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Berezhkovskii AM, Bezrukov SM. Counter-Intuitive Features of Particle Dynamics in Nanopores. Int J Mol Sci 2023; 24:15923. [PMID: 37958906 PMCID: PMC10648703 DOI: 10.3390/ijms242115923] [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: 09/22/2023] [Revised: 10/27/2023] [Accepted: 10/29/2023] [Indexed: 11/15/2023] Open
Abstract
Using the framework of a continuous diffusion model based on the Smoluchowski equation, we analyze particle dynamics in the confinement of a transmembrane nanopore. We briefly review existing analytical results to highlight consequences of interactions between the channel nanopore and the translocating particles. These interactions are described within a minimalistic approach by lumping together multiple physical forces acting on the particle in the pore into a one-dimensional potential of mean force. Such radical simplification allows us to obtain transparent analytical results, often in a simple algebraic form. While most of our findings are quite intuitive, some of them may seem unexpected and even surprising at first glance. The focus is on five examples: (i) attractive interactions between the particles and the nanopore create a potential well and thus cause the particles to spend more time in the pore but, nevertheless, increase their net flux; (ii) if the potential well-describing particle-pore interaction occupies only a part of the pore length, the mean translocation time is a non-monotonic function of the well length, first increasing and then decreasing with the length; (iii) when a rectangular potential well occupies the entire nanopore, the mean particle residence time in the pore is independent of the particle diffusivity inside the pore and depends only on its diffusivity in the bulk; (iv) although in the presence of a potential bias applied to the nanopore the "downhill" particle flux is higher than the "uphill" one, the mean translocation times and their distributions are identical, i.e., independent of the translocation direction; and (v) fast spontaneous gating affects nanopore selectivity when its characteristic time is comparable to that of the particle transport through the pore.
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Affiliation(s)
| | - Sergey M. Bezrukov
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA;
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2
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Ventura C, Junco M, Santiago Valtierra FX, Gooz M, Zhiwei Y, Townsend DM, Woster PM, Maldonado EN. Synergism of small molecules targeting VDAC with sorafenib, regorafenib or lenvatinib on hepatocarcinoma cell proliferation and survival. Eur J Pharmacol 2023; 957:176034. [PMID: 37652292 PMCID: PMC10586475 DOI: 10.1016/j.ejphar.2023.176034] [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: 05/14/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 09/02/2023]
Abstract
Voltage dependent anion channels (VDAC) in the outer mitochondrial membrane regulate the influx of metabolites that sustain mitochondrial metabolism and the efflux of ATP to the cytosol. Free tubulin and NADH close VDAC. The VDAC-binding small molecules X1 and SC18 modulate mitochondrial metabolism. X1 antagonizes the inhibitory effect of tubulin on VDAC. SC18 occupies an NADH-binding pocket in the inner wall of all VDAC isoforms. Here, we hypothesized that X1 and SC18 have a synergistic effect with sorafenib, regorafenib or lenvatinib to arrest proliferation and induce death in hepatocarcinoma cells. We used colony formation assays to determine cell proliferation, and a combination of calcein/propidium iodide, and trypan blue exclusion to assess cell death in the well differentiated Huh7 and the poorly differentiated SNU-449 cells. Synergism was assessed using the Chou-Talalay method. The inhibitory effect of X1, SC18, sorafenib, regorafenib and lenvatinib was concentration and time dependent. IC50s calculated from the inhibition of clonogenic capacity were lower than those determined from cell survival. At IC50s that inhibited cell proliferation, SC18 arrested cells in G0/G1. SC18 at 0.25-2 IC50s had a synergistic effect with sorafenib on clonogenic inhibition in Huh7 and SNU-449 cells, and with regorafenib or lenvatinib in SNU-449 cells. X1 or SC18 also had synergistic effects with sorafenib on promoting cell death at 0.5-2 IC50s for SC18 in Huh7 and SNU-449 cells. These results suggest that small molecules targeting VDAC represent a potential new class of drugs to treat liver cancer.
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Affiliation(s)
- C Ventura
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA; Institute for Immunological and Physiopathological Studies (IIFP), National Scientific and Technical Research Council (CONICET), Argentina
| | - M Junco
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - F X Santiago Valtierra
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - M Gooz
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - Y Zhiwei
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - D M Townsend
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - P M Woster
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - E N Maldonado
- Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA; Hollings Cancer Center, Medical University of South Carolina, Charleston, SC, USA.
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3
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Lemeshko VV. VDAC as a voltage-dependent mitochondrial gatekeeper under physiological conditions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184175. [PMID: 37201560 DOI: 10.1016/j.bbamem.2023.184175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 05/09/2023] [Accepted: 05/11/2023] [Indexed: 05/20/2023]
Abstract
Mitochondria, composed of two membranes, play a key role in energy production in eukaryotic cells. The main function of the inner membrane is oxidative phosphorylation, while the mitochondrial outer membrane (MOM) seems to control the energy flux and exchange of various charged metabolites between mitochondria and the cytosol. Metabolites cross MOM via the various isoforms of voltage-dependent anion channel (VDAC). In turn, VDACs interact with some enzymes, other proteins and molecules, including drugs. This work aimed to analyze various literature experimental data related to targeting mitochondrial VDACs and VDAC-kinase complexes on the basis of the hypothesis of generation of the outer membrane potential (OMP) and OMP-dependent reprogramming of cell energy metabolism. Our previous model of the VDAC-hexokinase-linked generation of OMP was further complemented in this study with an additional regulation of the MOM permeability by the OMP-dependent docking of cytosolic proteins like tubulin to VDACs. Computational analysis of the model suggests that OMP changes might be involved in the mechanisms of apoptosis promotion through the so-called transient hyperpolarization of mitochondria. The high concordance of the performed computational estimations with many published experimental data allows concluding that OMP generation under physiological conditions is highly probable and VDAC might function as an OMP-dependent gatekeeper of mitochondria, controlling cell life and death. The proposed model of OMP generation allows understanding in more detail the mechanisms of cancer death resistance and anticancer action of various drugs and treatments influencing VDAC voltage-gating properties, VDAC content, mitochondrial hexokinase activity and VDAC-kinase interactions in MOM.
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Affiliation(s)
- Victor V Lemeshko
- Universidad Nacional de Colombia, Sede Medellín, Carrera 65, Nro. 59A - 110, Medellín, Colombia.
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4
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Lemeshko VV. Apparent "mild depolarization of the inner mitochondrial membrane" as a result of a possible generation of the outer membrane potential. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184032. [PMID: 35985076 DOI: 10.1016/j.bbamem.2022.184032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/29/2022] [Accepted: 08/08/2022] [Indexed: 12/31/2022]
Abstract
Recently reported kinase-linked mild depolarization of mitochondria, which prevents the generation of the reactive oxygen species (ROS) and disappears in various organs of the old mice, has been assumed to represent a crucial component of the mitochondrial anti-aging program. To measure mitochondrial inner membrane potential (IMP), the authors used fluorescent probe safranin O+. It is widely accepted that the accumulation of such cationic probes in the mitochondrial matrix depends exclusively on IMP, thus completely ignoring the possibility of the outer membrane potential (OMP) generation. However, computational analysis performed in the presented work suggests that the kinase-linked generation of the positive OMP might take place under the described conditions, because the measured potential includes the algebraic sum of both IMP and OMP. Alternatively to the suggested mild depolarization of mitochondria, the reported experimental data might reflect mainly a change of the positive OMP generated by the VDAC-kinase complexes. We also demonstrate that the reported in the literature mitochondrial hyperpolarization induced by erastin (known to prevent VDAC-tubulin interactions) and the depolarization caused by the mitochondrial VDAC knockdowns in the cancer cells might actually represent a decrease or increase, respectively, of the magnitude of the kinase-linked positive OMP. This is consistent with our hypothesis that VDAC voltage gating by the kinase-linked metabolically-dependent OMP plays a very important physiological role in regulating the cell energy metabolism under normal and pathological conditions, in the maintenance of the cell death resistance and even in the genetic aging program.
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Affiliation(s)
- Victor V Lemeshko
- Escuela de Física, Facultad de Ciencias, Universidad Nacional de Colombia, Sede Medellín, Carrera 65, Nro. 59A - 110, Medellín, Colombia.
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5
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Rajendran M, Queralt-Martín M, Gurnev PA, Rosencrans WM, Rovini A, Jacobs D, Abrantes K, Hoogerheide DP, Bezrukov SM, Rostovtseva TK. Restricting α-synuclein transport into mitochondria by inhibition of α-synuclein-VDAC complexation as a potential therapeutic target for Parkinson's disease treatment. Cell Mol Life Sci 2022; 79:368. [PMID: 35718804 PMCID: PMC11072225 DOI: 10.1007/s00018-022-04389-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 05/13/2022] [Accepted: 05/20/2022] [Indexed: 11/03/2022]
Abstract
Involvement of alpha-synuclein (αSyn) in Parkinson's disease (PD) is complicated and difficult to trace on cellular and molecular levels. Recently, we established that αSyn can regulate mitochondrial function by voltage-activated complexation with the voltage-dependent anion channel (VDAC) on the mitochondrial outer membrane. When complexed with αSyn, the VDAC pore is partially blocked, reducing the transport of ATP/ADP and other metabolites. Further, αSyn can translocate into the mitochondria through VDAC, where it interferes with mitochondrial respiration. Recruitment of αSyn to the VDAC-containing lipid membrane appears to be a crucial prerequisite for both the blockage and translocation processes. Here we report an inhibitory effect of HK2p, a small membrane-binding peptide from the mitochondria-targeting N-terminus of hexokinase 2, on αSyn membrane binding, and hence on αSyn complex formation with VDAC and translocation through it. In electrophysiology experiments, the addition of HK2p at micromolar concentrations to the same side of the membrane as αSyn results in a dramatic reduction of the frequency of blockage events in a concentration-dependent manner, reporting on complexation inhibition. Using two complementary methods of measuring protein-membrane binding, bilayer overtone analysis and fluorescence correlation spectroscopy, we found that HK2p induces detachment of αSyn from lipid membranes. Experiments with HeLa cells using proximity ligation assay confirmed that HK2p impedes αSyn entry into mitochondria. Our results demonstrate that it is possible to regulate αSyn-VDAC complexation by a rationally designed peptide, thus suggesting new avenues in the search for peptide therapeutics to alleviate αSyn mitochondrial toxicity in PD and other synucleinopathies.
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Affiliation(s)
- Megha Rajendran
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - María Queralt-Martín
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
- Laboratory of Molecular Biophysics, Department of Physics, Universitat Jaume I, Castellón, 12071, Spain
| | - Philip A Gurnev
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - William M Rosencrans
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - Amandine Rovini
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - Daniel Jacobs
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - Kaitlin Abrantes
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - David P Hoogerheide
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Sergey M Bezrukov
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA
| | - Tatiana K Rostovtseva
- Section On Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 29B, Room 1G09, Bethesda, MD, 20892, USA.
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6
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NAD(H) Regulates the Permeability Transition Pore in Mitochondria through an External Site. Int J Mol Sci 2021; 22:ijms22168560. [PMID: 34445270 PMCID: PMC8395297 DOI: 10.3390/ijms22168560] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 07/28/2021] [Accepted: 08/05/2021] [Indexed: 11/17/2022] Open
Abstract
The opening of the permeability transition pore (mPTP) in mitochondria initiates cell death in numerous diseases. The regulation of mPTP by NAD(H) in the mitochondrial matrix is well established; however, the role of extramitochondrial (cytosolic) NAD(H) is still unclear. We studied the effect of added NADH and NAD+ on: (1) the Ca2+-retention capacity (CRC) of isolated rat liver, heart, and brain mitochondria; (2) the Ca2+-dependent mitochondrial swelling in media whose particles can (KCl) or cannot (sucrose) be extruded from the matrix by mitochondrial carriers; (3) the Ca2+-dependent mitochondrial depolarization and the release of entrapped calcein from mitochondria of permeabilized hepatocytes; and (4) the Ca2+-dependent mitochondrial depolarization and subsequent repolarization. NADH and NAD+ increased the CRC of liver, heart, and brain mitochondria 1.5-2.5 times, insignificantly affecting the rate of Ca2+-uptake and the free Ca2+ concentration in the medium. NAD(H) suppressed the Ca2+-dependent mitochondrial swelling both in KCl- and sucrose-based media but did not induce the contraction and repolarization of swollen mitochondria. By contrast, EGTA caused mitochondrial repolarization in both media and the contraction in KCl-based medium only. NAD(H) delayed the Ca2+-dependent depolarization and the release of calcein from individual mitochondria in hepatocytes. These data unambiguously demonstrate the existence of an external NAD(H)-dependent site of mPTP regulation.
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7
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Sander P, Gudermann T, Schredelseker J. A Calcium Guard in the Outer Membrane: Is VDAC a Regulated Gatekeeper of Mitochondrial Calcium Uptake? Int J Mol Sci 2021; 22:ijms22020946. [PMID: 33477936 PMCID: PMC7833399 DOI: 10.3390/ijms22020946] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 12/15/2022] Open
Abstract
Already in the early 1960s, researchers noted the potential of mitochondria to take up large amounts of Ca2+. However, the physiological role and the molecular identity of the mitochondrial Ca2+ uptake mechanisms remained elusive for a long time. The identification of the individual components of the mitochondrial calcium uniporter complex (MCUC) in the inner mitochondrial membrane in 2011 started a new era of research on mitochondrial Ca2+ uptake. Today, many studies investigate mitochondrial Ca2+ uptake with a strong focus on function, regulation, and localization of the MCUC. However, on its way into mitochondria Ca2+ has to pass two membranes, and the first barrier before even reaching the MCUC is the outer mitochondrial membrane (OMM). The common opinion is that the OMM is freely permeable to Ca2+. This idea is supported by the presence of a high density of voltage-dependent anion channels (VDACs) in the OMM, forming large Ca2+ permeable pores. However, several reports challenge this idea and describe VDAC as a regulated Ca2+ channel. In line with this idea is the notion that its Ca2+ selectivity depends on the open state of the channel, and its gating behavior can be modified by interaction with partner proteins, metabolites, or small synthetic molecules. Furthermore, mitochondrial Ca2+ uptake is controlled by the localization of VDAC through scaffolding proteins, which anchor VDAC to ER/SR calcium release channels. This review will discuss the possibility that VDAC serves as a physiological regulator of mitochondrial Ca2+ uptake in the OMM.
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Affiliation(s)
- Paulina Sander
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany; (P.S.); (T.G.)
| | - Thomas Gudermann
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany; (P.S.); (T.G.)
- Deutsches Zentrum für Herz-Kreislauf-Forschung, Partner Site Munich Heart Alliance, Munich, Germany
| | - Johann Schredelseker
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany; (P.S.); (T.G.)
- Deutsches Zentrum für Herz-Kreislauf-Forschung, Partner Site Munich Heart Alliance, Munich, Germany
- Correspondence: ; Tel.: +49-(0)89-2180-73831
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8
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Moras M, Hattab C, Gonzalez-Menendez P, Fader CM, Dussiot M, Larghero J, Le Van Kim C, Kinet S, Taylor N, Lefevre SD, Ostuni MA. Human erythroid differentiation requires VDAC1-mediated mitochondrial clearance. Haematologica 2021; 107:167-177. [PMID: 33406813 PMCID: PMC8719069 DOI: 10.3324/haematol.2020.257121] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Indexed: 11/10/2022] Open
Abstract
Erythroblast maturation in mammals is dependent on organelle clearance throughout terminal erythropoiesis. We studied the role of the outer mitochondrial membrane protein voltage-dependent anion channel-1 (VDAC1) in human terminal erythropoiesis. We show that short hairpin (shRNA)-mediated downregulation of VDAC1 accelerates erythroblast maturation. Thereafter, erythroblasts are blocked at the orthochromatic stage, exhibiting a significant decreased level of enucleation, concomitant with an increased cell death. We demonstrate that mitochondria clearance starts at the transition from basophilic to polychromatic erythroblast, and that VDAC1 downregulation induces the mitochondrial retention. In damaged mitochondria from non-erythroid cells, VDAC1 was identified as a target for Parkin-mediated ubiquitination to recruit the phagophore. Here, we showed that VDAC1 is involved in phagophore’s membrane recruitment regulating selective mitophagy of still functional mitochondria from human erythroblasts. These findings demonstrate for the first time a crucial role for VDAC1 in human erythroblast terminal differentiation, regulating mitochondria clearance.
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Affiliation(s)
- Martina Moras
- Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France; Institut National de Transfusion Sanguine, F-75015 Paris, France; Laboratoire d'Excellence GR-Ex, F-75015, Paris
| | - Claude Hattab
- Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France; Institut National de Transfusion Sanguine, F-75015 Paris, France; Laboratoire d'Excellence GR-Ex, F-75015, Paris
| | - Pedro Gonzalez-Menendez
- Laboratoire d'Excellence GR-Ex, F-75015, Paris, France; Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier
| | - Claudio M Fader
- Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología (IHEM), Universidad Nacional de Cuyo, CONICET, Mendoza, Argentina; Facultad de Odontología, Universidad Nacional de Cuyo, Mendoza
| | - Michael Dussiot
- Laboratoire d'Excellence GR-Ex, F-75015, Paris, France; Université de Paris, UMR_S1163, Laboratory of Cellular and Molecular Mechanisms of Hematological Disorders and Therapeutical Implication, Inserm, F-75014 Paris
| | - Jerome Larghero
- AP-HP, Hôpital Saint-Louis, Unité de Thérapie cellulaire, Paris
| | - Caroline Le Van Kim
- Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France; Institut National de Transfusion Sanguine, F-75015 Paris, France; Laboratoire d'Excellence GR-Ex, F-75015, Paris
| | - Sandrina Kinet
- Laboratoire d'Excellence GR-Ex, F-75015, Paris, France; Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier
| | - Naomi Taylor
- Laboratoire d'Excellence GR-Ex, F-75015, Paris, France; Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier, France; Pediatric Oncology Branch, Center for Cancer Research (CCR), National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, Maryland
| | - Sophie D Lefevre
- Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France; Institut National de Transfusion Sanguine, F-75015 Paris, France; Laboratoire d'Excellence GR-Ex, F-75015, Paris.
| | - Mariano A Ostuni
- Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France; Institut National de Transfusion Sanguine, F-75015 Paris, France; Laboratoire d'Excellence GR-Ex, F-75015, Paris.
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9
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Lemeshko VV. Electrical control of the cell energy metabolism at the level of mitochondrial outer membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183493. [PMID: 33132193 DOI: 10.1016/j.bbamem.2020.183493] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 09/21/2020] [Accepted: 10/07/2020] [Indexed: 12/11/2022]
Abstract
Energy, generated by the mitochondrial oxidative phosphorylation system, is transferred to the cytosol across the mitochondrial outer membrane (MOM), through the voltage-dependent anion channels (VDACs). The role of the VDAC's voltage-gating process to control the transfer of ATP, creatine phosphate and other negatively charged metabolites across MOM might be crucial for the cell energy metabolism regulation. However, it depends on the probability of the outer membrane potential (OMP) generation by a currently undefined mechanism that has usually been considered doubtful, based on the assumption that VDACs always stay in the electrically open state. Nevertheless, computational analysis of various possible metabolically-dependent mechanisms of OMP generation suggests that MOM is not a "coarse sieve", but in fact it functions as an electrical gatekeeper of cell energy metabolism, due to a probable OMP-dependent VDAC's gating. OMP generation could also be involved in the control of cell death resistance and mechanisms of various diseases.
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Affiliation(s)
- Victor V Lemeshko
- Escuela de Física, Facultad de Ciencias, Universidad Nacional de Colombia, Sede Medellín, Carrera 65, Nro. 59A - 110, Medellín, Colombia.
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10
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Damiati S, Schuster B. Electrochemical Biosensors Based on S-Layer Proteins. SENSORS (BASEL, SWITZERLAND) 2020; 20:E1721. [PMID: 32204503 PMCID: PMC7147708 DOI: 10.3390/s20061721] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/05/2020] [Accepted: 03/17/2020] [Indexed: 01/29/2023]
Abstract
Designing and development of electrochemical biosensors enable molecule sensing and quantification of biochemical compositions with multitudinous benefits such as monitoring, detection, and feedback for medical and biotechnological applications. Integrating bioinspired materials and electrochemical techniques promote specific, rapid, sensitive, and inexpensive biosensing platforms for (e.g., point-of-care testing). The selection of biomaterials to decorate a biosensor surface is a critical issue as it strongly affects selectivity and sensitivity. In this context, smart biomaterials with the intrinsic self-assemble capability like bacterial surface (S-) layer proteins are of paramount importance. Indeed, by forming a crystalline two-dimensional protein lattice on many sensors surfaces and interfaces, the S-layer lattice constitutes an immobilization matrix for small biomolecules and lipid membranes and a patterning structure with unsurpassed spatial distribution for sensing elements and bioreceptors. This review aims to highlight on exploiting S-layer proteins in biosensor technology for various applications ranging from detection of metal ions over small organic compounds to cells. Furthermore, enzymes immobilized on the S-layer proteins allow specific detection of several vital biomolecules. The special features of the S-layer protein lattice as part of the sensor architecture enhances surface functionalization and thus may feature an innovative class of electrochemical biosensors.
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Affiliation(s)
- Samar Damiati
- Department of Biochemistry, Faculty of Science, King Abdulaziz University (KAU), Jeddah 21589, Saudi Arabia;
- Institute for Synthetic Bioarchitectures, Department of NanoBiotechnology, BOKU - University of Natural Resources and Life Sciences, Vienna, Muthgasse 11, 1190 Vienna, Austria
- Current address: Division of Nanobiotechnology, Department of Protein Science, Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 171 21 Solna, Stockholm, Sweden
| | - Bernhard Schuster
- Institute for Synthetic Bioarchitectures, Department of NanoBiotechnology, BOKU - University of Natural Resources and Life Sciences, Vienna, Muthgasse 11, 1190 Vienna, Austria
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11
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Chia WX, Nishijo M, Kang S, Oh J, Nishimura T, Omori H, Longevial JF, Miyake Y, Kim D, Shinokubo H. Site-Selective N-Methylation of 5,15-Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues. Chemistry 2020; 26:2754-2760. [PMID: 31797461 DOI: 10.1002/chem.201905402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Indexed: 11/08/2022]
Abstract
N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels-Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity.
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Affiliation(s)
- Wen Xi Chia
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Mayu Nishijo
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Seongsoo Kang
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, South Korea
| | - Juwon Oh
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, South Korea
| | - Tsubasa Nishimura
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Hiroto Omori
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Jean-François Longevial
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Yoshihiro Miyake
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
| | - Dongho Kim
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, South Korea
| | - Hiroshi Shinokubo
- Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
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12
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Regulation of permeability transition pore opening in mitochondria by external NAD(H). Biochim Biophys Acta Gen Subj 2019; 1863:771-783. [PMID: 30763605 DOI: 10.1016/j.bbagen.2019.01.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 12/18/2018] [Accepted: 01/07/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND The opening of the permeability transition pore (PTP) in mitochondria plays a critical role in the pathogenesis of numerous diseases. Mitochondrial matrix pyridine nucleotides are potent regulators of the PTP, but the role of extramitochondrial nucleotides is unclear. METHODS The PTP opening was explored in isolated mitochondria and mitochondria in permeabilized differentiated and undifferentiated cells in the presence of added NAD(P)(H) in combination with Mg2+, adenine nucleotides (AN), and the inhibitors of AN translocase (ANT), voltage-dependent anion channel (VDAC), and cyclophilin D. RESULTS Added NAD(H) and AN, but not NADP(H), inhibited the PTP opening with comparable potency. PTP suppression required neither NAD(H) oxidation nor reduction. The protective effects of NAD(H) and cyclosporin A were synergistic, and the effects of NAD(H) and millimolar AN were additive. The conformation-specific ANT inhibitors were unable to cancel the protective effect of NADH even under total ANT inhibition. Besides, NAD(H) activated the efflux of mitochondrial AN via ANT. VDAC ligand (Mg2+) and blockers (G3139 and 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid) potentiated and attenuated the protective effect of NAD(H), respectively. However, in embryonic and cancer (undifferentiated) cells, in contrast to isolated differentiated hepatocytes and cardiocytes, the suppression of PTP opening by NADH was negligible though all cells tested possessed a full set of VDAC isoforms. CONCLUSIONS The study revealed a novel mechanism of PTP regulation by external (cytosolic) NAD(H) through the allosteric site in the OM or the intermembrane space. GENERAL SIGNIFICANCE The mechanism might contribute to the resistance of differentiated cells under different pathological conditions including ischemia/reperfusion.
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13
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Schuster B. S-Layer Protein-Based Biosensors. BIOSENSORS 2018; 8:E40. [PMID: 29641511 PMCID: PMC6023001 DOI: 10.3390/bios8020040] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 04/05/2018] [Accepted: 04/09/2018] [Indexed: 01/14/2023]
Abstract
The present paper highlights the application of bacterial surface (S-) layer proteins as versatile components for the fabrication of biosensors. One technologically relevant feature of S-layer proteins is their ability to self-assemble on many surfaces and interfaces to form a crystalline two-dimensional (2D) protein lattice. The S-layer lattice on the surface of a biosensor becomes part of the interface architecture linking the bioreceptor to the transducer interface, which may cause signal amplification. The S-layer lattice as ultrathin, highly porous structure with functional groups in a well-defined special distribution and orientation and an overall anti-fouling characteristics can significantly raise the limit in terms of variety and the ease of bioreceptor immobilization, compactness of bioreceptor molecule arrangement, sensitivity, specificity, and detection limit for many types of biosensors. The present paper discusses and summarizes examples for the successful implementation of S-layer lattices on biosensor surfaces in order to give a comprehensive overview on the application potential of these bioinspired S-layer protein-based biosensors.
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Affiliation(s)
- Bernhard Schuster
- Institute for Synthetic Bioarchitectures, Department of NanoBiotechnology, University of Natural Resources and Life Sciences, Vienna, Muthgasse 11, 1190 Vienna, Austria.
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14
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Berezhkovskii AM, Bezrukov SM. Stochastic Gating as a Novel Mechanism for Channel Selectivity. Biophys J 2018; 114:1026-1029. [PMID: 29448982 DOI: 10.1016/j.bpj.2018.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 12/22/2017] [Accepted: 01/08/2018] [Indexed: 11/25/2022] Open
Abstract
An ideal channel, responsible for metabolite fluxes in and out of the cells and cellular compartments, is supposed to be selective for a particular set of molecules only. However, such a channel has to be wide enough to accommodate relatively large metabolites, and, therefore, it allows passage of smaller solutes, for example, sodium, potassium, and chloride ions, thus compromising membrane's barrier function. Here we show that stochastic gating is able to provide a mechanism for the selectivity of wide channels in favor of large metabolites. Specifically, applying our recent theory of the stochastic gating effect on channel-facilitated transport, we demonstrate that under certain conditions gating hinders translocation of fast-diffusing small solutes to a significantly higher degree than that of large solutes that diffuse much slower. We hypothesize that this can be used by Nature to minimize the shunting effect of wide channels with respect to small solutes.
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Affiliation(s)
- Alexander M Berezhkovskii
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Mathematical and Statistical Computing Laboratory, Division for Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland
| | - Sergey M Bezrukov
- Section on Molecular Transport, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
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15
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VDAC electronics: 4. Novel electrical mechanism and thermodynamic estimations of glucose repression of yeast respiration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2213-2223. [DOI: 10.1016/j.bbamem.2017.09.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Revised: 08/06/2017] [Accepted: 09/05/2017] [Indexed: 01/19/2023]
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16
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Li Q, Qiao P, Chen X, Wang J, Bian L, Zheng X. Affinity chromatographic methodologies based on immobilized voltage dependent anion channel isoform 1 and application in protein-ligand interaction analysis and bioactive compounds screening from traditional medicine. J Chromatogr A 2017; 1495:31-45. [PMID: 28342583 DOI: 10.1016/j.chroma.2017.03.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 03/09/2017] [Accepted: 03/13/2017] [Indexed: 12/11/2022]
Abstract
Voltage dependent anion channel isoform 1 (VDAC-1) serves as an attractive target of anti-cancer drugs by mediating the entry and exit of metabolites between cytoplasm and mitochondria. This work reports on the preparation of a VDAC-1-based bioaffinity chromatographic stationary phase by linking the protein on lecithin modified microspheres. An assay of chromatographic methods including frontal analysis, zonal elution, injection dependent analysis and nonlinear chromatography were utilized to investigate the bindings of ATP, NADH and NADPH to VDAC-1. Electrostatic interactions were found to be main forces during these bindings. The calculated association constants of the three ligands to VDAC-1 showed good agreements between diverse chromatographic methods. Validated application of the stationary phase was performed by screening anti-cancer compounds of Rheum officinale Baill. using high performance affinity chromatography coupled with electrospray ionization-quadrupole time of flight mass spectrometry. Chrysophanol, emodin, rhein, aloe-emodin and catechin were identified as the bioactive components of the herb. These compounds targeted VDAC-1 through Thr207 and the N-terminal region of the protein. Taken together, the current stationary phase was possible to become a promising tool for protein-ligand interaction analysis and anti-cancer drug screening from complex matrices.
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Affiliation(s)
- Qian Li
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Pan Qiao
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Xiu Chen
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Jing Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China
| | - Liujiao Bian
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China.
| | - Xiaohui Zheng
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an 710069, China.
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17
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Abstract
Mitochondria are the "power house" of a cell continuously generating ATP to ensure its proper functioning. The constant production of ATP via oxidative phosphorylation demands a large electrochemical force that drives protons across the highly selective and low-permeable mitochondrial inner membrane. Besides the conventional role of generating ATP, mitochondria also play an active role in calcium signaling, generation of reactive oxygen species (ROS), stress responses, and regulation of cell-death pathways. Deficiencies in these functions result in several pathological disorders like aging, cancer, diabetes, neurodegenerative and cardiovascular diseases. A plethora of ion channels and transporters are present in the mitochondrial inner and outer membranes which work in concert to preserve the ionic equilibrium of a cell for the maintenance of cell integrity, in physiological as well as pathophysiological conditions. For, e.g., mitochondrial cation channels KATP and BKCa play a significant role in cardioprotection from ischemia-reperfusion injury. In addition to the cation channels, mitochondrial anion channels are equally essential, as they aid in maintaining electro-neutrality by regulating the cell volume and pH. This chapter focusses on the information on molecular identity, structure, function, and physiological relevance of mitochondrial chloride channels such as voltage dependent anion channels (VDACs), uncharacterized mitochondrial inner membrane anion channels (IMACs), chloride intracellular channels (CLIC) and the aspects of forthcoming chloride channels.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA.
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18
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VDAC electronics: 3. VDAC-Creatine kinase-dependent generation of the outer membrane potential in respiring mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1411-8. [DOI: 10.1016/j.bbamem.2016.04.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 04/07/2016] [Accepted: 04/08/2016] [Indexed: 01/08/2023]
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19
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Li Y, Zhang L, Qu T, Li L, Zhang G. Characterization of Oyster Voltage-Dependent Anion Channel 2 (VDAC2) Suggests Its Involvement in Apoptosis and Host Defense. PLoS One 2016; 11:e0146049. [PMID: 26727366 PMCID: PMC4700975 DOI: 10.1371/journal.pone.0146049] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 12/11/2015] [Indexed: 01/03/2023] Open
Abstract
Genomic and transcriptomic studies have revealed a sophisticated and powerful apoptosis regulation network in oyster, highlighting its adaptation to sessile life in a highly stressful intertidal environment. However, the functional molecular basis of apoptosis remains largely unexplored in oysters. In this study, we focused on a representative apoptotic gene encoding voltage-dependent anion channel 2 (VDAC2), a porin that abounds at the mitochondrial outer membrane. This is the first report on the identification and characterization of a VDAC gene in the Pacific oyster, Crassostrea gigas (CgVDAC2). The full length of CgVDAC2 was 1,738 bp with an open reading frame of 843 bp that encoded a protein of 281 amino acids. A four-element eukaryotic porin signature motif, a conserved ATP binding motif, and a VKAKV-like sequence were identified in the predicted CgVDAC2. Expression pattern analysis in different tissues and developmental stages as well as upon infection by ostreid herpesvirus 1 revealed the energy supply-related and immunity-related expression of CgVDAC2. CgVDAC2 was co-localized with mitochondria when it was transiently transfected into HeLa cells. Overexpression of CgVDAC2 in HEK293T cells suppressed the UV irradiation-induced apoptosis by inhibiting the pro-apoptotic function of CgBak. RNA interference induced reduction in CgVDAC2 expression showed a promoted apoptosis level upon UV light irradiation in hemocytes. The yeast two-hybrid system and co-immunoprecipitation assay indicated a direct interaction between CgVDAC2 and the pro-apoptotic protein CgBak. This study revealed the function of VDAC2 in oyster and provided new insights into its involvement in apoptosis modulation and host defense in mollusks.
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Affiliation(s)
- Yingxiang Li
- University of Chinese Academy of Sciences, Beijing, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Linlin Zhang
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Tao Qu
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Li Li
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- * E-mail: (LL); (GZ)
| | - Guofan Zhang
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- National & Local Joint Engineering Laboratory of Ecological Mariculture, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- * E-mail: (LL); (GZ)
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20
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Li Q, Duan MJ, Li SS, Zhang YL, Qiao P, Bian LJ. Recognition and binding of voltage-dependent anion channel-1 with ATP and NADH by spectroscopic analysis and molecular docking. RSC Adv 2016. [DOI: 10.1039/c5ra27694b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Recognition and binding of voltage-dependent anion channel-1 with ATP and NADH by spectroscopic analysis and molecular docking.
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Affiliation(s)
- Q. Li
- College of Life Science
- Northwest University
- Xi'an 710069
- China
| | - M. J. Duan
- College of Life Science
- Northwest University
- Xi'an 710069
- China
| | - S. S. Li
- College of Life Science
- Northwest University
- Xi'an 710069
- China
| | - Y. L. Zhang
- College of Life Science
- Northwest University
- Xi'an 710069
- China
| | - P. Qiao
- College of Life Science
- Northwest University
- Xi'an 710069
- China
| | - L. J. Bian
- College of Life Science
- Northwest University
- Xi'an 710069
- China
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21
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Chen J, Natte K, Man NY, Stewart SG, Wu XF. Convenient copper-mediated Chan–Lam coupling of 2-aminopyridine: facile synthesis of N-arylpyridin-2-amines. Tetrahedron Lett 2015. [DOI: 10.1016/j.tetlet.2015.06.092] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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22
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Krammer EM, Vu GT, Homblé F, Prévost M. Dual mechanism of ion permeation through VDAC revealed with inorganic phosphate ions and phosphate metabolites. PLoS One 2015; 10:e0121746. [PMID: 25860993 PMCID: PMC4393092 DOI: 10.1371/journal.pone.0121746] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 02/03/2015] [Indexed: 11/19/2022] Open
Abstract
In the exchange of metabolites and ions between the mitochondrion and the cytosol, the voltage-dependent anion channel (VDAC) is a key element, as it forms the major transport pathway for these compounds through the mitochondrial outer membrane. Numerous experimental studies have promoted the idea that VDAC acts as a regulator of essential mitochondrial functions. In this study, using a combination of molecular dynamics simulations, free-energy calculations, and electrophysiological measurements, we investigated the transport of ions through VDAC, with a focus on phosphate ions and metabolites. We showed that selectivity of VDAC towards small anions including monovalent phosphates arises from short-lived interactions with positively charged residues scattered throughout the pore. In dramatic contrast, permeation of divalent phosphate ions and phosphate metabolites (AMP and ATP) involves binding sites along a specific translocation pathway. This permeation mechanism offers an explanation for the decrease in VDAC conductance measured in the presence of ATP or AMP at physiological salt concentration. The binding sites occur at similar locations for the divalent phosphate ions, AMP and ATP, and contain identical basic residues. ATP features a marked affinity for a central region of the pore lined by two lysines and one arginine of the N-terminal helix. This cluster of residues together with a few other basic amino acids forms a "charged brush" which facilitates the passage of the anionic metabolites through the pore. All of this reveals that VDAC controls the transport of the inorganic phosphates and phosphate metabolites studied here through two different mechanisms.
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Affiliation(s)
- Eva-Maria Krammer
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Giang Thi Vu
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Fabrice Homblé
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Martine Prévost
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Brussels, Belgium
- * E-mail: (MP)
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23
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Chiong M, Cartes-Saavedra B, Norambuena-Soto I, Mondaca-Ruff D, Morales PE, García-Miguel M, Mellado R. Mitochondrial metabolism and the control of vascular smooth muscle cell proliferation. Front Cell Dev Biol 2014; 2:72. [PMID: 25566542 PMCID: PMC4266092 DOI: 10.3389/fcell.2014.00072] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/28/2014] [Indexed: 12/12/2022] Open
Abstract
Differentiation and dedifferentiation of vascular smooth muscle cells (VSMCs) are essential processes of vascular development. VSMC have biosynthetic, proliferative, and contractile roles in the vessel wall. Alterations in the differentiated state of the VSMC play a critical role in the pathogenesis of a variety of cardiovascular diseases, including atherosclerosis, hypertension, and vascular stenosis. This review provides an overview of the current state of knowledge of molecular mechanisms involved in the control of VSMC proliferation, with particular focus on mitochondrial metabolism. Mitochondrial activity can be controlled by regulating mitochondrial dynamics, i.e., mitochondrial fusion and fission, and by regulating mitochondrial calcium handling through the interaction with the endoplasmic reticulum (ER). Alterations in both VSMC proliferation and mitochondrial function can be triggered by dysregulation of mitofusin-2, a small GTPase associated with mitochondrial fusion and mitochondrial–ER interaction. Several lines of evidence highlight the relevance of mitochondrial metabolism in the control of VSMC proliferation, indicating a new area to be explored in the treatment of vascular diseases.
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Affiliation(s)
- Mario Chiong
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - Benjamín Cartes-Saavedra
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - Ignacio Norambuena-Soto
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - David Mondaca-Ruff
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - Pablo E Morales
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - Marina García-Miguel
- Faculty of Chemical and Pharmaceutical Sciences, Advanced Center for Chronic Diseases, University of Chile Santiago, Chile
| | - Rosemarie Mellado
- Faculty of Chemistry, Pontifical Catholic University of Chile Santiago, Chile
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24
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Nikiforova AB, Saris NEL, Kruglov AG. External mitochondrial NADH-dependent reductase of redox cyclers: VDAC1 or Cyb5R3? Free Radic Biol Med 2014; 74:74-84. [PMID: 24945955 DOI: 10.1016/j.freeradbiomed.2014.06.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 06/06/2014] [Accepted: 06/10/2014] [Indexed: 11/19/2022]
Abstract
It was reported that VDAC1 possesses an NADH oxidoreductase activity and plays an important role in the activation of xenobiotics in the outer mitochondrial membrane. In the present work, we evaluated the participation of VDAC1 and Cyb5R3 in the NADH-dependent activation of various redox cyclers in mitochondria. We show that external NADH oxidoreductase caused the redox cycling of menadione ≫ lucigenin>nitrofurantoin. Paraquat was predominantly activated by internal mitochondria oxidoreductases. An increase in the ionic strength stimulated and suppressed the redox cycling of negatively and positively charged acceptors, as was expected for the Cyb5R3-mediated reduction. Antibodies against Cyb5R3 but not VDAC substantially inhibited the NADH-related oxidoreductase activities. The specific VDAC blockers G3139 and erastin, separately or in combination, in concentrations sufficient for the inhibition of substrate transport, exhibited minimal effects on the redox cycler-dependent NADH oxidation, ROS generation, and reduction of exogenous cytochrome c. In contrast, Cyb5R3 inhibitors (6-propyl-2-thiouracil, p-chloromercuriobenzoate, quercetin, mersalyl, and ebselen) showed similar patterns of inhibition of ROS generation and cytochrome c reduction. The analysis of the spectra of the endogenous cytochromes b5 and c in the presence of nitrofurantoin and the inhibitors of VDAC and Cyb5R3 demonstrated that the redox cycler can transfer electrons from Cyb5R3 to endogenous cytochrome c. This caused the oxidation of outer membrane-bound cytochrome b5, which is in redox balance with Cyb5R3. The data obtained argue against VDAC1 and in favor of Cyb5R3 involvement in the activation of redox cyclers in the outer mitochondrial membrane.
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Affiliation(s)
- Anna B Nikiforova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Nils-Erik L Saris
- Department of Food and Environmental Sciences, University of Helsinki, FIN-00014 Helsinki, Finland
| | - Alexey G Kruglov
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia.
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25
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Schuster B, Sleytr UB. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules. J R Soc Interface 2014; 11:20140232. [PMID: 24812051 PMCID: PMC4032536 DOI: 10.1098/rsif.2014.0232] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 04/15/2014] [Indexed: 12/20/2022] Open
Abstract
Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems.
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Affiliation(s)
- Bernhard Schuster
- Department of NanoBiotechnology, University of Natural Resources and Life Sciences, Institute for Synthetic Bioarchitectures, Muthgasse 11, 1190 Vienna, Austria
| | - Uwe B. Sleytr
- Department of NanoBiotechnology, University of Natural Resources and Life Sciences, Institute for Biophysics, Muthgasse 11, 1190 Vienna, Austria
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26
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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27
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Regulators of mitochondrial Ca2+ homeostasis in cerebral ischemia. Cell Tissue Res 2014; 357:395-405. [DOI: 10.1007/s00441-014-1807-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2013] [Accepted: 01/10/2014] [Indexed: 02/06/2023]
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28
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Shen X, Wang T, Xu D, Lu L. Proteomic identification, characterization and expression analysis of Ctenopharyngodon idella VDAC1 upregulated by grass carp reovirus infection. FISH & SHELLFISH IMMUNOLOGY 2014; 37:96-107. [PMID: 24434647 DOI: 10.1016/j.fsi.2014.01.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 01/05/2014] [Accepted: 01/05/2014] [Indexed: 06/03/2023]
Abstract
Voltage-dependent anion channels (VDACs) located in the mitochondrial outer membrane are mitochondrial porins that play central roles in regulating cell life and death. In this present report, the VDAC protein 1 from grass carp Ctenopharyngodon idella (designated as CiVDAC1) was found to be upregulated by grass carp reovirus (GCRV) infection through two-dimensional gel electrophoresis and protein analysis of infected C. idella kidney (CIK) cells. The full-length cDNA of CiVDAC1 was 995 bp with an open reading frame (ORF) of 852 bp that encodes a putative 283-amino acid protein. Phylogenic analysis revealed that the complete ORF of CiVDAC1 demonstrated high identity with well characterized mammalian homologs. The deduced CiVDAC1 protein contains an α-helix at the amino terminal, 19 membrane-spanning β-strands, and one eukaryotic mitochondrial porin signature motif. Tissue tropism analysis indicated that CiVDAC1 is abundant in muscle, heart, skin, swim bladder, trunk kidney and spleen. Transcriptional expression profiles indicated that the CiVDAC1 gene was upregulated upon viral challenge in a manner similar to the Mx2 gene, which is a marker gene used to indicate activation of innate antiviral immunity. Similar expression patterns of the CiVDAC1 gene were observed in CIK cells stimulated with poly (I:C), as well as grass carp kidney tissue challenged with GCRV in vivo. CiVDAC1 silencing in CIK cells had no impact on progeny virus production, but over-expression of CiVDAC1 in vivo showed strongly protect against challenge with live virus. To interpret the role of other VDAC proteins in viral pathogenesis, CiVDAC2 was characterized and showed to respond positively to GCRV challenge, which suggested that CiVDAC2 might functionally complement CiVDAC1 in C. idella. The present data did demonstrate that CiVDAC1 might be mediated grass carp antiviral immune response.
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Affiliation(s)
- Xiaobao Shen
- Key Laboratory of Freshwater Fishery Germplasm Resources, Ministry of Agriculture of P. R. China, Shanghai Ocean University, Shanghai 201306, China
| | - Tu Wang
- Key Laboratory of Freshwater Fishery Germplasm Resources, Ministry of Agriculture of P. R. China, Shanghai Ocean University, Shanghai 201306, China
| | - Dan Xu
- Key Laboratory of Freshwater Fishery Germplasm Resources, Ministry of Agriculture of P. R. China, Shanghai Ocean University, Shanghai 201306, China
| | - Liqun Lu
- Key Laboratory of Freshwater Fishery Germplasm Resources, Ministry of Agriculture of P. R. China, Shanghai Ocean University, Shanghai 201306, China.
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Tan W. VDAC blockage by phosphorothioate oligonucleotides and its implication in apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1555-61. [PMID: 22236836 DOI: 10.1016/j.bbamem.2011.12.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 12/22/2011] [Accepted: 12/29/2011] [Indexed: 11/17/2022]
Abstract
Apoptosis is a crucial process that regulates the homeostasis of multicellular organisms. Impaired apoptosis contributes to cancer development, while enhanced apoptosis is detrimental in neurodegenerative diseases. The intrinsic apoptotic pathway is initiated by cytochrome c release from mitochondria. Research published in the recent decade has suggested that cytochrome c release can be influenced by the conducting states of VDAC, the channel in the mitochondrial outer membrane (MOM) responsible for metabolite flux. This review will describe the evidence that VDAC gating or blockage and subsequent changes in MOM permeability influence cytochrome c release and the onset of apoptosis. The blockage of VDAC by G3139, a proapoptotic phosphorothioate oligonucleotide, provides strong evidence for the role of VDAC in the initiation of apoptosis. The proapoptotic activity and VDAC blockage are linked in that both require the PS (phosphorothioate) modification, both are enhanced by an increase in oligonucleotide length, and both are insensitive to the nucleotide sequence. Thus, the mitochondrial outer membrane permeability regulated by VDAC gating may play an important role in mitochondrial function and in the control of apoptosis. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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Affiliation(s)
- Wenzhi Tan
- Farber Institute for Neurosciences, Weinberg Unit for ALS Research, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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30
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Homblé F, Krammer EM, Prévost M. Plant VDAC: facts and speculations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1486-501. [PMID: 22155681 DOI: 10.1016/j.bbamem.2011.11.028] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 11/12/2011] [Accepted: 11/22/2011] [Indexed: 01/01/2023]
Abstract
The voltage-dependent anion-selective channel (VDAC) is the most abundant protein in the mitochondrial outer membrane and the major transport pathway for a large variety of compounds ranging from ions to large polymeric molecules such as DNA and tRNA. Plant VDACs feature a secondary structure content and electrophysiological properties akin to those of VDACs from other organisms. They however undergo a specific regulation. The general importance of VDAC in plant physiology has only recently emerged. Besides their role in metabolite transport, plant VDACs are also involved in the programmed cell death triggered in response to biotic and abiotic stresses. Moreover, their colocalization in non-mitochondrial membranes suggests a diversity of function. This review summarizes our current understanding of the structure and function of plant VDACs. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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Affiliation(s)
- Fabrice Homblé
- Structure et Fontion des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles, Boulevard du Triomphe CP, Brussels, Belgium.
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31
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McCommis KS, Baines CP. The role of VDAC in cell death: friend or foe? BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1444-50. [PMID: 22062421 DOI: 10.1016/j.bbamem.2011.10.025] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/18/2011] [Accepted: 10/24/2011] [Indexed: 11/16/2022]
Abstract
As the voltage-dependent anion channel (VDAC) forms the interface between mitochondria and the cytosol, its importance in metabolism is well understood. However, research on VDAC's role in cell death is a rapidly growing field, unfortunately with much confusing and contradictory results. The fact that VDAC plays a role in outer mitochondrial membrane permeabilization is undeniable, however, the mechanisms behind this remain very poorly understood. In this review, we will summarize the studies that show evidence of VDAC playing a role in cell death. To begin, we will discuss the evidence for and against VDAC's involvement in mitochondrial permeability transition (MPT) and attempt to clarify that VDAC is not an essential component of the MPT pore (MPTP). Next, we will evaluate the remaining literature on VDAC in cell death which can be divided into three models: proapoptotic agents escaping through VDAC, VDAC homo- or hetero-oligomerization, or VDAC closure resulting in outer mitochondrial membrane permeabilization through an unknown pathway. We will then discuss the growing list of modulators of VDAC activity that have been associated with induction/protection against cell death. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism.
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Affiliation(s)
- Kyle S McCommis
- Department of Biomedical Sciences, University of Missouri, USA
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32
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Peixoto PM, Dejean LM, Kinnally KW. The therapeutic potential of mitochondrial channels in cancer, ischemia-reperfusion injury, and neurodegeneration. Mitochondrion 2011; 12:14-23. [PMID: 21406252 DOI: 10.1016/j.mito.2011.03.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/23/2011] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
Abstract
Mitochondria communicate with the rest of the cell through channels located in their inner and outer membranes. Most of the time, the message is encoded by the flow of anions and cations e.g., through VDAC and PTP, respectively. However, proteins are also both imported and exported across the mitochondrial membranes e.g., through TOM and MAC, respectively. Transport through mitochondrial channels is exquisitely regulated and controls a myriad of processes; from energy production to cell death. Here, we examine the role of some of the mitochondrial channels involved in neurodegeneration, ischemia-reperfusion injury and cancer in the context of their potential as therapeutic targets.
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Affiliation(s)
- Pablo M Peixoto
- New York University, College of Dentistry, 345 East 24th Street, New York, NY 10010, United States
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33
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Metabolic impact of increased NADH availability in Saccharomyces cerevisiae. Appl Environ Microbiol 2009; 76:851-9. [PMID: 20023106 DOI: 10.1128/aem.02040-09] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Engineering the level of metabolic cofactors to manipulate metabolic flux is emerging as an attractive strategy for bioprocess applications. We present the metabolic consequences of increasing NADH in the cytosol and the mitochondria of Saccharomyces cerevisiae. In a strain that was disabled in formate metabolism, we either overexpressed the native NAD(+)-dependent formate dehydrogenase in the cytosol or directed it into the mitochondria by fusing it with the mitochondrial signal sequence encoded by the CYB2 gene. Upon exposure to formate, the mutant strains readily consumed formate and induced fermentative metabolism even under conditions of glucose derepression. Cytosolic overexpression of formate dehydrogenase resulted in the production of glycerol, while when this enzyme was directed into the mitochondria, we observed glycerol and ethanol production. Clearly, these results point toward different patterns of compartmental regulation of redox homeostasis. When pulsed with formate, S. cerevisiae cells growing in a steady state on glucose immediately consumed formate. However, formate consumption ceased after 20 min. Our analysis revealed that metabolites at key branch points of metabolic pathways were affected the most by the genetic perturbations and that the intracellular concentrations of sugar phosphates were specifically affected by time. In conclusion, the results have implications for the design of metabolic networks in yeast for industrial applications.
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34
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Rizzuto R, Marchi S, Bonora M, Aguiari P, Bononi A, De Stefani D, Giorgi C, Leo S, Rimessi A, Siviero R, Zecchini E, Pinton P. Ca(2+) transfer from the ER to mitochondria: when, how and why. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1787:1342-51. [PMID: 19341702 PMCID: PMC2730423 DOI: 10.1016/j.bbabio.2009.03.015] [Citation(s) in RCA: 342] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/21/2009] [Accepted: 03/24/2009] [Indexed: 10/25/2022]
Abstract
The heterogenous subcellular distribution of a wide array of channels, pumps and exchangers allows extracellular stimuli to induce increases in cytoplasmic Ca(2+) concentration ([Ca(2+)]c) with highly defined spatial and temporal patterns, that in turn induce specific cellular responses (e.g. contraction, secretion, proliferation or cell death). In this extreme complexity, the role of mitochondria was considered marginal, till the direct measurement with targeted indicators allowed to appreciate that rapid and large increases of the [Ca(2+)] in the mitochondrial matrix ([Ca(2+)]m) invariably follow the cytosolic rises. Given the low affinity of the mitochondrial Ca(2+) transporters, the close proximity to the endoplasmic reticulum (ER) Ca(2+)-releasing channels was shown to be responsible for the prompt responsiveness of mitochondria. In this review, we will summarize the current knowledge of: i) the mitochondrial and ER Ca(2+) channels mediating the ion transfer, ii) the structural and molecular foundations of the signaling contacts between the two organelles, iii) the functional consequences of the [Ca(2+)]m increases, and iv) the effects of oncogene-mediated signals on mitochondrial Ca(2+) homeostasis. Despite the rapid progress carried out in the latest years, a deeper molecular understanding is still needed to unlock the secrets of Ca(2+) signaling machinery.
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Affiliation(s)
- Rosario Rizzuto
- Dept. Biomedical Sciences, University of Padua, Via Colombo 3, Padua 35121, Italy.
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35
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Shimada H, Hirai KI, Simamura E, Hatta T, Iwakiri H, Mizuki K, Hatta T, Sawasaki T, Matsunaga S, Endo Y, Shimizu S. Paraquat toxicity induced by voltage-dependent anion channel 1 acts as an NADH-dependent oxidoreductase. J Biol Chem 2009; 284:28642-9. [PMID: 19717555 PMCID: PMC2781408 DOI: 10.1074/jbc.m109.033431] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 08/07/2009] [Indexed: 11/06/2022] Open
Abstract
Paraquat (PQ), a herbicide used worldwide, causes fatal injury to organs upon high dose ingestion. Treatments for PQ poisoning are unreliable, and numerous deaths have been attributed inappropriate usage of the agent. It is generally speculated that a microsomal drug-metabolizing enzyme system is responsible for PQ toxicity. However, recent studies have demonstrated cytotoxicity via mitochondria, and therefore, the cytotoxic mechanism remains controversial. Here, we demonstrated that mitochondrial NADH-dependent PQ reductase containing a voltage-dependent anion channel 1 (VDAC1) is responsible for PQ cytotoxicity. When mitochondria were incubated with NADH and PQ, superoxide anion (O(2)(*)) was produced, and the mitochondria ruptured. Outer membrane extract oxidized NADH in a PQ dose-dependent manner, and oxidation was suppressed by VDAC inhibitors. Zymographic analysis revealed the presence of VDAC1 protein in the oxidoreductase, and the direct binding of PQ to VDAC1 was demonstrated using biotinylated PQ. VDAC1-overexpressing cells showed increased O(2)(*) production and cytotoxicity, both of which were suppressed in VDAC1 knockdown cells. These results indicated that a VDAC1-containing mitochondrial system is involved in PQ poisoning. These insights into the mechanism of PQ poisoning not only demonstrated novel physiological functions of VDAC protein, but they may facilitate the development of new therapeutic approaches.
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Affiliation(s)
- Hiroki Shimada
- Molecular and Cell Structural Science, Kanazawa Medical University, Uchinada, Ishikawa 920-0293, Japan.
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36
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Abstract
Proper cell activity requires an efficient exchange of molecules between mitochondria and cytoplasm. Lying in the outer mitochondrial membrane, VDAC assumes a crucial position in the cell, forming the main interface between the mitochondrial and the cellular metabolisms. As such, it has been recognized that VDAC plays a crucial role in regulating the metabolic and energetic functions of mitochondria. Indeed, down-regulation of VDAC1 expression by shRNA leads to a decrease in energy production and cell growth. VDAC has also been recognized as a key protein in mitochondria-mediated apoptosis through its involvement in the release of apoptotic proteins located in the inter-membranal space and as the proposed target of pro- and anti-apoptotic members of the Bcl2-family and of hexokinase. Questions, however, remain as to if and how VDAC mediates the transfer of apoptotic proteins from the inter-membranal space to the cytosol. The diameter of the VDAC pore is only about 2.5-3 nm, insufficient for the passage of a folded protein like cytochrome c. New work, however, suggests that pore formation involves the assembly of homo-oligomers of VDAC or hetero-oligomers composed of VDAC and pro-apoptotic proteins, such as Bax. Thus, VDAC appears to represent a convergence point for a variety of cell survival and cell death signals. This review provides insight into the central role of VDAC in mammalian cell life and death, emphasizing VDAC function in the regulation of mitochondria-mediated apoptosis and, as such, its potential as a rational target for new therapeutics.
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37
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Giorgi C, De Stefani D, Bononi A, Rizzuto R, Pinton P. Structural and functional link between the mitochondrial network and the endoplasmic reticulum. Int J Biochem Cell Biol 2009; 41:1817-27. [PMID: 19389485 DOI: 10.1016/j.biocel.2009.04.010] [Citation(s) in RCA: 297] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 04/09/2009] [Accepted: 04/14/2009] [Indexed: 01/10/2023]
Abstract
Mitochondrial and endoplasmic reticulum (ER) networks are fundamental for the maintenance of cellular homeostasis and for determination of cell fate under stress conditions. Recent structural and functional studies revealed the interaction of these networks. These zones of close contact between ER and mitochondria called MAM (mitochondria associated membranes) support communication between the two organelles including bioenergetics and cell survival. The existence of macromolecular complexes in these contact sites has also been revealed. In this contribution, we will review: (i) the ER and mitochondria structure and their dynamics, (ii) the basic principles of ER mitochondrial Ca(2+) transport, (iii) the physiological/pathological role of this cross-talk.
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Affiliation(s)
- Carlotta Giorgi
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Interdisciplinary Center for the Study of Inflammation (ICSI) and Emilia Romagna Laboratory BioPharmaNet, University of Ferrara, Via Borsari 46, 44100 Ferrara, Italy
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38
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Abstract
It was recently asserted that the voltage-dependent anion channel (VDAC) serves as a global regulator, or governor, of mitochondrial function (Lemasters and Holmuhamedov, Biochim Biophys Acta 1762:181-190, 2006). Indeed, VDAC, positioned on the interface between mitochondria and the cytosol (Colombini, Mol Cell Biochem 256:107-115, 2004), is at the control point of mitochondria life and death. This large channel plays the role of a "switch" that defines in which direction mitochondria will go: to normal respiration or to suppression of mitochondria metabolism that leads to apoptosis and cell death. As the most abundant protein in the mitochondrial outer membrane (MOM), VDAC is known to be responsible for ATP/ADP exchange and for the fluxes of other metabolites across MOM. It controls them by switching between the open and "closed" states that are virtually impermeable to ATP and ADP. This control has dual importance: in maintaining normal mitochondria respiration and in triggering apoptosis when cytochrome c and other apoptogenic factors are released from the intermembrane space into the cytosol. Emerging evidence indicates that VDAC closure promotes apoptotic signals without direct involvement of VDAC in the permeability transition pore or hypothetical Bax-containing cytochrome c permeable pores. VDAC gating has been studied extensively for the last 30 years on reconstituted VDAC channels. In this review we focus exclusively on physiologically relevant regulators of VDAC gating such as endogenous cytosolic proteins and mitochondrial lipids. Closure of VDAC induced by such dissimilar cytosolic proteins as pro-apoptotic tBid and dimeric tubulin is compared to show that the involved mechanisms are rather distinct. While tBid mostly modulates VDAC voltage gating, tubulin blocks the channel with the efficiency of blockage controlled by voltage. We also discuss how characteristic mitochondrial lipids, phospatidylethanolamine and cardiolipin, could regulate VDAC gating. Overall, we demonstrate that VDAC gating is not just an observation made under artificial conditions of channel reconstitution but is a major mechanism of MOM permeability control.
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Affiliation(s)
- Tatiana K. Rostovtseva
- Laboratory of Physical and Structural Biology, Program in Physical Biology, NICHD, National Institutes of Health, Bldg. 9, Rm. 1E-106, 9000 Rockville Pike, Bethesda, MD 20892, USA, e-mail:
| | - Sergey M. Bezrukov
- Laboratory of Physical and Structural Biology, Program in Physical Biology, NICHD, National Institutes of Health, Bldg. 9, Rm. 1E-106, 9000 Rockville Pike, Bethesda, MD 20892, USA, e-mail:
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39
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Yehezkel G, Abu-Hamad S, Shoshan-Barmatz V. An N-terminal nucleotide-binding site in VDAC1: involvement in regulating mitochondrial function. J Cell Physiol 2007; 212:551-61. [PMID: 17503466 DOI: 10.1002/jcp.21048] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In a previous study, we presented evidence for the existence of a nucleotide-binding site (NBS) in the N-terminal region of the voltage-dependent anion channel (VDAC1). In this study, further localization and possible roles of the proposed VDAC1-NBS were investigated using site-directed mutagenesis. The predicated NBS of murine VDAC1 (mVDAC1) was mutated by replacing two glycine residues with alanines or a conserved lysine residue with a serine. Expression of the G21A,G23A- and K20S-mVDAC1s in human T-REx-293 cells in which endogenous VDAC1 expression had been silenced affected cell growth and cytosolic ATP levels. While G21A,G23A-mVDAC1-expressing cells displayed growth rates similar to native-mVDAC1-expressing cells, the K20S-mVDAC1-expressing cells displayed significantly retarded growth and increased resistance to cell death. Cells expressing either mVDAC1 mutant also displayed significantly reduced cellular ATP levels. When K20S-mutant mVDAC1 was expressed in porin1-less yeast, the transformed cells grew slower on non-fermentable carbon sources, while isolated mitochondria expressing either mVDAC1 mutant showed significant reduction in ATP synthesis. Purified K20S-mVDAC1 displayed a significant decrease in [alpha-(32)P]BzATP-binding and altered channel properties, that is, reduced ion selectivity, while the G21A,G23A-mutant protein displayed only a mild reduction in channel selectivity. These results suggest that mutations in the proposed VDAC1-NBS, particularly the K20S, altered channel activity, thereby interfering with VDAC function as the major pathway for the transport of metabolites and adenine nucleotides across the outer mitochondrial membrane. Finally, involvement of the VDAC1-NBS in the control of mitochondrial ATP synthesis, cell growth and viability is discussed.
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Affiliation(s)
- Galit Yehezkel
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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40
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Lai JC, Brown BD, Voskresenskiy AM, Vonhoff S, Klussman S, Tan W, Colombini M, Weeratna R, Miller P, Benimetskaya L, Stein CA. Comparison of d-g3139 and its enantiomer L-g3139 in melanoma cells demonstrates minimal in vitro but dramatic in vivo chiral dependency. Mol Ther 2007; 15:270-8. [PMID: 17235304 DOI: 10.1038/sj.mt.6300037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
G3139 (Genasense), an 18mer phosphorothioate antisense oligonucleotide targeted to the initiation codon region of the Bcl-2 messenger RNA (mRNA), downregulates Bcl-2 protein and mRNA expression in many cell lines. However, both the in vitro and in vivo mechanisms of action of G3139 are still uncertain. The isosequential L-deoxyribose enantiomer L-G3139, which does not downregulate Bcl-2 expression, was synthesized to study the role of the Bcl-2 protein in melanoma cells. Both D-G3139 and L-G3139 bind nonspecifically to basic fibroblast growth factor with approximately the same K(c), and cause highly effective inhibition of net formation in 518A2 melanoma cells on Matrigel. The uptakes of D-G3139 and L-G3139 in melanoma cells were also similar. However, unlike D-G3139, L-G3139 does not produce poly ADP-ribose polymerase-1 and procaspase-3 cleavage at 9.5 h after the initiation of the transfection, but can activate the intrinsic pathway of apoptosis at approximately 48 h. Furthermore, treatment of A375 melanoma human xenografts in severe combined immunodeficiency (SCID) mice demonstrates that tumor growth is not inhibited by L-G3139, whereas D-G3139 significantly inhibits the rate of tumor growth. Furthermore, the immunostimulatory properties of L-G3139 appear to be nil, which differs dramatically from those of D-G3139. In conclusion, profound differences exist between D-G3139 and L-G3139 in vivo despite their similarities in vitro.
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MESH Headings
- Animals
- Apoptosis/drug effects
- Cell Line, Tumor
- Cell Movement/drug effects
- Cytochromes c/metabolism
- Dose-Response Relationship, Drug
- Fibroblast Growth Factor 2/metabolism
- Flow Cytometry
- Humans
- Interleukin-12/metabolism
- Interleukin-16/metabolism
- Melanoma, Experimental/drug therapy
- Melanoma, Experimental/metabolism
- Melanoma, Experimental/pathology
- Mice
- Mice, Inbred BALB C
- Mice, SCID
- Microscopy, Phase-Contrast
- Mitochondria/drug effects
- Mitochondria/metabolism
- Oligonucleotides, Antisense/metabolism
- Oligonucleotides, Antisense/pharmacokinetics
- Oligonucleotides, Antisense/pharmacology
- Protein Binding
- Proto-Oncogene Proteins c-bcl-2/genetics
- Spleen/cytology
- Spleen/drug effects
- Spleen/metabolism
- Stereoisomerism
- Xenograft Model Antitumor Assays
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Affiliation(s)
- Johnathan C Lai
- Department of Biomedical Engineering, Columbia University, New York, New York, USA
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41
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Safranow K, Rzeuski R, Listewnik MJ, Jakubowska K, Rać ME, Olszewska M, Chlubek D. Myocardial and coronary sinus purines as indicators of pig heart energy metabolism during reperfusion after extracorporeal circulation. ACTA ACUST UNITED AC 2006; 185:13-23. [PMID: 16128693 DOI: 10.1111/j.1365-201x.2005.01454.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM The precise understanding of myocardial metabolism is crucial for the optimization of cardiosurgical procedures. We attempted to gain a comprehensive insight into the purine metabolism of the porcine heart during reperfusion by measuring concentrations of nucleotides, nucleosides and oxypurines simultaneously in the myocardium and coronary sinus. METHODS Twenty-five pigs were subjected to sham cardiosurgery with extracorporeal circulation and cold cardioplegic arrest of 60 min. Myocardial biopsies, as well as coronary sinus and arterial blood samples were taken before aortic clamping and at 5, 20, 60 and 120 min of reperfusion. HPLC was used to measure concentrations of 17 purines in the bioptates and of 5 in plasma. RESULTS Reperfusion rapidly normalized the ischaemic decrease in the adenylate energy charge of the myocardium, but during 120 min failed to restore the reduced adenylate pool, because of irreversible loss of nucleosides by cardiomyocytes. Low adenylate energy charge and depletion of the adenylate pool were accompanied by analogous changes in the guanylates and growing deficit of NAD and NADP. Reperfusion was marked by significant release of inosine and guanosine from the heart, without any noticeable effect on hypoxanthine and xanthine. CONCLUSIONS Coronary sinus concentrations of purines provide only a limited insight into the metabolism of the porcine heart. Repeated biopsies of the heart muscle and HPLC determinations of purine profiles represent a comprehensive and unique method for the study of purine metabolism during ischaemia and reperfusion. Future research on myocardial metabolism in disease and during cardiosurgical procedures should additionally be oriented to deficits in guanine and pyridine nucleotides.
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Affiliation(s)
- K Safranow
- Department of Biochemistry and Chemistry, Pomeranian Medical University, Szczecin, Poland.
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42
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Yehezkel G, Hadad N, Zaid H, Sivan S, Shoshan-Barmatz V. Nucleotide-binding sites in the voltage-dependent anion channel: characterization and localization. J Biol Chem 2005; 281:5938-46. [PMID: 16354668 DOI: 10.1074/jbc.m510104200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we addressed the presence and location of nucleotide-binding sites in the voltage-dependent anion channel (VDAC). VDAC bound to reactive red 120-agarose, from which it was eluted by ATP, less effectively by ADP and AMP, but not by NADH. The photoreactive ATP analog, benzoyl-benzoyl-ATP (BzATP), was used to identify and characterize the ATP-binding sites in VDAC. [alpha-(32)P]BzATP bound to purified VDAC at two or more binding sites with apparent high and low binding affinities. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis of BzATP-labeled VDAC confirmed the binding of at least two BzATP molecules to VDAC. The VDAC BzATP-binding sites showed higher specificity for purine than for pyrimidine nucleotides and higher affinity for negatively charged nucleotide species. VDAC treatment with the lysyl residue modifying reagent, fluorescein 5'-isothiocyanate, markedly inhibited VDAC labeling with BzATP. The VDAC nucleotide-binding sites were localized using chemical and enzymatic cleavage. Digestion of [alpha-(32)P]BzATP-labeled VDAC with CNBr or V8 protease resulted in the appearance of approximately 17- and approximately 14-kDa labeled fragments. Further digestion, high performance liquid chromatography separation, and sequencing of the selected V8 peptides suggested that the labeled fragments originated from two different regions of the VDAC molecule. MALDI-TOF analysis of BzATP-labeled, tryptic VDAC fragments indicated and localized three nucleotide binding sites, two of which were at the N and C termini of VDAC. Thus, the presence of two or more nucleotide-binding sites in VDAC is suggested, and their possible function in the control of VDAC activity, and, thereby, of outer mitochondrial membrane permeability is discussed.
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Affiliation(s)
- Galit Yehezkel
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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43
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Abstract
Research on VDAC has accelerated as evidence grows of its importance in mitochondrial function and in apoptosis. New investigators entering the field are often confounded by the VDAC literature and its many apparent conflicts and contradictions. This review is an effort to shed light on the situation and identify reliable information from more questionable claims. Our views on the most important controversial issues are as follows: VDAC is only present in the mitochondrial outer membrane. VDAC functions as a monomer. VDAC functions normally with or without Ca(2+). It does not form channels that mediate the flux of proteins through membranes (peptides and unfolded proteins are excluded from this statement). Closure of VDAC, not VDAC opening, leads to mitochondria outer membrane permeabilization and apoptosis.
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Affiliation(s)
- Tatiana K Rostovtseva
- Laboratory of Physical and Structural Biology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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44
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Abstract
The mitochondrial outer membrane is not just a barrier but a site of regulation of mitochondrial function. The VDAC family of proteins are the major pathways for metabolite flux through the outer membrane. These can be regulated in a variety of ways and the integration of these regulatory inputs allows mitochondrial metabolism to be adjusted to changing cellular conditions. This includes total blockage of the flux of anionic metabolites leading to permeabilization of the outer membrane to small proteins followed by apoptotic cell death.
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Affiliation(s)
- Marco Colombini
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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45
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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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46
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Baker MA, Lane DJR, Ly JD, De Pinto V, Lawen A. VDAC1 Is a Transplasma Membrane NADH-Ferricyanide Reductase. J Biol Chem 2004; 279:4811-9. [PMID: 14573604 DOI: 10.1074/jbc.m311020200] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Porin isoform 1 or VDAC (voltage-dependent anion-selective channel) 1 is the predominant protein in the outer mitochondrial membrane. We demonstrated previously that a plasma membrane NADH-ferricyanide reductase activity becomes up-regulated upon mitochondrial perturbation, and therefore suggested that it functions as a cellular redox sensor. VDAC1 is known to be expressed in the plasma membrane; however, its function there remained a mystery. Here we show that VDAC1, when expressed in the plasma membrane, functions as a NADH-ferricyanide reductase. VDAC1 preparations purified from both plasma membrane and mitochondria fractions exhibit NADH-ferricyanide reductase activity, which can be immunoprecipitated with poly- and monoclonal antibodies directed against VDAC(1). Transfecting cells with pl-VDAC1-GFP, which carries an N-terminal signal peptide, directs VDAC1 to the plasma membrane, as shown by confocal microscopy and FACS analysis, and significantly increases the plasma membrane NADH-ferricyanide reductase activity of the transfected cells. This novel enzymatic activity of the well known VDAC1 molecule may provide an explanation for its role in the plasma membrane. Our data suggest that a major function of VDAC1 in the plasma membrane is that of a NADH(-ferricyanide) reductase that may be involved in the maintenance of cellular redox homeostasis.
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Affiliation(s)
- Mark A Baker
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Building 13D, 100 Wellington Road, Melbourne, Victoria 3800, Australia
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47
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Rapizzi E, Pinton P, Szabadkai G, Wieckowski MR, Vandecasteele G, Baird G, Tuft RA, Fogarty KE, Rizzuto R. Recombinant expression of the voltage-dependent anion channel enhances the transfer of Ca2+ microdomains to mitochondria. J Cell Biol 2002; 159:613-24. [PMID: 12438411 PMCID: PMC2173108 DOI: 10.1083/jcb.200205091] [Citation(s) in RCA: 339] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the physiological relevance of mitochondrial Ca2+ homeostasis is widely accepted, no information is yet available on the molecular identity of the proteins involved in this process. Here we analyzed the role of the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane in the transmission of Ca2+ signals between the ER and mitochondria by measuring cytosolic and organelle [Ca2+] with targeted aequorins and Ca2+-sensitive GFPs. In HeLa cells and skeletal myotubes, the transient expression of VDAC enhanced the amplitude of the agonist-dependent increases in mitochondrial matrix Ca2+ concentration by allowing the fast diffusion of Ca2+ from ER release sites to the inner mitochondrial membrane. Indeed, high speed imaging of mitochondrial and cytosolic [Ca2+] changes showed that the delay between the rises occurring in the two compartments is significantly shorter in VDAC-overexpressing cells. As to the functional consequences, VDAC-overexpressing cells are more susceptible to ceramide-induced cell death, thus confirming that mitochondrial Ca2+ uptake plays a key role in the process of apoptosis. These results reveal a novel function for the widely expressed VDAC channel, identifying it as a molecular component of the routes for Ca2+ transport across the mitochondrial membranes.
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Affiliation(s)
- Elena Rapizzi
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, Telethon Center for Cell Imaging and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Via Borsari 46, I-44100 Ferrara, Italy
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48
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Magel EA, Hillinger C, Wagner T, Höll W. Oxidative pentose phosphate pathway and pyridine nucleotides in relation to heartwood formation in Robinia pseudoacacia L. PHYTOCHEMISTRY 2001; 57:1061-1068. [PMID: 11430979 DOI: 10.1016/s0031-9422(01)00091-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Most tree species show in the inner parts of their woody axes often a dark colored zone, the heartwood. Its formation is a genetically determined, programmed cell death which is characterized by the activation of metabolic pathways which lead to the formation of phenolic heartwood extractives. In the present paper we report on the key position of the oxidative pentose phosphate pathway (OPP) for this process. The OPP plays a crucial role in anabolic processes and is involved in the interconversion and rearrangements of sugar-phosphates with the net production of NADPH. In tissues of Robinia pseudoacacia L. which are transferred to heartwood, enhanced activities of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) are present. A consequence of these increased enzyme activities is a shift in the pyridine nucleotide pool towards NADP+NADPH at the expense of NAD+NADH. These alterations in the metabolism and the redox status probably provide precursors and reduction equivalents being required for the synthesis of heartwood phenolics. The non heartwood forming species Acer pseudoplatanus L. shows neither a radial gradient nor seasonal changes in the amounts of pyridine nucleotides across the trunkwood. The results are discussed in connection with programmed cell death, mitochondrial activity, and heartwood formation.
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Affiliation(s)
- E A Magel
- Department of Botany, University of Tuebingen, Auf der Morgenstelle 1, 72076 Tuebingen, Germany.
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49
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Lemeshko SV, Lemeshko VV. Metabolically derived potential on the outer membrane of mitochondria: a computational model. Biophys J 2000; 79:2785-800. [PMID: 11106589 PMCID: PMC1301160 DOI: 10.1016/s0006-3495(00)76518-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The outer mitochondrial membrane (OMM) is permeable to various small substances because of the presence of a voltage-dependent anion channel (VDAC). The voltage dependence of VDAC's permeability is puzzling, because the existence of membrane potential on the OMM has never been shown. We propose that steady-state metabolically derived potential (MDP) may be generated on the OMM as the result of the difference in its permeability restriction for various charged metabolites. To demonstrate the possibility of MDP generation, two models were considered: a liposomal model and a simplified cell model with a creatine kinase energy channeling system. Quantitative computational analysis of the simplified cell model shows that a MDP of up to -5 mV, in addition to the Donnan potential, may be generated at high workloads, even if the OMM is highly permeable to small inorganic ions, including potassium. Calculations show that MDP and DeltapH, generated on the OMM, depend on the cytoplasmic pH and energy demand rate. Computational modeling suggests that MDP may be important for cell energy metabolism regulation in multiple ways, including VDAC's permeability modulation and the effect of electrodynamic compartmentation. The osmotic pressure difference between the mitochondrial intermembrane space and the cytoplasm, as related to the electrodynamic compartmentation effects, might explain the morphological changes in mitochondria under intense workloads.
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Affiliation(s)
- S V Lemeshko
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030 USA.
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50
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Torrance SM, Belanger MP, Wallen WJ, Wittnich C. Metabolic and functional response of neonatal pig hearts to the development of ischemic contracture: is recovery possible? Pediatr Res 2000; 48:191-9. [PMID: 10926294 DOI: 10.1203/00006450-200008000-00012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The potential for functional and metabolic recovery in neonatal hearts after the development of ischemic contracture remains controversial and undefined. This study documents post-ischemic recovery of metabolism and function in the in vivo neonatal heart after the development of onset and peak ischemic contracture. In piglets on cardiopulmonary bypass, hearts were reperfused after the development of either onset (TICo) or peak (TICp) ischemic contracture. Systolic (developed and systolic function, contractility) and diastolic (diastolic function, relaxation) performance was assessed throughout reperfusion. Biopsies were obtained at end-ischemia or end-reperfusion to assess metabolism. By end-ischemia, the metabolic profiles of both TICo and TICp hearts confirmed energy-store depletion and purine degradation that was quantitatively greater in TICp hearts. Hearts reperfused at TICo had consistent moderate impairment of developed function, contractility, diastolic function, and relaxation, whereas hearts reperfused at TICp had much more profound functional impairment. Diastolic function showed the worst functional recovery. In contrast, systolic function was not significantly altered in either study group and, thus, did not reflect the actual extent of injury. In addition, TICo hearts either did not further deplete or partially regenerated energy stores during reperfusion, whereas TICp hearts had further energy-store depletion and lactate accumulation. In summary, neonatal hearts reperfused after TICo maintained or partially restored energy stores and had significant but incomplete functional recovery. In contrast, further metabolic deterioration and profound functional impairment occurred with reperfusion after TICp, potentially indicating ongoing mitochondrial injury and compromised oxidative phosphorylation.
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Affiliation(s)
- S M Torrance
- Institute of Medical Science, University of Toronto, Ontario, Canada
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