1
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Williams ZJ, Alvarez-Laviada A, Hoagland D, Jourdan LJ, Poelzing S, Gorelik J, Gourdie RG. Development and characterization of the mode-of-action of inhibitory and agonist peptides targeting the voltage-gated sodium channel SCN1B beta-subunit. J Mol Cell Cardiol 2024:S0022-2828(24)00105-6. [PMID: 38942073 DOI: 10.1016/j.yjmcc.2024.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 06/07/2024] [Accepted: 06/19/2024] [Indexed: 06/30/2024]
Abstract
Cardiac arrhythmia treatment is a clinical challenge necessitating safer and more effective therapies. Recent studies have highlighted the role of the perinexus, an intercalated disc nanodomain enriched in voltage-gated sodium channels including both Nav1.5 and β1 subunits, adjacent to gap junctions. These findings offer insights into action potential conduction in the heart. A 19-amino acid SCN1B (β1/β1B) mimetic peptide, βadp1, disrupts VGSC beta subunit-mediated adhesion in cardiac perinexii, inducing arrhythmogenic changes. We aimed to explore βadp1's mechanism and develop novel SCN1B mimetic peptides affecting β1-mediated adhesion. Using patch clamp assays in neonatal rat cardiomyocytes and electric cell substrate impedance sensing (ECIS) in β1-expressing cells, we observed βadp1 maintained inhibitory effects for up to 5 h. A shorter peptide (LQLEED) based on the carboxyl-terminus of βadp1 mimicked this inhibitory effect, while dimeric peptides containing repeated LQLEED sequences paradoxically promoted intercellular adhesion over longer time courses. Moreover, we found a link between these peptides and β1-regulated intramembrane proteolysis (RIP) - a signaling pathway effecting gene transcription including that of VGSC subunits. βadp1 increased RIP continuously over 48 h, while dimeric agonists acutely boosted RIP for up to 6 h. In the presence of DAPT, an RIP inhibitor, βadp1's effects on ECIS-measured intercellular adhesion was reduced, suggesting a relationship between RIP and the peptide's inhibitory action. In conclusion, novel SCN1B (β1/β1B) mimetic peptides are reported with the potential to modulate intercellular VGSC β1-mediated adhesion, potentially through β1 RIP. These findings suggest a path towards the development of anti-arrhythmic drugs targeting the perinexus.
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Affiliation(s)
- Zachary J Williams
- Fralin Biomedical Research Institute, Virginia Polytechnic University, Roanoke, VA, United States
| | | | - Daniel Hoagland
- Fralin Biomedical Research Institute, Virginia Polytechnic University, Roanoke, VA, United States
| | - L Jane Jourdan
- Fralin Biomedical Research Institute, Virginia Polytechnic University, Roanoke, VA, United States
| | - Steven Poelzing
- Fralin Biomedical Research Institute, Virginia Polytechnic University, Roanoke, VA, United States; School of Medicine, Virgina Polytechnic University, Roanoke, VA, United States; Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Roanoke, VA, United States
| | - Julia Gorelik
- Department of Myocardial Function, Imperial College London, London, United Kingdom
| | - Robert G Gourdie
- Fralin Biomedical Research Institute, Virginia Polytechnic University, Roanoke, VA, United States; School of Medicine, Virgina Polytechnic University, Roanoke, VA, United States; Department of Biomedical Engineering and Mechanics, Virginia Polytechnic University, Roanoke, VA, United States.
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2
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Chen C, Ziobro J, Robinson-Cooper L, Hodges SL, Chen Y, Edokobi N, Lopez-Santiago L, Habig K, Moore C, Minton J, Bramson S, Scheuing C, Daddo N, Štěrbová K, Weckhuysen S, Parent JM, Isom LL. Epilepsy and sudden unexpected death in epilepsy in a mouse model of human SCN1B-linked developmental and epileptic encephalopathy. Brain Commun 2023; 5:fcad283. [PMID: 38425576 PMCID: PMC10903178 DOI: 10.1093/braincomms/fcad283] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/13/2023] [Accepted: 10/18/2023] [Indexed: 03/02/2024] Open
Abstract
Voltage-gated sodium channel β1 subunits are essential proteins that regulate excitability. They modulate sodium and potassium currents, function as cell adhesion molecules and regulate gene transcription following regulated intramembrane proteolysis. Biallelic pathogenic variants in SCN1B, encoding β1, are linked to developmental and epileptic encephalopathy 52, with clinical features overlapping Dravet syndrome. A recessive variant, SCN1B-c.265C>T, predicting SCN1B-p.R89C, was homozygous in two children of a non-consanguineous family. One child was diagnosed with Dravet syndrome, while the other had a milder phenotype. We identified an unrelated biallelic SCN1B-c.265C>T patient with a clinically more severe phenotype than Dravet syndrome. We used CRISPR/Cas9 to knock-in SCN1B-p.R89C to the mouse Scn1b locus (Scn1bR89/C89). We then rederived the line on the C57BL/6J background to allow comparisons between Scn1bR89/R89 and Scn1bC89/C89 littermates with Scn1b+/+ and Scn1b-/- mice, which are congenic on C57BL/6J, to determine whether the SCN1B-c.265C>T variant results in loss-of-function. Scn1bC89/C89 mice have normal body weights and ∼20% premature mortality, compared with severely reduced body weight and 100% mortality in Scn1b-/- mice. β1-p.R89C polypeptides are expressed in brain at comparable levels to wild type. In heterologous cells, β1-p.R89C localizes to the plasma membrane and undergoes regulated intramembrane proteolysis similar to wild type. Heterologous expression of β1-p.R89C results in sodium channel α subunit subtype specific effects on sodium current. mRNA abundance of Scn2a, Scn3a, Scn5a and Scn1b was increased in Scn1bC89/C89 somatosensory cortex, with no changes in Scn1a. In contrast, Scn1b-/- mouse somatosensory cortex is haploinsufficient for Scn1a, suggesting an additive mechanism for the severity of the null model via disrupted regulation of another Dravet syndrome gene. Scn1bC89/C89 mice are more susceptible to hyperthermia-induced seizures at post-natal Day 15 compared with Scn1bR89/R89 littermates. EEG recordings detected epileptic discharges in young adult Scn1bC89/C89 mice that coincided with convulsive seizures and myoclonic jerks. We compared seizure frequency and duration in a subset of adult Scn1bC89/C89 mice that had been exposed to hyperthermia at post-natal Day 15 versus a subset that were not hyperthermia exposed. No differences in spontaneous seizures were detected between groups. For both groups, the spontaneous seizure pattern was diurnal, occurring with higher frequency during the dark cycle. This work suggests that the SCN1B-c.265C>T variant does not result in complete loss-of-function. Scn1bC89/C89 mice more accurately model SCN1B-linked variants with incomplete loss-of-function compared with Scn1b-/- mice, which model complete loss-of-function, and thus add to our understanding of disease mechanisms as well as our ability to develop new therapeutic strategies.
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Affiliation(s)
- Chunling Chen
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Julie Ziobro
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | | | - Samantha L Hodges
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Yan Chen
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Nnamdi Edokobi
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Luis Lopez-Santiago
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Karl Habig
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Chloe Moore
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Joe Minton
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Sabrina Bramson
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Caroline Scheuing
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Noor Daddo
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Katalin Štěrbová
- Department of Pediatric Neurology, Charles University and Motol Hospital, V Úvalu 84, 150 06 Prague 5, Czech Republic
| | - Sarah Weckhuysen
- Applied & Translational Neurogenomics Group, VIB Center for Molecular Neurology, VIB, Universiteitsplein 1 B-2610 Antwerpen, Belgium
- Translational Neurosciences, Faculty of Medicine and Health Science, University of Antwerp, Universiteitsplein 1 B-2610 Antwerpen, Belgium
- Department of Neurology, Antwerp University Hospital, Universiteitsplein 1B-2610 Antwerpen, Belgium
- µNEURO Research Centre of Excellence, University of Antwerp, Universiteitsplein 1B-2610 Antwerpen, Belgium
| | - Jack M Parent
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Michigan Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Neurology, VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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3
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Wu LY, Song YJ, Zhang CL, Liu J. K V Channel-Interacting Proteins in the Neurological and Cardiovascular Systems: An Updated Review. Cells 2023; 12:1894. [PMID: 37508558 PMCID: PMC10377897 DOI: 10.3390/cells12141894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/08/2023] [Accepted: 07/10/2023] [Indexed: 07/30/2023] Open
Abstract
KV channel-interacting proteins (KChIP1-4) belong to a family of Ca2+-binding EF-hand proteins that are able to bind to the N-terminus of the KV4 channel α-subunits. KChIPs are predominantly expressed in the brain and heart, where they contribute to the maintenance of the excitability of neurons and cardiomyocytes by modulating the fast inactivating-KV4 currents. As the auxiliary subunit, KChIPs are critically involved in regulating the surface protein expression and gating properties of KV4 channels. Mechanistically, KChIP1, KChIP2, and KChIP3 promote the translocation of KV4 channels to the cell membrane, accelerate voltage-dependent activation, and slow the recovery rate of inactivation, which increases KV4 currents. By contrast, KChIP4 suppresses KV4 trafficking and eliminates the fast inactivation of KV4 currents. In the heart, IKs, ICa,L, and INa can also be regulated by KChIPs. ICa,L and INa are positively regulated by KChIP2, whereas IKs is negatively regulated by KChIP2. Interestingly, KChIP3 is also known as downstream regulatory element antagonist modulator (DREAM) because it can bind directly to the downstream regulatory element (DRE) on the promoters of target genes that are implicated in the regulation of pain, memory, endocrine, immune, and inflammatory reactions. In addition, all the KChIPs can act as transcription factors to repress the expression of genes involved in circadian regulation. Altered expression of KChIPs has been implicated in the pathogenesis of several neurological and cardiovascular diseases. For example, KChIP2 is decreased in failing hearts, while loss of KChIP2 leads to increased susceptibility to arrhythmias. KChIP3 is increased in Alzheimer's disease and amyotrophic lateral sclerosis, but decreased in epilepsy and Huntington's disease. In the present review, we summarize the progress of recent studies regarding the structural properties, physiological functions, and pathological roles of KChIPs in both health and disease. We also summarize the small-molecule compounds that regulate the function of KChIPs. This review will provide an overview and update of the regulatory mechanism of the KChIP family and the progress of targeted drug research as a reference for researchers in related fields.
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Affiliation(s)
- Le-Yi Wu
- Department of Pathophysiology, Shenzhen University Medical School, Shenzhen 518060, China
| | - Yu-Juan Song
- Department of Pathophysiology, Shenzhen University Medical School, Shenzhen 518060, China
| | - Cheng-Lin Zhang
- Department of Pathophysiology, Shenzhen University Medical School, Shenzhen 518060, China
| | - Jie Liu
- Department of Pathophysiology, Shenzhen University Medical School, Shenzhen 518060, China
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4
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Chen L, He Y, Wang X, Ge J, Li H. Ventricular voltage-gated ion channels: Detection, characteristics, mechanisms, and drug safety evaluation. Clin Transl Med 2021; 11:e530. [PMID: 34709746 PMCID: PMC8516344 DOI: 10.1002/ctm2.530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 02/06/2023] Open
Abstract
Cardiac voltage-gated ion channels (VGICs) play critical roles in mediating cardiac electrophysiological signals, such as action potentials, to maintain normal heart excitability and contraction. Inherited or acquired alterations in the structure, expression, or function of VGICs, as well as VGIC-related side effects of pharmaceutical drug delivery can result in abnormal cellular electrophysiological processes that induce life-threatening cardiac arrhythmias or even sudden cardiac death. Hence, to reduce possible heart-related risks, VGICs must be acknowledged as important targets in drug discovery and safety studies related to cardiac disease. In this review, we first summarize the development and application of electrophysiological techniques that are employed in cardiac VGIC studies alone or in combination with other techniques such as cryoelectron microscopy, optical imaging and optogenetics. Subsequently, we describe the characteristics, structure, mechanisms, and functions of various well-studied VGICs in ventricular myocytes and analyze their roles in and contributions to both physiological cardiac excitability and inherited cardiac diseases. Finally, we address the implications of the structure and function of ventricular VGICs for drug safety evaluation. In summary, multidisciplinary studies on VGICs help researchers discover potential targets of VGICs and novel VGICs in heart, enrich their knowledge of the properties and functions, determine the operation mechanisms of pathological VGICs, and introduce groundbreaking trends in drug therapy strategies, and drug safety evaluation.
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Affiliation(s)
- Lulan Chen
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Yue He
- Department of CardiologyShanghai Xuhui District Central Hospital & Zhongshan‐xuhui HospitalShanghaiChina
| | - Xiangdong Wang
- Institute of Clinical Science, Zhongshan HospitalFudan UniversityShanghaiChina
| | - Junbo Ge
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Hua Li
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
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5
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Gao X, Yu S, Guan Y, Shen Y, Xu L. Nucleoporin 50 mediates Kcna4 transcription to regulate cardiac electrical activity. J Cell Sci 2021; 134:271877. [PMID: 34409458 DOI: 10.1242/jcs.256818] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 08/12/2021] [Indexed: 11/20/2022] Open
Abstract
Emerging evidence has demonstrated that nucleoporins (Nups) play a pivotal role in cell-type-specific gene regulation, but how they control the expression and activity of ion channel genes in the heart remains unclear. Here, we show that Nup50, which is localized in the nucleus of cardiomyocytes, selectively induces an increase in the transcription and translation of Kcna4. The Kcna4 gene encodes a K+ voltage-gated channel of shaker-related subfamily member 4 and is essential for regulating the action potential in cardiac membranes. Using immunofluorescence imaging, luciferase assays and chromatin immunoprecipitation assays, we identified that the direct binding of the FG-repeat domain within Nup50 to the proximity of the Kcna4 promoter was required to activate the transcription and subsequent translation of Kcna4. Functionally, Nup50 overexpression increased the currents of KCNA4-encoded Ito,s channels, and reverse knockdown of Nup50 resulted in a remarkable decrease in the amplitude of Ito,s currents in cardiomyocytes. Moreover, a positive correlation between Nup50 and Kcna4 mRNA and protein expression was observed in heart tissues subjected to ischemic insults. These findings provide insights into the homeostatic control of cardiac electrophysiology through Nup-mediated regulation.
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Affiliation(s)
- Xueting Gao
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, Tongji University School of Medicine, Shanghai 200120, China.,Institute of Medical Genetics, Tongji University, Shanghai 200092, China
| | - Shuai Yu
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, Tongji University School of Medicine, Shanghai 200120, China.,Institute of Medical Genetics, Tongji University, Shanghai 200092, China
| | - Yi Guan
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, Tongji University School of Medicine, Shanghai 200120, China.,Institute of Medical Genetics, Tongji University, Shanghai 200092, China
| | - Yunli Shen
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, Tongji University School of Medicine, Shanghai 200120, China
| | - Liang Xu
- Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai 200120, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, Tongji University School of Medicine, Shanghai 200120, China.,Institute of Medical Genetics, Tongji University, Shanghai 200092, China
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6
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Zhu W, Wang W, Angsutararux P, Mellor RL, Isom LL, Nerbonne JM, Silva JR. Modulation of the effects of class Ib antiarrhythmics on cardiac NaV1.5-encoded channels by accessory NaVβ subunits. JCI Insight 2021; 6:e143092. [PMID: 34156986 PMCID: PMC8410097 DOI: 10.1172/jci.insight.143092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 06/17/2021] [Indexed: 01/28/2023] Open
Abstract
Native myocardial voltage-gated sodium (NaV) channels function in macromolecular complexes comprising a pore-forming (α) subunit and multiple accessory proteins. Here, we investigated the impact of accessory NaVβ1 and NaVβ3 subunits on the functional effects of 2 well-known class Ib antiarrhythmics, lidocaine and ranolazine, on the predominant NaV channel α subunit, NaV1.5, expressed in the mammalian heart. We showed that both drugs stabilized the activated conformation of the voltage sensor of domain-III (DIII-VSD) in NaV1.5. In the presence of NaVβ1, the effect of lidocaine on the DIII-VSD was enhanced, whereas the effect of ranolazine was abolished. Mutating the main class Ib drug-binding site, F1760, affected but did not abolish the modulation of drug block by NaVβ1/β3. Recordings from adult mouse ventricular myocytes demonstrated that loss of Scn1b (NaVβ1) differentially affected the potencies of lidocaine and ranolazine. In vivo experiments revealed distinct ECG responses to i.p. injection of ranolazine or lidocaine in WT and Scn1b-null animals, suggesting that NaVβ1 modulated drug responses at the whole-heart level. In the human heart, we found that SCN1B transcript expression was 3 times higher in the atria than ventricles, differences that could, in combination with inherited or acquired cardiovascular disease, dramatically affect patient response to class Ib antiarrhythmic therapies.
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Affiliation(s)
- Wandi Zhu
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Wei Wang
- Department of Internal Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Paweorn Angsutararux
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Rebecca L Mellor
- Department of Internal Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Jeanne M Nerbonne
- Department of Internal Medicine, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA.,Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Jonathan R Silva
- Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
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7
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Bouza AA, Edokobi N, Hodges SL, Pinsky AM, Offord J, Piao L, Zhao YT, Lopatin AN, Lopez-Santiago LF, Isom LL. Sodium channel β1 subunits participate in regulated intramembrane proteolysis-excitation coupling. JCI Insight 2021; 6:141776. [PMID: 33411695 PMCID: PMC7934843 DOI: 10.1172/jci.insight.141776] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 12/29/2020] [Indexed: 12/17/2022] Open
Abstract
Loss-of-function (LOF) variants in SCN1B, encoding voltage-gated sodium channel β1 subunits, are linked to human diseases with high risk of sudden death, including developmental and epileptic encephalopathy and cardiac arrhythmia. β1 Subunits modulate the cell-surface localization, gating, and kinetics of sodium channel pore-forming α subunits. They also participate in cell-cell and cell-matrix adhesion, resulting in intracellular signal transduction, promotion of cell migration, calcium handling, and regulation of cell morphology. Here, we investigated regulated intramembrane proteolysis (RIP) of β1 by BACE1 and γ-secretase and show that β1 subunits are substrates for sequential RIP by BACE1 and γ-secretase, resulting in the generation of a soluble intracellular domain (ICD) that is translocated to the nucleus. Using RNA sequencing, we identified a subset of genes that are downregulated by β1-ICD overexpression in heterologous cells but upregulated in Scn1b-null cardiac tissue, which lacks β1-ICD signaling, suggesting that the β1-ICD may normally function as a molecular brake on gene transcription in vivo. We propose that human disease variants resulting in SCN1B LOF cause transcriptional dysregulation that contributes to altered excitability. Moreover, these results provide important insights into the mechanism of SCN1B-linked channelopathies, adding RIP-excitation coupling to the multifunctionality of sodium channel β1 subunits.
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Affiliation(s)
- Alexandra A Bouza
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Nnamdi Edokobi
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Samantha L Hodges
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Alexa M Pinsky
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - James Offord
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lin Piao
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Yan-Ting Zhao
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anatoli N Lopatin
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Luis F Lopez-Santiago
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan, USA.,Department of Neurology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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8
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Ballouz S, Mangala MM, Perry MD, Heitmann S, Gillis JA, Hill AP, Vandenberg JI. Co-expression of calcium and hERG potassium channels reduces the incidence of proarrhythmic events. Cardiovasc Res 2020; 117:2216-2227. [PMID: 33002116 DOI: 10.1093/cvr/cvaa280] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 08/25/2020] [Accepted: 09/17/2020] [Indexed: 01/02/2023] Open
Abstract
AIMS Cardiac electrical activity is extraordinarily robust. However, when it goes wrong it can have fatal consequences. Electrical activity in the heart is controlled by the carefully orchestrated activity of more than a dozen different ion conductances. While there is considerable variability in cardiac ion channel expression levels between individuals, studies in rodents have indicated that there are modules of ion channels whose expression co-vary. The aim of this study was to investigate whether meta-analytic co-expression analysis of large-scale gene expression datasets could identify modules of co-expressed cardiac ion channel genes in human hearts that are of functional importance. METHODS AND RESULTS Meta-analysis of 3653 public human RNA-seq datasets identified a strong correlation between expression of CACNA1C (L-type calcium current, ICaL) and KCNH2 (rapid delayed rectifier K+ current, IKr), which was also observed in human adult heart tissue samples. In silico modelling suggested that co-expression of CACNA1C and KCNH2 would limit the variability in action potential duration seen with variations in expression of ion channel genes and reduce susceptibility to early afterdepolarizations, a surrogate marker for proarrhythmia. We also found that levels of KCNH2 and CACNA1C expression are correlated in human-induced pluripotent stem cell-derived cardiac myocytes and the levels of CACNA1C and KCNH2 expression were inversely correlated with the magnitude of changes in repolarization duration following inhibition of IKr. CONCLUSION Meta-analytic approaches of multiple independent human gene expression datasets can be used to identify gene modules that are important for regulating heart function. Specifically, we have verified that there is co-expression of CACNA1C and KCNH2 ion channel genes in human heart tissue, and in silico analyses suggest that CACNA1C-KCNH2 co-expression increases the robustness of cardiac electrical activity.
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Affiliation(s)
- Sara Ballouz
- Garvan-Weizmann Centre for Cellular Genomics, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst NSW 2010, Australia.,University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, One Bungtown Road, NY 11724, USA
| | - Melissa M Mangala
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Matthew D Perry
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Stewart Heitmann
- Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Jesse A Gillis
- Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, One Bungtown Road, NY 11724, USA
| | - Adam P Hill
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
| | - Jamie I Vandenberg
- University of New South Wales, Sydney, Kensington, NSW 2052, Australia.,Victor Chang Cardiac Research Institute, Lowy Packer Building, 405 Liverpool Street, Darlinghurst, New South Wales 2010, Australia
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9
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Aeby A, Sculier C, Bouza AA, Askar B, Lederer D, Schoonjans A, Vander Ghinst M, Ceulemans B, Offord J, Lopez‐Santiago LF, Isom LL. SCN1B-linked early infantile developmental and epileptic encephalopathy. Ann Clin Transl Neurol 2019; 6:2354-2367. [PMID: 31709768 PMCID: PMC6917350 DOI: 10.1002/acn3.50921] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 09/22/2019] [Accepted: 09/23/2019] [Indexed: 01/12/2023] Open
Abstract
OBJECTIVE Patients with Early Infantile Epileptic Encephalopathy (EIEE) 52 have inherited, homozygous variants in the gene SCN1B, encoding the voltage-gated sodium channel (VGSC) β1 and β1B non-pore-forming subunits. METHODS Here, we describe the detailed electroclinical features of a biallelic SCN1B patient with a previously unreported variant, p.Arg85Cys. RESULTS The female proband showed hypotonia from birth, multifocal myoclonus at 2.5 months, then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever. Auditory brainstem response (ABR) showed bilateral hearing loss. Epilepsy was refractory and the patient had virtually no development. Administration of fenfluramine resulted in a significant reduction in seizure frequency and resolution of SE episodes that persisted after a 2-year follow-up. The patient phenotype is more compatible with early infantile developmental and epileptic encephalopathy (DEE) than with typical Dravet syndrome (DS), as previously diagnosed for other patients with homozygous SCN1B variants. Biochemical and electrophysiological analyses of the SCN1B variant expressed in heterologous cells showed cell surface expression of the mutant β1 subunit, similar to wild-type (WT), but with loss of normal β1-mediated modification of human Nav 1.1-generated sodium current, suggesting that SCN1B-p.Arg85Cys is a loss-of-function (LOF) variant. INTERPRETATION Importantly, a review of the literature in light of our results suggests that the term, early infantile developmental and epileptic encephalopathy, is more appropriate than either EIEE or DS to describe biallelic SCN1B patients.
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Affiliation(s)
- Alec Aeby
- Pediatric NeurologyQueen Fabiola Children HospitalULBBrusselsBelgium
| | | | - Alexandra A. Bouza
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMI48109
| | - Brandon Askar
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMI48109
| | | | | | - Marc Vander Ghinst
- ENT DepartmentULB‐Hôpital ErasmeUniversité libre de Bruxelles (ULB)BrusselsBelgium
- Laboratoire de Cartographie fonctionnelle du CerveauUNI – ULB Neuroscience InstituteUniversité libre de Bruxelles (ULB)BrusselsBelgium
| | | | - James Offord
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMI48109
| | | | - Lori L. Isom
- Department of PharmacologyUniversity of Michigan Medical SchoolAnn ArborMI48109
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10
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Kernik DC, Morotti S, Wu H, Garg P, Duff HJ, Kurokawa J, Jalife J, Wu JC, Grandi E, Clancy CE. A computational model of induced pluripotent stem-cell derived cardiomyocytes incorporating experimental variability from multiple data sources. J Physiol 2019; 597:4533-4564. [PMID: 31278749 PMCID: PMC6767694 DOI: 10.1113/jp277724] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 07/05/2019] [Indexed: 12/22/2022] Open
Abstract
Key points Induced pluripotent stem cell‐derived cardiomyocytes (iPSC‐CMs) capture patient‐specific genotype–phenotype relationships, as well as cell‐to‐cell variability of cardiac electrical activity Computational modelling and simulation provide a high throughput approach to reconcile multiple datasets describing physiological variability, and also identify vulnerable parameter regimes We have developed a whole‐cell model of iPSC‐CMs, composed of single exponential voltage‐dependent gating variable rate constants, parameterized to fit experimental iPSC‐CM outputs We have utilized experimental data across multiple laboratories to model experimental variability and investigate subcellular phenotypic mechanisms in iPSC‐CMs This framework links molecular mechanisms to cellular‐level outputs by revealing unique subsets of model parameters linked to known iPSC‐CM phenotypes
Abstract There is a profound need to develop a strategy for predicting patient‐to‐patient vulnerability in the emergence of cardiac arrhythmia. A promising in vitro method to address patient‐specific proclivity to cardiac disease utilizes induced pluripotent stem cell‐derived cardiomyocytes (iPSC‐CMs). A major strength of this approach is that iPSC‐CMs contain donor genetic information and therefore capture patient‐specific genotype–phenotype relationships. A cited detriment of iPSC‐CMs is the cell‐to‐cell variability observed in electrical activity. We postulated, however, that cell‐to‐cell variability may constitute a strength when appropriately utilized in a computational framework to build cell populations that can be employed to identify phenotypic mechanisms and pinpoint key sensitive parameters. Thus, we have exploited variation in experimental data across multiple laboratories to develop a computational framework for investigating subcellular phenotypic mechanisms. We have developed a whole‐cell model of iPSC‐CMs composed of simple model components comprising ion channel models with single exponential voltage‐dependent gating variable rate constants, parameterized to fit experimental iPSC‐CM data for all major ionic currents. By optimizing ionic current model parameters to multiple experimental datasets, we incorporate experimentally‐observed variability in the ionic currents. The resulting population of cellular models predicts robust inter‐subject variability in iPSC‐CMs. This approach links molecular mechanisms to known cellular‐level iPSC‐CM phenotypes, as shown by comparing immature and mature subpopulations of models to analyse the contributing factors underlying each phenotype. In the future, the presented models can be readily expanded to include genetic mutations and pharmacological interventions for studying the mechanisms of rare events, such as arrhythmia triggers. Induced pluripotent stem cell‐derived cardiomyocytes (iPSC‐CMs) capture patient‐specific genotype–phenotype relationships, as well as cell‐to‐cell variability of cardiac electrical activity Computational modelling and simulation provide a high throughput approach to reconcile multiple datasets describing physiological variability, and also identify vulnerable parameter regimes We have developed a whole‐cell model of iPSC‐CMs, composed of single exponential voltage‐dependent gating variable rate constants, parameterized to fit experimental iPSC‐CM outputs We have utilized experimental data across multiple laboratories to model experimental variability and investigate subcellular phenotypic mechanisms in iPSC‐CMs This framework links molecular mechanisms to cellular‐level outputs by revealing unique subsets of model parameters linked to known iPSC‐CM phenotypes
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Affiliation(s)
- Divya C Kernik
- Department of Physiology and Membrane Biology, Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, USA
| | - Stefano Morotti
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
| | - HaoDi Wu
- Stanford Cardiovascular Institute, Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Priyanka Garg
- Stanford Cardiovascular Institute, Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Henry J Duff
- Libin Cardiovascular Institute of Alberta, Faculty of Medicine, University of Calgary, Calgary, AB, Canada
| | - Junko Kurokawa
- Department of Bio-Informational Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
| | - José Jalife
- Department of Internal Medicine, Center for Arrhythmia Research, Cardiovascular Research Center, University of Michigan, Ann Arbor, MI, USA.,Centro Nacional de Investigaciones Cardiovasculares (CNIC), and CIBERV, Madrid, Spain
| | - Joseph C Wu
- Stanford Cardiovascular Institute, Department of Medicine, Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Eleonora Grandi
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
| | - Colleen E Clancy
- Department of Physiology and Membrane Biology, Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, USA
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11
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Dynamic palmitoylation regulates trafficking of K channel interacting protein 2 (KChIP2) across multiple subcellular compartments in cardiac myocytes. J Mol Cell Cardiol 2019; 135:1-9. [PMID: 31362018 DOI: 10.1016/j.yjmcc.2019.07.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/26/2019] [Accepted: 07/26/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND K channel interacting protein 2 (KChIP2), initially cloned as Kv4 channel modulator, is a multi-tasking protein. In addition to modulating several cardiac ion channels at the plasma membrane, it can also modulate microRNA transcription inside nuclei, and interact with presenilins to modulate Ca release through RyR2 in the cytoplasm. However, the mechanism regulating its subcellular distribution is not clear. OBJECTIVE We tested whether palmitoylation drives KChIP2 trafficking and distribution in cells, and whether the distribution pattern of KChIP2 in cardiac myocytes is sensitive to cellular milieu. METHOD We conducted imaging and biochemical experiments on palmitoylatable and unpalmitoylatable KChIP2 variants expressed in COS-7 cells and in cardiomyocytes, and on native KChIP2 in myocytes. RESULTS In COS-7 cells, palmitoylatable KChIP2 clustered to plasma membrane, while unpalmitoylatable KChIP2 exhibited higher cytoplasmic mobility and faster nuclear entry. The same differences in distribution and mobility were observed when these KChIP2 variants were expressed in cardiac myocytes, indicating that the palmitoylation-dependent distribution and trafficking are intrinsic properties of KChIP2. Importantly, acute stress in a rat model of cardiac arrest/resuscitation induced changes in native KChIP2 resembling those of KChIP2 depalmitoylation, promoting KChIP2 nuclear entry. CONCLUSION The palmitoylation status of KChIP2 determines its subcellular distribution in cardiac myocytes. Stress promotes nuclear entry of KChIP2, diverting it from ion channel modulation at the plasma membrane to other functions in the nuclear compartment.
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12
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Lubbers ER, Murphy NP, Musa H, Huang CYM, Gupta R, Price MV, Han M, Daoud G, Gratz D, El Refaey M, Xu X, Hoeflinger NK, Friel EL, Lancione P, Wallace MJ, Cavus O, Simmons SL, Williams JL, Skaf M, Koenig SN, Janssen PML, Rasband MN, Hund TJ, Mohler PJ. Defining new mechanistic roles for αII spectrin in cardiac function. J Biol Chem 2019; 294:9576-9591. [PMID: 31064843 PMCID: PMC6579463 DOI: 10.1074/jbc.ra119.007714] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/22/2019] [Indexed: 01/04/2023] Open
Abstract
Spectrins are cytoskeletal proteins essential for membrane biogenesis and regulation and serve critical roles in protein targeting and cellular signaling. αII spectrin (SPTAN1) is one of two α spectrin genes and αII spectrin dysfunction is linked to alterations in axon initial segment formation, cortical lamination, and neuronal excitability. Furthermore, human αII spectrin loss-of-function variants cause neurological disease. As global αII spectrin knockout mice are embryonic lethal, the in vivo roles of αII spectrin in adult heart are unknown and untested. Here, based on pronounced alterations in αII spectrin regulation in human heart failure we tested the in vivo roles of αII spectrin in the vertebrate heart. We created a mouse model of cardiomyocyte-selective αII spectrin-deficiency (cKO) and used this model to define the roles of αII spectrin in cardiac function. αII spectrin cKO mice displayed significant structural, cellular, and electrical phenotypes that resulted in accelerated structural remodeling, fibrosis, arrhythmia, and mortality in response to stress. At the molecular level, we demonstrate that αII spectrin plays a nodal role for global cardiac spectrin regulation, as αII spectrin cKO hearts exhibited remodeling of αI spectrin and altered β-spectrin expression and localization. At the cellular level, αII spectrin deficiency resulted in altered expression, targeting, and regulation of cardiac ion channels NaV1.5 and KV4.3. In summary, our findings define critical and unexpected roles for the multifunctional αII spectrin protein in the heart. Furthermore, our work provides a new in vivo animal model to study the roles of αII spectrin in the cardiomyocyte.
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Affiliation(s)
- Ellen R Lubbers
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
- Medical Scientist Training Program
- the Departments of Physiology and Cell Biology and
| | - Nathaniel P Murphy
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
- Medical Scientist Training Program
- the Departments of Physiology and Cell Biology and
| | - Hassan Musa
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Claire Yu-Mei Huang
- the Department of Neuroscience and Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas 77030, and
| | - Rohan Gupta
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Morgan V Price
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Mei Han
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Georges Daoud
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Daniel Gratz
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
- the Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio 432310
| | - Mona El Refaey
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Xianyao Xu
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Nicole K Hoeflinger
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Emma L Friel
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Peter Lancione
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Michael J Wallace
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Omer Cavus
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Samantha L Simmons
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Jordan L Williams
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Michel Skaf
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Sara N Koenig
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
| | - Paul M L Janssen
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
- the Departments of Physiology and Cell Biology and
- Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, Ohio 432310
| | - Matthew N Rasband
- the Department of Neuroscience and Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, Texas 77030, and
| | - Thomas J Hund
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia
- the Department of Biomedical Engineering, The Ohio State University, Columbus, Ohio 432310
- Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, Ohio 432310
| | - Peter J Mohler
- From the Dorothy M. Davis Heart and Lung Research Institute and Frick Center for Heart Failure and Arrhythmia,
- the Departments of Physiology and Cell Biology and
- Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, Ohio 432310
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13
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Belau F, Metzner K, Christ T, Ravens U, Schaefer M, Künzel S, Li W, Wettwer E, Dobrev D, El-Armouche A, Kämmerer S. DPP10 is a new regulator of Nav1.5 channels in human heart. Int J Cardiol 2019; 284:68-73. [DOI: 10.1016/j.ijcard.2018.12.072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 12/14/2018] [Accepted: 12/27/2018] [Indexed: 10/27/2022]
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14
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Ni H, Rajamani S, Giles WR. Novel regulation of the mammalian cardiac Na + channel by dipeptidyl peptidase 10 interactions: An editorial comment. Int J Cardiol 2019; 284:74-76. [PMID: 30827732 DOI: 10.1016/j.ijcard.2019.02.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/07/2019] [Indexed: 11/29/2022]
Affiliation(s)
- H Ni
- Department of Pharmacology, University of California, Davis, CA, United States of America
| | - S Rajamani
- Cardiometabolic Disorders, Amgen Research, South San Francisco, CA, United States of America
| | - W R Giles
- Faculties of Medicine and Kinesiology, University of Calgary, Calgary, Canada.
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15
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Calloe K. Doctoral Dissertation: The transient outward potassium current in healthy and diseased hearts. Acta Physiol (Oxf) 2019; 225 Suppl 717:e13225. [PMID: 30628199 DOI: 10.1111/apha.13225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 11/20/2018] [Accepted: 11/21/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Kirstine Calloe
- Section for Anatomy; Biochemistry and Physiology; Department for Veterinary and Animal Sciences; Faculty of Health and Medical Sciences; University of Copenhagen; Frederiksberg C Denmark
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16
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The role of the gap junction perinexus in cardiac conduction: Potential as a novel anti-arrhythmic drug target. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 144:41-50. [PMID: 30241906 DOI: 10.1016/j.pbiomolbio.2018.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 07/09/2018] [Accepted: 08/10/2018] [Indexed: 12/16/2022]
Abstract
Cardiovascular disease remains the single largest cause of natural death in the United States, with a significant cause of mortality associated with cardiac arrhythmias. Presently, options for treating and preventing myocardial electrical dysfunction, including sudden cardiac death, are limited. Recent studies have indicated that conduction of electrical activation in the heart may have an ephaptic component, wherein intercellular coupling occurs via electrochemical signaling across narrow extracellular clefts between cardiomyocytes. The perinexus is a 100-200 nm-wide stretch of closely apposed membrane directly adjacent to connexin 43 gap junctions. Electron and super-resolution microscopy studies, as well as biochemical analyses, have provided evidence that perinexal nanodomains may be candidate structures for facilitating ephaptic coupling. This work has included characterization of the perinexus as a region of close inter-membrane contact between cardiomyocytes (<30 nm) containing dense clusters of voltage-gated sodium channels. Here, we review what is known about perinexal structure and function and the potential that the perinexus may have novel and pivotal roles in disorders of cardiac conduction. Of particular interest is the prospect that cell adhesion mediated by the cardiac sodium channel β subunit (Scn1b) may be a novel anti-arrhythmic target.
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17
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Yao H, Fan J, Cheng YJ, Chen XM, Ji CC, Liu LJ, Zheng ZH, Wu SH. SCN1Bβ mutations that affect their association with Kv4.3 underlie early repolarization syndrome. J Cell Mol Med 2018; 22:5639-5647. [PMID: 30160358 PMCID: PMC6201368 DOI: 10.1111/jcmm.13839] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 07/13/2018] [Indexed: 12/12/2022] Open
Abstract
Background Abnormal cardiac ion channels current, including transient outward potassium current (Ito), is associated with early repolarization syndrome (ERS). Previous studies showed that mutations in SCN1Bβ both to increase the Ito current and to decrease the sodium current. Yet its role in ERS remains unknown. Objective To determine the role of mutations in the SCN1Bβ subunits in ERS. Methods We screened for mutations in the SCN1B genes from four families with ERS. Wild‐type and mutant SCN1Bβ genes were co‐expressed with wild‐type KCND3 in human embryonic kidney cells (HEK293). Whole‐cell patch‐clamp technique and co‐immunoprecipitation were used to study the electrophysiological properties and explore the underlying mechanisms. Results S248R and R250T mutations in SCN1Bβ were detected in 4 families’ probands. Neither S248R nor R250T mutation had significant influence on the sodium channel current density (INa) when co‐expressed with SCN5A/WT. Co‐expression of KCND3/WT and SCN1Bβ/S248R or SCN1Bβ/R250T increased the transient outward potassium current Ito by 27.44% and 199.89%, respectively (P < 0.05 and P < 0.01, respectively) when compared with SCN1Bβ/WT. Electrophysiological properties showed that S248R and R250T mutations decreased the steady‐state inactivation and recovery from inactivation of Ito channel. Co‐immunoprecipitation study demonstrated an increased association between SCN1Bβ mutations and Kv4.3 compared with SCN1Bβ/WT (P < 0.05 and P < 0.01, respectively). Conclusion The S248R and R250T mutations of SCN1Bβ gene caused gain‐of‐function of Ito by associated with Kv4.3, which maybe underlie the ERS phenotype of the probands.
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Affiliation(s)
- Hao Yao
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Jun Fan
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Yun-Jiu Cheng
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Xu-Miao Chen
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Cheng-Cheng Ji
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Li-Juan Liu
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Zi-Heng Zheng
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
| | - Su-Hua Wu
- Department of Cardiology, the First Affiliated Hospital, Sun Yat-Sen University, and Key Laboratory on Assisted Circulation, NHC, Guangzhou, China
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Ni H, Morotti S, Grandi E. A Heart for Diversity: Simulating Variability in Cardiac Arrhythmia Research. Front Physiol 2018; 9:958. [PMID: 30079031 PMCID: PMC6062641 DOI: 10.3389/fphys.2018.00958] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 06/29/2018] [Indexed: 12/31/2022] Open
Abstract
In cardiac electrophysiology, there exist many sources of inter- and intra-personal variability. These include variability in conditions and environment, and genotypic and molecular diversity, including differences in expression and behavior of ion channels and transporters, which lead to phenotypic diversity (e.g., variable integrated responses at the cell, tissue, and organ levels). These variabilities play an important role in progression of heart disease and arrhythmia syndromes and outcomes of therapeutic interventions. Yet, the traditional in silico framework for investigating cardiac arrhythmias is built upon a parameter/property-averaging approach that typically overlooks the physiological diversity. Inspired by work done in genetics and neuroscience, new modeling frameworks of cardiac electrophysiology have been recently developed that take advantage of modern computational capabilities and approaches, and account for the variance in the biological data they are intended to illuminate. In this review, we outline the recent advances in statistical and computational techniques that take into account physiological variability, and move beyond the traditional cardiac model-building scheme that involves averaging over samples from many individuals in the construction of a highly tuned composite model. We discuss how these advanced methods have harnessed the power of big (simulated) data to study the mechanisms of cardiac arrhythmias, with a special emphasis on atrial fibrillation, and improve the assessment of proarrhythmic risk and drug response. The challenges of using in silico approaches with variability are also addressed and future directions are proposed.
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Affiliation(s)
| | | | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
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Edokobi N, Isom LL. Voltage-Gated Sodium Channel β1/β1B Subunits Regulate Cardiac Physiology and Pathophysiology. Front Physiol 2018; 9:351. [PMID: 29740331 PMCID: PMC5924814 DOI: 10.3389/fphys.2018.00351] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 03/20/2018] [Indexed: 12/19/2022] Open
Abstract
Cardiac myocyte contraction is initiated by a set of intricately orchestrated electrical impulses, collectively known as action potentials (APs). Voltage-gated sodium channels (NaVs) are responsible for the upstroke and propagation of APs in excitable cells, including cardiomyocytes. NaVs consist of a single, pore-forming α subunit and two different β subunits. The β subunits are multifunctional cell adhesion molecules and channel modulators that have cell type and subcellular domain specific functional effects. Variants in SCN1B, the gene encoding the Nav-β1 and -β1B subunits, are linked to atrial and ventricular arrhythmias, e.g., Brugada syndrome, as well as to the early infantile epileptic encephalopathy Dravet syndrome, all of which put patients at risk for sudden death. Evidence over the past two decades has demonstrated that Nav-β1/β1B subunits play critical roles in cardiac myocyte physiology, in which they regulate tetrodotoxin-resistant and -sensitive sodium currents, potassium currents, and calcium handling, and that Nav-β1/β1B subunit dysfunction generates substrates for arrhythmias. This review will highlight the role of Nav-β1/β1B subunits in cardiac physiology and pathophysiology.
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Affiliation(s)
| | - Lori L. Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, United States
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20
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Na V Channels: Assaying Biosynthesis, Trafficking, Function. Methods Mol Biol 2017. [PMID: 29264805 DOI: 10.1007/978-1-4939-7553-2_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Integral to the cell surface is channels, pumps, and exchanger proteins that facilitate the movement of ions across the membrane. Ion channels facilitate the passive movement of ions down an electrochemical gradient. Ion pumps actively use energy to actively translocate ions, often against concentration or voltage gradients, while ion exchangers utilize energy to couple the transport of different ion species such that one ion moves down its gradient and the released free energy is used to drive the movement of a different ion against its electrochemical gradient. Some ion pumps and exchangers may be electrogenic, i.e., the ion transport they support is not electrically neutral and generates a current. Functions of these pore-forming membrane proteins include the establishment of membrane potentials, gating of ions flows across the cell membrane to elicit action potentials and other electrical signals, as well as the regulation of cell volumes. The major forms of ion channels include voltage-, ligand-, and signal-gated channels. In this review, we describe mammalian voltage dependent Na (NaV) channels.
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Borghetti G, Eisenberg CA, Signore S, Sorrentino A, Kaur K, Andrade-Vicenty A, Edwards JG, Nerkar M, Qanud K, Sun D, Goichberg P, Leri A, Anversa P, Eisenberg LM, Jacobson JT, Hintze TH, Rota M. Notch signaling modulates the electrical behavior of cardiomyocytes. Am J Physiol Heart Circ Physiol 2017; 314:H68-H81. [PMID: 28939651 DOI: 10.1152/ajpheart.00587.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Notch receptor signaling is active during cardiac development and silenced in myocytes after birth. Conversely, outward K+ Kv currents progressively appear in postnatal myocytes leading to shortening of the action potential (AP) and acquisition of the mature electrical phenotype. In the present study, we tested the possibility that Notch signaling modulates the electrical behavior of cardiomyocytes by interfering with Kv currents. For this purpose, the effects of Notch receptor activity on electrophysiological properties of myocytes were evaluated using transgenic mice with inducible expression of the Notch1 intracellular domain (NICD), the functional fragment of the activated Notch receptor, and in neonatal myocytes after inhibition of the Notch transduction pathway. By patch clamp, NICD-overexpressing cells presented prolonged AP duration and reduced upstroke amplitude, properties that were coupled with reduced rapidly activating Kv and fast Na+ currents, compared with cells obtained from wild-type mice. In cultured neonatal myocytes, inhibition of the proteolitic release of NICD with a γ-secretase antagonist increased transcript levels of the Kv channel-interacting proteins 2 (KChIP2) and enhanced the density of Kv currents. Collectively, these results indicate that Notch signaling represents an important regulator of the electrophysiological behavior of developing and adult myocytes by repressing, at least in part, repolarizing Kv currents. NEW & NOTEWORTHY We investigated the effects of Notch receptor signaling on the electrical properties of cardiomyocytes. Our results indicate that the Notch transduction pathway interferes with outward K+ Kv currents, critical determinants of the electrical repolarization of myocytes.
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Affiliation(s)
- Giulia Borghetti
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Carol A Eisenberg
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Sergio Signore
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Andrea Sorrentino
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Keerat Kaur
- Department of Physiology, New York Medical College, Valhalla, New York
| | | | - John G Edwards
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Mriganka Nerkar
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Khaled Qanud
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Dong Sun
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Polina Goichberg
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Annarosa Leri
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | - Piero Anversa
- Departments of Anesthesia and Medicine, and Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School , Boston, Massachusetts
| | | | - Jason T Jacobson
- Department of Physiology, New York Medical College, Valhalla, New York.,Department of Cardiology, Westchester Medical Center, Valhalla, New York
| | - Thomas H Hintze
- Department of Physiology, New York Medical College, Valhalla, New York
| | - Marcello Rota
- Department of Physiology, New York Medical College, Valhalla, New York
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22
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Routh BN, Rathour RK, Baumgardner ME, Kalmbach BE, Johnston D, Brager DH. Increased transient Na + conductance and action potential output in layer 2/3 prefrontal cortex neurons of the fmr1 -/y mouse. J Physiol 2017; 595:4431-4448. [PMID: 28370141 PMCID: PMC5491866 DOI: 10.1113/jp274258] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 03/23/2017] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Layer 2/3 neurons of the prefrontal cortex display higher gain of somatic excitability, responding with a higher number of action potentials for a given stimulus, in fmr1-/y mice. In fmr1-/y L2/3 neurons, action potentials are taller, faster and narrower. Outside-out patch clamp recordings revealed that the maximum Na+ conductance density is higher in fmr1-/y L2/3 neurons. Measurements of three biophysically distinct K+ currents revealed a depolarizing shift in the activation of a rapidly inactivating (A-type) K+ conductance. Realistic neuronal simulations of the biophysical observations recapitulated the elevated action potential and repetitive firing phenotype. ABSTRACT Fragile X syndrome is the most common form of inherited mental impairment and autism. The prefrontal cortex is responsible for higher order cognitive processing, and prefrontal dysfunction is believed to underlie many of the cognitive and behavioural phenotypes associated with fragile X syndrome. We recently demonstrated that somatic and dendritic excitability of layer (L) 5 pyramidal neurons in the prefrontal cortex of the fmr1-/y mouse is significantly altered due to changes in several voltage-gated ion channels. In addition to L5 pyramidal neurons, L2/3 pyramidal neurons play an important role in prefrontal circuitry, integrating inputs from both lower brain regions and the contralateral cortex. Using whole-cell current clamp recording, we found that L2/3 pyramidal neurons in prefrontal cortex of fmr1-/y mouse fired more action potentials for a given stimulus compared with wild-type neurons. In addition, action potentials in fmr1-/y neurons were significantly larger, faster and narrower. Voltage clamp of outside-out patches from L2/3 neurons revealed that the transient Na+ current was significantly larger in fmr1-/y neurons. Furthermore, the activation curve of somatic A-type K+ current was depolarized. Realistic conductance-based simulations revealed that these biophysical changes in Na+ and K+ channel function could reliably reproduce the observed increase in action potential firing and altered action potential waveform. These results, in conjunction with our prior findings on L5 neurons, suggest that principal neurons in the circuitry of the medial prefrontal cortex are altered in distinct ways in the fmr1-/y mouse and may contribute to dysfunctional prefrontal cortex processing in fragile X syndrome.
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Affiliation(s)
- Brandy N Routh
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
| | - Rahul K Rathour
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
| | - Michael E Baumgardner
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
| | - Brian E Kalmbach
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
| | - Daniel Johnston
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
| | - Darrin H Brager
- Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, TX, 78712, USA
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23
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Nassal DM, Wan X, Liu H, Laurita KR, Deschênes I. KChIP2 regulates the cardiac Ca2+ transient and myocyte contractility by targeting ryanodine receptor activity. PLoS One 2017; 12:e0175221. [PMID: 28384221 PMCID: PMC5383259 DOI: 10.1371/journal.pone.0175221] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 03/22/2017] [Indexed: 12/20/2022] Open
Abstract
Pathologic electrical remodeling and attenuated cardiac contractility are featured characteristics of heart failure. Coinciding with these remodeling events is a loss of the K+ channel interacting protein, KChIP2. While, KChIP2 enhances the expression and stability of the Kv4 family of potassium channels, leading to a more pronounced transient outward K+ current, Ito,f, the guinea pig myocardium is unique in that Kv4 expression is absent, while KChIP2 expression is preserved, suggesting alternative consequences to KChIP2 loss. Therefore, KChIP2 was acutely silenced in isolated guinea pig myocytes, which led to significant reductions in the Ca2+ transient amplitude and prolongation of the transient duration. This change was reinforced by a decline in sarcomeric shortening. Notably, these results were unexpected when considering previous observations showing enhanced ICa,L and prolonged action potential duration following KChIP2 loss, suggesting a disruption of fundamental Ca2+ handling proteins. Evaluation of SERCA2a, phospholamban, RyR, and sodium calcium exchanger identified no change in protein expression. However, assessment of Ca2+ spark activity showed reduced spark frequency and prolonged Ca2+ decay following KChIP2 loss, suggesting an altered state of RyR activity. These changes were associated with a delocalization of the ryanodine receptor activator, presenilin, away from sarcomeric banding to more diffuse distribution, suggesting that RyR open probability are a target of KChIP2 loss mediated by a dissociation of presenilin. Typically, prolonged action potential duration and enhanced Ca2+ entry would augment cardiac contractility, but here we see KChIP2 fundamentally disrupts Ca2+ release events and compromises myocyte contraction. This novel role targeting presenilin localization and RyR activity reveals a significance for KChIP2 loss that reflects adverse remodeling observed in cardiac disease settings.
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Affiliation(s)
- Drew M. Nassal
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Xiaoping Wan
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Haiyan Liu
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Kenneth R. Laurita
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Isabelle Deschênes
- Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
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24
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Kubota T, Correa AM, Bezanilla F. Mechanism of functional interaction between potassium channel Kv1.3 and sodium channel NavBeta1 subunit. Sci Rep 2017; 7:45310. [PMID: 28349975 PMCID: PMC5368567 DOI: 10.1038/srep45310] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 02/22/2017] [Indexed: 11/29/2022] Open
Abstract
The voltage-gated potassium channel subfamily A member 3 (Kv1.3) dominantly expresses on T cells and neurons. Recently, the interaction between Kv1.3 and NavBeta1 subunits has been explored through ionic current measurements, but the molecular mechanism has not been elucidated yet. We explored the functional interaction between Kv1.3 and NavBeta1 through gating current measurements using the Cut-open Oocyte Voltage Clamp (COVC) technique. We showed that the N-terminal 1–52 sequence of hKv1.3 disrupts the channel expression on the Xenopus oocyte membrane, suggesting a potential role as regulator of hKv1.3 expression in neurons and lymphocytes. Our gating currents measurements showed that NavBeta1 interacts with the voltage sensing domain (VSD) of Kv1.3 through W172 in the transmembrane segment and modifies the gating operation. The comparison between G-V and Q-V with/without NavBeta1 indicates that NavBeta1 may strengthen the coupling between hKv1.3-VSD movement and pore opening, inducing the modification of kinetics in ionic activation and deactivation.
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Affiliation(s)
- Tomoya Kubota
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th street, Chicago, IL 60637, USA
| | - Ana M Correa
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th street, Chicago, IL 60637, USA
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th street, Chicago, IL 60637, USA
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25
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Nassal DM, Wan X, Liu H, Maleski D, Ramirez-Navarro A, Moravec CS, Ficker E, Laurita KR, Deschênes I. KChIP2 is a core transcriptional regulator of cardiac excitability. eLife 2017; 6. [PMID: 28263709 PMCID: PMC5338919 DOI: 10.7554/elife.17304] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 02/19/2017] [Indexed: 11/18/2022] Open
Abstract
Arrhythmogenesis from aberrant electrical remodeling is a primary cause of death among patients with heart disease. Amongst a multitude of remodeling events, reduced expression of the ion channel subunit KChIP2 is consistently observed in numerous cardiac pathologies. However, it remains unknown if KChIP2 loss is merely a symptom or involved in disease development. Using rat and human derived cardiomyocytes, we identify a previously unobserved transcriptional capacity for cardiac KChIP2 critical in maintaining electrical stability. Through interaction with genetic elements, KChIP2 transcriptionally repressed the miRNAs miR-34b and miR-34c, which subsequently targeted key depolarizing (INa) and repolarizing (Ito) currents altered in cardiac disease. Genetically maintaining KChIP2 expression or inhibiting miR-34 under pathologic conditions restored channel function and moreover, prevented the incidence of reentrant arrhythmias. This identifies the KChIP2/miR-34 axis as a central regulator in developing electrical dysfunction and reveals miR-34 as a therapeutic target for treating arrhythmogenesis in heart disease. DOI:http://dx.doi.org/10.7554/eLife.17304.001 The heart pumps blood throughout the body to provide oxygen and nourishment. To do so, proteins in the heart create electrical signals that tell the heart muscles to contract in a coordinated manner. Heart disease can cause cells to lose control of the production or activity of these proteins, creating disorganized electrical signals called arrhythmias that interfere with the heart’s ability to pump. Sometimes these arrhythmias lead to sudden death. Researchers do not know exactly what triggers these changes in the heart’s normal electrical rhythms. This has made it difficult to develop strategies to prevent these disruptions or to fix them when they occur. By studying rat and human heart cells, Nassal et al. now show that a protein called KChIP2 stops working properly during heart disease. Most importantly, because of the decreased level of KChIP2 in heart disease, KChIP2 loses the ability to restrict the production of two microRNA molecules – a role that KChIP2 was not previously known to perform. This loss of activity sets off a cascade of signals that worsens the balance of electrical activity in the heart cells, creating arrhythmias. Treatments that restored proper levels of the fully working KChIP2 protein to the heart cells or that blocked the signals set off by a lack of KChIP2 returned the electrical activity of the cells back to normal. This also stopped the development of arrhythmias. Further studies are now needed to investigate whether these treatments have the same effects in living mammals. If effective, this could ultimately lead to new treatments for heart diseases and arrhythmias. DOI:http://dx.doi.org/10.7554/eLife.17304.002
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Affiliation(s)
- Drew M Nassal
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, United States
| | - Xiaoping Wan
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Haiyan Liu
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Danielle Maleski
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Angelina Ramirez-Navarro
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Christine S Moravec
- Department of Molecular Cardiology, Cleveland Clinic, Cleveland, United States
| | - Eckhard Ficker
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Kenneth R Laurita
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States
| | - Isabelle Deschênes
- Heart and Vascular Research Center, Department of Medicine, Case Western Reserve University, Cleveland, United States.,Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, United States
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26
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Patel F, Brackenbury WJ. Dual roles of voltage-gated sodium channels in development and cancer. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2016; 59:357-66. [PMID: 26009234 DOI: 10.1387/ijdb.150171wb] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated Na(+) channels (VGSCs) are heteromeric protein complexes containing pore-forming α subunits together with non-pore-forming β subunits. There are nine α subunits, Nav1.1-Nav1.9, and four β subunits, β1-β4. The β subunits are multifunctional, modulating channel activity, cell surface expression, and are members of the immunoglobulin superfamily of cell adhesion molecules. VGSCs are classically responsible for action potential initiation and conduction in electrically excitable cells, including neurons and muscle cells. In addition, through the β1 subunit, VGSCs regulate neurite outgrowth and pathfinding in the developing central nervous system. Reciprocal signalling through Nav1.6 and β1 collectively regulates Na(+) current, electrical excitability and neurite outgrowth in cerebellar granule neurons. Thus, α and β subunits may have diverse interacting roles dependent on cell/tissue type. VGSCs are also expressed in non-excitable cells, including cells derived from a number of types of cancer. In cancer cells, VGSC α and β subunits regulate cellular morphology, migration, invasion and metastasis. VGSC expression associates with poor prognosis in several studies. It is hypothesised that VGSCs are up-regulated in metastatic tumours, favouring an invasive phenotype. Thus, VGSCs may have utility as prognostic markers, and/or as novel therapeutic targets for reducing/preventing metastatic disease burden. VGSCs appear to regulate a number of key cellular processes, both during normal postnatal development of the CNS and during cancer metastasis, by a combination of conducting (i.e. via Na(+) current) and non-conducting mechanisms.
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27
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Sottas V, Abriel H. Negative-dominance phenomenon with genetic variants of the cardiac sodium channel Nav1.5. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1791-8. [PMID: 26907222 DOI: 10.1016/j.bbamcr.2016.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/15/2016] [Accepted: 02/19/2016] [Indexed: 02/07/2023]
Abstract
During the past two decades, many pathological genetic variants in SCN5A, the gene encoding the pore-forming subunit of the cardiac (monomeric) sodium channel Na(v)1.5, have been described. Negative dominance is a classical genetic concept involving a "poison" mutant peptide that negatively interferes with the co-expressed wild-type protein, thus reducing its cellular function. This phenomenon has been described for genetic variants of multimeric K(+) channels, which mechanisms are well understood. Unexpectedly, several pathologic SCN5A variants that are linked to Brugada syndrome also demonstrate such a dominant-negative (DN) effect. The molecular determinants of these observations, however, are not yet elucidated. This review article summarizes recent findings that describe the mechanisms underlying the DN phenomenon of genetic variants of K(+), Ca(2+), Cl(-) and Na(+) channels, and in particular Brugada syndrome variants of Na(v)1.5. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.
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Affiliation(s)
- Valentin Sottas
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland
| | - Hugues Abriel
- Department of Clinical Research, Ion Channel Research Group, University of Bern, Switzerland.
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28
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Das S, Gilchrist J, Bosmans F, Van Petegem F. Binary architecture of the Nav1.2-β2 signaling complex. eLife 2016; 5. [PMID: 26894959 PMCID: PMC4769172 DOI: 10.7554/elife.10960] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 01/07/2016] [Indexed: 12/15/2022] Open
Abstract
To investigate the mechanisms by which β-subunits influence Nav channel function, we solved the crystal structure of the β2 extracellular domain at 1.35Å. We combined these data with known bacterial Nav channel structural insights and novel functional studies to determine the interactions of specific residues in β2 with Nav1.2. We identified a flexible loop formed by (72)Cys and (75)Cys, a unique feature among the four β-subunit isoforms. Moreover, we found that (55)Cys helps to determine the influence of β2 on Nav1.2 toxin susceptibility. Further mutagenesis combined with the use of spider toxins reveals that (55)Cys forms a disulfide bond with (910)Cys in the Nav1.2 domain II pore loop, thereby suggesting a 1:1 stoichiometry. Our results also provide clues as to which disulfide bonds are formed between adjacent Nav1.2 (912/918)Cys residues. The concepts emerging from this work will help to form a model reflecting the β-subunit location in a Nav channel complex.
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Affiliation(s)
- Samir Das
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - John Gilchrist
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Frank Bosmans
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, United States.,Solomon H Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, United States
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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29
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Myocardial KChIP2 Expression in Guinea Pig Resolves an Expanded Electrophysiologic Role. PLoS One 2016; 11:e0146561. [PMID: 26764482 PMCID: PMC4713065 DOI: 10.1371/journal.pone.0146561] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 12/18/2015] [Indexed: 11/19/2022] Open
Abstract
Cardiac ion channels and their respective accessory subunits are critical in maintaining proper electrical activity of the heart. Studies have indicated that the K+ channel interacting protein 2 (KChIP2), originally identified as an auxiliary subunit for the channel Kv4, a component of the transient outward K+ channel (Ito), is a Ca2+ binding protein whose regulatory function does not appear restricted to Kv4 modulation. Indeed, the guinea pig myocardium does not express Kv4, yet we show that it still maintains expression of KChIP2, suggesting roles for KChIP2 beyond this canonical auxiliary interaction with Kv4 to modulate Ito. In this study, we capitalize on the guinea pig as a system for investigating how KChIP2 influences the cardiac action potential, independent of effects otherwise attributed to Ito, given the endogenous absence of the current in this species. By performing whole cell patch clamp recordings on isolated adult guinea pig myocytes, we observe that knock down of KChIP2 significantly prolongs the cardiac action potential. This prolongation was not attributed to compromised repolarizing currents, as IKr and IKs were unchanged, but was the result of enhanced L-type Ca2+ current due to an increase in Cav1.2 protein. In addition, cells with reduced KChIP2 also displayed lowered INa from reduced Nav1.5 protein. Historically, rodent models have been used to investigate the role of KChIP2, where dramatic changes to the primary repolarizing current Ito may mask more subtle effects of KChIP2. Evaluation in the guinea pig where Ito is absent, has unveiled additional functions for KChIP2 beyond its canonical regulation of Ito, which defines KChIP2 as a master regulator of cardiac repolarization and depolarization.
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30
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Gawali V, Todt H. Mechanism of Inactivation in Voltage-Gated Na+ Channels. CURRENT TOPICS IN MEMBRANES 2016; 78:409-50. [DOI: 10.1016/bs.ctm.2016.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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31
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Abstract
Voltage-gated sodium channels (VGSCs) are responsible for the initiation and propagation of action potentials in excitable cells. VGSCs in mammalian brain are heterotrimeric complexes of α and β subunits. Although β subunits were originally termed auxiliary, we now know that they are multifunctional signaling molecules that play roles in both excitable and nonexcitable cell types and with or without the pore-forming α subunit present. β subunits function in VGSC and potassium channel modulation, cell adhesion, and gene regulation, with particularly important roles in brain development. Mutations in the genes encoding β subunits are linked to a number of diseases, including epilepsy, sudden death syndromes like SUDEP and SIDS, and cardiac arrhythmia. Although VGSC β subunit-specific drugs have not yet been developed, this protein family is an emerging therapeutic target.
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Affiliation(s)
- Heather A O'Malley
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109;
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32
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Groenendaal W, Ortega FA, Kherlopian AR, Zygmunt AC, Krogh-Madsen T, Christini DJ. Cell-specific cardiac electrophysiology models. PLoS Comput Biol 2015; 11:e1004242. [PMID: 25928268 PMCID: PMC4415772 DOI: 10.1371/journal.pcbi.1004242] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 03/16/2015] [Indexed: 01/25/2023] Open
Abstract
The traditional cardiac model-building paradigm involves constructing a composite model using data collected from many cells. Equations are derived for each relevant cellular component (e.g., ion channel, exchanger) independently. After the equations for all components are combined to form the composite model, a subset of parameters is tuned, often arbitrarily and by hand, until the model output matches a target objective, such as an action potential. Unfortunately, such models often fail to accurately simulate behavior that is dynamically dissimilar (e.g., arrhythmia) to the simple target objective to which the model was fit. In this study, we develop a new approach in which data are collected via a series of complex electrophysiology protocols from single cardiac myocytes and then used to tune model parameters via a parallel fitting method known as a genetic algorithm (GA). The dynamical complexity of the electrophysiological data, which can only be fit by an automated method such as a GA, leads to more accurately parameterized models that can simulate rich cardiac dynamics. The feasibility of the method is first validated computationally, after which it is used to develop models of isolated guinea pig ventricular myocytes that simulate the electrophysiological dynamics significantly better than does a standard guinea pig model. In addition to improving model fidelity generally, this approach can be used to generate a cell-specific model. By so doing, the approach may be useful in applications ranging from studying the implications of cell-to-cell variability to the prediction of intersubject differences in response to pharmacological treatment. Mathematical models of cardiac cell electrophysiology are widely used as predictive and illuminatory tools, but have been developed for decades using a suboptimal process. The models are typically constructed by manual adjustment of parameters to fit simple data and therefore often underperform when used to predict complex behavior such as arrhythmias. We present a novel method of model parameterization using automated optimization and dynamically rich fitting data and then demonstrate that this approach is better at finding the “real” model of a cell. Application of the method to cardiac myocytes leads to cell-specific models, which may enable well-controlled studies of both cellular- and subject-level population heterogeneity in disease propensity and response to therapies.
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Affiliation(s)
- Willemijn Groenendaal
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, New York, United States of America
| | - Francis A. Ortega
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | - Armen R. Kherlopian
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
| | | | - Trine Krogh-Madsen
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, New York, United States of America
- Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
| | - David J. Christini
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, New York, United States of America
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, United States of America
- Institute for Computational Biomedicine, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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33
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Abstract
Voltage- and ligand-gated ion channels form the molecular basis of cellular excitability. With >400 members and accounting for ∼1.5% of the human genome, ion channels are some of the most well studied of all proteins in heterologous expression systems. Yet, ion channels often exhibit unexpected properties in vivo because of their interaction with a variety of signaling/scaffolding proteins. Such interactions can influence the function and localization of ion channels, as well as their coupling to intracellular second messengers and pathways, thus increasing the signaling potential of these ion channels in neurons. Moreover, functions have been ascribed to ion channels that are largely independent of their ion-conducting roles. Molecular and functional dissection of the ion channel proteome/interactome has yielded new insights into the composition of ion channel complexes and how their dysregulation leads to human disease.
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Jerng HH, Pfaffinger PJ. Modulatory mechanisms and multiple functions of somatodendritic A-type K (+) channel auxiliary subunits. Front Cell Neurosci 2014; 8:82. [PMID: 24723849 PMCID: PMC3973911 DOI: 10.3389/fncel.2014.00082] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/03/2014] [Indexed: 12/13/2022] Open
Abstract
Auxiliary subunits are non-conducting, modulatory components of the multi-protein ion channel complexes that underlie normal neuronal signaling. They interact with the pore-forming α-subunits to modulate surface distribution, ion conductance, and channel gating properties. For the somatodendritic subthreshold A-type potassium (ISA) channel based on Kv4 α-subunits, two types of auxiliary subunits have been extensively studied: Kv channel-interacting proteins (KChIPs) and dipeptidyl peptidase-like proteins (DPLPs). KChIPs are cytoplasmic calcium-binding proteins that interact with intracellular portions of the Kv4 subunits, whereas DPLPs are type II transmembrane proteins that associate with the Kv4 channel core. Both KChIPs and DPLPs genes contain multiple start sites that are used by various neuronal populations to drive the differential expression of functionally distinct N-terminal variants. In turn, these N-terminal variants generate tremendous functional diversity across the nervous system. Here, we focus our review on (1) the molecular mechanism underlying the unique properties of different N-terminal variants, (2) the shaping of native ISA properties by the concerted actions of KChIPs and DPLP variants, and (3) the surprising ways that KChIPs and DPLPs coordinate the activity of multiple channels to fine-tune neuronal excitability. Unlocking the unique contributions of different auxiliary subunit N-terminal variants may provide an important opportunity to develop novel targeted therapeutics to treat numerous neurological disorders.
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Affiliation(s)
- Henry H. Jerng
- Department of Neuroscience, Baylor College of MedicineHouston, TX, USA
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Hoshi M, Du XX, Shinlapawittayatorn K, Liu H, Chai S, Wan X, Ficker E, Deschênes I. Brugada syndrome disease phenotype explained in apparently benign sodium channel mutations. ACTA ACUST UNITED AC 2014; 7:123-31. [PMID: 24573164 DOI: 10.1161/circgenetics.113.000292] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Brugada syndrome (BrS) is an arrhythmogenic disorder that has been linked to mutations in SCN5A, the gene encoding for the pore-forming α-subunit of the cardiac sodium channel. Typically, BrS mutations in SCN5A result in a reduction of sodium current with some mutations even exhibiting a dominant-negative effect on wild-type (WT) channels, thus leading to an even more prominent decrease in current amplitudes. However, there is also a category of apparently benign (atypical) BrS SCN5A mutations that in vitro demonstrates only minor biophysical defects. It is therefore not clear how these mutations produce a BrS phenotype. We hypothesized that similar to dominant-negative mutations, atypical mutations could lead to a reduction in sodium currents when coexpressed with WT to mimic the heterozygous patient genotype. METHODS AND RESULTS WT and atypical BrS mutations were coexpressed in Human Embryonic Kidney-293 cells, showing a reduction in sodium current densities similar to typical BrS mutations. Importantly, this reduction in sodium current was also seen when the atypical mutations were expressed in rat or human cardiomyocytes. This decrease in current density was the result of reduced surface expression of both mutant and WT channels. CONCLUSIONS Taken together, we have shown how apparently benign SCN5A BrS mutations can lead to the ECG abnormalities seen in patients with BrS through an induced defect that is only present when the mutations are coexpressed with WT channels. Our work has implications for risk management and stratification for some SCN5A-implicated BrS patients.
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Affiliation(s)
- Malcolm Hoshi
- Department of Medicine, Heart and Vascular Research Center, MetroHealth Campus and Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH; and Cardiac Electrophysiology Research and Training Center, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
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Yuan L, Koivumäki JT, Liang B, Lorentzen LG, Tang C, Andersen MN, Svendsen JH, Tfelt-Hansen J, Maleckar M, Schmitt N, Olesen MS, Jespersen T. Investigations of the Navβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada syndrome mutant. Am J Physiol Heart Circ Physiol 2014; 306:H1204-12. [PMID: 24561865 DOI: 10.1152/ajpheart.00405.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Brugada syndrome (BrS) is a rare inherited disease that can give rise to ventricular arrhythmia and ultimately sudden cardiac death. Numerous loss-of-function mutations in the cardiac sodium channel Nav1.5 have been associated with BrS. However, few mutations in the auxiliary Navβ1-4 subunits have been linked to this disease. Here we investigated differences in expression and function between Navβ1 and Navβ1b and whether the H162P/Navβ1b mutation found in a BrS patient is likely to be the underlying cause of disease. The impact of Navβ subunits was investigated by patch-clamp electrophysiology, and the obtained in vitro values were used for subsequent in silico modeling. We found that Navβ1b transcripts were expressed at higher levels than Navβ1 transcripts in the human heart. Navβ1 and Navβ1b coexpressed with Nav1.5 induced a negative shift on steady state of activation and inactivation compared with Nav1.5 alone. Furthermore, Navβ1b was found to increase the current level when coexpressed with Nav1.5, Navβ1b/H162P mutated subunit peak current density was reduced by 48% (-645 ± 151 vs. -334 ± 71 pA/pF), V1/2 steady-state inactivation shifted by -6.7 mV (-70.3 ± 1.5 vs. -77.0 ± 2.8 mV), and time-dependent recovery from inactivation slowed by >50% compared with coexpression with Navβ1b wild type. Computer simulations revealed that these electrophysiological changes resulted in a reduction in both action potential amplitude and maximum upstroke velocity. The experimental data thereby indicate that Navβ1b/H162P results in reduced sodium channel activity functionally affecting the ventricular action potential. This result is an important replication to support the notion that BrS can be linked to the function of Navβ1b and is associated with loss-of-function of the cardiac sodium channel.
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Affiliation(s)
- Lei Yuan
- Danish National Research Foundation Centre for Cardiac Arrhythmia (DARC), Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Calhoun JD, Isom LL. The role of non-pore-forming β subunits in physiology and pathophysiology of voltage-gated sodium channels. Handb Exp Pharmacol 2014; 221:51-89. [PMID: 24737232 DOI: 10.1007/978-3-642-41588-3_4] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Voltage-gated sodium channel β1 and β2 subunits were discovered as auxiliary proteins that co-purify with pore-forming α subunits in brain. The other family members, β1B, β3, and β4, were identified by homology and shown to modulate sodium current in heterologous systems. Work over the past 2 decades, however, has provided strong evidence that these proteins are not simply ancillary ion channel subunits, but are multifunctional signaling proteins in their own right, playing both conducting (channel modulatory) and nonconducting roles in cell signaling. Here, we discuss evidence that sodium channel β subunits not only regulate sodium channel function and localization but also modulate voltage-gated potassium channels. In their nonconducting roles, VGSC β subunits function as immunoglobulin superfamily cell adhesion molecules that modulate brain development by influencing cell proliferation and migration, axon outgrowth, axonal fasciculation, and neuronal pathfinding. Mutations in genes encoding β subunits are linked to paroxysmal diseases including epilepsy, cardiac arrhythmia, and sudden infant death syndrome. Finally, β subunits may be targets for the future development of novel therapeutics.
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Affiliation(s)
- Jeffrey D Calhoun
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, 48109-5632, USA
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Differential gene expression of cardiac ion channels in human dilated cardiomyopathy. PLoS One 2013; 8:e79792. [PMID: 24339868 PMCID: PMC3855055 DOI: 10.1371/journal.pone.0079792] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 09/25/2013] [Indexed: 11/23/2022] Open
Abstract
Background Dilated cardiomyopathy (DCM) is characterized by idiopathic dilation and systolic contractile dysfunction of the cardiac chambers. The present work aimed to study the alterations in gene expression of ion channels involved in cardiomyocyte function. Methods and Results Microarray profiling using the Affymetrix Human Gene® 1.0 ST array was performed using 17 RNA samples, 12 from DCM patients undergoing cardiac transplantation and 5 control donors (CNT). The analysis focused on 7 cardiac ion channel genes, since this category has not been previously studied in human DCM. SCN2B was upregulated, while KCNJ5, KCNJ8, CLIC2, CLCN3, CACNB2, and CACNA1C were downregulated. The RT-qPCR (21 DCM and 8 CNT samples) validated the gene expression of SCN2B (p < 0.0001), KCNJ5 (p < 0.05), KCNJ8 (p < 0.05), CLIC2 (p < 0.05), and CACNB2 (p < 0.05). Furthermore, we performed an IPA analysis and we found a functional relationship between the different ion channels studied in this work. Conclusion This study shows a differential expression of ion channel genes involved in cardiac contraction in DCM that might partly underlie the changes in left ventricular function observed in these patients. These results could be the basis for new genetic therapeutic approaches.
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Baroni D, Picco C, Barbieri R, Moran O. Antisense-mediated post-transcriptional silencing of SCN1B gene modulates sodium channel functional expression. Biol Cell 2013; 106:13-29. [PMID: 24138709 DOI: 10.1111/boc.201300040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 10/11/2013] [Indexed: 12/19/2022]
Abstract
BACKGROUND INFORMATION Voltage-dependent sodium channels are membrane proteins essential for cell excitability. They are composed by a pore-forming α-subunit and one or more β subunits. Nine α subunit and five β subunit isoforms have been identified in mammals: β1, its splice variant β1B, β2, β3 and β4. Although they do not form the ion channel pore, β subunits modulate both function as well as expression of sodium channels on cell membrane. RESULTS To investigate the role of β1 subunit on the modulation of sodium channel expression, we silenced this auxiliary subunit with specific antisense oligonucleotides (ASONs) in two rat cell lines, the GH3 and the H9C2, from neuro-ectoderm and cardiac myocyte origin, respectively. Treatment of cells with ASONs determined a reduction of about 50% of β1 subunit mRNA and protein expression in both cell lines. We found that this level of β1 subunit silencing resulted in an overall decrease of α subunit mRNA, protein expression and a decrease of sodium current density, without altering significantly the voltage-dependent and kinetic properties of the currents. In GH3 cells, the β1 subunit silencing reduced the expression of Nav1.1, Nav1.3 and Nav1.6 isoforms, whereas the Nav 1.2 isoform expression remained unaltered. The expression of the only α subunit present in H9C2 cells, the Nav1.5, was also reduced by β1 subunit silencing. CONCLUSIONS These results indicate that the β1 subunit may exert an isoform-specific fine-tuned modulation of sodium channel expression.
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Fotiadis P, Forger DB. Modeling the effects of the circadian clock on cardiac electrophysiology. J Biol Rhythms 2013; 28:69-78. [PMID: 23382593 DOI: 10.1177/0748730412469499] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
An internal circadian clock regulates the electrical activity of cardiac myocytes controlling the expression of potassium channel interacting protein-2 (KChIP2), which is a key regulator of cardiac electrical activity. Here, we examine how the circadian rhythm of KChIP2 expression affects the dynamics of human and murine ventricular action potentials (APs), as well as the intervals in the equivalent electrocardiograms (ECGs) reflecting the duration of depolarization and repolarization phases of the cardiac ventricular APs (QRS and QT intervals), with mathematical modeling. We show how the internal circadian clock can control the shape of APs and, in particular, predict AP, QRS, and QT interval prolongation following KChIP2 downregulation, as well as shortening of AP, QRS, and QT interval duration following KChIP2 upregulation. Based on the circadian expression of KChIP2, we can accurately predict the circadian rhythm in cardiac electrical activity and suggest the transient outward potassium currents as the key current for circadian rhythmicity. Our modeling work predicts a smaller effect of KChIP2 on AP and QT interval dynamics in humans. Taken together, these results support the role of KChIP2 as the key regulator of circadian rhythms in the electrical activity of the heart; we provide computational models that can be used to explore circadian rhythms in cardiac electrophysiology and susceptibility to arrhythmia.
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Affiliation(s)
- Panagiotis Fotiadis
- Department of Mathematics, Computational Medicine, and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
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Lehtoranta L, Vuolteenaho O, Laine VJ, Koskinen A, Soukka H, Kytö V, Määttä J, Haapsamo M, Ekholm E, Räsänen J. Maternal hyperglycemia leads to fetal cardiac hyperplasia and dysfunction in a rat model. Am J Physiol Endocrinol Metab 2013; 305:E611-9. [PMID: 23839525 DOI: 10.1152/ajpendo.00043.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Accelerated fetal myocardial growth with altered cardiac function is a well-documented complication of human diabetic pregnancy, but its pathophysiology is still largely unknown. Our aim was to explore the mechanisms of fetal cardiac remodeling and cardiovascular hemodynamics in a rat model of maternal pregestational streptozotocin-induced hyperglycemia. The hyperglycemic group comprised 107 fetuses (10 dams) and the control group 219 fetuses (20 dams). Fetal cardiac function was assessed serially by Doppler ultrasonography. Fetal cardiac to thoracic area ratio, newborn heart weight, myocardial cell proliferative and apoptotic activities, and cardiac gene expression patterns were determined. Maternal hyperglycemia was associated with increased cardiac size, proliferative, apoptotic and mitotic activities, upregulation of genes encoding A- and B-type natriuretic peptides, myosin heavy chain types 2 and 3, uncoupling proteins 2 and 3, and the angiogenetic tumor necrosis factor receptor superfamily member 12A. The genes encoding Kv channel-interacting protein 2, a regulator of electrical cardiac phenotype, and the insulin-regulated glucose transporter 4 were downregulated. The heart rate was lower in fetuses of hyperglycemic dams. At 13-14 gestational days, 98% of fetuses of hyperglycemic dams had holosystolic atrioventricular valve regurgitation and decreased outflow mean velocity, indicating diminished cardiac output. Maternal hyperglycemia may lead to accelerated fetal myocardial growth by cardiomyocyte hyperplasia. In fetuses of hyperglycemic dams, expression of key genes that control and regulate cardiomyocyte electrophysiological properties, contractility, and metabolism are altered and may lead to major functional and clinical implications on the fetal heart.
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Affiliation(s)
- Lara Lehtoranta
- Department of Obstetrics and Gynecology, University of Turku and Turku University Hospital, Turku, Finland
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Modulation of voltage-gated K+ channels by the sodium channel β1 subunit. Proc Natl Acad Sci U S A 2012; 109:18577-82. [PMID: 23090990 DOI: 10.1073/pnas.1209142109] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium (Na(V)) and potassium (K(V)) channels are critical components of neuronal action potential generation and propagation. Here, we report that Na(V)β1 encoded by SCN1b, an integral subunit of Na(V) channels, coassembles with and modulates the biophysical properties of K(V)1 and K(V)7 channels, but not K(V)3 channels, in an isoform-specific manner. Distinct domains of Na(V)β1 are involved in modulation of the different K(V) channels. Studies with channel chimeras demonstrate that Na(V)β1-mediated changes in activation kinetics and voltage dependence of activation require interaction of Na(V)β1 with the channel's voltage-sensing domain, whereas changes in inactivation and deactivation require interaction with the channel's pore domain. A molecular model based on docking studies shows Na(V)β1 lying in the crevice between the voltage-sensing and pore domains of K(V) channels, making significant contacts with the S1 and S5 segments. Cross-modulation of Na(V) and K(V) channels by Na(V)β1 may promote diversity and flexibility in the overall control of cellular excitability and signaling.
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Clatot J, Ziyadeh-Isleem A, Maugenre S, Denjoy I, Liu H, Dilanian G, Hatem SN, Deschênes I, Coulombe A, Guicheney P, Neyroud N. Dominant-negative effect of SCN5A N-terminal mutations through the interaction of Na(v)1.5 α-subunits. Cardiovasc Res 2012; 96:53-63. [PMID: 22739120 DOI: 10.1093/cvr/cvs211] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
AIMS Brugada syndrome (BrS) is an autosomal-inherited cardiac arrhythmia characterized by an ST-segment elevation in the right precordial leads of the electrocardiogram and an increased risk of syncope and sudden death. SCN5A, encoding the cardiac sodium channel Na(v)1.5, is the main gene involved in BrS. Despite the fact that several mutations have been reported in the N-terminus of Na(v)1.5, the functional role of this region remains unknown. We aimed to characterize two BrS N-terminal mutations, R104W and R121W, a construct where this region was deleted, ΔNter, and a construct where only this region was present, Nter. METHODS AND RESULTS Patch-clamp recordings in HEK293 cells demonstrated that R104W, R121W, and ΔNter abolished the sodium current I(Na). Moreover, R104W and R121W mutations exerted a strong dominant-negative effect on wild-type (WT) channels. Immunocytochemistry of rat neonatal cardiomyocytes revealed that both mutants were mostly retained in the endoplasmic reticulum and that their co-expression with WT channels led to WT channel retention. Furthermore, co-immunoprecipitation experiments showed that Na(v)1.5-subunits were interacting with each other, even when mutated, deciphering the mutation dominant-negative effect. Both mutants were mostly degraded by the ubiquitin-proteasome system, while ΔNter was addressed to the membrane, and Nter expression induced a two-fold increase in I(Na). In addition, the co-expression of N-terminal mutants with the gating-defective but trafficking-competent R878C-Na(v)1.5 mutant gave rise to a small I(Na). CONCLUSION This study reports for the first time the critical role of the Na(v)1.5 N-terminal region in channel function and the dominant-negative effect of trafficking-defective channels occurring through α-subunit interaction.
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The sodium channel accessory subunit Navβ1 regulates neuronal excitability through modulation of repolarizing voltage-gated K⁺ channels. J Neurosci 2012; 32:5716-27. [PMID: 22539834 DOI: 10.1523/jneurosci.6450-11.2012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The channel pore-forming α subunit Kv4.2 is a major constituent of A-type (I(A)) potassium currents and a key regulator of neuronal membrane excitability. Multiple mechanisms regulate the properties, subcellular targeting, and cell-surface expression of Kv4.2-encoded channels. In the present study, shotgun proteomic analyses of immunoprecipitated mouse brain Kv4.2 channel complexes unexpectedly identified the voltage-gated Na⁺ channel accessory subunit Navβ1. Voltage-clamp and current-clamp recordings revealed that knockdown of Navβ1 decreases I(A) densities in isolated cortical neurons and that action potential waveforms are prolonged and repetitive firing is increased in Scn1b-null cortical pyramidal neurons lacking Navβ1. Biochemical and voltage-clamp experiments further demonstrated that Navβ1 interacts with and increases the stability of the heterologously expressed Kv4.2 protein, resulting in greater total and cell-surface Kv4.2 protein expression and in larger Kv4.2-encoded current densities. Together, the results presented here identify Navβ1 as a component of native neuronal Kv4.2-encoded I(A) channel complexes and a novel regulator of I(A) channel densities and neuronal excitability.
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Martin CA, Siedlecka U, Kemmerich K, Lawrence J, Cartledge J, Guzadhur L, Brice N, Grace AA, Schwiening C, Terracciano CM, Huang CLH. Reduced Na(+) and higher K(+) channel expression and function contribute to right ventricular origin of arrhythmias in Scn5a+/- mice. Open Biol 2012; 2:120072. [PMID: 22773948 PMCID: PMC3390792 DOI: 10.1098/rsob.120072] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/11/2012] [Indexed: 12/17/2022] Open
Abstract
Brugada syndrome (BrS) is associated with ventricular tachycardia originating particularly in the right ventricle (RV). We explore electrophysiological features predisposing to such arrhythmic tendency and their possible RV localization in a heterozygotic Scn5a+/- murine model. Na(v)1.5 mRNA and protein expression were lower in Scn5a+/- than wild-type (WT), with a further reduction in the RV compared with the left ventricle (LV). RVs showed higher expression levels of K(v)4.2, K(v)4.3 and KChIP2 in both Scn5a+/- and WT. Action potential upstroke velocity and maximum Na(+) current (I(Na)) density were correspondingly decreased in Scn5a+/-, with a further reduction in the RV. The voltage dependence of inactivation was shifted to more negative values in Scn5a+/-. These findings are predictive of a localized depolarization abnormality leading to slowed conduction. Persistent Na(+) current (I(pNa)) density was decreased in a similar pattern to I(Na). RV transient outward current (I(to)) density was greater than LV in both WT and Scn5a+/-, and had larger time constants of inactivation. These findings were also consistent with the observation that AP durations were smallest in the RV of Scn5a+/-, fulfilling predictions of an increased heterogeneity of repolarization as an additional possible electrophysiological mechanism for arrhythmogenesis in BrS.
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Affiliation(s)
- Claire A Martin
- Physiological Laboratory, University of Cambridge, Downing Site, Cambridge CB2 3EG, UK.
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Grubb S, Calloe K, Thomsen MB. Impact of KChIP2 on Cardiac Electrophysiology and the Progression of Heart Failure. Front Physiol 2012; 3:118. [PMID: 22586403 PMCID: PMC3343377 DOI: 10.3389/fphys.2012.00118] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/11/2012] [Indexed: 01/16/2023] Open
Abstract
Electrophysiological remodeling of cardiac potassium ion channels is important in the progression of heart failure. A reduction of the transient outward potassium current (Ito) in mammalian heart failure is consistent with a reduced expression of potassium channel interacting protein 2 (KChIP2, a KV4 subunit). Approaches have been made to investigate the role of KChIP2 in shaping cardiac Ito, including the use of transgenic KChIP2 deficient mice and viral overexpression of KChIP2. The interplay between Ito and myocardial calcium handling is pivotal in the development of heart failure, and is further strengthened by the dual role of KChIP2 as a functional subunit on both KV4 and CaV1.2. Moreover, the potential arrhythmogenic consequence of reduced Ito may contribute to the high relative incidence of sudden death in the early phases of human heart failure. With this review, we offer an overview of the insights into the physiological and pathological roles of KChIP2 and we discuss the limitations of translating the molecular basis of electrophysiological remodeling from animal models of heart failure to the clinical setting.
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Affiliation(s)
- Søren Grubb
- Danish National Research Foundation Centre for Cardiac Arrhythmia, Department of Biomedical Sciences, University of Copenhagen Copenhagen, Denmark
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Holst AG, Saber S, Houshmand M, Zaklyazminskaya EV, Wang Y, Jensen HK, Refsgaard L, Haunsø S, Svendsen JH, Olesen MS, Tfelt-Hansen J. Sodium Current and Potassium Transient Outward Current Genes in Brugada Syndrome: Screening and Bioinformatics. Can J Cardiol 2012; 28:196-200. [DOI: 10.1016/j.cjca.2011.11.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/15/2011] [Accepted: 11/15/2011] [Indexed: 10/14/2022] Open
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Hu D, Barajas-Martínez H, Medeiros-Domingo A, Crotti L, Veltmann C, Schimpf R, Urrutia J, Alday A, Casis O, Pfeiffer R, Burashnikov E, Caceres G, Tester DJ, Wolpert C, Borggrefe M, Schwartz P, Ackerman MJ, Antzelevitch C. A novel rare variant in SCN1Bb linked to Brugada syndrome and SIDS by combined modulation of Na(v)1.5 and K(v)4.3 channel currents. Heart Rhythm 2011; 9:760-9. [PMID: 22155597 DOI: 10.1016/j.hrthm.2011.12.006] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Indexed: 10/14/2022]
Abstract
BACKGROUND Cardiac sodium channel β-subunit mutations have been associated with several inherited cardiac arrhythmia syndromes. OBJECTIVE To identify and characterize variations in SCN1Bb associated with Brugada syndrome (BrS) and sudden infant death syndrome (SIDS). METHODS All known exons and intron borders of the BrS-susceptibility genes were amplified and sequenced in both directions. Wild type (WT) and mutant genes were expressed in TSA201 cells and studied using co-immunoprecipitation and whole-cell patch-clamp techniques. RESULTS Patient 1 was a 44-year-old man with an ajmaline-induced type 1 ST-segment elevation in V1 and V2 supporting the diagnosis of BrS. Patient 2 was a 62-year-old woman displaying a coved-type BrS electrocardiogram who developed cardiac arrest during fever. Patient 3 was a 4-month-old female SIDS case. A R214Q variant was detected in exon 3A of SCN1Bb (Na(v)1B) in all three probands, but not in any other gene previously associated with BrS or SIDS. R214Q was identified in 4 of 807 ethnically-matched healthy controls (0.50%). Co-expression of SCN5A/WT + SCN1Bb/R214Q resulted in peak sodium channel current (I(Na)) 56.5% smaller compared to SCN5A/WT + SCN1Bb/WT (n = 11-12, P<0.05). Co-expression of KCND3/WT + SCN1Bb/R214Q induced a Kv4.3 current (transient outward potassium current, I(to)) 70.6% greater compared with KCND3/WT + SCN1Bb/WT (n = 10-11, P<0.01). Co-immunoprecipitation indicated structural association between Na(v)β1B and Na(v)1.5 and K(v)4.3. CONCLUSION Our results suggest that R214Q variation in SCN1Bb is a functional polymorphism that may serve as a modifier of the substrate responsible for BrS or SIDS phenotypes via a combined loss of function of sodium channel current and gain of function of transient outward potassium current.
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Affiliation(s)
- Dan Hu
- Masonic Medical Research Laboratory, Utica, NY, USA
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Brackenbury WJ, Isom LL. Na Channel β Subunits: Overachievers of the Ion Channel Family. Front Pharmacol 2011; 2:53. [PMID: 22007171 PMCID: PMC3181431 DOI: 10.3389/fphar.2011.00053] [Citation(s) in RCA: 221] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 09/12/2011] [Indexed: 11/13/2022] Open
Abstract
Voltage-gated Na+ channels (VGSCs) in mammals contain a pore-forming α subunit and one or more β subunits. There are five mammalian β subunits in total: β1, β1B, β2, β3, and β4, encoded by four genes: SCN1B–SCN4B. With the exception of the SCN1B splice variant, β1B, the β subunits are type I topology transmembrane proteins. In contrast, β1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC β subunits are multifunctional. While they do not form the ion channel pore, β subunits alter gating, voltage-dependence, and kinetics of VGSCα subunits and thus regulate cellular excitability in vivo. In addition to their roles in channel modulation, β subunits are members of the immunoglobulin superfamily of cell adhesion molecules and regulate cell adhesion and migration. β subunits are also substrates for sequential proteolytic cleavage by secretases. An example of the multifunctional nature of β subunits is β1, encoded by SCN1B, that plays a critical role in neuronal migration and pathfinding during brain development, and whose function is dependent on Na+ current and γ-secretase activity. Functional deletion of SCN1B results in Dravet Syndrome, a severe and intractable pediatric epileptic encephalopathy. β subunits are emerging as key players in a wide variety of physiopathologies, including epilepsy, cardiac arrhythmia, multiple sclerosis, Huntington’s disease, neuropsychiatric disorders, neuropathic and inflammatory pain, and cancer. β subunits mediate multiple signaling pathways on different timescales, regulating electrical excitability, adhesion, migration, pathfinding, and transcription. Importantly, some β subunit functions may operate independently of α subunits. Thus, β subunits perform critical roles during development and disease. As such, they may prove useful in disease diagnosis and therapy.
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