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Veron G, Maltsev VA, Stern MD, Maltsev AV. Elementary intracellular Ca signals approximated as a transition of release channel system from a metastable state. JOURNAL OF APPLIED PHYSICS 2023; 134:124701. [PMID: 37744735 PMCID: PMC10517864 DOI: 10.1063/5.0151255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 09/04/2023] [Indexed: 09/26/2023]
Abstract
Cardiac muscle contraction is initiated by an elementary Ca signal (called Ca spark) which is achieved by collective action of Ca release channels in a cluster. The mechanism of this synchronization remains uncertain. We approached Ca spark activation as an emergent phenomenon of an interactive system of release channels. We constructed a weakly lumped Markov chain that applies an Ising model formalism to such release channel clusters and probable open channel configurations and demonstrated that spark activation is described as a system transition from a metastable to an absorbing state, analogous to the pressure required to overcome surface tension in bubble formation. This yielded quantitative estimates of the spark generation probability as a function of various system parameters. We performed numerical simulations to find spark probabilities as a function of sarcoplasmic reticulum Ca concentration, obtaining similar values for spark activation threshold as our analytic model, as well as those reported in experimental studies. Our parametric sensitivity analyses also showed that the spark activation threshold decreased as Ca sensitivity of RyR activation and RyR cluster size increased.
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Affiliation(s)
- Guillermo Veron
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Victor A. Maltsev
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Michael D. Stern
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Anna V. Maltsev
- School of Mathematical Sciences, Queen Mary University of London, London E14NS, United Kingdom
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Ca 2+ Signaling as the Untact Mode during Signaling in Metastatic Breast Cancer. Cancers (Basel) 2021; 13:cancers13061473. [PMID: 33806911 PMCID: PMC8004807 DOI: 10.3390/cancers13061473] [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: 02/15/2021] [Revised: 03/21/2021] [Accepted: 03/22/2021] [Indexed: 01/06/2023] Open
Abstract
Simple Summary Intracellular Ca2+ signaling is a critical factor in breast cancer metastasis. In the proliferation stage, increases in intracellular Ca2+ concentration through voltage-dependent Ca2+ channels, P2Y2 channels, transient receptor potential (TRP) channels, store-operated Ca2+ channels (SOCCs), and IP3 receptors and a decrease in intracellular Ca2+ concentration through plasma membrane Ca2+ ATPases and secretory pathway Ca2+ ATPases (SPCA) activate breast cancer cell proliferation. TRPM7, SOCC, inositol trisphosphate receptor (IP3R), ryanodine receptor (RyR), and sarco-/endo-plasmic reticulum Ca2+-ATPase (SERCA) increase the expression of epithelial-to-mesenchymal transition (EMT)-related proteins; meanwhile, SPCA and the Na+/Ca2+ exchanger (NCX) control the activation of EMT-related proteins. Increased Ca2+ through TRPC1, TRPM7/8, P2X7, and SOCC enhances breast cancer cell migration. The stromal interaction molecule (STIM)-Orai complex, P2X7, and Ca2+ sensing receptors are involved in invadopodia. Various pharmacological agents for Ca2+ channels have been proposed against breast cancer and have provided potential strategies for treating metastatic processes. Abstract Metastatic features of breast cancer in the brain are considered a common pathology in female patients with late-stage breast cancer. Ca2+ signaling and the overexpression pattern of Ca2+ channels have been regarded as oncogenic markers of breast cancer. In other words, breast tumor development can be mediated by inhibiting Ca2+ channels. Although the therapeutic potential of inhibiting Ca2+ channels against breast cancer has been demonstrated, the relationship between breast cancer metastasis and Ca2+ channels is not yet understood. Thus, we focused on the metastatic features of breast cancer and summarized the basic mechanisms of Ca2+-related proteins and channels during the stages of metastatic breast cancer by evaluating Ca2+ signaling. In particular, we highlighted the metastasis of breast tumors to the brain. Thus, modulating Ca2+ channels with Ca2+ channel inhibitors and combined applications will advance treatment strategies for breast cancer metastasis to the brain.
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Kohno M, Kobayashi S, Yamamoto T, Yoshitomi R, Kajii T, Fujii S, Nakamura Y, Kato T, Uchinoumi H, Oda T, Okuda S, Watanabe K, Mizukami Y, Yano M. Enhancing calmodulin binding to cardiac ryanodine receptor completely inhibits pressure-overload induced hypertrophic signaling. Commun Biol 2020; 3:714. [PMID: 33244105 PMCID: PMC7691336 DOI: 10.1038/s42003-020-01443-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 10/28/2020] [Indexed: 12/12/2022] Open
Abstract
Cardiac hypertrophy is a well-known major risk factor for poor prognosis in patients with cardiovascular diseases. Dysregulation of intracellular Ca2+ is involved in the pathogenesis of cardiac hypertrophy. However, the precise mechanism underlying cardiac hypertrophy remains elusive. Here, we investigate whether pressure-overload induced hypertrophy can be induced by destabilization of cardiac ryanodine receptor (RyR2) through calmodulin (CaM) dissociation and subsequent Ca2+ leakage, and whether it can be genetically rescued by enhancing the binding affinity of CaM to RyR2. In the very initial phase of pressure-overload induced cardiac hypertrophy, when cardiac contractile function is preserved, reactive oxygen species (ROS)-mediated RyR2 destabilization already occurs in association with relaxation dysfunction. Further, stabilizing RyR2 by enhancing the binding affinity of CaM to RyR2 completely inhibits hypertrophic signaling and improves survival. Our study uncovers a critical missing link between RyR2 destabilization and cardiac hypertrophy.
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Affiliation(s)
- Michiaki Kohno
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Shigeki Kobayashi
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Takeshi Yamamoto
- Faculty of Health Sciences, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, 755-8505, Japan
| | - Ryosuke Yoshitomi
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Toshiro Kajii
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Shohei Fujii
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Yoshihide Nakamura
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Takayoshi Kato
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Hitoshi Uchinoumi
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Tetsuro Oda
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Shinichi Okuda
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan
| | - Kenji Watanabe
- Institute of Gene Research, Yamaguchi University Science Research Center, Yamaguchi, 755-8505, Japan
| | - Yoichi Mizukami
- Institute of Gene Research, Yamaguchi University Science Research Center, Yamaguchi, 755-8505, Japan
| | - Masafumi Yano
- Department of Medicine and Clinical Science, Division of Cardiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minamikogushi, Ube, Yamaguchi, 755-8505, Japan.
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Ottolini M, Hong K, Sonkusare SK. Calcium signals that determine vascular resistance. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2019; 11:e1448. [PMID: 30884210 PMCID: PMC6688910 DOI: 10.1002/wsbm.1448] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 02/07/2019] [Accepted: 02/14/2019] [Indexed: 12/19/2022]
Abstract
Small arteries in the body control vascular resistance, and therefore, blood pressure and blood flow. Endothelial and smooth muscle cells in the arterial walls respond to various stimuli by altering the vascular resistance on a moment to moment basis. Smooth muscle cells can directly influence arterial diameter by contracting or relaxing, whereas endothelial cells that line the inner walls of the arteries modulate the contractile state of surrounding smooth muscle cells. Cytosolic calcium is a key driver of endothelial and smooth muscle cell functions. Cytosolic calcium can be increased either by calcium release from intracellular stores through IP3 or ryanodine receptors, or the influx of extracellular calcium through ion channels at the cell membrane. Depending on the cell type, spatial localization, source of a calcium signal, and the calcium-sensitive target activated, a particular calcium signal can dilate or constrict the arteries. Calcium signals in the vasculature can be classified into several types based on their source, kinetics, and spatial and temporal properties. The calcium signaling mechanisms in smooth muscle and endothelial cells have been extensively studied in the native or freshly isolated cells, therefore, this review is limited to the discussions of studies in native or freshly isolated cells. This article is categorized under: Biological Mechanisms > Cell Signaling Laboratory Methods and Technologies > Imaging Models of Systems Properties and Processes > Mechanistic Models.
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Affiliation(s)
- Matteo Ottolini
- Robert M. Berne Cardiovascular Research Center, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
- Department of Pharmacology, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
| | - Kwangseok Hong
- Robert M. Berne Cardiovascular Research Center, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
- Department of Physical Education, Chung-Ang University, Seoul, 06974, South Korea
| | - Swapnil K. Sonkusare
- Robert M. Berne Cardiovascular Research Center, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
- Department of Pharmacology, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia-School of Medicine, Charlottesville, VA, 22908, USA
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Nakamura Y, Yamamoto T, Kobayashi S, Tamitani M, Hamada Y, Fukui G, Xu X, Nishimura S, Kato T, Uchinoumi H, Oda T, Okuda S, Yano M. Ryanodine receptor-bound calmodulin is essential to protect against catecholaminergic polymorphic ventricular tachycardia. JCI Insight 2019; 4:126112. [PMID: 31167968 DOI: 10.1172/jci.insight.126112] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 04/17/2019] [Indexed: 12/12/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is caused by a single point mutation in the cardiac type 2 ryanodine receptor (RyR2). Using a knockin (KI) mouse model (R2474S/+), we previously reported that a single point mutation within the RyR2 sensitizes the channel to agonists, primarily mediated by defective interdomain interaction within the RyR2 and subsequent dissociation of calmodulin (CaM) from the RyR2. Here, we examined whether CPVT can be genetically rescued by enhancing the binding affinity of CaM to the RyR2. We first determined whether there is a possible amino acid substitution within the CaM-binding domain in the RyR2 (3584-3603 residues) that can enhance its binding affinity to CaM and found that V3599K substitution showed the highest binding affinity of CaM to the CaM-binding domain. Hence, we generated a heterozygous KI mouse model (V3599K/+) with a single amino acid substitution in the CaM-binding domain of the RyR2 and crossbred it with the heterozygous CPVT-associated R2474S/+-KI mouse to obtain a double-heterozygous R2474S/V3599K-KI mouse model. The CPVT phenotypes - bidirectional or polymorphic ventricular tachycardia, spontaneous Ca2+ transients, and Ca2+ sparks - were all inhibited in the R2474S/V3599K mice. Thus, enhancement of the CaM-binding affinity of the RyR2 is essential to prevent CPVT-associated arrhythmogenesis.
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Affiliation(s)
- Yoshihide Nakamura
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Takeshi Yamamoto
- Faculty of Health Sciences, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
| | - Shigeki Kobayashi
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Masaki Tamitani
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Yoriomi Hamada
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Go Fukui
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Xiaojuan Xu
- Department of Pathology and Pathophysiology, School of Medicine, Tongji University, Shanghai, China
| | | | - Takayoshi Kato
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Hitoshi Uchinoumi
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Tetsuro Oda
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Shinichi Okuda
- Department of Medicine and Clinical Science, Division of Cardiology, and
| | - Masafumi Yano
- Department of Medicine and Clinical Science, Division of Cardiology, and
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Williams DW, Stephenson DG, Posterino GS. The effects of Suramin on Ca 2+ activated force and sarcoplasmic reticulum Ca 2+ release in skinned fast-twitch skeletal muscle fibers of the rat. Physiol Rep 2018; 5:5/14/e13333. [PMID: 28743820 PMCID: PMC5532480 DOI: 10.14814/phy2.13333] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 05/23/2017] [Indexed: 12/25/2022] Open
Abstract
Suramin has long been used in the treatment of various human diseases. Intravenous infusions of Suramin are commonly administered to patients over extended periods of time but there are a number of significant contraindications with peripheral muscle weakness being one of the most frequently reported. Previous work has shown that even after a single infusion (300 mg kg−1) Suramin remains in skeletal muscle in effective concentrations (11.6 μg mL−1; 84 days) for prolonged periods. These observations provide a strong rationale for investigation of the specific effects of Suramin on skeletal muscle function. Single mechanically skinned fibers were directly exposed to Suramin (10, 100 or 500 μmol L−1) for defined durations (2–10 min) in controlled physiological solutions that mimic the intracellular ionic environment of a fiber. Suramin treatment (10–500 μmol L−1) directly affected the contractile apparatus in a dose‐dependent manner causing a decrease in Ca2+‐sensitivity (pCa50 = −log (Ca2+) concentration, where 50% of maximum Ca2+‐ activated force is produced) by 0.14 to 0.42 pCa units and reduction in maximum Ca2+‐activated force by 14 to 62%. Suramin treatment (100 μmol L−1 for 10 min and 500 μmol L−1 for 2 min) also caused development of a Ca2+‐independent force corresponding to 2.89 ± 4.33 and 16.77 ± 7.50% of pretreatment maximum Ca2+‐activated force, respectively. Suramin treatment (100 μmol L−1, 2 min) also increased the rate of sarcoplasmic reticulum (SR) Ca2+ release without significant changes in SR Ca2+ uptake. We report new functional effects for Suramin related to alterations in both the contractile apparatus and SR Ca2+‐handling of skeletal muscle that may contribute to the peripheral muscle weakness noted in human pharmacological treatments.
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Affiliation(s)
- Dane W Williams
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | | | - Giuseppe S Posterino
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
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De Oliveira Moreira D, Santo Neto H, Marques MJ. P2Y 2 purinergic receptors are highly expressed in cardiac and diaphragm muscles of mdx mice, and their expression is decreased by suramin. Muscle Nerve 2016; 55:116-121. [PMID: 27220808 DOI: 10.1002/mus.25199] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 05/16/2016] [Accepted: 05/23/2016] [Indexed: 12/31/2022]
Abstract
INTRODUCTION In Duchenne muscular dystrophy (DMD) and in the mdx mouse model of DMD, the lack of dystrophin leads to increased calcium influx and muscle necrosis. Patients suffer progressive muscle loss, and cardiomyopathy is an important determinant of morbidity. P2 purinergic receptors participate in the increased calcium levels in dystrophic skeletal muscles. METHODS In this study, we evaluated whether P2 receptors are involved in cardiomyopathy in mdx mice at later stages of the disease. RESULTS Western blotting revealed that P2Y2 receptor levels were upregulated (54%) in dystrophic heart compared with a normal heart. Suramin reduced the levels of P2Y2 to almost normal values. Suramin also decreased heart necrosis (reduced CK-MB) and the expression of the stretch-activated calcium channel TRPC1. CONCLUSIONS This study suggests that P2Y2 may participate in cardiomyopathy in mdx mice. P2-selective drugs with specific actions in the dystrophic heart may ameliorate cardiomyopathy in dystrophinopathies. Muscle Nerve 55: 116-121, 2017.
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Affiliation(s)
- Drielen De Oliveira Moreira
- Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, 13083-970, Brazil
| | - Humberto Santo Neto
- Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, 13083-970, Brazil
| | - Maria Julia Marques
- Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, São Paulo, 13083-970, Brazil
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The ryanodine receptor provides high throughput Ca2+-release but is precisely regulated by networks of associated proteins: a focus on proteins relevant to phosphorylation. Biochem Soc Trans 2016; 43:426-33. [PMID: 26009186 DOI: 10.1042/bst20140297] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Once opened, ryanodine receptors (RyR) are efficient pathways for the release of Ca2+ from the endoplasmic/sarcoplasmic reticulum (ER/SR). The precise nature of the Ca2+-release event, however, requires fine-tuning for the specific process and type of cell involved. For example, the spatial organization of RyRs, the luminal [Ca2+] and the influence of soluble regulators that fluctuate under physiological and pathophysiological control mechanisms, all affect the amplitude and duration of RyR Ca2+ fluxes. Various proteins are docked tightly to the huge bulky structure of RyR and there is growing evidence that, together, they provide a sophisticated and integrated system for regulating RyR channel gating. This review focuses on those proteins that are relevant to phosphorylation of RyR channels with particular reference to the cardiac isoform of RyR (RyR2). How phosphorylation of RyR affects channel activity and whether proteins such as the FK-506 binding proteins (FKBP12 and FKBP12.6) are involved, have been highly controversial subjects for more than a decade. But that is expected given the large number of participating proteins, the relevance of phosphorylation in heart failure and inherited arrhythmic diseases, and the frustrations of predicting relationships between structure and function before the advent of a high resolution structure of RyR.
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Guo T, Nani A, Shonts S, Perryman M, Chen H, Shannon T, Gillespie D, Fill M. Sarcoplasmic reticulum K(+) (TRIC) channel does not carry essential countercurrent during Ca(2+) release. Biophys J 2014; 105:1151-60. [PMID: 24010658 DOI: 10.1016/j.bpj.2013.07.042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/17/2013] [Accepted: 07/15/2013] [Indexed: 01/30/2023] Open
Abstract
The charge translocation associated with sarcoplasmic reticulum (SR) Ca(2+) efflux is compensated for by a simultaneous SR K(+) influx. This influx is essential because, with no countercurrent, the SR membrane potential (Vm) would quickly (<1 ms) reach the Ca(2+) equilibrium potential and SR Ca(2+) release would cease. The SR K(+) trimeric intracellular cation (TRIC) channel has been proposed to carry the essential countercurrent. However, the ryanodine receptor (RyR) itself also carries a substantial K(+) countercurrent during release. To better define the physiological role of the SR K(+) channel, we compared SR Ca(2+) transport in saponin-permeabilized cardiomyocytes before and after limiting SR K(+) channel function. Specifically, we reduced SR K(+) channel conduction 35 and 88% by replacing cytosolic K(+) for Na(+) or Cs(+) (respectively), changes that have little effect on RyR function. Calcium sparks, SR Ca(2+) reloading, and caffeine-evoked Ca(2+) release amplitude (and rate) were unaffected by these ionic changes. Our results show that countercurrent carried by SR K(+) (TRIC) channels is not required to support SR Ca(2+) release (or uptake). Because K(+) enters the SR through RyRs during release, the SR K(+) (TRIC) channel most likely is needed to restore trans-SR K(+) balance after RyRs close, assuring SR Vm stays near 0 mV.
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Affiliation(s)
- Tao Guo
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois, USA
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Fauconnier J, Roberge S, Saint N, Lacampagne A. Type 2 ryanodine receptor: A novel therapeutic target in myocardial ischemia/reperfusion. Pharmacol Ther 2013; 138:323-32. [DOI: 10.1016/j.pharmthera.2013.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 01/22/2013] [Indexed: 10/27/2022]
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Guo T, Fruen BR, Nitu FR, Nguyen TD, Yang Y, Cornea RL, Bers DM. FRET detection of calmodulin binding to the cardiac RyR2 calcium release channel. Biophys J 2011; 101:2170-7. [PMID: 22067155 DOI: 10.1016/j.bpj.2011.09.030] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/07/2011] [Accepted: 09/22/2011] [Indexed: 12/13/2022] Open
Abstract
Calmodulin (CaM) binding to the type 2 ryanodine receptor (RyR2) regulates Ca release from the cardiac sarcoplasmic reticulum (SR). However, the structural basis of CaM regulation of the RyR2 is poorly defined, and the presence of other potential CaM binding partners in cardiac myocytes complicates resolution of CaM's regulatory interactions with RyR2. Here, we show that a fluorescence-resonance-energy-transfer (FRET)-based approach can effectively resolve RyR2 CaM binding, both in isolated SR membrane vesicles and in permeabilized ventricular myocytes. A small FRET donor was targeted to the RyR2 cytoplasmic assembly via fluorescent labeling of the FKBP12.6 subunit. Acceptor fluorophore was attached at discrete positions within either the N- or the C-lobe of CaM. FRET between FKBP12.6 and CaM bound to SR vesicles indicated CaM binding at a single high-affinity site within 60 Å of FKBP12.6. Micromolar Ca increased the apparent affinity of CaM binding and slowed CaM dissociation, but did not significantly affect maximal FRET efficiency at saturating CaM. FRET was strongest when the acceptor was attached at either of two positions within CaM's N-lobe versus sites in CaM's C-lobe, providing CaM orientation information. In permeabilized ventricular myocytes, FKBP12.6 and CaM colocalized to Z-lines, and the efficiency of energy transfer to both the N- and C-lobes of CaM was comparable to that observed in SR vesicle experiments. Results also indicate that both the location and orientation of CaM binding on the RyR2 are very similar to the skeletal muscle RyR1 isoform. Specific binding of CaM to functional RyR2 channels in the cardiac myocyte environment can be monitored using FKBP biosensors and FRET.
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Affiliation(s)
- Tao Guo
- Department of Pharmacology, University of California, Davis, California, USA
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12
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Pitt SJ, Park KH, Nishi M, Urashima T, Aoki S, Yamazaki D, Ma J, Takeshima H, Sitsapesan R. Charade of the SR K+-channel: two ion-channels, TRIC-A and TRIC-B, masquerade as a single K+-channel. Biophys J 2010; 99:417-26. [PMID: 20643059 DOI: 10.1016/j.bpj.2010.04.051] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 04/08/2010] [Accepted: 04/23/2010] [Indexed: 11/27/2022] Open
Abstract
The presence of a sarcoplasmic reticulum (SR) K+-selective ion-channel has been known for >30 years yet the molecular identity of this channel has remained a mystery. Recently, an SR trimeric intracellular cation channel (TRIC-A) was identified but it did not exhibit all expected characteristics of the SR K+-channel. We show that a related SR protein, TRIC-B, also behaves as a cation-selective ion-channel. Comparison of the single-channel properties of purified TRIC-A and TRIC-B in symmetrical 210 mM K+ solutions, show that TRIC-B has a single-channel conductance of 138 pS with subconductance levels of 59 and 35 pS, whereas TRIC-A exhibits full- and subconductance open states of 192 and 129 pS respectively. We suggest that the K+-current fluctuations observed after incorporating cardiac or skeletal SR into bilayers, can be explained by the gating of both TRIC-A and TRIC-B channels suggesting that the SR K+-channel is not a single, distinct entity. Importantly, TRIC-A is regulated strongly by trans-membrane voltage whereas TRIC-B is activated primarily by micromolar cytosolic Ca2+ and inhibited by luminal Ca2+. Thus, TRIC-A and TRIC-B channels are regulated by different mechanisms, thereby providing maximum flexibility and scope for facilitating monovalent cation flux across the SR membrane.
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Affiliation(s)
- Samantha J Pitt
- Department of Physiology and Pharmacology and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
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Sigalas C, Mayo-Martin MB, Jane DE, Sitsapesan R. Ca2+-calmodulin increases RyR2 open probability yet reduces ryanoid association with RyR2. Biophys J 2009; 97:1907-16. [PMID: 19804721 DOI: 10.1016/j.bpj.2009.07.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 07/17/2009] [Accepted: 07/20/2009] [Indexed: 11/17/2022] Open
Abstract
We have shown that physiological levels of Ca(2+)-calmodulin (Ca(2+)CaM; 50-100 nM) activate cardiac ryanodine receptors (RyR2) incorporated into bilayers and increase the frequency of Ca(2+) sparks and waves in cardiac cells. In contrast, it is well known that Ca(2+)CaM inhibits [(3)H]ryanodine binding to cardiac sarcoplasmic reticulum. Since the [(3)H]ryanodine binding technique does not reflect the effects of Ca(2+)CaM on RyR2 open probability (Po), we have investigated, using the reversible ryanoid, ryanodol, whether Ca(2+)CaM can directly influence the binding of ryanoids to single RyR2 channels independently of Po. We demonstrate that Ca(2+)CaM reduces the rate of ryanodol association to RyR2 without affecting the rate of dissociation. We also find that ryanodol-bound channels fluctuate between at least two distinct subconductance states, M(1) and M(2), in a voltage-dependent manner. Ca(2+)CaM significantly alters the equilibrium between these two states. The results suggest that Ca(2+)CaM binding to RyR2 causes a conformation change to regions of the channel that include the ryanoid binding site, thereby leading to a decrease in ryanoid association rate and modulation of gating within the ryanoid/RyR2 bound state. Our data provide a possible explanation for why the effects of Ca(2+)CaM at the single-channel level are not mirrored by [(3)H]ryanodine binding studies.
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Affiliation(s)
- Charalambos Sigalas
- Department of Physiology and Pharmacology and Bristol Heart Institute, University of Bristol, Bristol, United Kingdom
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Sigalas C, Bent S, Kitmitto A, O'Neill S, Sitsapesan R. Ca(2+)-calmodulin can activate and inactivate cardiac ryanodine receptors. Br J Pharmacol 2009; 156:794-806. [PMID: 19220289 DOI: 10.1111/j.1476-5381.2008.00092.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Ca(2+)-calmodulin (Ca(2+)CaM) is widely accepted as an inhibitor of cardiac ryanodine receptors (RyR2); however, the effects of physiologically relevant CaM concentrations have not been fully investigated. EXPERIMENTAL APPROACH We investigated the effects of low concentrations of Ca(2+)CaM (50-100 nmol.L(-1)) on the gating of native sheep RyR2, reconstituted into bilayers. Suramin displaces CaM from RyR2 and we have used a gel-shift assay to provide evidence of the mechanism underlying this effect. Finally, using suramin to displace endogenous CaM from RyR2 in permeabilized cardiac cells, we have investigated the effects of 50 nmol.L(-1) CaM on sarcoplasmic reticulum (SR) Ca(2+)-release. KEY RESULTS Ca(2+)CaM activated or inhibited single RyR2, but activation was much more likely at low (50-100 nmol.L(-1)) concentrations. Also, suramin displaced CaM from a peptide of the CaM binding domain of RyR2, indicating that, like the skeletal isoform (RyR1), suramin directly competes with CaM for its binding site on the channel. Pre-treatment of rat permeabilized ventricular myocytes with suramin to displace CaM, followed by addition of 50 nmol x L(-1) CaM to the mock cytoplasmic solution caused an increase in the frequency of spontaneous Ca(2+)-release events. Application of caffeine demonstrated that 50 nmol x L(-1) CaM reduced SR Ca(2+) content. CONCLUSIONS AND IMPLICATIONS We describe for the first time how Ca(2+)CaM is capable, not only of inactivating, but also of activating RyR2 channels in bilayers in a CaM kinase II-independent manner. Similarly, in cardiac cells, CaM stimulates SR Ca(2+)-release and the use of caffeine suggests that this is a RyR2-mediated effect.
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Affiliation(s)
- C Sigalas
- Department of Physiology and Pharmacology and Bristol Heart Institute, University of Bristol, Bristol, UK
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15
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Stewart R, Song L, Carter SM, Sigalas C, Zaccai NR, Kanamarlapudi V, Bhat MB, Takeshima H, Sitsapesan R. Single-channel characterization of the rabbit recombinant RyR2 reveals a novel inactivation property of physiological concentrations of ATP. J Membr Biol 2008; 222:65-77. [PMID: 18418540 DOI: 10.1007/s00232-008-9102-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Accepted: 03/05/2008] [Indexed: 10/22/2022]
Abstract
Ryanodine receptor 2 (RyR2) cDNA has been available for more than 15 years; however, due to the complex nature of ligand gating in this channel, many aspects of recombinant RyR2 function have been unresearched. We established a stable, inducible HEK 293 cell line expressing full-length rabbit RyR2 cDNA and assessed the single-channel properties of the recombinant RyR2, with particular reference to ligand regulation with Ca2+ as the permeant ion. We found that the single-channel conductances of recombinant RyR2 and RyR2 isolated from cardiac muscle are essentially identical, as is irreversible modification by ryanodine. Although it is known that RyR2 expressed in HEK 293 cells is not associated with FKBP12.6, we demonstrate that these channels do not exhibit any discernable disorganized gating characteristics or subconductance states. We also show that the gating of recombinant RyR2 is indistinguishable from that of channels isolated from cardiac muscle when activated by cytosolic Ca2+, caffeine or suramin. The mechanisms underlying ATP activation are also similar; however, the experiments highlighted a novel effect of ATP at physiologically relevant concentrations of 5-10 mM. With Ca2+ as permeant ion, 5-10 mM ATP consistently inactivated recombinant channels (15/16 experiments). Such inactivation was rarely observed with native RyR2 isolated from cardiac muscle (1 in 16 experiments). However, if the channels were purified, inactivation by ATP was then revealed in all experiments. This action of ATP may be relevant for inactivation of sarcoplasmic reticulum Ca2+ release during cardiac excitation-contraction coupling or may represent unnatural behavior that is revealed when RyR2 is purified or expressed in noncardiac systems.
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Affiliation(s)
- Richard Stewart
- Department of Physiology and Pharmacology, School of Medical Sciences, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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Santonastasi M, Wehrens XHT. Ryanodine receptors as pharmacological targets for heart disease. Acta Pharmacol Sin 2007; 28:937-44. [PMID: 17588328 DOI: 10.1111/j.1745-7254.2007.00582.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Calcium release from intracellular stores plays an important role in the regulation of muscle contraction and electrical signals that determine the heart rhythm. The ryanodine receptor (RyR) is the major calcium (Ca2+) release channel required for excitation-contraction coupling in the heart. Recent studies have demonstrated that RyR are macromolecular complexes comprising of 4 pore-forming channel subunits, each of which is associated with regulatory subunits. Clinical and experimental studies over the past 5 years have provided compelling evidence that intracellular Ca2+ release channels play a pivotal role in the development of cardiac arrhythmias and heart failure. Changes in the channel regulation and subunit composition are believed to cause diastolic calcium leakage from the sarcoplasmic reticulum, which could trigger arrhythmias and weaken cardiac contractility. Therefore, cardiac RyR have emerged as potential therapeutic targets for the treatment of heart disease. Consequently, there is a strong desire to identify and/or develop novel pharmacological agents that may target these Ca2+ signaling pathways. Pharmacological agents known to modulate RyR in the heart, and their potential application towards the treatment of heart disease are discussed in this review.
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Affiliation(s)
- Marco Santonastasi
- Departments of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
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Wolner I, Kassack MU, Ullmann H, Karel A, Hohenegger M. Use-dependent inhibition of the skeletal muscle ryanodine receptor by the suramin analogue NF676. Br J Pharmacol 2006; 146:525-33. [PMID: 16056233 PMCID: PMC1751178 DOI: 10.1038/sj.bjp.0706359] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The skeletal muscle Ca2+ release channel, the ryanodine receptor, is activated by the trypanocidal drug suramin via the calmodulin-binding site. As calmodulin activates and inhibits the ryanodine receptor depending on whether Ca2+ is absent or present, suramin analogues were screened for inhibition of the ryanodine receptor. Up to 300 microM, the novel suramin analogue, 4,4'-(carbonyl-bis(imino-4,1-phenylene-(2,5-benzimidazolylene)carbonylimino))-bis-benzenesulfonic acid disodium salt (NF676) was not able to significantly inhibit the basal [3H]ryanodine binding. However, kinetic analysis of the high affinity [3H]ryanodine binding elucidates a time-dependent increment of inhibition by NF676, which is indicative for an open channel blocker. Moreover, the ryanodine receptor was much more sensitive towards inhibition by NF676 when preactivated with caffeine or the nonhydrolysable ATP analogue, adenylyl-imidodiphosphate. Nonetheless, the suramin activated ryanodine receptor was not susceptible towards high-affinity NF676 inhibition, indicating an allosteric hindrance between the binding sites of suramin and NF676. In the line of this finding, NF676 per se was not capable to elute the purified ryanodine receptor from a calmodulin-Sepharose, but it prevented the elution by suramin. Other than suramin, NF676 did not inhibit the Ca2+ ATPase of the sarcoplasmic reticulum. However, suramin-induced Ca2+ release from sarcoplasmic reticulum was completely abrogated by preincubation with NF676. Taken together, we conclude from these data that NF676 represents a novel lead compound as a potent use-dependent blocker of the skeletal muscle ryanodine receptor via an allosteric interaction with the suramin-binding site.
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Affiliation(s)
- Ilse Wolner
- Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria
| | | | | | - Anton Karel
- Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria
| | - Martin Hohenegger
- Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13A, 1090 Vienna, Austria
- Author for correspondence:
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Nadif Kasri N, Bultynck G, Parys JB, Callewaert G, Missiaen L, De Smedt H. Suramin and disulfonated stilbene derivatives stimulate the Ca2+-induced Ca2+ -release mechanism in A7r5 cells. Mol Pharmacol 2005; 68:241-50. [PMID: 15851651 DOI: 10.1124/mol.105.013045] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We have described previously a novel Ca2+-induced Ca2+-release (CICR) mechanism in permeabilized A7r5 cells (embryonic rat aorta) and 16HBE14o-cells (human bronchial mucosa) cells (J Biol Chem 278:27548-27555, 2003). This CICR mechanism was activated upon the elevation of the free cytosolic calcium concentration [Ca2+]c and was not inhibited by pharmacological inhibitors of the inositol-1,4,5-trisphosphate (IP3) receptor nor of the ryanodine receptor. This CICR mechanism was inhibited by calmodulin (CaM)1234, a Ca2+-insensitive CaM mutant, and by different members of the superfamily of CaM-like Ca2+-binding proteins. Here, we present evidence that the CICR mechanism that is expressed in A7r5 and 16HBE14o-cells is strongly activated by suramin and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS). We found several indications that both activation mechanisms are indeed two different modes of the same release system. Suramin/DIDS-induced Ca2+ release was only detected in cells that displayed the CICR mechanism, and cell types that do not express this type of CICR mechanism did not exhibit suramin/DIDS-induced Ca2+ release. Furthermore, we show that the suramin-stimulated Ca2+ release is regulated by Ca2+ and CaM in a similar way as the previously described CICR mechanism. The pharmacological characterization of the suramin/DIDS-induced Ca2+ release further confirms its properties as a novel CaM-regulated Ca2+-release mechanism. We also investigated the effects of disulfonated stilbene derivatives on IP3-induced Ca2+ release and found, in contrast to the effect on CICR, a strong inhibition by DIDS and 4'-acetoamido-4'-isothiocyanostilbene-2',2'-disulfonic acid.
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Affiliation(s)
- Nael Nadif Kasri
- Laboratorium voor Fysiologie, Katholieke Universiteit Leuven Campus Gasthuisberg Herestraat 49/802, B-3000 Leuven, Belgium
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