1
|
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.
Collapse
|
2
|
Del Arco A, Contreras L, Pardo B, Satrustegui J. Calcium regulation of mitochondrial carriers. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2413-21. [PMID: 27033520 DOI: 10.1016/j.bbamcr.2016.03.024] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/23/2016] [Accepted: 03/23/2016] [Indexed: 11/16/2022]
Abstract
Mitochondrial function is regulated by calcium. In addition to the long known effects of matrix Ca(2+), regulation of metabolite transport by extramitochondrial Ca(2+) represents an alternative Ca(2+)-dependent mechanism to regulate mitochondrial function. The Ca(2+) regulated mitochondrial transporters (CaMCs) are well suited for that role, as they contain long N-terminal extensions harboring EF-hand Ca(2+) binding domains facing the intermembrane space. They fall in two groups, the aspartate/glutamate exchangers, AGCs, major components of the NADH malate aspartate shuttle (MAS) and urea cycle, and the ATP-Mg(2+)/Pi exchangers or short CaMCs (APCs or SCaMCs). The AGCs are activated by relatively low Ca(2+) levels only slightly higher than resting Ca(2+), whereas all SCaMCs studied so far require strong Ca(2+) signals, above micromolar, for activation. In addition, AGCs are not strictly Ca(2+) dependent, being active even in Ca(2+)-free conditions. Thus, AGCs are well suited to respond to small Ca(2+) signals and that do not reach mitochondria. In contrast, ATP-Mg(2+)/Pi carriers are inactive in Ca(2+) free conditions and activation requires Ca(2+) signals that will also activate the calcium uniporter (MCU). By changing the net content of adenine nucleotides of the matrix upon activation, SCaMCs regulate the activity of the permeability transition pore, and the Ca(2+) retention capacity of mitochondria (CRC), two functions synergizing with those of the MCU. The different Ca(2+) activation properties of the two CaMCs are discussed in relation to their newly obtained structures. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
Collapse
Affiliation(s)
- Araceli Del Arco
- Facultad de Ciencias Ambientales y Bioquímica, Centro RegionaI de Investigaciones Biomédicas, Universidad de Castilla la Mancha, Toledo 45071, Spain; CIBER de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain; Instituto de Investigaciones Sanitarias Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain
| | - Laura Contreras
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; CIBER de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain; Instituto de Investigaciones Sanitarias Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain
| | - Beatriz Pardo
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; CIBER de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain; Instituto de Investigaciones Sanitarias Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain
| | - Jorgina Satrustegui
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; CIBER de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain; Instituto de Investigaciones Sanitarias Fundación Jiménez Díaz (IIS-FJD), Madrid, Spain.
| |
Collapse
|
3
|
Bhosale G, Sharpe JA, Sundier SY, Duchen MR. Calcium signaling as a mediator of cell energy demand and a trigger to cell death. Ann N Y Acad Sci 2015; 1350:107-16. [PMID: 26375864 PMCID: PMC4949562 DOI: 10.1111/nyas.12885] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Calcium signaling is pivotal to a host of physiological pathways. A rise in calcium concentration almost invariably signals an increased cellular energy demand. Consistent with this, calcium signals mediate a number of pathways that together serve to balance energy supply and demand. In pathological states, calcium signals can precipitate mitochondrial injury and cell death, especially when coupled to energy depletion and oxidative or nitrosative stress. This review explores the mechanisms that couple cell signaling pathways to metabolic regulation or to cell death. The significance of these pathways is exemplified by pathological case studies, such as those showing loss of mitochondrial calcium uptake 1 in patients and ischemia/reperfusion injury.
Collapse
Affiliation(s)
- Gauri Bhosale
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London, United Kingdom
| | - Jenny A Sharpe
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London, United Kingdom
| | - Stephanie Y Sundier
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London, United Kingdom
| | - Michael R Duchen
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London, United Kingdom
| |
Collapse
|
4
|
Hoffman NE, Chandramoorthy HC, Shanmughapriya S, Zhang XQ, Vallem S, Doonan PJ, Malliankaraman K, Guo S, Rajan S, Elrod JW, Koch WJ, Cheung JY, Madesh M. SLC25A23 augments mitochondrial Ca²⁺ uptake, interacts with MCU, and induces oxidative stress-mediated cell death. Mol Biol Cell 2014; 25:936-47. [PMID: 24430870 PMCID: PMC3952861 DOI: 10.1091/mbc.e13-08-0502] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Emerging findings suggest that two lineages of mitochondrial Ca(2+) uptake participate during active and resting states: 1) the major eukaryotic membrane potential-dependent mitochondrial Ca(2+) uniporter and 2) the evolutionarily conserved exchangers and solute carriers, which are also involved in ion transport. Although the influx of Ca(2+) across the inner mitochondrial membrane maintains metabolic functions and cell death signal transduction, the mechanisms that regulate mitochondrial Ca(2+) accumulation are unclear. Solute carriers--solute carrier 25A23 (SLC25A23), SLC25A24, and SLC25A25--represent a family of EF-hand-containing mitochondrial proteins that transport Mg-ATP/Pi across the inner membrane. RNA interference-mediated knockdown of SLC25A23 but not SLC25A24 and SLC25A25 decreases mitochondrial Ca(2+) uptake and reduces cytosolic Ca(2+) clearance after histamine stimulation. Ectopic expression of SLC25A23 EF-hand-domain mutants exhibits a dominant-negative phenotype of reduced mitochondrial Ca(2+) uptake. In addition, SLC25A23 interacts with mitochondrial Ca(2+) uniporter (MCU; CCDC109A) and MICU1 (CBARA1) while also increasing IMCU. In addition, SLC25A23 knockdown lowers basal mROS accumulation, attenuates oxidant-induced ATP decline, and reduces cell death. Further, reconstitution with short hairpin RNA-insensitive SLC25A23 cDNA restores mitochondrial Ca(2+) uptake and superoxide production. These findings indicate that SLC25A23 plays an important role in mitochondrial matrix Ca(2+) influx.
Collapse
Affiliation(s)
- Nicholas E Hoffman
- Department of Biochemistry, Temple University, Philadelphia, PA 19140 Center for Translational Medicine, Temple University, Philadelphia, PA 19140
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
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
|
6
|
Tewari SG, Dash RK, Beard DA, Bazil JN. A biophysical model of the mitochondrial ATP-Mg/P(i) carrier. Biophys J 2012; 103:1616-25. [PMID: 23062354 DOI: 10.1016/j.bpj.2012.08.050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 08/10/2012] [Accepted: 08/29/2012] [Indexed: 10/27/2022] Open
Abstract
Mitochondrial adenine nucleotide (AdN) content is regulated through the Ca(2+)-activated, electroneutral ATP-Mg/P(i) carrier (APC). The APC is a protein in the mitochondrial carrier super family that localizes to the inner mitochondrial membrane (IMM). It is known to modulate a number of processes that depend on mitochondrial AdN content, such as gluconeogenesis, protein synthesis, and citrulline synthesis. Despite this critical role, a kinetic model of the underlying mechanism has not been developed and validated. Here, a biophysical model of the APC is developed that is thermodynamically balanced and accurately reproduces a number of reported data sets from isolated rat liver and rat kidney mitochondria. The model is based on an ordered bi-bi mechanism for heteroexchange of ATP and P(i) and includes homoexchanges of ATP and P(i) to explain both the initial rate and time course data on ATP and P(i) transport via the APC. The model invokes seven kinetic parameters regarding the APC mechanism and three parameters related to matrix pH regulation by external P(i). These parameters are estimated based on 19 independent data curves; the estimated parameters are validated using six additional data curves. The model takes into account the effects of pH, Mg(2+), and Ca(2+) on ATP and P(i) transport via the APC, and supports the conclusion that the pH gradient across the IMM serves as the primary driving force for AdN uptake or efflux. Moreover, computer simulations demonstrate that extramatrix Ca(2+) modulates the turnover rate of the APC and not the binding affinity of ATP, as previously suggested.
Collapse
Affiliation(s)
- Shivendra G Tewari
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | | | | |
Collapse
|
7
|
Anunciado-Koza RP, Zhang J, Ukropec J, Bajpeyi S, Koza RA, Rogers RC, Cefalu WT, Mynatt RL, Kozak LP. Inactivation of the mitochondrial carrier SLC25A25 (ATP-Mg2+/Pi transporter) reduces physical endurance and metabolic efficiency in mice. J Biol Chem 2011; 286:11659-71. [PMID: 21296886 DOI: 10.1074/jbc.m110.203000] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An ATP-Mg(2+/)P(i) inner mitochondrial membrane solute transporter (SLC25A25), which is induced during adaptation to cold stress in the skeletal muscle of mice with defective UCP1/brown adipose tissue thermogenesis, has been evaluated for its role in metabolic efficiency. SLC25A25 is thought to control ATP homeostasis by functioning as a Ca(2+)-regulated shuttle of ATP-Mg(2+) and P(i) across the inner mitochondrial membrane. Mice with an inactivated Slc25a25 gene have reduced metabolic efficiency as evidenced by enhanced resistance to diet-induced obesity and impaired exercise performance on a treadmill. Mouse embryo fibroblasts from Slc25a25(-/-) mice have reduced Ca(2+) flux across the endoplasmic reticulum, basal mitochondrial respiration, and ATP content. Although Slc25a25(-/-) mice are metabolically inefficient, the source of the inefficiency is not from a primary function in thermogenesis, because Slc25a25(-/-) mice maintain body temperature upon acute exposure to the cold (4 °C). Rather, the role of SLC25A25 in metabolic efficiency is most likely linked to muscle function as evidenced from the physical endurance test of mutant mice on a treadmill. Consequently, in the absence of SLC25A25 the efficiency of ATP production required for skeletal muscle function is diminished with secondary effects on adiposity. However, in the absence of UCP1-based thermogenesis, induction of Slc25a25 in mice with an intact gene may contribute to an alternative thermogenic pathway for the maintenance of body temperature during cold stress.
Collapse
|
8
|
Balaban RS. The role of Ca(2+) signaling in the coordination of mitochondrial ATP production with cardiac work. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1334-41. [PMID: 19481532 DOI: 10.1016/j.bbabio.2009.05.011] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 04/23/2009] [Accepted: 05/13/2009] [Indexed: 12/18/2022]
Abstract
The heart is capable of balancing the rate of mitochondrial ATP production with utilization continuously over a wide range of activity. This results in a constant phosphorylation potential despite a large change in metabolite turnover. The molecular mechanisms responsible for generating this energy homeostasis are poorly understood. The best candidate for a cytosolic signaling molecule reflecting ATP hydrolysis is Ca(2+). Since Ca(2+) initiates and powers muscle contraction as well as serves as the primary substrate for SERCA, Ca(2+) is an ideal feed-forward signal for priming ATP production. With the sarcoplasmic reticulum to cytosolic Ca(2+) gradient near equilibrium with the free energy of ATP, cytosolic Ca(2+) release is exquisitely sensitive to the cellular energy state providing a feedback signal. Thus, Ca(2+) can serve as a feed-forward and feedback regulator of ATP production. Consistent with this notion is the correlation of cytosolic and mitochondrial Ca(2+) with work in numerous preparations as well as the localization of mitochondria near Ca(2+) release sites. How cytosolic Ca(2+) signaling might regulate oxidative phosphorylation is a focus of this review. The relevant Ca(2+) sensitive sites include several dehydrogenases and substrate transporters together with a post-translational modification of F1-FO-ATPase and cytochrome oxidase. Thus, Ca(2+) apparently activates both the generation of the mitochondrial membrane potential as well as utilization to produce ATP. This balanced activation extends the energy homeostasis observed in the cytosol into the mitochondria matrix in the never resting heart.
Collapse
Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
9
|
Contreras L, Gomez-Puertas P, Iijima M, Kobayashi K, Saheki T, Satrústegui J. Ca2+ Activation kinetics of the two aspartate-glutamate mitochondrial carriers, aralar and citrin: role in the heart malate-aspartate NADH shuttle. J Biol Chem 2007; 282:7098-106. [PMID: 17213189 DOI: 10.1074/jbc.m610491200] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+) regulation of the Ca(2+) binding mitochondrial carriers for aspartate/glutamate (AGCs) is provided by their N-terminal extensions, which face the intermembrane space. The two mammalian AGCs, aralar and citrin, are members of the malate-aspartate NADH shuttle. We report that their N-terminal extensions contain up to four pairs of EF-hand motifs plus a single vestigial EF-hand, and have no known homolog. Aralar and citrin contain one fully canonical EF-hand pair and aralar two additional half-pairs, in which a single EF-hand is predicted to bind Ca(2+). Shuttle activity in brain or skeletal muscle mitochondria, which contain aralar as the major AGC, is activated by Ca(2+) with S(0.5) values of 280-350 nm; higher than those obtained in liver mitochondria (100-150 nm) that contain citrin as the major AGC. We have used aralar- and citrin-deficient mice to study the role of the two isoforms in heart, which expresses both AGCs. The S(0.5) for Ca(2+) activation of the shuttle in heart mitochondria is about 300 nm, and it remains essentially unchanged in citrin-deficient mice, although it undergoes a drastic reduction to about 100 nm in aralar-deficient mice. Therefore, aralar and citrin, when expressed as single isoforms in heart, confer differences in Ca(2+) activation of shuttle activity, probably associated with their structural differences. In addition, the results reveal that the two AGCs fully account for shuttle activity in mouse heart mitochondria and that no other glutamate transporter can replace the AGCs in this pathway.
Collapse
Affiliation(s)
- Laura Contreras
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, C.S.I.C., 28049 Madrid, Spain
| | | | | | | | | | | |
Collapse
|
10
|
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
|
11
|
Li CY, Liu JZ, Wu LP, Li B, Chen LF. Effects of hypobaric hypoxia on adenine nucleotide pools, adenine nucleotide transporter activity and protein expression in rat liver. World J Gastroenterol 2006; 12:2120-4. [PMID: 16610068 PMCID: PMC4087696 DOI: 10.3748/wjg.v12.i13.2120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the effect of hypobaric hypoxia on mitochondrial energy metabolism in rat liver.
METHODS: Adult male Wistar rats were exposed to a hypobaric chamber simulating 5000 m high altitude for 23 h every day for 0 (H0), 1 (H1), 5 (H5), 15 (H15) and 30 d (H30) respectively. Rats were sacrificed by decapitation and liver was removed. Liver mitochondria were isolated by differential centrifugation program. The size of adenine nucleotide pool (ATP, ADP, and AMP) in tissue and mitochondria was separated and measured by high performance liquid chromatography (HPLC). The adenine nucleotide transporter (ANT) activity was determined by isotopic technique. The ANT total protein level was determined by Western blot.
RESULTS: Compared with H0 group, intra-mitochondrial ATP content decreased in all hypoxia groups. However, the H5 group reached the lowest point (70.6%) (P < 0.01) when compared to the control group. Intra-mitochondrial ADP and AMP level showed similar change in all hypoxia groups and were significantly lower than that in H0 group. In addition, extra-mitochondrial ATP and ADP content decreased significantly in all hypoxia groups. Furthermore, extra-mitochondrial AMP in groups H5, H15 and H30 was significantly lower than that in H0 group, whereas H1 group had no marked change compared to the control situation. The activity of ANT in hypoxia groups decreased significantly, which was the lowest in H5 group (55.7%) (P < 0.01) when compared to H0 group. ANT activity in H30 group was higher than in H15 group, but still lower than that in H0 group. ANT protein level in H5, H15, H30 groups, compared with H0 group decreased significantly, which in H5 group was the lowest, being 27.1% of that in H0 group (P < 0.01). ANT protein level in H30 group was higher than in H15 group, but still lower than in H0 group.
CONCLUSION: Hypobaric hypoxia decreases the mitochondrial ATP content in rat liver, while mitochondrial ATP level recovers during long-term hypoxia exposure. The lower level of extra-mitochondrial ATP may be related to the decrease of ANT activity during hypoxia exposure.
Collapse
Affiliation(s)
- Cong-Yang Li
- Department of Pathophysiology, Institute of High Altitude Military Medicine, Third Military Medical University, Chongqing 400038, China
| | | | | | | | | |
Collapse
|
12
|
Cavero S, Traba J, Del Arco A, Satrústegui J. The calcium-dependent ATP-Mg/Pi mitochondrial carrier is a target of glucose-induced calcium signalling in Saccharomyces cerevisiae. Biochem J 2006; 392:537-44. [PMID: 16111475 PMCID: PMC1316293 DOI: 10.1042/bj20050806] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Sal1p is a mitochondrial protein that belongs to the SCaMC (short calcium-binding mitochondrial carrier) subfamily of mitochondrial carriers. The presence of calcium-binding motifs facing the extramitochondrial space allows the regulation of the transport activity of these carriers by cytosolic calcium and provides a new mechanism to transduce calcium signals in mitochondria without the requirement of calcium entry in the organelle. We have studied its transport activity, finding that it is a carboxyatractyloside-resistant ATP-Mg carrier. Mitochondria from a disruption mutant of SAL1 have a 50% reduction in the uptake of ATP. We have also found a clear stimulation of ATP-transport activity by calcium, with an S(0.5) of approx. 30 microM. Our results also suggest that Sal1p is a target of the glucose-induced calcium signal which is non-essential in wild-type cells, but becomes essential for transport of ATP into mitochondria in yeast lacking ADP/ATP translocases.
Collapse
Affiliation(s)
- Santiago Cavero
- *Departamento de Biología Molecular, Centro de Biología Molecular “Severo Ochoa” UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, 28049 Madrid, Spain
| | - Javier Traba
- *Departamento de Biología Molecular, Centro de Biología Molecular “Severo Ochoa” UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, 28049 Madrid, Spain
| | - Araceli Del Arco
- *Departamento de Biología Molecular, Centro de Biología Molecular “Severo Ochoa” UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, 28049 Madrid, Spain
- †Área de Bioquímica, Centro Regional de Investigaciones Biomédicas (CRIB), Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Av. Carlos III s/n, 45071 Toledo, Spain
| | - Jorgina Satrústegui
- *Departamento de Biología Molecular, Centro de Biología Molecular “Severo Ochoa” UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, 28049 Madrid, Spain
- To whom correspondence should be addressed (email )
| |
Collapse
|
13
|
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
|
14
|
Ainscow EK, Brand MD. The responses of rat hepatocytes to glucagon and adrenaline. Application of quantified elasticity analysis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 265:1043-55. [PMID: 10518800 DOI: 10.1046/j.1432-1327.1999.00820.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The internal control of hepatocyte metabolism has been previously analysed using metabolic control analysis. The aim of this paper is to extend this analysis to include the responses of the cells to hormonal stimulus. Hepatocyte metabolism was divided into nine reaction blocks: glycogen breakdown, glucose release, glycolysis, lactate production, NADH oxidation, pyruvate oxidation, proton leak, mitochondrial phosphorylation and ATP consumption, linked by five intermediates: mitochondrial membrane potential, cytoplasmic NADH/NAD and total cellular ATP, glucose 6-phosphate and pyruvate. The kinetic responses of the reaction blocks to the intermediates were determined previously in the absence of added hormones. In this study, the changes in flux and intermediate levels that occurred upon addition of either glucagon or adrenaline were measured. From comparison of the fractional changes in fluxes and intermediate levels with the known kinetics of the system, it was possible to determine the primary sites of action of the hormones. The results show that the majority of processes in the cell are responsive to the hormones. The notable exception to this is the failure of adrenaline to have a direct effect on glycolysis. The activity change of each metabolic block observed in the presence of either hormone was quantified and compared to the indirect effects on each block caused by changes in metabolite levels. The second stage of the analysis was to use the calculated activity changes and the known control pattern of the system to give a semiquantitative analysis of the regulatory pathways employed by the hormones to achieve the changes in fluxes and metabolite levels. This was instructive in analysing, for example, how glucagon caused a decrease in flux through glycolysis and an increase in oxidative phosphorylation without large changes in metabolite levels (homeostasis). Conversely, it could be seen that the failure of adrenaline to maintain a constant glucose 6-phosphate concentration was due to the stimulation of glycogen breakdown and inhibition of glucose release.
Collapse
Affiliation(s)
- E K Ainscow
- Department of Biochemistry, University of Cambridge, UK.
| | | |
Collapse
|
15
|
Schild L, Blair PV, Davis WI, Baugh S. Effect of adenine nucleotide pool size in mitochondria on intramitochondrial ATP levels. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1413:14-20. [PMID: 10524260 DOI: 10.1016/s0005-2728(99)00074-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Net adenine nucleotide transport into and out of the mitochondrial matrix via the ATP-Mg/Pi carrier is activated by micromolar calcium concentrations in rat liver mitochondria. The purpose of this study was to induce net adenine nucleotide transport by varying the substrate supply and/or extramitochondrial ATP consumption in order to evaluate the effect of the mitochondrial adenine nucleotide pool size on intramitochondrial adenine nucleotide patterns under phosphorylating conditions. Above 12 nmol/mg protein, intramitochondrial ATP/ADP increased with an increase in the mitochondrial adenine nucleotide pool. The relationship between the rate of respiration and the mitochondrial ADP concentration did not depend on the mitochondrial adenine nucleotide pool size up to 9 nmol ADP/mg mitochondrial protein. The results are compatible with the notion that net uptake of adenine nucleotides at low energy states supports intramitochondrial ATP consuming processes and energized mitochondria may lose adenine nucleotides. The decrease of the mitochondrial adenine nucleotide content below 9 nmol/mg protein inhibits oxidative phosphorylation. In particular, this could be the case within the postischemic phase which is characterized by low cytosolic adenine nucleotide concentrations and energized mitochondria.
Collapse
Affiliation(s)
- L Schild
- Institut für Klinische Chemie, Medizinische Fakultät der Otto-von Guericke-Universität Magdeburg, Germany.
| | | | | | | |
Collapse
|
16
|
Weber FE, Minestrini G, Dyer JH, Werder M, Boffelli D, Compassi S, Wehrli E, Thomas RM, Schulthess G, Hauser H. Molecular cloning of a peroxisomal Ca2+-dependent member of the mitochondrial carrier superfamily. Proc Natl Acad Sci U S A 1997; 94:8509-14. [PMID: 9238007 PMCID: PMC22978 DOI: 10.1073/pnas.94.16.8509] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/1996] [Accepted: 05/29/1997] [Indexed: 02/04/2023] Open
Abstract
A cDNA from a novel Ca2+-dependent member of the mitochondrial solute carrier superfamily was isolated from a rabbit small intestinal cDNA library. The full-length cDNA clone was 3,298 nt long and coded for a protein of 475 amino acids, with four elongation factor-hand motifs located in the N-terminal half of the molecule. The 25-kDa N-terminal polypeptide was expressed in Escherichia coli, and it was demonstrated that it bound Ca2+, undergoing a reversible and specific conformational change as a result. The conformation of the polypeptide was sensitive to Ca2+ which was bound with high affinity (Kd approximately 0.37 microM), the apparent Hill coefficient for Ca2+-induced changes being about 2.0. The deduced amino acid sequence of the C-terminal half of the molecule revealed 78% homology to Grave disease carrier protein and 67% homology to human ADP/ATP translocase; this sequence homology identified the protein as a new member of the mitochondrial transporter superfamily. Northern blot analysis revealed the presence of a single transcript of about 3,500 bases, and low expression of the transporter could be detected in the kidney but none in the liver. The main site of expression was the colon with smaller amounts found in the small intestine proximal to the ileum. Immunoelectron microscopy localized the transporter in the peroxisome, although a minor fraction was found in the mitochondria. The Ca2+ binding N-terminal half of the transporter faces the cytosol.
Collapse
Affiliation(s)
- F E Weber
- Klinik für Gesichts-und Kieferchirurgie, Universitätsspital Zürich, Frauenklinikstrasse 10, 8091 Zurich, Switzerland.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
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
|
18
|
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
|
19
|
Abstract
The ATP-Mg/Pi carrier in liver mitochondria is activated by micromolar Ca2+ and mediates net adenine nucleotide transport into and out of the mitochondrial matrix. The purpose of this study was to characterize certain features of ATP-Mg/Pi carrier activity that are essential for understanding how the mitochondrial adenine nucleotide content is regulated. The relative importance of ATP and ADP as transport substrates was investigated using specific trap assays to measure their separate rates of carrier-mediated efflux with Pi as the external counterion. Under energized conditions ATP efflux accounted for 88% of total ATP+ADP efflux. With oligomycin present to lower the matrix ATP/ADP ratio, ATP efflux was eliminated and ADP efflux was relatively unaffected. Mg2+ was stoichiometrically required for ATP influx and is probably transported simultaneously with ATP. Ca2+ and Mn2+ could substitute for the stoichiometric Mg2+ requirement. ADP influx and Pi-induced adenine nucleotide efflux were unaffected by external Mg2+. Experiments with Pi analogues suggested that Pi is transported as the divalent anion, HPO4(2-). The results show that ATP-Mg and divalent Pi are the major transport substrates; the most probable transport mechanism for the ATP-Mg/Pi carrier is an electroneutral exchange. The results are consistent with the hypothesis that the direction and magnitude of net adenine nucleotide movements are determined mainly by the (ATP-Mg)2- and HPO4(2-) concentration gradients across the inner mitochondrial membrane.
Collapse
Affiliation(s)
- M T Nosek
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| | | |
Collapse
|
20
|
Chapter 18 Hormonal regulation of cellular energy metabolism. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/s0167-7306(08)60186-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
21
|
The role of the matrix calcium level in the enhancement of mitochondrial pyruvate carboxylation by glucagon pretreatment. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)48504-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
22
|
Ayoub S, Monin G, Rock E, Younes A. Impairment of ATP-linked reactions in mitochondria isolated from skeletal muscle of halothane-sensitive pigs. Cell Biochem Funct 1990; 8:205-10. [PMID: 2272118 DOI: 10.1002/cbf.290080404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Oxygen consumption was depressed in mitochondria isolated from halothane sensitive pig (HP) muscle. The calculation of the respiratory control ratio (RCR) indicated that mitochondria were more affected at the site-I level of the respiratory chain. Calcium accumulation in these mitochondria was not altered when driven by the oxidation of succinate. This process was abolished when linked to ATP as a source of energy. ATP transport was completely inhibited in (HP) mitochondria.
Collapse
Affiliation(s)
- S Ayoub
- Institut National de Recherche Agronomique (INRA), Ceyrat, France
| | | | | | | |
Collapse
|
23
|
|
24
|
Asimakis GK, Sandhu GS, Conti VR, Sordahl LA, Zwischenberger JB. Intermittent ischemia produces a cumulative depletion of mitochondrial adenine nucleotides in the isolated perfused rat heart. Circ Res 1990; 66:302-10. [PMID: 2297805 DOI: 10.1161/01.res.66.2.302] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The purpose of the present study was to determine if repetitive myocardial ischemia would result in the cumulative loss of mitochondrial adenine nucleotides. Isolated perfused rat hearts were subjected to continuous or intermittent ischemia. A single 5-minute period of continuous ischemia did not result in a significant decrease in the mitochondrial adenine nucleotide pool; a single 10-minute period of ischemia resulted in a decrease of approximately 17%. Next, the adenine nucleotide content of mitochondria from preischemic and 30-minute continuous ischemic hearts was compared with two groups of hearts undergoing intermittent ischemia (both groups receiving a total of 30 minutes of ischemia). One group received three 10-minute episodes of ischemia interrupted by 5-minute periods of reperfusion (3 x 10-minute intermittent ischemia); the other intermittent ischemic group received six 5-minute episodes of ischemia interrupted by 5-minute periods of perfusion (6 x 5-minute intermittent ischemia). The mitochondrial adenine nucleotide content (expressed as nanomoles per nanomole cytochrome a) for the preischemic and 30-minute continuous ischemic hearts was 14.7 +/- 0.6 and 8.0 +/- 0.4, respectively. The mitochondrial adenine nucleotide content of the 3 x 10-minute intermittent ischemia group (8.5 +/- 0.5) was not significantly different from the 30-minute continuous ischemic group. The mitochondrial adenine nucleotide content of the 6 x 5-minute intermittent ischemia group (11.0 +/- 0.6) was significantly larger than that of the 30-minute continuous and the 3 x 10-minute intermittent ischemia groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- G K Asimakis
- Department of Surgery, University of Texas Medical Branch, Galveston 77550
| | | | | | | | | |
Collapse
|
25
|
Bronnikov G, Vinogradova S, Mezentseva V. Changes in kinetics of ATP-synthetase and in concentrations of adenine nucleotides in ground squirrel liver mitochondria during hibernation. ACTA ACUST UNITED AC 1990. [DOI: 10.1016/0305-0491(90)90137-i] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
26
|
Halestrap AP. The regulation of the matrix volume of mammalian mitochondria in vivo and in vitro and its role in the control of mitochondrial metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 973:355-82. [PMID: 2647140 DOI: 10.1016/s0005-2728(89)80378-0] [Citation(s) in RCA: 369] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The purpose of this article is to describe briefly the methods by which the intra-mitochondrial volume may be measured both in vitro and in situ, to summarise the mechanisms thought to regulate the mitochondrial volume and then to review in more detail the evidence that changes in the intra-mitochondrial volume play an important part in the regulation of liver mitochondrial metabolism by glucogenic hormones such as glucagon, adrenaline and vasopressin. It will be shown that these hormones cause an increase in matrix volume sufficient to produce significant activation of fatty acid oxidation, respiration and ATP production, pyruvate carboxylation, citrulline synthesis and glutamine hydrolysis. These are all processes activated by such hormones in vivo. I will go on to demonstrate that the increase in matrix volume is brought about by an increase in mitochondrial [PPi]. This is able to stimulate K+ entry into the matrix, perhaps through an interaction with the adenine nucleotide translocase. The rise in matrix [PPi] is a consequence of an increase in cytosolic and hence mitochondrial [Ca2+] which inhibits mitochondrial pyrophosphatase. In the final section of the review I provide evidence that changes in mitochondrial volume may be important in the responses of a variety of tissues to hormones and other stimuli. I write as a metabolist with a working knowledge of bioenergetics rather than the converse, and this will certainly be reflected in the approach taken. If I cause offence to any dedicated experts in the field of bioenergetic by my ignorance or lack of understanding of their studies I can only offer my apologies and ask to be corrected.
Collapse
Affiliation(s)
- A P Halestrap
- Department of Biochemistry, University of Bristol, U.K
| |
Collapse
|