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Hoogstraten CA, Schirris TJJ, Russel FGM. Unlocking mitochondrial drug targets: The importance of mitochondrial transport proteins. Acta Physiol (Oxf) 2024; 240:e14150. [PMID: 38666512 DOI: 10.1111/apha.14150] [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: 10/04/2023] [Revised: 03/02/2024] [Accepted: 04/12/2024] [Indexed: 05/12/2024]
Abstract
A disturbed mitochondrial function contributes to the pathology of many common diseases. These organelles are therefore important therapeutic targets. On the contrary, many adverse effects of drugs can be explained by a mitochondrial off-target effect, in particular, due to an interaction with carrier proteins in the inner membrane. Yet this class of transport proteins remains underappreciated and understudied. The aim of this review is to provide a deeper understanding of the role of mitochondrial carriers in health and disease and their significance as drug targets. We present literature-based evidence that mitochondrial carrier proteins are associated with prevalent diseases and emphasize their potential as drug (off-)target sites by summarizing known mitochondrial drug-transporter interactions. Studying these carriers will enhance our knowledge of mitochondrial drug on- and off-targets and provide opportunities to further improve the efficacy and safety of drugs.
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Affiliation(s)
- Charlotte A Hoogstraten
- Department of Pharmacy, Division of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, the Netherlands
- Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Tom J J Schirris
- Department of Pharmacy, Division of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, the Netherlands
- Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Frans G M Russel
- Department of Pharmacy, Division of Pharmacology and Toxicology, Radboud University Medical Center, Nijmegen, the Netherlands
- Radboud Center for Mitochondrial Medicine, Radboud University Medical Center, Nijmegen, the Netherlands
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2
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Raut S, Singh K, Sanghvi S, Loyo-Celis V, Varghese L, Singh E, Gururaja Rao S, Singh H. Chloride ions in health and disease. Biosci Rep 2024; 44:BSR20240029. [PMID: 38573803 PMCID: PMC11065649 DOI: 10.1042/bsr20240029] [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: 01/09/2024] [Revised: 03/26/2024] [Accepted: 04/04/2024] [Indexed: 04/06/2024] Open
Abstract
Chloride is a key anion involved in cellular physiology by regulating its homeostasis and rheostatic processes. Changes in cellular Cl- concentration result in differential regulation of cellular functions such as transcription and translation, post-translation modifications, cell cycle and proliferation, cell volume, and pH levels. In intracellular compartments, Cl- modulates the function of lysosomes, mitochondria, endosomes, phagosomes, the nucleus, and the endoplasmic reticulum. In extracellular fluid (ECF), Cl- is present in blood/plasma and interstitial fluid compartments. A reduction in Cl- levels in ECF can result in cell volume contraction. Cl- is the key physiological anion and is a principal compensatory ion for the movement of the major cations such as Na+, K+, and Ca2+. Over the past 25 years, we have increased our understanding of cellular signaling mediated by Cl-, which has helped in understanding the molecular and metabolic changes observed in pathologies with altered Cl- levels. Here, we review the concentration of Cl- in various organs and cellular compartments, ion channels responsible for its transportation, and recent information on its physiological roles.
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Affiliation(s)
- Satish K. Raut
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
| | - Kulwinder Singh
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
| | - Shridhar Sanghvi
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
- Department of Molecular Cellular and Developmental Biology, The Ohio State University, Columbus, OH, U.S.A
| | - Veronica Loyo-Celis
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
| | - Liyah Varghese
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
| | - Ekam R. Singh
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
| | | | - Harpreet Singh
- Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, U.S.A
- Department of Molecular Cellular and Developmental Biology, The Ohio State University, Columbus, OH, U.S.A
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3
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Ge WD, Du TT, Wang CY, Sun LN, Wang YQ. Calcium signaling crosstalk between the endoplasmic reticulum and mitochondria, a new drug development strategies of kidney diseases. Biochem Pharmacol 2024; 225:116278. [PMID: 38740223 DOI: 10.1016/j.bcp.2024.116278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 04/25/2024] [Accepted: 05/10/2024] [Indexed: 05/16/2024]
Abstract
Calcium (Ca2+) acts as a second messenger and constitutes a complex and large information exchange system between the endoplasmic reticulum (ER) and mitochondria; this process is involved in various life activities, such as energy metabolism, cell proliferation and apoptosis. Increasing evidence has suggested that alterations in Ca2+ crosstalk between the ER and mitochondria, including alterations in ER and mitochondrial Ca2+ channels and related Ca2+ regulatory proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), inositol 1,4,5-trisphosphate receptor (IP3R), and calnexin (CNX), are closely associated with the development of kidney disease. Therapies targeting intracellular Ca2+ signaling have emerged as an emerging field in the treatment of renal diseases. In this review, we focused on recent advances in Ca2+ signaling, ER and mitochondrial Ca2+ monitoring methods and Ca2+ homeostasis in the development of renal diseases and sought to identify new targets and insights for the treatment of renal diseases by targeting Ca2+ channels or related Ca2+ regulatory proteins.
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Affiliation(s)
- Wen-Di Ge
- Research Division of Clinical Pharmacology, the First Affiliated Hospital of Nanjing Medical University & Jiangsu Province Hospital, Nanjing, China; Department of Pharmacy, Nanjing Medical University, Nanjing, China
| | - Tian-Tian Du
- Research Division of Clinical Pharmacology, the First Affiliated Hospital of Nanjing Medical University & Jiangsu Province Hospital, Nanjing, China; Department of Pharmacy, Nanjing Medical University, Nanjing, China
| | - Cao-Yang Wang
- Research Division of Clinical Pharmacology, the First Affiliated Hospital of Nanjing Medical University & Jiangsu Province Hospital, Nanjing, China; Department of Pharmacy, Nanjing Medical University, Nanjing, China
| | - Lu-Ning Sun
- Research Division of Clinical Pharmacology, the First Affiliated Hospital of Nanjing Medical University & Jiangsu Province Hospital, Nanjing, China; Department of Pharmacy, Nanjing Medical University, Nanjing, China.
| | - Yong-Qing Wang
- Research Division of Clinical Pharmacology, the First Affiliated Hospital of Nanjing Medical University & Jiangsu Province Hospital, Nanjing, China; Department of Pharmacy, Nanjing Medical University, Nanjing, China.
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4
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Castillo-Velasquez C, Matamala E, Becerra D, Orio P, Brauchi SE. Optical recordings of organellar membrane potentials and the components of membrane conductance in lysosomes. J Physiol 2024; 602:1637-1654. [PMID: 38625711 DOI: 10.1113/jp283825] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 03/20/2024] [Indexed: 04/17/2024] Open
Abstract
The eukaryotic cell is highly compartmentalized with organelles. Owing to their function in transporting metabolites, metabolic intermediates and byproducts of metabolic activity, organelles are important players in the orchestration of cellular function. Recent advances in optical methods for interrogating the different aspects of organellar activity promise to revolutionize our ability to dissect cellular processes with unprecedented detail. The transport activity of organelles is usually coupled to the transport of charged species; therefore, it is not only associated with the metabolic landscape but also entangled with membrane potentials. In this context, the targeted expression of fluorescent probes for interrogating organellar membrane potential (Ψorg) emerges as a powerful approach, offering less-invasive conditions and technical simplicity to interrogate cellular signalling and metabolism. Different research groups have made remarkable progress in adapting a variety of optical methods for measuring and monitoring Ψorg. These approaches include using potentiometric dyes, genetically encoded voltage indicators, hybrid fluorescence resonance energy transfer sensors and photoinduced electron transfer systems. These studies have provided consistent values for the resting potential of single-membrane organelles, such as lysosomes, the Golgi and the endoplasmic reticulum. We can foresee the use of dynamic measurements of Ψorg to study fundamental problems in organellar physiology that are linked to serious cellular disorders. Here, we present an overview of the available techniques, a survey of the resting membrane potential of internal membranes and, finally, an open-source mathematical model useful to interpret and interrogate membrane-bound structures of small volume by using the lysosome as an example.
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Affiliation(s)
- Cristian Castillo-Velasquez
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
| | - Ella Matamala
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
| | - Diego Becerra
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Patricio Orio
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Instituto de Neurociencias, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Sebastian E Brauchi
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
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5
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Balderas E, Lee SH, Shankar TS, Yin X, Balynas AM, Kyriakopoulos CP, Selzman CH, Drakos SG, Chaudhuri D. Mitochondria possess a large, non-selective ionic current that is enhanced during cardiac injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.15.567241. [PMID: 38014208 PMCID: PMC10680780 DOI: 10.1101/2023.11.15.567241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Mitochondrial ion channels are essential for energy production and cell survival. To avoid depleting the electrochemical gradient used for ATP synthesis, channels so far described in the mitochondrial inner membrane open only briefly, are highly ion-selective, have restricted tissue distributions, or have small currents. Here, we identify a mitochondrial inner membrane conductance that has strikingly different behavior from previously described channels. It is expressed ubiquitously, and transports cations non-selectively, producing a large, up to nanoampere-level, current. The channel does not lead to inner membrane uncoupling during normal physiology because it only becomes active at depolarized voltages. It is inhibited by external Ca2+, corresponding to the intermembrane space, as well as amiloride. This large, ubiquitous, non-selective, amiloride-sensitive (LUNA) current appears most active when expression of the mitochondrial calcium uniporter is minimal, such as in the heart. In this organ, we find that LUNA current magnitude increases two- to threefold in multiple mouse models of injury, an effect also seen in cardiac mitochondria from human patients with heart failure with reduced ejection fraction. Taken together, these features lead us to speculate that LUNA current may arise from an essential protein that acts as a transporter under physiological conditions, but becomes a channel under conditions of mitochondrial stress and depolarization.
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Affiliation(s)
- Enrique Balderas
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Sandra H.J. Lee
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Thirupura S. Shankar
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Xue Yin
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Anthony M. Balynas
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Christos P. Kyriakopoulos
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
| | - Craig H. Selzman
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- Department of Surgery, Division of Cardiothoracic Surgery, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
| | - Stavros G. Drakos
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT
| | - Dipayan Chaudhuri
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT
- U.T.A.H. (Utah Transplant Affiliated Hospitals) Cardiac Transplant Program: University of Utah Healthcare and School of Medicine, Intermountain Medical Center, Salt Lake Veterans Affairs Health Care System, Salt Lake City, UT
- Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT
- Departments of Biochemistry, Biomedical Engineering, University of Utah, Salt Lake City, UT
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6
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Ernst P, Kim S, Yang Z, Liu XM, Zhou L. Characterization of the far-red fluorescent probe MitoView 633 for dynamic mitochondrial membrane potential measurement. Front Physiol 2023; 14:1257739. [PMID: 37936577 PMCID: PMC10627182 DOI: 10.3389/fphys.2023.1257739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 10/13/2023] [Indexed: 11/09/2023] Open
Abstract
Introduction: MitoView 633, a far-red fluorescent dye, exhibits the ability to accumulate within mitochondria in a membrane potential-dependent manner, as described by the Nernst equation. This characteristic renders it a promising candidate for bioenergetics studies, particularly as a robust indicator of mitochondrial membrane potential (DYm). Despite its great potential, its utility in live cell imaging has not been well characterized. Methods: This study seeks to characterize the spectral properties of MitoView 633 in live cells and evaluate its mitochondrial staining, resistance to photobleaching, and dynamics during DYm depolarization. The co-staining and imaging of MitoView 633 with other fluorophores such as MitoSOX Red and Fluo-4 AM were also examined in cardiomyocytes using confocal microscopy. Results and Discussion: Spectrum analysis showed that MitoView 633 emission could be detected at 660 ± 50 nm, and exhibited superior thermal stability compared to tetramethylrhodamine methyl ester (TMRM), a commonly used DYm indicator, which emits at 605 ± 25 nm. Confocal imaging unequivocally illustrated MitoView 633's specific localization within the mitochondrial matrix, corroborated by its colocalization with MitoTracker Green, a well-established mitochondrial marker. Furthermore, our investigation revealed that MitoView 633 exhibited minimal photobleaching at the recommended in vitro concentrations. Additionally, the dynamics of MitoView 633 fluoresce during carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP, a mitochondrial uncoupler)-induced DYm depolarization mirrored that of TMRM. Importantly, MitoView 633 demonstrated compatibility with co-staining alongside MitoSOX Red and Fluo-4 AM, enabling concurrent monitoring of DYm, mitochondrial ROS, and cytosolic Ca2+ in intact cells. Conclusion: These findings collectively underscore MitoView 633 as a superb molecular probe for the singular or combined assessment of DYm and other indicators in live cell imaging applications.
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Affiliation(s)
- Patrick Ernst
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Seulhee Kim
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Zengqiao Yang
- Department of Surgery, The Ohio State University, Columbus, OH, United States
| | - Xiaoguang Margaret Liu
- Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, United States
| | - Lufang Zhou
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States
- Department of Surgery, The Ohio State University, Columbus, OH, United States
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7
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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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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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9
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Szabo I, Szewczyk A. Mitochondrial Ion Channels. Annu Rev Biophys 2023; 52:229-254. [PMID: 37159294 DOI: 10.1146/annurev-biophys-092622-094853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Mitochondria are involved in multiple cellular tasks, such as ATP synthesis, metabolism, metabolite and ion transport, regulation of apoptosis, inflammation, signaling, and inheritance of mitochondrial DNA. The majority of the correct functioning of mitochondria is based on the large electrochemical proton gradient, whose component, the inner mitochondrial membrane potential, is strictly controlled by ion transport through mitochondrial membranes. Consequently, mitochondrial function is critically dependent on ion homeostasis, the disturbance of which leads to abnormal cell functions. Therefore, the discovery of mitochondrial ion channels influencing ion permeability through the membrane has defined a new dimension of the function of ion channels in different cell types, mainly linked to the important tasks that mitochondrial ion channels perform in cell life and death. This review summarizes studies on animal mitochondrial ion channels with special focus on their biophysical properties, molecular identity, and regulation. Additionally, the potential of mitochondrial ion channels as therapeutic targets for several diseases is briefly discussed.
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Affiliation(s)
- Ildiko Szabo
- Department of Biology, University of Padova, Italy;
| | - Adam Szewczyk
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland;
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Endlicher R, Drahota Z, Štefková K, Červinková Z, Kučera O. The Mitochondrial Permeability Transition Pore-Current Knowledge of Its Structure, Function, and Regulation, and Optimized Methods for Evaluating Its Functional State. Cells 2023; 12:cells12091273. [PMID: 37174672 PMCID: PMC10177258 DOI: 10.3390/cells12091273] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 04/19/2023] [Accepted: 04/25/2023] [Indexed: 05/15/2023] Open
Abstract
The mitochondrial permeability transition pore (MPTP) is a calcium-dependent, ion non-selective membrane pore with a wide range of functions. Although the MPTP has been studied for more than 50 years, its molecular structure remains unclear. Short-term (reversible) opening of the MPTP protects cells from oxidative damage and enables the efflux of Ca2+ ions from the mitochondrial matrix and cell signaling. However, long-term (irreversible) opening induces processes leading to cell death. Ca2+ ions, reactive oxygen species, and changes in mitochondrial membrane potential regulate pore opening. The sensitivity of the pore to Ca2+ ions changes as an organism ages, and MPTP opening plays a key role in the pathogenesis of many diseases. Most studies of the MPTP have focused on elucidating its molecular structure. However, understanding the mechanisms that will inhibit the MPTP may improve the treatment of diseases associated with its opening. To evaluate the functional state of the MPTP and its inhibitors, it is therefore necessary to use appropriate methods that provide reproducible results across laboratories. This review summarizes our current knowledge of the function and regulation of the MPTP. The latter part of the review introduces two optimized methods for evaluating the functional state of the pore under standardized conditions.
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Affiliation(s)
- René Endlicher
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
- Department of Anatomy, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
| | - Zdeněk Drahota
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
- Institute of Physiology, Czech Academy of Sciences, 142 00 Prague, Czech Republic
| | - Kateřina Štefková
- Department of Anatomy, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
| | - Zuzana Červinková
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
| | - Otto Kučera
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, 500 03 Hradec Králové, Czech Republic
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11
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Kumar S, Choudhary N, Faruq M, Kumar A, Saran RK, Indercanti PK, Singh V, Sait H, Jaitley S, Valis M, Kuca K, Polipalli SK, Kumar M, Singh T, Suravajhala P, Sharma R, Kapoor S. Anastrozole-mediated modulation of mitochondrial activity by inhibition of mitochondrial permeability transition pore opening: an initial perspective. J Biomol Struct Dyn 2023; 41:14063-14079. [PMID: 36815262 DOI: 10.1080/07391102.2023.2176927] [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] [Received: 09/12/2022] [Accepted: 01/31/2023] [Indexed: 02/24/2023]
Abstract
The mitochondrial permeability transition pore (mtPTP) plays a vital role in altering the structure and function of mitochondria. Cyclophilin D (CypD) is a mitochondrial protein that regulates mtPTP function and a known drug target for therapeutic studies involving mitochondria. While the effect of aromatase inhibition on the mtPTP has been studied previously, the effect of anastrozole on the mtPTP has not been completely elucidated. The role of anastrozole in modulating the mtPTP was evaluated by docking, molecular dynamics and network-guided studies using human CypD data. The peripheral blood mononuclear cells (PBMCs) of patients with mitochondrial disorders and healthy controls were treated with anastrozole and evaluated for mitochondrial permeability transition pore (mtPTP) function and apoptosis using a flow cytometer. Spectrophotometry was employed for estimating total ATP levels. The anastrozole-CypD complex is more stable than cyclosporin A (CsA)-CypD. Anastrozole performed better than cyclosporine in inhibiting mtPTP. Additional effects included inducing mitochondrial membrane depolarization and a reduction in mitochondrial swelling and superoxide generation, intrinsic caspase-3 activity and cellular apoptosis, along with an increase in ATP levels. Anastrozole may serve as a potential therapeutic agent for mitochondrial disorders and ameliorate the clinical phenotype by regulating the activity of mtPTP. However, further studies are required to substantiate our preliminary findings.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Somesh Kumar
- Pediatrics Genetics & Research Laboratory, Department of Pediatrics, Maulana Azad Medical College & Associated LN Hospital, Delhi, India
| | - Neha Choudhary
- Centre for Computational Biology and Bioinformatics, Central University of Himachal Pradesh, Dharamsala, India
| | - Mohammed Faruq
- Institute of Genomics and Integrative Biology, Council of Scientific and Industrial Research (CSIR), Delhi, India
| | - Arun Kumar
- Department of Emergency Medicine, All India Institute of Medical Sciences (AIIMS), New Delhi, India
- Department of Zoology, Kirori Mal College, University of Delhi, Delhi, India
| | - Ravindra K Saran
- Department of Pathology, Govind Ballabh Pant Institute of Postgraduate Medical Education and Research, Delhi, India
| | | | - Vikram Singh
- Centre for Computational Biology and Bioinformatics, Central University of Himachal Pradesh, Dharamsala, India
| | - Haseena Sait
- Pediatrics Genetics & Research Laboratory, Department of Pediatrics, Maulana Azad Medical College & Associated LN Hospital, Delhi, India
| | - Sunita Jaitley
- Department of Biomedical Sciences, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Martin Valis
- Department of Neurology of the Medical Faculty of Charles University and University Hospital in Hradec Králové, Hradec Králové, Czech Republic
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové, Czech Republic
| | - Sunil K Polipalli
- Pediatrics Genetics & Research Laboratory, Department of Pediatrics, Maulana Azad Medical College & Associated LN Hospital, Delhi, India
| | - Manoj Kumar
- Department of Emergency Medicine, All India Institute of Medical Sciences (AIIMS), New Delhi, India
- Department of Microbiology, World College of Medical Science and Research, Jhajjar, Haryana, India
| | - Tejveer Singh
- Molecular Oncology Laboratory, Department of Zoology, University of Delhi, Delhi, India
| | | | - Rohit Sharma
- Department of Rasa Shastra and Bhaishajya Kalpana, Faculty of Ayurveda, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - Seema Kapoor
- Pediatrics Genetics & Research Laboratory, Department of Pediatrics, Maulana Azad Medical College & Associated LN Hospital, Delhi, India
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12
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Methods of Measuring Mitochondrial Potassium Channels: A Critical Assessment. Int J Mol Sci 2022; 23:ijms23031210. [PMID: 35163132 PMCID: PMC8835872 DOI: 10.3390/ijms23031210] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/22/2022] Open
Abstract
In this paper, the techniques used to study the function of mitochondrial potassium channels are critically reviewed. The majority of these techniques have been known for many years as a result of research on plasma membrane ion channels. Hence, in this review, we focus on the critical evaluation of techniques used in the studies of mitochondrial potassium channels, describing their advantages and limitations. Functional analysis of mitochondrial potassium channels in comparison to that of plasmalemmal channels presents additional experimental challenges. The reliability of functional studies of mitochondrial potassium channels is often affected by the need to isolate mitochondria and by functional properties of mitochondria such as respiration, metabolic activity, swelling capacity, or high electrical potential. Three types of techniques are critically evaluated: electrophysiological techniques, potassium flux measurements, and biochemical techniques related to potassium flux measurements. Finally, new possible approaches to the study of the function of mitochondrial potassium channels are presented. We hope that this review will assist researchers in selecting reliable methods for studying, e.g., the effects of drugs on mitochondrial potassium channel function. Additionally, this review should aid in the critical evaluation of the results reported in various articles on mitochondrial potassium channels.
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13
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Patch Clamp: The First Four Decades of a Technique That Revolutionized Electrophysiology and Beyond. Rev Physiol Biochem Pharmacol 2022; 186:1-28. [PMID: 35471741 DOI: 10.1007/112_2022_71] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Forty years ago, the introduction of a new electrophysiological technique, the patch clamp, revolutionized the fields of Cellular Physiology and Biophysics, providing for the first time the possibility of describing the behavior of a single protein, an ion-permeable channel of the cell plasma membrane, in its physiological environment. The new approach was actually much more potent and versatile than initially envisaged, and it has evolved into several different modalities that have radically changed our knowledge of how cells (not only the classical "electrically excitable "ones, such as nerves and muscles) use electrical signaling to modulate and organize their activity. This review aims at telling the history of the background from which the new technique evolved and at analyzing some of its more recent developments.
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14
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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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15
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Kravenska Y, Checchetto V, Szabo I. Routes for Potassium Ions across Mitochondrial Membranes: A Biophysical Point of View with Special Focus on the ATP-Sensitive K + Channel. Biomolecules 2021; 11:1172. [PMID: 34439838 PMCID: PMC8393992 DOI: 10.3390/biom11081172] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 07/29/2021] [Accepted: 08/02/2021] [Indexed: 12/18/2022] Open
Abstract
Potassium ions can cross both the outer and inner mitochondrial membranes by means of multiple routes. A few potassium-permeable ion channels exist in the outer membrane, while in the inner membrane, a multitude of different potassium-selective and potassium-permeable channels mediate K+ uptake into energized mitochondria. In contrast, potassium is exported from the matrix thanks to an H+/K+ exchanger whose molecular identity is still debated. Among the K+ channels of the inner mitochondrial membrane, the most widely studied is the ATP-dependent potassium channel, whose pharmacological activation protects cells against ischemic damage and neuronal injury. In this review, we briefly summarize and compare the different hypotheses regarding the molecular identity of this patho-physiologically relevant channel, taking into account the electrophysiological characteristics of the proposed components. In addition, we discuss the characteristics of the other channels sharing localization to both the plasma membrane and mitochondria.
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Affiliation(s)
| | | | - Ildiko Szabo
- Department of Biology, University of Padova, 35131 Padova, Italy; (Y.K.); (V.C.)
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16
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Morciano G, Naumova N, Koprowski P, Valente S, Sardão VA, Potes Y, Rimessi A, Wieckowski MR, Oliveira PJ. The mitochondrial permeability transition pore: an evolving concept critical for cell life and death. Biol Rev Camb Philos Soc 2021; 96:2489-2521. [PMID: 34155777 DOI: 10.1111/brv.12764] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 05/28/2021] [Accepted: 06/04/2021] [Indexed: 02/06/2023]
Abstract
In this review, we summarize current knowledge of perhaps one of the most intriguing phenomena in cell biology: the mitochondrial permeability transition pore (mPTP). This phenomenon, which was initially observed as a sudden loss of inner mitochondrial membrane impermeability caused by excessive calcium, has been studied for almost 50 years, and still no definitive answer has been provided regarding its mechanisms. From its initial consideration as an in vitro artifact to the current notion that the mPTP is a phenomenon with physiological and pathological implications, a long road has been travelled. We here summarize the role of mitochondria in cytosolic calcium control and the evolving concepts regarding the mitochondrial permeability transition (mPT) and the mPTP. We show how the evolving mPTP models and mechanisms, which involve many proposed mitochondrial protein components, have arisen from methodological advances and more complex biological models. We describe how scientific progress and methodological advances have allowed milestone discoveries on mPTP regulation and composition and its recognition as a valid target for drug development and a critical component of mitochondrial biology.
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Affiliation(s)
- Giampaolo Morciano
- Maria Cecilia Hospital, GVM Care & Research, Via Corriera 1, Cotignola, Ravenna, 48033, Italy.,Department of Medical Sciences, Section of Experimental Medicine, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Via Fossato di Mortara 70, Ferrara, 44121, Italy
| | - Natalia Naumova
- Department of Cardiac Thoracic and Vascular Sciences and Public Health, University of Padua Medical School, Via Giustiniani 2, Padova, 35128, Italy
| | - Piotr Koprowski
- Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, Warsaw, 02-093, Poland
| | - Sara Valente
- CNC - Center for Neuroscience and Cell Biology, CIBB - Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, UC Biotech, Biocant Park, Cantanhede, 3060-197, Portugal
| | - Vilma A Sardão
- CNC - Center for Neuroscience and Cell Biology, CIBB - Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, UC Biotech, Biocant Park, Cantanhede, 3060-197, Portugal
| | - Yaiza Potes
- Laboratory of Mitochondrial Biology and Metabolism, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, Warsaw, 02-093, Poland
| | - Alessandro Rimessi
- Department of Medical Sciences, Section of Experimental Medicine, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Via Fossato di Mortara 70, Ferrara, 44121, Italy
| | - Mariusz R Wieckowski
- Laboratory of Mitochondrial Biology and Metabolism, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur Street, Warsaw, 02-093, Poland
| | - Paulo J Oliveira
- CNC - Center for Neuroscience and Cell Biology, CIBB - Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, UC Biotech, Biocant Park, Cantanhede, 3060-197, Portugal
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17
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Pedersen SF, Flinck M, Pardo LA. The Interplay between Dysregulated Ion Transport and Mitochondrial Architecture as a Dangerous Liaison in Cancer. Int J Mol Sci 2021; 22:ijms22105209. [PMID: 34069047 PMCID: PMC8156689 DOI: 10.3390/ijms22105209] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/08/2021] [Accepted: 05/11/2021] [Indexed: 02/06/2023] Open
Abstract
Transport of ions and nutrients is a core mitochondrial function, without which there would be no mitochondrial metabolism and ATP production. Both ion homeostasis and mitochondrial phenotype undergo pervasive changes during cancer development, and both play key roles in driving the malignancy. However, the link between these events has been largely ignored. This review comprehensively summarizes and critically discusses the role of the reciprocal relationship between ion transport and mitochondria in crucial cellular functions, including metabolism, signaling, and cell fate decisions. We focus on Ca2+, H+, and K+, which play essential and highly interconnected roles in mitochondrial function and are profoundly dysregulated in cancer. We describe the transport and roles of these ions in normal mitochondria, summarize the changes occurring during cancer development, and discuss how they might impact tumorigenesis.
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Affiliation(s)
- Stine F. Pedersen
- Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark;
- Correspondence: (S.F.P.); (L.A.P.)
| | - Mette Flinck
- Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark;
| | - Luis A. Pardo
- Oncophysiology Group, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
- Correspondence: (S.F.P.); (L.A.P.)
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18
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Checchetto V, Leanza L, De Stefani D, Rizzuto R, Gulbins E, Szabo I. Mitochondrial K + channels and their implications for disease mechanisms. Pharmacol Ther 2021; 227:107874. [PMID: 33930454 DOI: 10.1016/j.pharmthera.2021.107874] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 04/12/2021] [Indexed: 02/06/2023]
Abstract
The field of mitochondrial ion channels underwent a rapid development during the last decade, thanks to the molecular identification of some of the nuclear-encoded organelle channels and to advances in strategies allowing specific pharmacological targeting of these proteins. Thereby, genetic tools and specific drugs aided definition of the relevance of several mitochondrial channels both in physiological as well as pathological conditions. Unfortunately, in the case of mitochondrial K+ channels, efforts of genetic manipulation provided only limited results, due to their dual localization to mitochondria and to plasma membrane in most cases. Although the impact of mitochondrial K+ channels on human diseases is still far from being genuinely understood, pre-clinical data strongly argue for their substantial role in the context of several pathologies, including cardiovascular and neurodegenerative diseases as well as cancer. Importantly, these channels are druggable targets, and their in-depth investigation could thus pave the way to the development of innovative small molecules with huge therapeutic potential. In the present review we summarize the available experimental evidence that mechanistically link mitochondrial potassium channels to the above pathologies and underline the possibility of exploiting them for therapy.
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Affiliation(s)
| | - Luigi Leanza
- Department of Biology, University of Padova, Italy
| | | | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padova, Italy
| | - Erich Gulbins
- Department of Molecular Biology, University of Duisburg-Essen, Germany
| | - Ildiko Szabo
- Department of Biology, University of Padova, Italy; CNR Institute of Neurosciences, Italy.
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19
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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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20
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Neginskaya MA, Pavlov EV, Sheu SS. Electrophysiological properties of the mitochondrial permeability transition pores: Channel diversity and disease implication. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2021; 1862:148357. [PMID: 33359307 PMCID: PMC7954400 DOI: 10.1016/j.bbabio.2020.148357] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 11/26/2020] [Accepted: 12/15/2020] [Indexed: 02/07/2023]
Abstract
The mitochondrial permeability transition pore (mPTP) is a channel that, when open, is responsible for a dramatic increase in the permeability of the mitochondrial inner membrane, a process known as the mitochondrial permeability transition (mPT). mPTP activation during Ca2+ dyshomeostasis and oxidative stress disrupts normal mitochondrial function and induces cell death. mPTP opening has been implicated as a critical event in many diseases, including hypoxic injuries, neurodegeneration, and diabetes. Discoveries of recent years indicate that mPTP demonstrates very complicated behavior and regulation, and depending on specific induction or stress conditions, it can function as a high-conductance pore, a small channel, or a non-specific membrane leak. The focus of this review is to summarize the literature on the electrophysiological properties of the mPTP and to evaluate the evidence that it has multiple molecular identities. This review also provides perspective on how an electrophysiological approach can be used to quantitatively investigate the biophysical properties of the mPTP under physiological, pharmacological, pathophysiological, and disease conditions.
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Affiliation(s)
- M A Neginskaya
- Department of Molecular Pathobiology, New York University, New York, NY, USA.
| | - E V Pavlov
- Department of Molecular Pathobiology, New York University, New York, NY, USA
| | - S-S Sheu
- Department of Medicine, Center for Translational Medicine, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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21
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Neginskaya MA, Strubbe JO, Amodeo GF, West BA, Yakar S, Bazil JN, Pavlov EV. The very low number of calcium-induced permeability transition pores in the single mitochondrion. J Gen Physiol 2020; 152:e202012631. [PMID: 32810269 PMCID: PMC7537349 DOI: 10.1085/jgp.202012631] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 06/22/2020] [Accepted: 07/24/2020] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial permeability transition (PT) is a phenomenon of stress-induced increase in nonspecific permeability of the mitochondrial inner membrane that leads to disruption of oxidative phosphorylation and cell death. Quantitative measurement of the membrane permeability increase during PT is critically important for understanding the PT's impact on mitochondrial function. The elementary unit of PT is a PT pore (PTP), a single channel presumably formed by either ATP synthase or adenine nucleotide translocator (ANT). It is not known how many channels are open in a single mitochondrion during PT, which makes it difficult to quantitatively estimate the overall degree of membrane permeability. Here, we used wide-field microscopy to record mitochondrial swelling and quantitatively measure rates of single-mitochondrion volume increase during PT-induced high-amplitude swelling. PT was quantified by calculating the rates of water flux responsible for measured volume changes. The total water flux through the mitochondrial membrane of a single mitochondrion during PT was in the range of (2.5 ± 0.4) × 10-17 kg/s for swelling in 2 mM Ca2+ and (1.1 ± 0.2) × 10-17 kg/s for swelling in 200 µM Ca2+. Under these experimental conditions, a single PTP channel with ionic conductance of 1.5 nS could allow passage of water at the rate of 0.65 × 10-17 kg/s. Thus, we estimate the integral ionic conductance of the whole mitochondrion during PT to be 5.9 ± 0.9 nS for 2 mM concentration of Ca2+ and 2.6 ± 0.4 nS for 200 µM of Ca2+. The number of PTPs per mitochondrion ranged from one to nine. Due to the uncertainties in PTP structure and model parameters, PTP count results may be slightly underestimated. However, taking into account that each mitochondrion has ∼15,000 copies of ATP synthases and ANTs, our data imply that PTP activation is a rare event that occurs only in a small subpopulation of these proteins.
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Affiliation(s)
- Maria A. Neginskaya
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY
| | - Jasiel O. Strubbe
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI
- Department of Physiology, Michigan State University, East Lansing, MI
| | - Giuseppe F. Amodeo
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY
| | - Benjamin A. West
- Department of Physiology, Michigan State University, East Lansing, MI
| | - Shoshana Yakar
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY
| | - Jason N. Bazil
- Department of Physiology, Michigan State University, East Lansing, MI
| | - Evgeny V. Pavlov
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY
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22
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Nath S. A Novel Conceptual Model for the Dual Role of FOF1-ATP Synthase in Cell Life and Cell Death. Biomol Concepts 2020; 11:143-152. [PMID: 32827389 DOI: 10.1515/bmc-2020-0014] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 07/22/2020] [Indexed: 12/31/2022] Open
Abstract
The mitochondrial permeability transition (MPT) has been one of the longstanding enigmas in biology. Its cause is currently at the center of an extensive scientific debate, and several hypotheses on its molecular nature have been put forward. The present view holds that the transition arises from the opening of a high-conductance channel in the energy-transducing membrane, the permeability transition pore (PTP), also called the mitochondrial megachannel or the multiconductance channel (MMC). Here, the novel hypothesis is proposed that the aqueous access channels at the interface of the c-ring and the a-subunit of FO in the FOF1-ATP synthase are repurposed during induction of apoptosis and constitute the elusive PTP/ MMC. A unifying principle based on regulation by local potentials is advanced to rationalize the action of the myriad structurally and chemically diverse inducers and inhibitors of PTP/MMC. Experimental evidence in favor of the hypothesis and its differences from current models of PTP/MMC are summarized. The hypothesis explains in considerable detail how the binding of Ca2+ to a β-catalytic site (site 3) in the F1 portion of ATP synthase triggers the opening of the PTP/MMC. It is also shown to connect to longstanding proposals within Nath's torsional mechanism of energy transduction and ATP synthesis as to how the binding of MgADP to site 3 does not induce PTP/MMC, but instead catalyzes physiological ATP synthesis in cell life. In the author's knowledge, this is the first model that explains how Ca2+ transforms the FOF1-ATP synthase from an exquisite energy-conserving enzyme in cell life into an energy-dissipating structure that promotes cell death. This has major implications for basic as well as for clinical research, such as for the development of drugs that target the MPT, given the established role of PTP/MMC dysregulation in cancer, ischemia, cardiac hypertrophy, and various neurodegenerative diseases.
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Affiliation(s)
- Sunil Nath
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
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23
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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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24
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Carmeliet E. From Bernstein's rheotome to Neher-Sakmann's patch electrode. The action potential. Physiol Rep 2019; 7:e13861. [PMID: 30604910 PMCID: PMC6316177 DOI: 10.14814/phy2.13861] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 07/10/2018] [Accepted: 07/28/2018] [Indexed: 01/08/2023] Open
Abstract
The aim of this review was to provide an overview of the most important stages in the development of cellular electrophysiology. The period covered starts with Bernstein's formulation of the membrane hypothesis and the measurement of the nerve and muscle action potential. Technical innovations make discoveries possible. This was the case with the use of the squid giant axon, allowing the insertion of "large" intracellular electrodes and derivation of transmembrane potentials. Application of the newly developed voltage clamp method for measuring ionic currents, resulted in the formulation of the ionic theory. At the same time transmembrane measurements were made possible in smaller cells by the introduction of the microelectrode. An improvement of this electrode was the next major (r)evolution. The patch electrode made it possible to descend to the molecular level and record single ionic channel activity. The patch technique has been proven to be exceptionally versatile. In its whole-cell configuration it was the solution to measure voltage clamp currents in small cells. See also: https://doi.org/10.14814/phy2.13860 & https://doi.org/10.14814/phy2.13862.
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25
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Dolowy K. Calcium phosphate buffer formed in the mitochondrial matrix during preconditioning supports ΔpH formation and ischemic ATP production and prolongs cell survival -A hypothesis. Mitochondrion 2018; 47:210-217. [PMID: 30448366 DOI: 10.1016/j.mito.2018.11.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 05/06/2018] [Accepted: 11/14/2018] [Indexed: 10/27/2022]
Abstract
Ischemic preconditioning makes cells less sensitive to oxygen deprivation. A similar effect can be achieved by increasing the calcium concentration and applying potassium channel openers. A hypothetical mechanism of preconditioning is presented. In the mitochondrial matrix, there is a calcium hydroxide buffer consisting of a few insoluble calcium phosphate minerals. During ischemia, calcium ions stored in the matrix buffer start to leak out, forming an electric potential difference, while hydroxyl ions remain in the matrix, maintaining its pH and the matrix volume. Preconditioning factors increase the matrix buffer capacity. Production of ATP during ischemia might be the relic of a pre-endosymbiotic past.
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Affiliation(s)
- Krzysztof Dolowy
- Department of Biophysics, Warsaw University of Life Sciences - SGGW, Nowoursynowska 159, Warszawa 02-776, Poland.
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26
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Drummond‐Main CD, Rho JM. Electrophysiological characterization of a mitochondrial inner membrane chloride channel in rat brain. FEBS Lett 2018; 592:1545-1553. [DOI: 10.1002/1873-3468.13042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 03/09/2018] [Accepted: 03/12/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Christopher D. Drummond‐Main
- Developmental Neurosciences Research Program University of Calgary Alberta Canada
- Alberta Children's Hospital Research Institute University of Calgary Alberta Canada
| | - Jong M. Rho
- Developmental Neurosciences Research Program University of Calgary Alberta Canada
- Alberta Children's Hospital Research Institute University of Calgary Alberta Canada
- Departments of Pediatrics Clinical Neurosciences, and Physiology & Pharmacology University of Calgary Alberta Canada
- Hotchkiss Brain Institute Cumming School of Medicine University of Calgary Alberta Canada
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27
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Abstract
Mitochondrial ATP generation by oxidative phosphorylation combines the stepwise oxidation by the electron transport chain (ETC) of the reducing equivalents NADH and FADH2 with the generation of ATP by the ATP synthase. Recent studies show that the ATP synthase is not only essential for the generation of ATP but may also contribute to the formation of the mitochondrial permeability transition pore (PTP). We present a model, in which the PTP is located within the c-subunit ring in the Fo subunit of the ATP synthase. Opening of the PTP was long associated with uncoupling of the ETC and the initiation of programmed cell death. More recently, it was shown that PTP opening may serve a physiologic role: it can transiently open to regulate mitochondrial signaling in mature cells, and it is open in the embryonic mouse heart. This review will discuss how the ATP synthase paradoxically lies at the center of both ATP generation and cell death.
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28
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Shapovalov G, Ritaine A, Bidaux G, Slomianny C, Borowiec AS, Gordienko D, Bultynck G, Skryma R, Prevarskaya N. Organelle membrane derived patches: reshaping classical methods for new targets. Sci Rep 2017; 7:14082. [PMID: 29074990 PMCID: PMC5658434 DOI: 10.1038/s41598-017-13968-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/04/2017] [Indexed: 12/12/2022] Open
Abstract
Intracellular ion channels are involved in multiple signaling processes, including such crucial ones as regulation of cellular motility and fate. With 95% of the cellular membrane belonging to intracellular organelles, it is hard to overestimate the importance of intracellular ion channels. Multiple studies have been performed on these channels over the years, however, a unified approach allowing not only to characterize their activity but also to study their regulation by partner proteins, analogous to the patch clamp “golden standard”, is lacking. Here, we present a universal approach that combines the extraction of intracellular membrane fractions with the preparation of patchable substrates that allows to characterize these channels in endogenous protein environment and to study their regulation by partner proteins. We validate this method by characterizing activity of multiple intracellular ion channels localized to different organelles and by providing detailed electrophysiological characterization of the regulation of IP3R activity by endogenous Bcl-2. Thus, after synthesis and reshaping of the well-established approaches, organelle membrane derived patch clamp provides the means to assess ion channels from arbitrary cellular membranes at the single channel level.
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Affiliation(s)
- George Shapovalov
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Abigaël Ritaine
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Gabriel Bidaux
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Christian Slomianny
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Anne-Sophie Borowiec
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.,Laboratoire INSERM U1060, CarMeN Laboratory, Claude Bernard Lyon 1 University, 8, avenue Rockfeller, F-69373, Lyon, France
| | - Dmitri Gordienko
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, Herestraat 49, BE-3000, Leuven, Belgium
| | - Roman Skryma
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France.,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France
| | - Natalia Prevarskaya
- Inserm U1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université de Sciences et Technologies de Lille (USTL), F-59655, Villeneuve d'Ascq, France. .,Laboratory of Excellence, Ion Channels Science and Therapeutics; Université Lille I Sciences et Technologies, Villeneuve d'Ascq, France.
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29
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Tomasek M, Misak A, Grman M, Tomaskova Z. Subconductance states of mitochondrial chloride channels: implication for functionally-coupled tetramers. FEBS Lett 2017. [PMID: 28640976 DOI: 10.1002/1873-3468.12721] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Recently, it has been discovered that isoforms of intracellular chloride channels (CLIC) are present in cardiac mitochondria. By reconstituting rat cardiac mitochondrial chloride channels into bilayer lipid membranes, we detected three equally separated subconductance states with conductance increment of 45 pS and < 2% occupancy. The observed rare events of channel decomposition into substates, accompanied by disrupted gating, provide an insight into channel quaternary structure. Our findings suggest that the observed channels work as four functionally coupled subunits with synchronized gating. We discuss the putative connection of channel activity from native mitochondria with the recombinant CLIC channels. However, conclusive evidence is needed to prove this connection.
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Affiliation(s)
| | - Anton Misak
- Institute of Clinical and Translational Research, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovak
| | - Marian Grman
- Institute of Clinical and Translational Research, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovak
| | - Zuzana Tomaskova
- Institute of Molecular Physiology and Genetics, Centre of Biosciences, Slovak Academy of Sciences, Bratislava, Slovak
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30
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Fahanik-Babaei J, Shayanfar F, Khodaee N, Saghiri R, Eliassi A. Electro-pharmacological profiles of two brain mitoplast anion channels: Inferences from single channel recording. EXCLI JOURNAL 2017; 16:531-545. [PMID: 28694756 PMCID: PMC5491910 DOI: 10.17179/excli2016-808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/21/2017] [Indexed: 11/29/2022]
Abstract
We have characterized the conduction and blocking properties of two different chloride channels from brain mitochondrial inner membranes after incorporation into planar lipid bilayers. Our experiments revealed the existence of channels with a mean conductance of 158 ± 7 and 301 ± 8 pS in asymmetrical 200 mM cis/50 mM trans KCl solutions. We determined that the channels were ten times more permeable for Cl− than for K+, calculated from the reversal potential using the Goldman-Hodgkin-Katz equation. The channels were bell-shaped voltage dependent, with maximum open probability 0.9 at ± 20 mV. Two mitochondrial chloride channels were blocked after the addition of 10 µM DIDS. In addition, 158 pS chloride channel was blocked by 300 nM NPPB, acidic pH and 2.5 mM ATP, whereas the 301 pS chloride channel was blocked by 600 µM NPPB but not by acidic pH or ATP. Gating and conducting behaviors of these channels were unaffected by Ca2+. These results demonstrate that the 158 pS anion channel present in brain mitochondrial inner membrane, is probably identical to IMAC and 301 pS Cl channel displays different properties than those classically described for mitochondrial anion channels.
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Affiliation(s)
- Javad Fahanik-Babaei
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Farzad Shayanfar
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Naser Khodaee
- Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Faculty of Paramedical Sciences, AJA University of Medical Sciences, Tehran, Iran
| | - Reza Saghiri
- Department of Biochemistry, Pasteur Institute of Iran, Tehran, Iran
| | - Afsaneh Eliassi
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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31
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Zand K, Pham TDA, Li J, Zhou W, Wallace DC, Burke PJ. Resistive flow sensing of vital mitochondria with nanoelectrodes. Mitochondrion 2017; 37:8-16. [PMID: 28655663 DOI: 10.1016/j.mito.2017.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 02/23/2017] [Accepted: 06/21/2017] [Indexed: 12/15/2022]
Abstract
We report label-free detection of single mitochondria with high sensitivity using nanoelectrodes. Measurements of the conductance of carbon nanotube transistors show discrete changes of conductance as individual mitochondria flow over the nanoelectrodes in a microfluidic channel. Altering the bioenergetic state of the mitochondria by adding metabolites to the flow buffer induces changes in the mitochondrial membrane potential detected by the nanoelectrodes. During the time when mitochondria are transiently passing over the nanoelectrodes, this (nano) technology is sensitive to fluctuations of the mitochondrial membrane potential with a resolution of 10mV with temporal resolution of order milliseconds. Fluorescence based assays (in ideal, photon shot noise limited setups) are shown to be an order of magnitude less sensitive than this nano-electronic measurement technology. This opens a new window into the dynamics of an organelle critical to cellular function and fate.
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Affiliation(s)
- Katayoun Zand
- Integrated Nanosystems Research Facility, Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA 92697, United States
| | - Ted D A Pham
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92697, United States
| | - Jinfeng Li
- Integrated Nanosystems Research Facility, Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA 92697, United States
| | - Weiwei Zhou
- Integrated Nanosystems Research Facility, Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA 92697, United States
| | - Douglas C Wallace
- Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Peter J Burke
- Integrated Nanosystems Research Facility, Electrical Engineering and Computer Science, University of California, Irvine, Irvine, CA 92697, United States.
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32
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Giorgio V, Guo L, Bassot C, Petronilli V, Bernardi P. Calcium and regulation of the mitochondrial permeability transition. Cell Calcium 2017; 70:56-63. [PMID: 28522037 DOI: 10.1016/j.ceca.2017.05.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 05/05/2017] [Accepted: 05/05/2017] [Indexed: 12/11/2022]
Abstract
Recent years have seen renewed interest in the permeability transition pore, a high conductance channel responsible for permeabilization of the inner mitochondrial membrane, a process that leads to depolarization and Ca2+ release. Transient openings may be involved in physiological Ca2+ homeostasis while long-lasting openings may trigger and/or execute cell death. In this review we specifically focus (i) on the hypothesis that the PTP forms from the F-ATP synthase and (ii) on the mechanisms through which Ca2+ can reversibly switch this energy-conserving nanomachine into an energy-dissipating device.
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Affiliation(s)
- Valentina Giorgio
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padova, Italy
| | - Lishu Guo
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padova, Italy
| | - Claudio Bassot
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padova, Italy
| | - Valeria Petronilli
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padova, Italy
| | - Paolo Bernardi
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padova, Italy.
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33
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Grimm C, Chen CC, Wahl-Schott C, Biel M. Two-Pore Channels: Catalyzers of Endolysosomal Transport and Function. Front Pharmacol 2017; 8:45. [PMID: 28223936 PMCID: PMC5293812 DOI: 10.3389/fphar.2017.00045] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 01/20/2017] [Indexed: 01/17/2023] Open
Abstract
Two-pore channels (TPCs) have recently emerged as a novel class of non-selective cation channels in the endolysosomal system. There are two members in the human genome, TPC1 and TPC2. Studies with TPC knockout and knockdown models have revealed that these channels participate in the regulation of multiple endolysosomal trafficking pathways which when dysregulated can lead to or influence the development of a range of different diseases such as lysosomal storage, metabolic, or infectious diseases. TPCs have been demonstrated to be activated by different endogenous stimuli, PI(3,5)P2 and NAADP, and ATP has been found to block TPC activation via mTOR. Loss of TPCs can lead to obesity and hypercholesterolemia, and to a slow-down of intracellular virus and bacterial toxin trafficking, it can affect VEGF-induced neoangiogenesis, autophagy, human hair pigmentation or the acrosome reaction in sperm. Moreover, physiological roles of TPCs in cardiac myocytes and pancreatic β cells have been postulated.
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Affiliation(s)
- Christian Grimm
- Center for Integrated Protein Science Munich, Ludwig Maximilian University of MunichMunich, Germany
- Department of Pharmacy – Center for Drug Research, Ludwig Maximilian University of MunichMunich, Germany
| | - Cheng-Chang Chen
- Center for Integrated Protein Science Munich, Ludwig Maximilian University of MunichMunich, Germany
- Department of Pharmacy – Center for Drug Research, Ludwig Maximilian University of MunichMunich, Germany
| | - Christian Wahl-Schott
- Center for Integrated Protein Science Munich, Ludwig Maximilian University of MunichMunich, Germany
- Department of Pharmacy – Center for Drug Research, Ludwig Maximilian University of MunichMunich, Germany
| | - Martin Biel
- Center for Integrated Protein Science Munich, Ludwig Maximilian University of MunichMunich, Germany
- Department of Pharmacy – Center for Drug Research, Ludwig Maximilian University of MunichMunich, Germany
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34
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Mnatsakanyan N, Beutner G, Porter GA, Alavian KN, Jonas EA. Physiological roles of the mitochondrial permeability transition pore. J Bioenerg Biomembr 2017; 49:13-25. [PMID: 26868013 PMCID: PMC4981558 DOI: 10.1007/s10863-016-9652-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 02/04/2016] [Indexed: 01/01/2023]
Abstract
Neurons experience high metabolic demand during such processes as synaptic vesicle recycling, membrane potential maintenance and Ca2+ exchange/extrusion. The energy needs of these events are met in large part by mitochondrial production of ATP through the process of oxidative phosphorylation. The job of ATP production by the mitochondria is performed by the F1FO ATP synthase, a multi-protein enzyme that contains a membrane-inserted portion, an extra-membranous enzymatic portion and an extensive regulatory complex. Although required for ATP production by mitochondria, recent findings have confirmed that the membrane-confined portion of the c-subunit of the ATP synthase also houses a large conductance uncoupling channel, the mitochondrial permeability transition pore (mPTP), the persistent opening of which produces osmotic dysregulation of the inner mitochondrial membrane, uncoupling of oxidative phosphorylation and cell death. Recent advances in understanding the molecular components of mPTP and its regulatory mechanisms have determined that decreased uncoupling occurs in states of enhanced mitochondrial efficiency; relative closure of mPTP therefore contributes to cellular functions as diverse as cardiac development and synaptic efficacy.
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Affiliation(s)
- Nelli Mnatsakanyan
- Department Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA
| | - Gisela Beutner
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - George A Porter
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Kambiz N Alavian
- Division of Brain Sciences, Department of Medicine, Imperial College London, London, UK
| | - Elizabeth A Jonas
- Department Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA.
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35
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Abstract
Mitochondria are the "power house" of a cell continuously generating ATP to ensure its proper functioning. The constant production of ATP via oxidative phosphorylation demands a large electrochemical force that drives protons across the highly selective and low-permeable mitochondrial inner membrane. Besides the conventional role of generating ATP, mitochondria also play an active role in calcium signaling, generation of reactive oxygen species (ROS), stress responses, and regulation of cell-death pathways. Deficiencies in these functions result in several pathological disorders like aging, cancer, diabetes, neurodegenerative and cardiovascular diseases. A plethora of ion channels and transporters are present in the mitochondrial inner and outer membranes which work in concert to preserve the ionic equilibrium of a cell for the maintenance of cell integrity, in physiological as well as pathophysiological conditions. For, e.g., mitochondrial cation channels KATP and BKCa play a significant role in cardioprotection from ischemia-reperfusion injury. In addition to the cation channels, mitochondrial anion channels are equally essential, as they aid in maintaining electro-neutrality by regulating the cell volume and pH. This chapter focusses on the information on molecular identity, structure, function, and physiological relevance of mitochondrial chloride channels such as voltage dependent anion channels (VDACs), uncharacterized mitochondrial inner membrane anion channels (IMACs), chloride intracellular channels (CLIC) and the aspects of forthcoming chloride channels.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA.
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36
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Pottosin I, Dobrovinskaya O. Ion Channels in Native Chloroplast Membranes: Challenges and Potential for Direct Patch-Clamp Studies. Front Physiol 2015; 6:396. [PMID: 26733887 PMCID: PMC4686732 DOI: 10.3389/fphys.2015.00396] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 12/04/2015] [Indexed: 11/29/2022] Open
Abstract
Photosynthesis without any doubt depends on the activity of the chloroplast ion channels. The thylakoid ion channels participate in the fine partitioning of the light-generated proton-motive force (p.m.f.). By regulating, therefore, luminal pH, they affect the linear electron flow and non-photochemical quenching. Stromal ion homeostasis and signaling, on the other hand, depend on the activity of both thylakoid and envelope ion channels. Experimentally, intact chloroplasts and swollen thylakoids were proven to be suitable for direct measurements of the ion channels activity via conventional patch-clamp technique; yet, such studies became infrequent, although their potential is far from being exhausted. In this paper we wish to summarize existing challenges for direct patch-clamping of native chloroplast membranes as well as present available results on the activity of thylakoid Cl− (ClC?) and divalent cation-permeable channels, along with their tentative roles in the p.m.f. partitioning, volume regulation, and stromal Ca2+ and Mg2+ dynamics. Patch-clamping of the intact envelope revealed both large-conductance porin-like channels, likely located in the outer envelope membrane and smaller conductance channels, more compatible with the inner envelope location. Possible equivalent model for the sandwich-like arrangement of the two envelope membranes within the patch electrode will be discussed, along with peculiar properties of the fast-activated cation channel in the context of the stromal pH control.
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Affiliation(s)
- Igor Pottosin
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, Mexico
| | - Oxana Dobrovinskaya
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, Mexico
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37
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Bernardi P, Rasola A, Forte M, Lippe G. The Mitochondrial Permeability Transition Pore: Channel Formation by F-ATP Synthase, Integration in Signal Transduction, and Role in Pathophysiology. Physiol Rev 2015; 95:1111-55. [PMID: 26269524 DOI: 10.1152/physrev.00001.2015] [Citation(s) in RCA: 419] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The mitochondrial permeability transition (PT) is a permeability increase of the inner mitochondrial membrane mediated by a channel, the permeability transition pore (PTP). After a brief historical introduction, we cover the key regulatory features of the PTP and provide a critical assessment of putative protein components that have been tested by genetic analysis. The discovery that under conditions of oxidative stress the F-ATP synthases of mammals, yeast, and Drosophila can be turned into Ca(2+)-dependent channels, whose electrophysiological properties match those of the corresponding PTPs, opens new perspectives to the field. We discuss structural and functional features of F-ATP synthases that may provide clues to its transition from an energy-conserving into an energy-dissipating device as well as recent advances on signal transduction to the PTP and on its role in cellular pathophysiology.
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Affiliation(s)
- Paolo Bernardi
- Department of Biomedical Sciences and Consiglio Nazionale delle Ricerche Neuroscience Institute, University of Padova, Padova, Italy; Vollum Institute, Oregon Health and Sciences University, Portland, Oregon; and Department of Food Science, University of Udine, Udine, Italy
| | - Andrea Rasola
- Department of Biomedical Sciences and Consiglio Nazionale delle Ricerche Neuroscience Institute, University of Padova, Padova, Italy; Vollum Institute, Oregon Health and Sciences University, Portland, Oregon; and Department of Food Science, University of Udine, Udine, Italy
| | - Michael Forte
- Department of Biomedical Sciences and Consiglio Nazionale delle Ricerche Neuroscience Institute, University of Padova, Padova, Italy; Vollum Institute, Oregon Health and Sciences University, Portland, Oregon; and Department of Food Science, University of Udine, Udine, Italy
| | - Giovanna Lippe
- Department of Biomedical Sciences and Consiglio Nazionale delle Ricerche Neuroscience Institute, University of Padova, Padova, Italy; Vollum Institute, Oregon Health and Sciences University, Portland, Oregon; and Department of Food Science, University of Udine, Udine, Italy
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38
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Jonas EA, Porter GA, Beutner G, Mnatsakanyan N, Alavian KN. Cell death disguised: The mitochondrial permeability transition pore as the c-subunit of the F(1)F(O) ATP synthase. Pharmacol Res 2015; 99:382-92. [PMID: 25956324 PMCID: PMC4567435 DOI: 10.1016/j.phrs.2015.04.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 04/09/2015] [Accepted: 04/20/2015] [Indexed: 12/16/2022]
Abstract
Ion transport across the mitochondrial inner and outer membranes is central to mitochondrial function, including regulation of oxidative phosphorylation and cell death. Although essential for ATP production by mitochondria, recent findings have confirmed that the c-subunit of the ATP synthase also houses a large conductance uncoupling channel, the mitochondrial permeability transition pore (mPTP), the persistent opening of which produces osmotic dysregulation of the inner mitochondrial membrane and cell death. This review will discuss recent advances in understanding the molecular components of mPTP, its regulatory mechanisms and how these contribute directly to its physiological as well as pathological roles.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA.
| | - George A Porter
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Gisela Beutner
- Department of Pediatrics (Cardiology), University of Rochester Medical Center, Rochester, NY, USA
| | - Nelli Mnatsakanyan
- Department of Internal Medicine, Section of Endocrinology, Yale University, New Haven, CT, USA
| | - Kambiz N Alavian
- Division of Brain Sciences, Department of Medicine, Imperial College London, UK
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39
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Antonenkov VD, Isomursu A, Mennerich D, Vapola MH, Weiher H, Kietzmann T, Hiltunen JK. The Human Mitochondrial DNA Depletion Syndrome Gene MPV17 Encodes a Non-selective Channel That Modulates Membrane Potential. J Biol Chem 2015; 290:13840-61. [PMID: 25861990 DOI: 10.1074/jbc.m114.608083] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Indexed: 12/17/2022] Open
Abstract
The human MPV17-related mitochondrial DNA depletion syndrome is an inherited autosomal recessive disease caused by mutations in the inner mitochondrial membrane protein MPV17. Although more than 30 MPV17 gene mutations were shown to be associated with mitochondrial DNA depletion syndrome, the function of MPV17 is still unknown. Mice deficient in Mpv17 show signs of premature aging. In the present study, we used electrophysiological measurements with recombinant MPV17 to reveal that this protein forms a non-selective channel with a pore diameter of 1.8 nm and located the channel's selectivity filter. The channel was weakly cation-selective and showed several subconductance states. Voltage-dependent gating of the channel was regulated by redox conditions and pH and was affected also in mutants mimicking a phosphorylated state. Likewise, the mitochondrial membrane potential (Δψm) and the cellular production of reactive oxygen species were higher in embryonic fibroblasts from Mpv17(-/-) mice. However, despite the elevated Δψm, the Mpv17-deficient mitochondria showed signs of accelerated fission. Together, these observations uncover the role of MPV17 as a Δψm-modulating channel that apparently contributes to mitochondrial homeostasis under different conditions.
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Affiliation(s)
- Vasily D Antonenkov
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Antti Isomursu
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Daniela Mennerich
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Miia H Vapola
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - Hans Weiher
- the Heinrich Pette Institute, Leibniz Institute for Experimental Virology, 20251 Hamburg, Germany
| | - Thomas Kietzmann
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
| | - J Kalervo Hiltunen
- From the Faculty of Biochemistry and Molecular Medicine, Biocenter Oulu, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland and
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40
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Testai L, Rapposelli S, Martelli A, Breschi M, Calderone V. Mitochondrial Potassium Channels as Pharmacological Target for Cardioprotective Drugs. Med Res Rev 2014; 35:520-53. [DOI: 10.1002/med.21332] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- L. Testai
- Department of Pharmacy; University of Pisa; Pisa Italy
| | - S. Rapposelli
- Department of Pharmacy; University of Pisa; Pisa Italy
| | - A. Martelli
- Department of Pharmacy; University of Pisa; Pisa Italy
| | - M.C. Breschi
- Department of Pharmacy; University of Pisa; Pisa Italy
| | - V. Calderone
- Department of Pharmacy; University of Pisa; Pisa Italy
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41
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Zorov DB, Juhaszova M, Sollott SJ. Mitochondrial reactive oxygen species (ROS) and ROS-induced ROS release. Physiol Rev 2014; 94:909-50. [PMID: 24987008 DOI: 10.1152/physrev.00026.2013] [Citation(s) in RCA: 3115] [Impact Index Per Article: 311.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Byproducts of normal mitochondrial metabolism and homeostasis include the buildup of potentially damaging levels of reactive oxygen species (ROS), Ca(2+), etc., which must be normalized. Evidence suggests that brief mitochondrial permeability transition pore (mPTP) openings play an important physiological role maintaining healthy mitochondria homeostasis. Adaptive and maladaptive responses to redox stress may involve mitochondrial channels such as mPTP and inner membrane anion channel (IMAC). Their activation causes intra- and intermitochondrial redox-environment changes leading to ROS release. This regenerative cycle of mitochondrial ROS formation and release was named ROS-induced ROS release (RIRR). Brief, reversible mPTP opening-associated ROS release apparently constitutes an adaptive housekeeping function by the timely release from mitochondria of accumulated potentially toxic levels of ROS (and Ca(2+)). At higher ROS levels, longer mPTP openings may release a ROS burst leading to destruction of mitochondria, and if propagated from mitochondrion to mitochondrion, of the cell itself. The destructive function of RIRR may serve a physiological role by removal of unwanted cells or damaged mitochondria, or cause the pathological elimination of vital and essential mitochondria and cells. The adaptive release of sufficient ROS into the vicinity of mitochondria may also activate local pools of redox-sensitive enzymes involved in protective signaling pathways that limit ischemic damage to mitochondria and cells in that area. Maladaptive mPTP- or IMAC-related RIRR may also be playing a role in aging. Because the mechanism of mitochondrial RIRR highlights the central role of mitochondria-formed ROS, we discuss all of the known ROS-producing sites (shown in vitro) and their relevance to the mitochondrial ROS production in vivo.
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Affiliation(s)
- Dmitry B Zorov
- A. N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia; and Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Magdalena Juhaszova
- A. N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia; and Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - Steven J Sollott
- A. N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia; and Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, Maryland
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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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Gu XQ, Pamenter ME, Siemen D, Sun X, Haddad GG. Mitochondrial but not plasmalemmal BK channels are hypoxia-sensitive in human glioma. Glia 2014; 62:504-13. [PMID: 24446243 DOI: 10.1002/glia.22620] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 11/05/2022]
Abstract
Tumor cells are resistant to hypoxia but the underlying mechanism(s) of this tolerance remain poorly understood. In healthy brain cells, plasmalemmal Ca(2+)-activated K(+) channels ((plasma)BK) function as oxygen sensors and close under hypoxic conditions. Similarly, BK channels in the mitochondrial inner membrane ((mito)BK) are also hypoxia sensitive and regulate reactive oxygen species production and also permeability transition pore formation. Both channel populations are therefore well situated to mediate cellular responses to hypoxia. In tumors, BK channel expression increases with malignancy, suggesting these channels contribute to tumor growth; therefore, we hypothesized that the sensitivity of (plasma)BK and/or (mito)BK to hypoxia differs between glioma and healthy brain cells. To test this, we examined the electrophysiological properties of (plasma)BK and (mito)BK from a human glioma cell line during normoxia and hypoxia. We observed single channel activities in whole cells and isolated mitoplasts with slope conductance of 199 ± 8 and 278 ± 10 pA, respectively. These currents were Ca(2+)- and voltage-dependent, and were inhibited by the BK channel antagonist charybdotoxin (0.1 μM). (plasma)BK could only be activated at membrane potentials >+40 mV and had a low open probability (NPo) that was unchanged by hypoxia. Conversely, (mito)BK were active across a range of membrane potentials (-40 to +40 mV) and their NPo increased during hypoxia. Activating (plasma)BK, but not (mito)BK induced cell death and this effect was enhanced during hypoxia. We conclude that unlike in healthy brain cells, glioma (mito)BK channels, but not (plasma)BK channels are oxygen sensitive.
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Affiliation(s)
- Xiang Q Gu
- Section of Respiratory Medicine, Department of Pediatrics, University of California San Diego, La Jolla, California
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Misak A, Grman M, Malekova L, Novotova M, Markova J, Krizanova O, Ondrias K, Tomaskova Z. Mitochondrial chloride channels: electrophysiological characterization and pH induction of channel pore dilation. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2013; 42:709-20. [PMID: 23903554 DOI: 10.1007/s00249-013-0920-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/08/2013] [Accepted: 07/13/2013] [Indexed: 11/26/2022]
Abstract
Physiological and pathological functions of mitochondria are highly dependent on the properties and regulation of mitochondrial ion channels. There is still no clear understanding of the molecular identity, regulation, and properties of anion mitochondrial channels. The inner membrane anion channel (IMAC) was assumed to be equivalent to mitochondrial centum picosiemens (mCS). However, the different properties of IMAC and mCS channels challenges this opinion. In our study, we characterized the single-channel anion selectivity and pH regulation of chloride channels from purified cardiac mitochondria. We observed that channel conductance decreased in the order: Cl⁻ > Br⁻ > I⁻ > chlorate ≈ formate > acetate, and that gluconate did not permeate under control conditions. The selectivity sequence was Br⁻ ≥ chlorate ≥ I⁻ ≥ Cl⁻ ≥ formate ≈ acetate. Measurement of the concentration dependence of chloride conductance revealed altered channel gating kinetics, which was demonstrated by prolonged mean open time value with increasing chloride concentration. The observed mitochondrial chloride channels were in many respects similar to those of mCS, but not those of IMAC. Surprisingly, we observed that acidic pH increased channel conductance and that an increase of pH from 7.4 to 8.5 reduced it. The gluconate current appeared and gradually increased when pH decreased from pH 7.0 to 5.6. Our results indicate that pH regulates the channel pore diameter in such a way that dilation increases with more acidic pH. We assume this newly observed pH-dependent anion channel property may be involved in pH regulation of anion distribution in different mitochondrial compartments.
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Affiliation(s)
- Anton Misak
- Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 83334 Bratislava, Slovak Republic
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Activity of the mitochondrial calcium uniporter varies greatly between tissues. Nat Commun 2013; 3:1317. [PMID: 23271651 PMCID: PMC3818247 DOI: 10.1038/ncomms2325] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 11/20/2012] [Indexed: 01/05/2023] Open
Abstract
The mitochondrial calcium uniporter (MCU) is a highly selective channel responsible for mitochondrial Ca2+ uptake. The MCU shapes cytosolic Ca2+ signals, controls mitochondrial ATP production, and is involved in cell death. Here, using direct patch-clamp recording from the inner mitochondrial membrane, we compare MCU activity in mouse heart, skeletal muscle, liver, kidney, and brown fat. Surprisingly, heart mitochondria shows a dramatically lower MCU current density than the other tissues studied. Similarly, in Drosophila flight muscle, MCU activity is barely detectable compared to that in other fly tissues. Because mitochondria occupy up to 40% of the cell volume in highly metabolically active heart and flight muscle, low MCU activity is likely essential to avoid cytosolic Ca2+ sink due to excessive mitochondrial Ca2+ uptake. Simultaneously, low MCU activity may also prevent mitochondrial Ca2+ overload in such active tissues exposed to frequent cytosolic Ca2+ activity.
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Bernardi P. The mitochondrial permeability transition pore: a mystery solved? Front Physiol 2013; 4:95. [PMID: 23675351 PMCID: PMC3650560 DOI: 10.3389/fphys.2013.00095] [Citation(s) in RCA: 253] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 04/19/2013] [Indexed: 01/04/2023] Open
Abstract
The permeability transition (PT) denotes an increase of the mitochondrial inner membrane permeability to solutes with molecular masses up to about 1500 Da. It is presumed to be mediated by opening of a channel, the permeability transition pore (PTP), whose molecular nature remains a mystery. Here I briefly review the history of the PTP, discuss existing models, and present our new results indicating that reconstituted dimers of the FOF1 ATP synthase form a channel with properties identical to those of the mitochondrial megachannel (MMC), the electrophysiological equivalent of the PTP. Open questions remain, but there is now promise that the PTP can be studied by genetic methods to solve the large number of outstanding problems.
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Affiliation(s)
- Paolo Bernardi
- Department of Biomedical Sciences, University of Padova Padova, Italy
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Dolga AM, Netter MF, Perocchi F, Doti N, Meissner L, Tobaben S, Grohm J, Zischka H, Plesnila N, Decher N, Culmsee C. Mitochondrial small conductance SK2 channels prevent glutamate-induced oxytosis and mitochondrial dysfunction. J Biol Chem 2013; 288:10792-804. [PMID: 23430260 PMCID: PMC3624460 DOI: 10.1074/jbc.m113.453522] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 02/08/2013] [Indexed: 11/06/2022] Open
Abstract
Small conductance calcium-activated potassium (SK2/K(Ca)2.2) channels are known to be located in the neuronal plasma membrane where they provide feedback control of NMDA receptor activity. Here, we provide evidence that SK2 channels are also located in the inner mitochondrial membrane of neuronal mitochondria. Patch clamp recordings in isolated mitoplasts suggest insertion into the inner mitochondrial membrane with the C and N termini facing the intermembrane space. Activation of SK channels increased mitochondrial K(+) currents, whereas channel inhibition attenuated these currents. In a model of glutamate toxicity, activation of SK2 channels attenuated the loss of the mitochondrial transmembrane potential, blocked mitochondrial fission, prevented the release of proapoptotic mitochondrial proteins, and reduced cell death. Neuroprotection was blocked by specific SK2 inhibitory peptides and siRNA targeting SK2 channels. Activation of mitochondrial SK2 channels may therefore represent promising targets for neuroprotective strategies in conditions of mitochondrial dysfunction.
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Affiliation(s)
- Amalia M. Dolga
- From the Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, D-35032 Marburg, Germany
| | - Michael F. Netter
- Institut für Physiologie und Pathophysiologie, Vegetative Physiologie, Fachbereich Medizin, Philipps-Universität Marburg, D-35037 Marburg, Germany
| | - Fabiana Perocchi
- Department of Systems Biology and Medicine, Harvard Medical School and Massachusetts General Hospital, Boston, Massachusetts 02114
- Gene Center, Ludwig Maximilians University, Feodor-Lynen Strasse 25, 81377 Munich, Germany
| | - Nunzianna Doti
- From the Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, D-35032 Marburg, Germany
- Department of Neurodegeneration, Royal College of Surgeons in Ireland, Dublin 2, Ireland
- Institute of Biostructures and Bioimaging, National Research Council (CNR), 16-80131 Naples, Italy
| | - Lilja Meissner
- Institute of Stroke and Dementia Research, University of Munich Medical School, D-81377 Munich, Germany, and
| | - Svenja Tobaben
- From the Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, D-35032 Marburg, Germany
| | - Julia Grohm
- From the Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, D-35032 Marburg, Germany
| | - Hans Zischka
- Institute of Toxicology, Helmholtz Zentrum München-German Research Center for Environmental Health (GmbH), D-85764 Neuherberg, Germany
| | - Nikolaus Plesnila
- Department of Neurodegeneration, Royal College of Surgeons in Ireland, Dublin 2, Ireland
- Institute of Stroke and Dementia Research, University of Munich Medical School, D-81377 Munich, Germany, and
| | - Niels Decher
- Institut für Physiologie und Pathophysiologie, Vegetative Physiologie, Fachbereich Medizin, Philipps-Universität Marburg, D-35037 Marburg, Germany
| | - Carsten Culmsee
- From the Institut für Pharmakologie und Klinische Pharmazie, Fachbereich Pharmazie, Philipps-Universität Marburg, D-35032 Marburg, Germany
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48
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Inner mitochondrial maxi-K⁺ channels in neonatal renal tubular cells: novel therapeutic targets to control apoptosis. Med Hypotheses 2012; 78:800-1. [PMID: 22498048 DOI: 10.1016/j.mehy.2012.03.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 03/20/2012] [Indexed: 11/22/2022]
Abstract
In developing kidneys, the total cell population is partly regulated by apoptosis. Despite our understanding of the molecular involvement in the regulatory pathway of apoptosis, we know little about the physiological involvement. Cardiomyocytes express large conductance voltage- and Ca(2+)-activated K(+) (maxi-K(+)) channels in their inner mitochondrial membranes. Triggering the mitochondrial K(+) influx necessary to inhibit apoptosis, the channels play cytoprotective roles during ischemic injury. Since proximal tubular cells in neonatal kidneys are physiologically under hypoxic stress, and since the channel activity is stimulated by hypoxia, those cells would share the same regulatory mechanism of apoptosis with ischemic cardiomyocytes. Therefore, we hypothesize here that the proximal tubular cells in neonatal kidneys would also express the maxi-K(+) channels in their inner mitochondrial membranes, and that the channels would play regulatory roles in apoptosis. Our hypothesis is unique because it sheds light for the first time on a physiological mechanism that involves the mitochondrial membranes in developing kidneys. It is also important because the idea could have novel therapeutic implications for kidney diseases that are associated with apoptosis.
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49
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Kinnally KW, Martinez-Caballero S, Dejean LM. Detection of the mitochondrial apoptosis-induced channel (MAC) and its regulation by Bcl-2 family proteins. ACTA ACUST UNITED AC 2011; Chapter 2:Unit2.12. [PMID: 20941703 DOI: 10.1002/0471140856.tx0212s30] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Apoptosis is a phenomenon fundamental to higher eukaryotes that is integral to such diverse cellular processes as tissue homeostasis, organogenesis, and response to toxins. The release from mitochondria of apoptotic factors such as cytochrome c is a key step during apoptosis of most cells. Cytochrome c release occurs through the MAC (mitochondrial apoptosis-induced channel), a pore which forms in the mitochondrial outer membrane during early apoptosis and is exquisitely regulated by the Bcl-2 family of proteins. This unit presents basic and advanced tools for detecting MAC and defining its regulation by Bcl-2 family proteins and pharmacological agents. Protocols include the use of time-lapse video-microscopy to monitor the onset of apoptosis in living cells and patch-clamp techniques for mitochondria or proteoliposomes containing mitochondrial proteins, which allow direct detection of MAC. These approaches enable an evaluation of the role of MAC and mitochondria in apoptosis of a variety of cell types by many inducers.
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50
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Cheng Y, Gulbins E, Siemen D. Activation of the Permeability Transition Pore by Bax via Inhibition of the Mitochondrial BK Channel. Cell Physiol Biochem 2011; 27:191-200. [DOI: 10.1159/000327944] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/24/2011] [Indexed: 01/07/2023] Open
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