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Steele JW, Krishnan V, Finnell RH. Mechanisms of neurodevelopmental toxicity of topiramate. Crit Rev Toxicol 2024; 54:465-475. [PMID: 38995641 DOI: 10.1080/10408444.2024.2368552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Revised: 05/03/2024] [Accepted: 06/11/2024] [Indexed: 07/13/2024]
Abstract
Prescriptions for antiseizure medications (ASMs) have been rapidly growing over the last several decades due, in part, to an expanding list of clinical indications for which they are now prescribed. This trend has raised concern for potential adverse neurodevelopmental outcomes in ASM-exposed pregnancies. Recent large scale population studies have suggested that the use of topiramate (TOPAMAX, Janssen-Cilag), when prescribed for seizure control, migraines, and/or weight management, is associated with an increased risk for autism spectrum disorder (ASD), intellectual disability, and attention-deficit/hyperactivity disorder (ADHD) in exposed offspring. Here, we critically review epidemiologic evidence demonstrating the neurobehavioral teratogenicity of topiramate and speculate on the neuromolecular mechanisms by which prenatal exposure may perturb neurocognitive development. Specifically, we explore the potential role of topiramate's pharmacological interactions with ligand- and voltage-gated ion channels, especially GABAergic signaling, its effects on DNA methylation and histone acetylation, whether topiramate induces oxidative stress, and its association with fetal growth restriction as possible mechanisms contributing to neurodevelopmental toxicity. Resolving this biology will be necessary to reduce the risk of adverse pregnancy outcomes caused by topiramate or other ASMs.
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Affiliation(s)
- John W Steele
- Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, USA
- Department of Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Vaishnav Krishnan
- Departments of Neurology, Neuroscience and Psychiatry, and Behavioral Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Richard H Finnell
- Center for Precision Environmental Health, Baylor College of Medicine, Houston, TX, USA
- Department of Medicine, Baylor College of Medicine, Houston, TX, USA
- Departments of Molecular and Cellular Biology and Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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2
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Kurekci F, Akif Kilic M, Akbas S, Avci R, Oney C, Dilruba Aslanger A, Maras Genc H, Aydinli N, Pembegul Yildiz E. Voltage-gated sodium channel epilepsies in a tertiary care center: Phenotypic spectrum with correlation to predicted functional effects. Epilepsy Behav 2024; 158:109930. [PMID: 38964184 DOI: 10.1016/j.yebeh.2024.109930] [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: 02/29/2024] [Revised: 06/27/2024] [Accepted: 06/29/2024] [Indexed: 07/06/2024]
Abstract
BACKGROUND Variants in sodium channel genes (SCN) are strongly associated with epilepsy phenotypes. Our aim in this study to evaluate the genotype and phenotype correlation of patients with SCN variants in our tertiary care center. METHODS In this retrospective study, patients with SCN variants and epilepsy who were followed up at our clinic between 2018 and 2022 were evaluated. Our study discussed the demographics of the patients, the seizure types, the age of seizure onset, the SCN variants, the domains and the functions of the variants, the magnetic resonance imaging findings, the motor, cognitive, and psychiatric comorbidities, and the response to anti-seizure medication. Genetic testing was conducted using a next-generation sequencing gene panel (epilepsy panel) or a whole-exome sequencing. For evaluating variant function, we used a prediction tool (https://funnc.shinyapps.io/shinyappweb/ site). To assess protein domains, we used the PER viewer (http://per.broadinstitute.org/). RESULTS Twenty-three patients with SCN variants and epilepsy have been identified. Sixteen patients had variants in the SCN1A, six patients had variants in the SCN2A, and one patient had a variant in the SCN3A. Two novel SCN1A variants and two novel SCN2A variants were identified. The analysis revealed 14/23 missense, 6/23 nonsense, 2/23 frameshift, and 1/23 splice site variants in the SCN. There are seven variants predicted to be gain-of-function and 13 predicted to be loss-of-function. Among 23 patients; 11 had Dravet Syndrome, 6 had early infantile developmental and epileptic encephalopathy, three had genetic epilepsy with febrile seizures plus spectrum disorder, one had self-limited familial neonatal-infantile epilepsy, one had self-limited infantile epilepsy and one had infantile childhood development epileptic encephalopathy. CONCLUSION Our cohort consists of mainly SCN1 variants, most of them were predicted to be loss of function. Dravet syndrome was the most common phenotype. The prediction tool used in our study demonstrated overall compatibility with clinical findings. Due to the diverse clinical manifestations of variant functions, it may assist in guiding medication selection and predicting outcomes. We believe that such a tool will help the clinician in both prognosis prediction and solving therapeutic challenges in this group where refractory seizures are common.
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Affiliation(s)
- Fulya Kurekci
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye.
| | - Mehmet Akif Kilic
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Sinan Akbas
- Department of Medical Genetics, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Rıdvan Avci
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Ceyda Oney
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Ayca Dilruba Aslanger
- Department of Medical Genetics, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Hulya Maras Genc
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Nur Aydinli
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
| | - Edibe Pembegul Yildiz
- Department of Pediatrics, Division of Pediatric Neurology, Istanbul University, Istanbul Faculty of Medicine, Istanbul, Turkiye
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Wang C, Derderian KD, Hamada E, Zhou X, Nelson AD, Kyoung H, Ahituv N, Bouvier G, Bender KJ. Impaired cerebellar plasticity hypersensitizes sensory reflexes in SCN2A-associated ASD. Neuron 2024; 112:1444-1455.e5. [PMID: 38412857 PMCID: PMC11065582 DOI: 10.1016/j.neuron.2024.01.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 01/03/2024] [Accepted: 01/29/2024] [Indexed: 02/29/2024]
Abstract
Children diagnosed with autism spectrum disorder (ASD) commonly present with sensory hypersensitivity or abnormally strong reactions to sensory stimuli. Such hypersensitivity can be overwhelming, causing high levels of distress that contribute markedly to the negative aspects of the disorder. Here, we identify a mechanism that underlies hypersensitivity in a sensorimotor reflex found to be altered in humans and in mice with loss of function in the ASD risk-factor gene SCN2A. The cerebellum-dependent vestibulo-ocular reflex (VOR), which helps maintain one's gaze during movement, was hypersensitized due to deficits in cerebellar synaptic plasticity. Heterozygous loss of SCN2A-encoded NaV1.2 sodium channels in granule cells impaired high-frequency transmission to Purkinje cells and long-term potentiation, a form of synaptic plasticity important for modulating VOR gain. VOR plasticity could be rescued in mice via a CRISPR-activator approach that increases Scn2a expression, demonstrating that evaluation of a simple reflex can be used to assess and quantify successful therapeutic intervention.
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Affiliation(s)
- Chenyu Wang
- Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA, USA; Department of Neurology, University of California, San Francisco, San Francisco, CA, USA; Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Kimberly D Derderian
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA
| | - Elizabeth Hamada
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA
| | - Xujia Zhou
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA
| | - Andrew D Nelson
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA; Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, USA
| | - Henry Kyoung
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA
| | - Nadav Ahituv
- Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, USA; Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, CA, USA; Institute for Human Genetics, University of California, San Francisco, San Francisco, CA, USA
| | - Guy Bouvier
- Department of Physiology, University of California, San Francisco, San Francisco, CA, USA; Université Paris-Saclay, CNRS, Institut des Neurosciences Paris-Saclay, 91400 Saclay, France.
| | - Kevin J Bender
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA; Weill Institute for Neurosciences, University of California, San Francisco, San Francisco, CA, USA.
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Qu G, Merchant JP, Clatot J, DeFlitch LM, Frederick DJ, Tang S, Salvatore M, Zhang X, Li J, Anderson SA, Goldberg EM. Targeted blockade of aberrant sodium current in a stem cell-derived neuron model of SCN3A encephalopathy. Brain 2024; 147:1247-1263. [PMID: 37935051 PMCID: PMC10994535 DOI: 10.1093/brain/awad376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 09/30/2023] [Accepted: 10/20/2023] [Indexed: 11/09/2023] Open
Abstract
Missense variants in SCN3A encoding the voltage-gated sodium (Na+) channel α subunit Nav1.3 are associated with SCN3A-related neurodevelopmental disorder (SCN3A-NDD), a spectrum of disease that includes epilepsy and malformation of cortical development. How genetic variation in SCN3A leads to pathology remains unclear, as prior electrophysiological work on disease-associated variants has been performed exclusively in heterologous cell systems. To further investigate the mechanisms of SCN3A-NDD pathogenesis, we used CRISPR/Cas9 gene editing to modify a control human induced pluripotent stem cell (iPSC) line to express the recurrent de novo missense variant SCN3A c.2624T>C (p.Ile875Thr). With the established Ngn2 rapid induction protocol, we generated glutamatergic forebrain-like neurons (iNeurons), which we showed to express SCN3A mRNA and Nav1.3-mediated Na+ currents. We performed detailed whole-cell patch clamp recordings to determine the effect of the SCN3A-p.Ile875Thr variant on endogenous Na+ currents in, and intrinsic excitability of, human neurons. Compared to control iNeurons, variant-expressing iNeurons exhibit markedly increased slowly-inactivating/persistent Na+ current, abnormal firing patterns with paroxysmal bursting and plateau-like potentials with action potential failure, and a hyperpolarized voltage threshold for action potential generation. We then validated these findings using a separate iPSC line generated from a patient harbouring the SCN3A-p.Ile875Thr variant compared to a corresponding CRISPR-corrected isogenic control line. Finally, we found that application of the Nav1.3-selective blocker ICA-121431 normalizes action potential threshold and aberrant firing patterns in SCN3A-p.Ile1875Thr iNeurons; in contrast, consistent with action as a Na+ channel blocker, ICA-121431 decreases excitability of control iNeurons. Our findings demonstrate that iNeurons can model the effects of genetic variation in SCN3A yet reveal a complex relationship between gain-of-function at the level of the ion channel versus impact on neuronal excitability. Given the transient expression of SCN3A in the developing human nervous system, selective blockade or suppression of Nav1.3-containing Na+ channels could represent a therapeutic approach towards SCN3A-NDD.
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Affiliation(s)
- Guojie Qu
- Division of Neurology, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Julie P Merchant
- Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Jérôme Clatot
- Division of Neurology, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Leah M DeFlitch
- Division of Neurology, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Danny J Frederick
- Department of Child and Adolescent Psychiatry, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Sheng Tang
- Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Madeleine Salvatore
- Department of Child and Adolescent Psychiatry, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Xiaohong Zhang
- Division of Neurology, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Jianping Li
- Department of Child and Adolescent Psychiatry, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
| | - Stewart A Anderson
- The Epilepsy NeuroGenetics Initiative, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Child and Adolescent Psychiatry, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Ethan M Goldberg
- Division of Neurology, Department of Pediatrics, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative, The Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
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Abad-Rodríguez J, Brocca ME, Higuero AM. Glycans and Carbohydrate-Binding/Transforming Proteins in Axon Physiology. ADVANCES IN NEUROBIOLOGY 2023; 29:185-217. [PMID: 36255676 DOI: 10.1007/978-3-031-12390-0_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The mature nervous system relies on the polarized morphology of neurons for a directed flow of information. These highly polarized cells use their somatodendritic domain to receive and integrate input signals while the axon is responsible for the propagation and transmission of the output signal. However, the axon must perform different functions throughout development before being fully functional for the transmission of information in the form of electrical signals. During the development of the nervous system, axons perform environmental sensing functions, which allow them to navigate through other regions until a final target is reached. Some axons must also establish a regulated contact with other cells before reaching maturity, such as with myelinating glial cells in the case of myelinated axons. Mature axons must then acquire the structural and functional characteristics that allow them to perform their role as part of the information processing and transmitting unit that is the neuron. Finally, in the event of an injury to the nervous system, damaged axons must try to reacquire some of their immature characteristics in a regeneration attempt, which is mostly successful in the PNS but fails in the CNS. Throughout all these steps, glycans perform functions of the outermost importance. Glycans expressed by the axon, as well as by their surrounding environment and contacting cells, encode key information, which is fine-tuned by glycan modifying enzymes and decoded by glycan binding proteins so that the development, guidance, myelination, and electrical transmission functions can be reliably performed. In this chapter, we will provide illustrative examples of how glycans and their binding/transforming proteins code and decode instructive information necessary for fundamental processes in axon physiology.
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Affiliation(s)
- José Abad-Rodríguez
- Membrane Biology and Axonal Repair Laboratory, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain.
| | - María Elvira Brocca
- Membrane Biology and Axonal Repair Laboratory, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain
| | - Alonso Miguel Higuero
- Membrane Biology and Axonal Repair Laboratory, Hospital Nacional de Parapléjicos (SESCAM), Toledo, Spain
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Scala M, Efthymiou S, Sultan T, De Waele J, Panciroli M, Salpietro V, Maroofian R, Striano P, Van Petegem F, Houlden H, Bosmans F. Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function. Epilepsia 2021; 62:e82-e87. [PMID: 33901312 PMCID: PMC8585727 DOI: 10.1111/epi.16913] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 04/08/2021] [Accepted: 04/08/2021] [Indexed: 10/21/2022]
Abstract
We identified nine patients from four unrelated families harboring three biallelic variants in SCN1B (NM_001037.5: c.136C>T; p.[Arg46Cys], c.178C>T; p.[Arg60Cys], and c.472G>A; p.[Val158Met]). All subjects presented with early infantile epileptic encephalopathy 52 (EIEE52), a rare, severe developmental and epileptic encephalopathy featuring infantile onset refractory seizures followed by developmental stagnation or regression. Because SCN1B influences neuronal excitability through modulation of voltage-gated sodium (NaV ) channel function, we examined the effects of human SCN1BR46C (β1R46C ), SCN1BR60C (β1R60C ), and SCN1BV158M (β1V158M ) on the three predominant brain NaV channel subtypes NaV 1.1 (SCN1A), NaV 1.2 (SCN2A), and NaV 1.6 (SCN8A). We observed a shift toward more depolarizing potentials of conductance-voltage relationships (NaV 1.2/β1R46C , NaV 1.2/β1R60C , NaV 1.6/β1R46C , NaV 1.6/β1R60C , and NaV 1.6/β1V158M ) and channel availability (NaV 1.1/β1R46C , NaV 1.1/β1V158M , NaV 1.2/β1R46C , NaV 1.2/β1R60C , and NaV 1.6/β1V158M ), and detected a slower recovery from fast inactivation for NaV 1.1/β1V158M . Combined with modeling data indicating perturbation-induced structural changes in β1, these results suggest that the SCN1B variants reported here can disrupt normal NaV channel function in the brain, which may contribute to EIEE52.
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Affiliation(s)
- Marcello Scala
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, and Maternal and Child Health, University of Genoa, Genoa, Italy
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Stephanie Efthymiou
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Tipu Sultan
- Department of Pediatric Neurology, Children's Hospital and Institute of Child Health Lahore, Lahore, Pakistan
| | - Jolien De Waele
- Faculty of Medicine and Health Sciences, Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
| | - Marta Panciroli
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Vincenzo Salpietro
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, and Maternal and Child Health, University of Genoa, Genoa, Italy
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Reza Maroofian
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Pasquale Striano
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, and Maternal and Child Health, University of Genoa, Genoa, Italy
- Pediatric Neurology and Muscular Diseases Unit, G. Gaslini Institute, Genoa, Italy
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Henry Houlden
- Department of Neuromuscular Disorders, Institute of Neurology, University College London, London, UK
| | - Frank Bosmans
- Faculty of Medicine and Health Sciences, Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium
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Shimba K, Kotani K, Jimbo Y. Microfabricated Device to Record Axonal Conduction Under Pharmacological Treatment for Functional Evaluation of Axon Ion Channel. IEEE Trans Biomed Eng 2021; 68:3574-3581. [PMID: 33970856 DOI: 10.1109/tbme.2021.3078473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Neuronal networks are fundamental structures for information processing in the central nervous system. This processing function is severely impaired by abnormal axonal conduction from changes in functional ion channel expression. The evaluation of axonal conduction properties can be effective in the early diagnosis of information-processing abnormalities. However, little is known about functional ion channel expression in axons owing to lack of an appropriate method. In this study, we developed a device to measure changes in axonal conduction properties by selective pharmacological stimulation for the functional evaluation of Na channels expressed in axons. METHODS Axons of rat cortical neurons were guided across a pair of electrodes through microtunnel structures by employing surface patterning. RESULTS The developed device detected more than 50 axons while recording for 10 min. The conduction delay along the axons decreased by 22.5% with neuron maturation. Tetrodotoxin and lidocaine (Na channel blockers) increased the conduction delay in a concentration-dependent manner depending on their working concentrations, indicating the effectiveness of the device. Finally, selective Na channel blockers for various Na channel subtypes were used. Phrixotoxin, a Nav1.2 blocker, markedly increased the conduction delay, suggesting that Nav1.2 is functionally expressed in the unmyelinated axons of the cerebral cortex. CONCLUSION These results show that our device is feasible for the high-throughput functional evaluation of Na channel subtypes in axons. SIGNIFICANCE The results obtained can contribute to the understanding of the pathogenic mechanisms of neurological diseases that involve changes in the functional expression states of ion channels in axons.
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Sullo F, Pasquetti E, Patanè F, Lo Bianco M, Marino SD, Polizzi A, Falsaperla R, Ruggieri M, Zanghì A, Praticò AD. SCN1A and Its Related Epileptic Phenotypes. JOURNAL OF PEDIATRIC NEUROLOGY 2021. [DOI: 10.1055/s-0041-1727260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
AbstractEpilepsy is one of the most common neurological disorders, with a lifetime incidence of 1 in 26. Approximately two-thirds of epilepsy has a substantial genetic component in its etiology. As a result, simultaneous screening for mutations in multiple genes and performing whole exome sequencing (WES) are becoming very frequent in the clinical evaluation of children with epilepsy. In this setting, mutations in voltage-gated sodium channel (SCN) α-subunit genes are the most commonly identified cause of epilepsy, with sodium channel genes (i.e., SCN1A, SCN2A, SCN8A) being the most frequently identified causative genes. SCN1A mutations result in a wide spectrum of epilepsy phenotypes ranging from simple febrile seizures to Dravet syndrome, a severe epileptic encephalopathy. In case of mutation of SCN1A, it is also possible to observe behavioral alterations, such as impulsivity, inattentiveness, and distractibility, which can be framed in an attention deficit hyperactivity disorder (ADHD) like phenotype. Despite more than 1,200 SCN1A mutations being reported, it is not possible to assess a clear phenotype–genotype correlations. Treatment remains a challenge and seizure control is often partial and transitory.
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Affiliation(s)
- Federica Sullo
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Elisa Pasquetti
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Francesca Patanè
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Manuela Lo Bianco
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Simona D. Marino
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Agata Polizzi
- Chair of Pediatrics, Department of Educational Sciences, University of Catania, Catania, Italy
| | - Raffaele Falsaperla
- Unit of Pediatrics and Pediatric Emergency, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
- Unit of Neonatal Intensive Care and Neonatology, University Hospital “Policlinico Rodolico-San Marco,” Catania, Italy
| | - Martino Ruggieri
- Pediatrics Postgraduate Residency Program, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
| | - Antonio Zanghì
- Department of Medical and Surgical Sciences and Advanced Technology “G.F. Ingrassia,” University of Catania, Catania, Italy
| | - Andrea D. Praticò
- Unit of Rare Diseases of the Nervous System in Childhood, Department of Clinical and Experimental Medicine, Section of Pediatrics and Child Neuropsychiatry, University of Catania, Catania, Italy
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Mahling R, Rahlf CR, Hansen SC, Hayden MR, Shea MA. Ca 2+-saturated calmodulin binds tightly to the N-terminal domain of A-type fibroblast growth factor homologous factors. J Biol Chem 2021; 296:100458. [PMID: 33639159 PMCID: PMC8059062 DOI: 10.1016/j.jbc.2021.100458] [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: 12/17/2020] [Revised: 02/15/2021] [Accepted: 02/23/2021] [Indexed: 01/12/2023] Open
Abstract
Voltage-gated sodium channels (Navs) are tightly regulated by multiple conserved auxiliary proteins, including the four fibroblast growth factor homologous factors (FGFs), which bind the Nav EF-hand like domain (EFL), and calmodulin (CaM), a multifunctional messenger protein that binds the NaV IQ motif. The EFL domain and IQ motif are contiguous regions of NaV cytosolic C-terminal domains (CTD), placing CaM and FGF in close proximity. However, whether the FGFs and CaM act independently, directly associate, or operate through allosteric interactions to regulate channel function is unknown. Titrations monitored by steady-state fluorescence spectroscopy, structural studies with solution NMR, and computational modeling demonstrated for the first time that both domains of (Ca2+)4-CaM (but not apo CaM) directly bind two sites in the N-terminal domain (NTD) of A-type FGF splice variants (FGF11A, FGF12A, FGF13A, and FGF14A) with high affinity. The weaker of the (Ca2+)4-CaM-binding sites was known via electrophysiology to have a role in long-term inactivation of the channel but not known to bind CaM. FGF12A binding to a complex of CaM associated with a fragment of the NaV1.2 CTD increased the Ca2+-binding affinity of both CaM domains, consistent with (Ca2+)4-CaM interacting preferentially with its higher-affinity site in the FGF12A NTD. Thus, A-type FGFs can compete with NaV IQ motifs for (Ca2+)4-CaM. During spikes in the cytosolic Ca2+ concentration that accompany an action potential, CaM may translocate from the NaV IQ motif to the FGF NTD, or the A-type FGF NTD may recruit a second molecule of CaM to the channel.
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Affiliation(s)
- Ryan Mahling
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Cade R Rahlf
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Samuel C Hansen
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Matthew R Hayden
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Madeline A Shea
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
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Ravenscroft TA, Janssens J, Lee PT, Tepe B, Marcogliese PC, Makhzami S, Holmes TC, Aerts S, Bellen HJ. Drosophila Voltage-Gated Sodium Channels Are Only Expressed in Active Neurons and Are Localized to Distal Axonal Initial Segment-like Domains. J Neurosci 2020; 40:7999-8024. [PMID: 32928889 PMCID: PMC7574647 DOI: 10.1523/jneurosci.0142-20.2020] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 07/15/2020] [Accepted: 08/04/2020] [Indexed: 12/28/2022] Open
Abstract
In multipolar vertebrate neurons, action potentials (APs) initiate close to the soma, at the axonal initial segment. Invertebrate neurons are typically unipolar with dendrites integrating directly into the axon. Where APs are initiated in the axons of invertebrate neurons is unclear. Voltage-gated sodium (NaV) channels are a functional hallmark of the axonal initial segment in vertebrates. We used an intronic Minos-Mediated Integration Cassette to determine the endogenous gene expression and subcellular localization of the sole NaV channel in both male and female Drosophila, para Despite being the only NaV channel in the fly, we show that only 23 ± 1% of neurons in the embryonic and larval CNS express para, while in the adult CNS para is broadly expressed. We generated a single-cell transcriptomic atlas of the whole third instar larval brain to identify para expressing neurons and show that it positively correlates with markers of differentiated, actively firing neurons. Therefore, only 23 ± 1% of larval neurons may be capable of firing NaV-dependent APs. We then show that Para is enriched in an axonal segment, distal to the site of dendritic integration into the axon, which we named the distal axonal segment (DAS). The DAS is present in multiple neuron classes in both the third instar larval and adult CNS. Whole cell patch clamp electrophysiological recordings of adult CNS fly neurons are consistent with the interpretation that Nav-dependent APs originate in the DAS. Identification of the distal NaV localization in fly neurons will enable more accurate interpretation of electrophysiological recordings in invertebrates.SIGNIFICANCE STATEMENT The site of action potential (AP) initiation in invertebrates is unknown. We tagged the sole voltage-gated sodium (NaV) channel in the fly, para, and identified that Para is enriched at a distal axonal segment. The distal axonal segment is located distal to where dendrites impinge on axons and is the likely site of AP initiation. Understanding where APs are initiated improves our ability to model neuronal activity and our interpretation of electrophysiological data. Additionally, para is only expressed in 23 ± 1% of third instar larval neurons but is broadly expressed in adults. Single-cell RNA sequencing of the third instar larval brain shows that para expression correlates with the expression of active, differentiated neuronal markers. Therefore, only 23 ± 1% of third instar larval neurons may be able to actively fire NaV-dependent APs.
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Affiliation(s)
- Thomas A Ravenscroft
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
| | - Jasper Janssens
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium
- Department of Human Genetics, KU Leuven, Leuven 3000, Belgium
| | - Pei-Tseng Lee
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
| | - Burak Tepe
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
| | - Paul C Marcogliese
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
| | - Samira Makhzami
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium
- Department of Human Genetics, KU Leuven, Leuven 3000, Belgium
| | - Todd C Holmes
- Department of Physiology and Biophysics, School of Medicine, University of California at Irvine, Irvine, California 92697
| | - Stein Aerts
- VIB Center for Brain & Disease Research, KU Leuven, Leuven 3000, Belgium
- Department of Human Genetics, KU Leuven, Leuven 3000, Belgium
| | - Hugo J Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas 77030
- Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030
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11
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Accumulation of Lithium in the Hippocampus of Patients With Bipolar Disorder: A Lithium-7 Magnetic Resonance Imaging Study at 7 Tesla. Biol Psychiatry 2020; 88:426-433. [PMID: 32340717 DOI: 10.1016/j.biopsych.2020.02.1181] [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: 09/19/2019] [Revised: 01/14/2020] [Accepted: 02/03/2020] [Indexed: 01/02/2023]
Abstract
BACKGROUND Lithium (Li) is a first-line treatment for bipolar disorder (BD). To study its cerebral distribution and association with plasma concentrations, we used 7Li magnetic resonance imaging at 7T in euthymic patients with BD treated with Li carbonate for at least 2 years. METHODS Three-dimensional 7Li magnetic resonance imaging scans (N = 21) were acquired with an ultra-short echo-time sequence using a non-Cartesian k-space sampling scheme. Lithium concentrations ([Li]) were estimated using a phantom replacement approach accounting for differential T1 and T2 relaxation effects. In addition to the determination of mean regional [Li] from 7 broad anatomical areas, voxel- and parcellation-based group analyses were conducted for the first time for 7Li magnetic resonance imaging. RESULTS Using unprecedented spatial sensitivity and specificity, we were able to confirm the heterogeneity of the brain Li distribution and its interindividual variability, as well as the strong correlation between plasma and average brain [Li] ([Li]B ≈ 0.40 × [Li]P, R = .74). Remarkably, our statistical analysis led to the identification of a well-defined and significant cluster corresponding closely to the left hippocampus for which high Li content was displayed consistently across our cohort. CONCLUSIONS This observation could be of interest considering 1) the major role of the hippocampus in emotion processing and regulation, 2) the consistent atrophy of the hippocampus in untreated patients with BD, and 3) the normalization effect of Li on gray matter volumes. This study paves the way for the elucidation of the relationship between Li cerebral distribution and its therapeutic response, notably in newly diagnosed patients with BD.
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12
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Menezes LFS, Sabiá Júnior EF, Tibery DV, Carneiro LDA, Schwartz EF. Epilepsy-Related Voltage-Gated Sodium Channelopathies: A Review. Front Pharmacol 2020; 11:1276. [PMID: 33013363 PMCID: PMC7461817 DOI: 10.3389/fphar.2020.01276] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 07/31/2020] [Indexed: 12/29/2022] Open
Abstract
Epilepsy is a disease characterized by abnormal brain activity and a predisposition to generate epileptic seizures, leading to neurobiological, cognitive, psychological, social, and economic impacts for the patient. There are several known causes for epilepsy; one of them is the malfunction of ion channels, resulting from mutations. Voltage-gated sodium channels (NaV) play an essential role in the generation and propagation of action potential, and malfunction caused by mutations can induce irregular neuronal activity. That said, several genetic variations in NaV channels have been described and associated with epilepsy. These mutations can affect channel kinetics, modifying channel activation, inactivation, recovery from inactivation, and/or the current window. Among the NaV subtypes related to epilepsy, NaV1.1 is doubtless the most relevant, with more than 1500 mutations described. Truncation and missense mutations are the most observed alterations. In addition, several studies have already related mutated NaV channels with the electrophysiological functioning of the channel, aiming to correlate with the epilepsy phenotype. The present review provides an overview of studies on epilepsy-associated mutated human NaV1.1, NaV1.2, NaV1.3, NaV1.6, and NaV1.7.
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Affiliation(s)
- Luis Felipe Santos Menezes
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Elias Ferreira Sabiá Júnior
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Diogo Vieira Tibery
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
| | - Lilian Dos Anjos Carneiro
- Faculdade de Medicina, Centro Universitário Euro Americano, Brasília, Brazil.,Faculdade de Medicina, Centro Universitário do Planalto Central, Brasília, Brazil
| | - Elisabeth Ferroni Schwartz
- Laboratório de Neurofarmacologia, Departamento de Ciências Fisiológicas, Universidade de Brasília, Brasília, Brazil
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Zaman T, Helbig KL, Clatot J, Thompson CH, Kang SK, Stouffs K, Jansen AE, Verstraete L, Jacquinet A, Parrini E, Guerrini R, Fujiwara Y, Miyatake S, Ben‐Zeev B, Bassan H, Reish O, Marom D, Hauser N, Vu T, Ackermann S, Spencer CE, Lippa N, Srinivasan S, Charzewska A, Hoffman‐Zacharska D, Fitzpatrick D, Harrison V, Vasudevan P, Joss S, Pilz DT, Fawcett KA, Helbig I, Matsumoto N, Kearney JA, Fry AE, Goldberg EM. SCN3A
‐Related Neurodevelopmental Disorder: A Spectrum of Epilepsy and Brain Malformation. Ann Neurol 2020; 88:348-362. [DOI: 10.1002/ana.25809] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 05/05/2020] [Accepted: 05/25/2020] [Indexed: 12/19/2022]
Affiliation(s)
- Tariq Zaman
- Division of Neurology, Department of Pediatrics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
| | - Katherine L. Helbig
- Division of Neurology, Department of Pediatrics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Epilepsy NeuroGenetics Initiative Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
| | - Jérôme Clatot
- Division of Neurology, Department of Pediatrics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Epilepsy NeuroGenetics Initiative Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
| | - Christopher H. Thompson
- Department of Pharmacology Northwestern University Feinberg School of Medicine Chicago Illinois USA
| | - Seok Kyu Kang
- Department of Pharmacology Northwestern University Feinberg School of Medicine Chicago Illinois USA
| | - Katrien Stouffs
- Center for Medical Genetics/Research Center for Reproduction and Genetics University Hospital Brussels, Free University of Brussels Brussels Belgium
| | - Anna E. Jansen
- Pediatric Neurology Unit, Department of Pediatrics University Hospital Brussels Brussels Belgium
- Neurogenetics Research Group Free University of Brussels Brussels Belgium
| | | | - Adeline Jacquinet
- Human Genetics Service Sart Tilman University Hospital Center Liege Belgium
| | - Elena Parrini
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Department of Neuroscience A. Meyer Children's Hospital, University of Florence Florence Italy
| | - Renzo Guerrini
- Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Department of Neuroscience A. Meyer Children's Hospital, University of Florence Florence Italy
| | - Yuh Fujiwara
- Department of Pediatrics Yokohama City University Medical Center Yokohama Japan
| | - Satoko Miyatake
- Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama Japan
| | - Bruria Ben‐Zeev
- Pediatric Neurology Unit Edmond and Lili Safra Children's Hospital, Haim Sheba Medical Center Ramat Gan Israel
- Sackler School of Medicine Tel Aviv University Tel Aviv Israel
| | - Haim Bassan
- Sackler School of Medicine Tel Aviv University Tel Aviv Israel
- Pediatric Neurology & Development Center Shamir Medical Center (Assaf Harofe) Zerifin Israel
| | - Orit Reish
- Sackler School of Medicine Tel Aviv University Tel Aviv Israel
- Genetics Institute Shamir Medical Center (Assaf Harofe) Zerifin Zerifin Israel
| | - Daphna Marom
- Sackler School of Medicine Tel Aviv University Tel Aviv Israel
- Genetics Institute Shamir Medical Center (Assaf Harofe) Zerifin Zerifin Israel
| | - Natalie Hauser
- Inova Translational Medicine Institute Inova Health System Fairfax Virginia USA
| | - Thuy‐Anh Vu
- Department of Pediatric Neurology Children's National Medical Center, Washington, District of Columbia, and Pediatric Specialists of Virginia Fairfax Virginia USA
| | - Sally Ackermann
- Division of Paediatric Neurology, Department of Paediatrics and Child Health Red Cross War Memorial Children's Hospital, University of Cape Town Cape Town South Africa
| | - Careni E. Spencer
- Division of Human Genetics, Department of Medicine University of Cape Town, South Africa and Groote Schuur Hospital Cape Town South Africa
| | - Natalie Lippa
- Institute for Genomic Medicine Columbia University Medical Center New York New York USA
| | - Shraddha Srinivasan
- Department of Neurology Columbia University Medical Center New York New York USA
| | | | | | - David Fitzpatrick
- Medical Research Council Human Genetics Unit Medical Research Council Institute of Genetics and Molecular Medicine, University of Edinburgh Edinburgh United Kingdom
| | - Victoria Harrison
- Wessex Clinical Genetics Service Princess Anne Hospital Southampton United Kingdom
| | - Pradeep Vasudevan
- Department of Clinical Genetics University Hospitals Leicester National Health Service Trust Leicester United Kingdom
| | - Shelagh Joss
- West of Scotland Clinical Genetics Service Queen Elizabeth University Hospital Glasgow United Kingdom
| | - Daniela T. Pilz
- West of Scotland Clinical Genetics Service Queen Elizabeth University Hospital Glasgow United Kingdom
- Division of Cancer and Genetics School of Medicine, Cardiff University Cardiff United Kingdom
| | - Katherine A. Fawcett
- Medical Research Council (MRC) Computational Genomics Analysis and Training Programme, MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital Oxford United Kingdom
| | - Ingo Helbig
- Division of Neurology, Department of Pediatrics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Epilepsy NeuroGenetics Initiative Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Department of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
- Department of Biomedical and Health Informatics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
| | - Naomichi Matsumoto
- Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama Japan
| | - Jennifer A. Kearney
- Department of Pharmacology Northwestern University Feinberg School of Medicine Chicago Illinois USA
| | - Andrew E. Fry
- Division of Cancer and Genetics School of Medicine, Cardiff University Cardiff United Kingdom
- Institute of Medical Genetics University Hospital of Wales Cardiff United Kingdom
| | - Ethan M. Goldberg
- Division of Neurology, Department of Pediatrics Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Epilepsy NeuroGenetics Initiative Children's Hospital of Philadelphia Philadelphia Pennsylvania USA
- Department of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
- Department of Neuroscience Perelman School of Medicine, University of Pennsylvania Philadelphia Pennsylvania USA
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14
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Sills GJ, Rogawski MA. Mechanisms of action of currently used antiseizure drugs. Neuropharmacology 2020; 168:107966. [PMID: 32120063 DOI: 10.1016/j.neuropharm.2020.107966] [Citation(s) in RCA: 230] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 01/09/2020] [Accepted: 01/12/2020] [Indexed: 02/08/2023]
Abstract
Antiseizure drugs (ASDs) prevent the occurrence of seizures; there is no evidence that they have disease-modifying properties. In the more than 160 years that orally administered ASDs have been available for epilepsy therapy, most agents entering clinical practice were either discovered serendipitously or with the use of animal seizure models. The ASDs originating from these approaches act on brain excitability mechanisms to interfere with the generation and spread of epileptic hyperexcitability, but they do not address the specific defects that are pathogenic in the epilepsies for which they are prescribed, which in most cases are not well understood. There are four broad classes of such ASD mechanisms: (1) modulation of voltage-gated sodium channels (e.g. phenytoin, carbamazepine, lamotrigine), voltage-gated calcium channels (e.g. ethosuximide), and voltage-gated potassium channels [e.g. retigabine (ezogabine)]; (2) enhancement of GABA-mediated inhibitory neurotransmission (e.g. benzodiazepines, tiagabine, vigabatrin); (3) attenuation of glutamate-mediated excitatory neurotransmission (e.g. perampanel); and (4) modulation of neurotransmitter release via a presynaptic action (e.g. levetiracetam, brivaracetam, gabapentin, pregabalin). In the past two decades there has been great progress in identifying the pathophysiological mechanisms of many genetic epilepsies. Given this new understanding, attempts are being made to engineer specific small molecule, antisense and gene therapies that functionally reverse or structurally correct pathogenic defects in epilepsy syndromes. In the near future, these new therapies will begin a paradigm shift in the treatment of some rare genetic epilepsy syndromes, but targeted therapies will remain elusive for the vast majority of epilepsies until their causes are identified. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.
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Affiliation(s)
- Graeme J Sills
- School of Life Sciences, University of Glasgow, Glasgow, UK.
| | - Michael A Rogawski
- Department of Neurology, School of Medicine, University of California, Davis, Sacramento, CA, USA; Department of Pharmacology, School of Medicine, University of California, Davis, Sacramento, CA, USA
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15
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Hao X, Ou M, Zhang D, Zhao W, Yang Y, Liu J, Yang H, Zhu T, Li Y, Zhou C. The Effects of General Anesthetics on Synaptic Transmission. Curr Neuropharmacol 2020; 18:936-965. [PMID: 32106800 PMCID: PMC7709148 DOI: 10.2174/1570159x18666200227125854] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/20/2020] [Accepted: 02/26/2020] [Indexed: 02/08/2023] Open
Abstract
General anesthetics are a class of drugs that target the central nervous system and are widely used for various medical procedures. General anesthetics produce many behavioral changes required for clinical intervention, including amnesia, hypnosis, analgesia, and immobility; while they may also induce side effects like respiration and cardiovascular depressions. Understanding the mechanism of general anesthesia is essential for the development of selective general anesthetics which can preserve wanted pharmacological actions and exclude the side effects and underlying neural toxicities. However, the exact mechanism of how general anesthetics work is still elusive. Various molecular targets have been identified as specific targets for general anesthetics. Among these molecular targets, ion channels are the most principal category, including ligand-gated ionotropic receptors like γ-aminobutyric acid, glutamate and acetylcholine receptors, voltage-gated ion channels like voltage-gated sodium channel, calcium channel and potassium channels, and some second massager coupled channels. For neural functions of the central nervous system, synaptic transmission is the main procedure for which information is transmitted between neurons through brain regions, and intact synaptic function is fundamentally important for almost all the nervous functions, including consciousness, memory, and cognition. Therefore, it is important to understand the effects of general anesthetics on synaptic transmission via modulations of specific ion channels and relevant molecular targets, which can lead to the development of safer general anesthetics with selective actions. The present review will summarize the effects of various general anesthetics on synaptic transmissions and plasticity.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Yu Li
- Address correspondence to these authors at the Laboratory of Anesthesia & Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, P.R. China; E-mail: and Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, 610041, Sichuan, P.R. China; E-mail:
| | - Cheng Zhou
- Address correspondence to these authors at the Laboratory of Anesthesia & Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, P.R. China; E-mail: and Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, 610041, Sichuan, P.R. China; E-mail:
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16
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Dexpramipexole blocks Nav1.8 sodium channels and provides analgesia in multiple nociceptive and neuropathic pain models. Pain 2019; 161:831-841. [DOI: 10.1097/j.pain.0000000000001774] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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17
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Mäki-Marttunen T, Devor A, Phillips WA, Dale AM, Andreassen OA, Einevoll GT. Computational Modeling of Genetic Contributions to Excitability and Neural Coding in Layer V Pyramidal Cells: Applications to Schizophrenia Pathology. Front Comput Neurosci 2019; 13:66. [PMID: 31616272 PMCID: PMC6775251 DOI: 10.3389/fncom.2019.00066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 09/09/2019] [Indexed: 11/13/2022] Open
Abstract
Pyramidal cells in layer V of the neocortex are one of the most widely studied neuron types in the mammalian brain. Due to their role as integrators of feedforward and cortical feedback inputs, they are well-positioned to contribute to the symptoms and pathology in mental disorders-such as schizophrenia-that are characterized by a mismatch between the internal perception and external inputs. In this modeling study, we analyze the input/output properties of layer V pyramidal cells and their sensitivity to modeled genetic variants in schizophrenia-associated genes. We show that the excitability of layer V pyramidal cells and the way they integrate inputs in space and time are altered by many types of variants in ion-channel and Ca2+ transporter-encoding genes that have been identified as risk genes by recent genome-wide association studies. We also show that the variability in the output patterns of spiking and Ca2+ transients in layer V pyramidal cells is altered by these model variants. Importantly, we show that many of the predicted effects are robust to noise and qualitatively similar across different computational models of layer V pyramidal cells. Our modeling framework reveals several aspects of single-neuron excitability that can be linked to known schizophrenia-related phenotypes and existing hypotheses on disease mechanisms. In particular, our models predict that single-cell steady-state firing rate is positively correlated with the coding capacity of the neuron and negatively correlated with the amplitude of a prepulse-mediated adaptation and sensitivity to coincidence of stimuli in the apical dendrite and the perisomatic region of a layer V pyramidal cell. These results help to uncover the voltage-gated ion-channel and Ca2+ transporter-associated genetic underpinnings of schizophrenia phenotypes and biomarkers.
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Affiliation(s)
| | - Anna Devor
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States.,Martinos Center for Biomedical Imaging, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, United States
| | - William A Phillips
- Psychology, Faculty of Natural Sciences, University of Stirling, Stirling, United Kingdom
| | - Anders M Dale
- Department of Neurosciences, University of California San Diego, La Jolla, CA, United States.,Department of Radiology, University of California San Diego, La Jolla, CA, United States
| | - Ole A Andreassen
- NORMENT, Division of Mental Health and Addiction, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Gaute T Einevoll
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway.,Department of Physics, University of Oslo, Oslo, Norway
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18
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Zhou C, Johnson KW, Herold KF, Hemmings HC. Differential Inhibition of Neuronal Sodium Channel Subtypes by the General Anesthetic Isoflurane. J Pharmacol Exp Ther 2019; 369:200-211. [PMID: 30792243 DOI: 10.1124/jpet.118.254938] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 02/19/2019] [Indexed: 02/05/2023] Open
Abstract
Volatile anesthetics depress neurotransmitter release in a brain region- and neurotransmitter-selective manner by unclear mechanisms. Voltage-gated sodium channels (Navs), which are coupled to synaptic vesicle exocytosis, are inhibited by volatile anesthetics through reduction of peak current and modulation of gating. Subtype-selective effects of anesthetics on Nav might contribute to observed neurotransmitter-selective anesthetic effects on release. We analyzed anesthetic effects on Na+ currents mediated by the principal neuronal Nav subtypes Nav1.1, Nav1.2, and Nav1.6 heterologously expressed in ND7/23 neuroblastoma cells using whole-cell patch-clamp electrophysiology. Isoflurane at clinically relevant concentrations induced a hyperpolarizing shift in the voltage dependence of steady-state inactivation and slowed recovery from fast inactivation in all three Nav subtypes, with the voltage of half-maximal steady-state inactivation significantly more positive for Nav1.1 (-49.7 ± 3.9 mV) than for Nav1.2 (-57.5 ± 1.2 mV) or Nav1.6 (-58.0 ± 3.8 mV). Isoflurane significantly inhibited peak Na+ current (I Na) in a voltage-dependent manner: at a physiologically relevant holding potential of -70 mV, isoflurane inhibited peak I Na of Nav1.2 (16.5% ± 5.5%) and Nav1.6 (18.0% ± 7.8%), but not of Nav1.1 (1.2% ± 0.8%). Since Nav subtypes are differentially expressed both between neuronal types and within neurons, greater inhibition of Nav1.2 and Nav1.6 compared with Nav1.1 could contribute to neurotransmitter-selective effects of isoflurane on synaptic transmission.
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Affiliation(s)
- Cheng Zhou
- Departments of Anesthesiology (C.Z., K.W.J., K.F.H., H.C.H.) and Pharmacology (H.C.H.), Weill Cornell Medicine, New York, New York; and Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, Sichuan, People's Republic of China (C.Z.)
| | - Kenneth W Johnson
- Departments of Anesthesiology (C.Z., K.W.J., K.F.H., H.C.H.) and Pharmacology (H.C.H.), Weill Cornell Medicine, New York, New York; and Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, Sichuan, People's Republic of China (C.Z.)
| | - Karl F Herold
- Departments of Anesthesiology (C.Z., K.W.J., K.F.H., H.C.H.) and Pharmacology (H.C.H.), Weill Cornell Medicine, New York, New York; and Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, Sichuan, People's Republic of China (C.Z.)
| | - Hugh C Hemmings
- Departments of Anesthesiology (C.Z., K.W.J., K.F.H., H.C.H.) and Pharmacology (H.C.H.), Weill Cornell Medicine, New York, New York; and Laboratory of Anesthesia and Critical Care Medicine, Translational Neuroscience Center, West China Hospital of Sichuan University, Chengdu, Sichuan, People's Republic of China (C.Z.)
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19
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Goldberg EM, Helbig I. Reply to “Recurrent SCN3A
p.Ile875Thr variant in patients with polymicrogyria”. Ann Neurol 2018; 84:161. [DOI: 10.1002/ana.25254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 04/16/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Ethan M. Goldberg
- Division of Neurology, Department of Pediatrics; Children's Hospital of Philadelphia; Philadelphia PA
- Department of Neurology, Perelman School of Medicine at University of Pennsylvania; Philadelphia PA
- Department of Neuroscience; Perelman School of Medicine at University of Pennsylvania; Philadelphia PA
| | - Ingo Helbig
- Division of Neurology, Department of Pediatrics; Children's Hospital of Philadelphia; Philadelphia PA
- Department of Neurology, Perelman School of Medicine at University of Pennsylvania; Philadelphia PA
- Department of Neuropediatrics; University Medical Center Schleswig-Holstein, Christian Albrechts University; Kiel Germany
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20
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Cardoso FC, Lewis RJ. Sodium channels and pain: from toxins to therapies. Br J Pharmacol 2018; 175:2138-2157. [PMID: 28749537 PMCID: PMC5980290 DOI: 10.1111/bph.13962] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 07/11/2017] [Accepted: 07/17/2017] [Indexed: 12/16/2022] Open
Abstract
Voltage-gated sodium channels (NaV channels) are essential for the initiation and propagation of action potentials that critically influence our ability to respond to a diverse range of stimuli. Physiological and pharmacological studies have linked abnormal function of NaV channels to many human disorders, including chronic neuropathic pain. These findings, along with the description of the functional properties and expression pattern of NaV channel subtypes, are helping to uncover subtype specific roles in acute and chronic pain and revealing potential opportunities to target these with selective inhibitors. High-throughput screens and automated electrophysiology platforms have identified natural toxins as a promising group of molecules for the development of target-specific analgesics. In this review, the role of toxins in defining the contribution of NaV channels in acute and chronic pain states and their potential to be used as analgesic therapies are discussed. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc.
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Affiliation(s)
- Fernanda C Cardoso
- Department of Chemistry and Structural Biology, Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Richard J Lewis
- Department of Chemistry and Structural Biology, Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
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21
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Zaman T, Helbig I, Božović IB, DeBrosse SD, Bergqvist AC, Wallis K, Medne L, Maver A, Peterlin B, Helbig KL, Zhang X, Goldberg EM. Mutations in SCN3A cause early infantile epileptic encephalopathy. Ann Neurol 2018; 83:703-717. [PMID: 29466837 DOI: 10.1002/ana.25188] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 02/01/2018] [Accepted: 02/18/2018] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Voltage-gated sodium (Na+ ) channels underlie action potential generation and propagation and hence are central to the regulation of excitability in the nervous system. Mutations in the genes SCN1A, SCN2A, and SCN8A, encoding the Na+ channel pore-forming (α) subunits Nav1.1, 1.2, and 1.6, respectively, and SCN1B, encoding the accessory subunit β1 , are established causes of genetic epilepsies. SCN3A, encoding Nav1.3, is known to be highly expressed in brain, but has not previously been linked to early infantile epileptic encephalopathy. Here, we describe a cohort of 4 patients with epileptic encephalopathy and heterozygous de novo missense variants in SCN3A (p.Ile875Thr in 2 cases, p.Pro1333Leu, and p.Val1769Ala). METHODS All patients presented with treatment-resistant epilepsy in the first year of life, severe to profound intellectual disability, and in 2 cases (both with the variant p.Ile875Thr), diffuse polymicrogyria. RESULTS Electrophysiological recordings of mutant channels revealed prominent gain of channel function, with a markedly increased amplitude of the slowly inactivating current component, and for 2 of 3 mutants (p.Ile875Thr and p.Pro1333Leu), a leftward shift in the voltage dependence of activation to more hyperpolarized potentials. Gain of function was not observed for Nav1.3 variants known or presumed to be inherited (p.Arg1642Cys and p.Lys1799Gln). The antiseizure medications phenytoin and lacosamide selectively blocked slowly inactivating over transient current in wild-type and mutant Nav1.3 channels. INTERPRETATION These findings establish SCN3A as a new gene for infantile epileptic encephalopathy and suggest a potential pharmacologic intervention. These findings also reinforce the role of Nav1.3 as an important regulator of neuronal excitability in the developing brain, while providing additional insight into mechanisms of slow inactivation of Nav1.3. Ann Neurol 2018;83:703-717.
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Affiliation(s)
- Tariq Zaman
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA
| | - Ingo Helbig
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA.,Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian Albrecht University, Kiel, Germany.,Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Ivana Babić Božović
- Department of Biology and Medical Genetics, School of Medicine, University of Rijeka, Rijeka, Croatia
| | - Suzanne D DeBrosse
- Departments of Genetics and Genome Sciences, Pediatrics, and Neurology, and Center for Human Genetics, Case Western Reserve University School of Medicine, Cleveland, OH
| | - A Christina Bergqvist
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA
| | - Kimberly Wallis
- Departments of Genetics and Genome Sciences, Pediatrics, and Neurology, and Center for Human Genetics, Case Western Reserve University School of Medicine, Cleveland, OH
| | - Livija Medne
- Division of Human Genetics, Department of Pediatrics, Individualized Medical Genetics Center, Children's Hospital of Philadelphia, Philadelphia, PA
| | - Aleš Maver
- Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Borut Peterlin
- Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Katherine L Helbig
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA.,Division of Clinical Genomics, Ambry Genetics, Aliso Viejo, CA
| | - Xiaohong Zhang
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA
| | - Ethan M Goldberg
- Division of Neurology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, PA.,Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.,Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
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22
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Wang J, Ou SW, Wang YJ. Distribution and function of voltage-gated sodium channels in the nervous system. Channels (Austin) 2017; 11:534-554. [PMID: 28922053 DOI: 10.1080/19336950.2017.1380758] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are the basic ion channels for neuronal excitability, which are crucial for the resting potential and the generation and propagation of action potentials in neurons. To date, at least nine distinct sodium channel isoforms have been detected in the nervous system. Recent studies have identified that voltage-gated sodium channels not only play an essential role in the normal electrophysiological activities of neurons but also have a close relationship with neurological diseases. In this study, the latest research findings regarding the structure, type, distribution, and function of VGSCs in the nervous system and their relationship to neurological diseases, such as epilepsy, neuropathic pain, brain tumors, neural trauma, and multiple sclerosis, are reviewed in detail.
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Affiliation(s)
- Jun Wang
- a Department of Neurosurgery , The First Hospital of China Medical University , Shenyang , P.R. China
| | - Shao-Wu Ou
- a Department of Neurosurgery , The First Hospital of China Medical University , Shenyang , P.R. China
| | - Yun-Jie Wang
- a Department of Neurosurgery , The First Hospital of China Medical University , Shenyang , P.R. China
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23
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Soderlund DM, Tan J, He B. Functional reconstitution of rat Na v1.6 sodium channels in vitro for studies of pyrethroid action. Neurotoxicology 2017; 60:142-149. [PMID: 27013268 PMCID: PMC5031521 DOI: 10.1016/j.neuro.2016.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/17/2016] [Accepted: 03/17/2016] [Indexed: 01/14/2023]
Abstract
The ability to reconstitute sodium channel function and pharmacology in vitro using cloned subunits of known structure has greatly enhanced our understanding of the action of pyrethroid insecticides at this target and the structural determinants of resistance and interspecies selectivity. However, the use of reconstituted channels raises three critical questions: (1) Which subunits and subunit combinations should be used? (2) Which heterologous expression system is preferred? (3) Which combination of subunits and expression system best represents the function of native neuronal channels in the organism of interest? This review considers these questions from the perspective of recent research in this laboratory on the action of pyrethroid insecticides on rat Nav1.6 sodium channels by comparing the effects of heteroligomeric complex composition on channel function and insecticide response when channels are expressed in either Xenopus oocytes or stably-transformed HEK293 cells. These comparisons provide new insight into the influence of cellular context on the functional and pharmacological properties of expressed channels, the modulatory effects of sodium channel auxiliary subunits on the action of pyrethroids, and the relative fidelity of the Xenopus oocyte and HEK293 cell expression systems as model systems for studying of channel function and pyrethroid action.
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Affiliation(s)
- David M Soderlund
- Department of Entomology, Cornell University, Geneva, NY 14456, USA.
| | | | - Bingjun He
- College of Life Sciences, Nankai University, Tianjin 300071, China
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24
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Lamar T, Vanoye CG, Calhoun J, Wong JC, Dutton SBB, Jorge BS, Velinov M, Escayg A, Kearney JA. SCN3A deficiency associated with increased seizure susceptibility. Neurobiol Dis 2017; 102:38-48. [PMID: 28235671 DOI: 10.1016/j.nbd.2017.02.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 01/24/2017] [Accepted: 02/20/2017] [Indexed: 11/25/2022] Open
Abstract
Mutations in voltage-gated sodium channels expressed highly in the brain (SCN1A, SCN2A, SCN3A, and SCN8A) are responsible for an increasing number of epilepsy syndromes. In particular, mutations in the SCN3A gene, encoding the pore-forming Nav1.3 α subunit, have been identified in patients with focal epilepsy. Biophysical characterization of epilepsy-associated SCN3A variants suggests that both gain- and loss-of-function SCN3A mutations may lead to increased seizure susceptibility. In this report, we identified a novel SCN3A variant (L247P) by whole exome sequencing of a child with focal epilepsy, developmental delay, and autonomic nervous system dysfunction. Voltage clamp analysis showed no detectable sodium current in a heterologous expression system expressing the SCN3A-L247P variant. Furthermore, cell surface biotinylation demonstrated a reduction in the amount of SCN3A-L247P at the cell surface, suggesting the SCN3A-L247P variant is a trafficking-deficient mutant. To further explore the possible clinical consequences of reduced SCN3A activity, we investigated the effect of a hypomorphic Scn3a allele (Scn3aHyp) on seizure susceptibility and behavior using a gene trap mouse line. Heterozygous Scn3a mutant mice (Scn3a+/Hyp) did not exhibit spontaneous seizures nor were they susceptible to hyperthermia-induced seizures. However, they displayed increased susceptibility to electroconvulsive (6Hz) and chemiconvulsive (flurothyl and kainic acid) induced seizures. Scn3a+/Hyp mice also exhibited deficits in locomotor activity and motor learning. Taken together, these results provide evidence that loss-of-function of SCN3A caused by reduced protein expression or deficient trafficking to the plasma membrane may contribute to increased seizure susceptibility.
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Affiliation(s)
- Tyra Lamar
- Department of Human Genetics, Emory University, Atlanta, GA, USA
| | - Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Jeffrey Calhoun
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Jennifer C Wong
- Department of Human Genetics, Emory University, Atlanta, GA, USA
| | | | - Benjamin S Jorge
- Neuroscience Program, Vanderbilt University, Nashville, TN 37232, USA
| | - Milen Velinov
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA; Albert Einstein College of Medicine, Bronx, NY, USA
| | - Andrew Escayg
- Department of Human Genetics, Emory University, Atlanta, GA, USA.
| | - Jennifer A Kearney
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
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25
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Masocha W. Gene expression profile of sodium channel subunits in the anterior cingulate cortex during experimental paclitaxel-induced neuropathic pain in mice. PeerJ 2016; 4:e2702. [PMID: 27896032 PMCID: PMC5119229 DOI: 10.7717/peerj.2702] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 10/19/2016] [Indexed: 12/19/2022] Open
Abstract
Paclitaxel, a chemotherapeutic agent, causes neuropathic pain whose supraspinal pathophysiology is not fully understood. Dysregulation of sodium channel expression, studied mainly in the periphery and spinal cord level, contributes to the pathogenesis of neuropathic pain. We examined gene expression of sodium channel (Nav) subunits by real time polymerase chain reaction (PCR) in the anterior cingulate cortex (ACC) at day 7 post first administration of paclitaxel, when mice had developed paclitaxel-induced thermal hyperalgesia. The ACC was chosen because increased activity in the ACC has been observed during neuropathic pain. In the ACC of vehicle-treated animals the threshold cycle (Ct) values for Nav1.4, Nav1.5, Nav1.7, Nav1.8 and Nav1.9 were above 30 and/or not detectable in some samples. Thus, comparison in mRNA expression between untreated control, vehicle-treated and paclitaxel treated animals was done for Nav1.1, Nav1.2, Nav1.3, Nav1.6, Nax as well as Navβ1–Navβ4. There were no differences in the transcript levels of Nav1.1–Nav1.3, Nav1.6, Nax, Navβ1–Navβ3 between untreated and vehicle-treated mice, however, vehicle treatment increased Navβ4 expression. Paclitaxel treatment significantly increased the mRNA expression of Nav1.1, Nav1.2, Nav1.6 and Nax, but not Nav1.3, sodium channel alpha subunits compared to vehicle-treated animals. Treatment with paclitaxel significantly increased the expression of Navβ1 and Navβ3, but not Navβ2 and Navβ4, sodium channel beta subunits compared to vehicle-treated animals. These findings suggest that during paclitaxel-induced neuropathic pain (PINP) there is differential upregulation of sodium channels in the ACC, which might contribute to the increased neuronal activity observed in the area during neuropathic pain.
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Affiliation(s)
- Willias Masocha
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Kuwait University , Safat , Kuwait
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26
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Lin GW, Lu P, Zeng T, Tang HL, Chen YH, Liu SJ, Gao MM, Zhao QH, Yi YH, Long YS. GAPDH-mediated posttranscriptional regulations of sodium channel Scn1a and Scn3a genes under seizure and ketogenic diet conditions. Neuropharmacology 2016; 113:480-489. [PMID: 27816501 DOI: 10.1016/j.neuropharm.2016.11.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Revised: 10/28/2016] [Accepted: 11/01/2016] [Indexed: 01/12/2023]
Abstract
Abnormal expressions of sodium channel SCN1A and SCN3A genes alter neural excitability that are believed to contribute to the pathogenesis of epilepsy, a long-term risk of recurrent seizures. Ketogenic diet (KD), a high-fat and low-carbohydrate treatment for difficult-to-control (refractory) epilepsy in children, has been suggested to reverse gene expression patterns. Here, we reveal a novel role of GAPDH on the posttranscriptional regulation of mouse Scn1a and Scn3a expressions under seizure and KD conditions. We show that GAPDH binds to a conserved region in the 3' UTRs of human and mouse SCN1A and SCN3A genes, which decreases and increases genes' expressions by affecting mRNA stability through SCN1A 3' UTR and SCN3A 3' UTR, respectively. In seizure mice, the upregulation and phosphorylation of GAPDH enhance its binding to the 3' UTR, which lead to downregulation of Scn1a and upregulation of Scn3a. Furthermore, administration of KD generates β-hydroxybutyric acid which rescues the abnormal expressions of Scn1a and Scn3a by weakening the GAPDH's binding to the element. Taken together, these data suggest that GAPDH-mediated expression regulation of sodium channel genes may be associated with epilepsy and the anticonvulsant action of KD.
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Affiliation(s)
- Guo-Wang Lin
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Ping Lu
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Tao Zeng
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Hui-Ling Tang
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Yong-Hong Chen
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Shu-Jing Liu
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Mei-Mei Gao
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Qi-Hua Zhao
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Yong-Hong Yi
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China
| | - Yue-Sheng Long
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Guangzhou 501260, China.
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27
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Zhu H, Wang Z, Jin J, Pei X, Zhao Y, Wu H, Lin W, Tao J, Ji Y. Parkinson’s disease-like forelimb akinesia induced by BmK I, a sodium channel modulator. Behav Brain Res 2016; 308:166-76. [DOI: 10.1016/j.bbr.2016.04.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 04/16/2016] [Accepted: 04/19/2016] [Indexed: 12/16/2022]
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28
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Effects of the β1 auxiliary subunit on modification of Rat Na(v)1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin. Toxicol Appl Pharmacol 2015; 291:58-69. [PMID: 26708501 DOI: 10.1016/j.taap.2015.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/09/2015] [Accepted: 12/16/2015] [Indexed: 11/22/2022]
Abstract
We expressed rat Nav1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Nav1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~18 mV for tefluthrin and ~24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~10-14 mV in the voltage dependence of steady-state inactivation and increased in the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Nav1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons.
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29
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Scult MA, Trampush JW, Zheng F, Conley ED, Lencz T, Malhotra AK, Dickinson D, Weinberger DR, Hariri AR. A Common Polymorphism in SCN2A Predicts General Cognitive Ability through Effects on PFC Physiology. J Cogn Neurosci 2015; 27:1766-74. [PMID: 25961639 DOI: 10.1162/jocn_a_00826] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Here we provide novel convergent evidence across three independent cohorts of healthy adults (n = 531), demonstrating that a common polymorphism in the gene encoding the α2 subunit of neuronal voltage-gated type II sodium channels (SCN2A) predicts human general cognitive ability or "g." Using meta-analysis, we demonstrate that the minor T allele of a common polymorphism (rs10174400) in SCN2A is associated with significantly higher "g" independent of gender and age. We further demonstrate using resting-state fMRI data from our discovery cohort (n = 236) that this genetic advantage may be mediated by increased capacity for information processing between the dorsolateral PFC and dorsal ACC, which support higher cognitive functions. Collectively, these findings fill a gap in our understanding of the genetics of general cognitive ability and highlight a specific neural mechanism through which a common polymorphism shapes interindividual variation in "g."
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Affiliation(s)
| | | | | | | | - Todd Lencz
- The Zucker Hillside Hospital, Glen Oaks, NY
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30
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Wimmer VC, Harty RC, Richards KL, Phillips AM, Miyazaki H, Nukina N, Petrou S. Sodium channel β1 subunit localizes to axon initial segments of excitatory and inhibitory neurons and shows regional heterogeneity in mouse brain. J Comp Neurol 2015; 523:814-30. [PMID: 25421039 DOI: 10.1002/cne.23715] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 11/17/2014] [Accepted: 11/20/2014] [Indexed: 11/07/2022]
Abstract
The β1 subunit of voltage-gated sodium channels, Nav β1, plays multiple roles in neurons spanning electrophysiological modulation of sodium channel α subunits to cell adhesion and neurite outgrowth. This study used immunohistochemistry to investigate Nav β1 subneuronal and regional expression. Nav β1 was enriched at axon initial segments (AIS) and nodes of Ranvier. Nav β1 expression at the AIS was detected throughout the brain, predominantly in the hippocampus, cortex, and cerebellum. Despite expression of Nav β1 in both excitatory and inhibitory AIS, it displayed a marked and fine-grained heterogeneity of expression. Such heterogeneity could have important implications for the tuning of single neuronal and regional excitability, especially in view of the fact that Nav β1 coexpressed with Nav 1.1, Nav 1.2, and Nav 1.6 subunits. The disruption of Nav β1 AIS expression by a human epilepsy-causing C121W genetic mutation in Nav β1 was also investigated using a mouse model. AIS expression of Nav β1 was reduced by approximately 50% in mice heterozygous for the C121W mutation and was abolished in homozygotes, suggesting that loss of Nav α subunit modulation by Nav β1 contributes to the mechanism of epileptogenesis in these animals as well as in patients.
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Affiliation(s)
- Verena C Wimmer
- Florey Institute of Neuroscience and Mental Health, Victoria, 3010, Australia
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31
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Alteration of Scn3a expression is mediated via CpG methylation and MBD2 in mouse hippocampus during postnatal development and seizure condition. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:1-9. [PMID: 25459751 DOI: 10.1016/j.bbagrm.2014.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 10/13/2014] [Accepted: 11/12/2014] [Indexed: 12/21/2022]
Abstract
Increased expression of sodium channel SCN3A, an embryonic-expressed gene, has been identified in epileptic tissues, which is believed to contribute to the development of epilepsy. However, the regulatory mechanism of SCN3A expression under epileptic condition is still unknown. Here we showed a high level of Scn3a mRNA expression in mouse embryonic hippocampus with gradually decreasing to a low level during the postnatal development and a methylation of a specific CpG site (-39C) in the Scn3a promoter was increased in hippocampus during postnatal development, corresponding to the downregulation of Scn3a expression. Furthermore, in vitro methylation and -39C>T mutation of the Scn3a promoter decreased the reporter gene expression, suggesting an important role of the -39C site in regulating gene expression. We then demonstrated that the sequence containing -39C was a MBD2-binding motif and the CpG methylation of the promoter region increased the capability of MBD2's binding to the motif. Knockdown of MBD2 in mouse N1E-115 cells led to the -39C methylation and the downregulation of Scn3a transcription by decreasing the Scn3a promoter activity. In the hippocampus of seizure mice, the expressions of Scn3a and Mbd2 were upregulated after 10-day KA treatment. At the same time point, the -39C site was demethylated and the capability of MBD2's binding to the Scn3a promoter motif was decreased. Taken together, these findings suggest that CpG methylation and MBD2 are involved in altering Scn3a expression during postnatal development and seizure condition.
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32
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Clarkson YL, Perkins EM, Cairncross CJ, Lyndon AR, Skehel PA, Jackson M. β-III spectrin underpins ankyrin R function in Purkinje cell dendritic trees: protein complex critical for sodium channel activity is impaired by SCA5-associated mutations. Hum Mol Genet 2014; 23:3875-82. [PMID: 24603075 PMCID: PMC4065159 DOI: 10.1093/hmg/ddu103] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 02/21/2014] [Accepted: 03/03/2014] [Indexed: 01/05/2023] Open
Abstract
Beta III spectrin is present throughout the elaborate dendritic tree of cerebellar Purkinje cells and is required for normal neuronal morphology and cell survival. Spinocerebellar ataxia type 5 (SCA5) and spectrin associated autosomal recessive cerebellar ataxia type 1 are human neurodegenerative diseases involving progressive gait ataxia and cerebellar atrophy. Both disorders appear to result from loss of β-III spectrin function. Further elucidation of β-III spectrin function is therefore needed to understand disease mechanisms and identify potential therapeutic options. Here, we report that β-III spectrin is essential for the recruitment and maintenance of ankyrin R at the plasma membrane of Purkinje cell dendrites. Two SCA5-associated mutations of β-III spectrin both reduce ankyrin R levels at the cell membrane. Moreover, a wild-type β-III spectrin/ankyrin-R complex increases sodium channel levels and activity in cell culture, whereas mutant β-III spectrin complexes fail to enhance sodium currents. This suggests impaired ability to form stable complexes between the adaptor protein ankyrin R and its interacting partners in the Purkinje cell dendritic tree is a key mechanism by which mutant forms of β-III spectrin cause ataxia, initially by Purkinje cell dysfunction and exacerbated by subsequent cell death.
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Affiliation(s)
- Yvonne L Clarkson
- The Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
| | - Emma M Perkins
- The Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
| | | | - Alastair R Lyndon
- School of Life Sciences, Heriot-Watt University, John Muir Building, Riccarton, Edinburgh EH14 4AS, UK
| | - Paul A Skehel
- The Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
| | - Mandy Jackson
- The Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, The University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK and
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Electrophysiological Differences between the Same Pore Region Mutation in SCN1A and SCN3A. Mol Neurobiol 2014; 51:1263-70. [PMID: 24990319 DOI: 10.1007/s12035-014-8802-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 06/22/2014] [Indexed: 10/25/2022]
Abstract
Mutations in the sodium channel gene, SCN1A (NaV1.1), have been linked to a spectrum of epilepsy syndromes, and many of these mutations occur in the pore region of the channel. Electrophysiological characterization has revealed that most SCN1A mutations in the pore region result in complete loss of function. SCN3A mutations have also been identified in patients with epilepsy; however, mutations in this pore region maintain some degree of electrophysiological function. It is thus speculated that compared to SCN3A disruptions, SCN1A mutations have a more pronounced effect on electrophysiological function. In this study, we identified a novel mutation, N302S, in the SCN3A pore region of a child with epilepsy. To investigate if mutations at the pore regions of SCN3A and SCN1A have different impacts on channel function, we studied the electrophysiological properties of N302S in NaV1.3 and its homologous mutation (with the same amino acid substitution) in NaV1.1 (N301S). Functional analysis demonstrated that SCN1A-N301S had no measurable sodium current, indicating a complete loss of function, while SCN3A-N302S slightly reduced channel activity. This observation indicates that the same pore region mutation affects SCN1A more than SCN3A. Our study further revealed a huge difference in electrophysiological function between SCN1A and SCN3A mutations in the pore region; this might explain the more common SCN1A mutations detected in patients with epilepsy and the more severe phenotypes associated with these mutations.
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Gilchrist J, Dutton S, Diaz-Bustamante M, McPherson A, Olivares N, Kalia J, Escayg A, Bosmans F. Nav1.1 modulation by a novel triazole compound attenuates epileptic seizures in rodents. ACS Chem Biol 2014; 9:1204-12. [PMID: 24635129 PMCID: PMC4027953 DOI: 10.1021/cb500108p] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 03/17/2014] [Indexed: 12/19/2022]
Abstract
Here, we report the discovery of a novel anticonvulsant drug with a molecular organization based on the unique scaffold of rufinamide, an anti-epileptic compound used in a clinical setting to treat severe epilepsy disorders such as Lennox-Gastaut syndrome. Although accumulating evidence supports a working mechanism through voltage-gated sodium (Nav) channels, we found that a clinically relevant rufinamide concentration inhibits human (h)Nav1.1 activation, a distinct working mechanism among anticonvulsants and a feature worth exploring for treating a growing number of debilitating disorders involving hNav1.1. Subsequent structure-activity relationship experiments with related N-benzyl triazole compounds on four brain hNav channel isoforms revealed a novel drug variant that (1) shifts hNav1.1 opening to more depolarized voltages without further alterations in the gating properties of hNav1.1, hNav1.2, hNav1.3, and hNav1.6; (2) increases the threshold to action potential initiation in hippocampal neurons; and (3) greatly reduces the frequency of seizures in three animal models. Altogether, our results provide novel molecular insights into the rational development of Nav channel-targeting molecules based on the unique rufinamide scaffold, an outcome that may be exploited to design drugs for treating disorders involving particular Nav channel isoforms while limiting adverse effects.
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Affiliation(s)
- John Gilchrist
- Department
of Physiology, Johns Hopkins University,
School of Medicine, Baltimore, Maryland 21205, United States
| | - Stacey Dutton
- Department
of Human Genetics, Emory University, School
of Medicine, Atlanta, Georgia 30022, United
States
| | - Marcelo Diaz-Bustamante
- Lieber
Institute for Brain Development, Johns Hopkins
University, School of Medicine, Baltimore, Maryland 21205, United States
| | - Annie McPherson
- Department
of Human Genetics, Emory University, School
of Medicine, Atlanta, Georgia 30022, United
States
| | - Nicolas Olivares
- Lieber
Institute for Brain Development, Johns Hopkins
University, School of Medicine, Baltimore, Maryland 21205, United States
| | - Jeet Kalia
- Indian
Institute of Science Education and Research Pune, Pune, Maharashtra 411 008, India
| | - Andrew Escayg
- Department
of Human Genetics, Emory University, School
of Medicine, Atlanta, Georgia 30022, United
States
| | - Frank Bosmans
- Department
of Physiology, Johns Hopkins University,
School of Medicine, Baltimore, Maryland 21205, United States
- Solomon
H. Snyder Department of Neuroscience, Johns
Hopkins University, School of Medicine, Baltimore, Maryland 21205, United States
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Zhang Y, He JC, Liu XK, Zhang Y, Wang Y, Yu T. Assessment of the effect of etomidate on voltage-gated sodium channels and action potentials in rat primary sensory cortex pyramidal neurons. Eur J Pharmacol 2014; 736:55-62. [PMID: 24791681 DOI: 10.1016/j.ejphar.2014.04.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 04/22/2014] [Accepted: 04/23/2014] [Indexed: 11/17/2022]
Abstract
Although it is known that general anesthetics can suppress cortical neurons׳ activity, the underlying mechanisms are still poorly understood, especially the kinetic changes of voltage-gated Na(+) channels, which are mostly related to neuronal excitability. Some general anesthetics have been reported to affect the voltage-gated Na(+) channels in cell culture derived from humans and animals. However no one has ever investigated the effects of etomidate on voltage-gated Na(+) channels in pyramidal neurons using a brain slice. The present study uses a whole cell patch-clamp technique to investigate the changes of voltage-gated Na(+) channels on primary somatosensory cortex pyramidal neurons under the influence of etomidate. We found that etomidate dose-dependently inhibited Na(+) currents of primary somatosensory cortex pyramidal neurons, while shifted the steady-state inactivation curve towards the left and prolonged the recovery time from inactivation. Conversely, etomidate has no effects on the steady-state activation curve. We demonstrated the detailed suppression process of neural voltage-gated Na(+) channels by etomidate on slice condition. This may offer new insights into the mechanical explanation for the etomidate anesthesia. Finding the effects of anesthetics on primary somatosensory cortex also provides evidence to help elucidate the potential mechanism by which tactile information integrates during general anesthesia.
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Affiliation(s)
- Yu Zhang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China; Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical College, Zunyi, Guizhou, China
| | - Jiong-ce He
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China
| | - Xing-kui Liu
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China
| | - Yi Zhang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China
| | - Yuan Wang
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China
| | - Tian Yu
- Department of Anesthesiology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou, China; Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical College, Zunyi, Guizhou, China.
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Wang ZJ, Levinson SR, Sun L, Heinbockel T. Identification of both GABAA receptors and voltage-activated Na(+) channels as molecular targets of anticonvulsant α-asarone. Front Pharmacol 2014; 5:40. [PMID: 24653701 PMCID: PMC3949418 DOI: 10.3389/fphar.2014.00040] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 02/20/2014] [Indexed: 01/09/2023] Open
Abstract
Alpha (α)-asarone, a major effective component isolated from the Chinese medicinal herb Acorus tatarinowii, is clinically used as medication for treating epilepsy, cough, bronchitis, and asthma. In the present study, we demonstrated that α-asarone targets central nervous system GABAA receptor as well as voltage-gated Na(+) channels. Using whole-cell patch-clamp recording, α-asarone inhibited spontaneous firing of output neurons, mitral cells (MCs), in mouse olfactory bulb brain slice preparation and hyperpolarized the membrane potential of MCs. The inhibitory effect of α-asarone persisted in the presence of ionotropic glutamate receptor blockers but was eliminated after adding a GABAA receptor blocker, suggesting that GABAA receptors mediated the inhibition of MCs by α-asarone. This hypothesis was supported by the finding that α-asarone evoked an outward current, but did not influence inhibitory postsynaptic currents (IPSCs). In addition to inhibiting spontaneous firing, α-asarone also inhibited the Nav1.2 channel, a dominant rat brain Na(+) channel subtype. The effects of α-asarone on a defined Nav1.2 were characterized using transfected cells that stably expressed the Nav1.2 channel isoform. α-Asarone displayed strong tonic inhibition of Nav1.2 currents in a concentration- and membrane potential-dependent fashion. α-Asarone reduced channel availability in steady-state inactivation protocols by enhancing or stabilizing Na(+) channel inactivation. Both Na(+) channel blockade and activation of GABAA receptors provide a possible mechanism for the known anti-epileptic effects of α-asarone. It also suggests that α-asarone could benefit patients with cough possibly through inhibiting a Na(+) channel subtype to inhibit peripheral and/or central sensitization of cough reflexes.
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Affiliation(s)
- Ze-Jun Wang
- Department of Anatomy, College of Medicine, Howard University Washington, DC, USA
| | - Simon R Levinson
- Department of Physiology and Biophysics, University of Colorado Denver School of Medicine Aurora, CO, USA
| | - Liqin Sun
- Department of Anatomy, College of Medicine, Howard University Washington, DC, USA
| | - Thomas Heinbockel
- Department of Anatomy, College of Medicine, Howard University Washington, DC, USA
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Qiao X, Sun G, Clare JJ, Werkman TR, Wadman WJ. Properties of human brain sodium channel α-subunits expressed in HEK293 cells and their modulation by carbamazepine, phenytoin and lamotrigine. Br J Pharmacol 2014; 171:1054-67. [PMID: 24283699 PMCID: PMC3925043 DOI: 10.1111/bph.12534] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 11/08/2013] [Accepted: 11/21/2013] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND AND PURPOSE Voltage-activated Na(+) channels contain one distinct α-subunit. In the brain NaV 1.1, NaV 1.2, NaV 1.3 and NaV 1.6 are the four most abundantly expressed α-subunits. The antiepileptic drugs (AEDs) carbamazepine, phenytoin and lamotrigine have voltage-gated Na(+) channels as their primary therapeutic targets. This study provides a systematic comparison of the biophysical properties of these four α-subunits and characterizes their interaction with carbamazepine, phenytoin and lamotrigine. EXPERIMENTAL APPROACH Na(+) currents were recorded in voltage-clamp mode in HEK293 cells stably expressing one of the four α-subunits. KEY RESULTS NaV 1.2 and NaV 1.3 subunits have a relatively slow recovery from inactivation, compared with the other subunits and NaV 1.1 subunits generate the largest window current. Lamotrigine evokes a larger maximal shift of the steady-state inactivation relationship than carbamazepine or phenytoin. Carbamazepine shows the highest binding rate to the α-subunits. Lamotrigine binding to NaV 1.1 subunits is faster than to the other α-subunits. Lamotrigine unbinding from the α-subunits is slower than that of carbamazepine and phenytoin. CONCLUSIONS AND IMPLICATIONS The four Na(+) channel α-subunits show subtle differences in their biophysical properties, which, in combination with their (sub)cellular expression patterns in the brain, could contribute to differences in neuronal excitability. We also observed differences in the parameters that characterize AED binding to the Na(+) channel subunits. Particularly, lamotrigine binding to the four α-subunits suggests a subunit-specific response. Such differences will have consequences for the clinical efficacy of AEDs. Knowledge of the biophysical and binding parameters could be employed to optimize therapeutic strategies and drug development.
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Affiliation(s)
- Xin Qiao
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, The Netherlands
| | - Guangchun Sun
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, The Netherlands
| | | | - Taco R Werkman
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, The Netherlands
| | - Wytse J Wadman
- Center for NeuroScience, Swammerdam Institute for Life Sciences, University of AmsterdamAmsterdam, The Netherlands
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He B, Soderlund DM. Functional expression of Rat Nav1.6 voltage-gated sodium channels in HEK293 cells: modulation by the auxiliary β1 subunit. PLoS One 2014; 9:e85188. [PMID: 24404202 PMCID: PMC3880341 DOI: 10.1371/journal.pone.0085188] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 12/02/2013] [Indexed: 12/27/2022] Open
Abstract
The Nav1.6 voltage-gated sodium channel α subunit isoform is abundantly expressed in the adult rat brain. To assess the functional modulation of Nav1.6 channels by the auxiliary β1 subunit we expressed the rat Nav1.6 sodium channel α subunit by stable transformation in HEK293 cells either alone or in combination with the rat β1 subunit and assessed the properties of the reconstituted channels by recording sodium currents using the whole-cell patch clamp technique. Coexpression with the β1 subunit accelerated the inactivation of sodium currents and shifted the voltage dependence of channel activation and steady-state fast inactivation by approximately 5–7 mV in the direction of depolarization. By contrast the β1 subunit had no effect on the stability of sodium currents following repeated depolarizations at high frequencies. Our results define modulatory effects of the β1 subunit on the properties of rat Nav1.6-mediated sodium currents reconstituted in HEK293 cells that differ from effects measured previously in the Xenopus oocyte expression system. We also identify differences in the kinetic and gating properties of the rat Nav1.6 channel expressed in the absence of the β1 subunit compared to the properties of the orthologous mouse and human channels expressed in this system.
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Affiliation(s)
- Bingjun He
- College of Life Sciences, Nankai University, Tianjin, China
| | - David M. Soderlund
- Department of Entomology, Cornell University, Geneva, New York, United States of America
- * E-mail: .
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39
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Xiang J, Jiang Y. Regulation of Cu-Zn superoxide dismutase on SCN2A in SH-SY5Y cells as a potential therapy for temporal lobe epilepsy. Mol Med Rep 2013; 9:16-22. [PMID: 24220630 PMCID: PMC3868489 DOI: 10.3892/mmr.2013.1790] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Accepted: 10/10/2013] [Indexed: 01/15/2023] Open
Abstract
In order to evaluate SCN2A as a candidate gene for epileptic susceptibility and the use of a Cu-Zn superoxide dismutase (SOD) supplement as a potential therapy for epilepsy, SCN2A expression in the cortex and the correlation between SCN2A and Cu-Zn SOD in SH-SY5Y cells were examined. SCN2A expression and the concentration of Cu-Zn SOD in the cerebral cortexes of patients with primary and secondary temporal lobe epilepsy and normal brain cortex tissues were detected. By transfecting SH-SY5Y cells, the expression of SCN2A and the concentration of Cu-Zn SOD was analyzed and the single-cell patch clamp technique was employed in order to investigate the changes in sodium ion levels following SCN2A knockdown. SCN2A level restoration was also investigated with a Cu-Zn SOD supplement using an expression study and evaluated the changes in sodium ion levels following SCN2A knockdown. SCN2A expression and Cu-Zn SOD concentration decreased in the epileptic cerebral cortex. Following SCN2A knockdown, the concentration of Cu-Zn SOD declined and the si-SCN2A vector group showed a repeated discharge. Furthermore, the Cu-Zn SOD concentration was capable of restoring the expression of SCN2A following SCN2A knockdown in SH-SY5Y cells and the overexpression of Cu-Zn SOD prevented the repeated discharge caused by si-SCN2A. The results indicated that there is a low expression of SCN2A and Cu-Zn SOD in the epileptic cerebral cortex and provided novel insights into potential therapies for temporal lobe epilepsy.
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Affiliation(s)
- Jun Xiang
- Department of Neurosurgery, Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
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Qiao X, Werkman TR, Gorter JA, Wadman WJ, van Vliet EA. Expression of sodium channel α subunits 1.1, 1.2 and 1.6 in rat hippocampus after kainic acid-induced epilepsy. Epilepsy Res 2013; 106:17-28. [PMID: 23886654 DOI: 10.1016/j.eplepsyres.2013.06.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 05/30/2013] [Accepted: 06/25/2013] [Indexed: 12/19/2022]
Abstract
Voltage-gated Na(+) channels control neuronal excitability and are the primary target for the majority of anti-epileptic drugs. This study investigates the (sub)cellular expression patterns of three important brain-associated Na(+) channel α subunits: NaV1.1, NaV1.2 and NaV1.6 during epileptogenesis (induced by kainic acid) using time points that cover the period from induction to the chronic phase of epilepsy. NaV1.1 immunoreactivity was persistently reduced at 1 day, 3 weeks and 2 months after SE in CA1 and CA3. About 50% of the NaV1.1-positive interneurons was lost at one day after SE in all regions investigated. In the hilus a similar reduction in NeuN-positive neurons was found, while in the CA1 and CA3 region the loss in NeuN-positive neurons only reached 15% in the chronic phase of epilepsy. This implies a stronger shift in the balance between excitation and inhibition toward excitation in the CA1 and CA3 region than in the hilus. NaV1.2 immunoreactivity in the inner molecular layer of the dentate gyrus was lower than control at 1 day after SE. It increased at 3 weeks and 2 months after SE in the inner molecular layer and overlapped with sprouted mossy fibers. NaV1.6 immunoreactivity in the dendritic region of CA1 and CA3 was persistently reduced at all time-points during epileptogenesis. Some astrocytes expressed NaV1.1 and NaV1.6 at 3 weeks after SE. Expression data alone are not sufficient to explain changes in network stability, or infer causality in epileptogenesis. These results demonstrate that hippocampal sub-regional expression of NaV1.1, NaV1.2 and NaV1.6 Na(+) channel α subunits is altered during epileptogenesis in a time and location specific way. This implies that understanding epileptogenesis has to take into account several distinct and type-specific changes in sodium channel expression.
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Affiliation(s)
- Xin Qiao
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
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Meier S, Demirakca T, Brusniak W, Wolf I, Liebsch K, Tunc-Skarka N, Nieratschker V, Witt SH, Matthäus F, Ende G, Flor H, Rietschel M, Diener C, Schulze TG. SCN1A affects brain structure and the neural activity of the aging brain. Biol Psychiatry 2012; 72:677-83. [PMID: 22534457 DOI: 10.1016/j.biopsych.2012.03.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 03/13/2012] [Accepted: 03/13/2012] [Indexed: 01/22/2023]
Abstract
BACKGROUND The aging of the human brain is accompanied by changes in cortical structure as well as functional activity and variable degrees of cognitive decline. One-third of the observable inter-individual differences in cognitive decline are thought to be heritable. SCN1A encodes the sodium channel α subunit and is considered to be a susceptibility gene for several neurological disorders with prominent cognitive deficits. In a recent genome-wide association study the C allele of the SCN1A variant rs10930201 was observed to be significantly associated with poor short-term memory performance. rs10930201 was further observed to be related to differences in neural activity during a working memory task. METHODS The aim of the present study was to explore whether SCN1A modifies the vulnerability to aging processes of the human brain. Therefore we assessed the interacting effects of the SCN1A vulnerability allele rs10930201 and age in terms of brain activity and brain morphology in 62 healthy volunteers between 21 and 82 years of age. RESULTS In C allele carriers, activity in the right inferior frontal cortex and the posterior cingulate cortex increased with age. Moreover, exploratory analysis revealed regional effects of rs10930201 on brain structure, indicating reduced gray matter densities in the frontal and insular regions in the C allele carriers. CONCLUSIONS Collectively, the present results suggest that the SCN1A polymorphism has modulatory effects on brain morphology and vulnerability to age-related alterations in brain activity of cortical regions that subserve working memory.
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Affiliation(s)
- Sandra Meier
- Department of Genetic Epidemiology in Psychiatry, Central Institute of Mental Health, Heidelberg, Germany
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Abstract
Voltage-gated sodium channels (VGSCs) are integral membrane proteins. They are essential for normal neurologic function and are, currently, the most common recognized cause of genetic epilepsy. This review summarizes the neurobiology of VGSCs, their association with different epilepsy syndromes, and the ways in which we can experimentally interrogate their function. The most important sodium channel subunit of relevance to epilepsy is SCN1A, in which over 650 genetic variants have been discovered. SCN1A mutations are associated with a variety of epilepsy syndromes; the more severe syndromes are associated with truncation or complete loss of function of the protein. SCN2A is another important subtype associated with epilepsy syndromes, across a range of severe and less severe epilepsies. This subtype is localized primarily to excitatory neurons, and mutations have a range of functional effects on the channel. SCN8A is the other main adult subtype found in the brain and has recently emerged as an epilepsy gene, with the first human mutation discovered in a severe epilepsy syndrome. Mutations in the accessory β subunits, thought to modulate trafficking and function of the α subunits, have also been associated with epilepsy. Genome sequencing is continuing to become more affordable, and as such, the amount of incoming genetic data is continuing to increase. Current experimental approaches have struggled to keep pace with functional analysis of these mutations, and it has proved difficult to build associations between disease severity and the precise effect on channel function. These mutations have been interrogated with a range of experimental approaches, from in vitro, in vivo, to in silico. In vitro techniques will prove useful to scan mutations on a larger scale, particularly with the advance of high-throughput automated patch-clamp techniques. In vivo models enable investigation of mutation in the context of whole brains with connected networks and more closely model the human condition. In silico models can help us incorporate the impact of multiple genetic factors and investigate epistatic interactions and beyond.
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Affiliation(s)
- Megan Oliva
- Florey Neuroscience Institutes, University of Melbourne, Melbourne, Victoria, Australia
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Tan J, Choi JS, Soderlund DM. Coexpression with Auxiliary β Subunits Modulates the Action of Tefluthrin on Rat Na(v)1.6 and Na(v)1.3 Sodium Channels. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2011; 101:256-264. [PMID: 22577241 PMCID: PMC3346283 DOI: 10.1016/j.pestbp.2011.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We expressed the rat Na(v)1.3 and Na(v)1.6 sodium channel α subunit isoforms in Xenopus oocytes either alone or with the rat β1 and β2 auxiliary subunits in various combinations and assessed the sensitivity of the expressed channels to resting and use-dependent modification by the pyrethroid insecticide tefluthrin using the two-electrode voltage clamp technique. Coexpression with the β1 and β2 subunits, either individually or in combination, did not affecting the resting sensitivity of Na(v)1.6 channels to tefluthrin. Modification by tefluthrin of Na(v)1.6 channels in the absence of β subunits was not altered by the application of trains of high-frequency depolarizing prepulses. By contrast, coexpression of the Na(v)1.6 channel with the β1 subunit enhanced the extent of channel modification twofold following repeated depolarization. Coexpression of Na(v)1.6 with the β2 subunit also slightly enhanced modification following repeated depolarization, but coexpression of Na(v)1.6 with both β subunits caused enhanced modification following repeated depolarization that was indistinguishable from that found with Na(v)1.6+β1 channels. In contrast to Na(v)1.6, the resting modification by tefluthrin of Na(v)1.3 channels expressed in the absence of β subunits was reduced by repeated depolarization. However, tefluthrin modification of the Na(v)1.3 α subunit expressed with both β subunits was enhanced 1.7-fold by repeated depolarization, thereby confirming that β subunit modulation of use-dependent effects was not confined to the Na(v)1.6 isoform. These results show that the actions of pyrethroids on mammalian sodium channels in the Xenopus oocyte expression system are determined in part by the interactions of the sodium channel α subunit with the auxiliary β subunits that are part of the heteromultimeric sodium channel complexes found in neurons and other excitable cells.
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Affiliation(s)
- Jianguo Tan
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York 14456, USA
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44
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Differential state-dependent modification of rat Na(v)1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin. Toxicol Appl Pharmacol 2011; 257:377-87. [PMID: 21983428 DOI: 10.1016/j.taap.2011.09.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 09/16/2011] [Accepted: 09/20/2011] [Indexed: 11/23/2022]
Abstract
We expressed rat Na(v)1.6 sodium channels in combination with the rat β1 and β2 auxiliary subunits in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on expressed sodium currents using the whole-cell patch clamp technique. Both pyrethroids produced concentration-dependent, resting modification of Na(v)1.6 channels, prolonging the kinetics of channel inactivation and deactivation to produce persistent "late" currents during depolarization and tail currents following repolarization. Both pyrethroids also produced concentration dependent hyperpolarizing shifts in the voltage dependence of channel activation and steady-state inactivation. Maximal shifts in activation, determined from the voltage dependence of the pyrethroid-induced late and tail currents, were ~25mV for tefluthrin and ~20mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of ~5-10mV in the voltage dependence of steady-state inactivation. In addition to their effects on the voltage dependence of inactivation, both compounds caused concentration-dependent increases in the fraction of sodium current that was resistant to inactivation following strong depolarizing prepulses. We assessed the use-dependent effects of tefluthrin and deltamethrin on Na(v)1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by ~2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Na(v)1.6 channels in HEK293 cells using the conditions producing maximal modification as the basis for comparison. These findings show that the actions of tefluthrin and deltamethrin of Na(v)1.6 channels in HEK293 cells differ from the effects of these compounds on Na(v)1.6 channels in Xenopus oocytes and more closely reflect the actions of pyrethroids on channels in their native neuronal environment.
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45
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Neuronal maturation defect in induced pluripotent stem cells from patients with Rett syndrome. Proc Natl Acad Sci U S A 2011; 108:14169-74. [PMID: 21807996 DOI: 10.1073/pnas.1018979108] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Rett syndrome (RTT) is one of the most prevalent female neurodevelopmental disorders that cause severe mental retardation. Mutations in methyl CpG binding protein 2 (MeCP2) are mainly responsible for RTT. Patients with classical RTT exhibit normal development until age 6-18 mo, at which point they become symptomatic and display loss of language and motor skills, purposeful hand movements, and normal head growth. Murine genetic models and postmortem human brains have been used to study the disease and enable the molecular dissection of RTT. In this work, we applied a recently developed reprogramming approach to generate a novel in vitro human RTT model. Induced pluripotent stem cells (iPSCs) were derived from RTT fibroblasts by overexpressing the reprogramming factors OCT4, SOX2, KLF4, and MYC. Intriguingly, whereas some iPSCs maintained X chromosome inactivation, in others the X chromosome was reactivated. Thus, iPSCs were isolated that retained a single active X chromosome expressing either mutant or WT MeCP2, as well as iPSCs with reactivated X chromosomes expressing both mutant and WT MeCP2. When these cells underwent neuronal differentiation, the mutant monoallelic or biallelelic RTT-iPSCs displayed a defect in neuronal maturation consistent with RTT phenotypes. Our in vitro model of RTT is an important tool allowing the further investigation of the pathophysiology of RTT and the development of the curative therapeutics.
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Molecular mechanisms of pyrethroid insecticide neurotoxicity: recent advances. Arch Toxicol 2011; 86:165-81. [PMID: 21710279 DOI: 10.1007/s00204-011-0726-x] [Citation(s) in RCA: 327] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 06/09/2011] [Indexed: 12/19/2022]
Abstract
Synthetic pyrethroid insecticides were introduced into widespread use for the control of insect pests and disease vectors more than three decades ago. In addition to their value in controlling agricultural pests, pyrethroids are at the forefront of efforts to combat malaria and other mosquito-borne diseases and are also common ingredients of household insecticide and companion animal ectoparasite control products. The abundance and variety of pyrethroid uses contribute to the risk of exposure and adverse effects in the general population. The insecticidal actions of pyrethroids depend on their ability to bind to and disrupt voltage-gated sodium channels of insect nerves. Sodium channels are also important targets for the neurotoxic effects of pyrethroids in mammals but other targets, particularly voltage-gated calcium and chloride channels, have been implicated as alternative or secondary sites of action for a subset of pyrethroids. This review summarizes information published during the past decade on the action of pyrethroids on voltage-gated sodium channels as well as on voltage-gated calcium and chloride channels and provides a critical re-evaluation of the role of these three targets in pyrethroid neurotoxicity based on this information.
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Tan J, Soderlund DM. Independent and joint modulation of rat Nav1.6 voltage-gated sodium channels by coexpression with the auxiliary β1 and β2 subunits. Biochem Biophys Res Commun 2011; 407:788-92. [PMID: 21439942 DOI: 10.1016/j.bbrc.2011.03.101] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 03/19/2011] [Indexed: 10/18/2022]
Abstract
The Na(v)1.6 voltage-gated sodium channel α subunit isoform is the most abundant isoform in the brain and is implicated in the transmission of high frequency action potentials. Purification and immunocytochemical studies imply that Na(v)1.6 exist predominantly as Na(v)1.6+β1+β2 heterotrimeric complexes. We assessed the independent and joint effects of the rat β1 and β2 subunits on the gating and kinetic properties of rat Na(v)1.6 channels by recording whole-cell currents in the two-electrode voltage clamp configuration following transient expression in Xenopus oocytes. The β1 subunit accelerated fast inactivation of sodium currents but had no effect on the voltage dependence of their activation and steady-state inactivation and also prevented the decline of currents following trains of high-frequency depolarizing prepulses. The β2 subunit selectively retarded the fast phase of fast inactivation and shifted the voltage dependence of activation towards depolarization without affecting other gating properties and had no effect on the decline of currents following repeated depolarization. The β1 and β2 subunits expressed together accelerated both kinetic phases of fast inactivation, shifted the voltage dependence of activation towards hyperpolarization, and gave currents with a persistent component typical of those recorded from neurons expressing Na(v)1.6 sodium channels. These results identify unique effects of the β1 and β2 subunits and demonstrate that joint modulation by both auxiliary subunits gives channel properties that are not predicted by the effects of individual subunits.
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Affiliation(s)
- Jianguo Tan
- Cornell University, Department of Entomology, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
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Wang W, Takashima S, Segawa Y, Itoh M, Shi X, Hwang SK, Nabeshima K, Takeshita M, Hirose S. The developmental changes of Na(v)1.1 and Na(v)1.2 expression in the human hippocampus and temporal lobe. Brain Res 2011; 1389:61-70. [PMID: 21377452 DOI: 10.1016/j.brainres.2011.02.083] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 02/24/2011] [Accepted: 02/25/2011] [Indexed: 01/01/2023]
Abstract
Alterations of the genes encoding α1 and α2 subunits of voltage-gated sodium channels (SCN1A, SCN2A) have been reported as causes of various types of epilepsy, most of which occur during the first year of life; as yet, however, the detailed mechanisms are unclear. We suppose that developmental changes of SCN1A and SCN2A in the human brain, which are unknown yet, may play an important role. So here, we studied the developmental changes of their corresponding proteins (Na(v)1.1 and Na(v)1.2) in the human hippocampus and temporal lobe in 28 autopsy cases, which age from 13weeks of gestation (GW) to 63years of age (Y). Using comparative microscopic immunohistochemical (IHC) analysis, we found that Na(v)1.1 and Na(v)1.2 immunoreactivity first appeared at 19GW, simultaneously in the hippocampus and the white matter of temporal lobe. In nearly all age groups, Na(v)1.1 immunoreactivity was weak and relatively homogeneous. In general, Na(v)1.1 immunoreactive (IR) neurons and neurites increased during the late fetal and postnatal periods, reached their peaks 7-9months after birth (M), then decreased and remained stable at a relatively low level during childhood and adulthood. On the other hand, Na(v)1.2 immunoreactivity was strong and heterogeneous. In the hippocampus, Na(v)1.2 IR neurons increased gradually during the late fetal period, reached their peaks at 7-9M, sustained this high level during childhood, and then decreased slightly at adulthood. In the temporal lobe, Na(v)1.2 IR neurons reached a high level during the late fetal period, and maintained that level during subsequent developmental stages; Na(v)1.2 IR neurites also increased to a relatively high level during the late fetal period and continued to increase up to and during adulthood. Using double-staining IHC, we found that Na(v)1.1 and Na(v)1.2 had a relatively high colocalization rate with parvalbumin and showed distinct developmental changes. These findings extend our previous understanding of sodium channels and may help us discover the pathomechanisms of sodium channel-related age-dependent epilepsy.
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Affiliation(s)
- Wenze Wang
- Department of Pediatrics, School of Medicine, Fukuoka University, Fukuoka, Japan
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Deng GF, Qin JM, Sun XS, Kuang ZY, Su T, Zhao QH, Shi YW, Liu XR, Yu MJ, Yi YH, Liao WP, Long YS. Promoter analysis of mouse Scn3a gene and regulation of the promoter activity by GC box and CpG methylation. J Mol Neurosci 2011; 44:115-21. [PMID: 21271300 DOI: 10.1007/s12031-011-9492-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 01/11/2011] [Indexed: 01/04/2023]
Abstract
Voltage-gated sodium channel α-subunit type III (Na(v)1.3) is mainly expressed in the central nervous system and is associated with neurological disorders. The expression of mouse Scn3a product (Na(v)1.3) mainly occurs in embryonic and early postnatal brain but not in adult brain. Here, we report for the first time the identification and characterization of the mouse Scn3a gene promoter region and regulation of the promoter activity by GC box and CpG methylation. Luciferase assay showed that the promoter region F1.2 (nt -1,049 to +157) had significantly higher activity in PC12 cells, comparing with that in SH-SY5Y cells and HEK293 cells. A stepwise 5' truncation of the promoter region found that the minimal functional promoter located within the region nt -168 to +157. Deletion of a GC box (nt -254 to -258) in the mouse Scn3a promoter decreased the promoter activity. CpG methylation of the F1.2 without the GC box completely repressed the promoter activity, suggesting that the GC box is a critical element in the CpG-methylated Scn3a promoter. These results suggest that the GC box and CpG methylation might play important roles in regulating mouse Scn3a gene expression.
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Affiliation(s)
- Guang-Fei Deng
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and The Ministry of Education of China, Institute of Neuroscience and The Second Affiliated Hospital of Guangzhou Medical University, 250 Chang-gang-dong Road, Guangzhou, China
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Zakon HH, Jost MC, Lu Y. Expansion of voltage-dependent Na+ channel gene family in early tetrapods coincided with the emergence of terrestriality and increased brain complexity. Mol Biol Evol 2010; 28:1415-24. [PMID: 21148285 DOI: 10.1093/molbev/msq325] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mammals have ten voltage-dependent sodium (Nav) channel genes. Nav channels are expressed in different cell types with different subcellular distributions and are critical for many aspects of neuronal processing. The last common ancestor of teleosts and tetrapods had four Nav channel genes, presumably on four different chromosomes. In the lineage leading to mammals, a series of tandem duplications on two of these chromosomes more than doubled the number of Nav channel genes. It is unknown when these duplications occurred and whether they occurred against a backdrop of duplication of flanking genes on their chromosomes or as an expansion of ion channel genes in general. We estimated key dates of the Nav channel gene family expansion by phylogenetic analysis using teleost, elasmobranch, lungfish, amphibian, avian, lizard, and mammalian Nav channel sequences, as well as chromosomal synteny for tetrapod genes. We tested, and exclude, the null hypothesis that Nav channel genes reside in regions of chromosomes prone to duplication by demonstrating the lack of duplication or duplicate retention of surrounding genes. We also find no comparable expansion in other voltage-dependent ion channel gene families of tetrapods following the teleost-tetrapod divergence. We posit a specific expansion of the Nav channel gene family in the Devonian and Carboniferous periods when tetrapods evolved, diversified, and invaded the terrestrial habitat. During this time, the amniote forebrain evolved greater anatomical complexity and novel tactile sensory receptors appeared. The duplication of Nav channel genes allowed for greater regional specialization in Nav channel expression, variation in subcellular localization, and enhanced processing of somatosensory input.
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