1
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Medvedev RY, Afolabi SO, Turner DGP, Glukhov AV. Mechanisms of stretch-induced electro-anatomical remodeling and atrial arrhythmogenesis. J Mol Cell Cardiol 2024; 193:11-24. [PMID: 38797242 DOI: 10.1016/j.yjmcc.2024.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 05/15/2024] [Accepted: 05/21/2024] [Indexed: 05/29/2024]
Abstract
Atrial fibrillation (AF) is the most common cardiac rhythm disorder, often occurring in the setting of atrial distension and elevated myocardialstretch. While various mechano-electrochemical signal transduction pathways have been linked to AF development and progression, the underlying molecular mechanisms remain poorly understood, hampering AF therapies. In this review, we describe different aspects of stretch-induced electro-anatomical remodeling as seen in animal models and in patients with AF. Specifically, we focus on cellular and molecular mechanisms that are responsible for mechano-electrochemical signal transduction and the development of ectopic beats triggering AF from pulmonary veins, the most common source of paroxysmal AF. Furthermore, we describe structural changes caused by stretch occurring before and shortly after the onset of AF as well as during AF progression, contributing to longstanding forms of AF. We also propose mechanical stretch as a new dimension to the concept "AF begets AF", in addition to underlying diseases. Finally, we discuss the mechanisms of these electro-anatomical alterations in a search for potential therapeutic strategies and the development of novel antiarrhythmic drugs targeted at the components of mechano-electrochemical signal transduction not only in cardiac myocytes, but also in cardiac non-myocyte cells.
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Affiliation(s)
- Roman Y Medvedev
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| | - Saheed O Afolabi
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA; Department of Pharmacology and Therapeutics, University of Ilorin, Ilorin, Nigeria
| | - Daniel G P Turner
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA
| | - Alexey V Glukhov
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, USA.
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2
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Greene D, Shiferaw Y. A structure-based computational model of IP 3R1 incorporating Ca and IP3 regulation. Biophys J 2024; 123:1274-1288. [PMID: 38627970 PMCID: PMC11140470 DOI: 10.1016/j.bpj.2024.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/20/2024] [Accepted: 04/12/2024] [Indexed: 05/02/2024] Open
Abstract
The inositol 1,4,5-triphosphate receptor (IP3R) mediates Ca release in many cell types and is pivotal to a wide range of cellular processes. High-resolution cryoelectron microscopy studies have provided new structural details of IP3R type 1 (IP3R1), showing that channel function is determined by the movement of various domains within and between each of its four subunits. Channel properties are regulated by ligands, such as Ca and IP3, which bind at specific sites and control the interactions between these domains. However, it is not known how the various ligand-binding sites on IP3R1 interact to control the opening of the channel. In this study, we present a coarse-grained model of IP3R1 that accounts for the channel architecture and the location of specific Ca- and IP3-binding sites. This computational model accounts for the domain-domain interactions within and between the four subunits that form IP3R1, and it also describes how ligand binding regulates these interactions. Using a kinetic model, we explore how two Ca-binding sites on the cytosolic side of the channel interact with the IP3-binding site to regulate the channel open probability. Our primary finding is that the bell-shaped open probability of IP3R1 provides constraints on the relative strength of these regulatory binding sites. In particular, we argue that a specific Ca-binding site, whose function has not yet been established, is very likely a channel antagonist. Additionally, we apply our model to show that domain-domain interactions between neighboring subunits exert control over channel cooperativity and dictate the nonlinear response of the channel to Ca concentration. This suggests that specific domain-domain interactions play a pivotal role in maintaining the channel's stability, and a disruption of these interactions may underlie disease states associated with Ca dysregulation.
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Affiliation(s)
- D'Artagnan Greene
- Department of Physics & Astronomy, California State University, Northridge, California
| | - Yohannes Shiferaw
- Department of Physics & Astronomy, California State University, Northridge, California.
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3
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Hennis K, Piantoni C, Biel M, Fenske S, Wahl-Schott C. Pacemaker Channels and the Chronotropic Response in Health and Disease. Circ Res 2024; 134:1348-1378. [PMID: 38723033 PMCID: PMC11081487 DOI: 10.1161/circresaha.123.323250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/13/2024]
Abstract
Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.
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Affiliation(s)
- Konstantin Hennis
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Chiara Piantoni
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Stefanie Fenske
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Christian Wahl-Schott
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
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4
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Terrar DA. Timing mechanisms to control heart rhythm and initiate arrhythmias: roles for intracellular organelles, signalling pathways and subsarcolemmal Ca 2. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220170. [PMID: 37122228 PMCID: PMC10150226 DOI: 10.1098/rstb.2022.0170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Rhythms of electrical activity in all regions of the heart can be influenced by a variety of intracellular membrane bound organelles. This is true both for normal pacemaker activity and for abnormal rhythms including those caused by early and delayed afterdepolarizations under pathological conditions. The influence of the sarcoplasmic reticulum (SR) on cardiac electrical activity is widely recognized, but other intracellular organelles including lysosomes and mitochondria also contribute. Intracellular organelles can provide a timing mechanism (such as an SR clock driven by cyclic uptake and release of Ca2+, with an important influence of intraluminal Ca2+), and/or can act as a Ca2+ store involved in signalling mechanisms. Ca2+ plays many diverse roles including carrying electric current, driving electrogenic sodium-calcium exchange (NCX) particularly when Ca2+ is extruded across the surface membrane causing depolarization, and activation of enzymes which target organelles and surface membrane proteins. Heart function is also influenced by Ca2+ mobilizing agents (cADP-ribose, nicotinic acid adenine dinucleotide phosphate and inositol trisphosphate) acting on intracellular organelles. Lysosomal Ca2+ release exerts its effects via calcium/calmodulin-dependent protein kinase II to promote SR Ca2+ uptake, and contributes to arrhythmias resulting from excessive beta-adrenoceptor stimulation. A separate arrhythmogenic mechanism involves lysosomes, mitochondria and SR. Interacting intracellular organelles, therefore, have profound effects on heart rhythms and NCX plays a central role. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Derek A Terrar
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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5
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The Effect of the Tongyang Huoxue Recipe (TYHX) on the I to/ I Kur in Ischemia/Reperfusion Sinoatrial Node Cells. Cardiovasc Ther 2022; 2022:4114817. [PMID: 36605374 PMCID: PMC9794430 DOI: 10.1155/2022/4114817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 09/26/2022] [Accepted: 11/23/2022] [Indexed: 12/24/2022] Open
Abstract
Background The transient outward potassium current (I to) and the ultrarapid delayed rectifier potassium current (I Kur) are major potassium currents involved in the repolarization process of sinoatrial node cells (SNCs). Methods and Results The SNCs of neonatal rats were divided into control, ischemia/reperfusion (I/R), I/R+blank serum, and Tongyang Huoxue recipe (TYHX) serum groups. I to and I Kur were recorded using the whole cell patch-clamp technique, and the current-voltage (I-V), steady-state activation (SSA), steady-state inactivation (SSI), and recovery from inactivation (RFI) curves were plotted, respectively. Compared to the control group, both the peak current density and the current density at the voltage of I to and I Kur decreased obviously in SNCs after simulated I/R, the SSA curves moved right, and the SSI curves moved left. After TYHX was added to the extracellular solution of SNCs, both the peak current density and the current density at the voltage of I to and I Kur increased significantly, the SSA curves moved left, and the SSI curves moved right with a significant difference of V 1/2. The recovery from the I Kur RFI curves was slightly restored, and the I to curves did not change. Conclusions TYHX increases the peak current density, accelerates the activation, and decreases the inactivation of the I to and I Kur. This may be the mechanism of TYHX in shortening the action potential duration of repolarization, which accelerates spontaneous pulsation.
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6
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Demydenko K, Ekhteraei-Tousi S, Roderick HL. Inositol 1,4,5-trisphosphate receptors in cardiomyocyte physiology and disease. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210319. [PMID: 36189803 PMCID: PMC9527928 DOI: 10.1098/rstb.2021.0319] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The contraction of cardiac muscle underlying the pumping action of the heart is mediated by the process of excitation-contraction coupling (ECC). While triggered by Ca2+ entry across the sarcolemma during the action potential, it is the release of Ca2+ from the sarcoplasmic reticulum (SR) intracellular Ca2+ store via ryanodine receptors (RyRs) that plays the major role in induction of contraction. Ca2+ also acts as a key intracellular messenger regulating transcription underlying hypertrophic growth. Although Ca2+ release via RyRs is by far the greatest contributor to the generation of Ca2+ transients in the cardiomyocyte, Ca2+ is also released from the SR via inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs). This InsP3-induced Ca2+ release modifies Ca2+ transients during ECC, participates in directing Ca2+ to the mitochondria, and stimulates the transcription of genes underlying hypertrophic growth. Central to these specific actions of InsP3Rs is their localization to responsible signalling microdomains, the dyad, the SR-mitochondrial interface and the nucleus. In this review, the various roles of InsP3R in cardiac (patho)physiology and the mechanisms by which InsP3 signalling selectively influences the different cardiomyocyte cell processes in which it is involved will be presented. This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.
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Affiliation(s)
- Kateryna Demydenko
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - Samaneh Ekhteraei-Tousi
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
| | - H Llewelyn Roderick
- Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium
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7
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Foster DB, Gu JM, Kim EH, Wolfson DW, O’Meally R, Cole RN, Cho HC. Tbx18 Orchestrates Cytostructural Transdifferentiation of Cardiomyocytes to Pacemaker Cells by Recruiting the Epithelial-Mesenchymal Transition Program. J Proteome Res 2022; 21:2277-2292. [PMID: 36006872 PMCID: PMC9552783 DOI: 10.1021/acs.jproteome.2c00133] [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: 03/04/2022] [Indexed: 11/29/2022]
Abstract
Previously, we reported that heterologous expression of an embryonic transcription factor, Tbx18, reprograms ventricular cardiomyocytes into induced pacemaker cells (Tbx18-iPMs), though the key pathways are unknown. Here, we have used a tandem mass tag proteomic approach to characterize the impact of Tbx18 on neonatal rat ventricular myocytes. Tbx18 expression triggered vast proteome remodeling. Tbx18-iPMs exhibited increased expression of known pacemaker ion channels, including Hcn4 and Cx45 as well as upregulation of the mechanosensitive ion channels Piezo1, Trpp2 (PKD2), and TrpM7. Metabolic pathways were broadly downregulated, as were ion channels associated with ventricular excitation-contraction coupling. Tbx18-iPMs also exhibited extensive intracellular cytoskeletal and extracellular matrix remodeling, including 96 differentially expressed proteins associated with the epithelial-to-mesenchymal transition (EMT). RNAseq extended coverage of low abundance transcription factors, revealing upregulation of EMT-inducing Snai1, Snai2, Twist1, Twist2, and Zeb2. Finally, network diffusion mapping of >200 transcriptional regulators indicates EMT and heart development factors occupy adjacent network neighborhoods downstream of Tbx18 but upstream of metabolic control factors. In conclusion, transdifferentiation of cardiac myocytes into pacemaker cells entails massive electrogenic, metabolic, and cytostructural remodeling. Structural changes exhibit hallmarks of the EMT. The results aid ongoing efforts to maximize the yield and phenotypic stability of engineered biological pacemakers.
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Affiliation(s)
- D. Brian Foster
- Division
of Cardiology, Department of Medicine, The
Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Jin-mo Gu
- Department
of Pediatrics, Emory University, Atlanta, Georgia 30322, United States
| | - Elizabeth H. Kim
- Cedars-Sinai
Medical Center, Los Angeles, California 90048, United States
| | - David W. Wolfson
- Wallace
H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, United States
| | - Robert O’Meally
- Proteomics
Core Facility, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
| | - Robert N. Cole
- Proteomics
Core Facility, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
| | - Hee Cheol Cho
- Department
of Surgery, The Johns Hopkins University
School of Medicine, Baltimore, Maryland 21205, United States
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8
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Bose SJ, Read MJ, Akerman E, Capel RA, Ayagama T, Russell A, Terrar DA, Zaccolo M, Burton RAB. Inhibition of adenylyl cyclase 1 by ST034307 inhibits IP3-evoked changes in sino-atrial node beat rate. Front Pharmacol 2022; 13:951897. [PMID: 36105228 PMCID: PMC9465815 DOI: 10.3389/fphar.2022.951897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
Atrial arrhythmias, such as atrial fibrillation (AF), are a major mortality risk and a leading cause of stroke. The IP3 signalling pathway has been proposed as an atrial-specific target for AF therapy, and atrial IP3 signalling has been linked to the activation of calcium sensitive adenylyl cyclases AC1 and AC8. We investigated the involvement of AC1 in the response of intact mouse atrial tissue and isolated guinea pig atrial and sino-atrial node (SAN) cells to the α-adrenoceptor agonist phenylephrine (PE) using the selective AC1 inhibitor ST034307. The maximum rate change of spontaneously beating mouse right atrial tissue exposed to PE was reduced from 14.5% to 8.2% (p = 0.005) in the presence of 1 μM ST034307, whereas the increase in tension generated in paced left atrial tissue in the presence of PE was not inhibited by ST034307 (Control = 14.2%, ST034307 = 16.3%; p > 0.05). Experiments were performed using isolated guinea pig atrial and SAN cells loaded with Fluo-5F-AM to record changes in calcium transients (CaT) generated by 10 μM PE in the presence and absence of 1 μM ST034307. ST034307 significantly reduced the beating rate of SAN cells (0.34-fold decrease; p = 0.003) but did not inhibit changes in CaT amplitude in response to PE in atrial cells. The results presented here demonstrate pharmacologically the involvement of AC1 in the downstream response of atrial pacemaker activity to α-adrenoreceptor stimulation and IP3R calcium release.
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Affiliation(s)
- Samuel J. Bose
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Matthew J. Read
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Emily Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Rebecca A. Capel
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Angela Russell
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Derek A. Terrar
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca A. B. Burton
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- *Correspondence: Rebecca A. B. Burton,
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9
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Wagdi A, Malan D, Sathyanarayanan U, Beauchamp JS, Vogt M, Zipf D, Beiert T, Mansuroglu B, Dusend V, Meininghaus M, Schneider L, Kalthof B, Wiegert JS, König GM, Kostenis E, Patejdl R, Sasse P, Bruegmann T. Selective optogenetic control of G q signaling using human Neuropsin. Nat Commun 2022; 13:1765. [PMID: 35365606 PMCID: PMC8975936 DOI: 10.1038/s41467-022-29265-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 03/03/2022] [Indexed: 01/07/2023] Open
Abstract
Gq proteins are universally important for signal transduction in mammalian cells. The underlying kinetics and transformation from extracellular stimuli into intracellular signaling, however could not be investigated in detail so far. Here we present the human Neuropsin (hOPN5) for specific and repetitive manipulation of Gq signaling in vitro and in vivo with high spatio-temporal resolution. Properties and G protein specificity of hOPN5 are characterized by UV light induced IP3 generation, Ca2+ transients and inhibition of GIRK channel activity in HEK cells. In adult hearts from a transgenic animal model, light increases the spontaneous beating rate. In addition, we demonstrate light induced contractions in the small intestine, which are not detectable after pharmacological Gq protein block. All-optical high-throughput screening for TRPC6 inhibitors is more specific and sensitive than conventional pharmacological screening. Thus, we demonstrate specific Gq signaling of hOPN5 and unveil its potential for optogenetic applications.
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Affiliation(s)
- Ahmed Wagdi
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany ,grid.452396.f0000 0004 5937 5237German Center for Cardiovascular Research (DZHK), Partner site Göttingen, Göttingen, Germany ,grid.7450.60000 0001 2364 4210Present Address: Department of Cardiology and Pulmonology, University Medical Center Göttingen, Georg August University of Göttingen, Göttingen, Germany
| | - Daniela Malan
- grid.10388.320000 0001 2240 3300Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Udhayabhaskar Sathyanarayanan
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - Janosch S. Beauchamp
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - Markus Vogt
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - David Zipf
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Beiert
- grid.15090.3d0000 0000 8786 803XDepartment of Internal Medicine II, University Hospital Bonn, University of Bonn, Bonn, Germany
| | - Berivan Mansuroglu
- grid.10388.320000 0001 2240 3300Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany ,grid.10388.320000 0001 2240 3300Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Vanessa Dusend
- grid.10388.320000 0001 2240 3300Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany ,grid.10388.320000 0001 2240 3300Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Mark Meininghaus
- grid.420044.60000 0004 0374 4101Bayer AG, Research & Development, Pharmaceuticals, 42096 Wuppertal, Germany
| | - Linn Schneider
- grid.420044.60000 0004 0374 4101Bayer AG, Research & Development, Pharmaceuticals, 42096 Wuppertal, Germany
| | - Bernd Kalthof
- grid.420044.60000 0004 0374 4101Bayer AG, Research & Development, Pharmaceuticals, 42096 Wuppertal, Germany
| | - J. Simon Wiegert
- grid.13648.380000 0001 2180 3484Center for Molecular Neurobiology Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Gabriele M. König
- grid.10388.320000 0001 2240 3300Molecular, Cellular and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Evi Kostenis
- grid.10388.320000 0001 2240 3300Molecular, Cellular and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Robert Patejdl
- grid.413108.f0000 0000 9737 0454Oscar-Langendorff Institute of Physiology, Rostock University Medical Center, Rostock, Germany
| | - Philipp Sasse
- grid.10388.320000 0001 2240 3300Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany
| | - Tobias Bruegmann
- grid.411984.10000 0001 0482 5331Institute for Cardiovascular Physiology, University Medical Center Göttingen, Göttingen, Germany ,grid.452396.f0000 0004 5937 5237German Center for Cardiovascular Research (DZHK), Partner site Göttingen, Göttingen, Germany ,grid.10388.320000 0001 2240 3300Institute of Physiology I, Medical Faculty, University of Bonn, Bonn, Germany ,grid.10388.320000 0001 2240 3300Research Training Group 1873, University of Bonn, Bonn, Germany ,grid.7450.60000 0001 2364 4210Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC), University of Göttingen, Göttingen, Germany
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10
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Turner D, Kang C, Mesirca P, Hong J, Mangoni ME, Glukhov AV, Sah R. Electrophysiological and Molecular Mechanisms of Sinoatrial Node Mechanosensitivity. Front Cardiovasc Med 2021; 8:662410. [PMID: 34434970 PMCID: PMC8382116 DOI: 10.3389/fcvm.2021.662410] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/24/2021] [Indexed: 01/01/2023] Open
Abstract
The understanding of the electrophysiological mechanisms that underlie mechanosensitivity of the sinoatrial node (SAN), the primary pacemaker of the heart, has been evolving over the past century. The heart is constantly exposed to a dynamic mechanical environment; as such, the SAN has numerous canonical and emerging mechanosensitive ion channels and signaling pathways that govern its ability to respond to both fast (within second or on beat-to-beat manner) and slow (minutes) timescales. This review summarizes the effects of mechanical loading on the SAN activity and reviews putative candidates, including fast mechanoactivated channels (Piezo, TREK, and BK) and slow mechanoresponsive ion channels [including volume-regulated chloride channels and transient receptor potential (TRP)], as well as the components of mechanochemical signal transduction, which may contribute to SAN mechanosensitivity. Furthermore, we examine the structural foundation for both mechano-electrical and mechanochemical signal transduction and discuss the role of specialized membrane nanodomains, namely, caveolae, in mechanical regulation of both membrane and calcium clock components of the so-called coupled-clock pacemaker system responsible for SAN automaticity. Finally, we emphasize how these mechanically activated changes contribute to the pathophysiology of SAN dysfunction and discuss controversial areas necessitating future investigations. Though the exact mechanisms of SAN mechanosensitivity are currently unknown, identification of such components, their impact into SAN pacemaking, and pathological remodeling may provide new therapeutic targets for the treatment of SAN dysfunction and associated rhythm abnormalities.
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Affiliation(s)
- Daniel Turner
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Chen Kang
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Pietro Mesirca
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Juan Hong
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
| | - Matteo E Mangoni
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Alexey V Glukhov
- Department of Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI, United States
| | - Rajan Sah
- Cardiovascular Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, United States
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11
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Burton RAB, Terrar DA. Emerging Evidence for cAMP-calcium Cross Talk in Heart Atrial Nanodomains Where IP 3-Evoked Calcium Release Stimulates Adenylyl Cyclases. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211008341. [PMID: 37366374 PMCID: PMC10243587 DOI: 10.1177/25152564211008341] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/01/2021] [Accepted: 03/07/2021] [Indexed: 06/28/2023]
Abstract
Calcium handling is vital to normal physiological function in the heart. Human atrial arrhythmias, eg. atrial fibrillation, are a major morbidity and mortality burden, yet major gaps remain in our understanding of how calcium signaling pathways function and interact. Inositol trisphosphate (IP3) is a calcium-mobilizing second messenger and its agonist-induced effects have been observed in many tissue types. In the atria IP3 receptors (IR3Rs) residing on junctional sarcoplasmic reticulum augment cellular calcium transients and, when over-stimulated, lead to arrhythmogenesis. Recent studies have demonstrated that the predominant pathway for IP3 actions in atrial myocytes depends on stimulation of calcium-dependent forms of adenylyl cyclase (AC8 and AC1) by IP3-evoked calcium release from the sarcoplasmic reticulum. AC8 shows co-localisation with IP3Rs and AC1 appears to be nearby. These observations support crosstalk between calcium and cAMP pathways in nanodomains in atria. Similar mechanisms also appear to operate in the pacemaker region of the sinoatrial node. Here we discuss these significant advances in our understanding of atrial physiology and pathology, together with implications for the identification of potential novel targets and modulators for the treatment of atrial arrhythmias.
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Affiliation(s)
| | - Derek A. Terrar
- Department of Pharmacology, University of Oxford, Oxford, UK
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12
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Minimal contribution of IP 3R2 in cardiac differentiation and derived ventricular-like myocytes from human embryonic stem cells. Acta Pharmacol Sin 2020; 41:1576-1586. [PMID: 33037404 DOI: 10.1038/s41401-020-00528-w] [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: 05/14/2020] [Accepted: 09/03/2020] [Indexed: 02/06/2023] Open
Abstract
Type 2 inositol 1,4,5-trisphosphate receptor (IP3R2) regulates the intracellular Ca2+ release from endoplasmic reticulum in human embryonic stem cells (hESCs), cardiovascular progenitor cells (CVPCs), and mammalian cardiomyocytes. However, the role of IP3R2 in human cardiac development is unknown and its function in mammalian cardiomyocytes is controversial. hESC-derived cardiomyocytes have unique merits in disease modeling, cell therapy, and drug screening. Therefore, understanding the role of IP3R2 in the generation and function of human cardiomyocytes would be valuable for the application of hESC-derived cardiomyocytes. In the current study, we investigated the role of IP3R2 in the differentiation of hESCs to cardiomyocytes and in the hESC-derived cardiomyocytes. By using IP3R2 knockout (IP3R2KO) hESCs, we showed that IP3R2KO did not affect the self-renewal of hESCs as well as the differentiation ability of hESCs into CVPCs and cardiomyocytes. Furthermore, we demonstrated the ventricular-like myocyte characteristics of hESC-derived cardiomyocytes. Under the α1-adrenergic stimulation by phenylephrine (10 μmol/L), the amplitude and maximum rate of depolarization of action potential (AP) were slightly affected in the IP3R2KO hESC-derived cardiomyocytes at differentiation day 90, whereas the other parameters of APs and the Ca2+ transients did not show significant changes compared with these in the wide-type ones. These results demonstrate that IP3R2 has minimal contribution to the differentiation and function of human cardiomyocytes derived from hESCs, thus provide the new knowledge to the function of IP3R2 in the generation of human cardiac lineage cells and in the early cardiomyocytes.
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Capel RA, Bose SJ, Collins TP, Rajasundaram S, Ayagama T, Zaccolo M, Burton RAB, Terrar DA. IP 3-mediated Ca 2+ release regulates atrial Ca 2+ transients and pacemaker function by stimulation of adenylyl cyclases. Am J Physiol Heart Circ Physiol 2020; 320:H95-H107. [PMID: 33064562 PMCID: PMC7864251 DOI: 10.1152/ajpheart.00380.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inositol trisphosphate (IP3) is a Ca2+-mobilizing second messenger shown to modulate atrial muscle contraction and is thought to contribute to atrial fibrillation. Cellular pathways underlying IP3 actions in cardiac tissue remain poorly understood, and the work presented here addresses the question whether IP3-mediated Ca2+ release from the sarcoplasmic reticulum is linked to adenylyl cyclase activity including Ca2+-stimulated adenylyl cyclases (AC1 and AC8) that are selectively expressed in atria and sinoatrial node (SAN). Immunocytochemistry in guinea pig atrial myocytes identified colocalization of type 2 IP3 receptors with AC8, while AC1 was located in close vicinity. Intracellular photorelease of IP3 by UV light significantly enhanced the amplitude of the Ca2+ transient (CaT) evoked by electrical stimulation of atrial myocytes (31 ± 6% increase 60 s after photorelease, n = 16). The increase in CaT amplitude was abolished by inhibitors of adenylyl cyclases (MDL-12,330) or protein kinase A (H89), showing that cAMP signaling is required for this effect of photoreleased IP3. In mouse, spontaneously beating right atrial preparations, phenylephrine, an α-adrenoceptor agonist with effects that depend on IP3-mediated Ca2+ release, increased the maximum beating rate by 14.7 ± 0.5%, n = 10. This effect was substantially reduced by 2.5 µmol/L 2-aminoethyl diphenylborinate and abolished by a low dose of MDL-12,330, observations which are again consistent with a functional interaction between IP3 and cAMP signaling involving Ca2+ stimulation of adenylyl cyclases in the SAN pacemaker. Understanding the interaction between IP3 receptor pathways and Ca2+-stimulated adenylyl cyclases provides important insights concerning acute mechanisms for initiation of atrial arrhythmias. NEW & NOTEWORTHY This study provides evidence supporting the proposal that IP3 signaling in cardiac atria and sinoatrial node involves stimulation of Ca2+-activated adenylyl cyclases (AC1 and AC8) by IP3-evoked Ca2+ release from junctional sarcoplasmic reticulum. AC8 and IP3 receptors are shown to be located close together, while AC1 is nearby. Greater understanding of these novel aspects of the IP3 signal transduction mechanism is important for future study in atrial physiology and pathophysiology, particularly atrial fibrillation.
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Affiliation(s)
- Rebecca A Capel
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Samuel J Bose
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thomas P Collins
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Skanda Rajasundaram
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca-Ann Beatrice Burton
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Derek A Terrar
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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MacDonald EA, Rose RA, Quinn TA. Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans. Front Physiol 2020; 11:170. [PMID: 32194439 PMCID: PMC7063087 DOI: 10.3389/fphys.2020.00170] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 02/13/2020] [Indexed: 12/22/2022] Open
Abstract
The sinoatrial node is perhaps one of the most important tissues in the entire body: it is the natural pacemaker of the heart, making it responsible for initiating each-and-every normal heartbeat. As such, its activity is heavily controlled, allowing heart rate to rapidly adapt to changes in physiological demand. Control of sinoatrial node activity, however, is complex, occurring through the autonomic nervous system and various circulating and locally released factors. In this review we discuss the coupled-clock pacemaker system and how its manipulation by neurohumoral signaling alters heart rate, considering the multitude of canonical and non-canonical agents that are known to modulate sinoatrial node activity. For each, we discuss the principal receptors involved and known intracellular signaling and protein targets, highlighting gaps in our knowledge and understanding from experimental models and human studies that represent areas for future research.
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Affiliation(s)
- Eilidh A MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
| | - Robert A Rose
- Cumming School of Medicine, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada.,School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
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Abstract
The aim of this chapter is to discuss evidence concerning the many roles of calcium ions, Ca2+, in cell signaling pathways that control heart function. Before considering details of these signaling pathways, the control of contraction in ventricular muscle by Ca2+ transients accompanying cardiac action potentials is first summarized, together with a discussion of how myocytes from the atrial and pacemaker regions of the heart diverge from this basic scheme. Cell signaling pathways regulate the size and timing of the Ca2+ transients in the different heart regions to influence function. The simplest Ca2+ signaling elements involve enzymes that are regulated by cytosolic Ca2+. Particularly important examples to be discussed are those that are stimulated by Ca2+, including Ca2+-calmodulin-dependent kinase (CaMKII), Ca2+ stimulated adenylyl cyclases, Ca2+ stimulated phosphatase and NO synthases. Another major aspect of Ca2+ signaling in the heart concerns actions of the Ca2+ mobilizing agents, inositol trisphosphate (IP3), cADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate, (NAADP). Evidence concerning roles of these Ca2+ mobilizing agents in different regions of the heart is discussed in detail. The focus of the review will be on short term regulation of Ca2+ transients and contractile function, although it is recognized that Ca2+ regulation of gene expression has important long term functional consequences which will also be briefly discussed.
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Lang D, Glukhov AV. Functional Microdomains in Heart's Pacemaker: A Step Beyond Classical Electrophysiology and Remodeling. Front Physiol 2018; 9:1686. [PMID: 30538641 PMCID: PMC6277479 DOI: 10.3389/fphys.2018.01686] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/09/2018] [Indexed: 12/12/2022] Open
Abstract
Spontaneous beating of the sinoatrial node (SAN), the primary pacemaker of the heart, is initiated, sustained, and regulated by a complex system that integrates ion channels and transporters on the cell membrane surface (often referred to as "membrane clock") with subcellular calcium handling machinery (by parity of reasoning referred to as an intracellular "Ca2+ clock"). Stable, rhythmic beating of the SAN is ensured by a rigorous synchronization between these two clocks highlighted in the coupled-clock system concept of SAN timekeeping. The emerging results demonstrate that such synchronization of the complex pacemaking machinery at the cellular level depends on tightly regulated spatiotemporal signals which are restricted to precise sub-cellular microdomains and associated with discrete clusters of different ion channels, transporters, and regulatory receptors. It has recently become evident that within the microdomains, various proteins form an interacting network and work together as a part of a macromolecular signaling complex. These protein-protein interactions are tightly controlled and regulated by a variety of neurohormonal signaling pathways and the diversity of cellular responses achieved with a limited pool of second messengers is made possible through the organization of essential signal components in particular microdomains. In this review, we highlight the emerging understanding of the functionality of distinct subcellular microdomains in SAN myocytes and their functional role in the accumulation and neurohormonal regulation of proteins involved in cardiac pacemaking. We also demonstrate how changes in scaffolding proteins may lead to microdomain-targeted remodeling and regulation of pacemaker proteins contributing to SAN dysfunction.
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Affiliation(s)
- Di Lang
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Alexey V Glukhov
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
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MacDonald EA, Stoyek MR, Rose RA, Quinn TA. Intrinsic regulation of sinoatrial node function and the zebrafish as a model of stretch effects on pacemaking. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:198-211. [PMID: 28743586 DOI: 10.1016/j.pbiomolbio.2017.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 07/17/2017] [Accepted: 07/21/2017] [Indexed: 12/18/2022]
Abstract
Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight regulation of SAN function is essential for the maintenance of normal heart rhythm and the response to (patho-)physiological changes. The SAN is regulated by extrinsic (central nervous system) and intrinsic (neurons, peptides, mechanics) factors. The positive chronotropic response to stretch in particular is essential for beat-by-beat adaptation to changes in hemodynamic load. Yet, the mechanism of this stretch response is unknown, due in part to the lack of an appropriate experimental model for targeted investigations. We have been investigating the zebrafish as a model for the study of intrinsic regulation of SAN function. In this paper, we first briefly review current knowledge of the principal components of extrinsic and intrinsic SAN regulation, derived primarily from experiments in mammals, followed by a description of the zebrafish as a novel experimental model for studies of intrinsic SAN regulation. This mini-review is followed by an original investigation of the response of the zebrafish isolated SAN to controlled stretch. Stretch causes an immediate and continuous increase in beating rate in the zebrafish isolated SAN. This increase reaches a maximum part way through a period of sustained stretch, with the total change dependent on the magnitude and direction of stretch. This is comparable to what occurs in isolated SAN from most mammals (including human), suggesting that the zebrafish is a novel experimental model for the study of mechanisms involved in the intrinsic regulation of SAN function by mechanical effects.
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Affiliation(s)
- Eilidh A MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada
| | - Matthew R Stoyek
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada
| | - Robert A Rose
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, Canada.
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Daniels RE, Haq KT, Miller LS, Chia EW, Miura M, Sorrentino V, McGuire JJ, Stuyvers BD. Cardiac expression of ryanodine receptor subtype 3; a strategic component in the intracellular Ca 2+ release system of Purkinje fibers in large mammalian heart. J Mol Cell Cardiol 2017; 104:31-42. [PMID: 28111173 DOI: 10.1016/j.yjmcc.2017.01.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 12/08/2016] [Accepted: 01/18/2017] [Indexed: 10/20/2022]
Abstract
BACKGROUND Three distinct Ca2+ release channels were identified in dog P-cells: the ryanodine receptor subtype 2 (RyR2) was detected throughout the cell, while the ryanodine receptor subtype 3 (RyR3) and inositol phosphate sensitive Ca2+ release channel (InsP3R) were found in the cell periphery. How each of these channels contributes to the Ca2+ cycling of P-cells is unclear. Recent modeling of Ca2+ mobilization in P-cells suggested that Ca2+ sensitivity of Ca2+induced Ca2+release (CICR) was larger at the P-cell periphery. Our study examined whether this numerically predicted region of Ca2+ release exists in live P-cells. We compared the regional Ca2+ dynamics with the arrangement of intracellular Ca2+ release (CR) channels. METHODS Gene expression of CR channels was measured by qPCR in Purkinje fibers and myocardium of adult Yucatan pig hearts. We characterized the CR channels protein expression in isolated P-cells by immuno-fluorescence, laser scanning confocal microscopy, and 3D reconstruction. The spontaneous Ca2+ activity and electrically-evoked Ca2+ mobilization were imaged by 2D spinning disk confocal microscopy. Functional regions of P-cell were differentiated by the characteristics of local Ca2+ events. We used the Ca2+ propagation velocities as indicators of channel Ca2+ sensitivity. RESULTS RyR2 gene expression was identical in Purkinje fibers and myocardium (6 hearts) while RyR3 and InsP3R gene expressions were, respectively, 100 and 16 times larger in the Purkinje fibers. Specific fluorescent immuno-staining of Ca2+ release channels revealed an intermediate layer of RyR3 expression between a near-membrane InsP3R-region and a central RyR2-region. We found that cell periphery produced two distinct forms of spontaneous Ca2+-transients: (1) large asymmetrical Ca2+ sparks under the membrane, and (2) typical Ca2+-wavelets propagating exclusively around the core of the cell. Larger cell-wide Ca2+ waves (CWWs) appeared occasionally traveling in the longitudinal direction through the core of Pcells. Large sparks arose in a micrometric space overlapping the InsP3R expression. The InsP3R antagonists 2-aminoethoxydiphenyl borate (2-APB; 3μM) and xestospongin C (XeC; 50μM) dramatically reduced their frequency. The Ca2+ wavelets propagated in a 5-10μm thick layered space which matched the intermediate zone of RyR3 expression. The wavelet incidence was unchanged by 2-APB or XeC, but was reduced by 60% in presence of the RyR3 antagonist dantrolene (10μM). The velocity of wavelets was two times larger (86±16μm/s; n=14) compared to CWWs' (46±10μm/s; n=11; P<0.05). Electric stimulation triggered a uniform and large elevation of Ca2+ concentration under the membrane which preceded the propagation of Ca2+ into the interior of the cell. Elevated Cai propagated at 150μm/s (147±34μm/s; n=5) through the region equivalent to the zone of RyR3 expression. This velocity dropped by 50% (75±24μm/s; n=5) in the central region wherein predominant RyR2 expression was detected. CONCLUSION We identified two layers of distinct Ca2+ release channels in the periphery of Pcell: an outer layer of InsP3Rs under the membrane and an inner layer of RyR3s. The propagation of Ca2+ events in these layers revealed that Ca2+ sensitivity of Ca2+ release was larger in the RyR3 layer compared to that of other sub-cellular regions. We propose that RyR3 expression in P-cells plays a role in the stability of electric function of Purkinje fibers.
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Affiliation(s)
- Rebecca E Daniels
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Kazi T Haq
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Lawson S Miller
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Elizabeth W Chia
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Vincenzo Sorrentino
- Department of Molecular and Developmental Medicine, University of Siena, Siena, Italy
| | - John J McGuire
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Bruno D Stuyvers
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada.
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19
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Berridge MJ. The Inositol Trisphosphate/Calcium Signaling Pathway in Health and Disease. Physiol Rev 2016; 96:1261-96. [DOI: 10.1152/physrev.00006.2016] [Citation(s) in RCA: 377] [Impact Index Per Article: 47.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Many cellular functions are regulated by calcium (Ca2+) signals that are generated by different signaling pathways. One of these is the inositol 1,4,5-trisphosphate/calcium (InsP3/Ca2+) signaling pathway that operates through either primary or modulatory mechanisms. In its primary role, it generates the Ca2+ that acts directly to control processes such as metabolism, secretion, fertilization, proliferation, and smooth muscle contraction. Its modulatory role occurs in excitable cells where it modulates the primary Ca2+ signal generated by the entry of Ca2+ through voltage-operated channels that releases Ca2+ from ryanodine receptors (RYRs) on the internal stores. In carrying out this modulatory role, the InsP3/Ca2+ signaling pathway induces subtle changes in the generation and function of the voltage-dependent primary Ca2+ signal. Changes in the nature of both the primary and modulatory roles of InsP3/Ca2+ signaling are a contributory factor responsible for the onset of a large number human diseases.
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Affiliation(s)
- Michael J. Berridge
- Laboratory of Molecular Signalling, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, United Kingdom
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20
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Kapoor N, Tran A, Kang J, Zhang R, Philipson KD, Goldhaber JI. Regulation of calcium clock-mediated pacemaking by inositol-1,4,5-trisphosphate receptors in mouse sinoatrial nodal cells. J Physiol 2015; 593:2649-63. [PMID: 25903031 DOI: 10.1113/jp270082] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/15/2015] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Inositol-1,4,5-trisphosphate receptors (IP3 Rs) modulate pacemaking in embryonic heart, but their role in adult sinoatrial node (SAN) pacemaking is uncertain. We found that stimulation of IP3 Rs accelerates spontaneous pacing rate in isolated mouse SAN cells, whereas inhibition of IP3 Rs slows pacing. In atrial-specific sodium-calcium exchanger (NCX) knockout (KO) SAN cells, where the Ca(2+) clock is uncoupled from the membrane clock, IP3 R agonists and antagonists modulate the rate of spontaneous Ca(2+) waves, suggesting that IP3 R-mediated Ca(2+) release modulates the Ca(2+) clock. IP3 R modulation also regulates Ca(2+) spark parameters, a reflection of ryanodine receptor open probability, consistent with the effect of IP3 signalling on Ca(2+) clock frequency. Modulation of Ca(2+) clock frequency by IP3 signalling in NCX KO SAN cells demonstrates that the effect is independent of NCX. These findings support development of IP3 signalling modulators for regulation of heart rate, particularly in heart failure where IP3 Rs are upregulated. ABSTRACT Cardiac pacemaking initiated by the sinus node is attributable to the interplay of several membrane currents. These include the depolarizing 'funny current' (If ) and the sodium-calcium exchanger current (INCX ). The latter is activated by ryanodine receptor (RyR)-mediated calcium (Ca(2+) ) release from the sarcoplasmic reticulum (SR). Another SR Ca(2+) release channel, the inositol-1,4,5-triphosphate receptor (IP3 R), has been implicated in the generation of spontaneous Ca(2+) release in atrial and ventricular cardiomyocytes. Whether IP3 R-mediated Ca(2+) release also influences SAN automaticity is controversial, in part due to the confounding influence of periodic Ca(2+) flux through the sarcolemma accompanying each beat. We took advantage of atrial-specific sodium-calcium exchanger (NCX) knockout (KO) SAN cells to study the influence of IP3 signalling on cardiac pacemaking in a system where periodic intracellular Ca(2+) cycling persists despite the absence of depolarization or Ca(2+) flux across the sarcolemma. We recorded confocal line scans of spontaneous Ca(2+) release in WT and NCX KO SAN cells in the presence or absence of an IP3 R blocker (2-aminoethoxydiphenyl borate, 2-APB), or during block of IP3 production by the phospholipase C inhibitor U73122. 2-APB and U73122 decreased the frequency of spontaneous Ca(2+) transients and waves in WT and NCX KO cells, respectively. Alternatively, increased IP3 production induced by phenylephrine increased Ca(2+) transient and wave frequency. We conclude that IP3 R-mediated SR Ca(2+) flux is crucial for initiating and modulating the RyR-mediated Ca(2+) cycling that regulates SAN pacemaking. Our results in NCX KO SAN cells also demonstrate that RyRs, but not NCX, are required for IP3 to modulate Ca(2+) clock frequency.
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Affiliation(s)
- Nidhi Kapoor
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Andrew Tran
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Jeanney Kang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Rui Zhang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Kenneth D Philipson
- Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
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Ju YK, Lee BH, Trajanovska S, Hao G, Allen DG, Lei M, Cannell MB. The involvement of TRPC3 channels in sinoatrial arrhythmias. Front Physiol 2015; 6:86. [PMID: 25859221 PMCID: PMC4373262 DOI: 10.3389/fphys.2015.00086] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 03/04/2015] [Indexed: 01/08/2023] Open
Abstract
Atrial fibrillation (AF) is a significant contributor to cardiovascular morbidity and mortality. The currently available treatments are limited and AF continues to be a major clinical challenge. Clinical studies have shown that AF is frequently associated with dysfunction in the sino-atrial node (SAN). The association between AF and SAN dysfunction is probably related to the communication between the SAN and the surrounding atrial cells that form the SAN-atrial pacemaker complex and/or pathological processes that affect both the SAN and atrial simultaneously. Recent evidence suggests that Ca2+ entry through TRPC3 (Transient Receptor Potential Canonical-3) channels may underlie several pathophysiological conditions -including cardiac arrhythmias. However, it is still not known if atrial and sinoatrial node cells are also involved. In this article we will first briefly review TRPC3 and IP3R signaling that relate to store/receptor-operated Ca2+ entry (SOCE/ROCE) mechanisms and cardiac arrhythmias. We will then present some of our recent research progress in this field. Our experiments results suggest that pacing-induced AF in angiotensin II (Ang II) treated mice are significantly reduced in mice lacking the TRPC3 gene (TRPC3−/− mice) compared to wild type controls. We also show that pacemaker cells express TRPC3 and several other molecular components related to SOCE/ROCE signaling, including STIM1 and IP3R. Activation of G-protein coupled receptors (GPCRs) signaling that is able to modulate SOCE/ROCE and Ang II induced Ca2+ homeostasis changes in sinoatrial complex being linked to TRPC3. The results provide new evidence that TRPC3 may play a role in sinoatrial and atrial arrhythmias that are caused by GPCRs activation.
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Affiliation(s)
- Yue-Kun Ju
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Bon Hyang Lee
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Sofie Trajanovska
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Gouliang Hao
- Department of Pharmacology, University of Oxford Oxford, UK
| | - David G Allen
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Ming Lei
- Department of Pharmacology, University of Oxford Oxford, UK
| | - Mark B Cannell
- Department of Physiology and Pharmacology, University of Bristol Bristol, UK
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Capel RA, Terrar DA. The importance of Ca(2+)-dependent mechanisms for the initiation of the heartbeat. Front Physiol 2015; 6:80. [PMID: 25859219 PMCID: PMC4373508 DOI: 10.3389/fphys.2015.00080] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 03/02/2015] [Indexed: 01/01/2023] Open
Abstract
Mechanisms underlying pacemaker activity in the sinus node remain controversial, with some ascribing a dominant role to timing events in the surface membrane (“membrane clock”) and others to uptake and release of calcium from the sarcoplasmic reticulum (SR) (“calcium clock”). Here we discuss recent evidence on mechanisms underlying pacemaker activity with a particular emphasis on the many roles of calcium. There are particular areas of controversy concerning the contribution of calcium spark-like events and the importance of I(f) to spontaneous diastolic depolarisation, though it will be suggested that neither of these is essential for pacemaking. Sodium-calcium exchange (NCX) is most often considered in the context of mediating membrane depolarisation after spark-like events. We present evidence for a broader role of this electrogenic exchanger which need not always depend upon these spark-like events. Short (milliseconds or seconds) and long (minutes) term influences of calcium are discussed including direct regulation of ion channels and NCX, and control of the activity of calcium-dependent enzymes (including CaMKII, AC1, and AC8). The balance between the many contributory factors to pacemaker activity may well alter with experimental and clinical conditions, and potentially redundant mechanisms are desirable to ensure the regular spontaneous heart rate that is essential for life. This review presents evidence that calcium is central to the normal control of pacemaking across a range of temporal scales and seeks to broaden the accepted description of the “calcium clock” to cover these important influences.
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Affiliation(s)
- Rebecca A Capel
- British Heart Foundation Centre of Research Excellence, Department of Pharmacology, University of Oxford Oxford, UK
| | - Derek A Terrar
- British Heart Foundation Centre of Research Excellence, Department of Pharmacology, University of Oxford Oxford, UK
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Louch WE, Koivumäki JT, Tavi P. Calcium signalling in developing cardiomyocytes: implications for model systems and disease. J Physiol 2015; 593:1047-63. [PMID: 25641733 PMCID: PMC4358669 DOI: 10.1113/jphysiol.2014.274712] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 12/28/2014] [Indexed: 12/15/2022] Open
Abstract
Adult cardiomyocytes exhibit complex Ca(2+) homeostasis, enabling tight control of contraction and relaxation. This intricate regulatory system develops gradually, with progressive maturation of specialized structures and increasing capacity of Ca(2+) sources and sinks. In this review, we outline current understanding of these developmental processes, and draw parallels to pathophysiological conditions where cardiomyocytes exhibit a striking regression to an immature state of Ca(2+) homeostasis. We further highlight the importance of understanding developmental physiology when employing immature cardiomyocyte models such as cultured neonatal cells and stem cells.
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Affiliation(s)
- William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo0424, Oslo, Norway
- K. G. Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo0316, Oslo, Norway
| | - Jussi T Koivumäki
- Simula Research Laboratory, Center for Cardiological Innovation and Center for Biomedical ComputingOslo, Norway
| | - Pasi Tavi
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern FinlandKuopio, Finland
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Yaniv Y, Lakatta EG, Maltsev VA. From two competing oscillators to one coupled-clock pacemaker cell system. Front Physiol 2015; 6:28. [PMID: 25741284 PMCID: PMC4327306 DOI: 10.3389/fphys.2015.00028] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 01/17/2015] [Indexed: 01/01/2023] Open
Abstract
At the beginning of this century, debates regarding “what are the main control mechanisms that ignite the action potential (AP) in heart pacemaker cells” dominated the electrophysiology field. The original theory which prevailed for over 50 years had advocated that the ensemble of surface membrane ion channels (i.e., “M-clock”) is sufficient to ignite rhythmic APs. However, more recent experimental evidence in a variety of mammals has shown that the sarcoplasmic reticulum (SR) acts as a “Ca2+-clock” rhythmically discharges diastolic local Ca2+ releases (LCRs) beneath the cell surface membrane. LCRs activate an inward current (likely that of the Na+/Ca2+ exchanger) that prompts the surface membrane “M-clock” to ignite an AP. Theoretical and experimental evidence has mounted to indicate that this clock “crosstalk” operates on a beat-to-beat basis and determines both the AP firing rate and rhythm. Our review is focused on the evolution of experimental definition and numerical modeling of the coupled-clock concept, on how mechanisms intrinsic to pacemaker cell determine both the heart rate and rhythm, and on future directions to develop further the coupled-clock pacemaker cell concept.
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Affiliation(s)
- Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT Haifa, Israel
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
| | - Victor A Maltsev
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
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Kang M, Lin N, Li C, Meng Q, Zheng Y, Yan X, Deng J, Ou Y, Zhang C, He J, Luo D. Cx43 phosphorylation on S279/282 and intercellular communication are regulated by IP3/IP3 receptor signaling. Cell Commun Signal 2014; 12:58. [PMID: 25262337 PMCID: PMC4195880 DOI: 10.1186/s12964-014-0058-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 09/11/2014] [Indexed: 11/17/2022] Open
Abstract
Background Inositol 1,4,5-trisphosphate receptor (IP3R) plays a pivotal role in the Ca2+ release process in a variety of cell types. Additionally, IP3R is distributed in ventricular intercalated discs, but its function(s) in this particular site remains unknown. Connexin (Cx43), the predominant gap junction (GJ) protein in ventricular myocardium, is linked to several signaling pathways that regulate Cx43 properties by (de)phosphorylation on multiple residues. Here, we investigated the regulatory role of IP3R in cell-cell communication and the mechanism(s) underlying this effect. Results In neonatal rat and adult mouse ventricular myocytes IP3R co-localized and co-immunoprecipitated with Cx43 in GJ plaques detected by immunostaining and western blot assays. Blocking IP3R with antagonists or silencing pan-IP3R expression with shRNA hindered the 6-carboxyfluorescein (6-CFDA) diffusion through GJs and desynchronized Ca2+ transients among confluent neonatal myocytes in culture, whereas stimulation of IP3R with IP3 ester or ATP exerted the opposite effect. Likewise, 6-CFDA propagation through GJs was modulated by IP3R activation or inhibition in cell pairs of isolated adult cardiomyocytes. Furthermore, IP3R activation or IP3R suppression promoted or suppressed, respectively, Cx43 phosphorylation on S279/282. Site-directed mutagenesis indicated that expression of a mutant Cx43-S282A (alanine) inhibited S279/282 phosphorylation and GJ permeability, while the S279A mutant showed the opposite effect in ventricular myocytes. Expression of these mutants in HEK293 cells revealed that cells with a dual S279/282 mutation failed to express exogenous Cx43, whereas cells with a single S279 or S282 mutation displayed Cx43 overexpression with increased phosphorylation of S279/282 and promotion of intercellular communication. Conclusions These results demonstrated, for the first time, that IP3R physically interacts with Cx43 and participates in the regulation of Cx43 phosphorylation on S279/282, thereby affecting GJ intercellular communication in ventricular myocytes. Electronic supplementary material The online version of this article (doi:10.1186/s12964-014-0058-6) contains supplementary material, which is available to authorized users.
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Complete His-ventricular block, atrial flutter and ventricular tachycardia as arrhythmogenic activities in a patient with takotsubo cardiomyopathy. J Cardiol Cases 2014; 10:208-212. [PMID: 30534245 DOI: 10.1016/j.jccase.2014.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/18/2014] [Accepted: 07/18/2014] [Indexed: 11/21/2022] Open
Abstract
An association of atrial arrhythmias with takotsubo cardiomyopathy (TTC) has not been described previously. Here we report a 65-year-old male patient with TTC. The sudden appearance of atrioventricular block and subsequent bradycardia are believed to be key contributing factors for the development of TTC. Both ventricular tachyarrhythmia and various atrial arrhythmias, such as atrial flutter and atrial fibrillation, were observed during the initial management of the patient's TTC. We speculate that both the left ventricular contractile dysfunction and the arrhythmogenic activities may share a common underlying etiology in advanced heart failure patients with TTC. <Learning objective: We describe a case of TTC complicated by ventricular tachycardia, atrial tachyarrhythmias, and an atrioventricular conduction disturbance and discuss the etiology of arrhythmogenic activities in TTC.>.
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Camors E, Valdivia HH. CaMKII regulation of cardiac ryanodine receptors and inositol triphosphate receptors. Front Pharmacol 2014; 5:101. [PMID: 24847270 PMCID: PMC4021131 DOI: 10.3389/fphar.2014.00101] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/17/2014] [Indexed: 01/08/2023] Open
Abstract
Ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3Rs) are structurally related intracellular calcium release channels that participate in multiple primary or secondary amplified Ca(2+) signals, triggering muscle contraction and oscillatory Ca(2+) waves, or activating transcription factors. In the heart, RyRs play an indisputable role in the process of excitation-contraction coupling as the main pathway for Ca(2+) release from sarcoplasmic reticulum (SR), and a less prominent role in the process of excitation-transcription coupling. Conversely, InsP3Rs are believed to contribute in subtle ways, only, to contraction of the heart, and in more important ways to regulation of transcription factors. Because uncontrolled activity of either RyRs or InsP3Rs may elicit life-threatening arrhythmogenic and/or remodeling Ca(2+) signals, regulation of their activity is of paramount importance for normal cardiac function. Due to their structural similarity, many regulatory factors, accessory proteins, and post-translational processes are equivalent for RyRs and InsP3Rs. Here we discuss regulation of RyRs and InsP3Rs by CaMKII phosphorylation, but touch on other kinases whenever appropriate. CaMKII is emerging as a powerful modulator of RyR and InsP3R activity but interestingly, some of the complexities and controversies surrounding phosphorylation of RyRs also apply to InsP3Rs, and a clear-cut effect of CaMKII on either channel eludes investigators for now. Nevertheless, some effects of CaMKII on global cellular activity, such as SR Ca(2+) leak or force-frequency potentiation, appear clear now, and this constrains the limits of the controversies and permits a more tractable approach to elucidate the effects of phosphorylation at the single channel level.
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Affiliation(s)
- Emmanuel Camors
- Division of Cardiovascular Medicine, Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor MI, USA
| | - Héctor H Valdivia
- Division of Cardiovascular Medicine, Department of Internal Medicine, Center for Arrhythmia Research, University of Michigan, Ann Arbor MI, USA
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Stern MD, Maltseva LA, Juhaszova M, Sollott SJ, Lakatta EG, Maltsev VA. Hierarchical clustering of ryanodine receptors enables emergence of a calcium clock in sinoatrial node cells. J Gen Physiol 2014; 143:577-604. [PMID: 24778430 PMCID: PMC4003189 DOI: 10.1085/jgp.201311123] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 04/07/2014] [Indexed: 12/12/2022] Open
Abstract
The sinoatrial node, whose cells (sinoatrial node cells [SANCs]) generate rhythmic action potentials, is the primary pacemaker of the heart. During diastole, calcium released from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyRs) interacts with membrane currents to control the rate of the heartbeat. This "calcium clock" takes the form of stochastic, partially periodic, localized calcium release (LCR) events that propagate, wave-like, for limited distances. The detailed mechanisms controlling the calcium clock are not understood. We constructed a computational model of SANCs, including three-dimensional diffusion and buffering of calcium in the cytosol and SR; explicit, stochastic gating of individual RyRs and L-type calcium channels; and a full complement of voltage- and calcium-dependent membrane currents. We did not include an anatomical submembrane space or inactivation of RyRs, the two heuristic components that have been used in prior models but are not observed experimentally. When RyRs were distributed in discrete clusters separated by >1 µm, only isolated sparks were produced in this model and LCR events did not form. However, immunofluorescent staining of SANCs for RyR revealed the presence of bridging RyR groups between large clusters, forming an irregular network. Incorporation of this architecture into the model led to the generation of propagating LCR events. Partial periodicity emerged from the interaction of LCR events, as observed experimentally. This calcium clock becomes entrained with membrane currents to accelerate the beating rate, which therefore was controlled by the activity of the SERCA pump, RyR sensitivity, and L-type current amplitude, all of which are targets of β-adrenergic-mediated phosphorylation. Unexpectedly, simulations revealed the existence of a pathological mode at high RyR sensitivity to calcium, in which the calcium clock loses synchronization with the membrane, resulting in a paradoxical decrease in beating rate in response to β-adrenergic stimulation. The model indicates that the hierarchical clustering of surface RyRs in SANCs may be a crucial adaptive mechanism. Pathological desynchronization of the clocks may explain sinus node dysfunction in heart failure and RyR mutations.
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Affiliation(s)
- Michael D Stern
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
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Beiert T, Bruegmann T, Sasse P. Optogenetic activation of Gq signalling modulates pacemaker activity of cardiomyocytes. Cardiovasc Res 2014; 102:507-16. [PMID: 24576953 DOI: 10.1093/cvr/cvu046] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Investigation of Gq signalling with pharmacological agonists of Gq-coupled receptors lacks spatio-temporal precision. The aim of this study was to establish melanopsin, a light-sensitive Gq-coupled receptor, as a new tool for the investigation of spatial and temporal effects of Gq stimulation on pacemaking in cardiomyocytes at an early developmental stage. METHODS AND RESULTS A vector for ubiquitous expression of melanopsin was tested in HEK293FT cells, which showed light-induced production of inositol-1,4,5-trisphosphate and elevation of intracellular Ca(2+) concentration. Mouse embryonic stem cells were stably transfected with this plasmid and differentiated into spontaneously beating embryoid bodies (EBs). Cardiomyocytes within EBs showed melanopsin expression and illumination (60 s, 308.5 nW/mm(2), 470 nm) of EBs increased beating rate within 10.2 ± 1.7 s to 317.1 ± 16.3% of baseline frequency. Illumination as short as 5 s was sufficient for generating the maximal frequency response. After termination of illumination, baseline frequency was reached with a decay constant of 27.1 ± 2.5 s. The light-induced acceleration of beating frequency showed a sigmoid dependence on light intensity with a half maximal effective light intensity of 41.7 nW/mm(2). Interestingly, EBs showed a high rate of irregular contractions after termination of high-intensity illumination. Local Gq activation by illumination of a small region in a functional syncytium of cardiomyocytes led to pacemaker activity within the illuminated area. CONCLUSIONS Light-induced Gq activation in melanopsin-expressing cardiomyocytes increases beating rate and generates local pacemaker activity. We propose that melanopsin is a powerful optogenetic tool for the investigation of spatial and temporal aspects of Gq signalling in cardiovascular research.
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Affiliation(s)
- Thomas Beiert
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
| | - Tobias Bruegmann
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
| | - Philipp Sasse
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
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Karppinen S, Rapila R, Mäkikallio K, Hänninen SL, Rysä J, Vuolteenaho O, Tavi P. Endothelin-1 signalling controls early embryonic heart rate in vitro and in vivo. Acta Physiol (Oxf) 2014; 210:369-80. [PMID: 24325624 DOI: 10.1111/apha.12194] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 04/10/2013] [Accepted: 01/11/2013] [Indexed: 12/13/2022]
Abstract
AIM Spontaneous activity of embryonic cardiomyocytes originates from sarcoplasmic reticulum (SR) Ca(2+) release during early cardiogenesis. However, the regulation of heart rate during embryonic development is still not clear. The aim of this study was to determine how endothelin-1 (ET-1) affects the heart rate of embryonic mice, as well as the pathway through which it exerts its effects. METHODS The effects of ET-1 and ET-1 receptor inhibition on cardiac contraction were studied using confocal Ca(2+) imaging of isolated mouse embryonic ventricular cardiomyocytes and ultrasonographic examination of embryonic cardiac contractions in utero. In addition, the amount of ET-1 peptide and ET receptor a (ETa) and b (ETb) mRNA levels were measured during different stages of development of the cardiac muscle. RESULTS High ET-1 concentration and expression of both ETa and ETb receptors was observed in early cardiac tissue. ET-1 was found to increase the frequency of spontaneous Ca(2+) oscillations in E10.5 embryonic cardiomyocytes in vitro. Non-specific inhibition of ET receptors with tezosentan caused arrhythmia and bradycardia in isolated embryonic cardiomyocytes and in whole embryonic hearts both in vitro (E10.5) and in utero (E12.5). ET-1-mediated stimulation of early heart rate was found to occur via ETb receptors and subsequent inositol trisphosphate receptor activation and increased SR Ca(2+) leak. CONCLUSION Endothelin-1 is required to maintain a sufficient heart rate, as well as to prevent arrhythmia during early development of the mouse heart. This is achieved through ETb receptor, which stimulates Ca(2+) leak through IP3 receptors.
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Affiliation(s)
- S. Karppinen
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - R. Rapila
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
| | - K. Mäkikallio
- Department of Obstetrics and Gynecology; University of Oulu; Oulu Finland
| | - S. L. Hänninen
- Department of Physiology; Institute of Biomedicine; University of Oulu; Oulu Finland
| | - J. Rysä
- Department of Pharmacology and Toxicology; Institute of Biomedicine; University of Oulu; Oulu Finland
| | - O. Vuolteenaho
- Department of Physiology; Institute of Biomedicine; University of Oulu; Oulu Finland
| | - P. Tavi
- Department of Biotechnology and Molecular Medicine; A.I. Virtanen Institute for Molecular Sciences; University of Eastern Finland; Kuopio Finland
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Zeng Z, Zhang H, Lin N, Kang M, Zheng Y, Li C, Xu P, Wu Y, Luo D. Role of Inositol-1,4,5-Trisphosphate Receptor in the Regulation of Calcium Transients in Neonatal Rat Ventricular Myocytes. J Pharmacol Sci 2014. [DOI: 10.1254/jphs.14029fp] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Wang P, Tang M, Gao L, Luo H, Wang G, Ma X, Duan Y. Roles of I(f) and intracellular Ca2+ release in spontaneous activity of ventricular cardiomyocytes during murine embryonic development. J Cell Biochem 2013; 114:1852-62. [PMID: 23463619 DOI: 10.1002/jcb.24527] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 02/21/2013] [Indexed: 01/01/2023]
Abstract
In recent years, the contribution of I(f), an important pacemaker current, and intracellular Ca(2+) release (ICR) from sarcoplasmic reticulum to pacemaking and arrhythmia has been intensively studied. However, their functional roles in embryonic heart remain uncertain. Using patch clamp, Ca(2+) imaging, and RT-PCR, we found that I(f) regulated the firing rate in early and late stage embryonic ventricular cells, as ivabradine (30 µM), a specific blocker of I(f), slowed down action potential (AP) frequency. This inhibitory effect was even stronger in late stage cells, though I(f) was down-regulated. In contrast to I(f), ICR was found to be indispensable for the occurrence of APs in ventricular cells of different stages, because abolishment of ICR with ryanodine and 2-aminoethoxydiphenyl borate (2-APB), specific blockers of ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs), completely abolished APs. In addition, we noticed that RyR- and IP3R-mediated ICR coexisted in early-stage ventricular cells and RyRs functionally dominated. While at late stage RyRs, but not IP3Rs, mediated ICR. In both early and late stage ventricular cells, Na-Ca exchanger current (I(Na/Ca)) mediated ICR-triggered depolarization of membrane potential and resulted in the initiation of APs. We also observed that different from I(f), which presented as the substantial component of the earlier diastolic depolarization current, application of ryanodine, and/or 2-APB slowed the late phase of diastolic depolarization. Thus, we conclude that in murine embryonic ventricular cells I(f) regulates firing rate, while RyRs and IP3Rs (early stage) or RyRs (late stage)-mediated ICR determines the occurrence of APs.
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Affiliation(s)
- Peng Wang
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, China
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Drawnel FM, Archer CR, Roderick HL. The role of the paracrine/autocrine mediator endothelin-1 in regulation of cardiac contractility and growth. Br J Pharmacol 2013; 168:296-317. [PMID: 22946456 DOI: 10.1111/j.1476-5381.2012.02195.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2012] [Revised: 08/23/2012] [Accepted: 08/28/2012] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED Endothelin-1 (ET-1) is a critical autocrine and paracrine regulator of cardiac physiology and pathology. Produced locally within the myocardium in response to diverse mechanical and neurohormonal stimuli, ET-1 acutely modulates cardiac contractility. During pathological cardiovascular conditions such as ischaemia, left ventricular hypertrophy and heart failure, myocyte expression and activity of the entire ET-1 system is enhanced, allowing the peptide to both initiate and maintain maladaptive cellular responses. Both the acute and chronic effects of ET-1 are dependent on the activation of intracellular signalling pathways, regulated by the inositol-trisphosphate and diacylglycerol produced upon activation of the ET(A) receptor. Subsequent stimulation of protein kinases C and D, calmodulin-dependent kinase II, calcineurin and MAPKs modifies the systolic calcium transient, myofibril function and the activity of transcription factors that coordinate cellular remodelling. The precise nature of the cellular response to ET-1 is governed by the timing, localization and context of such signals, allowing the peptide to regulate both cardiomyocyte physiology and instigate disease. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.
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Affiliation(s)
- Faye M Drawnel
- Babraham Research Campus, Babraham Institute, Cambridge, UK
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Circulation Research
Thematic Synopsis. Circ Res 2013; 112:e157-79. [DOI: 10.1161/circresaha.113.301756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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35
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Ju Y, Kim J, Allen D. Mouse Pacemaker Cells Express NCS-1 that is up-regulated by Taxol. Heart Lung Circ 2013. [DOI: 10.1016/j.hlc.2013.05.232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Cooley N, Ouyang K, McMullen JR, Kiriazis H, Sheikh F, Wu W, Mu Y, Du XJ, Chen J, Woodcock EA. No contribution of IP3-R(2) to disease phenotype in models of dilated cardiomyopathy or pressure overload hypertrophy. Circ Heart Fail 2012; 6:318-25. [PMID: 23258573 DOI: 10.1161/circheartfailure.112.972158] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND We investigated the contribution of inositol(1,4,5)-trisphosphate (Ins(1,4,5)P3 [IP3]) receptors (IP3-R) to disease progression in mouse models of dilated cardiomyopathy (DCM) and pressure overload hypertrophy. Mice expressing mammalian sterile 20-like kinase and dominant-negative phosphatidylinositol-3-kinase in heart (Mst1×dn-PI3K-2Tg; DCM-2Tg) develop severe DCM and conduction block, associated with increased expression of type 2 IP3-R (IP3-R(2)) and heightened generation of Ins(1,4,5)P3. Similar increases in Ins(1,4,5)P3 and IP3-R(2) are caused by transverse aortic constriction. METHODS AND RESULTS To evaluate the contribution of IP3-R(2) to disease progression, the DCM-2Tg mice were further crossed with mice in which the type 2 IP3-R (IP3-R(2)-/-) had been deleted (DCM-2Tg×IP3-R(2)-/-) and transverse aortic constriction was performed on IP3-R(2)-/- mice. Hearts from DCM-2Tg mice and DCM-2Tg×IP3-R(2)-/- were similar in terms of chamber dilatation, atrial enlargement, and ventricular wall thinning. Electrophysiological changes were also similar in the DCM-2Tg mice, with and without IP3-R(2). Deletion of IP3-R(2) did not alter the progression of heart failure, because DCM-2Tg mice with and without IP3-R(2) had similarly reduced contractility, increased lung congestion, and atrial thrombus, and both strains died between 10 and 12 weeks of age. Loss of IP3-R(2) did not alter the progression of hypertrophy after transverse aortic constriction. CONCLUSIONS We conclude that IP3-R(2) do not contribute to the progression of DCM or pressure overload hypertrophy, despite increased expression and heightened generation of the ligand, Ins(1,4,5)P3.
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Affiliation(s)
- Nicola Cooley
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
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37
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Circulation Research
Thematic Synopsis. Circ Res 2012. [DOI: 10.1161/circresaha.112.280024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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38
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Blaauw B, Del Piccolo P, Rodriguez L, Hernandez Gonzalez VH, Agatea L, Solagna F, Mammano F, Pozzan T, Schiaffino S. No evidence for inositol 1,4,5-trisphosphate-dependent Ca2+ release in isolated fibers of adult mouse skeletal muscle. ACTA ACUST UNITED AC 2012; 140:235-41. [PMID: 22802359 PMCID: PMC3409103 DOI: 10.1085/jgp.201110747] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The presence and role of functional inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) in adult skeletal muscle are controversial. The current consensus is that, in adult striated muscle, the relative amount of IP3Rs is too low and the kinetics of Ca2+ release from IP3R is too slow compared with ryanodine receptors to contribute to the Ca2+ transient during excitation–contraction coupling. However, it has been suggested that IP3-dependent Ca2+ release may be involved in signaling cascades leading to regulation of muscle gene expression. We have reinvestigated IP3-dependent Ca2+ release in isolated flexor digitorum brevis (FDB) muscle fibers from adult mice. Although Ca2+ transients were readily induced in cultured C2C12 muscle cells by (a) UTP stimulation, (b) direct injection of IP3, or (c) photolysis of membrane-permeant caged IP3, no statistically significant change in calcium signal was detected in adult FDB fibers. We conclude that the IP3–IP3R system does not appear to affect global calcium levels in adult mouse skeletal muscle.
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Affiliation(s)
- Bert Blaauw
- Venetian Institute of Molecular Medicine, 35129 Padova, Italy
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Inositol 1,4,5-trisphosphate receptors and pacemaker rhythms. J Mol Cell Cardiol 2012; 53:375-81. [PMID: 22713798 DOI: 10.1016/j.yjmcc.2012.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 06/08/2012] [Indexed: 11/21/2022]
Abstract
Intracellular Ca(2+) plays an important role in the control of the heart rate through the interaction between Ca(2+) release by ryanodine receptors in the sarcoplasmic reticulum (SR) and the extrusion of Ca(2+) by the sodium-calcium exchanger which generates an inward current. A second type of SR Ca(2+) release channel, the inositol 1,4,5-trisphosphate receptor (IP(3)R), can release Ca(2+) from SR stores in many cell types, including cardiac myocytes. However, it is still uncertain whether IP(3)Rs play any functional role in regulating the heart rate. Accumulated evidence shows that IP(3) and IP(3)R are involved in rhythm control in non-cardiac pacemaker tissues and in the embryonic heart. In this review we focus on intracellular Ca(2+) oscillations generated by Ca(2+) release from IP(3)R that initiates membrane depolarization and provides a common mechanism producing spontaneous activity in a range of cells with pacemaker function. Emerging new evidence also suggests that IP(3)/IP(3)Rs play a functional role in normal and diseased hearts and in cardiac rhythm control. Several membrane currents, including a store-operated Ca(2+) current, might be activated by Ca(2+) release from IP(3)Rs. IP(3)/IP(3)R may thus add another dimension to the complex regulation of heart rate.
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Homers regulate calcium entry and aggregation in human platelets: a role for Homers in the association between STIM1 and Orai1. Biochem J 2012; 445:29-38. [DOI: 10.1042/bj20120471] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Homer is a family of cytoplasmic adaptor proteins that play different roles in cell function, including the regulation of G-protein-coupled receptors. These proteins contain an Ena (Enabled)/VASP (vasodilator-stimulated phosphoprotein) homology 1 domain that binds to the PPXXF sequence motif, which is present in different Ca2+-handling proteins such as IP3 (inositol 1,4,5-trisphosphate) receptors and TRPC (transient receptor potential canonical) channels. In the present study we show evidence for a role of Homer proteins in the STIM1 (stromal interaction molecule 1)–Orai1 association, as well as in the TRPC1–IP3RII (type II IP3 receptor) interaction, which might be of relevance in platelet function. Treatment of human platelets with thapsigargin or thrombin results in a Ca2+-independent association of Homer1 with TRPC1 and IP3RII. In addition, thapsigargin and thrombin enhanced the association of Homer1 with STIM1 and Orai1 in a Ca2+-dependent manner. Interference with Homer function by introduction of the synthetic PPKKFR peptide into cells, which emulates the proline-rich sequences of the PPXXF motif, reduced STIM1–Orai1 and TRPC1– IP3RII associations, as compared with the introduction of the inactive PPKKRR peptide. The PPKKFR peptide attenuates thrombin-evoked Ca2+ entry and the maintenance of thapsigargin-induced store-operated Ca2+ entry. Finally, the PPKKFR peptide attenuated thrombin-induced platelet aggregation. The findings of the present study support an important role for Homer proteins in thrombin-stimulated platelet function, which is likely to be mediated by the support of agonist-induced Ca2+ entry.
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Modulation by endothelin-1 of spontaneous activity and membrane currents of atrioventricular node myocytes from the rabbit heart. PLoS One 2012; 7:e33448. [PMID: 22479400 PMCID: PMC3315568 DOI: 10.1371/journal.pone.0033448] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 02/10/2012] [Indexed: 11/19/2022] Open
Abstract
Background The atrioventricular node (AVN) is a key component of the cardiac pacemaker-conduction system. Although it is known that receptors for the peptide hormone endothelin-1 (ET-1) are expressed in the AVN, there is very little information available on the modulatory effects of ET-1 on AVN electrophysiology. This study characterises for the first time acute modulatory effects of ET-1 on AVN cellular electrophysiology. Methods Electrophysiological experiments were conducted in which recordings were made from rabbit isolated AVN cells at 35–37°C using the whole-cell patch clamp recording technique. Results Application of ET-1 (10 nM) to spontaneously active AVN cells led rapidly (within ∼13 s) to membrane potential hyperpolarisation and cessation of spontaneous action potentials (APs). This effect was prevented by pre-application of the ETA receptor inhibitor BQ-123 (1 µM) and was not mimicked by the ETB receptor agonist IRL-1620 (300 nM). In whole-cell voltage-clamp experiments, ET-1 partially inhibited L-type calcium current (ICa,L) and rapid delayed rectifier K+ current (IKr), whilst it transiently activated the hyperpolarisation-activated current (If) at voltages negative to the pacemaking range, and activated an inwardly rectifying current that was inhibited by both tertiapin-Q (300 nM) and Ba2+ ions (2 mM); each of these effects was sensitive to ETA receptor inhibition. In cells exposed to tertiapin-Q, ET-1 application did not produce membrane potential hyperpolarisation or immediate cessation of spontaneous activity; instead, there was a progressive decline in AP amplitude and depolarisation of maximum diastolic potential. Conclusions Acutely applied ET-1 exerts a direct modulatory effect on AVN cell electrophysiology. The dominant effect of ET-1 in this study was activation of a tertiapin-Q sensitive inwardly rectifying K+ current via ETA receptors, which led rapidly to cell quiescence.
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