1
|
Kir6.2-D323 and SUR2A-Q1336: an intersubunit interaction pairing for allosteric information transfer in the KATP channel complex. Biochem J 2020; 477:671-689. [PMID: 31957808 PMCID: PMC7015859 DOI: 10.1042/bcj20190753] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 02/07/2023]
Abstract
ATP-sensitive potassium (KATP) channels are widely expressed and play key roles in many tissues by coupling metabolic state to membrane excitability. The SUR subunits confer drug and enhanced nucleotide sensitivity to the pore-forming Kir6 subunit, and so information transfer between the subunits must occur. In our previous study, we identified an electrostatic interaction between Kir6 and SUR2 subunits that was key for allosteric information transfer between the regulatory and pore-forming subunit. In this study, we demonstrate a second putative interaction between Kir6.2-D323 and SUR2A-Q1336 using patch clamp electrophysiological recording, where charge swap mutation of the residues on either side of the potential interaction compromise normal channel function. The Kir6.2-D323K mutation gave rise to a constitutively active, glibenclamide and ATP-insensitive KATP complex, further confirming the importance of information transfer between the Kir6 and SUR2 subunits. Sensitivity to modulators was restored when Kir6.2-D323K was co-expressed with a reciprocal charge swap mutant, SUR-Q1336E. Importantly, equivalent interactions have been identified in both Kir6.1 and Kir6.2 suggesting this is a second important interaction between Kir6 and the proximal C terminus of SUR.
Collapse
|
2
|
Jovanović A. SUR2A: How to exploit this protein to treat ischaemic heart disease? ARHIV ZA FARMACIJU 2020. [DOI: 10.5937/arhfarm2001001j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
|
3
|
Effects of corticotropin-releasing hormone on the expression of adenosine triphosphate-sensitive potassium channels (Kir6.1/SUR2B) in human term pregnant myometrium. Obstet Gynecol Sci 2018; 61:14-22. [PMID: 29372145 PMCID: PMC5780309 DOI: 10.5468/ogs.2018.61.1.14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/23/2017] [Accepted: 06/15/2017] [Indexed: 11/08/2022] Open
Abstract
Objective Corticotropin-releasing hormone (CRH) is a crucial regulator of human pregnancy and parturition. Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels are important for regulating myometrial quiescence during pregnancy. We investigated regulatory effects of different concentrations of CRH on KATP channel expression in human myometrial smooth muscle cells (HSMCs) in in vitro conditions. Methods After treating HSMCs with different concentrations of CRH (1, 10, 102, 103, 104 pmol/L), mRNA and protein expression of KATP channel subunits (Kir6.1 and SUR2B) was analyzed by reverse transcription-polymerase chain reaction and western blot. We investigated which CRH receptor was involved in the reaction and measured the effects of CRH on intracellular Ca2+ concentration when oxytocin was administered in HSMCs using Fluo-8 AM ester. Results When HSMCs were treated with low (1 pmol/L) and high (103, 104 pmol/L) CRH concentrations, KATP channel expression significantly increased and decreased, respectively. SUR2B mRNA expression at low and high CRH concentrations was significantly antagonized by antalarmin (CRH receptor-1 antagonist) and astressin 2b (CRH receptor-2 antagonist), respectively; however, Kir6.1 mRNA expression was not affected. After oxytocin treatment, the intracellular Ca2+ concentration in CRH-treated HSMCs was significantly lowered in low concentration of CRH (1 pmol/L), but not in high concentration of CRH (103 pmol/L), compared to control. Conclusion Our data demonstrated the regulatory effect was different when HSMCs were treated with low (early pregnancy-like) and high (labor-like) CRH concentrations and the KATP channel expression showed significant increase and decrease. This could cause inhibition and activation, respectively, of uterine muscle contraction, demonstrating opposite dual actions of CRH.
Collapse
|
4
|
Mohammed Abdul KS, Jovanović S, Jovanović A. Exposure to 15% oxygen in vivo up-regulates cardioprotective SUR2A without affecting ERK1/2 and AKT: a crucial role for AMPK. J Cell Mol Med 2017; 21:1342-1350. [PMID: 28121062 PMCID: PMC5487919 DOI: 10.1111/jcmm.13064] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/15/2016] [Indexed: 11/28/2022] Open
Abstract
SUR2A is an 'atypical' ABC protein that forms sarcolemmal ATP-sensitive K+ (KATP ) channels by binding to inward rectifier Kir6.2. Manipulation with SUR2A levels has been suggested to be a promising therapeutic strategy against ischaemic heart diseases and other diseases where increased heart resistance to stress is beneficial. Some years ago, it has been reported that high-altitude residents have lower mortality rates for ischaemic heart disease. The purpose of this study was to determine whether SUR2A is regulated by mild-to-severe hypoxic conditions (15% oxygen; oxygen tension equivalent to 3000 m above sea level) and elucidate the underlying mechanism. Mice were exposed to either to 21% (control) or 15% concentration of oxygen for 24 hrs. Twenty-four hours long exposure to 15% oxygen decreased partial pressure of O2 (PO2 ), but did not affect blood CO2 (PCO2 ), haematocrit nor levels of ATP, lactate and NAD+/NADH in the heart. Cardiac SUR2A levels were significantly increased while Kir6.2 levels were not affected. Hypoxia did not induce phosphorylation of extracellular signal-regulated kinases (ERK1/2) or protein kinase B (Akt), but triggered phosphorylation of AMP activated protein kinase (AMPK). AICAR, an activator of AMPK, increased the level of SUR2A in H9c2 cells. We conclude that oxygen increases SUR2A level by activating AMPK. This is the first account of AMPK-mediated regulation of SUR2A.
Collapse
Affiliation(s)
- Khaja Shameem Mohammed Abdul
- Division of Molecular & Clinical Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Sofija Jovanović
- Division of Molecular & Clinical Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Aleksandar Jovanović
- Division of Molecular & Clinical Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| |
Collapse
|
5
|
Mohammed Abdul KS, Jovanović S, Du Q, Sukhodub A, Jovanović A. Mild hypoxia in vivo regulates cardioprotective SUR2A: A role for Akt and LDH. Biochim Biophys Acta Mol Basis Dis 2015; 1852:709-19. [PMID: 25576887 PMCID: PMC4547089 DOI: 10.1016/j.bbadis.2015.01.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 12/19/2014] [Accepted: 01/01/2015] [Indexed: 12/13/2022]
Abstract
High-altitude residents have lower mortality rates for ischaemic heart disease and this is ascribed to cardiac gene remodelling by chronic hypoxia. SUR2A is a cardioprotective ABC protein serving as a subunit of sarcolemmal ATP-sensitive K+ channels. The purpose of this study was to determine whether SUR2A is regulated by mild hypoxia in vivo and to elucidate the underlying mechanism. Mice were exposed to either 21% (control) or 18% (mild hypoxia) oxygen for 24 h. Exposure to 18% oxygen did not affect partial pressure of O2 (PO2) and CO2 (PCO2) in the blood, haematocrit or level of ATP in the heart. However, hypoxia increased myocardial lactate dehydrogenase (LDH) and lactate as well as NAD+ without affecting total NAD. SUR2A levels were significantly increased as well as myocardial resistance to ischaemia–reperfusion. Exposure to 18% oxygen did not phosphorylate extracellular signal regulated kinases (ERK1/2) or AMP activated protein kinase (AMPK), but it phosphorylated protein kinase B (Akt). An inhibitor of phosphoinositide 3-kinases (PI3K), LY294002 (0.2 mg/mouse), abolished all observed effects of hypoxia. LDH inhibitors, galloflavin (50 μM) and sodium oxamate (80 mM) significantly decreased levels of SUR2A in heart embryonic H9c2 cells, while inactive mutant LDH form, gly193-M-LDH increased cellular sensitivity towards stress induced by 2,4-dinitrophenol (10 mM). Treatment of H9c2 cells with sodium lactate (30 mM) increased intracellular lactate, but did not affect LDH activity or SUR2A levels. We conclude that PI3K/Akt signalling pathway and LDH play a crucial role in increase of cardiac SUR2A induced by in vivo exposure to 18% oxygen. Mild hypoxia increases levels of cardioprotective SUR2A in the heart. Phosphorylation of Akt mediates mild hypoxia-induced increase in SUR2A. Phosphorylation of ERK1/2 and AMPK is not involved in observed increase in SUR2A. PI3K/Akt target LDH to regulate SUR2A levels in the myocardium. LDH mediates regulation of SUR2A in a lactate-independent manner.
Collapse
Affiliation(s)
- Khaja Shameem Mohammed Abdul
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Sofija Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Qingyou Du
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Andriy Sukhodub
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Aleksandar Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK.
| |
Collapse
|
6
|
Land SC, Walker DJ, Du Q, Jovanović A. Cardioprotective SUR2A promotes stem cell properties of cardiomyocytes. Int J Cardiol 2013; 168:5090-2. [PMID: 23932869 PMCID: PMC3819985 DOI: 10.1016/j.ijcard.2013.07.182] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/20/2013] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | - Aleksandar Jovanović
- Corresponding author at: Medical Research Institute, Division of Cardiovascular and Diabetic Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK. Tel.: + 44 1382 383 276; fax: + 44 1382 383 598.
| |
Collapse
|
7
|
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.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Aleksandar Jovanović
- Medical Research Institute, Division of Cardiovascular & Diabetes Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK
| |
Collapse
|
8
|
Cardioprotective effect of 3-iodothyronamine in perfused rat heart subjected to ischemia and reperfusion. Cardiovasc Drugs Ther 2011; 25:307-13. [PMID: 21786214 DOI: 10.1007/s10557-011-6320-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
3-iodothyronamine (T(1)AM) is an endogenous compound which shares structural and functional features with biogenic amines and is able to interact with a specific class of receptors, designed as trace amine associated receptors. T(1)AM has significant physiological effects in mammals and produces a reversible, dose-dependent negative inotropic and chronotropic effect in heart. The aim of the present study was to investigate if T(1)AM is able to reduce irreversible tissue injury in isolated rat hearts subjected to ischemia and reperfusion, as evaluated by triphenyltetrazolium chloride staining. We observed that T(1)AM reduced infarct size at concentrations (125 nM to 12.5 μM) which did not produce any significant hemodynamic action. The dose-response curve was bell-shaped and peaked at 1.25 μM. T(1)AM-induced cardioprotection was completely reversed by the administration of chelerythrine and glibenclamide, suggesting a protein kinase C and K (ATP) (+) -dependent pathway, while it was not additive to the protection induced by cyclosporine A, suggesting modulation of mitochondrial permeability transition. At cardioprotective concentration, T(1)AM reduced the time needed for cardiac attest during ischemia, but it did not affect sarcoplasmatic reticulum Ca(2+) handling, as demonstrated by unaltered ryanodine receptor binding properties. In conclusion, in isolated rat heart T(1)AM produces a cardioprotective effect which is mediated by a protein kinase C and K (ATP) (+) -dependent pathway and is probably linked to modulation of mitochondrial permeability transition and/or ischemic arrest time.
Collapse
|
9
|
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.
Collapse
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
Collapse
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
| |
Collapse
|
10
|
Sudhir R, Sukhodub A, Du Q, Jovanović S, Jovanović A. Ageing-induced decline in physical endurance in mice is associated with decrease in cardiac SUR2A and increase in cardiac susceptibility to metabolic stress: therapeutic prospects for up-regulation of SUR2A. Biogerontology 2011; 12:147-55. [PMID: 20972622 DOI: 10.1007/s10522-010-9306-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 10/08/2010] [Indexed: 10/18/2022]
Abstract
Ageing is characterized by decline in physical endurance which has been suggested to be partly due to diminished functional and adaptive reserve capacity of the heart. Ageing is associated with decrease in numbers of sarcolemmal ATP-sensitive K(+) (K(ATP)) channels, but whether this has anything to do with ageing-induced decline in physical endurance is yet to be determined. We have previously shown that the numbers of sarcolemmal K(ATP) channels are controlled by the level of expression of SUR2A, a K(ATP) channel regulatory subunit. Here, we have found that ageing decreases the level of SUR2A mRNA in the heart without affecting expression of pore-forming K(ATP) channel subunits, Kir6.1 and Kir6.2. This effect of ageing was associated with decrease in levels of fully-assembled sarcolemmal K(ATP) channels. At the same time, ageing was associated with decreased physical endurance. In order to determine whether increased expression of SUR2A would counteract ageing-induced decrease in physical endurance, we have taken advantage of mice which SUR2A levels are regulated by more efficient CMV promoter. These mice had increased resistance of cardiomyocytes to metabolic stress/hypoxia and increased physical endurance when compared to the wild type. In transgenic mice, ageing did not affect the level of SUR2A mRNA in the heart and the level of fully-assembled sarcolemmal K(ATP) channels. The effect of increased SUR2A to resistance of cardiomyocytes to hypoxia and physical endurance was retained in old mice. The magnitude of these effects was such that they were significantly increased even when compared to those in wild type young mice. We conclude that (1) the level of SUR2A expression in the heart is important factor in regulating physical endurance, (2) ageing-induced decrease in cardiac SUR2A is, at least in part, responsible for ageing-induced decline in physical fitness and (3) up-regulation of SUR2A could be a viable strategy to counteract ageing-induced decline in physical endurance.
Collapse
MESH Headings
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Aging/physiology
- Animals
- Cell Hypoxia
- Cell Survival
- Cells, Cultured
- Female
- Male
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Myocardium/cytology
- Myocardium/metabolism
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Physical Endurance/physiology
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Stress, Physiological/physiology
- Sulfonylurea Receptors
- Up-Regulation
Collapse
Affiliation(s)
- Rajni Sudhir
- Division of Medical Sciences/MACHS, Centre for Cardiovascular and Lung Biology, Ninewells Hospital & Medical School, University of Dundee, Scotland, UK
| | | | | | | | | |
Collapse
|
11
|
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.
Collapse
Affiliation(s)
- Leonid V Zingman
- Department of Internal Medicine, University of Iowa, Carver College of Medicine, Iowa City, IA 52242, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
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]
|
13
|
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.
Collapse
Affiliation(s)
- Qingyou Du
- Division of Medical Sciences/MACHS, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Jovanović A. Femininity and sarcolemmal KATP channels: a matter of the heart and the heart of the matter. J Physiol 2010; 587:5509-10. [PMID: 19959545 DOI: 10.1113/jphysiol.2009.183004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Aleksandar Jovanović
- Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, University of Dundee, Dundee DD1 9SY, UK.
| |
Collapse
|
15
|
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.
Collapse
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.
| |
Collapse
|
16
|
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.
Collapse
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
| | | | | | | |
Collapse
|
17
|
|