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Liu H, Fan W, Fan B. Necroptosis in apical periodontitis: A programmed cell death with multiple roles. J Cell Physiol 2023; 238:1964-1981. [PMID: 37431828 DOI: 10.1002/jcp.31073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 07/12/2023]
Abstract
Programmed cell death (PCD) has been a research focus for decades and different mechanisms of cell death, such as necroptosis, pyroptosis, ferroptosis, and cuproptosis have been discovered. Necroptosis, a form of inflammatory PCD, has gained increasing attention in recent years due to its critical role in disease progression and development. Unlike apoptosis, which is mediated by caspases and characterized by cell shrinkage and membrane blebbing, necroptosis is mediated by mixed lineage kinase domain-like protein (MLKL) and characterized by cell enlargement and plasma membrane rupture. Necroptosis can be triggered by bacterial infection, which on the one hand represents a host defense mechanism against the infection, but on the other hand can facilitate bacterial escape and worsen inflammation. Despite its importance in various diseases, a comprehensive review on the involvement and roles of necroptosis in apical periodontitis is still lacking. In this review, we tried to provide an overview of recent progresses in necroptosis research, summarized the pathways involved in apical periodontitis (AP) activation, and discussed how bacterial pathogens induce and regulated necroptosis and how necroptosis would inhibit bacteria. Furthermore, the interplay between various types of cell death in AP and the potential treatment strategy for AP by targeting necroptosis were also discussed.
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Affiliation(s)
- Hui Liu
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Wei Fan
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China
| | - Bing Fan
- The State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory of Oral Biomedicine Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China
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Yuan G, Cao C, Cao D, Li B, Li X, Li H, Shen H, Wang Z, Chen G. Receptor-interacting protein 3-phosphorylated Ca 2+ /calmodulin-dependent protein kinase II and mixed lineage kinase domain-like protein mediate intracerebral hemorrhage-induced neuronal necroptosis. J Neurochem 2023; 164:94-114. [PMID: 36424866 DOI: 10.1111/jnc.15731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/15/2022] [Accepted: 11/13/2022] [Indexed: 11/26/2022]
Abstract
Necroptosis-mediated cell death is an important mechanism in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI). Our previous study has demonstrated that receptor-interacting protein 1 (RIP1) mediated necroptosis in SBI after ICH. However, further mechanisms, such as the roles of receptor-interacting protein 3 (RIP3), mixed lineage kinase domain-like protein (MLKL), and Ca2+ /calmodulin-dependent protein kinase II (CaMK II), remain unclear. We hypothesized that RIP3, MLKL, and CaMK II might participate in necroptosis after ICH, including their phosphorylation. The ICH model was induced by autologous blood injection. First, we found the activation of necroptosis after ICH in brain tissues surrounding the hematoma (propidium iodide staining). Meanwhile, the phosphorylation and expression of RIP3, MLKL, and CaMK II were differently up-regulated (western blotting and immunofluorescent staining). The specific inhibitors could suppress RIP3, MLKL, and CaMK II (GSK'872 for RIP3, necrosulfonamide for MLKL, and KN-93 for CaMK II). We found the necroptosis surrounding the hematoma and the concrete interactions in RIP3-MLKL/RIP3-CaMK II also both decreased after the specific intervention (co-immunoprecipitation). Then we conducted the short-/long-term neurobehavioral tests, and the rats with specific inhibition mostly had better performance. We also found less blood-brain barrier (BBB) injury, and less neuron loss (Nissl staining) in intervention groups, which supported the neurobehavioral tests. Besides, oxidative stress and inflammation were also alleviated with intervention, which had significant less reactive oxygen species (ROS), tumor necrosis factor (TNF)-α, lactate dehydrogenase (LDH), Iba1, and GFAP surrounding the hematoma. These results confirmed that RIP3-phosphorylated MLKL and CaMK II participate in ICH-induced necroptosis and could provide potential targets for the treatment of ICH patients.
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Affiliation(s)
- Guiqiang Yuan
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Cheng Cao
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Demao Cao
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Bing Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Xiang Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Haiying Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Haitao Shen
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Zhong Wang
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
| | - Gang Chen
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, China
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Ogata G, Partida GJ, Fasoli A, Ishida AT. Calcium/calmodulin-dependent protein kinase II associates with the K + channel isoform Kv4.3 in adult rat optic nerve. Front Neuroanat 2022; 16:958986. [PMID: 36172564 PMCID: PMC9512010 DOI: 10.3389/fnana.2022.958986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/10/2022] [Indexed: 11/25/2022] Open
Abstract
Spikes are said to exhibit "memory" in that they can be altered by spikes that precede them. In retinal ganglion cell axons, for example, rapid spiking can slow the propagation of subsequent spikes. This increases inter-spike interval and, thus, low-pass filters instantaneous spike frequency. Similarly, a K+ ion channel blocker (4-aminopyridine, 4AP) increases the time-to-peak of compound action potentials recorded from optic nerve, and we recently found that reducing autophosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII) does too. These results would be expected if CaMKII modulates spike propagation by regulating 4AP-sensitive K+ channels. As steps toward identifying a possible substrate, we test whether (i) 4AP alters optic nerve spike shape in ways consistent with reducing K+ current, (ii) 4AP alters spike propagation consistent with effects of reducing CaMKII activation, (iii) antibodies directed against 4AP-sensitive and CaMKII-regulated K+ channels bind to optic nerve axons, and (iv) optic nerve CaMKII co-immunoprecipitates with 4AP-sensitive K+ channels. We find that, in adult rat optic nerve, (i) 4AP selectively slows spike repolarization, (ii) 4AP slows spike propagation, (iii) immunogen-blockable staining is achieved with anti-Kv4.3 antibodies but not with antibodies directed against Kv1.4 or Kv4.2, and (iv) CaMKII associates with Kv4.3. Kv4.3 may thus be a substrate that underlies activity-dependent spike regulation in adult visual system pathways.
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Affiliation(s)
- Genki Ogata
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA, United States
| | - Gloria J. Partida
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA, United States
| | - Anna Fasoli
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA, United States
| | - Andrew T. Ishida
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA, United States
- Department of Ophthalmology and Vision Science, University of California, Sacramento, Sacramento, CA, United States
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Abbott GW. Kv Channel Ancillary Subunits: Where Do We Go from Here? Physiology (Bethesda) 2022; 37:0. [PMID: 35797055 PMCID: PMC9394777 DOI: 10.1152/physiol.00005.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 01/10/2023] Open
Abstract
Voltage-gated potassium (Kv) channels each comprise four pore-forming α-subunits that orchestrate essential duties such as voltage sensing and K+ selectivity and conductance. In vivo, however, Kv channels also incorporate regulatory subunits-some Kv channel specific, others more general modifiers of protein folding, trafficking, and function. Understanding all the above is essential for a complete picture of the role of Kv channels in physiology and disease.
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California
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Imaizumi Y. Reciprocal Relationship between Ca 2+ Signaling and Ca 2+-Gated Ion Channels as a Potential Target for Drug Discovery. Biol Pharm Bull 2022; 45:1-18. [PMID: 34980771 DOI: 10.1248/bpb.b21-00896] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cellular Ca2+ signaling functions as one of the most common second messengers of various signal transduction pathways in cells and mediates a number of physiological roles in a cell-type dependent manner. Ca2+ signaling also regulates more general and fundamental cellular activities, including cell proliferation and apoptosis. Among ion channels, Ca2+-permeable channels in the plasma membrane as well as endo- and sarcoplasmic reticulum membranes play important roles in Ca2+ signaling by directly contributing to the influx of Ca2+ from extracellular spaces or its release from storage sites, respectively. Furthermore, Ca2+-gated ion channels in the plasma membrane often crosstalk reciprocally with Ca2+ signals and are central to the regulation of cellular functions. This review focuses on the physiological and pharmacological impact of i) Ca2+-gated ion channels as an apparatus for the conversion of cellular Ca2+ signals to intercellularly propagative electrical signals and ii) the opposite feedback regulation of Ca2+ signaling by Ca2+-gated ion channel activities in excitable and non-excitable cells.
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Affiliation(s)
- Yuji Imaizumi
- Department of Molecular and Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University
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Hyperglycemia regulates cardiac K + channels via O-GlcNAc-CaMKII and NOX2-ROS-PKC pathways. Basic Res Cardiol 2020; 115:71. [PMID: 33237428 DOI: 10.1007/s00395-020-00834-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 11/11/2020] [Indexed: 12/14/2022]
Abstract
Chronic hyperglycemia and diabetes lead to impaired cardiac repolarization, K+ channel remodeling and increased arrhythmia risk. However, the exact signaling mechanism by which diabetic hyperglycemia regulates cardiac K+ channels remains elusive. Here, we show that acute hyperglycemia increases inward rectifier K+ current (IK1), but reduces the amplitude and inactivation recovery time of the transient outward K+ current (Ito) in mouse, rat, and rabbit myocytes. These changes were all critically dependent on intracellular O-GlcNAcylation. Additionally, IK1 amplitude and Ito recovery effects (but not Ito amplitude) were prevented by the Ca2+/calmodulin-dependent kinase II (CaMKII) inhibitor autocamtide-2-related inhibitory peptide, CaMKIIδ-knockout, and O-GlcNAc-resistant CaMKIIδ-S280A knock-in. Ito reduction was prevented by inhibition of protein kinase C (PKC) and NADPH oxidase 2 (NOX2)-derived reactive oxygen species (ROS). In mouse models of chronic diabetes (streptozotocin, db/db, and high-fat diet), heart failure, and CaMKIIδ overexpression, both Ito and IK1 were reduced in line with the downregulated K+ channel expression. However, IK1 downregulation in diabetes was markedly attenuated in CaMKIIδ-S280A. We conclude that acute hyperglycemia enhances IK1 and Ito recovery via CaMKIIδ-S280 O-GlcNAcylation, but reduces Ito amplitude via a NOX2-ROS-PKC pathway. Moreover, chronic hyperglycemia during diabetes and CaMKII activation downregulate K+ channel expression and function, which may further increase arrhythmia susceptibility.
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Li L, Tong A, Zhang Q, Wei Y, Wei X. The molecular mechanisms of MLKL-dependent and MLKL-independent necrosis. J Mol Cell Biol 2020; 13:3-14. [PMID: 33064829 PMCID: PMC8035999 DOI: 10.1093/jmcb/mjaa055] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 07/27/2020] [Accepted: 08/14/2020] [Indexed: 02/05/2023] Open
Abstract
Necrosis, a type of unwanted and passive cell demise, usually occurs under the excessive external stress and is considered to be unregulated. However, under some special conditions such as caspase inhibition, necrosis is regulable in a well-orchestrated way. The term 'regulated necrosis' has been proposed to describe such programed necrosis. Recently, several forms of necrosis, including necroptosis, pyroptosis, ferroptosis, parthanatos, oxytosis, NETosis, and Na+/K+-ATPase-mediated necrosis, have been identified, and some crucial regulators governing regulated necrosis have also been discovered. Mixed lineage kinase domain-like pseudokinase (MLKL), a core regulator in necroptosis, acts as an executioner in response to ligands of death receptor family. Its activation requires the receptor-interacting protein kinases, RIP1 and RIP3. However, MLKL is only involved in necroptosis, i.e. MLKL is dispensable for necrosis. Therefore, this review is aimed at summarizing the molecular mechanisms of MLKL-dependent and MLKL-independent necrosis.
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Affiliation(s)
- Lu Li
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - An Tong
- Department of Gynecology and Obstetrics, Development and Related Disease of Women and Children Key Laboratory of Sichuan Province, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, West China Second Hospital, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Qiangsheng Zhang
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Yuquan Wei
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Xiawei Wei
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu 610041, China
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Chen X, Zhang C, Guo Y, Liu X, Ye T, Fo Y, Qu C, Liang J, Shi S, Yang B. Chronic stimulation of the sigma-1 receptor ameliorates ventricular ionic and structural remodeling in a rodent model of depression. Life Sci 2020; 257:118047. [PMID: 32629001 DOI: 10.1016/j.lfs.2020.118047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/26/2020] [Accepted: 06/30/2020] [Indexed: 10/23/2022]
Abstract
AIM The purpose of the study was to investigate what effects the sigma-1 receptor (S1R) could exert on the cardiac myocyte ion channels in a rodent model of depression and to explore the underlying mechanisms since depression is an independent risk factor for cardiovascular diseases including ventricular arrhythmias (VAs). MATERIALS AND METHODS To establish the depression model in rats, chronic mild unpredictable stress (CMUS) for 28 days was used. The S1R agonist fluvoxamine was injected intraperitoneally from the second week to the last week for 21 days in total, and the effects were evaluated by patch clamp, western blot analysis, and Masson staining. KEY FINDINGS We demonstrated that depression was improved after treatment with fluvoxamine. In addition, the prolongation of the corrected QT (QTc) interval under CMUS that increased vulnerability to VAs was significantly attenuated by stimulation of S1R due to the decreased amplitude of L-type calcium current (ICa-L) and the restoration of reduced transient outward potassium current (Ito) resulting from CMUS induction. The S1R also decelerated Ito inactivation and accelerated Ito recovery by activating Ca2+/calmodulin-dependent kinase II. Moreover, the stimulation of S1R ameliorated the structural remodeling as the substrate for maintenance of VAs. All these effects were abolished by the administration of S1R antagonist BD1047, which verified the roles for S1R. SIGNIFICANCE Activation of S1R could decrease the vulnerability to VAs by inhibiting ICa-L and restoring Ito, in addition to ameliorating the CMUS-induced depressive symptoms and structural remodeling.
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Affiliation(s)
- Xiuhuan Chen
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Cui Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Yan Guo
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Xin Liu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Tianxin Ye
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Yuhong Fo
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Chuan Qu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Jinjun Liang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China
| | - Shaobo Shi
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China.
| | - Bo Yang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan 430060, PR China.
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Li X, Li Z, Wang DWW, Wang DW, Wang Y. A Novel Gain-of-Function KCND3 Variant Associated with Brugada Syndrome. Cardiology 2020; 145:623-632. [PMID: 32818936 DOI: 10.1159/000508033] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 04/06/2020] [Indexed: 11/19/2022]
Abstract
Brugada syndrome (BrS) is a known cause of sudden cardiac death (SCD) characterized by abnormal electrocardiograms and fatal arrhythmias. The variants in KCND3 encoding the KV4.3 potassium-channel (the α-subunit of the Ito) have seldom been reported in BrS. This study aimed to identify novel KCND3 variants associated with BrS and elucidate BrS pathogenesis. High-depth targeted sequencing was performed and the electrophysiological properties of the variants were detected by whole-cell patch-clamp methods in a cultured-cell expressing system. The transcriptional levels of KV4.3 in different genotypes were studied by real-time PCR. Western blot was used to assess channel protein expression. A novel KCND3heterozygous variant, c.1292G>A (Arg431His, R431H), was found in the proband. Whole-cell patch-clamp results revealed a gain-of-function phenotype in the variant, with peak Ito current density increased and faster recovery from inactivation. The expression of mutant Kv4.3 membrane protein increased and the cytoplasmic protein decreased, demonstrating that the membrane/cytoplasm ratio was significantly different. In conclusion, a novel KCND3 heterozygous variant was associated with BrS. The increased Ito current explained the critical role of KCND3 in the pathogenesis of BrS. Genetic screening for KCND3 could be useful for understanding the pathogenesis of BrS and providing effective risk stratification in the clinic.
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Affiliation(s)
- Xianqing Li
- Division of Cardiology, Departments of Internal Medicine and Genetic Diagnosis Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiological Disorders, Huazhong University of Science and Technology, Wuhan, China
| | - Zongzhe Li
- Division of Cardiology, Departments of Internal Medicine and Genetic Diagnosis Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiological Disorders, Huazhong University of Science and Technology, Wuhan, China
| | - Dao Wen Wen Wang
- Division of Cardiology, Departments of Internal Medicine and Genetic Diagnosis Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiological Disorders, Huazhong University of Science and Technology, Wuhan, China
| | - Dao Wu Wang
- State Key Laboratory of Reproductive Medicine, the Center for Clinical Reproductive Medicine and Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Yan Wang
- Division of Cardiology, Departments of Internal Medicine and Genetic Diagnosis Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, .,Hubei Key Laboratory of Genetics and Molecular Mechanisms of Cardiological Disorders, Huazhong University of Science and Technology, Wuhan, China,
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Tinaquero D, Crespo-García T, Utrilla RG, Nieto-Marín P, González-Guerra A, Rubio-Alarcón M, Cámara-Checa A, Dago M, Matamoros M, Pérez-Hernández M, Tamargo M, Cebrián J, Jalife J, Tamargo J, Bernal JA, Caballero R, Delpón E. The p.P888L SAP97 polymorphism increases the transient outward current (I to,f) and abbreviates the action potential duration and the QT interval. Sci Rep 2020; 10:10707. [PMID: 32612162 PMCID: PMC7329876 DOI: 10.1038/s41598-020-67109-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 06/01/2020] [Indexed: 11/09/2022] Open
Abstract
Synapse-Associated Protein 97 (SAP97) is an anchoring protein that in cardiomyocytes targets to the membrane and regulates Na+ and K+ channels. Here we compared the electrophysiological effects of native (WT) and p.P888L SAP97, a common polymorphism. Currents were recorded in cardiomyocytes from mice trans-expressing human WT or p.P888L SAP97 and in Chinese hamster ovary (CHO)-transfected cells. The duration of the action potentials and the QT interval were significantly shorter in p.P888L-SAP97 than in WT-SAP97 mice. Compared to WT, p.P888L SAP97 significantly increased the charge of the Ca-independent transient outward (Ito,f) current in cardiomyocytes and the charge crossing Kv4.3 channels in CHO cells by slowing Kv4.3 inactivation kinetics. Silencing or inhibiting Ca/calmodulin kinase II (CaMKII) abolished the p.P888L-induced Kv4.3 charge increase, which was also precluded in channels (p.S550A Kv4.3) in which the CaMKII-phosphorylation is prevented. Computational protein-protein docking predicted that p.P888L SAP97 is more likely to form a complex with CaMKII than WT. The Na+ current and the current generated by Kv1.5 channels increased similarly in WT-SAP97 and p.P888L-SAP97 cardiomyocytes, while the inward rectifier current increased in WT-SAP97 but not in p.P888L-SAP97 cardiomyocytes. The p.P888L SAP97 polymorphism increases the Ito,f, a CaMKII-dependent effect that may increase the risk of arrhythmias.
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Affiliation(s)
- David Tinaquero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Teresa Crespo-García
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Raquel G Utrilla
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Paloma Nieto-Marín
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | | | - Marcos Rubio-Alarcón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Anabel Cámara-Checa
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - María Dago
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Marcos Matamoros
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Marta Pérez-Hernández
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - María Tamargo
- Cardiology Department, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - Jorge Cebrián
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | - José Jalife
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain.,Department of Internal Medicine/Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Juan Tamargo
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
| | | | - Ricardo Caballero
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain.
| | - Eva Delpón
- Department of Pharmacology and Toxicology. School of Medicine. Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón. CIBERCV, Madrid, Spain
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Fernández-Fernández D, Lamas JA. Metabotropic Modulation of Potassium Channels During Synaptic Plasticity. Neuroscience 2020; 456:4-16. [PMID: 32114098 DOI: 10.1016/j.neuroscience.2020.02.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 01/06/2023]
Abstract
Besides their primary function mediating the repolarization phase of action potentials, potassium channels exquisitely and ubiquitously regulate the resting membrane potential of neurons and therefore have a key role establishing their intrinsic excitability. This group of proteins is composed of a very diverse collection of voltage-dependent and -independent ion channels, whose specific distribution is finely tuned at the level of the synapse. Both at the presynaptic and postsynaptic membranes, different types of potassium channels are subjected to modulation by second messenger signaling cascades triggered by metabotropic receptors, which in this way serve as a link between neurotransmitter actions and changes in the neuron membrane excitability. On the one hand, by regulating the resting membrane potential of the postsynaptic membrane, potassium channels appear to be critical towards setting the threshold for the induction of long-term potentiation and depression. On the other hand, these channels maintain the presynaptic membrane potential under control, therefore influencing the probability of neurotransmitter release underlying different forms of short-term plasticity. In the present review, we examine in detail the role of metabotropic receptors translating their activation by different neurotransmitters into a final effect modulating several types of potassium channels. Furthermore, we evaluate the consequences that this interplay has on the induction and maintenance of different forms of synaptic plasticity.
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Affiliation(s)
- D Fernández-Fernández
- Laboratory of Neuroscience, Biomedical Research Center (CINBIO), University of Vigo, Vigo, Galicia, Spain.
| | - J A Lamas
- Laboratory of Neuroscience, Biomedical Research Center (CINBIO), University of Vigo, Vigo, Galicia, Spain
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12
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Soriani O, Kourrich S. The Sigma-1 Receptor: When Adaptive Regulation of Cell Electrical Activity Contributes to Stimulant Addiction and Cancer. Front Neurosci 2019; 13:1186. [PMID: 31780884 PMCID: PMC6861184 DOI: 10.3389/fnins.2019.01186] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/21/2019] [Indexed: 12/17/2022] Open
Abstract
The sigma-1 receptor (σ1R) is an endoplasmic reticulum (ER)-resident chaperone protein that acts like an inter-organelle signaling modulator. Among its several functions such as ER lipid metabolisms/transports and indirect regulation of genes transcription, one of its most intriguing feature is the ability to regulate the function and trafficking of a variety of functional proteins. To date, and directly relevant to the present review, σ1R has been found to regulate both voltage-gated ion channels (VGICs) belonging to distinct superfamilies (i.e., sodium, Na+; potassium, K+; and calcium, Ca2+ channels) and non-voltage-gated ion channels. This regulatory function endows σ1R with a powerful capability to fine tune cells’ electrical activity and calcium homeostasis—a regulatory power that appears to favor cell survival in pathological contexts such as stroke or neurodegenerative diseases. In this review, we present the current state of knowledge on σ1R’s role in the regulation of cellular electrical activity, and how this seemingly adaptive function can shift cell homeostasis and contribute to the development of very distinct chronic pathologies such as psychostimulant abuse and tumor cell growth in cancers.
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Affiliation(s)
| | - Saïd Kourrich
- Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, QC, Canada.,Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois, Université du Québec à Montréal, Montréal, QC, Canada.,Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, United States.,Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, United States
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13
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Hegyi B, Bers DM, Bossuyt J. CaMKII signaling in heart diseases: Emerging role in diabetic cardiomyopathy. J Mol Cell Cardiol 2019; 127:246-259. [PMID: 30633874 DOI: 10.1016/j.yjmcc.2019.01.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 01/04/2019] [Indexed: 02/07/2023]
Abstract
Calcium/calmodulin-dependent protein kinase II (CaMKII) is upregulated in diabetes and significantly contributes to cardiac remodeling with increased risk of cardiac arrhythmias. Diabetes is frequently associated with atrial fibrillation, coronary artery disease, and heart failure, which may further enhance CaMKII. Activation of CaMKII occurs downstream of neurohormonal stimulation (e.g. via G-protein coupled receptors) and involve various posttranslational modifications including autophosphorylation, oxidation, S-nitrosylation and O-GlcNAcylation. CaMKII signaling regulates diverse cellular processes in a spatiotemporal manner including excitation-contraction and excitation-transcription coupling, mechanics and energetics in cardiac myocytes. Chronic activation of CaMKII results in cellular remodeling and ultimately arrhythmogenic alterations in Ca2+ handling, ion channels, cell-to-cell coupling and metabolism. This review addresses the detrimental effects of the upregulated CaMKII signaling to enhance the arrhythmogenic substrate and trigger mechanisms in the heart. We also briefly summarize preclinical studies using kinase inhibitors and genetically modified mice targeting CaMKII in diabetes. The mechanistic understanding of CaMKII signaling, cardiac remodeling and arrhythmia mechanisms may reveal new therapeutic targets and ultimately better treatment in diabetes and heart disease in general.
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Affiliation(s)
- Bence Hegyi
- Department of Pharmacology, University of California Davis, Davis, CA, USA
| | - Donald M Bers
- Department of Pharmacology, University of California Davis, Davis, CA, USA.
| | - Julie Bossuyt
- Department of Pharmacology, University of California Davis, Davis, CA, USA
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14
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Groen C, Bähring R. Modulation of human Kv4.3/KChIP2 channel inactivation kinetics by cytoplasmic Ca 2. Pflugers Arch 2017; 469:1457-1470. [PMID: 28735419 DOI: 10.1007/s00424-017-2039-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/11/2017] [Accepted: 07/13/2017] [Indexed: 10/19/2022]
Abstract
The transient outward current (I to) in the human heart is mediated by Kv4.3 channels complexed with Kv channel interacting protein (KChIP) 2, a cytoplasmic Ca2+-binding EF-hand protein known to modulate Kv4.3 inactivation gating upon heterologous co-expression. We studied Kv4.3 channels co-expressed with wild-type (wt) or EF-hand-mutated (ΔEF) KChIP2 in human embryonic kidney (HEK) 293 cells. Co-expression took place in the absence or presence of BAPTA-AM, and macroscopic currents were recorded in the whole-cell patch-clamp configuration with different free Ca2+ concentrations in the patch-pipette. Our data indicate that Ca2+ is not necessary for Kv4.3/KChIP2 complex formation. The Kv4.3/KChIP2-mediated current decay was faster and the recovery of Kv4.3/KChIP2 channels from inactivation slower with 50 μM Ca2+ than with BAPTA (nominal Ca2+-free) in the patch-pipette. The apparent Ca2+-mediated slowing of recovery kinetics was still observed when EF-hand 4 of KChIP2 was mutated (ΔEF4) but not when EF-hand 2 (ΔEF2) was mutated, and turned into a Ca2+-mediated acceleration of recovery kinetics when EF-hand 3 (ΔEF3) was mutated. In the presence of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-93 cytoplasmic Ca2+ (50 μM) induced an acceleration of Kv4.3/KChIP2 recovery kinetics, which was still observed when EF-hand 2 was mutated (ΔEF2) but not when EF-hand 3 (ΔEF3) or EF-hand 4 (ΔEF4) was mutated. Our results support the notion that binding of Ca2+ to KChIP2 EF-hands can acutely modulate Kv4.3/KChIP2 channel inactivation gating, but the Ca2+-dependent gating modulation depends on CaMKII action. Our findings speak for an acute modulation of I to kinetics and frequency-dependent I to availability in cardiomyocytes under conditions with elevated Ca2+ levels and CaMKII activity.
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Affiliation(s)
- Christiane Groen
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany
| | - Robert Bähring
- Institut für Zelluläre und Integrative Physiologie, Zentrum für Experimentelle Medizin, Universitätsklinikum Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany.
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15
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Grootjans S, Vanden Berghe T, Vandenabeele P. Initiation and execution mechanisms of necroptosis: an overview. Cell Death Differ 2017; 24:1184-1195. [PMID: 28498367 PMCID: PMC5520172 DOI: 10.1038/cdd.2017.65] [Citation(s) in RCA: 377] [Impact Index Per Article: 53.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/23/2017] [Accepted: 03/30/2017] [Indexed: 12/17/2022] Open
Abstract
Necroptosis is a form of regulated cell death, which is induced by ligand binding to TNF family death domain receptors, pattern recognizing receptors and virus sensors. The common feature of these receptor systems is the implication of proteins, which contain a receptor interaction protein kinase (RIPK) homology interaction motif (RHIM) mediating recruitment and activation of receptor-interacting protein kinase 3 (RIPK3), which ultimately activates the necroptosis executioner mixed lineage kinase domain-like (MLKL). In case of the TNF family members, the initiator is the survival- and cell death-regulating RIPK1 kinase, in the case of Toll-like receptor 3/4 (TLR3/4), a RHIM-containing adaptor, called TRIF, while in the case of Z-DNA-binding protein ZBP1/DAI, the cytosolic viral sensor itself contains a RHIM domain. In this review, we discuss the different protein complexes that serve as nucleation platforms for necroptosis and the mechanism of execution of necroptosis. Transgenic models (knockout, kinase-dead knock-in) and pharmacologic inhibition indicate that RIPK1, RIPK3 or MLKL are implicated in many inflammatory, degenerative and infectious diseases. However, the conclusion of necroptosis being solely involved in the etiology of diseases is blurred by the pleiotropic roles of RIPK1 and RIPK3 in other cellular processes such as apoptosis and inflammasome activation.
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Affiliation(s)
- Sasker Grootjans
- Molecular Signaling and Cell Death unit, VIB Inflammation Research Center, 9000 Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
| | - Tom Vanden Berghe
- Molecular Signaling and Cell Death unit, VIB Inflammation Research Center, 9000 Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
| | - Peter Vandenabeele
- Molecular Signaling and Cell Death unit, VIB Inflammation Research Center, 9000 Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, 9000 Ghent, Belgium
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16
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Role of CaMKII and PKA in Early Afterdepolarization of Human Ventricular Myocardium Cell: A Computational Model Study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:4576313. [PMID: 28053652 PMCID: PMC5178856 DOI: 10.1155/2016/4576313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 10/31/2016] [Indexed: 11/30/2022]
Abstract
Early afterdepolarization (EAD) plays an important role in arrhythmogenesis. Many experimental studies have reported that Ca2+/calmodulin-dependent protein kinase II (CaMKII) and β-adrenergic signaling pathway are two important regulators. In this study, we developed a modified computational model of human ventricular myocyte to investigate the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs. Our simulation results showed that (1) CaMKII overexpression facilitates EADs through the prolongation of late sodium current's (INaL) deactivation progress; (2) the combined effect of CaMKII overexpression and activation of β-adrenergic signaling pathway further increases the risk of EADs, where EADs could occur at shorter cycle length (2000 ms versus 4000 ms) and lower rapid delayed rectifier K+ current (IKr) blockage (77% versus 85%). In summary, this study computationally demonstrated the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs, which could be useful for searching for therapy strategies to treat EADs related arrhythmogenesis.
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17
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Grandi E, Sanguinetti MC, Bartos DC, Bers DM, Chen-Izu Y, Chiamvimonvat N, Colecraft HM, Delisle BP, Heijman J, Navedo MF, Noskov S, Proenza C, Vandenberg JI, Yarov-Yarovoy V. Potassium channels in the heart: structure, function and regulation. J Physiol 2016; 595:2209-2228. [PMID: 27861921 DOI: 10.1113/jp272864] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 07/18/2016] [Indexed: 12/22/2022] Open
Abstract
This paper is the outcome of the fourth UC Davis Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias Symposium, a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2016 symposium was 'K+ Channels and Regulation'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies and challenges on the topic of cardiac K+ channels. This paper summarizes the topics of formal presentations and informal discussions from the symposium on the structural basis of voltage-gated K+ channel function, as well as the mechanisms involved in regulation of K+ channel gating, expression and membrane localization. Given the critical role for K+ channels in determining the rate of cardiac repolarization, it is hardly surprising that essentially every aspect of K+ channel function is exquisitely regulated in cardiac myocytes. This regulation is complex and highly interrelated to other aspects of myocardial function. K+ channel regulatory mechanisms alter, and are altered by, physiological challenges, pathophysiological conditions, and pharmacological agents. An accompanying paper focuses on the integrative role of K+ channels in cardiac electrophysiology, i.e. how K+ currents shape the cardiac action potential, and how their dysfunction can lead to arrhythmias, and discusses K+ channel-based therapeutics. A fundamental understanding of K+ channel regulatory mechanisms and disease processes is fundamental to reveal new targets for human therapy.
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Affiliation(s)
- Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, 84112, USA
| | - Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA.,Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, KY, 40536, USA
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA, 95616, USA
| | - Sergei Noskov
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Catherine Proenza
- Department of Physiology and Biophysics, University of Colorado - Anschutz Medical Campus, Denver, CO, 80045, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, 2010, Australia
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California, Davis, CA, 95616, USA
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18
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Yang KC, Nerbonne JM. Mechanisms contributing to myocardial potassium channel diversity, regulation and remodeling. Trends Cardiovasc Med 2015; 26:209-18. [PMID: 26391345 DOI: 10.1016/j.tcm.2015.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 07/11/2015] [Accepted: 07/12/2015] [Indexed: 01/19/2023]
Abstract
In the mammalian heart, multiple types of K(+) channels contribute to the control of cardiac electrical and mechanical functioning through the regulation of resting membrane potentials, action potential waveforms and refractoriness. There are similarly vast arrays of K(+) channel pore-forming and accessory subunits that contribute to the generation of functional myocardial K(+) channel diversity. Maladaptive remodeling of K(+) channels associated with cardiac and systemic diseases results in impaired repolarization and increased propensity for arrhythmias. Here, we review the diverse transcriptional, post-transcriptional, post-translational, and epigenetic mechanisms contributing to regulating the expression, distribution, and remodeling of cardiac K(+) channels under physiological and pathological conditions.
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Affiliation(s)
- Kai-Chien Yang
- Department of Pharmacology, National Taiwan University, Taipei, Taiwan; Division of Cardiology, Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Jeanne M Nerbonne
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO; Internal Medicine, Washington University School of Medicine, St. Louis, MO; Cardiovascular Division, Washington University School of Medicine, St. Louis, MO.
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19
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Abstract
Exposure to drugs of abuse, such as cocaine, leads to plastic changes in the activity of brain circuits, and a prevailing view is that these changes play a part in drug addiction. Notably, there has been intense focus on drug-induced changes in synaptic excitability and much less attention on intrinsic excitability factors (that is, excitability factors that are remote from the synapse). Accumulating evidence now suggests that intrinsic factors such as K+ channels are not only altered by cocaine but may also contribute to the shaping of the addiction phenotype.
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20
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21
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Chae YJ, Choi BH, Choi JS, Hahn SJ. Block of Kv4.3 potassium channel by trifluoperazine independent of CaMKII. Neurosci Lett 2014; 578:159-64. [PMID: 24993295 DOI: 10.1016/j.neulet.2014.06.045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/12/2014] [Accepted: 06/23/2014] [Indexed: 11/24/2022]
Abstract
Trifluoperazine, a trifluoro-methyl phenothiazine derivative, is widely used in the management of schizophrenia and related psychotic disorders. We studied the effects of trifluoperazine on Kv4.3 currents expressed in CHO cells using the whole-cell patch-clamp technique. Trifluoperazine blocked Kv4.3 in a concentration-dependent manner with an IC50 value of 8.0±0.4 μM and a Hill coefficient of 2.1±0.1. Trifluoperazine also accelerated the inactivation and activation (time-to-peak) kinetics in a concentration-dependent manner. The effects of trifluoperazine on Kv4.3 were completely reversible after washout. The effects of trifluoperazine were not affected by the pretreatment of KN93, which is another CaMKII inhibitor. In addition, the inclusion of CaMKII inhibitory peptide 281-309 in the pipette solution did not modify the effect of trifluoperazine on Kv4.3. Trifluoperazine shifted the activation curve of Kv4.3 in a hyperpolarizing direction but did not affect the slope factor. The block of Kv4.3 by trifluoperazine was voltage-dependent with a steep increase across the voltage range of channel activation. Voltage dependence was also observed over the full range of activation (δ=0.18). Trifluoperazine slowed the time course for recovery from inactivation of Kv4.3. Our results indicated that trifluoperazine blocked Kv4.3 by preferentially binding to the open state of the channel. This effect was not mediated via the inhibition of CaMKII activity.
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Affiliation(s)
- Yun Ju Chae
- Department of Physiology, Cell Death and Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea
| | - Bok Hee Choi
- Department of Pharmacology, Institute for Medical Science, Chonbuk National University Medical School, Jeonju, Jeonbuk 561-180, Republic of Korea
| | - Jin-Sung Choi
- College of Pharmacy, Integrated Research Institute of Pharmaceutical, The Catholic University of Korea, 43-1 Yeokgok 2-dong, Wonmi-gu, Bucheon, Gyeonggi-do, Republic of Korea
| | - Sang June Hahn
- Department of Physiology, Cell Death and Disease Research Center, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
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Schmitt N, Grunnet M, Olesen SP. Cardiac potassium channel subtypes: new roles in repolarization and arrhythmia. Physiol Rev 2014; 94:609-53. [PMID: 24692356 DOI: 10.1152/physrev.00022.2013] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K+ channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K+ channels drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K+ channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure. The underlying posttranscriptional and posttranslational remodeling of the individual K+ channels changes their activity and significance relative to each other, and they must be viewed together to understand their role in keeping a stable heart rhythm, also under menacing conditions like attacks of reentry arrhythmia.
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23
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Mustroph J, Maier LS, Wagner S. CaMKII regulation of cardiac K channels. Front Pharmacol 2014; 5:20. [PMID: 24600393 PMCID: PMC3930912 DOI: 10.3389/fphar.2014.00020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 01/31/2014] [Indexed: 11/23/2022] Open
Abstract
Cardiac K channels are critical determinants of cardiac excitability. In hypertrophied and failing myocardium, alterations in the expression and activity of voltage-gated K channels are frequently observed and contribute to the increased propensity for life-threatening arrhythmias. Thus, understanding the mechanisms of disturbed K channel regulation in heart failure (HF) is of critical importance. Amongst others, Ca/calmodulin-dependent protein kinase II (CaMKII) has been identified as an important regulator of K channel activity. In human HF but also various animal models, increased CaMKII expression and activity has been linked to deteriorated contractile function and arrhythmias. This review will discuss the current knowledge about CaMKII regulation of several K channels, its influence on action potential properties, dispersion of repolarization, and arrhythmias with special focus on HF.
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Affiliation(s)
- Julian Mustroph
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Lars S Maier
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Stefan Wagner
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
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24
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Abstract
Ca²⁺ plays a crucial role in connecting membrane excitability with contraction in myocardium. The hallmark features of heart failure are mechanical dysfunction and arrhythmias; defective intracellular Ca²⁺ homeostasis is a central cause of contractile dysfunction and arrhythmias in failing myocardium. Defective Ca²⁺ homeostasis in heart failure can result from pathological alteration in the expression and activity of an increasingly understood collection of Ca²⁺ homeostatic and structural proteins, ion channels, and enzymes. This review focuses on the molecular mechanisms of defective Ca²⁺ cycling in heart failure and considers how fundamental understanding of these pathways may translate into novel and innovative therapies.
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Affiliation(s)
- Min Luo
- Division of Cardiovascular Medicine, Department of Internal Medicine, Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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25
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Westenbrink BD, Edwards AG, McCulloch AD, Brown JH. The promise of CaMKII inhibition for heart disease: preventing heart failure and arrhythmias. Expert Opin Ther Targets 2013; 17:889-903. [PMID: 23789646 DOI: 10.1517/14728222.2013.809064] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Calcium-calmodulin-dependent protein kinase II (CaMKII) has emerged as a central mediator of cardiac stress responses which may serve several critical roles in the regulation of cardiac rhythm, cardiac contractility and growth. Sustained and excessive activation of CaMKII during cardiac disease has, however, been linked to arrhythmias, and maladaptive cardiac remodeling, eventually leading to heart failure (HF) and sudden cardiac death. AREAS COVERED In the current review, the authors describe the unique structural and biochemical properties of CaMKII and focus on its physiological effects in cardiomyocytes. Furthermore, they provide evidence for a role of CaMKII in cardiac pathologies, including arrhythmogenesis, myocardial ischemia and HF development. The authors conclude by discussing the potential for CaMKII as a target for inhibition in heart disease. EXPERT OPINION CaMKII provides a promising nodal point for intervention that may allow simultaneous prevention of HF progression and development of arrhythmias. For future studies and drug development there is a strong rationale for the development of more specific CaMKII inhibitors. In addition, an improved understanding of the differential roles of CaMKII subtypes is required.
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Affiliation(s)
- B Daan Westenbrink
- University of California, Department of Pharmacology, San Diego, La Jolla, CA, USA
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26
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Olesen MS, Refsgaard L, Holst AG, Larsen AP, Grubb S, Haunsø S, Svendsen JH, Olesen SP, Schmitt N, Calloe K. A novel KCND3 gain-of-function mutation associated with early-onset of persistent lone atrial fibrillation. Cardiovasc Res 2013; 98:488-95. [PMID: 23400760 DOI: 10.1093/cvr/cvt028] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
AIMS Atrial fibrillation (AF) is the most common cardiac arrhythmia, and early-onset lone AF has been linked to mutations in genes encoding ion channels. Mutations in the pore forming subunit KV4.3 leading to an increase in the transient outward potassium current (Ito) have previously been associated with the Brugada Syndrome. Here we aim to determine if mutations in KV4.3 or in the auxiliary subunit K(+) Channel-Interacting Protein (KChIP) 2 are associated with early-onset lone AF. METHODS AND RESULTS Two hundred and nine unrelated early-onset lone AF patients (<40 years) were recruited. The entire coding sequence of KCND3 and KCNIP2 was bidirectionally sequenced. One novel non-synonymous mutation A545P was found in KCND3 and was neither present in the control group (n = 432 alleles) nor in any publicly available database. The proband had onset of persistent AF at the age of 22, and no mutations in genes previously associated with AF were found. Electrophysiological analysis of KV4.3-A545P expressed in CHO-K1 cells, revealed that peak-current density was increased and the onset of inactivation was slower compared with WT, resulting in a significant gain-of-function both in the absence and the presence of KChIP2. CONCLUSION Gain-of-function mutations in KV4.3 have previously been described in Brugada Syndrome, however, this is the first report of a KV4.3 gain-of-function mutation in early-onset lone AF. This association of KV4.3 gain-of-function and early-onset lone AF further supports the hypothesis that increased potassium current enhances AF susceptibility.
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Affiliation(s)
- Morten Salling Olesen
- The Danish National Research Foundation Centre for Cardiac Arrhythmia, Copenhagen, Denmark.
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27
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Social networking among voltage-activated potassium channels. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 117:269-302. [PMID: 23663972 DOI: 10.1016/b978-0-12-386931-9.00010-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Voltage-activated potassium channels (Kv channels) are ubiquitously expressed proteins that subserve a wide range of cellular functions. From their birth in the endoplasmic reticulum, Kv channels assemble from multiple subunits in complex ways that determine where they live in the cell, their biophysical characteristics, and their role in enabling different kinds of cells to respond to specific environmental signals to generate appropriate functional responses. This chapter describes the types of protein-protein interactions among pore-forming channel subunits and their auxiliary protein partners, as well as posttranslational protein modifications that occur in various cell types. This complex oligomerization of channel subunits establishes precise cell type-specific Kv channel localization and function, which in turn drives a diverse range of cellular signal transduction mechanisms uniquely suited to the physiological contexts in which they are found.
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Swaminathan PD, Purohit A, Hund TJ, Anderson ME. Calmodulin-dependent protein kinase II: linking heart failure and arrhythmias. Circ Res 2012; 110:1661-77. [PMID: 22679140 DOI: 10.1161/circresaha.111.243956] [Citation(s) in RCA: 215] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Understanding relationships between heart failure and arrhythmias, important causes of suffering and sudden death, remains an unmet goal for biomedical researchers and physicians. Evidence assembled over the past decade supports a view that activation of the multifunctional Ca(2+) and calmodulin-dependent protein kinase II (CaMKII) favors myocardial dysfunction and cell membrane electrical instability. CaMKII activation follows increases in intracellular Ca(2+) or oxidation, upstream signals with the capacity to transition CaMKII into a Ca(2+) and calmodulin-independent constitutively active enzyme. Constitutively active CaMKII appears poised to participate in disease pathways by catalyzing the phosphorylation of classes of protein targets important for excitation-contraction coupling and cell survival, including ion channels and Ca(2+) homeostatic proteins, and transcription factors that drive hypertrophic and inflammatory gene expression. This rich diversity of downstream targets helps to explain the potential for CaMKII to simultaneously affect mechanical and electrical properties of heart muscle cells. Proof-of-concept studies from a growing number of investigators show that CaMKII inhibition is beneficial for improving myocardial performance and for reducing arrhythmias. We review the molecular physiology of CaMKII and discuss CaMKII actions at key cellular targets and results of animal models of myocardial hypertrophy, dysfunction, and arrhythmias that suggest CaMKII inhibition may benefit myocardial function while reducing arrhythmias.
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Affiliation(s)
- Paari Dominic Swaminathan
- Division of Cardiovascular Medicine, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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He XD, Goyal RK. CaMKII inhibition hyperpolarizes membrane and blocks nitrergic IJP by closing a Cl(-) conductance in intestinal smooth muscle. Am J Physiol Gastrointest Liver Physiol 2012; 303:G240-6. [PMID: 22538403 PMCID: PMC3404568 DOI: 10.1152/ajpgi.00102.2012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ionic basis of nitrergic "slow'" inhibitory junction potential (sIJP) is not fully understood. The purpose of the present study was to determine the nature and the role of calmodulin-dependent protein kinase II (CaMKII)-dependent ion conductance in nitrergic neurotransmission at the intestinal smooth muscle neuromuscular junction. Studies were performed in guinea pig ileum. The modified Tomita bath technique was used to induce passive hyperpolarizing electrotonic potentials (ETP) and membrane potential change due to sIJP or drug treatment in the same cell. Changes in membrane potential and ETP were recorded in the same smooth muscle cell, using sharp microelectrode. Nitrergic IJP was elicited by electrical field stimulation in nonadrenergic, noncholinergic conditions and chemical block of purinergic IJP. Modification of ETP during hyperpolarization reflected active conductance change in the smooth muscle. Nitrergic IJP was associated with decreased membrane conductance. The CAMKII inhibitor KN93 but not KN92, the Cl(-) channel blocker niflumic acid (NFA), and the K(ATP)-channel opener cromakalim hyperpolarized the membrane. However, KN93 and NFA were associated with decreased and cromakalim was associated with increased membrane conductance. After maximal NFA-induced hyperpolarization, hyperpolarization associated with KN93 or sIJP was not seen, suggesting a saturation block of the Cl(-) channel signaling. These studies suggest that inhibition of CaMKII-dependent Cl(-) conductance mediates nitrergic sIJP by causing maximal closure of the Cl(-) conductance.
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Affiliation(s)
- Xue-Dao He
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
| | - Raj K. Goyal
- Center for Swallowing and Motility Disorders, Veterans Affairs Boston HealthCare System and Harvard Medical School, Boston, Massachusetts
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AMPAR-independent effect of striatal αCaMKII promotes the sensitization of cocaine reward. J Neurosci 2012; 32:6578-86. [PMID: 22573680 DOI: 10.1523/jneurosci.6391-11.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Changes in CaMKII-regulated synaptic excitability are a means through which experience may modify neuronal function and shape behavior. While behavior in rodent addiction models is linked with CaMKII activity in the nucleus accumbens (NAc) shell, the key cellular adaptations that forge this link are unclear. Using a mouse strain with striatal-specific expression of autonomously active CaMKII (T286D), we demonstrate that while persistent CaMKII activity induces behaviors comparable to those in mice repeatedly exposed to psychostimulants, it is insufficient to increase AMPAR-mediated synaptic strength in NAc shell. However, autonomous CaMKII upregulates A-type K(+) current (IA) and decreases firing in shell neurons. Importantly, inactivating the transgene with doxycycline eliminates both the IA-mediated firing decrease and the elevated behavioral response to cocaine. This study identifies CaMKII regulation of IA in NAc shell neurons as a novel cellular contributor to the sensitization of cocaine reward.
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Ca²⁺/cAMP-sensitive covariation of I(A) and I(H) voltage dependences tunes rebound firing in dopaminergic neurons. J Neurosci 2012; 32:2166-81. [PMID: 22323729 DOI: 10.1523/jneurosci.5297-11.2012] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The level of expression of ion channels has been demonstrated to vary over a threefold to fourfold range from neuron to neuron, although the expression of distinct channels may be strongly correlated in the same neurons. We demonstrate that variability and covariation also apply to the biophysical properties of ion channels. We show that, in rat substantia nigra pars compacta dopaminergic neurons, the voltage dependences of the A-type (I(A)) and H-type (I(H)) currents exhibit a high degree of cell-to-cell variability, although they are strongly correlated in these cells. Our data also demonstrate that this cell-to-cell covariability of voltage dependences is sensitive to cytosolic cAMP and calcium levels. Finally, using dynamic clamp, we demonstrate that covarying I(A) and I(H) voltage dependences increases the dynamic range of rebound firing while covarying their amplitudes has a homeostatic effect on rebound firing. We propose that the covariation of voltage dependences of ion channels represents a flexible and energy-efficient way of tuning firing in neurons.
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Maier LS. Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) in the Heart. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:685-702. [DOI: 10.1007/978-94-007-2888-2_30] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Liang R, Liu X, Wei L, Wang W, Zheng P, Yan X, Zhao Y, Liu L, Cao X. The modulation of the excitability of primary sensory neurons by Ca2+–CaM–CaMKII pathway. Neurol Sci 2011; 33:1083-93. [DOI: 10.1007/s10072-011-0907-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/14/2011] [Indexed: 01/19/2023]
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Zhang YH, Wu W, Sun HY, Deng XL, Cheng LC, Li X, Tse HF, Lau CP, Li GR. Modulation of human cardiac transient outward potassium current by EGFR tyrosine kinase and Src-family kinases. Cardiovasc Res 2011; 93:424-33. [PMID: 22198508 DOI: 10.1093/cvr/cvr347] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
AIMS The human cardiac transient outward K(+) current I(to) (encoded by Kv4.3 or KCND3) plays an important role in phase 1 rapid repolarization of cardiac action potentials in the heart. However, modulation of I(to) by intracellular signal transduction is not fully understood. The present study was therefore designed to determine whether/how human atrial I(to) and hKv4.3 channels stably expressed in HEK 293 cells are regulated by protein tyrosine kinases (PTKs). METHODS AND RESULTS Whole-cell patch voltage-clamp, immunoprecipitation, western blotting, and site-directed mutagenesis approaches were employed in the present study. We found that human atrial I(to) was inhibited by the broad-spectrum PTK inhibitor genistein, the selective epidermal growth factor receptor (EGFR) kinase inhibitor AG556, and the Src-family kinases inhibitor PP2. The inhibitory effect was countered by the protein tyrosine phosphatase inhibitor orthovanadate. In HEK 293 cells stably expressing human KCND3, genistein, AG556, and PP2 significantly reduced the hKv4.3 current, and the reduction was antagonized by orthovanadate. Interestingly, orthovanadate also reversed the reduced tyrosine phosphorylation level of hKv4.3 channels by genistein, AG556, or PP2. Mutagenesis revealed that the hKv4.3 mutant Y136F lost the inhibitory response to AG556, while Y108F lost response to PP2. The double-mutant Y108F-Y136F hKv4.3 channels showed no response to either AG556 or PP2. CONCLUSION Our results demonstrate that human atrial I(to) and cloned hKv4.3 channels are modulated by EGFR kinase via phosphorylation of the Y136 residue and by Src-family kinases via phosphorylation of the Y108 residue; tyrosine phosphorylation of the channel may be involved in regulating cardiac electrophysiology.
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Affiliation(s)
- Yan-Hui Zhang
- Department of Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, L4-59, Laboratory Block, FMB, 21 Sassoon Road, Pokfulam, Hong Kong, China
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Varró A, Baczkó I. Cardiac ventricular repolarization reserve: a principle for understanding drug-related proarrhythmic risk. Br J Pharmacol 2011; 164:14-36. [PMID: 21545574 PMCID: PMC3171857 DOI: 10.1111/j.1476-5381.2011.01367.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/22/2011] [Accepted: 03/02/2011] [Indexed: 12/11/2022] Open
Abstract
Cardiac repolarization abnormalities can be caused by a wide range of cardiac and non-cardiac compounds and may lead to the development of life-threatening Torsades de Pointes (TdP) ventricular arrhythmias. Drug-induced torsades de pointes is associated with unexpected and unexplained sudden cardiac deaths resulting in the withdrawal of several compounds in the past. To better understand the mechanism of such unexpected sudden cardiac deaths, the concept of repolarization reserve has recently emerged. According to this concept, pharmacological, congenital or acquired impairment of one type of transmembrane ion channel does not necessarily result in excessive repolarization changes because other repolarizing currents can take over and compensate. In this review, the major factors contributing to repolarization reserve are discussed in the context of their clinical significance in physiological and pathophysiological conditions including drug administration, genetic defects, heart failure, diabetes mellitus, gender, renal failure, hypokalaemia, hypothyroidism and athletes' sudden deaths. In addition, pharmacological support of repolarization reserve as a possible therapeutic option is discussed. Some methods for the quantitative estimation of repolarization reserve are also recommended. It is concluded that repolarization reserve should be considered by safety pharmacologists to better understand, predict and prevent previously unexplained drug-induced sudden cardiac deaths.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.
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Perrino BA. Regulation of gastrointestinal motility by Ca2+/calmodulin-stimulated protein kinase II. Arch Biochem Biophys 2011; 510:174-81. [PMID: 21443856 DOI: 10.1016/j.abb.2011.03.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 03/15/2011] [Accepted: 03/21/2011] [Indexed: 12/30/2022]
Abstract
Gastrointestinal (GI) motility ultimately depends upon the contractile activity of the smooth muscle cells of the tunica muscularis. Integrated functioning of multiple tissues and cell types, including enteric neurons and interstitial cells of Cajal (ICC) is necessary to generate coordinated patterns of motor activity that control the movement of material through the digestive tract. The neurogenic mechanisms that govern GI motility patterns are superimposed upon intrinsic myogenic mechanisms regulating smooth muscle cell excitability. Several mechanisms regulate smooth muscle cell responses to neurogenic inputs, including the multifunctional Ca(2+)/calmodulin-stimulated protein kinase II (CaMKII). CaMKII can be activated by Ca(2+) transients from both extracellular and intracellular sources. Prolonging the activities of Ca(2+)-sensitive K(+) channels in the plasma membrane of GI smooth muscle cells is an important regulatory mechanism carried out by CaMKII. Phospholamban (PLN) phosphorylation by CaMKII activates the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA), increasing both the rate of Ca(2+) clearance from the myoplasm and the frequency of localized Ca(2+) release events from intracellular stores. Overall, CaMKII appears to moderate GI smooth muscle cell excitability. Finally, transcription factor activities may be facilitated by the neutralization of HDAC4 by CaMKII phosphorylation, which may contribute to the phenotypic plasticity of GI smooth muscle cells.
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Affiliation(s)
- Brian A Perrino
- Department of Physiology and Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, 89557, USA.
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Anderson ME, Brown JH, Bers DM. CaMKII in myocardial hypertrophy and heart failure. J Mol Cell Cardiol 2011; 51:468-73. [PMID: 21276796 DOI: 10.1016/j.yjmcc.2011.01.012] [Citation(s) in RCA: 338] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 01/13/2011] [Accepted: 01/13/2011] [Indexed: 02/08/2023]
Abstract
Many signals have risen and fallen in the tide of investigation into mechanisms of myocardial hypertrophy and heart failure (HF). In our opinion, the multifunctional Ca and calmodulin-dependent protein kinase II (CaMKII) has emerged as a molecule to watch, in part because a solid body of accumulated data essentially satisfy Koch's postulates, showing that the CaMKII pathway is a core mechanism for promoting myocardial hypertrophy and heart failure. Multiple groups have now confirmed the following: (1) that CaMKII activity is increased in hypertrophied and failing myocardium from animal models and patients; (2) CaMKII overexpression causes myocardial hypertrophy and HF and (3) CaMKII inhibition (by drugs, inhibitory peptides and gene deletion) improves myocardial hypertrophy and HF. Patients with myocardial disease die in equal proportion from HF and arrhythmias, and a major therapeutic obstacle is that drugs designed to enhance myocardial contraction promote arrhythmias. In contrast, inhibiting the CaMKII pathway appears to reduce arrhythmias and improve myocardial responses to pathological stimuli. This brief paper will introduce the molecular physiology of CaMKII and discuss the impact of CaMKII on ion channels, Ca handling proteins and transcription in myocardium. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".
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Affiliation(s)
- Mark E Anderson
- Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
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Nerbonne JM. Repolarizing cardiac potassium channels: multiple sites and mechanisms for CaMKII-mediated regulation. Heart Rhythm 2011; 8:938-41. [PMID: 21232627 DOI: 10.1016/j.hrthm.2011.01.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Indexed: 11/29/2022]
Affiliation(s)
- Jeanne M Nerbonne
- Department of Developmental Biology and Center for the Investigation of Membrane Excitability Diseases, Washington University Medical School, St. Louis, Missouri, USA.
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Kudryashova IV. Structural and functional characteristics of potassium channels and their role in neuroplasticity. NEUROCHEM J+ 2010. [DOI: 10.1134/s1819712410030013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Abstract
Calcium/calmodulin-dependent kinase II (CaMKII) is a multifunctional serine/threonine kinase expressed abundantly in the heart. CaMKII targets numerous proteins involved in excitation-contraction coupling and excitability, and its activation may simultaneously contribute to heart failure and cardiac arrhythmias. In this review, we summarize the modulatory effects of CaMKII on cardiac ion channel function and expression and illustrate potential implications in the onset of arrhythmias via a computer model.
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Li GR, Dong MQ. Pharmacology of Cardiac Potassium Channels. CARDIOVASCULAR PHARMACOLOGY - HEART AND CIRCULATION 2010; 59:93-134. [DOI: 10.1016/s1054-3589(10)59004-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Dwyer L, Kim HJ, Koh BH, Koh SD. Phospholipase C-independent effects of 3M3FBS in murine colon. Eur J Pharmacol 2009; 628:187-94. [PMID: 19931239 DOI: 10.1016/j.ejphar.2009.11.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 10/22/2009] [Accepted: 11/05/2009] [Indexed: 11/30/2022]
Abstract
The muscarinic receptor subtype M(3) is coupled to Gq/11 proteins. Muscarinic receptor agonists such as carbachol stimulate these receptors that result in activation of phospholipase C (PLC) which hydrolyzes phosphatidylinositol 4,5-bisphosphate into diacylglycerol and Ins(1,4,5)P(3). This pathway leads to excitation and smooth muscle contraction. In this study the PLC agonist, 2, 4, 6-trimethyl-N-(meta-3-trifluoromethyl-phenyl)-benezenesulfonamide (m-3M3FBS), was used to investigate whether direct PLC activation mimics carbachol-induced excitation. We examined the effects of m-3M3FBS and 2, 4, 6-trimethyl-N-(ortho-3-trifluoromethyl-phenyl)-benzenesulfonamide (o-3M3FBS), on murine colonic smooth muscle tissue and cells by performing conventional microelectrode recordings, isometric force measurements and patch clamp experiments. Application of m-3M3FBS decreased spontaneous contractility in murine colonic smooth muscle without affecting the resting membrane potential. Patch clamp studies revealed that delayed rectifier K(+) channels were reversibly inhibited by m-3M3FBS and o-3M3FBS. The PLC inhibitor, 1-(6-((17b-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), did not prevent this inhibition by m-3M3FBS. Both m-3M3FBS and o-3M3FBS decreased two components of delayed rectifier K(+) currents in the presence of tetraethylammonium chloride or 4-aminopyridine. Ca(2+) currents were significantly suppressed by m-3M3FBS and o-3M3FBS with a simultaneous increase in intracellular Ca(2+). Pretreatment with U73122 did not prevent the decrease in Ca(2+) currents upon m-3M3FBS application. In conclusion, both m-3M3FBS and o-3M3FBS inhibit inward and outward currents via mechanisms independent of PLC acting in an antagonistic manner. In contrast, both compounds also caused an increase in [Ca(2+)](i) in an agonistic manner. Therefore caution must be employed when interpreting their effects at the tissue and cellular level.
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Affiliation(s)
- Laura Dwyer
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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Diao F, Waro G, Tsunoda S. Fast inactivation of Shal (K(v)4) K+ channels is regulated by the novel interactor SKIP3 in Drosophila neurons. Mol Cell Neurosci 2009; 42:33-44. [PMID: 19463952 PMCID: PMC2730949 DOI: 10.1016/j.mcn.2009.05.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 05/08/2009] [Accepted: 05/13/2009] [Indexed: 01/09/2023] Open
Abstract
Shal K+ (K(v)4) channels across species carry the major A-type K+ current present in neurons. Shal currents are activated by small EPSPs and modulate post-synaptic potentials, backpropagation of action potentials, and induction of LTP. Fast inactivation of Shal channels regulates the impact of this post-synaptic modulation. Here, we introduce SKIP3, as the first protein interactor of Drosophila Shal K+ channels. The SKIP gene encodes three isoforms with multiple protein-protein interaction domains. SKIP3 is nervous system specific and co-localizes with Shal channels in neuronal cell bodies, and in puncta along processes. Using a genetic deficiency of SKIP, we show that the proportion of neurons displaying a very fast inactivation, consistent with Shal channels exclusively in a "fast" gating mode, is increased in the absence of SKIP3. As a scaffold-like protein, SKIP3 is likely to lead to the identification of a novel regulatory complex that modulates Shal channel inactivation.
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Affiliation(s)
- Fengqiu Diao
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA
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Xie C, Bondarenko VE, Morales MJ, Strauss HC. Closed-state inactivation in Kv4.3 isoforms is differentially modulated by protein kinase C. Am J Physiol Cell Physiol 2009; 297:C1236-48. [PMID: 19675305 DOI: 10.1152/ajpcell.00144.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Kv4.3, with its complex open- and closed-state inactivation (CSI) characteristics, is a primary contributor to early cardiac repolarization. The two alternatively spliced forms, Kv4.3-short (Kv4.3-S) and Kv4.3-long (Kv4.3-L), differ by the presence of a 19-amino acid insert downstream from the sixth transmembrane segment. The isoforms are similar kinetically; however, the longer form has a unique PKC phosphorylation site. To test the possibility that inactivation is differentially regulated by phosphorylation, we expressed the Kv4.3 isoforms in Xenopus oocytes and examined changes in their inactivation properties after stimulation of PKC activity. Whereas there was no difference in open-state inactivation, there were profound differences in CSI. In Kv4.3-S, PMA reduced the magnitude of CSI by 24% after 14.4 s at -50 mV. In contrast, the magnitude of CSI in Kv4.3-L increased by 25% under the same conditions. Mutation of a putatively phosphorylated threonine (T504) to aspartic acid within a PKC consensus recognition sequence unique to Kv4.3-L eliminated the PMA response. The change in CSI was independent of the intervention used to increase PKC activity; identical results were obtained with either PMA or injected purified PKC. Our previously published 11-state model closely simulated our experimental data. Our data demonstrate isoform-specific regulation of CSI by PKC in Kv4.3 and show that the carboxy terminus of Kv4.3 plays an important role in regulation of CSI.
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Affiliation(s)
- Chang Xie
- Key Laboratory of Molecular Biophysics, Huazhong University of Science and Technology, Ministry of Education, College of Life Science and Technology, Wuhan, Hubei, China
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Voltage-gated potassium channels in IB4-positive colonic sensory neurons mediate visceral hypersensitivity in the rat. Am J Gastroenterol 2009; 104:2014-27. [PMID: 19491827 DOI: 10.1038/ajg.2009.227] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Irritable bowel syndrome (IBS) is associated with a state of chronic visceral hypersensitivity, but the underlying molecular mechanisms of visceral hyperalgesia remain elusive. This study was designed to examine changes in the excitability and alterations of voltage-gated K+ currents in subpopulations of colonic dorsal root ganglion (DRG) neurons in a rat model of IBS-like visceral hypersensitivity. METHODS The model of IBS-like visceral hypersensitivity was induced by intracolonic infusion of 0.5% acetic acid (AA) in saline from postnatal days 8 -21. Experiments were conducted when rats became adults. DRG neurons innervating the colon were identified by 1,1'-dioleoyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate (DiI) fluorescence labeling and were immunostained for isolectin B4 (IB4) binding to classify these colonic neurons. Patch-clamp recordings were made from acutely dissociated DiI-labeled DRG neurons, and the expression of K+ channel in L6-S2 DRG was examined by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. RESULTS (1) Neonatal AA treatment induced long-lasting visceral hypersensitivity without significant inflammation but with mast cell hyperplasia. (2) Colonic DRG neurons contained IB4-positive and negative neurons with different electrophysiological properties. IB4-positive colonic neurons have longer action potentials (APs) and larger A-type K+ currents (I(A)) than the IB4-negative neurons, and IB4 phenotypic changes of colonic neurons were not involved in the chronic visceral hypersensitivity. (3) Neonatal AA treatment decreased I(A) density and changed the electrophysiological properties of I(A) and I(K) by shifting the steady-state inactivation toward a negative direction in IB4-positive colonic neurons. The excitability of these cells increased. (4) Kv4.3 was downregulated in neonatal AA-treated rats compared with control rats, which suggests a possible mechanism regarding the changes in electrical activity of DRG neurons in these rats. CONCLUSIONS A new model for chronic visceral hypersensitivity following a diluted AA stimulus in the neonatal period is described. The hypersensitivity may be associated with mast cell hyperplasia in the colon and increased excitability of IB4-positive colonic neurons as a result of suppression of I(A) density and a shift in the inactivation curves of I(A) and I(K) in a hyperpolarizing direction in these cells. This study identifies for the first time a specific molecular mechanism in subpopulations of colonic DRG neurons that underlies chronic visceral hypersensitivity.
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Niwa N, Nerbonne JM. Molecular determinants of cardiac transient outward potassium current (I(to)) expression and regulation. J Mol Cell Cardiol 2009; 48:12-25. [PMID: 19619557 DOI: 10.1016/j.yjmcc.2009.07.013] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 06/25/2009] [Accepted: 07/10/2009] [Indexed: 12/21/2022]
Abstract
Rapidly activating and inactivating cardiac transient outward K(+) currents, I(to), are expressed in most mammalian cardiomyocytes, and contribute importantly to the early phase of action potential repolarization and to plateau potentials. The rapidly recovering (I(t)(o,f)) and slowly recovering (I(t)(o,s)) components are differentially expressed in the myocardium, contributing to regional heterogeneities in action potential waveforms. Consistent with the marked differences in biophysical properties, distinct pore-forming (alpha) subunits underlie the two I(t)(o) components: Kv4.3/Kv4.2 subunits encode I(t)(o,f), whereas Kv1.4 encodes I(t)(o,s), channels. It has also become increasingly clear that cardiac I(t)(o) channels function as components of macromolecular protein complexes, comprising (four) Kvalpha subunits and a variety of accessory subunits and regulatory proteins that influence channel expression, biophysical properties and interactions with the actin cytoskeleton, and contribute to the generation of normal cardiac rhythms. Derangements in the expression or the regulation of I(t)(o) channels in inherited or acquired cardiac diseases would be expected to increase the risk of potentially life-threatening cardiac arrhythmias. Indeed, a recently identified Brugada syndrome mutation in KCNE3 (MiRP2) has been suggested to result in increased I(t)(o,f) densities. Continued focus in this area seems certain to provide new and fundamentally important insights into the molecular determinants of functional I(t)(o) channels and into the molecular mechanisms involved in the dynamic regulation of I(t)(o) channel functioning in the normal and diseased myocardium.
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Affiliation(s)
- Noriko Niwa
- Department of Developmental Biology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8103, St. Louis, MO 63110-1093, USA
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Wagner S, Hacker E, Grandi E, Weber SL, Dybkova N, Sossalla S, Sowa T, Fabritz L, Kirchhof P, Bers DM, Maier LS. Ca/calmodulin kinase II differentially modulates potassium currents. Circ Arrhythm Electrophysiol 2009; 2:285-94. [PMID: 19808479 DOI: 10.1161/circep.108.842799] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Potassium currents contribute to action potential duration (APD) and arrhythmogenesis. In heart failure, Ca/calmodulin-dependent protein kinase II (CaMKII) is upregulated and can alter ion channel regulation and expression. METHODS AND RESULTS We examine the influence of overexpressing cytoplasmic CaMKIIdelta(C), both acutely in rabbit ventricular myocytes (24-hour adenoviral gene transfer) and chronically in CaMKIIdelta(C)-transgenic mice, on transient outward potassium current (I(to)), and inward rectifying current (I(K1)). Acute and chronic CaMKII overexpression increases I(to,slow) amplitude and expression of the underlying channel protein K(V)1.4. Chronic but not acute CaMKII overexpression causes downregulation of I(to,fast), as well as K(V)4.2 and KChIP2, suggesting that K(V)1.4 expression responds faster and oppositely to K(V)4.2 on CaMKII activation. These amplitude changes were not reversed by CaMKII inhibition, consistent with CaMKII-dependent regulation of channel expression and/or trafficking. CaMKII (acute and chronic) greatly accelerated recovery from inactivation for both I(to) components, but these effects were acutely reversed by AIP (CaMKII inhibitor), suggesting that CaMKII activity directly accelerates I(to) recovery. Expression levels of I(K1) and Kir2.1 mRNA were downregulated by CaMKII overexpression. CaMKII acutely increased I(K1), based on inhibition by AIP (in both models). CaMKII overexpression in mouse prolonged APD (consistent with reduced I(to,fast) and I(K1)), whereas CaMKII overexpression in rabbit shortened APD (consistent with enhanced I(K1) and I(to,slow) and faster I(to) recovery). Computational models allowed discrimination of contributions of different channel effects on APD. CONCLUSIONS CaMKII has both acute regulatory effects and chronic expression level effects on I(to) and I(K1) with complex consequences on APD.
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Affiliation(s)
- Stefan Wagner
- Department of Cardiology and Pneumology, Georg-August-University Göttingen, Göttingen, Germany
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El-Haou S, Balse E, Neyroud N, Dilanian G, Gavillet B, Abriel H, Coulombe A, Jeromin A, Hatem SN. Kv4 potassium channels form a tripartite complex with the anchoring protein SAP97 and CaMKII in cardiac myocytes. Circ Res 2009; 104:758-69. [PMID: 19213956 DOI: 10.1161/circresaha.108.191007] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Membrane-associated guanylate kinase (MAGUK) proteins are major determinants of the organization of ion channels in the plasma membrane in various cell types. Here, we investigated the interaction between the MAGUK protein SAP97 and cardiac Kv4.2/3 channels, which account for a large part of the outward potassium current, I(to), in heart. We found that the Kv4.2 and Kv4.3 channels C termini interacted with SAP97 via a SAL amino acid sequence. SAP97 and Kv4.3 channels were colocalized in the sarcolemma of cardiomyocytes. In CHO cells, SAP97 clustered Kv4.3 channels in the plasma membrane and increased the current independently of the presence of KChIP and dipeptidyl peptidase-like protein-6. Suppression of SAP97 by using short hairpin RNA inhibited I(to) in cardiac myocytes, whereas its overexpression by using an adenovirus increased I(to). Kv4.3 channels without the SAL sequence were no longer regulated by Ca2+/calmodulin kinase (CaMK)II inhibitors. In cardiac myocytes, pull-down and coimmunoprecipitation assays showed that the Kv4 channel C terminus, SAP97, and CaMKII interact together, an interaction suppressed by SAP97 silencing and enhanced by SAP97 overexpression. In HEK293 cells, SAP97 silencing reproduced the effects of CaMKII inhibition on current kinetics and suppressed Kv4/CaMKII interactions. In conclusion, SAP97 is a major partner for surface expression and CaMKII-dependent regulation of cardiac Kv4 channels.
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Affiliation(s)
- Saïd El-Haou
- UMRS-956, Faculté de Médecine Pierre-Marie Curie, 91 Boulevard de l'Hôpital, 75013 Paris, France
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Abstract
Calcium/calmodulin-dependent kinase II (CaMKII) is a multifunctional serine/threonine kinase widely distributed in a number of tissue types. Activation of CaMKII has been linked to important downstream physiological processes, including apoptosis, hypertrophy, and arrhythmia in the heart. Pharmacological or genetic inhibition of CaMKII has been shown to improve health outcomes in a number of animal models. In this review, we summarize the structural and functional properties of CaMKII and detail its role in cardiac arrhythmia, structural heart disease, and sudden death.
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Affiliation(s)
- Jeffrey R Erickson
- Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242-1109, USA
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Lu Z, Abe JI, Taunton J, Lu Y, Shishido T, McClain C, Yan C, Xu SP, Spangenberg TM, Xu H. Reactive oxygen species-induced activation of p90 ribosomal S6 kinase prolongs cardiac repolarization through inhibiting outward K+ channel activity. Circ Res 2008; 103:269-78. [PMID: 18599872 DOI: 10.1161/circresaha.107.166678] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
p90 ribosomal S6 kinase (p90RSK) is activated in cardiomyopathies caused by conditions such as ischemia/reperfusion injury and diabetes mellitus in which prolongation of cardiac repolarization and frequent arrhythmias are common. Molecular mechanisms underlying the electric remodeling in cardiac diseases are largely unknown. In the present study, we determined the role of p90RSK activation in the modulation of voltage-gated K+ channel activity determining cardiac repolarization. Mice with increased cardiac p90RSK activity due to transgenic expression of p90RSK (p90RSK-Tg) had prolongation of QT intervals and of ventricular myocyte action potential durations. Fast transient outward K+ current (I(to,f)), slow delayed outward K+ current (I(K,slow)), and steady-state K+ current (I(SS)) were significantly decreased in p90RSK-Tg mouse ventricular myocytes. mRNA levels of Kv4.3, Kv4.2, Kv1.5, Kv2.1, and KChIP2 from ventricles between p90RSK-Tg and nontransgenic littermate control mice were similar, as assessed by quantitative reverse transcriptase-polymerase chain reaction, indicating that p90RSK regulates voltage-gated K+ channels through posttranslational modification. Kv4.3- and Kv1.5- rather than Kv4.2- and Kv2.1-encoded channels in HEK 293 cells were inhibited by p90RSK. In vitro phosphorylation analysis showed that Kv4.3 was phosphorylated by p90RSK at 2 conserved sites, Ser516 and Ser550. p90RSK expression significantly inhibited Kv4.3- and Kv4.3 and KChIP2-encoded channel activities in HEK 293 cells, whereas p90RSK's effects were blocked by amino acid mutation(s) at phosphorylation site(s) in Kv4.3. Hydrogen peroxide, a mediator of induced cardiac p90RSK activation in ischemia/reperfusion injury and diabetes mellitus, had effects similar to those of p90RSK on Kv4.3- or Kv4.3- and KChIP2-encoded channels. Fluoromethylketone, a specific p90RSK inhibitor, abolished hydrogen peroxide effects. These findings indicate that p90RSK activation is critical for reactive oxygen species-mediated inhibition of voltage-gated K+ channel activity and leads to prolongation of cardiac repolarization.
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Affiliation(s)
- Zhibo Lu
- Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY 14642, USA
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