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Uthayabalan S, Lake T, Stathopulos PB. MRS2 missense variation at Asp216 abrogates inhibitory Mg 2+ binding, potentiating cell migration and apoptosis resistance. Protein Sci 2024; 33:e5108. [PMID: 38989547 PMCID: PMC11237551 DOI: 10.1002/pro.5108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 06/06/2024] [Accepted: 06/24/2024] [Indexed: 07/12/2024]
Abstract
Mitochondrial magnesium (Mg2+) is a crucial modulator of protein stability, enzymatic activity, ATP synthesis, and cell death. Mitochondrial RNA splicing protein 2 (MRS2) is the main Mg2+ channel in the inner mitochondrial membrane that mediates influx into the matrix. Recent cryo-electron microscopy (cryo-EM) human MRS2 structures exhibit minimal conformational changes at high and low Mg2+, yet the regulation of human MRS2 and orthologues by Mg2+ binding to analogous matrix domains has been well established. Further, a missense variation at D216 has been identified associated with malignant melanoma and MRS2 expression and activity is implicated in gastric cancer. Thus, to gain more mechanistic and functional insight into Mg2+ sensing by the human MRS2 matrix domain and the association with proliferative disease, we assessed the structural, biophysical, and functional effects of a D216Q mutant. We show that the D216Q mutation is sufficient to abrogate Mg2+-binding and associated conformational changes including increased α-helicity, stability, and monomerization. Further, we reveal that the MRS2 matrix domains interact with ~μM affinity, which is weakened by up to two orders of magnitude in the presence of Mg2+ for wild-type but unaffected for D216Q. Finally, we demonstrate the importance of Mg2+ sensing by MRS2 to prevent matrix Mg2+ overload as HeLa cells overexpressing MRS2 show enhanced Mg2+ uptake, cell migration, and resistance to apoptosis while MRS2 D216Q robustly potentiates these cancer phenotypes. Collectively, our findings further define the MRS2 matrix domain as a critical Mg2+ sensor that undergoes conformational and assembly changes upon Mg2+ interactions dependent on D216 to temper matrix Mg2+ overload.
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Affiliation(s)
- Sukanthathulse Uthayabalan
- Department of Physiology and Pharmacology, Schulich School of Medicine and DentistryUniversity of Western OntarioLondonOntarioCanada
| | - Taylor Lake
- Department of Physiology and Pharmacology, Schulich School of Medicine and DentistryUniversity of Western OntarioLondonOntarioCanada
| | - Peter B. Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and DentistryUniversity of Western OntarioLondonOntarioCanada
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2
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Peng M, Mathew ND, Anderson VE, Falk MJ, Nakamaru-Ogiso E. N-Glycosylation of MRS2 balances aerobic and anaerobic energy production by reducing rapid mitochondrial Mg 2+ influx in conditions of high glucose or impaired respiratory chain function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.09.602756. [PMID: 39026824 PMCID: PMC11257584 DOI: 10.1101/2024.07.09.602756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
N-linked glycoproteins function in numerous biological processes, modulating enzyme activities as well as protein folding, stability, oligomerization, and trafficking. While N-glycosylation of mitochondrial proteins has been detected by untargeted MS-analyses, the physiological existence and roles of mitochondrial protein N-linked glycosylation remain under debate. Here, we report that MRS2, a mitochondrial inner membrane protein that functions as the high flux magnesium transporter, is N-glycosylated to various extents depending on cellular bioenergetic status. Both N-glycosylated and unglycosylated isoforms were consistently detected in mitochondria isolated from mouse liver, rat and mouse liver fibroblast cells (BRL 3A and AFT024, respectively) as well as human skin fibroblast cells. Immunoblotting of MRS2 showed it was bound to, and required stringent elution conditions to remove from, lectin affinity columns with covalently bound concanavalin A or Lens culinaris agglutinin. Following peptide:N-glycosidase F (PNGase F) digestion of the stringently eluted proteins, the higher Mr MRS2 bands gel-shifted to lower Mr and loss of lectin affinity was seen. BRL 3A cells treated with two different N-linked glycosylation inhibitors, tunicamycin or 6-diazo-5-oxo-l-norleucine, resulted in decreased intensity or loss of the higher Mr MRS2 isoform. To investigate the possible functional role of MRS2 N- glycosylation, we measured rapid Mg2+ influx capacity in intact mitochondria isolated from BRL 3A cells in control media or following treatment with tunicamycin or 6-diazo-5-oxo-l-norleucine. Interestingly, rapid Mg2+ influx capacity increased in mitochondria isolated from BRL 3A cells treated with either N-glycosylation inhibitor. Forcing reliance on mitochondrial respiration by treatment with either galactose media or the glycolytic inhibitor 2-deoxyglucose or by minimizing glucose concentration similarly reduced the N-glycosylated isoform of MRS2, with a correlated concomitant increase in rapid Mg2+ influx capacity. Conversely, inhibiting mitochondrial energy production in BRL 3A cells with either rotenone or oligomycin resulted in an increased fraction of N-glycosylated MRS2, with decreased rapid Mg2+ influx capacity. Collectively, these data provide strong evidence that MRS2 N-glycosylation is directly involved in the regulation of mitochondrial matrix Mg2+, dynamically communicating relative cellular nutrient status and bioenergetic capacity by serving as a physiologic brake on the influx of mitochondrial matrix Mg2+ under conditions of glucose excess or mitochondrial bioenergetic impairment.
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Affiliation(s)
- Min Peng
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104
| | - Neal D. Mathew
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104
| | - Vernon E. Anderson
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104
| | - Marni J. Falk
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
| | - Eiko Nakamaru-Ogiso
- Mitochondrial Medicine Frontier Program, Division of Human Genetics, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104
- Department of Pediatrics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
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3
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He Z, Tu YC, Tsai CW, Mount J, Zhang J, Tsai MF, Yuan P. Structure and function of the human mitochondrial MRS2 channel. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.12.553106. [PMID: 37645897 PMCID: PMC10462007 DOI: 10.1101/2023.08.12.553106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The human Mitochondrial RNA Splicing 2 protein (MRS2) has been implicated in Mg2+ transport across mitochondrial inner membranes, thus playing an important role in Mg2+ homeostasis critical for mitochondrial integrity and function. However, the molecular mechanisms underlying its fundamental channel properties such as ion selectivity and regulation remain unclear. Here, we present structural and functional investigation of MRS2. Cryo-electron microscopy structures in various ionic conditions reveal a pentameric channel architecture and the molecular basis of ion permeation and potential regulation mechanisms. Electrophysiological analyses demonstrate that MRS2 is a Ca2+-regulated, non-selective channel permeable to Mg2+, Ca2+, Na+ and K+, which contrasts with its prokaryotic ortholog, CorA, operating as a Mg2+-gated Mg2+ channel. Moreover, a conserved arginine ring within the pore of MRS2 functions to restrict cation movements, likely preventing the channel from collapsing the proton motive force that drives mitochondrial ATP synthesis. Together, our results provide a molecular framework for further understanding MRS2 in mitochondrial function and disease.
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Affiliation(s)
- Zhihui He
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- These authors contributed equally to this work
| | - Yung-Chi Tu
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- These authors contributed equally to this work
| | - Chen-Wei Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Jonathan Mount
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Ming-Feng Tsai
- Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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4
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Uthayabalan S, Vishnu N, Madesh M, Stathopulos PB. The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity. Life Sci Alliance 2023; 6:e202201742. [PMID: 36754568 PMCID: PMC9909464 DOI: 10.26508/lsa.202201742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 01/25/2023] [Accepted: 01/26/2023] [Indexed: 02/10/2023] Open
Abstract
Mitochondrial RNA splicing 2 (MRS2) forms a magnesium (Mg2+) entry protein channel in mitochondria. Whereas MRS2 contains two transmembrane domains constituting a pore on the inner mitochondrial membrane, most of the protein resides within the matrix. Yet, the precise structural and functional role of this obtrusive amino terminal domain (NTD) in human MRS2 is unknown. Here, we show that the MRS2 NTD self-associates into a homodimer, contrasting the pentameric assembly of CorA, an orthologous bacterial channel. Mg2+ and calcium suppress lower and higher order oligomerization of MRS2 NTD, whereas cobalt has no effect on the NTD but disassembles full-length MRS2. Mutating-pinpointed residues-mediating Mg2+ binding to the NTD not only selectively decreases Mg2+-binding affinity ∼sevenfold but also abrogates Mg2+ binding-induced secondary, tertiary, and quaternary structure changes. Disruption of NTD Mg2+ binding strikingly potentiates mitochondrial Mg2+ uptake in WT and Mrs2 knockout cells. Our work exposes a mechanism for human MRS2 autoregulation by negative feedback from the NTD and identifies a novel gain of function mutant with broad applicability to future Mg2+ signaling research.
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Affiliation(s)
- Sukanthathulse Uthayabalan
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
| | - Neelanjan Vishnu
- Center for Mitochondrial Medicine, Department of Medicine, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Muniswamy Madesh
- Center for Mitochondrial Medicine, Department of Medicine, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada
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5
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Madaris TR, Venkatesan M, Maity S, Stein MC, Vishnu N, Venkateswaran MK, Davis JG, Ramachandran K, Uthayabalan S, Allen C, Osidele A, Stanley K, Bigham NP, Bakewell TM, Narkunan M, Le A, Karanam V, Li K, Mhapankar A, Norton L, Ross J, Aslam MI, Reeves WB, Singh BB, Caplan J, Wilson JJ, Stathopulos PB, Baur JA, Madesh M. Limiting Mrs2-dependent mitochondrial Mg 2+ uptake induces metabolic programming in prolonged dietary stress. Cell Rep 2023; 42:112155. [PMID: 36857182 PMCID: PMC10134742 DOI: 10.1016/j.celrep.2023.112155] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 10/28/2022] [Accepted: 02/08/2023] [Indexed: 03/02/2023] Open
Abstract
The most abundant cellular divalent cations, Mg2+ (mM) and Ca2+ (nM-μM), antagonistically regulate divergent metabolic pathways with several orders of magnitude affinity preference, but the physiological significance of this competition remains elusive. In mice consuming a Western diet, genetic ablation of the mitochondrial Mg2+ channel Mrs2 prevents weight gain, enhances mitochondrial activity, decreases fat accumulation in the liver, and causes prominent browning of white adipose. Mrs2 deficiency restrains citrate efflux from the mitochondria, making it unavailable to support de novo lipogenesis. As citrate is an endogenous Mg2+ chelator, this may represent an adaptive response to a perceived deficit of the cation. Transcriptional profiling of liver and white adipose reveals higher expression of genes involved in glycolysis, β-oxidation, thermogenesis, and HIF-1α-targets, in Mrs2-/- mice that are further enhanced under Western-diet-associated metabolic stress. Thus, lowering mMg2+ promotes metabolism and dampens diet-induced obesity and metabolic syndrome.
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Affiliation(s)
- Travis R Madaris
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Manigandan Venkatesan
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Soumya Maity
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Miriam C Stein
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Neelanjan Vishnu
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Mridula K Venkateswaran
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - James G Davis
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Philadelphia, PA 19103, USA
| | - Karthik Ramachandran
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | | | - Cristel Allen
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Ayodeji Osidele
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Kristen Stanley
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Nicholas P Bigham
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Terry M Bakewell
- Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Melanie Narkunan
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Amy Le
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Varsha Karanam
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Kang Li
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Aum Mhapankar
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Luke Norton
- Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Jean Ross
- Department of Biological Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, DE 19711, USA
| | - M Imran Aslam
- Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - W Brian Reeves
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Brij B Singh
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Jeffrey Caplan
- Department of Biological Sciences, Delaware Biotechnology Institute, University of Delaware, Newark, DE 19711, USA
| | - Justin J Wilson
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Western University, London, ON N6A 5C1, Canada
| | - Joseph A Baur
- Department of Physiology and Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Philadelphia, PA 19103, USA.
| | - Muniswamy Madesh
- Department of Medicine, Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Department of Medicine, Cardiology/Diabetes Divisions, University of Texas Health San Antonio, San Antonio, TX 78229, USA.
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Abstract
Mitochondria have been recognized as key organelles in cardiac physiology and are potential targets for clinical interventions to improve cardiac function. Mitochondrial dysfunction has been accepted as a major contributor to the development of heart failure. The main function of mitochondria is to meet the high energy demands of the heart by oxidative metabolism. Ionic homeostasis in mitochondria directly regulates oxidative metabolism, and any disruption in ionic homeostasis causes mitochondrial dysfunction and eventually contractile failure. The mitochondrial ionic homeostasis is closely coupled with inner mitochondrial membrane potential. To regulate and maintain ionic homeostasis, mitochondrial membranes are equipped with ion transporting proteins. Ion transport mechanisms involving several different ion channels and transporters are highly efficient and dynamic, thus helping to maintain the ionic homeostasis of ions as well as their salts present in the mitochondrial matrix. In recent years, several novel proteins have been identified on the mitochondrial membranes and these proteins are actively being pursued in research for roles in the organ as well as organelle physiology. In this article, the role of mitochondrial ion channels in cardiac function is reviewed. In recent times, the major focus of the mitochondrial ion channel field is to establish molecular identities as well as assigning specific functions to them. Given the diversity of mitochondrial ion channels and their unique roles in cardiac function, they present novel and viable therapeutic targets for cardiac diseases.
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Affiliation(s)
- Harpreet Singh
- Department of Physiology and Cell Biology, The Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, Ohio
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7
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Jamsen JA, Sassa A, Shock DD, Beard WA, Wilson SH. Watching a double strand break repair polymerase insert a pro-mutagenic oxidized nucleotide. Nat Commun 2021; 12:2059. [PMID: 33824325 PMCID: PMC8024293 DOI: 10.1038/s41467-021-21354-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 12/08/2020] [Indexed: 01/07/2023] Open
Abstract
Oxidized dGTP (8-oxo-7,8-dihydro-2´-deoxyguanosine triphosphate, 8-oxodGTP) insertion by DNA polymerases strongly promotes cancer and human disease. How DNA polymerases discriminate against oxidized and undamaged nucleotides, especially in error-prone double strand break (DSB) repair, is poorly understood. High-resolution time-lapse X-ray crystallography snapshots of DSB repair polymerase μ undergoing DNA synthesis reveal that a third active site metal promotes insertion of oxidized and undamaged dGTP in the canonical anti-conformation opposite template cytosine. The product metal bridged O8 with product oxygens, and was not observed in the syn-conformation opposite template adenine (At). Rotation of At into the syn-conformation enabled undamaged dGTP misinsertion. Exploiting metal and substrate dynamics in a rigid active site allows 8-oxodGTP to circumvent polymerase fidelity safeguards to promote pro-mutagenic double strand break repair.
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Affiliation(s)
- Joonas A. Jamsen
- grid.280664.e0000 0001 2110 5790Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 USA
| | - Akira Sassa
- grid.136304.30000 0004 0370 1101Laboratory of Chromatin Metabolism and Epigenetics, Graduate School of Science, Chiba University, Chiba, Japan
| | - David D. Shock
- grid.280664.e0000 0001 2110 5790Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 USA
| | - William A. Beard
- grid.280664.e0000 0001 2110 5790Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 USA
| | - Samuel H. Wilson
- grid.280664.e0000 0001 2110 5790Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 USA
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8
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Stelling MP, Motta JM, Mashid M, Johnson WE, Pavão MS, Farrell NP. Metal ions and the extracellular matrix in tumor migration. FEBS J 2020; 286:2950-2964. [PMID: 31379111 DOI: 10.1111/febs.14986] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 05/22/2019] [Accepted: 07/06/2019] [Indexed: 12/15/2022]
Abstract
In this review, we explore the roles of divalent metal ions in structure and function within the extracellular matrix (ECM), specifically, their interaction with glycosaminoglycans (GAGs) during tumor progression. Metals and GAGs have been individually associated with physiological and pathological processes, however, their combined activities in regulating cell behavior and ECM remodeling have not been fully explored to date. During tumor progression, divalent metals and GAGs participate in central processes, such as cell migration and angiogenesis, either by modulating cell surface molecules, as well as soluble signaling factors. In addition, studies on metals and polysaccharides interactions have been of great value, as they provide structural information that can be correlated with function. Finally, we believe that understanding how metals are regulated in physiological and pathological conditions is paramount for the development of new treatment strategies, as well as diagnostic and exploratory tools.
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Affiliation(s)
- Mariana P Stelling
- Instituto Federal de Educacao, Educação, Ciência e Tecnologia do Rio de Janeiro, Brazil
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9
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Precipitation of Inorganic Salts in Mitochondrial Matrix. MEMBRANES 2020; 10:membranes10050081. [PMID: 32349446 PMCID: PMC7281443 DOI: 10.3390/membranes10050081] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/17/2020] [Accepted: 04/19/2020] [Indexed: 11/17/2022]
Abstract
In the mitochondrial matrix, there are insoluble, osmotically inactive complexes that maintain a constant pH and calcium concentration. In the present paper, we examine the properties of insoluble calcium and magnesium salts, such as phosphates, carbonates and polyphosphates, which might play this role. We find that non-stoichiometric, magnesium-rich carbonated apatite, with very low crystallinity, precipitates in the matrix under physiological conditions. Precipitated salt acts as pH buffer, and, hence, can contribute in maintaining ATP production in ischemic conditions, which delays irreversible damage to heart and brain cells after stroke.
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10
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Magnesium Is a Key Player in Neuronal Maturation and Neuropathology. Int J Mol Sci 2019; 20:ijms20143439. [PMID: 31336935 PMCID: PMC6678825 DOI: 10.3390/ijms20143439] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 07/06/2019] [Accepted: 07/09/2019] [Indexed: 01/05/2023] Open
Abstract
Magnesium (Mg) is the second most abundant cation in mammalian cells, and it is essential for numerous cellular processes including enzymatic reactions, ion channel functions, metabolic cycles, cellular signaling, and DNA/RNA stabilities. Because of the versatile and universal nature of Mg2+, the homeostasis of intracellular Mg2+ is physiologically linked to growth, proliferation, differentiation, energy metabolism, and death of cells. On the cellular and tissue levels, maintaining Mg2+ within optimal levels according to the biological context, such as cell types, developmental stages, extracellular environments, and pathophysiological conditions, is crucial for development, normal functions, and diseases. Hence, Mg2+ is pathologically involved in cancers, diabetes, and neurodegenerative diseases, such as Parkinson's disease, Alzheimer's disease, and demyelination. In the research field regarding the roles and mechanisms of Mg2+ regulation, numerous controversies caused by its versatility and complexity still exist. As Mg2+, at least, plays critical roles in neuronal development, healthy normal functions, and diseases, appropriate Mg2+ supplementation exhibits neurotrophic effects in a majority of cases. Hence, the control of Mg2+ homeostasis can be a candidate for therapeutic targets in neuronal diseases. In this review, recent results regarding the roles of intracellular Mg2+ and its regulatory system in determining the cell phenotype, fate, and diseases in the nervous system are summarized, and an overview of the comprehensive roles of Mg2+ is provided.
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11
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Jiao H, Yin Y, Liu Z. Structures of the Mitochondrial CDP-DAG Synthase Tam41 Suggest a Potential Lipid Substrate Pathway from Membrane to the Active Site. Structure 2019; 27:1258-1269.e4. [PMID: 31178220 DOI: 10.1016/j.str.2019.04.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 03/14/2019] [Accepted: 04/29/2019] [Indexed: 11/18/2022]
Abstract
In mitochondria, CDP-diacylglycerol (CDP-DAG) is a crucial precursor for cardiolipin biosynthesis. Mitochondrial CDP-DAG is synthesized by the translocator assembly and maintenance protein 41 (Tam41) through an elusive process. Here we show that Tam41 adopts sequential catalytic mechanism, and report crystal structures of the bulk N-terminal region of Tam41 from Schizosaccharomyces pombe in the apo and CTP-bound state. The structure reveals that Tam41 contains a nucleotidyltransferase (NTase) domain and a winged helix domain. CTP binds to an "L"-shaped pocket sandwiched between the two domains. Rearrangement of a loop region near the active site is essential for opening the CTP-binding pocket. Docking of phosphatidic acid/CDP-DAG in the structure suggests a lipid entry/exit pathway connected to the "L"-shaped pocket. The C-terminal region of SpTam41 contains a positively charged amphipathic helix crucial for membrane association and participates in binding phospholipids. These results provide detailed insights into the mechanism of CDP-DAG biosynthesis in mitochondria.
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Affiliation(s)
- Haizhan Jiao
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Beijing 100101, China; University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China
| | - Yan Yin
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Beijing 100101, China; University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China
| | - Zhenfeng Liu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, No. 15 Datun Road, Beijing 100101, China; University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China.
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12
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Chang YK, Huang YP, Liu XX, Ko TP, Bessho Y, Kawano Y, Maestre-Reyna M, Wu WJ, Tsai MD. Human DNA Polymerase μ Can Use a Noncanonical Mechanism for Multiple Mn 2+-Mediated Functions. J Am Chem Soc 2019; 141:8489-8502. [PMID: 31067051 DOI: 10.1021/jacs.9b01741] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Recent research on the structure and mechanism of DNA polymerases has continued to generate fundamentally important features, including a noncanonical pathway involving "prebinding" of metal-bound dNTP (MdNTP) in the absence of DNA. While this noncanonical mechanism was shown to be a possible subset for African swine fever DNA polymerase X (Pol X) and human Pol λ, it remains unknown whether it could be the primary pathway for a DNA polymerase. Pol μ is a unique member of the X-family with multiple functions and with unusual Mn2+ preference. Here we report that Pol μ not only prebinds MdNTP in a catalytically active conformation but also exerts a Mn2+ over Mg2+ preference at this early stage of catalysis, for various functions: incorporation of dNTP into a single nucleotide gapped DNA, incorporation of rNTP in the nonhomologous end joining (NHEJ) repair, incorporation of dNTP to an ssDNA, and incorporation of an 8-oxo-dGTP opposite template dA (mismatched) or dC (matched). The structural basis of this noncanonical mechanism and Mn2+ over Mg2+ preference in these functions was analyzed by solving 19 structures of prebinding binary complexes, precatalytic ternary complexes, and product complexes. The results suggest that the noncanonical pathway is functionally relevant for the multiple functions of Pol μ. Overall, this work provides the structural and mechanistic basis for the long-standing puzzle in the Mn2+ preference of Pol μ and expands the landscape of the possible mechanisms of DNA polymerases to include both mechanistic pathways.
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Affiliation(s)
- Yao-Kai Chang
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan.,Institute of Biochemical Sciences , National Taiwan University , Taipei 106 , Taiwan
| | - Ya-Ping Huang
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan
| | - Xiao-Xia Liu
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan
| | - Tzu-Ping Ko
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan
| | - Yoshitaka Bessho
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan.,RIKEN SPring-8 Center , 1-1-1 Kouto , Sayo , Hyogo 679-5148 , Japan
| | - Yoshiaki Kawano
- RIKEN SPring-8 Center , 1-1-1 Kouto , Sayo , Hyogo 679-5148 , Japan
| | - Manuel Maestre-Reyna
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan
| | - Wen-Jin Wu
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan
| | - Ming-Daw Tsai
- Institute of Biological Chemistry, Academia Sinica , 128 Academia Road Sec. 2 , Nankang, Taipei 115 , Taiwan.,Institute of Biochemical Sciences , National Taiwan University , Taipei 106 , Taiwan
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13
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Magnesium Extravaganza: A Critical Compendium of Current Research into Cellular Mg 2+ Transporters Other than TRPM6/7. Rev Physiol Biochem Pharmacol 2018; 176:65-105. [PMID: 30406297 DOI: 10.1007/112_2018_15] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Magnesium research has boomed within the last 20 years. The real breakthrough came at the start of the new millennium with the discovery of a plethora of possible Mg homeostatic factors that, in particular, included putative Mg2+ transporters. Until that point, Mg research was limited to biochemical and physiological work, as no target molecular entities were known that could be used to explore the molecular biology of Mg homeostasis at the level of the cell, tissue, organ, or organism and to translate such knowledge into the field of clinical medicine and pharmacology. Because of the aforementioned, Mg2+ and Mg homeostasis, both of which had been heavily marginalized within the biomedical field in the twentieth century, have become overnight a focal point of many studies ranging from primary biomedical research to translational medicine.The amount of literature concerning cellular Mg2+ transport and cellular Mg homeostasis is increasing, together with a certain amount of confusion, especially about the function(s) of the newly discovered and, in the majority of instances, still only putative Mg2+ transporters/Mg2+ homeostatic factors. Newcomers to the field of Mg research will thus find it particularly difficult to orient themselves.Here, we briefly but critically summarize the status quo of the current understanding of the molecular entities behind cellular Mg2+ homeostasis in mammalian/human cells other than TRPM6/7 chanzymes, which have been universally accepted as being unspecific cation channel kinases allowing the flux of Mg2+ while constituting the major gateway for Mg2+ to enter the cell.
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14
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Alevriadou BR, Shanmughapriya S, Patel A, Stathopulos PB, Madesh M. Mitochondrial Ca 2+ transport in the endothelium: regulation by ions, redox signalling and mechanical forces. J R Soc Interface 2017; 14:rsif.2017.0672. [PMID: 29237825 DOI: 10.1098/rsif.2017.0672] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 11/16/2017] [Indexed: 02/07/2023] Open
Abstract
Calcium (Ca2+) transport by mitochondria is an important component of the cell Ca2+ homeostasis machinery in metazoans. Ca2+ uptake by mitochondria is a major determinant of bioenergetics and cell fate. Mitochondrial Ca2+ uptake occurs via the mitochondrial Ca2+ uniporter (MCU) complex, an inner mitochondrial membrane protein assembly consisting of the MCU Ca2+ channel, as its core component, and the MCU complex regulatory/auxiliary proteins. In this review, we summarize the current knowledge on the molecular nature of the MCU complex and its regulation by intra- and extramitochondrial levels of divalent ions and reactive oxygen species (ROS). Intracellular Ca2+ concentration ([Ca2+]i), mitochondrial Ca2+ concentration ([Ca2+]m) and mitochondrial ROS (mROS) are intricately coupled in regulating MCU activity. Here, we highlight the contribution of MCU activity to vascular endothelial cell (EC) function. Besides the ionic and oxidant regulation, ECs are continuously exposed to haemodynamic forces (either pulsatile or oscillatory fluid mechanical shear stresses, depending on the precise EC location within the arteries). Thus, we also propose an EC mechanotransduction-mediated regulation of MCU activity in the context of vascular physiology and atherosclerotic vascular disease.
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Affiliation(s)
- B Rita Alevriadou
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA .,Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH 43210, USA.,Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Santhanam Shanmughapriya
- Department of Medical Genetics and Molecular Biochemistry, Temple University, Philadelphia, PA 19140, USA.,Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Akshar Patel
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH 43210, USA.,Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH 43210, USA.,Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Western University, London, Ontario, Canada N6A 5C1
| | - Muniswamy Madesh
- Department of Medical Genetics and Molecular Biochemistry, Temple University, Philadelphia, PA 19140, USA .,Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
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15
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Morais MAB, Giuseppe PO, Souza TACB, Castro H, Honorato RV, Oliveira PSL, Netto LES, Tomas AM, Murakami MT. Calcium and magnesium ions modulate the oligomeric state and function of mitochondrial 2-Cys peroxiredoxins in Leishmania parasites. J Biol Chem 2017; 292:7023-7039. [PMID: 28292930 PMCID: PMC5409470 DOI: 10.1074/jbc.m116.762039] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 03/07/2017] [Indexed: 12/16/2022] Open
Abstract
Leishmania parasites have evolved a number of strategies to cope with the harsh environmental changes during mammalian infection. One of these mechanisms involves the functional gain that allows mitochondrial 2-Cys peroxiredoxins to act as molecular chaperones when forming decamers. This function is critical for parasite infectivity in mammals, and its activation has been considered to be controlled exclusively by the enzyme redox state under physiological conditions. Herein, we have revealed that magnesium and calcium ions play a major role in modulating the ability of these enzymes to act as molecular chaperones, surpassing the redox effect. These ions are directly involved in mitochondrial metabolism and participate in a novel mechanism to stabilize the decameric form of 2-Cys peroxiredoxins in Leishmania mitochondria. Moreover, we have demonstrated that a constitutively dimeric Prx1m mutant impairs the survival of Leishmania under heat stress, supporting the central role of the chaperone function of Prx1m for Leishmania parasites during the transition from insect to mammalian hosts.
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Affiliation(s)
- Mariana A B Morais
- From the Biosciences National Laboratory, National Center for Research in Energy and Materials, Rua Giuseppe Maximo Scolfaro 10000, 13083-100 Campinas/SP, Brazil
| | - Priscila O Giuseppe
- From the Biosciences National Laboratory, National Center for Research in Energy and Materials, Rua Giuseppe Maximo Scolfaro 10000, 13083-100 Campinas/SP, Brazil
| | - Tatiana A C B Souza
- the Proteomics and Protein Engineering Laboratory, Carlos Chagas Institute, Fiocruz, Rua Professor Algacyr Munhoz Mader 2135, 81310-020 Curitiba/PR, Brazil
| | - Helena Castro
- the i3S-Institute for Investigation and Innovation in Health, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- the Institute of Molecular and Cell Biology (IBMC), University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
| | - Rodrigo V Honorato
- From the Biosciences National Laboratory, National Center for Research in Energy and Materials, Rua Giuseppe Maximo Scolfaro 10000, 13083-100 Campinas/SP, Brazil
| | - Paulo S L Oliveira
- From the Biosciences National Laboratory, National Center for Research in Energy and Materials, Rua Giuseppe Maximo Scolfaro 10000, 13083-100 Campinas/SP, Brazil
| | - Luis E S Netto
- the Department of Genetics and Evolutionary Biology, Institute of Biosciences, University of the State of São Paulo, Rua do Matão 14, 05508-090 São Paulo/SP, Brazil, and
| | - Ana M Tomas
- the i3S-Institute for Investigation and Innovation in Health, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- the Institute of Molecular and Cell Biology (IBMC), University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal
- the Abel Salazar Biomedical Sciences Institute, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
| | - Mario T Murakami
- From the Biosciences National Laboratory, National Center for Research in Energy and Materials, Rua Giuseppe Maximo Scolfaro 10000, 13083-100 Campinas/SP, Brazil,
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16
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Lee SK, Shanmughapriya S, Mok MC, Dong Z, Tomar D, Carvalho E, Rajan S, Junop MS, Madesh M, Stathopulos PB. Structural Insights into Mitochondrial Calcium Uniporter Regulation by Divalent Cations. Cell Chem Biol 2016; 23:1157-1169. [PMID: 27569754 PMCID: PMC5035232 DOI: 10.1016/j.chembiol.2016.07.012] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/04/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022]
Abstract
Calcium (Ca(2+)) flux into the matrix is tightly controlled by the mitochondrial Ca(2+) uniporter (MCU) due to vital roles in cell death and bioenergetics. However, the precise atomic mechanisms of MCU regulation remain unclear. Here, we solved the crystal structure of the N-terminal matrix domain of human MCU, revealing a β-grasp-like fold with a cluster of negatively charged residues that interacts with divalent cations. Binding of Ca(2+) or Mg(2+) destabilizes and shifts the self-association equilibrium of the domain toward monomer. Mutational disruption of the acidic face weakens oligomerization of the isolated matrix domain and full-length human protein similar to cation binding and markedly decreases MCU activity. Moreover, mitochondrial Mg(2+) loading or blockade of mitochondrial Ca(2+) extrusion suppresses MCU Ca(2+)-uptake rates. Collectively, our data reveal that the β-grasp-like matrix region harbors an MCU-regulating acidic patch that inhibits human MCU activity in response to Mg(2+) and Ca(2+) binding.
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Affiliation(s)
- Samuel K. Lee
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, N6A 5C1
| | - Santhanam Shanmughapriya
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Mac C.Y. Mok
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada, L8S 4K1
| | - Zhiwei Dong
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Dhanendra Tomar
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Edmund Carvalho
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Sudarsan Rajan
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Murray S. Junop
- Department of Biochemistry, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, N6A 5C1
| | - Muniswamy Madesh
- Department of Molecular Genetics and Molecular Biochemistry, Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA, USA, 19140
| | - Peter B. Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, Western University, London, ON, Canada, N6A 5C1
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17
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Solute carrier 41A3 encodes for a mitochondrial Mg(2+) efflux system. Sci Rep 2016; 6:27999. [PMID: 27302215 PMCID: PMC4908428 DOI: 10.1038/srep27999] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 05/24/2016] [Indexed: 02/06/2023] Open
Abstract
The important role of magnesium (Mg2+) in normal cellular physiology requires flexible, yet tightly regulated, intracellular Mg2+ homeostasis (IMH). However, only little is known about Mg2+ transporters of subcellular compartments such as mitochondria, despite their obvious importance for the deposition and reposition of intracellular Mg2+ pools. In particular, knowledge about mechanisms responsible for extrusion of Mg2+ from mitochondria is lacking. Based on circumstantial evidence, two possible mechanisms of Mg2+ release from mitochondria were predicted: (1) Mg2+ efflux coupled to ATP translocation via the ATP-Mg/Pi carrier, and (2) Mg2+ efflux via a H+/Mg2+ exchanger. Regardless, the identity of the H+-coupled Mg2+ efflux system is unknown. We demonstrate here that member A3 of solute carrier (SLC) family 41 is a mitochondrial Mg2+ efflux system. Mitochondria of HEK293 cells overexpressing SLC41A3 exhibit a 60% increase in the extrusion of Mg2+ compared with control cells. This efflux mechanism is Na+-dependent and temperature sensitive. Our data identify SLC41A3 as the first mammalian mitochondrial Mg2+ efflux system, which greatly enhances our understanding of intracellular Mg2+ homeostasis.
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18
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MLKL forms cation channels. Cell Res 2016; 26:517-28. [PMID: 27033670 PMCID: PMC4856759 DOI: 10.1038/cr.2016.26] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 02/01/2016] [Accepted: 02/01/2016] [Indexed: 12/17/2022] Open
Abstract
The mixed lineage kinase domain-like (MLKL) protein is a key factor in tumor necrosis factor-induced necroptosis. Recent studies on necroptosis execution revealed a commitment role of MLKL in membrane disruption. However, our knowledge of how MLKL functions on membrane remains very limited. Here we demonstrate that MLKL forms cation channels that are permeable preferentially to Mg2+ rather than Ca2+ in the presence of Na+ and K+. Moreover, the N-terminal domain containing six helices (H1-H6) is sufficient to form channels. Using the substituted cysteine accessibility method, we further determine that helix H1, H2, H3, H5 and H6 are transmembrane segments, while H4 is located in the cytoplasm. Finally, MLKL-induced membrane depolarization and cell death exhibit a positive correlation to its channel activity. The Mg2+-preferred permeability and five transmembrane segment topology distinguish MLKL from previously identified Mg2+-permeable channels and thus establish MLKL as a novel class of cation channels.
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19
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Kantner K, Ashraf S, Carregal-Romero S, Carrillo-Carrion C, Collot M, Del Pino P, Heimbrodt W, De Aberasturi DJ, Kaiser U, Kazakova LI, Lelle M, de Baroja NM, Montenegro JM, Nazarenus M, Pelaz B, Peneva K, Gil PR, Sabir N, Schneider LM, Shabarchina LI, Sukhorukov GB, Vazquez M, Yang F, Parak WJ. Particle-based optical sensing of intracellular ions at the example of calcium - what are the experimental pitfalls? SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:896-904. [PMID: 25504784 DOI: 10.1002/smll.201402110] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/24/2014] [Indexed: 06/04/2023]
Abstract
Colloidal particles with fluorescence read-out are commonly used as sensors for the quantitative determination of ions. Calcium, for example, is a biologically highly relevant ion in signaling, and thus knowledge of its spatio-temporal distribution inside cells would offer important experimental data. However, the use of particle-based intracellular sensors for ion detection is not straightforward. Important associated problems involve delivery and intracellular location of particle-based fluorophores, crosstalk of the fluorescence read-out with pH, and spectral overlap of the emission spectra of different fluorophores. These potential problems are outlined and discussed here with selected experimental examples. Potential solutions are discussed and form a guideline for particle-based intracellular imaging of ions.
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Affiliation(s)
- Karsten Kantner
- Fachbereich Physik, Philipps- Universität Marburg, Marburg, Germany
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20
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Venø ST, Witt MB, Kulikowicz T, Bohr VA, Stevnsner T. Regulation of the human Suv3 helicase on DNA by inorganic cofactors. Biochimie 2014; 108:160-8. [PMID: 25446650 DOI: 10.1016/j.biochi.2014.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 11/05/2014] [Indexed: 11/19/2022]
Abstract
Mitochondria are essential organelles and consequently proper expression and maintenance of the mitochondrial genome are indispensable for proper cell function. The mitochondrial Suv3 (SUPV3L1) helicase is known to have a central role in mitochondrial RNA metabolism and to be essential for maintenance of mitochondrial DNA stability. Here we have performed biochemical investigations to determine the potential regulation of the human Suv3 (hSuv3) helicase function by inorganic cofactors. We find that hSuv3 helicase and ATPase activity in vitro is strictly dependent on the presence of specific divalent cations. Interestingly, we show that divalent cations and nucleotide concentration have a direct effect on helicase substrate stability. Also, hSuv3 helicase is able to utilize several different nucleotide cofactors including both NTPs and dNTPs. Intriguingly, the potency of the individual nucleotide as energy source for hSuv3 unwinding differed depending on the included divalent cation and nucleotide concentration. At low concentrations, all four NTPs could support helicase activity with varying effectiveness depending on the included divalent cation. However, at higher nucleotide concentrations, only ATP was able to elicit the helicase activity of hSuv3. Consequently, we speculate that the capacity of hSuv3 DNA unwinding activity might be sensitive to the local availability of specific inorganic cofactors.
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Affiliation(s)
- Susanne T Venø
- Danish Center of Molecular Gerontology and Danish Aging Research Center, University of Aarhus, Department of Molecular Biology and Genetics, Aarhus C DK-8000, Denmark
| | - Marie B Witt
- Danish Center of Molecular Gerontology and Danish Aging Research Center, University of Aarhus, Department of Molecular Biology and Genetics, Aarhus C DK-8000, Denmark
| | - Tomasz Kulikowicz
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Vilhelm A Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Tinna Stevnsner
- Danish Center of Molecular Gerontology and Danish Aging Research Center, University of Aarhus, Department of Molecular Biology and Genetics, Aarhus C DK-8000, Denmark.
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21
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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22
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Lindenburg LH, Vinkenborg JL, Oortwijn J, Aper SJA, Merkx M. MagFRET: the first genetically encoded fluorescent Mg2+ sensor. PLoS One 2013; 8:e82009. [PMID: 24312622 PMCID: PMC3846734 DOI: 10.1371/journal.pone.0082009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/29/2013] [Indexed: 01/14/2023] Open
Abstract
Magnesium has important structural, catalytic and signaling roles in cells, yet few tools exist to image this metal ion in real time and at subcellular resolution. Here we report the first genetically encoded sensor for Mg2+, MagFRET-1. This sensor is based on the high-affinity Mg2+ binding domain of human centrin 3 (HsCen3), which undergoes a transition from a molten-globular apo form to a compactly-folded Mg2+-bound state. Fusion of Cerulean and Citrine fluorescent domains to the ends of HsCen3, yielded MagFRET-1, which combines a physiologically relevant Mg2+ affinity (Kd = 148 µM) with a 50% increase in emission ratio upon Mg2+ binding due to a change in FRET efficiency between Cerulean and Citrine. Mutations in the metal binding sites yielded MagFRET variants whose Mg2+ affinities were attenuated 2- to 100-fold relative to MagFRET-1, thus covering a broad range of Mg2+ concentrations. In situ experiments in HEK293 cells showed that MagFRET-1 can be targeted to the cytosol and the nucleus. Clear responses to changes in extracellular Mg2+ concentration were observed for MagFRET-1-expressing HEK293 cells when they were permeabilized with digitonin, whereas similar changes were not observed for intact cells. Although MagFRET-1 is also sensitive to Ca2+, this affinity is sufficiently attenuated (Kd of 10 µM) to make the sensor insensitive to known Ca2+ stimuli in HEK293 cells. While the potential and limitations of the MagFRET sensors for intracellular Mg2+ imaging need to be further established, we expect that these genetically encoded and ratiometric fluorescent Mg2+ sensors could prove very useful in understanding intracellular Mg2+ homeostasis and signaling.
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Affiliation(s)
- Laurens H. Lindenburg
- Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Jan L. Vinkenborg
- Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Jorn Oortwijn
- Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Stijn J. A. Aper
- Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Maarten Merkx
- Laboratory of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- * E-mail:
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24
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Romani AMP. Cellular magnesium homeostasis. Arch Biochem Biophys 2011; 512:1-23. [PMID: 21640700 PMCID: PMC3133480 DOI: 10.1016/j.abb.2011.05.010] [Citation(s) in RCA: 354] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/16/2011] [Accepted: 05/17/2011] [Indexed: 12/12/2022]
Abstract
Magnesium, the second most abundant cellular cation after potassium, is essential to regulate numerous cellular functions and enzymes, including ion channels, metabolic cycles, and signaling pathways, as attested by more than 1000 entries in the literature. Despite significant recent progress, however, our understanding of how cells regulate Mg(2+) homeostasis and transport still remains incomplete. For example, the occurrence of major fluxes of Mg(2+) in either direction across the plasma membrane of mammalian cells following metabolic or hormonal stimuli has been extensively documented. Yet, the mechanisms ultimately responsible for magnesium extrusion across the cell membrane have not been cloned. Even less is known about the regulation in cellular organelles. The present review is aimed at providing the reader with a comprehensive and up-to-date understanding of the mechanisms enacted by eukaryotic cells to regulate cellular Mg(2+) homeostasis and how these mechanisms are altered under specific pathological conditions.
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Affiliation(s)
- Andrea M P Romani
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA.
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25
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Kominkova V, Malekova L, Tomaskova Z, Slezak P, Szewczyk A, Ondrias K. Modulation of intracellular chloride channels by ATP and Mg2+. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1300-12. [PMID: 20206596 DOI: 10.1016/j.bbabio.2010.02.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 02/03/2010] [Accepted: 02/26/2010] [Indexed: 12/15/2022]
Abstract
We report the effects of ATP and Mg2+ on the activity of intracellular chloride channels. Mitochondrial and lysosomal membrane vesicles isolated from rat hearts were incorporated into bilayer lipid membranes, and single chloride channel currents were measured. The observed chloride channels (n=112) possessed a wide variation in single channel parameters and sensitivities to ATP. ATP (0.5-2 mmol/l) modulated and/or inhibited the chloride channel activities (n=38/112) in a concentration-dependent manner. The inhibition effect was irreversible (n=5/93) or reversible (n=15/93). The non-hydrolysable ATP analogue AMP-PNP had a similar inhibition effect as ATP, indicating that phosphorylation did not play a role in the ATP inhibition effect. ATP modulated the gating properties of the channels (n=6/93), decreased the channels' open dwell times and increased the gating transition rates. ATP (0.5-2 mmol/l) without the presence of Mg2+ decreased the chloride channel current (n=12/14), whereas Mg2+ significantly reversed the effect (n=4/4). We suggest that ATP-intracellular chloride channel interactions and Mg2+ modulation of these interactions may regulate different physiological and pathological processes.
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Affiliation(s)
- Viera Kominkova
- Institute of Molecular Physiology and Genetics, Centre of Excellence for Cardiovascular Research, Slovak Academy of Sciences, 83334 Bratislava, Slovakia
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26
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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.
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Denton RM. Regulation of mitochondrial dehydrogenases by calcium ions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1309-16. [PMID: 19413950 DOI: 10.1016/j.bbabio.2009.01.005] [Citation(s) in RCA: 601] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 11/21/2008] [Revised: 01/08/2009] [Accepted: 01/09/2009] [Indexed: 11/24/2022]
Abstract
Studies in Bristol in the 1960s and 1970s, led to the recognition that four mitochondrial dehydrogenases are activated by calcium ions. These are FAD-glycerol phosphate dehydrogenase, pyruvate dehydrogenase, NAD-isocitrate dehydrogenase and oxoglutarate dehydrogenase. FAD-glycerol phosphate dehydrogenase is located on the outer surface of the inner mitochondrial membrane and is influenced by changes in cytoplasmic calcium ion concentration. The other three enzymes are located within mitochondria and are regulated by changes in mitochondrial matrix calcium ion concentration. These and subsequent studies on purified enzymes, mitochondria and intact cell preparations have led to the widely accepted view that the activation of these enzymes is important in the stimulation of the respiratory chain and hence ATP supply under conditions of increased ATP demand in many stimulated mammalian cells. The effects of calcium ions on FAD-isocitrate dehydrogenase involve binding to an EF-hand binding motif within this enzyme but the binding sites involved in the effects of calcium ions on the three intramitochondrial dehydrogenases remain to be fully established. It is also emphasised in this article that these three dehydrogenases appear only to be regulated by calcium ions in vertebrates and that this raises some interesting and potentially important developmental issues.
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Affiliation(s)
- Richard M Denton
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 ITD, UK.
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28
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Romani A. Regulation of magnesium homeostasis and transport in mammalian cells. Arch Biochem Biophys 2006; 458:90-102. [PMID: 16949548 DOI: 10.1016/j.abb.2006.07.012] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Accepted: 07/21/2006] [Indexed: 02/06/2023]
Abstract
Magnesium is the second most abundant cation within the cell after potassium and plays an important role in numerous biological functions. Several pieces of experimental evidence indicate that mammalian cells tightly regulate Mg(2+) content by precise control mechanisms operating at the level of Mg(2+) entry and efflux across the cell membrane, as well as at the level of intracellular Mg(2+) buffering and organelle compartmentation under resting conditions and following hormonal stimuli. This review will attempt to elucidate the mechanisms involved in hormonal-mediated Mg(2+) extrusion and accumulation, as well as the physiological implications of changes in cellular Mg(2+) content following hormonal stimuli.
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Affiliation(s)
- Andrea Romani
- Department of Physiology and Biophysics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA.
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Bradshaw PC, Pfeiffer DR. Release of Ca2+ and Mg2+ from yeast mitochondria is stimulated by increased ionic strength. BMC BIOCHEMISTRY 2006; 7:4. [PMID: 16460565 PMCID: PMC1386685 DOI: 10.1186/1471-2091-7-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 02/06/2006] [Indexed: 11/10/2022]
Abstract
Background Divalent cations are required for many essential functions of mitochondrial metabolism. Yet the transporters that mediate the flux of these molecules into and out of the mitochondrion remain largely unknown. Previous studies in yeast have led to the molecular identification of a component of the major mitochondrial electrophoretic Mg2+ uptake system in this organism as well as a functional mammalian homolog. Other yeast mitochondrial studies have led to the characterization of an equilibrative fatty acid-stimulated Ca2+ transport activity. To gain a deeper understanding of the regulation of mitochondrial divalent cation levels we further characterized the efflux of Ca2+ and Mg2+ from yeast mitochondria. Results When isolated mitochondria from the yeast Saccharomyces cerevisiae were suspended in a salt-based suspension medium, Ca2+ and Mg2+ were released from the matrix space. Release did not spontaneously occur in a non-ionic mannitol media. When energized mitochondria were suspended in a mannitol medium in the presence of Ca2+ they were able to accumulate Ca2+ by the addition of the electrogenic Ca2+ ionophore ETH-129. However, in a KCl or choline Cl medium under the same conditions, they were unable to retain the Ca2+ that was taken up due to the activation of the Ca2+ efflux pathway, although a substantial membrane potential driving Ca2+ uptake was maintained. This Ca2+ efflux was independent of fatty acids, which have previously been shown to activate Ca2+ transport. Endogenous mitochondrial Mg2+ was also released when mitochondria were suspended in an ionic medium, but was retained in mitochondria upon fatty acid addition. When suspended in a mannitol medium, metal chelators released mitochondrial Mg2+, supporting the existence of an external divalent cation-binding site regulating release. Matrix space Mg2+ was also slowly released from mitochondria by the addition of Ca2+, respiratory substrates, increasing pH, or the nucleotides ATP, ADP, GTP, and ATP-gamma-S. Conclusion In isolated yeast mitochondria Ca2+ and Mg2+ release was activated by increased ionic strength. Free nucleotides, metal ion chelators, and increased pH also stimulated release. In yeast cells this release is likely an important mechanism in the regulation of mitochondrial matrix space divalent cation concentrations.
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Affiliation(s)
| | - Douglas R Pfeiffer
- Department of Molecular and Cellular Biochemistry, Department of Internal Medicine, Institute for Mitochondrial Biology, The Ohio State University, Columbus, OH, USA
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Yehezkel G, Hadad N, Zaid H, Sivan S, Shoshan-Barmatz V. Nucleotide-binding sites in the voltage-dependent anion channel: characterization and localization. J Biol Chem 2005; 281:5938-46. [PMID: 16354668 DOI: 10.1074/jbc.m510104200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we addressed the presence and location of nucleotide-binding sites in the voltage-dependent anion channel (VDAC). VDAC bound to reactive red 120-agarose, from which it was eluted by ATP, less effectively by ADP and AMP, but not by NADH. The photoreactive ATP analog, benzoyl-benzoyl-ATP (BzATP), was used to identify and characterize the ATP-binding sites in VDAC. [alpha-(32)P]BzATP bound to purified VDAC at two or more binding sites with apparent high and low binding affinities. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis of BzATP-labeled VDAC confirmed the binding of at least two BzATP molecules to VDAC. The VDAC BzATP-binding sites showed higher specificity for purine than for pyrimidine nucleotides and higher affinity for negatively charged nucleotide species. VDAC treatment with the lysyl residue modifying reagent, fluorescein 5'-isothiocyanate, markedly inhibited VDAC labeling with BzATP. The VDAC nucleotide-binding sites were localized using chemical and enzymatic cleavage. Digestion of [alpha-(32)P]BzATP-labeled VDAC with CNBr or V8 protease resulted in the appearance of approximately 17- and approximately 14-kDa labeled fragments. Further digestion, high performance liquid chromatography separation, and sequencing of the selected V8 peptides suggested that the labeled fragments originated from two different regions of the VDAC molecule. MALDI-TOF analysis of BzATP-labeled, tryptic VDAC fragments indicated and localized three nucleotide binding sites, two of which were at the N and C termini of VDAC. Thus, the presence of two or more nucleotide-binding sites in VDAC is suggested, and their possible function in the control of VDAC activity, and, thereby, of outer mitochondrial membrane permeability is discussed.
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Affiliation(s)
- Galit Yehezkel
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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Kucejova B, Kucej M, Petrezselyova S, Abelovska L, Tomaska L. A screen for nigericin-resistant yeast mutants revealed genes controlling mitochondrial volume and mitochondrial cation homeostasis. Genetics 2005; 171:517-26. [PMID: 16020778 PMCID: PMC1456768 DOI: 10.1534/genetics.105.046540] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Little is known about the regulation of ion transport across the inner mitochondrial membrane in Saccharomyces cerevisiae. To approach this problem, we devised a screening procedure for facilitating the identification of proteins involved in mitochondrial ion homeostasis. Taking advantage of the growth inhibition of yeast cells by electroneutral K(+)/H(+) ionophore nigericin, we screened for genetic mutations that would render cells tolerant to this drug when grown on a nonfermentable carbon source and identified several candidate genes including MDM31, MDM32, NDI1, YMR088C (VBA1), CSR2, RSA1, YLR024C, and YNL136W (EAF7). Direct examination of intact cells by electron microscopy indicated that mutants lacking MDM31 and/or MDM32 genes contain dramatically enlarged, spherical mitochondria and that these morphological abnormalities can be alleviated by nigericin. Mitochondria isolated from the Deltamdm31 and Deltamdm32 mutants exhibited limited swelling in an isotonic solution of potassium acetate even in the presence of an exogenous K(+)/H(+) antiport. In addition, growth of the mutants was inhibited on ethanol-containing media in the presence of high concentrations of salts (KCl, NaCl, or MgSO(4)) and their mitochondria exhibited two- (Deltamdm31 and Deltamdm32) to threefold (Deltamdm31Deltamdm32) elevation in magnesium content. Taken together, these data indicate that Mdm31p and Mdm32p control mitochondrial morphology through regulation of mitochondrial cation homeostasis and the maintenance of proper matrix osmolarity.
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Affiliation(s)
- Blanka Kucejova
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic
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Tursun P, Tashiro M, Konishi M. Modulation of Mg2+ efflux from rat ventricular myocytes studied with the fluorescent indicator furaptra. Biophys J 2005; 88:1911-24. [PMID: 15626700 PMCID: PMC1305244 DOI: 10.1529/biophysj.104.055517] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Accepted: 12/22/2004] [Indexed: 11/18/2022] Open
Abstract
The fluorescent Mg(2+) indicator furaptra (mag-fura-2) was introduced into single ventricular myocytes by incubation with its acetoxy-methyl ester form. The ratio of furaptra's fluorescence intensity at 382 and 350 nm was used to estimate the apparent cytoplasmic [Mg(2+)] ([Mg(2+)](i)). In Ca(2+)-free extracellular conditions (0.1 mM EGTA) at 25 degrees C, [Mg(2+)](i) averaged 0.842 +/- 0.019 mM. After the cells were loaded with Mg(2+) by exposure to high extracellular [Mg(2+)] ([Mg(2+)](o)), reduction of [Mg(2+)](o) to 1 mM (in the presence of extracellular Na(+)) induced a decrease in [Mg(2+)](i). The rate of decrease in [Mg(2+)](i) was higher at higher [Mg(2+)](i), whereas raising [Mg(2+)](o) slowed the decrease in [Mg(2+)](i) with 50% reduction of the rate at approximately 10 mM [Mg(2+)](o). Because a part of the furaptra molecules were likely trapped inside intracellular organelles, we assessed possible contribution of the indicator fluorescence emitted from the organelles. When the cell membranes of furaptra-loaded myocytes were permeabilized with saponin (25 microg/ml for 5 min), furaptra fluorescence intensity at 350-nm excitation decreased to 22%; thus approximately 78% of furaptra fluorescence appeared to represent cytoplasmic [Mg(2+)] ([Mg(2+)](c)), whereas the residual 22% likely represented [Mg(2+)] in organelles (primarily mitochondria as revealed by fluorescence imaging). [Mg(2+)] calibrated from the residual furaptra fluorescence ([Mg(2+)](r)) was 0.6-0.7 mM in bathing solution [Mg(2+)] (i.e., [Mg(2+)](c) of the skinned myocytes) of either 0.8 mM or 4.0 mM, suggesting that [Mg(2+)](r) was lower than and virtually insensitive to [Mg(2+)](c). We therefore corrected furaptra fluorescence signals measured in intact myocytes for this insensitive fraction of fluorescence to estimate [Mg(2+)](c). In addition, by utilizing concentration and dissociation constant values of known cytoplasmic Mg(2+) buffers, we calculated changes in total Mg concentration to obtain quantitative information on Mg(2+) flux across the cell membrane. The calculations indicate that, in the presence of extracellular Na(+), Mg(2+) efflux is markedly activated by [Mg(2+)](c) above the normal basal level (approximately 0.9 mM), with a half-maximal activation of approximately 1.9 mM [Mg(2+)](c). We conclude that [Mg(2+)](c) is tightly regulated by an Mg(2+) efflux that is dependent on extracellular [Na(+)].
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Affiliation(s)
- Pulat Tursun
- Department of Physiology, Tokyo Medical University, 6-1-1 Shinjuku-ku, Tokyo 160-8402, Japan
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Kubota T, Shindo Y, Tokuno K, Komatsu H, Ogawa H, Kudo S, Kitamura Y, Suzuki K, Oka K. Mitochondria are intracellular magnesium stores: investigation by simultaneous fluorescent imagings in PC12 cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2004; 1744:19-28. [PMID: 15878394 DOI: 10.1016/j.bbamcr.2004.10.013] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2004] [Revised: 10/14/2004] [Accepted: 10/15/2004] [Indexed: 12/15/2022]
Abstract
To determine the nature of intracellular Mg2+ stores and Mg2+ release mechanisms in differentiated PC12 cells, Mg2+ and Ca2+ mobilizations were measured simultaneously in living cells with KMG-104, a fluorescent Mg2+ indicator, and fura-2, respectively. Treatment with the mitochondrial uncoupler, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), increased both the intracellular Mg2+ concentration ([Mg2+]i) and the [Ca2+]i in these cells. Possible candidates as intracellular Mg2+ stores under these conditions include intracellular divalent cation binding sites, endoplasmic reticulum (ER), Mg-ATP and mitochondria. Given that no change in [Mg2+]i was induced by caffeine application, intracellular IP3 or Ca2+ liberated by photolysis, it appears that no Mg2+ release mechanism thus exists that is mediated via the action of Ca2+ on membrane-bound receptors in the ER or via the offloading of Mg2+ from binding sites as a result of the increased [Ca2+]i. FCCP treatment for 2 min did not alter the intracellular ATP content, indicating that Mg2+ was not released from Mg-ATP, at least in the first 2 min following exposure to FCCP. FCCP-induced [Mg2+]i increase was observed at mitochondria localized area, and vice versa. These results suggest that the mitochondria serve as the intracellular Mg2+ store in PC12 cell. Simultaneous measurements of [Ca2+]i and mitochondrial membrane potential, and also of [Ca2+]i and [Mg2+]i, revealed that the initial rise in [Mg2+]i followed that of mitochondrial depolarization for several seconds. These findings show that the source of Mg2+ in the FCCP-induced [Mg2+]i increase in PC12 cells is mitochondria, and that mitochondrial depolarization triggers the Mg2+ release.
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Affiliation(s)
- Takeshi Kubota
- School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan
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Liu T, Lu B, Lee I, Ondrovicová G, Kutejová E, Suzuki CK. DNA and RNA binding by the mitochondrial lon protease is regulated by nucleotide and protein substrate. J Biol Chem 2004; 279:13902-10. [PMID: 14739292 DOI: 10.1074/jbc.m309642200] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ATP-dependent Lon protease belongs to a unique group of proteases that bind DNA. Eukaryotic Lon is a homo-oligomeric ring-shaped complex localized to the mitochondrial matrix. In vitro, human Lon binds specifically to a single-stranded GT-rich DNA sequence overlapping the light strand promoter of human mitochondrial DNA (mtDNA). We demonstrate that Lon binds GT-rich DNA sequences found throughout the heavy strand of mtDNA and that it also interacts specifically with GU-rich RNA. ATP inhibits the binding of Lon to DNA or RNA, whereas the presence of protein substrate increases the DNA binding affinity of Lon 3.5-fold. We show that nucleotide inhibition and protein substrate stimulation coordinately regulate DNA binding. In contrast to the wild type enzyme, a Lon mutant lacking both ATPase and protease activity binds nucleic acid; however, protein substrate fails to stimulate binding. These results suggest that conformational changes in the Lon holoenzyme induced by nucleotide and protein substrate modulate the binding affinity for single-stranded mtDNA and RNA in vivo. Co-immunoprecipitation experiments show that Lon interacts with mtDNA polymerase gamma and the Twinkle helicase, which are components of mitochondrial nucleoids. Taken together, these results suggest that Lon participates directly in the metabolism of mtDNA.
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Affiliation(s)
- Tong Liu
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA
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Kolisek M, Zsurka G, Samaj J, Weghuber J, Schweyen RJ, Schweigel M. Mrs2p is an essential component of the major electrophoretic Mg2+ influx system in mitochondria. EMBO J 2003; 22:1235-44. [PMID: 12628916 PMCID: PMC151051 DOI: 10.1093/emboj/cdg122] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Steady-state concentrations of mitochondrial Mg(2+) previously have been shown to vary with the expression of Mrs2p, a component of the inner mitochondrial membrane with two transmembrane domains. While its structural and functional similarity to the bacterial Mg(2+) transport protein CorA suggested a role for Mrs2p in Mg(2+) influx into the organelle, other functions in cation homeostasis could not be excluded. Making use of the fluorescent dye mag-fura 2 to measure free Mg(2+) concentrations continuously, we describe here a high capacity, rapid Mg(2+) influx system in isolated yeast mitochondria, driven by the mitochondrial membrane potential Deltapsi and inhibited by cobalt(III)hexaammine. Overexpression of Mrs2p increases influx rates 5-fold, while the deletion of the MRS2 gene abolishes this high capacity Mg(2+) influx. Mg(2+) efflux from isolated mitochondria, observed with low Deltapsi only, also requires the presence of Mrs2p. Cross-linking experiments revealed the presence of Mrs2p-containing complexes in the mitochondrial membrane, probably constituting Mrs2p homo- oligomers. Taken together, these findings characterize Mrs2p as the first molecularly identified metal ion channel protein in the inner mitochondrial membrane.
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Affiliation(s)
| | | | | | | | - Rudolf J. Schweyen
- Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, Dr Bohrgasse, A-1030 Vienna, Austria and
Free University Berlin, Institute of Veterinary Physiology, Oertzenweg 19b, D-14163 Berlin, Germany Corresponding authors e-mail: or
| | - Monika Schweigel
- Vienna Biocenter, Institute of Microbiology and Genetics, University of Vienna, Dr Bohrgasse, A-1030 Vienna, Austria and
Free University Berlin, Institute of Veterinary Physiology, Oertzenweg 19b, D-14163 Berlin, Germany Corresponding authors e-mail: or
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Abstract
The aim of this review is to provide basic information on the electrophysiological changes during acute ischemia and reperfusion from the level of ion channels up to the level of multicellular preparations. After an introduction, section II provides a general description of the ion channels and electrogenic transporters present in the heart, more specifically in the plasma membrane, in intracellular organelles of the sarcoplasmic reticulum and mitochondria, and in the gap junctions. The description is restricted to activation and permeation characterisitics, while modulation is incorporated in section III. This section (ischemic syndromes) describes the biochemical (lipids, radicals, hormones, neurotransmitters, metabolites) and ion concentration changes, the mechanisms involved, and the effect on channels and cells. Section IV (electrical changes and arrhythmias) is subdivided in two parts, with first a description of the electrical changes at the cellular and multicellular level, followed by an analysis of arrhythmias during ischemia and reperfusion. The last short section suggests possible developments in the study of ischemia-related phenomena.
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Affiliation(s)
- E Carmeliet
- Centre for Experimental Surgery and Anesthesiology, University of Leuven, Leuven, Belgium
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Kennedy HJ, Pouli AE, Ainscow EK, Jouaville LS, Rizzuto R, Rutter GA. Glucose generates sub-plasma membrane ATP microdomains in single islet beta-cells. Potential role for strategically located mitochondria. J Biol Chem 1999; 274:13281-91. [PMID: 10224088 DOI: 10.1074/jbc.274.19.13281] [Citation(s) in RCA: 254] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increases in the concentration of free ATP within the islet beta-cell may couple elevations in blood glucose to insulin release by closing ATP-sensitive K+ (KATP) channels and activating Ca2+ influx. Here, we use recombinant targeted luciferases and photon counting imaging to monitor changes in free [ATP] in subdomains of single living MIN6 and primary beta-cells. Resting [ATP] in the cytosol ([ATP]c), in the mitochondrial matrix ([ATP]m), and beneath the plasma membrane ([ATP]pm) were similar ( approximately 1 mM). Elevations in extracellular glucose concentration (3-30 mM) increased free [ATP] in each domain with distinct kinetics. Thus, sustained increases in [ATP]m and [ATP]pm were observed, but only a transient increase in [ATP]c. However, detectable increases in [ATP]c and [ATP]pm, but not [ATP]m, required extracellular Ca2+. Enhancement of glucose-induced Ca2+ influx with high [K+] had little effect on the apparent [ATP]c and [ATP]m increases but augmented the [ATP]pm increase. Underlying these changes, glucose increased the mitochondrial proton motive force, an effect mimicked by high [K+]. These data support a model in which glucose increases [ATP]m both through enhanced substrate supply and by progressive Ca2+-dependent activation of mitochondrial enzymes. This may then lead to a privileged elevation of [ATP]pm, which may be essential for the sustained closure of KATP channels. Luciferase imaging would appear to be a useful new tool for dynamic in vivo imaging of free ATP concentration.
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Affiliation(s)
- H J Kennedy
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom
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Wolf FI, Covacci V, Bruzzese N, Di Francesco A, Sacchetti A, Corda D, Cittadini A. Differentiation of HL-60 promyelocytic leukemia cells is accompanied by a modification of magnesium homeostasis. J Cell Biochem 1998; 71:441-8. [PMID: 9831080 DOI: 10.1002/(sici)1097-4644(19981201)71:3<441::aid-jcb12>3.0.co;2-o] [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: 12/22/2022]
Abstract
Magnesium homeostasis in HL-60 promyelocytic leukemia cells was compared to that in neutrophyl-like HL-60 cells obtained by 1.3% DMSO treatment. Magnesium homeostasis was studied by the characterization of magnesium efflux, the identification of intracellular magnesium pools, and the regulation of intracellular ionized Mg2+. In both undifferentiated and neutrophyl-like HL-60 cells, magnesium efflux occurred via the Na-Mg antiporter which was inhibited by imipramine and stimulated by db cAMP and forskolin. Receptor-mediated signals such as ATP, IFN-alpha, or PGE1, which can trigger cAMP-dependent magnesium efflux, were ineffective in undifferentiated HL-60 cells but induced 60-70% increase of magnesium efflux in neutrophyl-like HL-60 cells. Selective membrane permeabilization by the cation ionophore A23187 induced a large magnesium release when cells were treated with rotenone. In both cell populations, the addition of glucose to rotenone-treated cells restored magnesium release to the control level. Permeabilization by 0.005% digitonin provoked the release of 90% cell total magnesium in both cell types. Intracellular [Mg2+]i was 0.15 and 0.26 mM in undifferentiated and neutrophyl-like HL-60 cells, respectively. Stimuli that triggered magnesium efflux, such as db cAMP in undifferentiated and IFN-alpha in neutrophyl-like HL-60 cells, induced a slow but consistent increase of [Mg2+]i which was independent from Ca2+ movements. Overall, these data indicate that magnesium homeostasis is regulated by receptor-mediated magnesium efflux which was modified during differentiation of HL-60 cells. Stimulation of magnesium efflux is paralleled by an increase of [Mg2+]i which reflects a release of magnesium from the bound cation pool.
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Affiliation(s)
- F I Wolf
- Institute of General Pathology and Giovanni XXIII Cancer Research Center, Catholic University of Sacred Heart, Roma, Italy.
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39
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Rodríguez-Zavala JS, Moreno-Sánchez R. Modulation of oxidative phosphorylation by Mg2+ in rat heart mitochondria. J Biol Chem 1998; 273:7850-5. [PMID: 9525878 DOI: 10.1074/jbc.273.14.7850] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effect of varying the Mg2+ concentration on the 2-oxoglutarate dehydrogenase (2-OGDH) activity and the rate of oxidative phosphorylation of rat heart mitochondria was studied. The ionophore A23187 was used to modify the mitochondrial free Mg2+ concentration. Half-maximal stimulation (K0.5) of ATP synthesis by Mg2+ was obtained with 0.13 +/- 0.02 mM (n = 7) with succinate (+rotenone) and 0.48 +/- 0.13 mM (n = 6) with 2-oxoglutarate (2-OG) as substrates. Similar K0.5 values were found for NAD(P)H formation, generation of membrane potential, and state 4 respiration with 2-OG. In the presence of ADP, an increase in Pi concentration promoted a decrease in the K0.5 values of ATP synthesis, membrane potential formation and state 4 respiration for Mg2+ with 2-OG, but not with succinate. These results indicate that 2-OGDH is the main step of oxidative phosphorylation modulated by Mg2+ when 2-OG is the oxidizable substrate; with succinate, the ATP synthase is the Mg2+-sensitive step. Replacement of Pi by acetate, which promotes changes on intramitochondrial pH abolished Mg2+ activation of 2-OGDH. Thus, the modulation of the 2-OGDH activity by Mg2+ has an essential requirement for Pi (and ADP) in intact mitochondria which is not associated to variations in matrix pH.
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Affiliation(s)
- J S Rodríguez-Zavala
- Departamento de Bioquímica, Instituto Nacional de Cardiología, México, D.F. 14080, México
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40
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Jung DW, Panzeter E, Baysal K, Brierley GP. On the relationship between matrix free Mg2+ concentration and total Mg2+ in heart mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1320:310-20. [PMID: 9230923 DOI: 10.1016/s0005-2728(97)00036-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The matrix free magnesium ion concentration, [Mg2+]m, estimated using the fluorescent probe furaptra, averaged 0.67 mM in 15 preparations of beef heart mitochondria containing an average of 21 nmol total Mg2+ per mg protein. [Mg2+]m was compared with total Mg2+ during respiration-dependent uptake and efflux of Mg2+ and during osmotic swelling. In the absence of external Pi these mitochondria contain about 32 nmol/mg non-diffusible Mg-binding sites with an apparent Kd of 0.34 mM. [Mg2+]m depends on both the size of the total Mg2+ pool and the ability of matrix anions to provide Mg-ligands. Pi interacts strongly with Mg2+ to decrease [Mg2+]m and, in the absence of external Mg2+, promotes respiration-dependent Mg2+ efflux and a decrease in [Mg2+]m to very low levels. The uptake of Pi by respiring mitochondria converts delta pH to membrane potential (delta psi) and provides additional Mg-binding sites. This permits large accumulations of Mg2+ and Pi with little change in [Mg2+]m. Nigericin also converts delta pH to delta psi in respiring mitochondria and induces a large and rapid increase in both total Mg2+ and [Mg2+]m. Mersalyl increases the permeability of the mitochondrial membrane to cations and this also induces a marked increase in both total Mg2+ and [Mg2+]m. These results suggest that mitochondria take up Mg2+ by electrophoretic flux through membrane leak pathways, rather than via a specific Mg2+ transporter. Mitochondria swollen by respiration dependent uptake of potassium phosphate show decreased [Mg2+]m, whereas those swollen to the same extent in potassium acetate do not. This suggests that [Mg2+]m is well-buffered during osmotic volume changes unless there is also a change in ligand availability.
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Affiliation(s)
- D W Jung
- Department of Medical Biochemistry, Ohio State University, Columbus 43210-1218, USA
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Szmacinski H, Lakowicz JR. Fluorescence lifetime characterization of magnesium probes: Improvement of Mg(2+) dynamic range and sensitivity using phase-modulation fluorometry. J Fluoresc 1996; 6:83-95. [PMID: 24227082 PMCID: PMC6897576 DOI: 10.1007/bf00732047] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/1995] [Accepted: 04/05/1996] [Indexed: 11/25/2022]
Abstract
We measured the Mg(2+)-dependent absorption spectra, emission spectra, quantum yields, and intensity decays of most presently available fluorescent magnesium probes. The lifetimes were found to be strongly Mg(2+) dependent for Mag-quin-1, Mag-quin-2, magnesium green, and magnesium orange and increased 2- to 10-fold upon binding of Mg(2+). The lifetimes of Mag-fura-2, Mag-fura-5, Mag-fura red, and Mag-indo-1 were similar in the presence and absence of Mg(2+). Detailed timeresolved measurements were carried out for Mag-quin-2 and magnesium green using phase-modulation fluorometry. Apparent dissociation constants (K d) were determined from the steady-state and time-resolved data. Their values were compared and discussed. Mg(2+) sensing is described using phase and modulation data measured at a single modulation frequency. Phase angle and modulation data showed the possibility of obtaining a wider Mg(2+)-sensitive range than available from intensity measurements. A significant expansion in the Mg(2+)-sensitive range was found for Mag-quin-2 using excitation wavelengths from 343 to 375 nm, where the apparentK d from the phase angle was found to vary from 0.3 to about 100 mM. Discrimination against Ca(2+) was also measured for Mag-quin-2 and magnesium green. Significant phototransformation and/or photode-composition, which affect the sensitivity to Mg(2+), were observed for Mag-quin-2 and magnesium green under intense and long illumination.
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Affiliation(s)
- H Szmacinski
- Center for Fluorescence Spectroscopy and Medical Biotechnology Center, Department of Biological Chemistry, University of Maryland School of Medicine, 108 North Greene Street, 21201, Baltimore, MD
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[15] A practical guide to the use of fluorescent indicators for the measurement of cytosolic free magnesium. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1043-9471(06)80018-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Nicotera P, Zhivotovsky B, Orrenius S. Nuclear calcium transport and the role of calcium in apoptosis. Cell Calcium 1994; 16:279-88. [PMID: 7820847 DOI: 10.1016/0143-4160(94)90091-4] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The last decade has been the rapid development of research investigating the molecular mechanisms whereby hormones, peptide growth factors and cytokines regulate cell metabolism, differentiation and proliferation. One general signalling mechanism used to transfer the information delivered by agonists into appropriate intracellular compartments involves the rapid Ca2+ redistribution throughout the cell, which results in transient elevations of the cytosolic free Ca2+ concentration. Ca2+ signals are required for a number of cellular functions, including the activation of nuclear processes such as gene transcription and cell cycle events. The latter requires that appropriate Ca2+ signals elicited in response to agonists be transduced across the nuclear envelope. It has generally been assumed that small molecules, metabolites and ions could diffuse freely across the nuclear envelope. Nevertheless, several findings during the past few years have suggested that nuclear pore permeability can be regulated and that ion transport systems and ion-selective channels may exist in the nuclear membranes and regulate intranuclear processes. Intranuclear Ca2+ fluctuations can affect chromatin organization, induce gene expression and also activate cleavage of nuclear DNA by nucleases during programmed cell death or apoptosis. The possible mechanisms involved in nuclear Ca2+ transport and the regulation of nuclear Ca(2+)-dependent enzymes in apoptosis are discussed in the following sections.
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Affiliation(s)
- P Nicotera
- Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden
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Brierley GP, Baysal K, Jung DW. Cation transport systems in mitochondria: Na+ and K+ uniports and exchangers. J Bioenerg Biomembr 1994; 26:519-26. [PMID: 7896767 DOI: 10.1007/bf00762736] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
It is now well established that mitochondria contain three antiporters that transport monovalent cations. A latent, allosterically regulated K+/H+ antiport appears to serve as a cation-extruding device that helps maintain mitochondrial volume homeostasis. An apparently unregulated Na+/H+ antiport keeps matrix [Na+] low and the Na(+)-gradient equal to the H(+)-gradient. A Na+/Ca2+ antiport provides a Ca(2+)-extruding mechanism that permits the mitochondrion to regulate matrix [Ca2+] by balancing Ca2+ efflux against influx on the Ca(2+)-uniport. All three antiports have well-defined physiological roles and their molecular properties and regulatory features are now being determined. Mitochondria also contain monovalent cation uniports, such as the recently described ATP- and glibenclamide-sensitive K+ channel and ruthenium red-sensitive uniports for Na+ and K+. A physiological role of such uniports has not been established and their properties are just beginning to be defined.
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Affiliation(s)
- G P Brierley
- Department of Medical Biochemistry, Ohio State University, Columbus 43210
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Abstract
The pathways for the uptake and extrusion of Mg2+ by mitochondria are now well defined, the present evidence suggests that uptake occurs by nonspecific diffusive pathways in response to elevated membrane potential. There is disagreement as to some of the properties of Mg2+ efflux from mitochondria, but the reaction resembles K+ efflux in many ways and may occur in exchange for H+. Matrix free magnesium ion concentration, [Mg2+], can be measured using fluorescent probes and is set very close to cytosol [Mg2+] by a balance between influx and efflux and by the availability of ligands, such as Pi. There are indications that matrix [Mg2+] may be under hormonal control and that it contributes to the regulation of mitochondrial metabolism and transport reactions.
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Affiliation(s)
- D W Jung
- Department of Medical Biochemistry, Ohio State University, Columbus 43210
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Abstract
The last decade has seen the rapid development of research investigating the molecular mechanisms whereby hormones, peptide growth factors and cytokines regulate cell metabolism, differentiation and proliferation. One general signalling mechanism used to transfer the information delivered by agonists into appropriate intracellular compartments involves the rapid Ca2+ redistribution throughout the cell, which results in transient elevations of the cytosolic free Ca2+ concentration. Ca2+ signals are required for a number of cellular processes including the activation of nuclear processes such as gene transcription and cell cycle events. The latter require that appropriate Ca2+ signals elicited in response to agonists be transduced across the nuclear envelope. It has generally been assumed that small molecules, metabolites and ions could freely diffuse across the nuclear envelope. Nevertheless several findings during the past few years have suggested that nuclear pore permeability can be regulated and that ion transport systems and ion-selective channels may exist on the nuclear membranes and regulate intranuclear processes. Intranuclear Ca2+ fluctuations can affect chromatin organization, induce gene expression and also activate cleavage of nuclear DNA by nucleases during programmed cell death or apoptosis. The possible mechanisms involved in nuclear Ca2+ transport and the control of nuclear Ca(2+)-dependent enzymes in apoptosis is discussed below.
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Affiliation(s)
- P Nicotera
- Institute of Environmental Medicine, Division of Toxicology, Stockhom, Sweden
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Abstract
This review highlights the important roles played by magnesium in the growth and metabolic functions of microbial and animal cells, and therefore assigns a key role for magnesium ions in biotechnology. The fundamental biochemical and physiological actions of magnesium as a regulatory cation are outlined. Such actions are deemed to be relevant in an applied sense, because Mg2+ availability in cell culture and fermentation media can dramatically influence growth and metabolism of cells. Manipulation of extracellular and intracellular magnesium ions can thus be envisaged as a relatively simplistic, but nevertheless versatile, means of physiological cell engineering. In addition, biological antagonism between calcium and magnesium at the molecular level may have profound consequences for the optimization of biotechnological processes that exploit cells. In fermentation, for example, it is argued that the efficiency of microbial conversion of substrate to product may be improved by altering Mg:Ca concentration ratios in industrial feedstocks in a way that makes more magnesium available to the cells. With particular respect to yeast-based biotechnologies, magnesium availability is seen as being crucially important in governing central pathways of carbohydrate catabolism, especially ethanolic fermentation. It is proposed that such influences of magnesium ions are expressed at the combined levels of key enzyme activation and cell membrane stabilization. The former ensures optimum flow of substrate to ethanol and the latter acts to protect yeasts from physical and chemical stress.
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Affiliation(s)
- G M Walker
- Department of Molecular and Life Sciences, University of Abertay Dundee, Scotland
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Rizzuto R, Brini M, Murgia M, Pozzan T. Microdomains with high Ca2+ close to IP3-sensitive channels that are sensed by neighboring mitochondria. Science 1993; 262:744-7. [PMID: 8235595 DOI: 10.1126/science.8235595] [Citation(s) in RCA: 938] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Microdomains of high intracellular calcium ion concentration, [Ca2+]i, have been hypothesized to occur in living cells exposed to stimuli that generate inositol 1,4,5-trisphosphate (IP3). Mitochondrially targeted recombinant aequorin was used to show that IP3-induced Ca2+ mobilization from intracellular stores caused increases of mitochondrial Ca2+ concentration, [Ca2+]m, the speed and amplitude of which are not accounted for by the relatively small increases in mean [Ca2+]i. A similar response was obtained by the addition of IP3 to permeabilized cells but not by perfusion of cells with Ca2+ at concentrations similar to those measured in intact cells. It is concluded that in vivo, domains of high [Ca2+]i are transiently generated close to IP3-gated channels and sensed by nearby mitochondria; this may provide an efficient mechanism for optimizing mitochondrial activity upon cell stimulation.
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Affiliation(s)
- R Rizzuto
- Department of Biomedical Sciences, University of Padova, Italy
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Rutter G, Theler J, Murgia M, Wollheim C, Pozzan T, Rizzuto R. Stimulated Ca2+ influx raises mitochondrial free Ca2+ to supramicromolar levels in a pancreatic beta-cell line. Possible role in glucose and agonist-induced insulin secretion. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)41540-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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