1
|
Li E, Kool W, Woolschot L, van der Heyden MAG. Chronic Propafenone Application Increases Functional K IR2.1 Expression In Vitro. Pharmaceuticals (Basel) 2023; 16:ph16030404. [PMID: 36986503 PMCID: PMC10056987 DOI: 10.3390/ph16030404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 02/28/2023] [Accepted: 03/04/2023] [Indexed: 03/30/2023] Open
Abstract
Expression and activity of inwardly rectifying potassium (KIR) channels within the heart are strictly regulated. KIR channels have an important role in shaping cardiac action potentials, having a limited conductance at depolarized potentials but contributing to the final stage of repolarization and resting membrane stability. Impaired KIR2.1 function causes Andersen-Tawil Syndrome (ATS) and is associated with heart failure. Restoring KIR2.1 function by agonists of KIR2.1 (AgoKirs) would be beneficial. The class 1c antiarrhythmic drug propafenone is identified as an AgoKir; however, its long-term effects on KIR2.1 protein expression, subcellular localization, and function are unknown. Propafenone's long-term effect on KIR2.1 expression and its underlying mechanisms in vitro were investigated. KIR2.1-carried currents were measured by single-cell patch-clamp electrophysiology. KIR2.1 protein expression levels were determined by Western blot analysis, whereas conventional immunofluorescence and advanced live-imaging microscopy were used to assess the subcellular localization of KIR2.1 proteins. Acute propafenone treatment at low concentrations supports the ability of propafenone to function as an AgoKir without disturbing KIR2.1 protein handling. Chronic propafenone treatment (at 25-100 times higher concentrations than in the acute treatment) increases KIR2.1 protein expression and KIR2.1 current densities in vitro, which are potentially associated with pre-lysosomal trafficking inhibition.
Collapse
Affiliation(s)
- Encan Li
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Willy Kool
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Liset Woolschot
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| |
Collapse
|
2
|
Kim JE, Kim EM, Lee HA, Kim KS. Effective derivation of ventricular cardiomyocytes from hPSCs using ascorbic acid-containing maturation medium. Anim Cells Syst (Seoul) 2023; 27:82-92. [PMID: 36999134 PMCID: PMC10044166 DOI: 10.1080/19768354.2023.2189932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/01/2023] Open
Abstract
Cardiomyocytes derived from human pluripotent stem cells (hPSCs) can be used in various applications including disease modeling, drug safety screening, and novel cell-based cardiac therapies. Here, we report an optimized selection and maturation method to induce maturation of cardiomyocytes into a specific subtype after differentiation driven by the regulation of Wnt signaling. The medium used to optimize selection and maturation was in a glucose starvation conditions, supplemented with either a nutrition complex or ascorbic acid. Following optimized selection and maturation, more cardiac Troponin T (cTnT)-positive cardiomyocytes were detected using albumin and ascorbic acid than B27. In addition, ascorbic acid enriched maturation of ventricular cardiomyocytes. We compared cardiomyocyte-specific gene expression patterns under different selection and maturation conditions by next-generation sequencing (NGS) analysis. Our optimized conditions will enable simple and efficient maturation and specification of the desired cardiomyocyte subtype, facilitating both biomedical research and clinical applications.
Collapse
Affiliation(s)
- Ji-eun Kim
- Dongguk University, Seoul, Republic of Korea
| | - Eun-Mi Kim
- Korea Institute of Toxicology, Daejeon, Republic of Korea
| | - Hyang-Ae Lee
- Korea Institute of Toxicology, Daejeon, Republic of Korea
| | - Ki-Suk Kim
- Korea Institute of Toxicology, Daejeon, Republic of Korea
- Ki-Suk Kim Korea Institute of Toxicolgoy, 141 Gajeong-ro, Yuseong-gu, Daejeon34114, Republic of Korea
| |
Collapse
|
3
|
Du J, Li Z, Wang X, Li J, Liu D, Wang X, Wei J, Ma S, Zhang Y, Hou Y. Long noncoding RNA TCONS-00106987 promotes atrial electrical remodelling during atrial fibrillation by sponging miR-26 to regulate KCNJ2. J Cell Mol Med 2020; 24:12777-12788. [PMID: 32954646 PMCID: PMC7687017 DOI: 10.1111/jcmm.15869] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/06/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
Long noncoding RNAs (lncRNAs) have been suggested to play indispensable roles in multiple heart diseases. However, the correlations between lncRNAs and atrial fibrillation (AF) are unclear. In this study, we performed comprehensive lncRNA profiling via high-throughput RNA sequencing analysis using non-AF and AF rabbit models. Based on a series of filtering pipelines and bioinformatics analyses, TCONS-00106987 was selected for further research. TCONS-00106987 levels were increased in the atria during AF. Moreover, the atrial effective refractory period was shortened and the AF inducibility was increased in vivo in response to lentiviral-mediated up-regulation of TCONS-00106987. TCONS-00106987 repression resulted in the opposite effects. Further studies indicated that TCONS-00106987 expression was positively correlated with the expression of the protein-coding gene KCNJ2. Luciferase reporter assays and whole-cell patch-clamp recording confirmed that TCONS-00106987 promoted electrical remodelling via endogenous competition with microRNA-26 (miR-26) to induce transcription of its target gene KCNJ2, thereby increasing inward-rectifier K+ current (IK1 ). In conclusion, our study reveals a pathogenic lncRNA-miRNA regulatory network specific to atrial electrical remodelling that offers potential therapeutic targets for AF.
Collapse
Affiliation(s)
- Juanjuan Du
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Zhan Li
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Xiao Wang
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Jianhua Li
- Department of Critical Care Medicine, The First Affiliated Hospital of Xiamen University, Xiamen, China
| | - Donglu Liu
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Ximin Wang
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Jinqiu Wei
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Shenzhou Ma
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Yujiao Zhang
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Yinglong Hou
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Cheeloo College of Medicine, Shandong University, Jinan, China
| |
Collapse
|
4
|
Fusi F, Trezza A, Tramaglino M, Sgaragli G, Saponara S, Spiga O. The beneficial health effects of flavonoids on the cardiovascular system: Focus on K+ channels. Pharmacol Res 2020; 152:104625. [DOI: 10.1016/j.phrs.2019.104625] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 12/14/2019] [Accepted: 12/31/2019] [Indexed: 01/17/2023]
|
5
|
Kim HS, Yoon JW, Li H, Jeong GO, Park JJ, Shin SE, Jang IH, Kim JH, Park WS. Functional expression and pharmaceutical efficacy of cardiac-specific ion channels in human embryonic stem cell-derived cardiomyocytes. Sci Rep 2017; 7:13821. [PMID: 29062050 PMCID: PMC5653792 DOI: 10.1038/s41598-017-14198-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/21/2017] [Indexed: 01/08/2023] Open
Abstract
Cardiomyocytes differentiated from human pluripotent stem cells provide promising tools for screening of cardiotoxic drugs. For evaluation of human pluripotent stem cell-derived cardiomyocytes for cardiotoxicity test, in the present study, human embryonic stem cells (hESCs) were differentiated to cardiomyocytes, followed by metabolic selection to enrich the differentiated cardiomyocytes. The highly purified hESC-derived cardiomyocytes (hESC-CMs) expressed several cardiomyocyte-specific markers including cTnT, MLC2a, and α-SA, but not pluripotency markers, such as OCT4 and NANOG. Patch clamp technique and RT-PCR revealed the expression of cardiomyocyte-specific Na+, Ca2+, and K+ channels and cardiac action potential in hESC-CMs. To explore the potential use of hESC-CMs as functional cardiomyocytes for drug discovery and cardiotoxicity screening, we examined the effects of bisindolylmaleimide (BIM) (I), which inhibits native cardiac Ca2+ channels, on the Ca2+ channel activity of hESC-CMs. We observed a similar response for the BIM (I)-induced modulation of Ca2+ channels between hESC-CMs and native cardiomyocytes through L-type Ca2+ channel current. These results suggest that hESC-CMs can be useful for evaluation of pharmaceutical efficacy and safety of novel drug candidate in cardiac research.
Collapse
Affiliation(s)
- Han Sol Kim
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, Republic of Korea
| | - Jung Won Yoon
- Department of Physiology, School of Medicine, Pusan National University, Yangsan, 50612, Republic of Korea
| | - Hongliang Li
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, Republic of Korea
| | - Geun Ok Jeong
- Department of Physiology, School of Medicine, Pusan National University, Yangsan, 50612, Republic of Korea
| | - Jin Ju Park
- Department of Physiology, School of Medicine, Pusan National University, Yangsan, 50612, Republic of Korea
| | - Sung Eun Shin
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, Republic of Korea
| | - Il Ho Jang
- Department of Oral Biochemistry and Molecular Biology, Pusan National University School of Dentistry, Yangsan, 50612, Republic of Korea
| | - Jae Ho Kim
- Department of Physiology, School of Medicine, Pusan National University, Yangsan, 50612, Republic of Korea. .,Research Institute of Convergence Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, 50612, Republic of Korea.
| | - Won Sun Park
- Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 24341, Republic of Korea.
| |
Collapse
|
6
|
Larbig R, Reda S, Paar V, Trost A, Leitner J, Weichselbaumer S, Motloch KA, Wernly B, Arrer A, Strauss B, Lichtenauer M, Reitsamer HA, Eckardt L, Seebohm G, Hoppe UC, Motloch LJ. Through modulation of cardiac Ca2+handling, UCP2 affects cardiac electrophysiology and influences the susceptibility for Ca2+-mediated arrhythmias. Exp Physiol 2017; 102:650-662. [DOI: 10.1113/ep086209] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 03/28/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Robert Larbig
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital Münster; Münster Germany
| | - Sara Reda
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Vera Paar
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Andrea Trost
- Research Program for Ophthalmology and Glaucoma Research, University Clinic of Ophthalmology and Optometry; Paracelsus Medical University/SALK; Salzburg Austria
| | - Johannes Leitner
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | | | - Karolina A. Motloch
- Research Program for Ophthalmology and Glaucoma Research, University Clinic of Ophthalmology and Optometry; Paracelsus Medical University/SALK; Salzburg Austria
| | - Bernhard Wernly
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Andreas Arrer
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Benjamin Strauss
- Cardiovascular Institute; Icahn School of Medicine at Mount Sinai; New York NY USA
| | - Michael Lichtenauer
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Herbert A. Reitsamer
- Research Program for Ophthalmology and Glaucoma Research, University Clinic of Ophthalmology and Optometry; Paracelsus Medical University/SALK; Salzburg Austria
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine; University Hospital Münster; Münster Germany
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IFGH), Department of Cardiovascular Medicine; University Hospital Münster; Münster Germany
| | - Uta C. Hoppe
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| | - Lukas J. Motloch
- Department of Internal Medicine II; Paracelsus Medical University/SALK; Salzburg Austria
| |
Collapse
|
7
|
Intrafamilial phenotypic variability in Andersen–Tawil syndrome: A diagnostic challenge in a potentially treatable condition. Neuromuscul Disord 2017; 27:294-297. [DOI: 10.1016/j.nmd.2016.11.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 11/12/2016] [Indexed: 11/18/2022]
|
8
|
Kuroda Y, Yuasa S, Watanabe Y, Ito S, Egashira T, Seki T, Hattori T, Ohno S, Kodaira M, Suzuki T, Hashimoto H, Okata S, Tanaka A, Aizawa Y, Murata M, Aiba T, Makita N, Furukawa T, Shimizu W, Kodama I, Ogawa S, Kokubun N, Horigome H, Horie M, Kamiya K, Fukuda K. Flecainide ameliorates arrhythmogenicity through NCX flux in Andersen-Tawil syndrome-iPS cell-derived cardiomyocytes. Biochem Biophys Rep 2017; 9:245-256. [PMID: 28956012 PMCID: PMC5614591 DOI: 10.1016/j.bbrep.2017.01.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 12/09/2016] [Accepted: 01/10/2017] [Indexed: 12/15/2022] Open
Abstract
Andersen-Tawil syndrome (ATS) is a rare inherited channelopathy. The cardiac phenotype in ATS is typified by a prominent U wave and ventricular arrhythmia. An effective treatment for this disease remains to be established. We reprogrammed somatic cells from three ATS patients to generate induced pluripotent stem cells (iPSCs). Multi-electrode arrays (MEAs) were used to record extracellular electrograms of iPSC-derived cardiomyocytes, revealing strong arrhythmic events in the ATS-iPSC-derived cardiomyocytes. Ca2+ imaging of cells loaded with the Ca2+ indicator Fluo-4 enabled us to examine intracellular Ca2+ handling properties, and we found a significantly higher incidence of irregular Ca2+ release in the ATS-iPSC-derived cardiomyocytes than in control-iPSC-derived cardiomyocytes. Drug testing using ATS-iPSC-derived cardiomyocytes further revealed that antiarrhythmic agent, flecainide, but not the sodium channel blocker, pilsicainide, significantly suppressed these irregular Ca2+ release and arrhythmic events, suggesting that flecainide's effect in these cardiac cells was not via sodium channels blocking. A reverse-mode Na+/Ca2+exchanger (NCX) inhibitor, KB-R7943, was also found to suppress the irregular Ca2+ release, and whole-cell voltage clamping of isolated guinea-pig cardiac ventricular myocytes confirmed that flecainide could directly affect the NCX current (INCX). ATS-iPSC-derived cardiomyocytes recapitulate abnormal electrophysiological phenotypes and flecainide suppresses the arrhythmic events through the modulation of INCX. iPS cells are generated from three patients with ATS. ATS-iPS cell-derived cardiomyocytes show abnormal electrophysiological phenotypes. Flecainide suppresses abnormal electrophysiological phenotypes in ATS-iPS cell-derived cardiomyocytes.
Collapse
Affiliation(s)
- Yusuke Kuroda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Shinsuke Yuasa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yasuhide Watanabe
- Division of Pharmacological Science, Department of Health Science, Hamamatsu University School of Medicine, Shizuoka, Japan
| | - Shogo Ito
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Toru Egashira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomohisa Seki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tetsuhisa Hattori
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Seiko Ohno
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Shiga, Japan
| | - Masaki Kodaira
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Tomoyuki Suzuki
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan.,Department of Cardiology, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Hisayuki Hashimoto
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Shinichiro Okata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Atsushi Tanaka
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Yoshiyasu Aizawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Mitsushige Murata
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan.,Department of Laboratory Medicine, Keio University School of Medicine, Tokyo, Japan
| | - Takeshi Aiba
- Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Naomasa Makita
- Department of Molecular Pathophysiology-1, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Tetsushi Furukawa
- Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wataru Shimizu
- Department of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
| | - Itsuo Kodama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Satoshi Ogawa
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| | - Norito Kokubun
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Hitoshi Horigome
- Department of Child Health, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Minoru Horie
- Department of Cardiovascular Medicine, Shiga University of Medical Science, Shiga, Japan
| | - Kaichiro Kamiya
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Aichi, Japan
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
| |
Collapse
|
9
|
Fabian E, Schiller D, Tomaschitz A, Langner C, Pilz S, Quasthoff S, Raggam RB, Schoefl R, Krejs GJ. Clinical-Pathological Conference Series from the Medical University of Graz : Case No 160: 33-year-old woman with tetraparesis on Easter Sunday. Wien Klin Wochenschr 2016; 128:719-727. [PMID: 27682153 PMCID: PMC5052289 DOI: 10.1007/s00508-016-1085-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 08/19/2016] [Indexed: 11/24/2022]
Affiliation(s)
- Elisabeth Fabian
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria
| | - Dietmar Schiller
- Department of Internal Medicine IV, Elisabethinen Hospital, Linz, Austria
| | - Andreas Tomaschitz
- Division of Cardiology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Cord Langner
- Department of Pathology, Medical University of Graz, Graz, Austria
| | - Stefan Pilz
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Stefan Quasthoff
- Department of Neurology, Medical University of Graz, Graz, Austria
| | - Reinhard B Raggam
- Division of Angiology, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Rainer Schoefl
- Department of Internal Medicine IV, Elisabethinen Hospital, Linz, Austria
| | - Guenter J Krejs
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 15, 8036, Graz, Austria.
| |
Collapse
|
10
|
Motloch LJ, Gebing T, Reda S, Schwaiger A, Wolny M, Hoppe UC. UCP3 Regulates Single-Channel Activity of the Cardiac mCa1. J Membr Biol 2016; 249:577-84. [PMID: 27371160 PMCID: PMC4942494 DOI: 10.1007/s00232-016-9913-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 06/15/2016] [Indexed: 12/14/2022]
Abstract
Mitochondrial Ca(2+) uptake (mCa(2+) uptake) is thought to be mediated by the mitochondrial Ca(2+) uniporter (MCU). UCP2 and UCP3 belong to a superfamily of mitochondrial ion transporters. Both proteins are expressed in the inner mitochondrial membrane of the heart. Recently, UCP2 was reported to modulate the function of the cardiac MCU related channel mCa1. However, the possible role of UCP3 in modulating cardiac mCa(2+) uptake via the MCU remains inconclusive. To understand the role of UCP3, we analyzed cardiac mCa1 single-channel activity in mitoplast-attached single-channel recordings from isolated murine cardiac mitoplasts, from adult wild-type controls (WT), and from UCP3 knockout mice (UCP3(-/-)). Single-channel registrations in UCP3(-/-) confirmed a murine voltage-gated Ca(2+) channel, i.e., mCa1, which was inhibited by Ru360. Compared to WT, mCa1 in UCP3(-/-) revealed similar single-channel characteristics. However, in UCP3(-/-) the channel exhibited decreased single-channel activity, which was insensitive to adenosine triphosphate (ATP) inhibition. Our results suggest that beyond UCP2, UCP3 also exhibits regulatory effects on cardiac mCa1/MCU function. Furthermore, we speculate that UCP3 might modulate previously described inhibitory effects of ATP on mCa1/MCU activity as well.
Collapse
Affiliation(s)
- Lukas J Motloch
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria.
| | - Tina Gebing
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria
| | - Sara Reda
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria
| | - Astrid Schwaiger
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria
| | - Martin Wolny
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria
| | - Uta C Hoppe
- Department of Internal Medicine II, Paracelsus Medical University, Muellner Hauptstr. 48, A-5020, Salzburg, Austria
| |
Collapse
|
11
|
Mitragynine and its potential blocking effects on specific cardiac potassium channels. Toxicol Appl Pharmacol 2016; 305:22-39. [PMID: 27260674 DOI: 10.1016/j.taap.2016.05.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 05/30/2016] [Accepted: 05/31/2016] [Indexed: 02/07/2023]
Abstract
Mitragyna speciosa Korth is known for its euphoric properties and is frequently used for recreational purposes. Several poisoning and fatal cases involving mitragynine have been reported but the underlying causes remain unclear. Human ether-a-go-go-related gene (hERG) encodes the cardiac IKr current which is a determinant of the duration of ventricular action potentials and QT interval. On the other hand, IK1, a Kir current mediated by Kir2.1 channel and IKACh, a receptor-activated Kir current mediated by GIRK channel are also known to be important in maintaining the cardiac function. This study investigated the effects of mitragynine on the current, mRNA and protein expression of hERG channel in hERG-transfected HEK293 cells and Xenopus oocytes. The effects on Kir2.1 and GIRK channels currents were also determined in the oocytes. The hERG tail currents following depolarization pulses were inhibited by mitragynine with an IC50 value of 1.62μM and 1.15μM in the transfected cell line and Xenopus oocytes, respectively. The S6 point mutations of Y652A and F656A attenuated the inhibitor effects of mitragynine, indicating that mitragynine interacts with these high affinity drug-binding sites in the hERG channel pore cavity which was consistent with the molecular docking simulation. Interestingly, mitragynine does not affect the hERG expression at the transcriptional level but inhibits the protein expression. Mitragynine is also found to inhibit IKACh current with an IC50 value of 3.32μM but has no significant effects on IK1. Blocking of both hERG and GIRK channels may cause additive cardiotoxicity risks.
Collapse
|
12
|
Motloch LJ, Larbig R, Gebing T, Reda S, Schwaiger A, Leitner J, Wolny M, Eckardt L, Hoppe UC. By Regulating Mitochondrial Ca2+-Uptake UCP2 Modulates Intracellular Ca2+. PLoS One 2016; 11:e0148359. [PMID: 26849136 PMCID: PMC4746117 DOI: 10.1371/journal.pone.0148359] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 01/19/2016] [Indexed: 12/31/2022] Open
Abstract
Introduction The possible role of UCP2 in modulating mitochondrial Ca2+-uptake (mCa2+-uptake) via the mitochondrial calcium uniporter (MCU) is highly controversial. Methods Thus, we analyzed mCa2+-uptake in isolated cardiac mitochondria, MCU single-channel activity in cardiac mitoplasts, dual Ca2+-transients from mitochondrial ((Ca2+)m) and intracellular compartment ((Ca2+)c) in the whole-cell configuration in cardiomyocytes of wild-type (WT) and UCP2-/- mice. Results Isolated mitochondria showed a Ru360 sensitive mCa2+-uptake, which was significantly decreased in UCP2-/- (229.4±30.8 FU vs. 146.3±23.4 FU, P<0.05). Single-channel registrations confirmed a Ru360 sensitive voltage-gated Ca2+-channel in mitoplasts, i.e. mCa1, showing a reduced single-channel activity in UCP2-/- (Po,total: 0.34±0.05% vs. 0.07±0.01%, P<0.05). In UCP2-/- cardiomyocytes (Ca2+)m was decreased (0.050±0.009 FU vs. 0.021±0.005 FU, P<0.05) while (Ca2+)c was unchanged (0.032±0.002 FU vs. 0.028±0.004 FU, P>0.05) and transsarcolemmal Ca2+-influx was inhibited suggesting a possible compensatory mechanism. Additionally, we observed an inhibitory effect of ATP on mCa2+-uptake in WT mitoplasts and (Ca2+)m of cardiomyocytes leading to an increase of (Ca2+)c while no ATP dependent effect was observed in UCP2-/-. Conclusion Our results indicate regulatory effects of UCP2 on mCa2+-uptake. Furthermore, we propose, that previously described inhibitory effects on MCU by ATP may be mediated via UCP2 resulting in changes of excitation contraction coupling.
Collapse
Affiliation(s)
- Lukas Jaroslaw Motloch
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
- * E-mail:
| | - Robert Larbig
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany
| | - Tina Gebing
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Sara Reda
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Astrid Schwaiger
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Johannes Leitner
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Martin Wolny
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany
| | - Uta C. Hoppe
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| |
Collapse
|
13
|
Abstract
Ion channels are critical for all aspects of cardiac function, including rhythmicity and contractility. Consequently, ion channels are key targets for therapeutics aimed at cardiac pathophysiologies such as atrial fibrillation or angina. At the same time, off-target interactions of drugs with cardiac ion channels can be the cause of unwanted side effects. This manuscript aims to review the physiology and pharmacology of key cardiac ion channels. The intent is to highlight recent developments for therapeutic development, as well as elucidate potential mechanisms for drug-induced cardiac side effects, rather than present an in-depth review of each channel subtype.
Collapse
|
14
|
Motloch LJ, Reda S, Wolny M, Hoppe UC. UCP2 Modulates Cardioprotective Effects of Ru360 in Isolated Cardiomyocytes during Ischemia. Pharmaceuticals (Basel) 2015; 8:474-82. [PMID: 26248074 PMCID: PMC4588178 DOI: 10.3390/ph8030474] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 07/17/2015] [Accepted: 07/29/2015] [Indexed: 01/23/2023] Open
Abstract
INTRODUCTION Ruthenium 360 (Ru360) has been shown to induce cardioprotective mechanisms in perfused hearts. The agent is a specific blocker of the main cardiac mitochondrial uptake mechanism, the mitochondrial calcium uniporter (MCU). UCP2, a mitochondrial membrane protein, which influences cardiac ROS formation was reported to interact with the MCU. METHODS To prove whether Ru360 affects ischemic cell injury on the singular cell level, cell viability (CV) in isolated cardiomyocytes from wild type mice (WT) was measured in a model of pelleting hypoxia (PH). To explore a possible influence of UCP2 on cellular survival, as well as on Ru360 function, cardiomyocytes from UCP2-/- mice were investigated. RESULTS During PH, Ru360 significantly improved CV in WT cardiomyocytes (Control 26.32% ± 1.58% vs. PH 13.60% ± 1.20% vs. PH+Ru360 19.98% ± 0.98%, n = 6; p < 0.05). No differences in the rate of apoptosis were observed in UCP2-/- vs. WT. In UCP2-/- cardiomyocytes, Ru360 reduced the rate of cell death. However, the effect was less pronounced compared to WT cardiomyocytes. CONCLUSION Ru360 significantly reduces hypoxic cell injury by preventing single cell apoptosis in WT cardiomyoctes. UCP2 does not affect cell survival in hypoxic cardiomyocytes, but it might modulate cardioprotective effects of Ru360 during ischemia.
Collapse
Affiliation(s)
- Lukas J Motloch
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg 5020, Austria.
| | - Sara Reda
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg 5020, Austria.
| | - Martin Wolny
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg 5020, Austria.
| | - Uta C Hoppe
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg 5020, Austria.
| |
Collapse
|
15
|
|
16
|
Zhang DY, Wu W, Deng XL, Lau CP, Li GR. Genistein and tyrphostin AG556 inhibit inwardly-rectifying Kir2.1 channels expressed in HEK 293 cells via protein tyrosine kinase inhibition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1993-9. [DOI: 10.1016/j.bbamem.2011.04.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Revised: 04/13/2011] [Accepted: 04/29/2011] [Indexed: 11/28/2022]
|
17
|
Doi T, Makiyama T, Morimoto T, Haruna Y, Tsuji K, Ohno S, Akao M, Takahashi Y, Kimura T, Horie M. A Novel
KCNJ2
Nonsense Mutation, S369X, Impedes Trafficking and Causes a Limited Form of Andersen-Tawil Syndrome. ACTA ACUST UNITED AC 2011; 4:253-60. [DOI: 10.1161/circgenetics.110.958157] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Background—
Mutations in
KCNJ2
, a gene encoding the inward rectifier K
+
channel Kir2.1, are associated with Andersen-Tawil syndrome (ATS), which is characterized by (1) ventricular tachyarrhythmias associated with QT (QU)-interval prolongation, (2) periodic paralysis, and (3) dysmorphic features.
Methods and Results—
We identified a novel
KCNJ2
mutation, S369X, in a 13-year-old boy with prominent QU-interval prolongation and mild periodic paralysis. The mutation results in the truncation at the middle of the cytoplasmic C-terminal domain that eliminates the endoplasmic reticulum (ER)-to-Golgi export signal. Current recordings from Chinese hamster ovary cells transfected with
KCNJ2
-S369X exhibited significantly smaller K
+
currents compared with
KCNJ2
wild type (WT) (1 μg each) (−84±14 versus −542±46 picoamperes per picofarad [pA/pF]; −140 mV;
P
<0.0001). Coexpression of the WT and S369X subunits did not show a dominant-negative suppression effect but yielded larger currents than those of WT+S369X (−724±98 pA/pF>−[84+542] pA/pF; 1 μg each; −140 mV). Confocal microscopy analysis showed that the fluorescent protein-tagged S369X subunits were predominantly retained in the ER when expressed alone; however, the expression of S369X subunits to the plasma membrane was partially restored when coexpressed with WT. Fluorescence resonance energy transfer analysis demonstrated direct protein-protein interactions between WT and S369X subunits in the intracellular compartment.
Conclusions—
The S369X mutation causes a loss of the ER export motif. However, the trafficking deficiency can be partially rescued by directly assembling with the WT protein, resulting in a limited restoration of plasma membrane localization and channel function. This alleviation may explain why our patient presented with a relatively mild ATS phenotype.
Collapse
Affiliation(s)
- Takahiro Doi
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeru Makiyama
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeshi Morimoto
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Yoshisumi Haruna
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Keiko Tsuji
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Seiko Ohno
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Masaharu Akao
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Yoshiaki Takahashi
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Takeshi Kimura
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| | - Minoru Horie
- From the Department of Cardiovascular Medicine (T.D., T. Makiyama, Y.H., K.T., S.O., T.K.) and Center for Medical Education (T. Morimoto), Kyoto University, Graduate School of Medicine, Kyoto, Japan; Department of Cardiovascular Medicine, National Hospital Organization Kyoto Medical Center, Kyoto, Japan (M.A.); Takahashi Clinic for Pediatric Cardiology, Otsu, Japan (Y.T.); and Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan (M.H.)
| |
Collapse
|
18
|
Goldoni D, Zhao Y, Green BD, McDermott BJ, Collins A. Inward rectifier potassium channels in the HL-1 cardiomyocyte-derived cell line. J Cell Physiol 2010; 225:751-6. [PMID: 20568224 DOI: 10.1002/jcp.22278] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
HL-1 is a line of immortalized cells of cardiomyocyte origin that are a useful complement to native cardiomyocytes in studies of cardiac gene regulation. Several types of ion channel have been identified in these cells, but not the physiologically important inward rectifier K(+) channels. Our aim was to identify and characterize inward rectifier K(+) channels in HL-1 cells. External Ba(2+) (100 µM) inhibited 44 ± 0.05% (mean ± s.e.m., n = 11) of inward current in whole-cell patch-clamp recordings. The reversal potential of the Ba(2+)-sensitive current shifted with external [K(+)] as expected for K(+)-selective channels. The slope conductance of the inward Ba(2+)-sensitive current increased with external [K(+)]. The apparent Kd for Ba(2+) was voltage dependent, ranging from 15 µM at -150 mV to 148 µM at -75 mV in 120 mM external K(+). This current was insensitive to 10 µM glybenclamide. A component of whole-cell current was sensitive to 150 µM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), although it did not correspond to the Ba(2+)-sensitive component. The effect of external 1 mM Cs(+) was similar to that of Ba(2+). Polymerase chain reaction using HL-1 cDNA as template and primers specific for the cardiac inward rectifier K(ir)2.1 produced a fragment of the expected size that was confirmed to be K(ir)2.1 by DNA sequencing. In conclusion, HL-1 cells express a current that is characteristic of cardiac inward rectifier K(+) channels, and express K(ir)2.1 mRNA. This cell line may have use as a system for studying inward rectifier gene regulation in a cardiomyocyte phenotype.
Collapse
Affiliation(s)
- Dana Goldoni
- Cardiovascular Remodelling Group, Centre for Vision and Vascular Science, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast, UK
| | | | | | | | | |
Collapse
|
19
|
de Boer TP, Houtman MJC, Compier M, van der Heyden MAG. The mammalian K(IR)2.x inward rectifier ion channel family: expression pattern and pathophysiology. Acta Physiol (Oxf) 2010; 199:243-56. [PMID: 20331539 DOI: 10.1111/j.1748-1716.2010.02108.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Inward rectifier currents based on K(IR)2.x subunits are regarded as essential components for establishing a stable and negative resting membrane potential in many excitable cell types. Pharmacological inhibition, null mutation in mice and dominant positive and negative mutations in patients reveal some of the important functions of these channels in their native tissues. Here we review the complex mammalian expression pattern of K(IR)2.x subunits and relate these to the outcomes of functional inhibition of the resultant channels. Correlations between expression and function in muscle and bone tissue are observed, while we recognize a discrepancy between neuronal expression and function.
Collapse
Affiliation(s)
- T P de Boer
- Department of Medical Physiology, UMCU, Utrecht, the Netherlands
| | | | | | | |
Collapse
|
20
|
Rottlaender D, Boengler K, Wolny M, Michels G, Endres-Becker J, Motloch LJ, Schwaiger A, Buechert A, Schulz R, Heusch G, Hoppe UC. Connexin 43 acts as a cytoprotective mediator of signal transduction by stimulating mitochondrial KATP channels in mouse cardiomyocytes. J Clin Invest 2010; 120:1441-53. [PMID: 20364086 DOI: 10.1172/jci40927] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Potassium (K+) channels in the inner mitochondrial membrane influence cell function and survival. Increasing evidence indicates that multiple signaling pathways and pharmacological actions converge on mitochondrial ATP-sensitive K+ (mitoKATP) channels and PKC to confer cytoprotection against necrotic and apoptotic cell injury. However, the molecular structure of mitoKATP channels remains unresolved, and the mitochondrial phosphoprotein(s) that mediate cytoprotection by PKC remain to be determined. As mice deficient in the main sarcolemmal gap junction protein connexin 43 (Cx43) lack this cytoprotection, we set out to investigate a possible link among mitochondrial Cx43, mitoKATP channel function, and PKC activation. By patch-clamping the inner membrane of subsarcolemmal murine cardiac mitochondria, we found that genetic Cx43 deficiency, pharmacological connexin inhibition by carbenoxolone, and Cx43 blockade by the mimetic peptide 43GAP27 each substantially reduced diazoxide-mediated stimulation of mitoKATP channels. Suppression of mitochondrial Cx43 inhibited mitoKATP channel activation by PKC. MitoKATP channels of interfibrillar mitochondria, which do not contain any detectable Cx43, were insensitive to both PKC activation and diazoxide, further demonstrating the role of Cx43 in mitoKATP channel stimulation and the compartmentation of mitochondria in cell signaling. Our results define a role for mitochondrial Cx43 in protecting cardiac cells from death and provide a link between cytoprotective stimuli and mitoKATP channel opening, making Cx43 an attractive therapeutic target for protection against cell injury.
Collapse
Affiliation(s)
- Dennis Rottlaender
- Department of Internal Medicine III, University of Cologne, Cologne, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Hibino H, Inanobe A, Furutani K, Murakami S, Findlay I, Kurachi Y. Inwardly rectifying potassium channels: their structure, function, and physiological roles. Physiol Rev 2010; 90:291-366. [PMID: 20086079 DOI: 10.1152/physrev.00021.2009] [Citation(s) in RCA: 1055] [Impact Index Per Article: 75.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Inwardly rectifying K(+) (Kir) channels allow K(+) to move more easily into rather than out of the cell. They have diverse physiological functions depending on their type and their location. There are seven Kir channel subfamilies that can be classified into four functional groups: classical Kir channels (Kir2.x) are constitutively active, G protein-gated Kir channels (Kir3.x) are regulated by G protein-coupled receptors, ATP-sensitive K(+) channels (Kir6.x) are tightly linked to cellular metabolism, and K(+) transport channels (Kir1.x, Kir4.x, Kir5.x, and Kir7.x). Inward rectification results from pore block by intracellular substances such as Mg(2+) and polyamines. Kir channel activity can be modulated by ions, phospholipids, and binding proteins. The basic building block of a Kir channel is made up of two transmembrane helices with cytoplasmic NH(2) and COOH termini and an extracellular loop which folds back to form the pore-lining ion selectivity filter. In vivo, functional Kir channels are composed of four such subunits which are either homo- or heterotetramers. Gene targeting and genetic analysis have linked Kir channel dysfunction to diverse pathologies. The crystal structure of different Kir channels is opening the way to understanding the structure-function relationships of this simple but diverse ion channel family.
Collapse
Affiliation(s)
- Hiroshi Hibino
- Department of Pharmacology, Graduate School of Medicine and The Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan
| | | | | | | | | | | |
Collapse
|
22
|
Grunnet M. Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle? Acta Physiol (Oxf) 2010; 198 Suppl 676:1-48. [PMID: 20132149 DOI: 10.1111/j.1748-1716.2009.02072.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.
Collapse
Affiliation(s)
- M Grunnet
- NeuroSearch A/S, Ballerup, and Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Denmark.
| |
Collapse
|
23
|
Brandt MC, Endres-Becker J, Zagidullin N, Motloch LJ, Er F, Rottlaender D, Michels G, Herzig S, Hoppe UC. Effects of KCNE2 on HCN isoforms: distinct modulation of membrane expression and single channel properties. Am J Physiol Heart Circ Physiol 2009; 297:H355-63. [DOI: 10.1152/ajpheart.00154.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Hyperpolarization-activated cation (HCN) channels give rise to an inward current with similar but not identical characteristics compared with the pacemaker current ( If), suggesting that HCN channel function is modulated by regulatory β-subunits in native tissue. KCNE2 has been proposed to serve as a β-subunit of HCN channels; however, available data remain contradictory. To further clarify this situation, we therefore analyzed the effect of KCNE2 on whole cell currents, single channel properties, and membrane protein expression of all cardiac HCN isoforms in the CHO cell system. On the whole cell level, current densities of all HCN isoforms were significantly increased by KCNE2 without altering voltage dependence or current reversal. While these results correlated well with the KCNE2-mediated 2.2-fold and 1.6-fold increases of membrane protein levels of HCN2 and HCN4, respectively, no effect of KCNE2 on HCN1 expression was obtained. All HCN subtypes displayed faster activation kinetics upon coexpression with KCNE2. Most importantly, for the first time, we demonstrated modulation of single channel function by KCNE2, thus supporting direct functional interaction with HCN subunits. In the presence of KCNE2, the single channel amplitudes and conductance of HCN1, HCN2, and HCN4 were significantly increased versus control recordings. Mean open time was significantly increased in cells coexpressing HCN2 + KCNE2, whereas it was unaffected in HCN1 + KCNE2 cotransfected cells and reduced in HCN4 + KCNE2 cotransfected cells compared with the respective HCN subunits alone. Thus, we demonstrate KCNE2-mediated distinct effects on HCN membrane expression and direct functional modulation of HCN isoforms, further supporting that KCNE2 surves as a regulatory β-subunit of HCN channels.
Collapse
|
24
|
|
25
|
Abstract
OBJECTIVE To review the current knowledge about primary periodic paralyses (PPs). RESULTS Periodic paralyses are a heterogeneous group of disorders, clinically characterized by episodes of flaccid muscle weakness, occurring at irregular intervals. PPs are divided into primary (hereditary) and secondary (acquired) forms of which the secondary PPs are much more common than the primary PPs. Primary PPs are due to mutations in genes encoding for subunits of channel proteins of the skeletal muscle membrane, such as the muscular sodium, potassium or calcium channels, or the SCL4A1 protein. Primary PPs include entities such as hyperkalemic PP, hypokalemic PP, paramyotonia congenita von Eulenburg, Andersen's syndrome, thyrotoxic PP, distal renal tubular acidosis, X-linked episodic muscle weakness syndrome and congenital myasthenic syndromes. Attacks of weakness or myotonia may be triggered or enhanced by vigorous exercise, cold, potassium-rich food, emotional stress, drugs such as glucocorticosteroids, insulin or diuretics, or pregnancy. Depending on the pathomechanism, episodes of weakness may respond to mild exercise, ingestion of potassium, carbohydrates, salbutamol, calcium gluconate, thiazide diuretics, carboanhydrase inhibitors, such as acetazolamide or dichlorphenamine, and episodes may be prevented by avoidance of potassium-rich food, or drugs, which increase serum potassium. CONCLUSION This review presents and discusses current knowledge and recent advances in the etiology, molecular genetics, genotype-phenotype correlations, pathogenesis, diagnosis and treatment of primary PPs.
Collapse
Affiliation(s)
- J Finsterer
- Neurological Department, Krankenanstalt Rudolfstiftung, Vienna, Austria.
| |
Collapse
|
26
|
Tani Y, Miura D, Kurokawa J, Nakamura K, Ouchida M, Shimizu K, Ohe T, Furukawa T. T75M-KCNJ2 mutation causing Andersen–Tawil syndrome enhances inward rectification by changing Mg2+ sensitivity. J Mol Cell Cardiol 2007; 43:187-96. [PMID: 17582433 DOI: 10.1016/j.yjmcc.2007.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Revised: 04/04/2007] [Accepted: 05/04/2007] [Indexed: 10/23/2022]
Abstract
Andersen-Tawil syndrome (ATS) is a multisystem inherited disease exhibiting periodic paralysis, cardiac arrhythmias, and dysmorphic features. In this study, we characterized the KCNJ2 channels with an ATS mutation (T75M) which is associated with cardiac phenotypes of bi-directional ventricular tachycardia, syncope, and QT(c) prolongation. Confocal imaging of GFP-KCNJ2 fusion proteins showed that the T75M mutation impaired membrane localization of the channel protein, which was restored by co-expression of WT channels with T75M channels. Whole-cell patch-clamp experiments in CHO-K1 cells showed that the T75M mutation produced a loss-of-function of the channel. When both WT and the T75M were co-expressed, the T75M mutation showed dominant-negative effects on inward rectifier K+ current densities, with prominent suppression of outward currents at potentials between 0 mV and +80 mV over the E(K). Inside-out patch experiments in HEK293T cells revealed that co-expression of WT and the T75M channels enhanced voltage-dependent block of the channels by internal Mg2+, resulting in enhanced inward rectification at potentials 50 mV more positive than the E(K). We suggest that the T75M mutation causes dominant-negative suppression of the co-expressed WT KCNJ2 channels. In addition, the T75M mutation caused alteration of gating kinetics of the mutated KCNJ2 channels, i.e., increased sensitivity to intracellular Mg2+ and resultant enhancement of inward rectification. The data presented suggest that the mutation may influence clinical features, but it does not directly show this.
Collapse
Affiliation(s)
- Yoshinori Tani
- Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, 2-3-10 Kandasurugadai, Chiyoda-ku, Tokyo 101-0062, Japan
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Peters S, Schulze-Bahr E, Etheridge SP, Tristani-Firouzi M. Sudden cardiac death in Andersen-Tawil syndrome. Europace 2007; 9:162-6. [PMID: 17272325 DOI: 10.1093/europace/eul188] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Andersen-Tawil syndrome (ATS) is an autosomal dominant or sporadic disorder characterized by periodic paralysis, dysmorphic features, and ventricular arrhythmias. Although ventricular tachycardia burden is quite high sudden cardiac death in ATS is rare. We describe a case with sudden cardiac death due to electrical storm a few days after ICD implantation in KCNJ2 mutation-negative ATS.
Collapse
Affiliation(s)
- Stefan Peters
- Klinikum Dorothea Christiane Erxleben Quedlinburg, Academic Teaching Hospital of the University Hospital Magdeburg, Innere Medizin II-Kardiologie, Ditfurter Weg 24, 06484 Quedlinburg, Germany.
| | | | | | | |
Collapse
|
28
|
Sung RJ, Wu SN, Wu JS, Chang HD, Luo CH. Electrophysiological mechanisms of ventricular arrhythmias in relation to Andersen-Tawil syndrome under conditions of reduced IK1: a simulation study. Am J Physiol Heart Circ Physiol 2006; 291:H2597-605. [PMID: 16877549 DOI: 10.1152/ajpheart.00393.2006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Patients with Andersen-Tawil syndrome (ATS) mostly have mutations on the KCNJ2 gene, producing loss of function or dominant-negative suppression of the inward rectifier K(+) channel Kir2.1. However, clinical manifestations of ATS including dysmorphic features, periodic paralysis (hypo-, hyper-, or normokalemic), long QT, and ventricular arrhythmias (VAs) are considerably variable. Using a modified dynamic Luo-Rudy simulation model of cardiac ventricular myocytes, we attempted to elucidate mechanisms of VA in ATS by analyzing effects of the inward rectifier K(+) channel current (I(K1)) on the action potential (AP). During pacing at 1.0 Hz with extracellular K(+) concentration ([K(+)](o)) at 4.5 mM, a stepwise 10% reduction of Kir2.1 channel conductance progressively prolonged the terminal repolarization phase of the AP along with gradual depolarization of the resting membrane potential (RMP). At 90% reduction, early afterdepolarizations (EADs) became inducible and RMP was depolarized to -52.0 mV (control: -89.8 mV), followed by emergence of spontaneous APs. Both EADs and spontaneous APs were facilitated by a decrease in [K(+)](o) and suppressed by an increase in [K(+)](o). Simulated beta-adrenergic stimulation enhanced delayed afterdepolarizations (DADs) and could also facilitate EADs as well as spontaneous APs in the setting of low [K(+)](o) and reduced Kir2.1 channel conductance. In conclusion, the spectrum of VAs in ATS may include 1) triggered activity mediated by EADs and/or DADs and 2) abnormal automaticity manifested as spontaneous APs. These VAs can be aggravated by a decrease in [K(+)](o) and beta-adrenergic stimulation and may potentially induce torsade de pointes and cause sudden death. In patients with ATS, the hypokalemic form of periodic paralysis should have the highest propensity to VAs, especially during physical activity.
Collapse
MESH Headings
- Action Potentials/physiology
- Andersen Syndrome/genetics
- Andersen Syndrome/physiopathology
- Animals
- Arrhythmias, Cardiac/etiology
- Arrhythmias, Cardiac/physiopathology
- Calcium/metabolism
- Death, Sudden, Cardiac
- Electrocardiography
- Electrophysiology
- Guinea Pigs
- Hypokalemic Periodic Paralysis/physiopathology
- Membrane Potentials/physiology
- Models, Theoretical
- Mutation/genetics
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Myocytes, Cardiac/physiology
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/physiology
- Receptors, Adrenergic, beta/physiology
- Ventricular Dysfunction/etiology
- Ventricular Dysfunction/physiopathology
Collapse
Affiliation(s)
- Ruey J Sung
- Dept. of Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan 704.
| | | | | | | | | |
Collapse
|
29
|
de Boer TP, van Veen TAB, Houtman MJC, Jansen JA, van Amersfoorth SCM, Doevendans PA, Vos MA, van der Heyden MAG. Inhibition of cardiomyocyte automaticity by electrotonic application of inward rectifier current from Kir2.1 expressing cells. Med Biol Eng Comput 2006; 44:537-42. [PMID: 16937189 DOI: 10.1007/s11517-006-0059-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 03/28/2006] [Indexed: 10/24/2022]
Abstract
A biological pacemaker might be created by generation of a cellular construct consisting of cardiac cells that display spontaneous membrane depolarization, and that are electrotonically coupled to surrounding myocardial cells by means of gap junctions. Depending on the frequency of the spontaneously beating cells, frequency regulation might be required. We hypothesized that application of Kir2.1 expressing non-cardiac cells, which provide I (K1) to spontaneously active neonatal cardiomyocytes (NCMs) by electrotonic coupling in such a cellular construct, would generate an opportunity for pacemaker frequency control. Non-cardiac Kir2.1 expressing cells were co-cultured with spontaneously active rat NCMs. Electrotonic coupling between the two cell types resulted in hyperpolarization of the cardiomyocyte membrane potential and silencing of spontaneous activity. Either blocking of gap-junctional communication by halothane or inhibition of I (K1) by BaCl(2) restored the original membrane potential and spontaneous activity of the NCMs. Our results demonstrate the power of electrotonic coupling for the application of specific ion currents into an engineered cellular construct such as a biological pacemaker.
Collapse
Affiliation(s)
- Teun P de Boer
- Department of Medical Physiology, Heart Lung Center Utrecht, University Medical Center Utrecht, Yalelaan 50, 3584, Utrecht, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
30
|
Tsuboi M, Antzelevitch C. Cellular basis for electrocardiographic and arrhythmic manifestations of Andersen-Tawil syndrome (LQT7). Heart Rhythm 2006; 3:328-35. [PMID: 16500306 PMCID: PMC1474110 DOI: 10.1016/j.hrthm.2005.11.026] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 11/23/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND Andersen-Tawil syndrome, a skeletal muscle syndrome associated with periodic paralysis and long QT intervals on the ECG, has been linked to defects in KCNJ2, the gene encoding for the inward rectifier potassium channel (I(K1).) OBJECTIVES The purpose of this study was to examine the cellular mechanisms underlying the ECG and arrhythmic manifestations of Andersen-Tawil syndrome. METHODS To investigate the effects of KCNJ2 loss-of-function mutations responsible for Andersen-Tawil syndrome, we used barium chloride (BaCl(2)) to inhibit I(K1) in arterially perfused wedge preparation. Transmembrane action potentials (APs) were simultaneously recorded from endocardial, midmyocardial, and epicardial cells, together with a transmural ECG. RESULTS BaCl(2) (1 to 30 microM) produced a concentration-dependent prolongation of the QT interval, secondary to a homogeneous prolongation of AP duration of the three cell types. QT interval was prolonged without an increase in transmural dispersion of repolarization (TDR). Low extracellular potassium (2.0 mM), isoproterenol (20-50 nM), and an abrupt increase in temperature (36 degrees C-39 degrees C) in the presence of 10 microM BaCl(2) did not significantly increase TDR but increased ectopic extrasystolic activity. Early afterdepolarizations were not observed under any condition. Spontaneous torsades de pointes arrhythmias were never observed, nor could they be induced with programmed electrical stimulation under any of the conditions studied. CONCLUSION Our results provide an understanding of why QT prolongation associated with Andersen-Tawil syndrome is relatively benign in the clinic and provide further support for the hypothesis that the increase in TDR, rather than QT interval, is responsible for development of torsades de pointes.
Collapse
Affiliation(s)
- Masato Tsuboi
- Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY 13501-1787, USA
| | | |
Collapse
|
31
|
Roepke TK, Abbott GW. Pharmacogenetics and cardiac ion channels. Vascul Pharmacol 2006; 44:90-106. [PMID: 16344000 DOI: 10.1016/j.vph.2005.07.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Accepted: 07/01/2005] [Indexed: 12/19/2022]
Abstract
Ion channels control electrical excitability in living cells. In mammalian heart, the opposing actions of Na(+) and Ca(2+) ion influx, and K(+) ion efflux, through cardiac ion channels determine the morphology and duration of action potentials in cardiac myocytes, thus controlling the heartbeat. The last decade has seen a leap in our understanding of the molecular genetic origins of inherited cardiac arrhythmia, largely through identification of mutations in cardiac ion channels and the proteins that regulate them. Further, recent advances have shown that 'acquired arrhythmias', which occur more commonly than inherited arrhythmias, arise due to a variety of environmental factors including side effects of therapeutic drugs and often have a significant genetic component. Here, we review the pharmacogenetics of cardiac ion channels-the interplay between genetic and pharmacological factors that underlie human cardiac arrhythmias.
Collapse
Affiliation(s)
- Torsten K Roepke
- Greenberg Division of Cardiology, Department of Medicine, Cornell University, Weill Medical College, 520 East 70th Street, New York, NY 10021, USA
| | | |
Collapse
|
32
|
Abstract
The heart is a rhythmic electromechanical pump, the functioning of which depends on action potential generation and propagation, followed by relaxation and a period of refractoriness until the next impulse is generated. Myocardial action potentials reflect the sequential activation and inactivation of inward (Na(+) and Ca(2+)) and outward (K(+)) current carrying ion channels. In different regions of the heart, action potential waveforms are distinct, owing to differences in Na(+), Ca(2+), and K(+) channel expression, and these differences contribute to the normal, unidirectional propagation of activity and to the generation of normal cardiac rhythms. Changes in channel functioning, resulting from inherited or acquired disease, affect action potential repolarization and can lead to the generation of life-threatening arrhythmias. There is, therefore, considerable interest in understanding the mechanisms that control cardiac repolarization and rhythm generation. Electrophysiological studies have detailed the properties of the Na(+), Ca(2+), and K(+) currents that generate cardiac action potentials, and molecular cloning has revealed a large number of pore forming (alpha) and accessory (beta, delta, and gamma) subunits thought to contribute to the formation of these channels. Considerable progress has been made in defining the functional roles of the various channels and in identifying the alpha-subunits encoding these channels. Much less is known, however, about the functioning of channel accessory subunits and/or posttranslational processing of the channel proteins. It has also become clear that cardiac ion channels function as components of macromolecular complexes, comprising the alpha-subunits, one or more accessory subunit, and a variety of other regulatory proteins. In addition, these macromolecular channel protein complexes appear to interact with the actin cytoskeleton and/or the extracellular matrix, suggesting important functional links between channel complexes, as well as between cardiac structure and electrical functioning. Important areas of future research will be the identification of (all of) the molecular components of functional cardiac ion channels and delineation of the molecular mechanisms involved in regulating the expression and the functioning of these channels in the normal and the diseased myocardium.
Collapse
Affiliation(s)
- Jeanne M Nerbonne
- Dept. of Molecular Biology and Pharmacology, Washington University Medical School, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
| | | |
Collapse
|
33
|
Venance SL, Cannon SC, Fialho D, Fontaine B, Hanna MG, Ptacek LJ, Tristani-Firouzi M, Tawil R, Griggs RC. The primary periodic paralyses: diagnosis, pathogenesis and treatment. ACTA ACUST UNITED AC 2005; 129:8-17. [PMID: 16195244 DOI: 10.1093/brain/awh639] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Periodic paralyses (PPs) are rare inherited channelopathies that manifest as abnormal, often potassium (K)-sensitive, muscle membrane excitability leading to episodic flaccid paralysis. Hypokalaemic (HypoPP) and hyperkalaemic PP and Andersen-Tawil syndrome are genetically heterogeneous. Over the past decade mutations in genes encoding three ion channels, CACN1AS, SCN4A and KCNJ2, have been identified and account for at least 70% of the identified cases of PP and several allelic disorders. No prospective clinical studies have followed sufficiently large cohorts with characterized molecular lesions to draw precise conclusions. We summarize current knowledge of the clinical diagnosis, molecular genetics, genotype-phenotype correlations, pathophysiology and treatment in the PPs. We focus on unresolved issues including (i) Are there additional ion channel defects in cases without defined mutations? (ii) What is the mechanism for depolarization-induced weakness in Hypo PP? and finally (iii) Will detailed electrophysiological studies be able to correctly identify specific channel mutations? Understanding the pathophysiology of the potassium-sensitive PPs ought to reduce genetic complexity, allow subjects to be stratified during future clinical trials and increase the likelihood of observing true clinical effects. Ideally, therapy for the PPs will prevent attacks, avoid permanent weakness and improve quality of life. Moreover, understanding the skeletal muscle channelopathies will hopefully lead to insights into the more common central nervous system channel diseases such as migraine and epilepsy.
Collapse
Affiliation(s)
- S L Venance
- Department of Clinical Neurological Sciences, London Health Sciences Centre, London, ON, Canada.
| | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Bendahhou S, Fournier E, Sternberg D, Bassez G, Furby A, Sereni C, Donaldson MR, Larroque MM, Fontaine B, Barhanin J. In vivo and in vitro functional characterization of Andersen's syndrome mutations. J Physiol 2005; 565:731-41. [PMID: 15831539 PMCID: PMC1464553 DOI: 10.1113/jphysiol.2004.081620] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The inward rectifier K(+) channel Kir2.1 carries all Andersen's syndrome mutations identified to date. Patients exhibit symptoms of periodic paralysis, cardiac dysrhythmia and multiple dysmorphic features. Here, we report the clinical manifestations found in three families with Andersen's syndrome. Molecular genetics analysis identified two novel missense mutations in the KCNJ2 gene leading to amino acid changes C154F and T309I of the Kir2.1 open reading frame. Patch clamp experiments showed that the two mutations produced a loss of channel function. When co-expressed with Kir2.1 wild-type (WT) channels, both mutations exerted a dominant-negative effect leading to a loss of the inward rectifying K(+) current. Confocal microscopy imaging in HEK293 cells is consistent with a co-assembly of the EGFP-fused mutant proteins with WT channels and proper traffick to the plasma membrane to produce silent channels alone or as hetero-tetramers with WT. Functional expression in C2C12 muscle cell line of newly as well as previously reported Andersen's syndrome mutations confirmed that these mutations act through a dominant-negative effect by altering channel gating or trafficking. Finally, in vivo electromyographic evaluation showed a decrease in muscle excitability in Andersen's syndrome patients. We hypothesize that Andersen's syndrome-associated mutations and hypokalaemic periodic paralysis-associated calcium channel mutations may lead to muscle membrane hypoexcitability via a common mechanism.
Collapse
Affiliation(s)
- Saïd Bendahhou
- Université de Nice Sophia Antipolis, UMR 6097 CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Romanenko VG, Fang Y, Byfield F, Travis AJ, Vandenberg CA, Rothblat GH, Levitan I. Cholesterol sensitivity and lipid raft targeting of Kir2.1 channels. Biophys J 2004; 87:3850-61. [PMID: 15465867 PMCID: PMC1304896 DOI: 10.1529/biophysj.104.043273] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study investigates how changes in the level of cellular cholesterol affect inwardly rectifying K+ channels belonging to a family of strong rectifiers (Kir2). In an earlier study we showed that an increase in cellular cholesterol suppresses endogenous K+ current in vascular endothelial cells, presumably due to effects on underlying Kir2.1 channels. Here we show that, indeed, cholesterol increase strongly suppressed whole-cell Kir2.1 current when the channels were expressed in a null cell line. However, cholesterol level had no effect on the unitary conductance and only little effect on the open probability of the channels. Moreover, no cholesterol effect was observed either on the total level of Kir2.1 protein or on its surface expression. We suggest, therefore, that cholesterol modulates not the total number of Kir2.1 channels in the plasma membrane but rather the transition of the channels between active and silent states. Comparing the effects of cholesterol on members of the Kir2.x family shows that Kir2.1 and Kir2.2 have similar high sensitivity to cholesterol, Kir2.3 is much less sensitive, and Kir2.4 has an intermediate sensitivity. Finally, we show that Kir2.x channels partition virtually exclusively into Triton-insoluble membrane fractions indicating that the channels are targeted into cholesterol-rich lipid rafts.
Collapse
Affiliation(s)
- Victor G Romanenko
- Institute for Medicine and Engineering, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | | | | | | | | | | | | |
Collapse
|
36
|
Kobori A, Sarai N, Shimizu W, Nakamura Y, Murakami Y, Makiyama T, Ohno S, Takenaka K, Ninomiya T, Fujiwara Y, Matsuoka S, Takano M, Noma A, Kita T, Horie M. Additional Gene Variants Reduce Effectiveness of Beta-Blockers in the LQT1 Form of Long QT Syndrome. J Cardiovasc Electrophysiol 2004; 15:190-9. [PMID: 15028050 DOI: 10.1046/j.1540-8167.2004.03212.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION Beta-blockers are widely used to prevent the lethal cardiac events associated with the long QT syndrome (LQTS), especially in KCNQ1-related LQTS (LQT1) patients. Some LQT1 patients, however, are refractory to this therapy. METHODS AND RESULTS Eighteen symptomatic LQTS patients (12 families) were genetically diagnosed as having heterozygous KCNQ1 variants and received beta-blocker therapy. Cardiac events recurred in 4 members (3 families) despite continued therapy during mean follow-up of 70 months. Three of these patients (2 families) had the same mutation [A341V (KCNQ1)]; and the other had R243H (KCNQ1). The latter patient took aprindine, which seemed to be responsible for the event. By functional assay using a heterologous mammalian expression system, we found that A341V (KCNQ1) is a loss-of-function type mutation (not dominant negative). Further genetic screening revealed that one A341V (KCNQ1) family cosegregated with S706C (KCNH2) and another with G144S (KCNJ2). Functional assay of the S706C (KCNH2) mutation was found to reduce the current density of expressed heterozygous KCNH2 channels with a positive shift (+8 mV) of the activation curve. Action potential simulation study was conducted based on the KYOTO model to estimate the influence of additional gene modifiers. In both models mimicking LQT1 plus 2 and LQT1 plus 7, the incidence of early afterdepolarization was increased compared with the LQT1 model under the setting of beta-adrenergic stimulation. CONCLUSION Multiple mutations in different LQTS-related genes may modify clinical characteristics. Expanded gene survey may be required in LQT1 patients who are resistant to beta-blocker therapy.
Collapse
Affiliation(s)
- Atsushi Kobori
- Department of Cardiovascular Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|