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Rioux AV, Nsimba-Batomene TR, Slimani S, Bergeron NAD, Gravel MAM, Schreiber SV, Fiola MJ, Haydock L, Garneau AP, Isenring P. Navigating the multifaceted intricacies of the Na +-Cl - cotransporter, a highly regulated key effector in the control of hydromineral homeostasis. Physiol Rev 2024; 104:1147-1204. [PMID: 38329422 DOI: 10.1152/physrev.00027.2023] [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: 07/20/2023] [Revised: 01/01/2024] [Accepted: 02/03/2024] [Indexed: 02/09/2024] Open
Abstract
The Na+-Cl- cotransporter (NCC; SLC12A3) is a highly regulated integral membrane protein that is known to exist as three splice variants in primates. Its primary role in the kidney is to mediate the cosymport of Na+ and Cl- across the apical membrane of the distal convoluted tubule. Through this role and the involvement of other ion transport systems, NCC allows the systemic circulation to reclaim a fraction of the ultrafiltered Na+, K+, Cl-, and Mg+ loads in exchange for Ca2+ and [Formula: see text]. The physiological relevance of the Na+-Cl- cotransport mechanism in humans is illustrated by several abnormalities that result from NCC inactivation through the administration of thiazides or in the setting of hereditary disorders. The purpose of the present review is to discuss the molecular mechanisms and overall roles of Na+-Cl- cotransport as the main topics of interest. On reading the narrative proposed, one will realize that the knowledge gained in regard to these themes will continue to progress unrelentingly no matter how refined it has now become.
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Affiliation(s)
- A V Rioux
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - T R Nsimba-Batomene
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - S Slimani
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - N A D Bergeron
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - M A M Gravel
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - S V Schreiber
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - M J Fiola
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
| | - L Haydock
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
- Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, INSERM U1151, Université Paris Cité, Paris, France
| | - A P Garneau
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
- Service de Néphrologie-Transplantation Rénale Adultes, Hôpital Necker-Enfants Malades, AP-HP, INSERM U1151, Université Paris Cité, Paris, France
| | - P Isenring
- Department of Medicine, Nephrology Research Group, Laval University, Quebec City, Quebec, Canada
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Birkedal R, Laasmaa M, Branovets J, Vendelin M. Ontogeny of cardiomyocytes: ultrastructure optimization to meet the demand for tight communication in excitation-contraction coupling and energy transfer. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210321. [PMID: 36189816 PMCID: PMC9527910 DOI: 10.1098/rstb.2021.0321] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The ontogeny of the heart describes its development from the fetal to the adult stage. In newborn mammals, blood pressure and thus cardiac performance are relatively low. The cardiomyocytes are thin, and with a central core of mitochondria surrounded by a ring of myofilaments, while the sarcoplasmic reticulum (SR) is sparse. During development, as blood pressure and performance increase, the cardiomyocytes become more packed with structures involved in excitation–contraction (e-c) coupling (SR and myofilaments) and the generation of ATP (mitochondria) to fuel the contraction. In parallel, the e-c coupling relies increasingly on calcium fluxes through the SR, while metabolism relies increasingly on fatty acid oxidation. The development of transverse tubules and SR brings channels and transporters interacting via calcium closer to each other and is crucial for e-c coupling. However, for energy transfer, it may seem counterintuitive that the increased structural density restricts the overall ATP/ADP diffusion. In this review, we discuss how this is because of the organization of all these structures forming modules. Although the overall diffusion across modules is more restricted, the energy transfer within modules is fast. A few studies suggest that in failing hearts this modular design is disrupted, and this may compromise intracellular energy transfer. This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.
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Affiliation(s)
- Rikke Birkedal
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Martin Laasmaa
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Jelena Branovets
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
| | - Marko Vendelin
- Laboratory of Systems Biology, Department of Cybernetics, Tallinn University of Technology, Akadeemia 15, room SCI-218, 12618 Tallinn, Estonia
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Mahdi H, Jovanović A. SUR2A as a base for cardioprotective therapeutic strategies. Mol Biol Rep 2022; 49:6717-6723. [PMID: 35301655 DOI: 10.1007/s11033-022-07281-9] [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: 11/30/2021] [Revised: 02/13/2022] [Accepted: 02/16/2022] [Indexed: 10/18/2022]
Abstract
BACKGROUND ATP-sensitive K+ (KATP) channels link the metabolic state of the cell with membrane excitability and SUR2A serves as a regulatory subunit of sarcolemmal KATP channels. The aim of the present study was to review SUR2A-mediated cardioprotection. METHODS AND RESULTS A related literature search in PubMed, Scopus, Web of Science, Google Scholar, and Science direct was performed. Levels of SUR2A regulate number of fully assembled KATP channels in the sarcolemma. Increased numbers of sarcolemmal KATP channels protect cardiomyocytes against different types of stress by improving the timing of KATP channels opening, but, also, by catalyzing ATP production in subsarcolemmal space. Fully-assembled sarcolemmal KATP channels protein complex contain ATP-producing enzymes in addition to channel subunits, SUR2A and Kir6.2. An increase in the number of fully-assembled channels results in increased levels of ATP-producing enzymes and subsarcolemmal ATP, which is beneficial in ischemia. Expression of SUR2A is regulated by diverse mechanisms, including AMPK, PI3K/Akt, and ERK1/2 as well as intracellular levels of NAD+/NADH and ATP. There are many compounds and treatments that can be used to regulate SUR2A and some of them seem to be clinically viable options. The most suitable medication to use to increase SUR2A and confer cardioprotection in the clinical setting seems to be nicotinamide. It is one of the safest compounds used in clinical practice and all pre-clinical studies demonstrated that it is an efficient cardioprotective agent. CONCLUSIONS Taken all together, SUR2A-based cardioprotection is a likely efficient and safe cardioprotective strategy that can be quickly introduced into clinical practice.
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Affiliation(s)
- Habib Mahdi
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, 21 Ilia Papakyriakou Engomi, P.O. Box 24005, 2414, CY-1700, Nicosia, Cyprus
| | - Aleksandar Jovanović
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, 21 Ilia Papakyriakou Engomi, P.O. Box 24005, 2414, CY-1700, Nicosia, Cyprus. .,Center for Neuroscience and Integrative Brain Research (CENIBRE), University of Nicosia Medical School, Nicosia, Cyprus.
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Sudhir R, Jaafar N, Du Q, Sukhodub A, Jovanović S, Kreouzi M, Jovanović A. Increase in cardioprotective SUR2A does not alter heart rate and heart rate regulation by physical activity and diurnal rhythm. J Basic Clin Physiol Pharmacol 2021; 33:619-624. [PMID: 34870381 DOI: 10.1515/jbcpp-2021-0289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/03/2021] [Indexed: 12/21/2022]
Abstract
OBJECTIVES SUR2A is an ABC protein serving as a regulatory subunit of ATP-sensitive (KATP) channels. An increase in SUR2A levels is cardioprotective and it is a potential therapeutic strategy against ischaemic heart disease, heart failure and other diseases. However, whether overexpression of this protein has any adverse effects is yet to be fully understood. Here, we examined the heart rate and the heart rate diurnal variation in mice overexpressing SUR2A (SUR2A+) and their littermate controls (WT) using ECG telemetry that was continuously recorded for 14 days (days 8-23 post-radiotransmitter implantation). METHODS Using SigmaPlot 14.0 and Microsoft Excel, Area Under the Curve (AUC) for each parameter was calculated and plotted in a graph. RESULTS Both WT and SUR2A+ mice were more physically active during nights and there were no significant differences between two phenotypes. Physical activity was associated with increased heart rate in both phenotypes, but there were no differences in heart rate between phenotypes irrespective of physical activity or time of the day. A diurnal heart rate variation was preserved in the SUR2A+ mice. As area under the curve (AUC) analysis has the potential to reveal differences that are invisible with other statistical methods, we compared AUC of heart rate in SUR2A+ and WT mice. This analysis did not yield anything different from traditional analysis. CONCLUSIONS We conclude that increased SUR2A levels are not associated with changes in physical activity, heart rate and/or circadian rhythm influence on the heart rate. This lack of adverse effects supports a notion that manipulation with SUR2A levels is a promising cardioprotective strategy.
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Affiliation(s)
- Rajni Sudhir
- Department of Molecular and Clinical Medicine, University of Dundee, Dundee, Scotland, UK
| | - Nadim Jaafar
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, Nicosia, Cyprus
| | - Qingyou Du
- Department of Molecular and Clinical Medicine, University of Dundee, Dundee, Scotland, UK
| | - Andriy Sukhodub
- Department of Molecular and Clinical Medicine, University of Dundee, Dundee, Scotland, UK
| | - Sofija Jovanović
- Department of Molecular and Clinical Medicine, University of Dundee, Dundee, Scotland, UK
| | - Magdalini Kreouzi
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, Nicosia, Cyprus
| | - Aleksandar Jovanović
- Department of Basic and Clinical Sciences, University of Nicosia Medical School, Nicosia, Cyprus.,Center for Neuroscience and Integrative Brain Research (CENIBRE), University of Nicosia Medical School, Nicosia, Cyprus
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Hostrup M, Bangsbo J. Limitations in intense exercise performance of athletes - effect of speed endurance training on ion handling and fatigue development. J Physiol 2016; 595:2897-2913. [PMID: 27673449 DOI: 10.1113/jp273218] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 09/21/2016] [Indexed: 01/10/2023] Open
Abstract
Mechanisms underlying fatigue development and limitations for performance during intense exercise have been intensively studied during the past couple of decades. Fatigue development may involve several interacting factors and depends on type of exercise undertaken and training level of the individual. Intense exercise (½-6 min) causes major ionic perturbations (Ca2+ , Cl- , H+ , K+ , lactate- and Na+ ) that may reduce sarcolemmal excitability, Ca2+ release and force production of skeletal muscle. Maintenance of ion homeostasis is thus essential to sustain force production and power output during intense exercise. Regular speed endurance training (SET), i.e. exercise performed at intensities above that corresponding to maximum oxygen consumption (V̇O2, max ), enhances intense exercise performance. However, most of the studies that have provided mechanistic insight into the beneficial effects of SET have been conducted in untrained and recreationally active individuals, making extrapolation towards athletes' performance difficult. Nevertheless, recent studies indicate that only a few weeks of SET enhances intense exercise performance in highly trained individuals. In these studies, the enhanced performance was not associated with changes in V̇O2, max and muscle oxidative capacity, but rather with adaptations in muscle ion handling, including lowered interstitial concentrations of K+ during and in recovery from intense exercise, improved lactate- -H+ transport and H+ regulation, and enhanced Ca2+ release function. The purpose of this Topical Review is to provide an overview of the effect of SET and to discuss potential mechanisms underlying enhancements in performance induced by SET in already well-trained individuals with special emphasis on ion handling in skeletal muscle.
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Affiliation(s)
- Morten Hostrup
- Section of Integrated Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark.,Department of Respiratory Research, Bispebjerg University Hospital, Denmark
| | - Jens Bangsbo
- Section of Integrated Physiology, Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark
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Abstract
KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.
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Affiliation(s)
- Monique N Foster
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
| | - William A Coetzee
- Departments of Pediatrics, Physiology & Neuroscience, and Biochemistry and Molecular Pharmacology, NYU School of Medicine, New York, New York
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Jovanović S, Ballantyne T, Du Q, Blagojević M, Jovanović A. Phenylephrine preconditioning in embryonic heart H9c2 cells is mediated by up-regulation of SUR2B/Kir6.2: A first evidence for functional role of SUR2B in sarcolemmal KATP channels and cardioprotection. Int J Biochem Cell Biol 2015; 70:23-8. [PMID: 26556311 PMCID: PMC4711337 DOI: 10.1016/j.biocel.2015.10.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 10/22/2015] [Accepted: 10/30/2015] [Indexed: 02/07/2023]
Abstract
ATP-sensitive K+ (KATP) channels were originally described in cardiomyocytes, where physiological levels of intracellular ATP keep them in a closed state. Structurally, these channels are composed of pore-forming inward rectifier, Kir6.1 or Kir6.2, and a regulatory, ATP-binding subunit, SUR1, SUR2A or SUR2B. SUR1 and Kir6.2 form pancreatic type of KATP channels, SUR2A and Kir6.2 form cardiac type of KATP channels, SUR2B and Kir6.1 form vascular smooth muscle type of KATP channels. The presence of SUR2B has been described in cardiomyocytes, but its functional significance and role has remained unknown. Pretreatment with phenylephrine (100 nM) for 24 h increased mRNA levels of SUR2B and Kir6.2, without affecting those levels of SUR1, SUR2A and Kir6.1 in embryonic heart H9c2 cells. Such increase was associated with increased K+ current through KATP channels and Kir6.2/SUR2B protein complexes as revealed by whole cell patch clamp electrophysiology and immunoprecipitation/Western blotting respectively. Pretreatment with phenylephrine (100 nM) generated a cellular phenotype that acquired resistance to chemical hypoxia induced by 2,4-dinitrophenol (DNP; 10 mM), which was accompanied by increased in K+ current in response to DNP (10 mM). Cytoprotection afforded by phenylephrine (100 nM) was abolished by infection of H9c2 cells with adenovirus containing Kir6.2AFA, a mutant form of Kir6.2 with largely reduced K+ conductance. Taking all together, the present findings demonstrate that the activation of α1-adrenoceptors up-regulates SUR2B/Kir6.2 to confer cardioprotection. This is the first account of possible physiological role of SUR2B in cardiomyocytes.
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Affiliation(s)
- Sofija Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK
| | - Thomas Ballantyne
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK
| | - Qingyou Du
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK
| | - Miloš Blagojević
- Department of Anatomy, Faculty of Veterinary Medicine, University of Belgrade, Belgrade, Serbia
| | - Aleksandar Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, UK.
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Turrell HE, Thaitirarot C, Crumbie H, Rodrigo G. Remote ischemic preconditioning of cardiomyocytes inhibits the mitochondrial permeability transition pore independently of reduced calcium-loading or sarcKATP channel activation. Physiol Rep 2014; 2:2/11/e12231. [PMID: 25428953 PMCID: PMC4255825 DOI: 10.14814/phy2.12231] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Ischemic preconditioning (IPC) inhibits Ca2+‐loading during ischemia which contributes to cardioprotection by inhibiting mechanical injury due to hypercontracture and biochemical injury through mitochondrial permeability transition (MPT) pores during reperfusion. However, whether remote‐IPC reduced Ca2+‐loading during ischemia and its subsequent involvement in inhibiting MPT pore formation during reperfusion has not been directly shown. We have developed a cellular model of remote IPC to look at the impact of remote conditioning on Ca2+‐regulation and MPT pore opening during simulated ischemia and reperfusion, using fluorescence microscopy. Ventricular cardiomyocytes were isolated from control rat hearts, hearts preconditioned with three cycles of ischemia/reperfusion or naïve myocytes remotely conditioned with effluent collected from preconditioned hearts. Both conventional‐IPC and remote‐IPC reduced the loss of Ca2+‐homeostasis and contractile function following reenergization of metabolically inhibited cells and protected myocytes against ischemia/reperfusion injury. However, only conventional‐IPC reduced the Ca2+‐loading during metabolic inhibition and this was independent of any change in sarcKATP channel activity but was associated with a reduction in Na+‐loading, reflecting a decrease in Na/H exchanger activity. Remote‐IPC delayed opening of the MPT pores in response to ROS, which was dependent on PKCε and NOS‐signaling. These data show that remote‐IPC inhibits MPT pore opening to a similar degree as conventional IPC, however, the contribution of MPT pore inhibition to protection against reperfusion injury is independent of Ca2+‐loading in remote IPC. We suggest that inhibition of the MPT pore and not Ca2+‐loading is the common link in cardioprotection between conventional and remote IPC. Remote ischemic preconditioning (IPC) provides a similar level of protection against ischemia–reperfusion injury to that of conventional‐IPC. This study shows that unlike conventional‐IPC, this was independent of any reduction in Na or Ca2+‐loading during the simulated ischemic event but results from a direct PKCε‐dependent inhibition of the mitochondrial permeability transition pore.
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Affiliation(s)
- Helen E Turrell
- Department of Cardiovascular Sciences, University of Leicester, Glenfield General Hospital, Leicester, UK
| | - Chokanan Thaitirarot
- Department of Cardiovascular Sciences, University of Leicester, Glenfield General Hospital, Leicester, UK
| | - Hayley Crumbie
- Department of Cardiovascular Sciences, University of Leicester, Glenfield General Hospital, Leicester, UK
| | - Glenn Rodrigo
- Department of Cardiovascular Sciences, University of Leicester, Glenfield General Hospital, Leicester, UK
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10
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Birkedal R, Laasmaa M, Vendelin M. The location of energetic compartments affects energetic communication in cardiomyocytes. Front Physiol 2014; 5:376. [PMID: 25324784 PMCID: PMC4178378 DOI: 10.3389/fphys.2014.00376] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 09/10/2014] [Indexed: 01/08/2023] Open
Abstract
The heart relies on accurate regulation of mitochondrial energy supply to match energy demand. The main regulators are Ca2+ and feedback of ADP and Pi. Regulation via feedback has intrigued for decades. First, the heart exhibits a remarkable metabolic stability. Second, diffusion of ADP and other molecules is restricted specifically in heart and red muscle, where a fast feedback is needed the most. To explain the regulation by feedback, compartmentalization must be taken into account. Experiments and theoretical approaches suggest that cardiomyocyte energetic compartmentalization is elaborate with barriers obstructing diffusion in the cytosol and at the level of the mitochondrial outer membrane (MOM). A recent study suggests the barriers are organized in a lattice with dimensions in agreement with those of intracellular structures. Here, we discuss the possible location of these barriers. The more plausible scenario includes a barrier at the level of MOM. Much research has focused on how the permeability of MOM itself is regulated, and the importance of the creatine kinase system to facilitate energetic communication. We hypothesize that at least part of the diffusion restriction at the MOM level is not by MOM itself, but due to the close physical association between the sarcoplasmic reticulum (SR) and mitochondria. This will explain why animals with a disabled creatine kinase system exhibit rather mild phenotype modifications. Mitochondria are hubs of energetics, but also ROS production and signaling. The close association between SR and mitochondria may form a diffusion barrier to ADP added outside a permeabilized cardiomyocyte. But in vivo, it is the structural basis for the mitochondrial-SR coupling that is crucial for the regulation of mitochondrial Ca2+-transients to regulate energetics, and for avoiding Ca2+-overload and irreversible opening of the mitochondrial permeability transition pore.
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Affiliation(s)
- Rikke Birkedal
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
| | - Martin Laasmaa
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
| | - Marko Vendelin
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
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Tinker A, Aziz Q, Thomas A. The role of ATP-sensitive potassium channels in cellular function and protection in the cardiovascular system. Br J Pharmacol 2014; 171:12-23. [PMID: 24102106 DOI: 10.1111/bph.12407] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 07/30/2013] [Accepted: 08/26/2013] [Indexed: 12/14/2022] Open
Abstract
ATP-sensitive potassium channels (K(ATP)) are widely distributed and present in a number of tissues including muscle, pancreatic beta cells and the brain. Their activity is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels. Thus, they link cellular metabolism with membrane excitability. Recent studies using genetically modified mice and genomic studies in patients have implicated K(ATP) channels in a number of physiological and pathological processes. In this review, we focus on their role in cellular function and protection particularly in the cardiovascular system.
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Affiliation(s)
- Andrew Tinker
- William Harvey Heart Centre, Barts and The London School of Medicine and Dentistry, London, UK
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12
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Fahrenbach JP, Stoller D, Kim G, Aggarwal N, Yerokun B, Earley JU, Hadhazy M, Shi NQ, Makielski JC, McNally EM. Abcc9 is required for the transition to oxidative metabolism in the newborn heart. FASEB J 2014; 28:2804-15. [PMID: 24648545 DOI: 10.1096/fj.13-244459] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The newborn heart adapts to postnatal life by shifting from a fetal glycolytic metabolism to a mitochondrial oxidative metabolism. Abcc9, an ATP-binding cassette family member, increases expression concomitant with this metabolic shift. Abcc9 encodes a membrane-associated receptor that partners with a potassium channel to become the major potassium-sensitive ATP channel in the heart. Abcc9 also encodes a smaller protein enriched in the mitochondria. We now deleted exon 5 of Abcc9 to ablate expression of both plasma membrane and mitochondria-associated Abcc9-encoded proteins, and found that the myocardium failed to acquire normal mature metabolism, resulting in neonatal cardiomyopathy. Unlike wild-type neonatal cardiomyocytes, mitochondria from Ex5 cardiomyocytes were unresponsive to the KATP agonist diazoxide, consistent with loss of KATP activity. When exposed to hydrogen peroxide to induce cell stress, Ex5 neonatal cardiomyocytes displayed a rapid collapse of mitochondria membrane potential, distinct from wild-type cardiomyocytes. Ex5 cardiomyocytes had reduced fatty acid oxidation, reduced oxygen consumption and reserve. Morphologically, Ex5 cardiac mitochondria exhibited an immature pattern with reduced cross-sectional area and intermitochondrial contacts. In the absence of Abcc9, the newborn heart fails to transition normally from fetal to mature myocardial metabolism.-Fahrenbach, J. P., Stoller, D., Kim, G., Aggarwal, N., Yerokun, B., Earley, J. U., Hadhazy, M., Shi, N.-Q., Makielski, J. C., McNally, E. M. Abcc9 is required for the transition to oxidative metabolism in the newborn heart.
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Affiliation(s)
| | - Douglas Stoller
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Gene Kim
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Nitin Aggarwal
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | | | - Judy U Earley
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Michele Hadhazy
- Department of Medicine, Division of Cardiovascular Medicine, and
| | - Nian-Qing Shi
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | - Jonathan C Makielski
- Department of Medicine, Division of Cardiology, University of Wisconsin, Madison, Wisconsin, USA
| | - Elizabeth M McNally
- Department of Medicine, Division of Cardiovascular Medicine, and Department of Human Genetics, The University of Chicago, Chicago, Illinois, USA; and
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13
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Branovets J, Sepp M, Kotlyarova S, Jepihhina N, Sokolova N, Aksentijevic D, Lygate CA, Neubauer S, Vendelin M, Birkedal R. Unchanged mitochondrial organization and compartmentation of high-energy phosphates in creatine-deficient GAMT-/- mouse hearts. Am J Physiol Heart Circ Physiol 2013; 305:H506-20. [PMID: 23792673 DOI: 10.1152/ajpheart.00919.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Disruption of the creatine kinase (CK) system in hearts of CK-deficient mice leads to changes in the ultrastructure and regulation of mitochondrial respiration. We expected to see similar changes in creatine-deficient mice, which lack the enzyme guanidinoacetate methyltransferase (GAMT) to produce creatine. The aim of this study was to characterize the changes in cardiomyocyte mitochondrial organization, regulation of respiration, and intracellular compartmentation associated with GAMT deficiency. Three-dimensional mitochondrial organization was assessed by confocal microscopy. On populations of permeabilized cardiomyocytes, we recorded ADP and ATP kinetics of respiration, competition between mitochondria and pyruvate kinase for ADP produced by ATPases, ADP kinetics of endogenous pyruvate kinase, and ATP kinetics of ATPases. These data were analyzed by mathematical models to estimate intracellular compartmentation. Quantitative analysis of morphological and kinetic data as well as derived model fits showed no difference between GAMT-deficient and wild-type mice. We conclude that inactivation of the CK system by GAMT deficiency does not alter mitochondrial organization and intracellular compartmentation in relaxed cardiomyocytes. Thus, our results suggest that the healthy heart is able to preserve cardiac function at a basal level in the absence of CK-facilitated energy transfer without compromising intracellular organization and the regulation of mitochondrial energy homeostasis. This raises questions on the importance of the CK system as a spatial energy buffer in unstressed cardiomyocytes.
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Affiliation(s)
- Jelena Branovets
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Tallinn, Estonia; and
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14
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Beall C, Watterson KR, McCrimmon RJ, Ashford MLJ. AMPK modulates glucose-sensing in insulin-secreting cells by altered phosphotransfer to KATP channels. J Bioenerg Biomembr 2013; 45:229-41. [PMID: 23575945 DOI: 10.1007/s10863-013-9509-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 03/22/2013] [Indexed: 10/27/2022]
Abstract
Glucose-sensing (GS) behaviour in pancreatic β-cells is dependent on ATP-sensitive K(+) channel (KATP) activity, which is controlled by the relative levels of the KATP ligands ATP and ADP, responsible for closing and opening KATP, respectively. However, the mechanism by which β-cells transfer energy status from mitochondria to KATP, and hence to altered electrical excitability and insulin secretion, is presently unclear. Recent work has demonstrated a critical role for AMP-activated protein kinase (AMPK) in GS behaviour of cells. Electrophysiological recordings, coupled with measurements of gene and protein expression were made from rat insulinoma cells to investigate whether AMPK activity regulates this energy transfer process. Using the whole-cell recording configuration with sufficient intracellular ATP to keep KATP closed, raised AMPK activity induced GS electrical behaviour. This effect was prevented by the AMPK inhibitor, compound C and required a phosphotransfer process. Indeed, high levels of intracellular phosphocreatine or the presence of the adenylate kinase (AK) inhibitor AP5A blocked this action of AMPK. Using conditions that maximised AMPK-induced KATP opening, there was a significant increase in AK1, AK2 and UCP2 mRNA expression. Thus we propose that KATP opening in response to lowered glucose concentration requires AMPK activity, perhaps in concert with increased AK and UCP2 to enable mitochondrial-derived ADP signals to be transferred to plasma membrane KATP by phosphotransfer cascades.
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Affiliation(s)
- Craig Beall
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland, UK
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15
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Ballantyne T, Du Q, Jovanović S, Neemo A, Holmes R, Sinha S, Jovanović A. Testosterone protects female embryonic heart H9c2 cells against severe metabolic stress by activating estrogen receptors and up-regulating IES SUR2B. Int J Biochem Cell Biol 2013; 45:283-91. [PMID: 23085378 PMCID: PMC3573229 DOI: 10.1016/j.biocel.2012.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 10/11/2012] [Accepted: 10/12/2012] [Indexed: 11/02/2022]
Abstract
A recent clinical study demonstrated that a testosterone supplementation improves functional capacity in elderly female patients suffering from heart failure. These findings prompted us to consider possible mechanisms of testosterone-induced cardioprotection in females. To address this question we have used a pure female population of rat heart embryonic H9c2 cells. Pre-treatment of cells with testosterone for 24h significantly increased survival of H9c2 cells exposed to 2,4-dinitrophenol (DNP), an inhibitor of oxidative phosphorylation. These cells expressed low level of androgen receptors and the effect of testosterone was not modified by hydroxyflutamide, an antagonist of androgen receptor. In contrast, cyclohexamide, an inhibitor of protein biosynthesis, and tamoxifene, a partial agonist of estrogen receptors, abolished cardioprotection afforded by testosterone. In addition, finasteride, an inhibitor of 5α-reductase, and anastrazole, an inhibitor of α-aromatase, also blocked testosterone-induced cytoprotection. Real time RT-PCR revealed that testosterone did not regulate the expression of nine subunits and accessory proteins of sarcolemmal ATP-sensitive K(+) (K(ATP)) channels. On the other hand, testosterone, as well as 17β-estradiol, up-regulated a putative mitochondrial K(ATP) channel subunit, mitochondrial sulfonylurea receptor 2B intraexonics splice variant (IES SUR2B), without affecting expression of IES SUR2A. Tamoxifene inhibited testosterone-induced up-regulation of IES SUR2B without affecting IES SUR2A. In conclusion, this study has shown that testosterone protect female embryonic heart H9c2 cells against severe metabolic stress by its conversion into metabolites that activate estrogen receptors and up-regulate IES SUR2B.
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Affiliation(s)
| | | | | | | | | | | | - Aleksandar Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetes Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK
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16
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Kefaloyianni E, Lyssand JS, Moreno C, Delaroche D, Hong M, Fenyö D, Mobbs CV, Neubert TA, Coetzee WA. Comparative proteomic analysis of the ATP-sensitive K+ channel complex in different tissue types. Proteomics 2013. [PMID: 23197389 DOI: 10.1002/pmic.201200324] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
ATP-sensitive K(+) (K(ATP)) channels are expressed ubiquitously, but have diverse roles in various organs and cells. Their diversity can partly be explained by distinct tissue-specific compositions of four copies of the pore-forming inward rectifier potassium channel subunits (Kir6.1 and/or Kir6.2) and four regulatory sulfonylurea receptor subunits (SUR1 and/or SUR2). Channel function and/or subcellular localization also can be modified by the proteins with which they transiently or permanently interact to generate even more diversity. We performed a quantitative proteomic analysis of K(ATP) channel complexes in the heart, endothelium, insulin-secreting min6 cells (pancreatic β-cell like), and the hypothalamus to identify proteins with which they interact in different tissues. Glycolysis is an overrepresented pathway in identified proteins of the heart, min6 cells, and the endothelium. Proteins with other energy metabolic functions were identified in the hypothalamic samples. These data suggest that the metabolo-electrical coupling conferred by K(ATP) channels is conferred partly by proteins with which they interact. A large number of identified cytoskeletal and trafficking proteins suggests endocytic recycling may help control K(ATP) channel surface density and/or subcellular localization. Overall, our data demonstrate that K(ATP) channels in different tissues may assemble with proteins having common functions, but that tissue-specific complex organization also occurs.
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17
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Abstract
The concept of the cytosol as a space that contains discrete zones of metabolites is discussed relative to the contribution of GAPDH. GAPDH is directed to very specific cell compartments. This chapter describes the utilization of GAPDH's enzymatic function for focal demands (i.e. ATP/ADP and NAD(+)/NADH), and offers a speculative role for GAPDH as perhaps moderating local concentrations of inorganic phosphate and hydrogen ions (i.e. co-substrate and co-product of the glycolytic reaction, respectively). Where known, the structural features of the binding between GAPDH and the compartment components are discussed. The nuances, which are associated with the intracellular distribution of GAPDH, appear to be specific to the cell-type, particularly with regards to the various plasma membrane proteins to which GAPDH binds. The chapter includes discussion on the curious observation of GAPDH being localized to the external surface of the plasma membrane in a human cell type. The default perspective has been that GAPDH localization is synonymous with compartmentation of glycolytic energy. The chapter discusses GAPDH translocation to the nucleus and to non-nuclear cellular structures, emphasizing its glycolytic function. Nevertheless, it is becoming clear that alternate functions of GAPDH play a role in compartmentation, particularly in the translocation to the nucleus.
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Affiliation(s)
- Norbert W Seidler
- Department of Biochemistry, Kansas City University of Medicine and Biosciences, Kansas City, MO, USA
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18
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Mele A, Buttiglione M, Cannone G, Vitiello F, Camerino DC, Tricarico D. Opening/blocking actions of pyruvate kinase antibodies on neuronal and muscular KATP channels. Pharmacol Res 2012; 66:401-8. [PMID: 22967932 DOI: 10.1016/j.phrs.2012.07.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 07/20/2012] [Accepted: 07/30/2012] [Indexed: 11/30/2022]
Abstract
ATP-sensitive-K(+) (KATP) channels couple metabolism to the electrical activity of the cells. This channel is associated with glycolytic enzymes to form complexes regulating the channel activity in various tissues. The pyruvate-kinase (PK) enzyme is an antigen in the Paediatric Autoimmune Neuropsychiatric Disorders Associated Streptococcal infection known as PANDAS which is characterized by an abnormal production of auto-antibodies against PK. Here, the effects of the anti-pyruvate kinase antibody (anti-PK-ab) on the muscle and neuronal KATP channels were investigated in native rat skeletal muscle fibres and human neuroblastoma cell-line (SH-SY5Y), respectively. Furthermore, the interaction of PK with the inwardly rectifier potassium channel (Kir6.1/Kir6.2) subunits of the KATP channels was investigated by co-immunoprecipitation experiments in mouse brain using the anti-PK-ab. Patch-clamp experiments showed that the short-term incubation (1h) of the fibres with the anti-PK-ab at the dilutions of 1:500 and 1:300 enhanced the KATP current of 19.6% and 33.5%, respectively. As opposite, the long-term incubation (24h) of the fibres with the anti-PK-ab at the dilutions of 1:500 and 1:300 reduced the KATP current of 16% and 24%, respectively, reducing the diameter with atrophy. The direct application of the anti-PK-ab to the excised patches in the absence of intracellular ATP caused channel block, while in the presence of nucleotide channel opened. In neuronal cell line, in the short-term the anti-PK-ab potentiated KATP currents without affecting survival, while in the long-term the anti-PK-ab reduced KATP currents inducing neuronal death. Opening/blocking actions of the anti-PK antibodies on the KATP channels were observed, the blocking action causes fibre atrophy and neuronal death. We demonstrated that PK and Kir subunits are physically/functionally coupled in neurons. The KATP/PK complex can be proposed a novel target in the autoimmune diseases associated with anti-PK production as in PANDAS.
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Affiliation(s)
- Antonietta Mele
- Unit of Pharmacology, Department of Pharmacy, via Orabona no. 4, University of Bari, I-70126 Bari, Italy
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19
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Ischemic and hypoxic preconditioning protect cardiac muscles via intracellular ROS signaling. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11515-012-1225-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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20
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Alekseev AE, Reyes S, Selivanov VA, Dzeja PP, Terzic A. Compartmentation of membrane processes and nucleotide dynamics in diffusion-restricted cardiac cell microenvironment. J Mol Cell Cardiol 2012; 52:401-9. [PMID: 21704043 PMCID: PMC3264845 DOI: 10.1016/j.yjmcc.2011.06.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 01/08/2023]
Abstract
Orchestrated excitation-contraction coupling in heart muscle requires adequate spatial arrangement of systems responsible for ion movement and metabolite turnover. Co-localization of regulatory and transporting proteins into macromolecular complexes within an environment of microanatomical cell components raises intracellular diffusion barriers that hamper the mobility of metabolites and signaling molecules. Compared to substrate diffusion in the cytosol, diffusional restrictions underneath the sarcolemma are much larger and could impede ion and nucleotide movement by a factor of 10(3)-10(5). Diffusion barriers thus seclude metabolites within the submembrane space enabling rapid and vectorial effector targeting, yet hinder energy supply from the bulk cytosolic space implicating the necessity for a shunting transfer mechanism. Here, we address principles of membrane protein compartmentation, phosphotransfer enzyme-facilitated interdomain energy transfer, and nucleotide signal dynamics at the subsarcolemma-cytosol interface. This article is part of a Special Issue entitled "Local Signaling in Myocytes".
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Affiliation(s)
- Alexey E. Alekseev
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Santiago Reyes
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Vitaly A. Selivanov
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Departament de Bioquimica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, and IBUB Barcelona, Gran Via de les Corts Catalanes 585, 08007 Barcelona, Spain
| | - Petras P. Dzeja
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
| | - Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Internal Medicine, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Molecular Pharmacology & Experimental Therapeutics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
- Department of Medical Genetics, Mayo Clinic, 200 First St. SW, Rochester, MN, USA
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21
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Lopaschuk GD, Jaswal JS. Hypoxia-induced adaptation to mitral regurgitation: a role for K ATP channel up-regulation? J Am Coll Cardiol 2012; 59:397-9. [PMID: 22133354 DOI: 10.1016/j.jacc.2011.09.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 09/20/2011] [Indexed: 12/25/2022]
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22
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Kefaloyianni E, Bao L, Rindler MJ, Hong M, Patel T, Taskin E, Coetzee WA. Measuring and evaluating the role of ATP-sensitive K+ channels in cardiac muscle. J Mol Cell Cardiol 2012; 52:596-607. [PMID: 22245446 DOI: 10.1016/j.yjmcc.2011.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2011] [Revised: 12/06/2011] [Accepted: 12/23/2011] [Indexed: 11/27/2022]
Abstract
Since ion channels move electrical charge during their activity, they have traditionally been studied using electrophysiological approaches. This was sometimes combined with mathematical models, for example with the description of the ionic mechanisms underlying the initiation and propagation of action potentials in the squid giant axon by Hodgkin and Huxley. The methods for studying ion channels also have strong roots in protein chemistry (limited proteolysis, the use of antibodies, etc.). The advent of the molecular cloning and the identification of genes coding for specific ion channel subunits in the late 1980s introduced a multitude of new techniques with which to study ion channels and the field has been rapidly expanding ever since (e.g. antibody development against specific peptide sequences, mutagenesis, the use of gene targeting in animal models, determination of their protein structures) and new methods are still in development. This review focuses on techniques commonly employed to examine ion channel function in an electrophysiological laboratory. The focus is on the K(ATP) channel, but many of the techniques described are also used to study other ion channels.
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23
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Renigunta A, Mutig K, Rottermann K, Schlichthörl G, Preisig-Müller R, Daut J, Waldegger S, Renigunta V. The glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenase and enolase interact with the renal epithelial K+ channel ROMK2 and regulate its function. Cell Physiol Biochem 2011; 28:663-72. [PMID: 22178878 DOI: 10.1159/000335761] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2011] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND/AIMS ROMK channels mediate potassium secretion and regulate NaCl reabsorption in the kidney. The aim was to study the functional implications of the interaction between ROMK2 (Kir1.1b) and two glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and enolase-α, which were identified as potential regulatory subunits of the channel complex. METHODS We performed a membrane yeast-two-hybrid screen of a human kidney cDNA library with ROMK2 as a bait. Interaction of ROMK2 with GAPDH and enolase was verified using GST pull-down, co-immunoprecipitation, immunohistochemistry and co-expression in Xenopus oocytes. RESULTS Confocal imaging showed co-localisation of enolase and GAPDH with ROMK2 in the apical membrane of the renal epithelial cells of the thick ascending limb. Over-expression of GAPDH or enolase-α in Xenopus oocytes markedly reduced the amplitude of ROMK2 currents but did not affect the surface expression of the channels. Co-expression of the glycolytically inactive GAPDH mutant C149G did not have any effect on ROMK2 current amplitude. CONCLUSION Our results suggest that the glycolytic enzymes GAPDH and enolase are part of the ROMK2 channel supramolecular complex and may serve to couple salt reabsorption in the thick ascending limb of the loop of Henle to the metabolic status of the renal epithelial cells.
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Affiliation(s)
- Aparna Renigunta
- Department of Paediatric Nephrology, Children's Hospital, University of Marburg, Baldingerstrasse, Marburg, Germany
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24
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Lang V, Youssef N, Light PE. The molecular genetics of sulfonylurea receptors in the pathogenesis and treatment of insulin secretory disorders and type 2 diabetes. Curr Diab Rep 2011; 11:543-51. [PMID: 21968738 DOI: 10.1007/s11892-011-0233-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Sulfonylurea receptors (SURs) form an integral part of the ATP-sensitive potassium (K(ATP)) channel complex that is present in most excitable cell types. K(ATP) channels couple cellular metabolism to electrical activity and provide a wide range of cellular functions including stimulus secretion coupling in pancreatic β cells. K(ATP) channels are composed of SURs and inward rectifier potassium channel (Kir6.x) subunits encoded by the ABCC8/9 and KCNJ8/11 genes, respectively. Recent advances in the genetics, molecular biology, and pharmacology of SURs have led to an increased understanding of these channels in the etiology and treatment of rare genetic insulin secretory disorders. Furthermore, common genetic variants in these genes are associated with an increased risk for type 2 diabetes. In this review we summarize the molecular biology, pharmacology, and physiology of SURs and K(ATP) channels, highlighting recent advances in their genetics and understanding of rare insulin secretory disorders and susceptibility to type 2 diabetes.
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Affiliation(s)
- Veronica Lang
- Department of Pharmacology, Alberta Diabetes Institute and Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
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25
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Graciotti L, Becker J, Granata AL, Procopio AD, Tessarollo L, Fulgenzi G. Dystrophin is required for the normal function of the cardio-protective K(ATP) channel in cardiomyocytes. PLoS One 2011; 6:e27034. [PMID: 22066028 PMCID: PMC3205025 DOI: 10.1371/journal.pone.0027034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Accepted: 10/09/2011] [Indexed: 12/19/2022] Open
Abstract
Duchenne and Becker muscular dystrophy patients often develop a cardiomyopathy for which the pathogenesis is still unknown. We have employed the murine animal model of Duchenne muscular dystrophy (mdx), which develops a cardiomyopathy that includes some characteristics of the human disease, to study the molecular basis of this pathology. Here we show that the mdx mouse heart has defects consistent with alteration in compounds that regulate energy homeostasis including a marked decrease in creatine-phosphate (PC). In addition, the mdx heart is more susceptible to anoxia than controls. Since the cardio-protective ATP sensitive potassium channel (KATP) complex and PC have been shown to interact we investigated whether deficits in PC levels correlate with other molecular events including KATP ion channel complex presence, its functionality and interaction with dystrophin. We found that this channel complex is present in the dystrophic cardiac cell membrane but its ability to sense a drop in the intracellular ATP concentration and consequently open is compromised by the absence of dystrophin. We further demonstrate that the creatine kinase muscle isoform (CKm) is displaced from the plasma membrane of the mdx cardiac cells. Considering that CKm is a determinant of KATP channel complex function we hypothesize that dystrophin acts as a scaffolding protein organizing the KATP channel complex and the enzymes necessary for its correct functioning. Therefore, the lack of proper functioning of the cardio-protective KATP system in the mdx cardiomyocytes may be part of the mechanism contributing to development of cardiac disease in dystrophic patients.
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Affiliation(s)
- Laura Graciotti
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
| | - Jodi Becker
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Anna Luisa Granata
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
| | - Antonio Domenico Procopio
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
- Center of Clinical Pathology and Innovative Therapy, INRCA, Ancona, Italy
| | - Lino Tessarollo
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- * E-mail: (GF); (LT)
| | - Gianluca Fulgenzi
- Department of Clinical and Molecular Sciences, Università Politecnica delle Marche, Ancona, Italy
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- * E-mail: (GF); (LT)
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26
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Terzic A, Alekseev AE, Yamada S, Reyes S, Olson TM. Advances in cardiac ATP-sensitive K+ channelopathies from molecules to populations. Circ Arrhythm Electrophysiol 2011; 4:577-85. [PMID: 21846889 DOI: 10.1161/circep.110.957662] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Internal Medicine, Department of Molecular Pharmacology and Experimental Therapeutics, Department of Medical Genetics, Mayo Clinic, Rochester, MN, USA.
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27
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Chao C, Liang T, Kang Y, Lin X, Xie H, Feng ZP, Gaisano HY. Syntaxin-1A inhibits KATP channels by interacting with specific conserved motifs within sulfonylurea receptor 2A. J Mol Cell Cardiol 2011; 51:790-802. [PMID: 21884702 DOI: 10.1016/j.yjmcc.2011.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 07/25/2011] [Accepted: 08/13/2011] [Indexed: 11/19/2022]
Abstract
We previously demonstrated that syntaxin (Syn)-1A is present in the sarcolemma of rat cardiomyocytes and binds sulfonylurea receptor (SUR) 2A nucleotide binding folds (NBFs) to inhibit ATP-sensitive potassium (K(ATP)) channel. Here, we examined for the precise domains within the NBFs of SUR2A that may interact with Syn-1A. Specifically, we tested truncated NBF protein segments encompassing the conserved motifs Walker A (W(A)), signature/Linker (L), and Walker B (W(B)). In vitro binding results indicate that the domains encompassing W(A) and L of NBF-1 and all three conserved motifs of NBF-2 bound Syn-1A. Electrophysiological studies, employing inside-out patch-clamp recordings from SUR2A/Kir6.2 expressing HEK cells and mouse cardiomyocytes, show that W(B) and L of NBF-1 and all three NBF-2 truncated protein segments reduced Syn-1A inhibition of SUR2A/K(ATP) channels. Remarkably, these same NBF-1 and -2 truncated proteins could independently disrupt the intimate FRET interactions of full length SUR2A (-mCherry) and Syn-1A (-EGFP). These results taken together indicate that Syn-1A possibly maintains inhibition of cardiac ventricular K(ATP) channels by binding to large regions of NBF-1 and NBF-2 to stabilize the NBF-1-NBF-2 heterodimer formation and prevent ATP-binding and ATP hydrolysis. Since K(ATP) channels are closely coupled to metabolic states, we postulate that these very intimate Syn-1A-SUR2A interactions are critically important for myocardial protection during stress, in which profound changes in metabolic factors (pH, ATP) could modulate these Syn-1A-SUR2A interactions.
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MESH Headings
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Adenosine Triphosphate/biosynthesis
- Amino Acid Motifs
- Animals
- Binding Sites
- Cell Membrane/metabolism
- Conserved Sequence
- Fluorescence Resonance Energy Transfer
- HEK293 Cells
- Humans
- KATP Channels/chemistry
- KATP Channels/genetics
- KATP Channels/metabolism
- Male
- Mice
- Microscopy, Fluorescence
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Oligopeptides/chemistry
- Oligopeptides/genetics
- Oligopeptides/metabolism
- Patch-Clamp Techniques
- Plasmids
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/chemistry
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Protein Binding
- Protein Structure, Tertiary
- Receptors, Drug/chemistry
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Recombinant Proteins/chemistry
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Signal Transduction/physiology
- Sulfonylurea Receptors
- Syntaxin 1/chemistry
- Syntaxin 1/genetics
- Syntaxin 1/metabolism
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Affiliation(s)
- Christin Chao
- Department of Medicine, University of Toronto, Room 7368, Medical Sciences Building, Toronto, ON, Canada
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28
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Sukhodub A, Sudhir R, Du Q, Jovanović S, Reyes S, Jovanović A. Nicotinamide-rich diet improves physical endurance by up-regulating SUR2A in the heart. J Cell Mol Med 2011; 15:1703-12. [PMID: 20731746 PMCID: PMC4373361 DOI: 10.1111/j.1582-4934.2010.01156.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 07/14/2010] [Indexed: 11/29/2022] Open
Abstract
SUR2A is an ATP-binding protein that serves as a regulatory subunit of cardioprotective ATP-sensitive K(+) (K(ATP) ) channels. Based on signalling pathway regulating SUR2A expression and SUR2A role in regulating numbers of fully assembled K(ATP) channels, we have suggested that nicotinamide-rich diet could improve physical endurance by stimulating SUR2A expression. We have found that mice on nicotinamide-rich diet significantly improved physical endurance, which was associated with significant increase in expression of SUR2A. Transgenic mice with solely overexpressed SUR2A on control diet had increased physical endurance in a similar manner as the wild-type mice on nicotinamide-rich diet. The experiments focused on action membrane potential and intracellular Ca(2+) concentration have demonstrated that increased SUR2A expression was associated with the activation of sarcolemmal K(ATP) channels and steady Ca(2+) levels in cardiomyocytes in response to β-adrenergic stimulation. In contrast, the same challenge in the wild-type was characterized by a lack of the channel activation and rise in intracellular Ca(2+) . Nicotinamide-rich diet was ineffective to increase physical endurance in mice lacking K(ATP) channels. This study has shown that nicotinamide-rich diet improves physical endurance by increasing expression of SUR2A and that this is a sole mechanism of the nicotinamide-rich diet effect. The obtained results suggest that oral nicotinamide is a regulator of SUR2A expression and has a potential as a drug that can improve physical endurance in conditions where this effect would be desirable.
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MESH Headings
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Adrenergic beta-Agonists/pharmacology
- Animals
- Calcium/metabolism
- Cells, Cultured
- Diet
- Female
- Gene Expression/drug effects
- Heart Ventricles/cytology
- Heart Ventricles/drug effects
- Heart Ventricles/metabolism
- Isoproterenol/pharmacology
- Male
- Membrane Potentials/drug effects
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Motor Activity/drug effects
- Myocardium/cytology
- Myocardium/metabolism
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/physiology
- Niacinamide/administration & dosage
- Niacinamide/pharmacology
- Physical Conditioning, Animal/physiology
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sulfonylurea Receptors
- Up-Regulation/drug effects
- Vitamin B Complex/administration & dosage
- Vitamin B Complex/pharmacology
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Affiliation(s)
- Andriy Sukhodub
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of DundeeDundee, UK
| | - Rajni Sudhir
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of DundeeDundee, UK
| | - Qingyou Du
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of DundeeDundee, UK
| | - Sofija Jovanović
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of DundeeDundee, UK
| | | | - Aleksandar Jovanović
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of DundeeDundee, UK
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29
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Lader JM, Vasquez C, Bao L, Maass K, Qu J, Kefalogianni E, Fishman GI, Coetzee WA, Morley GE. Remodeling of atrial ATP-sensitive K⁺ channels in a model of salt-induced elevated blood pressure. Am J Physiol Heart Circ Physiol 2011; 301:H964-74. [PMID: 21724863 DOI: 10.1152/ajpheart.00410.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hypertension is associated with the development of atrial fibrillation; however, the electrophysiological consequences of this condition remain poorly understood. ATP-sensitive K(+) (K(ATP)) channels, which contribute to ventricular arrhythmias, are also expressed in the atria. We hypothesized that salt-induced elevated blood pressure (BP) leads to atrial K(ATP) channel activation and increased arrhythmia inducibility. Elevated BP was induced in mice with a high-salt diet (HS) for 4 wk. High-resolution optical mapping was used to measure atrial arrhythmia inducibility, effective refractory period (ERP), and action potential duration at 90% repolarization (APD(90)). Excised patch clamping was performed to quantify K(ATP) channel properties and density. K(ATP) channel protein expression was also evaluated. Atrial arrhythmia inducibility was 22% higher in HS hearts compared with control hearts. ERP and APD(90) were significantly shorter in the right atrial appendage and left atrial appendage of HS hearts compared with control hearts. Perfusion with 1 μM glibenclamide or 300 μM tolbutamide significantly decreased arrhythmia inducibility and prolonged APD(90) in HS hearts compared with untreated HS hearts. K(ATP) channel density was 156% higher in myocytes isolated from HS animals compared with control animals. Sulfonylurea receptor 1 protein expression was increased in the left atrial appendage and right atrial appendage of HS animals (415% and 372% of NS animals, respectively). In conclusion, K(ATP) channel activation provides a mechanistic link between salt-induced elevated BP and increased atrial arrhythmia inducibility. The findings of this study have important implications for the treatment and prevention of atrial arrhythmias in the setting of hypertensive heart disease and may lead to new therapeutic approaches.
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Affiliation(s)
- Joshua M Lader
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, New York 10016, USA
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30
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Phenylephrine preconditioning involves modulation of cardiac sarcolemmal K(ATP) current by PKC delta, AMPK and p38 MAPK. J Mol Cell Cardiol 2011; 51:370-80. [PMID: 21740910 DOI: 10.1016/j.yjmcc.2011.06.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 06/17/2011] [Accepted: 06/20/2011] [Indexed: 11/23/2022]
Abstract
Preconditioning of hearts with the α(1)-adrenoceptor agonist phenylephrine decreases infarct size and increases the functional recovery of the heart following ischaemia-reperfusion. However, the cellular mechanisms responsible for this protection are not known. We investigated the role of protein kinase C ε and δ (PKCε and PKCδ), AMP-activated protein kinase (AMPK), p38 MAPK (p38) and sarcolemmal ATP-sensitive potassium (sarcK(ATP)) channels in phenylephrine preconditioning using isolated rat ventricular myocytes. Preconditioning of ventricular myocytes with phenylephrine increased the recovery of contractile activity following metabolic inhibition and re-energisation from 30.1±1.9% to 66.5±5.2% (P<0.01) and increased the peak sarcK(ATP) current activated during metabolic inhibition from 32.1±1.8 pA/pF to 46.0±5.0 pA/pF (P<0.05), which was required for protection. Phenylephrine preconditioning resulted in a sustained activation of PKCε and PKCδ, and transient activation of AMPK, which was dependent upon activation of PKCδ but not PKCε. P38 was also activated by phenylephrine preconditioning and this was blocked by inhibitors of PKCε, PKCδ or AMPK. Inhibition of PKCδ, AMPK or p38 was sufficient to prevent the increase in current, suggesting that these kinases are involved in modulation of sarcK(ATP) channel current by phenylephrine preconditioning. However, whilst inhibition of AMPK and p38 prevented the protection from phenylephrine preconditioning, PKCδ inhibition paradoxically had no effect. The increase in sarcK(ATP) current induced by phenylephrine preconditioning requires PKCδ, AMPK and p38 and may contribute to the observed improvement in contractile recovery.
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31
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Zingman LV, Zhu Z, Sierra A, Stepniak E, Burnett CML, Maksymov G, Anderson ME, Coetzee WA, Hodgson-Zingman DM. Exercise-induced expression of cardiac ATP-sensitive potassium channels promotes action potential shortening and energy conservation. J Mol Cell Cardiol 2011; 51:72-81. [PMID: 21439969 DOI: 10.1016/j.yjmcc.2011.03.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Revised: 02/19/2011] [Accepted: 03/14/2011] [Indexed: 12/25/2022]
Abstract
Physical activity is one of the most important determinants of cardiac function. The ability of the heart to increase delivery of oxygen and metabolic fuels relies on an array of adaptive responses necessary to match bodily demand while avoiding exhaustion of cardiac resources. The ATP-sensitive potassium (K(ATP)) channel has the unique ability to adjust cardiac membrane excitability in accordance with ATP and ADP levels, and up-regulation of its expression that occurs in response to exercise could represent a critical element of this adaption. However, the mechanism by which K(ATP) channel expression changes result in a beneficial effect on cardiac excitability and function remains to be established. Here, we demonstrate that an exercise-induced rise in K(ATP) channel expression enhanced the rate and magnitude of action potential shortening in response to heart rate acceleration. This adaptation in membrane excitability promoted significant reduction in cardiac energy consumption under escalating workloads. Genetic disruption of normal K(ATP) channel pore function abolished the exercise-related changes in action potential duration adjustment and caused increased cardiac energy consumption. Thus, an expression-driven enhancement in the K(ATP) channel-dependent membrane response to alterations in cardiac workload represents a previously unrecognized mechanism for adaptation to physical activity and a potential target for cardioprotection.
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Affiliation(s)
- Leonid V Zingman
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA.
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32
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Chao CC, Mihic A, Tsushima RG, Gaisano HY. SNARE protein regulation of cardiac potassium channels and atrial natriuretic factor secretion. J Mol Cell Cardiol 2011; 50:401-7. [DOI: 10.1016/j.yjmcc.2010.11.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 11/17/2010] [Accepted: 11/19/2010] [Indexed: 01/28/2023]
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33
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Arrell DK, Zlatkovic Lindor J, Yamada S, Terzic A. K(ATP) channel-dependent metaboproteome decoded: systems approaches to heart failure prediction, diagnosis, and therapy. Cardiovasc Res 2011; 90:258-66. [PMID: 21321057 DOI: 10.1093/cvr/cvr046] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Systems biology provides an integrative platform by which to account for the biological complexity related to cardiac health and disease. In this way, consequences of ATP-sensitive K(+) (K(ATP)) channel deficiency for heart failure prediction, diagnosis, and therapy were resolved recently at a proteomic level. Under stress-free conditions, knockout of the Kir6.2 K(ATP) channel pore induced metabolic proteome remodelling, revealing overrepresentation of markers of cardiovascular disease. Imposed stress precipitated structural and functional defects in Kir6.2-knockout hearts, decreasing survival and validating prediction of disease susceptibility. In the setting of hypertension, a leading risk for heart failure development, proteomic analysis diagnosed the metabolism-centric impact of K(ATP) channel deficiency in disease. Bioinformatic interrogation of K(ATP) channel-dependent proteome prioritized heart-specific adverse effects, exposing cardiomyopathic traits of aggravated contractility, fibrosis, and ventricular hypertrophy. In dilated cardiomyopathy induced by Kir6.2-knockout pressure overload, proteomic remodelling was exacerbated, underlying a multifaceted molecular pathology that indicates the necessity for a broad-based strategy to achieve repair. Embryonic stem cell intervention in cardiomyopathic K(ATP) channel knockout hearts elicited a distinct proteome signature that forecast amelioration of adverse cardiac outcomes. Functional/structural measurements validated improved contractile performance, reduced ventricular size, and decreased cardiac damage in the treated cohort, while systems assessment unmasked cardiovascular development as a prioritized biological function in stem cell-reconstructed hearts. Thus, proteomic deconvolution of K(ATP) channel-deficient hearts provides definitive evidence for the channel's homeostatic contribution to the cardiac metaboproteome and establishes the utility of systems-oriented approaches to predict disease susceptibility, diagnose consequences of heart failure progression, and monitor therapy outcome.
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Affiliation(s)
- D Kent Arrell
- Marriott Heart Disease Research Program, Mayo Clinic, Stabile 5, 200 First Street SW, Rochester, MN, USA
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34
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Jovanović S, Du Q, Mukhopadhyay S, Swingler R, Buckley R, McEachen J, Jovanović A. A patient suffering from hypokalemic periodic paralysis is deficient in skeletal muscle ATP-sensitive K channels. Clin Transl Sci 2010; 1:71-4. [PMID: 20396605 DOI: 10.1111/j.1752-8062.2008.00007.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Hypokalemic periodic paralysis (HOPP) is a rare disease associated with attacks of muscle weakness and hypokalemia. In the present study, immunoprecipitation/Western blotting has shown that a HOPP patient was deficient in sarcolemmal K(ATP) channels. Real-time RT-PCR has revealed that HOPP has decreased mRNA levels of Kir6.2, a pore-forming K(ATP) channel subunit, without affecting the expression of other K(ATP) channel-forming proteins. Based on these findings, we conclude that HOPP could be associated with impaired expression of Kir6.2 which leads to deficiency in skeletal muscle K(ATP) channels, which may explain the symptoms and clinical signs of this disease.
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Affiliation(s)
- Sofija Jovanović
- Maternal and Child Health Sciences, Ninewells Hospital & Medical School, University of Dundee, Dundee, Scotland, UK
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35
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Reyes S, Park S, Terzic A, Alekseev AE. K(ATP) channels process nucleotide signals in muscle thermogenic response. Crit Rev Biochem Mol Biol 2010; 45:506-19. [PMID: 20925594 DOI: 10.3109/10409238.2010.513374] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Uniquely gated by intracellular adenine nucleotides, sarcolemmal ATP-sensitive K(+) (K(ATP)) channels have been typically assigned to protective cellular responses under severe energy insults. More recently, K(ATP) channels have been instituted in the continuous control of muscle energy expenditure under non-stressed, physiological states. These advances raised the question of how K(ATP) channels can process trends in cellular energetics within a milieu where each metabolic system is set to buffer nucleotide pools. Unveiling the mechanistic basis of the K(ATP) channel-driven thermogenic response in muscles thus invites the concepts of intracellular compartmentalization of energy and proteins, along with nucleotide signaling over diffusion barriers. Furthermore, it requires gaining insight into the properties of reversibility of intrinsic ATPase activity associated with K(ATP) channel complexes. Notwithstanding the operational paradigm, the homeostatic role of sarcolemmal K(ATP) channels can be now broadened to a wider range of environmental cues affecting metabolic well-being. In this way, under conditions of energy deficit such as ischemic insult or adrenergic stress, the operation of K(ATP) channel complexes would result in protective energy saving, safeguarding muscle performance and integrity. Under energy surplus, downregulation of K(ATP) channel function may find potential implications in conditions of energy imbalance linked to obesity, cold intolerance and associated metabolic disorders.
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Affiliation(s)
- Santiago Reyes
- Marriott Heart Diseases Research Program, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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36
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Du Q, Jovanović S, Sukhodub A, Barratt E, Drew E, Whalley KM, Kay V, McLaughlin M, Telfer EE, Barratt CLR, Jovanović A. Human oocytes express ATP-sensitive K(+) channels. Hum Reprod 2010; 25:2774-82. [PMID: 20847183 DOI: 10.1093/humrep/deq245] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND ATP-sensitive K(+) (K(ATP)) channels link intracellular metabolism with membrane excitability and play crucial roles in cellular physiology and protection. The K(ATP) channel protein complex is composed of pore forming, Kir6.x (Kir6.1 or Kir6.2) and regulatory, SURx (SUR2A, SUR2B or SUR1), subunits that associate in different combinations. The objective of this study was to determine whether mammalian oocytes (human, bovine, porcine) express K(ATP) channels. METHODS Supernumerary human oocytes at different stages of maturation were obtained from patients undergoing assisted conception treatments. Bovine and porcine oocytes in the germinal vesicle (GV) stage were obtained by aspirating antral follicles from abattoir-derived ovaries. The presence of mRNA for K(ATP) channel subunits was determined using real-time RT-PCR with primers specific for Kir6.2, Kir6.1, SUR1, SUR2A and SUR2B. To assess whether functional K(ATP) channels are present in human oocytes, traditional and perforated patch whole cell electrophysiology and immunoprecipitation/western blotting were used. RESULTS Real-time PCR revealed that mRNA for Kir6.1, Kir6.2, SUR2A and SUR2B, but not SUR1, were present in human oocytes of different stages. Only SUR2B and Kir6.2 mRNAs were detected in GV stage bovine and porcine oocytes. Immunoprecipitation with SUR2 antibody and western blotting with Kir6.1 antibody identified bands corresponding to these subunits in human oocytes. In human oocytes, 2,4-dinitrophenol (400 µM), a metabolic inhibitor known to decrease intracellular ATP and activate K(ATP) channels, increased whole cell K(+) current. On the other hand, K(+) current induced by low intracellular ATP was inhibited by extracellular glibenclamide (30 µM), an oral antidiabetic known to block the opening of K(ATP) channels. CONCLUSIONS In conclusion, mammalian oocytes express K(ATP) channels. This opens a new avenue of research into the complex relationship between metabolism and membrane excitability in oocytes under different conditions, including conception.
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Affiliation(s)
- Qingyou Du
- Division of Medical Sciences/MACHS, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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37
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Flagg TP, Enkvetchakul D, Koster JC, Nichols CG. Muscle KATP channels: recent insights to energy sensing and myoprotection. Physiol Rev 2010; 90:799-829. [PMID: 20664073 DOI: 10.1152/physrev.00027.2009] [Citation(s) in RCA: 202] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are present in the surface and internal membranes of cardiac, skeletal, and smooth muscle cells and provide a unique feedback between muscle cell metabolism and electrical activity. In so doing, they can play an important role in the control of contractility, particularly when cellular energetics are compromised, protecting the tissue against calcium overload and fiber damage, but the cost of this protection may be enhanced arrhythmic activity. Generated as complexes of Kir6.1 or Kir6.2 pore-forming subunits with regulatory sulfonylurea receptor subunits, SUR1 or SUR2, the differential assembly of K(ATP) channels in different tissues gives rise to tissue-specific physiological and pharmacological regulation, and hence to the tissue-specific pharmacological control of contractility. The last 10 years have provided insights into the regulation and role of muscle K(ATP) channels, in large part driven by studies of mice in which the protein determinants of channel activity have been deleted or modified. As yet, few human diseases have been correlated with altered muscle K(ATP) activity, but genetically modified animals give important insights to likely pathological roles of aberrant channel activity in different muscle types.
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Affiliation(s)
- Thomas P Flagg
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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38
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Yang YC, Fann MJ, Chang WH, Tai LH, Jiang JH, Kao LS. Regulation of sodium-calcium exchanger activity by creatine kinase under energy-compromised conditions. J Biol Chem 2010; 285:28275-85. [PMID: 20576602 DOI: 10.1074/jbc.m110.141424] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na(+)/Ca(2+) exchanger (NCX) is one of the major mechanisms for removing Ca(2+) from the cytosol especially in cardiac myocytes and neurons, where their physiological activities are triggered by an influx of Ca(2+). NCX contains a large intracellular loop (NCXIL) that is responsible for regulating NCX activity. Recent evidence has shown that proteins, including kinases and phosphatases, associate with NCX1IL to form a NCX1 macromolecular complex. To search for the molecules that interact with NCX1IL and regulate NCX1 activity, we used the yeast two-hybrid method to screen a human heart cDNA library and found that the C-terminal region of sarcomeric mitochondrial creatine kinase (sMiCK) interacted with NCX1IL. Moreover, both sMiCK and the muscle-type creatine kinase (CKM) coimmunoprecipitated with NCX1 using lysates of cardiacmyocytes and HEK293T cells that transiently expressed NCX1 and various creatine kinases. Both sMiCK and CKM were able to produce a recovery in the decreased NCX1 activity that was lost under energy-compromised conditions. This regulation is mediated through a putative PKC phosphorylation site of sMiCK and CKM. The autophosphorylation and the catalytic activity of sMiCK and CKM are not required for their regulation of NCX1 activity. Our results suggest a novel mechanism for the regulation of NCX1 activity.
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Affiliation(s)
- Ya-Chi Yang
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
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39
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Drews G, Krippeit-Drews P, Düfer M. Electrophysiology of islet cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:115-63. [PMID: 20217497 DOI: 10.1007/978-90-481-3271-3_7] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Stimulus-Secretion Coupling (SSC) of pancreatic islet cells comprises electrical activity. Changes of the membrane potential (V(m)) are regulated by metabolism-dependent alterations in ion channel activity. This coupling is best explored in beta-cells. The effect of glucose is directly linked to mitochondrial metabolism as the ATP/ADP ratio determines the open probability of ATP-sensitive K(+) channels (K(ATP) channels). Nucleotide sensitivity and concentration in the direct vicinity of the channels are controlled by several factors including phospholipids, fatty acids, and kinases, e.g., creatine and adenylate kinase. Closure of K(ATP) channels leads to depolarization of beta-cells via a yet unknown depolarizing current. Ca(2+) influx during action potentials (APs) results in an increase of the cytosolic Ca(2+) concentration ([Ca(2+)](c)) that triggers exocytosis. APs are elicited by the opening of voltage-dependent Na(+) and/or Ca(2+) channels and repolarized by voltage- and/or Ca(2+)-dependent K(+) channels. At a constant stimulatory glucose concentration APs are clustered in bursts that are interrupted by hyperpolarized interburst phases. Bursting electrical activity induces parallel fluctuations in [Ca(2+)](c) and insulin secretion. Bursts are terminated by I(Kslow) consisting of currents through Ca(2+)-dependent K(+) channels and K(ATP) channels. This review focuses on structure, characteristics, physiological function, and regulation of ion channels in beta-cells. Information about pharmacological drugs acting on K(ATP) channels, K(ATP) channelopathies, and influence of oxidative stress on K(ATP) channel function is provided. One focus is the outstanding significance of L-type Ca(2+) channels for insulin secretion. The role of less well characterized beta-cell channels including voltage-dependent Na(+) channels, volume sensitive anion channels (VSACs), transient receptor potential (TRP)-related channels, and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels is discussed. A model of beta-cell oscillations provides insight in the interplay of the different channels to induce and maintain electrical activity. Regulation of beta-cell electrical activity by hormones and the autonomous nervous system is discussed. alpha- and delta-cells are also equipped with K(ATP) channels, voltage-dependent Na(+), K(+), and Ca(2+) channels. Yet the SSC of these cells is less clear and is not necessarily dependent on K(ATP) channel closure. Different ion channels of alpha- and delta-cells are introduced and SSC in alpha-cells is described in special respect of paracrine effects of insulin and GABA secreted from beta-cells.
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Affiliation(s)
- Gisela Drews
- Institute of Pharmacy, Department of Pharmacology and Clinical Pharmacy, University of Tübingen, 72076 Tübingen, Germany.
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40
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Abstract
Abstract
Sarcolemmal ATP-sensitive K+ (KATP) channels are abundant in cardiac myocytes where they couple the cellular metabolic state with membrane excitability. Structurally, these channels are composed of Kir6.2, a pore-forming subunit, SUR2A, a regulatory subunit, and at least four accessory proteins. The activation of KATP channels occurs during ischaemia to promote cardiac viability under this adverse condition. Age-dependent changes in the myocardial susceptibility to ischaemia have been reported in experimental animals as well as in humans. Recent research has demonstrated that ageing is associated with a decrease in the number of cardiac sarcolemmal KATP channels in hearts from females, but not males. This alteration is likely to be due to an age-dependent decrease in the concentration of circulating estrogens. In the heart, SUR2A is the least expressed protein of all KATP channel-forming proteins. The consequence of this phenomenon is that the level of SUR2A is the main factor controlling the number of sarcolemmal KATP channels. Estrogens specifically up-regulate SUR2A and govern the number of sarcolemmal KATP channels, and this may explain the effect of decreasing estrogen levels on the heart. An age-dependent decrease in the number of sarcolemmal KATP channels generates a cardiac phenotype more sensitive to ischaemia, which seems to be responsible for the ageing-associated decrease in myocardial tolerance to stress that occurs in elderly women.
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Affiliation(s)
- Aleksandar Jovanović
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.
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41
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Du Q, Jovanović S, Sukhodub A, Jovanović A. Infection with AV-SUR2A protects H9C2 cells against metabolic stress: a mechanism of SUR2A-mediated cytoprotection independent from the K(ATP) channel activity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:405-15. [PMID: 20123112 PMCID: PMC2881534 DOI: 10.1016/j.bbamcr.2010.01.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/18/2009] [Accepted: 01/22/2010] [Indexed: 11/17/2022]
Abstract
Transgenic mice overexpressing SUR2A, a subunit of ATP-sensitive K(+) (K(ATP)) channels, acquire resistance to myocardial ischaemia. However, the mechanism of SUR2A-mediated cytoprotection is yet to be fully understood. Adenoviral SUR2A construct (AV-SUR2A) increased SUR2A expression, number of K(ATP) channels and subsarcolemmal ATP in glycolysis-sensitive manner in H9C2 cells. It also increased K(+) current in response to chemical hypoxia, partially preserved subsarcolemmal ATP and increased cell survival. Kir6.2AFA, a mutant form of Kir6.2 with largely decreased K(+) conductance, abolished the effect of SUR2A on K(+) current, did not affect SUR2A-induced increase in subsarcolemmal ATP and partially inhibited SUR2A-mediated cytoprotection. Infection with 193gly-M-LDH, an inactive mutant of muscle lactate dehydrogenase, abolished the effect of SUR2A on K(+) current, subsarcolemmal ATP and cell survival; the effect of 193gly-M-LDH on cell survival was significantly more pronounced than those of Kir6.2AFA. We conclude that AV-SUR2A increases resistance to metabolic stress in H9C2 cells by increasing the number of sarcolemmal K(ATP) channels and subsarcolemmal ATP.
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Affiliation(s)
| | | | | | - Aleksandar Jovanović
- Corresponding author. Division of Medical Sciences/MACHS, Ninewells
Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, Scotland,
UK. Tel.: +44 1382 496 269; fax: +44 1382 632 597.
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Arrell DK, Zlatkovic J, Kane GC, Yamada S, Terzic A. ATP-sensitive K+ channel knockout induces cardiac proteome remodeling predictive of heart disease susceptibility. J Proteome Res 2010; 8:4823-34. [PMID: 19673485 DOI: 10.1021/pr900561g] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Forecasting disease susceptibility requires detection of maladaptive signatures prior to onset of overt symptoms. A case-in-point are cardiac ATP-sensitive K+ (K(ATP)) channelopathies, for which the substrate underlying disease vulnerability remains to be identified. Resolving molecular pathobiology, even for single genetic defects, mandates a systems platform to reliably diagnose disease predisposition. High-throughput proteomic analysis was here integrated with network biology to decode consequences of Kir6.2 K(ATP) channel pore deletion. Differential two-dimensional gel electrophoresis reproducibly resolved >800 protein species from hearts of asymptomatic wild-type and Kir6.2-knockout counterparts. K(ATP) channel ablation remodeled the cardiac proteome, significantly altering 71 protein spots, from which 102 unique identities were assigned following hybrid linear ion trap quadrupole-Orbitrap tandem mass spectrometry. Ontological annotation stratified the K(ATP) channel-dependent protein cohort into a predominant bioenergetic module (63 resolved identities), with additional focused sets representing signaling molecules (6), oxidoreductases (8), chaperones (6), and proteins involved in catabolism (6), cytostructure (8), and transcription and translation (5). Protein interaction mapping, in conjunction with expression level changes, localized a K(ATP) channel-associated subproteome within a nonstochastic scale-free network. Global assessment of the K(ATP) channel deficient environment verified the primary impact on metabolic pathways and revealed overrepresentation of markers associated with cardiovascular disease. Experimental imposition of graded stress precipitated exaggerated structural and functional myocardial defects in the Kir6.2-knockout, decreasing survivorship and validating the forecast of disease susceptibility. Proteomic cartography thus provides an integral view of molecular remodeling in the heart induced by K(ATP) channel deletion, establishing a systems approach that predicts outcome at a presymptomatic stage.
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Affiliation(s)
- D Kent Arrell
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA
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43
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Sukhodub A, Du Q, Jovanović S, Jovanović A. Nicotinamide-rich diet protects the heart against ischaemia-reperfusion in mice: a crucial role for cardiac SUR2A. Pharmacol Res 2010; 61:564-70. [PMID: 20083200 PMCID: PMC2859200 DOI: 10.1016/j.phrs.2010.01.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 01/11/2010] [Accepted: 01/11/2010] [Indexed: 11/15/2022]
Abstract
It is a consensus view that a strategy to increase heart resistance to ischaemia-reperfusion is a warranted. Here, based on our previous study, we have hypothesized that a nicotinamide-rich diet could increase myocardial resistance to ischaemia-reperfusion. Therefore, the purpose of this study was to determine whether nicotinamide-rich diet would increase heart resistance to ischaemia-reperfusion and what is the underlying mechanism. Experiments have been done on mice on control and nicotinamide-rich diet (mice were a week on nicotinamide-rich diet) as well as on transgenic mice overexpressing SUR2A (SUR2A mice), a regulatory subunit of cardioprotective ATP-sensitive K(+) (K(ATP)) channels and their littermate controls (WT). The levels of mRNA in heart tissue were measured by real-time RT-PCR, whole heart and single cell resistance to ischaemia-reperfusion and severe hypoxia was measured by TTC staining and laser confocal microscopy, respectively. Nicotinamide-rich diet significantly decreased the size of myocardial infarction induced by ischaemia-reperfusion (from 42.5+/-4.6% of the area at risk zone in mice on control diet to 26.8+/-1.8% in mice on nicotinamide-rich diet, n=6-12, P=0.031). The cardioprotective effect of nicotinamide-rich diet was associated with 11.46+/-1.22 times (n=6) increased mRNA levels of SUR2A in the heart. HMR1098, a selective inhibitor of the sarcolemmal K(ATP) channels opening, abolished cardioprotection afforded by nicotinamide-rich diet. Transgenic mice with a sole increase in SUR2A expression had also increased cardiac resistance to ischaemia-reperfusion. We conclude that nicotinamide-rich diet up-regulate SUR2A and increases heart resistance to ischaemia-reperfusion.
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Affiliation(s)
- Andriy Sukhodub
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
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Glukhov AV, Flagg TP, Fedorov VV, Efimov IR, Nichols CG. Differential K(ATP) channel pharmacology in intact mouse heart. J Mol Cell Cardiol 2010; 48:152-60. [PMID: 19744493 PMCID: PMC2813353 DOI: 10.1016/j.yjmcc.2009.08.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 08/13/2009] [Accepted: 08/29/2009] [Indexed: 11/29/2022]
Abstract
Classically, cardiac sarcolemmal K(ATP) channels have been thought to be composed of Kir6.2 (KCNJ11) and SUR2A (ABCC9) subunits. However, the evidence is strong that SUR1 (sulfonylurea receptor type 1, ABCC8) subunits are also expressed in the heart and that they play a significant functional role in the atria. To examine this further, we have assessed the effects of isotype-specific potassium channel-opening drugs, diazoxide (specific to SUR1>SUR2A) and pinacidil (SUR2A>SUR1), in intact hearts from wild-type mice (WT, n=6), SUR1(-/-) (n=6), and Kir6.2(-/-) mice (n=5). Action potential durations (APDs) in both atria and ventricles were estimated by optical mapping of the posterior surface of Langendorff-perfused hearts. To confirm the atrial effect of both openers, isolated atrial preparations were mapped in both WT (n=4) and SUR1(-/-) (n=3) mice. The glass microelectrode technique was also used to validate optical action potentials. In WT hearts, diazoxide (300 microM) decreased APD in atria (from 33.8+/-1.9 ms to 24.2+/-1.1 ms, p<0.001) but was without effect in ventricles (APD 60.0+/-7.6 ms vs. 60.8+/-7.5 ms, respectively, NS), consistent with an atrial-specific role for SUR1. The absence of SUR1 resulted in loss of efficacy of diazoxide in SUR1(-/-) atria (APD 36.8+/-1.9 ms vs. 36.8+/-2.8 ms, respectively, NS). In contrast, pinacidil (300 microM) significantly decreased ventricular APD in both WT and SUR1(-/-) hearts (from 60.0+/-7.6 ms to 29.8+/-3.5 ms in WT, p<0.001, and from 63.5+/-2.1 ms to 24.8+/-3.8 ms in SUR1(-/-), p<0.001), but did not decrease atrial APD in either WT or SUR1(-/-) hearts. Glibenclamide (10 microM) reversed the effect of pinacidil in ventricles and restored APD to control values. The absence of Kir6.2 subunits in Kir6.2(-/-) hearts resulted in loss of efficacy of both openers (APD 47.2+/-2.2 ms vs. 47.6+/-2.1 ms and 50.8+/-2.4 ms, and 90.6+/-5.7 ms vs. 93.2+/-6.5 ms and 117.3+/-6.4 ms, for atria and ventricle in control versus diazoxide and pinacidil, respectively). Collectively, these results indicate that in the same mouse heart, significant differential K(ATP) pharmacology in atria and ventricles, resulting from SUR1 predominance in forming the atrial channel, leads to differential effects of potassium channel openers on APD in the two chambers.
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Affiliation(s)
- Alexey V. Glukhov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Thomas P. Flagg
- Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO, 63110
| | - Vadim V. Fedorov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Igor R. Efimov
- Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, MO, 63110
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Kimura A, Tyacke RJ, Robinson JJ, Husbands SM, Minchin MC, Nutt DJ, Hudson AL. Identification of an imidazoline binding protein: creatine kinase and an imidazoline-2 binding site. Brain Res 2009; 1279:21-8. [PMID: 19410564 PMCID: PMC2722693 DOI: 10.1016/j.brainres.2009.04.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Revised: 03/28/2009] [Accepted: 04/22/2009] [Indexed: 12/11/2022]
Abstract
Drugs that bind to imidazoline binding proteins have major physiological actions. To date, three subtypes of such proteins, I(1), I(2) and I(3), have been proposed, although characterisations of these binding proteins are lacking. I(2) binding sites are found throughout the brain, particularly dense in the arcuate nucleus of the hypothalamus. Selective I(2) ligands demonstrate antidepressant-like activity and the identity of the proteins that respond to such ligands remained unknown until now. Here we report the isolation of a approximately 45 kDa imidazoline binding protein from rabbit and rat brain using a high affinity ligand for the I(2) subtype, 2-BFI, to generate an affinity column. Following protein sequencing of the isolated approximately 45 kDa imidazoline binding protein, we identified it to be brain creatine kinase (B-CK). B-CK shows high binding capacity to selective I(2) ligands; [(3)H]-2-BFI (5 nM) specifically bound to B-CK (2330+/-815 fmol mg protein(-1)). We predicted an I(2) binding pocket near the active site of B-CK using molecular modelling. Furthermore, B-CK activity was inhibited by a selective I(2) irreversible ligand, where 20 microM BU99006 reduced the enzyme activity by 16%, confirming the interaction between B-CK and the I(2) ligand. In summary, we have identified B-CK to be the approximately 45 kDa imidazoline binding protein and we have demonstrated the existence of an I(2) binding site within this enzyme. The importance of B-CK in regulating neuronal activity and neurotransmitter release may well explain the various actions of I(2) ligands in brain and the alterations in densities of I(2) binding sites in psychiatric disorders.
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Key Words
- 2-bfi, 2-(2-benzofuranyl)2-imidazoline
- bu224, 2-(4,5-dihydroimidaz-2-yl)quinoline
- bu99006, 5-isothiocyanoato-2-benzofuranyl-2-imidazoline
- b-ck, brain creatine kinase
- ck, creatine kinase
- gold, genetic optimisation for ligand docking
- gr, glucose-responsive
- i2, imidazoline-2 subtype
- katp channel, atp sensitive potassium channel
- mao, monoamine oxidase
- moe, molecular operating environment
- imidazoline binding protein
- creatine kinase
- 2-bfi
- harmane and psychiatric disorders
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Affiliation(s)
- Atsuko Kimura
- Psychopharmacology Unit, University of Bristol, BS1 3NY, UK
| | | | - James J. Robinson
- Department of Pharmacy and Pharmacology, University of Bath, BA2 7AY, UK
| | | | | | - David J. Nutt
- Psychopharmacology Unit, University of Bristol, BS1 3NY, UK
| | - Alan L. Hudson
- Department of Pharmacology, 9-70 Medical Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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Zlatkovic J, Arrell DK, Kane GC, Miki T, Seino S, Terzic A. Proteomic profiling of KATP channel-deficient hypertensive heart maps risk for maladaptive cardiomyopathic outcome. Proteomics 2009; 9:1314-25. [PMID: 19253285 DOI: 10.1002/pmic.200800718] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
KCNJ11 null mutants, lacking Kir6.2 ATP-sensitive K(+) (K(ATP)) channels, exhibit a marked susceptibility towards hypertension (HTN)-induced heart failure. To gain insight into the molecular alterations induced by knockout of this metabolic sensor under hemodynamic stress, wild-type (WT) and Kir6.2 knockout (Kir6.2-KO) cardiac proteomes were profiled by comparative 2-DE and Orbitrap MS. Despite equivalent systemic HTN produced by chronic hyperaldosteronism, 114 unique proteins were altered in Kir6.2-KO compared to WT hearts. Bioinformatic analysis linked the primary biological function of the K(ATP) channel-dependent protein cohort to energetic metabolism (64% of proteins), followed by signaling infrastructure (36%) including oxidoreductases, stress-related chaperones, processes supporting protein degradation, transcription and translation, and cytostructure. Mapped protein-protein relationships authenticated the primary impact on metabolic pathways, delineating the K(ATP) channel-dependent subproteome within a nonstochastic network. Iterative systems interrogation of the proteomic web prioritized heart-specific adverse effects, i.e., "Cardiac Damage", "Cardiac Enlargement", and "Cardiac Fibrosis", exposing a predisposition for the development of cardiomyopathic traits in the hypertensive Kir6.2-KO. Validating this maladaptive forecast, phenotyping documented an aggravated myocardial contractile performance, a massive interstitial fibrosis and an exaggerated left ventricular size, all prognostic indices of poor outcome. Thus, Kir6.2 ablation engenders unfavorable proteomic remodeling in hypertensive hearts, providing a composite molecular substrate for pathologic stress-associated cardiovascular disease.
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Affiliation(s)
- Jelena Zlatkovic
- Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
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M-LDH physically associated with sarcolemmal K ATP channels mediates cytoprotection in heart embryonic H9C2 cells. Int J Biochem Cell Biol 2009; 41:2295-301. [PMID: 19464385 PMCID: PMC2758067 DOI: 10.1016/j.biocel.2009.05.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Revised: 04/24/2009] [Accepted: 05/17/2009] [Indexed: 11/21/2022]
Abstract
Muscle form of lactate dehydrogenase (M-LDH) physically associate with KATP channel subunits, Kir6.2 and SUR2A, and is an integral part of the ATP-sensitive K+ (KATP) channel protein complex in the heart. Here, we have shown that concomitant introduction of viral constructs containing truncated and mutated forms of M-LDH (ΔM-LDH) and 193gly-M-LDH respectively, generate a phenotype of rat heart embryonic H9C2 cells that do not contain functional M-LDH as a part of the KATP channel protein complex. The K+ current was increased in wild type cells, but not in cells expressing ΔM-LDH/193gly-M-LDH, when they were exposed to chemical hypoxia induced by 2,4 dinitrophenol (DNP; 10 mM). At the same time, the outcome of chemical hypoxia was much worse in ΔM-LDH/193gly-M-LDH phenotype than in the control one, and that was associated with increased loss of intracellular ATP in cells infected with ΔM-LDH/193gly-M-LDH. On the other hand, cells expressing Kir6.2AFA, a Kir6.2 mutant that abolishes KATP channel conductance without affecting intracellular ATP levels, survived chemical hypoxia much better than cells expressing ΔM-LDH/193gly-M-LDH. Based on the obtained results, we conclude that M-LDH physically associated with Kir6.2/SUR2A regulates the activity of sarcolemmal KATP channels as well as an intracellular ATP production during metabolic stress, both of which are important for cell survival.
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Jovanović S, Du Q, Sukhodub A, Jovanović A. A dual mechanism of cytoprotection afforded by M-LDH in embryonic heart H9C2 cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:1379-86. [PMID: 19406174 PMCID: PMC2719797 DOI: 10.1016/j.bbamcr.2009.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/05/2009] [Accepted: 04/21/2009] [Indexed: 01/01/2023]
Abstract
Muscle form of lactate dehydrogenase (M-LDH), a minor LDH form in cardiomyocytes, physically interacts with ATP-sensitive K+ (K ATP) channel-forming subunits. Here, we have shown that expression of 193gly-M-LDH, an inactive mutant of M-LDH, inhibit regulation of the K ATP channels activity by LDH substrates in embryonic rat heart H9C2 cells. In cells expressing 193gly-M-LDH chemical hypoxia has failed to activate K ATP channels. The similar results were obtained in H9C2 cells expressing Kir6.2AFA, a mutant form of Kir6.2 with largely decreased K+ conductance. Kir6.2AFA has slightly, but significantly, reduced cellular survival under chemical hypoxia while the deleterious effect of 193gly-M-LDH was significantly more pronounced. The levels of total and subsarcolemmal ATP in H9C2 cells were not affected by Kir6.2AFA, but the expression of 193gly-M-LDH led to lower levels of subsarcolemmal ATP during chemical hypoxia. We conclude that M-LDH regulates both the channel activity and the levels of subsarcolemmal ATP and that both mechanism contribute to the M-LDH-mediated cytoprotection.
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Affiliation(s)
- Sofija Jovanović
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY Scotland, UK
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Philosophical basis and some historical aspects of systems biology: from Hegel to Noble - applications for bioenergetic research. Int J Mol Sci 2009; 10:1161-92. [PMID: 19399243 PMCID: PMC2672024 DOI: 10.3390/ijms10031161] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/07/2009] [Accepted: 03/12/2009] [Indexed: 12/13/2022] Open
Abstract
We live in times of paradigmatic changes for the biological sciences. Reductionism, that for the last six decades has been the philosophical basis of biochemistry and molecular biology, is being displaced by Systems Biology, which favors the study of integrated systems. Historically, Systems Biology - defined as the higher level analysis of complex biological systems - was pioneered by Claude Bernard in physiology, Norbert Wiener with the development of cybernetics, and Erwin Schrödinger in his thermodynamic approach to the living. Systems Biology applies methods inspired by cybernetics, network analysis, and non-equilibrium dynamics of open systems. These developments follow very precisely the dialectical principles of development from thesis to antithesis to synthesis discovered by Hegel. Systems Biology opens new perspectives for studies of the integrated processes of energy metabolism in different cells. These integrated systems acquire new, system-level properties due to interaction of cellular components, such as metabolic compartmentation, channeling and functional coupling mechanisms, which are central for regulation of the energy fluxes. State of the art of these studies in the new area of Molecular System Bioenergetics is analyzed.
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Aittoniemi J, Fotinou C, Craig TJ, de Wet H, Proks P, Ashcroft FM. Review. SUR1: a unique ATP-binding cassette protein that functions as an ion channel regulator. Philos Trans R Soc Lond B Biol Sci 2009; 364:257-67. [PMID: 18990670 DOI: 10.1098/rstb.2008.0142] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
SUR1 is an ATP-binding cassette (ABC) transporter with a novel function. In contrast to other ABC proteins, it serves as the regulatory subunit of an ion channel. The ATP-sensitive (KATP) channel is an octameric complex of four pore-forming Kir6.2 subunits and four regulatory SUR1 subunits, and it links cell metabolism to electrical activity in many cell types. ATPase activity at the nucleotide-binding domains of SUR results in an increase in KATP channel open probability. Conversely, ATP binding to Kir6.2 closes the channel. Metabolic regulation is achieved by the balance between these two opposing effects. Precisely how SUR1 talks to Kir6.2 remains unclear, but recent studies have identified some residues and domains that are involved in both physical and functional interactions between the two proteins. The importance of these interactions is exemplified by the fact that impaired regulation of Kir6.2 by SUR1 results in human disease, with loss-of-function SUR1 mutations causing congenital hyperinsulinism and gain-of-function SUR1 mutations leading to neonatal diabetes. This paper reviews recent data on the regulation of Kir6.2 by SUR1 and considers the molecular mechanisms by which SUR1 mutations produce disease.
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Affiliation(s)
- Jussi Aittoniemi
- Department of Physiology, Henry Wellcome Centre for Gene Function, University of Oxford, Parks Road, Oxford, UK
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