c release occurs through the MAC (mitochondrial apoptosis-induced channel), a pore which forms in the mitochondrial outer membrane during early apoptosis and is exquisitely regulated by the Bcl-2 family of proteins. This unit presents basic and advanced tools for detecting MAC and defining its regulation by Bcl-2 family proteins and pharmacological agents. Protocols include the use of time-lapse video-microscopy to monitor the onset of apoptosis in living cells and patch-clamp techniques for mitochondria or proteoliposomes containing mitochondrial proteins, which allow direct detection of MAC. These approaches enable an evaluation of the role of MAC and mitochondria in apoptosis of a variety of cell types by many inducers.
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Kinnally KW, Peixoto PM, Ryu SY, Dejean LM. Is mPTP the gatekeeper for necrosis, apoptosis, or both? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:616-22. [PMID: 20888866 DOI: 10.1016/j.bbamcr.2010.09.013] [Citation(s) in RCA: 230] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 09/22/2010] [Accepted: 09/23/2010] [Indexed: 02/01/2023]
Abstract
Permeabilization of the mitochondrial membranes is a crucial step in apoptosis and necrosis. This phenomenon allows the release of mitochondrial death factors, which trigger or facilitate different signaling cascades ultimately causing the execution of the cell. The mitochondrial permeability transition pore (mPTP) has long been known as one of the main regulators of mitochondria during cell death. mPTP opening can lead to matrix swelling, subsequent rupture of the outer membrane, and a nonspecific release of intermembrane space proteins into the cytosol. While mPTP was purportedly associated with early apoptosis, recent observations suggest that mitochondrial permeabilization mediated by mPTP is generally more closely linked to events of late apoptosis and necrosis. Mechanisms of mitochondrial membrane permeabilization during cell death, involving three different mitochondrial channels, have been postulated. These include the mPTP in the inner membrane, and the mitochondrial apoptosis-induced channel (MAC) and voltage-dependent anion-selective channel (VDAC) in the outer membrane. New developments on mPTP structure and function, and the involvement of mPTP, MAC, and VDAC in permeabilization of mitochondrial membranes during cell death are explored. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
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Affiliation(s)
- Kathleen W Kinnally
- New York University College of Dentistry, Department Basic Sciences 345 East 24th Street, New York, NY 10010, USA
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12
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Peixoto PM, Ryu SY, Kinnally KW. Mitochondrial ion channels as therapeutic targets. FEBS Lett 2010; 584:2142-52. [PMID: 20178788 PMCID: PMC2872129 DOI: 10.1016/j.febslet.2010.02.046] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 02/12/2010] [Accepted: 02/16/2010] [Indexed: 12/31/2022]
Abstract
The study of mitochondrial ion channels changed our perception of these double-wrapped organelles from being just the power house of a cell to the guardian of a cell's fate. Mitochondria communicate with the cell through these special channels. Most of the time, the message is encoded by ion flow across the mitochondrial outer and inner membranes. Potassium, sodium, calcium, protons, nucleotides, and proteins traverse the mitochondrial membranes in an exquisitely regulated manner to control a myriad of processes, from respiration and mitochondrial morphology to cell proliferation and cell death. This review is an update on both well established and putative mitochondrial channels regarding their composition, function, regulation, and therapeutic potential.
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Affiliation(s)
| | - Shin-Young Ryu
- New York University College of Dentistry, New York, NY, 10002
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Ganesan V, Perera MN, Colombini D, Datskovskiy D, Chadha K, Colombini M. Ceramide and activated Bax act synergistically to permeabilize the mitochondrial outer membrane. Apoptosis 2010; 15:553-62. [DOI: 10.1007/s10495-009-0449-0] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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14
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Dejean LM, Ryu SY, Martinez-Caballero S, Teijido O, Peixoto PM, Kinnally KW. MAC and Bcl-2 family proteins conspire in a deadly plot. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1231-8. [PMID: 20083086 DOI: 10.1016/j.bbabio.2010.01.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 01/06/2010] [Accepted: 01/09/2010] [Indexed: 12/31/2022]
Abstract
Apoptosis is an elemental form of programmed cell death; it is fundamental to higher eukaryotes and essential to mechanisms controlling tissue homeostasis. Apoptosis is also involved in many pathologies including cancer, neurodegenerative diseases, aging, and infarcts. This cell death program is tightly regulated by Bcl-2 family proteins by controlling the formation of the mitochondrial apoptosis-induced channel or MAC. Assembly of MAC corresponds to permeabilization of the mitochondrial outer membrane, which is the so called commitment step of apoptosis. MAC provides the pathway through the mitochondrial outer membrane for the release of cytochrome c and other pro-apoptotic factors from the intermembrane space. While overexpression of anti-apoptotic Bcl-2 eliminates MAC activity, oligomers of the pro-apoptotic members Bax and/or Bak are essential structural component(s) of MAC. Assembly of MAC from Bax or Bak was monitored in real time by directly patch-clamping mitochondria with micropipettes containing the sentinel tBid, a direct activator of Bax and Bak. Herein, a variety of high affinity inhibitors of MAC (iMAC) that may prove to be crucial tools in mechanistic studies have recently been identified. This review focuses on characterization of MAC activity, its regulation by Bcl-2 family proteins, and a discussion of how MAC can be pharmacologically turned on or off depending on the pathology to be treated.
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Affiliation(s)
- Laurent M Dejean
- Department Basic Sci., 345 East 24th St., New York University, College of Dentistry, New York, NY 10010, USA
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15
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Liu W, Mu R, Nie FF, Yang Y, Wang J, Dai QS, Lu N, Qi Q, Rong JJ, Hu R, Wang XT, You QD, Guo QL. MAC related mitochondrial pathway in oroxylin A induces apoptosis in human hepatocellular carcinoma HepG2 cells. Cancer Lett 2009; 284:198-207. [DOI: 10.1016/j.canlet.2009.04.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Revised: 04/14/2009] [Accepted: 04/17/2009] [Indexed: 11/15/2022]
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16
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Ferecatu I, Bergeaud M, Rodríguez-Enfedaque A, Le Floch N, Oliver L, Rincheval V, Renaud F, Vallette FM, Mignotte B, Vayssière JL. Mitochondrial localization of the low level p53 protein in proliferative cells. Biochem Biophys Res Commun 2009; 387:772-7. [DOI: 10.1016/j.bbrc.2009.07.111] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Accepted: 07/22/2009] [Indexed: 11/30/2022]
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17
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Ferecatu I, Le Floch N, Bergeaud M, Rodríguez-Enfedaque A, Rincheval V, Oliver L, Vallette FM, Mignotte B, Vayssière JL. Evidence for a mitochondrial localization of the retinoblastoma protein. BMC Cell Biol 2009; 10:50. [PMID: 19555499 PMCID: PMC2711044 DOI: 10.1186/1471-2121-10-50] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 06/25/2009] [Indexed: 11/10/2022] Open
Abstract
Background The retinoblastoma protein (Rb) plays a central role in the regulation of cell cycle, differentiation and apoptosis. In cancer cells, ablation of Rb function or its pathway is a consequence of genetic inactivation, viral oncoprotein binding or deregulated hyperphosphorylation. Some recent data suggest that Rb relocation could also account for the regulation of its tumor suppressor activity, as is the case for other tumor suppressor proteins, such as p53. Results In this reported study, we present evidence that a fraction of the total amount of Rb protein can localize to the mitochondria in proliferative cells taken from both rodent and human cells. This result is also supported by the use of Rb siRNAs, which substantially reduced the amount of mitochondrial Rb, and by acellular assays, in which [35S]-Methionine-labeled Rb proteins bind strongly to mitochondria isolated from rat liver. Moreover, endogenous Rb is found in an internal compartment of the mitochondria, within the inner-membrane. This is consistent with the protection of Rb from alkaline treatment, which destroys any interaction of proteins that are weakly bound to mitochondria. Conclusion Although a few data regarding an unspecific cytosolic localization of Rb protein have been reported for some tumor cells, our results are the first evidence of a mitochondrial localization of Rb. The mitochondrial localization of Rb is observed in parallel with its classic nuclear location and paves the way for the study of potential as-yet-unknown roles of Rb at this site.
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Affiliation(s)
- Ioana Ferecatu
- Laboratoire de génétique et biologie cellulaire - CNRS UMR 8159, Université de Versailles Saint-Quentin-en-Yvelines, Versailles, France.
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Martinez-Caballero S, Dejean LM, Kinnally MS, Oh KJ, Mannella CA, Kinnally KW. Assembly of the mitochondrial apoptosis-induced channel, MAC. J Biol Chem 2009; 284:12235-45. [PMID: 19261612 DOI: 10.1074/jbc.m806610200] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although Bcl-2 family proteins control intrinsic apoptosis, the mechanisms underlying this regulation are incompletely understood. Patch clamp studies of mitochondria isolated from cells deficient in one or both of the pro-apoptotic proteins Bax and Bak show that at least one of the proteins must be present for formation of the cytochrome c-translocating channel, mitochondrial apoptosis-induced channel (MAC), and that the single channel behaviors of MACs containing exclusively Bax or Bak are similar. Truncated Bid catalyzes MAC formation in isolated mitochondria containing Bax and/or Bak with a time course of minutes and does not require VDAC1 or VDAC3. Mathematical analysis of the stepwise changes in conductance associated with MAC formation is consistent with pore assembly by a barrel-stave model. Assuming the staves are two transmembrane alpha-helices in Bax and Bak, mature MAC pores would typically contain approximately 9 monomers and have diameters of 5.5-6 nm. The mitochondrial permeability data are inconsistent with formation of lipidic pores capable of transporting megadalton-sized macromolecules as observed with recombinant Bax in liposomes.
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Affiliation(s)
- Sonia Martinez-Caballero
- Department of Basic Sciences, New York University College of Dentistry, New York, New York 10010, USA
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19
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Schafer B, Quispe J, Choudhary V, Chipuk JE, Ajero TG, Du H, Schneiter R, Kuwana T. Mitochondrial outer membrane proteins assist Bid in Bax-mediated lipidic pore formation. Mol Biol Cell 2009; 20:2276-85. [PMID: 19244344 DOI: 10.1091/mbc.e08-10-1056] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mitochondrial outer membrane permeabilization (MOMP) is a critical step in apoptosis and is regulated by Bcl-2 family proteins. In vitro systems using cardiolipin-containing liposomes have demonstrated the key features of MOMP induced by Bax and cleaved Bid; however, the nature of the "pores" and how they are formed remain obscure. We found that mitochondrial outer membranes contained very little cardiolipin, far less than that required for liposome permeabilization, despite their responsiveness to Bcl-2 family proteins. Strikingly, the incorporation of isolated mitochondrial outer membrane (MOM) proteins into liposomes lacking cardiolipin conferred responsiveness to cleaved Bid and Bax. Cardiolipin dependence was observed only when permeabilization was induced with cleaved Bid but not with Bid or Bim BH3 peptide or oligomerized Bax. Therefore, we conclude that MOM proteins specifically assist cleaved Bid in Bax-mediated permeabilization. Cryoelectron microscopy of cardiolipin-liposomes revealed that cleaved Bid and Bax produced large round holes with diameters of 25-100 nm, suggestive of lipidic pores. In sum, we propose that activated Bax induces lipidic pore formation and that MOM proteins assist cleaved Bid in this process in the absence of cardiolipin.
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Affiliation(s)
- Blanca Schafer
- Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, 52242, USA
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20
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Belizário JE, Alves J, Occhiucci JM, Garay-Malpartida M, Sesso A. A mechanistic view of mitochondrial death decision pores. ACTA ACUST UNITED AC 2008; 40:1011-24. [PMID: 17665037 DOI: 10.1590/s0100-879x2006005000109] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Accepted: 02/16/2007] [Indexed: 11/22/2022]
Abstract
Mitochondria increase their outer and inner membrane permeability to solutes, protons and metabolites in response to a variety of extrinsic and intrinsic signaling events. The maintenance of cellular and intraorganelle ionic homeostasis, particularly for Ca2+, can determine cell survival or death. Mitochondrial death decision is centered on two processes: inner membrane permeabilization, such as that promoted by the mitochondrial permeability transition pore, formed across inner membranes when Ca2+ reaches a critical threshold, and mitochondrial outer membrane permeabilization, in which the pro-apoptotic proteins BID, BAX, and BAK play active roles. Membrane permeabilization leads to the release of apoptogenic proteins: cytochrome c, apoptosis-inducing factor, Smac/Diablo, HtrA2/Omi, and endonuclease G. Cytochrome c initiates the proteolytic activation of caspases, which in turn cleave hundreds of proteins to produce the morphological and biochemical changes of apoptosis. Voltage-dependent anion channel, cyclophilin D, adenine nucleotide translocase, and the pro-apoptotic proteins BID, BAX, and BAK may be part of the molecular composition of membrane pores leading to mitochondrial permeabilization, but this remains a central question to be resolved. Other transporting pores and channels, including the ceramide channel, the mitochondrial apoptosis-induced channel, as well as a non-specific outer membrane rupture may also be potential release pathways for these apoptogenic factors. In this review, we discuss the mechanistic models by which reactive oxygen species and caspases, via structural and conformational changes of membrane lipids and proteins, promote conditions for inner/outer membrane permeabilization, which may be followed by either opening of pores or a rupture of the outer mitochondrial membrane.
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Affiliation(s)
- J E Belizário
- Departamento de Farmacologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-900 São Paulo, Brazil.
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21
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Abstract
The crucial step in the intrinsic, or mitochondrial, apoptotic pathway is permeabilization of the mitochondrial outer membrane. Permeabilization triggers release of apoptogenic factors, such as cytochrome c, from the mitochondrial intermembrane space into the cytosol where these factors ensure propagation of the apoptotic cascade and execution of cell death. However, the mechanism(s) underlying permeabilization of the outer membrane remain controversial. Two mechanisms, involving opening of two different mitochondrial channels, have been proposed to be responsible for the permeabilization; the permeability transition pore (PTP) in the inner membrane and the mitochondrial apoptosis-induced channel (MAC) in the outer membrane. Opening of PTP would lead to matrix swelling, subsequent rupture of the outer membrane, and an unspecific release of intermembrane proteins into the cytosol. However, many believe PTP opening is a consequence of apoptosis and this channel is thought to principally play a role in necrosis, not apoptosis. Activation of MAC is exquisitely regulated by Bcl-2 family proteins, which are the sentinels of apoptosis. MAC provides specific pores in the outer membrane for the passage of intermembrane proteins, in particular cytochrome c, to the cytosol. The electrophysiological characteristics of MAC are very similar to Bax channels and depletion of Bax significantly diminishes MAC activity, suggesting that Bax is an essential constituent of MAC in some systems. The characteristics of various mitochondrial channels and Bax are compared. The involvement of MAC and PTP activities in apoptosis of disease and their pharmacology are discussed.
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Affiliation(s)
- Kathleen W Kinnally
- Department of Basic Sciences, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA.
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22
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Chalah A, Khosravi-Far R. The Mitochondrial Death Pathway. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 615:25-45. [DOI: 10.1007/978-1-4020-6554-5_3] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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23
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Arokium H, Ouerfelli H, Velours G, Camougrand N, Vallette FM, Manon S. Substitutions of Potentially Phosphorylatable Serine Residues of Bax Reveal How They May Regulate Its Interaction with Mitochondria. J Biol Chem 2007; 282:35104-12. [PMID: 17911107 DOI: 10.1074/jbc.m704891200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
During apoptosis, the pro-apoptotic protein Bax relocalizes from the cytosol to the mitochondrial outer membrane. This relocalization is associated to major conformational changes, namely at the N- and C-terminal ends of the protein. Substitution of residues located at critical positions within the protein potentially stimulates or inhibits this process. In the present study, we investigated the hypothesis that phosphorylation of serine residues might trigger these conformational changes, with a focus on Ser(163) and Ser(184), which have been shown to be phosphorylatable by protein kinases GSK3beta and Akt/PKB, respectively, and on Ser(60), which is located in a consensus target sequence for PKA. Substitutions of these serine residues by alanine or aspartate were done in wild type or previously characterized Bax mutants, and the capacity of the resulting proteins to interact with mitochondria and to release cytochrome c was assayed in yeast, which provides a tool to study the function of Bax, independently of the rest of the apoptotic network. We conclude that sequential phosphorylation of these serine residues might participate in the triggering of the different conformational changes associated with Bax activation during apoptosis.
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Affiliation(s)
- Hubert Arokium
- CNRS, UMR5095, Université de Bordeaux 2, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
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24
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Kessova IG, Cederbaum AI. Mitochondrial alterations in livers of Sod1-/- mice fed alcohol. Free Radic Biol Med 2007; 42:1470-80. [PMID: 17448893 PMCID: PMC1924491 DOI: 10.1016/j.freeradbiomed.2007.01.044] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 01/23/2007] [Accepted: 01/30/2007] [Indexed: 12/18/2022]
Abstract
Chronic alcohol consumption induced liver injury in Cu,Zn-superoxide dismutase-deficient mice (Sod1-/-), with extensive centrilobular necrosis and inflammation and a reduction in hepatic ATP content. Mechanisms by which ethanol decreased ATP in these mice remain unclear. We investigated alterations in mitochondria of Sod1-/- mice produced by chronic ethanol treatment. These mitochondria had an increase in State 4 oxygen consumption with succinate and especially with glutamate plus malate compared to mitochondria from pair-fed Sod1-/- mice or mitochondria from wild-type mice fed dextrose or ethanol. This uncoupling was associated with a decrease in ADP/O and respiratory control ratios, a decline in mitochondrial membrane potential, enhanced mitochondrial permeability transition, and decreased aconitase activity. Total thiols and uncoupling protein 2 levels were elevated in the pair-fed Sod1-/- mitochondria, perhaps an adaptive response to oxidant stress. However, no such increases were found with the ethanol-fed Sod1-/- mitochondria, suggesting a failure to develop these adaptations. The mitochondria from the ethanol-fed Sod1-/- mice had elevated levels of cleaved Bax, Bak, Bcl-xl, and adenine nucleotide translocator. Immunoprecipitation studies revealed increased association of Bax and Bak with the adenine nucleotide translocator. ADP-ATP exchange was very low in the ethanol-fed Sod1-/- mitochondria. These results suggest that ethanol treatment of Sod1-/- mice produces uncoupling and a decline in Deltapsi, swelling, increased association of proapoptotic proteins involved in the permeability transition, and decreased adenine nucleotide translocator activity, which may be responsible for the decline in ATP levels and development of necrosis in this model of alcohol-induced liver injury.
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Affiliation(s)
- Irina G Kessova
- Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, Box 1603, One Gustave L. Levy Place, New York, NY 10029, USA
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25
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Abstract
In work spanning more than a century, mitochondria have been recognized for their multifunctional roles in metabolism, energy transduction, ion transport, inheritance, signaling, and cell death. Foremost among these tasks is the continuous production of ATP through oxidative phosphorylation, which requires a large electrochemical driving force for protons across the mitochondrial inner membrane. This process requires a membrane with relatively low permeability to ions to minimize energy dissipation. However, a wealth of evidence now indicates that both selective and nonselective ion channels are present in the mitochondrial inner membrane, along with several known channels on the outer membrane. Some of these channels are active under physiological conditions, and others may be activated under pathophysiological conditions to act as the major determinants of cell life and death. This review summarizes research on mitochondrial ion channels and efforts to identify their molecular correlates. Except in a few cases, our understanding of the structure of mitochondrial ion channels is limited, indicating the need for focused discovery in this area.
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Affiliation(s)
- Brian O'Rourke
- Institute of Molecular Cardiobiology, Division of Cardiology, Department of Medicine, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
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26
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Er E, Oliver L, Cartron PF, Juin P, Manon S, Vallette FM. Mitochondria as the target of the pro-apoptotic protein Bax. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1301-11. [PMID: 16836974 DOI: 10.1016/j.bbabio.2006.05.032] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2006] [Revised: 04/20/2006] [Accepted: 05/23/2006] [Indexed: 11/21/2022]
Abstract
During apoptosis, engagement of the mitochondrial pathway involves the permeabilization of the outer mitochondrial membrane (OMM), which leads to the release of cytochrome c and other apoptogenic proteins such as Smac/DIABLO, AIF, EndoG, Omi/HtraA2 and DDP/TIMM8a. OMM permeabilization depends on activation, translocation and oligomerization of multidomain Bcl-2 family proteins such as Bax or Bak. Factors involved in Bax conformational change and the function(s) of the distinct domains controlling the addressing and the insertion of Bax into mitochondria are described in this review. We also discuss our current knowledge on Bax oligomerization and on the molecular mechanisms underlying the different models accounting for OMM permeabilization during apoptosis.
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Affiliation(s)
- Emine Er
- UMR 601 INSERM, Université de Nantes, 9 Quai Moncousu F-44035 Nantes, Cedex 01 France
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27
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Dejean LM, Martinez-Caballero S, Kinnally KW. Is MAC the knife that cuts cytochrome c from mitochondria during apoptosis? Cell Death Differ 2006; 13:1387-95. [PMID: 16676005 DOI: 10.1038/sj.cdd.4401949] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Apoptosis is a phenomenon fundamental to higher eukaryotes and essential to mechanisms controlling tissue homeostasis. Bcl-2 family proteins tightly control this cell death program by regulating the permeabilization of the mitochondrial outer membrane and, hence, the release of cytochrome c and other proapoptotic factors. Mitochondrial apoptosis-induced channel (MAC) is the mitochondrial apoptosis-induced channel and is responsible for cytochrome c release early in apoptosis. MAC activity is detected by patch clamping mitochondria at the time of cytochrome c release. The Bcl-2 family proteins regulate apoptosis by controlling the formation of MAC. Depending on cell type and apoptotic inducer, Bax and/or Bak are structural component(s) of MAC. Overexpression of the antiapoptotic protein Bcl-2 eliminates MAC activity. The focus of this review is a biophysical characterization of MAC activity and its regulation by Bcl-2 family proteins, and ends with some discussion of therapeutic targets.
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Affiliation(s)
- L M Dejean
- Department of Basic Sciences, College of Dentistry, New York University, NY 10010, USA
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28
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Pouliquen D, Bellot G, Guihard G, Fichet P, Meflah K, Vallette FM. Mitochondrial membrane permeabilization produced by PTP, Bax and apoptosis: a 1H-NMR relaxation study. Cell Death Differ 2006; 13:301-10. [PMID: 16052238 DOI: 10.1038/sj.cdd.4401731] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
To analyze the involvement of structured water (bound to macromolecules) in apoptosis-induced mitochondrial outer-membrane permeability, we compared the dynamics of water protons from nuclear magnetic resonance (NMR) data in apoptotic liver mitochondria with that of control mitochondria incubated in vitro with free Ca(2+) (opening of the permeability transition pore, PTP) or with Bax alpha. Our results demonstrate that water molecules in apoptotic mitochondria exhibit an accelerated translational motion of structured water common with that induced by the opening of the PTP, but limited in amplitude. On the other hand, no significant quantitative change in structured water was observed in apoptotic mitochondria, a phenomenon also observed with Bax alpha-induced permeability. We conclude that the changes observed in the different water phases differ both quantitatively and qualitatively during the opening of the PTP and the Bax alpha-induced permeability, and that the apoptotic mitochondria exhibit mixed properties between these model situations.
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Affiliation(s)
- D Pouliquen
- Inserm UMR 601, Equipe 4, Institut de Biologie, 9 Quai Moncousu, 44035 Nantes cédex, France.
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29
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Martinez-Caballero S, Dejean LM, Jonas EA, Kinnally KW. The role of the mitochondrial apoptosis induced channel MAC in cytochrome c release. J Bioenerg Biomembr 2006; 37:155-64. [PMID: 16167172 DOI: 10.1007/s10863-005-6570-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Permeabilization of the mitochondrial outer membrane is a crucial event during apoptosis. It allows the release of proapoptotic factors, like cytochrome c, from the intermembrane space, and represents the commitment step in apoptosis. The mitochondrial apoptosis-induced channel, MAC, is a high-conductance channel that forms during early apoptosis and is the putative cytochrome c release channel. Unlike activation of the permeability transition pore, MAC formation occurs without loss of outer membrane integrity and depolarization. The single channel behavior and pharmacology of reconstituted MAC has been characterized with patch-clamp techniques. Furthermore, MAC's activity is compared to that detected in mitochondria inside the cells at the time cytochrome c is released. Finally, the regulation of MAC by the Bcl-2 family proteins and insights concerning its molecular composition are also discussed.
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Affiliation(s)
- Sonia Martinez-Caballero
- Department of Basic Sciences, New York University College of Dentistry, 345 East 24th Street, New York, NY 10010, USA
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30
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Dejean LM, Martinez-Caballero S, Manon S, Kinnally KW. Regulation of the mitochondrial apoptosis-induced channel, MAC, by BCL-2 family proteins. Biochim Biophys Acta Mol Basis Dis 2005; 1762:191-201. [PMID: 16055309 DOI: 10.1016/j.bbadis.2005.07.002] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 06/21/2005] [Accepted: 07/04/2005] [Indexed: 10/25/2022]
Abstract
Programmed cell death or apoptosis is central to many physiological processes and pathological conditions such as organogenesis, tissue homeostasis, cancer, and neurodegenerative diseases. Bcl-2 family proteins tightly control this cell death program by regulating the permeabilization of the mitochondrial outer membrane and, hence, the release of cytochrome c and other pro-apoptotic factors. Control of the formation of the mitochondrial apoptosis-induced channel, or MAC, is central to the regulation of apoptosis by Bcl-2 family proteins. MAC is detected early in apoptosis by patch clamping the mitochondrial outer membrane. The focus of this review is on the regulation of MAC activity by Bcl-2 family proteins. The role of MAC as the putative cytochrome c release channel during early apoptosis and insights concerning its molecular composition are also discussed.
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Affiliation(s)
- Laurent M Dejean
- Department Basic Sciences, New York University, College of Dentistry, 345 East 24th Street, New York, NY 10010, USA
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31
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Dejean LM, Martinez-Caballero S, Guo L, Hughes C, Teijido O, Ducret T, Ichas F, Korsmeyer SJ, Antonsson B, Jonas EA, Kinnally KW. Oligomeric Bax is a component of the putative cytochrome c release channel MAC, mitochondrial apoptosis-induced channel. Mol Biol Cell 2005; 16:2424-32. [PMID: 15772159 PMCID: PMC1087246 DOI: 10.1091/mbc.e04-12-1111] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Bcl-2 family proteins regulate apoptosis, in part, by controlling formation of the mitochondrial apoptosis-induced channel (MAC), which is a putative cytochrome c release channel induced early in the intrinsic apoptotic pathway. This channel activity was never observed in Bcl-2-overexpressing cells. Furthermore, MAC appears when Bax translocates to mitochondria and cytochrome c is released in cells dying by intrinsic apoptosis. Bax is a component of MAC of staurosporine-treated HeLa cells because MAC activity is immunodepleted by Bax antibodies. MAC is preferentially associated with oligomeric, not monomeric, Bax. The single channel behavior of recombinant oligomeric Bax and MAC is similar. Both channel activities are modified by cytochrome c, consistent with entrance of this protein into the pore. The mean conductance of patches of mitochondria isolated after green fluorescent protein-Bax translocation is significantly higher than those from untreated cells, consistent with onset of MAC activity. In contrast, the mean conductance of patches of mitochondria indicates MAC activity is present in apoptotic cells deficient in Bax but absent in apoptotic cells deficient in both Bax and Bak. These findings indicate Bax is a component of MAC in staurosporine-treated HeLa cells and suggest Bax and Bak are functionally redundant as components of MAC.
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Affiliation(s)
- Laurent M Dejean
- Department of Basic Sciences, College of Dentistry, New York University, New York, NY 10010, USA
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Cartron PF, Arokium H, Oliver L, Meflah K, Manon S, Vallette FM. Distinct Domains Control the Addressing and the Insertion of Bax into Mitochondria. J Biol Chem 2005; 280:10587-98. [PMID: 15590655 DOI: 10.1074/jbc.m409714200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The translocation of Bax from the cytosol into the mitochondrial outer membrane is a central event during apoptosis. We report that beyond the addressing step, which involves its first alpha-helix (halpha1), the helices alpha5 and alpha6 (halpha5alpha6) are responsible for the insertion of Bax into mitochondrial outer membrane bilayer. The translocation of Bax to mitochondria is associated with specific changes in the conformation of the protein that are under the control of two prolines: Pro-13, which controls the unfolding of halpha1, and Pro-168, a proline located immediately before the hydrophobic carboxyl-terminal end (i.e. helix alpha9, halpha9), which controls the disclosure of halpha5alpha6. An additional step, the disruption of an electrostatic bond formed between Asp-33 (halpha1) and Lys-64 (BH3), allows the mitochondria addressing of Bax. We conclude that, although the intramolecular interactions of halpha1 with the BH3 region control the addressing of Bax to mitochondria, the Pro-168 is involved in the control of its membrane insertion through halpha5alpha6.
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Affiliation(s)
- Pierre-François Cartron
- Unité Mixte de Recherche 601 INSERM/Université de Nantes, Institut Fédératif de Recherche 26, Equipe 4, Apoptosis & Tumor Progression (Equipe Labellisée Ligue) 9, Quai Moncousu, 44035 Nantes, Cedex 01, France
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