1
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Boileve A, Romito O, Hof T, Levallois A, Brard L, d'Hers S, Fouchet A, Simard C, Guinamard R, Brette F, Sallé L. EPAC1 and 2 inhibit K + currents via PLC/PKC and NOS/PKG pathways in rat ventricular cardiomyocytes. Am J Physiol Cell Physiol 2024; 327:C557-C570. [PMID: 38985989 DOI: 10.1152/ajpcell.00582.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 05/29/2024] [Accepted: 06/19/2024] [Indexed: 07/12/2024]
Abstract
The exchange protein directly activated by cAMP (EPAC) has been implicated in cardiac proarrhythmic signaling pathways including spontaneous diastolic Ca2+ leak from sarcoplasmic reticulum and increased action potential duration (APD) in isolated ventricular cardiomyocytes. The action potential (AP) lengthening following acute EPAC activation is mainly due to a decrease of repolarizing steady-state K+ current (IKSS) but the mechanisms involved remain unknown. This study aimed to assess the role of EPAC1 and EPAC2 in the decrease of IKSS and to investigate the underlying signaling pathways. AP and K+ currents were recorded with the whole cell configuration of the patch-clamp technique in freshly isolated rat ventricular myocytes. EPAC1 and EPAC2 were pharmacologically activated with 8-(4-chlorophenylthio)-2'-O-methyl-cAMP acetoxymethyl ester (8-CPTAM, 10 µmol/L) and inhibited with R-Ce3F4 and ESI-05, respectively. Inhibition of EPAC1 and EPAC2 significantly decreased the effect of 8-CPTAM on APD and IKSS showing that both EPAC isoforms are involved in these effects. Unexpectedly, calmodulin-dependent protein kinase II (CaMKII) inhibition by AIP or KN-93, and Ca2+ chelation by intracellular BAPTA, did not impact the response to 8-CPTAM. However, inhibition of PLC/PKC and nitric oxide synthase (NOS)/PKG pathways partially prevents the 8-CPTAM-dependent decrease of IKSS. Finally, the cumulative inhibition of PKC and PKG blocked the 8-CPTAM effect, suggesting that these two actors work along parallel pathways to regulate IKSS upon EPAC activation. On the basis of such findings, we propose that EPAC1 and EPAC2 are involved in APD lengthening by inhibiting a K+ current via both PLC/PKC and NOS/PKG pathways. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy.NEW & NOTEWORHTY Exchange protein directly activated by cAMP (EPAC) proteins modulate ventricular electrophysiology at the cellular level. Both EPAC1 and EPAC2 isoforms participate in this effect. Mechanistically, PLC/PKC and nitric oxide synthase (NO)/PKG pathways are involved in regulating K+ repolarizing current whereas the well-known downstream effector of EPAC, calmodulin-dependent protein kinase II (CaMKII), does not participate. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy. Thus, EPAC inhibition may be a new approach to prevent arrhythmias under pathological conditions.
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Affiliation(s)
- Arthur Boileve
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Olivier Romito
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Thomas Hof
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Aurélia Levallois
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Laura Brard
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Sarah d'Hers
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Alexandre Fouchet
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Christophe Simard
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Romain Guinamard
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
| | - Fabien Brette
- PhyMedExp, INSERM U1046, CNRS 9412, Université de Montpellier, Montpellier, France
| | - Laurent Sallé
- UR 4650 PSIR, GIP Cyceron, Caen, France
- Normandie University, Caen, France
- UNICAEN, Caen, France
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2
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Franco D, Hove-Madsen L, Daimi H. Editorial: Molecular, structural and electrophysiological remodeling in atrial fibrillation. Front Physiol 2023; 14:1303328. [PMID: 37900957 PMCID: PMC10602880 DOI: 10.3389/fphys.2023.1303328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 10/09/2023] [Indexed: 10/31/2023] Open
Affiliation(s)
- Diego Franco
- Cardiovascular Development Group, Department of Experimental Biology, University of Jaén, Jaén, Spain
- Fundación Medina, Granada, Spain
| | - Leif Hove-Madsen
- Cardiac Rhythm and Contraction Group, Department of Experimental Pathology, Biomedical Research Institute of Barcelona (IIBB-CSIC), Barcelona, Spain
- Biomedical Research Institute Sant Pau, (IIB, Sant Pau), Barcelona, Spain
- CIBER Enfermedades Cardiovasculares (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Houria Daimi
- Laboratory of Human Genome and Multifactorial Diseases (LR12ES07), Faculty of Pharmacy, University of Monastir, Monastir, Tunisia
- Department of Biology, Faculty of Sciences, University of Gabès, Gabès, Tunisia
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3
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Guillot B, Boileve A, Walton R, Harfoush A, Conte C, Sainte-Marie Y, Charron S, Bernus O, Recalde A, Sallé L, Brette F, Lezoualc'h F. Inhibition of EPAC1 signaling pathway alters atrial electrophysiology and prevents atrial fibrillation. Front Physiol 2023; 14:1120336. [PMID: 36909224 PMCID: PMC9992743 DOI: 10.3389/fphys.2023.1120336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 02/09/2023] [Indexed: 02/24/2023] Open
Abstract
Introduction: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with increased mortality and morbidity. The Exchange Protein directly Activated by cAMP (EPAC), has been implicated in pro-arrhythmic signaling pathways in the atria, but the underlying mechanisms remain unknown. Methods: In this study, we investigated the involvement of EPAC1 and EPAC2 isoforms in the genesis of AF in wild type (WT) mice and knockout (KO) mice for EPAC1 or EPAC2. We also employed EPAC pharmacological modulators to selectively activate EPAC proteins (8-CPT-AM; 10 μM), or inhibit either EPAC1 (AM-001; 20 μM) or EPAC2 (ESI-05; 25 μM). Transesophageal stimulation was used to characterize the induction of AF in vivo in mice. Optical mapping experiments were performed on isolated mouse atria and cellular electrophysiology was examined by whole-cell patch-clamp technique. Results: In wild type mice, we found 8-CPT-AM slightly increased AF susceptibility and that this was blocked by the EPAC1 inhibitor AM-001 but not the EPAC2 inhibitor ESI-05. Consistent with this, in EPAC1 KO mice, occurrence of AF was observed in 3/12 (vs. 4/10 WT littermates) and 4/10 in EPAC2 KO (vs. 5/10 WT littermates). In wild type animals, optical mapping experiments revealed that 8-CPT-AM perfusion increased action potential duration even in the presence of AM-001 or ESI-05. Interestingly, 8-CPT-AM perfusion decreased conduction velocity, an effect blunted by AM-001 but not ESI-05. Patch-clamp experiments demonstrated action potential prolongation after 8-CPT-AM perfusion in both wild type and EPAC1 KO mice and this effect was partially prevented by AM-001 in WT. Conclusion: Together, these results indicate that EPAC1 and EPAC2 signaling pathways differentially alter atrial electrophysiology but only the EPAC1 isoform is involved in the genesis of AF. Selective blockade of EPAC1 with AM-001 prevents AF in mice.
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Affiliation(s)
- Bastien Guillot
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France
| | - Arthur Boileve
- UR 4650 PSIR, GIP Cyceron, Caen, France.,Université de Caen-Normandie, Caen, France
| | - Richard Walton
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France
| | - Alexandre Harfoush
- UR 4650 PSIR, GIP Cyceron, Caen, France.,Université de Caen-Normandie, Caen, France
| | - Caroline Conte
- Université de Toulouse-Paul Sabatier, Toulouse, France.,Institut des maladies métaboliques et cardiovasculaires, INSERM UMR-1297, Toulouse, France
| | - Yannis Sainte-Marie
- Université de Toulouse-Paul Sabatier, Toulouse, France.,Institut des maladies métaboliques et cardiovasculaires, INSERM UMR-1297, Toulouse, France
| | - Sabine Charron
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France
| | - Olivier Bernus
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France
| | - Alice Recalde
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France
| | - Laurent Sallé
- UR 4650 PSIR, GIP Cyceron, Caen, France.,Université de Caen-Normandie, Caen, France
| | - Fabien Brette
- IHU LIRYC -CRCTB U1045, Pessac, France.,INSERM U1045 -Université de Bordeaux, Bordeaux, France.,PhyMedExp, INSERM U1046, CNRS 9412, Université de Montpellier, Montpellier, France
| | - Frank Lezoualc'h
- Université de Toulouse-Paul Sabatier, Toulouse, France.,Institut des maladies métaboliques et cardiovasculaires, INSERM UMR-1297, Toulouse, France
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4
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Tan YQ, Li J, Chen HW. Epac, a positive or negative signaling molecule in cardiovascular diseases. Pharmacotherapy 2022; 148:112726. [DOI: 10.1016/j.biopha.2022.112726] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/14/2022] [Accepted: 02/15/2022] [Indexed: 02/08/2023]
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5
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Gruscheski L, Brand T. The Role of POPDC Proteins in Cardiac Pacemaking and Conduction. J Cardiovasc Dev Dis 2021; 8:160. [PMID: 34940515 PMCID: PMC8706714 DOI: 10.3390/jcdd8120160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/17/2021] [Accepted: 11/20/2021] [Indexed: 11/17/2022] Open
Abstract
The Popeye domain-containing (POPDC) gene family, consisting of Popdc1 (also known as Bves), Popdc2, and Popdc3, encodes transmembrane proteins abundantly expressed in striated muscle. POPDC proteins have recently been identified as cAMP effector proteins and have been proposed to be part of the protein network involved in cAMP signaling. However, their exact biochemical activity is presently poorly understood. Loss-of-function mutations in animal models causes abnormalities in skeletal muscle regeneration, conduction, and heart rate adaptation after stress. Likewise, patients carrying missense or nonsense mutations in POPDC genes have been associated with cardiac arrhythmias and limb-girdle muscular dystrophy. In this review, we introduce the POPDC protein family, and describe their structure function, and role in cAMP signaling. Furthermore, the pathological phenotypes observed in zebrafish and mouse models and the clinical and molecular pathologies in patients carrying POPDC mutations are described.
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Affiliation(s)
| | - Thomas Brand
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK;
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6
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Zhu D, Zhu R, Zhou X, Shi E, Zhang X, Zhou Z, Li D, Zou J, Wang Y. Exchange proteins directly activated by cAMP mediate cardiac repolarization and arrhythmogenesis during chronic heart failure. Can J Physiol Pharmacol 2021; 99:729-736. [PMID: 33175603 DOI: 10.1139/cjpp-2020-0122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Most sudden cardiac death in chronic heart failure (CHF) is caused by malignant ventricular arrhythmia (VA); however, the molecular mechanism remains unclear. This study aims to explore the effect of exchange proteins directly activated by cAMP (Epac) on VA in CHF and the potential molecular mechanism. Transaortic constriction was performed to prepare CHF guinea pigs. Epac activation model was obtained with 8-pCPT administration. Programmed electrical stimulation (PES) was performed to detect effective refractory period (ERP) or induce VA. Isolated adult cardiomyocytes were treated with 8-pCPT and (or) the Epac inhibitor. Cellular electrophysiology was examined by whole-cell patch clamp. With Epac activation, corrected QT duration was lengthened by 12.6%. The 8-pCPT increased action potential duration (APD) (APD50: 236.9 ± 18.07 ms vs. 328.8 ± 11.27 ms, p < 0.05; APD90: 264.6 ± 18.22 ms vs. 388.6 ± 6.47 ms, p < 0.05) and decreased rapid delayed rectifier potassium (IKr) current (tail current density: 1.1 ± 0.08 pA/pF vs. 0.7 ± 0.03 pA/pF, p < 0.05). PES induced more malignant arrhythmias in the 8-pCPT group than in the control group (3/4 vs. 0/8, p < 0.05). The selective Epac1 inhibitor CE3F4 rescued the drop in IKr after 8-pCPT stimulation (tail current density: 0.5 ± 0.02 pA/pF vs. 0.6 ± 0.03 pA/pF, p < 0.05). In conclusion, Epac1 regulates IKr, APD, and ERP in guinea pigs, which could contribute to the proarrhythmic effect of Epac1 in CHF.
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Affiliation(s)
- Didi Zhu
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
- Department of Cardiology, Zhongda Hospital Affiliated to Southeast University, Nanjing, China
| | - Rui Zhu
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xiaozhu Zhou
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Erdan Shi
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Xinwei Zhang
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Zihao Zhou
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Dongcheng Li
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Jiangang Zou
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yao Wang
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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7
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The Role of Cyclic AMP Signaling in Cardiac Fibrosis. Cells 2019; 9:cells9010069. [PMID: 31888098 PMCID: PMC7016856 DOI: 10.3390/cells9010069] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 12/18/2022] Open
Abstract
Myocardial stress and injury invariably promote remodeling of the cardiac tissue, which is associated with cardiomyocyte death and development of fibrosis. The fibrotic process is initially triggered by the differentiation of resident cardiac fibroblasts into myofibroblasts. These activated fibroblasts display increased proliferative capacity and secrete large amounts of extracellular matrix. Uncontrolled myofibroblast activation can thus promote heart stiffness, cardiac dysfunction, arrhythmias, and progression to heart failure. Despite the well-established role of myofibroblasts in mediating cardiac disease, our current knowledge on how signaling pathways promoting fibrosis are regulated and coordinated in this cell type is largely incomplete. In this respect, cyclic adenosine monophosphate (cAMP) signaling acts as a major modulator of fibrotic responses activated in fibroblasts of injured or stressed hearts. In particular, accumulating evidence now suggests that upstream cAMP modulators including G protein-coupled receptors, adenylyl cyclases (ACs), and phosphodiesterases (PDEs); downstream cAMP effectors such as protein kinase A (PKA) and the guanine nucleotide exchange factor Epac; and cAMP signaling organizers such as A-kinase anchoring proteins (AKAPs) modulate a variety of fundamental cellular processes involved in myocardial fibrosis including myofibroblast differentiation, proliferation, collagen secretion, and invasiveness. The current review will discuss recent advances highlighting the role of cAMP and AKAP-mediated signaling in regulating pathophysiological responses controlling cardiac fibrosis.
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8
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Abstract
The Popeye domain containing (POPDC) genes encode transmembrane proteins, which are abundantly expressed in striated muscle cells. Hallmarks of the POPDC proteins are the presence of three transmembrane domains and the Popeye domain, which makes up a large part of the cytoplasmic portion of the protein and functions as a cAMP-binding domain. Interestingly, despite the prediction of structural similarity between the Popeye domain and other cAMP binding domains, at the protein sequence level they strongly differ from each other suggesting an independent evolutionary origin of POPDC proteins. Loss-of-function experiments in zebrafish and mouse established an important role of POPDC proteins for cardiac conduction and heart rate adaptation after stress. Loss-of function mutations in patients have been associated with limb-girdle muscular dystrophy and AV-block. These data suggest an important role of these proteins in the maintenance of structure and function of striated muscle cells.
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9
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Laudette M, Zuo H, Lezoualc'h F, Schmidt M. Epac Function and cAMP Scaffolds in the Heart and Lung. J Cardiovasc Dev Dis 2018; 5:jcdd5010009. [PMID: 29401660 PMCID: PMC5872357 DOI: 10.3390/jcdd5010009] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 01/25/2018] [Accepted: 01/29/2018] [Indexed: 12/13/2022] Open
Abstract
Evidence collected over the last ten years indicates that Epac and cAMP scaffold proteins play a critical role in integrating and transducing multiple signaling pathways at the basis of cardiac and lung physiopathology. Some of the deleterious effects of Epac, such as cardiomyocyte hypertrophy and arrhythmia, initially described in vitro, have been confirmed in genetically modified mice for Epac1 and Epac2. Similar recent findings have been collected in the lung. The following sections will describe how Epac and cAMP signalosomes in different subcellular compartments may contribute to cardiac and lung diseases.
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Affiliation(s)
- Marion Laudette
- Inserm UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université Toulouse III, 31432 Toulouse, France.
| | - Haoxiao Zuo
- Department of Molecular Pharmacology, University of Groningen, 9713AV Groningen, The Netherlands.
- Groningen Research Institute for Asthma and COPD (GRIAC), University Medical Center Groningen, University of Groningen, 9713AV Groningen, The Netherlands.
| | - Frank Lezoualc'h
- Inserm UMR-1048, Institut des Maladies Métaboliques et Cardiovasculaires, Université Toulouse III, 31432 Toulouse, France.
| | - Martina Schmidt
- Department of Molecular Pharmacology, University of Groningen, 9713AV Groningen, The Netherlands.
- Groningen Research Institute for Asthma and COPD (GRIAC), University Medical Center Groningen, University of Groningen, 9713AV Groningen, The Netherlands.
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10
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Leroy J, Vandecasteele G, Fischmeister R. Cyclic AMP signaling in cardiac myocytes. CURRENT OPINION IN PHYSIOLOGY 2018. [DOI: 10.1016/j.cophys.2017.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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11
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Lezcano N, Mariángelo JIE, Vittone L, Wehrens XHT, Said M, Mundiña-Weilenmann C. Early effects of Epac depend on the fine-tuning of the sarcoplasmic reticulum Ca 2+ handling in cardiomyocytes. J Mol Cell Cardiol 2018; 114:1-9. [PMID: 29037982 PMCID: PMC5801154 DOI: 10.1016/j.yjmcc.2017.10.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 09/19/2017] [Accepted: 10/09/2017] [Indexed: 12/30/2022]
Abstract
In cardiac muscle, signaling through cAMP governs many fundamental cellular functions, including contractility, relaxation and automatism. cAMP cascade leads to the activation of the classic protein kinase A but also to the stimulation of the recently discovered exchange protein directly activated by cAMP (Epac). The role of Epac in the regulation of intracellular Ca2+ homeostasis and contractility in cardiac myocytes is still matter of debate. In this study we showed that the selective Epac activator, 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3', 5'-cyclic monophosphate (8-CPT), produced a positive inotropic effect when adult rat cardiac myocytes were stabilized at low [Ca2+]o (0.5mM), no changes at 1mM [Ca2+]o and a negative inotropic effect when [Ca2+]o was increased to 1.8mM. These effects were associated to parallel variations in sarcoplasmic reticulum (SR) Ca2+ content. At all [Ca2+]o studied, 8-CPT induced an increase in Ca2+ spark frequency and enhanced CaMKII autophosphorylation and the CaMKII-dependent phosphorylation of SR proteins: phospholamban (PLN, at Thr17 site) and ryanodine receptor (RyR2, at Ser2814 site). We used transgenic mice lacking PLN CaMKII phosphorylation site (PLN-DM) and knock-in mice with an inactivated CaMKII site S2814 on RyR2 (RyR2-S2814A) to investigate the involvement of these processes in the effects of Epac stimulation. In PLN-DM mice, 8-CPT failed to induce the positive inotropic effect at low [Ca2+]o and RyR2-S2814A mice showed no propensity to arrhythmic events when compared to wild type mice myocytes. We conclude that stimulation of Epac proteins could have either beneficial or deleterious effects depending on the steady-state Ca2+ levels at which the myocyte is functioning, favoring the prevailing mechanism of SR Ca2+ handling (uptake vs. leak) in the different situations.
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Affiliation(s)
- N Lezcano
- Centro de Investigaciones Cardiovasculares, CCT-CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina
| | - J I E Mariángelo
- Centro de Investigaciones Cardiovasculares, CCT-CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina
| | - L Vittone
- Centro de Investigaciones Cardiovasculares, CCT-CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina
| | - X H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, United States
| | - M Said
- Centro de Investigaciones Cardiovasculares, CCT-CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina
| | - C Mundiña-Weilenmann
- Centro de Investigaciones Cardiovasculares, CCT-CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Argentina.
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12
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Fujita T, Umemura M, Yokoyama U, Okumura S, Ishikawa Y. The role of Epac in the heart. Cell Mol Life Sci 2017; 74:591-606. [PMID: 27549789 PMCID: PMC11107744 DOI: 10.1007/s00018-016-2336-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/21/2016] [Accepted: 08/09/2016] [Indexed: 02/08/2023]
Abstract
As one of the most important second messengers, 3',5'-cyclic adenosine monophosphate (cAMP) mediates various extracellular signals including hormones and neurotransmitters, and induces appropriate responses in diverse types of cells. Since cAMP was formerly believed to transmit signals through only two direct target molecules, protein kinase A and the cyclic nucleotide-gated channel, the sensational discovery in 1998 of another novel direct effecter of cAMP [exchange proteins directly activated by cAMP (Epac)] attracted a great deal of scientific interest in cAMP signaling. Numerous studies on Epac have since disclosed its important functions in various tissues in the body. Recently, observations of genetically manipulated mice in various pathogenic models have begun to reveal the in vivo significance of previous in vitro or cellular-level findings. Here, we focused on the function of Epac in the heart. Accumulating evidence has revealed that both Epac1 and Epac2 play important roles in the structure and function of the heart under physiological and pathological conditions. Accordingly, developing the ability to regulate cAMP-mediated signaling through Epac may lead to remarkable new therapies for the treatment of cardiac diseases.
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Affiliation(s)
- Takayuki Fujita
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
| | - Masanari Umemura
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Utako Yokoyama
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Satoshi Okumura
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Yokohama, Japan
- Tsurumi University School of Dental Medicine, Yokohama, Japan
| | - Yoshihiro Ishikawa
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
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13
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Lezoualc'h F, Fazal L, Laudette M, Conte C. Cyclic AMP Sensor EPAC Proteins and Their Role in Cardiovascular Function and Disease. Circ Res 2016; 118:881-97. [PMID: 26941424 DOI: 10.1161/circresaha.115.306529] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
cAMP is a universal second messenger that plays central roles in cardiovascular regulation influencing gene expression, cell morphology, and function. A crucial step toward a better understanding of cAMP signaling came 18 years ago with the discovery of the exchange protein directly activated by cAMP (EPAC). The 2 EPAC isoforms, EPAC1 and EPAC2, are guanine-nucleotide exchange factors for the Ras-like GTPases, Rap1 and Rap2, which they activate independently of the classical effector of cAMP, protein kinase A. With the development of EPAC pharmacological modulators, many reports in the literature have demonstrated the critical role of EPAC in the regulation of various cAMP-dependent cardiovascular functions, such as calcium handling and vascular tone. EPAC proteins are coupled to a multitude of effectors into distinct subcellular compartments because of their multidomain architecture. These novel cAMP sensors are not only at the crossroads of different physiological processes but also may represent attractive therapeutic targets for the treatment of several cardiovascular disorders, including cardiac arrhythmia and heart failure.
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Affiliation(s)
- Frank Lezoualc'h
- From the Department of Cardiac and Renal Remodeling of the Institute of Metabolic and Cardiovascular Diseases (I2MC), Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-1048, Toulouse, France (F.L., L.F., M.L., C.C.); and Université Toulouse III-Paul Sabatier, Toulouse, France (F.L., L.F., M.L., C.C.).
| | - Loubina Fazal
- From the Department of Cardiac and Renal Remodeling of the Institute of Metabolic and Cardiovascular Diseases (I2MC), Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-1048, Toulouse, France (F.L., L.F., M.L., C.C.); and Université Toulouse III-Paul Sabatier, Toulouse, France (F.L., L.F., M.L., C.C.)
| | - Marion Laudette
- From the Department of Cardiac and Renal Remodeling of the Institute of Metabolic and Cardiovascular Diseases (I2MC), Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-1048, Toulouse, France (F.L., L.F., M.L., C.C.); and Université Toulouse III-Paul Sabatier, Toulouse, France (F.L., L.F., M.L., C.C.)
| | - Caroline Conte
- From the Department of Cardiac and Renal Remodeling of the Institute of Metabolic and Cardiovascular Diseases (I2MC), Institut National de la Santé et de la Recherche Médicale (INSERM), UMR-1048, Toulouse, France (F.L., L.F., M.L., C.C.); and Université Toulouse III-Paul Sabatier, Toulouse, France (F.L., L.F., M.L., C.C.)
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Hof T, Sallé L, Coulbault L, Richer R, Alexandre J, Rouet R, Manrique A, Guinamard R. TRPM4 non-selective cation channels influence action potentials in rabbit Purkinje fibres. J Physiol 2015; 594:295-306. [PMID: 26548780 DOI: 10.1113/jp271347] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/29/2015] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The transient receptor potential melastatin 4 (TRPM4) inhibitor 9-phenanthrol reduces action potential duration in rabbit Purkinje fibres but not in ventricle. TRPM4-like single channel activity is observed in isolated rabbit Purkinje cells but not in ventricular cells. The TRPM4-like current develops during the notch and early repolarization phases of the action potential in Purkinje cells. ABSTRACT Transient receptor potential melastatin 4 (TRPM4) Ca(2+)-activated non-selective cation channel activity has been recorded in cardiomyocytes and sinus node cells from mammals. In addition, TRPM4 gene mutations are associated with human diseases of cardiac conduction, suggesting that TRPM4 plays a role in this aspect of cardiac function. Here we evaluate the TRPM4 contribution to cardiac electrophysiology of Purkinje fibres. Ventricular strips with Purkinje fibres were isolated from rabbit hearts. Intracellular microelectrodes recorded Purkinje fibre activity and the TRPM4 inhibitor 9-phenanthrol was applied to unmask potential TRPM4 contributions to the action potential. 9-Phenanthrol reduced action potential duration measured at the point of 50 and 90% repolarization with an EC50 of 32.8 and 36.1×10(-6) mol l(-1), respectively, but did not modulate ventricular action potentials. Inside-out patch-clamp recordings were used to monitor TRPM4 activity in isolated Purkinje cells. TRPM4-like single channel activity (conductance = 23.8 pS; equal permeability for Na(+) and K(+); sensitivity to voltage, Ca(2+) and 9-phenanthrol) was observed in 43% of patches from Purkinje cells but not from ventricular cells (0/16). Action potential clamp experiments performed in the whole-cell configuration revealed a transient inward 9-phenanthrol-sensitive current (peak density = -0.65 ± 0.15 pA pF(-1); n = 5) during the plateau phases of the Purkinje fibre action potential. These results show that TRPM4 influences action potential characteristics in rabbit Purkinje fibres and thus could modulate cardiac conduction and be involved in triggering arrhythmias.
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Affiliation(s)
- Thomas Hof
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Laurent Sallé
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Laurent Coulbault
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Romain Richer
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Joachim Alexandre
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - René Rouet
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Alain Manrique
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
| | - Romain Guinamard
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, Unicaen, Normandie Université, EA 4650, Caen, France
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15
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Alexandre J, Hof T, Puddu PE, Rouet R, Guinamard R, Manrique A, Beygui F, Sallé L, Milliez P. Rapid and MR-Independent IK1 Activation by Aldosterone during Ischemia-Reperfusion. PLoS One 2015. [PMID: 26222262 PMCID: PMC4519293 DOI: 10.1371/journal.pone.0132592] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In ST elevation myocardial infarction (STEMI) context, clinical studies have shown the deleterious effect of high aldosterone levels on ventricular arrhythmia occurrence and cardiac mortality. Previous in vitro reports showed that during ischemia-reperfusion, aldosterone modulates K+ currents involved in the holding of the resting membrane potential (RMP). The aim of this study was to assess the electrophysiological impact of aldosterone on IK1 current during myocardial ischemia-reperfusion. We used an in vitro model of “border zone” using right rabbit ventricle and standard microelectrode technique followed by cell-attached recordings from freshly isolated rabbit ventricular cardiomyocytes. In microelectrode experiments, aldosterone (10 and 100 nmol/L, n=7 respectively) increased the action potential duration (APD) dispersion at 90% between ischemic and normoxic zones (from 95±4 ms to 116±6 ms and 127±5 ms respectively, P<0.05) and reperfusion-induced sustained premature ventricular contractions occurrence (from 2/12 to 5/7 preparations, P<0.05). Conversely, potassium canrenoate 100 nmol/L and RU 28318 1 μmol/l alone did not affect AP parameters and premature ventricular contractions occurrence (except Vmax which was decreased by potassium canrenoate during simulated-ischemia). Furthermore, aldosterone induced a RMP hyperpolarization, evoking an implication of a K+ current involved in the holding of the RMP. Cell-attached recordings showed that aldosterone 10 nmol/L quickly activated (within 6.2±0.4 min) a 30 pS K+-selective current, inward rectifier, with pharmacological and biophysical properties consistent with the IK1 current (NPo =1.9±0.4 in control vs NPo=3.0±0.4, n=10, P<0.05). These deleterious effects persisted in presence of RU 28318, a specific MR antagonist, and were successfully prevented by potassium canrenoate, a non specific MR antagonist, in both microelectrode and patch-clamp recordings, thus indicating a MR-independent IK1 activation. In this ischemia-reperfusion context, aldosterone induced rapid and MR-independent deleterious effects including an arrhythmia substrate (increased APD90 dispersion) and triggered activities (increased premature ventricular contractions occurrence on reperfusion) possibly related to direct IK1 activation.
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Affiliation(s)
- Joachim Alexandre
- CHU de Caen, Department of Cardiology, Caen, France
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
| | - Thomas Hof
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
| | | | - René Rouet
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
| | - Romain Guinamard
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
| | - Alain Manrique
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
| | - Farzin Beygui
- CHU de Caen, Department of Cardiology, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
| | - Laurent Sallé
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
| | - Paul Milliez
- CHU de Caen, Department of Cardiology, Caen, France
- Université de Caen Basse-Normandie, EA 4650 Signalisation, électrophysiologie et imagerie des lésions d'ischémie-reperfusion myocardique, Caen, France
- Université de Caen Basse-Normandie, Medical School, Caen, F-14000, France
- * E-mail:
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16
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Zhang Y, Guo Q, Li X, Gao J, Liu Y, Yang J, Li Q. P2Y purinergic receptor-regulated insulin secretion is mediated by a cAMP/Epac/Kv channel pathway. Biochem Biophys Res Commun 2015; 460:850-6. [PMID: 25839655 DOI: 10.1016/j.bbrc.2015.03.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 03/21/2015] [Indexed: 10/23/2022]
Abstract
Enhancement of insulin secretion is a major therapeutic approach for type 2 diabetes (T2D). Activation of P2Y purinergic receptor (P2YR) causes potentiation of insulin secretion in a glucose-dependent manner, making it a promising therapeutic target for T2D. Here we show that activation of P2YR to potentiate insulin secretion is mediated by adenylyl cyclase/cyclic AMP (cAMP) and the downstream effector, exchange protein directly activated by cAMP (Epac), leading to inhibition of voltage-dependent potassium (Kv) channels. P2YR-mediated Kv channel inhibition results in prolongation of action potential duration, and in turn elevates intracellular Ca(2+) level and insulin secretion. Taken together, the data indicate that cAMP/Epac/Kv channel pathway mediates P2YR-regulated insulin secretion, which may have important therapeutic implications for T2D.
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Affiliation(s)
- Yi Zhang
- Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
| | - Qing Guo
- Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
| | - Xiaodong Li
- Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
| | - Jingying Gao
- Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
| | - Yunfeng Liu
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China.
| | - Jing Yang
- Department of Endocrinology, the First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China.
| | - Qingshan Li
- School of Pharmaceutical Sciences, Shanxi Medical University, Taiyuan, China.
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Novel Epac fluorescent ligand reveals distinct Epac1 vs. Epac2 distribution and function in cardiomyocytes. Proc Natl Acad Sci U S A 2015; 112:3991-6. [PMID: 25829540 DOI: 10.1073/pnas.1416163112] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Exchange proteins directly activated by cAMP (Epac1 and Epac2) have been recently recognized as key players in β-adrenergic-dependent cardiac arrhythmias. Whereas Epac1 overexpression can lead to cardiac hypertrophy and Epac2 activation can be arrhythmogenic, it is unknown whether distinct subcellular distribution of Epac1 vs. Epac2 contributes to differential functional effects. Here, we characterized and used a novel fluorescent cAMP derivate Epac ligand 8-[Pharos-575]-2'-O-methyladenosine-3',5'-cyclic monophosphate (Φ-O-Me-cAMP) in mice lacking either one or both isoforms (Epac1-KO, Epac2-KO, or double knockout, DKO) to assess isoform localization and function. Fluorescence of Φ-O-Me-cAMP was enhanced by binding to Epac. Unlike several Epac-specific antibodies tested, Φ-O-Me-cAMP exhibited dramatically reduced signals in DKO myocytes. In WT, the apparent binding affinity (Kd = 10.2 ± 0.8 µM) is comparable to that of cAMP and nonfluorescent Epac-selective agonist 8-(4-chlorophenylthio)-2-O-methyladenosine-3'-,5'-cyclicmonophosphate (OMe-CPT). Φ-O-Me-cAMP readily entered intact myocytes, but did not activate PKA and its binding was competitively inhibited by OMe-CPT, confirming its Epac specificity. Φ-O-Me-cAMP is a weak partial agonist for purified Epac, but functioned as an antagonist for four Epac signaling pathways in myocytes. Epac2 and Epac1 were differentially concentrated along T tubules and around the nucleus, respectively. Epac1-KO abolished OMe-CPT-induced nuclear CaMKII activation and export of transcriptional regulator histone deacetylase 5. In conclusion, Epac1 is localized and functionally involved in nuclear signaling, whereas Epac2 is located at the T tubules and regulates arrhythmogenic sarcoplasmic reticulum Ca leak.
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18
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Okumura S, Fujita T, Cai W, Jin M, Namekata I, Mototani Y, Jin H, Ohnuki Y, Tsuneoka Y, Kurotani R, Suita K, Kawakami Y, Hamaguchi S, Abe T, Kiyonari H, Tsunematsu T, Bai Y, Suzuki S, Hidaka Y, Umemura M, Ichikawa Y, Yokoyama U, Sato M, Ishikawa F, Izumi-Nakaseko H, Adachi-Akahane S, Tanaka H, Ishikawa Y. Epac1-dependent phospholamban phosphorylation mediates the cardiac response to stresses. J Clin Invest 2014; 124:2785-801. [PMID: 24892712 DOI: 10.1172/jci64784] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
PKA phosphorylates multiple molecules involved in calcium (Ca2+) handling in cardiac myocytes and is considered to be the predominant regulator of β-adrenergic receptor-mediated enhancement of cardiac contractility; however, recent identification of exchange protein activated by cAMP (EPAC), which is independently activated by cAMP, has challenged this paradigm. Mice lacking Epac1 (Epac1 KO) exhibited decreased cardiac contractility with reduced phospholamban (PLN) phosphorylation at serine-16, the major PKA-mediated phosphorylation site. In Epac1 KO mice, intracellular Ca2+ storage and the magnitude of Ca2+ movement were decreased; however, PKA expression remained unchanged, and activation of PKA with isoproterenol improved cardiac contractility. In contrast, direct activation of EPAC in cardiomyocytes led to increased PLN phosphorylation at serine-16, which was dependent on PLC and PKCε. Importantly, Epac1 deletion protected the heart from various stresses, while Epac2 deletion was not protective. Compared with WT mice, aortic banding induced a similar degree of cardiac hypertrophy in Epac1 KO; however, lack of Epac1 prevented subsequent cardiac dysfunction as a result of decreased cardiac myocyte apoptosis and fibrosis. Similarly, Epac1 KO animals showed resistance to isoproterenol- and aging-induced cardiomyopathy and attenuation of arrhythmogenic activity. These data support Epac1 as an important regulator of PKA-independent PLN phosphorylation and indicate that Epac1 regulates cardiac responsiveness to various stresses.
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19
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Aflaki M, Qi XY, Xiao L, Ordog B, Tadevosyan A, Luo X, Maguy A, Shi Y, Tardif JC, Nattel S. Exchange protein directly activated by cAMP mediates slow delayed-rectifier current remodeling by sustained β-adrenergic activation in guinea pig hearts. Circ Res 2014; 114:993-1003. [PMID: 24508724 DOI: 10.1161/circresaha.113.302982] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
RATIONALE β-Adrenoceptor activation contributes to sudden death risk in heart failure. Chronic β-adrenergic stimulation, as occurs in patients with heart failure, causes potentially arrhythmogenic reductions in slow delayed-rectifier K(+) current (IKs). OBJECTIVE To assess the molecular mechanisms of IKs downregulation caused by chronic β-adrenergic activation, particularly the role of exchange protein directly activated by cAMP (Epac). METHODS AND RESULTS Isolated guinea pig left ventricular cardiomyocytes were incubated in primary culture and exposed to isoproterenol (1 μmol/L) or vehicle for 30 hours. Sustained isoproterenol exposure decreased IKs density (whole cell patch clamp) by 58% (P<0.0001), with corresponding decreases in potassium voltage-gated channel subfamily E member 1 (KCNE1) mRNA and membrane protein expression (by 45% and 51%, respectively). Potassium voltage-gated channel, KQT-like subfamily, member 1 (KCNQ1) mRNA expression was unchanged. The β1-adrenoceptor antagonist 1-[2-((3-Carbamoyl-4-hydroxy)phenoxy)ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl)phenoxy]-2-propanol dihydrochloride (CGP-20712A) prevented isoproterenol-induced IKs downregulation, whereas the β2-antagonist ICI-118551 had no effect. The selective Epac activator 8-pCPT-2'-O-Me-cAMP decreased IKs density to an extent similar to isoproterenol exposure, and adenoviral-mediated knockdown of Epac1 prevented isoproterenol-induced IKs/KCNE1 downregulation. In contrast, protein kinase A inhibition with a cell-permeable highly selective peptide blocker did not affect IKs downregulation. 1,2-Bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetate-AM acetoxymethyl ester (BAPTA-AM), cyclosporine, and inhibitor of nuclear factor of activated T cell (NFAT)-calcineurin association-6 (INCA6) prevented IKs reduction by isoproterenol and INCA6 suppressed isoproterenol-induced KCNE1 downregulation, consistent with signal-transduction via the Ca(2+)/calcineurin/NFAT pathway. Isoproterenol induced nuclear NFATc3/c4 translocation (immunofluorescence), which was suppressed by Epac1 knockdown. Chronic in vivo administration of isoproterenol to guinea pigs reduced IKs density and KCNE1 mRNA and protein expression while inducing cardiac dysfunction and action potential prolongation. Selective in vivo activation of Epac via sp-8-pCPT-2'-O-Me-cAMP infusion decreased IKs density and KCNE1 mRNA/protein expression. CONCLUSIONS Prolonged β1-adrenoceptor stimulation suppresses IKs by downregulating KCNE1 mRNA and protein via Epac-mediated Ca(2+)/calcineurin/NFAT signaling. These results provide new insights into the molecular basis of K(+) channel remodeling under sustained adrenergic stimulation.
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Affiliation(s)
- Mona Aflaki
- From the Department of Medicine, Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Quebec, Canada (M.A., X.-Y.Q., L.X., B.O., A.T., X.L., A.M., Y.S., J.-C.T., S.N.); and Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada (M.A., S.N.)
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20
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Guinamard R, Hof T, Sallé L. Current recordings at the single channel level in adult mammalian isolated cardiomyocytes. Methods Mol Biol 2014; 1183:291-307. [PMID: 25023317 DOI: 10.1007/978-1-4939-1096-0_19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This chapter describes appropriate methods to investigate mammalian cardiac channels properties at the single channel level. Cell isolation is performed from new born or adult heart by enzymatic digestion on minced tissue or using the Langendorff apparatus. Isolation proceeding is suitable for rabbit, rat, and mouse hearts. In addition, isolation of human atrial cardiomyocytes is described. Such freshly isolated cells or cells maintained in primary culture are suitable for patch-clamp studies. Here we describe the single channel variants of the patch-clamp technique (cell-attached, inside-out, outside-out) used to investigate channel properties. Proceedings for the evaluation of biophysical properties such as conductance, ionic selectivity, regulations by extracellular and intracellular mechanisms are described. To illustrate the study, we provide an example by the characterization of a calcium-activated non-selective cation channel (TRPM4).
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Affiliation(s)
- Romain Guinamard
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie/Reperfusion Myocardique, EA4650, Normandie Université, Esplanade de la Paix, 14032, Caen Cedex, France,
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