1
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Matzer I, Voglhuber J, Kiessling M, Djalinac N, Trummer-Herbst V, Mabotuwana N, Rech L, Holzer M, Sossalla S, Rainer PP, Zirlik A, Ljubojevic-Holzer S. β-Adrenergic Receptor Stimulation Maintains NCX-CaMKII Axis and Prevents Overactivation of IL6R-Signaling in Cardiomyocytes upon Increased Workload. Biomedicines 2022; 10:biomedicines10071648. [PMID: 35884952 PMCID: PMC9313457 DOI: 10.3390/biomedicines10071648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/30/2022] [Accepted: 07/05/2022] [Indexed: 12/01/2022] Open
Abstract
Excessive β-adrenergic stimulation and tachycardia are potent triggers of cardiac remodeling; however, their exact cellular effects remain elusive. Here, we sought to determine the potency of β-adrenergic stimulation and tachycardia to modulate gene expression profiles of cardiomyocytes. Using neonatal rat ventricular cardiomyocytes, we showed that tachycardia caused a significant upregulation of sodium–calcium exchanger (NCX) and the activation of calcium/calmodulin-dependent kinase II (CaMKII) in the nuclear region. Acute isoprenaline treatment ameliorated NCX-upregulation and potentiated CaMKII activity, specifically on the sarcoplasmic reticulum and the nuclear envelope, while preincubation with the β-blocker propranolol abolished both isoprenaline-mediated effects. On a transcriptional level, screening for hypertrophy-related genes revealed tachycardia-induced upregulation of interleukin-6 receptor (IL6R). While isoprenaline prevented this effect, pharmacological intervention with propranolol or NCX inhibitor ORM-10962 demonstrated that simultaneous CaMKII activation on the subcellular Ca2+ stores and prevention of NCX upregulation are needed for keeping IL6R activation low. Finally, using hypertensive Dahl salt-sensitive rats, we showed that blunted β-adrenergic signaling is associated with NCX upregulation and enhanced IL6R signaling. We therefore propose a previously unrecognized protective role of β-adrenergic signaling, which is compromised in cardiac pathologies, in preventing IL6R overactivation under increased workload. A better understanding of these processes may contribute to refinement of therapeutic options for patients receiving β-blockers.
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Affiliation(s)
- Ingrid Matzer
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Julia Voglhuber
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
- BioTechMed-Graz, 8010 Graz, Austria;
- Correspondence: (J.V.); (S.L.-H.)
| | - Mara Kiessling
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Nataša Djalinac
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Viktoria Trummer-Herbst
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Nishani Mabotuwana
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
- College of Health, Medicine and Wellbeing, The University of Newcastle, Newcastle, NSW 2308, Australia
- Hunter Medical Research Institute, Newcastle, NSW 2305, Australia
| | - Lavinia Rech
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Michael Holzer
- BioTechMed-Graz, 8010 Graz, Austria;
- Otto-Loewi Research Centre, Division of Pharmacology, Medical University of Graz, 8036 Graz, Austria
| | - Samuel Sossalla
- Department of Internal Medicine II, University Medical Centre Regensburg, 93053 Regensburg, Germany;
| | - Peter P. Rainer
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
- BioTechMed-Graz, 8010 Graz, Austria;
| | - Andreas Zirlik
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
| | - Senka Ljubojevic-Holzer
- Department of Cardiology, Medical University of Graz, 8036 Graz, Austria; (I.M.); (M.K.); (N.D.); (V.T.-H.); (N.M.); (L.R.); (P.P.R.); (A.Z.)
- BioTechMed-Graz, 8010 Graz, Austria;
- Gottfried Schatz Research Center, Division of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
- Correspondence: (J.V.); (S.L.-H.)
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2
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Ottolia M, John S, Hazan A, Goldhaber JI. The Cardiac Na + -Ca 2+ Exchanger: From Structure to Function. Compr Physiol 2021; 12:2681-2717. [PMID: 34964124 DOI: 10.1002/cphy.c200031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ca2+ homeostasis is essential for cell function and survival. As such, the cytosolic Ca2+ concentration is tightly controlled by a wide number of specialized Ca2+ handling proteins. One among them is the Na+ -Ca2+ exchanger (NCX), a ubiquitous plasma membrane transporter that exploits the electrochemical gradient of Na+ to drive Ca2+ out of the cell, against its concentration gradient. In this critical role, this secondary transporter guides vital physiological processes such as Ca2+ homeostasis, muscle contraction, bone formation, and memory to name a few. Herein, we review the progress made in recent years about the structure of the mammalian NCX and how it relates to function. Particular emphasis will be given to the mammalian cardiac isoform, NCX1.1, due to the extensive studies conducted on this protein. Given the degree of conservation among the eukaryotic exchangers, the information highlighted herein will provide a foundation for our understanding of this transporter family. We will discuss gene structure, alternative splicing, topology, regulatory mechanisms, and NCX's functional role on cardiac physiology. Throughout this article, we will attempt to highlight important milestones in the field and controversial topics where future studies are required. © 2021 American Physiological Society. Compr Physiol 12:1-37, 2021.
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Affiliation(s)
- Michela Ottolia
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Scott John
- Department of Medicine (Cardiology), UCLA, Los Angeles, California, USA
| | - Adina Hazan
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, California, USA
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3
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Wanichawan P, Skogestad J, Lunde M, Støle TP, Stensland M, Nyman TA, Sjaastad I, Sejersted OM, Aronsen JM, Carlson CR. Design of a Proteolytically Stable Sodium-Calcium Exchanger 1 Activator Peptide for In Vivo Studies. Front Pharmacol 2021; 12:638646. [PMID: 34163352 PMCID: PMC8215385 DOI: 10.3389/fphar.2021.638646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 05/14/2021] [Indexed: 11/13/2022] Open
Abstract
The cardiac sodium–calcium exchanger (NCX1) is important for normal Na+- and Ca2+-homeostasis and cardiomyocyte relaxation and contraction. It has been suggested that NCX1 activity is reduced by phosphorylated phospholemman (pSer68-PLM); however its direct interaction with PLM is debated. Disruption of the potentially inhibitory pSer68-PLM-NCX1 interaction might be a therapeutic strategy to increase NCX1 activity in cardiac disease. In the present study, we aimed to analyze the binding affinities and kinetics of the PLM-NCX1 and pSer68-PLM-NCX1 interactions by surface plasmon resonance (SPR) and to develop a proteolytically stable NCX1 activator peptide for future in vivo studies. The cytoplasmic parts of PLM (PLMcyt) and pSer68-PLM (pSer68-PLMcyt) were found to bind strongly to the intracellular loop of NCX1 (NCX1cyt) with similar KD values of 4.1 ± 1.0 nM and 4.3 ± 1.9 nM, but the PLMcyt-NCX1cyt interaction showed higher on/off rates. To develop a proteolytically stable NCX1 activator, we took advantage of a previously designed, high-affinity PLM binding peptide (OPT) that was derived from the PLM binding region in NCX1 and that reverses the inhibitory PLM (S68D)-NCX1 interaction in HEK293. We performed N- and C-terminal truncations of OPT and identified PYKEIEQLIELANYQV as the minimum sequence required for pSer68-PLM binding. To increase peptide stability in human serum, we replaced the proline with an N-methyl-proline (NOPT) after identification of N-terminus as substitution tolerant by two-dimensional peptide array analysis. Mass spectrometry analysis revealed that the half-life of NOPT was increased 17-fold from that of OPT. NOPT pulled down endogenous PLM from rat left ventricle lysate and exhibited direct pSer68-PLM binding in an ELISA-based assay and bound to pSer68-PLMcyt with a KD of 129 nM. Excess NOPT also reduced the PLMcyt-NCX1cyt interaction in an ELISA-based competition assay, but in line with that NCX1 and PLM form oligomers, NOPT was not able to outcompete the physical interaction between endogenous full length proteins. Importantly, cell-permeable NOPT-TAT increased NCX1 activity in cardiomyocytes isolated from both SHAM-operated and aorta banded heart failure (HF) mice, indicating that NOPT disrupted the inhibitory pSer68-PLM-NCX1 interaction. In conclusion, we have developed a proteolytically stable NCX1-derived PLM binding peptide that upregulates NCX1 activity in SHAM and HF cardiomyocytes.
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Affiliation(s)
- Pimthanya Wanichawan
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Jonas Skogestad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Marianne Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Thea Parsberg Støle
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Maria Stensland
- Department of Immunology, Institute of Clinical Medicine, University of Oslo and Rikshospitalet Oslo, Oslo, Norway
| | - Tuula A Nyman
- Department of Immunology, Institute of Clinical Medicine, University of Oslo and Rikshospitalet Oslo, Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Ole M Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
| | - Jan Magnus Aronsen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Pharmacology, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Cathrine Rein Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,The KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway
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4
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James AF. Enigmatic variations: The many facets of CFTR function in the heart. Acta Physiol (Oxf) 2020; 230:e13525. [PMID: 32562586 DOI: 10.1111/apha.13525] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Andrew F. James
- School of Physiology Pharmacology & Neuroscience University of Bristol Bristol UK
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5
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Beserra SS, Santos-Miranda A, Sarmento JO, Miranda VM, Roman-Campos D. Effects of amiodarone on rodent ventricular cardiomyocytes: Novel perspectives from a cellular model of Long QT Syndrome Type 3. Life Sci 2020; 255:117814. [PMID: 32439300 DOI: 10.1016/j.lfs.2020.117814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 05/04/2020] [Accepted: 05/15/2020] [Indexed: 10/24/2022]
Abstract
AIMS Amiodarone (AMIO) is currently used in medical practice to reverse ventricular tachycardia. Here we determine the effects of AMIO in the electromechanical properties of isolated left ventricle myocyte (LVM) from mice and guinea pig and in a cellular model of Long QT Syndrome Type 3 (LQTS-3) using anemone neurotoxin 2 (ATX II), which induces increase of late sodium current in LVM. MAIN METHODS AND KEY FINDINGS Using patch-clamp technique, fluorescence imaging to detect cellular Ca2+ transient and sarcomere detection systems we evaluate the effect of AMIO in healthy LVM. AMIO produced a significant reduction in the percentage of sarcomere shortening (0.1, 1 and 10 μM) in a range of pacing frequencies, however, without significant attenuation of Ca2+ transient. Also, 10 μM of AMIO caused the opposite effect on action potential repolarization of mouse and guinea pig LVM. When LVM from mouse and guinea pig were paced in a range of pacing frequencies and exposed to ATX (10 nM), AMIO (10 μM) was only able to abrogate electromechanical arrhythmias in LVM from guinea pig at lower pacing frequency. SIGNIFICANCE AMIO has negative inotropic effect with opposite effect on action potential waveform in mouse and guinea pig LVM. Furthermore, the antiarrhythmic action of AMIO in LQTS-3 is species and frequency-dependent, which indicates that AMIO may be beneficial for some types of arrhythmias related to late sodium current.
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Affiliation(s)
- Samuel Santos Beserra
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Brazil
| | - Artur Santos-Miranda
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Brazil
| | - Jaqueline Oliveira Sarmento
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Brazil
| | - Victor Martins Miranda
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Brazil
| | - Danilo Roman-Campos
- Laboratory of CardioBiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Brazil.
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6
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Lillo MA, Himelman E, Shirokova N, Xie LH, Fraidenraich D, Contreras JE. S-nitrosylation of connexin43 hemichannels elicits cardiac stress-induced arrhythmias in Duchenne muscular dystrophy mice. JCI Insight 2019; 4:130091. [PMID: 31751316 DOI: 10.1172/jci.insight.130091] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 11/07/2019] [Indexed: 01/16/2023] Open
Abstract
Patients with Duchenne muscular dystrophy (DMD) commonly present with severe ventricular arrhythmias that contribute to heart failure. Arrhythmias and lethality are also consistently observed in adult Dmdmdx mice, a mouse model of DMD, after acute β-adrenergic stimulation. These pathological features were previously linked to aberrant expression and remodeling of the cardiac gap junction protein connexin43 (Cx43). Here, we report that remodeled Cx43 protein forms Cx43 hemichannels in the lateral membrane of Dmdmdx cardiomyocytes and that the β-adrenergic agonist isoproterenol (Iso) aberrantly activates these hemichannels. Block of Cx43 hemichannels or a reduction in Cx43 levels (using Dmdmdx Cx43+/- mice) prevents the abnormal increase in membrane permeability, plasma membrane depolarization, and Iso-evoked electrical activity in these cells. Additionally, Iso treatment promotes nitric oxide (NO) production and S-nitrosylation of Cx43 hemichannels in Dmdmdx heart. Importantly, inhibition of NO production prevents arrhythmias evoked by Iso. We found that NO directly activates Cx43 hemichannels by S-nitrosylation of cysteine at position 271. Our results demonstrate that opening of remodeled and S-nitrosylated Cx43 hemichannels plays a key role in the development of arrhythmias in DMD mice and that these channels may serve as therapeutic targets to prevent fatal arrhythmias in patients with DMD .
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Affiliation(s)
| | - Eric Himelman
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | | | - Lai-Hua Xie
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, New Jersey, USA
| | - Diego Fraidenraich
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, New Jersey, USA
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7
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Chen M, Yin D, Guo S, Xu DZ, Wang Z, Chen Z, Rubart-von der Lohe M, Lin SF, Everett Iv TH, Weiss JN, Chen PS. Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles. J Physiol 2018; 596:4299-4322. [PMID: 29917243 DOI: 10.1113/jp275681] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/11/2018] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+ -voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. ABSTRACT Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25 ) more prominently than APD at the level of 80% repolarization (APD80 ), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+ -voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+ -voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Thomas H Everett Iv
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, CA, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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8
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Lubelwana Hafver T, Wanichawan P, Manfra O, de Souza GA, Lunde M, Martinsen M, Louch WE, Sejersted OM, Carlson CR. Mapping the in vitro interactome of cardiac sodium (Na + )-calcium (Ca 2+ ) exchanger 1 (NCX1). Proteomics 2017; 17. [PMID: 28755400 DOI: 10.1002/pmic.201600417] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 07/03/2017] [Accepted: 07/26/2017] [Indexed: 11/07/2022]
Abstract
The sodium (Na+ )-calcium (Ca2+ ) exchanger 1 (NCX1) is an antiporter membrane protein encoded by the SLC8A1 gene. In the heart, it maintains cytosolic Ca2+ homeostasis, serving as the primary mechanism for Ca2+ extrusion during relaxation. Dysregulation of NCX1 is observed in end-stage human heart failure. In this study, we used affinity purification coupled with MS in rat left ventricle lysates to identify novel NCX1 interacting proteins in the heart. Two screens were conducted using: (1) anti-NCX1 against endogenous NCX1 and (2) anti-His (where His is histidine) with His-trigger factor-NCX1cyt recombinant protein as bait. The respective methods identified 112 and 350 protein partners, of which several were known NCX1 partners from the literature, and 29 occurred in both screens. Ten novel protein partners (DYRK1A, PPP2R2A, SNTB1, DMD, RABGGTA, DNAJB4, BAG3, PDE3A, POPDC2, STK39) were validated for binding to NCX1, and two partners (DYRK1A, SNTB1) increased NCX1 activity when expressed in HEK293 cells. A cardiac NCX1 protein-protein interaction map was constructed. The map was highly connected, containing distinct clusters of proteins with different biological functions, where "cell communication" and "signal transduction" formed the largest clusters. The NCX1 interactome was also significantly enriched with proteins/genes involved in "cardiovascular disease" which can be explored as novel drug targets in future research.
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Affiliation(s)
- Tandekile Lubelwana Hafver
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Pimthanya Wanichawan
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Ornella Manfra
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Gustavo Antonio de Souza
- Department of Immunology and Centre for Immune Regulation, Oslo University Hospital HF Rikshospitalet, University of Oslo, Oslo, Norway.,The Brain Institute, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil.,Bioinformatics Multidisciplinary Environment, Instituto Metrópole Digital, UFRN, Natal, RN, Brazil
| | - Marianne Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Marita Martinsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - William Edward Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Ole Mathias Sejersted
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Cathrine Rein Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
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9
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Differential regulation of the Na +-Ca 2+ exchanger 3 (NCX3) by protein kinase PKC and PKA. Cell Calcium 2017; 65:52-62. [PMID: 28233567 DOI: 10.1016/j.ceca.2017.02.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 02/09/2017] [Accepted: 02/09/2017] [Indexed: 11/21/2022]
Abstract
Isoform 3 of the Na+-Ca2+ exchanger (NCX3) participates in the Ca2+ fluxes across the plasma membrane. Among the NCX family, NCX3 carries out a peculiar role due to its specific functions in skeletal muscle and the immune system and to its neuroprotective effect under stress exposure. In this context, proper understanding of the regulation of NCX3 is primordial to consider its potential use as a drug target. In this study, we demonstrated the regulation of NCX3 by protein kinase A (PKA) and C (PKC). Disparity in regulation has been previously reported among the splice variants of NCX3 therefore the activity of Ca2+ uptake and extrusion of the two murine variants was measured using fura-2-based Ca2+ imaging and revealed that both variants are similarly regulated. PKC stimulation diminished the Ca2+ uptake performed by NCX3 in the reverse mode, triggered by a rise in [Ca2+]i or [Na+]i, whereas an opposite response was observed upon PKA stimulation, with a significant increase of the Ca2+ uptake after a rise in [Ca2+]i. The latter stimulation affected similarly the efflux capacity of NCX3 whereas Ca2+ extrusion capacity remained unaffected under activation of PKC. Next, using site-directed mutagenesis, the sensitivity of NCX3 to PKC was abolished by singly mutating its predicted phosphorylation sites T529 or S695. The sensitivity to PKC might be due to the influence of T529 phosphorylation on the Ca2+-binding domain 1. Additionally, we showed that stimulation of NCX3 by PKA occurred through residue S524. This effect may well participate in the fight-or-flight response in skeletal muscle and the long-term potentiation in hippocampus.
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10
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Feldman AM, Gordon J, Wang J, Song J, Zhang XQ, Myers VD, Tilley DG, Gao E, Hoffman NE, Tomar D, Madesh M, Rabinowitz J, Koch WJ, Su F, Khalili K, Cheung JY. BAG3 regulates contractility and Ca(2+) homeostasis in adult mouse ventricular myocytes. J Mol Cell Cardiol 2016; 92:10-20. [PMID: 26796036 PMCID: PMC4789075 DOI: 10.1016/j.yjmcc.2016.01.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 01/14/2016] [Accepted: 01/17/2016] [Indexed: 12/22/2022]
Abstract
Bcl2-associated athanogene 3 (BAG3) is a 575 amino acid anti-apoptotic protein that is constitutively expressed in the heart. BAG3 mutations, including mutations leading to loss of protein, are associated with familial cardiomyopathy. Furthermore, BAG3 levels have been found to be reduced in end-stage non-familial failing myocardium. In contrast to neonatal myocytes in which BAG3 is found in the cytoplasm and involved in protein quality control and apoptosis, in adult mouse left ventricular (LV) myocytes BAG3 co-localized with Na(+)-K(+)-ATPase and L-type Ca(2+) channels in the sarcolemma and t-tubules. BAG3 co-immunoprecipitated with β1-adrenergic receptor, L-type Ca(2+) channels and phospholemman. To simulate decreased BAG3 protein levels observed in human heart failure, we targeted BAG3 by shRNA (shBAG3) in adult LV myocytes. Reducing BAG3 by 55% resulted in reduced contraction and [Ca(2+)]i transient amplitudes in LV myocytes stimulated with isoproterenol. L-type Ca(2+) current (ICa) and sarcoplasmic reticulum (SR) Ca(2+) content but not Na(+)/Ca(2+) exchange current (INaCa) or SR Ca(2+) uptake were reduced in isoproterenol-treated shBAG3 myocytes. Forskolin or dibutyryl cAMP restored ICa amplitude in shBAG3 myocytes to that observed in WT myocytes, consistent with BAG3 having effects upstream and at the level of the receptor. Resting membrane potential and action potential amplitude were unaffected but APD50 and APD90 were prolonged in shBAG3 myocytes. Protein levels of Ca(2+) entry molecules and other important excitation-contraction proteins were unchanged in myocytes with lower BAG3. Our findings that BAG3 is localized at the sarcolemma and t-tubules while modulating myocyte contraction and action potential duration through specific interaction with the β1-adrenergic receptor and L-type Ca(2+) channel provide novel insight into the role of BAG3 in cardiomyopathies and increased arrhythmia risks in heart failure.
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MESH Headings
- Action Potentials/drug effects
- Adaptor Proteins, Signal Transducing/biosynthesis
- Adaptor Proteins, Signal Transducing/genetics
- Animals
- Apoptosis Regulatory Proteins/biosynthesis
- Apoptosis Regulatory Proteins/genetics
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/metabolism
- Arrhythmias, Cardiac/pathology
- Calcium/metabolism
- Calcium Channels, L-Type/metabolism
- Cardiomyopathy, Dilated/genetics
- Cardiomyopathy, Dilated/metabolism
- Cardiomyopathy, Dilated/pathology
- Excitation Contraction Coupling
- Heart Failure/genetics
- Heart Failure/metabolism
- Heart Failure/pathology
- Heart Ventricles/metabolism
- Heart Ventricles/pathology
- Homeostasis
- Humans
- Isoproterenol/administration & dosage
- Membrane Proteins/metabolism
- Mice
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Phosphoproteins/metabolism
- RNA, Small Interfering/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Sarcolemma/metabolism
- Sodium-Potassium-Exchanging ATPase/metabolism
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Affiliation(s)
- Arthur M Feldman
- Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jennifer Gordon
- Comprehensive NeuroAIDS Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - JuFang Wang
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jianliang Song
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Xue-Qian Zhang
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Valerie D Myers
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Douglas G Tilley
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Erhe Gao
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Nicholas E Hoffman
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Dhanendra Tomar
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Muniswamy Madesh
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Joseph Rabinowitz
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Walter J Koch
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Feifei Su
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Cardiology, Tangdu Hospital, the Fourth Military Medical University, Xi'an, China
| | - Kamel Khalili
- Comprehensive NeuroAIDS Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Joseph Y Cheung
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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11
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Negroni JA, Morotti S, Lascano EC, Gomes AV, Grandi E, Puglisi JL, Bers DM. β-adrenergic effects on cardiac myofilaments and contraction in an integrated rabbit ventricular myocyte model. J Mol Cell Cardiol 2015; 81:162-75. [PMID: 25724724 DOI: 10.1016/j.yjmcc.2015.02.014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 01/10/2015] [Accepted: 02/17/2015] [Indexed: 12/21/2022]
Abstract
A five-state model of myofilament contraction was integrated into a well-established rabbit ventricular myocyte model of ion channels, Ca(2+) transporters and kinase signaling to analyze the relative contribution of different phosphorylation targets to the overall mechanical response driven by β-adrenergic stimulation (β-AS). β-AS effect on sarcoplasmic reticulum Ca(2+) handling, Ca(2+), K(+) and Cl(-) currents, and Na(+)/K(+)-ATPase properties was included based on experimental data. The inotropic effect on the myofilaments was represented as reduced myofilament Ca(2+) sensitivity (XBCa) and titin stiffness, and increased cross-bridge (XB) cycling rate (XBcy). Assuming independent roles of XBCa and XBcy, the model reproduced experimental β-AS responses on action potentials and Ca(2+) transient amplitude and kinetics. It also replicated the behavior of force-Ca(2+), release-restretch, length-step, stiffness-frequency and force-velocity relationships, and increased force and shortening in isometric and isotonic twitch contractions. The β-AS effect was then switched off from individual targets to analyze their relative impact on contractility. Preventing β-AS effects on L-type Ca(2+) channels or phospholamban limited Ca(2+) transients and contractile responses in parallel, while blocking phospholemman and K(+) channel (IKs) effects enhanced Ca(2+) and inotropy. Removal of β-AS effects from XBCa enhanced contractile force while decreasing peak Ca(2+) (due to greater Ca(2+) buffering), but had less effect on shortening. Conversely, preventing β-AS effects on XBcy preserved Ca(2+) transient effects, but blunted inotropy (both isometric force and especially shortening). Removal of titin effects had little impact on contraction. Finally, exclusion of β-AS from XBCa and XBcy while preserving effects on other targets resulted in preserved peak isometric force response (with slower kinetics) but nearly abolished enhanced shortening. β-AS effects on XBCa and XBcy have greater impact on isometric and isotonic contraction, respectively.
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Affiliation(s)
- Jorge A Negroni
- Department of Comparative, Cellular and Molecular Biology, Universidad Favaloro, Buenos Aires, Argentina.
| | - Stefano Morotti
- Department of Pharmacology, University of California Davis, CA, USA
| | - Elena C Lascano
- Department of Comparative, Cellular and Molecular Biology, Universidad Favaloro, Buenos Aires, Argentina
| | - Aldrin V Gomes
- Department of Neurobiology, Physiology and Behavior, University of California Davis, CA, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California Davis, CA, USA
| | - José L Puglisi
- Department of Pharmacology, University of California Davis, CA, USA
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, CA, USA.
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12
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cAMP and Ca²⁺ signaling in secretory epithelia: crosstalk and synergism. Cell Calcium 2014; 55:385-93. [PMID: 24613710 DOI: 10.1016/j.ceca.2014.01.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 01/29/2014] [Accepted: 01/30/2014] [Indexed: 12/15/2022]
Abstract
The Ca(2+) and cAMP/PKA pathways are the primary signaling systems in secretory epithelia that control virtually all secretory gland functions. Interaction and crosstalk in Ca(2+) and cAMP signaling occur at multiple levels to control and tune the activity of each other. Physiologically, Ca(2+) and cAMP signaling operate at 5-10% of maximal strength, but synergize to generate the maximal response. Although synergistic action of the Ca(2+) and cAMP signaling is the common mode of signaling and has been known for many years, we know very little of the molecular mechanism and mediators of the synergism. In this review, we discuss crosstalk between the Ca(2+) and cAMP signaling and the function of IRBIT (IP3 receptors binding protein release with IP3) as a third messenger that mediates the synergistic action of the Ca(2+) and cAMP signaling.
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13
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Wang J, Song J, Gao E, Zhang XQ, Gu T, Yu D, Koch WJ, Feldman AM, Cheung JY. Induced overexpression of phospholemman S68E mutant improves cardiac contractility and mortality after ischemia-reperfusion. Am J Physiol Heart Circ Physiol 2014; 306:H1066-77. [PMID: 24486513 DOI: 10.1152/ajpheart.00861.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phospholemman (PLM), when phosphorylated at Ser(68), inhibits cardiac Na+ / Ca2+ exchanger 1 (NCX1) and relieves its inhibition on Na+ -K+ -ATPase. We have engineered mice in which expression of the phosphomimetic PLM S68E mutant was induced when dietary doxycycline was removed at 5 wk. At 8-10 wk, compared with noninduced or wild-type hearts, S68E expression in induced hearts was ∼35-75% that of endogenous PLM, but protein levels of sarco(endo)plasmic reticulum Ca2+ -ATPase, α1- and α2-subunits of Na+ -K+ -ATPase, α1c-subunit of L-type Ca2+ channel, and phosphorylated ryanodine receptor were unchanged. The NCX1 protein level was increased by ∼47% but the NCX1 current was depressed by ∼34% in induced hearts. Isoproterenol had no effect on NCX1 currents but stimulated Na+ -K+ -ATPase currents equally in induced and noninduced myocytes. At baseline, systolic intracellular Ca2+ concentrations ([Ca2+]i), sarcoplasmic reticulum Ca2+ contents, and [Ca(2+)]i transient and contraction amplitudes were similar between induced and noninduced myocytes. Isoproterenol stimulation resulted in much higher systolic [Ca2+]i, sarcoplasmic reticulum Ca2+ content, and [Ca2+]i transient and contraction amplitudes in induced myocytes. Echocardiography and in vivo close-chest catheterization demonstrated similar baseline myocardial function, but isoproterenol induced a significantly higher +dP/dt in induced compared with noninduced hearts. In contrast to the 50% mortality observed in mice constitutively overexpressing the S68E mutant, induced mice had similar survival as wild-type and noninduced mice. After ischemia-reperfusion, despite similar areas at risk and left ventricular infarct sizes, induced mice had significantly higher +dP/dt and -dP/dt and lower perioperative mortality compared with noninduced mice. We propose that phosphorylated PLM may be a novel therapeutic target in ischemic heart disease.
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Affiliation(s)
- JuFang Wang
- Center of Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania
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14
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Krishna A, Valderrábano M, Palade PT, Clark JW. Rate-dependent Ca2+ signalling underlying the force-frequency response in rat ventricular myocytes: a coupled electromechanical modeling study. Theor Biol Med Model 2013; 10:54. [PMID: 24020888 PMCID: PMC3848742 DOI: 10.1186/1742-4682-10-54] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 06/03/2013] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Rate-dependent effects on the Ca2+ sub-system in a rat ventricular myocyte are investigated. Here, we employ a deterministic mathematical model describing various Ca2+ signalling pathways under voltage clamp (VC) conditions, to better understand the important role of calmodulin (CaM) in modulating the key control variables Ca2+/calmodulin-dependent protein kinase-II (CaMKII), calcineurin (CaN), and cyclic adenosine monophosphate (cAMP) as they affect various intracellular targets. In particular, we study the frequency dependence of the peak force generated by the myofilaments, the force-frequency response (FFR). METHODS Our cell model incorporates frequency-dependent CaM-mediated spatially heterogenous interaction of CaMKII and CaN with their principal targets (dihydropyridine (DHPR) and ryanodine (RyR) receptors and the SERCA pump). It also accounts for the rate-dependent effects of phospholamban (PLB) on the SERCA pump; the rate-dependent role of cAMP in up-regulation of the L-type Ca2+ channel (ICa,L); and the enhancement in SERCA pump activity via phosphorylation of PLB. RESULTS Our model reproduces positive peak FFR observed in rat ventricular myocytes during voltage-clamp studies both in the presence/absence of cAMP mediated β-adrenergic stimulation. This study provides quantitative insight into the rate-dependence of Ca2+-induced Ca2+-release (CICR) by investigating the frequency-dependence of the trigger current (ICa,L) and RyR-release. It also highlights the relative role of the sodium-calcium exchanger (NCX) and the SERCA pump at higher frequencies, as well as the rate-dependence of sarcoplasmic reticulum (SR) Ca2+ content. A rigorous Ca2+ balance imposed on our investigation of these Ca2+ signalling pathways clarifies their individual roles. Here, we present a coupled electromechanical study emphasizing the rate-dependence of isometric force developed and also investigate the temperature-dependence of FFR. CONCLUSIONS Our model provides mechanistic biophysically based explanations for the rate-dependence of CICR, generating useful and testable hypotheses. Although rat ventricular myocytes exhibit a positive peak FFR in the presence/absence of beta-adrenergic stimulation, they show a characteristic increase in the positive slope in FFR due to the presence of Norepinephrine or Isoproterenol. Our study identifies cAMP-mediated stimulation, and rate-dependent CaMKII-mediated up-regulation of ICa,L as the key mechanisms underlying the aforementioned positive FFR.
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Affiliation(s)
- Abhilash Krishna
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas, USA
| | - Miguel Valderrábano
- Methodist Hospital Research Institute, Methodist DeBakey Heart & Vascular Center, Houston, Texas, USA
| | - Philip T Palade
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - John W Clark
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas, USA
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15
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Functional comparison of the reverse mode of Na+/Ca2+ exchangers NCX1.1 and NCX1.5 expressed in CHO cells. Acta Pharmacol Sin 2013; 34:691-8. [PMID: 23564083 DOI: 10.1038/aps.2013.4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
AIM To investigate the reverse mode function of Na(+)/Ca(2+) exchangers NCX1.1 and NCX1.5 expressed in CHO cells as well as their modulations by PKC and PKA. METHODS CHO-K1 cells were transfected with pcDNA3.1 (+) plasmid carrying cDNA of rat cardiac NCX1.1 and brain NCX1.5. The expression of NCX1.1 and NCX1.5 was examined using Western blot analysis. The intracellular Ca(2+) level ([Ca(2+)]i) was measured using Ca(2+) imaging. Whole-cell NCX currents were recorded using patch-clamp technique. Reverse mode NCX activity was elicited by perfusion with Na(+)-free medium. Ca(2+) paradox was induced by Ca(2+)-free EBSS medium, followed by Ca(2+)-containing solution (1.8 or 3.8 mmol/L CaCl2). RESULTS The protein levels of NCX1.1 and NCX1.5 expressed in CHO cells had no significant difference. The reverse modes of NCX1.1 and NCX1.5 in CHO cells exhibited a transient increase of [Ca(2+)]i, which was followed by a Ca(2+) level plateau at higher external Ca(2+) concentrations. In contrast, the wild type CHO cells showed a steady increase of [Ca(2+)]i at higher external Ca(2+) concentrations. The PKC activator PMA (0.3-10 μmol/L) and PKA activator 8-Br-cAMP (10-100 μmol/L) significantly enhanced the reverse mode activity of NCX1.1 and NCX1.5 in CHO cells. NCX1.1 was 2.4-fold more sensitive to PKC activation than NCX1.5, whereas the sensitivity of the two NCX isoforms to PKA activation had no difference. Both PKC- and PKA-enhanced NCX reverse mode activities in CHO cells were suppressed by NCX inhibitor KB-R7943 (30 μmol/L). CONCLUSION Both NCX1.1 and NCX1.5 are functional in regulating and maintaining stable [Ca(2+)]i in CHO cells and differentially regulated by PKA and PKC. The two NCX isoforms might be useful drug targets for heart and brain protection.
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16
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Barman PP, Cheng H, Hancox JC, James AF. Nickel inhibits β-1 adrenoceptor mediated activation of cardiac CFTR chloride channels. Biochem Biophys Res Commun 2013; 432:46-51. [PMID: 23376720 PMCID: PMC3686155 DOI: 10.1016/j.bbrc.2013.01.087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 01/25/2013] [Indexed: 11/24/2022]
Abstract
Cardiac ventricular myocytes exhibit a protein kinase A-dependent Cl(-) current (ICl.PKA) mediated by the cystic fibrosis transmembrane conductance regulator (CFTR). There is conflicting evidence regarding the ability of the divalent cation nickel (Ni(2+)), which has been used widely in vitro in the study of other cardiac ionic conductances, to inhibit ICl.PKA. Here the action of Ni(2+) on ICl.PKA activated by β-adrenergic stimulation has been elucidated. Whole-cell patch-clamp recordings were made from rabbit isolated ventricular myocytes. Externally applied Ni(2+) blocked ICl.PKA activated by 1 μM isoprenaline with a log IC50 (M) of -4.107 ± 0.075 (IC50=78.1 μM) at +100 mV and -4.322 ± 0.107 (IC50=47.6 μM) at -100 mV. Thus, the block of ICl.PKA by Ni(2+) was not strongly voltage dependent. Ni(2+) applied internally via the patch-pipette was ineffective at inhibiting isoprenaline-activated ICl,PKA, but in the same experiments the current was suppressed by external Ni(2+) application, indicative of an external site of Ni(2+) action. In the presence of 1 μM atenolol isoprenaline was ineffective at activating ICl.PKA, but in the presence of the β2-adrenoceptor inhibitor ICI 118,551 isoprenaline still activated Ni(2+)-sensitive ICl.PKA. Collectively, these data demonstrate that Ni(2+) ions produce marked inhibition of β1-adrenoceptor activated ventricular ICl.PKA at submillimolar [Ni(2+)]: an action that is likely to involve an interaction between Ni(2+) and β1-adrenoceptors. The concentration-dependence for ICl.PKA inhibition seen here indicates the potential for confounding effects on ICl,PKA to occur even at comparatively low Ni(2+) concentrations, when Ni(2+) is used to study other cardiac ionic currents under conditions of β-adrenergic agonism.
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Affiliation(s)
| | | | - Jules C. Hancox
- Cardiovascular Research Laboratories, School of Physiology & Pharmacology and Bristol Heart Institute, University of Bristol, Bristol BS8 1TD, UK
| | - Andrew F. James
- Cardiovascular Research Laboratories, School of Physiology & Pharmacology and Bristol Heart Institute, University of Bristol, Bristol BS8 1TD, UK
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17
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NHE-1 blockade reversed changes in calcium transient in myocardial slices from isoproterenol-induced hypertrophied rat left ventricle. Biochem Biophys Res Commun 2012; 419:431-5. [DOI: 10.1016/j.bbrc.2012.02.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 02/07/2012] [Indexed: 11/24/2022]
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18
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Morad M, Cleemann L, Menick DR. NCX1 phosphorylation dilemma: a little closer to resolution. Focus on “Full-length cardiac Na+/Ca2+ exchanger 1 protein is not phosphorylated by protein kinase A”. Am J Physiol Cell Physiol 2011; 300:C970-3. [DOI: 10.1152/ajpcell.00064.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Martin Morad
- Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina and Clemson University and
| | - Lars Cleemann
- Cardiac Signaling Center of University of South Carolina, Medical University of South Carolina and Clemson University and
| | - Donald R. Menick
- Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
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19
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Barman P, Choisy SCM, Hancox JC, James AF. β-Adrenoceptor/PKA-stimulation, Na(+)-Ca(2+) exchange and PKA-activated Cl(-) currents in rabbit cardiomyocytes: a conundrum. Cell Calcium 2011; 49:233-9. [PMID: 21439639 PMCID: PMC3092849 DOI: 10.1016/j.ceca.2011.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Investigations into the functional modulation of the cardiac Na(+)-Ca(2+) exchanger (NCX) by acute β-adrenoceptor/PKA stimulation have produced conflicting results. Here, we investigated (i) whether or not β-adrenoceptor activation/PKA stimulation activates current in rabbit cardiac myocytes under NCX-'selective' conditions and (ii) if so, whether a PKA-activated Cl(-)-current may contribute to the apparent modulation of NCX current (I(NCX)). Whole-cell voltage-clamp experiments were conducted at 37°C on rabbit ventricular and atrial myocytes. The β-adrenoceptor-activated currents both in NCX-'selective' and Cl(-)-selective recording conditions were found to be sensitive to 10mM Ni(2+). In contrast, the PKA-activated Cl(-) current was not sensitive to Ni(2+), when it was activated downstream to the β-adrenoceptors using 10μM forskolin (an adenylyl cyclase activator). When 10μM forskolin was applied under NCX-selective recording conditions, the Ni(2+)-sensitive current did not differ between control and forskolin. These findings suggest that in rabbit myocytes: (a) a PKA-activated Cl(-) current contributes to the Ni(2+)-sensitive current activated via β-adrenoceptor stimulation under recording conditions previously considered selective for I(NCX); (b) downstream activation of PKA does not augment Ni(2+)-sensitive I(NCX), when this is measured under conditions where the Ni(2+)-sensitive PKA-activated Cl(-) current is not present.
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Affiliation(s)
- Palash Barman
- Bristol Heart Institute, Cardiovascular Research Laboratories, School of Physiology & Pharmacology, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK
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20
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Wanichawan P, Louch WE, Hortemo KH, Austbø B, Lunde PK, Scott JD, Sejersted OM, Carlson CR. Full-length cardiac Na+/Ca2+ exchanger 1 protein is not phosphorylated by protein kinase A. Am J Physiol Cell Physiol 2011; 300:C989-97. [PMID: 21289289 DOI: 10.1152/ajpcell.00196.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cardiac Na(+)/Ca(2+) exchanger 1 (NCX1) is an important regulator of intracellular Ca(2+) homeostasis and cardiac function. Several studies have indicated that NCX1 is phosphorylated by the cAMP-dependent protein kinase A (PKA) in vitro, which increases its activity. However, this finding is controversial and no phosphorylation site has so far been identified. Using bioinformatic analysis and peptide arrays, we screened NCX1 for putative PKA phosphorylation sites. Although several NCX1 synthetic peptides were phosphorylated by PKA in vitro, only one PKA site (threonine 731) was identified after mutational analysis. To further examine whether NCX1 protein could be PKA phosphorylated, wild-type and alanine-substituted NCX1-green fluorescent protein (GFP)-fusion proteins expressed in human embryonic kidney (HEK)293 cells were generated. No phosphorylation of full-length or calpain- or caspase-3 digested NCX1-GFP was observed with purified PKA-C and [γ-(32)P]ATP. Immunoblotting experiments with anti-PKA substrate and phosphothreonine-specific antibodies were further performed to investigate phosphorylation of endogenous NCX1. Phospho-NCX1 levels were also not increased after forskolin or isoproterenol treatment in vivo, in isolated neonatal cardiomyocytes, or in total heart homogenate. These data indicate that the novel in vitro PKA phosphorylation site is inaccessible in full-length as well as in calpain- or caspase-3 digested NCX1 protein, suggesting that NCX1 is not a direct target for PKA phosphorylation.
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Affiliation(s)
- Pimthanya Wanichawan
- Institute for Experimental Medical Research, Oslo Univ. Hospital, Ullevaal, Oslo, Norway.
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21
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Chase A, Orchard CH. Ca efflux via the sarcolemmal Ca ATPase occurs only in the t-tubules of rat ventricular myocytes. J Mol Cell Cardiol 2010; 50:187-93. [PMID: 20971118 DOI: 10.1016/j.yjmcc.2010.10.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 10/07/2010] [Accepted: 10/08/2010] [Indexed: 10/18/2022]
Abstract
The transverse (t-) tubule network is an important site for Ca influx and release during excitation-contraction coupling in cardiac ventricular myocytes; however, its role in Ca extrusion is less clear. The present study was designed to investigate the relative contributions of Ca extrusion pathways across the t-tubule and surface membranes. Ventricular myocytes were isolated from the hearts of adult male Wistar rats and detubulated using formamide. Intracellular Ca was monitored using fluo-3 and confocal microscopy. Caffeine (20 mmol/L) was used to induce SR Ca release; carboxyeosin (20 μmol/L) and nickel (10 mmol/L) were used to inhibit the sarcolemmal Ca ATPase and Na/Ca exchanger (NCX) respectively. Carboxyeosin decreased the rate constant of decay of the caffeine-induced Ca transient in control cells, but had no effect in detubulated cells, suggesting that Ca extrusion via the Ca ATPase occurs only across the t-tubule membrane. However nickel decreased the rate constant of the caffeine-induced Ca transient in control and detubulated cells, although its effect was greater in control cells, suggesting that Ca extrusion via NCX occurs across the surface and t-tubule membranes. The PKA inhibitor H-89 (10 μmol/L) was used to investigate the role of basal PKA activity in Ca extrusion; H-89 appeared to have no effect on Ca extrusion via the Ca ATPase, but reduced Ca extrusion via NCX at the t-tubules but not the surface membrane. Thus it appears that Ca extrusion via the sarcolemmal Ca ATPase occurs only at the t-tubules, and is not regulated by basal PKA activity, while Ca extrusion via NCX occurs across both the surface and t-tubule membranes, but predominantly across the t-tubule membrane due, in part, to localised stimulation of NCX by PKA at the t-tubules. This may be important in heart disease, in which changes in t-tubule structure and protein phosphorylation occur.
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Affiliation(s)
- Anabelle Chase
- Department of Physiology and Pharmacology, Faculty of Medical and Veterinary Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK
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Abstract
During activation of the sympathetic nervous system, cardiac performance is increased as part of the fight-or-flight stress response. The increase in contractility with sympathetic stimulation is an orchestrated combination of intrinsic inotropic, lusitropic, and chronotropic effects, mediated in part by activation of beta-adrenergic receptors and protein kinase A. This causes phosphorylation of several Ca cycling proteins in cardiac myocytes (increasing Ca entry via L-type Ca channels, sarcoplasmic reticulum Ca pumping, and the dissociation rate of Ca from the myofilaments). Here, we discuss how stimulation of the Na/K-ATPase, mediated by phosphorylation of phospholemman (a small sarcolemmal protein that associates with and modulates Na/K-ATPase), is an additional important player in the sympathetic fight-or-flight response. Enhancement of Na/K- ATPase activity limits the rise in [Na](i) caused by the higher level of Na influx and by doing so limits the rise in cellular and sarcoplasmic reticulum Ca load by favoring Ca extrusion via the Na/Ca exchanger. Thus, phospholemman-mediated activation of the Na/K-ATPase may prevent Ca overload and triggered arrhythmias during stress.
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Lin X, Jo H, Ishii TM, Fujita M, Fu M, Tambara K, Yamamoto M, Tabata Y, Komeda M, Matsuoka S. Controlled Release of Matrix Metalloproteinase-1 Plasmid DNA Prevents Left Ventricular Remodeling in Chronic Myocardial Infarction of Rats. Circ J 2009; 73:2315-21. [DOI: 10.1253/circj.cj-09-0379] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Xue Lin
- Department of Cardiovascular Surgery, Graduate School of Medicine, Kyoto University
- Human Health Sciences, Graduate School of Medicine, Kyoto University
| | - Hikari Jo
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University
| | - Takahiro M Ishii
- Department of Physiology, Neurobiology, Graduate School of Medicine, Kyoto University
| | - Masatoshi Fujita
- Human Health Sciences, Graduate School of Medicine, Kyoto University
| | - Michael Fu
- Department of Cardiovascular Research, Sahlgrenska University Hospital/Sahlgrenska, University of Göteborg
| | - Keiichi Tambara
- Department of Cardiovascular Surgery, Graduate School of Medicine, Kyoto University
| | - Masaya Yamamoto
- Department of Biomaterials, Field of Tissue Engineering, Institute for Frontier Medical Sciences, Kyoto University
| | - Yasuhiko Tabata
- Department of Biomaterials, Field of Tissue Engineering, Institute for Frontier Medical Sciences, Kyoto University
| | - Masashi Komeda
- Department of Cardiovascular Surgery, Graduate School of Medicine, Kyoto University
- Department of Cardiovascular Surgery, Nagoya Heart Center
| | - Satoshi Matsuoka
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University
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Shimizu J, Yamashita D, Misawa H, Tohne K, Matsuoka S, Kim B, Takeuchi A, Nakajima-Takenaka C, Takaki M. Increased O2 consumption in excitation-contraction coupling in hypertrophied rat heart slices related to increased Na+ -Ca2+ exchange activity. J Physiol Sci 2009; 59:63-74. [PMID: 19340563 PMCID: PMC10717199 DOI: 10.1007/s12576-008-0006-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Accepted: 10/31/2008] [Indexed: 10/20/2022]
Abstract
The goal of our study was to evaluate the origin of the increased O(2) consumption in electrically stimulated left ventricular slices of isoproterenol-induced hypertrophied rat hearts with normal left ventricular pressure. O(2) consumption per minute (mVO(2)) of mechanically unloaded left ventricular slices was measured in the absence and presence of 1-Hz field stimulation. Basal metabolic mVO(2), i.e., mVO(2) without electrical stimulation, was significantly smaller, but mVO(2) for the total Ca(2+) handling in excitation-contraction coupling (E-C coupling mVO(2)), i.e., delta mVO(2) (=mVO(2) with stimulation - mVO(2) without stimulation), was significantly larger in the hypertrophied heart. Furthermore, the fraction of E-C coupling mVO(2) was markedly altered in the hypertrophied heart. Namely, mVO(2) consumed by sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2) was depressed by 40%; mVO(2) consumed by the Na(+)/K(+)-ATPase (NKA)-Na(+)/Ca(2+) exchange (NCX) coupling was increased by 100%. The depressed mVO(2) consumption by SERCA2 was supported by lower protein expressions of phosphorylated-Ser(16) phospholamban and SERCA2. The increase in NKA-NCX coupling mVO(2) was supported by marked augmentation of NCX current. However, the increase in NCX current was not due to the increase in NCX1 protein expression, but was attributable to attenuation of the intrinsic inactivation mechanisms. The present results demonstrated that the altered origin of the increased E-C coupling mVO(2) in hypertrophy was derived from decreased SERCA2 activity (1ATP: 2Ca(2+)) and increased NCX activity coupled to NKA activity (1ATP: Ca(2+)). Taken together, we conclude that the energetically less efficient Ca(2+) extrusion pathway evenly contributes to Ca(2+) handling in E-C coupling in the present hypertrophy model.
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Affiliation(s)
- Juichiro Shimizu
- Department of Physiology II, Nara Medical University, 840 Shijo-Cho, Kashihara, 634-8521 Japan
| | - Daisuke Yamashita
- Department of Physiology II, Nara Medical University, 840 Shijo-Cho, Kashihara, 634-8521 Japan
| | - Hiromi Misawa
- Department of Physiology II, Nara Medical University, 840 Shijo-Cho, Kashihara, 634-8521 Japan
| | - Kiyoe Tohne
- Department of Physiology II, Nara Medical University, 840 Shijo-Cho, Kashihara, 634-8521 Japan
| | - Satoshi Matsuoka
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501 Japan
| | - Bongju Kim
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501 Japan
| | - Ayako Takeuchi
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto, 606-8501 Japan
| | | | - Miyako Takaki
- Department of Physiology II, Nara Medical University, 840 Shijo-Cho, Kashihara, 634-8521 Japan
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25
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Zhang YH, Hancox JC. Regulation of cardiac Na+-Ca2+ exchanger activity by protein kinase phosphorylation--still a paradox? Cell Calcium 2008; 45:1-10. [PMID: 18614228 DOI: 10.1016/j.ceca.2008.05.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 04/14/2008] [Accepted: 05/27/2008] [Indexed: 11/18/2022]
Abstract
The cardiac Na+-Ca2+ exchanger (NCX) is an important regulator of intracellular ion homeostasis and cardiac function. Gaining insight into modulation of the NCX is therefore important in order to understand ion handling in the heart under physiological and pathological conditions. Typically, the functional contribution of the NCX is often regarded as "secondary" to the changes in luminal Na+ and Ca2+. Whilst it is well accepted that the NCX can be regulated by various factors, including the concentrations of transported ions, direct receptor-mediated modulation of the cardiac NCX is more controversial. Evidence from several different laboratories supports the notion that the cardiac NCX is a direct target of neurotransmitters and hormones and their downstream signalling pathways; however, the issue remains unresolved due to conflicting data showing a lack of direct modulation. The present review summarizes overall findings regarding the modulation of the cardiac NCX, in particular on molecular mechanisms of direct phosphorylation of NCX by beta-adrenergic/adenylate cyclase/protein kinase A and (for comparative purposes) on endothelin-1/protein kinase C signalling pathways. It also aims to consider whether it is currently possible to reconcile discrepancies between studies in the interpretation of the regulation of the cardiac NCX by agents stimulating the beta-adrenoceptor/PKA pathway.
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Affiliation(s)
- Yin Hua Zhang
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
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26
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Abstract
Calcium (Ca) is a universal intracellular second messenger. In muscle, Ca is best known for its role in contractile activation. However, in recent years the critical role of Ca in other myocyte processes has become increasingly clear. This review focuses on Ca signaling in cardiac myocytes as pertaining to electrophysiology (including action potentials and arrhythmias), excitation-contraction coupling, modulation of contractile function, energy supply-demand balance (including mitochondrial function), cell death, and transcription regulation. Importantly, although such diverse Ca-dependent regulations occur simultaneously in a cell, the cell can distinguish distinct signals by local Ca or protein complexes and differential Ca signal integration.
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Affiliation(s)
- Donald M Bers
- Department of Physiology and Cardiovascular Institute, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA.
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27
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Endothelial nitric oxide attenuates Na+/Ca2+ exchanger-mediated vasoconstriction in rat aorta. Br J Pharmacol 2008; 154:982-90. [PMID: 18469841 DOI: 10.1038/bjp.2008.178] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE The Na+/Ca2+ exchanger (NCX) may be an important modulator of Ca2+ entry and exit. The present study investigated whether NCX was affected by prostacyclin and nitric oxide (NO) released from the vascular endothelium, as NCX contains phosphorylation sites for PKA and PKG. EXPERIMENTAL APPROACH Rat aortic rings were set up in organ baths. Tension was measured across the ring with a force transducer. KEY RESULTS Lowering extracellular [Na+] ([Na+]o) to 1.18 mM induced vasoconstriction in rat endothelium-denuded aortic rings. This effect was blocked by the NCX inhibitor KB-R7943 (2-2-[4-(4-nitrobenzyloxy)phenyl] ethyl isothiourea methanesulphonate; 1 microM). In endothelium-intact aortic rings, decreasing [Na+]o did not constrict the aortic rings significantly, but after treatment with the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; 1 microM) or the NOS inhibitor L-NAME (N(omega)-nitro-L-arginine methyl ester; 50 microM), a vasoconstriction that was similar in size to that in endothelium-denuded preparations was evident. The vasorelaxation induced by the NO donor sodium nitroprusside sodium nitroprusside dihydrate (30 nM) was the same in the endothelium-denuded aortic rings preconstricted with either low Na+ (1.18 mM), the thromboxane A2 agonist U46619 (9,11-dideoxy-9alpha, 11alpha-methanoepoxy prostaglandin F(2alpha); 0.1 microM) or high K+ (80 mM). CONCLUSIONS AND IMPLICATIONS The results suggest that the endothelium inhibits NCX operation via guanylate cyclase/NO. This is stronger than for other constrictors such as phenylephrine and may relate to concomitant NCX-stimulated NO release from the endothelium. This finding may be important where NCX operates in reverse mode, such as during ischaemia, and highlights a new mechanism whereby the endothelium modulates Ca2+ homoeostasis in vascular smooth muscle.
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Despa S, Tucker AL, Bers DM. Phospholemman-mediated activation of Na/K-ATPase limits [Na]i and inotropic state during beta-adrenergic stimulation in mouse ventricular myocytes. Circulation 2008; 117:1849-55. [PMID: 18362230 DOI: 10.1161/circulationaha.107.754051] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Cardiac Na/K-ATPase (NKA) regulates intracellular Na ([Na](i)), which in turn affects intracellular Ca and thus contractility via Na/Ca exchange. Recent evidence shows that phosphorylation of the NKA-associated small transmembrane protein phospholemman (PLM) mediates beta-adrenergic-induced NKA stimulation. METHODS AND RESULTS Here, we tested whether PLM phosphorylation during beta-adrenergic activation limits the rise in [Na](i), Ca transient amplitude, and triggered arrhythmias in mouse ventricular myocytes. In myocytes from wild-type (WT) mice, [Na](i) increased on field stimulation at 2 Hz from 11.1+/-1.8 mmol/L to a plateau of 15.2+/-1.5 mmol/L. Isoproterenol induced a decrease in [Na](i) to 12.0+/-1.2 mmol/L. In PLM knockout (PLM-KO) mice in which beta-adrenergic stimulation does not activate NKA, [Na](i) also increased at 2 Hz (from 10.4+/-1.2 to 17.0+/-1.5 mmol/L) but was unaltered by isoproterenol. The PLM-mediated decrease in [Na](i) in WT mice could limit the isoproterenol-induced inotropic state. Indeed, the isoproterenol-induced increase in the amplitude of Ca transients was significantly smaller in the WT mice (5.2+/-0.4- versus 7.1+/-0.5-fold in PLM-KO mice). This also was the case for the sarcoplasmic reticulum Ca content, which increased by 1.27+/-0.09-fold in WT mice versus 1.53+/-0.09-fold in PLM-KO mice. The higher sarcoplasmic reticulum Ca content in PLM-KO versus WT mice was associated with an increased propensity for spontaneous Ca transients and contractions in PLM-KO mice. CONCLUSIONS These data suggest that PLM phosphorylation and NKA stimulation are an integral part of the sympathetic fight-or-flight response, tempering the rise in [Na](i) and cellular Ca loading and perhaps limiting Ca overload-induced arrhythmias.
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Affiliation(s)
- Sanda Despa
- Department of Physiology, Loyola University Chicago, Maywood, Ill, USA
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Kim B, Matsuoka S. Cytoplasmic Na+-dependent modulation of mitochondrial Ca2+ via electrogenic mitochondrial Na+-Ca2+ exchange. J Physiol 2008; 586:1683-97. [PMID: 18218682 DOI: 10.1113/jphysiol.2007.148726] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
To clarify the role of mitochondrial Na(+)-Ca(2+) exchange (NCX(mito)) in regulating mitochondrial Ca(2+) (Ca(2+)(mito)) concentration at intact and depolarized mitochondrial membrane potential (DeltaPsi(mito)), we measured Ca(2+)(mito) and DeltaPsi(mito) using fluorescence probes Rhod-2 and TMRE, respectively, in the permeabilized rat ventricular cells. Applying 300 nm cytoplasmic Ca(2+) (Ca(2+)(c)) increased Ca(2+)(mito) and this increase was attenuated by cytoplasmic Na(+) (Na(+)(c)) with an IC(50) of 2.4 mm. To the contrary, when DeltaPsi(mito) was depolarized by FCCP, a mitochondrial uncoupler, Na(+)(c) enhanced the Ca(2+)(c)-induced increase in Ca(2+)(mito) with an EC(50) of about 4 mm. This increase was not significantly affected by ruthenium red or cyclosporin A. The inhibition of NCX(mito) by CGP-37157 further increased Ca(2+)(mito) when DeltaPsi(mito) was intact, while it suppressed the Ca(2+)(mito) increase when DeltaPsi(mito) was depolarized, suggesting that DeltaPsi(mito) depolarization changed the exchange mode from forward to reverse. Furthermore, DeltaPsi(mito) depolarization significantly reduced the Ca(2+)(mito) decrease via forward mode, and augmented the Ca(2+)(mito) increase via reverse mode. When the respiratory chain was attenuated, the induction of the reverse mode of NCX(mito) hyperpolarized DeltaPsi(mito), while DeltaPsi(mito) depolarized upon inducing the forward mode of NCX(mito). Both changes in DeltaPsi(mito) were remarkably inhibited by CGP-37157. The above experimental data indicated that NCX(mito) is voltage dependent and electrogenic. This notion was supported theoretically by computer simulation studies with an NCX(mito) model constructed based on present and previous studies, presuming a consecutive and electrogenic Na(+)-Ca(2+) exchange and a depolarization-induced increase in Na(+) flux. It is concluded that Ca(2+)(mito) concentration is dynamically modulated by Na(+)(c) and DeltaPsi(mito) via electrogenic NCX(mito).
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Affiliation(s)
- Bongju Kim
- Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
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30
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Affiliation(s)
- David E Stec
- Department of Physiology and Biophysics, Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, MS 39216-4505, USA.
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Kuzumoto M, Takeuchi A, Nakai H, Oka C, Noma A, Matsuoka S. Simulation analysis of intracellular Na+ and Cl− homeostasis during β1-adrenergic stimulation of cardiac myocyte. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2008; 96:171-86. [PMID: 17826821 DOI: 10.1016/j.pbiomolbio.2007.07.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
To quantitatively understand intracellular Na+ and Cl- homeostasis as well as roles of Na+/K+ pump and cystic fibrosis transmembrane conductance regulator Cl- channel (ICFTR) during the beta1-adrenergic stimulation in cardiac myocyte, we constructed a computer model of beta1-adrenergic signaling and implemented it into an excitation-contraction coupling model of the guinea-pig ventricular cell, which can reproduce membrane excitation, intracellular ion changes (Na+, K+, Ca2+ and Cl-), contraction, cell volume, and oxidative phosphorylation. An application of isoproterenol to the model cell resulted in the shortening of action potential duration (APD) after a transient prolongation, the increases in both Ca2+ transient and cell shortening, and the decreases in both Cl- concentration and cell volume. These results are consistent with experimental data. Increasing the density of ICFTR shortened APD and augmented the peak amplitudes of the L-type Ca2+ current (ICaL) and the Ca2+ transient during the beta1-adrenergic stimulation. This indirect inotropic effect was elucidated by the increase in the driving force of ICaL via a decrease in plateau potential. Our model reproduced the experimental data demonstrating the decrease in intracellular Na+ during the beta-adrenergic stimulation at 0 or 0.5 Hz electrical stimulation. The decrease is attributable to the increase in Na+ affinity of Na+/K+ pump by protein kinase A. However it was predicted that Na+increases at higher beating rate because of larger Na+ influx through forward Na+/Ca2+ exchange. It was demonstrated that dynamic changes in Na+ and Cl- fluxes remarkably affect the inotropic action of isoproterenol in the ventricular myocytes.
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Affiliation(s)
- Masanori Kuzumoto
- Cell/Biodynamics Simulation Project Kyoto University, Graduate School of Medicine, Kyoto University, Japan
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32
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Abstract
Mammalian Na+/Ca2+ exchangers are members of three branches of a much larger family of transport proteins [the CaCA (Ca2+/cation antiporter) superfamily] whose main role is to provide control of Ca2+ flux across the plasma membranes or intracellular compartments. Since cytosolic levels of Ca2+ are much lower than those found extracellularly or in sequestered stores, the major function of Na+/Ca2+ exchangers is to extrude Ca2+ from the cytoplasm. The exchangers are, however, fully reversible and thus, under special conditions of subcellular localization and compartmentalized ion gradients, Na+/Ca2+ exchangers may allow Ca2+ entry and may play more specialized roles in Ca2+ movement between compartments. The NCX (Na+/Ca2+ exchanger) [SLC (solute carrier) 8] branch of Na+/Ca2+ exchangers comprises three members: NCX1 has been most extensively studied, and is broadly expressed with particular abundance in heart, brain and kidney, NCX2 is expressed in brain, and NCX3 is expressed in brain and skeletal muscle. The NCX proteins subserve a variety of roles, depending upon the site of expression. These include cardiac excitation-contraction coupling, neuronal signalling and Ca2+ reabsorption in the kidney. The NCKX (Na2+/Ca2+-K+ exchanger) (SLC24) branch of Na+/Ca2+ exchangers transport K+ and Ca2+ in exchange for Na+, and comprises five members: NCKX1 is expressed in retinal rod photoreceptors, NCKX2 is expressed in cone photoreceptors and in neurons throughout the brain, NCKX3 and NCKX4 are abundant in brain, but have a broader tissue distribution, and NCKX5 is expressed in skin, retinal epithelium and brain. The NCKX proteins probably play a particularly prominent role in regulating Ca2+ flux in environments which experience wide and frequent fluctuations in Na+ concentration. Until recently, the range of functions that NCKX proteins play was generally underappreciated. This situation is now changing rapidly as evidence emerges for roles including photoreceptor adaptation, synaptic plasticity and skin pigmentation. The CCX (Ca2+/cation exchanger) branch has only one mammalian member, NCKX6 or NCLX (Na+/Ca2+-Li+ exchanger), whose physiological function remains unclear, despite a broad pattern of expression.
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Affiliation(s)
- Jonathan Lytton
- Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
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33
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Török TL. Electrogenic Na+/Ca2+-exchange of nerve and muscle cells. Prog Neurobiol 2007; 82:287-347. [PMID: 17673353 DOI: 10.1016/j.pneurobio.2007.06.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 04/12/2007] [Accepted: 06/12/2007] [Indexed: 12/19/2022]
Abstract
The plasma membrane Na(+)/Ca(2+)-exchanger is a bi-directional electrogenic (3Na(+):1Ca(2+)) and voltage-sensitive ion transport mechanism, which is mainly responsible for Ca(2+)-extrusion. The Na(+)-gradient, required for normal mode operation, is created by the Na(+)-pump, which is also electrogenic (3Na(+):2K(+)) and voltage-sensitive. The Na(+)/Ca(2+)-exchanger operational modes are very similar to those of the Na(+)-pump, except that the uncoupled flux (Na(+)-influx or -efflux?) is missing. The reversal potential of the exchanger is around -40 mV; therefore, during the upstroke of the AP it is probably transiently activated, leading to Ca(2+)-influx. The Na(+)/Ca(2+)-exchange is regulated by transported and non-transported external and internal cations, and shows ATP(i)-, pH- and temperature-dependence. The main problem in determining the role of Na(+)/Ca(2+)-exchange in excitation-secretion/contraction coupling is the lack of specific (mode-selective) blockers. During recent years, evidence has been accumulated for co-localisation of the Na(+)-pump, and the Na(+)/Ca(2+)-exchanger and their possible functional interaction in the "restricted" or "fuzzy space." In cardiac failure, the Na(+)-pump is down-regulated, while the exchanger is up-regulated. If the exchanger is working in normal mode (Ca(2+)-extrusion) during most of the cardiac cycle, upregulation of the exchanger may result in SR Ca(2+)-store depletion and further impairment in contractility. If so, a normal mode selective Na(+)/Ca(2+)-exchange inhibitor would be useful therapy for decompensation, and unlike CGs would not increase internal Na(+). In peripheral sympathetic nerves, pre-synaptic alpha(2)-receptors may regulate not only the VSCCs but possibly the reverse Na(+)/Ca(2+)-exchange as well.
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Affiliation(s)
- Tamás L Török
- Department of Pharmacodynamics, Semmelweis University, P.O. Box 370, VIII. Nagyvárad-tér 4, H-1445 Budapest, Hungary.
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34
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Reppel M, Fleischmann BK, Reuter H, Pillekamp F, Schunkert H, Hescheler J. Regulation of Na+/Ca2+ exchange current in the normal and failing heart. Ann N Y Acad Sci 2007; 1099:361-72. [PMID: 17446476 DOI: 10.1196/annals.1387.065] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cardiac NCX is modulated by diverse regulatory elements. Although there is consensus about the regulatory function of Na+ and Ca2+ and other elements, for example, ATP, there is still a controversial debate about the functional role of cyclic nucleotides and protein kinases. Future studies should focus on that topic since disturbances of cAMP/cGMP concentration and kinase activity may lead to severe functional disorders in the diseased heart. S100A1 is presumably a novel regulator of NCX.
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Affiliation(s)
- Michael Reppel
- Institute of Neurophysiology, University of Cologne, D-50931 Cologne, Germany.
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35
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Shigekawa M, Katanosaka Y, Wakabayashi S. Regulation of the cardiac Na+/Ca2+ exchanger by calcineurin and protein kinase C. Ann N Y Acad Sci 2007; 1099:53-63. [PMID: 17446445 DOI: 10.1196/annals.1387.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Na+/Ca2+ exchanger (NCX) activity is markedly inhibited in hypertrophic neonatal rat cardiomyocytes subjected to chronic phenylephrine treatment. This inhibition is reversed partially and independently by acute inhibition of calcineurin and protein kinase C (PKC) activities. Similar NCX inhibition occurs in CCL39 cells expressing cloned wild-type NCX1, when they are infected with adenoviral vectors carrying activated calcineurin A and then treated acutely with phorbol myristoyl acetate or protein phosphatase-1 inhibitors. The data obtained with these cells suggest that calcineurin activity, PKCalpha-mediated NCX1 phosphorylation, and the central loop of NCX1 (possibly its beta1 repeat) are required for the observed NCX inhibition. We observe partial inhibition of NCX activity independent of NCX1 phosphorylation when CCL39 cells are infected with activated calcineurin A but not further treated with phorbol myristoyl acetate or phosphatase inhibitors. Calcineurin thus appears to downregulate NCX activity via two independent mechanisms, one involving NCX1 phosphorylation and the other not involving NCX1 phosphorylation. These data indicate the existence of a novel regulatory mechanism for NCX1 involving calcineurin and PKC, which may be important in cardiac pathology.
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Affiliation(s)
- Munekazu Shigekawa
- Department of Human Life Sciences, Senri-Kinran University, Fujishiro-dai 5-25-1, Suita, Osaka 565-0873, Japan.
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Nath KA, d'Uscio LV, Juncos JP, Croatt AJ, Manriquez MC, Pittock ST, Katusic ZS. An analysis of the DOCA-salt model of hypertension in HO-1-/- mice and the Gunn rat. Am J Physiol Heart Circ Physiol 2007; 293:H333-42. [PMID: 17351069 DOI: 10.1152/ajpheart.00870.2006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heme oxygenase-1 (HO-1) is induced in the vasculature in the DOCA-salt model of hypertension in rats. Whereas the HO system and its products may exert vasodilator effects, recent studies have suggested that the HO system may predispose to hypertension. The present study examined the effects of selected components of the HO system, specifically, the HO-1 isozyme and the product bilirubin in the DOCA-salt model of systemic hypertension; the experimental approach employed mutant rodent models, namely, the HO-1(-/-) mouse and the hyperbilirubinemic Gunn rat. DOCA-salt induced HO-1 protein in the aorta in HO-1(+/+) mice and provoked a significant rise in systolic arterial pressure in HO-1(-/-) mice but not in HO-1(+/+) mice; this effect could not be ascribed to impaired urinary sodium excretion or impaired glomerular filtration rate in the DOCA-salt-treated HO-1(-/-) mice. The administration of DOCA salt to uninephrectomized rats significantly increased systolic arterial pressure in wild-type rats, an effect that was attenuated in the mutant Gunn rat; this reduction in systemic hypertension in the DOCA-salt-treated Gunn rat was not due to a greater induction of HO-1 in the vasculature or to a more avid urinary sodium excretion. DOCA-salt impaired endothelium-dependent and endothelium-independent vasorelaxation in wild-type rats but not in Gunn rats; prior exposure to bilirubin repaired the defect in endothelium-dependent vasorelaxation in aortic rings in DOCA-salt-treated rats. DOCA salt stimulated vascular production of superoxide anion in wild-type but not in Gunn rats. We suggest that HO-1 and the product bilirubin may exert a countervailing effect in the DOCA-salt model of systemic hypertension.
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Affiliation(s)
- Karl A Nath
- Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
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Wei SK, Ruknudin AM, Shou M, McCurley JM, Hanlon SU, Elgin E, Schulze DH, Haigney MCP. Muscarinic modulation of the sodium-calcium exchanger in heart failure. Circulation 2007; 115:1225-33. [PMID: 17339552 DOI: 10.1161/circulationaha.106.650416] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The Na-Ca exchanger (NCX) is a critical calcium efflux pathway in excitable cells, but little is known regarding its autonomic regulation. METHODS AND RESULTS We investigated beta-adrenergic receptor and muscarinic receptor regulation of the cardiac NCX in control and heart failure (HF) conditions in atrially paced pigs. NCX current in myocytes from control swine hearts was significantly increased by isoproterenol, and this response was reversed by concurrent muscarinic receptor stimulation with the addition of carbachol, demonstrating "accentuated antagonism." Okadaic acid eliminated the inhibitory effect of carbachol on isoproterenol-stimulated NCX current, indicating that muscarinic receptor regulation operates via protein phosphatase-induced dephosphorylation. However, in myocytes from atrially paced tachycardia-induced HF pigs, the NCX current was significantly larger at baseline but less responsive to isoproterenol compared with controls, whereas carbachol failed to inhibit isoproterenol-stimulated NCX current, and 8-Br-cGMP did not restore muscarinic responsiveness. Protein phosphatase type 1 dialysis significantly reduced NCX current in failing but not control cells, consistent with NCX hyperphosphorylation in HF. Protein phosphatase type 1 levels associated with NCX were significantly depressed in HF pigs compared with control, and total phosphatase activity associated with NCX was significantly decreased. CONCLUSIONS We conclude that the NCX is autonomically modulated, but HF reduces the level and activity of associated phosphatases; defective dephosphorylation then "locks" the exchanger in a highly active state.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Animals
- Carbachol/pharmacology
- Cardiac Pacing, Artificial
- Cell Separation
- Cells, Cultured
- Cyclic GMP/analogs & derivatives
- Cyclic GMP/pharmacology
- Disease Models, Animal
- Drug Antagonism
- Female
- Heart Failure/complications
- Heart Failure/metabolism
- Isoproterenol/pharmacology
- Male
- Muscarinic Agonists/pharmacology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Niflumic Acid/pharmacology
- Patch-Clamp Techniques
- Phosphoprotein Phosphatases/metabolism
- Phosphorylation
- Receptors, Adrenergic, beta/drug effects
- Receptors, Adrenergic, beta/metabolism
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/metabolism
- Sodium-Calcium Exchanger/metabolism
- Swine
- Tachycardia/complications
- Tachycardia/metabolism
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Affiliation(s)
- Shao-kui Wei
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD 20814, USA
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Ruknudin AM, Wei SK, Haigney MC, Lederer WJ, Schulze DH. Phosphorylation and Other Conundrums of Na/Ca Exchanger, NCX1. Ann N Y Acad Sci 2007; 1099:103-18. [PMID: 17446449 DOI: 10.1196/annals.1387.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The Na+/Ca2+ exchanger (NCX) is an important Ca2+ transport mechanism in virtually all cells in the body. There are three genes that control the expression of NCX in mammals. There are at least 16 alternatively spliced isoforms of NCX1 that target muscle and nerve and other tissues. Here we briefly discuss three remarkable regulatory issues or "conundrums" that involve the most prevalently expressed gene, NCX1. (1) How is NCX1 regulated by phosphorylation? We suggest that the macromolecular complex of NCX1 plays a critical role in the regulation of NCX. The role of the macromolecular complex and evidence supporting its existence and functional importance is presented. (2) Can there be transport block of a single "mode" of NCX1 transport by drugs or therapeutic agents? The simple answer is "no." A brief explanation is provided. (3) How can NCX1 knockout mice live? The answer is "by other compensatory regulatory mechanisms." These conundrums highlight important features in NCX1 and lay the foundation for new experiments to elucidate function and regulation of NCX1 and provide a context for investigations that seek to understand novel therapeutic agents.
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Affiliation(s)
- Abdul M Ruknudin
- Department of Microbiology and Immunology, 660 W. Redwood Street, Baltimore, MD 21201, USA.
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Yamamoto S, Ichishima K, Ehara T. Regulation of extracellular UTP-activated Cl- current by P2Y-PLC-PKC signaling and ATP hydrolysis in mouse ventricular myocytes. J Physiol Sci 2007; 57:85-94. [PMID: 17291397 DOI: 10.2170/physiolsci.rp011406] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Accepted: 02/08/2007] [Indexed: 11/05/2022]
Abstract
The intracellular signaling pathways responsible for extracellualr uridine-5'-triphosphate (UTPo)-induced chloride (Cl-) currents (I(Cl.UTP)) were studied in mouse ventricular myocytes with the whole-cell clamp technique. UTPo (0.1 to 100 microM) activated a whole-cell current that showed a time-independent activation, a linear current-voltage relationship in symmetrical Cl- solutions, an anion selectivity of Cl- > iodide > aspartate, and an inhibition by a thiazolidinone-derived specific inhibitor (CFTR(inh)-172, 10 microM) of cystic fibrosis transmembrane conductance regulator (CFTR), but not by a disulfonic stilbene derivative (DIDS, 100 microM), these properties matching those of CFTR Cl- channels. The potency order of nucleotides for an activation of the Cl- current was UTP = ATP > uridine-5'-diphosphate (UDP) = ADP. Suramin (100 microM), a P2Y receptor antagonist, strongly inhibited the UTPo -activation of the Cl- current, whereas pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS, 100 microM), another P2Y receptor antagonist, induced little inhibition of I(Cl.UTP). The activation of I(Cl.UTP) was sensitive to protein kinase C (PKC) inhibitor, phospholipase C (PLC) inhibitor, intracellular GDPbetaS (nonhydrolyzable GDP analogue) or anti-Gq/11 antibody. UTPo failed to activate the Cl- current when the cells were dialyzed with nonhydrolyzable ATP analogues (ATPS or AMP-PNP) without ATP, suggesting that ATP hydrolysis is a prerequisite for the current activation. I(Cl.UTP) was persistently activated with a mixture of ATPgammaS + ATP in the pipette, suggesting the involvement of phosphorylation reaction in the current activation process. Our results strongly suggest that I(Cl.UTP) is due to the activation of CFTR Cl- channels through Gq/11-coupled P2Y2 receptor-PLC-PKC signaling and ATP hydrolysis in mouse heart.
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Affiliation(s)
- Shintaro Yamamoto
- Department of Physiology, Saga University Faculty of Medicine, Saga, 849-8501 Japan.
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Dulhunty AF, Beard NA, Pouliquin P, Casarotto MG. Agonists and antagonists of the cardiac ryanodine receptor: Potential therapeutic agents? Pharmacol Ther 2007; 113:247-63. [PMID: 17055586 DOI: 10.1016/j.pharmthera.2006.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Accepted: 08/16/2006] [Indexed: 10/24/2022]
Abstract
This review addresses the potential use of the intracellular ryanodine receptor (RyR) Ca(2+) release channel as a therapeutic target in heart disease. Heart disease encompasses a wide range of conditions with the major contributors to mortality and morbidity being ischaemic heart disease and heart failure (HF). In addition there are many rare, but devastating conditions, some of which are either genetically linked to the RyR and its regulatory proteins or involve drug-induced modification of the proteins. The defects in Ca(2+) signalling vary with the nature of the heart disease and the stage in its progress and therefore specific corrections require different modifications of Ca(2+) signalling. Compounds that activate the RyR are potential inotropic agents to increase the Ca(2+) transient and strength of contraction. Compounds that reduce RyR activity are potentially useful in conditions where excess RyR activity initiates arrhythmias, or depletes the Ca(2+) store, as in end stage HF. It has recently been discovered that the cardio-protective action of the drug JTV519 can be attributed partly to its ability to stabilise the interaction between the RyR and the 12.6 kDa binding protein for the commonly used immunosuppressive drug FK506 (FKBP12.6, known as tacrolimus). This has established the credibility of the RyR as a therapeutic target. We explore the possibility that mutations causing the rare RyR-linked arrhythmias will open the door to identification of novel RyR-based therapeutic agents. The use of regulatory binding sites within the RyR complex or on its associated proteins as templates for drug design is discussed.
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Affiliation(s)
- Angela F Dulhunty
- Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, P.O. Box 334, ACT, 2601, Australia
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Takeuchi A, Tatsumi S, Sarai N, Terashima K, Matsuoka S, Noma A. Ionic mechanisms of cardiac cell swelling induced by blocking Na+/K+ pump as revealed by experiments and simulation. J Gen Physiol 2006; 128:495-507. [PMID: 17074975 PMCID: PMC2151580 DOI: 10.1085/jgp.200609646] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 09/28/2006] [Indexed: 11/20/2022] Open
Abstract
Although the Na(+)/K(+) pump is one of the key mechanisms responsible for maintaining cell volume, we have observed experimentally that cell volume remained almost constant during 90 min exposure of guinea pig ventricular myocytes to ouabain. Simulation of this finding using a comprehensive cardiac cell model (Kyoto model incorporating Cl(-) and water fluxes) predicted roles for the plasma membrane Ca(2+)-ATPase (PMCA) and Na(+)/Ca(2+) exchanger, in addition to low membrane permeabilities for Na(+) and Cl(-), in maintaining cell volume. PMCA might help maintain the [Ca(2+)] gradient across the membrane though compromised, and thereby promote reverse Na(+)/Ca(2+) exchange stimulated by the increased [Na(+)](i) as well as the membrane depolarization. Na(+) extrusion via Na(+)/Ca(2+) exchange delayed cell swelling during Na(+)/K(+) pump block. Supporting these model predictions, we observed ventricular cell swelling after blocking Na(+)/Ca(2+) exchange with KB-R7943 or SEA0400 in the presence of ouabain. When Cl(-) conductance via the cystic fibrosis transmembrane conductance regulator (CFTR) was activated with isoproterenol during the ouabain treatment, cells showed an initial shrinkage to 94.2 +/- 0.5%, followed by a marked swelling 52.0 +/- 4.9 min after drug application. Concomitantly with the onset of swelling, a rapid jump of membrane potential was observed. These experimental observations could be reproduced well by the model simulations. Namely, the Cl(-) efflux via CFTR accompanied by a concomitant cation efflux caused the initial volume decrease. Then, the gradual membrane depolarization induced by the Na(+)/K(+) pump block activated the window current of the L-type Ca(2+) current, which increased [Ca(2+)](i). Finally, the activation of Ca(2+)-dependent cation conductance induced the jump of membrane potential, and the rapid accumulation of intracellular Na(+) accompanied by the Cl(-) influx via CFTR, resulting in the cell swelling. The pivotal role of L-type Ca(2+) channels predicted in the simulation was demonstrated in experiments, where blocking Ca(2+) channels resulted in a much delayed cell swelling.
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Affiliation(s)
- Ayako Takeuchi
- Cell/Biodynamics Simulation Project and Department of Physiology and Biophysics, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan
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Haigney MCP, Wei SK, Schulze DH, Ruknudin AM, Matsuoka S. Response to “β-adrenergic stimulation does not activate Na+/Ca2+ exchange current in guinea pig, mouse, and rat ventricular myocytes”. Am J Physiol Cell Physiol 2006; 290:C1271; author reply C1271-2. [PMID: 16531570 DOI: 10.1152/ajpcell.00541.2005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Zhang XQ, Ahlers BA, Tucker AL, Song J, Wang J, Moorman JR, Mounsey JP, Carl LL, Rothblum LI, Cheung JY. Phospholemman inhibition of the cardiac Na+/Ca2+ exchanger. Role of phosphorylation. J Biol Chem 2006; 281:7784-92. [PMID: 16434394 PMCID: PMC1405234 DOI: 10.1074/jbc.m512092200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have demonstrated previously that phospholemman (PLM), a 15-kDa integral sarcolemmal phosphoprotein, inhibits the cardiac Na+/Ca2+ exchanger (NCX1). In addition, protein kinase A phosphorylates serine 68, whereas protein kinase C phosphorylates both serine 63 and serine 68 of PLM. Using human embryonic kidney 293 cells that are devoid of both endogenous PLM and NCX1, we first demonstrated that the exogenous NCX1 current (I(NaCa)) was increased by phorbol 12-myristate 13-acetate (PMA) but not by forskolin. When co-expressed with NCX1, PLM resulted in: (i) decreases in I(NaCa), (ii) attenuation of the increase in I(NaCa) by PMA, and (iii) additional reduction in I(NaCa) in cells treated with forskolin. Mutating serine 63 to alanine (S63A) preserved the sensitivity of PLM to forskolin in terms of suppression of I(NaCa), whereas mutating serine 68 to alanine (S68A) abolished the inhibitory effect of PLM on I(NaCa). Mutating serine 68 to glutamic acid (phosphomimetic) resulted in additional suppression of I(NaCa) as compared with wild-type PLM. These results suggest that PLM phosphorylated at serine 68 inhibited I(NaCa). The physiological significance of inhibition of NCX1 by phosphorylated PLM was evaluated in PLM-knock-out (KO) mice. When compared with wild-type myocytes, I(NaCa) was significant larger in PLM-KO myocytes. In addition, the PMA-induced increase in I(NaCa) was significantly higher in PLM-KO myocytes. By contrast, forskolin had no effect on I(NaCa) in wild-type myocytes. We conclude that PLM, when phosphorylated at serine 68, inhibits Na+/Ca2+ exchange in the heart.
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Key Words
- anova, analysis of variance
- 8-br-camp, 8-bromoadenosine 3′, 5′ cyclic monophosphate
- [ca2+]o, extracellular ca2+ concentration; cm, whole cell membrane capacitance
- cmv, cytomegalovirus
- dmem, dulbecco’s modified eagle’s medium
- dmso, dimethylsulfoxide
- egta, ethylene glycol-bis-(β-aminoethyl ether)n,n,n’,n’-tetraacetic acid
- em, membrane potential
- em., emission
- ex., excitation
- enaca, equilibrium potential for na+, ca2+ exchange current
- fbs, fetal bovine serum
- gfp, green fluorescent protein
- hek, human embryonic kidney
- hepes, n-2-hydroxyethylpiperazine-n’-2-ethanesulfonic acid
- inaca, na+, ca2+ exchange current
- ko, knock-out
- mem, minimal essential media
- ncx1, na+, ca2+ exchanger
- nima, never in mitosis a
- pka, protein kinase a
- pkc, protein kinase c
- plm, phospholemman
- pma, phorbol 12-myristate 13-acetate
- pmsf, phenylmethylsulfonyl fluoride
- pvdf, polyvinylidene difluoride
- se, standard error
- serca2, sarco(endo)plasmic reticulum ca2+-atpase
- sr, sarcoplasmic reticulum
- sds-page, sodium dodecyl sulfate- polyacrylamide gel electrophoresis
- vmax, maximum velocity
- wt, wild-type
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Affiliation(s)
| | | | - Amy L. Tucker
- Department of Internal Medicine (Cardiovascular Division), University of Virginia Health Sciences Center, Charlottesville, VA 22908
| | | | - JuFang Wang
- Department of Cellular and Molecular Physiology and
| | - J. Randall Moorman
- Department of Internal Medicine (Cardiovascular Division), University of Virginia Health Sciences Center, Charlottesville, VA 22908
| | - J. Paul Mounsey
- Department of Internal Medicine (Cardiovascular Division), University of Virginia Health Sciences Center, Charlottesville, VA 22908
| | - Lois L. Carl
- Department of Cellular and Molecular Physiology and
| | | | - Joseph Y. Cheung
- Department of Cellular and Molecular Physiology and
- Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey, PA 17033
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