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Kumari A, Nguyen DM, Garg V. Patch-clamp technique to study mitochondrial membrane biophysics. J Gen Physiol 2023; 155:e202313347. [PMID: 37347216 PMCID: PMC10287547 DOI: 10.1085/jgp.202313347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 04/12/2023] [Accepted: 06/08/2023] [Indexed: 06/23/2023] Open
Abstract
Mitochondria are double-membrane organelles crucial for oxidative phosphorylation, enabling efficient ATP synthesis by eukaryotic cells. Both of the membranes, the highly selective inner mitochondrial membrane (IMM) and a relatively porous outer membrane (OMM), harbor a number of integral membrane proteins that help in the transport of biological molecules. These transporters are especially enriched in the IMM, where they help maintain transmembrane gradients for H+, K+, Ca2+, PO43-, and metabolites like ADP/ATP, citrate, etc. Impaired activity of these transporters can affect the efficiency of energy-transducing processes and can alter cellular redox state, leading to activation of cell-death pathways or metabolic syndromes in vivo. Although several methodologies are available to study ion flux through membrane proteins, the patch-clamp technique remains the gold standard for quantitatively analyzing electrogenic ion exchange across membranes. Direct patch-clamp recordings of mitoplasts (mitochondria devoid of outer membrane) in different modes, such as whole-mitoplast or excised-patch mode, allow researchers the opportunity to study the biophysics of mitochondrial transporters in the native membrane, in real time, in isolation from other fluxes or confounding factors due to changes in ion gradients, pH, or mitochondrial potential (ΔΨ). Here, we summarize the use of patch clamp to investigate several membrane proteins of mitochondria. We demonstrate how this technique can be reliably applied to record whole-mitoplast Ca2+ currents mediated via mitochondrial calcium uniporter or H+ currents mediated by uncoupling protein 1 and discuss critical considerations while recording currents from these small vesicles of the IMM (mitoplast diameter = 2-5 µm).
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Affiliation(s)
- Anshu Kumari
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Baltimore, MD, USA
| | - Dung M. Nguyen
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Baltimore, MD, USA
| | - Vivek Garg
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, Baltimore, MD, USA
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2
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Neginskaya MA, Pavlov EV. Investigation of Properties of the Mitochondrial Permeability Transition Pore Using Whole-Mitoplast Patch-Clamp Technique. DNA Cell Biol 2023; 42:481-487. [PMID: 37311169 PMCID: PMC10460960 DOI: 10.1089/dna.2023.0171] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/09/2023] [Accepted: 05/09/2023] [Indexed: 06/15/2023] Open
Abstract
The mitochondrial permeability transition pore (mPTP) is a channel in the mitochondrial inner membrane that is activated by excessive calcium uptake. In this study, we used a whole-mitoplast patch-clamp approach to investigate the ionic currents associated with mPTP at the level of the whole single mitochondrion. The whole-mitoplast conductance was at the level of 5 to 7 nS, which is consistent with the presence of three to six single mPTP channels per mitochondrion. We found that mPTP currents are voltage dependent and inactivate at negative potential. The currents were inhibited by cyclosporine A and adenosine diphosphate. When mPTP was induced by oxidative stress, currents were partially blocked by the adenine nucleotide translocase inhibitor bongkrekic acid. Our data suggest that the whole-mitoplast patch-clamp approach is a useful method for investigating the biophysical properties and regulation of the mPTP.
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Affiliation(s)
- Maria A. Neginskaya
- Department of Molecular Pathobiology, New York University, New York, New York, USA
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Evgeny V. Pavlov
- Department of Molecular Pathobiology, New York University, New York, New York, USA
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3
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Seegren PV, Harper LR, Downs TK, Zhao XY, Viswanathan SB, Stremska ME, Olson RJ, Kennedy J, Ewald SE, Kumar P, Desai BN. Reduced mitochondrial calcium uptake in macrophages is a major driver of inflammaging. NATURE AGING 2023:10.1038/s43587-023-00436-8. [PMID: 37277641 DOI: 10.1038/s43587-023-00436-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 05/09/2023] [Indexed: 06/07/2023]
Abstract
Mitochondrial dysfunction is linked to age-associated inflammation or inflammaging, but underlying mechanisms are not understood. Analyses of 700 human blood transcriptomes revealed clear signs of age-associated low-grade inflammation. Among changes in mitochondrial components, we found that the expression of mitochondrial calcium uniporter (MCU) and its regulatory subunit MICU1, genes central to mitochondrial Ca2+ (mCa2+) signaling, correlated inversely with age. Indeed, mCa2+ uptake capacity of mouse macrophages decreased significantly with age. We show that in both human and mouse macrophages, reduced mCa2+ uptake amplifies cytosolic Ca2+ oscillations and potentiates downstream nuclear factor kappa B activation, which is central to inflammation. Our findings pinpoint the mitochondrial calcium uniporter complex as a keystone molecular apparatus that links age-related changes in mitochondrial physiology to systemic macrophage-mediated age-associated inflammation. The findings raise the exciting possibility that restoring mCa2+ uptake capacity in tissue-resident macrophages may decrease inflammaging of specific organs and alleviate age-associated conditions such as neurodegenerative and cardiometabolic diseases.
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Affiliation(s)
- Philip V Seegren
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Logan R Harper
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Taylor K Downs
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Xiao-Yu Zhao
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA
- Microbiology, Immunology, and Cancer Biology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | | | - Marta E Stremska
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA
- Microbiology, Immunology, and Cancer Biology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Rachel J Olson
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Joel Kennedy
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Sarah E Ewald
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA
- Microbiology, Immunology, and Cancer Biology Department, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Pankaj Kumar
- Biochemistry and Molecular Genetics Department, University of Virginia School of Medicine, Charlottesville, VA, USA
- University of Virginia, Bioinformatics Core, Charlottesville, VA, USA
| | - Bimal N Desai
- Pharmacology Department, University of Virginia School of Medicine, Charlottesville, VA, USA.
- Carter Immunology Center, University of Virginia School of Medicine, Charlottesville, VA, USA.
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4
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Delgado BD, Long SB. Mechanisms of ion selectivity and throughput in the mitochondrial calcium uniporter. SCIENCE ADVANCES 2022; 8:eade1516. [PMID: 36525497 PMCID: PMC9757755 DOI: 10.1126/sciadv.ade1516] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
The mitochondrial calcium uniporter, which regulates aerobic metabolism by catalyzing mitochondrial Ca2+ influx, is arguably the most selective ion channel known. The mechanisms for this exquisite Ca2+ selectivity have not been defined. Here, using a reconstituted system, we study the electrical properties of the channel's minimal Ca2+-conducting complex, MCU-EMRE, from Tribolium castaneum to probe ion selectivity mechanisms. The wild-type TcMCU-EMRE complex recapitulates hallmark electrophysiological properties of endogenous Uniporter channels. Through interrogation of pore-lining mutants, we find that a ring of glutamate residues, the "E-locus," serves as the channel's selectivity filter. Unexpectedly, a nearby "D-locus" at the mouth of the pore has diminutive influence on selectivity. Anomalous mole fraction effects indicate that multiple Ca2+ ions are accommodated within the E-locus. By facilitating ion-ion interactions, the E-locus engenders both exquisite Ca2+ selectivity and high ion throughput. Direct comparison with structural information yields the basis for selective Ca2+ conduction by the channel.
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Affiliation(s)
- Bryce D. Delgado
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
- Graduate Program in Biochemistry and Structural Biology, Cell and Developmental Biology, and Molecular Biology, Weill Cornell Medicine Graduate School of Medical Sciences, New York, NY 10065, USA
| | - Stephen B. Long
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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Chang R, Edwards RH. Whole Endosome Recording of Vesicular Neurotransmitter Transporter Currents. Methods Mol Biol 2022; 2417:29-44. [PMID: 35099789 DOI: 10.1007/978-1-0716-1916-2_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The analysis of organellar membrane transporters presents many technical problems. In general, their activity depends on a H+ electrochemical driving force (ΔμH+). However, transport itself influences the expression of ΔμH+ in standard radiotracer flux assays, making it difficult to disentangle the role of the chemical component ΔpH and the membrane potential Δψ. Whole endosome recording in voltage clamp circumvents many of these problems, controlling ionic conditions as well as membrane potential inside and outside the organelle . This approach has been used primarily to study the properties of endolysosomal channels, which generate substantial currents (Saito et al., J Biol Chem 282(37):27327-27333, 2007; Cang et al., Nat Chem Biol 10(6):463-469, 2014; Cang et al., Cell 152(4):778-790, 2013; Chen et al., Nat Protoc 12(8):1639-1658, 2017; Samie et al., Dev Cell 26(5):511-524, 2013; Wang et al., Cell 151(2):372-383, 2012). Electrogenic transport produces much smaller currents, but we have recently reported the detection of transport currents and an uncoupled Cl- conductance associated with the vesicular glutamate transporters (VGLUTs) that fill synaptic vesicles with glutamate (Chang et al., eLife 7:e34896, 2018). In this protocol, we will focus on the measurement of transport currents on enlarged endosomes of heterologous mammalian cells.
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Affiliation(s)
- Roger Chang
- Department of Physiology, UCSF School of Medicine, San Francisco, CA, USA
- Department of Neurology, UCSF School of Medicine, San Francisco, CA, USA
- Graduate Program in Biomedical Sciences, UCSF School of Medicine, San Francisco, CA, USA
| | - Robert H Edwards
- Department of Physiology, UCSF School of Medicine, San Francisco, CA, USA.
- Department of Neurology, UCSF School of Medicine, San Francisco, CA, USA.
- Graduate Program in Biomedical Sciences, UCSF School of Medicine, San Francisco, CA, USA.
- Kavli Institute for Fundamental Neuroscience, UCSF School of Medicine, San Francisco, CA, USA.
- Weill Institute for Neurosciences, UCSF School of Medicine, San Francisco, CA, USA.
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6
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Quantitative assays to measure the transport activity of the mitochondrial calcium uniporter in cell lines or Xenopus oocytes. STAR Protoc 2021; 2:100979. [PMID: 34877549 PMCID: PMC8633362 DOI: 10.1016/j.xpro.2021.100979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mitochondrial calcium uniporter, which mediates mitochondrial Ca2+ uptake, regulates key cellular functions, including intracellular Ca2+ signaling, cell-fate determination, and mitochondrial bioenergetics. Here, we describe two complementary strategies to quantify the uniporter's transport activity. First, we detail a mitochondrial Ca2+ radionuclide uptake assay in cultured cell lines. Second, we describe electrophysiological recordings of the uniporter expressed in Xenopus oocytes. These approaches enable a detailed kinetic analysis of the uniporter to link its molecular properties to physiological functions. For complete details on the use and execution of this protocol, please refer to Tsai and Tsai (2018) and Phillips et al. (2019).
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Garg V, Suzuki J, Paranjpe I, Unsulangi T, Boyman L, Milescu LS, Lederer WJ, Kirichok Y. The mechanism of MICU-dependent gating of the mitochondrial Ca 2+uniporter. eLife 2021; 10:e69312. [PMID: 34463251 PMCID: PMC8437439 DOI: 10.7554/elife.69312] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 08/09/2021] [Indexed: 12/11/2022] Open
Abstract
Ca2+ entry into mitochondria is through the mitochondrial calcium uniporter complex (MCUcx), a Ca2+-selective channel composed of five subunit types. Two MCUcx subunits (MCU and EMRE) span the inner mitochondrial membrane, while three Ca2+-regulatory subunits (MICU1, MICU2, and MICU3) reside in the intermembrane space. Here, we provide rigorous analysis of Ca2+ and Na+ fluxes via MCUcx in intact isolated mitochondria to understand the function of MICU subunits. We also perform direct patch clamp recordings of macroscopic and single MCUcx currents to gain further mechanistic insights. This comprehensive analysis shows that the MCUcx pore, composed of the EMRE and MCU subunits, is not occluded nor plugged by MICUs during the absence or presence of extramitochondrial Ca2+ as has been widely reported. Instead, MICUs potentiate activity of MCUcx as extramitochondrial Ca2+ is elevated. MICUs achieve this by modifying the gating properties of MCUcx allowing it to spend more time in the open state.
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Affiliation(s)
- Vivek Garg
- Department of Physiology, University of California San FranciscoSan FranciscoUnited States
- Department of Physiology, University of MarylandBaltimoreUnited States
| | - Junji Suzuki
- Department of Physiology, University of California San FranciscoSan FranciscoUnited States
| | - Ishan Paranjpe
- Department of Physiology, University of California San FranciscoSan FranciscoUnited States
| | - Tiffany Unsulangi
- Department of Physiology, University of California San FranciscoSan FranciscoUnited States
| | - Liron Boyman
- Department of Physiology, University of MarylandBaltimoreUnited States
| | - Lorin S Milescu
- Department of Biology, University of MarylandCollege ParkUnited States
| | | | - Yuriy Kirichok
- Department of Physiology, University of California San FranciscoSan FranciscoUnited States
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Mollo N, Esposito M, Aurilia M, Scognamiglio R, Accarino R, Bonfiglio F, Cicatiello R, Charalambous M, Procaccini C, Micillo T, Genesio R, Calì G, Secondo A, Paladino S, Matarese G, Vita GD, Conti A, Nitsch L, Izzo A. Human Trisomic iPSCs from Down Syndrome Fibroblasts Manifest Mitochondrial Alterations Early during Neuronal Differentiation. BIOLOGY 2021; 10:biology10070609. [PMID: 34209429 PMCID: PMC8301075 DOI: 10.3390/biology10070609] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 06/25/2021] [Accepted: 06/27/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND The presence of mitochondrial alterations in Down syndrome suggests that it might affect neuronal differentiation. We established a model of trisomic iPSCs, differentiating into neural precursor cells (NPCs) to monitor the occurrence of differentiation defects and mitochondrial dysfunction. METHODS Isogenic trisomic and euploid iPSCs were differentiated into NPCs in monolayer cultures using the dual-SMAD inhibition protocol. Expression of pluripotency and neural differentiation genes was assessed by qRT-PCR and immunofluorescence. Meta-analysis of expression data was performed on iPSCs. Mitochondrial Ca2+, reactive oxygen species (ROS) and ATP production were investigated using fluorescent probes. Oxygen consumption rate (OCR) was determined by Seahorse Analyzer. RESULTS NPCs at day 7 of induction uniformly expressed the differentiation markers PAX6, SOX2 and NESTIN but not the stemness marker OCT4. At day 21, trisomic NPCs expressed higher levels of typical glial differentiation genes. Expression profiles indicated that mitochondrial genes were dysregulated in trisomic iPSCs. Trisomic NPCs showed altered mitochondrial Ca2+, reduced OCR and ATP synthesis, and elevated ROS production. CONCLUSIONS Human trisomic iPSCs can be rapidly and efficiently differentiated into NPC monolayers. The trisomic NPCs obtained exhibit greater glial-like differentiation potential than their euploid counterparts and manifest mitochondrial dysfunction as early as day 7 of neuronal differentiation.
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Affiliation(s)
- Nunzia Mollo
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Matteo Esposito
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Miriam Aurilia
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Roberta Scognamiglio
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Rossella Accarino
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Ferdinando Bonfiglio
- CEINGE-Biotecnologie Avanzate s.c.ar.l., 80145 Naples, Italy;
- Department of Chemical, Materials and Production Engineering, University of Naples Federico II, 80125 Naples, Italy
| | - Rita Cicatiello
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Maria Charalambous
- Institute of Experimental Endocrinology and Oncology “G. Salvatore”, National Research Council, 80131 Naples, Italy; (M.C.); (C.P.); (G.C.)
| | - Claudio Procaccini
- Institute of Experimental Endocrinology and Oncology “G. Salvatore”, National Research Council, 80131 Naples, Italy; (M.C.); (C.P.); (G.C.)
- Neuroimmunology Unit, IRCCS, Fondazione Santa Lucia, 00143 Rome, Italy;
| | - Teresa Micillo
- Neuroimmunology Unit, IRCCS, Fondazione Santa Lucia, 00143 Rome, Italy;
| | - Rita Genesio
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Gaetano Calì
- Institute of Experimental Endocrinology and Oncology “G. Salvatore”, National Research Council, 80131 Naples, Italy; (M.C.); (C.P.); (G.C.)
| | - Agnese Secondo
- Department of Neuroscience, Reproductive and Odontostomatological Sciences, University of Naples Federico II, 80131 Naples, Italy;
| | - Simona Paladino
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Giuseppe Matarese
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
- Institute of Experimental Endocrinology and Oncology “G. Salvatore”, National Research Council, 80131 Naples, Italy; (M.C.); (C.P.); (G.C.)
| | - Gabriella De Vita
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Anna Conti
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
| | - Lucio Nitsch
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
- Institute of Experimental Endocrinology and Oncology “G. Salvatore”, National Research Council, 80131 Naples, Italy; (M.C.); (C.P.); (G.C.)
| | - Antonella Izzo
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, 80131 Naples, Italy; (N.M.); (M.E.); (M.A.); (R.S.); (R.A.); (R.C.); (R.G.); (S.P.); (G.M.); (G.D.V.); (A.C.); (L.N.)
- Correspondence: ; Tel.: +39-081-746-3237
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Boyman L, Greiser M, Lederer WJ. Calcium influx through the mitochondrial calcium uniporter holocomplex, MCU cx. J Mol Cell Cardiol 2021; 151:145-154. [PMID: 33147447 PMCID: PMC7880866 DOI: 10.1016/j.yjmcc.2020.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 10/20/2020] [Accepted: 10/28/2020] [Indexed: 12/11/2022]
Abstract
Ca2+ flux into the mitochondrial matrix through the MCU holocomplex (MCUcx) has recently been measured quantitatively and with milliseconds resolution for the first time under physiological conditions in both heart and skeletal muscle. Additionally, the dynamic levels of Ca2+ in the mitochondrial matrix ([Ca2+]m) of cardiomyocytes were measured as it was controlled by the balance between influx of Ca2+ into the mitochondrial matrix through MCUcx and efflux through the mitochondrial Na+ / Ca2+ exchanger (NCLX). Under these conditions [Ca2+]m was shown to regulate ATP production by the mitochondria at only a few critical sites. Additional functions attributed to [Ca2+]m continue to be reported in the literature. Here we review the new findings attributed to MCUcx function and provide a framework for understanding and investigating mitochondrial Ca2+ influx features, many of which remain controversial. The properties and functions of the MCUcx subunits that constitute the holocomplex are challenging to tease apart. Such distinct subunits include EMRE, MCUR1, MICUx (i.e. MICU1, MICU2, MICU3), and the pore-forming subunits (MCUpore). Currently, the specific set of functions of each subunit remains non-quantitative and controversial. The more contentious issues are discussed in the context of the newly measured native MCUcx Ca2+ flux from heart and skeletal muscle. These MCUcx Ca2+ flux measurements have been shown to be a highly-regulated, tissue-specific with femto-Siemens Ca2+ conductances and with distinct extramitochondrial Ca2+ ([Ca2+]i) dependencies. These data from cardiac and skeletal muscle mitochondria have been examined quantitatively for their threshold [Ca2+]i levels and for hypothesized gatekeeping function and are discussed in the context of model cell (e.g. HeLa, MEF, HEK293, COS7 cells) measurements. Our new findings on MCUcx dependent matrix [Ca2+]m signaling provide a quantitative basis for on-going and new investigations of the roles of MCUcx in cardiac function ranging from metabolic fuel selection, capillary blood-flow control and the pathological activation of the mitochondrial permeability transition pore (mPTP). Additionally, this review presents the use of advanced new methods that can be readily adapted by any investigator to enable them to carry out quantitative Ca2+ measurements in mitochondria while controlling the inner mitochondrial membrane potential, ΔΨm.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA; The Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.
| | - Maura Greiser
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA; The Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA; The Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA.
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Hsu SS, Liang WZ. Cytotoxic Effects of Mesaconitine, the Aconitum carmichaelii Debx Bioactive Compound, on HBEC-5i Human Brain Microvascular Endothelial Cells: Role of Ca 2+ Signaling-Mediated Pathway. Neurotox Res 2020; 39:256-265. [PMID: 32588354 DOI: 10.1007/s12640-020-00249-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/30/2020] [Accepted: 06/22/2020] [Indexed: 10/24/2022]
Abstract
Mesaconitine, one of Aconitum carmichaelii Debx bioactive compounds, was shown to evoke Ca2+ homeostasis and its related physiological effects in endothelial cell types. However, the effect of mesaconitine on Ca2+ signaling and cell viability in human brain microvascular endothelial cells is unclear. This study focused on exploring whether mesaconitine changed cytosolic Ca2+ concentrations ([Ca2+]i), affected cell viability, and established the relationship between Ca2+ signaling and viability in HBEC-5i human brain microvascular endothelial cells. In HBEC-5i cells, cell viability was measured by the cell proliferation reagent (WST-1). [Ca2+]i was measured by the Ca2+-sensitive fluorescent dye fura-2. Mesaconitine (10-100 μM) concentration dependently induced [Ca2+]i rises. Ca2+ removal reduced the signal by approximately 25%. Mesaconitine (40-100 μM) caused cytotoxicity in HBEC-5i cells. This cytotoxic response was significantly reversed by chelation of cytosolic Ca2+ with BAPTA/AM. In Ca2+-containing medium, mesaconitine-induced Ca2+ entry was inhibited by 25% by modulators of store-operated Ca2+ channels and protein kinase C (PKC). Furthermore, mesaconitine also induced Mn2+ influx suggesting of Ca2+ entry. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin abolished mesaconitine-evoked [Ca2+]i rises. Conversely, treatment with mesaconitine abolished thapsigargin-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 abolished mesaconitine-induced [Ca2+]i rises. In sum, mesaconitine caused cytotoxicity that was triggered by preceding [Ca2+]i rises. Furthermore, mesaconitine induced [Ca2+]i rises by evoking Ca2+ entry via PKC-sensitive store-operated Ca2+ channels and PLC-dependent Ca2+ release from the endoplasmic reticulum. It suggests that Ca2+ signaling have a potential cytotoxic effect on mesaconitine-treated human brain microvascular endothelial cells.
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Affiliation(s)
- Shu-Shong Hsu
- Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, 81362, Taiwan.,Department of Surgery, National Defense Medical Center, Taipei, 11490, Taiwan.,College of Health and Nursing, Meiho University, Neipu, Pingtung, 91202, Taiwan
| | - Wei-Zhe Liang
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, 81362, Taiwan. .,Department of Pharmacy and Master Program, College of Pharmacy and Health Care, Tajen University, Pingtung County, 90741, Taiwan.
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Bertholet AM, Kirichok Y. Patch-Clamp Analysis of the Mitochondrial H + Leak in Brown and Beige Fat. Front Physiol 2020; 11:326. [PMID: 32351404 PMCID: PMC7174661 DOI: 10.3389/fphys.2020.00326] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 03/20/2020] [Indexed: 01/27/2023] Open
Abstract
Mitochondria convert the chemical energy of metabolic substrates into adenosine triphosphate (ATP) and heat. Although ATP production has become a focal point of research in bioenergetics, mitochondrial thermogenesis is also crucial for energy metabolism. Mitochondria generate heat due to H+ leak across the inner mitochondrial membrane (IMM) which is mediated by mitochondrial uncoupling proteins. The mitochondrial H+ leak was first identified, and studied for many decades, using mitochondrial respiration technique. Unfortunately, this method measures H+ leak indirectly, and its precision is insufficient for the rigorous insight into the mitochondrial function at the molecular level. Direct patch-clamp recording of H+ leak would have a significantly higher amplitude and time resolution, but application of the patch-clamp technique to a small subcellular organelle such as mitochondria has been challenging. We developed a method that facilitates patch-clamp recording from the whole IMM, enabling the direct measurement of small H+ leak currents via uncoupling proteins and thus, providing a rigorous understanding of the molecular mechanisms involved. In this paper we cover the methodology of measuring the H+ leak in mitochondria of specialized thermogenic tissues brown and beige fat.
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Affiliation(s)
- Ambre M. Bertholet
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
| | - Yuriy Kirichok
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
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12
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The Interplay between Ca 2+ Signaling Pathways and Neurodegeneration. Int J Mol Sci 2019; 20:ijms20236004. [PMID: 31795242 PMCID: PMC6928941 DOI: 10.3390/ijms20236004] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/18/2019] [Accepted: 11/25/2019] [Indexed: 12/13/2022] Open
Abstract
Calcium (Ca2+) homeostasis is essential for cell maintenance since this ion participates in many physiological processes. For example, the spatial and temporal organization of Ca2+ signaling in the central nervous system is fundamental for neurotransmission, where local changes in cytosolic Ca2+ concentration are needed to transmit information from neuron to neuron, between neurons and glia, and even regulating local blood flow according to the required activity. However, under pathological conditions, Ca2+ homeostasis is altered, with increased cytoplasmic Ca2+ concentrations leading to the activation of proteases, lipases, and nucleases. This review aimed to highlight the role of Ca2+ signaling in neurodegenerative disease-related apoptosis, where the regulation of intracellular Ca2+ homeostasis depends on coordinated interactions between the endoplasmic reticulum, mitochondria, and lysosomes, as well as specific transport mechanisms. In neurodegenerative diseases, alterations-increased oxidative stress, energy metabolism alterations, and protein aggregation have been identified. The aggregation of α-synuclein, β-amyloid peptide (Aβ), and huntingtin all adversely affect Ca2+ homeostasis. Due to the mounting evidence for the relevance of Ca2+ signaling in neuroprotection, we would focus on the expression and function of Ca2+ signaling-related proteins, in terms of the effects on autophagy regulation and the onset and progression of neurodegenerative diseases.
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Tarasova NV, Vishnyakova PA, Logashina YA, Elchaninov AV. Mitochondrial Calcium Uniporter Structure and Function in Different Types of Muscle Tissues in Health and Disease. Int J Mol Sci 2019; 20:ijms20194823. [PMID: 31569359 PMCID: PMC6801532 DOI: 10.3390/ijms20194823] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 09/12/2019] [Accepted: 09/26/2019] [Indexed: 02/07/2023] Open
Abstract
Calcium ions (Ca2+) influx to mitochondrial matrix is crucial for the life of a cell. Mitochondrial calcium uniporter (mtCU) is a protein complex which consists of the pore-forming subunit (MCU) and several regulatory subunits. MtCU is the main contributor to inward Ca2+ currents through the inner mitochondrial membrane. Extensive investigations of mtCU involvement into normal and pathological molecular pathways started from the moment of discovery of its molecular components. A crucial role of mtCU in the control of these pathways is now recognized in both health and disease. In particular, impairments of mtCU function have been demonstrated for cardiovascular and skeletal muscle-associated pathologies. This review summarizes the current state of knowledge on mtCU structure, regulation, and function in different types of muscle tissues in health and disease.
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Affiliation(s)
- Nadezhda V Tarasova
- Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Trubetskaya str. 8, bld. 2, Moscow 119991, Russia.
| | - Polina A Vishnyakova
- National Medical Research Center for Obstetrics, Gynecology and Perinatology Named after Academician V.I. Kulakov of Ministry of Healthcare of Russian Federation, 4 Oparina Street, Moscow 117997, Russia.
| | - Yulia A Logashina
- Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Trubetskaya str. 8, bld. 2, Moscow 119991, Russia.
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street 16/10, Moscow 117997, Russia.
| | - Andrey V Elchaninov
- National Medical Research Center for Obstetrics, Gynecology and Perinatology Named after Academician V.I. Kulakov of Ministry of Healthcare of Russian Federation, 4 Oparina Street, Moscow 117997, Russia.
- Scientific Research Institute of Human Morphology, 3 Tsurupa Street, Moscow 117418, Russia.
- Peoples' Friendship University of Russia, 6 Miklukho-Maklaya Street, Moscow 117198, Russia.
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