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Xu W, Liu H. Is CaMKII friend or foe for cell apoptosis in eye?: A narrative review. Medicine (Baltimore) 2023; 102:e36136. [PMID: 38050317 PMCID: PMC10695602 DOI: 10.1097/md.0000000000036136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 10/25/2023] [Indexed: 12/06/2023] Open
Abstract
Ca2+/calmodulin-dependent protein kinase II (CaMKII) controls cell proliferation, differentiation, apoptosis, and other biological processes that have an essential role in eye diseases. However, it seems that previous studies have generated conflicting conclusions about the effect of CaMKII on cell apoptosis. In this review, we explore the positive and potentially deleterious effects of CaMKII on eye cell apoptosis. We can safely conclude that the early elevation of CaMKII could be viewed as a promoter of cell apoptosis. Overexpression of CaMKII by transfection or pretreatment with drugs helped combat cell apoptosis.
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Affiliation(s)
- Weixing Xu
- School of Graduate, Dalian Medical University, Dalian, China
- The Third Affiliated Hospital of Jinzhou Medical University, Jinzhou, China
| | - Hua Liu
- School of Graduate, Dalian Medical University, Dalian, China
- School of Graduate, Jinzhou Medical University, Jinzhou, China
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2
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Hegner P, Lebek S, Schaner B, Ofner F, Gugg M, Maier LS, Arzt M, Wagner S. CaMKII-Dependent Contractile Dysfunction and Pro-Arrhythmic Activity in a Mouse Model of Obstructive Sleep Apnea. Antioxidants (Basel) 2023; 12:antiox12020315. [PMID: 36829874 PMCID: PMC9952298 DOI: 10.3390/antiox12020315] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 01/31/2023] Open
Abstract
Left ventricular contractile dysfunction and arrhythmias frequently occur in patients with sleep-disordered breathing (SDB). The CaMKII-dependent dysregulation of cellular Ca homeostasis has recently been described in SDB patients, but these studies only partly explain the mechanism and are limited by the patients' heterogeneity. Here, we analyzed contractile function and Ca homeostasis in a mouse model of obstructive sleep apnea (OSA) that is not limited by confounding comorbidities. OSA was induced by artificial tongue enlargement with polytetrafluorethylene (PTFE) injection into the tongue of wildtype mice and mice with a genetic ablation of the oxidative activation sites of CaMKII (MMVV knock-in). After eight weeks, cardiac function was assessed with echocardiography. Reactive oxygen species (ROS) and Ca transients were measured using confocal and epifluorescence microscopy, respectively. Wildtype PTFE mice exhibited an impaired ejection fraction, while MMVV PTFE mice were fully protected. As expected, isolated cardiomyocytes from PTFE mice showed increased ROS production. We further observed decreased levels of steady-state Ca transients, decreased levels of caffeine-induced Ca transients, and increased pro-arrhythmic activity (defined as deviations from the diastolic Ca baseline) only in wildtype but not in MMVV PTFE mice. In summary, in the absence of any comorbidities, OSA was associated with contractile dysfunction and pro-arrhythmic activity and the inhibition of the oxidative activation of CaMKII conveyed cardioprotection, which may have therapeutic implications.
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Affiliation(s)
- Philipp Hegner
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Simon Lebek
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Benedikt Schaner
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Florian Ofner
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Mathias Gugg
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Lars Siegfried Maier
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Michael Arzt
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
| | - Stefan Wagner
- Department of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany
- Correspondence:
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3
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Sy MR, Keefe JA, Sutton JP, Wehrens XHT. Cardiac function, structural, and electrical remodeling by microgravity exposure. Am J Physiol Heart Circ Physiol 2023; 324:H1-H13. [PMID: 36399385 PMCID: PMC9762974 DOI: 10.1152/ajpheart.00611.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/19/2022]
Abstract
Space medicine is key to the human exploration of outer space and pushes the boundaries of science, technology, and medicine. Because of harsh environmental conditions related to microgravity and other factors and hazards in outer space, astronauts and spaceflight participants face unique health and medical challenges, including those related to the heart. In this review, we summarize the literature regarding the effects of spaceflight on cardiac structure and function. We also provide an in-depth review of the literature regarding the effects of microgravity on cardiac calcium handling. Our review can inform future mechanistic and therapeutic studies and is applicable to other physiological states similar to microgravity such as prolonged horizontal bed rest and immobilization.
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Affiliation(s)
- Mary R Sy
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas
- Department of Integrative Physiology, Baylor College of Medicine, Houston, Texas
| | - Joshua A Keefe
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas
- Department of Integrative Physiology, Baylor College of Medicine, Houston, Texas
| | - Jeffrey P Sutton
- Center for Space Medicine, Baylor College of Medicine, Houston, Texas
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Xander H T Wehrens
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, Texas
- Department of Integrative Physiology, Baylor College of Medicine, Houston, Texas
- Center for Space Medicine, Baylor College of Medicine, Houston, Texas
- Department of Medicine, Baylor College of Medicine, Houston, Texas
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas
- Department of Pediatrics, Baylor College of Medicine, Houston, Texas
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4
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Molecular, Subcellular, and Arrhythmogenic Mechanisms in Genetic RyR2 Disease. Biomolecules 2022; 12:biom12081030. [PMID: 35892340 PMCID: PMC9394283 DOI: 10.3390/biom12081030] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 07/22/2022] [Accepted: 07/24/2022] [Indexed: 11/17/2022] Open
Abstract
The ryanodine receptor (RyR2) has a critical role in controlling Ca2+ release from the sarcoplasmic reticulum (SR) throughout the cardiac cycle. RyR2 protein has multiple functional domains with specific roles, and four of these RyR2 protomers are required to form the quaternary structure that comprises the functional channel. Numerous mutations in the gene encoding RyR2 protein have been identified and many are linked to a wide spectrum of arrhythmic heart disease. Gain of function mutations (GoF) result in a hyperactive channel that causes excessive spontaneous SR Ca2+ release. This is the predominant cause of the inherited syndrome catecholaminergic polymorphic ventricular tachycardia (CPVT). Recently, rare hypoactive loss of function (LoF) mutations have been identified that produce atypical effects on cardiac Ca2+ handling that has been termed calcium release deficiency syndrome (CRDS). Aberrant Ca2+ release resulting from both GoF and LoF mutations can result in arrhythmias through the Na+/Ca2+ exchange mechanism. This mini-review discusses recent findings regarding the role of RyR2 domains and endogenous regulators that influence RyR2 gating normally and with GoF/LoF mutations. The arrhythmogenic consequences of GoF/LoF mutations will then be discussed at the macromolecular and cellular level.
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5
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Sadredini M, Manotheepan R, Lehnart SE, Anderson ME, Sjaastad I, Stokke MK. The oxidation-resistant CaMKII-MM281/282VV mutation does not prevent arrhythmias in CPVT1. Physiol Rep 2021; 9:e15030. [PMID: 34558218 PMCID: PMC8461029 DOI: 10.14814/phy2.15030] [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] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 08/11/2021] [Accepted: 08/16/2021] [Indexed: 11/24/2022] Open
Abstract
Catecholaminergic polymorphic ventricular tachycardia type 1 (CPVT1) is an inherited arrhythmogenic disorder caused by missense mutations in the cardiac ryanodine receptors (RyR2), that result in increased β-adrenoceptor stimulation-induced diastolic Ca2+ leak. We have previously shown that exercise training prevents arrhythmias in CPVT1, potentially by reducing the oxidation of Ca2+ /calmodulin-dependent protein kinase type II (CaMKII). Therefore, we tested whether an oxidation-resistant form of CaMKII protects mice carrying the CPVT1-causative mutation RyR2-R2474S (RyR2-RS) against arrhythmias. Antioxidant treatment (N-acetyl-L-cysteine) reduced the frequency of β-adrenoceptor stimulation-induced arrhythmogenic Ca2+ waves in isolated cardiomyocytes from RyR2-RS mice. To test whether the prevention of CaMKII oxidation exerts an antiarrhythmic effect, mice expressing the oxidation-resistant CaMKII-MM281/282VV variant (MMVV) were crossed with RyR2-RS mice to create a double transgenic model (RyR2-RS/MMVV). Wild-type mice served as controls. Telemetric ECG surveillance revealed an increased incidence of ventricular tachycardia and an increased arrhythmia score in both RyR2-RS and RyR2-RS/MMVV compared to wild-type mice, both following a β-adrenoceptor challenge (isoprenaline i.p.), and following treadmill exercise combined with a β-adrenoceptor challenge. There were no differences in the incidence of arrhythmias between RyR2-RS and RyR2-RS/MMVV mice. Furthermore, no differences were observed in β-adrenoceptor stimulation-induced Ca2+ waves in RyR2-RS/MMVV compared to RyR2-RS. In conclusion, antioxidant treatment reduces β-adrenoceptor stimulation-induced Ca2+ waves in RyR2-RS cardiomyocytes. However, oxidation-resistant CaMKII-MM281/282VV does not protect RyR2-RS mice from β-adrenoceptor stimulation-induced Ca2+ waves or arrhythmias. Hence, alternative oxidation-sensitive targets need to be considered to explain the beneficial effect of antioxidant treatment on Ca2+ waves in cardiomyocytes from RyR2-RS mice.
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Affiliation(s)
- Mani Sadredini
- Institute for Experimental Medical Research and KG Jebsen Cardiac Research CentreOslo University Hospital and University of OsloOsloNorway
| | - Ravinea Manotheepan
- Institute for Experimental Medical Research and KG Jebsen Cardiac Research CentreOslo University Hospital and University of OsloOsloNorway
| | - Stephan E. Lehnart
- Heart Research Center GöttingenDepartment of Cardiology and PulmonologyUniversity Medical Center GöttingenGeorg August University GöttingenGöttingenGermany
- Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC)University of GöttingenGöttingenGermany
- DZHK (German Centre for Cardiovascular Research)GöttingenGermany
| | - Mark E. Anderson
- Division of CardiologyDepartment of MedicineThe Johns Hopkins University School of MedicineBaltimoreUSA
| | - Ivar Sjaastad
- Institute for Experimental Medical Research and KG Jebsen Cardiac Research CentreOslo University Hospital and University of OsloOsloNorway
| | - Mathis K. Stokke
- Institute for Experimental Medical Research and KG Jebsen Cardiac Research CentreOslo University Hospital and University of OsloOsloNorway
- Department of CardiologyOslo University HospitalRikshospitaletOsloNorway
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6
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Sadredini M, Haugsten Hansen M, Frisk M, Louch WE, Lehnart SE, Sjaastad I, Stokke MK. CaMKII inhibition has dual effects on spontaneous Ca 2+ release and Ca 2+ alternans in ventricular cardiomyocytes from mice with a gain-of-function RyR2 mutation. Am J Physiol Heart Circ Physiol 2021; 321:H446-H460. [PMID: 34270372 DOI: 10.1152/ajpheart.00011.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In conditions with abnormally increased activity of the cardiac ryanodine receptor (RyR2), Ca2+/calmodulin-dependent protein kinase II (CaMKII) can contribute to a further destabilization of RyR2 that results in triggered arrhythmias. Therefore, inhibition of CaMKII in such conditions has been suggested as a strategy to suppress RyR2 activity and arrhythmias. However, suppression of RyR2 activity can lead to the development of arrhythmogenic Ca2+ alternans. The aim of this study was to test whether the suppression of RyR2 activity caused by inhibition of CaMKII increases propensity for Ca2+ alternans. We studied spontaneous Ca2+ release events and Ca2+ alternans in isolated left ventricular cardiomyocytes from mice carrying the gain-of-function RyR2 mutation RyR2-R2474S and from wild-type mice. CaMKII inhibition by KN-93 effectively decreased the frequency of spontaneous Ca2+ release events in RyR2-R2474S cardiomyocytes exposed to the β-adrenoceptor agonist isoprenaline. However, KN-93-treated RyR2-R2474S cardiomyocytes also showed increased propensity for Ca2+ alternans and increased Ca2+ alternans ratio compared with both an inactive analog of KN-93 and with vehicle-treated controls. This increased propensity for Ca2+ alternans was explained by prolongation of Ca2+ release refractoriness. Importantly, the increased propensity for Ca2+ alternans in KN-93-treated RyR2-R2474S cardiomyocytes did not surpass that of wild type. In conclusion, inhibition of CaMKII efficiently reduces spontaneous Ca2+ release but promotes Ca2+ alternans in RyR2-R2474S cardiomyocytes with a gain-of-function RyR2 mutation. The dominant effect in RyR2-R2474S is to reduce spontaneous Ca2+ release, which supports this intervention as a therapeutic strategy in this specific condition. However, future studies on CaMKII inhibition in conditions with increased propensity for Ca2+ alternans should include investigation of both phenomena.NEW & NOTEWORTHY Genetically increased RyR2 activity promotes arrhythmogenic Ca2+ release. Inhibition of CaMKII suppresses RyR2 activity and arrhythmogenic Ca2+ release. Suppression of RyR2 activity prolongs refractoriness of Ca2+ release. Prolonged refractoriness of Ca2+ release leads to arrhythmogenic Ca2+ alternans. CaMKII inhibition promotes Ca2+ alternans by prolonging Ca2+ release refractoriness.
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Affiliation(s)
- Mani Sadredini
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Marie Haugsten Hansen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Michael Frisk
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Stephan E Lehnart
- Department of Cardiology and Pulmonology, Heart Research Center Göttingen, University Medical Center Göttingen, Göttingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.,DZHK (German Centre for Cardiovascular Research), Göttingen, Germany
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway
| | - Mathis Korseberg Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,KG Jebsen Cardiac Research Centre, University of Oslo, Oslo, Norway.,Department of Cardiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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7
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Yan J, Bare DJ, DeSantiago J, Zhao W, Mei Y, Chen Z, Ginsburg K, Solaro RJ, Wolska BM, Bers DM, Chen SW, Ai X. JNK2, a Newly-Identified SERCA2 Enhancer, Augments an Arrhythmic [Ca 2+] SR Leak-Load Relationship. Circ Res 2021; 128:455-470. [PMID: 33334123 PMCID: PMC7897290 DOI: 10.1161/circresaha.120.318409] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RATIONALE We recently discovered pivotal contributions of stress kinase JNK2 (c-Jun N-terminal kinase isoform 2) in increased risk of atrial fibrillation through enhanced diastolic sarcoplasmic reticulum (SR) calcium (Ca2+) leak via RyR2 (ryanodine receptor isoform 2). However, the role of JNK2 in the function of the SERCA2 (SR Ca2+-ATPase), essential in maintaining SR Ca2+ content cycling during each heartbeat, is completely unknown. OBJECTIVE To test the hypothesis that JNK2 increases SERCA2 activity SR Ca2+ content and exacerbates an arrhythmic SR Ca2+ content leak-load relationship. METHODS AND RESULTS We used confocal Ca2+ imaging in myocytes and HEK-RyR2 (ryanodine receptor isoform 2-expressing human embryonic kidney 293 cells) cells, biochemistry, dual Ca2+/voltage optical mapping in intact hearts from alcohol-exposed or aged mice (where JNK2 is activated). We found that JNK2, but not JNK1 (c-Jun N-terminal kinase isoform 1), increased SERCA2 uptake and consequently elevated SR Ca2+ content load. JNK2 also associates with and phosphorylates SERCA2 proteins. JNK2 causally enhances SERCA2-ATPase activity via increased maximal rate, without altering Ca2+ affinity. Unlike the CaMKII (Ca2+/calmodulin-dependent kinase II)-dependent JNK2 action in SR Ca2+ leak, JNK2-driven SERCA2 function was CaMKII independent (not prevented by CaMKII inhibition). With CaMKII blocked, the JNK2-driven SR Ca2+ loading alone did not significantly raise leak. However, with JNK2-CaMKII-driven SR Ca2+ leak present, the JNK2-enhanced SR Ca2+ uptake limited leak-induced reduction in SR Ca2+, normalizing Ca2+ transient amplitude, but at a higher arrhythmogenic SR Ca2+ leak. JNK2-specific inhibition completely normalized SR Ca2+ handling, attenuated arrhythmic Ca2+ activities, and alleviated atrial fibrillation susceptibility in aged and alcohol-exposed myocytes and intact hearts. CONCLUSIONS We have identified a novel JNK2-induced activation of SERCA2. The dual action of JNK2 in CaMKII-dependent arrhythmic SR Ca2+ leak and a CaMKII-independent uptake exacerbates atrial arrhythmogenicity, while helping to maintain normal levels of Ca2+ transients and heart function. JNK2 modulation may be a novel therapeutic target for atrial fibrillation prevention and treatment.
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Affiliation(s)
- Jiajie Yan
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
| | - Dan J Bare
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
| | - Jaime DeSantiago
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
| | - Weiwei Zhao
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
| | - Yiming Mei
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
| | | | | | - R John Solaro
- Physiology, University of Illinois at Chicago, Chicago, IL
| | - Beata M Wolska
- Physiology, University of Illinois at Chicago, Chicago, IL
- Medicine, Division of Cardiology, University of Illinois at Chicago, Chicago, IL
| | - Donald M Bers
- Pharmacology, University of California Davis, Davis, CA
| | - S.R. Wayne Chen
- Physiology and Pharmacology, the Libin Cardiovascular Institute, University of Calgary, Calgary, Canada
| | - Xun Ai
- Physiology & Biophysics, Rush University Medical Center, Chicago, IL
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Lu S, Liao Z, Lu X, Katschinski DM, Mercola M, Chen J, Heller Brown J, Molkentin JD, Bossuyt J, Bers DM. Hyperglycemia Acutely Increases Cytosolic Reactive Oxygen Species via O-linked GlcNAcylation and CaMKII Activation in Mouse Ventricular Myocytes. Circ Res 2020; 126:e80-e96. [PMID: 32134364 DOI: 10.1161/circresaha.119.316288] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
RATIONALE Diabetes mellitus is a complex, multisystem disease, affecting large populations worldwide. Chronic CaMKII (Ca2+/calmodulin-dependent kinase II) activation may occur in diabetes mellitus and be arrhythmogenic. Diabetic hyperglycemia was shown to activate CaMKII by (1) O-linked attachment of N-acetylglucosamine (O-GlcNAc) at S280 leading to arrhythmia and (2) a reactive oxygen species (ROS)-mediated oxidation of CaMKII that can increase postinfarction mortality. OBJECTIVE To test whether high extracellular glucose (Hi-Glu) promotes ventricular myocyte ROS generation and the role played by CaMKII. METHODS AND RESULTS We tested how extracellular Hi-Glu influences ROS production in adult ventricular myocytes, using DCF (2',7'-dichlorodihydrofluorescein diacetate) and genetically targeted Grx-roGFP2 redox sensors. Hi-Glu (30 mmol/L) significantly increased the rate of ROS generation-an effect prevented in myocytes pretreated with CaMKII inhibitor KN-93 or from either global or cardiac-specific CaMKIIδ KO (knockout) mice. CaMKII KO or inhibition also prevented Hi-Glu-induced sarcoplasmic reticulum Ca2+ release events (Ca2+ sparks). Thus, CaMKII activation is required for Hi-Glu-induced ROS generation and sarcoplasmic reticulum Ca2+ leak in cardiomyocytes. To test the involvement of O-GlcNAc-CaMKII pathway, we inhibited GlcNAcylation removal by Thiamet G (ThmG), which mimicked the Hi-Glu-induced ROS production. Conversely, inhibition of GlcNAcylation (OSMI-1 [(αR)-α-[[(1,2-dihydro-2-oxo-6-quinolinyl)sulfonyl]amino]-N-(2-furanylmethyl)-2-methoxy-N-(2-thienylmethyl)-benzeneacetamide]) prevented ROS induction in response to either Hi-Glu or ThmG. Moreover, in a CRSPR-based knock-in mouse in which the functional GlcNAcylation site on CaMKIIδ was ablated (S280A), neither Hi-Glu nor ThmG induced myocyte ROS generation. So CaMKIIδ-S280 is required for the Hi-Glu-induced (and GlcNAc dependent) ROS production. To identify the ROS source(s), we used different inhibitors of NOX (NADPH oxidase) 2 (Gp91ds-tat peptide), NOX4 (GKT137831), mitochondrial ROS (MitoTempo), and NOS (NO synthase) pathway inhibitors (L-NAME, L-NIO, and L-NPA). Only NOX2 inhibition or KO prevented Hi-Glu/ThmG-induced ROS generation. CONCLUSIONS Diabetic hyperglycemia induces acute cardiac myocyte ROS production by NOX2 that requires O-GlcNAcylation of CaMKIIδ at S280. This novel ROS induction may exacerbate pathological consequences of diabetic hyperglycemia.
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Affiliation(s)
- Shan Lu
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Zhandi Liao
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Xiyuan Lu
- Department of Cardiology, Renji Hospital School of Medicine, Jiaotong University, Shanghai, China (X.L.)
| | - Dörthe M Katschinski
- Institute of Cardiovascular Physiology, University Medical Centre Göttingen, Germany (D.M.K.)
- German Center for Cardiovascular Research, Partner Site, Göttingen (D.M.K.)
| | - Mark Mercola
- Stanford Cardiovascular Institute and Department of Medicine, Stanford University, CA (M.M.)
| | - Ju Chen
- Department of Medicine (J.C.), University of California San Diego, La Jolla
| | - Joan Heller Brown
- Department of Pharmacology (J.H.B.), University of California San Diego, La Jolla
| | - Jeffery D Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, OH (J.D.M.)
| | - Julie Bossuyt
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
| | - Donald M Bers
- From the Department of Pharmacology, University of California, Davis School of Medicine (S.L., Z.L., J.B., D.M.B.)
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9
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Eisner DA, Caldwell JL, Trafford AW, Hutchings DC. The Control of Diastolic Calcium in the Heart: Basic Mechanisms and Functional Implications. Circ Res 2020; 126:395-412. [PMID: 31999537 PMCID: PMC7004450 DOI: 10.1161/circresaha.119.315891] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Normal cardiac function requires that intracellular Ca2+ concentration be reduced to low levels in diastole so that the ventricle can relax and refill with blood. Heart failure is often associated with impaired cardiac relaxation. Little, however, is known about how diastolic intracellular Ca2+ concentration is regulated. This article first discusses the reasons for this ignorance before reviewing the basic mechanisms that control diastolic intracellular Ca2+ concentration. It then considers how the control of systolic and diastolic intracellular Ca2+ concentration is intimately connected. Finally, it discusses the changes that occur in heart failure and how these may result in heart failure with preserved versus reduced ejection fraction.
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Affiliation(s)
- David A Eisner
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - Jessica L Caldwell
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - Andrew W Trafford
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
| | - David C Hutchings
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, United Kingdom
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10
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Qu J, Mei Q, Niu R. Oxidative CaMKII as a potential target for inflammatory disease (Review). Mol Med Rep 2019; 20:863-870. [PMID: 31173191 DOI: 10.3892/mmr.2019.10309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 05/22/2019] [Indexed: 11/06/2022] Open
Abstract
CaMKII is a calcium‑activated kinase, proved to be modulated by oxidation. Currently, the oxidative activation of CaMKII exists in several models of asthma, chronic rhinosinusitis with nasal polyps, cardiovascular disease, diabetes mellitus, acute ischemic stroke and cancer. Oxidized CaMKII (ox‑CaMKII) may be important in several of these diseases. The present review examines the mechanism underlying the oxidative activation of CaMKII and summarizes the current findings associated with the function of ox‑CaMKII in inflammatory diseases. Taken together, the findings of this review aim to improve current understanding of the function of ox‑CaMKII and provide novel insights for future research.
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Affiliation(s)
- Jingjing Qu
- Department of Lung Cancer and Gastroenterology, Hunan Cancer Hospital, Affiliated Tumor Hospital of Xiangya Medical School of Central South University, Changsha, Hunan 410008, P.R. China
| | - Quanhui Mei
- Department of Intensive Care Unit, The First People's Hospital of Changde City, Changde, Hunan 410005, P.R. China
| | - Ruichao Niu
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, P.R. China
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11
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Zhang JC, Wu HL, Chen Q, Xie XT, Zou T, Zhu C, Dong Y, Xiang GJ, Ye L, Li Y, Zhu PL. Calcium-Mediated Oscillation in Membrane Potentials and Atrial-Triggered Activity in Atrial Cells of Casq2 R33Q/R33Q Mutation Mice. Front Physiol 2018; 9:1447. [PMID: 30450052 PMCID: PMC6224359 DOI: 10.3389/fphys.2018.01447] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 09/24/2018] [Indexed: 12/11/2022] Open
Abstract
Aim: We investigated the underlying mechanisms in atrial fibrillation (AF) associated with R33Q mutation and Ca2+-triggered activity. Methods and Results: We examined AF susceptibility with intraesophageal burst pacing in the sarcoplasmic reticulum (SR) Ca2+ leak model calsequestrin 2 R33Q (Casq2R33Q/R33Q) mice. Atrial trigger appeared in R33Q mice but not WT mice (17.24%, 5/29 vs. 0.00%, 0/32, P < 0.05). AF was induced by 25 Hz pacing in R33Q mice (48.27%, 14/29 vs. 6.25%, 2/32, P < 0.01). The mice were given 1.5 mg/kg isoproterenol (Iso), and the incidences of AF increased (65.51%, 19/29 vs. 9.21%, 3/32, P < 0.01). Electrophysiology experiments and the recording of intracellular Ca2+ indicated significant increases in the Ca2+ sparks (5.24 ± 0.75 100 μM-1.s-1 vs. 0.29 ± 0.04 100 μM-1.s-1, n = 20, P < 0.05), intracellular free Ca2+ (0.238 ± 0.009 μM vs. 0.172 ± 0.006 μM, n = 20, P < 0.05), Ca2+ wave (11.74% vs. 2.24%, n = 20, P < 0.05), transient inward current (ITi) (-0.56 ± 0.02 pA/pF vs. -0.42 ± 0.01 pA/pF, n = 10, P < 0.05), and oscillation in membrane potentials (10.71%, 3/28 vs. 4.16%, 1/24, P < 0.05) in the R33Q group, but there was no significant difference in the L-type calcium current. These effects were enhanced by Iso, and the inhibition of calmodulin-dependent protein kinase II (CaMKII) by 1 μM KN93 reversed the effects of Iso on Ca2+ sparks (5.01 ± 0.66 100 μm-1.s-1 vs. 11.33 ± 1.63 100 μm-1.s-1, P < 0.05), intracellular Ca2+ (0.245 ± 0.005 μM vs. 0.324 ± 0.008 μM, P < 0.05), Ca2+ wave (12.35% vs. 17.83%, P < 0.05), ITi (-0.61 ± 0.02 pA/pF vs. -0.78 ± 0.03 pA/pF, n = 10, P < 0.05), and oscillation in membrane potential (17.85% 5/28 vs. 32.17% 9/28, P < 0.05). The reduction of ryanodine receptor 2 (RyR2) stable subunits (Casq2, triadin, and junctin) rather than RYR2 and the increase in CaMKII, phosphor-CaMKII, phosphor-RyR2 (Ser 2814), SERCA, and NCX1.1 was reflected in the R33Q group. Conclusion: This study demonstrates that the increase in spontaneous calcium elevations corresponding to ITi that may trigger the oscillation in membrane potentials in the R33Q group, thereby increasing the risk of AF. The occurrence of spontaneous calcium elevations in R33Q atrial myocytes is due to the dysfunction of RyR2 stable subunits, CaMKII hyperactivity, and CaMKII-mediated RyR phosphorylation. An effective therapeutic strategy to intervene in Ca2+-induced AF associated with the R33Q mutation may be through CaMKII inhibition.
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Affiliation(s)
- Jian-Cheng Zhang
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Hong-Lin Wu
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Qian Chen
- Department of Critical Care Medicine Division Four, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Xiao-Ting Xie
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Tian Zou
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Chao Zhu
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Ying Dong
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Guo-Jian Xiang
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Lei Ye
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Yang Li
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Peng-Li Zhu
- Department of Geriatric Medicine, Fujian Provincial Center for Geriatrics, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
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12
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Johnson DM, Antoons G. Arrhythmogenic Mechanisms in Heart Failure: Linking β-Adrenergic Stimulation, Stretch, and Calcium. Front Physiol 2018; 9:1453. [PMID: 30374311 PMCID: PMC6196916 DOI: 10.3389/fphys.2018.01453] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/25/2018] [Indexed: 12/22/2022] Open
Abstract
Heart failure (HF) is associated with elevated sympathetic tone and mechanical load. Both systems activate signaling transduction pathways that increase cardiac output, but eventually become part of the disease process itself leading to further worsening of cardiac function. These alterations can adversely contribute to electrical instability, at least in part due to the modulation of Ca2+ handling at the level of the single cardiac myocyte. The major aim of this review is to provide a definitive overview of the links and cross talk between β-adrenergic stimulation, mechanical load, and arrhythmogenesis in the setting of HF. We will initially review the role of Ca2+ in the induction of both early and delayed afterdepolarizations, the role that β-adrenergic stimulation plays in the initiation of these and how the propensity for these may be altered in HF. We will then go onto reviewing the current data with regards to the link between mechanical load and afterdepolarizations, the associated mechano-sensitivity of the ryanodine receptor and other stretch activated channels that may be associated with HF-associated arrhythmias. Furthermore, we will discuss how alterations in local Ca2+ microdomains during the remodeling process associated the HF may contribute to the increased disposition for β-adrenergic or stretch induced arrhythmogenic triggers. Finally, the potential mechanisms linking β-adrenergic stimulation and mechanical stretch will be clarified, with the aim of finding common modalities of arrhythmogenesis that could be targeted by novel therapeutic agents in the setting of HF.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
| | - Gudrun Antoons
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
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13
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Vinogradova TM, Tagirova Sirenko S, Lakatta EG. Unique Ca 2+-Cycling Protein Abundance and Regulation Sustains Local Ca 2+ Releases and Spontaneous Firing of Rabbit Sinoatrial Node Cells. Int J Mol Sci 2018; 19:ijms19082173. [PMID: 30044420 PMCID: PMC6121616 DOI: 10.3390/ijms19082173] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/20/2018] [Accepted: 07/23/2018] [Indexed: 11/16/2022] Open
Abstract
Spontaneous beating of the heart pacemaker, the sinoatrial node, is generated by sinoatrial node cells (SANC) and caused by gradual change of the membrane potential called diastolic depolarization (DD). Submembrane local Ca2+ releases (LCR) from sarcoplasmic reticulum (SR) occur during late DD and activate an inward Na+/Ca2+ exchange current, which accelerates the DD rate leading to earlier occurrence of an action potential. A comparison of intrinsic SR Ca2+ cycling revealed that, at similar physiological Ca2+ concentrations, LCRs are large and rhythmic in permeabilized SANC, but small and random in permeabilized ventricular myocytes (VM). Permeabilized SANC spontaneously released more Ca2+ from SR than VM, despite comparable SR Ca2+ content in both cell types. In this review we discuss specific patterns of expression and distribution of SR Ca2+ cycling proteins (SR Ca2+ ATPase (SERCA2), phospholamban (PLB) and ryanodine receptors (RyR)) in SANC and ventricular myocytes. We link ability of SANC to generate larger and rhythmic LCRs with increased abundance of SERCA2, reduced abundance of the SERCA inhibitor PLB. In addition, an increase in intracellular [Ca2+] increases phosphorylation of both PLB and RyR exclusively in SANC. The differences in SR Ca2+ cycling protein expression between SANC and VM provide insights into diverse regulation of intrinsic SR Ca2+ cycling that drives automaticity of SANC.
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Affiliation(s)
- Tatiana M Vinogradova
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
| | - Syevda Tagirova Sirenko
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, 251 Bayview Blvd, Room 8B-123, Baltimore, MD 21224, USA.
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14
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Yan J, Zhao W, Thomson JK, Gao X, DeMarco DM, Carrillo E, Chen B, Wu X, Ginsburg KS, Bakhos M, Bers DM, Anderson ME, Song LS, Fill M, Ai X. Stress Signaling JNK2 Crosstalk With CaMKII Underlies Enhanced Atrial Arrhythmogenesis. Circ Res 2018; 122:821-835. [PMID: 29352041 DOI: 10.1161/circresaha.117.312536] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
RATIONALE Atrial fibrillation (AF) is the most common arrhythmia, and advanced age is an inevitable and predominant AF risk factor. However, the mechanisms that couple aging and AF propensity remain unclear, making targeted therapeutic interventions unattainable. OBJECTIVE To explore the functional role of an important stress response JNK (c-Jun N-terminal kinase) in sarcoplasmic reticulum Ca2+ handling and consequently Ca2+-mediated atrial arrhythmias. METHODS AND RESULTS We used a series of cutting-edge electrophysiological and molecular techniques, exploited the power of transgenic mouse models to detail the molecular mechanism, and verified its clinical applicability in parallel studies on donor human hearts. We discovered that significantly increased activity of the stress response kinase JNK2 (JNK isoform 2) in the aged atria is involved in arrhythmic remodeling. The JNK-driven atrial proarrhythmic mechanism is supported by a pathway linking JNK, CaMKII (Ca2+/calmodulin-dependent kinase II), and sarcoplasmic reticulum Ca2+ release RyR2 (ryanodine receptor) channels. JNK2 activates CaMKII, a critical proarrhythmic molecule in cardiac muscle. In turn, activated CaMKII upregulates diastolic sarcoplasmic reticulum Ca2+ leak mediated by RyR2 channels. This leads to aberrant intracellular Ca2+ waves and enhanced AF propensity. In contrast, this mechanism is absent in young atria. In JNK challenged animal models, this is eliminated by JNK2 ablation or CaMKII inhibition. CONCLUSIONS We have identified JNK2-driven CaMKII activation as a novel mode of kinase crosstalk and a causal factor in atrial arrhythmic remodeling, making JNK2 a compelling new therapeutic target for AF prevention and treatment.
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Affiliation(s)
- Jiajie Yan
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Weiwei Zhao
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Justin K Thomson
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Xianlong Gao
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Dominic M DeMarco
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Elena Carrillo
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Biyi Chen
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Xiaomin Wu
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Kenneth S Ginsburg
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Mamdouh Bakhos
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Donald M Bers
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Mark E Anderson
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Long-Sheng Song
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Michael Fill
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.)
| | - Xun Ai
- From the Department of Physiology and Biophysics, Rush University, Chicago, IL (J.Y., W.Z., D.M.D., E.C., M.F., X.A.); Department of Cell and Molecular Physiology (J.Y., W.Z., J.K.T., X.G., D.M.D., E.C., X.W., X.A.) and Department of Thoracic and Cardiovascular Surgery (M.B.), Loyola University Chicago, Maywood, IL; Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City (B.C., L.-S.S.); Department of Pharmacology, University of California at Davis (K.S.G., D.M.B.); and Department of Internal Medicine, Johns Hopkins University, Baltimore, MD (M.E.A.).
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15
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Abstract
Supplemental Digital Content is available in the text. Rationale: The development of a refractory period for Ca2+ spark initiation after Ca2+ release in cardiac myocytes should inhibit further Ca2+ release during the action potential plateau. However, Ca2+ release sites that did not initially activate or which have prematurely recovered from refractoriness might release Ca2+ later during the action potential and alter the cell-wide Ca2+ transient. Objective: To investigate the possibility of late Ca2+ spark (LCS) activity in intact isolated cardiac myocytes using fast confocal line scanning with improved confocality and signal to noise. Methods and Results: We recorded Ca2+ transients from cardiac ventricular myocytes isolated from rabbit hearts. Action potentials were produced by electric stimulation, and rapid solution changes were used to modify the L-type Ca2+ current. After the upstroke of the Ca2+ transient, LCSs were detected which had increased amplitude compared with diastolic Ca2+ sparks. LCS are triggered by both L-type Ca2+ channel activity during the action potential plateau, as well as by the increase of cytosolic Ca2+ associated with the Ca2+ transient itself. Importantly, a mismatch between sarcoplasmic reticulum load and L-type Ca2+ trigger can increase the number of LCS. The likelihood of triggering an LCS also depends on recovery from refractoriness that appears after prior activation. Consequences of LCS include a reduced rate of decline of the Ca2+ transient and, if frequent, formation of microscopic propagating Ca2+ release events (Ca2+ ripples). Ca2+ ripples resemble Ca2+ waves in terms of local propagation velocity but spread for only a short distance because of limited regeneration. Conclusions: These new types of Ca2+ signaling behavior extend our understanding of Ca2+-mediated signaling. LCS may provide an arrhythmogenic substrate by slowing the Ca2+ transient decline, as well as by amplifying maintained Ca2+ current effects on intracellular Ca2+ and consequently Na+/Ca2+ exchange current.
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Affiliation(s)
- Ewan D Fowler
- From the School of Physiology, Pharmacology & Neuroscience, Faculty of Biomedical Sciences, University of Bristol, University Walk, United Kingdom
| | - Cherrie H T Kong
- From the School of Physiology, Pharmacology & Neuroscience, Faculty of Biomedical Sciences, University of Bristol, University Walk, United Kingdom
| | - Jules C Hancox
- From the School of Physiology, Pharmacology & Neuroscience, Faculty of Biomedical Sciences, University of Bristol, University Walk, United Kingdom
| | - Mark B Cannell
- From the School of Physiology, Pharmacology & Neuroscience, Faculty of Biomedical Sciences, University of Bristol, University Walk, United Kingdom.
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16
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Stewart BD, Scott CE, McCoy TP, Yin G, Despa F, Despa S, Kekenes-Huskey PM. Computational modeling of amylin-induced calcium dysregulation in rat ventricular cardiomyocytes. Cell Calcium 2017; 71:65-74. [PMID: 29604965 DOI: 10.1016/j.ceca.2017.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 11/30/2017] [Accepted: 11/30/2017] [Indexed: 01/08/2023]
Abstract
Hyperamylinemia is a condition that accompanies obesity and precedes type II diabetes, and it is characterized by above-normal blood levels of amylin, the pancreas-derived peptide. Human amylin oligomerizes easily and can deposit in the pancreas [1], brain [2], and heart [3], where they have been associated with calcium dysregulation. In the heart, accumulating evidence suggests that human amylin oligomers form moderately cation-selective [4,5] channels that embed in the cell sarcolemma (SL). The oligomers increase membrane conductance in a concentration-dependent manner [5], which is correlated with elevated cytosolic Ca2+. These findings motivate our core hypothesis that non-selective inward Ca2+ conduction afforded by human amylin oligomers increase cytosolic and sarcoplasmic reticulum (SR) Ca2+ load, which thereby magnifies intracellular Ca2+ transients. Questions remain however regarding the mechanism of amylin-induced Ca2+ dysregulation, including whether enhanced SL Ca2+ influx is sufficient to elevate cytosolic Ca2+ load [6], and if so, how might amplified Ca2+ transients perturb Ca2+-dependent cardiac pathways. To investigate these questions, we modified a computational model of cardiomyocytes Ca2+ signaling to reflect experimentally-measured changes in SL membrane permeation and decreased sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) function stemming from acute and transgenic human amylin peptide exposure. With this model, we confirmed the hypothesis that increasing SL permeation alone was sufficient to enhance Ca2+ transient amplitudes. Our model indicated that amplified cytosolic transients are driven by increased Ca2+ loading of the SR and that greater fractional release may contribute to the Ca2+-dependent activation of calmodulin, which could prime the activation of myocyte remodeling pathways. Importantly, elevated Ca2+ in the SR and dyadic space collectively drive greater fractional SR Ca2+ release for human amylin expressing rats (HIP) and acute amylin-exposed rats (+Amylin) mice, which contributes to the inotropic rise in cytosolic Ca2+ transients. These findings suggest that increased membrane permeation induced by oligomeratization of amylin peptide in cell sarcolemma contributes to Ca2+ dysregulation in pre-diabetes.
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Affiliation(s)
- Bradley D Stewart
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA
| | - Caitlin E Scott
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA
| | - Thomas P McCoy
- Department of Family & Community Nursing, University of North Carolina - Greensboro, 1008 Administration Dr. McIver Building, Greensboro, NC 27412, USA
| | - Guo Yin
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA
| | - Florin Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA
| | - Sanda Despa
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, UK Medical Center, MN 150, Lexington, KY 40536, USA.
| | - Peter M Kekenes-Huskey
- Department of Chemistry, University of Kentucky, 505 Rose St. Chemistry-Physics Building, Lexington, KY 40506, USA.
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17
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Abstract
Cardiac contractility is regulated by changes in intracellular Ca concentration ([Ca2+]i). Normal function requires that [Ca2+]i be sufficiently high in systole and low in diastole. Much of the Ca needed for contraction comes from the sarcoplasmic reticulum and is released by the process of calcium-induced calcium release. The factors that regulate and fine-tune the initiation and termination of release are reviewed. The precise control of intracellular Ca cycling depends on the relationships between the various channels and pumps that are involved. We consider 2 aspects: (1) structural coupling: the transporters are organized within the dyad, linking the transverse tubule and sarcoplasmic reticulum and ensuring close proximity of Ca entry to sites of release. (2) Functional coupling: where the fluxes across all membranes must be balanced such that, in the steady state, Ca influx equals Ca efflux on every beat. The remainder of the review considers specific aspects of Ca signaling, including the role of Ca buffers, mitochondria, Ca leak, and regulation of diastolic [Ca2+]i.
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Affiliation(s)
- David A Eisner
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom.
| | - Jessica L Caldwell
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
| | - Kornél Kistamás
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
| | - Andrew W Trafford
- From the Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Manchester Academic Health Sciences Centre, University of Manchester, United Kingdom
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Sobie EA, Williams GSB, Lederer WJ. Ambiguous interactions between diastolic and SR Ca 2+ in the regulation of cardiac Ca 2+ release. J Gen Physiol 2017; 149:847-855. [PMID: 28798276 PMCID: PMC5583714 DOI: 10.1085/jgp.201711814] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 07/21/2017] [Indexed: 01/20/2023] Open
Abstract
Sobie et al. highlight unresolved issues concerning the regulation of sarcoplasmic reticulum calcium release in cardiac myocytes.
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Affiliation(s)
- Eric A Sobie
- Department of Pharmacological Sciences, Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - George S B Williams
- BioMET, Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD
| | - W J Lederer
- BioMET, Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD
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19
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Ottesen AH, Carlson CR, Louch WE, Dahl MB, Sandbu RA, Johansen RF, Jarstadmarken H, Bjørås M, Høiseth AD, Brynildsen J, Sjaastad I, Stridsberg M, Omland T, Christensen G, Røsjø H. Glycosylated Chromogranin A in Heart Failure: Implications for Processing and Cardiomyocyte Calcium Homeostasis. Circ Heart Fail 2017; 10:CIRCHEARTFAILURE.116.003675. [PMID: 28209766 DOI: 10.1161/circheartfailure.116.003675] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 01/11/2017] [Indexed: 01/02/2023]
Abstract
BACKGROUND Chromogranin A (CgA) levels have previously been found to predict mortality in heart failure (HF), but currently no information is available regarding CgA processing in HF and whether the CgA fragment catestatin (CST) may directly influence cardiomyocyte function. METHODS AND RESULTS CgA processing was characterized in postinfarction HF mice and in patients with acute HF, and the functional role of CST was explored in experimental models. Myocardial biopsies from HF, but not sham-operated mice, demonstrated high molecular weight CgA bands. Deglycosylation treatment attenuated high molecular weight bands, induced a mobility shift, and increased shorter CgA fragments. Adjusting for established risk indices and biomarkers, circulating CgA levels were found to be associated with mortality in patients with acute HF, but not in patients with acute exacerbation of chronic obstructive pulmonary disease. Low CgA-to-CST conversion was also associated with increased mortality in acute HF, thus, supporting functional relevance of impaired CgA processing in cardiovascular disease. CST was identified as a direct inhibitor of CaMKIIδ (Ca2+/calmodulin-dependent protein kinase IIδ) activity, and CST reduced CaMKIIδ-dependent phosphorylation of phospholamban and the ryanodine receptor 2. In line with CaMKIIδ inhibition, CST reduced Ca2+ spark and wave frequency, reduced Ca2+ spark dimensions, increased sarcoplasmic reticulum Ca2+ content, and augmented the magnitude and kinetics of cardiomyocyte Ca2+ transients and contractions. CONCLUSIONS CgA-to-CST conversion in HF is impaired because of hyperglycosylation, which is associated with clinical outcomes in acute HF. The mechanism for increased mortality may be dysregulated cardiomyocyte Ca2+ handling because of reduced CaMKIIδ inhibition.
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Affiliation(s)
- Anett Hellebø Ottesen
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Cathrine R Carlson
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - William E Louch
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Mai Britt Dahl
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Ragnhild A Sandbu
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Rune Forstrøm Johansen
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Hilde Jarstadmarken
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Magnar Bjørås
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Arne Didrik Høiseth
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Jon Brynildsen
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Ivar Sjaastad
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Mats Stridsberg
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Torbjørn Omland
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Geir Christensen
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.)
| | - Helge Røsjø
- From the Division of Medicine, Akershus University Hospital, Lørenskog, Norway and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., M.B.D., R.A.S., A.D.H., J.B., T.O., H.R.); Institute for Experimental Medical Research, Oslo University Hospital and Center for Heart Failure Research, University of Oslo, Norway (A.H.O., C.R.C., W.E.L., R.A.S., H.J., I.S., G.C.); Department of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway and Institute for Clinical Medicine, University of Oslo, Norway (M.B.D., R.A.S.); Department of Microbiology, Oslo University Hospital, Rikshospitalet, Norway, and University of Oslo, Norway (R.F.J., M.B.); Department of Medical Sciences, Uppsala University, Sweden (M.S.).
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20
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Oxidative stress and ca(2+) release events in mouse cardiomyocytes. Biophys J 2016; 107:2815-2827. [PMID: 25517148 DOI: 10.1016/j.bpj.2014.10.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/30/2014] [Accepted: 10/24/2014] [Indexed: 12/31/2022] Open
Abstract
Cellular oxidative stress, associated with a variety of common cardiac diseases, is well recognized to affect the function of several key proteins involved in Ca(2+) signaling and excitation-contraction coupling, which are known to be exquisitely sensitive to reactive oxygen species. These include the Ca(2+) release channels of the sarcoplasmic reticulum (ryanodine receptors or RyR2s) and the Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Oxidation of RyR2s was found to increase the open probability of the channel, whereas CaMKII can be activated independent of Ca(2+) through oxidation. Here, we investigated how oxidative stress affects RyR2 function and SR Ca(2+) signaling in situ, by analyzing Ca(2+) sparks in permeabilized mouse cardiomyocytes under a broad range of oxidative conditions. The results show that with increasing oxidative stress Ca(2+) spark duration is prolonged. In addition, long and very long-lasting (up to hundreds of milliseconds) localized Ca(2+) release events started to appear, eventually leading to sarcoplasmic reticulum (SR) Ca(2+) depletion. These changes of release duration could be prevented by the CaMKII inhibitor KN93 and did not occur in mice lacking the CaMKII-specific S2814 phosphorylation site on RyR2. The appearance of long-lasting Ca(2+) release events was paralleled by an increase of RyR2 oxidation, but also by RyR-S2814 phosphorylation, and by CaMKII oxidation. Our results suggest that in a strongly oxidative environment oxidation-dependent activation of CaMKII leads to RyR2 phosphorylation and thereby contributes to the massive prolongation of SR Ca(2+) release events.
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21
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Sankaranarayanan R, Li Y, Greensmith DJ, Eisner DA, Venetucci L. Biphasic decay of the Ca transient results from increased sarcoplasmic reticulum Ca leak. J Physiol 2016; 594:611-23. [PMID: 26537441 PMCID: PMC4785612 DOI: 10.1113/jp271473] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 10/30/2015] [Indexed: 01/25/2023] Open
Abstract
Key points Ca leak from the sarcoplasmic reticulum through the ryanodine receptor (RyR) reduces the amplitude of the Ca transient and slows its rate of decay. In the presence of β‐adrenergic stimulation, RyR‐mediated Ca leak produces a biphasic decay of the Ca transient with a fast early phase and a slow late phase. Two forms of Ca leak have been studied, Ca‐sensitising (induced by caffeine) and non‐sensitising (induced by ryanodine) and both induce biphasic decay of the Ca transient. Only Ca‐sensitising leak can be reversed by traditional RyR inhibitors such as tetracaine. Ca leak can also induce Ca waves. At low levels of leak, waves occur. As leak is increased, first biphasic decay and then slowed monophasic decay is seen. The level of leak has major effects on the shape of the Ca transient.
Abstract In heart failure, a reduction in Ca transient amplitude and contractile dysfunction can by caused by Ca leak through the sarcoplasmic reticulum (SR) Ca channel (ryanodine receptor, RyR) and/or decreased activity of the SR Ca ATPase (SERCA). We have characterised the effects of two forms of Ca leak (Ca‐sensitising and non‐sensitising) on calcium cycling and compared with those of SERCA inhibition. We measured [Ca2+]i with fluo‐3 in voltage‐clamped rat ventricular myocytes. Increasing SR leak with either caffeine (to sensitise the RyR to Ca activation) or ryanodine (non‐sensitising) had similar effects to SERCA inhibition: decreased systolic [Ca2+]i, increased diastolic [Ca2+]i and slowed decay. However, in the presence of isoproterenol, leak produced a biphasic decay of the Ca transient in the majority of cells while SERCA inhibition produced monophasic decay. Tetracaine reversed the effects of caffeine but not of ryanodine. When caffeine (1 mmol l−1) was added to a cell which displayed Ca waves, the wave frequency initially increased before waves disappeared and biphasic decay developed. Eventually (at higher caffeine concentrations), the biphasic decay was replaced by slow decay. We conclude that, in the presence of adrenergic stimulation, Ca leak can produce biphasic decay; the slow phase results from the leak opposing Ca uptake by SERCA. The degree of leak determines whether decay of Ca waves, biphasic or monophasic, occurs. Ca leak from the sarcoplasmic reticulum through the ryanodine receptor (RyR) reduces the amplitude of the Ca transient and slows its rate of decay. In the presence of β‐adrenergic stimulation, RyR‐mediated Ca leak produces a biphasic decay of the Ca transient with a fast early phase and a slow late phase. Two forms of Ca leak have been studied, Ca‐sensitising (induced by caffeine) and non‐sensitising (induced by ryanodine) and both induce biphasic decay of the Ca transient. Only Ca‐sensitising leak can be reversed by traditional RyR inhibitors such as tetracaine. Ca leak can also induce Ca waves. At low levels of leak, waves occur. As leak is increased, first biphasic decay and then slowed monophasic decay is seen. The level of leak has major effects on the shape of the Ca transient.
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Affiliation(s)
- Rajiv Sankaranarayanan
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences University of Manchester, Manchester, UK
| | - Yatong Li
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences University of Manchester, Manchester, UK
| | - David J Greensmith
- Biomedical Research Centre, School of Environment & Life Sciences, University of Salford, Salford, UK
| | - David A Eisner
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences University of Manchester, Manchester, UK
| | - Luigi Venetucci
- Unit of Cardiac Physiology, Institute of Cardiovascular Sciences University of Manchester, Manchester, UK.,Manchester Heart Centre, Manchester Royal Infirmary, Central Manchester Foundation Trust, Manchester, UK
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Bell JR, Raaijmakers AJA, Janssens JV, Delbridge LMD. CaMKIIδand cardiomyocyte Ca2+signalling new perspectives on splice variant targeting. Clin Exp Pharmacol Physiol 2015; 42:1327-32. [DOI: 10.1111/1440-1681.12489] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 08/27/2015] [Accepted: 08/28/2015] [Indexed: 12/29/2022]
Affiliation(s)
- James R Bell
- Department of Physiology; University of Melbourne; Victoria Australia
| | | | | | - Lea MD Delbridge
- Department of Physiology; University of Melbourne; Victoria Australia
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Chang CJ, Cheng CC, Yang TF, Chen YC, Lin YK, Chen SA, Chen YJ. Selective and non-selective non-steroidal anti-inflammatory drugs differentially regulate pulmonary vein and atrial arrhythmogenesis. Int J Cardiol 2015; 184:559-567. [PMID: 25767017 DOI: 10.1016/j.ijcard.2015.03.066] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 01/12/2015] [Accepted: 03/03/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Non-steroidal anti-inflammatory drugs (NSAIDs) increase the risk of atrial fibrillation (AF). This study investigated whether selective and non-selective NSAIDs differentially regulate the arrhythmogenesis of pulmonary veins and atria. METHODS Conventional microelectrodes were used to record action potentials (APs) in isolated rabbit PVs, sinoatrial node (SAN), left atrium (LA), and right atrium (RA) preparations before and after celecoxib or indomethacin administration. A whole-cell patch clamp was used to record the sodium-calcium exchanger (NCX) current, L-type calcium current (ICa-L), and late sodium current (INa-late) before and after celecoxib administration in isolated PV cardiomyocytes. RESULTS Celecoxib (0.3, 1, and 3 μM) reduced PV spontaneous beating rates, and induced delayed afterdepolarizations and burst firings in four of eight PV preparations (50%, p<0.05). Celecoxib also reduced SAN beating rates and decreased AP durations (APDs) in RA and LA, but did not change the resting membrane potential. Indomethacin (0.3, 1, 3, and 10 μM) changed neither the PV or SAN beating rates nor RA APDs, but it reduced LA APDs. Celecoxib (3 μM) significantly increased the NCX current and decreased the ICa-L, but did not change the INa-late. Ranolazine (10 μM) suppressed celecoxib (3 μM)-induced PV burst firings in 6 (86%, p<0.05) of 7 PVs. KB-R7943 (10 μM) suppressed celecoxib (3 μM)-induced PV burst firings in 5 (71%, p<0.05) of 7 PVs. CONCLUSIONS Selective and non-selective NSAIDs differentially modulate PV and atrial electrophysiological characteristics. Celecoxib increased PV triggered activity through enhancement of the NCX current, which contributed to its arrhythmogenesis.
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Affiliation(s)
- Chien-Jung Chang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan; Division of Cardiology, Tungs' Taichung MetroHarbor Hospital, Taichung, Taiwan
| | - Chen-Chuan Cheng
- Division of Cardiology, Chi-Mei Medical Center, Tainan, Taiwan; School of Medicine, Chung Shan Medical University, Taichung, Taiwan
| | - Ten-Fang Yang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
| | - Yao-Chang Chen
- Department of Biomedical Engineering, and Institute of Physiology, National Defense Medical Center, Taipei, Taiwan
| | - Yung-Kuo Lin
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Shih-Ann Chen
- National Yang-Ming University, School of Medicine, Taipei, Taiwan; Division of Cardiology and Cardiovascular Research Center, Veterans General Hospital-Taipei, Taipei, Taiwan
| | - Yi-Jen Chen
- Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
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Abstract
Synchronized SR calcium (Ca) release is critical to normal cardiac myocyte excitation-contraction coupling, and ideally this release shuts off completely between heartbeats. However, other SR Ca release events are referred to collectively as SR Ca leak (which includes Ca sparks and waves as well as smaller events not detectable as Ca sparks). Much, but not all, of the SR Ca leak occurs via ryanodine receptors and can be exacerbated in pathological states such as heart failure. The extent of SR Ca leak is important because it can (a) reduce SR Ca available for release, causing systolic dysfunction; (b) elevate diastolic [Ca]i, contributing to diastolic dysfunction; (c) cause triggered arrhythmias; and (d) be energetically costly because of extra ATP used to repump Ca. This review addresses quantitative aspects and manifestations of SR Ca leak and its measurement, and how leak is modulated by Ca, associated proteins, and posttranslational modifications in health and disease.
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Affiliation(s)
- Donald M Bers
- Department of Pharmacology, University of California, Davis, California 95616;
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25
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Yang Y, Guo T, Oda T, Chakraborty A, Chen L, Uchinoumi H, Knowlton AA, Fruen BR, Cornea RL, Meissner G, Bers DM. Cardiac myocyte Z-line calmodulin is mainly RyR2-bound, and reduction is arrhythmogenic and occurs in heart failure. Circ Res 2013; 114:295-306. [PMID: 24186966 DOI: 10.1161/circresaha.114.302857] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
RATIONALE Calmodulin (CaM) associates with cardiac ryanodine receptor type-2 (RyR2) as an important regulator. Defective CaM-RyR2 interaction may occur in heart failure, cardiac hypertrophy, and catecholaminergic polymorphic ventricular tachycardia. However, the in situ binding properties for CaM-RyR2 are unknown. OBJECTIVE We sought to measure the in situ binding affinity and kinetics for CaM-RyR2 in normal and heart failure ventricular myocytes, estimate the percentage of Z-line-localized CaM that is RyR2-bound, and test cellular function of defective CaM-RyR2 interaction. METHODS AND RESULTS Using fluorescence resonance energy transfer in permeabilized myocytes, we specifically resolved RyR2-bound CaM from other potential binding targets and measured CaM-RyR2 binding affinity in situ (Kd=10-20 nmol/L). Using RyR2(ADA/+) knock-in mice, in which half of the CaM-RyR2 binding is suppressed, we estimated that >90% of Z-line CaM is RyR2-bound. Functional tests indicated a higher propensity for Ca2+ wave production and stress-induced ventricular arrhythmia in RyR2(ADA/+) mice. In a post-myocardial infarction rat heart failure model, we detected a decrease in the CaM-RyR2 binding affinity (Kd≈51 nmol/L; ≈3-fold increase) and unaltered RyR2 affinity for the FK506-binding protein FKBP12.6 (Kd~0.8 nmol/L). CONCLUSIONS CaM binds to RyR2 with high affinity in cardiac myocytes. Physiologically, CaM is bound to >70% of RyR2 monomers and inhibits sarcoplasmic reticulum Ca2+ release. RyR2 is the major binding site for CaM along the Z-line in cardiomyocytes, and dissociating CaM from RyR2 can cause severe ventricular arrhythmia. In heart failure, RyR2 shows decreased CaM affinity, but unaltered FKBP 12.6 affinity.
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Affiliation(s)
- Yi Yang
- From the Department of Pharmacology (Y.Y., T.G., T.O., H.U., A.A.K., D.M.B.), and Molecular and Cellular Cardiology Division, Department of Medicine (L.C., A.A.K.), University of California, Davis, CA; Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC (A.C., G.M.); and Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN (B.R.F., R.L.C.)
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Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
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Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
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Liu N, Denegri M, Dun W, Boncompagni S, Lodola F, Protasi F, Napolitano C, Boyden PA, Priori SG. Abnormal propagation of calcium waves and ultrastructural remodeling in recessive catecholaminergic polymorphic ventricular tachycardia. Circ Res 2013; 113:142-52. [PMID: 23674379 DOI: 10.1161/circresaha.113.301783] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE The recessive form of catecholaminergic polymorphic ventricular tachycardia is caused by mutations in the cardiac calsequestrin-2 gene; this variant of catecholaminergic polymorphic ventricular tachycardia is less well characterized than the autosomal-dominant form caused by mutations in the ryanodine receptor-2 gene. OBJECTIVE We characterized the intracellular Ca²⁺ homeostasis, electrophysiological properties, and ultrastructural features of the Ca²⁺ release units in the homozygous calsequestrin 2-R33Q knock-in mouse model (R33Q) R33Q knock-in mouse model. METHODS AND RESULTS We studied isolated R33Q and wild-type ventricular myocytes and observed properties not previously identified in a catecholaminergic polymorphic ventricular tachycardia model. As compared with wild-type cells, R33Q myocytes (1) show spontaneous Ca²⁺ waves unable to propagate as cell-wide waves; (2) show smaller Ca²⁺sparks with shortened coupling intervals, suggesting a reduced refractoriness of Ca²⁺ release events; (3) have a reduction of the area of membrane contact, of the junctions between junctional sarcoplasmic reticulum and T tubules (couplons), and of junctional sarcoplasmic reticulum volume; (4) have a propensity to develop phase 2 to 4 afterdepolarizations that can elicit triggered beats; and (5) involve viral gene transfer with wild-type cardiac calsequestrin-2 that is able to normalize structural abnormalities and to restore cell-wide calcium wave propagation. CONCLUSIONS Our data show that homozygous cardiac calsequestrin-2-R33Q myocytes develop spontaneous Ca²⁺ release events with a broad range of intervals coupled to preceding beats, leading to the formation of early and delayed afterdepolarizations. They also display a major disruption of the Ca²⁺ release unit architecture that leads to fragmentation of spontaneous Ca²⁺ waves. We propose that these 2 substrates in R33Q myocytes synergize to provide a new arrhythmogenic mechanism for catecholaminergic polymorphic ventricular tachycardia.
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Affiliation(s)
- Nian Liu
- Leon H. Charney Division of Cardiology, Cardiovascular Genetics Program, New York University School of Medicine, New York, NY, USA
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Phosphorylation at Ser²⁶ in the ATP-binding site of Ca²⁺/calmodulin-dependent kinase II as a mechanism for switching off the kinase activity. Biosci Rep 2013; 33:BSR20120116. [PMID: 23289753 PMCID: PMC3566533 DOI: 10.1042/bsr20120116] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
CaMKII (Ca2+/calmodulin-dependent kinase II) is a serine/threonine phosphotransferase that is capable of long-term retention of activity due to autophosphorylation at a specific threonine residue within each subunit of its oligomeric structure. The γ isoform of CaMKII is a significant regulator of vascular contractility. Here, we show that phosphorylation of CaMKII γ at Ser26, a residue located within the ATP-binding site, terminates the sustained activity of the enzyme. To test the physiological importance of phosphorylation at Ser26, we generated a phosphospecific Ser26 antibody and demonstrated an increase in Ser26 phosphorylation upon depolarization and contraction of blood vessels. To determine if the phosphorylation of Ser26 affects the kinase activity, we mutated Ser26 to alanine or aspartic acid. The S26D mutation mimicking the phosphorylated state of CaMKII causes a dramatic decrease in Thr287 autophosphorylation levels and greatly reduces the catalytic activity towards an exogenous substrate (autocamtide-3), whereas the S26A mutation has no effect. These data combined with molecular modelling indicate that a negative charge at Ser26 of CaMKII γ inhibits the catalytic activity of the enzyme towards its autophosphorylation site at Thr287 most probably by blocking ATP binding. We propose that Ser26 phosphorylation constitutes an important mechanism for switching off CaMKII activity.
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