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Yao Q, Mascarenhas Dos Santos AC, Zhang H, Mañas A, Hussaini A, Kim U, Xu C, Basheer S, Tasaki S, Xiang J. Unconventional Source of Neurotoxic Protein Aggregation from Organelle Off-Target Bax∆2 in Alzheimer's Disease. Biomolecules 2023; 13:970. [PMID: 37371550 DOI: 10.3390/biom13060970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
Protein aggregates are a hallmark of Alzheimer's disease (AD). Extensive studies have focused on β-amyloid plaques and Tau tangles. Here, we illustrate a novel source of protein aggregates in AD neurons from organelle off-target proteins. Bax is a mitochondrial pore-forming pro-death protein. What happens to Bax if it fails to target mitochondria? We previously showed that a mitochondrial target-deficient alternatively spliced variant, Bax∆2, formed large cytosolic protein aggregates and triggered caspase 8-mediated cell death. Bax∆2 protein levels were low in most normal organs and the proteins were quickly degraded in cancer. Here, we found that 85% of AD patients had Bax∆2 required alternative splicing. Increased Bax∆2 proteins were mostly accumulated in neurons of AD-susceptible brain regions. Intracellularly, Bax∆2 aggregates distributed independently of Tau tangles. Interestingly, Bax∆2 aggregates triggered the formation of stress granules (SGs), a large protein-RNA complex involved in AD pathogenesis. Although the functional domains required for aggregation and cell death are the same as in cancer cells, Bax∆2 relied on SGs, not caspase 8, for neuronal cell death. These results imply that the aggregation of organelle off-target proteins, such as Bax∆2, broadens the scope of traditional AD pathogenic proteins that contribute to the neuronal stress responses and AD pathogenesis.
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Affiliation(s)
- Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | | | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Adriana Mañas
- Department of Laboratory Medicine, Lund University, 22381 Lund, Sweden
| | - Ammarah Hussaini
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Ujin Kim
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Congtai Xu
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sana Basheer
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Shinya Tasaki
- Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, IL 60612, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
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2
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Pore-forming proteins as drivers of membrane permeabilization in cell death pathways. Nat Rev Mol Cell Biol 2022; 24:312-333. [PMID: 36543934 DOI: 10.1038/s41580-022-00564-w] [Citation(s) in RCA: 47] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2022] [Indexed: 12/24/2022]
Abstract
Regulated cell death (RCD) relies on activation and recruitment of pore-forming proteins (PFPs) that function as executioners of specific cell death pathways: apoptosis regulator BAX (BAX), BCL-2 homologous antagonist/killer (BAK) and BCL-2-related ovarian killer protein (BOK) for apoptosis, gasdermins (GSDMs) for pyroptosis and mixed lineage kinase domain-like protein (MLKL) for necroptosis. Inactive precursors of PFPs are converted into pore-forming entities through activation, membrane recruitment, membrane insertion and oligomerization. These mechanisms involve protein-protein and protein-lipid interactions, proteolytic processing and phosphorylation. In this Review, we discuss the structural rearrangements incurred by RCD-related PFPs and describe the mechanisms that manifest conversion from autoinhibited to membrane-embedded molecular states. We further discuss the formation and maturation of membrane pores formed by BAX/BAK/BOK, GSDMs and MLKL, leading to diverse pore architectures. Lastly, we highlight commonalities and differences of PFP mechanisms involving BAX/BAK/BOK, GSDMs and MLKL and conclude with a discussion on how, in a population of challenged cells, the coexistence of cell death modalities may have profound physiological and pathophysiological implications.
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3
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Abstract
Bax and Bak, two functionally similar, pro-apoptotic proteins of the Bcl-2 family, are known as the gateway to apoptosis because of their requisite roles as effectors of mitochondrial outer membrane permeabilization (MOMP), a major step during mitochondria-dependent apoptosis. The mechanism of how cells turn Bax/Bak from inert molecules into fully active and lethal effectors had long been the focal point of a major debate centered around two competing, but not mutually exclusive, models: direct activation and indirect activation. After intensive research efforts for over two decades, it is now widely accepted that to initiate apoptosis, some of the BH3-only proteins, a subclass of the Bcl-2 family, directly engage Bax/Bak to trigger their conformational transformation and activation. However, a series of recent discoveries, using previously unavailable CRISPR-engineered cell systems, challenge the basic premise that undergirds the consensus and provide evidence for a novel and surprisingly simple model of Bax/Bak activation: the membrane (lipids)-mediated spontaneous model. This review will discuss the evidence, rationale, significance, and implications of this new model.
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Affiliation(s)
- Xu Luo
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Alaska Medical Center, Omaha, ME, 68198-7696, USA.,Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, 68198-6805, USA
| | - Katelyn L O'Neill
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Alaska Medical Center, Omaha, ME, 68198-7696, USA
| | - Kai Huang
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Alaska Medical Center, Omaha, ME, 68198-7696, USA.,Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE, 68198-6805, USA
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4
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Zhang L, Townsend DM, Morris M, Maldonado EN, Jiang YL, Broome AM, Bethard JR, Ball LE, Tew KD. Voltage-Dependent Anion Channels Influence Cytotoxicity of ME-344, a Therapeutic Isoflavone. J Pharmacol Exp Ther 2020; 374:308-318. [PMID: 32546528 PMCID: PMC7372917 DOI: 10.1124/jpet.120.000009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/19/2020] [Indexed: 01/27/2023] Open
Abstract
ME-344 is a second-generation cytotoxic isoflavone with anticancer activity promulgated through interference with mitochondrial functions. Using a click chemistry version of the drug together with affinity-enriched mass spectrometry, voltage-dependent anion channels (VDACs) 1 and 2 were identified as drug targets. To determine the importance of VDAC1 or 2 to cytotoxicity, we used lung cancer cells that were either sensitive (H460) or intrinsically resistant (H596) to the drug. In H460 cells, depletion of VDAC1 and VDAC2 by small interfering RNA impacted ME-344 effects by diminishing generation of reactive oxygen species (ROS), preventing mitochondrial membrane potential dissipation, and moderating ME-344-induced cytotoxicity and mitochondrial-mediated apoptosis. Mechanistically, VDAC1 and VDAC2 knockdown prevented ME-344-induced apoptosis by inhibiting Bax mitochondrial translocation and cytochrome c release as well as apoptosis in these H460 cells. We conclude that VDAC1 and 2, as mediators of the response to oxidative stress, have roles in modulating ROS generation, Bax translocation, and cytochrome c release during mitochondrial-mediated apoptosis caused by ME-344. SIGNIFICANCE STATEMENT: Dissecting preclinical drug mechanisms are of significance in development of a drug toward eventual Food and Drug Administration approval.
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Affiliation(s)
- Leilei Zhang
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Danyelle M Townsend
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Morgan Morris
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Eduardo N Maldonado
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Yu-Lin Jiang
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Ann-Marie Broome
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Jennifer R Bethard
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Lauren E Ball
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
| | - Kenneth D Tew
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics (L.Z., M.M., E.N.M., Y.-L.J., A.-M.B., J.R.B., L.E.B., K.D.T.) and Department of Pharmaceutical and Biomedical Sciences (D.M.T.), Medical University of South Carolina, Charleston, South Carolina
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5
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A Structural Model for Bax∆2-Mediated Activation of Caspase 8-Dependent Apoptosis. Int J Mol Sci 2020; 21:ijms21155476. [PMID: 32751845 PMCID: PMC7432750 DOI: 10.3390/ijms21155476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 07/26/2020] [Accepted: 07/29/2020] [Indexed: 01/28/2023] Open
Abstract
Bax∆2 is a pro-apoptotic anti-tumor protein in the Bax family. While most of the Bax family causes cell death by targeting mitochondria, Bax∆2 forms cytosolic aggregates and activates caspase 8-dependent cell death. We previously showed that the Bax∆2 helix α9 is critical for caspase 8 recruitment. However, the interaction between these two proteins at the structural level is unknown. In this in silico study, we performed molecular dynamics (MD) simulations and protein-protein docking on Bax∆2 variants. The results suggest that the Bax∆2 variants have different stable states. Mutating the Baxα mitochondria-targeting signal [L26P/L27P] appears to introduce a kink into helix α1. Protein-protein docking suggests that helices α9 of both wild-type Bax∆2 and Bax∆2 caspase 8 binding-deficient mutant [L164P] can fit in the same caspase 8 binding site, but the mutant is unable to fit as well as wild-type Bax∆2. Together, these data point to a structural basis for explaining Bax∆2 function in caspase 8-dependent cell death.
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6
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Gong G, Jiao Y, Pan Q, Tang H, An Y, Yuan A, Wang K, Huang C, Dai W, Lu Y, Wang S, Zhang J, Su H. Antitumor Effect and Toxicity of an Albumin-Paclitaxel Nanocarrier System Constructed via Controllable Alkali-Induced Conformational Changes. ACS Biomater Sci Eng 2019; 5:1895-1906. [PMID: 33405563 DOI: 10.1021/acsbiomaterials.9b00312] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guangming Gong
- Department of Pharmaceutics, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, China
| | - Yongjun Jiao
- Institute of Pathogenic Microbiology, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, Jiangsu 210009, China
| | - Qinqin Pan
- HLA Laboratory, the First Affiliated Hospital with Nanjing Medical University, Nanjing, Jiangsu, 210029, People’s Republic of China
| | - Hao Tang
- Department of Pharmaceutics, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, China
| | - Yanli An
- Jiangsu Key Laboratory of Molecular and Functional Imaging, Department of Radiology, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu 210009, China
| | - Ahu Yuan
- State Key Laboratory of Pharmaceutical Biotechnology, Medical School of Nanjing University, Nanjing, Jiangsu 210093, China
| | - Kaikai Wang
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, Jiangsu 210009, P.R. China
| | - Canping Huang
- Research Department, Ringpu Bio-Tech, Tianjin, China
| | - Weimin Dai
- Administrative Committee of Taizhou Medical Hi-tech Zone, China Medical City, Taizhou, Zhejiang 225316, P.R. China
| | - Ying Lu
- Department of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Shudong Wang
- Department of Pharmaceutics, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, China
| | - Jian Zhang
- National Laboratory of Solid State, Microstructure and Department of Physics, Nanjing University, Nanjing, Jiangsu 210093, China
| | - Hua Su
- Department of Pharmaceutics, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, China
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7
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Farmer T, O'Neill KL, Naslavsky N, Luo X, Caplan S. Retromer facilitates the localization of Bcl-xL to the mitochondrial outer membrane. Mol Biol Cell 2019; 30:1138-1146. [PMID: 30840537 PMCID: PMC6724524 DOI: 10.1091/mbc.e19-01-0044] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The anti-apoptotic Bcl-2 family protein Bcl-xL plays a critical role in cell survival by protecting the integrity of the mitochondrial outer membrane (MOM). The mechanism through which Bcl-xL is recruited to the MOM has not been fully discerned. The retromer is a conserved endosomal scaffold complex involved in membrane trafficking. Here we identify VPS35 and VPS26, two core components of the retromer, as novel regulators of Bcl-xL. We observed interactions and colocalization between Bcl-xL, VPS35, VPS26, and MICAL-L1, a protein involved in recycling endosome biogenesis that also interacts with the retromer. We also found that upon VPS35 depletion, levels of nonmitochondrial Bcl-xL were increased. In addition, retromer-depleted cells displayed more rapid Bax activation and apoptosis. These results suggest that the retromer regulates apoptosis by facilitating Bcl-xL's transport to the MOM. Importantly, our studies suggest a previously uncharacterized relationship between the machineries of cell death/survival and endosomal trafficking.
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Affiliation(s)
- Trey Farmer
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198-5870
| | - Katelyn L O'Neill
- Eppley Institute for Research in Cancer and Allied Diseases, The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198-5870
| | - Naava Naslavsky
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198-5870
| | - Xu Luo
- Eppley Institute for Research in Cancer and Allied Diseases, The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198-5870
| | - Steve Caplan
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198-5870.,Eppley Institute for Research in Cancer and Allied Diseases, The Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198-5870
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8
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Lim W, Yang C, Jeong M, Bazer FW, Song G. Coumestrol induces mitochondrial dysfunction by stimulating ROS production and calcium ion influx into mitochondria in human placental choriocarcinoma cells. Mol Hum Reprod 2017; 23:786-802. [DOI: 10.1093/molehr/gax052] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 10/06/2017] [Indexed: 12/11/2022] Open
Affiliation(s)
- Whasun Lim
- Department of Biomedical Sciences, Catholic Kwandong University, Gangneung 25601, Republic of Korea
| | - Changwon Yang
- Department of Biotechnology, Institute of Animal Molecular Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Muhah Jeong
- Department of Biotechnology, Institute of Animal Molecular Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Fuller W Bazer
- Department of Animal Science, Center for Animal Biotechnology and Genomics, Texas A&M University, College Station, 77843–2471, TX, USA
| | - Gwonhwa Song
- Department of Biotechnology, Institute of Animal Molecular Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
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9
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O'Neill KL, Huang K, Zhang J, Chen Y, Luo X. Inactivation of prosurvival Bcl-2 proteins activates Bax/Bak through the outer mitochondrial membrane. Genes Dev 2016; 30:973-88. [PMID: 27056669 PMCID: PMC4840302 DOI: 10.1101/gad.276725.115] [Citation(s) in RCA: 225] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/18/2016] [Indexed: 02/06/2023]
Abstract
In this study, O'Neill et al. used genome editing to generate cells deficient for all eight proapoptotic BH3-only proteins (OctaKO) and cells that lack the entire Bcl-2 family (Bcl-2 allKO). Their findings suggest that the outer mitochondrial membrane (OMM), not BH3-only proteins or p53/Rb, is the direct activator of Bax/Bak following BH3-only-mediated neutralization of anti-apoptotic Bcl-2 proteins. The mechanism of Bax/Bak activation remains a central question in mitochondria-dependent apoptotic signaling. While it is established that all proapoptotic Bcl-2 homology 3 (BH3)-only proteins bind and neutralize the anti-apoptotic Bcl-2 family proteins, how this neutralization leads to Bax/Bak activation has been actively debated. Here, genome editing was used to generate cells deficient for all eight proapoptotic BH3-only proteins (OctaKO) and those that lack the entire Bcl-2 family (Bcl-2 allKO). Although the OctaKO cells were resistant to most apoptotic stimuli tested, they underwent Bax/Bak-dependent and p53/Rb-independent apoptosis efficiently when both Bcl-xL and Mcl-1, two anti-apoptotic Bcl-2 proteins, were inactivated or eliminated. Strikingly, when expressed in the Bcl-2 allKO cells, both Bax and Bak spontaneously associated with the outer mitochondrial membrane (OMM) through their respective helix 9, and this association triggered their homo-oligomerization/activation. Together, these results strongly suggest that the OMM, not BH3-only proteins or p53/Rb, is the long-sought-after direct activator of Bax/Bak following BH3-only-mediated neutralization of anti-apoptotic Bcl-2 proteins.
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Affiliation(s)
- Katelyn L O'Neill
- Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA
| | - Kai Huang
- Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA
| | - Jingjing Zhang
- Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA; Xiangya Hospital, Central South University, Changsha 410008, China
| | - Yi Chen
- Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA
| | - Xu Luo
- Eppley Institute for Research in Cancer and Allied Diseases, Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198, USA
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10
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Heat stress induced apoptosis is triggered by transcription-independent p53, Ca(2+) dyshomeostasis and the subsequent Bax mitochondrial translocation. Sci Rep 2015; 5:11497. [PMID: 26105784 PMCID: PMC4478470 DOI: 10.1038/srep11497] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 05/22/2015] [Indexed: 12/22/2022] Open
Abstract
In this study, We demonstrated that Bax mitochondrial translocation plays a vital role in the initiation of the mitochondrial signaling pathway upon activation by heat stress. In addition, both p53 mitochondrial translocation and Ca2+ signal mediated MPTP opening activate Bax mitochondrial translocation. Employing pifithrin-α (a p53 mitochondrial translocation inhibitor) and CsA (a permeability transition pore (MPTP) inhibitor), we found that heat stress induced Bax mitochondrial translocation was significantly inhibited in cells pretreated with both PFT and CsA. Furthermore, we demonstrated that generation of reactive oxygen species (ROS) is a critical mediator in heat stress induced apoptosis and that the antioxidant MnTBAP significantly decreased heat stress induced p53 mitochondrial translocation and Ca2+ signal mediated MPTP opening, as well as the subsequent Bax mitochondrial translocation and activation of the caspase cascade. Taken together, our results indicate that heat stress induces apoptosis through the mitochondrial pathway with ROS dependent mitochondrial p53 translocation and Ca2+ dyshomeostasis, and the ensuing intro Bax mitochondrial translocation as the upstream events involved in triggering the apoptotic process observed upon cellular exposure to heat stress.
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11
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Landeta O, Landajuela A, Garcia-Saez A, Basañez G. Minimalist Model Systems Reveal Similarities and Differences between Membrane Interaction Modes of MCL1 and BAK. J Biol Chem 2015; 290:17004-19. [PMID: 25987560 DOI: 10.1074/jbc.m114.602193] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Indexed: 11/06/2022] Open
Abstract
Proteins belonging to the BCL2 family are key modulators of apoptosis that establish a complex network of interactions among themselves and with other cellular factors to regulate cell fate. It is well established that mitochondrial membranes are the main locus of action of all BCL2 family proteins, but it is difficult to obtain a precise view of how BCL2 family members operate at the native mitochondrial membrane environment during apoptosis. Here, we used minimalist model systems and multiple fluorescence-based techniques to examine selected membrane activities of MCL1 and BAK under apoptotic-like conditions. We show that three distinct apoptosis-related factors (i.e. the BCL2 homology 3 ligand cBID, the mitochondrion-specific lipid cardiolipin, and membrane geometrical curvature) all promote membrane association of BCL2-like structural folds belonging to both MCL1 and BAK. However, at the same time, the two proteins exhibited distinguishing features in their membrane association modes under apoptotic-like conditions. In addition, scanning fluorescence cross-correlation spectroscopy and FRET measurements revealed that the BCL2-like structural fold of MCL1, but not that of BAK, forms stable heterodimeric complexes with cBID in a manner adjustable by membrane cardiolipin content and curvature degree. Our results add significantly to a growing body of evidence indicating that the mitochondrial membrane environment plays a complex and active role in the mode of action of BCL2 family proteins.
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Affiliation(s)
- Olatz Landeta
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain,
| | - Ane Landajuela
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain
| | - Ana Garcia-Saez
- the Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany, and the Max-Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany, and the German Cancer Research Center, BioQuant, ImNeuenheimer Feld 267, 69120 Heidelberg, Germany
| | - Gorka Basañez
- From the Unidad de Biofísica, Centro Mixto Centro Superior de Investigaciones Científicas (CSIC)-EuskalHerriko Unibertsitatea/Universidad del País Vasco (EHU/UPV), Barrio Sarriena s/n, Leioa 48940, Spain,
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12
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Bcl-2 family in inter-organelle modulation of calcium signaling; roles in bioenergetics and cell survival. J Bioenerg Biomembr 2014; 46:1-15. [PMID: 24078116 DOI: 10.1007/s10863-013-9527-7] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 08/27/2013] [Indexed: 01/01/2023]
Abstract
Bcl-2 family proteins, known for their apoptosis functioning at the mitochondria, have been shown to localize to other cellular compartments to mediate calcium (Ca2+) signals. Since the proper supply of Ca2+ in cells serves as an important mechanism for cellular survival and bioenergetics, we propose an integrating role for Bcl-2 family proteins in modulating Ca2+ signaling. The endoplasmic reticulum (ER) is the main Ca2+ storage for the cell and Bcl-2 family proteins competitively regulate its Ca2+ concentration. Bcl-2 family proteins also regulate the flux of Ca2+ from the ER by physically interacting with inositol 1,4,5-trisphosphate receptors (IP3Rs) to mediate their opening. Type 1 IP3Rs reside at the bulk ER to coordinate cytosolic Ca2+ signals, while type 3 IP3Rs reside at mitochondria-associated ER membrane (MAM) to facilitate mitochondrial Ca2+ uptake. In healthy cells, mitochondrial Ca2+ drives pyruvate into the citric acid (TCA) cycle to facilitate ATP production, while a continuous accumulation of Ca2+ can trigger the release of cytochrome c, thus initiating apoptosis. Since multiple organelles and Bcl-2 family proteins are involved in Ca2+ signaling, we aim to clarify the role that Bcl-2 family proteins play in facilitating Ca2+ signaling and how mitochondrial Ca2+ is relevant in both bioenergetics and apoptosis. We also explore how these insights could be useful in controlling bioenergetics in apoptosis-resistant cell lines.
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13
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Bleicken S, Jeschke G, Stegmueller C, Salvador-Gallego R, García-Sáez AJ, Bordignon E. Structural model of active Bax at the membrane. Mol Cell 2014; 56:496-505. [PMID: 25458844 DOI: 10.1016/j.molcel.2014.09.022] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 07/28/2014] [Accepted: 09/25/2014] [Indexed: 11/18/2022]
Abstract
Bax plays a central role in the mitochondrial pathway of apoptosis. Upon activation, cytosolic Bax monomers oligomerize on the surface of mitochondria and change conformation concertedly to punch holes into the outer membrane. The subsequent release of cytochrome c initiates cell death. However, the structure of membrane-inserted Bax and its mechanism of action remain largely unknown. Here, we propose a 3D model of active Bax at the membrane based on double electron-electron resonance (DEER) spectroscopy in liposomes and isolated mitochondria. We show that active Bax is organized at the membrane as assemblies of dimers. In addition to a stable dimerization domain, each monomer contains a more flexible piercing domain involved in interdimer interactions and pore formation. The most important structural change during Bax activation is the opening of the hairpin formed by helices 5 and 6, which adopts a clamp-like conformation central to the mechanism of mitochondrial permeabilization.
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Affiliation(s)
- Stephanie Bleicken
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany; German Cancer Research Center, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
| | - Carolin Stegmueller
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany; German Cancer Research Center, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany
| | - Raquel Salvador-Gallego
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany; German Cancer Research Center, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany
| | - Ana J García-Sáez
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany; German Cancer Research Center, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany; Interfaculty Institute of Biochemistry, Eberhard Karls University Tübingen, Hoppe-Seyler-Strasse 4, 72076 Tübingen, Germany.
| | - Enrica Bordignon
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland; Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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14
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Lindenboim L, Sasson T, Worman HJ, Borner C, Stein R. Cellular stress induces Bax-regulated nuclear bubble budding and rupture followed by nuclear protein release. Nucleus 2014; 5:527-41. [PMID: 25482068 PMCID: PMC4615202 DOI: 10.4161/19491034.2014.970105] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/31/2014] [Accepted: 09/15/2014] [Indexed: 11/19/2022] Open
Abstract
Cellular stress triggers many pathways including nuclear protein redistribution. We previously discovered that this process is regulated by Bax but the underlying mechanism has not yet been studied. Here we define this mechanism by showing that apoptotic stimuli cause Bax-regulated disturbances in lamin A/C and nuclear envelope (NE)-associated proteins which results in the generation and subsequent rupture of nuclear protein-containing bubbles. The bubbles do not contain DNA and are encapsulated by impaired nuclear pore-depleted NE. Stress-induced generation and rupture of nuclear bubbles ultimately leads to the discharge of nuclear proteins into the cytoplasm. This process precedes morphological changes of apoptosis and occurs independently of caspases. Rescue experiments revealed that this Bax effect is non-canonical, i.e. it requires the BH3 domain and α-helices 5 and 6 but it is not inhibited by Bcl(-)xL. Targeting Bax to the NE by the Klarsicht/ANC-1/Syne-1 homology (KASH) domain effectively triggers the generation and rupture of nuclear bubbles. Overall, our findings provide evidence for a novel stress-response, which is regulated by a non-canonical action of Bax on the NE.
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Key Words
- Bax
- Bax/Bak, Bax and Bak
- DKO, double knockout
- INM, inner nuclear membrane
- KASH, Klarsicht: ANC-1, Syne homology
- LAP, lamina-associated polypeptide
- LINC, links nucleoskeleton and cytoskeleton
- MEFs, mouse embryonic fibroblasts
- MOMP, mitochondrial outer membrane permeabilization
- NE, nuclear envelope
- NPCs, nuclear pore complexes
- NPM, nucleophosmin
- NPR, nuclear protein redistribution
- ONM, outer nuclear membrane
- PI, propidium iodide
- Q-VD-OPH, quinoline-Val-Asp(OMe)-CH2-OPH.
- SIGRUNB, stress-induced generation and rupture of nuclear bubbles
- apoptosis
- lamin
- nuclear envelope
- nucleus
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Affiliation(s)
- Liora Lindenboim
- Department of Neurobiology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Ramat Aviv, Israel
| | - Tiki Sasson
- Department of Neurobiology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Ramat Aviv, Israel
| | - Howard J Worman
- Department of Medicine and Department of Pathology and Cell Biology; College of Physicians and Surgeons; Columbia University; New York, NY, USA
| | - Christoph Borner
- Institute of Molecular Medicine and Cell Research; Albert Ludwigs University Freiburg; Freiburg, Germany
- Spemann Graduate School of Biology and Medicine (SGBM); Albert Ludwigs University Freiburg; Freiburg, Germany
- Excellence Cluster, Centre for Biological Signaling Studies (BIOSS); Albert Ludwigs University Freiburg; Freiburg, Germany
| | - Reuven Stein
- Department of Neurobiology; George S. Wise Faculty of Life Sciences; Tel Aviv University; Ramat Aviv, Israel
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15
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Infante SK, Oberhauser AF, Perez-Polo JR. Bax phosphorylation association with nucleus and oligomerization after neonatal Hypoxia-ischemia. J Neurosci Res 2013; 91:1152-64. [DOI: 10.1002/jnr.23224] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Revised: 02/25/2013] [Accepted: 02/27/2013] [Indexed: 11/07/2022]
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16
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Ballesta A, Lopez J, Popgeorgiev N, Gonzalo P, Doumic M, Gillet G. Data-driven modeling of SRC control on the mitochondrial pathway of apoptosis: implication for anticancer therapy optimization. PLoS Comput Biol 2013; 9:e1003011. [PMID: 23592961 PMCID: PMC3616992 DOI: 10.1371/journal.pcbi.1003011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 02/08/2013] [Indexed: 11/18/2022] Open
Abstract
Src tyrosine kinases are deregulated in numerous cancers and may favor tumorigenesis and tumor progression. We previously described that Src activation in NIH-3T3 mouse fibroblasts promoted cell resistance to apoptosis. Indeed, Src was found to accelerate the degradation of the pro-apoptotic BH3-only protein Bik and compromised Bax activation as well as subsequent mitochondrial outer membrane permeabilization. The present study undertook a systems biomedicine approach to design optimal anticancer therapeutic strategies using Src-transformed and parental fibroblasts as a biological model. First, a mathematical model of Bik kinetics was designed and fitted to biological data. It guided further experimental investigation that showed that Bik total amount remained constant during staurosporine exposure, and suggested that Bik protein might undergo activation to induce apoptosis. Then, a mathematical model of the mitochondrial pathway of apoptosis was designed and fitted to experimental results. It showed that Src inhibitors could circumvent resistance to apoptosis in Src-transformed cells but gave no specific advantage to parental cells. In addition, it predicted that inhibitors of Bcl-2 antiapoptotic proteins such as ABT-737 should not be used in this biological system in which apoptosis resistance relied on the deficiency of an apoptosis accelerator but not on the overexpression of an apoptosis inhibitor, which was experimentally verified. Finally, we designed theoretically optimal therapeutic strategies using the data-calibrated model. All of them relied on the observed Bax overexpression in Src-transformed cells compared to parental fibroblasts. Indeed, they all involved Bax downregulation such that Bax levels would still be high enough to induce apoptosis in Src-transformed cells but not in parental ones. Efficacy of this counterintuitive therapeutic strategy was further experimentally validated. Thus, the use of Bax inhibitors might be an unexpected way to specifically target cancer cells with deregulated Src tyrosine kinase activity.
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17
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McNally MA, Soane L, Roelofs BA, Hartman AL, Hardwick JM. The N-terminal helix of Bcl-xL targets mitochondria. Mitochondrion 2013; 13:119-24. [PMID: 23333404 DOI: 10.1016/j.mito.2013.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Revised: 12/16/2012] [Accepted: 01/07/2013] [Indexed: 11/26/2022]
Abstract
Anti- and pro-apoptotic Bcl-2 family members regulate the mitochondrial phase of apoptotic cell death. The mitochondrial targeting mechanisms of Bcl-2 family proteins are tightly regulated. Known outer mitochondrial membrane targeting sequences include the C-terminal tail and central helical hairpin. Bcl-xL also localizes to the inner mitochondrial membrane, but these targeting sequences are unknown. Here we investigate the possibility that the N-terminus of Bcl-xL also contains mitochondrial targeting information. Amino acid residues 1-28 of Bcl-xL fused to EGFP are sufficient to target mitochondria. Although positive charges and helical propensity are required for targeting, similar to import sequences the N-terminus is not sufficient for efficient mitochondrial import.
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Affiliation(s)
- Melanie A McNally
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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18
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µ-Calpain conversion of antiapoptotic Bfl-1 (BCL2A1) into a prodeath factor reveals two distinct alpha-helices inducing mitochondria-mediated apoptosis. PLoS One 2012; 7:e38620. [PMID: 22745672 PMCID: PMC3379997 DOI: 10.1371/journal.pone.0038620] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Accepted: 05/09/2012] [Indexed: 01/09/2023] Open
Abstract
Anti-apoptotic Bfl-1 and pro-apoptotic Bax, two members of the Bcl-2 family sharing a similar structural fold, are classically viewed as antagonist regulators of apoptosis. However, both proteins were reported to be death inducers following cleavage by the cysteine protease µ-calpain. Here we demonstrate that calpain-mediated cleavage of full-length Bfl-1 induces the release of C-terminal membrane active α-helices that are responsible for its conversion into a pro-apoptotic factor. A careful comparison of the different membrane-active regions present in the Bfl-1 truncated fragments with homologous domains of Bax show that helix α5, but not α6, of Bfl-1 induces cell death and cytochrome c release from purified mitochondria through a Bax/Bak-dependent mechanism. In contrast, both helices α5 and α6 of Bax permeabilize mitochondria regardless of the presence of Bax or Bak. Moreover, we provide evidence that the α9 helix of Bfl-1 promotes cytochrome c release and apoptosis through a unique membrane-destabilizing action whereas Bax-α9 does not display such activities. Hence, despite a common 3D-structure, C-terminal toxic domains present on Bfl-1 and Bax function in a dissimilar manner to permeabilize mitochondria and induce apoptosis. These findings provide insights for designing therapeutic approaches that could exploit the cleavage of endogenous Bcl-2 family proteins or the use of Bfl-1/Bax-derived peptides to promote tumor cell clearance.
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19
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Gall JM, Wang Z, Liesa M, Molina A, Havasi A, Schwartz JH, Shirihai O, Borkan SC, Bonegio RGB. Role of mitofusin 2 in the renal stress response. PLoS One 2012; 7:e31074. [PMID: 22292091 PMCID: PMC3266928 DOI: 10.1371/journal.pone.0031074] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 01/02/2012] [Indexed: 11/19/2022] Open
Abstract
The role of mitofusin 2 (MFN2), a key regulator of mitochondrial morphology and function in the renal stress response is unknown. To assess its role, the MFN2 floxed gene was conditionally deleted in the kidney of mice (MFN2 cKO) by Pax2 promoter driven Cre expression (Pax2Cre). MFN2 cKO caused severe mitochondrial fragmentation in renal epithelial cells that are critical for normal kidney tubular function. However, despite a small (20%) decrease in nephron number, newborn cKO pups had organ or tubular function that did not differ from littermate Cre-negative pups. MFN2 deficiency in proximal tubule epithelial cells in primary culture induced mitochondrial fragmentation but did not significantly alter ATP turnover, maximal mitochondrial oxidative reserve capacity, or the low level of oxygen consumption during cyanide exposure. MFN2 deficiency also did not increase apoptosis of tubule epithelial cells under non-stress conditions. In contrast, metabolic stress caused by ATP depletion exacerbated mitochondrial outer membrane injury and increased apoptosis by 80% in MFN2 deficient vs. control cells. Despite similar stress-induced Bax 6A7 epitope exposure in MFN2 deficient and control cells, MFN2 deficiency significantly increased mitochondrial Bax accumulation and was associated with greater release of both apoptosis inducing factor and cytochrome c. In conclusion, MFN2 deficiency in the kidney causes mitochondrial fragmentation but does not affect kidney or tubular function during development or under non-stress conditions. However, MFN2 deficiency exacerbates renal epithelial cell injury by promoting Bax-mediated mitochondrial outer membrane injury and apoptosis.
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Affiliation(s)
- Jonathan M Gall
- Renal Section, Boston Medical Center, Boston, Massachusetts, United States of America.
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20
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Pang X, Moussa SH, Targy NM, Bose JL, George NM, Gries C, Lopez H, Zhang L, Bayles KW, Young R, Luo X. Active Bax and Bak are functional holins. Genes Dev 2011; 25:2278-90. [PMID: 22006182 DOI: 10.1101/gad.171645.111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The mechanism of Bax/Bak-dependent mitochondrial outer membrane permeabilization (MOMP), a central apoptotic event primarily controlled by the Bcl-2 family proteins, remains not well understood. Here, we express active Bax/Bak in bacteria, the putative origin of mitochondria, and examine their functional similarities to the λ bacteriophage (λ) holin. As critical effectors for bacterial lysis, holin oligomers form membrane lesions, through which endolysin, a muralytic enzyme, escapes the cytoplasm to attack the cell wall at the end of the infection cycle. We found that active Bax/Bak, but not any other Bcl-2 family protein, displays holin behavior, causing bacterial lysis by releasing endolysin in an oligomerization-dependent manner. Strikingly, replacing the holin gene with active alleles of Bax/Bak results in plaque-forming phages. Furthermore, we provide evidence that active Bax produces large membrane holes, the size of which is controlled by structural elements of Bax. Notably, lysis by active Bax is inhibited by Bcl-xL, and the lysis activity of the wild-type Bax is stimulated by a BH3-only protein. Together, these results mechanistically link MOMP to holin-mediated hole formation in the bacterial plasma membrane.
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Affiliation(s)
- Xiaming Pang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, USA
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21
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BAX unleashed: the biochemical transformation of an inactive cytosolic monomer into a toxic mitochondrial pore. Trends Biochem Sci 2011; 36:642-52. [PMID: 21978892 DOI: 10.1016/j.tibs.2011.08.009] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/26/2011] [Accepted: 08/31/2011] [Indexed: 02/07/2023]
Abstract
BAX, the BCL-2-associated X protein, is a cardinal proapoptotic member of the BCL-2 family, which regulates the critical balance between cellular life and death. Because so many medical conditions can be categorized as diseases of either too many or too few cells, dissecting the biochemistry of BCL-2 family proteins and developing pharmacological strategies to target them have become high priority scientific objectives. Here, we focus on BAX, a latent, cytosolic and monomeric protein that transforms into a lethal mitochondrial oligomer in response to cellular stress. New insights into the structural location of BAX's 'on switch', and the multi-step conformational changes that ensue upon BAX activation, are providing fresh opportunities to modulate BAX for potential benefit in human diseases characterized by pathologic cell survival or unwanted cellular demise.
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22
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Babiychuk EB, Atanassoff AP, Monastyrskaya K, Brandenberger C, Studer D, Allemann C, Draeger A. The targeting of plasmalemmal ceramide to mitochondria during apoptosis. PLoS One 2011; 6:e23706. [PMID: 21886813 PMCID: PMC3158777 DOI: 10.1371/journal.pone.0023706] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 07/22/2011] [Indexed: 12/11/2022] Open
Abstract
Ceramide is a key lipid mediator of cellular processes such as differentiation, proliferation, growth arrest and apoptosis. During apoptosis, ceramide is produced within the plasma membrane. Although recent data suggest that the generation of intracellular ceramide increases mitochondrial permeability, the source of mitochondrial ceramide remains unknown. Here, we determine whether a stress-mediated plasmalemmal pool of ceramide might become available to the mitochondria of apoptotic cells. We have previously established annexin A1—a member of a family of Ca2+ and membrane-binding proteins—to be a marker of ceramide platforms. Using fluorescently tagged annexin A1, we show that, upon its generation within the plasma membrane, ceramide self-associates into platforms that subsequently invaginate and fuse with mitochondria. An accumulation of ceramide within the mitochondria of apoptotic cells was also confirmed using a ceramide-specific antibody. Electron microscopic tomography confirmed that upon the formation of ceramide platforms, the invaginated regions of the plasma membrane extend deep into the cytoplasm forming direct physical contacts with mitochondrial outer membranes. Ceramide might thus be directly transferred from the plasma membrane to the mitochondrial outer membrane. It is conceivable that this “kiss-of-death” increases the permeability of the mitochondrial outer membrane thereby triggering apoptosis.
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Affiliation(s)
| | | | | | | | - Daniel Studer
- Institute of Anatomy, University of Bern, Bern, Switzerland
| | | | - Annette Draeger
- Institute of Anatomy, University of Bern, Bern, Switzerland
- * E-mail:
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23
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Nickells RW. WITHDRAWN: Reprint of: Variations in the rheostat model of apoptosis: What studies of retinal ganglion cell death tell us about the functions of the Bcl2 family proteins. Exp Eye Res 2011:S0014-4835(11)00226-0. [PMID: 21819979 DOI: 10.1016/j.exer.2011.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 03/06/2010] [Indexed: 11/17/2022]
Abstract
The Publisher regrets that this article is an accidental duplication of an article that has already been published, doi:10.1016/j.exer.2010.03.004. The duplicate article has therefore been withdrawn.
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Affiliation(s)
- Robert W Nickells
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 6640 MSC, 1300 University Ave, Madison, WI 53706, USA
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24
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Jiao S, Li Z. Nonapoptotic function of BAD and BAX in long-term depression of synaptic transmission. Neuron 2011; 70:758-72. [PMID: 21609830 PMCID: PMC3102234 DOI: 10.1016/j.neuron.2011.04.004] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2011] [Indexed: 11/17/2022]
Abstract
It has recently been found that caspases not only function in apoptosis, but are also crucial for nonapoptotic processes such as NMDA receptor-dependent long-term depression (LTD) of synaptic transmission. It remains unknown, however, how caspases are activated and how neurons escape death in LTD. Here we show that caspase-3 is activated by the BAD-BAX cascade for LTD induction. This cascade is required specifically for NMDA receptor-dependent LTD but not for mGluR-LTD, and its activation is sufficient to induce synaptic depression. In contrast to apoptosis, however, BAD is activated only moderately and transiently and BAX is not translocated to mitochondria, resulting in only modest caspase-3 activation. We further demonstrate that the intensity and duration of caspase-3 activation determine whether it leads to cell death or LTD, thus fine-tuning of caspase-3 activation is critical in distinguishing between these two pathways.
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Affiliation(s)
- Song Jiao
- Unit on Synapse Development and Plasticity, Genes, Cognition and Psychosis Program, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zheng Li
- Unit on Synapse Development and Plasticity, Genes, Cognition and Psychosis Program, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Valero JG, Sancey L, Kucharczak J, Guillemin Y, Gimenez D, Prudent J, Gillet G, Salgado J, Coll JL, Aouacheria A. Bax-derived membrane-active peptides act as potent and direct inducers of apoptosis in cancer cells. J Cell Sci 2011; 124:556-64. [PMID: 21245196 PMCID: PMC3428271 DOI: 10.1242/jcs.076745] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Although many cancer cells are primed for apoptosis, they usually develop resistance to cell death at several levels. Permeabilization of the outer mitochondrial membrane, which is mediated by proapoptotic Bcl-2 family members such as Bax, is considered as a point of no return for initiating apoptotic cell death. This crucial role has placed Bcl-2 family proteins as recurrent targets for anticancer drug development. Here, we propose and demonstrate a new concept based on minimal active versions of Bax to induce cell death independently of endogenous Bcl-2 proteins. We show that membrane-active segments of Bax can directly induce the release of mitochondria-residing apoptogenic factors and commit tumor cells promptly and irreversibly to caspase-dependent apoptosis. On this basis, we designed a peptide encompassing part of the Bax pore-forming domain, which can target mitochondria, induce cytochrome c release and trigger caspase-dependent apoptosis. Moreover, this Bax-derived 'poropeptide' produced effective tumor regression after peritumoral injection in a nude mouse xenograft model. Thus, peptides derived from proteins that form pores in the mitochondrial outer membrane represent novel templates for anticancer agents.
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Affiliation(s)
- Juan Garcia Valero
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Lucie Sancey
- Institut d'oncologie/développement Albert Bonniot de Grenoble
INSERM : U823CHU GrenobleEFSUniversité Joseph Fourier - Grenoble IInstitut Albert Bonniot, BP170, 38042 Grenoble Cedex 9,FR
| | - Jérôme Kucharczak
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Yannis Guillemin
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Diana Gimenez
- Instituto de Ciencia Molecular
Universidad de ValenciaPolígono La Coma, s/n, 46980 Paterna, Valencia,ES
| | - Julien Prudent
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Germain Gillet
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
| | - Jesús Salgado
- Instituto de Ciencia Molecular
Universidad de ValenciaPolígono La Coma, s/n, 46980 Paterna, Valencia,ES
- Departamento de Bioquímica y Biología Molecular
Universidad de ValenciaC/ Doctor Moliner, 50, 46100 Burjassot, Valencia,ES
| | - Jean-Luc Coll
- Institut d'oncologie/développement Albert Bonniot de Grenoble
INSERM : U823CHU GrenobleEFSUniversité Joseph Fourier - Grenoble IInstitut Albert Bonniot, BP170, 38042 Grenoble Cedex 9,FR
| | - Abdel Aouacheria
- IBCP, Institut de biologie et chimie des protéines [Lyon]
CNRS : UMR5086Université Claude Bernard - Lyon I7 Passage du Vercors 69367 LYON CEDEX 07,FR
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26
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Landes T, Martinou JC. Mitochondrial outer membrane permeabilization during apoptosis: the role of mitochondrial fission. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:540-5. [PMID: 21277336 DOI: 10.1016/j.bbamcr.2011.01.021] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 01/13/2011] [Accepted: 01/13/2011] [Indexed: 01/25/2023]
Abstract
Mitochondria continually fuse and divide to yield a dynamic interconnected network throughout the cell. During apoptosis, concomitantly with permeabilization of the mitochondrial outer membrane (MOMP) and cytochrome c release, mitochondria undergo massive fission. This results in the formation of small, round organelles that tend to aggregate around the nucleus. Under some circumstances, preceding their fission, mitochondria tend to elongate and to hyperfuse, a process that is interpreted as a cell defense mechanism. Since many years, there is a controversy surrounding the physiological relevance of mitochondrial fragmentation in apoptosis. In this review, we present recent advances in this field, describe the mechanisms that underlie this process, and discuss how they could cooperate with Bax to trigger MOMP and cytochrome c release. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
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Affiliation(s)
- Thomas Landes
- Department of Cell Biology, University of Geneva, Sciences III, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland
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27
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BH3-triggered structural reorganization drives the activation of proapoptotic BAX. Mol Cell 2010; 40:481-92. [PMID: 21070973 DOI: 10.1016/j.molcel.2010.10.019] [Citation(s) in RCA: 234] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 06/16/2010] [Accepted: 08/13/2010] [Indexed: 12/29/2022]
Abstract
BAX is a proapoptotic BCL-2 family member that lies dormant in the cytosol until converted into a killer protein in response to cellular stress. Having recently identified the elusive trigger site for direct BAX activation, we now delineate by NMR and biochemical methods the essential allosteric conformational changes that transform ligand-triggered BAX into a fully activated monomer capable of propagating its own activation. Upon BAX engagement by a triggering BH3 helix, the unstructured loop between α helices 1 and 2 is displaced, the carboxy-terminal helix 9 is mobilized for membrane translocation, and the exposed BAX BH3 domain propagates the death signal through an autoactivating interaction with the trigger site of inactive BAX monomers. Our structure-activity analysis of this seminal apoptotic process reveals pharmacologic opportunities to modulate cell death by interceding at key steps of the BAX activation pathway.
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28
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Cheng S, Gao N, Zhang Z, Chen G, Budhraja A, Ke Z, Son YO, Wang X, Luo J, Shi X. Quercetin induces tumor-selective apoptosis through downregulation of Mcl-1 and activation of Bax. Clin Cancer Res 2010; 16:5679-91. [PMID: 21138867 PMCID: PMC3069720 DOI: 10.1158/1078-0432.ccr-10-1565] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE To investigate the in vivo antitumor efficacy of quercetin in U937 xenografts and the functional roles of Mcl-1 and Bax in quercetin-induced apoptosis in human leukemia. EXPERIMENTAL DESIGN Leukemia cells were treated with quercetin, after which apoptosis, Mcl-1 expression, and Bax activation and translocation were evaluated. The efficacy of quercetin as well as Mcl-1 expression and Bax activation were investigated in xenografts of U937 cells. RESULTS Administration of quercetin caused pronounced apoptosis in both transformed and primary leukemia cells but not in normal blood peripheral mononuclear cells. Quercetin-induced apoptosis was accompanied by Mcl-1 downregulation and Bax conformational change and mitochondrial translocation that triggered cytochrome c release. Knockdown of Bax by siRNA reversed quercetin-induced apoptosis and abrogated the activation of caspase and apoptosis. Ectopic expression of Mcl-1 attenuated quercetin-mediated Bax activation, translocation, and cell death. Conversely, interruption of Mcl-1 by siRNA enhanced Bax activation and translocation, as well as lethality induced by quercetin. However, the absence of Bax had no effect on quercetin-mediated Mcl-1 downregulation. Furthermore, in vivo administration of quercetin attenuated tumor growth in U937 xenografts. The TUNEL-positive apoptotic cells in tumor sections increased in quercetin-treated mice as compared with controls. Mcl-1 downregulation and Bax activation were also observed in xenografts. CONCLUSIONS These data suggest that quercetin may be useful for the treatment of leukemia by preferentially inducing apoptosis in leukemia versus normal hematopoietic cells through a process involving Mcl-1 downregulation, which, in turn, potentiates Bax activation and mitochondrial translocation, culminating in apoptosis.
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Affiliation(s)
- Senping Cheng
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Ning Gao
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Zhuo Zhang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Gang Chen
- Department of Internal Medicine, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Amit Budhraja
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Zunji Ke
- Department of Internal Medicine, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Young-ok Son
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Xin Wang
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Jia Luo
- Department of Internal Medicine, College of Medicine, University of Kentucky, Lexington, Kentucky
| | - Xianglin Shi
- Graduate Center for Toxicology, College of Medicine, University of Kentucky, Lexington, Kentucky
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van der Wal DE, DU VX, Lo KSL, Rasmussen JT, Verhoef S, Akkerman JWN. Platelet apoptosis by cold-induced glycoprotein Ibα clustering. J Thromb Haemost 2010; 8:2554-62. [PMID: 20735720 DOI: 10.1111/j.1538-7836.2010.04043.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND Cold-storage of platelets followed by rewarming induces changes in Glycoprotein (GP) Ibα-distribution indicative of receptor clustering and initiates thromboxane A(2) -formation. GPIbα is associated with 14-3-3 proteins, which contribute to GPIbα-signaling and in nucleated cells take part in apoptosis regulation. OBJECTIVES AND METHODS We investigated whether GPIbα-clustering induces platelet apoptosis through 14-3-3 proteins during cold (4 h 0 °C)-rewarming (1 h 37 °C). RESULTS During cold-rewarming, 14-3-3 proteins associate with GPIbα and dissociate from Bad inducing Bad-dephosphorylation and activation. This initiates pro-apoptosis changes in Bax/Bcl-x(L) and Bax-translocation to the mitochondria, inducing cytochrome c release. The result is activation of caspase-9, which triggers phosphatidylserine exposure and platelet phagocytosis by macrophages. Responses are prevented by N-acetyl-D-glucosamine (GN), which blocks GPIbα-clustering, and by O-sialoglycoprotein endopeptidase, which removes extracellular GPIbα. CONCLUSIONS Cold-rewarming triggers apoptosis through a GN-sensitive GPIbα-change indicative of receptor clustering. Attempts to improve platelet transfusion by cold-storage should focus on prevention of the GPIbα-change.
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Affiliation(s)
- D E van der Wal
- Department of Clinical Chemistry and Haematology, University Medical Centre Utrecht, Utrecht, The Netherlands
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Wang X, Han W, Du X, Zhu C, Carlsson Y, Mallard C, Jacotot E, Hagberg H. Neuroprotective Effect of Bax-Inhibiting Peptide on Neonatal Brain Injury. Stroke 2010; 41:2050-5. [DOI: 10.1161/strokeaha.110.589051] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Xiaoyang Wang
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Wei Han
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Xiaonan Du
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Changlian Zhu
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Ylva Carlsson
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Carina Mallard
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Etienne Jacotot
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
| | - Henrik Hagberg
- From the Perinatal Center (X.W., W.H., X.D., Y.C., C.M., E.J., H.H.), Department of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden; the Department of Pediatrics (X.W., W.H., X.D., C.Z.), The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China; the Center for Brain Repair and Rehabilitation (C.Z.), Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden; the Perinatal Center (Y.C., H.H.), Department of
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Anthracenedione derivatives as anticancer agents isolated from secondary metabolites of the mangrove endophytic fungi. Mar Drugs 2010; 8:1469-81. [PMID: 20479985 PMCID: PMC2866493 DOI: 10.3390/md8041469] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 04/01/2010] [Accepted: 04/21/2010] [Indexed: 01/21/2023] Open
Abstract
In this article, we report anticancer activity of 14 anthracenedione derivatives separated from the secondary metabolites of the mangrove endophytic fungi Halorosellinia sp. (No. 1403) and Guignardia sp. (No. 4382). Some of them inhibited potently the growth of KB and KBv200 cells, among which compound 6 displayed strong cytotoxicity with IC50 values of 3.17 and 3.21 μM to KB and KBv200 cells, respectively. Furthermore, we demonstrate that the mechanism involved in the apoptosis induced by compound 6 is probably related to mitochondrial dysfunction. Additionally, the structure-activity relationships of these compounds are discussed.
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Nickells RW. Variations in the rheostat model of apoptosis: what studies of retinal ganglion cell death tell us about the functions of the Bcl2 family proteins. Exp Eye Res 2010; 91:2-8. [PMID: 20230818 DOI: 10.1016/j.exer.2010.03.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 02/22/2010] [Accepted: 03/06/2010] [Indexed: 10/19/2022]
Abstract
Studies of the functions of members of the Bcl2 gene family suggested that apoptosis was controlled by a rheostat in which anti-apoptotic proteins like BCL2 bound and sequestered pro-apoptotic proteins like BAX. Our current understanding of these proteins suggests that this is a simplistic model. The new rheostat model predicts that BH3-only peptides act as neutralizing ligands for the anti-apoptotic proteins, thus allowing molecules like BAX to become activated and initiate mitochondrial dysfunction - a critical step in the intrinsic apoptotic program. Studies of retinal ganglion cell apoptosis indicate that a threshold of BAX expression is required for its successful activation, which is independent of the overall concentration of anti-apoptotic proteins in these cells.
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Affiliation(s)
- Robert W Nickells
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 1300 University Ave, Madison, WI 53706, USA.
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