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Matsubara H, Tanaka R, Tateishi T, Yoshida H, Yamaguchi M, Kataoka T. The human Bcl-2 family member Bcl-rambo and voltage-dependent anion channels manifest a genetic interaction in Drosophila and cooperatively promote the activation of effector caspases in human cultured cells. Exp Cell Res 2019; 381:223-234. [PMID: 31102594 DOI: 10.1016/j.yexcr.2019.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 05/09/2019] [Accepted: 05/11/2019] [Indexed: 02/07/2023]
Abstract
We previously reported that the Bcl-2 family member human Bcl-rambo, also known as BCL2L13, induces apoptosis in human embryonic kidney 293T cells. Mouse Bcl-rambo has recently been reported to mediate mitochondrial fragmentation and mitophagy. In the present study, we showed that the transfection of human Bcl-rambo and its microtubule-associated protein light chain 3-interacting region motif mutant (W276A/I279A) caused mitochondrial fragmentation and the perinuclear accumulation of fragmented mitochondria in human lung adenocarcinoma A549 cells. In comprehensive screening using the Drosophila model in which human Bcl-rambo was ectopically expressed in eye imaginal discs, voltage-dependent anion channels (VDAC), also known as mitochondrial porin, were found to manifest a genetic interaction with human Bcl-rambo. In addition to human adenine nucleotide translocase (ANT) 1 and ANT2, the human Bcl-rambo protein bound to human VDAC1, albeit to a lesser extent than ANT2. Moreover, human VDAC1 and human VDAC2 in particular promoted the activation of effector caspases only when they were co-expressed with human Bcl-rambo in 293T cells. Bcl-rambo induced the perinuclear accumulation of fragmented mitochondria by the knockdown of VDAC1, VDAC2, and VDAC3 in A549 cells. Thus, the present study revealed that human Bcl-rambo and VDAC cooperatively promote the activation of effector caspases in human cultured cells.
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Affiliation(s)
- Hisanori Matsubara
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan
| | - Reiji Tanaka
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan
| | - Tatsuya Tateishi
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan
| | - Hideki Yoshida
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan; Advanced Insect Research Promotion Center, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan
| | - Masamitsu Yamaguchi
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan; Advanced Insect Research Promotion Center, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan
| | - Takao Kataoka
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan; Advanced Insect Research Promotion Center, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
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2
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Leggio L, Guarino F, Magrì A, Accardi-Gheit R, Reina S, Specchia V, Damiano F, Tomasello MF, Tommasino M, Messina A. Mechanism of translation control of the alternative Drosophila melanogaster Voltage Dependent Anion-selective Channel 1 mRNAs. Sci Rep 2018; 8:5347. [PMID: 29593233 PMCID: PMC5871876 DOI: 10.1038/s41598-018-23730-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 03/19/2018] [Indexed: 01/08/2023] Open
Abstract
The eukaryotic porin, also called the Voltage Dependent Anion-selective Channel (VDAC), is the main pore-forming protein of the outer mitochondrial membrane. In Drosophila melanogaster, a cluster of genes evolutionarily linked to VDAC is present on chromosome 2L. The main VDAC isoform, called VDAC1 (Porin1), is expressed from the first gene of the cluster. The porin1 gene produces two splice variants, 1A-VDAC and 1B-VDAC, with the same coding sequence but different 5' untranslated regions (UTRs). Here, we studied the influence of the two 5' UTRs, 1A-5' UTR and 1B-5' UTR, on transcription and translation of VDAC1 mRNAs. In porin-less yeast cells, transformation with a construct carrying 1A-VDAC results in the expression of the corresponding protein and in complementation of a defective cell phenotype, whereas the 1B-VDAC sequence actively represses VDAC expression. Identical results were obtained using constructs containing the two 5' UTRs upstream of the GFP reporter. A short region of 15 nucleotides in the 1B-5' UTR should be able to pair with an exposed helix of 18S ribosomal RNA (rRNA), and this interaction could be involved in the translational repression. Our data suggest that contacts between the 5' UTR and 18S rRNA sequences could modulate the translation of Drosophila 1B-VDAC mRNA. The evolutionary significance of this finding is discussed.
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Affiliation(s)
- L Leggio
- Department of Biological, University of Catania, Geological and Environmental Sciences, Catania, 95125, Italy.,Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, 95123, Italy
| | - F Guarino
- Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, 95123, Italy.,National Institute of Biostructures and Biosystems (INBB), Catania, Italy
| | - A Magrì
- Department of Biological, University of Catania, Geological and Environmental Sciences, Catania, 95125, Italy
| | - R Accardi-Gheit
- International Agency for Research on Cancer (IARC), World Health Organization, Lyon, 69372, France
| | - S Reina
- Department of Biological, University of Catania, Geological and Environmental Sciences, Catania, 95125, Italy.,Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, 95123, Italy
| | - V Specchia
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Lecce, Italy
| | - F Damiano
- Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Lecce, Italy
| | - M F Tomasello
- IBB-CNR, Institute of Biostructure and Bioimaging, Section of Catania, Via Paolo Gaifami, 18-95126, Catania, Italy
| | - M Tommasino
- International Agency for Research on Cancer (IARC), World Health Organization, Lyon, 69372, France
| | - A Messina
- Department of Biological, University of Catania, Geological and Environmental Sciences, Catania, 95125, Italy. .,National Institute of Biostructures and Biosystems (INBB), Catania, Italy.
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3
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Deletion of β-strands 9 and 10 converts VDAC1 voltage-dependence in an asymmetrical process. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:793-805. [PMID: 23541892 DOI: 10.1016/j.bbabio.2013.03.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 03/06/2013] [Accepted: 03/18/2013] [Indexed: 11/21/2022]
Abstract
Voltage-dependent anion selective channel isoform1 maintains the permeability of the outer mitochondrial membrane. Its voltage-gating properties are relevant in bioenergetic metabolism and apoptosis. The N-terminal domain is suspected to be involved in voltage-gating, due to its peculiar localization. However this issue is still controversial. In this work we exchanged or deleted the β-strands that take contact with the N-terminal domain. The exchange of the whole hVDAC1 β-barrel with the homologous hVDAC3 β-barrel produces a chimeric protein that, in reconstituted systems, loses completely voltage-dependence. hVDAC3 β-barrel has most residues in common with hVDAC1, including V143 and L150 considered anchor points for the N-terminus. hVDAC1 mutants completely lacking either the β-strand 9 or both β-strands 9 and 10 were expressed, refolded and reconstituted in artificial bilayers. The mutants formed smaller pores. Molecular dynamics simulations of the mutant structure supported its ability to form smaller pores. The mutant lacking both β-strands 9 and 10 showed a new voltage-dependence feature resulting in a fully asymmetric behavior. These data indicate that a network of β-strands in the pore-walls, and not single residues, are required for voltage-gating in addition to the N-terminus.
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4
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Park J, Kim Y, Choi S, Koh H, Lee SH, Kim JM, Chung J. Drosophila Porin/VDAC affects mitochondrial morphology. PLoS One 2010; 5:e13151. [PMID: 20949033 PMCID: PMC2951900 DOI: 10.1371/journal.pone.0013151] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 09/08/2010] [Indexed: 11/18/2022] Open
Abstract
Voltage-dependent anion channel (VDAC) has been suggested to be a mediator of mitochondrial-dependent cell death induced by Ca(2+) overload, oxidative stress and Bax-Bid activation. To confirm this hypothesis in vivo, we generated and characterized Drosophila VDAC (porin) mutants and found that Porin is not required for mitochondrial apoptosis, which is consistent with the previous mouse studies. We also reported a novel physiological role of Porin. Loss of porin resulted in locomotive defects and male sterility. Intriguingly, porin mutants exhibited elongated mitochondria in indirect flight muscle, whereas Porin overexpression produced fragmented mitochondria. Through genetic analysis with the components of mitochondrial fission and fusion, we found that the elongated mitochondria phenotype in porin mutants were suppressed by increased mitochondrial fission, but enhanced by increased mitochondrial fusion. Furthermore, increased mitochondrial fission by Drp1 expression suppressed the flight defects in the porin mutants. Collectively, our study showed that loss of Drosophila Porin results in mitochondrial morphological defects and suggested that the defective mitochondrial function by Porin deficiency affects the mitochondrial remodeling process.
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Affiliation(s)
- Jeehye Park
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Korea
| | - Yongsung Kim
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Korea
- School of Biological Sciences, Seoul National University, Seoul, Korea
| | - Sekyu Choi
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Korea
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Hyongjong Koh
- Department of Pharmacology, Dong-A University College of Medicine, Busan, Korea
| | - Sang-Hee Lee
- Department of Pathology, Chungnam National University School of Medicine, Daejeon, Korea
| | - Jin-Man Kim
- Department of Pathology, Chungnam National University School of Medicine, Daejeon, Korea
| | - Jongkyeong Chung
- National Creative Research Initiatives Center for Energy Homeostasis Regulation, Seoul National University, Seoul, Korea
- School of Biological Sciences, Seoul National University, Seoul, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul, Korea
- * E-mail:
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5
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VDAC, a multi-functional mitochondrial protein regulating cell life and death. Mol Aspects Med 2010; 31:227-85. [PMID: 20346371 DOI: 10.1016/j.mam.2010.03.002] [Citation(s) in RCA: 530] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 03/17/2010] [Indexed: 01/22/2023]
Abstract
Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca(2+) homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure-function relations. Understanding structure-function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.
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6
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Porin isoform 2 has a different localization in Drosophila melanogaster ovaries than porin 1. J Bioenerg Biomembr 2008; 40:219-26. [DOI: 10.1007/s10863-008-9149-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 05/22/2008] [Indexed: 11/25/2022]
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Lee S, Leung HT, Kim E, Jang J, Lee E, Baek K, Pak WL, Yoon J. Effects of a mutation in the Drosophila porin gene encoding mitochondrial voltage-dependent anion channel protein on phototransduction. Dev Neurobiol 2007; 67:1533-45. [PMID: 17525991 DOI: 10.1002/dneu.20526] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mitochondrial porins, also know as VDACs (voltage-dependent anion channels), play an important role in regulating energy metabolism, apoptosis, and the transport of metabolites across the mitochondrial outer membrane. So far three distinct isoforms of VDAC (VDAC1-3) have been reported in vertebrates, but their functions remain unknown. The annotation database of the Drosophila melanogaster genome sequence has identified four genes (porin, CG17137, CG17139, and CG17140) encoding different isoforms of VDACs. We identified post-translational modifications of PORIN that are specific to D. melanogaster eyes. We also identified the P-element insertion in the porin gene, porin(G2294), that is homozygous viable whereas all the porin mutants previously reported are homozygous lethal at the pupal stage. The mutant does not show any defects in fly morphology, survival, and photoreceptor structure. The mutant, however, produces <10% of the normal level of wild-type (WT) porin transcripts and 16.5% of WT level of the PORIN protein. The P-element insertion affects only the expression of Class I transcript but not Class II transcript of the porin gene. Unlike in WT, the mutant displays an ERG (electroretinogram) that is not maintained during a prolonged light stimulus. The revertant obtained from remobilization of the P-element in the mutant produces the WT level of porin transcripts and PORIN protein, and shows a normal ERG response. Our data suggest that the PORIN protein is important in maintaining a photoreceptor response during prolonged stimulation.
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Affiliation(s)
- Sunji Lee
- Graduate School of Biotechnology, KyungHee University, Yongin-si, Gyeonggi-do, Korea
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8
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Guarino F, Specchia V, Zapparoli G, Messina A, Aiello R, Bozzetti MP, De Pinto V. Expression and localization in spermatozoa of the mitochondrial porin isoform 2 in Drosophila melanogaster. Biochem Biophys Res Commun 2006; 346:665-70. [PMID: 16774740 DOI: 10.1016/j.bbrc.2006.05.172] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 05/19/2006] [Indexed: 11/26/2022]
Abstract
Mitochondrial porins or VDACs (voltage-dependent anion-selective channels) are transmembrane pore-forming proteins. In eukaryotic genomes multiple genes coding for VDAC homologues have been discovered, but their function remains unknown. In Drosophila melanogaster three additional genes homologous to the gene porin have been found. In a previous report we have expressed in vitro Porin 2 (gene GC17137) and we have found that the reconstituted protein shows pore-forming activity but it is cation-selective and poorly dependent from voltage. In this work we have characterized the expression pattern of Porin 2. Amplification upon germinal and somatic or stage specific mRNA showed that the highest transcription level of Porin 2 is in testis. Western blot analysis performed with antibodies raised against the recombinant Porin 2 confirmed a high level of expression in the fly spermatozoa. Immuno-histochemical studies indicate that Porin 2 is selectively present in spermatozoa tail, where the mitochondria are located, but not in spermatocytes. A lethal mutant of D. melanogaster carrying a P-element in the first intron of the porin (Porin 1) gene hinders the expression of both Porin 1 and 2. Our results suggest that Porin 2 is truly expressed and that it is required for functional germinal tissues.
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Affiliation(s)
- Francesca Guarino
- Department of Chemical Sciences, University of Catania, Catania, Italy
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9
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Graham BH, Craigen WJ. Mitochondrial voltage-dependent anion channel gene family in Drosophila melanogaster: complex patterns of evolution, genomic organization, and developmental expression. Mol Genet Metab 2005; 85:308-17. [PMID: 15886041 DOI: 10.1016/j.ymgme.2005.03.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Revised: 03/12/2005] [Accepted: 03/23/2005] [Indexed: 10/25/2022]
Abstract
Voltage-dependent anion channels (VDACs), also known as mitochondrial porins, are a family of small pore-forming proteins of the mitochondrial outer membrane found in all eukaryotes. VDACs play important roles in the regulated flux of metabolites between the cytosolic and mitochondrial compartments, energy metabolism, and apoptosis. Annotation of the genome sequence of Drosophila melanogaster revealed three genes (CG17137, CG31722-A, and CG31722-B) with homology to porin, the previously described Drosophila VDAC. Molecular analysis reveals a complex pattern of organization and expression. The genomic organization of these four genes and sequence comparisons with other insect VDAC homologs indicate that this gene family evolved through a mechanism of duplication and divergence from an ancestral VDAC gene during the radiation of the genus Drosophila. CG17137, CG31722-A, and CG31722-B are expressed in a male-specific pattern on both transcriptional and translational levels, while porin is equally expressed in both male and female flies. Additionally, CG31722-A and CG31722-B are expressed as a dicistronic transcript. Western blot analysis and immunofluorescence microscopy confirm that these proteins localize to the mitochondrion. Further expression analysis showed that CG17137 and CG31722-B are abundant in testes, while porin is ubiquitously expressed. While porin, CG17137, and CG31722-B are expressed to different degrees during embryogenesis, all of these proteins are dramatically reduced relative to cytochrome c content during larvogenesis. These studies illustrate a complex genomic organization and spatiotemporal pattern of expression for Drosophila VDACs as well as an evolutionary history consistent with either a partitioning of VDAC functions or an acquisition of novel functions among isoforms.
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Affiliation(s)
- Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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Aiello R, Messina A, Schiffler B, Benz R, Tasco G, Casadio R, De Pinto V. Functional Characterization of a Second Porin Isoform in Drosophila melanogaster. J Biol Chem 2004; 279:25364-73. [PMID: 15054101 DOI: 10.1074/jbc.m310572200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial porins or voltage-dependent anion-selective channels are channel-forming proteins mainly found in the mitochondrial outer membrane. Genome sequencing of the fruit fly Drosophila melanogaster revealed the presence of three additional porin-like genes. No functional information was available for the different gene products. In this work we have studied the function of the gene product closest to the known Porin gene (CG17137 coding for DmPorin2). Its coding sequence was expressed in Escherichia coli. The recombinant DmPorin2 protein is able to form channels similar to those formed by DmPorin1 reconstituted in artificial membranes. Furthermore, DmPorin2 is clearly voltage-independent and cation-selective, whereas its counterpart isoform 1 is voltage-dependent and anion-selective. Sequence comparison of the two porin isoforms indicates the exchange of four lysines in DmPorin1 for four glutamic acids in DmPorin2. We have mutated two of them (Glu-66 and Glu-163) to lysines to investigate their role in the functional features of the pore. The mutants E163K and E66K/E163K are endowed with an almost full inversion of the ion selectivity. Both single mutations partially restore the voltage dependence of the pore. We found that an additional effect with the double mutant E66K/E163K was the restoration of voltage dependence. Protein structure predictions highlight a 16 beta-strand pattern, typical for porins. In a three-dimensional model of DmPorin2, Glu-66 and Glu-163 are close to the rim of the channel, on two opposite sides. DmPorin2 is expressed in all the fly tissues and in all the developmental stages tested. Our main conclusions are as follows. 1) The CG17137 gene may express a porin with a functional role in D. melanogaster. 2) We have identified two amino acids of major relevance for the voltage dependence of the porin pore.
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Affiliation(s)
- Rita Aiello
- Department of Chemical Sciences, University of Catania, 95125 Catania, Italy
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11
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Graham BH, Craigen WJ. Genetic approaches to analyzing mitochondrial outer membrane permeability. Curr Top Dev Biol 2004; 59:87-118. [PMID: 14975248 DOI: 10.1016/s0070-2153(04)59004-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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12
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Messina A, Guarino F, Oliva M, van den Heuvel LP, Smeitink J, De Pinto V. Characterization of the human porin isoform 1 (HVDAC1) gene by amplification on the whole human genome: A tool for porin deficiency analysis. Biochem Biophys Res Commun 2000; 270:787-92. [PMID: 10772903 DOI: 10.1006/bbrc.2000.2487] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The deficiency of porin isoform 1 (HVDAC1) in human skeletal muscle has been associated with a pathological phenotype related to defects in the bioenergetic metabolism. In the best studied case, porin deficiency was not apparent in cultured fibroblasts: this observation raised the conclusion that no molecular defect was in the cDNA sequence coding for the protein. To get more insight in the pathogenetic mechanism that is involved in porin isoform 1 deficiency, we have determined the whole structure of the corresponding human gene. On the basis of the corresponding mouse gene structure and the human cDNA sequence, we designed long extension PCR amplifications using the whole genomic DNA as a template. Exonic/intronic regions were isolated and the exons and surrounding introns sequenced. The 5' and 3' extremities of the gene were determined by genome walking. The porin isoform 1 human gene is made up of 9 exons and spans about 33 kbp. A whole panel of PCR parameters was set and is now ready to be used for specific amplification upon patients' genomic DNA. The analysis of the putative promoter sequence was performed. It revealed the presence of a sterol Repressor element (SRE), an SRY, the testis-determining factor, and a nuclear respiratory factor 2 (NRF-2) binding site. These sites, according to results from literature, could be involved in the functional modulation of the gene expression.
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Affiliation(s)
- A Messina
- Department of Chemical Sciences, Laboratory of Biochemistry and Molecular Biology, Università di Catania, viale A. Doria 6, Catania, I-95125, Italy.
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Báthori G, Parolini I, Szabó I, Tombola F, Messina A, Oliva M, Sargiacomo M, De Pinto V, Zoratti M. Extramitochondrial porin: facts and hypotheses. J Bioenerg Biomembr 2000; 32:79-89. [PMID: 11768765 DOI: 10.1023/a:1005516513313] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Mitochondrial porin, or VDAC, is a pore-forming protein abundant in the outer mitochondrial membrane. Several publications have reported extramitochondrial localizations as well, but the evidence was considered insufficient by many, and the presence of porin in nonmitochondrial cellular compartments has remained in doubt for a long time. We have now obtained new data indicating that the plasma membrane of hematopoietic cells contains porin, probably located mostly in caveolae or caveolae-like domains. Porin was purified from the plasma membrane of intact cells by a procedure utilizing the membrane-impermeable labeling reagent NH-SS-biotin and streptavidin affinity chromatography, and shown to have the same properties as mitochondrial porin. A channel with properties similar to that of isolated VDAC was observed by patch-clamping intact cells. This review discusses the evidence supporting extramitochondrial localization, the putative identification of the plasma membrane porin with the "maxi" chloride channel, the hypothetical mechanisms of sorting porin to various cellular membrane structures, and its possible functions.
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Affiliation(s)
- G Báthori
- Department of Physiology, Semmelweis Medical University, Budapest, Hungary.
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14
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Bàthori G, Parolini I, Tombola F, Szabò I, Messina A, Oliva M, De Pinto V, Lisanti M, Sargiacomo M, Zoratti M. Porin is present in the plasma membrane where it is concentrated in caveolae and caveolae-related domains. J Biol Chem 1999; 274:29607-12. [PMID: 10514428 DOI: 10.1074/jbc.274.42.29607] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial porin, or voltage-dependent anion channel, is a pore-forming protein first discovered in the outer mitochondrial membrane. Later investigations have provided indications for its presence also in other cellular membranes, including the plasma membrane, and in caveolae. This extra-mitochondrial localization is debated and no clear-cut conclusion has been reached up to now. In this work, we used biochemical and electrophysiological techniques to detect and characterize porin within isolated caveolae and caveolae-like domains (low density Triton-insoluble fractions). A new procedure was used to isolate porin from plasma membrane. The outer surface of cultured CEM cells was biotinylated by an impermeable reagent. Low density Triton-insoluble fractions were prepared from the labeled cells and used as starting material to purify a biotinylated protein with the same electrophoretic mobility and immunoreactivity of mitochondrial porin. In planar bilayers, the porin from these sources formed slightly anion-selective pores with properties indistinguishable from those of mitochondrial porin. This work thus provides a strong indication of the presence of porin in the plasma membrane, and specifically in caveolae and caveolae-like domains.
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Affiliation(s)
- G Bàthori
- CNR Centro Studi Biomembrane, Dipartimento Scienze Biomediche Sperimentali, viale G. Colombo 3, 35121 Padova, Italy
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