1
|
Monné M, Daddabbo L, Giannossa LC, Nicolardi MC, Palmieri L, Miniero DV, Mangone A, Palmieri F. Mitochondrial ATP-Mg/phosphate carriers transport divalent inorganic cations in complex with ATP. J Bioenerg Biomembr 2017; 49:369-380. [PMID: 28695448 DOI: 10.1007/s10863-017-9721-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 06/22/2017] [Indexed: 12/16/2022]
Abstract
The ATP-Mg/phosphate carriers (APCs) modulate the intramitochondrial adenine nucleotide pool size. In this study the concentration-dependent effects of Mg2+ and other divalent cations (Me2+) on the transport of [3H]ATP in liposomes reconstituted with purified human and Arabidopsis APCs (hAPCs and AtAPCs, respectively, including some lacking their N-terminal domains) have been investigated. The transport of Me2+ mediated by these proteins was also measured. In the presence of a low external concentration of [3H]ATP (12 μM) and increasing concentrations of Me2+, Mg2+ stimulated the activity (measured as initial transport rate of [3H]ATP) of hAPCs and decreased that of AtAPCs; Fe2+ and Zn2+ stimulated markedly hAPCs and moderately AtAPCs; Ca2+ and Mn2+ markedly AtAPCs and moderately hAPCs; and Cu2+ decreased the activity of both hAPCs and AtAPCs. All the Me2+-dependent effects correlated well with the amount of ATP-Me complex present. The transport of [14C]AMP, which has a much lower ability of complexation than ATP, was not affected by the presence of the Me2+ tested, except Cu2+. Furthermore, the transport of [3H]ATP catalyzed by the ATP/ADP carrier, which is known to transport only free ATP and ADP, was inhibited by all the Me2+ tested in an inverse relationship with the formation of the ATP-Me complex. Finally, direct measurements of Mg2+, Mn2+, Fe2+, Zn2+ and Cu2+ showed that they are cotransported with ATP by both hAPCs and AtAPCs. It is likely that in vivo APCs transport free ATP and ATP-Mg complex to different degrees, and probably trace amounts of other Me2+ in complex with ATP.
Collapse
Affiliation(s)
- Magnus Monné
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy.,Department of Sciences, University of Basilicata, Via Ateneo Lucano 10, 85100, Potenza, Italy
| | - Lucia Daddabbo
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy
| | | | - Maria Cristina Nicolardi
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy
| | - Luigi Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy.,Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, Consiglio Nazionale delle Ricerche, 70126, Bari, Italy
| | - Daniela Valeria Miniero
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy
| | - Annarosa Mangone
- Department of Chemistry, University of Bari, Via E. Orabona 4, 70126, Bari, Italy
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari, Via E. Orabona 4, 70125, Bari, Italy. .,Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, Consiglio Nazionale delle Ricerche, 70126, Bari, Italy.
| |
Collapse
|
2
|
Lytovchenko O, Kunji ERS. Expression and putative role of mitochondrial transport proteins in cancer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:641-654. [PMID: 28342810 DOI: 10.1016/j.bbabio.2017.03.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/20/2017] [Accepted: 03/21/2017] [Indexed: 02/07/2023]
Abstract
Cancer cells undergo major changes in energy and biosynthetic metabolism. One of them is the Warburg effect, in which pyruvate is used for fermentation rather for oxidative phosphorylation. Another major one is their increased reliance on glutamine, which helps to replenish the pool of Krebs cycle metabolites used for other purposes, such as amino acid or lipid biosynthesis. Mitochondria are central to these alterations, as the biochemical pathways linking these processes run through these organelles. Two membranes, an outer and inner membrane, surround mitochondria, the latter being impermeable to most organic compounds. Therefore, a large number of transport proteins are needed to link the biochemical pathways of the cytosol and mitochondrial matrix. Since the transport steps are relatively slow, it is expected that many of these transport steps are altered when cells become cancerous. In this review, changes in expression and regulation of these transport proteins are discussed as well as the role of the transported substrates. This article is part of a Special Issue entitled Mitochondria in Cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.
Collapse
Affiliation(s)
- Oleksandr Lytovchenko
- Medical Research Council, Mitochondrial Biology Unit, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
| | - Edmund R S Kunji
- Medical Research Council, Mitochondrial Biology Unit, Cambridge Biomedical Campus, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK.
| |
Collapse
|
3
|
Llorente-Folch I, Rueda CB, Pardo B, Szabadkai G, Duchen MR, Satrustegui J. The regulation of neuronal mitochondrial metabolism by calcium. J Physiol 2016; 593:3447-62. [PMID: 25809592 DOI: 10.1113/jp270254] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/18/2015] [Indexed: 12/24/2022] Open
Abstract
Calcium signalling is fundamental to the function of the nervous system, in association with changes in ionic gradients across the membrane. Although restoring ionic gradients is energetically costly, a rise in intracellular Ca(2+) acts through multiple pathways to increase ATP synthesis, matching energy supply to demand. Increasing cytosolic Ca(2+) stimulates metabolite transfer across the inner mitochondrial membrane through activation of Ca(2+) -regulated mitochondrial carriers, whereas an increase in matrix Ca(2+) stimulates the citric acid cycle and ATP synthase. The aspartate-glutamate exchanger Aralar/AGC1 (Slc25a12), a component of the malate-aspartate shuttle (MAS), is stimulated by modest increases in cytosolic Ca(2+) and upregulates respiration in cortical neurons by enhancing pyruvate supply into mitochondria. Failure to increase respiration in response to small (carbachol) and moderate (K(+) -depolarization) workloads and blunted stimulation of respiration in response to high workloads (veratridine) in Aralar/AGC1 knockout neurons reflect impaired MAS activity and limited mitochondrial pyruvate supply. In response to large workloads (veratridine), acute stimulation of respiration occurs in the absence of MAS through Ca(2+) influx through the mitochondrial calcium uniporter (MCU) and a rise in matrix [Ca(2+) ]. Although the physiological importance of the MCU complex in work-induced stimulation of respiration of CNS neurons is not yet clarified, abnormal mitochondrial Ca(2+) signalling causes pathology. Indeed, loss of function mutations in MICU1, a regulator of MCU complex, are associated with neuromuscular disease. In patient-derived MICU1 deficient fibroblasts, resting matrix Ca(2+) is increased and mitochondria fragmented. Thus, the fine tuning of Ca(2+) signals plays a key role in shaping mitochondrial bioenergetics.
Collapse
Affiliation(s)
- I Llorente-Folch
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - C B Rueda
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - B Pardo
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| | - G Szabadkai
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, UK.,Department of Biomedical Sciences, University of Padua and Consiglio Nazionale delle Ricerche Neuroscience Institute, Padua, Italy
| | - M R Duchen
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, UK
| | - J Satrustegui
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid-(CSIC-UAM), Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, Madrid, Spain
| |
Collapse
|
4
|
The transport mechanism of the mitochondrial ADP/ATP carrier. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2379-93. [PMID: 27001633 DOI: 10.1016/j.bbamcr.2016.03.015] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 12/18/2022]
Abstract
The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix, which are key transport steps for oxidative phosphorylation in eukaryotic organisms. The transport protein belongs to the mitochondrial carrier family, a large transporter family in the inner membrane of mitochondria. It is one of the best studied members of the family and serves as a paradigm for the molecular mechanism of mitochondrial carriers. Structurally, the carrier consists of three homologous domains, each composed of two transmembrane α-helices linked with a loop and short α-helix on the matrix side. The transporter cycles between a cytoplasmic and matrix state in which a central substrate binding site is alternately accessible to these compartments for binding of ADP or ATP. On both the cytoplasmic and matrix side of the carrier are networks consisting of three salt bridges each. In the cytoplasmic state, the matrix salt bridge network is formed and the cytoplasmic network is disrupted, opening the central substrate binding site to the intermembrane space and cytosol, whereas the converse occurs in the matrix state. In the transport cycle, tighter substrate binding in the intermediate states allows the interconversion of conformations by lowering the energy barrier for disruption and formation of these networks, opening and closing the carrier to either side of the membrane in an alternating way. Conversion between cytoplasmic and matrix states might require the simultaneous rotation of three domains around a central translocation pathway, constituting a unique mechanism among transport proteins. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
Collapse
|
5
|
Lorenz A, Lorenz M, Vothknecht UC, Niopek-Witz S, Neuhaus HE, Haferkamp I. In vitro analyses of mitochondrial ATP/phosphate carriers from Arabidopsis thaliana revealed unexpected Ca(2+)-effects. BMC PLANT BIOLOGY 2015; 15:238. [PMID: 26444389 PMCID: PMC4595200 DOI: 10.1186/s12870-015-0616-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 09/12/2015] [Indexed: 05/05/2023]
Abstract
BACKGROUND Adenine nucleotide/phosphate carriers (APCs) from mammals and yeast are commonly known to adapt the mitochondrial adenine nucleotide pool in accordance to cellular demands. They catalyze adenine nucleotide--particularly ATP-Mg--and phosphate exchange and their activity is regulated by calcium. Our current knowledge about corresponding proteins from plants is comparably limited. Recently, the three putative APCs from Arabidopsis thaliana were shown to restore the specific growth phenotype of APC yeast loss-of-function mutants and to interact with calcium via their N-terminal EF--hand motifs in vitro. In this study, we performed biochemical characterization of all three APC isoforms from A. thaliana to gain further insights into their functional properties. RESULTS Recombinant plant APCs were functionally reconstituted into liposomes and their biochemical characteristics were determined by transport measurements using radiolabeled substrates. All three plant APCs were capable of ATP, ADP and phosphate exchange, however, high preference for ATP-Mg, as shown for orthologous carriers, was not detectable. By contrast, the obtained data suggest that in the liposomal system the plant APCs rather favor ATP-Ca as substrate. Moreover, investigation of a representative mutant APC protein revealed that the observed calcium effects on ATP transport did not primarily/essentially involve Ca(2+)-binding to the EF-hand motifs in the N-terminal domain of the carrier. CONCLUSION Biochemical characteristics suggest that plant APCs can mediate net transport of adenine nucleotides and hence, like their pendants from animals and yeast, might be involved in the alteration of the mitochondrial adenine nucleotide pool. Although, ATP-Ca was identified as an apparent import substrate of plant APCs in vitro it is arguable whether ATP-Ca formation and thus the corresponding transport can take place in vivo.
Collapse
Affiliation(s)
- André Lorenz
- Cellular Physiology/Membrane Transport, University of Kaiserslautern, 67653, Kaiserslautern, Germany.
| | - Melanie Lorenz
- Cellular Physiology/Membrane Transport, University of Kaiserslautern, 67653, Kaiserslautern, Germany.
| | - Ute C Vothknecht
- Department of Biology I, Botany, LMU Munich, Großhaderner Str. 2, D-82152, Planegg-Martinsried, Germany.
| | - Sandra Niopek-Witz
- Plant Physiology, University of Kaiserslautern, 67653, Kaiserslautern, Germany.
| | - H Ekkehard Neuhaus
- Plant Physiology, University of Kaiserslautern, 67653, Kaiserslautern, Germany.
| | - Ilka Haferkamp
- Cellular Physiology/Membrane Transport, University of Kaiserslautern, 67653, Kaiserslautern, Germany.
| |
Collapse
|
6
|
Amigo I, Traba J, González-Barroso MM, Rueda CB, Fernández M, Rial E, Sánchez A, Satrústegui J, Del Arco A. Glucagon regulation of oxidative phosphorylation requires an increase in matrix adenine nucleotide content through Ca2+ activation of the mitochondrial ATP-Mg/Pi carrier SCaMC-3. J Biol Chem 2013; 288:7791-7802. [PMID: 23344948 DOI: 10.1074/jbc.m112.409144] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
It has been known for a long time that mitochondria isolated from hepatocytes treated with glucagon or Ca(2+)-mobilizing agents such as phenylephrine show an increase in their adenine nucleotide (AdN) content, respiratory activity, and calcium retention capacity (CRC). Here, we have studied the role of SCaMC-3/slc25a23, the mitochondrial ATP-Mg/Pi carrier present in adult mouse liver, in the control of mitochondrial AdN levels and respiration in response to Ca(2+) signals as a candidate target of glucagon actions. With the use of SCaMC-3 knock-out (KO) mice, we have found that the carrier is responsible for the accumulation of AdNs in liver mitochondria in a strictly Ca(2+)-dependent way with an S0.5 for Ca(2+) activation of 3.3 ± 0.9 μm. Accumulation of matrix AdNs allows a SCaMC-3-dependent increase in CRC. In addition, SCaMC-3-dependent accumulation of AdNs is required to acquire a fully active state 3 respiration in AdN-depleted liver mitochondria, although further accumulation of AdNs is not followed by increases in respiration. Moreover, glucagon addition to isolated hepatocytes increases oligomycin-sensitive oxygen consumption and maximal respiratory rates in cells derived from wild type, but not SCaMC-3-KO mice and glucagon administration in vivo results in an increase in AdN content, state 3 respiration and CRC in liver mitochondria in wild type but not in SCaMC-3-KO mice. These results show that SCaMC-3 is required for the increase in oxidative phosphorylation observed in liver mitochondria in response to glucagon and Ca(2+)-mobilizing agents, possibly by allowing a Ca(2+)-dependent accumulation of mitochondrial AdNs and matrix Ca(2+), events permissive for other glucagon actions.
Collapse
Affiliation(s)
- Ignacio Amigo
- Departmento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-CSIC; Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER) 28049 Madrid
| | - Javier Traba
- Departmento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-CSIC; Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER) 28049 Madrid
| | - M Mar González-Barroso
- Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biológicas (CIB), Consejo Superior de Investigaciones Científicas 28040 Madrid
| | - Carlos B Rueda
- Departmento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-CSIC; Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER) 28049 Madrid
| | - Margarita Fernández
- Departamento de Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense de Madrid 28040 Madrid
| | - Eduardo Rial
- Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biológicas (CIB), Consejo Superior de Investigaciones Científicas 28040 Madrid
| | - Aránzazu Sánchez
- Departamento de Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense de Madrid 28040 Madrid
| | - Jorgina Satrústegui
- Departmento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-CSIC; Centro de Investigaciones Biomédicas en Red de Enfermedades Raras (CIBERER) 28049 Madrid.
| | - Araceli Del Arco
- Área de Bioquímica, Centro Regional de Investigaciones Biomédicas, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla La Mancha (UCLM), Avda. Carlos III s/n, Toledo 45071, Spain.
| |
Collapse
|
7
|
A novel kinetic assay of mitochondrial ATP-ADP exchange rate mediated by the ANT. Biophys J 2009; 96:2490-504. [PMID: 19289073 DOI: 10.1016/j.bpj.2008.12.3915] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/08/2008] [Accepted: 12/17/2008] [Indexed: 11/23/2022] Open
Abstract
A novel method exploiting the differential affinity of ADP and ATP to Mg(2+) was developed to measure mitochondrial ADP-ATP exchange rate. The rate of ATP appearing in the medium after addition of ADP to energized mitochondria, is calculated from the measured rate of change in free extramitochondrial [Mg(2+)] reported by the membrane-impermeable 5K(+) salt of the Mg(2+)-sensitive fluorescent indicator, Magnesium Green, using standard binding equations. The assay is designed such that the adenine nucleotide translocase (ANT) is the sole mediator of changes in [Mg(2+)] in the extramitochondrial volume, as a result of ADP-ATP exchange. We also provide data on the dependence of ATP efflux rate within the 6.8-7.8 matrix pH range as a function of membrane potential. Finally, by comparing the ATP-ADP steady-state exchange rate to the amount of the ANT in rat brain synaptic, brain nonsynaptic, heart and liver mitochondria, we provide molecular turnover numbers for the known ANT isotypes.
Collapse
|
8
|
Satrústegui J, Pardo B, Del Arco A. Mitochondrial Transporters as Novel Targets for Intracellular Calcium Signaling. Physiol Rev 2007; 87:29-67. [PMID: 17237342 DOI: 10.1152/physrev.00005.2006] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca2+signaling in mitochondria is important to tune mitochondrial function to a variety of extracellular stimuli. The main mechanism is Ca2+entry in mitochondria via the Ca2+uniporter followed by Ca2+activation of three dehydrogenases in the mitochondrial matrix. This results in increases in mitochondrial NADH/NAD ratios and ATP levels and increased substrate uptake by mitochondria. We review evidence gathered more than 20 years ago and recent work indicating that substrate uptake, mitochondrial NADH/NAD ratios, and ATP levels may be also activated in response to cytosolic Ca2+signals via a mechanism that does not require the entry of Ca2+in mitochondria, a mechanism depending on the activity of Ca2+-dependent mitochondrial carriers (CaMC). CaMCs fall into two groups, the aspartate-glutamate carriers (AGC) and the ATP-Mg/Picarriers, also named SCaMC (for short CaMC). The two mammalian AGCs, aralar and citrin, are members of the malate-aspartate NADH shuttle, and citrin, the liver AGC, is also a member of the urea cycle. Both types of CaMCs are activated by Ca2+in the intermembrane space and function together with the Ca2+uniporter in decoding the Ca2+signal into a mitochondrial response.
Collapse
Affiliation(s)
- Jorgina Satrústegui
- Departamento de Biología Molecular Centro de Biología Molecular "Severo Ochoa" UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, Madrid, Spain.
| | | | | |
Collapse
|
9
|
Kunji ERS, Robinson AJ. The conserved substrate binding site of mitochondrial carriers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1237-48. [PMID: 16759636 DOI: 10.1016/j.bbabio.2006.03.021] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 03/10/2006] [Accepted: 03/24/2006] [Indexed: 10/24/2022]
Abstract
Mitochondrial carriers transport nucleotides, co-factors and metabolic intermediates across the inner mitochondrial membrane permeability barrier. They belong to a family of transporters unique to eukaryotes and they differ in structure and transport mechanism from other secondary transporters. The main structural fold consists of a barrel of six transmembrane alpha-helices closed at the matrix side by a salt-bridge network at the bottom of the cavity. The significant sequence conservation in the mitochondrial carrier family suggests that specific recognition of substrates is coupled to a common mechanism of transport. We have identified a common substrate binding site comprising residues that are highly conserved and, as demonstrated by mutagenesis, are essential for function. The binding site explains substrate selectivity, ion coupling and the effects of the membrane potential on transport. The main contact points in the site are related by threefold symmetry like the common structural fold. The substrate is bound at the midpoint of the membrane and may function as a pivot point for the movements of the transmembrane alpha-helices as the carrier changes conformation. The trigger for the translocation event is likely to be the substrate-induced perturbation of the salt bridge network at the bottom of the cavity.
Collapse
Affiliation(s)
- Edmund R S Kunji
- The Medical Research Council, Dunn Human Nutrition Unit, CB2 2XY, Cambridge, UK.
| | | |
Collapse
|
10
|
Robinson AJ, Kunji ERS. Mitochondrial carriers in the cytoplasmic state have a common substrate binding site. Proc Natl Acad Sci U S A 2006; 103:2617-22. [PMID: 16469842 PMCID: PMC1413793 DOI: 10.1073/pnas.0509994103] [Citation(s) in RCA: 192] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial carriers link biochemical pathways in the cytosol and mitochondrial matrix by transporting substrates across the inner mitochondrial membrane. Substrate recognition is specific for each carrier, but sequence similarities suggest the carriers have similar structures and mechanisms of substrate translocation. By considering conservation of amino acids, distance and chemical constraints, and by modeling family members on the known structure of the ADP/ATP translocase, we have identified a common substrate binding site. It explains substrate selectivity and proton coupling and provides a mechanistic link to carrier opening by substrate-induced perturbation of the salt bridges that seal the pathway to and from the mitochondrial matrix. It enables the substrate specificity of uncharacterized mitochondrial carriers to be predicted.
Collapse
Affiliation(s)
- Alan J. Robinson
- Dunn Human Nutrition Unit, Medical Research Council, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Edmund R. S. Kunji
- Dunn Human Nutrition Unit, Medical Research Council, Hills Road, Cambridge CB2 2XY, United Kingdom
| |
Collapse
|
11
|
Fiermonte G, De Leonardis F, Todisco S, Palmieri L, Lasorsa FM, Palmieri F. Identification of the mitochondrial ATP-Mg/Pi transporter. Bacterial expression, reconstitution, functional characterization, and tissue distribution. J Biol Chem 2004; 279:30722-30. [PMID: 15123600 DOI: 10.1074/jbc.m400445200] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites, nucleotides, and cofactors through this membrane and thereby connect and/or regulate cytoplasm and matrix functions. ATP-Mg is transported in exchange for phosphate, but no protein has ever been associated with this activity. We have isolated three human cDNAs that encode proteins of 458, 468, and 489 amino acids with 66-75% similarity and with the characteristic features of the mitochondrial carrier family in their C-terminal domains and three EF-hand Ca(2+)-binding motifs in their N-terminal domains. These proteins have been overexpressed in Escherichia coli and reconstituted into phospholipid vesicles. Their transport properties and their targeting to mitochondria demonstrate that they are isoforms of the ATP-Mg/Pi carrier described in the past in whole mitochondria. The tissue specificity of the three isoforms shows that at least one isoform was present in all of the tissues investigated. Because phosphate recycles via the phosphate carrier in mitochondria, the three isoforms of the ATP-Mg/Pi carrier are most likely responsible for the net uptake or efflux of adenine nucleotides into or from the mitochondria and hence for the variation in the matrix adenine nucleotide content, which has been found to change in many physiopathological situations.
Collapse
Affiliation(s)
- Giuseppe Fiermonte
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via Orabona 4, Italy
| | | | | | | | | | | |
Collapse
|
12
|
DasGupta SF, Rapoport SI, Gerschenson M, Murphy E, Fiskum G, Russell SJ, Chandrasekaran K. ATP synthesis is coupled to rat liver mitochondrial RNA synthesis. Mol Cell Biochem 2001; 221:3-10. [PMID: 11506183 DOI: 10.1023/a:1010812128765] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Rat liver mitochondria respond to changes in energy demand by modulating the amount of RNA synthesized. Coupled rat liver mitochondria were used to determine the relationship between mitochondrial respiration, ATP levels, and mitochondrial transcription. This system included oxidizable substrates (malate and glutamate) and constituents that could support both mitochondrial respiration and transcription. The respiratory inhibitor rotenone, phosphorylation inhibitor oligomycin, and the uncoupler of oxidative phosphorylation carbonyl-cyanide p-triflouromethoxyphehylhydrazone inhibited RNA synthesis. Addition of ADP stimulated mitochondrial transcription and peak RNA synthesis was observed at 1-2 mM ADP. At ADP concentrations above 2 mM, RNA synthesis decreased. These results demonstrate that mitochondrial transcription is tightly coupled to ATP levels.
Collapse
Affiliation(s)
- S F DasGupta
- Section on Brain Physiology and Metabolism, NIA, NIH, Bethesda, MD, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
Henke W, Hagen T, Jung K, Loening SA. Periodate-oxidized ATP stimulates the permeability transition of rat liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1363:209-16. [PMID: 9518617 DOI: 10.1016/s0005-2728(97)00103-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Periodate-oxidized ADP (oADP)2 and periodate-oxidized ATP (oATP) stimulate the permeability transition in energized rat liver mitochondria measured as the Ca2+-efflux induced by Ca2+ and Pi. In the presence of Mg2+ and Pi, mitochondria lose intramitochondrial adenine nucleotides at a slow rate. oATP induces a strong decrease of the matrix adenine nucleotides which is inhibited by carboxyatractyloside. Under these conditions, Mg2+ prevents the opening of the permeability transition pore. EGTA prevents the Pi-induced slow efflux of adenine nucleotides, but is without effect on the oATP-induced strong decrease of adenine nucleotides. This oATP-induced strong adenine nucleotide efflux is inhibited by ADP. oATP reduces the increase of matrix adenine nucleotides occurring when the mitochondria are incubated with Mg2+ and ATP. This effect of oATP is also prevented by carboxyatractyloside. oATP is not taken up by the mitochondria. It is suggested that oATP induces a strong efflux of matrix adenine nucleotides by the interaction with the ADP/ATP carrier from the cytosolic side. The induction of the mitochondrial permeability transition by oADP and oATP is attributed to two mechanisms-a strong decrease in the intramitochondrial adenine nucleotide content, especially that of ADP, and a stabilization of the c-conformation of the ADP/ATP carrier.
Collapse
Affiliation(s)
- W Henke
- Research Division, Department of Urology, University Hospital Charité, Humboldt University, Schumannstrasse 20/21, D-10098 Berlin, Germany.
| | | | | | | |
Collapse
|
14
|
García MV, Hernández-Berciano R, López-Mediavilla C, Orfao A, Medina JM. cAMP and Ca2+ involvement in the mitochondrial response of cultured fetal rat hepatocytes to adrenaline. Exp Cell Res 1997; 237:403-9. [PMID: 9434636 DOI: 10.1006/excr.1997.3804] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of adrenaline on the control of respiratory activity of mitochondria from fetal hepatocytes in primary culture was studied. In the absence of adrenaline, the respiratory control ratio (RCR) of mitochondria increased during the first 3 days of culture due to a decrease in the rate of state 4 respiration. The presence of adrenaline in the incubation medium further increased the mitochondrial RCR through a decrease in the rate of respiration in state 4 and to an increase in the respiration rate in state 3. The effect of adrenaline was mimicked by dibutyryl-cAMP, forskolin, and isobutyl methyl xanthine. All these compounds increased cAMP concentrations, suggesting that cAMP may be involved in the effect of adrenaline. The increase in intracellular free Ca2+ concentrations caused by phenylephrine, vasopressin, or thapsigargin was also accompanied by an increase in the RCR, suggesting that both phenomena are associated. Dibutyryl-cAMP also increased free Ca2+ concentrations, suggesting that the effects of cAMP may be mediated by free Ca2+ concentrations. Adrenaline, dibutyryl-cAMP, phenylephrine, vasopressin, and thapsigargin promoted adenine nucleotide accumulation in mitochondria; this may be an intermediate step in the activation of mitochondrial respiratory function. These results suggest that the stimulatory effect of adrenaline on mitochondrial maturation in cultured fetal rat hepatocytes may be exerted through a mechanism in which both cAMP and Ca2+ act as second messengers. It is concluded that the effect of adrenaline on mitochondrial maturation is exerted by both alpha- and beta-adrenergic mechanisms and is mediated by the increase in adenine nucleotide contents of mitochondria.
Collapse
Affiliation(s)
- M V García
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Salamanca, Spain
| | | | | | | | | |
Collapse
|
15
|
Enríquez JA, Fernández-Silva P, Pérez-Martos A, López-Pérez MJ, Montoya J. The synthesis of mRNA in isolated mitochondria can be maintained for several hours and is inhibited by high levels of ATP. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 237:601-10. [PMID: 8647103 DOI: 10.1111/j.1432-1033.1996.0601p.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The dependence for the maintenance of the synthesis and maturation of mitochondrial RNA on the supply of nucleo-cytoplasmic factors has been investigated by a novel in organello RNA synthesis system. We found that mitochondrial DNA transcription can be maintained for several hours in isolated mitochondria. Analysis of the individual mitochondrial RNA species revealed that: the processing of the rRNA precursors and the stability of the mature rRNAs, but not the transcription itself, is severely impaired after short periods of incubation, indicating that these processes are strongly dependent on the mitochondrial interaction with the nucleo-cytoplasmic compartment; the events that lead to the synthesis, processing and turnover of the mitochondrial mRNAs do not require the continuous supply of nucleo-cytoplasmic factors, that are accumulated in excess by mitochondria. Furthermore, we present evidence indicating an inhibition of high ATP levels on the mitochondrial RNA polymerase activity, both in organello and in vitro. Consequently, it is proposed that mitochondrial mRNA synthesis can be regulated in response to changes in intramitochondrial ATP levels. This regulation of mitochondrial mRNA synthesis together with their very rapid turnover described here and elsewhere [Gelfand, R. & Attardi, G. (1981) Mol. Cell Biol. 1, 497-511], could represent a mechanism that would allow each individual mitochondrion to adjust its optimal levels of mRNA, and hence its translation capacity, in response to local energetic demands.
Collapse
Affiliation(s)
- J A Enríquez
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Spain
| | | | | | | | | |
Collapse
|
16
|
Kwast KE, Hand SC. Oxygen and pH regulation of protein synthesis in mitochondria from Artemia franciscana embryos. Biochem J 1996; 313 ( Pt 1):207-13. [PMID: 8546685 PMCID: PMC1216884 DOI: 10.1042/bj3130207] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To identify factors responsible for the down-regulation of mitochondrial biosynthetic processes during anoxia in encysted Artemia franciscana embryos, the effects of oxygen limitation and pH on protein synthesis were investigated in isolated mitochondria. At the optimal pH of 7.5, exposure of mitochondria to anoxia decreases the protein synthesis rate by 79%. Rates were suppressed by a further 10% at pH 6.8, the intracellular pH (pHi) measured under anoxia in vivo. Matrix pH, measured under identical conditions, was 8.43 +/- 0.01 at an extra-mitochondrial pH of 7.9 (mean +/- S.E.M., n = 3), 8.05 +/- 0.01 at pH 7.5, and 7.10 +/- 0.01 at pH 6.8. The matrix pH did not vary (P > or = 0.20) as a function of oxygen availability during the 1 h assays. Intramitochondrial purine nucleotides varied little as a function of pH. In contrast, after 1 h of protein synthesis under anoxia, ATP levels decreased by up to 40%, whereas AMP, ADP and GDP concentrations increased, and GTP and GMP concentrations remained relatively constant. The addition of 1 mM ATP at the onset of anoxia maintained the ATP/ADP ratio at the aerobic value, but did not stabilized the GTP/GDP ratio or rescue rates of protein synthesis. Thus, at present, we cannot eliminate the possibility that the decrease in the GTP/GDP ratio during anoxia may contribute to the suppression of protein synthesis. The effect of anoxia was reversible; the rate of protein synthesis upon reoxygenation after a 30 min bout of anoxia was comparable (P = 0.14) with the pre-anoxic rate (193 +/- 17 and 174 +/- 6 pmol of leucine per mg of protein respectively, mean +/- S.E.M., n = 3). The array of mitochondrial translation products did not differ qualitatively as a function of either oxygen availability or pH. Finally, similar pH profiles for protein synthesis were obtained with either [3H]leucine or [3H]histidine (known to use different transporters). Consequently, it is improbable that the pH-sensitivity of protein synthesis can be explained by a specific protein effect on the import of the radiolabelled amino acid used. In summary, both oxygen limitation and acidic pH suppress rates of mitochondrial protein synthesis and are likely to contribute to the arrest of mitochondrial anabolic processes during anoxia-induced quiescence in A. franciscana embryos.
Collapse
Affiliation(s)
- K E Kwast
- Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder 80309-0334, USA
| | | |
Collapse
|
17
|
Affiliation(s)
- M Zoratti
- CNR Unit for the Physiology of Mitochondria, Department of Biomedical Sciences, Padova, Italy
| | | |
Collapse
|
18
|
Valcarce C, Izquierdo JM, Chamorro M, Cuezva JM. Mammalian adaptation to extrauterine environment: mitochondrial functional impairment caused by prematurity. Biochem J 1994; 303 ( Pt 3):855-62. [PMID: 7980455 PMCID: PMC1137625 DOI: 10.1042/bj3030855] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In this paper we report that, compared with term rat neonates, both mitochondrial content and function are diminished in liver of preterm neonates (delivered 24 h before full term) compromising cellular energy provision in the postnatal period. In addition, there is a parallel reduction in the content of mRNAs encoding mitochondrial proteins in preterm rats. Also, efficient oxidative phosphorylation is not attained in these pups until 3 h after birth. Although isolated liver mitochondria from preterm neonates show a two-fold increase in F1-ATPase beta-subunit and cytochrome c oxidase activity 1 h after birth, the abnormal coupling efficiency between respiration and oxidative phosphorylation (ADP/O ratio) is due to maintenance of high H(+)-leakage values in the inner mitochondrial membrane. Postnatal reduction of the H+ leak occurs concomitantly with an increase in intra-mitochondrial adenine nucleotide concentration. Accumulation of adenine nucleotides in preterm and term liver mitochondria parallels the postnatal increase in total liver adenine nucleotides. Delayed postnatal induction of adenine biosynthesis most likely accounts for the lower adenine nucleotide pool in the liver of preterm neonates. The delayed postnatal accumulation of adenine nucleotides in mitochondria is thus responsible for the impairment in oxidative phosphorylation displayed by organelles of the preterm liver.
Collapse
Affiliation(s)
- C Valcarce
- Departamento de Biología Molecular Severo Ochoa, Universidad Autóma de Madrid, Spain
| | | | | | | |
Collapse
|
19
|
Lapidus R, Sokolove P. The mitochondrial permeability transition. Interactions of spermine, ADP, and inorganic phosphate. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32256-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
20
|
Abstract
The mitochondrial ATP-Mg/P(i) carrier functions to modulate the matrix adenine nucleotide pool size (ATP + ADP + AMP). Micromolar Ca2+ is required to activate the carrier. Net adenine nucleotide transport occurs as an electroneutral divalent exchange of ATP-Mg2- for HPO4(2-). A steady-state adenine nucleotide pool size is attained when the HPO4(2-) and ATP-Mg2- matrix/cytoplasm concentration ratios are the same. This means that ATP-Mg2- can be accumulated against a concentration gradient in proportion to the [HPO4(2-)] gradient that is normally maintained by the P(i)/OH- carrier. In liver, changes in matrix adenine nucleotide concentrations that are brought about by the ATP-Mg/P(i) carrier can affect the activity of adenine nucleotide-dependent enzymes that are in the mitochondrial compartment. These enzymes in turn contribute to the overall regulation of bioenergetic function, flux through the gluconeogenesis and urea synthesis pathways, and organelle biogenesis. The ATP-Mg/P(i) carrier is distinct from other mitochondrial transport systems with respect to kinetics and to substrate and inhibitor sensitivity. It is the only carrier regulated by Ca2+. This carrier is present in kidney and liver mitochondria, but not in heart.
Collapse
Affiliation(s)
- J R Aprille
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| |
Collapse
|
21
|
The ATP-Mg/Pi carrier of rat liver mitochondria catalyzes a divalent electroneutral exchange. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)41761-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|