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Pekson R, Liang FG, Axelrod JL, Lee J, Qin D, Wittig AJH, Paulino VM, Zheng M, Peixoto PM, Kitsis RN. The mitochondrial ATP synthase is a negative regulator of the mitochondrial permeability transition pore. Proc Natl Acad Sci U S A 2023; 120:e2303713120. [PMID: 38091291 PMCID: PMC10743364 DOI: 10.1073/pnas.2303713120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Accepted: 10/24/2023] [Indexed: 12/18/2023] Open
Abstract
The mitochondrial permeability transition pore (mPTP) is a channel in the inner mitochondrial membrane whose sustained opening in response to elevated mitochondrial matrix Ca2+ concentrations triggers necrotic cell death. The molecular identity of mPTP is unknown. One proposed candidate is the mitochondrial ATP synthase, whose canonical function is to generate most ATP in multicellular organisms. Here, we present mitochondrial, cellular, and in vivo evidence that, rather than serving as mPTP, the mitochondrial ATP synthase inhibits this pore. Our studies confirm previous work showing persistence of mPTP in HAP1 cell lines lacking an assembled mitochondrial ATP synthase. Unexpectedly, however, we observe that Ca2+-induced pore opening is markedly sensitized by loss of the mitochondrial ATP synthase. Further, mPTP opening in cells lacking the mitochondrial ATP synthase is desensitized by pharmacological inhibition and genetic depletion of the mitochondrial cis-trans prolyl isomerase cyclophilin D as in wild-type cells, indicating that cyclophilin D can modulate mPTP through substrates other than subunits in the assembled mitochondrial ATP synthase. Mitoplast patch clamping studies showed that mPTP channel conductance was unaffected by loss of the mitochondrial ATP synthase but still blocked by cyclophilin D inhibition. Cardiac mitochondria from mice whose heart muscle cells we engineered deficient in the mitochondrial ATP synthase also demonstrate sensitization of Ca2+-induced mPTP opening and desensitization by cyclophilin D inhibition. Further, these mice exhibit strikingly larger myocardial infarctions when challenged with ischemia/reperfusion in vivo. We conclude that the mitochondrial ATP synthase does not function as mPTP and instead negatively regulates this pore.
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Affiliation(s)
- Ryan Pekson
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY10461
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
| | - Felix G. Liang
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY10461
| | - Joshua L. Axelrod
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY10461
| | - Jaehoon Lee
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY10461
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
| | - Dongze Qin
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY10461
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
| | - Andre J. H. Wittig
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY10461
| | - Victor M. Paulino
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY10461
| | - Min Zheng
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY10461
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
| | - Pablo M. Peixoto
- Department of Natural Sciences, Baruch College and Program in Molecular, Cellular, and Developmental Biology, Graduate Center, City University of New York, New York, NY10010
| | - Richard N. Kitsis
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY10461
- Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, Bronx, NY10461
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY10461
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Kadam A, Jadiya P, Tomar D. Post-translational modifications and protein quality control of mitochondrial channels and transporters. Front Cell Dev Biol 2023; 11:1196466. [PMID: 37601094 PMCID: PMC10434574 DOI: 10.3389/fcell.2023.1196466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 07/24/2023] [Indexed: 08/22/2023] Open
Abstract
Mitochondria play a critical role in energy metabolism and signal transduction, which is tightly regulated by proteins, metabolites, and ion fluxes. Metabolites and ion homeostasis are mainly mediated by channels and transporters present on mitochondrial membranes. Mitochondria comprise two distinct compartments, the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM), which have differing permeabilities to ions and metabolites. The OMM is semipermeable due to the presence of non-selective molecular pores, while the IMM is highly selective and impermeable due to the presence of specialized channels and transporters which regulate ion and metabolite fluxes. These channels and transporters are modulated by various post-translational modifications (PTMs), including phosphorylation, oxidative modifications, ions, and metabolites binding, glycosylation, acetylation, and others. Additionally, the mitochondrial protein quality control (MPQC) system plays a crucial role in ensuring efficient molecular flux through the mitochondrial membranes by selectively removing mistargeted or defective proteins. Inefficient functioning of the transporters and channels in mitochondria can disrupt cellular homeostasis, leading to the onset of various pathological conditions. In this review, we provide a comprehensive overview of the current understanding of mitochondrial channels and transporters in terms of their functions, PTMs, and quality control mechanisms.
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Affiliation(s)
- Ashlesha Kadam
- Department of Internal Medicine, Section of Cardiovascular Medicine, Section of Molecular Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, United States
| | - Pooja Jadiya
- Department of Internal Medicine, Section of Gerontology and Geriatric Medicine, Section of Molecular Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, United States
| | - Dhanendra Tomar
- Department of Internal Medicine, Section of Cardiovascular Medicine, Section of Molecular Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, United States
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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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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: 18] [Impact Index Per Article: 9.0] [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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5
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Svoronos AA, Campbell SG, Engelman DM. MicroRNA function can be reversed by altering target gene expression levels. iScience 2021; 24:103208. [PMID: 34755085 PMCID: PMC8560630 DOI: 10.1016/j.isci.2021.103208] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/14/2021] [Accepted: 09/29/2021] [Indexed: 11/17/2022] Open
Abstract
Paradoxically, many microRNAs appear to exhibit entirely opposite functions when placed in different contexts. For example, miR-125b has been shown to be pro-apoptotic in some studies, but anti-apoptotic in others. To investigate this phenomenon, we combine computational modeling with experimental approaches to examine how the function of miR-125b in apoptosis varies with respect to the expression levels of its pro-apoptotic and anti-apoptotic targets. In doing so, we elucidate a general trend that miR-125b is more pro-apoptotic when its anti-apoptotic targets are overexpressed, whereas it is more anti-apoptotic when its pro-apoptotic targets are overexpressed. We show that it is possible to completely reverse miR-125b′s function in apoptosis by modifying the expression levels of its target genes. Furthermore, miR-125b′s function may also be altered by the presence of anticancer drugs. These results suggest that the function of a microRNA can vary substantially and is dependent on its target gene expression levels. Many miRNAs exhibit entirely opposite functions when placed in different contexts miR-125b can be pro- or anti-apoptotic depending on target gene expression levels The function of a miRNA can be reversed by altering target gene expression levels The presence of anticancer drugs can also alter a miRNA's function
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Affiliation(s)
- Alexander A Svoronos
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA.,Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Av., P.O. Box 208114, New Haven, CT 06520, USA
| | - Stuart G Campbell
- Department of Biomedical Engineering, Yale University, New Haven, CT 06520, USA
| | - Donald M Engelman
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Av., P.O. Box 208114, New Haven, CT 06520, USA
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6
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Shahar N, Larisch S. Inhibiting the inhibitors: Targeting anti-apoptotic proteins in cancer and therapy resistance. Drug Resist Updat 2020; 52:100712. [DOI: 10.1016/j.drup.2020.100712] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/29/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
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7
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Karch J, Bround MJ, Khalil H, Sargent MA, Latchman N, Terada N, Peixoto PM, Molkentin JD. Inhibition of mitochondrial permeability transition by deletion of the ANT family and CypD. SCIENCE ADVANCES 2019; 5:eaaw4597. [PMID: 31489369 PMCID: PMC6713508 DOI: 10.1126/sciadv.aaw4597] [Citation(s) in RCA: 148] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 07/25/2019] [Indexed: 05/19/2023]
Abstract
The mitochondrial permeability transition pore (MPTP) has resisted molecular identification. The original model of the MPTP that proposed the adenine nucleotide translocator (ANT) as the inner membrane pore-forming component was challenged when mitochondria from Ant1/2 double null mouse liver still had MPTP activity. Because mice express three Ant genes, we reinvestigated whether the ANTs comprise the MPTP. Liver mitochondria from Ant1, Ant2, and Ant4 deficient mice were highly refractory to Ca2+-induced MPTP formation, and when also given cyclosporine A (CsA), the MPTP was completely inhibited. Moreover, liver mitochondria from mice with quadruple deletion of Ant1, Ant2, Ant4, and Ppif (cyclophilin D, target of CsA) lacked Ca2+-induced MPTP formation. Inner-membrane patch clamping in mitochondria from Ant1, Ant2, and Ant4 triple null mouse embryonic fibroblasts showed a loss of MPTP activity. Our findings suggest a model for the MPTP consisting of two distinct molecular components: The ANTs and an unknown species requiring CypD.
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Affiliation(s)
- Jason Karch
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Baylor College of Medicine, Houston TX, USA
| | - Michael J. Bround
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Hadi Khalil
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Michelle A. Sargent
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Nadina Latchman
- Baruch College and Graduate Center of City University of New York, NY, USA
| | - Naohiro Terada
- Department of Pathology, University of Florida College of Medicine, Gainesville, FL, USA
| | - Pablo M. Peixoto
- Baruch College and Graduate Center of City University of New York, NY, USA
| | - Jeffery D. Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
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8
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Berzabá-Evoli E, Zazueta C, Cruz Hernández JH, Gómez-Crisóstomo NP, Juárez-Rojop IE, De la Cruz-Hernández EN, Martínez-Abundis E. Leptin Modifies the Rat Heart Performance Associated with Mitochondrial Dysfunction Independently of Its Prohypertrophic Effects. Int J Endocrinol 2018; 2018:6081415. [PMID: 30154842 PMCID: PMC6093050 DOI: 10.1155/2018/6081415] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 06/15/2018] [Accepted: 07/03/2018] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Functional receptors for leptin were described on the surface of cardiomyocytes, and there was a prohypertrophic effect with high concentrations of the cytokine. Therefore, leptin could be a link between obesity and the prevalence of cardiovascular diseases. On the other hand, a deleterious effect of leptin on mitochondrial performance was described, which was also associated with the evolution of cardiac hypertrophy to heart failure. The goal of our study was to analyze the effect of the exposure of rat hearts to a high concentration of leptin on cardiac and mitochondrial function. METHODS Rat hearts were perfused continuously with or without 3.1 nM leptin for 1, 2, 3, or 4 hours. Homogenates and mitochondria were prepared by centrifugation and analyzed for cardiac actin, STAT3, and pSTAT3 by Western blotting, as well as for mitochondrial oxidative phosphorylation, membrane potential, swelling, calcium transport, and content of oxidized lipids. RESULTS In our results, leptin induced an increased rate-pressure product as a result of increased heart rate and contraction force, as well oxidative stress. In addition, mitochondrial dysfunction expressed as a loss of membrane potential, decreased ability for calcium transport and retention, faster swelling, and less respiratory control was observed. CONCLUSIONS Our results support the role of leptin as a deleterious factor for cardiac function and indicates that mitochondrial dysfunction could be a trigger for cardiac hypertrophy and failure.
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Affiliation(s)
- Edna Berzabá-Evoli
- Laboratory of Research in Metabolic and Infectious Diseases, Multidisciplinary Academic Division of Comalcalco, Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
| | - Cecilia Zazueta
- Departamento de Biomedicina Cardiovascular, Instituto Nacional de Cardiología (I. Ch.), 14080 Tlalpan, MEX, Mexico
| | - Jarumi Hishel Cruz Hernández
- Laboratory of Research in Metabolic and Infectious Diseases, Multidisciplinary Academic Division of Comalcalco, Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
| | - Nancy Patricia Gómez-Crisóstomo
- Laboratory of Research in Metabolic and Infectious Diseases, Multidisciplinary Academic Division of Comalcalco, Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
| | - Isela Esther Juárez-Rojop
- Research Center, Academic Division of Health Sciences (DACS), Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
| | - Erick Natividad De la Cruz-Hernández
- Laboratory of Research in Metabolic and Infectious Diseases, Multidisciplinary Academic Division of Comalcalco, Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
| | - Eduardo Martínez-Abundis
- Laboratory of Research in Metabolic and Infectious Diseases, Multidisciplinary Academic Division of Comalcalco, Juarez Autonomous University of Tabasco, Villahermosa, TAB, Mexico
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N-terminal acetylation modulates Bax targeting to mitochondria. Int J Biochem Cell Biol 2017; 95:35-42. [PMID: 29233735 DOI: 10.1016/j.biocel.2017.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 11/28/2017] [Accepted: 12/06/2017] [Indexed: 01/13/2023]
Abstract
The pro-apoptotic Bax protein is the main effector of mitochondrial permeabilization during apoptosis. Bax is controlled at several levels, including post-translational modifications such as phosphorylation and S-palmitoylation. However, little is known about the contribution of other protein modifications to Bax activity. Here, we used heterologous expression of human Bax in yeast to study the involvement of N-terminal acetylation by yNaa20p (yNatB) on Bax function. We found that human Bax is N-terminal (Nt-)acetylated by yNaa20p and that Nt-acetylation of Bax is essential to maintain Bax in an inactive conformation in the cytosol of yeast and Mouse Embryonic Fibroblast (MEF) cells. Bax accumulates in the mitochondria of yeast naa20Δ and Naa25-/- MEF cells, but does not promote cytochrome c release, suggesting that an additional step is required for full activation of Bax. Altogether, our results show that Bax N-terminal acetylation by NatB is involved in its mitochondrial targeting.
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Kim HK, Noh YH, Nilius B, Ko KS, Rhee BD, Kim N, Han J. Current and upcoming mitochondrial targets for cancer therapy. Semin Cancer Biol 2017. [PMID: 28627410 DOI: 10.1016/j.semcancer.2017.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mitochondria are essential intracellular organelles that regulate energy metabolism, cell death, and signaling pathways that are important for cell proliferation and differentiation. Therefore, mitochondria are fundamentally implicated in cancer biology, including initiation, growth, metastasis, relapse, and acquired drug resistance. Based on these implications, mitochondria have been proposed as a major therapeutic target for cancer treatment. In addition to classical view of mitochondria in cancer biology, recent studies found novel pathophysiological roles of mitochondria in cancer. In this review, we introduce recent concepts of mitochondrial roles in cancer biology including mitochondrial DNA mutation and epigenetic modulation, energy metabolism reprogramming, mitochondrial channels, involvement in metastasis and drug resistance, and cancer stem cells. We also discuss the role of mitochondria in emerging cancer therapeutic strategies, especially cancer immunotherapy and CRISPR-Cas9 system gene therapy.
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Affiliation(s)
- Hyoung Kyu Kim
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea; Department of Integrated Biomedical Science, College of Medicine, Inje University, Busan, Republic of Korea
| | - Yeon Hee Noh
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Bernd Nilius
- KU Leuven, Department Cell Mol Medicine, Leuven, 3000, Belgium
| | - Kyung Soo Ko
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Byoung Doo Rhee
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Nari Kim
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea
| | - Jin Han
- National Research Laboratory for Mitochondrial Signaling, Department of Physiology, Department of Health Sciences and Technology, BK21 Plus Project Team, College of Medicine, Cardiovascular and Metabolic Disease Center, Inje University, Busan, Republic of Korea.
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11
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Zhang M, Zheng J, Nussinov R, Ma B. Release of Cytochrome C from Bax Pores at the Mitochondrial Membrane. Sci Rep 2017; 7:2635. [PMID: 28572603 PMCID: PMC5453941 DOI: 10.1038/s41598-017-02825-7] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 04/19/2017] [Indexed: 12/12/2022] Open
Abstract
How cytochrome C is released from the mitochondria to the cytosol via Bax oligomeric pores, a process which is required for apoptosis, is still a mystery. Based on experimentally measured residue-residue distances, we recently solved the first atomic model for Bax oligomeric pores at the membranes using computational approaches. Here, we investigate the mechanism at the microsecond time- and nanometer space- scale using MD simulations. Our free energy landscape depicts a low barrier for the permeation of cytochrome C into the Bax C-terminal mouth, with the pathway proceeding to the inner cavity and exiting via the N-terminal mouth. Release is guided by organized charged/hydrophilic surfaces. The hydrophilicity and negative charge of the pore surface gradually increase along the release pathway from the pore entry to the exit opening. Rather than inert passing of the cytochrome C through a rigid pore, the flexible pore may selectively aid the cytochrome C passage. Once the Bax pore is formed in the membrane, with a low energy barrier, the release of cytochrome C may be readily achieved through energy fluctuations. Collectively, our work provides mechanistic insight in atomic detail into the release of cytochrome C through Bax oligomeric pores.
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Affiliation(s)
- Mingzhen Zhang
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio, 44325, USA
| | - Jie Zheng
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio, 44325, USA
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD, 21702, USA
- Sackler Inst. of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD, 21702, USA.
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12
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Simonyan L, Légiot A, Lascu I, Durand G, Giraud MF, Gonzalez C, Manon S. The substitution of Proline 168 favors Bax oligomerization and stimulates its interaction with LUVs and mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1144-1155. [DOI: 10.1016/j.bbamem.2017.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 02/28/2017] [Accepted: 03/14/2017] [Indexed: 12/23/2022]
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13
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Xu D, Jin J, Yu H, Zhao Z, Ma D, Zhang C, Jiang H. Chrysin inhibited tumor glycolysis and induced apoptosis in hepatocellular carcinoma by targeting hexokinase-2. J Exp Clin Cancer Res 2017; 36:44. [PMID: 28320429 PMCID: PMC5359903 DOI: 10.1186/s13046-017-0514-4] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 03/14/2017] [Indexed: 11/15/2022] Open
Abstract
Background Hexokinase-2(HK-2) plays dual roles in glucose metabolism and mediation of cell apoptosis, making it an attractive target for cancer therapy. Chrysin is a natural flavone found in plant extracts which are widely used as herb medicine in China. In the present study, we investigated the antitumor activity of chrysin against hepatocellular carcinoma (HCC) and the role of HK-2 played for chrysin to exert its function. Methods The expression of HK-2 in HCC cell line and tumor tissue was examined by western blotting and immunohistochemistry staining. The activities of chrysin against HCC cell proliferation and tumor glycolysis were investigated. Chrysin-induced apoptosis was analyzed by flow cytometry. The effect of chrysin on HK-2 expression and the underlying mechanisms by which induced HCC cell apoptosis were studied. In HK-2 exogenous overexpression cell, the changes of chrysin-induced cell apoptosis and glycolysis suppression were investigated. HCC cell xenograft model was used to confirm the antitumor activity of chrysin in vivo and the effect on HK-2 was tested in chrysin-treated tumor tissue. Results In contrast with normal cell lines and tissue, HK-2 expression was substantially elevated in the majority of tested HCC cell lines and tumor tissue. Owing to the decrease of HK-2 expression, glucose uptake and lactate production in HCC cells were substantially inhibited after exposure to chrysin. After chrysin treatment, HK-2 which combined with VDAC-1 on mitochondria was significantly declined, resulting in the transfer of Bax from cytoplasm to mitochondria and induction of cell apoptosis. Chrysin-mediated cell apoptosis and glycolysis suppression were dramatically impaired in HK-2 exogenous overexpression cells. Tumor growth in HCC xenograft models was significantly restrained after chrysin treatment and significant decrease of HK-2 expression was observed in chrysin-treated tumor tissue. Conclusion Through suppressing glycolysis and inducing apoptosis in HCC, chrysin, or its derivative has a promising potential to be a novel therapeutic for HCC management, especially for those patients with high HK-2 expression.
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Affiliation(s)
- Dong Xu
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Junzhe Jin
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Hao Yu
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Zheming Zhao
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Dongyan Ma
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Chundong Zhang
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China
| | - Honglei Jiang
- Department of General Surgery, the fourth affiliated hospital of China Medical University, The No.4 Chongshan east road Huanggu District, Shenyang, 110032, LiaoNing, China.
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14
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Garenne D, Renault TT, Manon S. Bax mitochondrial relocation is linked to its phosphorylation and its interaction with Bcl-xL. MICROBIAL CELL 2016; 3:597-605. [PMID: 28357332 PMCID: PMC5348979 DOI: 10.15698/mic2016.12.547] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The heterologous expression of Bax, and other Bcl-2 family members, in the yeast Saccharomyces cerevisiae, has proved to be a valuable reporter system to investigate the molecular mechanisms underlying their interaction with mitochondria. By combining the co-expression of Bax and Bcl-xL mutants with analyzes of their localization and interaction in mitochondria and post-mitochondrial supernatants, we showed that the ability of Bax and Bcl-xL to interact is dependent both on Bax phosphorylation - mimicked by a substitution S184D - and by Bax and Bcl-xL localization. This, and previous data, provide the molecular basis for a model of dynamic equilibrium for Bax localization and activation, regulated both by phosphorylation and Bcl-xL.
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Affiliation(s)
- David Garenne
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France. ; Present address: INRA, UMR1332, 71 Avenue Edouard Bourlaud, 33882 Villenave d'Ornon, France
| | - Thibaud T Renault
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France. ; Present address: Department of Regulation in Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
| | - Stéphen Manon
- Institut de Biochimie et de Génétique Cellulaires, UMR5095, CNRS & Université de Bordeaux, CS61390, 146 Rue Léo Saignat, 33077 Bordeaux, France
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15
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Zhang M, Zheng J, Nussinov R, Ma B. Oncogenic Mutations Differentially Affect Bax Monomer, Dimer, and Oligomeric Pore Formation in the Membrane. Sci Rep 2016; 6:33340. [PMID: 27630059 PMCID: PMC5024136 DOI: 10.1038/srep33340] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 08/25/2016] [Indexed: 12/20/2022] Open
Abstract
Dysfunction of Bax, a pro-apoptotic regulator of cellular metabolism is implicated in neurodegenerative diseases and cancer. We have constructed the first atomistic models of the Bax oligomeric pore consisting with experimental residue-residue distances. The models are stable, capturing well double electron-electron resonance (DEER) spectroscopy measurements and provide structural details in line with the DEER data. Comparison with the latest experimental results revealed that our models agree well with both Bax and Bak pores, pointed to a converged structural arrangement for Bax and Bak pore formation. Using multi-scale molecular dynamics simulations, we probed mutational effects on Bax transformation from monomer → dimer → membrane pore formation at atomic resolution. We observe that two cancer-related mutations, G40E and S118I, allosterically destabilize the monomer and stabilize an off-pathway swapped dimer, preventing productive pore formation. This observation suggests a mechanism whereby the mutations may work mainly by over-stabilizing the monomer → dimer transformation toward an unproductive off-pathway swapped-dimer state. Our observations point to misfolded Bax states, shedding light on the molecular mechanism of Bax mutation-elicited cancer. Most importantly, the structure of the Bax pore facilitates future study of releases cytochrome C in atomic detail.
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Affiliation(s)
- Mingzhen Zhang
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio 44325
| | - Jie Zheng
- Department of Chemical & Biomolecular Engineering, the University of Akron, Akron, Ohio 44325
| | - Ruth Nussinov
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD 21702, USA
- Sackler Inst. of Molecular Medicine, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
| | - Buyong Ma
- Basic Science Program, Leidos Biomedical Research, Inc. Cancer and Inflammation Program, National Cancer Institute, Frederick, MD 21702, USA
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16
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Mandal T, Shin S, Aluvila S, Chen HC, Grieve C, Choe JY, Cheng EH, Hustedt EJ, Oh KJ. Assembly of Bak homodimers into higher order homooligomers in the mitochondrial apoptotic pore. Sci Rep 2016; 6:30763. [PMID: 27488021 PMCID: PMC4973285 DOI: 10.1038/srep30763] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/08/2016] [Indexed: 11/09/2022] Open
Abstract
In mitochondrial apoptosis, Bak is activated by death signals to form pores of unknown structure on the mitochondrial outer membrane via homooligomerization. Cytochrome c and other apoptotic factors are released from the intermembrane space through these pores, initiating downstream apoptosis events. Using chemical crosslinking and double electron electron resonance (DEER)-derived distance measurements between specific structural elements in Bak, here we clarify how the Bak pore is assembled. We propose that previously described BH3-in-groove homodimers (BGH) are juxtaposed via the 'α3/α5' interface, in which the C-termini of helices α3 and α5 are in close proximity between two neighboring Bak homodimers. This interface is observed concomitantly with the well-known 'α6:α6' interface. We also mapped the contacts between Bak homodimers and the lipid bilayer based on EPR spectroscopy topology studies. Our results suggest a model for the lipidic Bak pore, whereby the mitochondrial targeting C-terminal helix does not change topology to accommodate the lining of the pore lumen by BGH.
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Affiliation(s)
- Tirtha Mandal
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Seungjin Shin
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Sreevidya Aluvila
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Hui-Chen Chen
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Carter Grieve
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Jun-Yong Choe
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
| | - Emily H Cheng
- Human Oncology and Pathogenesis Program and Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Eric J Hustedt
- Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Kyoung Joon Oh
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA
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17
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Luna-Vargas MP, Chipuk JE. The deadly landscape of pro-apoptotic BCL-2 proteins in the outer mitochondrial membrane. FEBS J 2016; 283:2676-89. [PMID: 26662859 PMCID: PMC4907887 DOI: 10.1111/febs.13624] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/11/2015] [Accepted: 12/08/2015] [Indexed: 01/06/2023]
Abstract
Apoptosis is a biological process that removes damaged, excess or infected cells through a genetically controlled mechanism. This process plays a crucial role in organismal development, immunity and tissue homeostasis, and alterations in apoptosis contribute to human diseases including cancer and auto-immunity. In the past two decades, significant efforts have focused on understanding the function of the BCL-2 proteins, a complex family of pro-survival and pro-apoptotic α-helical proteins that directly control the mitochondrial pathway of apoptosis. Diverse structural investigations of the BCL-2 family members have broadened our mechanistic understanding of their individual functions. However, an often over-looked aspect of the mitochondrial pathway of apoptosis is how the BCL-2 family specifically interacts with and targets the outer mitochondrial membrane to initiate apoptosis. Structural information on the relationship between the BCL-2 family and the outer mitochondrial membrane is missing; likewise, knowledge of the biophysical mechanisms by which the outer mitochondrial membrane affects and effects apoptosis is lacking. In this mini-review, we provide a current overview of the BCL-2 family members and discuss the latest structural insights into BAK/BAX activation and oligomerization in the context of the outer mitochondrial membrane and mitochondrial biology.
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Affiliation(s)
- Mark P.A. Luna-Vargas
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
| | - Jerry E. Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Diabetes, Obesity, and Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
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18
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Jiang X, Li L, Ying Z, Pan C, Huang S, Li L, Dai M, Yan B, Li M, Jiang H, Chen S, Zhang Z, Wang X. A Small Molecule That Protects the Integrity of the Electron Transfer Chain Blocks the Mitochondrial Apoptotic Pathway. Mol Cell 2016; 63:229-239. [DOI: 10.1016/j.molcel.2016.06.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 05/16/2016] [Accepted: 06/08/2016] [Indexed: 11/28/2022]
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19
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Pro-apoptotic Bax molecules densely populate the edges of membrane pores. Sci Rep 2016; 6:27299. [PMID: 27255832 PMCID: PMC4891688 DOI: 10.1038/srep27299] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 05/16/2016] [Indexed: 11/28/2022] Open
Abstract
How the pro-apoptotic Bax protein permeabilizes the mitochondrial outer membrane is not fully understood. Previously, using cryo-electron microscopy (cryo-EM), we showed that activated Bax forms large, growing pores. Whether formed in liposomes or in mitochondrial outer membranes, Bax-induced pores exhibit the same morphology, with negative curvature flanking the edges and with no visible protein structure protruding from the membranes. Here we used cryo-EM to show that gold-labeled Bax molecules, after activation by Bid, became localized strictly at pore edges. This argues that Bax acts at short range to deform the membrane. Also, Bax molecules populated the walls of both small and large pores at the same density, implying that Bax is continuously recruited to the pores as they widen. Moreover, because all Bax molecules became oligomerized after membrane insertion, we infer that Bax oligomers are present at pore edges. We suggest that oligomerization may promote pore enlargement.
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20
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Revisiting trends on mitochondrial mega-channels for the import of proteins and nucleic acids. J Bioenerg Biomembr 2016; 49:75-99. [DOI: 10.1007/s10863-016-9662-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/25/2016] [Indexed: 12/14/2022]
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21
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Renault TT, Dejean LM, Manon S. A brewing understanding of the regulation of Bax function by Bcl-xL and Bcl-2. Mech Ageing Dev 2016; 161:201-210. [PMID: 27112371 DOI: 10.1016/j.mad.2016.04.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 04/19/2016] [Accepted: 04/22/2016] [Indexed: 12/17/2022]
Abstract
Bcl-2 family members form a network of protein-protein interactions that regulate apoptosis through permeabilization of the mitochondrial outer membrane. Deciphering this intricate network requires streamlined experimental models, including the heterologous expression in yeast. This approach had previously enabled researchers to identify domains and residues that underlie the conformational changes driving the translocation, the insertion and the oligomerization of the pro-apoptotic protein Bax at the level of the mitochondrial outer membrane. Recent studies that combine experiments in yeast and in mammalian cells have shown the unexpected effect of the anti-apoptotic protein Bcl-xL on the priming of Bax. As demonstrated with the BH3-mimetic molecule ABT-737, this property of Bcl-xL, and of Bcl-2, is crucial to elaborate about how apoptosis could be reactivated in tumoral cells.
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Affiliation(s)
- Thibaud T Renault
- Helmholtz Center for Infection Research, Junior Research Group Infection Biology of Salmonella, Inhoffenstraße 7, 38124 Braunschweig, Germany; Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
| | - Laurent M Dejean
- California State University of Fresno, Department of Chemistry, 2555 E. San Ramon Ave M/S SB70, Fresno, CA 93740-8034, USA
| | - Stéphen Manon
- CNRS, UMR5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France; Université de Bordeaux, 146 Rue Léo Saignat, 33076 Bordeaux, France.
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22
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Große L, Wurm CA, Brüser C, Neumann D, Jans DC, Jakobs S. Bax assembles into large ring-like structures remodeling the mitochondrial outer membrane in apoptosis. EMBO J 2016; 35:402-13. [PMID: 26783364 PMCID: PMC4755111 DOI: 10.15252/embj.201592789] [Citation(s) in RCA: 215] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/23/2015] [Accepted: 12/01/2015] [Indexed: 12/05/2022] Open
Abstract
The Bcl-2 family proteins Bax and Bak are essential for the execution of many apoptotic programs. During apoptosis, Bax translocates to the mitochondria and mediates the permeabilization of the outer membrane, thereby facilitating the release of pro-apoptotic proteins. Yet the mechanistic details of the Bax-induced membrane permeabilization have so far remained elusive. Here, we demonstrate that activated Bax molecules, besides forming large and compact clusters, also assemble, potentially with other proteins including Bak, into ring-like structures in the mitochondrial outer membrane. STED nanoscopy indicates that the area enclosed by a Bax ring is devoid of mitochondrial outer membrane proteins such as Tom20, Tom22, and Sam50. This strongly supports the view that the Bax rings surround an opening required for mitochondrial outer membrane permeabilization (MOMP). Even though these Bax assemblies may be necessary for MOMP, we demonstrate that at least in Drp1 knockdown cells, these assemblies are not sufficient for full cytochrome c release. Together, our super-resolution data provide direct evidence in support of large Bax-delineated pores in the mitochondrial outer membrane as being crucial for Bax-mediated MOMP in cells.
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Affiliation(s)
- Lena Große
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian A Wurm
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian Brüser
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel Neumann
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel C Jans
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Stefan Jakobs
- Department of Neurology, University Medical Center of Göttingen, Göttingen, Germany Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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23
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Complex formation and turnover of mitochondrial transporters and ion channels. J Bioenerg Biomembr 2016; 49:101-111. [DOI: 10.1007/s10863-016-9648-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 01/19/2016] [Indexed: 02/07/2023]
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24
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Goldar S, Khaniani MS, Derakhshan SM, Baradaran B. Molecular mechanisms of apoptosis and roles in cancer development and treatment. Asian Pac J Cancer Prev 2016; 16:2129-44. [PMID: 25824729 DOI: 10.7314/apjcp.2015.16.6.2129] [Citation(s) in RCA: 365] [Impact Index Per Article: 45.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Programmed cell death (PCD) or apoptosis is a mechanism which is crucial for all multicellular organisms to control cell proliferation and maintain tissue homeostasis as well as eliminate harmful or unnecessary cells from an organism. Defects in the physiological mechanisms of apoptosis may contribute to different human diseases like cancer. Identification of the mechanisms of apoptosis and its effector proteins as well as the genes responsible for apoptosis has provided a new opportunity to discover and develop novel agents that can increase the sensitivity of cancer cells to undergo apoptosis or reset their apoptotic threshold. These novel targeted therapies include those targeting anti-apoptotic Bcl-2 family members, p53, the extrinsic pathway, FLICE-inhibitory protein (c-FLIP), inhibitor of apoptosis (IAP) proteins, and the caspases. In recent years a number of these novel agents have been assessed in preclinical and clinical trials. In this review, we introduce some of the key regulatory molecules that control the apoptotic pathways, extrinsic and intrinsic death receptors, discuss how defects in apoptotic pathways contribute to cancer, and list several agents being developed to target apoptosis.
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Affiliation(s)
- Samira Goldar
- Department of Biochemistry and Clinical Labratorary, Division of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran E-mail :
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25
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Teijido O, Ganesan YT, Llanos R, Peton A, Urtecho JB, Soprani A, Villamayor A, Antonsson B, Manon S, Dejean L. A sandwich ELISA for the conformation-specific quantification of the activated form of human Bax. Anal Biochem 2015; 497:90-4. [PMID: 26748144 DOI: 10.1016/j.ab.2015.12.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 11/25/2015] [Accepted: 12/22/2015] [Indexed: 01/12/2023]
Abstract
Bcl-2 family proteins are critical regulators of mitochondrial outer membrane permeabilization (MOMP), which represents the point of no return of apoptotic cell death. The exposure of the Bax N-terminus at the mitochondria reflects Bax activation; and this activated configuration of the Bax protein is associated with MOMP. N-terminal exposure can be detected using specific monoclonal and/or polyclonal antibodies, and the onset of activated Bax has extensively been used as an early marker of apoptosis. The protocols of immunoprecipitation and/or immunocytochemistry commonly used to detect activated Bax are long and tedious, and allow semiquantification of the antigen at best. The sandwich ELISA protocol we developed has a 5 ng/mL detection limit and is highly specific for the activated conformation of Bax. This ELISA allows a rapid quantification of activated human Bax in whole cells and isolated mitochondria protein extracts. These properties grant this assay the potential to further clarify the prognostic and diagnostic value of activated Bax in disorders associated with deregulated apoptotic pathways such as degenerative diseases or cancer.
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Affiliation(s)
- Oscar Teijido
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Care and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yogesh Tengarai Ganesan
- Human Oncology and Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, NY 10065, USA
| | - Raul Llanos
- Department of Chemistry, California State University, Fresno, CA 93740, USA
| | - Ashley Peton
- Department of Chemistry, California State University, Fresno, CA 93740, USA
| | | | - Adauri Soprani
- Department of Basic Sciences, New York University, College of Dentistry, New York, NY 10010, USA
| | - Aimee Villamayor
- Department of Basic Sciences, New York University, College of Dentistry, New York, NY 10010, USA
| | - Bruno Antonsson
- Merck Serono S.A. Geneva Research Center, Geneva, Switzerland
| | - Stéphen Manon
- CNRS, Université de Bordeaux, UMR5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux, France
| | - Laurent Dejean
- Department of Chemistry, California State University, Fresno, CA 93740, USA.
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26
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Simonyan L, Renault TT, da Costa Novais MJ, Sousa MJ, Côrte-Real M, Camougrand N, Gonzalez C, Manon S. Regulation of Bax/mitochondria interaction by AKT. FEBS Lett 2015; 590:13-21. [DOI: 10.1002/1873-3468.12030] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 11/23/2015] [Accepted: 11/24/2015] [Indexed: 12/19/2022]
Affiliation(s)
| | | | | | | | | | | | | | - Stéphen Manon
- CNRS; Université de Bordeaux, UMR5095; Bordeaux France
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27
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MAC inhibitors antagonize the pro-apoptotic effects of tBid and disassemble Bax / Bak oligomers. J Bioenerg Biomembr 2015; 49:65-74. [PMID: 26698318 DOI: 10.1007/s10863-015-9635-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 12/06/2015] [Indexed: 01/06/2023]
Abstract
Mitochondrial Apoptotic Channel inhibitors or iMACs are di-bromocarbazole derivatives with anti-apoptotic function which have been tested and validated in several mouse models of brain injury and neurodegeneration. Owing to the increased therapeutic potential of these compounds, we sought to expand our knowledge of their mechanism of action. We investigated the kinetics of MAC inhibition in mitochondria from wild type, Bak, and Bax knockout cell lines using patch clamp electrophysiology, fluorescence microscopy, ELISA, and semiquantitative western blot analyses. Our results show that iMACs work through at least two mechanisms: 1) by blocking relocation of the cytoplasmic Bax protein to mitochondria and 2) by disassembling Bax and Bak oligomers in the mitochondrial outer membrane. iMACs exert comparable effects on channel conductance of Bax or Bak and similarly affect cytochrome c release from Bax or Bak-containing mitochondria. Interestingly, wild type mitochondria were more susceptible to inhibition than the Bak or Bax knockouts. Western blot analysis showed that wild type mitochondria had lower steady state levels of Bak in the absence of apoptotic stimulation.
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28
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Madamba SM, Damri KN, Dejean LM, Peixoto PM. Mitochondrial Ion Channels in Cancer Transformation. Front Oncol 2015; 5:120. [PMID: 26090338 PMCID: PMC4455240 DOI: 10.3389/fonc.2015.00120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Accepted: 05/15/2015] [Indexed: 11/13/2022] Open
Abstract
Cancer transformation involves reprograming of mitochondrial function to avert cell death mechanisms, monopolize energy metabolism, accelerate mitotic proliferation, and promote metastasis. Mitochondrial ion channels have emerged as promising therapeutic targets because of their connection to metabolic and apoptotic functions. This mini review discusses how mitochondrial channels may be associated with cancer transformation and expands on the possible involvement of mitochondrial protein import complexes in pathophysiological process.
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Affiliation(s)
- Stephen M. Madamba
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
- City University of New York Graduate Center, New York, NY, USA
| | - Kevin N. Damri
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
| | - Laurent M. Dejean
- Department of Chemistry, College of Science and Mathematics, California State University Fresno, Fresno, CA, USA
| | - Pablo M. Peixoto
- Department of Natural Sciences, Baruch College, City University of New York, New York, NY, USA
- City University of New York Graduate Center, New York, NY, USA
- Department of Basic Sciences, New York University College of Dentistry, New York, NY, USA
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29
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Williams SB, Ye Y, Huang M, Chang DW, Kamat AM, Pu X, Dinney CP, Wu X. Mitochondrial DNA Content as Risk Factor for Bladder Cancer and Its Association with Mitochondrial DNA Polymorphisms. Cancer Prev Res (Phila) 2015; 8:607-13. [PMID: 25896234 DOI: 10.1158/1940-6207.capr-14-0414] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 04/01/2015] [Indexed: 01/05/2023]
Abstract
Mitochondrial DNA (mtDNA) content has been shown to be associated with cancer susceptibility. We identified 926 bladder cancer patients and compared these with 926 healthy controls frequency matched on age, gender, and ethnicity. Patients diagnosed with bladder cancer had significantly decreased mtDNA content when compared with control subjects (median, 0.98 vs. 1.04, P < 0.001). Low mtDNA content (i.e., less than the median in control subjects) was associated with a statistically significant increased risk of bladder cancer, when compared with high mtDNA content [Odds ratio (OR), 1.37; 95% confidence interval (CI), 1.13-1.66; P < 0.001). In a trend analysis, a statistically significant dose-response relationship was detected between lower mtDNA content and increasing risk of bladder cancer (Ptrend <0.001). When stratified by host characteristics, advanced age (>65 years), male sex and positive smoking history were significantly associated with low mtDNA content and increased risk of bladder cancer. We identified two unique mtDNA polymorphisms significantly associated with risk of bladder cancer: mitot10464c (OR, 1.39; 95% CI, 1.00-1.93; P = 0.048) and mitoa4918g (OR, 1.40; 95% CI, 1.00-1.95; P = 0.049). Analysis of the joint effect of low mtDNA content and unfavorable mtDNA polymorphisms revealed a 2.5-fold increased risk of bladder cancer (OR, 2.50; 95% CI, 1.60-3.94; P < 0.001). Significant interaction was observed between mitoa4918g and mtDNA content (Pinteraction = 0.028). Low mtDNA content was associated with increased risk of bladder cancer and we identified new susceptibility mtDNA alleles associated with increased risk that require further investigation into the biologic underpinnings of bladder carcinogenesis.
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Affiliation(s)
- Stephen B Williams
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas. Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Yuanqing Ye
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Maosheng Huang
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - David W Chang
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Ashish M Kamat
- Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Xia Pu
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Colin P Dinney
- Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Xifeng Wu
- Department of Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
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30
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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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Shoshan-Barmatz V, Ben-Hail D, Admoni L, Krelin Y, Tripathi SS. The mitochondrial voltage-dependent anion channel 1 in tumor cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:2547-75. [PMID: 25448878 DOI: 10.1016/j.bbamem.2014.10.040] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 10/20/2014] [Accepted: 10/24/2014] [Indexed: 02/06/2023]
Abstract
VDAC1 is found at the crossroads of metabolic and survival pathways. VDAC1 controls metabolic cross-talk between mitochondria and the rest of the cell by allowing the influx and efflux of metabolites, ions, nucleotides, Ca2+ and more. The location of VDAC1 at the outer mitochondrial membrane also enables its interaction with proteins that mediate and regulate the integration of mitochondrial functions with cellular activities. As a transporter of metabolites, VDAC1 contributes to the metabolic phenotype of cancer cells. Indeed, this protein is over-expressed in many cancer types, and silencing of VDAC1 expression induces an inhibition of tumor development. At the same time, along with regulating cellular energy production and metabolism, VDAC1 is involved in the process of mitochondria-mediated apoptosis by mediating the release of apoptotic proteins and interacting with anti-apoptotic proteins. The engagement of VDAC1 in the release of apoptotic proteins located in the inter-membranal space involves VDAC1 oligomerization that mediates the release of cytochrome c and AIF to the cytosol, subsequently leading to apoptotic cell death. Apoptosis can also be regulated by VDAC1, serving as an anchor point for mitochondria-interacting proteins, such as hexokinase (HK), Bcl2 and Bcl-xL, some of which are also highly expressed in many cancers. By binding to VDAC1, HK provides both a metabolic benefit and apoptosis-suppressive capacity that offer the cell a proliferative advantage and increase its resistance to chemotherapy. Thus, these and other functions point to VDAC1 as an excellent target for impairing the re-programed metabolism of cancer cells and their ability to evade apoptosis. Here, we review current evidence pointing to the function of VDAC1 in cell life and death, and highlight these functions in relation to both cancer development and therapy. In addressing the recently solved 3D structures of VDAC1, this review will point to structure-function relationships of VDAC as critical for deciphering how this channel can perform such a variety of roles, all of which are important for cell life and death. Finally, this review will also provide insight into VDAC function in Ca2+ homeostasis, protection against oxidative stress, regulation of apoptosis and involvement in several diseases, as well as its role in the action of different drugs. We will discuss the use of VDAC1-based strategies to attack the altered metabolism and apoptosis of cancer cells. These strategies include specific siRNA able to impair energy and metabolic homeostasis, leading to arrested cancer cell growth and tumor development, as well VDAC1-based peptides that interact with anti-apoptotic proteins to induce apoptosis, thereby overcoming the resistance of cancer cell to chemotherapy. Finally, small molecules targeting VDAC1 can induce apoptosis. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.
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Affiliation(s)
- Varda Shoshan-Barmatz
- Department of Life Sciences, and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
| | - Danya Ben-Hail
- Department of Life Sciences, and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Lee Admoni
- Department of Life Sciences, and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Yakov Krelin
- Department of Life Sciences, and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Shambhoo Sharan Tripathi
- Department of Life Sciences, and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Activation of mitochondrial protease OMA1 by Bax and Bak promotes cytochrome c release during apoptosis. Proc Natl Acad Sci U S A 2014; 111:14782-7. [PMID: 25275009 DOI: 10.1073/pnas.1417253111] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intrinsic apoptotic stimuli initiate mammalian cells' apoptotic program by first activating the proteins that have only Bcl-2 homology domain 3 (BH3), such as Bcl-2 interacting mediator of cell death (Bim) and truncated BH3 interacting death domain agonist (tBid), which in turn trigger conformational changes in BCL2-associated X (Bax) and BCL2-antagonist/killer (Bak) proteins that enable oligomer formation on the mitochondria, causing cytochrome c and other apoptogenic proteins in the intermembrane space to leak out. Leaked cytochrome c then initiates apoptotic caspase activation through a well-defined biochemical pathway. However, how oligomerized Bax and Bak cause cytochrome c release from mitochondria remains unknown. We report here the establishment of cell lines in which Bim or tBid can be inducibly expressed to initiate apoptosis in a controlled, quantitative manner. We used these cell lines to examine apoptotic events after Bax and Bak oligomerization but before cytochrome c release. The mitochondrial metalloprotease OMA1 was activated in this system in a Bax- and Bak-dependent fashion. Activated OMA1 cleaved the dynamin-like GTPase, optical nerve atrophy 1, an event that is critical for remodeling of mitochondrial cristae. Knockdown or knockout of OMA1 in these cells attenuated cytochrome c release. Thus it is clear that oligomerized Bax and Bak trigger apoptosis by causing both the permeabilization of the mitochondrial outer membrane and activation OMA1.
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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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Apoptotic pore formation is associated with in-plane insertion of Bak or Bax central helices into the mitochondrial outer membrane. Proc Natl Acad Sci U S A 2014; 111:E4076-85. [PMID: 25228770 DOI: 10.1073/pnas.1415142111] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The pivotal step on the mitochondrial pathway to apoptosis is permeabilization of the mitochondrial outer membrane (MOM) by oligomers of the B-cell lymphoma-2 (Bcl-2) family members Bak or Bax. However, how they disrupt MOM integrity is unknown. A longstanding model is that activated Bak and Bax insert two α-helices, α5 and α6, as a hairpin across the MOM, but recent insights on the oligomer structures question this model. We have clarified how these helices contribute to MOM perforation by determining that, in the oligomers, Bak α5 (like Bax α5) remains part of the protein core and that a membrane-impermeable cysteine reagent can label cysteines placed at many positions in α5 and α6 of both Bak and Bax. The results are inconsistent with the hairpin insertion model but support an in-plane model in which α5 and α6 collapse onto the membrane and insert shallowly to drive formation of proteolipidic pores.
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Chi X, Kale J, Leber B, Andrews DW. Regulating cell death at, on, and in membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2100-13. [PMID: 24927885 DOI: 10.1016/j.bbamcr.2014.06.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 05/29/2014] [Accepted: 06/03/2014] [Indexed: 11/17/2022]
Abstract
Bcl-2 family proteins are central regulators of apoptosis. Various family members are located in the cytoplasm, endoplasmic reticulum, and mitochondrial outer membrane in healthy cells. However during apoptosis most of the interactions between family members that determine the fate of the cell occur at the membranes of intracellular organelles. It has become evident that interactions with membranes play an active role in the regulation of Bcl-2 family protein interactions. Here we provide an overview of various models proposed to explain how the Bcl-2 family regulates apoptosis and discuss how membrane binding affects the structure and function of each of the three categories of Bcl-2 proteins (pro-apoptotic, pore-forming, and anti-apoptotic). We also examine how the Bcl-2 family regulates other aspects of mitochondrial and ER physiology relevant to cell death.
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Affiliation(s)
- Xiaoke Chi
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Justin Kale
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - Brian Leber
- Department of Medicine, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
| | - David W Andrews
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Biological Sciences, Sunnybrook Research Institute, Toronto, Ontario M4N 3M5, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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36
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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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37
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Abstract
Bax, despite being a cytosolic protein, has the distinct ability to form channels in the mitochondrial outer membrane, which are capable of releasing proteins that initiate the execution phase of apoptosis. When studied in a planar phospholipid membrane system, full-length activated Bax can form conducting entities consistent with linearly organized three-channel units displaying steep voltage-gating (n=14) that rivals that of channels in excitable membranes. In addition, the channels display strong positive co-operativity possibly arising from the charge distribution of the voltage sensors. On the basis of functional behaviour, one of the channels in this functional triplet is oriented in the opposite direction to the others often resulting in conflicts between the effects of the electric field and the positive co-operativity of adjacent channels. The closure of the first channel occurs at positive potentials and this permits the second to close, but at negative potentials. The closure of the second channel in turn permits closure of the third, but at positive potentials. Positive co-operativity manifests itself in a number of ways including the second and the third channels opening virtually simultaneously. This extraordinary behaviour must have important, although as yet undefined, physiological roles.
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38
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Lindner AU, Prehn JHM, Huber HJ. The indirect activation model of mitochondrial outer membrane permeabilisation (MOMP) initiation requires a trade-off between robustness in the absence of and sensitivity in the presence of stress. MOLECULAR BIOSYSTEMS 2014; 9:2359-69. [PMID: 23824068 DOI: 10.1039/c3mb70076c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondrial outer membrane permeabilisation (MOMP) is a hallmark of apoptosis and is controlled by antagonising members of the BCL 2 protein family. However, whether the effector proteins for MOMP, BAX and BAK, require a separate activation step (direct activation model) or if the sole inhibition of otherwise active effectors by anti-apoptotic BCL 2 proteins suffices (indirect activation model) is controversial. To address this question, we recently identified that, in most cells, effector proteins were more abundant than their inhibitors. We now employ systems modelling to elucidate fundamental consequences of this imbalance for the indirect activation model by integrating its key features into the recently validated implementation of the direct activation model. First, by modelling constitutively active BAK, several cell lines were predicted to be unstable against MOMP even in the absence of stress. This instability could be rectified by assuming BAK pores to be subject to degradation, which however demanded BAK to underlie a high and biologically unreasonable protein turnover. Stability against MOMP in the absence of stress was similarly reconstituted by assuming BAK oligomerisation to be weak, but predicted some cells to be MOMP resistant even under high stress. Assuming also BAX to be constitutively active required highly effective BAX re-translocation to the cytosol along with weak BAX oligomerisation, which again rendered some cells insensitive to induce MOMP in the presence of stress. Our results suggest that an activation step of the two effectors is required to allow stability against MOMP in the absence of stress and execution of MOMP under stress.
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Affiliation(s)
- Andreas U Lindner
- Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons, 123 St. Stephens Green, Dublin 2, Ireland
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39
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Mitochondrial ion channels as oncological targets. Oncogene 2014; 33:5569-81. [DOI: 10.1038/onc.2013.578] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 12/04/2013] [Accepted: 12/05/2013] [Indexed: 02/06/2023]
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40
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Tokar T, Ulicny J. The mathematical model of the Bcl-2 family mediated MOMP regulation can perform a non-trivial pattern recognition. PLoS One 2013; 8:e81861. [PMID: 24386084 PMCID: PMC3873269 DOI: 10.1371/journal.pone.0081861] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 10/21/2013] [Indexed: 12/22/2022] Open
Abstract
Interactions between individual members of the B-cell lymphoma 2 (Bcl-2) family of proteins form a regulatory network governing mitochondrial outer membrane permeabilization (MOMP). Bcl-2 family initiated MOMP causes release of the inter-membrane pro-apoptotic proteins to cytosol and creates a cytosolic environment suitable for the executionary phase of apoptosis. We designed the mathematical model of this regulatory network where the synthesis rates of the Bcl-2 family members served as the independent inputs. Using computational simulations, we have then analyzed the response of the model to up-/downregulation of the Bcl-2 proteins. Under several assumptions, and using estimated reaction parameters, a non-linear stimulus-response emerged, whose characteristics are associated with bistability and switch-like behavior. Interestingly, using the principal component analysis (PCA) we have shown that the given model of the Bcl-2 family interactions classifies the random combinations of inputs into two distinct classes, and responds to these by one of the two qualitatively distinct outputs. As we showed, the emergence of this behavior requires specific organization of the interactions between particular Bcl-2 proteins.
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Affiliation(s)
- Tomas Tokar
- Department of Biophysics, University of P. J. Safarik in Kosice, Kosice, Slovakia
| | - Jozef Ulicny
- Department of Biophysics, University of P. J. Safarik in Kosice, Kosice, Slovakia
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41
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Aluvila S, Mandal T, Hustedt E, Fajer P, Choe JY, Oh KJ. Organization of the mitochondrial apoptotic BAK pore: oligomerization of the BAK homodimers. J Biol Chem 2013; 289:2537-51. [PMID: 24337568 DOI: 10.1074/jbc.m113.526806] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The multidomain pro-apoptotic Bcl-2 family proteins BAK and BAX are believed to form large oligomeric pores in the mitochondrial outer membrane during apoptosis. Formation of these pores results in the release of apoptotic factors including cytochrome c from the intermembrane space into the cytoplasm, where they initiate the cascade of events that lead to cell death. Using the site-directed spin labeling method of electron paramagnetic resonance (EPR) spectroscopy, we have determined the conformational changes that occur in BAK when the protein targets to the membrane and forms pores. The data showed that helices α1 and α6 disengage from the rest of the domain, leaving helices α2-α5 as a folded unit. Helices α2-α5 were shown to form a dimeric structure, which is structurally homologous to the recently reported BAX "BH3-in-groove homodimer." Furthermore, the EPR data and a chemical cross-linking study demonstrated the existence of a hitherto unknown interface between BAK BH3-in-groove homodimers in the oligomeric BAK. This novel interface involves the C termini of α3 and α5 helices. The results provide further insights into the organization of the BAK oligomeric pores by the BAK homodimers during mitochondrial apoptosis, enabling the proposal of a BAK-induced lipidic pore with the topography of a "worm hole."
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Affiliation(s)
- Sreevidya Aluvila
- From the Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
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Mevalonate kinase deficiency and neuroinflammation: balance between apoptosis and pyroptosis. Int J Mol Sci 2013; 14:23274-88. [PMID: 24287904 PMCID: PMC3876043 DOI: 10.3390/ijms141223274] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/08/2013] [Accepted: 11/13/2013] [Indexed: 12/20/2022] Open
Abstract
Mevalonic aciduria, a rare autosomal recessive disease, represents the most severe form of the periodic fever, known as Mevalonate Kinase Deficiency. This disease is caused by the mutation of the MVK gene, which codes for the enzyme mevalonate kinase, along the cholesterol pathway. Mevalonic aciduria patients show recurrent fever episodes with associated inflammatory symptoms, severe neurologic impairments, or death, in early childhood. The typical neurodegeneration occurring in mevalonic aciduria is linked both to the intrinsic apoptosis pathway (caspase-3 and -9), which is triggered by mitochondrial damage, and to pyroptosis (caspase-1). These cell death mechanisms seem to be also related to the assembly of the inflammasome, which may, in turn, activate pro-inflammatory cytokines and chemokines. Thus, this particular molecular platform may play a crucial role in neuroinflammation mechanisms. Nowadays, a specific therapy is still lacking and the pathogenic mechanisms involving neuroinflammation and neuronal dysfunction have not yet been completely understood, making mevalonic aciduria an orphan drug disease. This review aims to analyze the relationship among neuroinflammation, mitochondrial damage, programmed cell death, and neurodegeneration. Targeting inflammation and degeneration in the central nervous system might help identify promising treatment approaches for mevalonic aciduria or other diseases in which these mechanisms are involved.
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Renault TT, Chipuk JE. Death upon a kiss: mitochondrial outer membrane composition and organelle communication govern sensitivity to BAK/BAX-dependent apoptosis. ACTA ACUST UNITED AC 2013; 21:114-23. [PMID: 24269152 DOI: 10.1016/j.chembiol.2013.10.009] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 10/03/2013] [Accepted: 10/21/2013] [Indexed: 01/24/2023]
Abstract
For stressed cells to induce the mitochondrial pathway of apoptosis, a cohort of pro-apoptotic BCL-2 proteins must collaborate with the outer mitochondrial membrane to permeabilize it. BAK and BAX are the two pro-apoptotic BCL-2 family members that are required for mitochondrial outer membrane permeabilization. While biochemical and structural insights of BAK/BAX function have expanded in recent years, very little is known about the role of the outer mitochondrial membrane in regulating BAK/BAX activity. In this review, we will highlight the impact of mitochondrial composition (both protein and lipid) and mitochondrial interactions with cellular organelles on BAK/BAX function and cellular commitment to apoptosis. A better understanding of how BAK/BAX and mitochondrial biology are mechanistically linked will likely reveal novel insights into homeostatic and pathological mechanisms associated with apoptosis.
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Affiliation(s)
- Thibaud T Renault
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA
| | - Jerry E Chipuk
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Metabolism Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA; The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1130, New York, NY 10029, USA.
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44
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The rheostat in the membrane: BCL-2 family proteins and apoptosis. Cell Death Differ 2013; 21:206-15. [PMID: 24162659 DOI: 10.1038/cdd.2013.153] [Citation(s) in RCA: 164] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/22/2013] [Accepted: 09/17/2013] [Indexed: 12/19/2022] Open
Abstract
Apoptosis, a mechanism for programmed cell death, has key roles in human health and disease. Many signals for cellular life and death are regulated by the BCL-2 family proteins and converge at mitochondria, where cell fate is ultimately decided. The BCL-2 family includes both pro-life (e.g. BCL-XL) and pro-death (e.g. BAX, BAK) proteins. Previously, it was thought that a balance between these opposing proteins, like a simple 'rheostat', could control the sensitivity of cells to apoptotic stresses. Later, this rheostat concept had to be extended, when it became clear that BCL-2 family proteins regulate each other through a complex network of bimolecular interactions, some transient and some relatively stable. Now, studies have shown that the apoptotic circuitry is even more sophisticated, in that BCL-2 family interactions are spatially dynamic, even in nonapoptotic cells. For example, BAX and BCL-XL can shuttle between the cytoplasm and the mitochondrial outer membrane (MOM). Upstream signaling pathways can regulate the cytoplasmic-MOM equilibrium of BAX and thereby adjust the sensitivity of cells to apoptotic stimuli. Thus, we can view the MOM as the central locale of a dynamic life-death rheostat. BAX invariably forms extensive homo-oligomers after activation in membranes. However, recent studies, showing that activated BAX monomers determine the kinetics of MOM permeabilization (MOMP), perturb the lipid bilayer and form nanometer size pores, pose questions about the role of the oligomerization. Other lingering questions concern the molecular mechanisms of BAX redistribution between MOM and cytoplasm and the details of BAX/BAK-membrane assemblies. Future studies need to delineate how BCL-2 family proteins regulate MOMP, in concert with auxiliary MOM proteins, in a dynamic membrane environment. Technologies aimed at elucidating the structure and function of the full-length proteins in membranes are needed to illuminate some of these critical issues.
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Bleicken S, Landeta O, Landajuela A, Basañez G, García-Sáez AJ. Proapoptotic Bax and Bak proteins form stable protein-permeable pores of tunable size. J Biol Chem 2013; 288:33241-52. [PMID: 24100034 DOI: 10.1074/jbc.m113.512087] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The Bcl-2 proapoptotic proteins Bax and Bak mediate the permeabilization of the mitochondrial outer membrane during apoptosis. Current models consider that Bax and Bak form pores at the mitochondrial outer membrane that are responsible for the release of cytochrome c and other larger mitochondrial apoptotic factors (i.e. Smac/DIABLO, AIF, and endoglycosidase G). However, the properties and nature of Bax/Bak apoptotic pores remain enigmatic. Here, we performed a detailed analysis of the membrane permeabilizing activity of Bax and Bak at the single vesicle level. We directly visualized that cBid-activated Bax and BakΔC21 can form membrane pores large enough to release not only cytochrome c, but also allophycocyanine, a protein of 104 kDa. Interestingly, the size of Bax and BakΔC21 pores is not constant, as typically observed in purely proteinaceous channels, but evolves with time and depends on protein concentration. We found that Bax and BakΔC21 formed long-lived pores, whose areas changed with the amount of Bax/BakΔC21 but not with cardiolipin concentration. Altogether, our results demonstrate that Bax and BakΔC21 follow similar mechanisms of membrane permeabilization characterized by the formation of protein-permeable pores of dynamic size, in agreement with the proteolipidic nature of these apoptotic pores.
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Affiliation(s)
- Stephanie Bleicken
- From the German Cancer Research Center, BioQuant, ImNeuenheimer Feld 267, 69120 Heidelberg, Germany
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46
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Programming biological models in Python using PySB. Mol Syst Biol 2013; 9:646. [PMID: 23423320 PMCID: PMC3588907 DOI: 10.1038/msb.2013.1] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 01/07/2013] [Indexed: 12/19/2022] Open
Abstract
PySB is a framework for creating biological models as Python programs using a
high-level, action-oriented vocabulary that promotes transparency, extensibility and
reusability. PySB interoperates with many existing modeling tools and supports
distributed model development. ![]()
PySB models are programs and leverage existing programming tools for documentation, testing, and collaborative development. Reusable functions can encode common low-level biochemical processes as well as high-level modules, making models transparent and concise. Modeling workflow is accelerated through close integration with Python numerical tools and interoperability with existing modeling software. We demonstrate the use of PySB to encode 15 alternative hypotheses for the mitochondrial regulation of apoptosis, including a new ‘Embedded Together' model based on recent biochemical findings.
Mathematical equations are fundamental to modeling biological networks, but as
networks get large and revisions frequent, it becomes difficult to manage equations
directly or to combine previously developed models. Multiple simultaneous efforts to
create graphical standards, rule-based languages, and integrated software
workbenches aim to simplify biological modeling but none fully meets the need for
transparent, extensible, and reusable models. In this paper we describe PySB, an
approach in which models are not only created using programs, they are programs.
PySB draws on programmatic modeling concepts from little b and ProMot, the
rule-based languages BioNetGen and Kappa and the growing library of Python numerical
tools. Central to PySB is a library of macros encoding familiar biochemical actions
such as binding, catalysis, and polymerization, making it possible to use a
high-level, action-oriented vocabulary to construct detailed models. As Python
programs, PySB models leverage tools and practices from the open-source software
community, substantially advancing our ability to distribute and manage the work of
testing biochemical hypotheses. We illustrate these ideas using new and previously
published models of apoptosis.
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Leanza L, Biasutto L, Managò A, Gulbins E, Zoratti M, Szabò I. Intracellular ion channels and cancer. Front Physiol 2013; 4:227. [PMID: 24027528 PMCID: PMC3759743 DOI: 10.3389/fphys.2013.00227] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/05/2013] [Indexed: 02/02/2023] Open
Abstract
Several types of channels play a role in the maintenance of ion homeostasis in subcellular organelles including endoplasmatic reticulum, nucleus, lysosome, endosome, and mitochondria. Here we give a brief overview of the contribution of various mitochondrial and other organellar channels to cancer cell proliferation or death. Much attention is focused on channels involved in intracellular calcium signaling and on ion fluxes in the ATP-producing organelle mitochondria. Mitochondrial K+ channels (Ca2+-dependent BKCa and IKCa, ATP-dependent KATP, Kv1.3, two-pore TWIK-related Acid-Sensitive K+ channel-3 (TASK-3)), Ca2+ uniporter MCU, Mg2+-permeable Mrs2, anion channels (voltage-dependent chloride channel VDAC, intracellular chloride channel CLIC) and the Permeability Transition Pore (MPTP) contribute importantly to the regulation of function in this organelle. Since mitochondria play a central role in apoptosis, modulation of their ion channels by pharmacological means may lead to death of cancer cells. The nuclear potassium channel Kv10.1 and the nuclear chloride channel CLIC4 as well as the endoplasmatic reticulum (ER)-located inositol 1,4,5-trisphosphate (IP3) receptor, the ER-located Ca2+ depletion sensor STIM1 (stromal interaction molecule 1), a component of the store-operated Ca2+ channel and the ER-resident TRPM8 are also mentioned. Furthermore, pharmacological tools affecting organellar channels and modulating cancer cell survival are discussed. The channels described in this review are summarized on Figure 1. Overall, the view is emerging that intracellular ion channels may represent a promising target for cancer treatment.
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Affiliation(s)
- Luigi Leanza
- Department of Biology, University of Padova Padova, Italy
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48
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Tait SWG, Green DR. Mitochondrial regulation of cell death. Cold Spring Harb Perspect Biol 2013; 5:5/9/a008706. [PMID: 24003207 DOI: 10.1101/cshperspect.a008706] [Citation(s) in RCA: 338] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Although required for life, paradoxically, mitochondria are often essential for initiating apoptotic cell death. Mitochondria regulate caspase activation and cell death through an event termed mitochondrial outer membrane permeabilization (MOMP); this leads to the release of various mitochondrial intermembrane space proteins that activate caspases, resulting in apoptosis. MOMP is often considered a point of no return because it typically leads to cell death, even in the absence of caspase activity. Because of this pivotal role in deciding cell fate, deregulation of MOMP impacts on many diseases and represents a fruitful site for therapeutic intervention. Here we discuss the mechanisms underlying mitochondrial permeabilization and how this key event leads to cell death through caspase-dependent and -independent means. We then proceed to explore how the release of mitochondrial proteins may be regulated following MOMP. Finally, we discuss mechanisms that enable cells sometimes to survive MOMP, allowing them, in essence, to return from the point of no return.
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Affiliation(s)
- Stephen W G Tait
- Beatson Institute, Institute of Cancer Sciences, University of Glasgow, Glasgow G61 1BD, United Kingdom.
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Karch J, Kwong JQ, Burr AR, Sargent MA, Elrod JW, Peixoto PM, Martinez-Caballero S, Osinska H, Cheng EHY, Robbins J, Kinnally KW, Molkentin JD. Bax and Bak function as the outer membrane component of the mitochondrial permeability pore in regulating necrotic cell death in mice. eLife 2013; 2:e00772. [PMID: 23991283 PMCID: PMC3755340 DOI: 10.7554/elife.00772] [Citation(s) in RCA: 209] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 07/24/2013] [Indexed: 12/13/2022] Open
Abstract
A critical event in ischemia-based cell death is the opening of the mitochondrial permeability transition pore (MPTP). However, the molecular identity of the components of the MPTP remains unknown. Here, we determined that the Bcl-2 family members Bax and Bak, which are central regulators of apoptotic cell death, are also required for mitochondrial pore-dependent necrotic cell death by facilitating outer membrane permeability of the MPTP. Loss of Bax/Bak reduced outer mitochondrial membrane permeability and conductance without altering inner membrane MPTP function, resulting in resistance to mitochondrial calcium overload and necrotic cell death. Reconstitution with mutants of Bax that cannot oligomerize and form apoptotic pores, but still enhance outer membrane permeability, permitted MPTP-dependent mitochondrial swelling and restored necrotic cell death. Our data predict that the MPTP is an inner membrane regulated process, although in the absence of Bax/Bak the outer membrane resists swelling and prevents organelle rupture to prevent cell death. DOI:http://dx.doi.org/10.7554/eLife.00772.001 In all multicellular plants and animals, cells are continuously dying and being replaced. There are a number of different types of cell death, but two of the best studied are apoptosis and necrosis. Apoptosis, sometimes referred to as ‘cell suicide’, is a form of programmed cell death that is generally beneficial to the organism. Necrosis, however, occurs whenever cells are damaged—for example, due to a lack of oxygen—and can trigger harmful inflammation in surrounding tissue. Although the processes leading up to apoptosis and necrosis are very different, they both involve regulated changes in mitochondria—the organelles that supply cells with chemical energy. Mitochondria have a distinctive appearance, being enclosed by two membranes, the innermost of which is highly folded. During apoptosis, large pores form in the outer membranes of mitochondria. These pores are generated by two proteins—Bax and Bak—and they enable the mitochondrion to release proteins that activate processes involved in apoptosis. Pores also form in the mitochondrial membrane during necrosis. However, these mitochondrial permeability transition pores (MPTPs) occur simultaneously in both the inner and outer membranes and are thought to lead to swelling and rupture of mitochondria. Now, Karch et al. have shown that Bax and Bak are also involved in the formation of these permeability pores that underlie necrosis. When mouse cells that had been genetically modified to lack Bak and Bax were grown in cell culture, they were found to be resistant to substances that normally induce necrosis. Instead, their mitochondria continued to function normally, suggesting that MPTPs cannot form in the absence of Bak and Bax. Karch et al. then generated mice with heart cells that lack Bax and Bak, and deprived their hearts of oxygen to simulate a heart attack. Compared to normal mice, the genetically modified animals experienced less damage to their heart muscle, suggesting that the absence of Bax and Bak prevents cell death due to necrosis. If Bax and Bak are involved in both apoptosis and necrosis, inhibiting them could be a powerful therapeutic approach for preventing all forms of cell death during heart attacks or in certain degenerative diseases. DOI:http://dx.doi.org/10.7554/eLife.00772.002
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Affiliation(s)
- Jason Karch
- Department of Pediatrics , Cincinnati Children's Hospital Medical Center, University of Cincinnati , Cincinnati , United States
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50
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Lindner AU, Concannon CG, Boukes GJ, Cannon MD, Llambi F, Ryan D, Boland K, Kehoe J, McNamara DA, Murray F, Kay EW, Hector S, Green DR, Huber HJ, Prehn JHM. Systems analysis of BCL2 protein family interactions establishes a model to predict responses to chemotherapy. Cancer Res 2013; 73:519-28. [PMID: 23329644 DOI: 10.1158/0008-5472.can-12-2269] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Apoptotic desensitization is a hallmark of cancer cells, but present knowledge of molecular systems controlling apoptosis has yet to provide significant prognostic insights. Here, we report findings from a systems study of the intrinsic pathway of apoptosis by BCL2 family proteins and clinical translation of its findings into a model with applications in colorectal cancer (CRC). By determining absolute protein quantifications in CRC cells and patient tumor samples, we found that BAK and BAX were expressed more highly than their antiapoptotic inhibitors. This counterintuitive finding suggested that sole inhibition of effector BAX and BAK could not be sufficient for systems stability in nonstressed cells. Assuming a model of direct effector activation by BH3-only proteins, we calculated that the amount of stress-induced BH3-only proteins required to activate mitochondrial apoptosis could predict individual death responses of CRC cells to 5-fluorouracil/oxaliplatin. Applying this model predictor to protein profiles in tumor and matched normal tissue samples from 26 patients with CRCs, we found that differences in protein quantities were sufficient to model the increased tumor sensitivity to chemotherapy compared with normal tissue. In addition, these differences were sufficient to differentiate clinical responders from nonresponders with high confidence. Applications of our model, termed DR_MOMP, were used to assess the impact of apoptosis-sensitizing drugs in lowering the necessary dose of state-of-the-art chemotherapy in individual patients. Together, our findings offer a ready clinical tool with the potential to tailor chemotherapy to individual patients.
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Affiliation(s)
- Andreas U Lindner
- Centre for Systems Medicine, Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
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