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Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. Proc Natl Acad Sci U S A 2024; 121:e2319476121. [PMID: 38621120 PMCID: PMC11047089 DOI: 10.1073/pnas.2319476121] [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: 11/07/2023] [Accepted: 03/13/2024] [Indexed: 04/17/2024] Open
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases." These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far-overlooked role in membrane dynamics as scramblases.
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Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Cristian Rocha-Roa
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
| | - Matthew A. Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Stefano Vanni
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
- Swiss National Center for Competence in Research Bio-Inspired Materials, University of Fribourg, FribourgCH-1700, Switzerland
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2
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Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555937. [PMID: 37693532 PMCID: PMC10491306 DOI: 10.1101/2023.09.01.555937] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases". These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit-card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place, and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far overlooked role in membrane dynamics as scramblases.
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Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | | | - Matthew A Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Karin M Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Stefano Vanni
- Department of Biology, University of Fribourg, Switzerland
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3
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Crawford H, Dimitriadi M, Bassin J, Cook MT, Abelha TF, Calvo‐Castro J. Mitochondrial Targeting and Imaging with Small Organic Conjugated Fluorophores: A Review. Chemistry 2022; 28:e202202366. [PMID: 36121738 PMCID: PMC10092527 DOI: 10.1002/chem.202202366] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Indexed: 12/30/2022]
Abstract
The last decade has seen an increasingly large number of studies reporting on the development of novel small organic conjugated systems for mitochondrial imaging exploiting optical signal transduction pathways. Mitochondria are known to play a critical role in a number of key biological processes, including cellular metabolism. Importantly, irregularities on their working function are nowadays understood to be intimately linked to a range of clinical conditions, highlighting the importance of targeting mitochondria for therapeutic benefits. In this work we carry out an in-depth evaluation on the progress to date in the field to pave the way for the realization of superior alternatives to those currently existing. The manuscript is structured by commonly used chemical scaffolds and comprehensively covers key aspects factored in design strategies such as synthetic approaches as well as photophysical and biological characterization, to foster collaborative work among organic and physical chemists as well as cell biologists.
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Affiliation(s)
- Hannah Crawford
- School of Life and Medical SciencesUniversity of HertfordshireAL109ABHatfieldUK
| | - Maria Dimitriadi
- School of Life and Medical SciencesUniversity of HertfordshireAL109ABHatfieldUK
| | - Jatinder Bassin
- School of Life and Medical SciencesUniversity of HertfordshireAL109ABHatfieldUK
| | - Michael T. Cook
- School of Life and Medical SciencesUniversity of HertfordshireAL109ABHatfieldUK
| | - Thais Fedatto Abelha
- Department of Pharmacology, Toxicology and Therapeutic ChemistryFaculty of Pharmacy and Food ScienceUniversity of Barcelona08028BarcelonaSpain
- Institute of Nanoscience and NanotechnologyUniversity of Barcelona (IN2UB)08028BarcelonaSpain
| | - Jesus Calvo‐Castro
- School of Life and Medical SciencesUniversity of HertfordshireAL109ABHatfieldUK
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4
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Shvetsova A, Masud AJ, Schneider L, Bergmann U, Monteuuis G, Miinalainen IJ, Hiltunen JK, Kastaniotis AJ. A hunt for OM45 synthetic petite interactions in Saccharomyces cerevisiae reveals a role for Miro GTPase Gem1p in cristae structure maintenance. Microbiologyopen 2021; 10:e1238. [PMID: 34713605 PMCID: PMC8501180 DOI: 10.1002/mbo3.1238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 09/09/2021] [Accepted: 09/09/2021] [Indexed: 11/28/2022] Open
Abstract
Om45 is a major protein of the yeast's outer mitochondrial membrane under respiratory conditions. However, the cellular role of the protein has remained obscure. Previously, deletion mutant phenotypes have not been found, and clear amino acid sequence similarities that would allow inferring its functional role are not available. In this work, we describe synthetic petite mutants of GEM1 and UGO1 that depend on the presence of OM45 for respiratory growth, as well as the identification of several multicopy suppressors of the synthetic petite phenotypes. In the analysis of our mutants, we demonstrate that Om45p and Gem1p have a collaborative role in the maintenance of mitochondrial morphology, cristae structure, and mitochondrial DNA maintenance. A group of multicopy suppressors rescuing the synthetic lethal phenotypes of the mutants on non-fermentable carbon sources additionally supports this result. Our results imply that the synthetic petite phenotypes we observed are due to the disturbance of the inner mitochondrial membrane and point to this mitochondrial sub-compartment as the main target of action of Om45p, Ugo1p, and the yeast Miro GTPase Gem1p.
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Affiliation(s)
- Antonina Shvetsova
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
| | - Ali J. Masud
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
| | - Laura Schneider
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
| | - Ulrich Bergmann
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
| | - Geoffray Monteuuis
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
- Present address:
Department of Biochemistry and Developmental BiologyUniversity of HelsinkiHelsinkiFinland
| | - Ilkka J. Miinalainen
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
| | - J. Kalervo Hiltunen
- Faculty of Biochemistry and Molecular Medicine and Biocenter OuluUniversity of OuluOuluFinland
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5
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Harada T, Sada R, Osugi Y, Matsumoto S, Matsuda T, Hayashi-Nishino M, Nagai T, Harada A, Kikuchi A. Palmitoylated CKAP4 regulates mitochondrial functions through an interaction with VDAC2 at ER-mitochondria contact sites. J Cell Sci 2020; 133:jcs249045. [PMID: 33067255 DOI: 10.1242/jcs.249045] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 09/29/2020] [Indexed: 12/11/2022] Open
Abstract
Cytoskeleton-associated protein 4 (CKAP4) is a palmitoylated type II transmembrane protein localized to the endoplasmic reticulum (ER). Here, we found that knockout (KO) of CKAP4 in HeLaS3 cells induces the alteration of mitochondrial structures and increases the number of ER-mitochondria contact sites. To understand the involvement of CKAP4 in mitochondrial functions, the binding proteins of CKAP4 were explored, enabling identification of the mitochondrial porin voltage-dependent anion-selective channel protein 2 (VDAC2), which is localized to the outer mitochondrial membrane. Palmitoylation at Cys100 of CKAP4 was required for the binding between CKAP4 and VDAC2. In CKAP4 KO cells, the binding of inositol trisphosphate receptor (IP3R) and VDAC2 was enhanced, the intramitochondrial Ca2+ concentration increased and the mitochondrial membrane potential decreased. In addition, CKAP4 KO decreased the oxidative consumption rate, in vitro cancer cell proliferation under low-glucose conditions and in vivo xenograft tumor formation. The phenotypes were not rescued by expression of a palmitoylation-deficient CKAP4 mutant. These results suggest that CKAP4 plays a role in maintaining mitochondrial functions through the binding to VDAC2 at ER-mitochondria contact sites and that palmitoylation is required for this novel function of CKAP4.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Takeshi Harada
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
| | - Ryota Sada
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
| | - Yoshito Osugi
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
| | - Shinji Matsumoto
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
| | - Tomoki Matsuda
- Department of Biomolecular Science and Engineering, The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, 8-1 Mihogaoka, Osaka 567-0047, Japan
| | - Mitsuko Hayashi-Nishino
- Department of Biomolecular Science and Regulation and Artificial Intelligence Research Center, The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, 8-1 Mihogaoka, Osaka 567-0047, Japan
| | - Takeharu Nagai
- Department of Biomolecular Science and Engineering, The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, 8-1 Mihogaoka, Osaka 567-0047, Japan
| | - Akihiro Harada
- Department of Cell Biology, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
| | - Akira Kikuchi
- Department of Molecular Biology and Biochemistry, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita 565-0871, Japan
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6
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Prokaryotic and Mitochondrial Lipids: A Survey of Evolutionary Origins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019. [PMID: 31502197 DOI: 10.1007/978-3-030-21162-2_2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
Mitochondria and bacteria share a myriad of properties since it is believed that the powerhouses of the eukaryotic cell have evolved from a prokaryotic origin. Ribosomal RNA sequences, DNA architecture and metabolism are strikingly similar in these two entities. Proteins and nucleic acids have been a hallmark for comparison between mitochondria and prokaryotes. In this chapter, similarities (and differences) between mitochondrial and prokaryotic membranes are addressed with a focus on structure-function relationship of different lipid classes. In order to be suitable for the theme of the book, a special emphasis is reserved to the effects of bioactive sphingolipids, mainly ceramide, on mitochondrial membranes and their roles in initiating programmed cell death.
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7
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Fulghum KL, Rood BR, Shang VO, McNally LA, Riggs DW, Zheng YT, Hill BG. Mitochondria-associated lactate dehydrogenase is not a biologically significant contributor to bioenergetic function in murine striated muscle. Redox Biol 2019; 24:101177. [PMID: 30939431 PMCID: PMC6441728 DOI: 10.1016/j.redox.2019.101177] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/08/2019] [Accepted: 03/21/2019] [Indexed: 12/17/2022] Open
Abstract
Previous studies indicate that mitochondria-localized lactate dehydrogenase (mLDH) might be a significant contributor to metabolism. In the heart, the presence of mLDH could provide cardiac mitochondria with a higher capacity to generate reducing equivalents directly available for respiration, especially during exercise when circulating lactate levels are high. The purpose of this study was to test the hypothesis that mLDH contributes to striated muscle bioenergetic function. Mitochondria isolated from murine cardiac and skeletal muscle lacked an appreciable ability to respire on lactate in the absence or presence of exogenous NAD+. Although three weeks of treadmill running promoted physiologic cardiac growth, mitochondria isolated from the hearts of acutely exercised or exercise-adapted mice showed no further increase in lactate oxidation capacity. In all conditions tested, cardiac mitochondria respired at >20-fold higher levels with provision of pyruvate compared with lactate. Similarly, skeletal muscle mitochondria showed little capacity to respire on lactate. Protease protection assays of isolated cardiac mitochondria confirmed that LDH is not localized within the mitochondrion. We conclude that mLDH does not contribute to cardiac bioenergetics in mice.
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Affiliation(s)
- Kyle L Fulghum
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Physiology and Biophysics, University of Louisville, Louisville, KY, USA
| | - Benjamin R Rood
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
| | - Velma O Shang
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, USA
| | - Lindsey A McNally
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
| | - Daniel W Riggs
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Bioinformatics and Biostatistics, University of Louisville, Louisville, KY, USA
| | - Yu-Ting Zheng
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA
| | - Bradford G Hill
- Diabetes and Obesity Center, Envirome Institute, Department of Medicine, University of Louisville, Louisville, KY, USA; Department of Physiology and Biophysics, University of Louisville, Louisville, KY, USA; Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY, USA.
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8
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Thoma J, Sapra KT, Müller DJ. Single-Molecule Force Spectroscopy of Transmembrane β-Barrel Proteins. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2018; 11:375-395. [PMID: 29894225 DOI: 10.1146/annurev-anchem-061417-010055] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Single-molecule force spectroscopy (SMFS) has been widely applied to study the mechanical unfolding and folding of transmembrane proteins. Here, we review the recent progress in characterizing bacterial and human transmembrane β-barrel proteins by SMFS. First, we describe the mechanical unfolding of transmembrane β-barrels, which follows a general mechanism dictated by the sequential unfolding and extraction of individual β-strands and β-hairpins from membranes. Upon force relaxation, the unfolded polypeptide can insert stepwise into the membrane as single β-strands or β-hairpins to fold as the native β-barrel. The refolding can be followed at a high spatial and temporal resolution, showing that small β-barrels are able to fold without assistance, whereas large and complex β-barrels require chaperone cofactors. Applied in the dynamic mode, SMFS can quantify the kinetic and mechanical properties of single β-hairpins and reveal complementary insight into the membrane protein structure and function relationship. We further outline the challenges that SMFS experiments must overcome for a comprehensive understanding of the folding and function of transmembrane β-barrel proteins.
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Affiliation(s)
- Johannes Thoma
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland;
| | | | - Daniel J Müller
- Department of Biosystems Science and Engineering, ETH Zürich, 4058 Basel, Switzerland;
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9
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Affiliation(s)
- Shao-Hua Yang
- Center for Neuroscience Discovery, Institute for Healthy Aging, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Ran Liu
- Center for Neuroscience Discovery, Institute for Healthy Aging, University of North Texas Health Science Center, Fort Worth, TX, USA
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10
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Affiliation(s)
- Jennifer Pfizenmaier
- University of Stuttgart; Institute of Biochemical Engineering; Allmandring 31 70569 Stuttgart Germany
| | - Ralf Takors
- University of Stuttgart; Institute of Biochemical Engineering; Allmandring 31 70569 Stuttgart Germany
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11
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Cryopreservation of lipid bilayers by LEA proteins from Artemia franciscana and trehalose. Cryobiology 2016; 73:240-7. [DOI: 10.1016/j.cryobiol.2016.07.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/04/2016] [Indexed: 12/23/2022]
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12
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Singh K, Briggs JM. Functional Implications of the spectrum of BCL2 mutations in Lymphoma. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2016; 769:1-18. [PMID: 27543313 DOI: 10.1016/j.mrrev.2016.06.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 06/09/2016] [Accepted: 06/12/2016] [Indexed: 12/12/2022]
Abstract
Mutations in the translocated BCL2 gene are often detected in diffuse large B-cell lymphomas (DLBCLs), indicating both their significance and pervasiveness. Large series genome sequencing of more than 200 DLBCLs has identified frequent BCL2 mutations clustered in the exons coding for the BH4 domain and the folded loop domain (FLD) of the protein. However, BCL2 mutations are mostly contemplated to represent bystander events with negligible functional impact on the pathogenesis of DLBCL. BCL2 arbitrates apoptosis through a classic interaction between its hydrophobic groove forming BH1-3 domains and the BH3 domain of pro-apoptotic members of the BCL2 family. The effects of mutations are mainly determined by the ability of the mutated BCL2 to mediate apoptosis by this inter-member protein binding. Nevertheless, BCL2 regulates diverse non-canonical pathways that are unlikely to be explained by canonical interactions. In this review, first, we identify recurrent missense mutations in the BH4 domain and the FLD reported in independent lymphoma sequencing studies. Second, we discuss the probable consequences of mutations on the binding ability of BCL2 to non-BCL2 family member proteins crucial for 1) maintaining mitochondrial energetics and calcium hemostasis such as VDAC, IP3R, and RyR and 2) oncogenic pathways implicated in the acquisition of the 'hallmarks of cancer' such as SOD, Raf-1, NFAT, p53, HIF-1α, and gelsolin. The study also highlights the likely ramifications of mutations on binding of BCL2 antagonists and BH3 profiling. Based on our analysis, we believe that an in-depth focus on BCL2 interactions mediated by these domains is warranted to elucidate the functional significance of missense mutations in DLBCL. In summary, we provide an extensive overview of the pleiotropic functions of BCL2 mediated by its physical binding interaction with other proteins and the various ways BCL2 mutations would affect the normal function of the cell leading to the development of DLBCL.
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Affiliation(s)
- Khushboo Singh
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | - James M Briggs
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA.
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13
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Miao F, Zhang W, Sun Y, Zhang R, Liu Y, Guo F, Song G, Tian M, Yu X. Novel fluorescent probes for highly selective two-photon imaging of mitochondria in living cells. Biosens Bioelectron 2014; 55:423-9. [DOI: 10.1016/j.bios.2013.12.044] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/12/2013] [Accepted: 12/20/2013] [Indexed: 12/16/2022]
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14
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Duvvuri B, Duvvuri VR, Wang C, Chen L, Wagar LE, Jamnik V, Wu J, Yeung RSM, Grigull J, Watts TH, Wu GE. The human immune system recognizes neopeptides derived from mitochondrial DNA deletions. THE JOURNAL OF IMMUNOLOGY 2014; 192:4581-91. [PMID: 24733843 DOI: 10.4049/jimmunol.1300774] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mutations in mitochondrial (mt) DNA accumulate with age and can result in the generation of neopeptides. Immune surveillance of such neopeptides may allow suboptimal mitochondria to be eliminated, thereby avoiding mt-related diseases, but may also contribute to autoimmunity in susceptible individuals. To date, the direct recognition of neo-mtpeptides by the adaptive immune system has not been demonstrated. In this study we used bioinformatics approaches to predict MHC binding of neopeptides identified from known deletions in mtDNA. Six such peptides were confirmed experimentally to bind to HLA-A*02. Pre-existing human CD4(+) and CD8(+) T cells from healthy donors were shown to recognize and respond to these neopeptides. One remarkably promiscuous immunodominant peptide (P9) could be presented by diverse MHC molecules to CD4(+) and/or CD8(+) T cells from 75% of the healthy donors tested. The common soil microbe, Bacillus pumilus, encodes a 9-mer that differs by one amino acid from P9. Similarly, the ATP synthase F0 subunit 6 from normal human mitochondria encodes a 9-mer with a single amino acid difference from P9 with 89% homology to P9. T cells expanded from human PBMCs using the B. pumilus or self-mt peptide bound to P9/HLA-A2 tetramers, arguing for cross-reactivity between T cells with specificity for self and foreign homologs of the altered mt peptide. These findings provide proof of principal that the immune system can recognize peptides arising from spontaneous somatic mutations and that such responses might be primed by foreign peptides and/or be cross-reactive with self.
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Affiliation(s)
- Bhargavi Duvvuri
- School of Kinesiology and Health Science, York University, Toronto, Ontario M3J 1P3, Canada
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15
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Andrade IDS, Vianez-Júnior JL, Goulart CL, Homblé F, Ruysschaert JM, Almeida von Krüger WM, Bisch PM, de Souza W, Mohana-Borges R, Motta MCM. Characterization of a porin channel in the endosymbiont of the trypanosomatid protozoan Crithidia deanei. MICROBIOLOGY-SGM 2011; 157:2818-2830. [PMID: 21757490 DOI: 10.1099/mic.0.049247-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Crithidia deanei is a trypanosomatid protozoan that harbours a symbiotic bacterium. The partners maintain a mutualistic relationship, thus constituting an excellent model for studying metabolic exchanges between the host and the symbiont, the origin of organelles and cellular evolution. According to molecular analysis, symbionts of different trypanosomatid species share high identity and descend from a common ancestor, a β-proteobacterium of the genus Bordetella. The endosymbiont is surrounded by two membranes, like Gram-negative bacteria, but its envelope presents special features, since phosphatidylcholine is a major membrane component and the peptidoglycan layer is highly reduced, as described in other obligate intracellular bacteria. Like the process that generated mitochondria and plastids, the endosymbiosis in trypanosomatids depends on pathways that facilitate the intensive metabolic exchanges between the bacterium and the host protozoan. A search of the annotated symbiont genome database identified one sequence with identity to porin-encoding genes of the genus Bordetella. Considering that the symbiont outer membrane has a great accessibility to cytoplasm host factors, it was important to characterize this single porin-like protein using biochemical, molecular, computational and ultrastructural approaches. Antiserum against the recombinant porin-like molecule revealed that it is mainly located in the symbiont envelope. Secondary structure analysis and comparative modelling predicted the protein 3D structure as an 18-domain β-barrel, which is consistent with porin channels. Electrophysiological measurements showed that the porin displays a slight preference for cations over anions. Taken together, the data presented herein suggest that the C. deanei endosymbiont porin is phylogenetically and structurally similar to those described in Gram-negative bacteria, representing a diffusion channel that might contribute to the exchange of nutrients and metabolic precursors between the symbiont and its host cell.
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Affiliation(s)
- Iamara da Silva Andrade
- Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Genômica Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil
| | - João Lídio Vianez-Júnior
- Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil
| | - Carolina Lage Goulart
- Laboratoire de Structure et Fonction des Membranes Biologiques (SFMB), Université Libre de Bruxelles, Campus Plaine (CP 206/2), B-1050 Bruxelles, Belgium.,Unidade Multidisciplinar de Genômica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Fabrice Homblé
- Laboratoire de Structure et Fonction des Membranes Biologiques (SFMB), Université Libre de Bruxelles, Campus Plaine (CP 206/2), B-1050 Bruxelles, Belgium
| | - Jean-Marie Ruysschaert
- Laboratoire de Structure et Fonction des Membranes Biologiques (SFMB), Université Libre de Bruxelles, Campus Plaine (CP 206/2), B-1050 Bruxelles, Belgium
| | - Wanda Maria Almeida von Krüger
- Unidade Multidisciplinar de Genômica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Paulo Mascarello Bisch
- Unidade Multidisciplinar de Genômica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Física Biológica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil
| | - Wanderley de Souza
- Instituto Nacional de Metrologia, Normalização e Qualidade Industrial, Inmetro, Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil
| | - Ronaldo Mohana-Borges
- Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Genômica Estrutural, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil
| | - Maria Cristina Machado Motta
- Instituto Nacional de Ciência e Tecnologia em Bioimagens e Biologia Estrutural, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, 21941-590 Rio de Janeiro, Brazil.,Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, Brazil
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16
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Millar AH, Whelan J, Soole KL, Day DA. Organization and regulation of mitochondrial respiration in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:79-104. [PMID: 21332361 DOI: 10.1146/annurev-arplant-042110-103857] [Citation(s) in RCA: 385] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mitochondrial respiration in plants provides energy for biosynthesis, and its balance with photosynthesis determines the rate of plant biomass accumulation. We describe recent advances in our understanding of the mitochondrial respiratory machinery of cells, including the presence of a classical oxidative phosphorylation system linked to the cytosol by transporters, discussed alongside nonphosphorylating (and, therefore, non-energy conserving) bypasses that alter the efficiency of ATP synthesis and play a role in oxidative stress responses in plants. We consider respiratory regulation in the context of the contrasting roles mitochondria play in different tissues, from photosynthetic leaves to nutrient-acquiring roots. We focus on the molecular nature of this regulation at transcriptional and post-transcriptional levels that allow the respiratory apparatus of plants to help shape organ development and the response of plants to environmental stress. We highlight the challenges for future research considering spatial and temporal changes of respiration in response to changing climatic conditions.
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Affiliation(s)
- A Harvey Millar
- Australian Research Council Center of Excellence in Plant Energy Biology, University of Western Australia, M316 Crawley, Western Australia 6009, Australia
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17
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Abstract
Gram-negative bacteria and mitochondria are both covered by two distinct biological membranes. These membrane systems have been maintained during the course of evolution from an early evolutionary precursor. Both outer membranes accommodate channels of the porin family, which are designed for the uptake and exchange of metabolites, including ions and small molecules, such as nucleosides or sugars. In bacteria, the structure of the outer membrane porin protein family of β-barrels is generally characterized by an even number of β-strands; usually 14, 16 or 18 strands are observed forming the bacterial porin barrel wall. In contrast, the recent structures of the mitochondrial porin, also known as VDAC (voltage-dependent anion channel), show an uneven number of 19 β-strands, but a similar molecular architecture. Despite the lack of a clear evolutionary link between these protein families, their common principles and differences in assembly, architecture and function are summarized in the present review.
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18
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Abstract
H2DCF-DA (dihydrodichlorofluorescein diacetate) is widely used to evaluate ‘cellular oxidative stress’. After passing through the plasma membrane, this lipophilic and non-fluorescent compound is de-esterified to a hydrophilic alcohol [H2DCF (dihydrodichlorofluorescein)] that may be oxidized to fluorescent DCF (2′,7′-dichlorofluorescein) by a process usually considered to involve ROS (reactive oxygen species). It is, however, not always recognized that, being a hydrophilic molecule, H2DCF does not cross membranes, except for the outer fenestrated mitochondrial ones. It is also not generally realized that oxidation of H2DCF is dependent either on Fenton-type reactions or on unspecific enzymatic oxidation by cytochrome c, for neither superoxide, nor H2O2, directly oxidizes H2DCF. Consequently, oxidation of H2DCF requires the presence of either cytochrome c or of both redox-active transition metals and H2O2. Redox-active metals exist mainly within lysosomes, whereas cytochrome c resides bound to the outer side of the inner mitochondrial membrane. Following exposure to H2DCF-DA, weak mitochondrial fluorescence was found in both the oxidation-resistant ARPE-19 cells and the much more sensitive J774 cells. This fluorescence was only marginally enhanced following short exposure to H2O2, showing that by itself it is unable to oxidize H2DCF. Cells that were either exposed to the lysosomotropic detergent MSDH (O-methylserine dodecylamide hydrochloride), exposed to prolonged oxidative stress, or spontaneously apoptotic showed lysosomal permeabilization and strong DCF-induced fluorescence. The results suggest that DCF-dependent fluorescence largely reflects relocation to the cytosol of lysosomal iron and/or mitochondrial cytochrome c.
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19
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Millar AH, Small ID, Day DA, Whelan J. Mitochondrial biogenesis and function in Arabidopsis. THE ARABIDOPSIS BOOK 2008; 6:e0111. [PMID: 22303236 DOI: 10.1199/tab.0105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Mitochondria represent the powerhouse of cells through their synthesis of ATP. However, understanding the role of mitochondria in the growth and development of plants will rely on a much deeper appreciation of the complexity of this organelle. Arabidopsis research has provided clear identification of mitochondrial components, allowed wide-scale analysis of gene expression, and has aided reverse genetic manipulation to test the impact of mitochondrial component loss on plant function. Forward genetics in Arabidopsis has identified mitochondrial involvement in mutations with notable impacts on plant metabolism, growth and development. Here we consider the evidence for components involved in mitochondria biogenesis, metabolism and signalling to the nucleus.
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20
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Millar AH, Small ID, Day DA, Whelan J. Mitochondrial biogenesis and function in Arabidopsis. THE ARABIDOPSIS BOOK 2008; 6:e0111. [PMID: 22303236 PMCID: PMC3243404 DOI: 10.1199/tab.0111] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Mitochondria represent the powerhouse of cells through their synthesis of ATP. However, understanding the role of mitochondria in the growth and development of plants will rely on a much deeper appreciation of the complexity of this organelle. Arabidopsis research has provided clear identification of mitochondrial components, allowed wide-scale analysis of gene expression, and has aided reverse genetic manipulation to test the impact of mitochondrial component loss on plant function. Forward genetics in Arabidopsis has identified mitochondrial involvement in mutations with notable impacts on plant metabolism, growth and development. Here we consider the evidence for components involved in mitochondria biogenesis, metabolism and signalling to the nucleus.
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Affiliation(s)
- A. Harvey Millar
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
| | - Ian D. Small
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
| | - David A. Day
- School of Biological Sciences, The University of Sydney 2006, NSW, Australia
| | - James Whelan
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
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21
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Prabhudesai SG, Rekhraj S, Roberts G, Darzi AW, Ziprin P. Apoptosis and chemo-resistance in colorectal cancer. J Surg Oncol 2007; 96:77-88. [PMID: 17443738 DOI: 10.1002/jso.20785] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Systemic chemotherapy plays an integral part in treating advanced colorectal cancer. However 50% of patients respond poorly or have disease progression due to resistance to chemotherapeutic agents. This article reviews the pathways that regulate apoptosis, apoptotic mechanisms through which chemotherapeutic agents mediate their effect and how deregulation of apoptotic proteins may contribute to chemo-resistance. Also discussed are potential therapeutic strategies designed to target these proteins and thereby improve response rates to chemotherapy in colorectal cancer.
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Affiliation(s)
- S G Prabhudesai
- Department of Biosurgery & Surgical Technology, Faculty of Medicine, Imperial College, London, St. Mary's Hospital Campus, Praed Street, London W2 1NY, United Kingdom
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22
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Haferkamp I. The diverse members of the mitochondrial carrier family in plants. FEBS Lett 2007; 581:2375-9. [PMID: 17321523 DOI: 10.1016/j.febslet.2007.02.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 02/08/2007] [Accepted: 02/09/2007] [Indexed: 10/23/2022]
Abstract
Sequencing of plant genomes allowed the identification of various members of the mitochondrial carrier family (MCF). In plants, these structurally related proteins are involved in the transport of solutes like nucleotides, phosphate, di- and tricarboxylates across the mitochondrial membrane and therefore exhibit physiological functions similar to known isoforms from animal or yeast mitochondria. Interestingly, various studies led to the recognition of MCF proteins which mediate the transport of different substrates like folates, S-adenosylmethionine, ADPglucose or ATP, ADP and AMP in plastids.
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Affiliation(s)
- Ilka Haferkamp
- Zelluläre Physiologie/Membrantransport, Universität Kaiserslautern, D-67663 Kaiserslautern, Germany.
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23
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Haridas V, Li X, Mizumachi T, Higuchi M, Lemeshko VV, Colombini M, Gutterman JU. Avicins, a novel plant-derived metabolite lowers energy metabolism in tumor cells by targeting the outer mitochondrial membrane. Mitochondrion 2007; 7:234-40. [PMID: 17317337 DOI: 10.1016/j.mito.2006.12.005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2006] [Revised: 11/27/2006] [Accepted: 12/27/2006] [Indexed: 11/30/2022]
Abstract
Avicins are pro-apoptotic, anti-inflammatory molecules with antioxidant effects both in vitro and in vivo. Based on their ability to perturb mitochondrial functions and initiate apoptosis in tumor cells, we chose to study the bioenergetic effects of avicins on tumor cell mitochondria. Avicin-treated Jurkat cells, showed a decrease in the levels of cellular ATP as well as the rate of oxygen consumption. These effects on cellular metabolism appear to be a result of avicin's actions on the outer mitochondrial membrane (OMM). We speculate that avicins might initially inhibit the exchange of metabolites across the OMM leading to its subsequent permeabilization to cytochrome c. This speculation is supported by biophysical studies using lipid bilayers, which suggest that upstream of these effects, avicins target and close the voltage dependent anion channel (VDAC). Closure of VDAC would lead to an overall lowering of the cell energy metabolism, subsequently pushing these cells towards the apoptotic pathway by permeabilization of the OMM and release of cyt-c. Avicins therefore not only represent a novel pharmacological tool for treatment of cancers, but also highlight the influence ancient plant metabolites could have on human health.
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Affiliation(s)
- Valsala Haridas
- Department of Molecular Therapeutics, Box 184, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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24
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Salnikov V, Lukyánenko YO, Frederick CA, Lederer WJ, Lukyánenko V. Probing the outer mitochondrial membrane in cardiac mitochondria with nanoparticles. Biophys J 2006; 92:1058-71. [PMID: 17098804 PMCID: PMC1779971 DOI: 10.1529/biophysj.106.094318] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The outer mitochondrial membrane (OMM) is the last barrier between the mitochondrion and the cytoplasm. Breaches of OMM integrity result in the release of cytochrome c oxidase, triggering apoptosis. In this study, we used calibrated gold nanoparticles to probe the OMM in rat permeabilized ventricular cells and in isolated cardiac mitochondria under quasi-physiological ionic conditions and during permeability transition. Our experiments showed that under control conditions, the OMM is not permeable to 6-nm particles. However, 3-nm particles could enter the mitochondrial intermembrane space in mitochondria of permeabilized cells and isolated cardiac mitochondria. Known inhibitors of the voltage-dependent anion channel (VDAC), König polyanion, and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid inhibited this entrance. Thus, 3-nm particles must have entered the mitochondrial intermembrane space through the VDAC. The permeation of the isolated cardiac mitochondria OMM for 3-nm particles was approximately 20 times that in permeabilized cells, suggesting low availability of VDAC pores within the cell. Experiments with expressed green fluorescent protein showed the existence of intracellular barriers restricting the VDAC pore availability in vivo. Thus, our data showed that 1), the physical diameter of VDAC pores in cardiac mitochondria is >or=3 nm but <or=6 nm, and 2), permeability transition-related mitochondrial swelling results in breaching and disruption of the OMM.
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Affiliation(s)
- V Salnikov
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA
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25
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Herget M, Tampé R. Intracellular peptide transporters in human--compartmentalization of the "peptidome". Pflugers Arch 2006; 453:591-600. [PMID: 16710701 DOI: 10.1007/s00424-006-0083-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2006] [Accepted: 03/27/2006] [Indexed: 01/09/2023]
Abstract
In the human genome, the five adenosine triphosphate (ATP)-binding cassette (ABC) half transporters ABCB2 (TAP1), ABCB3 (TAP2), ABCB9 (TAP-like), and in part, also ABCB8 and ABCB10 are closely related with regard to their structural and functional properties. Although targeted to different cellular compartments such as the endoplasmic reticulum (ER), lysosomes, and mitochondria, they are involved in intracellular peptide trafficking across membranes. The transporter associated with antigen processing (TAP1 and TAP2) constitute a key machinery in the major histocompatibility complex (MHC) class I-mediated cellular immune defense against infected or malignantly transformed cells. TAP translocates the cellular "peptidome" derived primarily from cytosolic proteasomal degradation into the ER lumen for presentation by MHC class I molecules. The homodimeric ABCB9 (TAP-like) complex located in lysosomal compartments shares structural and functional similarities to TAP; however, its biological role seems to be different from the MHC I antigen processing. ABCB8 and ABCB10 are targeted to the inner mitochondrial membrane. MDL1, the yeast homologue of ABCB10, is involved in the export of peptides derived from proteolysis of inner-membrane proteins into the intermembrane space. As such peptides are presented as minor histocompatibility antigens on the surface of mammalian cells, a physiological role of ABCB10 in the antigen processing can be accounted.
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Affiliation(s)
- Meike Herget
- Institute of Biochemistry, Biocenter, Goethe-University Frankfurt, Frankfurt, Germany
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26
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Abstract
Lewy bodies (LB) in the substantia nigra are a cardinal pathological feature of Parkinson's disease, but they occur in a number of neurodegenerative diseases and can be widespread in the nervous system. The characteristics, locations, and composition of LB are reviewed, with particular attention to alpha-synuclein (alpha-SYN), which appears to be the major component of LB. The propensity for alpha-SYN, a presynaptic protein widely expressed in the brain, to aggregate is because of an amyloidogenic central region. The factors that favor the aggregation of alpha-SYN and mechanisms of toxicity are examined, and a mechanism through which aggregates of alpha-SYN could induce mitochondrial dysfunction and/or release of proapoptotic molecules is proposed.
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Affiliation(s)
- Clifford W Shults
- Department of Neurosciences, University of California at San Diego, La Jolla, CA 92093, USA.
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27
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Parfenov AS, Salnikov V, Lederer WJ, Lukyánenko V. Aqueous diffusion pathways as a part of the ventricular cell ultrastructure. Biophys J 2005; 90:1107-19. [PMID: 16284268 PMCID: PMC1367097 DOI: 10.1529/biophysj.105.071787] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The physical organization of the ventricular myocyte includes barriers for the movement of objects of varying dimensions ranging from ions to solid particles. There are two kinds of diffusion in the cell: lateral (in membranes) and aqueous. Here we examine the size constraints of aqueous diffusion pathways and discuss their impact on cellular physiology. Calibrated gold nanoparticles were used to probe the accessibility of the entire transverse-axial tubular system (TATS), the sarcoplasm, and intracellular structures. The TATS tubules, although up to 300 nm in diameter, permitted only particles </=11 nm to enter. When calibrated nanoparticles were added to permeabilized ventricular cells, particles </=11 nm were found in the sarcoplasm. The distribution of nanoparticles in the cells allowed us to conclude that 1), the TATS and the sarcoplasm are accessible only for particles </=11 nm; 2), the gaps between T-tubules and junctional sarcoplasmic reticulum (jSR), jSR and mitochondria, and intermitochondrial contacts are inaccessible for particles with physical size >3 nm; 3), the mitochondrial voltage-dependent anion channel and the nuclear pore complex in ventricular cells could not be penetrated by particles >/=6 nm; and 4), there is a difference in size clearance between transversal and longitudinal sarcoplasmic diffusional pathways.
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Affiliation(s)
- A S Parfenov
- Medical Biotechnology Center, University of Maryland Biotechnology Institute, Baltimore, Maryland, USA
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28
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Liu XH, Aksan A, Menze MA, Hand SC, Toner M. Trehalose loading through the mitochondrial permeability transition pore enhances desiccation tolerance in rat liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1717:21-6. [PMID: 16242115 DOI: 10.1016/j.bbamem.2005.09.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Revised: 08/28/2005] [Accepted: 09/06/2005] [Indexed: 11/27/2022]
Abstract
Trehalose has extensively been used to improve the desiccation tolerance of mammalian cells. To test whether trehalose improves desiccation tolerance of mammalian mitochondria, we introduced trehalose into the matrix of isolated rat liver mitochondria by reversibly permeabilizing the inner membrane using the mitochondrial permeability transition pore (MPTP). Measurement of the trehalose concentration inside mitochondria using high performance liquid chromatography showed that the sugar permeated rapidly into the matrix upon opening the MPTP. The concentration of intra-matrix trehalose reached 0.29 mmol/mg protein (approximately 190 mM) in 5 min. Mitochondria, with and without trehalose loaded into the matrix, were desiccated in a buffer containing 0.25 M trehalose by diffusive drying. After re-hydration, the inner membrane integrity was assessed by measurement of mitochondrial membrane potential with the fluorescent probe JC-1. The results showed that following drying to similar water contents, the mitochondria loaded with trehalose had significantly higher inner membrane integrity than those without trehalose loading. These findings suggest the presence of trehalose in the mitochondrial matrix affords improved desiccation tolerance to the isolated mitochondria.
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Affiliation(s)
- Xiang-Hong Liu
- Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Harvard Medical School and Shriners Hospitals for Children, Boston, 02114, USA
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29
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Duarte NC, Herrgård MJ, Palsson BØ. Reconstruction and validation of Saccharomyces cerevisiae iND750, a fully compartmentalized genome-scale metabolic model. Genome Res 2004; 14:1298-309. [PMID: 15197165 PMCID: PMC442145 DOI: 10.1101/gr.2250904] [Citation(s) in RCA: 435] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A fully compartmentalized genome-scale metabolic model of Saccharomyces cerevisiae that accounts for 750 genes and their associated transcripts, proteins, and reactions has been reconstructed and validated. All of the 1149 reactions included in this in silico model are both elementally and charge balanced and have been assigned to one of eight cellular locations (extracellular space, cytosol, mitochondrion, peroxisome, nucleus, endoplasmic reticulum, Golgi apparatus, or vacuole). When in silico predictions of 4154 growth phenotypes were compared to two published large-scale gene deletion studies, an 83% agreement was found between iND750's predictions and the experimental studies. Analysis of the failure modes showed that false predictions were primarily caused by iND750's limited inclusion of cellular processes outside of metabolism. This study systematically identified inconsistencies in our knowledge of yeast metabolism that require specific further experimental investigation.
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Affiliation(s)
- Natalie C Duarte
- Department of Bioengineering, University of California-San Diego, La Jolla, California 92093-0412, USA
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30
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Wang Z, Pesacreta TC. A subclass of myosin XI is associated with mitochondria, plastids, and the molecular chaperone subunit TCP-1? in maize. ACTA ACUST UNITED AC 2004; 57:218-32. [PMID: 14752806 DOI: 10.1002/cm.10168] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The role and regulation of specific plant myosins in cyclosis is not well understood. In the present report, an affinity-purified antibody generated against a conserved tail region of some class XI plant myosin isoforms was used for biochemical and immunofluorescence studies of Zea mays. Myosin XI co-localized with plastids and mitochondria but not with nuclei, the Golgi apparatus, endoplasmic reticulum, or peroxisomes. This suggests that myosin XI is involved in the motility of specific organelles. Myosin XI was more than 50% co-localized with tailless complex polypeptide-1alpha (TCP-1alpha) in tissue sections of mature tissues located more than 1.0 mm from the apex, and the two proteins co-eluted from gel filtration and ion exchange columns. On Western blots, TCP-1alpha isoforms showed a developmental shift from the youngest 5.0 mm of the root to more mature regions that were more than 10.0 mm from the apex. This developmental shift coincided with a higher percentage of myosin XI /TCP-1alpha co-localization, and faster degradation of myosin XI by serine protease. Our results suggest that class XI plant myosin requires TCP-1alpha for regulating folding or providing protection against denaturation.
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Affiliation(s)
- Zhengyuan Wang
- Biology Department, University of Louisiana, Lafayette 70504, USA
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31
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Hajnóczky G, Csordás G, Yi M. Old players in a new role: mitochondria-associated membranes, VDAC, and ryanodine receptors as contributors to calcium signal propagation from endoplasmic reticulum to the mitochondria. Cell Calcium 2002; 32:363-77. [PMID: 12543096 DOI: 10.1016/s0143416002001872] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In many cell types, IP(3) and ryanodine receptor (IP(3)R/RyR)-mediated Ca(2+) mobilization from the sarcoendoplasmic reticulum (ER/SR) results in an elevation of mitochondrial matrix [Ca(2+)]. Although delivery of the released Ca(2+) to the mitochondria has been established as a fundamental signaling process, the molecular mechanism underlying mitochondrial Ca(2+) uptake remains a challenge for future studies. The Ca(2+) uptake can be divided into the following three steps: (1) Ca(2+) movement from the IP(3)R/RyR to the outer mitochondrial membrane (OMM); (2) Ca(2+) transport through the OMM; and (3) Ca(2+) transport through the inner mitochondrial membrane (IMM). Evidence has been presented that Ca(2+) delivery to the OMM is facilitated by a local coupling between closely apposed regions of the ER/SR and mitochondria. Recent studies of the dynamic changes in mitochondrial morphology and visualization of the subcellular pattern of the calcium signal provide important clues to the organization of the ER/SR-mitochondrial interface. Interestingly, key steps of phospholipid synthesis and transfer to the mitochondria have also been confined to subdomains of the ER tightly associated with the mitochondria, referred as mitochondria-associated membranes (MAMs). Through the OMM, the voltage-dependent anion channels (VDAC, porin) have been thought to permit free passage of ions and other small molecules. However, recent studies suggest that the VDAC may represent a regulated step in Ca(2+) transport from IP(3)R/RyR to the IMM. A novel proposal regarding the IMM Ca(2+) uptake site is a mitochondrial RyR that would mediate rapid Ca(2+) uptake by mitochondria in excitable cells. An overview of the progress in these directions is described in the present paper.
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Affiliation(s)
- G Hajnóczky
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 19107, Philadelphia, PA, USA.
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32
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Csordás G, Madesh M, Antonsson B, Hajnóczky G. tcBid promotes Ca(2+) signal propagation to the mitochondria: control of Ca(2+) permeation through the outer mitochondrial membrane. EMBO J 2002; 21:2198-206. [PMID: 11980717 PMCID: PMC125984 DOI: 10.1093/emboj/21.9.2198] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Calcium spikes established by IP(3) receptor-mediated Ca(2+) release from the endoplasmic reticulum (ER) are transmitted effectively to the mitochondria, utilizing local Ca(2+) interactions between closely associated subdomains of the ER and mitochondria. Since the outer mitochondrial membrane (OMM) has been thought to be freely permeable to Ca(2+), investigations have focused on IP(3)-driven Ca(2+) transport through the inner mitochondrial membrane (IMM). Here we demonstrate that selective permeabilization of the OMM by tcBid, a proapoptotic protein, results in an increase in the magnitude of the IP(3)-induced mitochondrial [Ca(2+)] signal. This effect of tcBid was due to promotion of activation of Ca(2+) uptake sites in the IMM and, in turn, to facilitation of mitochondrial Ca(2+) uptake. In contrast, tcBid failed to control the delivery of sustained and global Ca(2+) signals to the mitochondria. Thus, our data support a novel model that Ca(2+) permeability of the OMM at the ER- mitochondrial interface is an important determinant of local Ca(2+) signalling. Facilitation of Ca(2+) delivery to the mitochondria by tcBid may also support recruitment of mitochondria to the cell death machinery.
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Affiliation(s)
| | | | - Bruno Antonsson
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA and
Department of Protein Biochemistry, Serono Pharmaceutical Research Institute, CH-1228 Geneva, Switzerland Corresponding author e-mail:
| | - György Hajnóczky
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA and
Department of Protein Biochemistry, Serono Pharmaceutical Research Institute, CH-1228 Geneva, Switzerland Corresponding author e-mail:
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33
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Vander Heiden MG, Li XX, Gottleib E, Hill RB, Thompson CB, Colombini M. Bcl-xL promotes the open configuration of the voltage-dependent anion channel and metabolite passage through the outer mitochondrial membrane. J Biol Chem 2001; 276:19414-9. [PMID: 11259441 DOI: 10.1074/jbc.m101590200] [Citation(s) in RCA: 288] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The diffusion of metabolites across the outer mitochondrial membrane is essential for coupled cellular respiration. The outer membrane of mitochondria isolated from growth factor-deprived cells is impaired in its ability to exchange metabolic anions. When added to mitochondria, recombinant Bcl-x(L) restores metabolite exchange across the outer membrane without inducing the loss of cytochrome c from the intermembrane space. Restoration of outer membrane permeability to anionic metabolites does not occur directly through Bcl-x(L) ion channels. Instead, recombinant Bcl-x(L) maintains the outer mitochondrial membrane channel, VDAC, in an open configuration. Consistent with these findings, when ADP-induced oxidative phosphorylation is limited by exogenous beta-NADH, recombinant Bcl-x(L) can sustain outer mitochondrial membrane permeability to ADP. beta-NADH limits respiration by promoting the closed configuration of VDAC. Together these results demonstrate that following an apoptotic signal, Bcl-x(L) can maintain metabolite exchange across the outer mitochondrial membrane by inhibiting VDAC closure.
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Affiliation(s)
- M G Vander Heiden
- Abramson Family Cancer Research Institute, Department of Cancer Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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34
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Young L, Leonhard K, Tatsuta T, Trowsdale J, Langer T. Role of the ABC transporter Mdl1 in peptide export from mitochondria. Science 2001; 291:2135-8. [PMID: 11251115 DOI: 10.1126/science.1056957] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
ATP-binding cassette (ABC) adenosine triphosphatases actively transport a wide variety of compounds across biological membranes. Here, the ABC protein Mdl1 was identified as an intracellular peptide transporter localized in the inner membrane of yeast mitochondria. Mdl1 was required for mitochondrial export of peptides with molecular masses of approximately 2100 to 600 daltons generated by proteolysis of inner-membrane proteins by the m-AAA protease in the mitochondrial matrix. Proteolysis by the i-AAA protease in the intermembrane space led to the release of similar-sized peptides independent of Mdl1. Thus, two pathways of peptide efflux from mitochondria exist that may allow communication between mitochondria and their cellular environment.
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Affiliation(s)
- L Young
- Division of Immunology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
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35
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Massa R, Marliera LN, Martorana A, Cicconi S, Pierucci D, Giacomini P, De Pinto V, Castellani L. Intracellular localization and isoform expression of the voltage-dependent anion channel (VDAC) in normal and dystrophic skeletal muscle. J Muscle Res Cell Motil 2001; 21:433-42. [PMID: 11129434 DOI: 10.1023/a:1005688901635] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Voltage-dependent anion channels (VDACs) are a family of pore-forming proteins encoded by different genes, with at least three protein products expressed in mammalian tissues. The major recognized functional role of VDACs is to permit the almost free permeability of the outer mitochondrial membrane (OMM). Although VDAC1 is the best known among VDAC isoforms, its exclusively mitochondrial location is still debated. Therefore, we have measured its co-localization with markers of cellular organelles or compartments in skeletal muscle fibers by single or double immunofluorescence and traditional as well as confocal microscopy. Our results show that VDAC1 immunoreactivity corresponds to mitochondria and sarcoplasmic reticulum, while sarcolemmal reactivity, previously reported, was not observed. Since VDAC1 has been suggested to be involved in the control of oxidative phosphorylation, we sought for possible gene regulation of VDAC1, VDAC2 and VDAC3 in skeletal muscle of the dystrophin-deficient mdx mouse, which suffers of an impaired control of energy metabolism. Our results show that, while VDAC1 mRNA and protein and VDAC2 mRNA are normally expressed. VDAC3 mRNA is markedly down-regulated in mdx mouse muscle at different ages (before, during and after the outburst of myofiber necrosis). This finding suggests a possible involvement of VDAC3 expression in the early pathogenic events of the mdx muscular dystrophy.
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Affiliation(s)
- R Massa
- Dipartimento di Neuroscienze, Laboratorio di Medicina Molecolare, Università di Roma Tor Vergata, Italy.
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36
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Metzler DE, Metzler CM, Sauke DJ. Lipids, Membranes, and Cell Coats. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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37
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Metzler DE, Metzler CM, Sauke DJ. Electron Transport, Oxidative Phosphorylation, and Hydroxylation. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50021-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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38
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Harris MH, Thompson CB. The role of the Bcl-2 family in the regulation of outer mitochondrial membrane permeability. Cell Death Differ 2000; 7:1182-91. [PMID: 11175255 DOI: 10.1038/sj.cdd.4400781] [Citation(s) in RCA: 390] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mitochondria are well known as sites of electron transport and generators of cellular ATP. Mitochondria also appear to be sites of cell survival regulation. In the process of programmed cell death, mediators of apoptosis can be released from mitochondria through disruptions in the outer mitochondrial membrane; these mediators then participate in the activation of caspases and of DNA degradation. Thus the regulation of outer mitochondrial membrane integrity is an important control point for apoptosis. The Bcl-2 family is made up of outer mitochondrial membrane proteins that can regulate cell survival, but the mechanisms by which Bcl-2 family proteins act remain controversial. Most metabolites are permeant to the outer membrane through the voltage dependent anion channel (VDAC), and Bcl-2 family proteins appear to be able to regulate VDAC function. In addition, many Bcl-2 family proteins can form channels in vitro, and some pro-apoptotic members may form multimeric channels large enough to release apoptosis promoting proteins from the intermembrane space. Alternatively, Bcl-2 family proteins have been hypothesized to coordinate the permeability of both the outer and inner mitochondrial membranes through the permeability transition (PT) pore. Increasing evidence suggests that alterations in cellular metabolism can lead to pro-apoptotic changes, including changes in intracellular pH, redox potential and ion transport. By regulating mitochondrial membrane physiology, Bcl-2 proteins also affect mitochondrial energy generation, and thus influence cellular bioenergetics. Cell Death and Differentiation (2000) 7, 1182 - 1191
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Affiliation(s)
- M H Harris
- Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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39
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Koebnik R, Locher KP, Van Gelder P. Structure and function of bacterial outer membrane proteins: barrels in a nutshell. Mol Microbiol 2000; 37:239-53. [PMID: 10931321 DOI: 10.1046/j.1365-2958.2000.01983.x] [Citation(s) in RCA: 834] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The outer membrane protects Gram-negative bacteria against a harsh environment. At the same time, the embedded proteins fulfil a number of tasks that are crucial to the bacterial cell, such as solute and protein translocation, as well as signal transduction. Unlike membrane proteins from all other sources, integral outer membrane proteins do not consist of transmembrane alpha-helices, but instead fold into antiparallel beta-barrels. Over recent years, the atomic structures of several outer membrane proteins, belonging to six families, have been determined. They include the OmpA membrane domain, the OmpX protein, phospholipase A, general porins (OmpF, PhoE), substrate-specific porins (LamB, ScrY) and the TonB-dependent iron siderophore transporters FhuA and FepA. These crystallographic studies have yielded invaluable insight into and decisively advanced the understanding of the functions of these intriguing proteins. Our review is aimed at discussing their common principles and peculiarities as well as open questions associated with them.
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Affiliation(s)
- R Koebnik
- Biozentrum Basel, Abteilung Mikrobiologie, Klingelbergstr. 50, CH-4056 Basel, Switzerland.
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40
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Vander Heiden MG, Chandel NS, Li XX, Schumacker PT, Colombini M, Thompson CB. Outer mitochondrial membrane permeability can regulate coupled respiration and cell survival. Proc Natl Acad Sci U S A 2000; 97:4666-71. [PMID: 10781072 PMCID: PMC18290 DOI: 10.1073/pnas.090082297] [Citation(s) in RCA: 322] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Coupled cellular respiration requires that ATP and ADP be efficiently exchanged between the cytosol and the mitochondrial matrix. When growth factors are withdrawn from dependent cells, metabolism is disrupted by a defect in ATP/ADP exchange across the mitochondrial membranes. Unexpectedly, we find that this defect results from loss of outer mitochondrial membrane permeability to metabolic anions. This decrease in anion permeability correlates with the changes in conductance properties that accompany closure of the voltage-dependent anion channel (also known as mitochondrial porin). Loss of outer membrane permeability (i) results in the accumulation of stored metabolic energy within the intermembrane space in the form of creatine phosphate, (ii) is prevented by the outer mitochondrial membrane proteins Bcl-x(L) and Bcl-2, and (iii) can be reversed by growth factor readdition. If outer membrane impermeability persists, the disruption of mitochondrial homeostasis culminates in loss of outer mitochondrial membrane integrity, cytochrome c redistribution, and apoptosis. The recognition that outer membrane permeability is regulated under physiological conditions has important implications for the understanding of bioenergetics and cell survival.
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Affiliation(s)
- M G Vander Heiden
- Gwen Knapp Center and Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
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41
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42
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Kluck RM, Esposti MD, Perkins G, Renken C, Kuwana T, Bossy-Wetzel E, Goldberg M, Allen T, Barber MJ, Green DR, Newmeyer DD. The pro-apoptotic proteins, Bid and Bax, cause a limited permeabilization of the mitochondrial outer membrane that is enhanced by cytosol. J Cell Biol 1999; 147:809-22. [PMID: 10562282 PMCID: PMC2156156 DOI: 10.1083/jcb.147.4.809] [Citation(s) in RCA: 256] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/1999] [Accepted: 10/12/1999] [Indexed: 01/01/2023] Open
Abstract
During apoptosis, an important pathway leading to caspase activation involves the release of cytochrome c from the intermembrane space of mitochondria. Using a cell-free system based on Xenopus egg extracts, we examined changes in the outer mitochondrial membrane accompanying cytochrome c efflux. The pro-apoptotic proteins, Bid and Bax, as well as factors present in Xenopus egg cytosol, each induced cytochrome c release when incubated with isolated mitochondria. These factors caused a permeabilization of the outer membrane that allowed the corelease of multiple intermembrane space proteins: cytochrome c, adenylate kinase and sulfite oxidase. The efflux process is thus nonspecific. None of the cytochrome c-releasing factors caused detectable mitochondrial swelling, arguing that matrix swelling is not required for outer membrane permeability in this system. Bid and Bax caused complete release of cytochrome c but only a limited permeabilization of the outer membrane, as measured by the accessibility of inner membrane-associated respiratory complexes III and IV to exogenously added cytochrome c. However, outer membrane permeability was strikingly increased by a macromolecular cytosolic factor, termed PEF (permeability enhancing factor). We hypothesize that PEF activity could help determine whether cells can recover from mitochondrial cytochrome c release.
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Affiliation(s)
- Ruth M. Kluck
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Mauro Degli Esposti
- Department of Biochemistry and Molecular Biology, University of South Florida, College of Medicine, Tampa, Florida 33612
| | - Guy Perkins
- Department of Neurosciences, University of California San Diego, San Diego, California 92093
| | - Christian Renken
- Biology Department, San Diego State University, San Diego, California 92182
| | - Tomomi Kuwana
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Ella Bossy-Wetzel
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Martin Goldberg
- Paterson Institute, Christie Hospital NHS Trust, Manchester M20 9BX, United Kingdom
| | - Terry Allen
- Paterson Institute, Christie Hospital NHS Trust, Manchester M20 9BX, United Kingdom
| | - Michael J. Barber
- Department of Biochemistry and Molecular Biology, University of South Florida, College of Medicine, Tampa, Florida 33612
| | - Douglas R. Green
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
| | - Donald D. Newmeyer
- Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
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Röhl T, Motzkus M, Soll J. The outer envelope protein OEP24 from pea chloroplasts can functionally replace the mitochondrial VDAC in yeast. FEBS Lett 1999; 460:491-4. [PMID: 10556523 DOI: 10.1016/s0014-5793(99)01399-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The chloroplastic outer envelope protein OEP24 from pea forms a high-conductance low specificity solute channel as shown by in vitro studies. In order to establish its function also in an in vivo-like system, the gene encoding OEP24 was transformed into a yeast strain which lacks the general mitochondria solute channel porin, also known as voltage-dependent anion channel (VDAC). Transformation of the yeast VDAC(-) strain with the OEP24 gene resulted in the recovery of a phenotype indistinguishable from the wild-type. The OEP24 polypeptide is targeted to the mitochondrial outer membrane in this heterologous system. We conclude that OEP24 forms a solute channel in pea chloroplasts in planta.
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Affiliation(s)
- T Röhl
- Botanisches Institut, Universität Kiel, Am Botanischen Garten 1-9, D-24118, Kiel, Germany
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Abstract
The aim of this review is to provide basic information on the electrophysiological changes during acute ischemia and reperfusion from the level of ion channels up to the level of multicellular preparations. After an introduction, section II provides a general description of the ion channels and electrogenic transporters present in the heart, more specifically in the plasma membrane, in intracellular organelles of the sarcoplasmic reticulum and mitochondria, and in the gap junctions. The description is restricted to activation and permeation characterisitics, while modulation is incorporated in section III. This section (ischemic syndromes) describes the biochemical (lipids, radicals, hormones, neurotransmitters, metabolites) and ion concentration changes, the mechanisms involved, and the effect on channels and cells. Section IV (electrical changes and arrhythmias) is subdivided in two parts, with first a description of the electrical changes at the cellular and multicellular level, followed by an analysis of arrhythmias during ischemia and reperfusion. The last short section suggests possible developments in the study of ischemia-related phenomena.
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Affiliation(s)
- E Carmeliet
- Centre for Experimental Surgery and Anesthesiology, University of Leuven, Leuven, Belgium
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45
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Meir A, Ginsburg S, Butkevich A, Kachalsky SG, Kaiserman I, Ahdut R, Demirgoren S, Rahamimoff R. Ion channels in presynaptic nerve terminals and control of transmitter release. Physiol Rev 1999; 79:1019-88. [PMID: 10390521 DOI: 10.1152/physrev.1999.79.3.1019] [Citation(s) in RCA: 220] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The primary function of the presynaptic nerve terminal is to release transmitter quanta and thus activate the postsynaptic target cell. In almost every step leading to the release of transmitter quanta, there is a substantial involvement of ion channels. In this review, the multitude of ion channels in the presynaptic terminal are surveyed. There are at least 12 different major categories of ion channels representing several tens of different ion channel types; the number of different ion channel molecules at presynaptic nerve terminals is many hundreds. We describe the different ion channel molecules at the surface membrane and inside the nerve terminal in the context of their possible role in the process of transmitter release. Frequently, a number of different ion channel molecules, with the same basic function, are present at the same nerve terminal. This is especially evident in the cases of calcium channels and potassium channels. This abundance of ion channels allows for a physiological and pharmacological fine tuning of the process of transmitter release and thus of synaptic transmission.
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Affiliation(s)
- A Meir
- Department of Physiology and the Bernard Katz Minerva Centre for Cell Biophysics, Hebrew University Hadassah Medical School, Jerusalem, Israel
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46
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Vander Heiden MG, Chandel NS, Schumacker PT, Thompson CB. Bcl-xL prevents cell death following growth factor withdrawal by facilitating mitochondrial ATP/ADP exchange. Mol Cell 1999; 3:159-67. [PMID: 10078199 DOI: 10.1016/s1097-2765(00)80307-x] [Citation(s) in RCA: 385] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Growth factor withdrawal is associated with a metabolic arrest that can result in apoptosis. Cell death is preceded by loss of outer mitochondrial membrane integrity and cytochrome c release. These mitochondrial events appear to follow a relative increase in mitochondrial membrane potential. This change in membrane potential results from the failure of the adenine nucleotide translocator (ANT)/voltage-dependent anion channel (VDAC) complex to maintain ATP/ADP exchange. Bcl-xL expression allows growth factor-deprived cells to maintain sufficient mitochondrial ATP/ADP exchange to sustain coupled respiration. These data demonstrate that mitochondrial adenylate transport is under active regulation. Efficient exchange of ADP for ATP is promoted by Bcl-xL expression permitting oxidative phosphorylation to be regulated by cellular ATP/ADP levels and allowing mitochondria to adapt to changes in metabolic demand.
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47
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Minn AJ, Swain RE, Ma A, Thompson CB. Recent progress on the regulation of apoptosis by Bcl-2 family members. Adv Immunol 1998; 70:245-79. [PMID: 9755339 DOI: 10.1016/s0065-2776(08)60388-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- A J Minn
- Gwen Knapp Center for Lupus and Immunology Research, University of Chicago, Illinois 60637, USA
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48
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Künkele KP, Heins S, Dembowski M, Nargang FE, Benz R, Thieffry M, Walz J, Lill R, Nussberger S, Neupert W. The preprotein translocation channel of the outer membrane of mitochondria. Cell 1998; 93:1009-19. [PMID: 9635430 DOI: 10.1016/s0092-8674(00)81206-4] [Citation(s) in RCA: 305] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The preprotein translocase of the outer membrane of mitochondria (TOM complex) facilitates the recognition, insertion, and translocation of nuclear-encoded mitochondrial preproteins. We have purified the TOM complex from Neurospora crassa and analyzed its composition and functional properties. The TOM complex contains a cation-selective high-conductance channel. Upon reconstitution into liposomes, it mediates integration of proteins into and translocation across the lipid bilayer. TOM complex particles have a diameter of about 138 A, as revealed by electron microscopy and image analysis; they contain two or three centers of stain-filled openings, which we interpret as pores with an apparent diameter of about 20 A. We conclude that the structure reported here represents the protein-conducting channel of the mitochondrial outer membrane.
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Affiliation(s)
- K P Künkele
- Institut für Physiologische Chemie, Physikalische Biochemie, und Zellbiologie der Universität München, Germany
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49
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Mannella CA. Conformational changes in the mitochondrial channel protein, VDAC, and their functional implications. J Struct Biol 1998; 121:207-18. [PMID: 9615439 DOI: 10.1006/jsbi.1997.3954] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The voltage-dependent, anion-selective channel (VDAC) is generally considered the main pathway for metabolite diffusion across the mitochondrial outer membrane. It also interacts with several mitochondrial and cytosolic proteins, including kinases and cytochrome c. Sequence analysis and circular dichroism suggest that the channel is a bacterial porin-like beta-barrel. However, unlike bacterial porins, VDAC does not form tight trimeric complexes and is easily gated (reversibly closed) by membrane potential and low pH. Circular dichroism indicates that the protein undergoes a major conformational change at pH < 5, involving decreased beta-sheet and increased alpha-helical content. Electron microscopy of two-dimensional crystals of fungal VDAC provides direct information about the size and shape of its lumen and suggests that the N-terminal domain forms a mobile alpha-helix. It is proposed that the N-terminal domain normally resides in a groove in the lumen wall and that gating stimuli favor its displacement, destabilizing the putative beta-barrel. Partial closure would result from subsequent larger-scale structural rearrangements in the protein, possibly corresponding to the conformational change observed at pH < 5.
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Affiliation(s)
- C A Mannella
- Wadsworth Center, New York State Department of Health, Albany 12201-0509, USA
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50
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Huizing M, Ruitenbeek W, van den Heuvel LP, Dolce V, Iacobazzi V, Smeitink JA, Palmieri F, Trijbels JM. Human mitochondrial transmembrane metabolite carriers: tissue distribution and its implication for mitochondrial disorders. J Bioenerg Biomembr 1998; 30:277-84. [PMID: 9733094 DOI: 10.1023/a:1020501021222] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Mitochondrial transmembrane carrier deficiencies are a recently discovered group of disorders, belonging to the so-called mitochondriocytopathies. We examined the human tissue distribution of carriers which are involved in the process of oxidative phosphorylation (adenine nucleotide translocator, phosphate carrier, and voltage-dependent anion channel) and some mitochondrial substrate carriers (2-oxoglutarate carrier, carnitine-acylcarnitine carrier, and citrate carrier). The tissue distribution on mRNA level of mitochondrial transport proteins appears to be roughly in correlation with the dependence of these tissues on mitochondrial energy production capacity. In general the main mRNA expression of carriers involved in mitochondrial energy metabolism occurs in skeletal muscle and heart. Expression in liver and pancreas differs between carriers. Expression in brain, placenta, lung, and kidney is lower than in the other tissues. Western and Northern blotting experiments show a comparable HVDAC1 protein and mRNA distribution for the tested tissues. Patient's studies showed that cultured skin fibroblasts may not be a reliable alternative for skeletal muscle in screening for human mitochondrial carrier defects.
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Affiliation(s)
- M Huizing
- Department of Pediatrics, University Hospital, Nijmegen, The Netherlands
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