Progress in Understanding and Treating SCN2A-Mediated Disorders

DEFF Research Database (Denmark)

Sanders, Stephan J.; Campbell, Arthur J.; Cottrell, Jeffrey R.

2018-01-01

Advances in gene discovery for neurodevelopmental disorders have identified SCN2A dysfunction as a leading cause of infantile seizures, autism spectrum disorder, and intellectual disability. SCN2A encodes the neuronal sodium channel NaV1.2. Functional assays demonstrate strong correlation between...... of neurodevelopmental disorders more generally. Here, we discuss the progress made, through the concerted efforts of a diverse group of academic and industry scientists as well as policy advocates, in understanding and treating SCN2A-related disorders....

Sodium Channel Voltage-Gated Beta 2 Plays a Vital Role in Brain Aging Associated with Synaptic Plasticity and Expression of COX5A and FGF-2.

Science.gov (United States)

XiYang, Yan-Bin; Wang, You-Cui; Zhao, Ya; Ru, Jin; Lu, Bing-Tuan; Zhang, Yue-Ning; Wang, Nai-Chao; Hu, Wei-Yan; Liu, Jia; Yang, Jin-Wei; Wang, Zhao-Jun; Hao, Chun-Guang; Feng, Zhong-Tang; Xiao, Zhi-Cheng; Dong, Wei; Quan, Xiong-Zhi; Zhang, Lian-Feng; Wang, Ting-Hua

2016-03-01

The role of sodium channel voltage-gated beta 2 (SCN2B) in brain aging is largely unknown. The present study was therefore designed to determine the role of SCN2B in brain aging by using the senescence-accelerated mice prone 8 (SAMP8), a brain senescence-accelerated animal model, together with the SCN2B transgenic mice. The results showed that SAMP8 exhibited impaired learning and memory functions, assessed by the Morris water maze test, as early as 8 months of age. The messenger RNA (mRNA) and protein expressions of SCN2B were also upregulated in the prefrontal cortex at this age. Treatment with traditional Chinese anti-aging medicine Xueshuangtong (Panax notoginseng saponins, PNS) significantly reversed the SCN2B expressions in the prefrontal cortex, resulting in improved learning and memory. Moreover, SCN2B knockdown transgenic mice were generated and bred to determine the roles of SCN2B in brain senescence. A reduction in the SCN2B level by 60.68% resulted in improvement in the hippocampus-dependent spatial recognition memory and long-term potential (LTP) slope of field excitatory postsynaptic potential (fEPSP), followed by an upregulation of COX5A mRNA levels and downregulation of fibroblast growth factor-2 (FGF-2) mRNA expression. Together, the present findings indicated that SCN2B could play an important role in the aging-related cognitive deterioration, which is associated with the regulations of COX5A and FGF-2. These findings could provide the potential strategy of candidate target to develop antisenescence drugs for the treatment of brain aging.

Autosomal dominant SCN8A mutation with an unusually mild phenotype.

Science.gov (United States)

Anand, G; Collett-White, F; Orsini, A; Thomas, S; Jayapal, S; Trump, N; Zaiwalla, Z; Jayawant, S

2016-09-01

Mutations in SCN8A, coding for the voltage-gated sodium channel Nav 1.6, have been described in relation to infantile onset epilepsy with developmental delay and cognitive impairment, in particular early onset epileptic encephalopathy (EIEE) type 13. Here we report an infant and his father with early onset focal epileptic seizures but without cognitive or neurological impairment in whom next generation sequence analysis identified a heterozygous mutation (c.5630A > G, p. (Asn1877Ser)) in the SCN8A gene. This mutation, confirmed by Sanger sequence analysis, affects a highly conserved amino acid and in silico tools predicts that it may be pathogenic. The reported infant has a normal developmental profile at 16-month follow-up. His father also had normal development and has no cognitive impairment at 42 years. This is the second known SCN8A mutation associated with a phenotype of benign familial infantile epilepsy. Good seizure control was achieved in our patients with sodium channel blockers. Based on our proband and a recently described group of families with benign familial infantile epilepsy and SCN8A variant we suggest expanding testing to patients with infantile epilepsy and no cognitive impairment. In addition, the same SCN8A variant (c.5630A > G, p. (Asn1877Ser)) is also found in patients with epilepsy and developmental delay highlighting the phenotypic variability and the possible role of other protective genetic factors. Copyright © 2016. Published by Elsevier Ltd.

Epidural Analgesia with Ropivacaine during Labour in a Patient with a SCN5A Gene Mutation

Directory of Open Access Journals (Sweden)

A. L. M. J. van der Knijff-van Dortmont

2016-01-01

Full Text Available SCN5A gene mutations can lead to ion channel defects which can cause cardiac conduction disturbances. In the presence of specific ECG characteristics, this mutation is called Brugada syndrome. Many drugs are associated with adverse events, making anesthesia in patients with SCN5A gene mutations or Brugada syndrome challenging. In this case report, we describe a pregnant patient with this mutation who received epidural analgesia using low dose ropivacaine and sufentanil during labour.

Cardiac sodium channel NaV1.5 distribution in myocytes via interacting proteins: the multiple pool model.

Science.gov (United States)

Shy, Diana; Gillet, Ludovic; Abriel, Hugues

2013-04-01

The cardiac sodium current (INa) is responsible for the rapid depolarization of cardiac cells, thus allowing for their contraction. It is also involved in regulating the duration of the cardiac action potential (AP) and propagation of the impulse throughout the myocardium. Cardiac INa is generated by the voltage-gated Na(+) channel, NaV1.5, a 2016-residue protein which forms the pore of the channel. Over the past years, hundreds of mutations in SCN5A, the human gene coding for NaV1.5, have been linked to many cardiac electrical disorders, including the congenital and acquired long QT syndrome, Brugada syndrome, conduction slowing, sick sinus syndrome, atrial fibrillation, and dilated cardiomyopathy. Similar to many membrane proteins, NaV1.5 has been found to be regulated by several interacting proteins. In some cases, these different proteins, which reside in distinct membrane compartments (i.e. lateral membrane vs. intercalated disks), have been shown to interact with the same regulatory domain of NaV1.5, thus suggesting that several pools of NaV1.5 channels may co-exist in cardiac cells. The aim of this review article is to summarize the recent works that demonstrate its interaction with regulatory proteins and illustrate the model that the sodium channel NaV1.5 resides in distinct and different pools in cardiac cells. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction. Copyright © 2012 Elsevier B.V. All rights reserved.

Pathophysiological mechanisms of sino-atrial dysfunction and ventricular conduction disease associated with SCN5A deficiency: insights from mouse models

Directory of Open Access Journals (Sweden)

Christopher L-H Huang

2012-07-01

Full Text Available Genetically modified mice provide a number of models for studying cardiac channelopathies related to cardiac Na+ channel (SCN5A abnormalities. We review key pathophysiological features in these murine models that may underlie clinical features observed in sinus node dysfunction and progressive cardiac conduction disease, thereby providing insights into their pathophysiological mechanisms. We describe loss of Na+ channel function and fibrotic changes associated with both loss and gain-of-function Na+ channel mutations. Recent reports further relate the progressive fibrotic changes to upregulation of TGF-β1 production and the transcription factors, Atf3, a stress-inducible gene, and Egr1, to the presence of heterozygous Scn5a inactivation. Both changes are thus directly implicated in the clinically observed disruptions in sino-atrial node pacemaker function, and sino-atrial and ventricular conduction, and their progression with age. Murine systems with genetic modifications in Scn5a thus prove a useful tool to address questions concerning roles of genetic and environmental modifiers on human SCN5A disease phenotypes.

Comparison and optimization of in silico algorithms for predicting the pathogenicity of sodium channel variants in epilepsy.

Science.gov (United States)

Holland, Katherine D; Bouley, Thomas M; Horn, Paul S

2017-07-01

Variants in neuronal voltage-gated sodium channel α-subunits genes SCN1A, SCN2A, and SCN8A are common in early onset epileptic encephalopathies and other autosomal dominant childhood epilepsy syndromes. However, in clinical practice, missense variants are often classified as variants of uncertain significance when missense variants are identified but heritability cannot be determined. Genetic testing reports often include results of computational tests to estimate pathogenicity and the frequency of that variant in population-based databases. The objective of this work was to enhance clinicians' understanding of results by (1) determining how effectively computational algorithms predict epileptogenicity of sodium channel (SCN) missense variants; (2) optimizing their predictive capabilities; and (3) determining if epilepsy-associated SCN variants are present in population-based databases. This will help clinicians better understand the results of indeterminate SCN test results in people with epilepsy. Pathogenic, likely pathogenic, and benign variants in SCNs were identified using databases of sodium channel variants. Benign variants were also identified from population-based databases. Eight algorithms commonly used to predict pathogenicity were compared. In addition, logistic regression was used to determine if a combination of algorithms could better predict pathogenicity. Based on American College of Medical Genetic Criteria, 440 variants were classified as pathogenic or likely pathogenic and 84 were classified as benign or likely benign. Twenty-eight variants previously associated with epilepsy were present in population-based gene databases. The output provided by most computational algorithms had a high sensitivity but low specificity with an accuracy of 0.52-0.77. Accuracy could be improved by adjusting the threshold for pathogenicity. Using this adjustment, the Mendelian Clinically Applicable Pathogenicity (M-CAP) algorithm had an accuracy of 0.90 and a

Large-scale structural alteration of brain in epileptic children with SCN1A mutation

OpenAIRE

Lee, Yun-Jeong; Yum, Mi-Sun; Kim, Min-Jee; Shim, Woo-Hyun; Yoon, Hee Mang; Yoo, Il Han; Lee, Jiwon; Lim, Byung Chan; Kim, Ki Joong; Ko, Tae-Sung

2017-01-01

Objective: Mutations in SCN1A gene encoding the alpha 1 subunit of the voltage gated sodium channel are associated with several epilepsy syndromes including genetic epilepsy with febrile seizures plus (GEFS+) and severe myoclonic epilepsy of infancy (SMEI). However, in most patients with SCN1A mutation, brain imaging has reported normal or non-specific findings including cerebral or cerebellar atrophy. The aim of this study was to investigate differences in brain morphometry in epileptic chil...

Genetic and phenotypic heterogeneity suggest therapeutic implications in SCN2A-related disorders

NARCIS (Netherlands)

Wolff, Markus; Johannesen, Katrine M; Hedrich, Ulrike B S; Masnada, Silvia; Rubboli, Guido; Gardella, Elena; Lesca, Gaetan; Ville, Dorothée; Milh, Mathieu; Villard, Laurent; Afenjar, Alexandra; Chantot-Bastaraud, Sandra; Mignot, Cyril; Lardennois, Caroline; Nava, Caroline; Schwarz, Niklas; Gérard, Marion; Perrin, Laurence; Doummar, Diane; Auvin, Stéphane; Miranda, Maria J; Hempel, Maja; Brilstra, Eva; Knoers, Nine; Verbeek, Nienke; van Kempen, Marjan; Braun, Kees P; Mancini, Grazia; Biskup, Saskia; Hörtnagel, Konstanze; Döcker, Miriam; Bast, Thomas; Loddenkemper, Tobias; Wong-Kisiel, Lily; Baumeister, Friedrich M; Fazeli, Walid; Striano, Pasquale; Dilena, Robertino; Fontana, Elena; Zara, Federico; Kurlemann, Gerhard; Klepper, Joerg; Thoene, Jess G; Arndt, Daniel H; Deconinck, Nicolas; Schmitt-Mechelke, Thomas; Maier, Oliver; Muhle, Hiltrud; Wical, Beverly; Finetti, Claudio; Brückner, Reinhard; Pietz, Joachim; Golla, Günther; Jillella, Dinesh; Linnet, Karen M; Charles, Perrine; Moog, Ute; Õiglane-Shlik, Eve; Mantovani, John F; Park, Kristen; Deprez, Marie; Lederer, Damien; Mary, Sandrine; Scalais, Emmanuel; Selim, Laila; Van Coster, Rudy; Lagae, Lieven; Nikanorova, Marina; Hjalgrim, Helle; Korenke, G Christoph; Trivisano, Marina; Specchio, Nicola; Ceulemans, Berten; Dorn, Thomas; Helbig, Katherine L; Hardies, Katia; Stamberger, Hannah; de Jonghe, Peter; Weckhuysen, Sarah; Lemke, Johannes R; Krägeloh-Mann, Ingeborg; Helbig, Ingo; Kluger, Gerhard; Lerche, Holger; Møller, Rikke S

2017-01-01

Mutations in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been associated with a spectrum of epilepsies and neurodevelopmental disorders. Here, we report the phenotypes of 71 patients and review 130 previously reported patients. We found that (i) encephalopathies with

Genetic and phenotypic heterogeneity suggest therapeutic implications in SCN2A-related disorders

DEFF Research Database (Denmark)

Wolff, Markus; Johannesen, Katrine M.; Hedrich, Ulrike B. S.

2017-01-01

Mutations in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been associated with a spectrum of epilepsies and neurodevelopmental disorders. Here, we report the phenotypes of 71 patients and review 130 previously reported patients. We found that (i) encephalopathies with infa...

Common and rare variants in SCN10A modulate the risk of atrial fibrillation

DEFF Research Database (Denmark)

Jabbari, Javad; Olesen, Morten S; Yuan, Lei

2015-01-01

BACKGROUND: Genome-wide association studies have shown that the common single nucleotide polymorphism rs6800541 located in SCN10A, encoding the voltage-gated Nav1.8 sodium channel, is associated with PR-interval prolongation and atrial fibrillation (AF). Single nucleotide polymorphism rs6800541...... is in high linkage disequilibrium with the nonsynonymous variant in SCN10A, rs6795970 (V1073A, r(2)=0.933). We therefore sought to determine whether common and rare SCN10A variants are associated with early onset AF. METHODS AND RESULTS: SCN10A was sequenced in 225 AF patients in whom there was no evidence...... of other cardiovascular disease or dysfunction (lone AF). In an association study of the rs6795970 single nucleotide polymorphism variant, we included 515 AF patients and 2 control cohorts of 730 individuals free of AF and 6161 randomly sampled individuals. Functional characterization of SCN10A variants...

β1-C121W Is Down But Not Out: Epilepsy-Associated Scn1b-C121W Results in a Deleterious Gain-of-Function

Science.gov (United States)

Kruger, Larisa C.; O'Malley, Heather A.; Hull, Jacob M.; Kleeman, Amanda; Patino, Gustavo A.

2016-01-01

Voltage-gated sodium channel (VGSC) β subunits signal through multiple pathways on multiple time scales. In addition to modulating sodium and potassium currents, β subunits play nonconducting roles as cell adhesion molecules, which allow them to function in cell–cell communication, neuronal migration, neurite outgrowth, neuronal pathfinding, and axonal fasciculation. Mutations in SCN1B, encoding VGSC β1 and β1B, are associated with epilepsy. Autosomal-dominant SCN1B-C121W, the first epilepsy-associated VGSC mutation identified, results in genetic epilepsy with febrile seizures plus (GEFS+). This mutation has been shown to disrupt both the sodium-current-modulatory and cell-adhesive functions of β1 subunits expressed in heterologous systems. The goal of this study was to compare mice heterozygous for Scn1b-C121W (Scn1b+/W) with mice heterozygous for the Scn1b-null allele (Scn1b+/−) to determine whether the C121W mutation results in loss-of-function in vivo. We found that Scn1b+/W mice were more susceptible than Scn1b+/− and Scn1b+/+ mice to hyperthermia-induced convulsions, a model of pediatric febrile seizures. β1-C121W subunits are expressed at the neuronal cell surface in vivo. However, despite this, β1-C121W polypeptides are incompletely glycosylated and do not associate with VGSC α subunits in the brain. β1-C121W subcellular localization is restricted to neuronal cell bodies and is not detected at axon initial segments in the cortex or cerebellum or at optic nerve nodes of Ranvier of Scn1bW/W mice. These data, together with our previous results showing that β1-C121W cannot participate in trans-homophilic cell adhesion, lead to the hypothesis that SCN1B-C121W confers a deleterious gain-of-function in human GEFS+ patients. SIGNIFICANCE STATEMENT The mechanisms underlying genetic epilepsy syndromes are poorly understood. Closing this gap in knowledge is essential to the development of new medicines to treat epilepsy. We have used mouse models to

Common and rare variants in SCN10A> modulate the risk of atrial fibrillation

DEFF Research Database (Denmark)

Jabbari, Javad; Olesen, Morten S.; Yuan, Lei

2015-01-01

Background: Genome-wide assocn. studies have shown that the common single nucleotide polymorphism rs6800541 located in SCN10A, encoding the voltage-gated Nav1.8 sodium channel, is assocd. with PR-interval prolongation and atrial fibrillation (AF). Single nucleotide polymorphism rs6800541 is in hi...

A case of recurrent encephalopathy with SCN2A missense mutation.

Science.gov (United States)

Fukasawa, Tatsuya; Kubota, Tetsuo; Negoro, Tamiko; Saitoh, Makiko; Mizuguchi, Masashi; Ihara, Yukiko; Ishii, Atsushi; Hirose, Shinichi

2015-06-01

Voltage-gated sodium channels regulate neuronal excitability, as well as survival and the patterning of neuronal connectivity during development. Mutations in SCN2A, which encodes the Na(+) channel Nav1.2, cause epilepsy syndromes and predispose children to acute encephalopathy. Here, we report the case of a young male with recurrent acute encephalopathy who carried a novel missense mutation in the SCN2A gene. He was born by normal delivery and developed repetitive apneic episodes at 2days of age. Diffusion-weighted imaging revealed high-intensity areas in diffuse subcortical white matter, bilateral thalami, and basal nuclei. His symptoms improved gradually without any specific treatment, but he exhibited a motor milestone delay after the episode. At the age of 10months, he developed acute cerebellopathy associated with a respiratory syncytial viral infection. He received high-dose intravenous gammaglobulin and methylprednisolone pulse therapy and seemed to have no obvious sequelae after the episode. He then developed severe diffuse encephalopathy associated with gastroenteritis at the age of 14months. He received high-dose intravenous gammaglobulin and methylprednisolone pulse therapy but was left with severe neurological sequelae. PCR-based analysis revealed a novel de novo missense mutation, c.4979T>G (p.Leu1660Trp), in the SCN2A gene. This case suggests that SCN2A mutations might predispose children to repetitive encephalopathy with variable clinical and imaging findings. Copyright © 2014 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Multiple loss-of-function mechanisms contribute to SCN5A-related familial sick sinus syndrome.

Directory of Open Access Journals (Sweden)

Junhong Gui

2010-06-01

Full Text Available To identify molecular mechanisms underlying SCN5A-related sick sinus syndrome (SSS, a rare type of SSS, in parallel experiments we elucidated the electrophysiological properties and the cell surface localization of thirteen human Na(v1.5 (hNa(v1.5 mutant channels previously linked to this disease.Mutant hNa(v1.5 channels expressed by HEK293 cells and Xenopus oocytes were investigated by whole-cell patch clamp and two-microelectrode voltage clamp, respectively. HEK293 cell surface biotinylation experiments quantified the fraction of correctly targeted channel proteins. Our data suggested three distinct mutant channel subtypes: Group 1 mutants (L212P, P1298L, DelF1617, R1632H gave peak current densities and cell surface targeting indistinguishable from wild-type hNa(v1.5. Loss-of-function of these mutants resulted from altered channel kinetics, including a negative shift of steady-state inactivation and a reduced voltage dependency of open-state inactivation. Group 2 mutants (E161K, T220I, D1275N gave significantly reduced whole-cell currents due to impaired cell surface localization (D1275N, altered channel properties at unchanged cell surface localization (T220I, or a combination of both (E161K. Group 3 mutant channels were non-functional, due to an almost complete lack of protein at the plasma membrane (T187I, W1421X, K1578fs/52, R1623X or a probable gating/permeation defect with normal surface localisation (R878C, G1408R.This study indicates that multiple molecular mechanisms, including gating abnormalities, trafficking defects, or a combination of both, are responsible for SCN5A-related familial SSS.

Linkage between increased nociception and olfaction via a SCN9A haplotype.

Directory of Open Access Journals (Sweden)

Dirk Heimann

Full Text Available BACKGROUND AND AIMS: Mutations reducing the function of Nav1.7 sodium channels entail diminished pain perception and olfactory acuity, suggesting a link between nociception and olfaction at ion channel level. We hypothesized that if such link exists, it should work in both directions and gain-of-function Nav1.7 mutations known to be associated with increased pain perception should also increase olfactory acuity. METHODS: SCN9A variants were assessed known to enhance pain perception and found more frequently in the average population. Specifically, carriers of SCN9A variants rs41268673C>A (P610T; n = 14 or rs6746030C>T (R1150W; n = 21 were compared with non-carriers (n = 40. Olfactory function was quantified by assessing odor threshold, odor discrimination and odor identification using an established olfactory test. Nociception was assessed by measuring pain thresholds to experimental nociceptive stimuli (punctate and blunt mechanical pressure, heat and electrical stimuli. RESULTS: The number of carried alleles of the non-mutated SCN9A haplotype rs41268673C/rs6746030C was significantly associated with the comparatively highest olfactory threshold (0 alleles: threshold at phenylethylethanol dilution step 12 of 16 (n = 1, 1 allele: 10.6±2.6 (n = 34, 2 alleles: 9.5±2.1 (n = 40. The same SCN9A haplotype determined the pain threshold to blunt pressure stimuli (0 alleles: 21.1 N/m(2, 1 allele: 29.8±10.4 N/m(2, 2 alleles: 33.5±10.2 N/m(2. CONCLUSIONS: The findings established a working link between nociception and olfaction via Nav1.7 in the gain-of-function direction. Hence, together with the known reduced olfaction and pain in loss-of-function mutations, a bidirectional genetic functional association between nociception and olfaction exists at Nav1.7 level.

The incidence of SCN1A-related Dravet syndrome in Denmark is 1:22,000

DEFF Research Database (Denmark)

Bayat, Allan; Hjalgrim, Helle; Møller, Rikke S.

2015-01-01

Dravet syndrome is a severe infantile-onset epileptic encephalopathy associated with mutations in the sodium channel alpha-1 subunit gene SCN1A. We aimed to describe the incidence of Dravet syndrome in the Danish population. Based on a 6-year birth cohort from 2004 to 2009, we propose an incidenc...

Localisation of SCN10A gene product Na(v)1.8 and novel pain-related ion channels in human heart.

Science.gov (United States)

Facer, Paul; Punjabi, Prakash P; Abrari, Andleeb; Kaba, Riyaz A; Severs, Nicholas J; Chambers, John; Kooner, Jaspal S; Anand, Praveen

2011-01-01

We have shown that the gene SCN10A encoding the sodium channel Na(v)1.8 is a susceptibility factor for heart block and serious ventricular arrhythmia. Since Na(v)1.8 is known to be present in nerve fibres that mediate pain, it may be related to both cardiac pain and dysrhythmia. The localisation of Na(v)1.8 and other key nociceptive ion channels, including Na(v)1.7, Na(v)1.9, capsaicin receptor TRPV1, and purinergic receptor P2X(3), have not been reported in human heart. The aim of this study was to determine the distribution of Na(v)1.8, related sodium and other sensory channels in human cardiac tissue, and correlate their density with sympathetic nerves, regenerating nerves (GAP-43), and vascularity. Human heart atrial appendage tissues (n = 13) were collected during surgery for valve disease. Tissues were investigated by immunohistology using specific antibodies to Na(v)1.8 and other markers. Na(v)1.8 immunoreactivity was detected in nerve fibres and fascicles in the myocardium, often closely associated with small capillaries. Na(v)1.8 nerve fibres per mm(2) correlated significantly with vascular markers. Na(v)1.8-immunoreactivity was present also in cardiomyocytes with a similar distribution pattern to that seen with connexins, the specialised gap junction proteins of myocardial intercalated discs. Na(v)1.5-immunoreactivity was detected in cardiomyocytes but not in nerve fibres. Na(v)1.7, Na(v)1.9, TRPV1, P2X(3)/P2X(2), and GAP43 positive nerve fibres were relatively sparse, whereas sympathetic innervation and connexin43 were abundant. We conclude that sodium channel Na(v)1.8 is present in sensory nerves and cardiomyocytes of human heart. Na(v)1.8 and other pain channels provide new targets for the understanding and treatment of cardiac pain and dysrhythmia.

Genetic and phenotypic heterogeneity suggest therapeutic implications in SCN2A-related disorders.

Science.gov (United States)

Wolff, Markus; Johannesen, Katrine M; Hedrich, Ulrike B S; Masnada, Silvia; Rubboli, Guido; Gardella, Elena; Lesca, Gaetan; Ville, Dorothée; Milh, Mathieu; Villard, Laurent; Afenjar, Alexandra; Chantot-Bastaraud, Sandra; Mignot, Cyril; Lardennois, Caroline; Nava, Caroline; Schwarz, Niklas; Gérard, Marion; Perrin, Laurence; Doummar, Diane; Auvin, Stéphane; Miranda, Maria J; Hempel, Maja; Brilstra, Eva; Knoers, Nine; Verbeek, Nienke; van Kempen, Marjan; Braun, Kees P; Mancini, Grazia; Biskup, Saskia; Hörtnagel, Konstanze; Döcker, Miriam; Bast, Thomas; Loddenkemper, Tobias; Wong-Kisiel, Lily; Baumeister, Friedrich M; Fazeli, Walid; Striano, Pasquale; Dilena, Robertino; Fontana, Elena; Zara, Federico; Kurlemann, Gerhard; Klepper, Joerg; Thoene, Jess G; Arndt, Daniel H; Deconinck, Nicolas; Schmitt-Mechelke, Thomas; Maier, Oliver; Muhle, Hiltrud; Wical, Beverly; Finetti, Claudio; Brückner, Reinhard; Pietz, Joachim; Golla, Günther; Jillella, Dinesh; Linnet, Karen M; Charles, Perrine; Moog, Ute; Õiglane-Shlik, Eve; Mantovani, John F; Park, Kristen; Deprez, Marie; Lederer, Damien; Mary, Sandrine; Scalais, Emmanuel; Selim, Laila; Van Coster, Rudy; Lagae, Lieven; Nikanorova, Marina; Hjalgrim, Helle; Korenke, G Christoph; Trivisano, Marina; Specchio, Nicola; Ceulemans, Berten; Dorn, Thomas; Helbig, Katherine L; Hardies, Katia; Stamberger, Hannah; de Jonghe, Peter; Weckhuysen, Sarah; Lemke, Johannes R; Krägeloh-Mann, Ingeborg; Helbig, Ingo; Kluger, Gerhard; Lerche, Holger; Møller, Rikke S

2017-05-01

Mutations in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been associated with a spectrum of epilepsies and neurodevelopmental disorders. Here, we report the phenotypes of 71 patients and review 130 previously reported patients. We found that (i) encephalopathies with infantile/childhood onset epilepsies (≥3 months of age) occur almost as often as those with an early infantile onset (<3 months), and are thus more frequent than previously reported; (ii) distinct phenotypes can be seen within the late onset group, including myoclonic-atonic epilepsy (two patients), Lennox-Gastaut not emerging from West syndrome (two patients), and focal epilepsies with an electrical status epilepticus during slow sleep-like EEG pattern (six patients); and (iii) West syndrome constitutes a common phenotype with a major recurring mutation (p.Arg853Gln: two new and four previously reported children). Other known phenotypes include Ohtahara syndrome, epilepsy of infancy with migrating focal seizures, and intellectual disability or autism without epilepsy. To assess the response to antiepileptic therapy, we retrospectively reviewed the treatment regimen and the course of the epilepsy in 66 patients for which well-documented medical information was available. We find that the use of sodium channel blockers was often associated with clinically relevant seizure reduction or seizure freedom in children with early infantile epilepsies (<3 months), whereas other antiepileptic drugs were less effective. In contrast, sodium channel blockers were rarely effective in epilepsies with later onset (≥3 months) and sometimes induced seizure worsening. Regarding the genetic findings, truncating mutations were exclusively seen in patients with late onset epilepsies and lack of response to sodium channel blockers. Functional characterization of four selected missense mutations using whole cell patch-clamping in tsA201 cells-together with data from the literature-suggest that

SCN5A mutations and polymorphisms in patients with ventricular fibrillation during acute myocardial infarction.

Science.gov (United States)

Boehringer, Tim; Bugert, Peter; Borggrefe, Martin; Elmas, Elif

2014-10-01

Mutations in the SCN5A gene encoding the Nav1.5 channel α-subunit are known to be risk factors of arrhythmia, including Brugada Syndrome and Long QT syndrome subtype 3. The present study focused on the role of SCN5A variants in the development of ventricular fibrillation (VF) during acute myocardial infarction (AMI). Since VF during AMI is the major cause of sudden death in the Western world, SCN5A mutations represent genetic risk factors for sudden death. By exon re-sequencing, the entire coding region and flanking intron regions were sequenced in 46 AMI/VF+ patients. In total, nine single nucleotide variants were identified of which four represented common single nucleotide polymorphisms (SNPs; 87G>A, 1673A>G, IVS16‑6C>T and 5457T>A). Only five rare variants were identified, each in only one patient. Only two of the rare variants represented missense mutations (3578G>A and 4786T>A). The common SNPs and the missense mutations were also genotyped using polymerase chain reaction methods in 79 AMI/VF‑ patients and 480 healthy controls. The SNPs did not demonstrate significant differences in allele and genotype frequencies between the study groups. The 3578G>A mutation was identified in one out of the 480 controls, whereas the 4786T>A mutation was not present in AMI/VF- patients and controls. In conclusion, the majority of AMI/VF+ patients demonstrated a wild type sequence or common SNPs in SCN5A. Only two out of 46 (4.3%) AMI/VF+ patients revealed mutations that may be involved in Nav1.5 dysfunction and VF. However, this requires further functional validation.

Large-scale structural alteration of brain in epileptic children with SCN1A mutation.

Science.gov (United States)

Lee, Yun-Jeong; Yum, Mi-Sun; Kim, Min-Jee; Shim, Woo-Hyun; Yoon, Hee Mang; Yoo, Il Han; Lee, Jiwon; Lim, Byung Chan; Kim, Ki Joong; Ko, Tae-Sung

2017-01-01

Mutations in SCN1A gene encoding the alpha 1 subunit of the voltage gated sodium channel are associated with several epilepsy syndromes including genetic epilepsy with febrile seizures plus (GEFS +) and severe myoclonic epilepsy of infancy (SMEI). However, in most patients with SCN1A mutation, brain imaging has reported normal or non-specific findings including cerebral or cerebellar atrophy. The aim of this study was to investigate differences in brain morphometry in epileptic children with SCN1A mutation compared to healthy control subjects. We obtained cortical morphology (thickness, and surface area) and brain volume (global, subcortical, and regional) measurements using FreeSurfer (version 5.3.0, https://surfer.nmr.mgh.harvard.edu) and compared measurements of children with epilepsy and SCN1A gene mutation ( n  = 21) with those of age and gender matched healthy controls ( n  = 42). Compared to the healthy control group, children with epilepsy and SCN1A gene mutation exhibited smaller total brain, total gray matter and white matter, cerebellar white matter, and subcortical volumes, as well as mean surface area and mean cortical thickness. A regional analysis revealed significantly reduced gray matter volume in the patient group in the bilateral inferior parietal, left lateral orbitofrontal, left precentral, right postcentral, right isthmus cingulate, right middle temporal area with smaller surface area and white matter volume in some of these areas. However, the regional cortical thickness was not significantly different in two groups. This study showed large-scale developmental brain changes in patients with epilepsy and SCN1A gene mutation, which may be associated with the core symptoms of the patients. Further longitudinal MRI studies with larger cohorts are required to confirm the effect of SCN1A gene mutation on structural brain development.

Autistic-like behaviour in Scn1a+/- mice and rescue by enhanced GABA-mediated neurotransmission.

Science.gov (United States)

Han, Sung; Tai, Chao; Westenbroek, Ruth E; Yu, Frank H; Cheah, Christine S; Potter, Gregory B; Rubenstein, John L; Scheuer, Todd; de la Iglesia, Horacio O; Catterall, William A

2012-09-20

Haploinsufficiency of the SCN1A gene encoding voltage-gated sodium channel Na(V)1.1 causes Dravet's syndrome, a childhood neuropsychiatric disorder including recurrent intractable seizures, cognitive deficit and autism-spectrum behaviours. The neural mechanisms responsible for cognitive deficit and autism-spectrum behaviours in Dravet's syndrome are poorly understood. Here we report that mice with Scn1a haploinsufficiency exhibit hyperactivity, stereotyped behaviours, social interaction deficits and impaired context-dependent spatial memory. Olfactory sensitivity is retained, but novel food odours and social odours are aversive to Scn1a(+/-) mice. GABAergic neurotransmission is specifically impaired by this mutation, and selective deletion of Na(V)1.1 channels in forebrain interneurons is sufficient to cause these behavioural and cognitive impairments. Remarkably, treatment with low-dose clonazepam, a positive allosteric modulator of GABA(A) receptors, completely rescued the abnormal social behaviours and deficits in fear memory in the mouse model of Dravet's syndrome, demonstrating that they are caused by impaired GABAergic neurotransmission and not by neuronal damage from recurrent seizures. These results demonstrate a critical role for Na(V)1.1 channels in neuropsychiatric functions and provide a potential therapeutic strategy for cognitive deficit and autism-spectrum behaviours in Dravet's syndrome.

Identification of an Nav1.1 sodium channel (SCN1A) loss-of-function mutation associated with familial simple febrile seizures

Science.gov (United States)

Mantegazza, Massimo; Gambardella, Antonio; Rusconi, Raffaella; Schiavon, Emanuele; Annesi, Ferdinanda; Cassulini, Rita Restano; Labate, Angelo; Carrideo, Sara; Chifari, Rosanna; Canevini, Maria Paola; Canger, Raffaele; Franceschetti, Silvana; Annesi, Grazia; Wanke, Enzo; Quattrone, Aldo

2005-01-01

Febrile seizures (FS) affect 5–12% of infants and children up to 6 years of age. There is now epidemiological evidence that FS are associated with subsequent afebrile and unprovoked seizures in ≈7% of patients, which is 10 times more than in the general population. Extensive genetic studies have demonstrated that various loci are responsible for familial FS, and the FEB3 autosomal-dominant locus has been identified on chromosome 2q23–24, where the SCN1A gene is mapped. However, gene mutations causing simple FS have not been found yet. Here we show that the M145T mutation of a well conserved amino acid in the first transmembrane segment of domain I of the human Nav1.1 channel α-subunit cosegregates in all 12 individuals of a large Italian family affected by simple FS. Functional studies in mammalian cells demonstrate that the mutation causes a 60% reduction of current density and a 10-mV positive shift of the activation curve. Thus, M145T is a loss-of-function mutant. These results show that monogenic FS should also be considered a channelopathy. PMID:16326807

Cloning and expression of a zebrafish SCN1B ortholog and identification of a species-specific splice variant

Directory of Open Access Journals (Sweden)

Slat Emily A

2007-07-01

Full Text Available Abstract Background Voltage-gated Na+ channel β1 (Scn1b subunits are multi-functional proteins that play roles in current modulation, channel cell surface expression, cell adhesion, cell migration, and neurite outgrowth. We have shown previously that β1 modulates electrical excitability in vivo using a mouse model. Scn1b null mice exhibit spontaneous seizures and ataxia, slowed action potential conduction, decreased numbers of nodes of Ranvier in myelinated axons, alterations in nodal architecture, and differences in Na+ channel α subunit localization. The early death of these mice at postnatal day 19, however, make them a challenging model system to study. As a first step toward development of an alternative model to investigate the physiological roles of β1 subunits in vivo we cloned two β1-like subunit cDNAs from D. rerio. Results Two β1-like subunit mRNAs from zebrafish, scn1ba_tv1 and scn1ba_tv2, arise from alternative splicing of scn1ba. The deduced amino acid sequences of Scn1ba_tv1 and Scn1ba_tv2 are identical except for their C-terminal domains. The C-terminus of Scn1ba_tv1 contains a tyrosine residue similar to that found to be critical for ankyrin association and Na+ channel modulation in mammalian β1. In contrast, Scn1ba_tv2 contains a unique, species-specific C-terminal domain that does not contain a tyrosine. Immunohistochemical analysis shows that, while the expression patterns of Scn1ba_tv1 and Scn1ba_tv2 overlap in some areas of the brain, retina, spinal cord, and skeletal muscle, only Scn1ba_tv1 is expressed in optic nerve where its staining pattern suggests nodal expression. Both scn1ba splice forms modulate Na+ currents expressed by zebrafish scn8aa, resulting in shifts in channel gating mode, increased current amplitude, negative shifts in the voltage dependence of current activation and inactivation, and increases in the rate of recovery from inactivation, similar to the function of mammalian β1 subunits. In

Metaflumizone is a novel sodium channel blocker insecticide.

Science.gov (United States)

Salgado, V L; Hayashi, J H

2007-12-15

Metaflumizone is a novel semicarbazone insecticide, derived chemically from the pyrazoline sodium channel blocker insecticides (SCBIs) discovered at Philips-Duphar in the early 1970s, but with greatly improved mammalian safety. This paper describes studies confirming that the insecticidal action of metaflumizone is due to the state-dependent blockage of sodium channels. Larvae of the moth Spodoptera eridania injected with metaflumizone became paralyzed, concomitant with blockage of all nerve activity. Furthermore, tonic firing of abdominal stretch receptor organs from Spodoptera frugiperda was blocked by metaflumizone applied in the bath, consistent with the block of voltage-dependent sodium channels. Studies on native sodium channels, in primary-cultured neurons isolated from the CNS of the larvae of the moth Manduca sexta and on Para/TipE sodium channels heterologously expressed in Xenopus (African clawed frog) oocytes, confirmed that metaflumizone blocks sodium channels by binding selectively to the slow-inactivated state, which is characteristic of the SCBIs. The results confirm that metaflumizone is a novel sodium channel blocker insecticide.

Common variants at SCN5A-SCN10A and HEY2 are associated with Brugada syndrome, a rare disease with high risk of sudden cardiac death

DEFF Research Database (Denmark)

Bezzina, Connie; Barc, Julien; Mizusawa, Yuka

2013-01-01

Brugada syndrome is a rare cardiac arrhythmia disorder, causally related to SCN5A mutations in around 20% of cases. Through a genome-wide association study of 312 individuals with Brugada syndrome and 1,115 controls, we detected 2 significant association signals at the SCN10A locus (rs10428132) a...

Thyrotoxic periodic paralysis associated with a mutation in the sodium channel gene SCN4A.

Science.gov (United States)

Lane, Andrew H; Markarian, Katherine; Braziunene, Ieva

2004-12-01

Thyrotoxic hypokalemic periodic paralysis (THypoKPP) is an uncommon disorder with an unknown etiology. We describe a family in which the proband presented with paralysis and thyrotoxicosis. Because of similarities between familial hypokalemic periodic paralysis (FHypoKPP) and THypoKPP, we sequenced exon 12 of the SCN4A gene, which is known to be mutated in FHypoKPP. We identified an Arg672Ser mutation in the proband and his affected father, as well as the proband's brother. As the brother has paralysis without thyrotoxicosis, our finding suggests that the genetic spectrum of FHypoKPP and THypoKPP overlap. We speculate that thyroid hormone may exert a threshold or permissive effect in hypokalemic periodic paralysis. Non-thyrotoxic family members of individuals with THypoKPP may have an unrecognized risk for paralysis.

Preliminary Plugging tests in Narrow Sodium Channels by Sodium and Carbon Dioxide reaction

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-05-15

This report is on the investigation of the physical/chemical phenomena that a slow loss of CO{sub 2} inventory into sodium after the sodium-CO{sub 2} boundary failure in PCHEs in realistic operating conditions. The first phenomenon is potential channel plugging inside the narrow PCHE channel. Unlike a conventional shell and- tube type HXs, failures in a PCHE are expected to be small cracks. If the faulted channel is blocked, it may have a positive function for plant safety because the pressure boundary would automatically recover due to this self-plugging. The other one is damage propagation on pressure boundary, which is referred to as potential wastage with combined corrosion/erosion effect. Physical/chemical phenomena that a slow loss of CO{sub 2} inventory into sodium after the sodium-CO{sub 2} boundary failure in printed circuit heat exchangers (PCHEs) were investigated. Our preliminary experimental results of plugging show that sodium flow immediately stopped as CO{sub 2} was injected through the nozzle at 300-400 .deg. C in 3 mm sodium channels, whereas sodium flow stopped about 60 min after CO{sub 2} injection in 5 mm sodium channels.

Identification of SCN1A and PCDH19 mutations in Chinese children with Dravet syndrome.

Directory of Open Access Journals (Sweden)

Anna Ka-Yee Kwong

Full Text Available BACKGROUND: Dravet syndrome is a severe form of epilepsy. Majority of patients have a mutation in SCN1A gene, which encodes a voltage-gated sodium channel. A recent study has demonstrated that 16% of SCN1A-negative patients have a mutation in PCDH19, the gene encoding protocadherin-19. Mutations in other genes account for only a very small proportion of families. TSPYL4 is a novel candidate gene within the locus 6q16.3-q22.31 identified by linkage study. OBJECTIVE: The present study examined the mutations in epileptic Chinese children with emphasis on Dravet syndrome. METHODS: A hundred children with severe epilepsy were divided into Dravet syndrome and non-Dravet syndrome groups and screened for SCN1A mutations by direct sequencing. SCN1A-negative Dravet syndrome patients and patients with phenotypes resembling Dravet syndrome were checked for PCDH19 and TSPYL4 mutations. RESULTS: Eighteen patients (9 males, 9 females were diagnosed to have Dravet syndrome. Among them, 83% (15/18 had SCN1A mutations including truncating (7, splice site (2 and missense mutations (6. The truncating/splice site mutations were associated with moderate to severe degree of intellectual disability (p<0.05. During the progression of disease, 73% (11/15 had features fitting into the diagnostic criteria of autism spectrum disorder and 53% (8/15 had history of vaccination-induced seizures. A novel PCDH19 p.D377N mutation was identified in one SCN1A-negative female patient with Dravet syndrome and a known PCDH19 p.N340S mutation in a female non-Dravet syndrome patient. The former also inherited a TSPYL4 p.G60R variant. CONCLUSION: A high percentage of SCN1A mutations was identified in our Chinese cohort of Dravet syndrome patients but none in the rest of patients. We demonstrated that truncating/splice site mutations were linked to moderate to severe intellectual disability in these patients. A de novo PCDH19 missense mutation together with an inherited TSPYL4 missense

Changes in action potentials and intracellular ionic homeostasis in a ventricular cell model related to a persistent sodium current in SCN5A mutations underlying LQT3

Czech Academy of Sciences Publication Activity Database

Christé, G.; Chahine, M.; Chevalier, P.; Pásek, Michal

2008-01-01

Roč. 96, - (2008), s. 281-293 ISSN 0079-6107 Institutional research plan: CEZ:AV0Z20760514 Keywords : cardiac cell * SCN5A mutation * Long QT syndrome * quantitative modelling Subject RIV: BO - Biophysics Impact factor: 6.388, year: 2008

Voltage-Gated Sodium Channel β1/β1B Subunits Regulate Cardiac Physiology and Pathophysiology

Directory of Open Access Journals (Sweden)

Nnamdi Edokobi

2018-04-01

Full Text Available Cardiac myocyte contraction is initiated by a set of intricately orchestrated electrical impulses, collectively known as action potentials (APs. Voltage-gated sodium channels (NaVs are responsible for the upstroke and propagation of APs in excitable cells, including cardiomyocytes. NaVs consist of a single, pore-forming α subunit and two different β subunits. The β subunits are multifunctional cell adhesion molecules and channel modulators that have cell type and subcellular domain specific functional effects. Variants in SCN1B, the gene encoding the Nav-β1 and -β1B subunits, are linked to atrial and ventricular arrhythmias, e.g., Brugada syndrome, as well as to the early infantile epileptic encephalopathy Dravet syndrome, all of which put patients at risk for sudden death. Evidence over the past two decades has demonstrated that Nav-β1/β1B subunits play critical roles in cardiac myocyte physiology, in which they regulate tetrodotoxin-resistant and -sensitive sodium currents, potassium currents, and calcium handling, and that Nav-β1/β1B subunit dysfunction generates substrates for arrhythmias. This review will highlight the role of Nav-β1/β1B subunits in cardiac physiology and pathophysiology.

Evaluation of Presumably Disease Causing SCN1A Variants in a Cohort of Common Epilepsy Syndromes

DEFF Research Database (Denmark)

Lal, Dennis; Reinthaler, Eva M; Dejanovic, Borislav

2016-01-01

OBJECTIVE: The SCN1A gene, coding for the voltage-gated Na+ channel alpha subunit NaV1.1, is the clinically most relevant epilepsy gene. With the advent of high-throughput next-generation sequencing, clinical laboratories are generating an ever-increasing catalogue of SCN1A variants. Variants are...

Targeting sodium channels in cardiac arrhythmia

NARCIS (Netherlands)

Remme, Carol Ann; Wilde, Arthur A. M.

2014-01-01

Cardiac voltage-gated sodium channels are responsible for proper electrical conduction in the heart. During acquired pathological conditions and inherited sodium channelopathies, altered sodium channel function causes conduction disturbances and ventricular arrhythmias. Although the clinical,

Amiloride-Sensitive Sodium Channels and Pulmonary Edema

Directory of Open Access Journals (Sweden)

Mike Althaus

2011-01-01

Full Text Available The development of pulmonary edema can be considered as a combination of alveolar flooding via increased fluid filtration, impaired alveolar-capillary barrier integrity, and disturbed resolution due to decreased alveolar fluid clearance. An important mechanism regulating alveolar fluid clearance is sodium transport across the alveolar epithelium. Transepithelial sodium transport is largely dependent on the activity of sodium channels in alveolar epithelial cells. This paper describes how sodium channels contribute to alveolar fluid clearance under physiological conditions and how deregulation of sodium channel activity might contribute to the pathogenesis of lung diseases associated with pulmonary edema. Furthermore, sodium channels as putative molecular targets for the treatment of pulmonary edema are discussed.

Compound heterozygosity for mutations (W156X and R225W) in SCN5A associated with severe cardiac conduction disturbances and degenerative changes in the conduction system

NARCIS (Netherlands)

Bezzina, Connie R.; Rook, Martin B.; Groenewegen, W. Antoinette; Herfst, Lucas J.; van der Wal, Allard C.; Lam, Jan; Jongsma, Habo J.; Wilde, Arthur A. M.; Mannens, Marcel M. A. M.

2003-01-01

Cardiac conduction defects associate with mutations in SCN5A, the gene encoding the cardiac Na+ channel. In the present study, we characterized a family in which the proband was born in severe distress with irregular wide complex tachycardia. His older sister died at 1 year of age from severe

Pseudohalide (SCN(-))-Doped MAPbI3 Perovskites: A Few Surprises.

Science.gov (United States)

Halder, Ansuman; Chulliyil, Ramya; Subbiah, Anand S; Khan, Tuhin; Chattoraj, Shyamtanu; Chowdhury, Arindam; Sarkar, Shaibal K

2015-09-03

Pseudohalide thiocyanate anion (SCN(-)) has been used as a dopant in a methylammonium lead tri-iodide (MAPbI3) framework, aiming for its use as an absorber layer for photovoltaic applications. The substitution of SCN(-) pseudohalide anion, as verified using Fourier transform infrared (FT-IR) spectroscopy, results in a comprehensive effect on the optical properties of the original material. Photoluminescence measurements at room temperature reveal a significant enhancement in the emission quantum yield of MAPbI3-x(SCN)x as compared to MAPbI3, suggestive of suppression of nonradiative channels. This increased intensity is attributed to a highly edge specific emission from MAPbI3-x(SCN)x microcrystals as revealed by photoluminescence microscopy. Fluoresence lifetime imaging measurements further established contrasting carrier recombination dynamics for grain boundaries and the bulk of the doped material. Spatially resolved emission spectroscopy on individual microcrystals of MAPbI3-x(SCN)x reveals that the optical bandgap and density of states at various (local) nanodomains are also nonuniform. Surprisingly, several (local) emissive regions within MAPbI3-x(SCN)x microcrystals are found to be optically unstable under photoirradiation, and display unambiguous temporal intermittency in emission (blinking), which is extremely unusual and intriguing. We find diverse blinking behaviors for the undoped MAPbI3 crystals as well, which leads us to speculate that blinking may be a common phenomenon for most hybrid perovskite materials.

Design of a Nested Eight-Channel Sodium and Four-Channel Proton Coil for 7 Tesla Knee Imaging

Science.gov (United States)

Brown, Ryan; Madelin, Guillaume; Lattanzi, Riccardo; Chang, Gregory; Regatte, Ravinder R.; Sodickson, Daniel K.; Wiggins, Graham C.

2012-01-01

The critical design aim for a dual-tuned sodium/proton coil is to maximize sodium sensitivity and transmit field (B1+) homogeneity while simultaneously providing adequate proton sensitivity and homogeneity. While most dual-frequency coils utilize lossy high-impedance trap circuits or PIN diodes to allow dual-resonance, we explored a nested-coil design for sodium/proton knee imaging at 7T. A stand-alone eight-channel sodium receive array was implemented without standard dual-resonance circuitry to provide improved sodium signal-to-noise ratio (SNR) over a volume coil. A detunable sodium birdcage was added for homogeneous sodium excitation and a four-channel proton transmit-receive array was added to provide anatomical reference imaging and B0 shimming capability. Both modules were implemented with minimal disturbance to the eight-channel sodium array by managing their respective resonances and geometrical arrangement. In vivo sodium SNR was 1.2 to 1.7 times greater in the developed eight-channel array than in a mono-nuclear sodium birdcage coil, while the developed four-channel proton array provided SNR similar to that of a commercial mono-nuclear proton birdcage coil. PMID:22887123

Sodium Channel (Dys)Function and Cardiac Arrhythmias

NARCIS (Netherlands)

Remme, Carol Ann; Bezzina, Connie R.

2010-01-01

P>Cardiac voltage-gated sodium channels are transmembrane proteins located in the cell membrane of cardiomyocytes. Influx of sodium ions through these ion channels is responsible for the initial fast upstroke of the cardiac action potential. This inward sodium current thus triggers the initiation

Molecular and kinetic determinants of local anaesthetic action on sodium channels.

Science.gov (United States)

French, R J; Zamponi, G W; Sierralta, I E

1998-11-23

(1) Local anaesthetics (LA) rely for their clinical actions on state-dependent inhibition of voltage-dependent sodium channels. (2) Single, batrachoxin-modified sodium channels in planar lipid bilayers allow direct observation of drug-channel interactions. Two modes of inhibition of single-channel current are observed: fast block of the open channels and prolongation of a long-lived closed state, some of whose properties resemble those of the inactivated state of unmodified channels. (3) Analogues of different parts of the LA molecule separately mimic each blocking mode: amines--fast block, and water-soluble aromatics--closed state prolongation. (4) Interaction between a mu-conotoxin derivative and diethylammonium indicate an intrapore site of fast, open-state block. (5) Site-directed mutagenesis studies suggest that hydrophobic residues in transmembrane segment 6 of repeat domain 4 of sodium channels are critical for both LA binding and stabilization of the inactivated state.

Investigation of Plugging of Narrow Sodium Channels by Sodium and Carbon Dioxide Interaction

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong; Kim, Tae-joon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

The supercritical CO{sub 2} Brayton cycle system is known to be a promising power conversion system for improving the efficiency and preventing the sodium water reaction (SWR) of the current SFR concept using a Rankine steam cycle. PCHEs are known to have potential for reducing the volume occupied by the sodium-to-CO{sub 2} exchangers as well as the heat exchanger mass relative to traditional shell-and-tube heat exchangers. Here, we report a study on a plugging test by the interaction of sodium and CO{sub 2} to investigate design parameters of sodium channels in the realistic operating conditions. We investigated a plugging test by an interaction of sodium and CO{sub 2} with different cross sectional areas of the sodium channels. It was found that the flow rate of sodium decreased earlier and faster with a narrower cross sectional area compared to a wider one. Our experimental results are expected to be used for determining the sodium channel areas of PCHEs.

Cardiac safety implications of hNav1.5 blockade and a framework for preclinical evaluation

Directory of Open Access Journals (Sweden)

Gul eErdemli

2012-01-01

Full Text Available The human cardiac sodium channel (hNav1.5, encoded by the SCN5A gene is critical for action potential generation and propagation in the heart. Drug-induced sodium channel inhibition decreases the rate of cardiomyocyte depolarization and consequently conduction velocity and can have serious implications for cardiac safety. Genetic mutations in hNav1.5 have also been linked to a number of cardiac diseases. Therefore, off-target hNav1.5 inhibition may be considered a risk marker for a drug candidate. Given the potential safety implications for patients and the costs of late stage drug development, detection and mitigation of hNav1.5 liabilities early in drug discovery and development becomes important. In this review, we describe a preclinical strategy to identify hNav1.5 liabilities that incorporates in vitro, in vivo, and in silico techniques and the application of this information in the integrated risk assessment at different stages of drug discovery and development.

Activation of protein kinase C alters the intracellular distribution and mobility of cardiac Na+ channels.

Science.gov (United States)

Hallaq, Haifa; Wang, Dao W; Kunic, Jennifer D; George, Alfred L; Wells, K Sam; Murray, Katherine T

2012-02-01

Na(+) current derived from expression of the cardiac isoform SCN5A is reduced by receptor-mediated or direct activation of protein kinase C (PKC). Previous work has suggested a possible role for loss of Na(+) channels at the plasma membrane in this effect, but the results are controversial. In this study, we tested the hypothesis that PKC activation acutely modulates the intracellular distribution of SCN5A channels and that this effect can be visualized in living cells. In human embryonic kidney cells that stably expressed SCN5A with green fluorescent protein (GFP) fused to the channel COOH-terminus (SCN5A-GFP), Na(+) currents were suppressed by an exposure to PKC activation. Using confocal microscopy, colocalization of SCN5A-GFP channels with the plasma membrane under control and stimulated conditions was quantified. A separate population of SCN5A channels containing an extracellular epitope was immunolabeled to permit temporally stable labeling of the plasma membrane. Our results demonstrated that Na(+) channels were preferentially trafficked away from the plasma membrane by PKC activation, with a major contribution by Ca(2+)-sensitive or conventional PKC isoforms, whereas stimulation of protein kinase A (PKA) had the opposite effect. Removal of the conserved PKC site Ser(1503) or exposure to the NADPH oxidase inhibitor apocynin eliminated the PKC-mediated effect to alter channel trafficking, indicating that both channel phosphorylation and ROS were required. Experiments using fluorescence recovery after photobleaching demonstrated that both PKC and PKA also modified channel mobility in a manner consistent with the dynamics of channel distribution. These results demonstrate that the activation of protein kinases can acutely regulate the intracellular distribution and molecular mobility of cardiac Na(+) channels in living cells.

Cation gating and selectivity in a purified, reconstituted, voltage-dependent sodium channel

International Nuclear Information System (INIS)

Barchi, R.L.; Tanaka, J.C.

1984-01-01

In excitable membranes, the voltage-dependent sodium channel controls the primary membrane conductance change necessary for the generation of an action potential. Over the past four decades, the time- and voltage-dependent sodium currents gated by this channel have been thoroughly documented with increasingly sophisticated voltage-clamp techniques. Recent advances in the biochemistry of membrane proteins have led to the solubilization and purification of this channel protein from nerve (6) and from muscle (4) or muscle-derived (1) membranes, and have provided an approach to the correlation of the channel's molecular structure with its functional properties. Each of these sodium channel preparations appears to contain a large glycoprotein either as its sole component (2) or in association with several small subunits (6, 3). Evidence that these purified proteins represent the excitable membrane sodium channel is presented. 8 refs., 1 fig., 1 tab

Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family.

Science.gov (United States)

Kaufman, I; Luchinsky, D G; Tindjong, R; McClintock, P V E; Eisenberg, R S

2013-11-01

We use Brownian dynamics (BD) simulations to study the ionic conduction and valence selectivity of a generic electrostatic model of a biological ion channel as functions of the fixed charge Q(f) at its selectivity filter. We are thus able to reconcile the discrete calcium conduction bands recently revealed in our BD simulations, M0 (Q(f)=1e), M1 (3e), M2 (5e), with a set of sodium conduction bands L0 (0.5e), L1 (1.5e), thereby obtaining a completed pattern of conduction and selectivity bands vs Q(f) for the sodium-calcium channels family. An increase of Q(f) leads to an increase of calcium selectivity: L0 (sodium-selective, nonblocking channel) → M0 (nonselective channel) → L1 (sodium-selective channel with divalent block) → M1 (calcium-selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L0 band is putatively identified with the eukaryotic sodium channel The scheme created is able to account for the experimentally observed mutation-induced transformations between nonselective channels, sodium-selective channels, and calcium-selective channels, which we interpret as transitions between different rows of the identification table. By considering the potential energy changes during permeation, we show explicitly that the multi-ion conduction bands of calcium and sodium channels arise as the result of resonant barrierless conduction. The pattern of periodic conduction bands is explained on the basis of sequential neutralization taking account of self-energy, as Q(f)(z,i)=ze(1/2+i), where i is the order of the band and z is the valence of the ion. Our results confirm the crucial influence of electrostatic interactions on conduction and on the Ca(2+)/Na(+) valence selectivity of calcium and sodium ion channels. The model and results could be also applicable to biomimetic nanopores with charged walls.

Visualizing individual sodium channels on the move.

Science.gov (United States)

Heinemann, Stefan H

2012-07-27

Visualization of voltage-gated sodium channels at work is an important requirement for the understanding of rapid electrical signaling in nerve cells. In this issue of Chemistry & Biology, Ondrus and colleagues have mastered this challenge by chemical synthesis of a fluorescent antagonist and by monitoring single sodium channels in living cells with unprecedented optical resolution. Copyright © 2012 Elsevier Ltd. All rights reserved.

Slack, Slick, and Sodium-Activated Potassium Channels

Science.gov (United States)

Kaczmarek, Leonard K.

2013-01-01

The Slack and Slick genes encode potassium channels that are very widely expressed in the central nervous system. These channels are activated by elevations in intracellular sodium, such as those that occur during trains of one or more action potentials, or following activation of nonselective cationic neurotransmitter receptors such as AMPA receptors. This review covers the cellular and molecular properties of Slack and Slick channels and compares them with findings on the properties of sodium-activated potassium currents (termed KNa currents) in native neurons. Human mutations in Slack channels produce extremely severe defects in learning and development, suggesting that KNa channels play a central role in neuronal plasticity and intellectual function. PMID:24319675

Sodium Channel Mutations and Pyrethroid Resistance in Aedes aegypti

Directory of Open Access Journals (Sweden)

Yuzhe Du

2016-10-01

Full Text Available Pyrethroid insecticides are widely used to control insect pests and human disease vectors. Voltage-gated sodium channels are the primary targets of pyrethroid insecticides. Mutations in the sodium channel have been shown to be responsible for pyrethroid resistance, known as knockdown resistance (kdr, in various insects including mosquitoes. In Aedes aegypti mosquitoes, the principal urban vectors of dengue, zika, and yellow fever viruses, multiple single nucleotide polymorphisms in the sodium channel gene have been found in pyrethroid-resistant populations and some of them have been functionally confirmed to be responsible for kdr in an in vitro expression system, Xenopus oocytes. This mini-review aims to provide an update on the identification and functional characterization of pyrethroid resistance-associated sodium channel mutations from Aedes aegypti. The collection of kdr mutations not only helped us develop molecular markers for resistance monitoring, but also provided valuable information for computational molecular modeling of pyrethroid receptor sites on the sodium channel.

Reduced Penetrance and Variable Expression of SCN5A Mutations and the Importance of Co-inherited Genetic Variants: Case Report and Review of the Literature

Directory of Open Access Journals (Sweden)

T. Robyns, MD.

2014-05-01

Full Text Available Mutations in the SCN5A gene are responsible for multiple phenotypical presentations including Brugada syndrome, long QT syndrome, progressive familial heart block, sick sinus syndrome, dilated cardiomyopathy, lone atrial fibrillation and multiple overlap syndromes. These different phenotypic expressions of a mutation in a single gene can be explained by variable expression and reduced penetrance. One of the possible explanations of these phenomena is the co-inheritance of genetic variants. We describe a family where the individuals exhibit a compound heterozygosity in the SCN5A gene including a mutation (R1632H and a new variant (M858L. Individuals with both the mutation and new variant present with a more severe phenotype including spontaneous atrial tachyarrhythmia at young age. We give an overview of the different phenotypes of "SCN5A disease" and discuss the importance of co-inherited genetic variants in the expression of SCN5A disease.

Functionalized Fullerene Targeting Human Voltage-Gated Sodium Channel, hNav1.7.

Science.gov (United States)

Hilder, Tamsyn A; Robinson, Anna; Chung, Shin-Ho

2017-08-16

Mutations of hNa v 1.7 that cause its activities to be enhanced contribute to severe neuropathic pain. Only a small number of hNa v 1.7 specific inhibitors have been identified, most of which interact with the voltage-sensing domain of the voltage-activated sodium ion channel. In our previous computational study, we demonstrated that a [Lys 6 ]-C 84 fullerene binds tightly (affinity of 46 nM) to Na v Ab, the voltage-gated sodium channel from the bacterium Arcobacter butzleri. Here, we extend this work and, using molecular dynamics simulations, demonstrate that the same [Lys 6 ]-C 84 fullerene binds strongly (2.7 nM) to the pore of a modeled human sodium ion channel hNa v 1.7. In contrast, the fullerene binds only weakly to a mutated model of hNa v 1.7 (I1399D) (14.5 mM) and a model of the skeletal muscle hNa v 1.4 (3.7 mM). Comparison of one representative sequence from each of the nine human sodium channel isoforms shows that only hNa v 1.7 possesses residues that are critical for binding the fullerene derivative and blocking the channel pore.

Simplified numerical simulation of hot channel in sodium cooled reactor

International Nuclear Information System (INIS)

Fonseca, F. de A.S. da; Silva Filho, E.

1988-12-01

The thermal-hydraulic parameter values that restrict the operation of a liquid sodium cooled reactor are not established by the average conditions of the coolant in the reactor core but by the extreme conditions of the hot channel. The present work was developed to analysis of hot channel of a sodium cooled reactor, adapting to this reactor an existent simplified model for hot channel of pressurized water reactor. The model was applied for a standard sodium reactor and the results are considered satisfatory. (author) [pt

Role of aquaporin and sodium channel in pleural water movement.

Science.gov (United States)

Jiang, Jinjun; Hu, Jie; Bai, Chunxue

2003-12-16

The role of the ENaC sodium channel and aquaporin-1 (AQP1) water channel on pleural fluid dynamics in mice was investigated. 0.25 ml of hypertonic or isosmolar fluid was infused into the pleural space in anesthetized wildtype and AQP1 null mice. Pleural fluid was sampled at specified times to quantify the osmolality and volume. The sodium channel activator terbutaline increased isosmolar fluid clearance by 90% while the sodium channel inhibitor amiloride decreased it by 15%, but had no effect on osmotically driven water transport. AQP1 deletion significantly decreased osmotic water transport in pleural space by twofold, but it had no effect on isosmolar fluid clearance. Pretreatment with dexamethasone increased pleural osmotic fluid entry by 25%, while intravenous injection of HgCl2 decreased osmotic pleural water movement by 43%. These results provided evidence for a role of a sodium channel in pleural fluid absorption; AQP1 plays a major role in osmotic liquid transport but it does not affect isosmolar fluid clearance.

Rab27a regulates epithelial sodium channel (ENaC) activity through synaptotagmin-like protein (SLP-5) and Munc13-4 effector mechanism

International Nuclear Information System (INIS)

Saxena, Sunil K.; Horiuchi, Hisanori; Fukuda, Mitsunori

2006-01-01

Liddle's syndrome (excessive absorption of sodium ions) and PHA-1 (pseudohypoaldosteronism type 1) with decreased sodium absorption are caused by the mutations in the amiloride-sensitive epithelial sodium channel ENaC. Rab proteins are small GTPases involved in vesicle transport, docking, and fusion. Earlier, we reported that Rab27a inhibits ENaC-mediated currents through protein-protein interaction in HT-29 cells. We hereby report that Rab27a-dependent inhibition is associated with the GTP/GDP status as constitutively active or GTPase-deficient mutant Q78L inhibits amiloride-sensitive currents whereas GDP-locked inactive mutant T23N showed no effect. In order to further explore the molecular mechanism of this regulation, we performed competitive assays with two Rab27a-binding proteins: synaptotagmin-like protein (SLP-5) and Munc13-4 (a putative priming factor for exocytosis). Both proteins eliminate negative modulation of Rab27a on ENaC function. The SLP-5 reversal of Rab27a effect was restricted to C-terminal C2A/C2B domains assigned for putative phospholipids-binding function while the Rab27a-binding SHD motif imparted higher inhibition. The ENaC-mediated currents remain unaffected by Rab27a though SLP-5 appears to strongly bind it. The immunoprecipitation experiments suggest that in the presence of excessive Munc13-4 and SLP-5 proteins, Rab27a interaction with ENaC is diminished. Munc13-4 and SLP-5 limit the Rab27a availability to ENaC, thus minimizing its effect on channel function. These observations decisively prove that Rab27a inhibits ENaC function through a complex mechanism that involves GTP/GDP status, and protein-protein interactions involving Munc13-4 and SLP-5 effector proteins

Generation of the SCN1A epilepsy mutation in hiPS cells using the TALEN technique

Science.gov (United States)

Chen, Wanjuan; Liu, Jingxin; Zhang, Longmei; Xu, Huijuan; Guo, Xiaogang; Deng, Sihao; Liu, Lipeng; Yu, Daiguan; Chen, Yonglong; Li, Zhiyuan

2014-06-01

Human induced pluripotent stem cells (iPSC) can be used to understand the pathological mechanisms of human disease. These cells are a promising source for cell-replacement therapy. However, such studies require genetically defined conditions. Such genetic manipulations can be performed using the novel Transcription Activator-Like Effector Nucleases (TALENs), which generate site-specific double-strand DNA breaks (DSBs) with high efficiency and precision. Combining the TALEN and iPSC methods, we developed two iPS cell lines by generating the point mutation A5768G in the SCN1A gene, which encodes the voltage-gated sodium channel Nav1.1 α subunit. The engineered iPSC maintained pluripotency and successfully differentiated into neurons with normal functional characteristics. The two cell lines differ exclusively at the epilepsy-susceptibility variant. The ability to robustly introduce disease-causing point mutations in normal hiPS cell lines can be used to generate a human cell model for studying epileptic mechanisms and for drug screening.

Voltage-gated sodium channels: action players with many faces

NARCIS (Netherlands)

Koopmann, Tamara T.; Bezzina, Connie R.; Wilde, Arthur A. M.

2006-01-01

Voltage-gated sodium channels are responsible for the upstroke of the action potential and thereby play an important role in propagation of the electrical impulse in excitable tissues like muscle, nerve and the heart. Duplication of the sodium channels encoding genes during evolution generated the

A negative charge in transmembrane segment 1 of domain II of the cockroach sodium channel is critical for channel gating and action of pyrethroid insecticides

International Nuclear Information System (INIS)

Du Yuzhe; Song Weizhong; Groome, James R.; Nomura, Yoshiko; Luo Ningguang; Dong Ke

2010-01-01

Voltage-gated sodium channels are the primary target of pyrethroids, an important class of synthetic insecticides. Pyrethroids bind to a distinct receptor site on sodium channels and prolong the open state by inhibiting channel deactivation and inactivation. Recent studies have begun to reveal sodium channel residues important for pyrethroid binding. However, how pyrethroid binding leads to inhibition of sodium channel deactivation and inactivation remains elusive. In this study, we show that a negatively charged aspartic acid residue at position 802 (D802) located in the extracellular end of transmembrane segment 1 of domain II (IIS1) is critical for both the action of pyrethroids and the voltage dependence of channel activation. Charge-reversing or -neutralizing substitutions (K, G, or A) of D802 shifted the voltage dependence of activation in the depolarizing direction and reduced channel sensitivity to deltamethrin, a pyrethroid insecticide. The charge-reversing mutation D802K also accelerated open-state deactivation, which may have counteracted the inhibition of sodium channel deactivation by deltamethrin. In contrast, the D802G substitution slowed open-state deactivation, suggesting an additional mechanism for neutralizing the action of deltamethrin. Importantly, Schild analysis showed that D802 is not involved in pyrethroid binding. Thus, we have identified a sodium channel residue that is critical for regulating the action of pyrethroids on the sodium channel without affecting the receptor site of pyrethroids.

Vibrational Analysis of (SCN)2 and the Transient (SCN)2

DEFF Research Database (Denmark)

Jensen, N. H.; Wilbrandt, Robert Walter; Pagsberg, Palle Bjørn

1979-01-01

The vibrational spectra of thiocyanogen and the transient radical anion (SCN)2− are interpreted in detail through molecular orbital and normal coordinate calculations. The results support the assignment of (SCN)2− to the anion of thiocyanogen and indicate a substantial weakening of the S–S and C......≡N bonds in going from the parent molecule to its radical anion....

Cardiac sodium channel Na(v)1.5 interacts with and is regulated by the protein tyrosine phosphatase PTPH1

DEFF Research Database (Denmark)

Jespersen, Thomas; Gavillet, Bruno; van Bemmelen, Miguel X

2006-01-01

In order to identify proteins interacting with the cardiac voltage-gated sodium channel Na(v)1.5, we used the last 66 amino acids of the C-terminus of the channel as bait to screen a human cardiac cDNA library. We identified the protein tyrosine phosphatase PTPH1 as an interacting protein. Pull......-down experiments confirmed the interaction, and indicated that it depends on the PDZ-domain binding motif of Na(v)1.5. Co-expression experiments in HEK293 cells showed that PTPH1 shifts the Na(v)1.5 availability relationship toward hyperpolarized potentials, whereas an inactive PTPH1 or the tyrosine kinase Fyn...... does the opposite. The results of this study suggest that tyrosine phosphorylation destabilizes the inactivated state of Na(v)1.5....

(Liquid + liquid) equilibria for benzene + cyclohexane + N,N-dimethylformamide + sodium thiocyanate

International Nuclear Information System (INIS)

Dong, Hongxing; Yang, Xiaoguang; Yue, Guojun; Zhang, Wei; Zhang, Jin

2013-01-01

Graphical abstract: On the left, the figure was phase diagram about the LLE date. On the right, the figure was about the effects of mass fraction of benzene in the raffinate phase to the selectivity(S) coefficient under different salt concentration. ■, the NaSCN and DMF in ratio of 5/95; • , the NaSCN and DMF in ratio of 10/90; ▴, the NaSCN and DMF in ratio of 15/85; ★, the NaSCN and DMF in ratio of 20/80; ▾, the NaSCN and DMF in ratio of 23/77. ♦, only DMF was used extractant (the selectivity coefficient was calculated by literature 17). w 22 , refer to the mass fraction of benzene in the raffinate phase (cyclohexane-rich phase). Highlights: • (Liquid + liquid) equilibrium for quaternary system was measured. • The components include benzene, cyclohexane, N,N-dimethylformamide, sodium thiocyanate. • The (liquid + liquid) equilibrium data can be well correlated by the NRTL model. • Separation of benzene and cyclohexane by NaSCN + DMF was discussed. -- Abstract: (Liquid + liquid) equilibrium (LLE) data for benzene + cyclohexane + N,N-dimethylformamide (DMF) + sodium thiocyanate (NaSCN) were measured experimentally at atmospheric pressure and 303.15 K. The selectivity coefficients from these LLE data were calculated and compared to those previously reported in the literature for the systems (benzene + cyclohexane + DMF) and (benzene + cyclohexane + DMF + KSCN). The NRTL equation was used to correlate the experimental data. The agreement between the predicted and experimental results was good. It was found that the selectivity coefficients of DMF + NaSCN for benzene ranged from 2.45 to 11.99. Considering the relatively high extraction capacity and selectivity for benzene, DMF + NaSCN may be used as a potential extracting solvent for the separation of benzene from cyclohexane

Intracellular calcium modulation of voltage-gated sodium channels in ventricular myocytes

NARCIS (Netherlands)

Casini, Simona; Verkerk, Arie O.; van Borren, Marcel M. G. J.; van Ginneken, Antoni C. G.; Veldkamp, Marieke W.; de Bakker, Jacques M. T.; Tan, Hanno L.

2009-01-01

AIMS: Cardiac voltage-gated sodium channels control action potential (AP) upstroke and cell excitability. Intracellular calcium (Ca(i)(2+)) regulates AP properties by modulating various ion channels. Whether Ca(i)(2+) modulates sodium channels in ventricular myocytes, is unresolved. We studied

Development and utilization of a fluorescence-based receptor-binding assay for the site 5 voltage-sensitive sodium channel ligands brevetoxin and ciguatoxin.

Science.gov (United States)

McCall, Jennifer R; Jacocks, Henry M; Niven, Susan C; Poli, Mark A; Baden, Daniel G; Bourdelais, Andrea J

2014-01-01

Brevetoxins are a family of ladder-frame polyether toxins produced during blooms of the marine dinoflagellate Karenia brevis. Consumption of fish exposed to K. brevis blooms can lead to the development of neurotoxic shellfish poisoning. The toxic effects of brevetoxins are due to activation of voltage-sensitive sodium channels (VSSCs) in cell membranes. Binding of toxins has historically been measured using a radioligand competition assay that is fraught with difficulty. In this study, we developed a novel fluorescence-based binding assay for the brevetoxin receptor. Several fluorophores were conjugated to polyether brevetoxin-2 and used as the labeled ligand. Brevetoxin analogs were able to compete for binding with the fluorescent ligands. This assay was qualified against the standard radioligand receptor assay for the brevetoxin receptor. Furthermore, the fluorescence-based assay was used to determine relative concentrations of toxins in raw extracts of K. brevis culture, and to determine ciguatoxin affinity to site 5 of VSSCs. The fluorescence-based assay was quicker, safer, and far less expensive. As such, this assay can be used to replace the current radioligand assay and will be a vital tool for future experiments examining the binding affinity of various ligands for site 5 on sodium channels.

Comparative effects of sodium channel blockers in short term rat whole embryo culture

Energy Technology Data Exchange (ETDEWEB)

Nilsson, Mats F, E-mail: Mats.Nilsson@farmbio.uu.se [Department of Pharmaceutical Biosciences, Uppsala University (Sweden); Sköld, Anna-Carin; Ericson, Ann-Christin; Annas, Anita; Villar, Rodrigo Palma [AstraZeneca R and D Södertälje (Sweden); Cebers, Gvido [AstraZeneca R and D, iMed, 141 Portland Street, Cambridge, MA 02139 (United States); Hellmold, Heike; Gustafson, Anne-Lee [AstraZeneca R and D Södertälje (Sweden); Webster, William S [Department of Anatomy and Histology, University of Sydney (Australia)

2013-10-15

This study was undertaken to examine the effect on the rat embryonic heart of two experimental drugs (AZA and AZB) which are known to block the sodium channel Nav1.5, the hERG potassium channel and the L-type calcium channel. The sodium channel blockers bupivacaine, lidocaine, and the L-type calcium channel blocker nifedipine were used as reference substances. The experimental model was the gestational day (GD) 13 rat embryo cultured in vitro. In this model the embryonic heart activity can be directly observed, recorded and analyzed using computer assisted image analysis as it responds to the addition of test drugs. The effect on the heart was studied for a range of concentrations and for a duration up to 3 h. The results showed that AZA and AZB caused a concentration-dependent bradycardia of the embryonic heart and at high concentrations heart block. These effects were reversible on washout. In terms of potency to cause bradycardia the compounds were ranked AZB > bupivacaine > AZA > lidocaine > nifedipine. Comparison with results from previous studies with more specific ion channel blockers suggests that the primary effect of AZA and AZB was sodium channel blockage. The study shows that the short-term rat whole embryo culture (WEC) is a suitable system to detect substances hazardous to the embryonic heart. - Highlights: • Study of the effect of sodium channel blocking drugs on embryonic heart function • We used a modified method rat whole embryo culture with image analysis. • The drugs tested caused a concentration dependent bradycardia and heart block. • The effect of drugs acting on multiple ion channels is difficult to predict. • This method may be used to detect cardiotoxicity in prenatal development.

Comparative effects of sodium channel blockers in short term rat whole embryo culture

International Nuclear Information System (INIS)

Nilsson, Mats F; Sköld, Anna-Carin; Ericson, Ann-Christin; Annas, Anita; Villar, Rodrigo Palma; Cebers, Gvido; Hellmold, Heike; Gustafson, Anne-Lee; Webster, William S

2013-01-01

This study was undertaken to examine the effect on the rat embryonic heart of two experimental drugs (AZA and AZB) which are known to block the sodium channel Nav1.5, the hERG potassium channel and the L-type calcium channel. The sodium channel blockers bupivacaine, lidocaine, and the L-type calcium channel blocker nifedipine were used as reference substances. The experimental model was the gestational day (GD) 13 rat embryo cultured in vitro. In this model the embryonic heart activity can be directly observed, recorded and analyzed using computer assisted image analysis as it responds to the addition of test drugs. The effect on the heart was studied for a range of concentrations and for a duration up to 3 h. The results showed that AZA and AZB caused a concentration-dependent bradycardia of the embryonic heart and at high concentrations heart block. These effects were reversible on washout. In terms of potency to cause bradycardia the compounds were ranked AZB > bupivacaine > AZA > lidocaine > nifedipine. Comparison with results from previous studies with more specific ion channel blockers suggests that the primary effect of AZA and AZB was sodium channel blockage. The study shows that the short-term rat whole embryo culture (WEC) is a suitable system to detect substances hazardous to the embryonic heart. - Highlights: • Study of the effect of sodium channel blocking drugs on embryonic heart function • We used a modified method rat whole embryo culture with image analysis. • The drugs tested caused a concentration dependent bradycardia and heart block. • The effect of drugs acting on multiple ion channels is difficult to predict. • This method may be used to detect cardiotoxicity in prenatal development

On conduction in a bacterial sodium channel.

Directory of Open Access Journals (Sweden)

Simone Furini

Full Text Available Voltage-gated Na⁺-channels are transmembrane proteins that are responsible for the fast depolarizing phase of the action potential in nerve and muscular cells. Selective permeability of Na⁺ over Ca²⁺ or K⁺ ions is essential for the biological function of Na⁺-channels. After the emergence of the first high-resolution structure of a Na⁺-channel, an anionic coordination site was proposed to confer Na⁺ selectivity through partial dehydration of Na⁺ via its direct interaction with conserved glutamate side chains. By combining molecular dynamics simulations and free-energy calculations, a low-energy permeation pathway for Na⁺ ion translocation through the selectivity filter of the recently determined crystal structure of a prokaryotic sodium channel from Arcobacter butzleri is characterised. The picture that emerges is that of a pore preferentially occupied by two ions, which can switch between different configurations by crossing low free-energy barriers. In contrast to K⁺-channels, the movements of the ions appear to be weakly coupled in Na⁺-channels. When the free-energy maps for Na⁺ and K⁺ ions are compared, a selective site is characterised in the narrowest region of the filter, where a hydrated Na⁺ ion, and not a hydrated K⁺ ion, is energetically stable.

Modification of sodium and potassium channel kinetics by diethyl ether and studies on sodium channel inactivation in the crayfish giant axon membrane

Energy Technology Data Exchange (ETDEWEB)

Bean, Bruce Palmer [Univ. of Rochester, NY (United States)

1979-01-01

The effects of ether and halothane on membrane currents in the voltage clamped crayfish giant axon membrane were investigated. Concentrations of ether up to 300 mM and of halothane up to 32 mM had no effect on resting potential or leakage conductance. Ether and halothane reduced the size of sodium currents without changing the voltage dependence of the peak currents or their reversal potential. Ether and halothane also produced a reversible, dose-dependent speeding of sodium current decay at all membrane potentials. Ether reduced the time constants for inactivation, and also shifted the midpoint of the steady-state inactivation curve in the hyperpolarizing direction. Potassium currents were smaller with ether present, with no change in the voltage dependence of steady-state currents. The activation of potassium channels was faster with ether present. There was no apparent change in the capacitance of the crayfish giant axon membrane with ether concentrations of up to 100 mM. Experiments on sodium channel inactivation kinetics were performed using 4-aminopyridine to block potassium currents. Sodium currents decayed with a time course generally fit well by a single exponential. The time constant of decay was a steep function of voltage, especially in the negative resistance region of the peak current vs voltage relation.The time course of inactivation was very similar to that of the decay of the current at the same potential. The measurement of steady-state inactivation curves with different test pulses showed no shifts along the voltage asix. The voltage-dependence of the integral of sodium conductance was measured to test models of sodium channel inactivation in which channels must open before inactivating; the results appear inconsistent with some of the simplest cases of such models.

Local anesthetics disrupt energetic coupling between the voltage-sensing segments of a sodium channel.

Science.gov (United States)

Muroi, Yukiko; Chanda, Baron

2009-01-01

Local anesthetics block sodium channels in a state-dependent fashion, binding with higher affinity to open and/or inactivated states. Gating current measurements show that local anesthetics immobilize a fraction of the gating charge, suggesting that the movement of voltage sensors is modified when a local anesthetic binds to the pore of the sodium channel. Here, using voltage clamp fluorescence measurements, we provide a quantitative description of the effect of local anesthetics on the steady-state behavior of the voltage-sensing segments of a sodium channel. Lidocaine and QX-314 shifted the midpoints of the fluorescence-voltage (F-V) curves of S4 domain III in the hyperpolarizing direction by 57 and 65 mV, respectively. A single mutation in the S6 of domain IV (F1579A), a site critical for local anesthetic block, abolished the effect of QX-314 on the voltage sensor of domain III. Both local anesthetics modestly shifted the F-V relationships of S4 domain IV toward hyperpolarized potentials. In contrast, the F-V curve of the S4 domain I was shifted by 11 mV in the depolarizing direction upon QX-314 binding. These antagonistic effects of the local anesthetic indicate that the drug modifies the coupling between the voltage-sensing domains of the sodium channel. Our findings suggest a novel role of local anesthetics in modulating the gating apparatus of the sodium channel.

Ligand-based design and synthesis of novel sodium channel blockers from a combined phenytoin–lidocaine pharmacophore

OpenAIRE

Wang, Yuesheng; Jones, Paulianda J.; Batts, Timothy W.; Landry, Victoria; Patel, Manoj K.; Brown, Milton L.

2008-01-01

The voltage-gated sodium channel remains a rich area for the development of novel blockers. In this study we used comparative molecular field analysis (CoMFA), a ligand-based design strategy, to generate a 3D model based upon local anesthetics, hydantoins, and α-hydroxyphenylamides to elucidate a SAR for their binding site in the neuronal sodium channel. Correlation by partial least squares (PLS) analysis of in vitro sodium channel binding activity (expressed as pIC50) and the CoMFA descripto...

A Novel SCN5A Mutation in a Patient with Coexistence of Brugada Syndrome Traits and Ischaemic Heart Disease

Directory of Open Access Journals (Sweden)

Anders G. Holst

2009-01-01

Full Text Available Brugada syndrome (BrS is a primary electrical heart disease, which can lead to sudden cardiac death. In older patients with BrS, the disease may coexist with ischaemic heart disease (IHD and recent studies support a synergistic proarrhythmic effect of the two disease entities. We report a case that illustrates this. The index patient was a middle-aged patient with BrS traits, IHD, and aborted sudden cardiac death. Mutation analysis discovered a novel mutation P468L in the NaV1.5 sodium channel. Surprisingly, voltage-clamp experiments on the wild-type and mutant NaV1.5 channels expressed in HEK cells revealed no functional effect of the mutation. In a patient like ours, the distinction between IHD and BrS as the cause of an aborted sudden cardiac death is hard to establish and mounting evidence shows that coexistence of the two may have a synergistic proarrhythmic effect.

Differential effects of common variants in SCN2A on general cognitive ability, brain physiology, and messenger RNA expression in schizophrenia cases and control individuals.

Science.gov (United States)

Dickinson, Dwight; Straub, Richard E; Trampush, Joey W; Gao, Yuan; Feng, Ningping; Xie, Bin; Shin, Joo Heon; Lim, Hun Ki; Ursini, Gianluca; Bigos, Kristin L; Kolachana, Bhaskar; Hashimoto, Ryota; Takeda, Masatoshi; Baum, Graham L; Rujescu, Dan; Callicott, Joseph H; Hyde, Thomas M; Berman, Karen F; Kleinman, Joel E; Weinberger, Daniel R

2014-06-01

One approach to understanding the genetic complexity of schizophrenia is to study associated behavioral and biological phenotypes that may be more directly linked to genetic variation. To identify single-nucleotide polymorphisms associated with general cognitive ability (g) in people with schizophrenia and control individuals. Genomewide association study, followed by analyses in unaffected siblings and independent schizophrenia samples, functional magnetic resonance imaging studies of brain physiology in vivo, and RNA sequencing in postmortem brain samples. The discovery cohort and unaffected siblings were participants in the National Institute of Mental Health Clinical Brain Disorders Branch schizophrenia genetics studies. Additional schizophrenia cohorts were from psychiatric treatment settings in the United States, Japan, and Germany. The discovery cohort comprised 339 with schizophrenia and 363 community control participants. Follow-up analyses studied 147 unaffected siblings of the schizophrenia cases and independent schizophrenia samples including a total of an additional 668 participants. Imaging analyses included 87 schizophrenia cases and 397 control individuals. Brain tissue samples were available for 64 cases and 61 control individuals. We studied genomewide association with g, by group, in the discovery cohort. We used selected genotypes to test specific associations in unaffected siblings and independent schizophrenia samples. Imaging analyses focused on activation in the prefrontal cortex during working memory. Brain tissue studies yielded messenger RNA expression levels for RefSeq transcripts. The schizophrenia discovery cohort showed genomewide-significant association of g with polymorphisms in sodium channel gene SCN2A, accounting for 10.4% of g variance (rs10174400, P = 9.27 × 10(-10)). Control individuals showed a trend for g/genotype association with reversed allelic directionality. The genotype-by-group interaction was also genomewide

Propylparaben reduces the excitability of hippocampal neurons by blocking sodium channels.

Science.gov (United States)

Lara-Valderrábano, Leonardo; Rocha, Luisa; Galván, Emilio J

2016-12-01

Propylparaben (PPB) is an antimicrobial preservative widely used in food, cosmetics, and pharmaceutics. Virtual screening methodologies predicted anticonvulsant activity of PPB that was confirmed in vivo. Thus, we explored the effects of PPB on the excitability of hippocampal neurons by using standard patch clamp techniques. Bath perfusion of PPB reduced the fast-inactivating sodium current (I Na ) amplitude, causing a hyperpolarizing shift in the inactivation curve of the I Na, and markedly delayed the sodium channel recovery from the inactivation state. Also, PPB effectively suppressed the riluzole-sensitive, persistent sodium current (I NaP ). PPB perfusion also modified the action potential kinetics, and higher concentrations of PPB suppressed the spike activity. Nevertheless, the modulatory effects of PPB did not occur when PPB was internally applied by whole-cell dialysis. These results indicate that PPB reduces the excitability of CA1 pyramidal neurons by modulating voltage-dependent sodium channels. The mechanistic basis of this effect is a marked delay in the recovery from inactivation state of the voltage-sensitive sodium channels. Our results indicate that similar to local anesthetics and anticonvulsant drugs that act on sodium channels, PPB acts in a use-dependent manner. Copyright © 2016 Elsevier B.V. All rights reserved.

High Prevalence of Long QT Syndrome Associated SCN5A Variants in Patients with Early-Onset Lone Atrial Fibrillation

DEFF Research Database (Denmark)

Olesen, Morten S; Yuan, Lei; Liang, Bo

2012-01-01

a mechanistic overlap between LQTS3 and early-onset lone AF. In 9 of 10 identified mutations and rare variants, we observed compromised biophysical properties affecting the transient peak current. CONCLUSIONS: In a cohort of patients with early-onset lone AF, we identified a high prevalence of SCN5A mutations...

Voltage-Gated Sodium Channels: Evolutionary History and Distinctive Sequence Features.

Science.gov (United States)

Kasimova, M A; Granata, D; Carnevale, V

2016-01-01

Voltage-gated sodium channels (Nav) are responsible for the rising phase of the action potential. Their role in electrical signal transmission is so relevant that their emergence is believed to be one of the crucial factors enabling development of nervous system. The presence of voltage-gated sodium-selective channels in bacteria (BacNav) has raised questions concerning the evolutionary history of the ones in animals. Here we review some of the milestones in the field of Nav phylogenetic analysis and discuss some of the most important sequence features that distinguish these channels from voltage-gated potassium channels and transient receptor potential channels. Copyright © 2016 Elsevier Inc. All rights reserved.

Contrast between the mechanisms for dissociative electron attachment to CH3SCN and CH3NCS

Science.gov (United States)

Miller, Thomas M.; Viggiano, Albert A.; Shuman, Nicholas S.

2018-05-01

The kinetics of thermal electron attachment to methyl thiocyanate (CH3SCN), methyl isothiocyanate (CH3NCS), and ethyl thiocyanate (C2H5SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3SCN and C2H5SCN undergo inefficient dissociative attachment to yield primarily SCN- at 300 K (k = 2 × 10-10 cm3 s-1), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3SCN) and 0.14 eV (C2H5SCN). CN- product is formed at product but at a rate at 300 K that is below our detection threshold (k differentiating the two mechanisms. The kinetic modeling reproduces the CH3NCS data only if dissociation through the transient anion is considered.

Compensation of native donor doping in ScN: Carrier concentration control and p-type ScN

Science.gov (United States)

Saha, Bivas; Garbrecht, Magnus; Perez-Taborda, Jaime A.; Fawey, Mohammed H.; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Hultman, Lars; Sands, Timothy D.

2017-06-01

Scandium nitride (ScN) is an emerging indirect bandgap rocksalt semiconductor that has attracted significant attention in recent years for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices and as a substrate material for high quality GaN growth. Due to the presence of oxygen impurities and native defects such as nitrogen vacancies, sputter-deposited ScN thin-films are highly degenerate n-type semiconductors with carrier concentrations in the (1-6) × 1020 cm-3 range. In this letter, we show that magnesium nitride (MgxNy) acts as an efficient hole dopant in ScN and reduces the n-type carrier concentration, turning ScN into a p-type semiconductor at high doping levels. Employing a combination of high-resolution X-ray diffraction, transmission electron microscopy, and room temperature optical and temperature dependent electrical measurements, we demonstrate that p-type Sc1-xMgxN thin-film alloys (a) are substitutional solid solutions without MgxNy precipitation, phase segregation, or secondary phase formation within the studied compositional region, (b) exhibit a maximum hole-concentration of 2.2 × 1020 cm-3 and a hole mobility of 21 cm2/Vs, (c) do not show any defect states inside the direct gap of ScN, thus retaining their basic electronic structure, and (d) exhibit alloy scattering dominating hole conduction at high temperatures. These results demonstrate MgxNy doped p-type ScN and compare well with our previous reports on p-type ScN with manganese nitride (MnxNy) doping.

Synthesis and characterizations of AgSCN nanospheres using AgCl as the precursor

International Nuclear Information System (INIS)

Yang Ming; Ma Jing

2009-01-01

Nanospheres of AgSCN with an average radius of 30-80 nm have been prepared by a simple reaction between AgCl suspension and KSCN in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of SCN - ions to AgCl surfaces and coagulation of the growing AgSCN in producing the spherical AgSCN nanoparticles. The products were characterized by X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectra techniques. The electrical conductivity of thin films of as-prepared AgSCN nanoparticles and polyethylene oxide (PEO) at room temperature was measured. The maximum value of electrical conductivity of as-prepared AgSCN-PEO was 1.53 x 10 -5 S cm -1 .

Action of insecticidal N-alkylamides at site 2 of the voltage-sensitive sodium channel

International Nuclear Information System (INIS)

Ottea, J.A.; Payne, G.T.; Soderlund, D.M.

1990-01-01

Nine synthetic N-alkylamides were examined as inhibitors of the specific binding of [ 3 H]batrachotoxinin A 20α-benzoate ([ 3 H]BTX-B) to sodium channels and as activators of sodium uptake in mouse brain synaptoneurosomes. In the presence of scorpion (Leiurus quinquestriatus) venom, the six insecticidal analogues were active as both inhibitors of [ 3 H]BTX-B binding and stimulators of sodium uptake. These findings are consistent with an action of these compounds at the alkaloid activator recognition site (site 2) of the voltage-sensitive sodium channel. The three noninsecticidal N-alkylamides also inhibited [ 3 H]BTX-B binding but were ineffective as activators of sodium uptake. Concentration-response studies revealed that some of the insecticidal amides also enhanced sodium uptake through a second, high-affinity interaction that does not involve site 2, but this secondary effect does not appear to be correlated with insecticidal activity. The activities of N-alkylamides as sodium channel activators were influenced by the length of the alkenyl chain and the location of unsaturation within the molecule. These results further define the actions of N-alkylamides on sodium channels and illustrate the significance of the multiple binding domains of the sodium channel as target sites for insect control agents

Physiological regulation of epithelial sodium channel by proteolysis

DEFF Research Database (Denmark)

Svenningsen, Per; Friis, Ulla G; Bistrup, Claus

2011-01-01

PURPOSE OF REVIEW: Activation of epithelial sodium channel (ENaC) by proteolysis appears to be relevant for day-to-day physiological regulation of channel activity in kidney and other epithelial tissues. Pathophysiogical, proteolytic activation of ENaC in kidney has been demonstrated in proteinuric...

Brugada syndrome with a novel missense mutation in SCN5A gene: A case report from Bangladesh

Directory of Open Access Journals (Sweden)

Md. Zahidus Sayeed

2014-01-01

Full Text Available Brugada syndrome is an inherited cardiac arrhythmia that follows autosomal dominant transmission and can cause sudden death. We report a case of Brugada syndrome in a 55-year-old male patient presented with recurrent palpitation, atypical chest pain and presyncope. ECG changes were consistent with type 1 Brugada. Gene analysis revealed a novel missense mutation in SCN5A gene with a genetic variation of D785N and a nucleotide change at 2353G-A. One of his children also had the same mutation. To our knowledge this is the first genetically proved case of Brugada syndrome in Bangladesh.

The sodium channel activator Lu AE98134 normalizes the altered firing properties of fast spiking interneurons in Dlx5/6+/- mice

DEFF Research Database (Denmark)

von Schoubye, Nadia Lybøl; Frederiksen, Kristen; Kristiansen, Uffe

2018-01-01

Mental disorders such as schizophrenia are associated with impaired firing properties of fast spiking inhibitory interneurons (FSINs) causing reduced task-evoked gamma-oscillation in prefrontal cortex. The voltage-gated sodium channel NaV1.1 is highly expressed in PV-positive interneurons, but only...... at low levels in principal cells. Positive modulators of Nav1.1 channels are for this reason considered potential candidates for the treatment of cognitive disorders. Here we examined the effect of the novel positive modulator of voltage-gated sodium channels Lu AE98134. We found that Lu AE98134...... facilitated the sodium current mediated by NaV1.1 expressed in HEK cells by shifting its activation to more negative values, decreasing its inactivation kinetics and promoting a persistent inward current. In a slice preparation from the brain of adult mice, Lu AE98134 promoted the excitability of fast spiking...

β1 subunit stabilises sodium channel Nav1.7 against mechanical stress.

Science.gov (United States)

Körner, Jannis; Meents, Jannis; Machtens, Jan-Philipp; Lampert, Angelika

2018-06-01

The voltage-gated sodium channel Nav1.7 is a key player in neuronal excitability and pain signalling. In addition to voltage sensing, the channel is also modulated by mechanical stress. Using whole-cell patch-clamp experiments, we discovered that the sodium channel subunit β1 is able to prevent the impact of mechanical stress on Nav1.7. An intramolecular disulfide bond of β1 was identified to be essential for stabilisation of inactivation, but not activation, against mechanical stress using molecular dynamics simulations, homology modelling and site-directed mutagenesis. Our results highlight the role of segment 6 of domain IV in fast inactivation. We present a candidate mechanism for sodium channel stabilisation against mechanical stress, ensuring reliable channel functionality in living systems. Voltage-gated sodium channels are key players in neuronal excitability and pain signalling. Precise gating of these channels is crucial as even small functional alterations can lead to pathological phenotypes such as pain or heart failure. Mechanical stress has been shown to affect sodium channel activation and inactivation. This suggests that stabilising components are necessary to ensure precise channel gating in living organisms. Here, we show that mechanical shear stress affects voltage dependence of activation and fast inactivation of the Nav1.7 channel. Co-expression of the β1 subunit, however, protects both gating modes of Nav1.7 against mechanical shear stress. Using molecular dynamics simulation, homology modelling and site-directed mutagenesis, we identify an intramolecular disulfide bond of β1 (Cys21-Cys43) which is partially involved in this process: the β1-C43A mutant prevents mechanical modulation of voltage dependence of activation, but not of fast inactivation. Our data emphasise the unique role of segment 6 of domain IV for sodium channel fast inactivation and confirm previous reports that the intracellular process of fast inactivation can be

Identification of sodium channel isoforms that mediate action potential firing in lamina I/II spinal cord neurons

Directory of Open Access Journals (Sweden)

Smith Paula L

2011-09-01

Full Text Available Abstract Background Voltage-gated sodium channels play key roles in acute and chronic pain processing. The molecular, biophysical, and pharmacological properties of sodium channel currents have been extensively studied for peripheral nociceptors while the properties of sodium channel currents in dorsal horn spinal cord neurons remain incompletely understood. Thus far, investigations into the roles of sodium channel function in nociceptive signaling have primarily focused on recombinant channels or peripheral nociceptors. Here, we utilize recordings from lamina I/II neurons withdrawn from the surface of spinal cord slices to systematically determine the functional properties of sodium channels expressed within the superficial dorsal horn. Results Sodium channel currents within lamina I/II neurons exhibited relatively hyperpolarized voltage-dependent properties and fast kinetics of both inactivation and recovery from inactivation, enabling small changes in neuronal membrane potentials to have large effects on intrinsic excitability. By combining biophysical and pharmacological channel properties with quantitative real-time PCR results, we demonstrate that functional sodium channel currents within lamina I/II neurons are predominantly composed of the NaV1.2 and NaV1.3 isoforms. Conclusions Overall, lamina I/II neurons express a unique combination of functional sodium channels that are highly divergent from the sodium channel isoforms found within peripheral nociceptors, creating potentially complementary or distinct ion channel targets for future pain therapeutics.

Distribution and function of voltage-gated sodium channels in the nervous system.

Science.gov (United States)

Wang, Jun; Ou, Shao-Wu; Wang, Yun-Jie

2017-11-02

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.

Mechanism of sodium channel block by local anesthetics, antiarrhythmics, and anticonvulsants.

Science.gov (United States)

Tikhonov, Denis B; Zhorov, Boris S

2017-04-03

Local anesthetics, antiarrhythmics, and anticonvulsants include both charged and electroneutral compounds that block voltage-gated sodium channels. Prior studies have revealed a common drug-binding region within the pore, but details about the binding sites and mechanism of block remain unclear. Here, we use the x-ray structure of a prokaryotic sodium channel, NavMs, to model a eukaryotic channel and dock representative ligands. These include lidocaine, QX-314, cocaine, quinidine, lamotrigine, carbamazepine (CMZ), phenytoin, lacosamide, sipatrigine, and bisphenol A. Preliminary calculations demonstrated that a sodium ion near the selectivity filter attracts electroneutral CMZ but repels cationic lidocaine. Therefore, we further docked electroneutral and cationic drugs with and without a sodium ion, respectively. In our models, all the drugs interact with a phenylalanine in helix IVS6. Electroneutral drugs trap a sodium ion in the proximity of the selectivity filter, and this same site attracts the charged group of cationic ligands. At this position, even small drugs can block the permeation pathway by an electrostatic or steric mechanism. Our study proposes a common pharmacophore for these diverse drugs. It includes a cationic moiety and an aromatic moiety, which are usually linked by four bonds. © 2017 Tikhonov and Zhorov.

Ab initio study of structural, electronic and optical properties of MnHg(SCN)4 and FeHg(SCN)4

International Nuclear Information System (INIS)

He, K.H.; Zheng, G.; Chen, G.; Lue, T.; Wan, M.; Ji, G.F.

2007-01-01

The structural, electronic and optical properties of MnHg(SCN) 4 and FeHg(SCN) 4 were studied by means of quantum-mechanical calculations based on the density-functional theory and pseudopotential method. The lattice constants can be compared with the experimental values when the effects of temperature are considered. The peaks of partial density of states of S, C, N and Hg of FeHg(SCN) 4 have a tendency of shifting to the higher energy levels relative to those of MnHg(SCN) 4 . The distributions of the 3d electronic states in the transition metal atoms show quite large difference and decide different optical properties. We found that absorptional peaks of FeHg(SCN) 4 lag behind those of MnHg(SCN) 4 and the peak in the infrared range has a higher absorptional intensity, which are in accord with the experimental results. By analyzing the distributions and transitions of the 3d electronic states, we explained the different absorption phenomena

Substituted 4-phenyl-2-aminoimidazoles and 4-phenyl-4,5-dihydro-2-aminoimidazoles as voltage-gated sodium channel modulators.

Science.gov (United States)

Zidar, Nace; Jakopin, Žiga; Madge, David J; Chan, Fiona; Tytgat, Jan; Peigneur, Steve; Dolenc, Marija Sollner; Tomašić, Tihomir; Ilaš, Janez; Mašič, Lucija Peterlin; Kikelj, Danijel

2014-03-03

Voltage-gated sodium channels play an integral part in neurotransmission and their dysfunction is frequently a cause of various neurological disorders. On the basis of the structure of marine alkaloid clathrodin, twenty eight new analogs were designed, synthesized and tested for their ability to block human NaV1.3, NaV1.4 and NaV1.7 channels, as well as for their selectivity against human cardiac isoform NaV1.5, using automated patch clamp electrophysiological assay. Several compounds exhibited promising activities on different NaV channel isoforms in the medium micromolar range and some of the compounds showed also moderate isoform selectivities. The most promising results were obtained for the NaV1.3 channel, for which four compounds were found to possess IC₅₀ values lower than 15 μM. All of the active compounds bind to the open-inactivated states of the channels and therefore act as state-dependent modulators. The obtained results validate the approach of using natural products driven chemistry for drug discovery starting points and represent a good foundation for future design of selective NaV modulators. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Potential Roles of Amiloride-Sensitive Sodium Channels in Cancer Development

Directory of Open Access Journals (Sweden)

Siguang Xu

2016-01-01

Full Text Available The ENaC/degenerin ion channel superfamily includes the amiloride-sensitive epithelial sodium channel (ENaC and acid sensitive ionic channel (ASIC. ENaC is a multimeric ion channel formed by heteromultimeric membrane glycoproteins, which participate in a multitude of biological processes by mediating the transport of sodium (Na+ across epithelial tissues such as the kidney, lungs, bladder, and gut. Aberrant ENaC functions contribute to several human disease states including pseudohypoaldosteronism, Liddle syndrome, cystic fibrosis, and salt-sensitive hypertension. Increasing evidence suggests that ion channels not only regulate ion homeostasis and electric signaling in excitable cells but also play important roles in cancer cell behaviors such as proliferation, apoptosis, invasion, and migration. Indeed, ENaCs/ASICs had been reported to be associated with cancer characteristics. Given their cell surface localization and pharmacology, pharmacological strategies to target ENaC/ASIC family members may be promising cancer therapeutics.

Reduction of the thermal conductivity of the thermoelectric material ScN by Nb alloying

DEFF Research Database (Denmark)

Tureson, Nina; Van Nong, Ngo; Fournier, Daniele

2017-01-01

) orientation. The crystal structure, morphology, thermal conductivity, and thermoelectric and electrical properties were investigated. The ScN reference film exhibited a Seebeck coefficient of −45 μV/K and a power factor of 6 × 10−4 W/m K2 at 750 K. Estimated from room temperature Hall measurements, all...... samples exhibit a high carrier density of the order of 1021 cm−3. Inclusion of heavy transition metals into ScN enables the reduction in thermal conductivity by an increase in phonon scattering. The Nb inserted ScN thin films exhibited a thermal conductivity lower than the value of the ScN reference (10.......5 W m−1 K−1) down to a minimum value of 2.2 Wm−1 K−1. Insertion of Nb into ScN thus resulted in a reduction in thermal conductivity by a factor of ∼5 due to the mass contrast in ScN, which increases the phonon scattering in the material....

Safety and efficacy of a Nav1.7 selective sodium channel blocker in patients with trigeminal neuralgia

DEFF Research Database (Denmark)

Zakrzewska, Joanna M; Palmer, Joanne; Morisset, Valerie

2017-01-01

BACKGROUND: Current standard of care for trigeminal neuralgia is treatment with the sodium channel blockers carbamazepine and oxcarbazepine, which although effective are associated with poor tolerability and the need for titration. BIIB074, a Nav1.7-selective, state-dependent sodium-channel blocker...

Epoxyeicosatrienoic acid analogue lowers blood pressure through vasodilation and sodium channel inhibition

Czech Academy of Sciences Publication Activity Database

Khan, M. A. H.; Pavlov, T. S.; Christain, S. V.; Neckář, Jan; Staruschenko, A.; Gauthier, K. M.; Capdevila, J. H.; Falck, J. R.; Campbell, W. B.; Imig, J. D.

2014-01-01

Roč. 127, č. 7 (2014), s. 463-474 ISSN 0143-5221 Institutional support: RVO:67985823 Keywords : angiotensin II * epithelial sodium channel (ENaC) * epoxyeicosatrienoic acid analogue * hypertension Subject RIV: FA - Cardiovascular Diseases incl. Cardiotharic Surgery Impact factor: 5.598, year: 2014

A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel.

Science.gov (United States)

Tang, Cheng; Zhou, Xi; Nguyen, Phuong Tran; Zhang, Yunxiao; Hu, Zhaotun; Zhang, Changxin; Yarov-Yarovoy, Vladimir; DeCaen, Paul G; Liang, Songping; Liu, Zhonghua

2017-07-01

Voltage-gated sodium channels (Na V s) are activated by transiting the voltage sensor from the deactivated to the activated state. The crystal structures of several bacterial Na V s have captured the voltage sensor module (VSM) in an activated state, but structure of the deactivated voltage sensor remains elusive. In this study, we sought to identify peptide toxins stabilizing the deactivated VSM of bacterial Na V s. We screened fractions from several venoms and characterized a cystine knot toxin called JZTx-27 from the venom of tarantula Chilobrachys jingzhao as a high-affinity antagonist of the prokaryotic Na V s Ns V Ba (nonselective voltage-gated Bacillus alcalophilus ) and NaChBac (bacterial sodium channel from Bacillus halodurans ) (IC 50 = 112 nM and 30 nM, respectively). JZTx-27 was more efficacious at weaker depolarizing voltages and significantly slowed the activation but accelerated the deactivation of Ns V Ba, whereas the local anesthetic drug lidocaine was shown to antagonize Ns V Ba without affecting channel gating. Mutation analysis confirmed that JZTx-27 bound to S3-4 linker of Ns V Ba, with F98 being the critical residue in determining toxin affinity. All electrophysiological data and in silico analysis suggested that JZTx-27 trapped VSM of Ns V Ba in one of the deactivated states. In mammalian Na V s, JZTx-27 preferably inhibited the inactivation of Na V 1.5 by targeting the fourth transmembrane domain. To our knowledge, this is the first report of peptide antagonist for prokaryotic Na V s. More important, we proposed that JZTx-27 stabilized the Ns V Ba VSM in the deactivated state and may be used as a probe to determine the structure of the deactivated VSM of Na V s.-Tang, C., Zhou, X., Nguyen, P. T., Zhang, Y., Hu, Z., Zhang, C., Yarov-Yarovoy, V., DeCaen, P. G., Liang, S., Liu, Z. A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel. © FASEB.

Molecular Surface of JZTX-V (β-Theraphotoxin-Cj2a Interacting with Voltage-Gated Sodium Channel Subtype NaV1.4

Directory of Open Access Journals (Sweden)

Ji Luo

2014-07-01

Full Text Available Voltage-gated sodium channels (VGSCs; NaV1.1–NaV1.9 have been proven to be critical in controlling the function of excitable cells, and human genetic evidence shows that aberrant function of these channels causes channelopathies, including epilepsy, arrhythmia, paralytic myotonia, and pain. The effects of peptide toxins, especially those isolated from spider venom, have shed light on the structure–function relationship of these channels. However, most of these toxins have not been analyzed in detail. In particular, the bioactive faces of these toxins have not been determined. Jingzhaotoxin (JZTX-V (also known as β-theraphotoxin-Cj2a is a 29-amino acid peptide toxin isolated from the venom of the spider Chilobrachys jingzhao. JZTX-V adopts an inhibitory cysteine knot (ICK motif and has an inhibitory effect on voltage-gated sodium and potassium channels. Previous experiments have shown that JZTX-V has an inhibitory effect on TTX-S and TTX-R sodium currents on rat DRG cells with IC50 values of 27.6 and 30.2 nM, respectively, and is able to shift the activation and inactivation curves to the depolarizing and the hyperpolarizing direction, respectively. Here, we show that JZTX-V has a much stronger inhibitory effect on NaV1.4, the isoform of voltage-gated sodium channels predominantly expressed in skeletal muscle cells, with an IC50 value of 5.12 nM, compared with IC50 values of 61.7–2700 nM for other heterologously expressed NaV1 subtypes. Furthermore, we investigated the bioactive surface of JZTX-V by alanine-scanning the effect of toxin on NaV1.4 and demonstrate that the bioactive face of JZTX-V is composed of three hydrophobic (W5, M6, and W7 and two cationic (R20 and K22 residues. Our results establish that, consistent with previous assumptions, JZTX-V is a Janus-faced toxin which may be a useful tool for the further investigation of the structure and function of sodium channels.

The human Nav1.5 F1486 deletion associated with long QT syndrome leads to impaired sodium channel inactivation and reduced lidocaine sensitivity

Science.gov (United States)

Song, Weihua; Xiao, Yucheng; Chen, Hanying; Ashpole, Nicole M; Piekarz, Andrew D; Ma, Peilin; Hudmon, Andy; Cummins, Theodore R; Shou, Weinian

2012-01-01

The deletion of phenylalanine 1486 (F1486del) in the human cardiac voltage-gated sodium channel (hNav1.5) is associated with fatal long QT (LQT) syndrome. In this study we determined how F1486del impairs the functional properties of hNav1.5 and alters action potential firing in heterologous expression systems (human embryonic kidney (HEK) 293 cells) and their native cardiomyocyte background. Cells expressing hNav1.5-F1486del exhibited a loss-of-function alteration, reflected by an 80% reduction of peak current density, and several gain-of-function alterations, including reduced channel inactivation, enlarged window current, substantial augmentation of persistent late sodium current and an increase in ramp current. We also observed substantial action potential duration (APD) prolongation and prominent early afterdepolarizations (EADs) in neonatal cardiomyocytes expressing the F1486del channels, as well as in computer simulations of myocyte activity. In addition, lidocaine sensitivity was dramatically reduced, which probably contributed to the poor therapeutic outcome observed in the patient carrying the hNav1.5-F1486del mutation. Therefore, despite the significant reduction in peak current density, the F1486del mutation also leads to substantial gain-of-function alterations that are sufficient to cause APD prolongation and EADs, the predominant characteristic of LQTs. These data demonstrate that hNav1.5 mutations can have complex functional consequences and highlight the importance of identifying the specific molecular defect when evaluating potential treatments for individuals with prolonged QT intervals. PMID:22826127

SCN1A, ABCC2 and UGT2B7 gene polymorphisms in association with individualized oxcarbazepine therapy.

Science.gov (United States)

Ma, Chun-Lai; Wu, Xun-Yi; Jiao, Zheng; Hong, Zhen; Wu, Zhi-Yuan; Zhong, Ming-Kang

2015-01-01

Associations between the effects of SCN1A, SCN2A, ABCC2 and UGT2B7 genetic polymorphisms and oxcarbazepine (OXC) maintenance doses in Han Chinese epileptic patients were investigated. Genetic polymorphisms were detected in 184 epileptic patients receiving OXC monotherapy by high-resolution melting curve and TaqMan method. Carriers of the SCN1A IVS5-91G>A, UGT2B7 c.802T>C and ABCC2 c.1249G>A variant alleles required significantly higher OXC maintenance doses than noncarriers (p GA > AA. SCN1A, UGT2B7 and ABCC2 genetic polymorphisms are associated with OXC maintenance doses and may be useful for the personalization of OXC therapy in epileptic patients. Further studies are needed. Original submitted 6 June 2014; Revision submitted 5 September 2014.

Evaluation of Presumably Disease Causing SCN1A Variants in a Cohort of Common Epilepsy Syndromes.

Science.gov (United States)

Lal, Dennis; Reinthaler, Eva M; Dejanovic, Borislav; May, Patrick; Thiele, Holger; Lehesjoki, Anna-Elina; Schwarz, Günter; Riesch, Erik; Ikram, M Arfan; van Duijn, Cornelia M; Uitterlinden, Andre G; Hofman, Albert; Steinböck, Hannelore; Gruber-Sedlmayr, Ursula; Neophytou, Birgit; Zara, Federico; Hahn, Andreas; Gormley, Padhraig; Becker, Felicitas; Weber, Yvonne G; Cilio, Maria Roberta; Kunz, Wolfram S; Krause, Roland; Zimprich, Fritz; Lemke, Johannes R; Nürnberg, Peter; Sander, Thomas; Lerche, Holger; Neubauer, Bernd A

2016-01-01

The SCN1A gene, coding for the voltage-gated Na+ channel alpha subunit NaV1.1, is the clinically most relevant epilepsy gene. With the advent of high-throughput next-generation sequencing, clinical laboratories are generating an ever-increasing catalogue of SCN1A variants. Variants are more likely to be classified as pathogenic if they have already been identified previously in a patient with epilepsy. Here, we critically re-evaluate the pathogenicity of this class of variants in a cohort of patients with common epilepsy syndromes and subsequently ask whether a significant fraction of benign variants have been misclassified as pathogenic. We screened a discovery cohort of 448 patients with a broad range of common genetic epilepsies and 734 controls for previously reported SCN1A mutations that were assumed to be disease causing. We re-evaluated the evidence for pathogenicity of the identified variants using in silico predictions, segregation, original reports, available functional data and assessment of allele frequencies in healthy individuals as well as in a follow up cohort of 777 patients. We identified 8 known missense mutations, previously reported as pathogenic, in a total of 17 unrelated epilepsy patients (17/448; 3.80%). Our re-evaluation indicates that 7 out of these 8 variants (p.R27T; p.R28C; p.R542Q; p.R604H; p.T1250M; p.E1308D; p.R1928G; NP_001159435.1) are not pathogenic. Only the p.T1174S mutation may be considered as a genetic risk factor for epilepsy of small effect size based on the enrichment in patients (P = 6.60 x 10-4; OR = 0.32, fishers exact test), previous functional studies but incomplete penetrance. Thus, incorporation of previous studies in genetic counseling of SCN1A sequencing results is challenging and may produce incorrect conclusions.

BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

Directory of Open Access Journals (Sweden)

Jack Kent

Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

Increased renal sodium absorption by inhibition of prostaglandin synthesis during fasting in healthy man. A possible role of the epithelial sodium channels

Directory of Open Access Journals (Sweden)

Graffe Carolina C

2010-10-01

Full Text Available Abstract Background Treatment with prostaglandin inhibitors can reduce renal function and impair renal water and sodium excretion. We tested the hypotheses that a reduction in prostaglandin synthesis by ibuprofen treatment during fasting decreased renal water and sodium excretion by increased absorption of water and sodium via the aquaporin2 water channels and the epithelial sodium channels. Methods The effect of ibuprofen, 600 mg thrice daily, was measured during fasting in a randomized, placebo-controlled, double-blinded crossover study of 17 healthy humans. The subjects received a standardized diet on day 1, fasted at day 2, and received an IV infusion of 3% NaCl on day 3. The effect variables were urinary excretions of aquaporin2 (u-AQP2, the beta-fraction of the epithelial sodium channel (u-ENaCbeta, cyclic-AMP (u-cAMP, prostaglandin E2 (u-PGE2. Free water clearance (CH2O, fractional excretion of sodium (FENa, and plasma concentrations of vasopressin, angiotensin II, aldosterone, atrial-, and brain natriuretic peptide. Results Ibuprofen decreased u-AQP2, u-PGE2, and FENa at all parts of the study. During the same time, ibuprofen significantly increased u-ENaCbeta. Ibuprofen did not change the response in p-AVP, u-c-AMP, urinary output, and free water clearance during any of these periods. Atrial-and brain natriuretic peptide were higher. Conclusion During inhibition of prostaglandin synthesis, urinary sodium excretion decreased in parallel with an increase in sodium absorption and increase in u-ENaCbeta. U-AQP2 decreased indicating that water transport via AQP2 fell. The vasopressin-c-AMP-axis did not mediate this effect, but it may be a consequence of the changes in the natriuretic peptide system and/or the angiotensin-aldosterone system Trial Registration Clinical Trials Identifier: NCT00281762

Ionizing radiation alters the properties of sodium channels in rat brain synaptosomes

Energy Technology Data Exchange (ETDEWEB)

Mullin, M J; Hunt, W A; Harris, R A

1986-08-01

The effect of ionizing radiation on neuronal membrane function was assessed by measurement of neurotoxin-stimulated /sup 22/Na/sup +/ uptake by rat brain synaptosomes. High-energy electrons and gamma photons were equally effective in reducing the maximal uptake of /sup 22/Na/sup +/ with no significant change in the affinity of veratridine for its binding site in the channel. Ionizing radiation reduced the veratridine-stimulated uptake at the earliest times measured (3 and 5 s), when the rate of uptake was greatest. Batrachotoxin-stimulated /sup 22/Na/sup +/ uptake was less sensitive to inhibition by radiation. The binding of (/sup 3/H)saxitoxin to its receptor in the sodium channel was unaffected by exposure to ionizing radiation. The effect of ionizing radiation on the lipid order of rat brain synaptic plasma membranes was measured by the fluorescence polarization of the molecular probes 1,6-diphenyl-1,3,5-hexatriene and 1-(4-(trimethylammonium)phenyl)-6-phenyl-1,3,5-hexatriene. A dose of radiation that reduced the veratridine-stimulated uptake of /sup 22/Na/sup +/ had no effect on the fluorescence polarization of either probe. These results demonstrate an inhibitory effect of ionizing radiation on the voltage-sensitive sodium channels in rat brain synaptosomes. This effect of radiation is not dependent on changes in the order of membrane lipids.

Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Nav1.6 sodium channels

International Nuclear Information System (INIS)

Tan Jianguo; Soderlund, David M.

2010-01-01

We expressed rat Na v 1.6 sodium channels in combination with the rat β 1 and β 2 auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 μM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ∼ 9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 μM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 μM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin ∼ 15-fold and that tefluthrin was ∼ 10-fold more potent than deltamethrin as a use-dependent modifier of Na v 1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Na v 1.2 sodium channel coexpressed with the rat β 1 and β 2 subunits in oocytes showed that the Na v 1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na v 1.2 isoform. These results implicate sodium channels containing the Na v 1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.

Action potential generation requires a high sodium channel density in the axon initial segment

NARCIS (Netherlands)

Kole, Maarten H. P.; Ilschner, Susanne U.; Kampa, Björn M.; Williams, Stephen R.; Ruben, Peter C.; Stuart, Greg J.

2008-01-01

The axon initial segment ( AIS) is a specialized region in neurons where action potentials are initiated. It is commonly assumed that this process requires a high density of voltage-gated sodium ( Na(+)) channels. Paradoxically, the results of patch-clamp studies suggest that the Na(+) channel

Loss-of-Function Sodium Channel Mutations in Infancy A Pattern Unfolds

NARCIS (Netherlands)

Chockalingam, Priya; Wilde, Arthur A. M.

2012-01-01

The role of channelopathies in the pathogenesis of sudden cardiac death (SCD) in patients with structurally normal hearts is a rapidly evolving story.(1) Many ion channels are involved, including loss-of-function sodium channelopathies of which the phenotypic spectrum ranges from lethal arrhythmias

Ab initio study of structural, electronic and optical properties of MnHg(SCN){sub 4} and FeHg(SCN){sub 4}

Energy Technology Data Exchange (ETDEWEB)

He, K.H. [College of Maths and Physics, China University of Geosciences, Wuhan 430074 (China)]. E-mail: he23981006@126.com; Zheng, G. [College of Maths and Physics, China University of Geosciences, Wuhan 430074 (China)]. E-mail: gzheng25@yahoo.com; Chen, G. [College of Maths and Physics, China University of Geosciences, Wuhan 430074 (China); Lue, T. [College of Maths and Physics, China University of Geosciences, Wuhan 430074 (China); Wan, M. [College of Maths and Physics, China University of Geosciences, Wuhan 430074 (China); Ji, G.F. [Laboratory for Shock Wave and Detonation Physics, China Academy of Engineering Physics, Mianyang 621900 (China)

2007-03-01

The structural, electronic and optical properties of MnHg(SCN){sub 4} and FeHg(SCN){sub 4} were studied by means of quantum-mechanical calculations based on the density-functional theory and pseudopotential method. The lattice constants can be compared with the experimental values when the effects of temperature are considered. The peaks of partial density of states of S, C, N and Hg of FeHg(SCN){sub 4} have a tendency of shifting to the higher energy levels relative to those of MnHg(SCN){sub 4}. The distributions of the 3d electronic states in the transition metal atoms show quite large difference and decide different optical properties. We found that absorptional peaks of FeHg(SCN){sub 4} lag behind those of MnHg(SCN){sub 4} and the peak in the infrared range has a higher absorptional intensity, which are in accord with the experimental results. By analyzing the distributions and transitions of the 3d electronic states, we explained the different absorption phenomena.

Luminescence studies of Sm(III) and Cm(III) complexes in NaSCN/DHDECMP extraction systems

CERN Document Server

Chung, D Y; Kimura, T

1999-01-01

Laser-induced fluorescence (LIF) studies of Sm(III) and Cm(III) complexes in the NaSCN/DHDECMP solvent extraction system were carried out. Luminescence lifetimes were measured to determine the number of water molecules coordinated to Sm(III), Tb(III), Dy(III), and Cm(III) in the sodium thiocyanate solution and in the DHDECMP phase. The hydration number of Sm(III), Tb(III), Dy(III), and Cm(III) in the sodium thiocyanate solution decreased linearly with increasing sodium thiocyanate concentration. The hydration numbers of Sm(III), Dy(III), and Cm(III) in the DHDECMP phase decreased with increasing sodium thiocyanate concentration. The water molecules in the inner coordination sphere of Sm(III) and Dy(III) extracted into the DHDECMP were not completely removed at low sodium thiocyanate concentration but decreased with increasing sodium thiocyanate concentration. However, in the case of Cm(III) extracted into the DHDECMP phase from the sodium thiocyanate solution, there was no water in the inner coordination sphe...

Pitfalls in genetic testing: the story of missed SCN1A mutations.

Science.gov (United States)

Djémié, Tania; Weckhuysen, Sarah; von Spiczak, Sarah; Carvill, Gemma L; Jaehn, Johanna; Anttonen, Anna-Kaisa; Brilstra, Eva; Caglayan, Hande S; de Kovel, Carolien G; Depienne, Christel; Gaily, Eija; Gennaro, Elena; Giraldez, Beatriz G; Gormley, Padhraig; Guerrero-López, Rosa; Guerrini, Renzo; Hämäläinen, Eija; Hartmann, Corinna; Hernandez-Hernandez, Laura; Hjalgrim, Helle; Koeleman, Bobby P C; Leguern, Eric; Lehesjoki, Anna-Elina; Lemke, Johannes R; Leu, Costin; Marini, Carla; McMahon, Jacinta M; Mei, Davide; Møller, Rikke S; Muhle, Hiltrud; Myers, Candace T; Nava, Caroline; Serratosa, Jose M; Sisodiya, Sanjay M; Stephani, Ulrich; Striano, Pasquale; van Kempen, Marjan J A; Verbeek, Nienke E; Usluer, Sunay; Zara, Federico; Palotie, Aarno; Mefford, Heather C; Scheffer, Ingrid E; De Jonghe, Peter; Helbig, Ingo; Suls, Arvid

2016-07-01

Sanger sequencing, still the standard technique for genetic testing in most diagnostic laboratories and until recently widely used in research, is gradually being complemented by next-generation sequencing (NGS). No single mutation detection technique is however perfect in identifying all mutations. Therefore, we wondered to what extent inconsistencies between Sanger sequencing and NGS affect the molecular diagnosis of patients. Since mutations in SCN1A, the major gene implicated in epilepsy, are found in the majority of Dravet syndrome (DS) patients, we focused on missed SCN1A mutations. We sent out a survey to 16 genetic centers performing SCN1A testing. We collected data on 28 mutations initially missed using Sanger sequencing. All patients were falsely reported as SCN1A mutation-negative, both due to technical limitations and human errors. We illustrate the pitfalls of Sanger sequencing and most importantly provide evidence that SCN1A mutations are an even more frequent cause of DS than already anticipated.

To4, the first Tityus obscurus β-toxin fully electrophysiologically characterized on human sodium channel isoforms.

Science.gov (United States)

Duque, Harry Morales; Mourão, Caroline Barbosa Farias; Tibery, Diogo Vieira; Barbosa, Eder Alves; Campos, Leandro Ambrósio; Schwartz, Elisabeth Ferroni

2017-09-01

Many scorpion toxins that act on sodium channels (NaScTxs) have been characterized till date. These toxins may act modulating the inactivation or the activation of sodium channels and are named α- or β-types, respectively. Some venom toxins from Tityus obscurus (Buthidae), a scorpion widely distributed in the Brazilian Amazon, have been partially characterized in previous studies; however, little information about their electrophysiological role on sodium ion channels has been published. In the present study, we describe the purification, identification and electrophysiological characterization of a NaScTx, which was first described as Tc54 and further fully sequenced and renamed To4. This toxin shows a marked β-type effect on different sodium channel subtypes (hNa v 1.1-hNa v 1.7) at low concentrations, and has more pronounced activity on hNa v 1.1, hNa v 1.2 and hNa v 1.4. By comparing To4 primary structure with other Tityus β-toxins which have already been electrophysiologically tested, it is possible to establish some key amino acid residues for the sodium channel activity. Thus, To4 is the first toxin from T. obscurus fully electrophysiologically characterized on different human sodium channel isoforms. Copyright © 2017 Elsevier Inc. All rights reserved.

Evaluation of Presumably Disease Causing SCN1A Variants in a Cohort of Common Epilepsy Syndromes.

Directory of Open Access Journals (Sweden)

Dennis Lal

Full Text Available The SCN1A gene, coding for the voltage-gated Na+ channel alpha subunit NaV1.1, is the clinically most relevant epilepsy gene. With the advent of high-throughput next-generation sequencing, clinical laboratories are generating an ever-increasing catalogue of SCN1A variants. Variants are more likely to be classified as pathogenic if they have already been identified previously in a patient with epilepsy. Here, we critically re-evaluate the pathogenicity of this class of variants in a cohort of patients with common epilepsy syndromes and subsequently ask whether a significant fraction of benign variants have been misclassified as pathogenic.We screened a discovery cohort of 448 patients with a broad range of common genetic epilepsies and 734 controls for previously reported SCN1A mutations that were assumed to be disease causing. We re-evaluated the evidence for pathogenicity of the identified variants using in silico predictions, segregation, original reports, available functional data and assessment of allele frequencies in healthy individuals as well as in a follow up cohort of 777 patients.We identified 8 known missense mutations, previously reported as pathogenic, in a total of 17 unrelated epilepsy patients (17/448; 3.80%. Our re-evaluation indicates that 7 out of these 8 variants (p.R27T; p.R28C; p.R542Q; p.R604H; p.T1250M; p.E1308D; p.R1928G; NP_001159435.1 are not pathogenic. Only the p.T1174S mutation may be considered as a genetic risk factor for epilepsy of small effect size based on the enrichment in patients (P = 6.60 x 10-4; OR = 0.32, fishers exact test, previous functional studies but incomplete penetrance. Thus, incorporation of previous studies in genetic counseling of SCN1A sequencing results is challenging and may produce incorrect conclusions.

Expression, purification and functional reconstitution of slack sodium-activated potassium channels.

Science.gov (United States)

Yan, Yangyang; Yang, Youshan; Bian, Shumin; Sigworth, Fred J

2012-11-01

The slack (slo2.2) gene codes for a potassium-channel α-subunit of the 6TM voltage-gated channel family. Expression of slack results in Na(+)-activated potassium channel activity in various cell types. We describe the purification and reconstitution of Slack protein and show that the Slack α-subunit alone is sufficient for potassium channel activity activated by sodium ions as assayed in planar bilayer membranes and in membrane vesicles.

Cognitive performance as a zeitgeber: cognitive oscillators and cholinergic modulation of the SCN entrain circadian rhythms.

Directory of Open Access Journals (Sweden)

Howard J Gritton

Full Text Available The suprachiasmatic nucleus (SCN is the primary circadian pacemaker in mammals that can synchronize or entrain to environmental cues. Although light exerts powerful influences on SCN output, other non-photic stimuli can modulate the SCN as well. We recently demonstrated that daily performance of a cognitive task requiring sustained periods of attentional effort that relies upon basal forebrain (BF cholinergic activity dramatically alters circadian rhythms in rats. In particular, normally nocturnal rats adopt a robust diurnal activity pattern that persists for several days in the absence of cognitive training. Although anatomical and pharmacological data from non-performing animals support a relationship between cholinergic signaling and circadian rhythms, little is known about how endogenous cholinergic signaling influences SCN function in behaving animals. Here we report that BF cholinergic projections to the SCN provide the principal signal allowing for the expression of cognitive entrainment in light-phase trained animals. We also reveal that oscillator(s outside of the SCN drive cognitive entrainment as daily timed cognitive training robustly entrains SCN-lesioned arrhythmic animals. Ablation of the SCN, however, resulted in significant impairments in task acquisition, indicating that SCN-mediated timekeeping benefits new learning and cognitive performance. Taken together, we conclude that cognition entrains non-photic oscillators, and cholinergic signaling to the SCN serves as a temporal timestamp attenuating SCN photic-driven rhythms, thereby permitting cognitive demands to modulate behavior.

Antiepileptic drugs targeting sodium channels: subunit and neuron-type specific interactions

NARCIS (Netherlands)

Qiao, X.

2013-01-01

Certain antiepileptic drugs (e.g. carbamazepine and lamotrigine) block sodium channels in an use-dependent manner and this mechanism contributes to the anti-convulsant properties of these drugs. There are, however, subtle differences in sodium current blocking properties of the antiepileptic drugs

Deletion of FoxO1 Leads to Shortening of QRS by Increasing Na+ Channel Activity through Enhanced Expression of both Cardiac NaV1.5 and β3 Subunit

OpenAIRE

Cai, Benzhi; Wang, Ning; Mao, Weike; You, Tao; Lu, Yan; Li, Xiang; Ye, Bo; Li, Faqian; Xu, Haodong

2014-01-01

Our in vitro studies revealed that a transcription factor, Forkhead box protein O1 (FoxO1), negatively regulates the expression of NaV1.5, a main α subunit of the cardiac Na+ channel, by altering the promoter activity of SCN5a in HL-1 cardiomyocytes. The in vivo role of FoxO1 in the regulation of cardiac NaV1.5 expression remains unknown. The present study aimed to define the role of FoxO1 in the regulation of NaV1.5 expression and cardiac Na+ channel activity in mouse ventricular cardiomyocy...

Modulation of epithelial sodium channel trafficking and function by sodium 4-phenylbutyrate in human nasal epithelial cells.

Science.gov (United States)

Prulière-Escabasse, Virginie; Planès, Carole; Escudier, Estelle; Fanen, Pascale; Coste, André; Clerici, Christine

2007-11-23

Sodium 4-phenylbutyrate (4-PBA) has been shown to correct the cellular trafficking of several mutant or nonmutant plasma membrane proteins such as cystic fibrosis transmembrane conductance regulator through the expression of 70-kDa heat shock proteins. The objective of the study was to determine whether 4-PBA may influence the functional expression of epithelial sodium channels (ENaC) in human nasal epithelial cells (HNEC). Using primary cultures of HNEC, we demonstrate that 4-PBA (5 mm for 6 h) markedly stimulated amiloride-sensitive sodium channel activity and that this was related to an increased abundance of alpha-, beta-, and gamma-ENaC subunits in the apical membrane. The increase in ENaC cell surface expression (i) was due to insertion of newly ENaC subunits as determined by brefeldin A experiments and (ii) was not associated with cell surface retention of ENaC subunits because endocytosis of ENaC subunits was unchanged. In addition, we find that ENaC co-immunoprecipitated with the heat shock protein constitutively expressed Hsc70, that has been reported to modulate ENaC trafficking, and that 4-PBA decreased Hsc70 protein level. Finally, we report that in cystic fibrosis HNEC obtained from two cystic fibrosis patients, 4-PBA increased functional expression of ENaC as demonstrated by the increase in amiloride-sensitive sodium transport and in alpha-, beta-, and gamma-ENaC subunit expression in the apical membrane. Our results suggest that in HNEC, 4-PBA increases the functional expression of ENaC through the insertion of new alpha-, beta-, and gamma-ENaC subunits into the apical membrane and also suggest that 4-PBA could modify ENaC trafficking by reducing Hsc70 protein expression.

Gating transitions in the selectivity filter region of a sodium channel are coupled to the domain IV voltage sensor.

Science.gov (United States)

Capes, Deborah L; Arcisio-Miranda, Manoel; Jarecki, Brian W; French, Robert J; Chanda, Baron

2012-02-14

Voltage-dependent ion channels are crucial for generation and propagation of electrical activity in biological systems. The primary mechanism for voltage transduction in these proteins involves the movement of a voltage-sensing domain (D), which opens a gate located on the cytoplasmic side. A distinct conformational change in the selectivity filter near the extracellular side has been implicated in slow inactivation gating, which is important for spike frequency adaptation in neural circuits. However, it remains an open question whether gating transitions in the selectivity filter region are also actuated by voltage sensors. Here, we examine conformational coupling between each of the four voltage sensors and the outer pore of a eukaryotic voltage-dependent sodium channel. The voltage sensors of these sodium channels are not structurally symmetric and exhibit functional specialization. To track the conformational rearrangements of individual voltage-sensing domains, we recorded domain-specific gating pore currents. Our data show that, of the four voltage sensors, only the domain IV voltage sensor is coupled to the conformation of the selectivity filter region of the sodium channel. Trapping the outer pore in a particular conformation with a high-affinity toxin or disulphide crossbridge impedes the return of this voltage sensor to its resting conformation. Our findings directly establish that, in addition to the canonical electromechanical coupling between voltage sensor and inner pore gates of a sodium channel, gating transitions in the selectivity filter region are also coupled to the movement of a voltage sensor. Furthermore, our results also imply that the voltage sensor of domain IV is unique in this linkage and in the ability to initiate slow inactivation in sodium channels.

Single sodium channels from human skeletal muscle in planar lipid bilayers: characterization and response to pentobarbital

NARCIS (Netherlands)

Wartenberg, Hans C.; Urban, Bernd W.

2004-01-01

PURPOSE: To investigate the response to general anesthetics of different sodium-channel subtypes, we examined the effects of pentobarbital, a close thiopental analogue, on single sodium channels from human skeletal muscle and compared them to existing data from human brain and human ventricular

Structure-based assessment of disease-related mutations in human voltage-gated sodium channels

Directory of Open Access Journals (Sweden)

Weiyun Huang

2017-02-01

Full Text Available ABSTRACT Voltage-gated sodium (Nav channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Nav channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Nav channels, with Nav1.1 and Nav1.5 each harboring more than 400 mutations. Nav channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Nav channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Cav channel Cav1.1 provides a template for homology-based structural modeling of the evolutionarily related Nav channels. In this Resource article, we summarized all the reported disease-related mutations in human Nav channels, generated a homologous model of human Nav1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Nav channels, the analysis presented here serves as the base framework for mechanistic investigation of Nav channelopathies and for potential structure-based drug discovery.

Structure-based assessment of disease-related mutations in human voltage-gated sodium channels.

Science.gov (United States)

Huang, Weiyun; Liu, Minhao; Yan, S Frank; Yan, Nieng

2017-06-01

Voltage-gated sodium (Na v ) channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Na v channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Na v channels, with Na v 1.1 and Na v 1.5 each harboring more than 400 mutations. Na v channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Na v channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Ca v ) channel Ca v 1.1 provides a template for homology-based structural modeling of the evolutionarily related Na v channels. In this Resource article, we summarized all the reported disease-related mutations in human Na v channels, generated a homologous model of human Na v 1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Na v channels, the analysis presented here serves as the base framework for mechanistic investigation of Na v channelopathies and for potential structure-based drug discovery.

Slick (Kcnt2 Sodium-Activated Potassium Channels Limit Peptidergic Nociceptor Excitability and Hyperalgesia

Directory of Open Access Journals (Sweden)

Danielle L Tomasello

2017-09-01

Full Text Available The Slick (Kcnt2 sodium-activated potassium (K Na channel is a rapidly gating and weakly voltage-dependent and sodium-dependent potassium channel with no clearly defined physiological function. Within the dorsal root ganglia (DRGs, we show Slick channels are exclusively expressed in small-sized and medium-sized calcitonin gene–related peptide (CGRP-containing DRG neurons, and a pool of channels are localized to large dense-core vesicles (LDCV-containing CGRP. We stimulated DRG neurons for CGRP release and found Slick channels contained within CGRP-positive LDCV translocated to the neuronal membrane. Behavioral studies in Slick knockout (KO mice indicated increased basal heat detection and exacerbated thermal hyperalgesia compared with wild-type littermate controls during neuropathic and chronic inflammatory pain. Electrophysiologic recordings of DRG neurons from Slick KO mice revealed that Slick channels contribute to outward current, propensity to fire action potentials (APs, and to AP properties. Our data suggest that Slick channels restrain the excitability of CGRP-containing neurons, diminishing pain behavior after inflammation and injury.

Deriving freshwater quality criteria of sulphocyanic sodium for the protection of aquatic life in China

Institute of Scientific and Technical Information of China (English)

1998-01-01

The freshwater quality criteria of sulphocyanic sodium(NaSCN) were studied on the basis of the features of the aquaticbiota in China, and with Reference to U.S.EPA's guidelines. Acutetests were performed on twelve different domestic species todetermine 48h-EC50/96h-EC50 (or 96h-LC50) values for NaSCN. 21dsurvival-reproduction test with Daphnia magna, 60d fry-juvenilepart life stage test with Carassius auratus gibelio and 96h growthinhibition test with Lemna minor were also conducted to estimatelower chronic limit/upper chronic limit values. In the acute tests,D.magna was the most sensitive species to NaSCN followed by Tilapiamossambia, Cyprinus carpio and C.auratus gibelio in turn. The finalacute value of NaSCN was 2.699 mg/L. In the chronic tests,reproduction of daphnids were significantly reduced by NaSCN at 1.0mg/L. Acute-to-chronic ratios ranged from 5.96 to 19.1. A finalchronic value of 0.2530 mg/L was obtained and a final plant valuewas 1346 mg/L. A criterion maximum concentration (1.349 mg/L) anda criterion continuous concentration (0.2530 mg/L) were derivedrespectively. The results of this study may provide useful data toderive national WQC for NaSCN as well as the procedures of derivingWQC of other chemicals for the protection of aquatic biota in China.

Native pyroglutamation of huwentoxin-IV: a post-translational modification that increases the trapping ability to the sodium channel.

Science.gov (United States)

Rong, Mingqiang; Duan, Zhigui; Chen, Juliang; Li, Jianglin; Xiao, Yuchen; Liang, Songping

2013-01-01

Huwentoxin-IV (HWTX-IV), a tetrodotoxin-sensitive (TTX-s) sodium channel antagonist, is found in the venom of the Chinese spider Ornithoctonus huwena. A naturally modified HWTX-IV (mHWTX-IV), having a molecular mass 18 Da lower than HWTX-IV, has also been isolated from the venom of the same spider. By a combination of enzymatic fragmentation and MS/MS de novo sequencing, mHWTX-IV has been shown to have the same amino acid sequence as that of HWTX-IV, except that the N-terminal glutamic acid replaced by pyroglutamic acid. mHWTX-IV inhibited tetrodotoxin-sensitive voltage-gated sodium channels of dorsal root ganglion neurons with an IC50 nearly equal to native HWTX-IV. mHWTX-IV showed the same activation and inactivation kinetics seen for native HWTX-IV. In contrast with HWTX-IV, which dissociates at moderate voltage depolarization voltages (+50 mV, 180000 ms), mHWTX-IV inhibition of TTX-sensitive sodium channels is not reversed by strong depolarization voltages (+200 mV, 500 ms). Recovery of Nav1.7current was voltage-dependent and was induced by extreme depolarization in the presence of HWTX-IV, but no obvious current was elicited after application of mHWTX-IV. Our data indicate that the N-terminal modification of HWTX-IV gives the peptide toxin a greater ability to trap the voltage sensor in the sodium channel. Loss of a negative charge, caused by cyclization at the N-terminus, is a possible reason why the modified toxin binds much stronger. To our knowledge, this is the first report of a pyroglutamic acid residue in a spider toxin; this modification seems to increase the trapping ability of the voltage sensor in the sodium channel.

Native pyroglutamation of huwentoxin-IV: a post-translational modification that increases the trapping ability to the sodium channel.

Directory of Open Access Journals (Sweden)

Mingqiang Rong

Full Text Available Huwentoxin-IV (HWTX-IV, a tetrodotoxin-sensitive (TTX-s sodium channel antagonist, is found in the venom of the Chinese spider Ornithoctonus huwena. A naturally modified HWTX-IV (mHWTX-IV, having a molecular mass 18 Da lower than HWTX-IV, has also been isolated from the venom of the same spider. By a combination of enzymatic fragmentation and MS/MS de novo sequencing, mHWTX-IV has been shown to have the same amino acid sequence as that of HWTX-IV, except that the N-terminal glutamic acid replaced by pyroglutamic acid. mHWTX-IV inhibited tetrodotoxin-sensitive voltage-gated sodium channels of dorsal root ganglion neurons with an IC50 nearly equal to native HWTX-IV. mHWTX-IV showed the same activation and inactivation kinetics seen for native HWTX-IV. In contrast with HWTX-IV, which dissociates at moderate voltage depolarization voltages (+50 mV, 180000 ms, mHWTX-IV inhibition of TTX-sensitive sodium channels is not reversed by strong depolarization voltages (+200 mV, 500 ms. Recovery of Nav1.7current was voltage-dependent and was induced by extreme depolarization in the presence of HWTX-IV, but no obvious current was elicited after application of mHWTX-IV. Our data indicate that the N-terminal modification of HWTX-IV gives the peptide toxin a greater ability to trap the voltage sensor in the sodium channel. Loss of a negative charge, caused by cyclization at the N-terminus, is a possible reason why the modified toxin binds much stronger. To our knowledge, this is the first report of a pyroglutamic acid residue in a spider toxin; this modification seems to increase the trapping ability of the voltage sensor in the sodium channel.

A novel and lethal de novo LQT-3 mutation in a newborn with distinct molecular pharmacology and therapeutic response.

Directory of Open Access Journals (Sweden)

John R Bankston

2007-12-01

Full Text Available SCN5A encodes the alpha-subunit (Na(v1.5 of the principle Na(+ channel in the human heart. Genetic lesions in SCN5A can cause congenital long QT syndrome (LQTS variant 3 (LQT-3 in adults by disrupting inactivation of the Na(v1.5 channel. Pharmacological targeting of mutation-altered Na(+ channels has proven promising in developing a gene-specific therapeutic strategy to manage specifically this LQTS variant. SCN5A mutations that cause similar channel dysfunction may also contribute to sudden infant death syndrome (SIDS and other arrhythmias in newborns, but the prevalence, impact, and therapeutic management of SCN5A mutations may be distinct in infants compared with adults.Here, in a multidisciplinary approach, we report a de novo SCN5A mutation (F1473C discovered in a newborn presenting with extreme QT prolongation and differential responses to the Na(+ channel blockers flecainide and mexiletine. Our goal was to determine the Na(+ channel phenotype caused by this severe mutation and to determine whether distinct effects of different Na(+ channel blockers on mutant channel activity provide a mechanistic understanding of the distinct therapeutic responsiveness of the mutation carrier. Sequence analysis of the proband revealed the novel missense SCN5A mutation (F1473C and a common variant in KCNH2 (K897T. Patch clamp analysis of HEK 293 cells transiently transfected with wild-type or mutant Na(+ channels revealed significant changes in channel biophysics, all contributing to the proband's phenotype as predicted by in silico modeling. Furthermore, subtle differences in drug action were detected in correcting mutant channel activity that, together with both the known genetic background and age of the patient, contribute to the distinct therapeutic responses observed clinically.The results of our study provide further evidence of the grave vulnerability of newborns to Na(+ channel defects and suggest that both genetic background and age are

Marine Toxins That Target Voltage-gated Sodium Channels

Directory of Open Access Journals (Sweden)

Robert J. French

2006-04-01

Full Text Available Abstract: Eukaryotic, voltage-gated sodium (NaV channels are large membrane proteins which underlie generation and propagation of rapid electrical signals in nerve, muscle and heart. Nine different NaV receptor sites, for natural ligands and/or drugs, have been identified, based on functional analyses and site-directed mutagenesis. In the marine ecosystem, numerous toxins have evolved to disrupt NaV channel function, either by inhibition of current flow through the channels, or by modifying the activation and inactivation gating processes by which the channels open and close. These toxins function in their native environment as offensive or defensive weapons in prey capture or deterrence of predators. In composition, they range from organic molecules of varying size and complexity to peptides consisting of ~10-70 amino acids. We review the variety of known NaV-targeted marine toxins, outlining, where known, their sites of interaction with the channel protein and their functional effects. In a number of cases, these natural ligands have the potential applications as drugs in clinical settings, or as models for drug development.

Hereditary sensory and autonomic neuropathy type IID caused by an SCN9A mutation.

Science.gov (United States)

Yuan, Junhui; Matsuura, Eiji; Higuchi, Yujiro; Hashiguchi, Akihiro; Nakamura, Tomonori; Nozuma, Satoshi; Sakiyama, Yusuke; Yoshimura, Akiko; Izumo, Shuji; Takashima, Hiroshi

2013-04-30

To identify the clinical features of Japanese patients with suspected hereditary sensory and autonomic neuropathy (HSAN) on the basis of genetic diagnoses. On the basis of clinical, in vivo electrophysiologic, and pathologic findings, 9 Japanese patients with sensory and autonomic nervous dysfunctions were selected. Eleven known HSAN disease-causing genes and 5 related genes were screened using a next-generation sequencer. A homozygous mutation, c.3993delGinsTT, was identified in exon 22 of SCN9A from 2 patients/families. The clinical phenotype was characterized by adolescent or congenital onset with loss of pain and temperature sensation, autonomic nervous dysfunctions, hearing loss, and hyposmia. Subsequently, this mutation was discovered in one of patient 1's sisters, who also exhibited sensory and autonomic nervous system dysfunctions, with recurrent fractures being the most predominant feature. Nerve conduction studies revealed definite asymmetric sensory nerve involvement in patient 1. In addition, sural nerve pathologic findings showed loss of large myelinated fibers in patient 1, whereas the younger patient showed normal sural nerve pathology. We identified a novel homozygous mutation in SCN9A from 2 Japanese families with autosomal recessive HSAN. This loss-of-function SCN9A mutation results in disturbances in the sensory, olfactory, and autonomic nervous systems. We propose that SCN9A mutation results in the new entity of HSAN type IID, with additional symptoms including hyposmia, hearing loss, bone dysplasia, and hypogeusia.

Voltage-gated sodium channels as targets for pyrethroid insecticides.

Science.gov (United States)

Field, Linda M; Emyr Davies, T G; O'Reilly, Andrias O; Williamson, Martin S; Wallace, B A

2017-10-01

The pyrethroid insecticides are a very successful group of compounds that have been used extensively for the control of arthropod pests of agricultural crops and vectors of animal and human disease. Unfortunately, this has led to the development of resistance to the compounds in many species. The mode of action of pyrethroids is known to be via interactions with the voltage-gated sodium channel. Understanding how binding to the channel is affected by amino acid substitutions that give rise to resistance has helped to elucidate the mode of action of the compounds and the molecular basis of their selectivity for insects vs mammals and between insects and other arthropods. Modelling of the channel/pyrethroid interactions, coupled with the ability to express mutant channels in oocytes and study function, has led to knowledge of both how the channels function and potentially how to design novel insecticides with greater species selectivity.

Probing the early stages of salt nucleation—Experimental and theoretical investigations of sodium/potassium thiocyanate cluster anions

Science.gov (United States)

Deng, S. H. M.; Kong, Xiang-Yu; Wang, Xue-Bin

2015-01-01

Due to the fast solvent evaporation in electrospray ionization (ESI), the concentration of initially dilute electrolyte solutions rapidly increases to afford the formation of supersaturated droplets and generation of various pristine anhydrous salt clusters in the gas phase. The size, composition, and charge distributions of these clusters, in principle, witness the nucleation evolution in solutions. Herein, we report a microscopic study on the initial stage of nucleation and crystallization of sodium/potassium thiocyanate salt solutions simulated in the ESI process. Singly charged M x (SCN)x + 1 - , doubly charged M y (SCN)y + 2 2 - (M = Na, K), and triply charged K z (SCN)z + 3 3 - anion clusters (x, y, and z stand for the number of alkali atoms in the singly, doubly, and triply charged clusters, respectively) were produced via electrospray of the corresponding salt solutions and were characterized by negative ion photoelectron spectroscopy (NIPES). The vertical detachment energies (VDEs) of these sodium/potassium thiocyanate cluster anions were obtained, and theoretical calculations were carried out for the sodium thiocyanate clusters in assisting spectral identification. The measured VDEs of singly charged anions M x (SCN)x + 1 - (M = Na and K) demonstrate that they are superhalogen anions. The existence of doubly charged anions M y (SCN)y + 2 2 - (y = 2x, x ≥ 4 and 3 for M = Na and K, respectively) and triply charged anions K z (SCN)z + 3 3 - (z = 3x, x ≥ 6) was initially discovered from the photoelectron spectra for those singly charged anions of M x (SCN)x + 1 - with the same mass-to-charge ratio (m/z), and later independently confirmed by the observation of their distinct mass spectral distributions and by taking their NIPE spectra for those pure multiply charged anions with their m/z different from the singly charged species. For large clusters, multiply charged clusters were found to become preferred, but at higher temperatures, those multiply charged

Molecular cloning and analysis of zebrafish voltage-gated sodium channel beta subunit genes: implications for the evolution of electrical signaling in vertebrates

Directory of Open Access Journals (Sweden)

Zhong Tao P

2007-07-01

Full Text Available Abstract Background Action potential generation in excitable cells such as myocytes and neurons critically depends on voltage-gated sodium channels. In mammals, sodium channels exist as macromolecular complexes that include a pore-forming alpha subunit and 1 or more modulatory beta subunits. Although alpha subunit genes have been cloned from diverse metazoans including flies, jellyfish, and humans, beta subunits have not previously been identified in any non-mammalian species. To gain further insight into the evolution of electrical signaling in vertebrates, we investigated beta subunit genes in the teleost Danio rerio (zebrafish. Results We identified and cloned single zebrafish gene homologs for beta1-beta3 (zbeta1-zbeta3 and duplicate genes for beta4 (zbeta4.1, zbeta4.2. Sodium channel beta subunit loci are similarly organized in fish and mammalian genomes. Unlike their mammalian counterparts, zbeta1 and zbeta2 subunit genes display extensive alternative splicing. Zebrafish beta subunit genes and their splice variants are differentially-expressed in excitable tissues, indicating tissue-specific regulation of zbeta1-4 expression and splicing. Co-expression of the genes encoding zbeta1 and the zebrafish sodium channel alpha subunit Nav1.5 in Chinese Hamster Ovary cells increased sodium current and altered channel gating, demonstrating functional interactions between zebrafish alpha and beta subunits. Analysis of the synteny and phylogeny of mammalian, teleost, amphibian, and avian beta subunit and related genes indicated that all extant vertebrate beta subunits are orthologous, that beta2/beta4 and beta1/beta3 share common ancestry, and that beta subunits are closely related to other proteins sharing the V-type immunoglobulin domain structure. Vertebrate sodium channel beta subunit genes were not identified in the genomes of invertebrate chordates and are unrelated to known subunits of the para sodium channel in Drosophila. Conclusion The

Eslicarbazepine and the enhancement of slow inactivation of voltage-gated sodium channels: a comparison with carbamazepine, oxcarbazepine and lacosamide.

Science.gov (United States)

Hebeisen, Simon; Pires, Nuno; Loureiro, Ana I; Bonifácio, Maria João; Palma, Nuno; Whyment, Andrew; Spanswick, David; Soares-da-Silva, Patrício

2015-02-01

This study aimed at evaluating the effects of eslicarbazepine, carbamazepine (CBZ), oxcarbazepine (OXC) and lacosamide (LCM) on the fast and slow inactivated states of voltage-gated sodium channels (VGSC). The anti-epileptiform activity was evaluated in mouse isolated hippocampal slices. The anticonvulsant effects were evaluated in MES and the 6-Hz psychomotor tests. The whole-cell patch-clamp technique was used to investigate the effects of eslicarbazepine, CBZ, OXC and LCM on sodium channels endogenously expressed in N1E-115 mouse neuroblastoma cells. CBZ and eslicarbazepine exhibit similar concentration dependent suppression of epileptiform activity in hippocampal slices. In N1E-115 mouse neuroblastoma cells, at a concentration of 250 μM, the voltage dependence of the fast inactivation was not influenced by eslicarbazepine, whereas LCM, CBZ and OXC shifted the V0.5 value (mV) by -4.8, -12.0 and -16.6, respectively. Eslicarbazepine- and LCM-treated fast-inactivated channels recovered similarly to control conditions, whereas CBZ- and OXC-treated channels required longer pulses to recover. CBZ, eslicarbazepine and LCM shifted the voltage dependence of the slow inactivation (V0.5, mV) by -4.6, -31.2 and -53.3, respectively. For eslicarbazepine, LCM, CBZ and OXC, the affinity to the slow inactivated state was 5.9, 10.4, 1.7 and 1.8 times higher than to the channels in the resting state, respectively. In conclusion, eslicarbazepine did not share with CBZ and OXC the ability to alter fast inactivation of VGSC. Both eslicarbazepine and LCM reduce VGSC availability through enhancement of slow inactivation, but LCM demonstrated higher interaction with VGSC in the resting state and with fast inactivation gating. Copyright © 2014 Elsevier Ltd. All rights reserved.

Molecular Basis of Paraltyic Neurotoxin Action on Voltage-Sensitive Sodium Channels

Science.gov (United States)

1985-10-14

of 9,700 daltons isolated from the coral Goni2oora gy. (1). The toxin enhances neurally mediated contraction of blood vessels and taenia coli of the...sites on the solium channel and to identify the site of GPT action within the structure of the sodium channel protein. 2. Site of Action of Brvyetoxin

Prevalence of SCN1A-related dravet syndrome among children reported with seizures following vaccination: a population-based ten-year cohort study.

Directory of Open Access Journals (Sweden)

Nienke E Verbeek

Full Text Available OBJECTIVES: To determine the prevalence of Dravet syndrome, an epileptic encephalopathy caused by SCN1A-mutations, often with seizure onset after vaccination, among infants reported with seizures following vaccination. To determine differences in characteristics of reported seizures after vaccination in children with and without SCN1A-related Dravet syndrome. METHODS: Data were reviewed of 1,269 children with seizures following immunization in the first two years of life, reported to the safety surveillance system of the Dutch national immunization program between 1 January 1997 and 31 December 2006. Selective, prospective follow-up was performed of children with clinical characteristics compatible with a diagnosis of Dravet syndrome. RESULTS: In 21.9% (n = 279 of children, a diagnosis of Dravet syndrome could not be excluded based on available clinical data (median age at follow-up 16 months. Additional follow-up data were obtained in 83.9% (n = 234 of these children (median age 8.5 years. 15 (1.2% of 1,269; 95%CI:0.6 to 1.8% children were diagnosed with SCN1A-related Dravet syndrome. Of all reported seizures following vaccinations in the first year of life, 2.5% (95%CI:1.3 to 3.6% were due to SCN1A-related Dravet syndrome, as were 5.9% of reported seizures (95%CI:3.1 to 8.7% after 2(nd or 3(rd DTP-IPV-Hib vaccination. Seizures in children with SCN1A-related Dravet syndrome occurred more often with a body temperature below 38.5°C (57.9% vs. 32.6%, p = 0.020 and reoccurred more often after following vaccinations (26.7% vs. 4.0%, p = 0.003, than in children without a diagnosis of SCN1A-related Dravet Syndrome. CONCLUSIONS: Although Dravet syndrome is a rare genetic epilepsy syndrome, 2.5% of reported seizures following vaccinations in the first year of life in our cohort occurred in children with this disorder. Knowledge on the specific characteristics of vaccination-related seizures in this syndrome might promote early diagnosis

The genetic basis of Brugada syndrome: a mutation update

DEFF Research Database (Denmark)

Hedley, Paula L; Jørgensen, Poul; Schlamowitz, Sarah

2009-01-01

of inheritance with an average prevalence of 5:10,000 worldwide. Currently, more than 100 mutations in seven genes have been associated with BrS. Loss-of-function mutations in SCN5A, which encodes the alpha-subunit of the Na(v)1.5 sodium ion channel conducting the depolarizing I(Na) current, causes 15-20% of Br......S cases. A few mutations have been described in GPD1L, which encodes glycerol-3-phosphate dehydrogenase-1 like protein; CACNA1C, which encodes the alpha-subunit of the Ca(v)1.2 ion channel conducting the depolarizing I(L,Ca) current; CACNB2, which encodes the stimulating beta2-subunit of the Ca(v)1.2 ion...

Individual variation and hormonal modulation of a sodium channel beta subunit in the electric organ correlate with variation in a social signal.

Science.gov (United States)

Liu, He; Wu, Ming-Ming; Zakon, Harold H

2007-09-01

The sodium channel beta1 subunit affects sodium channel gating and surface density, but little is known about the factors that regulate beta1 expression or its participation in the fine control of cellular excitability. In this study we examined whether graded expression of the beta1 subunit contributes to the gradient in sodium current inactivation, which is tightly controlled and directly related to a social behavior, the electric organ discharge (EOD), in a weakly electric fish Sternopygus macrurus. We found the mRNA and protein levels of beta1 in the electric organ both correlate with EOD frequency. We identified a novel mRNA splice form of this gene and found the splicing preference for this novel splice form also correlates with EOD frequency. Androgen implants lowered EOD frequency and decreased the beta1 mRNA level but did not affect splicing. Coexpression of each splice form in Xenopus oocytes with either the human muscle sodium channel gene, hNav1.4, or a Sternopygus ortholog, smNav1.4b, sped the rate of inactivation of the sodium current and shifted the steady-state inactivation toward less negative membrane potentials. The translational product of the novel mRNA splice form lacks a previously identified important tyrosine residue but still functions normally. The properties of the fish alpha and coexpressed beta1 subunits in the oocyte replicate those of the electric organ's endogenous sodium current. These data highlight the role of ion channel beta subunits in regulating cellular excitability.

Upregulation of Haploinsufficient Gene Expression in the Brain by Targeting a Long Non-coding RNA Improves Seizure Phenotype in a Model of Dravet Syndrome.

Science.gov (United States)

Hsiao, J; Yuan, T Y; Tsai, M S; Lu, C Y; Lin, Y C; Lee, M L; Lin, S W; Chang, F C; Liu Pimentel, H; Olive, C; Coito, C; Shen, G; Young, M; Thorne, T; Lawrence, M; Magistri, M; Faghihi, M A; Khorkova, O; Wahlestedt, C

2016-07-01

Dravet syndrome is a devastating genetic brain disorder caused by heterozygous loss-of-function mutation in the voltage-gated sodium channel gene SCN1A. There are currently no treatments, but the upregulation of SCN1A healthy allele represents an appealing therapeutic strategy. In this study we identified a novel, evolutionary conserved mechanism controlling the expression of SCN1A that is mediated by an antisense non-coding RNA (SCN1ANAT). Using oligonucleotide-based compounds (AntagoNATs) targeting SCN1ANAT we were able to induce specific upregulation of SCN1A both in vitro and in vivo, in the brain of Dravet knock-in mouse model and a non-human primate. AntagoNAT-mediated upregulation of Scn1a in postnatal Dravet mice led to significant improvements in seizure phenotype and excitability of hippocampal interneurons. These results further elucidate the pathophysiology of Dravet syndrome and outline a possible new approach for the treatment of this and other genetic disorders with similar etiology. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Upregulation of Haploinsufficient Gene Expression in the Brain by Targeting a Long Non-coding RNA Improves Seizure Phenotype in a Model of Dravet Syndrome

Directory of Open Access Journals (Sweden)

J. Hsiao

2016-07-01

Full Text Available Dravet syndrome is a devastating genetic brain disorder caused by heterozygous loss-of-function mutation in the voltage-gated sodium channel gene SCN1A. There are currently no treatments, but the upregulation of SCN1A healthy allele represents an appealing therapeutic strategy. In this study we identified a novel, evolutionary conserved mechanism controlling the expression of SCN1A that is mediated by an antisense non-coding RNA (SCN1ANAT. Using oligonucleotide-based compounds (AntagoNATs targeting SCN1ANAT we were able to induce specific upregulation of SCN1A both in vitro and in vivo, in the brain of Dravet knock-in mouse model and a non-human primate. AntagoNAT-mediated upregulation of Scn1a in postnatal Dravet mice led to significant improvements in seizure phenotype and excitability of hippocampal interneurons. These results further elucidate the pathophysiology of Dravet syndrome and outline a possible new approach for the treatment of this and other genetic disorders with similar etiology.

Actions of the pyrethroid insecticide bifenthrin on sodium channels expressed in rat cerebral cortical neurons.

Science.gov (United States)

Yang, Lin; Li, Li

2015-01-01

Voltage-gated sodium channels are important sites for the neurotoxic actions of pyrethroid insecticides in mammals. Here, we studied the mode of action of bifenthrin on the native sodium channels in cerebral cortical neurons prepared from newborn rat brain, where the toxic effects are largely generated. Bifenthrin caused a pronounced late current that persisted at the end of a depolarizing pulse, a slowly-decaying tail current following repolarization and significant resting modification (25.3% modification at 10 μM). No significant bifenthrin-induced effect was observed at the peak current. Bifenthrin also caused a concentration-dependent hyperpolarizing shift in steady-state activation and inactivation as well as slowed recovery from channel inactivation. Repetitive depolarization increased the potency of bifenthrin with high frequency. There was approximately 64% inhibition of modification upon repetitive activation by 10-Hz trains of depolarizing pulses. These results suggest that bifenthrin binds to and modifies sodium channels in both the closed and open states and exhibits the behavior between type I and type II.

Differential gene expression of cardiac ion channels in human dilated cardiomyopathy.

Directory of Open Access Journals (Sweden)

Maria Micaela Molina-Navarro

Full Text Available BACKGROUND: Dilated cardiomyopathy (DCM is characterized by idiopathic dilation and systolic contractile dysfunction of the cardiac chambers. The present work aimed to study the alterations in gene expression of ion channels involved in cardiomyocyte function. METHODS AND RESULTS: Microarray profiling using the Affymetrix Human Gene® 1.0 ST array was performed using 17 RNA samples, 12 from DCM patients undergoing cardiac transplantation and 5 control donors (CNT. The analysis focused on 7 cardiac ion channel genes, since this category has not been previously studied in human DCM. SCN2B was upregulated, while KCNJ5, KCNJ8, CLIC2, CLCN3, CACNB2, and CACNA1C were downregulated. The RT-qPCR (21 DCM and 8 CNT samples validated the gene expression of SCN2B (p < 0.0001, KCNJ5 (p < 0.05, KCNJ8 (p < 0.05, CLIC2 (p < 0.05, and CACNB2 (p < 0.05. Furthermore, we performed an IPA analysis and we found a functional relationship between the different ion channels studied in this work. CONCLUSION: This study shows a differential expression of ion channel genes involved in cardiac contraction in DCM that might partly underlie the changes in left ventricular function observed in these patients. These results could be the basis for new genetic therapeutic approaches.

Modulation of epithelial sodium channel in human alveolar epithelial ...

African Journals Online (AJOL)

Modulation of epithelial sodium channel in human alveolar epithelial cells by lipoxin A4 through AhR-cAMP-dependent pathway. Bi-Huan Cheng1,2, Li-Wei Pan2, Sheng-Rong Zhang3, Bin-Yu Ying2, Ben-Ji. Wang2, Guo-Liang Lin2 and Shi-Fang Ding1*. 1Department of Critical Care Medicine, Qilu Hospital of Shandong ...

Flecainide provocation reveals concealed brugada syndrome in a long QT syndrome family with a novel L1786Q mutation in SCN5A

DEFF Research Database (Denmark)

Kanters, Jørgen K.; Yuan, Lei; Hedley, Paula L

2014-01-01

BACKGROUND: Mutations in SCN5A can result in both long QT type 3 (LQT3) and Brugada syndrome (BrS), and a few mutations have been found to have an overlapping phenotype. Long QT syndrome is characterized by prolonged QT interval, and a prerequisite for a BrS diagnosis is ST elevation in the right...... interval. The proband presented with an aborted cardiac arrest, and his mother died suddenly and unexpectedly at the age of 65. Flecainide treatment revealed coved ST elevation in all mutation carriers. Electrophysiological investigations of the mutant in HEK293 cells indicated a reduced peak current...

Adaptive evolution of the vertebrate skeletal muscle sodium channel

Directory of Open Access Journals (Sweden)

Jian Lu

2011-01-01

Full Text Available Tetrodotoxin (TTX is a highly potent neurotoxin that blocks the action potential by selectively binding to voltage-gated sodium channels (Na v. The skeletal muscle Na v (Na v1.4 channels in most pufferfish species and certain North American garter snakes are resistant to TTX, whereas in most mammals they are TTX-sensitive. It still remains unclear as to whether the difference in this sensitivity among the various vertebrate species can be associated with adaptive evolution. In this study, we investigated the adaptive evolution of the vertebrate Na v1.4 channels. By means of the CODEML program of the PAML 4.3 package, the lineages of both garter snakes and pufferfishes were denoted to be under positive selection. The positively selected sites identified in the p-loop regions indicated their involvement in Na v1.4 channel sensitivity to TTX. Most of these sites were located in the intracellular regions of the Na v1.4 channel, thereby implying the possible association of these regions with the regulation of voltage-sensor movement.

Two novel sodium channel mutations associated with resistance to indoxacarb and metaflumizone in the diamondback moth, Plutella xylostella.

Science.gov (United States)

Wang, Xing-Liang; Su, Wen; Zhang, Jian-Heng; Yang, Yi-Hua; Dong, Ke; Wu, Yi-Dong

2016-02-01

Indoxacarb and metaflumizone belong to a relatively new class of sodium channel blocker insecticides (SCBIs). Due to intensive use of indoxacarb, field-evolved indoxacarb resistance has been reported in several lepidopteran pests, including the diamondback moth Plutella xylostella, a serious pest of cruciferous crops. In particular, the BY12 population of P. xylostella, collected from Baiyun, Guangdong Province of China in 2012, was 750-fold more resistant to indoxacarb and 70-fold more resistant to metaflumizone compared with the susceptible Roth strain. Comparison of complementary DNA sequences encoding the sodium channel genes of Roth and BY12 revealed two point mutations (F1845Y and V1848I) in the sixth segment of domain IV of the PxNav protein in the BY population. Both mutations are located within a highly conserved sequence region that is predicted to be involved in the binding sites of local anesthetics and SCBIs based on mammalian sodium channels. A significant correlation was observed among 10 field-collected populations between the mutant allele (Y1845 or I1848) frequencies (1.7% to 52.5%) and resistance levels to both indoxacarb (34- to 870-fold) and metaflumizone (1- to 70-fold). The two mutations were never found to co-exist in the same allele of PxNav , suggesting that they arose independently. This is the first time that sodium channel mutations have been associated with high levels of resistance to SCBIs. F1845Y and V1848I are molecular markers for resistance monitoring in the diamondback moth and possibly other insect pest species. © 2015 Institute of Zoology, Chinese Academy of Sciences.

Structure of a eukaryotic voltage-gated sodium channel at near-atomic resolution.

Science.gov (United States)

Shen, Huaizong; Zhou, Qiang; Pan, Xiaojing; Li, Zhangqiang; Wu, Jianping; Yan, Nieng

2017-03-03

Voltage-gated sodium (Na v ) channels are responsible for the initiation and propagation of action potentials. They are associated with a variety of channelopathies and are targeted by multiple pharmaceutical drugs and natural toxins. Here, we report the cryogenic electron microscopy structure of a putative Na v channel from American cockroach (designated Na v PaS) at 3.8 angstrom resolution. The voltage-sensing domains (VSDs) of the four repeats exhibit distinct conformations. The entrance to the asymmetric selectivity filter vestibule is guarded by heavily glycosylated and disulfide bond-stabilized extracellular loops. On the cytoplasmic side, a conserved amino-terminal domain is placed below VSD I , and a carboxy-terminal domain binds to the III-IV linker. The structure of Na v PaS establishes an important foundation for understanding function and disease mechanism of Na v and related voltage-gated calcium channels. Copyright © 2017, American Association for the Advancement of Science.

Mining Protein Evolution for Insights into Mechanisms of Voltage-Dependent Sodium Channel Auxiliary Subunits.

Science.gov (United States)

Molinarolo, Steven; Granata, Daniele; Carnevale, Vincenzo; Ahern, Christopher A

2018-02-21

Voltage-gated sodium channel (VGSC) beta (β) subunits have been called the "overachieving" auxiliary ion channel subunit. Indeed, these subunits regulate the trafficking of the sodium channel complex at the plasma membrane and simultaneously tune the voltage-dependent properties of the pore-forming alpha-subunit. It is now known that VGSC β-subunits are capable of similar modulation of multiple isoforms of related voltage-gated potassium channels, suggesting that their abilities extend into the broader voltage-gated channels. The gene family for these single transmembrane immunoglobulin beta-fold proteins extends well beyond the traditional VGSC β1-β4 subunit designation, with deep roots into the cell adhesion protein family and myelin-related proteins - where inherited mutations result in a myriad of electrical signaling disorders. Yet, very little is known about how VGSC β-subunits support protein trafficking pathways, the basis for their modulation of voltage-dependent gating, and, ultimately, their role in shaping neuronal excitability. An evolutionary approach can be useful in yielding new clues to such functions as it provides an unbiased assessment of protein residues, folds, and functions. An approach is described here which indicates the greater emergence of the modern β-subunits roughly 400 million years ago in the early neurons of Bilateria and bony fish, and the unexpected presence of distant homologues in bacteriophages. Recent structural breakthroughs containing α and β eukaryotic sodium channels containing subunits suggest a novel role for a highly conserved polar contact that occurs within the transmembrane segments. Overall, a mixture of approaches will ultimately advance our understanding of the mechanism for β-subunit interactions with voltage-sensor containing ion channels and membrane proteins.

The Sodium-Activated Potassium Channel Slack Is Required for Optimal Cognitive Flexibility in Mice

Science.gov (United States)

Bausch, Anne E.; Dieter, Rebekka; Nann, Yvette; Hausmann, Mario; Meyerdierks, Nora; Kaczmarek, Leonard K.; Ruth, Peter; Lukowski, Robert

2015-01-01

"Kcnt1" encoded sodium-activated potassium channels (Slack channels) are highly expressed throughout the brain where they modulate the firing patterns and general excitability of many types of neurons. Increasing evidence suggests that Slack channels may be important for higher brain functions such as cognition and normal intellectual…

Bromodomain-containing Protein 4 Activates Voltage-gated Sodium Channel 1.7 Transcription in Dorsal Root Ganglia Neurons to Mediate Thermal Hyperalgesia in Rats.

Science.gov (United States)

Hsieh, Ming-Chun; Ho, Yu-Cheng; Lai, Cheng-Yuan; Wang, Hsueh-Hsiao; Lee, An-Sheng; Cheng, Jen-Kun; Chau, Yat-Pang; Peng, Hsien-Yu

2017-11-01

Bromodomain-containing protein 4 binds acetylated promoter histones and promotes transcription; however, the role of bromodomain-containing protein 4 in inflammatory hyperalgesia remains unclear. Male Sprague-Dawley rats received hind paw injections of complete Freund's adjuvant to induce hyperalgesia. The dorsal root ganglia were examined to detect changes in bromodomain-containing protein 4 expression and the activation of genes involved in the expression of voltage-gated sodium channel 1.7, which is a key pain-related ion channel. The intraplantar complete Freund's adjuvant injections resulted in thermal hyperalgesia (4.0 ± 1.5 s; n = 7). The immunohistochemistry and immunoblotting results demonstrated an increase in the bromodomain-containing protein 4-expressing dorsal root ganglia neurons (3.78 ± 0.38 fold; n = 7) and bromodomain-containing protein 4 protein levels (2.62 ± 0.39 fold; n = 6). After the complete Freund's adjuvant injection, histone H3 protein acetylation was enhanced in the voltage-gated sodium channel 1.7 promoter, and cyclin-dependent kinase 9 and phosphorylation of RNA polymerase II were recruited to this area. Furthermore, the voltage-gated sodium channel 1.7-mediated currents were enhanced in neurons of the complete Freund's adjuvant rats (55 ± 11 vs. 19 ± 9 pA/pF; n = 4 to 6 neurons). Using bromodomain-containing protein 4-targeted antisense small interfering RNA to the complete Freund's adjuvant-treated rats, the authors demonstrated a reduction in the expression of bromodomain-containing protein 4 (0.68 ± 0.16 fold; n = 7), a reduction in thermal hyperalgesia (7.5 ± 1.5 s; n = 7), and a reduction in the increased voltage-gated sodium channel 1.7 currents (21 ± 4 pA/pF; n = 4 to 6 neurons). Complete Freund's adjuvant triggers enhanced bromodomain-containing protein 4 expression, ultimately leading to the enhanced excitability of nociceptive neurons and thermal hyperalgesia. This effect is

Affinity purification of the voltage-sensitive sodium channel from electroplax with resins selective for sialic acid

Energy Technology Data Exchange (ETDEWEB)

James, W.M.; Emerick, M.C.; Agnew, W.S. (Yale Univ. School of medicine, New Haven, CT (USA))

1989-07-11

The voltage-sensitive sodium channel present in the eel (Electrophorus electricus) has an unusually high content of sialic acid, including {alpha}-(2{yields}8)-linked polysialic acid, not found in other electroplax membrane glycopeptides. Lectins from Limax flavus (LFA) and wheat germ (WGA) proved the most effective of 11 lectin resins tried. The most selective resin was prepared from IgM antibodies against Neisseria meningitidis {alpha}-(2{yields}8)-polysialic acid which were affinity purified and coupled to Sepharose 4B. The sodium channel was found to bind to WGA, LFA, and IgM resins and was readily eluted with the appropriate soluble carbohydrates. Experiments with LFA and IgM resins demonstrated binding and unbinding rates and displacement kinetics, which suggest highly specific binding at multiple sites on the sodium channel protein. In preparative-scale purification of protein previously fractionated by anion-exchange chromatography, without stabilizing TTX, high yields were reproducibly obtained. Further, when detergent extracts were prepared from electroplax membranes fractionated by low-speed sedimentation, a single step over the IgM resin provided a 70-fold purification, yielding specific activities of 3,200 pmol of ({sup 3}H)TTX-binding sites/mg of protein and a single polypeptide of {approximately}285,000 Da on SDS-acrylamide gels. No small peptides were observed after this 5-h isolation. The authors describe a cation-dependent stabilization with millimolar levels of monovalent and micromolar levels of divalent species.

Distribution and function of sodium channel subtypes in human atrial myocardium

NARCIS (Netherlands)

Kaufmann, Susann G.; Westenbroek, Ruth E.; Maass, Alexander H.; Lange, Volkmar; Renner, Andre; Wischmeyer, Erhard; Bonz, Andreas; Muck, Jenny; Ertl, Georg; Catterall, William A.; Scheuer, Todd; Maier, Sebastian K. G.

Voltage-gated sodium channels composed of a pore-forming alpha subunit and auxiliary beta subunits are responsible for the upstroke of the action potential in cardiac muscle. However, their localization and expression patterns in human myocardium have not yet been clearly defined. We used

Toxins That Affect Voltage-Gated Sodium Channels.

Science.gov (United States)

Ji, Yonghua

2017-10-26

Voltage-gated sodium channels (VGSCs) are critical in generation and conduction of electrical signals in multiple excitable tissues. Natural toxins, produced by animal, plant, and microorganisms, target VGSCs through diverse strategies developed over millions of years of evolutions. Studying of the diverse interaction between VGSC and VGSC-targeting toxins has been contributing to the increasing understanding of molecular structure and function, pharmacology, and drug development potential of VGSCs. This chapter aims to summarize some of the current views on the VGSC-toxin interaction based on the established receptor sites of VGSC for natural toxins.

Hydrogen sulfide prevents hydrogen peroxide-induced activation of epithelial sodium channel through a PTEN/PI(3,4,5P3 dependent pathway.

Directory of Open Access Journals (Sweden)

Jianing Zhang

Full Text Available Sodium reabsorption through the epithelial sodium channel (ENaC at the distal segment of the kidney plays an important role in salt-sensitive hypertension. We reported previously that hydrogen peroxide (H2O2 stimulates ENaC in A6 distal nephron cells via elevation of phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5P3 in the apical membrane. Here we report that H2S can antagonize H2O2-induced activation of ENaC in A6 cells. Our cell-attached patch-clamp data show that ENaC open probability (PO was significantly increased by exogenous H2O2, which is consistent with our previous finding. The aberrant activation of ENaC induced by exogenous H2O2 was completely abolished by H2S (0.1 mM NaHS. Pre-treatment of A6 cells with H2S slightly decreased ENaC P(O; however, in these cells H2O2 failed to elevate ENaC PO . Confocal microscopy data show that application of exogenous H2O2 to A6 cells significantly increased intracellular reactive oxygen species (ROS level and induced accumulation of PI(3,4,5P3 in the apical compartment of the cell membrane. These effects of exogenous H2O2 on intracellular ROS levels and on apical PI(3,4,5P3 levels were almost completely abolished by treatment of A6 cells with H2S. In addition, H2S significantly inhibited H2O2-induced oxidative inactivation of the tumor suppressor phosphatase and tensin homolog (PTEN which is a negative regulator of PI(3,4,5P3. Moreover, BPV(pic, a specific inhibitor of PTEN, elevated PI(3,4,5P3 and ENaC activity in a manner similar to that of H2O2 in A6 cells. Our data show, for the first time, that H2S prevents H2O2-induced activation of ENaC through a PTEN-PI(3,4,5P3 dependent pathway.

Elevated peritoneal expression and estrogen regulation of nociceptive ion channels in endometriosis.

Science.gov (United States)

Greaves, Erin; Grieve, Kelsey; Horne, Andrew W; Saunders, Philippa T K

2014-09-01

Ovarian suppression is a common treatment for endometriosis-associated pelvic pain. Its exact mechanism of action is poorly understood, although it is assumed to reflect reduced production/action of estrogens. The objective of the study was to measure the expression of mRNAs encoded by nociceptive genes in the peritoneum of women with chronic pelvic pain (CPP) with or without endometriosis and to investigate whether estrogens alter nociceptive gene expression in human sensory neurons. The study was performed using human tissue analysis and cell culture. The study was conducted at a university research institute. Peritoneal biopsies were obtained from women with CPP and endometriosis (n = 12), CPP and no endometriosis (n = 10), and no pain or endometriosis (n = 5). Endometriosis lesions were obtained from women with endometriosis (n = 18). mRNAs encoding ion channels (P2RX3, SCN9A, SCN11A, TRPA1, TRPV1) and the neurotransmitter TAC1 were measured in human tissue samples and in human embryonic stem cell-derived sensory neurons treated with estrogens. TRPV1, TRPA1, and SCN11A mRNAs were significantly higher in the peritoneum from women with endometriosis (P endometriosis lesions (P endometriosis (P endometriosis-associated pain. Strategies directly targeting ion channels may offer an alternative option for the management of CPP.

Large-scale structural alteration of brain in epileptic children with SCN1A mutation

Directory of Open Access Journals (Sweden)

Yun-Jeong Lee

2017-01-01

Significance: This study showed large-scale developmental brain changes in patients with epilepsy and SCN1A gene mutation, which may be associated with the core symptoms of the patients. Further longitudinal MRI studies with larger cohorts are required to confirm the effect of SCN1A gene mutation on structural brain development.

International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels.

Science.gov (United States)

Kaczmarek, Leonard K; Aldrich, Richard W; Chandy, K George; Grissmer, Stephan; Wei, Aguan D; Wulff, Heike

2017-01-01

A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Structure-activity relationships for the action of 11 pyrethroid insecticides on rat Nav1.8 sodium channels expressed in Xenopus oocytes

International Nuclear Information System (INIS)

Choi, J.-S.; Soderlund, David M.

2006-01-01

Pyrethroid insecticides bind to voltage-sensitive sodium channels and modify their gating kinetics, thereby disrupting nerve function. This paper describes the action of 11 structurally diverse commercial pyrethroid insecticides on the rat Na v 1.8 sodium channel isoform, the principal carrier of the tetrodotoxin-resistant, pyrethroid-sensitive sodium current of sensory neurons, expressed in Xenopus laevis oocytes. All 11 compounds produced characteristic sodium tail currents following a depolarizing pulse that ranged from rapidly-decaying monoexponential currents (allethrin, cismethrin and permethrin) to persistent biexponential currents (cyfluthrin, cyhalothrin, cypermethrin and deltamethrin). Tail currents for the remaining compounds (bifenthrin, fenpropathrin, fenvalerate and tefluthrin) were monoexponential and decayed with kinetics intermediate between these extremes. Reconstruction of currents carried solely by the pyrethroid-modified subpopulation of channels revealed two types of pyrethroid-modified currents. The first type, found with cismethrin, allethrin, permethrin and tefluthrin, activated relatively rapidly and inactivated partially during a 40-ms depolarization. The second type, found with cypermethrin, cyfluthrin, cyhalothrin, deltamethrin, fenpropathrin and fenvalerate, activated more slowly and did not detectably inactivate during a 40-ms depolarization. Only bifenthrin did not produce modified currents that fit clearly into either of these categories. In all cases, the rate of activation of modified channels was strongly correlated with the rate of tail current decay following repolarization. Modification of Na v 1.8 sodium channels by cyfluthrin, cyhalothrin, cypermethrin and deltamethrin was enhanced 2.3- to 3.4-fold by repetitive stimulation; this effect appeared to result from the accumulation of persistently open channels rather than preferential binding to open channel states. Fenpropathrin was the most effective compound against Na v 1

Re-determination of succinonitrile (SCN) camphor phase diagram

Science.gov (United States)

Teng, Jing; Liu, Shan

2006-04-01

Low-melting temperature transparent organic materials have been extensively used to study the pattern formation and microstructure evolution. It proves to be very challenging to accurately determine the phase diagram since there is no viable way to measure the composition microscopically. In this paper, we presented the detailed experimental characterization of the phase diagram of succinonitrile (SCN)-camphor binary system. Differential scanning calorimetry, a ring-heater, and the directional solidification technique have been combined to determine the details of the phase diagram by using the purified materials. The advantages and disadvantages have been discussed for the different experimental techniques. SCN and camphor constitute a simple binary eutectic system with the eutectic composition at 23.6 wt% camphor and eutectic temperature at 37.65 °C. The solidus and the solubility of the SCN base solid solution have been precisely determined for the first time in this binary system.

Depolarized Inactivation Overcomes Impaired Activation to Produce DRG Neuron Hyperexcitability in a Nav1.7 Mutation in a Patient with Distal Limb Pain

NARCIS (Netherlands)

Huang, J.; Yang, Y; Dib-Hajj, S.D.; Es, M. van; Zhao, P.; Salomon, J.; Drenth, J.P.; Waxman, S.G.

2014-01-01

Sodium channel Nav1.7, encoded by SCN9A, is expressed in DRG neurons and regulates their excitability. Genetic and functional studies have established a critical contribution of Nav1.7 to human pain disorders. We have now characterized a novel Nav1.7 mutation (R1279P) from a female human subject

Molecular basis for class Ib anti-arrhythmic inhibition of cardiac sodium channels

DEFF Research Database (Denmark)

Pless, Stephan Alexander; Galpin, Jason D; Frankel, Adam

2011-01-01

Cardiac sodium channels are established therapeutic targets for the management of inherited and acquired arrhythmias by class I anti-arrhythmic drugs (AADs). These drugs share a common target receptor bearing two highly conserved aromatic side chains, and are subdivided by the Vaughan-Williams...

Thermoelectric properties of epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrates

Science.gov (United States)

Burmistrova, Polina V.; Maassen, Jesse; Favaloro, Tela; Saha, Bivas; Salamat, Shuaib; Rui Koh, Yee; Lundstrom, Mark S.; Shakouri, Ali; Sands, Timothy D.

2013-04-01

Epitaxial ScN(001) thin films were grown on MgO(001) substrates by dc reactive magnetron sputtering. The deposition was performed in an Ar/N2 atmosphere at 2 × 10-3 Torr at a substrate temperature of 850 °C in a high vacuum chamber with a base pressure of 10-8 Torr. In spite of oxygen contamination of 1.6 ± 1 at. %, the electrical resistivity, electron mobility, and carrier concentration obtained from a typical film grown under these conditions by room temperature Hall measurements are 0.22 mΩ cm, 106 cm2 V-1 s-1, and 2.5 × 1020 cm-3, respectively. These films exhibit remarkable thermoelectric power factors of 3.3-3.5 × 10-3 W/mK2 in the temperature range of 600 K to 840 K. The cross-plane thermal conductivity is 8.3 W/mK at 800 K yielding an estimated ZT of 0.3. Theoretical modeling of the thermoelectric properties of ScN calculated using a mean-free-path of 23 nm at 300 K is in very good agreement with the experiment. These results also demonstrate that further optimization of the power factor of ScN is possible. First-principles density functional theory combined with the site occupancy disorder technique was used to investigate the effect of oxygen contamination on the electronic structure and thermoelectric properties of ScN. The computational results suggest that oxygen atoms in ScN mix uniformly on the N site forming a homogeneous solid solution alloy. Behaving as an n-type donor, oxygen causes a shift of the Fermi level in ScN into the conduction band without altering the band structure and the density of states.

Gene expression profile of sodium channel subunits in the anterior cingulate cortex during experimental paclitaxel-induced neuropathic pain in mice

Directory of Open Access Journals (Sweden)

Willias Masocha

2016-11-01

Full Text Available 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.

Essential Oils and Their Constituents Targeting the GABAergic System and Sodium Channels as Treatment of Neurological Diseases

Directory of Open Access Journals (Sweden)

Ze-Jun Wang

2018-05-01

Full Text Available Essential oils and the constituents in them exhibit different pharmacological activities, such as antinociceptive, anxiolytic-like, and anticonvulsant effects. They are widely applied as a complementary therapy for people with anxiety, insomnia, convulsion, pain, and cognitive deficit symptoms through inhalation, oral administration, and aromatherapy. Recent studies show that essential oils are emerging as a promising source for modulation of the GABAergic system and sodium ion channels. This review summarizes the recent findings regarding the pharmacological properties of essential oils and compounds from the oils and the mechanisms underlying their effects. Specifically, the review focuses on the essential oils and their constituents targeting the GABAergic system and sodium channels, and their antinociceptive, anxiolytic, and anticonvulsant properties. Some constituents target transient receptor potential (TRP channels to exert analgesic effects. Some components could interact with multiple therapeutic target proteins, for example, inhibit the function of sodium channels and, at the same time, activate GABAA receptors. The review concentrates on perspective compounds that could be better candidates for new drug development in the control of pain and anxiety syndromes.

Substitutions in the domain III voltage-sensing module enhance the sensitivity of an insect sodium channel to a scorpion beta-toxin.

Science.gov (United States)

Song, Weizhong; Du, Yuzhe; Liu, Zhiqi; Luo, Ningguang; Turkov, Michael; Gordon, Dalia; Gurevitz, Michael; Goldin, Alan L; Dong, Ke

2011-05-06

Scorpion β-toxins bind to the extracellular regions of the voltage-sensing module of domain II and to the pore module of domain III in voltage-gated sodium channels and enhance channel activation by trapping and stabilizing the voltage sensor of domain II in its activated state. We investigated the interaction of a highly potent insect-selective scorpion depressant β-toxin, Lqh-dprIT(3), from Leiurus quinquestriatus hebraeus with insect sodium channels from Blattella germanica (BgNa(v)). Like other scorpion β-toxins, Lqh-dprIT(3) shifts the voltage dependence of activation of BgNa(v) channels expressed in Xenopus oocytes to more negative membrane potentials but only after strong depolarizing prepulses. Notably, among 10 BgNa(v) splice variants tested for their sensitivity to the toxin, only BgNa(v)1-1 was hypersensitive due to an L1285P substitution in IIIS1 resulting from a U-to-C RNA-editing event. Furthermore, charge reversal of a negatively charged residue (E1290K) at the extracellular end of IIIS1 and the two innermost positively charged residues (R4E and R5E) in IIIS4 also increased the channel sensitivity to Lqh-dprIT(3). Besides enhancement of toxin sensitivity, the R4E substitution caused an additional 20-mV negative shift in the voltage dependence of activation of toxin-modified channels, inducing a unique toxin-modified state. Our findings provide the first direct evidence for the involvement of the domain III voltage-sensing module in the action of scorpion β-toxins. This hypersensitivity most likely reflects an increase in IIS4 trapping via allosteric mechanisms, suggesting coupling between the voltage sensors in neighboring domains during channel activation.

Hydration status regulates sodium flux and inflammatory pathways through epithelial sodium channel (ENaC) in the skin.

Science.gov (United States)

Xu, Wei; Hong, Seok Jong; Zeitchek, Michael; Cooper, Garry; Jia, Shengxian; Xie, Ping; Qureshi, Hannan A; Zhong, Aimei; Porterfield, Marshall D; Galiano, Robert D; Surmeier, D James; Mustoe, Thomas A

2015-03-01

Although it is known that the inflammatory response that results from disruption of epithelial barrier function after injury results in excessive scarring, the upstream signals remain unknown. It has also been observed that epithelial disruption results in reduced hydration status and that the use of occlusive dressings that prevent water loss from wounds decreases scar formation. We hypothesized that hydration status changes sodium homeostasis and induces sodium flux in keratinocytes, which result in activation of pathways responsible for keratinocyte-fibroblast signaling and ultimately lead to activation of fibroblasts. Here, we demonstrate that perturbations in epithelial barrier function lead to increased sodium flux in keratinocytes. We identified that sodium flux in keratinocytes is mediated by epithelial sodium channels (ENaCs) and causes increased secretion of proinflammatory cytokines, which activate fibroblast via the cyclooxygenase 2 (COX-2)/prostaglandin E2 (PGE2) pathway. Similar changes in signal transduction and sodium flux occur by increased sodium concentration, which simulates reduced hydration, in the media in epithelial cultures or human ex vivo skin cultures. Blockade of ENaC, prostaglandin synthesis, or PGE2 receptors all reduce markers of fibroblast activation and collagen synthesis. In addition, employing a validated in vivo excessive scar model in the rabbit ear, we demonstrate that utilization of either an ENaC blocker or a COX-2 inhibitor results in a marked reduction in scarring. Other experiments demonstrate that the activation of COX-2 in response to increased sodium flux is mediated through the PIK3/Akt pathway. Our results indicate that ENaC responds to small changes in sodium concentration with inflammatory mediators and suggest that the ENaC pathway is a potential target for a strategy to prevent fibrosis.

Site of anticonvulsant action on sodium channels: autoradiographic and electrophysiological studies in rat brain

International Nuclear Information System (INIS)

Worley, P.F.; Baraban, J.M.

1987-01-01

The anticonvulsants phenytoin and carbamazepine interact allosterically with the batrachotoxin binding site of sodium channels. In the present study, we demonstrate an autoradiographic technique to localize the batrachotoxin binding site on sodium channels in rat brain using [ 3 H]batrachotoxinin-A 20-alpha-benzoate (BTX-B). Binding of [ 3 H]BTX-B to brain sections is dependent on potentiating allosteric interactions with scorpion venom and is displaced by BTX-B (Kd approximately 200 nM), aconitine, veratridine, and phenytoin with the same rank order of potencies as described in brain synaptosomes. The maximum number of [ 3 H]BTX-B binding sites in forebrain sections also agrees with biochemical determinations. Autoradiographic localizations indicate that [ 3 H]BTX-B binding sites are not restricted to cell bodies and axons but are present in synaptic zones throughout the brain. For example, a particularly dense concentration of these sites in the substantia nigra is associated with afferent terminals of the striatonigral projection. By contrast, myelinated structures possess much lower densities of binding sites. In addition, we present electrophysiological evidence that synaptic transmission, as opposed to axonal conduction, is preferentially sensitive to the action of aconitine and veratridine. Finally, the synaptic block produced by these sodium channel activators is inhibited by phenytoin and carbamazepine at therapeutic anticonvulsant concentrations

Differential calcium sensitivity in NaV 1.5 mixed syndrome mutants.

Science.gov (United States)

Abdelsayed, Mena; Baruteau, Alban-Elouen; Gibbs, Karen; Sanatani, Shubhayan; Krahn, Andrew D; Probst, Vincent; Ruben, Peter C

2017-09-15

SCN5a mutations may express gain-of-function (Long QT Syndrome-3), loss-of-function (Brugada Syndrome 1) or both (mixed syndromes), depending on the mutation and environmental triggers. One such trigger may be an increase in cytosolic calcium, accompanying exercise. Many mixed syndromes mutants, including ∆KPQ, E1784K, 1795insD and Q1909R, are found in calcium-sensitive regions. Elevated cytosolic calcium attenuates gain-of-function properties in ∆KPQ, 1795insD and Q1909R, but not in E1784K. By contrast, elevated cytosolic calcium further exacerbates gain-of-function in E1784K by destabilizing slow inactivation. Action potential modelling, using a modified O'Hara Rudy model, suggests that elevated heart rate rescues action potential duration in ∆KPQ, 1795insD and Q1909R, but not in E1784K. Action potential simulations suggest that E1784K carriers have an increased intracellular sodium-to-calcium ratio under bradycardia and tachycardia conditions. Elevated cytosolic calcium, which is common during high heart rates, ameliorates or exacerbates the mixed syndrome phenotype depending on the genetic signature. Inherited arrhythmias may arise from mutations in the gene for SCN5a, which encodes the cardiac voltage-gated sodium channel, Na V 1.5. Mutants in Na V 1.5 result in Brugada Syndrome (BrS1), Long-QT Syndrome (LQT3) or mixed syndromes (an overlap of BrS1/LQT3). Exercise is a potential arrhythmogenic trigger in mixed syndromes. We aimed to determine the effects of elevated cytosolic calcium, which is common during exercise, in mixed syndrome Na V 1.5 mutants. We used whole-cell patch clamp to assess the biophysical properties of Na V 1.5 wild-type (WT), ∆KPQ, E1784K, 1795insD and Q1909R mutants in human embryonic kidney 293 cells transiently transfected with the Na V 1.5 α subunit (WT or mutants), β1 subunit and enhanced green fluorescent protein. Voltage-dependence and kinetics were measured at cytosolic calcium levels of approximately 0, 500 and 2500�

Conduction velocity is regulated by sodium channel inactivation in unmyelinated axons innervating the rat cranial meninges.

Science.gov (United States)

De Col, Roberto; Messlinger, Karl; Carr, Richard W

2008-02-15

Axonal conduction velocity varies according to the level of preceding impulse activity. In unmyelinated axons this typically results in a slowing of conduction velocity and a parallel increase in threshold. It is currently held that Na(+)-K(+)-ATPase-dependent axonal hyperpolarization is responsible for this slowing but this has long been equivocal. We therefore examined conduction velocity changes during repetitive activation of single unmyelinated axons innervating the rat cranial meninges. In direct contradiction to the currently accepted postulate, Na(+)-K(+)-ATPase blockade actually enhanced activity-induced conduction velocity slowing, while the degree of velocity slowing was curtailed in the presence of lidocaine (10-300 microm) and carbamazepine (30-500 microm) but not tetrodotoxin (TTX, 10-80 nm). This suggests that a change in the number of available sodium channels is the most prominent factor responsible for activity-induced changes in conduction velocity in unmyelinated axons. At moderate stimulus frequencies, axonal conduction velocity is determined by an interaction between residual sodium channel inactivation following each impulse and the retrieval of channels from inactivation by a concomitant Na(+)-K(+)-ATPase-mediated hyperpolarization. Since the process is primarily dependent upon sodium channel availability, tracking conduction velocity provides a means of accessing relative changes in the excitability of nociceptive neurons.

Distinct molecular sites of anaesthetic action: pentobarbital block of human brain sodium channels is alleviated by removal of fast inactivation

NARCIS (Netherlands)

Wartenberg, H. C.; Urban, B. W.; Duch, D. S.

1999-01-01

Fast inactivation of sodium channel function is modified by anaesthetics. Its quantitative contribution to the overall anaesthetic effect is assessed by removing the fast inactivation mechanism enzymatically. Sodium channels from human brain cortex were incorporated into planar lipid bilayers. After

Development of Field-Controlled Smart Optic Materials (ScN, AlN) with Rare Earth Dopants

Science.gov (United States)

Kim, Hyun-Jung; Park, Yeonjoon; King, Glen C.; Choi, Sang H.

2012-01-01

The purpose of this investigation is to develop the fundamental materials and fabrication technology for field-controlled spectrally active optics that are essential for industry, NASA, and DOD applications such as: membrane optics, filters for LIDARs, windows for sensors, telescopes, spectroscopes, cameras, flat-panel displays, etc. ScN and AlN thin films were fabricated on c-axis Sapphire (0001) or quartz substrate with the RF and DC magnetron sputtering. The crystal structure of AlN in fcc (rocksalt) and hcp (wurtzite) were controlled. Advanced electrical characterizations were performed, including I-V and Hall Effect Measurement. ScN film has a free carrier density of 5.8 x 10(exp 20)/per cubic centimeter and a conductivity of 1.1 x 10(exp 3) per centimeter. The background ntype conductivity of as-grown ScN has enough free electrons that can readily interact with the photons. The high density of free electrons and relatively low mobility indicate that these films contain a high level of shallow donors as well as deep levels. Also, the UV-Vis spectrum of ScN and AlN thin films with rare earth elements (Er or Ho) were measured at room temperature. Their optical band gaps were estimated to be about 2.33eV and 2.24eV, respectively, which are obviously smaller than that of undoped thin film ScN (2.4eV). The red-shifted absorption onset gives direct evidence for the decrease of band gap (Eg) and the energy broadening of valence band states are attributable to the doping. As the doped elements enter the ScN crystal lattices, the localized band edge states form at the doped sites with a reduction of Eg. Using a variable angle spectroscopic ellipsometer, the decrease in refractive index with applied field is observed with a smaller shift in absorption coefficient.

Atom-transfer radical polymerization of methyl methacrylate (MMA) using CuSCN as the catalyst

NARCIS (Netherlands)

Singha, N.K.; Klumperman, B.

2000-01-01

The effect of CuSCN as a catalyst in atom-transfer radical polymerization (ATRP) was investigated. CuSCN can successfully be used for the ATRP of MMA. Substituted bipyridines as well as imines can be used to stabilize the copper complex in solution. CuSCN induces faster polymerization compared to

Synthetic Ciguatoxins Selectively Activate Nav1.8-derived Chimeric Sodium Channels Expressed in HEK293 Cells*

Science.gov (United States)

Yamaoka, Kaoru; Inoue, Masayuki; Miyazaki, Keisuke; Hirama, Masahiro; Kondo, Chie; Kinoshita, Eiji; Miyoshi, Hiroshi; Seyama, Issei

2009-01-01

The synthetic ciguatoxin CTX3C has been shown to activate tetrodotoxin (TTX)-sensitive sodium channels (Nav1.2, Nav1.4, and Nav1.5) by accelerating activation kinetics and shifting the activation curve toward hyperpolarization (Yamaoka, K., Inoue, M., Miyahara, H., Miyazaki, K., and Hirama, M. (2004) Br. J. Pharmacol. 142, 879–889). In this study, we further explored the effects of CTX3C on the TTX-resistant sodium channel Nav1.8. TTX-resistant channels have been shown to be involved in transducing pain and related sensations (Akopian, A. N., Sivilotti, L., and Wood, J. N. (1996) Nature 379, 257–262). Thus, we hypothesized that ciguatoxin-induced activation of the Nav1.8 current would account for the neurological symptoms of ciguatera poisoning. We found that 0.1 μm CTX3C preferentially affected the activation process of the Nav1.8 channel compared with those of the Nav1.2 and Nav1.4 channels. Importantly, without stimulation, 0.1 μm CTX3C induced a large leakage current (IL). The conductance of the IL calculated relative to the maximum conductance (Gmax) was 10 times larger than that of Nav1.2 or Nav1.4. To determine the molecular domain of Nav1.8 responsible for conferring higher sensitivity to CTX3C, we made two chimeric constructs from Nav1.4 and Nav1.8. Chimeras containing the N-terminal half of Nav1.8 exhibited a large response similar to wild-type Nav1.8, indicating that the region conferring high sensitivity to ciguatoxin action is located in the D1 or D2 domains. PMID:19164297

A Novel Nonsense Variant in Nav1.5 Cofactor MOG1 Eliminates Its Sodium Current Increasing Effect and May Increase the Risk of Arrhythmias

DEFF Research Database (Denmark)

Olesen, Morten S; Jensen, Niels F; Holst, Anders G

2011-01-01

at a lower frequency (1.8% vs 0.4%, P = 0.078). Electrophysiological investigation showed that the p.E61X variant completely eliminates the sodium current-increasing effect of MOG1 and thereby causes loss of function in the sodium current. When mimicking heterozygosity by coexpression of Nav1.5 with wild......BACKGROUND: The protein MOG1 is a cofactor of the cardiac sodium channel, Nav1.5. Overexpression of MOG1 in Nav1.5-expressing cells increases sodium current markedly. Mutations in the genes encoding Nav1.5 and its accessory proteins have been associated with cardiac arrhythmias of significant...... and 23 were patients with Brugada syndrome. The effect of one variant was investigated functionally by patch-clamping CHO-K1 cells coexpressing Nav1.5 with MOG1. RESULTS: We uncovered a novel heterozygous nonsense variant, c.181G>T (p.E61X), that, however, was also present in control subjects, albeit...

High-Efficiency Fullerene Solar Cells Enabled by a Spontaneously Formed Mesostructured CuSCN-Nanowire Heterointerface

KAUST Repository

Sit, Wai-Yu

2018-02-02

Fullerenes and their derivatives are widely used as electron acceptors in bulk-heterojunction organic solar cells as they combine high electron mobility with good solubility and miscibility with relevant semiconducting polymers. However, studies on the use of fullerenes as the sole photogeneration and charge-carrier material are scarce. Here, a new type of solution-processed small-molecule solar cell based on the two most commonly used methanofullerenes, namely [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM), as the light absorbing materials, is reported. First, it is shown that both fullerene derivatives exhibit excellent ambipolar charge transport with balanced hole and electron mobilities. When the two derivatives are spin-coated over the wide bandgap p-type semiconductor copper (I) thiocyanate (CuSCN), cells with power conversion efficiency (PCE) of ≈1%, are obtained. Blending the CuSCN with PC70BM is shown to increase the performance further yielding cells with an open-circuit voltage of ≈0.93 V and a PCE of 5.4%. Microstructural analysis reveals that the key to this success is the spontaneous formation of a unique mesostructured p–n-like heterointerface between CuSCN and PC70BM. The findings pave the way to an exciting new class of single photoactive material based solar cells.

Mining the Virgin Land of Neurotoxicology: A Novel Paradigm of Neurotoxic Peptides Action on Glycosylated Voltage-Gated Sodium Channels

Directory of Open Access Journals (Sweden)

Zhirui Liu

2012-01-01

Full Text Available Voltage-gated sodium channels (VGSCs are important membrane protein carrying on the molecular basis for action potentials (AP in neuronal firings. Even though the structure-function studies were the most pursued spots, the posttranslation modification processes, such as glycosylation, phosphorylation, and alternative splicing associating with channel functions captured less eyesights. The accumulative research suggested an interaction between the sialic acids chains and ion-permeable pores, giving rise to subtle but significant impacts on channel gating. Sodium channel-specific neurotoxic toxins, a family of long-chain polypeptides originated from venomous animals, are found to potentially share the binding sites adjacent to glycosylated region on VGSCs. Thus, an interaction between toxin and glycosylated VGSC might hopefully join the campaign to approach the role of glycosylation in modulating VGSCs-involved neuronal network activity. This paper will cover the state-of-the-art advances of researches on glycosylation-mediated VGSCs function and the possible underlying mechanisms of interactions between toxin and glycosylated VGSCs, which may therefore, fulfill the knowledge in identifying the pharmacological targets and therapeutic values of VGSCs.

Sodium-23 MRI of whole spine at 3 Tesla using a 5-channel receive-only phased-array and a whole-body transmit resonator

Energy Technology Data Exchange (ETDEWEB)

Malzacher, Matthias; Kalayciyan, Raffi; Konstandin, Simon; Schad, Lothar R. [Heidelberg Univ., Mannheim (Germany). Computer Assisted Clinical Medicine; Haneder, Stefan [Heidelberg Univ., Mannheim (Germany). Clinical Radiology and Nuclear Medicine; University Hospital of Cologne, Koeln (Germany). Dept. of Radiology

2016-05-01

Sodium magnetic resonance imaging ({sup 23}Na MRI) is a unique and non-invasive imaging technique which provides important information on cellular level about the tissue of the human body. Several applications for {sup 23}Na MRI were investigated with regard to the examination of the tissue viability and functionality for example in the brain, the heart or the breast. The {sup 23}Na MRI technique can also be integrated as a potential monitoring instrument after radiotherapy or chemotherapy. The main contribution in this work was the adaptation of {sup 23}Na MRI for spine imaging, which can provide essential information on the integrity of the intervertebral disks with respect to the early detection of disk degeneration. In this work, a transmit-only receive-only dual resonator system was designed and developed to cover the whole human spine using {sup 23}Na MRI and increase the receive sensitivity. The resonator system consisted of an already presented {sup 23}Na whole-body resonator and a newly developed 5-channel receive-only phased-array. The resonator system was first validated using bench top and phantom measurements. A threefold SNR improvement at the depth of the spine (∝7 cm) over the whole-body resonator was achieved using the spine array. {sup 23}Na MR measurements of the human spine using the transmit-only receive-only resonator system were performed on a healthy volunteer within an acquisition time of 10 minutes. A density adapted 3D radial sequence was chosen with 6 mm isotropic resolution, 49 ms repetition time and a short echo time of 540 μs. Furthermore, it was possible to quantify the tissue sodium concentration in the intervertebral discs in the lumbar region (120 ms repetition time) using this setup.

Patrón de Brugada tipo II desencadenado por fiebre secundaria a una pielonefritis aguda por Enterobacter aerogenes.

Directory of Open Access Journals (Sweden)

Gema García García

2013-03-01

Brugada syndrome is a cause of sudden cardiac death in patients without structural heart disease. This syndrome is associated with mutations in the genes encoding the alpha subunit of the sodium channel of the heart. The Brugada syndrome is an autosomal dominant defect in cardiac conduction, which up to one third of patients is caused by mutations in the SCN5A gene. It is characterized by ST segment changes in leads V1-V3 resembling a right bundle branch block and confers high risk for ventricular arrhythmias and death súbita.

Structural inferences for the native skeletal muscle sodium channel as derived from patterns of endogenous proteolysis

International Nuclear Information System (INIS)

Kraner, S.; Yang, J.; Barchi, R.

1989-01-01

The alpha subunit (Mr approximately 260,000) of the rat skeletal muscle sodium channel is sensitive to cleavage by endogenous proteases during the isolation of muscle surface membrane. Antisera against synthetic oligopeptides were used to map the resultant fragments in order to identify protease-sensitive regions of the channel's structure in its native membrane environment. Antibodies to the amino terminus labeled major fragments of Mr approximately 130,000 and 90,000 and lesser amounts of other peptides as small as Mr approximately 12,000. Antisera to epitopes within the carboxyl-terminal half of the primary sequence recognized two fragments of Mr approximately 110,000 and 78,000. Individual antisera also selectively labeled smaller polypeptides in the most extensively cleaved preparations. The immunoreactivity patterns of monoclonal antibodies previously raised against the purified channel were then surveyed. The binding sites for one group of monoclonals, including several that recognize subtype-specific epitopes in the channel structure, were localized within a 12-kDa fragment near the amino terminus. The distribution of carbohydrate along the primary structure of the channel was also assessed by quantitating 125 I-wheat germ agglutinin and 125I-concanavalin A binding to the proteolytic peptides. Most of the carbohydrate detected by these lectins was located between 22 and 90 kDa from the amino terminus of the protein. No lectin binding was detected to fragments arising from carboxyl-terminal half of the protein. These results were analyzed in terms of current models of sodium channel tertiary structure. In its normal membrane environment, the skeletal muscle sodium channel appears sensitive to cleavage by endogenous proteases in regions predicted to link the four repeat domains on the cytoplasmic side of the membrane while the repeat domains themselves are resistant to proteolysis

Synthetic ciguatoxins selectively activate Nav1.8-derived chimeric sodium channels expressed in HEK293 cells.

Science.gov (United States)

Yamaoka, Kaoru; Inoue, Masayuki; Miyazaki, Keisuke; Hirama, Masahiro; Kondo, Chie; Kinoshita, Eiji; Miyoshi, Hiroshi; Seyama, Issei

2009-03-20

The synthetic ciguatoxin CTX3C has been shown to activate tetrodotoxin (TTX)-sensitive sodium channels (Na(v)1.2, Na(v)1.4, and Na(v)1.5) by accelerating activation kinetics and shifting the activation curve toward hyperpolarization (Yamaoka, K., Inoue, M., Miyahara, H., Miyazaki, K., and Hirama, M. (2004) Br. J. Pharmacol. 142, 879-889). In this study, we further explored the effects of CTX3C on the TTX-resistant sodium channel Na(v)1.8. TTX-resistant channels have been shown to be involved in transducing pain and related sensations (Akopian, A. N., Sivilotti, L., and Wood, J. N. (1996) Nature 379, 257-262). Thus, we hypothesized that ciguatoxin-induced activation of the Na(v)1.8 current would account for the neurological symptoms of ciguatera poisoning. We found that 0.1 mum CTX3C preferentially affected the activation process of the Na(v)1.8 channel compared with those of the Na(v)1.2 and Na(v)1.4 channels. Importantly, without stimulation, 0.1 mum CTX3C induced a large leakage current (I (L)). The conductance of the I (L) calculated relative to the maximum conductance (G (max)) was 10 times larger than that of Na(v)1.2 or Na(v)1.4. To determine the molecular domain of Na(v)1.8 responsible for conferring higher sensitivity to CTX3C, we made two chimeric constructs from Na(v)1.4 and Na(v)1.8. Chimeras containing the N-terminal half of Na(v)1.8 exhibited a large response similar to wild-type Na(v)1.8, indicating that the region conferring high sensitivity to ciguatoxin action is located in the D1 or D2 domains.

Alterations of sodium and potassium channels of RGCs in RCS rat with the development of retinal degeneration.

Science.gov (United States)

Chen, Zhongshan; Song, Yanping; Yao, Junping; Weng, Chuanhuang; Yin, Zheng Qin

2013-11-01

All know that retinitis pigmentosa (RP) is a group of hereditary retinal degenerative diseases characterized by progressive dysfunction of photoreceptors and associated with progressive cells loss; nevertheless, little is known about how rods and cones loss affects the surviving inner retinal neurons and networks. Retinal ganglion cells (RGCs) process and convey visual information from retina to visual centers in the brain. The healthy various ion channels determine the normal reception and projection of visual signals from RGCs. Previous work on the Royal College of Surgeons (RCS) rat, as a kind of classical RP animal model, indicated that, at late stages of retinal degeneration in RCS rat, RGCs were also morphologically and functionally affected. Here, retrograde labeling for RGCs with Fluorogold was performed to investigate the distribution, density, and morphological changes of RGCs during retinal degeneration. Then, patch clamp recording, western blot, and immunofluorescence staining were performed to study the channels of sodium and potassium properties of RGCs, so as to explore the molecular and proteinic basis for understanding the alterations of RGCs membrane properties and firing functions. We found that the resting membrane potential, input resistance, and capacitance of RGCs changed significantly at the late stage of retinal degeneration. Action potential could not be evoked in a part of RGCs. Inward sodium current and outward potassium current recording showed that sodium current was impaired severely but only slightly in potassium current. Expressions of sodium channel protein were impaired dramatically at the late stage of retinal degeneration. The results suggested that the density of RGCs decreased, process ramification impaired, and sodium ion channel proteins destructed, which led to the impairment of electrophysiological functions of RGCs and eventually resulted in the loss of visual function.

Asymmetric functional contributions of acidic and aromatic side chains in sodium channel voltage-sensor domains

DEFF Research Database (Denmark)

Pless, Stephan Alexander; Elstone, Fisal D; Niciforovic, Ana P

2014-01-01

largely enigmatic. To this end, natural and unnatural side chain substitutions were made in the S2 hydrophobic core (HC), the extracellular negative charge cluster (ENC), and the intracellular negative charge cluster (INC) of the four VSDs of the skeletal muscle sodium channel isoform (NaV1......Voltage-gated sodium (NaV) channels mediate electrical excitability in animals. Despite strong sequence conservation among the voltage-sensor domains (VSDs) of closely related voltage-gated potassium (KV) and NaV channels, the functional contributions of individual side chains in Nav VSDs remain.......4). The results show that the highly conserved aromatic side chain constituting the S2 HC makes distinct functional contributions in each of the four NaV domains. No obvious cation-pi interaction exists with nearby S4 charges in any domain, and natural and unnatural mutations at these aromatic sites produce...

Pacemaker rate and depolarization block in nigral dopamine neurons: a somatic sodium channel balancing act

Science.gov (United States)

Tucker, Kristal R.; Huertas, Marco A.; Horn, John P.; Canavier, Carmen C.; Levitan, Edwin S.

2012-01-01

Midbrain dopamine (DA) neurons are slow intrinsic pacemakers that undergo depolarization (DP) block upon moderate stimulation. Understanding DP block is important because it has been correlated with the clinical efficacy of chronic antipsychotic drug treatment. Here we describe how voltage-gated sodium (NaV) channels regulate DP block and pacemaker activity in DA neurons of the substantia nigra using rat brain slices. The distribution, density and gating of NaV currents were manipulated by blocking native channels with tetrodotoxin and by creating virtual channels and anti-channels with dynamic clamp. Although action potentials initiate in the axon initial segment (AIS) and NaV channels are distributed in multiple dendrites, selective reduction of NaV channel activity in the soma was sufficient to decrease pacemaker frequency and increase susceptibility to DP block. Conversely, increasing somatic NaV current density raised pacemaker frequency and lowered susceptibility to DP block. Finally, when NaV currents were restricted to the soma, pacemaker activity occurred at abnormally high rates due to excessive local subthreshold NaV current. Together with computational simulations, these data show that both the slow pacemaker rate and the sensitivity to DP block that characterizes DA neurons result from the low density of somatic NaV channels. More generally, we conclude that the somatodendritic distribution of NaV channels is a major determinant of repetitive spiking frequency. PMID:23077037

Biological activity of the functional epitope of ciguatoxin fragment AB on the neuroblastoma sodium channel in tissue culture.

Science.gov (United States)

Hokama, Y; Chun, K E; Campora, C E; Higa, N; Suma, C; Hamajima, A; Isobe, M

2006-01-01

It is well established that the targeted receptor for ciguatoxin (CTX) in mammalian tissues is the sodium channel, affecting the influx of sodium into cells and altering the action potential and function of the cell. Since the syntheses of fragments of CTX has become available, our focus has been on the receptor functions of the west sphere AB and east sphere JKLM fragments using the neuroblastoma cell assay, guinea pig atrium assay, and the membrane immunobead assay (MIA). The data presented here suggest that the west sphere AB of the ciguatoxin molecule is the active portion and is responsible for the activation of the sodium channels. (c) 2006 Wiley-Liss, Inc.

The Regulatory Factor ZFHX3 Modifies Circadian Function in SCN via an AT Motif-Driven Axis

Science.gov (United States)

Parsons, Michael J.; Brancaccio, Marco; Sethi, Siddharth; Maywood, Elizabeth S.; Satija, Rahul; Edwards, Jessica K.; Jagannath, Aarti; Couch, Yvonne; Finelli, Mattéa J.; Smyllie, Nicola J.; Esapa, Christopher; Butler, Rachel; Barnard, Alun R.; Chesham, Johanna E.; Saito, Shoko; Joynson, Greg; Wells, Sara; Foster, Russell G.; Oliver, Peter L.; Simon, Michelle M.; Mallon, Ann-Marie; Hastings, Michael H.; Nolan, Patrick M.

2015-01-01

Summary We identified a dominant missense mutation in the SCN transcription factor Zfhx3, termed short circuit (Zfhx3Sci), which accelerates circadian locomotor rhythms in mice. ZFHX3 regulates transcription via direct interaction with predicted AT motifs in target genes. The mutant protein has a decreased ability to activate consensus AT motifs in vitro. Using RNA sequencing, we found minimal effects on core clock genes in Zfhx3Sci/+ SCN, whereas the expression of neuropeptides critical for SCN intercellular signaling was significantly disturbed. Moreover, mutant ZFHX3 had a decreased ability to activate AT motifs in the promoters of these neuropeptide genes. Lentiviral transduction of SCN slices showed that the ZFHX3-mediated activation of AT motifs is circadian, with decreased amplitude and robustness of these oscillations in Zfhx3Sci/+ SCN slices. In conclusion, by cloning Zfhx3Sci, we have uncovered a circadian transcriptional axis that determines the period and robustness of behavioral and SCN molecular rhythms. PMID:26232227

Development and validation of a thallium flux-based functional assay for the sodium channel NaV1.7 and its utility for lead discovery and compound profiling.

Science.gov (United States)

Du, Yu; Days, Emily; Romaine, Ian; Abney, Kris K; Kaufmann, Kristian; Sulikowski, Gary; Stauffer, Shaun; Lindsley, Craig W; Weaver, C David

2015-06-17

Ion channels are critical for life, and they are targets of numerous drugs. The sequencing of the human genome has revealed the existence of hundreds of different ion channel subunits capable of forming thousands of ion channels. In the face of this diversity, we only have a few selective small-molecule tools to aid in our understanding of the role specific ion channels in physiology which may in turn help illuminate their therapeutic potential. Although the advent of automated electrophysiology has increased the rate at which we can screen for and characterize ion channel modulators, the technique's high per-measurement cost and moderate throughput compared to other high-throughput screening approaches limit its utility for large-scale high-throughput screening. Therefore, lower cost, more rapid techniques are needed. While ion channel types capable of fluxing calcium are well-served by low cost, very high-throughput fluorescence-based assays, other channel types such as sodium channels remain underserved by present functional assay techniques. In order to address this shortcoming, we have developed a thallium flux-based assay for sodium channels using the NaV1.7 channel as a model target. We show that the assay is able to rapidly and cost-effectively identify NaV1.7 inhibitors thus providing a new method useful for the discovery and profiling of sodium channel modulators.

Facile synthesis of silver/silver thiocyanate (Ag@AgSCN plasmonic nanostructures with enhanced photocatalytic performance

Directory of Open Access Journals (Sweden)

Xinfu Zhao

2017-12-01

Full Text Available A nanostructured plasmonic photocatalyst, silver/silver thiocyanate (Ag@AgSCN, has been prepared by a simple precipitation method followed by UV-light-induced reduction. The ratio of Ag to silver thiocyanate (AgSCN can be controlled by simply adjusting the photo-induced reduction time. The formation mechanism of the product was investigated based on the time-dependent experiments. Further experiments indicated that the prepared Ag@AgSCN nanostructures with an atomic ratio of Ag/AgSCN = 0.0463 exhibited high photocatalytic activity and long-term stability for the degradation of oxytetracycline (84% under visible-light irradiation. In addition to the microstructure and high specific surface area, the enhanced photocatalytic activity was mainly caused by the surface plasmon resonance of Ag nanoparticles, and the high stability of AgSCN resulted in the long-term stability of the photocatalyst product.

The hitchhiker’s guide to the voltage-gated sodium channel galaxy

Science.gov (United States)

2016-01-01

Eukaryotic voltage-gated sodium (Nav) channels contribute to the rising phase of action potentials and served as an early muse for biophysicists laying the foundation for our current understanding of electrical signaling. Given their central role in electrical excitability, it is not surprising that (a) inherited mutations in genes encoding for Nav channels and their accessory subunits have been linked to excitability disorders in brain, muscle, and heart; and (b) Nav channels are targeted by various drugs and naturally occurring toxins. Although the overall architecture and behavior of these channels are likely to be similar to the more well-studied voltage-gated potassium channels, eukaryotic Nav channels lack structural and functional symmetry, a notable difference that has implications for gating and selectivity. Activation of voltage-sensing modules of the first three domains in Nav channels is sufficient to open the channel pore, whereas movement of the domain IV voltage sensor is correlated with inactivation. Also, structure–function studies of eukaryotic Nav channels show that a set of amino acids in the selectivity filter, referred to as DEKA locus, is essential for Na+ selectivity. Structures of prokaryotic Nav channels have also shed new light on mechanisms of drug block. These structures exhibit lateral fenestrations that are large enough to allow drugs or lipophilic molecules to gain access into the inner vestibule, suggesting that this might be the passage for drug entry into a closed channel. In this Review, we will synthesize our current understanding of Nav channel gating mechanisms, ion selectivity and permeation, and modulation by therapeutics and toxins in light of the new structures of the prokaryotic Nav channels that, for the time being, serve as structural models of their eukaryotic counterparts. PMID:26712848

The Novel SCN''- Ion-selective Electrode Based on the 1-Benzyl-3-(4-nitrophenyl) thio-urea Ionophore

Energy Technology Data Exchange (ETDEWEB)

Lee, Kyung Mi; Kang, Dong Hyeon; Choe, Ju Eun; You, Jung Min; Go, Min Jeong; Lee, Jung Seong; Jeon, Seung Won [Chungnam National University, Daejeon (Korea, Republic of)

2014-09-15

A potentiometric sensor based on the 1-benzyl-3-(4-nitrophenyl) thio-urea was synthesized and tested as an ionophore in PVC based membrane sensor towards SCN - ions. This membrane exhibits a linear stable response over a wide concentration range (1.0 × 10''-5 to 1.0 × 10''-2 M) with a slope of -59.2 mV/dec., a detection limit of log[SCN''- ] = -5.05, and a selectivity coefficient for thiocyanate against perchlorate anion of logK{sub s}cn''pot = -0.133. The selectivity series of the membrane is as follows: SCN''- > ClO{sub 4}''- > I''- >NO{sub 3}''- >HSO{sub 3}''- > Cl''-HSO{sub '}'-''4 > F''- > CH{sub 3}COO''- > HCO''-''3 > Br''- > H{sub 2}PO{sub 4}''- > SO{sub 3}''-''2 > SO{sub 4}''-''2 > CO{sub 3}''-''2. The proposed electrode showed good selectivity and a good response for the SCN''- ion over a wide variety of other anions in pH 6.0 buffer solutions and has a fast response time of about < 5s.. The influences of the membrane by pH, ionophore, and plasticizer were studied.

Pitfalls in genetic testing: the story of missed SCN1A mutations

OpenAIRE

Jennings, Lawrence J.; Kirschmann, Dawn

2016-01-01

Investigators from the EuroEPINOMICS rare epilepsy syndromes Dravet working group performed whole-exome sequencing on 31 trios that had been reported negative for SCN1A mutations by Sanger sequencing.

Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%

Science.gov (United States)

Arora, Neha; Dar, M. Ibrahim; Hinderhofer, Alexander; Pellet, Norman; Schreiber, Frank; Zakeeruddin, Shaik Mohammed; Grätzel, Michael

2017-11-01

Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized only with expensive organic hole-transporting materials. We demonstrate PSCs that achieve stabilized efficiencies exceeding 20% with copper(I) thiocyanate (CuSCN) as the hole extraction layer. A fast solvent removal method enabled the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The PSCs showed high thermal stability under long-term heating, although their operational stability was poor. This instability originated from potential-induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours under full solar intensity at 60°C. Under both continuous full-sun illumination and thermal stress, CuSCN-based devices surpassed the stability of spiro-OMeTAD-based PSCs.

Drosophila SLC5A11 Mediates Hunger by Regulating K(+) Channel Activity.

Science.gov (United States)

Park, Jin-Yong; Dus, Monica; Kim, Seonil; Abu, Farhan; Kanai, Makoto I; Rudy, Bernardo; Suh, Greg S B

2016-08-08

Hunger is a powerful drive that stimulates food intake. Yet, the mechanism that determines how the energy deficits that result in hunger are represented in the brain and promote feeding is not well understood. We previously described SLC5A11-a sodium/solute co-transporter-like-(or cupcake) in Drosophila melanogaster, which is required for the fly to select a nutritive sugar over a sweeter nonnutritive sugar after periods of food deprivation. SLC5A11 acts on approximately 12 pairs of ellipsoid body (EB) R4 neurons to trigger the selection of nutritive sugars, but the underlying mechanism is not understood. Here, we report that the excitability of SLC5A11-expressing EB R4 neurons increases dramatically during starvation and that this increase is abolished in the SLC5A11 mutation. Artificial activation of SLC5A11-expresssing neurons is sufficient to promote feeding and hunger-driven behaviors; silencing these neurons has the opposite effect. Notably, SLC5A11 transcript levels in the brain increase significantly when flies are starved and decrease shortly after starved flies are refed. Furthermore, expression of SLC5A11 is sufficient for promoting hunger-driven behaviors and enhancing the excitability of SLC5A11-expressing neurons. SLC5A11 inhibits the function of the Drosophila KCNQ potassium channel in a heterologous expression system. Accordingly, a knockdown of dKCNQ expression in SLC5A11-expressing neurons produces hunger-driven behaviors even in fed flies, mimicking the overexpression of SLC5A11. We propose that starvation increases SLC5A11 expression, which enhances the excitability of SLC5A11-expressing neurons by suppressing dKCNQ channels, thereby conferring the hunger state. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trafficking regulates the subcellular distribution of voltage-gated sodium channels in primary sensory neurons.

Science.gov (United States)

Bao, Lan

2015-09-30

Voltage-gated sodium channels (Navs) comprise at least nine pore-forming α subunits. Of these, Nav1.6, Nav1.7, Nav1.8 and Nav1.9 are the most frequently studied in primary sensory neurons located in the dorsal root ganglion and are mainly localized to the cytoplasm. A large pool of intracellular Navs raises the possibility that changes in Nav trafficking could alter channel function. The molecular mediators of Nav trafficking mainly consist of signals within the Navs themselves, interacting proteins and extracellular factors. The surface expression of Navs is achieved by escape from the endoplasmic reticulum and proteasome degradation, forward trafficking and plasma membrane anchoring, and it is also regulated by channel phosphorylation and ubiquitination in primary sensory neurons. Axonal transport and localization of Navs in afferent fibers involves the motor protein KIF5B and scaffold proteins, including contactin and PDZ domain containing 2. Localization of Nav1.6 to the nodes of Ranvier in myelinated fibers of primary sensory neurons requires node formation and the submembrane cytoskeletal protein complex. These findings inform our understanding of the molecular and cellular mechanisms underlying Nav trafficking in primary sensory neurons.

Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

Energy Technology Data Exchange (ETDEWEB)

Yong Shee Meng, Alvin [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia); Zainal, Norzaini, E-mail: norzaini@usm.my [Nano Optoelectronics Research and Laboratory, Universiti Sains Malaysia, sains@usm, Persiaran Bukit Jambul, 11900, Bayan Lepas, Penang (Malaysia); Hassan, Zainuriah; Ibrahim, Kamarulazizi [Institute of Nano Optoelectronics Research and Technology (INOR), sains@usm, Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang (Malaysia)

2015-12-30

Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH{sub 3} annealing thermal has been successfully demonstrated. • NH{sub 3} annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH{sub 3}) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

Formation of scandium nitride (ScN) layer on gallium arsenide (GaAs) substrate using a combined technique of e-beam evaporator and ammonia annealing treatment

International Nuclear Information System (INIS)

Yong Shee Meng, Alvin; Zainal, Norzaini; Hassan, Zainuriah; Ibrahim, Kamarulazizi

2015-01-01

Graphical abstract: - Highlights: • Forming ScN layer using electron e-beam evaporator with successive NH_3 annealing thermal has been successfully demonstrated. • NH_3 annealing played the role in changing the grain structure of the ScN layer. • The existence of Sc−N bonds was confirmed by XPS measurement. • The 900 °C annealed ScN layer showed the best structural and optical characteristics. • ScN layer annealed at 980 °C exhibited poor structural and optical characteristics. - Abstract: A demonstration on a new technique of growing ScN using electron beam (e-beam) evaporator, coupled with successive ammonia (NH_3) annealing treatment is presented in this paper. The annealing temperature was varied at 750, 800, 850, 900 and 980 °C in order to obtain the best ScN layer. It was found that as the annealing temperature increased, the surface morphology of the ScN layer changed and ScN grains formed abundantly on the surface. The best surface of ScN layer was found in the 900 °C annealed sample. However, the roughness of the ScN increased with temperature. The photoluminescence (PL) peak of the near-to-band-edge (NBE) of ScN was observable in all samples and its intensity was the highest in the 900 °C annealed sample. Note that when the annealing treatment was conducted at 980 °C, the GaN PL peak is observable. Raman peaks of TO(X) of ScN were much evident at the annealing temperature above 900 °C. The formation of Sc−N bonds was confirmed by X-ray spectroscopy (XPS) measurement. In the end of this work, we propose that the formation of ScN using the above techniques was successful, with thermal annealing at the temperature of 900 °C.

Sodium Channel Nav1.8 Underlies TTX-Resistant Axonal Action Potential Conduction in Somatosensory C-Fibers of Distal Cutaneous Nerves.

Science.gov (United States)

Klein, Amanda H; Vyshnevska, Alina; Hartke, Timothy V; De Col, Roberto; Mankowski, Joseph L; Turnquist, Brian; Bosmans, Frank; Reeh, Peter W; Schmelz, Martin; Carr, Richard W; Ringkamp, Matthias

2017-05-17

Voltage-gated sodium (Na V ) channels are responsible for the initiation and conduction of action potentials within primary afferents. The nine Na V channel isoforms recognized in mammals are often functionally divided into tetrodotoxin (TTX)-sensitive (TTX-s) channels (Na V 1.1-Na V 1.4, Na V 1.6-Na V 1.7) that are blocked by nanomolar concentrations and TTX-resistant (TTX-r) channels (Na V 1.8 and Na V 1.9) inhibited by millimolar concentrations, with Na V 1.5 having an intermediate toxin sensitivity. For small-diameter primary afferent neurons, it is unclear to what extent different Na V channel isoforms are distributed along the peripheral and central branches of their bifurcated axons. To determine the relative contribution of TTX-s and TTX-r channels to action potential conduction in different axonal compartments, we investigated the effects of TTX on C-fiber-mediated compound action potentials (C-CAPs) of proximal and distal peripheral nerve segments and dorsal roots from mice and pigtail monkeys ( Macaca nemestrina ). In the dorsal roots and proximal peripheral nerves of mice and nonhuman primates, TTX reduced the C-CAP amplitude to 16% of the baseline. In contrast, >30% of the C-CAP was resistant to TTX in distal peripheral branches of monkeys and WT and Na V 1.9 -/- mice. In nerves from Na V 1.8 -/- mice, TTX-r C-CAPs could not be detected. These data indicate that Na V 1.8 is the primary isoform underlying TTX-r conduction in distal axons of somatosensory C-fibers. Furthermore, there is a differential spatial distribution of Na V 1.8 within C-fiber axons, being functionally more prominent in the most distal axons and terminal regions. The enrichment of Na V 1.8 in distal axons may provide a useful target in the treatment of pain of peripheral origin. SIGNIFICANCE STATEMENT It is unclear whether individual sodium channel isoforms exert differential roles in action potential conduction along the axonal membrane of nociceptive, unmyelinated peripheral nerve

Voltage-gated sodium channels: pharmaceutical targets via anticonvulsants to treat epileptic syndromes.

Science.gov (United States)

Abdelsayed, Mena; Sokolov, Stanislav

2013-01-01

Epilepsy is a brain disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels, Nav1.1 and Nav1.2. The effects of antiepileptic drugs (AEDs) as effective therapies for epilepsy have been characterized by extensive research. Most of the classic AEDs targeting Nav share a common mechanism of action by stabilizing the channel's fast-inactivated state. In contrast, novel AEDs, such as lacosamide, stabilize the slow-inactivated state in neuronal Nav1.1 and Nav1.7 isoforms. This paper reviews the different mechanisms by which this stabilization occurs to determine new methods for treatment.

Molecular Genetics of Drug-resistance in Epilepsies

Directory of Open Access Journals (Sweden)

Kurupath Radhakrishnan

2015-06-01

Full Text Available Nearly one-third of newly diagnosed patients with epilepsy remain unresponsive to antiepileptic drugs (AEDs, etiopathogenesis of which is poorly understood. The genes encoding the proteins that regulate the pharmacokinetics such as P-glycoprotein [ABCBI], major vault protein [MVP gene] and drug metabolizing enzymes [ABCB1, ABCG2, MVP, CYP2C9, CYP2C19, CYP3A4, CYP3A5, EPHX1, UGT1A1, UGT2B7], and pharmacodynamics such as sodium channels [SCN1A, SCN2A] and GABA receptors [GABRA1, GABRA6, GABRB2, GABRG2] of AEDs are under intense investigation to unravel the mysteries of AED-resistance. However, till today, a consistent and reliable result that could help the clinician either to predict drug resistance or to overcome it has not been forthcoming. The discrepant results may be related to variations in the definition of drug-resistance, heterogeneous patient populations, ethnic variations in the frequency distribution of single nucleotide polymorphisms (SNPs and the selection of SNPs. Understanding of these limitations of existing studies, hopefully, will help in designing better studies. Nearly one-third of newly diagnosed patients with epilepsy remain unresponsive toantiepileptic drugs (AEDs, etiopathogenesis of which is poorly understood. The genesencoding the proteins that regulate the pharmacokinetics such as P-glycoprotein[ABCBI], major vault protein [MVP gene] and drug metabolizing enzymes [ABCB1,ABCG2, MVP, CYP2C9, CYP2C19, CYP3A4, CYP3A5, EPHX1, UGT1A1, UGT2B7],and pharmacodynamics such as sodium channels [SCN1A, SCN2A] and GABAreceptors [GABRA1, GABRA6, GABRB2, GABRG2] of AEDs are under intenseinvestigation to unravel the mysteries of AED-resistance. However, till today, aconsistent and reliable result that could help the clinician either to predict drugresistanceor to overcome it has not been forthcoming. The discrepant results may berelated to variations in the definition of drug-resistance, heterogeneous patientpopulations, ethnic

Physiological and pathophysiological insights of Nav1.4 and Nav1.5 comparison

Directory of Open Access Journals (Sweden)

Gildas eLoussouarn

2016-01-01

Full Text Available Mutations in Nav1.4 and Nav1.5 α-subunits have been associated with muscular and cardiac channelopathies, respectively. Despite intense research on the structure and function of these channels, a lot of information is still missing to delineate the various physiological and pathophysiological processes underlying their activity at the molecular level. Nav1.4 and Nav1.5 sequences are similar, suggesting structural and functional homologies between the two orthologous channels. This also suggests that any characteristics described for one channel subunit may shed light on the properties of the counterpart channel subunit. In this review article, after a brief clinical description of the muscular and cardiac channelopathies related to Nav1.4 and Nav1.5 mutations, respectively, we compare the knowledge accumulated in different aspects of the expression and function of Nav1.4 and Nav1.5 α-subunits: the regulation of the two encoding genes (SCN4A and SCN5A, the associated/regulatory proteins and at last, the functional effect of the same missense mutations detected in Nav1.4 and Nav1.5. First, it appears that more is known on Nav1.5 expression and accessory proteins. Because of the high homologies of Nav1.5 binding sites and equivalent Nav1.4 sites, Nav1.5-related results may guide future investigations on Nav1.4. Second, the analysis of the same missense mutations in Nav1.4 and Nav1.5 revealed intriguing similarities regarding their effects on membrane excitability and alteration in channel biophysics. We believe that such comparison may bring new cues to the physiopathology of cardiac and muscular diseases.

Interactions Between Flavonoid-Rich Extracts and Sodium Caseinate Modulate Protein Functionality and Flavonoid Bioaccessibility in Model Food Systems.

Science.gov (United States)

Elegbede, Jennifer L; Li, Min; Jones, Owen G; Campanella, Osvaldo H; Ferruzzi, Mario G

2018-05-01

With growing interest in formulating new food products with added protein and flavonoid-rich ingredients for health benefits, direct interactions between these ingredient classes becomes critical in so much as they may impact protein functionality, product quality, and flavonoids bioavailability. In this study, sodium caseinate (SCN)-based model products (foams and emulsions) were formulated with grape seed extract (GSE, rich in galloylated flavonoids) and green tea extract (GTE, rich in nongalloylated flavonoids), respectively, to assess changes in functional properties of SCN and impacts on flavonoid bioaccessibility. Experiments with pure flavonoids suggested that galloylated flavonoids reduced air-water interfacial tension of 0.01% SCN dispersions more significantly than nongalloylated flavonoids at high concentrations (>50 μg/mL). This observation was supported by changes in stability of 5% SCN foam, which showed that foam stability was increased at high levels of GSE (≥50 μg/mL, P < 0.05) but was not affected by GTE. However, flavonoid extracts had modest effects on SCN emulsion. In addition, galloylated flavonoids had higher bioaccessibility in both SCN foam and emulsion. These results suggest that SCN-flavonoid binding interactions can modulate protein functionality leading to difference in performance and flavonoid bioaccessibility of protein-based products. As information on the beneficial health effects of flavonoids expands, it is likely that usage of these ingredients in consumer foods will increase. However, the necessary levels to provide such benefits may exceed those that begin to impact functionality of the macronutrients such as proteins. Flavonoid inclusion within protein matrices may modulate protein functionality in a food system and modify critical consumer traits or delivery of these beneficial plant-derived components. The product matrices utilized in this study offer relevant model systems to evaluate how fortification with flavonoid

(1-Butyl-4-methyl-pyridinium)[Cu(SCN)2]: a coordination polymer and ionic liquid.

Science.gov (United States)

Spielberg, Eike T; Edengeiser, Eugen; Mallick, Bert; Havenith, Martina; Mudring, Anja-Verena

2014-04-25

The compound (C4C1py)[Cu(SCN)2], (C4C1py = 1-Butyl-4-methyl-pyridinium), which can be obtained from CuSCN and the ionic liquid (C4C1py)(SCN), turns out to be a new organic-inorganic hybrid material as it qualifies both, as a coordination polymer and an ionic liquid. It features linked [Cu(SCN)2](-) units, in which the thiocyanates bridge the copper ions in a μ1,3-fashion. The resulting one-dimensional chains run along the a axis, separated by the C4C1py counterions. Powder X-ray diffraction not only confirms the single-crystal X-ray structure solution but proves the reformation of the coordination polymer from an isotropic melt. However, the materials shows a complex thermal behavior often encountered for ionic liquids such as a strong tendency to form a supercooled melt. At a relatively high cooling rate, glass formation is observed. When heating this melt in differential scanning calorimetry (DSC) and temperature-dependent polarizing optical microscopy (POM), investigations reveal the existence of a less thermodynamically stable crystalline polymorph. Raman measurements conducted at 10 and 100 °C point towards the formation of polyanionic chain fragments in the melt. Solid-state UV/Vis spectroscopy shows a broad absorption band around 18,870 cm(-1) (530 nm) and another strong one below 20,000 cm(-1) (<500 nm). The latter is attributed to the d(Cu(I))→π*(SCN)-MLCT (metal-to-ligand charge transfer) transition within the coordination polymer yielding an energy gap of 2.4 eV. At room temperature and upon irradiation with UV light, the material shows a weak fluorescence band at 15,870 cm(-1) (630 nm) with a quantum efficiency of 0.90(2) % and a lifetime of 131(2) ns. Upon lowering the temperature, the luminescence intensity strongly increases. Simultaneously, the band around 450 nm in the excitation spectrum decreases. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sodium channels in axons and glial cells of the optic nerve of Necturus maculosa.

Science.gov (United States)

Tang, C M; Strichartz, G R; Orkand, R K

1979-11-01

Experiments investigating both the binding of radioactively labelled saxitoxin (STX) and the electrophysiological response to drugs that increase the sodium permeability of excitable membranes were conducted in an effort to detect sodium channels in glial cells of the optic nerve of Necturus maculosa, the mudpuppy. Glial cells in nerves from chronically enucleated animals, which lack optic nerve axons, show no saturable uptake of STX whereas a saturable uptake is clearly present in normal optic nerves. The normal nerve is depolarized by aconitine, batrachotoxin, and veratridine (10(-6)-10(-5) M), whereas the all-glial preparation is only depolarized by veratridine and at concentrations greater than 10(-3) M. Unlike the depolarization caused by veratridine in normal nerves, the response in the all-glial tissue is not blocked by tetrodotoxin nor enhanced by scorpion venom (Leiurus quinquestriatus). In glial cells of the normal nerve, where axons are also present, the addition of 10(-5) M veratridine does lead to a transient depolarization; however, it is much briefer than the axonal response to veratridine in this same tissue. This glial response to veratridine could be caused by the efflux of K+ from the drug-depolarized axons, and is similar to the glial response to extracellular K+ accumulation resulting from action potentials in the axon.

Sodium channel Nav1.7 immunoreactivity in painful human dental pulp and burning mouth syndrome

Directory of Open Access Journals (Sweden)

Yiangou Yiangos

2010-06-01

Full Text Available Abstract Background Voltage gated sodium channels Nav1.7 are involved in nociceptor nerve action potentials and are known to affect pain sensitivity in clinical genetic disorders. Aims and Objectives To study Nav1.7 levels in dental pulpitis pain, an inflammatory condition, and burning mouth syndrome (BMS, considered a neuropathic orofacial pain disorder. Methods Two groups of patients were recruited for this study. One group consisted of patients with dental pulpitis pain (n = 5 and controls (n = 12, and the other patients with BMS (n = 7 and controls (n = 10. BMS patients were diagnosed according to the International Association for the Study of Pain criteria; a pain history was collected, including the visual analogue scale (VAS. Immunohistochemistry with visual intensity and computer image analysis were used to evaluate levels of Nav1.7 in dental pulp tissue samples from the dental pulpitis group, and tongue biopsies from the BMS group. Results There was a significantly increased visual intensity score for Nav1.7 in nerve fibres in the painful dental pulp specimens, compared to controls. Image analysis showed a trend for an increase of the Nav1.7 immunoreactive % area in the painful pulp group, but this was not statistically significant. When expressed as a ratio of the neurofilament % area, there was a strong trend for an increase of Nav1.7 in the painful pulp group. Nav1.7 immunoreactive fibres were seen in abundance in the sub-mucosal layer of tongue biopsies, with no significant difference between BMS and controls. Conclusion Nav1.7 sodium channel may play a significant role in inflammatory dental pain. Clinical trials with selective Nav1.7 channel blockers should prioritise dental pulp pain rather than BMS.

Sodium channel Nav1.7 immunoreactivity in painful human dental pulp and burning mouth syndrome

Science.gov (United States)

2010-01-01

Background Voltage gated sodium channels Nav1.7 are involved in nociceptor nerve action potentials and are known to affect pain sensitivity in clinical genetic disorders. Aims and Objectives To study Nav1.7 levels in dental pulpitis pain, an inflammatory condition, and burning mouth syndrome (BMS), considered a neuropathic orofacial pain disorder. Methods Two groups of patients were recruited for this study. One group consisted of patients with dental pulpitis pain (n = 5) and controls (n = 12), and the other patients with BMS (n = 7) and controls (n = 10). BMS patients were diagnosed according to the International Association for the Study of Pain criteria; a pain history was collected, including the visual analogue scale (VAS). Immunohistochemistry with visual intensity and computer image analysis were used to evaluate levels of Nav1.7 in dental pulp tissue samples from the dental pulpitis group, and tongue biopsies from the BMS group. Results There was a significantly increased visual intensity score for Nav1.7 in nerve fibres in the painful dental pulp specimens, compared to controls. Image analysis showed a trend for an increase of the Nav1.7 immunoreactive % area in the painful pulp group, but this was not statistically significant. When expressed as a ratio of the neurofilament % area, there was a strong trend for an increase of Nav1.7 in the painful pulp group. Nav1.7 immunoreactive fibres were seen in abundance in the sub-mucosal layer of tongue biopsies, with no significant difference between BMS and controls. Conclusion Nav1.7 sodium channel may play a significant role in inflammatory dental pain. Clinical trials with selective Nav1.7 channel blockers should prioritise dental pulp pain rather than BMS. PMID:20529324

21 CFR 184.1697 - Riboflavin-5′-phosphate (sodium).

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Riboflavin-5â²-phosphate (sodium). 184.1697 Section... SAFE Listing of Specific Substances Affirmed as GRAS § 184.1697 Riboflavin-5′-phosphate (sodium). (a) Riboflavin-5′-phosphate (sodium) (C17H20N4O9PNa·2H2O, CAS Reg. No 130-40-5) occurs as the dihydrate in yellow...

THEORETICAL RESEARCH ON THE MULTI-CHANNEL REACTION MECHANISM AND KINETICS OF HNCS WITH OH-

Directory of Open Access Journals (Sweden)

Li-Jie Hou

Full Text Available We presented a theoretical study on the detailed reaction mechanism and kinetics of the HNCS molecule with the OH-. The barrierless minimum energy path and the most favorable entrance channel have been determined by study the thermodynamic and kinetic characters of the channel with low energy barrier. The B3LYP/6-311++G** method was employed for all the geometrical optimizations and a multi-level extrapolation method based on the G3 energies was employed for further energy refinements. In addition, the analysis of the combining interaction between hydroxide ion and HNCS was performed by natural bond orbitals (NBO analysis. The calculation results indicated that the reaction of OH- with HNCS had four channels, and the channel of H-atom in HNCS direct extraction to OH- (OH-+HNCS→IM1→TS3→IM4→P2(SCN- +H2O in singlet state was the main channel with the low potential energy and high equilibrium constant and reaction rate constant. SCN- and H2O were main products.

Modeling and Validation of Sodium Plugging for Heat Exchangers in Sodium-cooled Fast Reactor Systems

Energy Technology Data Exchange (ETDEWEB)

Ferroni, Paolo [Westinghouse Electric Company LLC, Cranberry Township, PA (United States). Global Technology Development; Tatli, Emre [Westinghouse Electric Company LLC, Cranberry Township, PA (United States); Czerniak, Luke [Westinghouse Electric Company LLC, Cranberry Township, PA (United States); Sienicki, James J. [Argonne National Lab. (ANL), Argonne, IL (United States); Chien, Hual-Te [Argonne National Lab. (ANL), Argonne, IL (United States); Yoichi, Momozaki [Argonne National Lab. (ANL), Argonne, IL (United States); Bakhtiari, Sasan [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-06-29

The project “Modeling and Validation of Sodium Plugging for Heat Exchangers in Sodium-cooled Fast Reactor Systems” was conducted jointly by Westinghouse Electric Company (Westinghouse) and Argonne National Laboratory (ANL), over the period October 1, 2013- March 31, 2016. The project’s motivation was the need to provide designers of Sodium Fast Reactors (SFRs) with a validated, state-of-the-art computational tool for the prediction of sodium oxide (Na₂O) deposition in small-diameter sodium heat exchanger (HX) channels, such as those in the diffusion bonded HXs proposed for SFRs coupled with a supercritical CO₂ (sCO₂) Brayton cycle power conversion system. In SFRs, Na₂O deposition can potentially occur following accidental air ingress in the intermediate heat transport system (IHTS) sodium and simultaneous failure of the IHTS sodium cold trap. In this scenario, oxygen can travel through the IHTS loop and reach the coldest regions, represented by the cold end of the sodium channels of the HXs, where Na₂O precipitation may initiate and continue. In addition to deteriorating HX heat transfer and pressure drop performance, Na₂O deposition can lead to channel plugging especially when the size of the sodium channels is small, which is the case for diffusion bonded HXs whose sodium channel hydraulic diameter is generally below 5 mm. Sodium oxide melts at a high temperature well above the sodium melting temperature such that removal of a solid plug such as through dissolution by pure sodium could take a lengthy time. The Sodium Plugging Phenomena Loop (SPPL) was developed at ANL, prior to this project, for investigating Na₂O deposition phenomena within sodium channels that are prototypical of the diffusion bonded HX channels envisioned for SFR-sCO₂ systems. In this project, a Computational Fluid Dynamic (CFD) model capable of simulating the thermal-hydraulics of the SPPL test

Electronic structure and physical properties of ScN in pressure: density-functional theory calculations

International Nuclear Information System (INIS)

Guan Pengfei; Wang Chongyu; Yu Tao

2008-01-01

Local density functional is investigated by using the full-potential linearized augmented plane wave (FP-LAPW) method for ScN in the hexagonal structure and the rocksalt structure and for hexagonal structures linking a layered hexagonal phase with wurtzite structure along a homogeneous strain transition path. It is found that the wurtzite ScN is unstable and the layered hexagonal phase, labelled as h o , in which atoms are approximately fivefold coordinated, is metastable, and the rocksalt ScN is stable. The electronic structure, the physical properties of the intermediate structures and the energy band structure along the transition are presented. It is found that the band gaps change from 4.0 to 1.0 eV continuously when c/a value varies from 1.68 to 1.26. It is noticeable that the study of ScN provides an opportunity to apply this kind of material (in wurtzite[h]-derived phase). (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Determining the Advantages, Costs, and Trade-Offs of a Novel Sodium Channel Mutation in the Copepod Acartia hudsonica to Paralytic Shellfish Toxins (PST.

Directory of Open Access Journals (Sweden)

Michael Finiguerra

Full Text Available The marine copepod Acartia hudsonica was shown to be adapted to dinoflagellate prey, Alexandrium fundyense, which produce paralytic shellfish toxins (PST. Adaptation to PSTs in other organisms is caused by a mutation in the sodium channel. Recently, a mutation in the sodium channel in A. hudsonica was found. In this study, we rigorously tested for advantages, costs, and trade-offs associated with the mutant isoform of A. hudsonica under toxic and non-toxic conditions. We combined fitness with wild-type: mutant isoform ratio measurements on the same individual copepod to test our hypotheses. All A. hudsonica copepods express both the wild-type and mutant sodium channel isoforms, but in different proportions; some individuals express predominantly mutant (PMI or wild-type isoforms (PWI, while most individuals express relatively equal amounts of each (EI. There was no consistent pattern of improved performance as a function of toxin dose for egg production rate (EPR, ingestion rate (I, and gross growth efficiency (GGE for individuals in the PMI group relative to individuals in the PWI expression group. Neither was there any evidence to indicate a fitness benefit to the mutant isoform at intermediate toxin doses. No clear advantage under toxic conditions was associated with the mutation. Using a mixed-diet approach, there was also no observed relationship between individual wild-type: mutant isoform ratios and among expression groups, on both toxic and non-toxic diets, for eggs produced over three days. Lastly, expression of the mutant isoform did not mitigate the negative effects of the toxin. That is, the reductions in EPR from a toxic to non-toxic diet for copepods were independent of expression groups. Overall, the results did not support our hypotheses; the mutant sodium channel isoform does not appear to be related to adaptation to PST in A. hudsonica. Other potential mechanisms responsible for the adaptation are discussed.

Morphometric relations of fractal-skeletal based channel network model

Directory of Open Access Journals (Sweden)

B. S. Daya Sagar

1998-01-01

Full Text Available A fractal-skeletal based channel network (F-SCN model is proposed. Four regular sided initiator-basins are transformed as second order fractal basins by following a specific generating mechanism with non-random rule. The morphological skeletons, hereafter referred to as channel networks, are extracted from these fractal basins. The morphometric and fractal relationships of these F-SCNs are shown. The fractal dimensions of these fractal basins, channel networks, and main channel lengths (computed through box counting method are compared with those of estimated length–area measures. Certain morphometric order ratios to show fractal relations are also highlighted.

A clinical case of epilepsy in a female patient with double mutations in the SCN2A and PCDH19 genes

Directory of Open Access Journals (Sweden)

M. B. Mironov

2017-01-01

Full Text Available The paper describes a 6-year-old female patient with epilepsy caused by mutations in the SCN2A and PCDH19 genes, which clinically appears as epileptic seizures, drug-resistant epilepsy, secondary microcephaly, mental retardation, and autism. It reviews the literature regarding both mutations. World literature lacks publications on a combination of two SCN2A and PCDH19 mutations in one female patient with epileptic encephalopathies.

Trans-channel interactions in batrachotoxin-modified skeletal muscle sodium channels: voltage-dependent block by cytoplasmic amines, and the influence of mu-conotoxin GIIIA derivatives and permeant ions.

Science.gov (United States)

Pavlov, Evgeny; Britvina, Tatiana; McArthur, Jeff R; Ma, Quanli; Sierralta, Iván; Zamponi, Gerald W; French, Robert J

2008-11-01

External mu-conotoxins and internal amine blockers inhibit each other's block of voltage-gated sodium channels. We explore the basis of this interaction by measuring the shifts in voltage-dependence of channel inhibition by internal amines induced by two mu-conotoxin derivatives with different charge distributions and net charges. Charge changes on the toxin were made at residue 13, which is thought to penetrate most deeply into the channel, making it likely to have the strongest individual interaction with an internal charged ligand. When an R13Q or R13E molecule was bound to the channel, the voltage dependence of diethylammonium (DEA)-block shifted toward more depolarized potentials (23 mV for R13Q, and 16 mV for R13E). An electrostatic model of the repulsion between DEA and the toxin simulated these data, with a distance between residue 13 of the mu-conotoxin and the DEA-binding site of approximately 15 A. Surprisingly, for tetrapropylammonium, the shifts were only 9 mV for R13Q, and 7 mV for R13E. The smaller shifts associated with R13E, the toxin with a smaller net charge, are generally consistent with an electrostatic interaction. However, the smaller shifts observed for tetrapropylammonium than for DEA suggest that other factors must be involved. Two observations indicate that the coupling of permeant ion occupancy of the channel to blocker binding may contribute to the overall amine-toxin interaction: 1), R13Q binding decreases the apparent affinity of sodium for the conducting pore by approximately 4-fold; and 2), increasing external [Na(+)] decreases block by DEA at constant voltage. Thus, even though a number of studies suggest that sodium channels are occupied by no more than one ion most of the time, measurable coupling occurs between permeant ions and toxin or amine blockers. Such interactions likely determine, in part, the strength of trans-channel, amine-conotoxin interactions.

Biophysical and Pharmacological Characterization of Nav1.9 Voltage Dependent Sodium Channels Stably Expressed in HEK-293 Cells.

Directory of Open Access Journals (Sweden)

Zhixin Lin

Full Text Available The voltage dependent sodium channel Nav1.9, is expressed preferentially in peripheral sensory neurons and has been linked to human genetic pain disorders, which makes it target of interest for the development of new pain therapeutics. However, characterization of Nav1.9 pharmacology has been limited due in part to the historical difficulty of functionally expressing recombinant channels. Here we report the successful generation and characterization of human, mouse and rat Nav1.9 stably expressed in human HEK-293 cells. These cells exhibit slowly activating and inactivating inward sodium channel currents that have characteristics of native Nav1.9. Optimal functional expression was achieved by coexpression of Nav1.9 with β1/β2 subunits. While recombinantly expressed Nav1.9 was found to be sensitive to sodium channel inhibitors TC-N 1752 and tetracaine, potency was up to 100-fold less than reported for other Nav channel subtypes despite evidence to support an interaction with the canonical local anesthetic (LA binding region on Domain 4 S6. Nav1.9 Domain 2 S6 pore domain contains a unique lysine residue (K799 which is predicted to be spatially near the local anesthetic interaction site. Mutation of this residue to the consensus asparagine (K799N resulted in an increase in potency for tetracaine, but a decrease for TC-N 1752, suggesting that this residue can influence interaction of inhibitors with the Nav1.9 pore. In summary, we have shown that stable functional expression of Nav1.9 in the widely used HEK-293 cells is possible, which opens up opportunities to better understand channel properties and may potentially aid identification of novel Nav1.9 based pharmacotherapies.

Trans-Channel Interactions in Batrachotoxin-Modified Skeletal Muscle Sodium Channels: Voltage-Dependent Block by Cytoplasmic Amines, and the Influence of μ-Conotoxin GIIIA Derivatives and Permeant Ions

Science.gov (United States)

Pavlov, Evgeny; Britvina, Tatiana; McArthur, Jeff R.; Ma, Quanli; Sierralta, Iván; Zamponi, Gerald W.; French, Robert J.

2008-01-01

External μ-conotoxins and internal amine blockers inhibit each other's block of voltage-gated sodium channels. We explore the basis of this interaction by measuring the shifts in voltage-dependence of channel inhibition by internal amines induced by two μ-conotoxin derivatives with different charge distributions and net charges. Charge changes on the toxin were made at residue 13, which is thought to penetrate most deeply into the channel, making it likely to have the strongest individual interaction with an internal charged ligand. When an R13Q or R13E molecule was bound to the channel, the voltage dependence of diethylammonium (DEA)-block shifted toward more depolarized potentials (23 mV for R13Q, and 16 mV for R13E). An electrostatic model of the repulsion between DEA and the toxin simulated these data, with a distance between residue 13 of the μ-conotoxin and the DEA-binding site of ∼15 Å. Surprisingly, for tetrapropylammonium, the shifts were only 9 mV for R13Q, and 7 mV for R13E. The smaller shifts associated with R13E, the toxin with a smaller net charge, are generally consistent with an electrostatic interaction. However, the smaller shifts observed for tetrapropylammonium than for DEA suggest that other factors must be involved. Two observations indicate that the coupling of permeant ion occupancy of the channel to blocker binding may contribute to the overall amine-toxin interaction: 1), R13Q binding decreases the apparent affinity of sodium for the conducting pore by ∼4-fold; and 2), increasing external [Na+] decreases block by DEA at constant voltage. Thus, even though a number of studies suggest that sodium channels are occupied by no more than one ion most of the time, measurable coupling occurs between permeant ions and toxin or amine blockers. Such interactions likely determine, in part, the strength of trans-channel, amine-conotoxin interactions. PMID:18658222

Differential state-dependent modification of rat Na{sub v}1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin

Energy Technology Data Exchange (ETDEWEB)

He, Bingjun [College of Life Sciences, Nankai University, Tianjin 300071 (China); Soderlund, David M., E-mail: dms6@cornell.edu [Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456 (United States)

2011-12-15

We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}1 and {beta}2 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{sub 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 {approx} 25 mV for tefluthrin and {approx} 20 mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of {approx} 5-10 mV 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{sub v}1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7 Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by {approx} 2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Na{sub 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{sub v}1.6 channels

Copper(I) Thiocyanate (CuSCN) Hole-Transport Layers Processed from Aqueous Precursor Solutions and Their Application in Thin-Film Transistors and Highly Efficient Organic and Organometal Halide Perovskite Solar Cells

KAUST Repository

Wijeyasinghe, Nilushi

2017-07-28

This study reports the development of copper(I) thiocyanate (CuSCN) hole-transport layers (HTLs) processed from aqueous ammonia as a novel alternative to conventional n-alkyl sulfide solvents. Wide bandgap (3.4–3.9 eV) and ultrathin (3–5 nm) layers of CuSCN are formed when the aqueous CuSCN–ammine complex solution is spin-cast in air and annealed at 100 °C. X-ray photoelectron spectroscopy confirms the high compositional purity of the formed CuSCN layers, while the high-resolution valence band spectra agree with first-principles calculations. Study of the hole-transport properties using field-effect transistor measurements reveals that the aqueous-processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl sulfide solutions with the maximum values approaching 0.1 cm2 V−1 s−1. A further interesting characteristic is the low surface roughness of the resulting CuSCN layers, which in the case of solar cells helps to planarize the indium tin oxide anode. Organic bulk heterojunction and planar organometal halide perovskite solar cells based on aqueous-processed CuSCN HTLs yield power conversion efficiency of 10.7% and 17.5%, respectively. Importantly, aqueous-processed CuSCN-based cells consistently outperform devices based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate HTLs. This is the first report on CuSCN films and devices processed via an aqueous-based synthetic route that is compatible with high-throughput manufacturing and paves the way for further developments.

Structure of a prokaryotic sodium channel pore reveals essential gating elements and an outer ion binding site common to eukaryotic channels.

Science.gov (United States)

Shaya, David; Findeisen, Felix; Abderemane-Ali, Fayal; Arrigoni, Cristina; Wong, Stephanie; Nurva, Shailika Reddy; Loussouarn, Gildas; Minor, Daniel L

2014-01-23

Voltage-gated sodium channels (NaVs) are central elements of cellular excitation. Notwithstanding advances from recent bacterial NaV (BacNaV) structures, key questions about gating and ion selectivity remain. Here, we present a closed conformation of NaVAe1p, a pore-only BacNaV derived from NaVAe1, a BacNaV from the arsenite oxidizer Alkalilimnicola ehrlichei found in Mono Lake, California, that provides insight into both fundamental properties. The structure reveals a pore domain in which the pore-lining S6 helix connects to a helical cytoplasmic tail. Electrophysiological studies of full-length BacNaVs show that two elements defined by the NaVAe1p structure, an S6 activation gate position and the cytoplasmic tail "neck", are central to BacNaV gating. The structure also reveals the selectivity filter ion entry site, termed the "outer ion" site. Comparison with mammalian voltage-gated calcium channel (CaV) selectivity filters, together with functional studies, shows that this site forms a previously unknown determinant of CaV high-affinity calcium binding. Our findings underscore commonalities between BacNaVs and eukaryotic voltage-gated channels and provide a framework for understanding gating and ion permeation in this superfamily. © 2013. Published by Elsevier Ltd. All rights reserved.

Effects of n-3 polyunsaturated fatty acids on cardiac ion channels

Directory of Open Access Journals (Sweden)

Cristina eMoreno

2012-07-01

Full Text Available Dietary n-3 polyunsaturated fatty acids (PUFAs have been reported to exhibit antiarrhythmic properties, attributed to their capability to modulate ion channels. In the present review, we will focus on the effects of PUFAs on cardiac sodium channel (Nav1.5 and two potassium channels (Kv (Kv1.5 and Kv11.1. n-3 marine (docohexaenoic and eicohexapentaenoic acid and plant origin (alpha-linolenic acid PUFAs block Kv1.5 and Kv11.1 channels at physiological concentrations. Also, DHA and EPA decreased Nav1.5 and calcium channels. These effects on Na and Ca channels theoretically should shorten the cardiac APD, whereas the blocking actions of n-3 PUFAs of Kv channels should lengthen the cardiac action potential. Experiments performed in female rabbits fed with a diet rich in n-3 PUFAs show a longer cardiac action potential and effective refractory period. This study was performed to analyze if their antiarrhythmic effects are due to a reduction of triangulation, reverse use-dependence, instability and dispersion of the cardiac action potential (TRIaD as a measure of proarrhythmic effects. Dietary n-3 PUFAs supplementation markedly reduced dofetilide-induced TRIaD and abolished dofetilide-induced torsades de pointes (TdP. Ultrafast sodium channel block by DHA may account for the antiarrhythmic protection of dietary supplements of n-3 PUFAs against dofetilide induced proarrhythmia observed in this animal model. The cardiac effects of n-3 PUFAs resemble those of amiodarone: both block sodium, calcium and potassium channels, have anti-adrenergic properties, can prolong the cardiac action potential, reverse TRIaD and suppress TdP. The main difference is that sodium channel block by n-3 PUFAs has a much faster onset and offset kinetics. Therefore, the electrophysiological profile of n-3 PUFAs appears more desirable: the duration of reduced sodium current (facilitates re-entry is much shorter. The n-3 PUFAs appear as a safer alternative to other antiarrhythmic

Genetic mutation in Korean patients of sudden cardiac arrest as a surrogating marker of idiopathic ventricular arrhythmia.

Science.gov (United States)

Son, Myoung Kyun; Ki, Chang-Seok; Park, Seung-Jung; Huh, June; Kim, June Soo; On, Young Keun

2013-07-01

Mutation or common intronic variants in cardiac ion channel genes have been suggested to be associated with sudden cardiac death caused by idiopathic ventricular tachyarrhythmia. This study aimed to find mutations in cardiac ion channel genes of Korean sudden cardiac arrest patients with structurally normal heart and to verify association between common genetic variation in cardiac ion channel and sudden cardiac arrest by idiopathic ventricular tachyarrhythmia in Koreans. Study participants were Korean survivors of sudden cardiac arrest caused by idiopathic ventricular tachycardia or fibrillation. All coding exons of the SCN5A, KCNQ1, and KCNH2 genes were analyzed by Sanger sequencing. Fifteen survivors of sudden cardiac arrest were included. Three male patients had mutations in SCN5A gene and none in KCNQ1 and KCNH2 genes. Intronic variant (rs2283222) in KCNQ1 gene showed significant association with sudden cardiac arrest (OR 4.05). Four male sudden cardiac arrest survivors had intronic variant (rs11720524) in SCN5A gene. None of female survivors of sudden cardiac arrest had SCN5A gene mutations despite similar frequencies of intronic variants between males and females in 55 normal controls. Common intronic variant in KCNQ1 gene is associated with sudden cardiac arrest caused by idiopathic ventricular tachyarrhythmia in Koreans.

Reduced muscle-fiber conduction but normal slowing after cold exposure in paramyotonia congenita

NARCIS (Netherlands)

Blijham, P.J.; Drost, G; Stegeman, D.F.; Zwarts, M.J.

2008-01-01

In this study we investigated a family with paramyotonia (PC) congenita caused by a Gly1306Val mutation in the voltage-gated sodium-channel gene SCN4A. A previous study showed that exposure to cold aggravates the muscle stiffness in patients with this mutation. However, the mechanism behind cold

Role of common and rare variants in SCN10A

DEFF Research Database (Denmark)

Behr, Elijah R.; Savio-Galimberti, Eleonora; Barc, Julien

2015-01-01

AIMS: Brugada syndrome (BrS) remains genetically heterogeneous and is associated with slowed cardiac conduction. We aimed to identify genetic variation in BrS cases at loci associated with QRS duration. METHODS AND RESULTS: A multi-centre study sequenced seven candidate genes (SCN10A, HAND1, PLN,...

Conotoxins Targeting Neuronal Voltage-Gated Sodium Channel Subtypes: Potential Analgesics?

Directory of Open Access Journals (Sweden)

Jeffrey R. McArthur

2012-11-01

Full Text Available Voltage-gated sodium channels (VGSC are the primary mediators of electrical signal amplification and propagation in excitable cells. VGSC subtypes are diverse, with different biophysical and pharmacological properties, and varied tissue distribution. Altered VGSC expression and/or increased VGSC activity in sensory neurons is characteristic of inflammatory and neuropathic pain states. Therefore, VGSC modulators could be used in prospective analgesic compounds. VGSCs have specific binding sites for four conotoxin families: μ-, μO-, δ- and ί-conotoxins. Various studies have identified that the binding site of these peptide toxins is restricted to well-defined areas or domains. To date, only the μ- and μO-family exhibit analgesic properties in animal pain models. This review will focus on conotoxins from the μ- and μO-families that act on neuronal VGSCs. Examples of how these conotoxins target various pharmacologically important neuronal ion channels, as well as potential problems with the development of drugs from conotoxins, will be discussed.

Regulation of sodium channel function by bilayer elasticity: the importance of hydrophobic coupling. Effects of Micelle-forming amphiphiles and cholesterol

DEFF Research Database (Denmark)

Lundbæk, Jens August; Birn, Pia; Hansen, Anker J

2004-01-01

, Triton X-100, and reduced Triton X-100) that make lipid bilayers less "stiff", as measured using gA channels, shift the voltage dependence of sodium channel inactivation toward more hyperpolarized potentials. At low amphiphile concentration, the magnitude of the shift is linearly correlated to the change...

Amiloride blocks lithium entry through the sodium channel thereby attenuating the resultant nephrogenic diabetes insipidus.

NARCIS (Netherlands)

Kortenoeven, M.L.A.; Li, Y.; Shaw, S.M.; Gaeggeler, H.P.; Rossier, B.C.; Wetzels, J.F.M.; Deen, P.M.T.

2009-01-01

Lithium therapy frequently induces nephrogenic diabetes insipidus; amiloride appears to prevent its occurrence in some clinical cases. Amiloride blocks the epithelial sodium channel (ENaC) located in the apical membrane of principal cells; hence one possibility is that ENaC is the main entry site

Differential roles of AVP and VIP signaling in the postnatal changes of neural networks for coherent circadian rhythms in the SCN

Science.gov (United States)

Ono, Daisuke; Honma, Sato; Honma, Ken-ichi

2016-01-01

The suprachiasmatic nucleus (SCN) is the site of the master circadian clock in mammals. The SCN neural network plays a critical role in expressing the tissue-level circadian rhythm. Previously, we demonstrated postnatal changes in the SCN network in mice, in which the clock gene products CRYPTOCHROMES (CRYs) are involved. Here, we show that vasoactive intestinal polypeptide (VIP) signaling is essential for the tissue-level circadian PER2::LUC rhythm in the neonatal SCN of CRY double-deficient mice (Cry1,2−/−). VIP and arginine vasopressin (AVP) signaling showed redundancy in expressing the tissue-level circadian rhythm in the SCN. AVP synthesis was significantly attenuated in the Cry1,2−/− SCN, which contributes to aperiodicity in the adult mice together with an attenuation of VIP signaling as a natural process of ontogeny. The SCN network consists of multiple clusters of cellular circadian rhythms that are differentially integrated by AVP and VIP signaling, depending on the postnatal period. PMID:27626074

Predictive 3D modelling of the interactions of pyrethroids with the voltage-gated sodium channels of ticks and mites.

Science.gov (United States)

O'Reilly, Andrias O; Williamson, Martin S; González-Cabrera, Joel; Turberg, Andreas; Field, Linda M; Wallace, B A; Davies, T G Emyr

2014-03-01

The pyrethroid insecticides are a very successful group of compounds that target invertebrate voltage-gated sodium channels and are widely used in the control of insects, ticks and mites. It is well established that some pyrethroids are good insecticides whereas others are more effective as acaricides. This species specificity is advantageous for controlling particular pest(s) in the presence of another non-target invertebrate, for example controlling the Varroa mite in honeybee colonies. We applied in silico techniques to compare the voltage-gated sodium channels of insects versus ticks and mites and their interactions with a range of pyrethroids and DDT analogues. We identified a single amino acid difference within the pyrethroid binding pocket of ticks/mites that may have significant impact on the effectiveness of pyrethroids as acaricides. Other individual amino acid differences within the binding pocket in distinct tick and mite species may provide a basis for future acaricidal selectivity. Three-dimensional modelling of the pyrethroid/DDT receptor site has led to a new hypothesis to explain the preferential binding of acaricidal pyrethroids to the sodium channels of ticks/mites. This is important for understanding pyrethroid selectivity and the potential effects of mutations that can give rise to resistance to pyrethroids in commercially-important pest species. © 2013 Society of Chemical Industry.

Resonance Raman Spectrum of the Transient (SCN)2 Free Radical Anion

DEFF Research Database (Denmark)

Wilbrandt, Robert Walter; Jensen, N. H.; Pagsberg, Palle Bjørn

1979-01-01

The resonance Raman spectrum of the transient species (λmax = 475 nm, τ½ = 1.6 μs) formed by pulse radiolysis of aqueous solutions of thiocyanate, SCN2−, is reported. The spectrum is discussed in terms of the previous assignment of this transient to the radical anion, (SCN)−2. The observed...... vibrational frequencies of the radical anion are consistent with substantial weakening of the S---S and the Ctriple bond; length as m-dashN bonds are compared with neutral thiocyanogen....

Energy analysis of a diffusion absorption cooling system using lithium nitrate, sodium thiocyanate and water as absorbent substances and ammonia as the refrigerant

International Nuclear Information System (INIS)

Acuña, A.; Velázquez, N.; Cerezo, J.

2013-01-01

A diffusion absorption cooling system is analyzed to determine the appropriate fluid for the unit, based on the coefficient of performance (COP) and operating conditions, by comparing lithium nitrate (LiNO 3 ), sodium thiocyanate (NaSCN) and water (H 2 O) as absorbent substances and by using ammonia (NH 3 ) as the refrigerant. The presence of crystallization in the system is analyzed as a function of the generator and absorber temperatures. Additionally, the effects on the efficiency of the system from adding the inert gas helium (He) or hydrogen (H 2 ) are studied. A mathematical model is developed and compared to experimental studies reported in the literature. At an evaporator temperature of −15 °C, a generator temperature of 120 °C and absorber and condenser temperatures of 40 °C, the results show that the best performance is achieved by the NH 3 –LiNO 3 –He mixture, with a COP of 0.48. This mixture performs 27–46% more efficient than the NH 3 –NaSCN mixture. The NH 3 –H 2 O mixture is 52–69% less efficient than the NH 3 –LiNO 3 mixture. However, when the evaporator runs at 7.5 °C, the NH 3 –H 2 O–He mixture achieves a more efficient COP than does the NH 3 –LiNO 3 –He mixture, and the NH 3 –NaSCN–He and NH 3 –LiNO 3 –He mixtures achieve the same COP when the evaporator is at 10 °C. At temperatures below 7.5 °C, the NH 3 –NaSCN–He mixture achieves a higher COP than does the NH 3 –H 2 O–He mixture. The NH 3 –LiNO 3 mixture shows crystallization at higher temperatures in the generator than does the NH 3 –NaSCN mixture. Moreover, at the same evaporator temperature, the NH 3 –LiNO 3 mixture works at activation temperatures lower than does the NH 3 –NaSCN mixture. -- Highlights: ► We studied a diffusion absorption cooling system with different working mixtures. ► The NH 3 –LiNO 3 mixture showed more efficiency than NH 3 –H 2 O mixture and NH 3 –NaSCN mixture. ► The generator and absorber temperature

Efficient and stable CH3NH3PbI3-x(SCN)x planar perovskite solar cells fabricated in ambient air with low-temperature process

Science.gov (United States)

Zhang, Zongbao; Zhou, Yang; Cai, Yangyang; Liu, Hui; Qin, Qiqi; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

2018-02-01

Planar perovskite solar cells (PSCs) based on CH3NH3PbI3-x(SCN)x (SCN: thiocyanate) active layer and low-temperature processed TiO2 films are fabricated by a sequential two-step method in ambient air. Here, alkali thiocyanates (NaSCN, KSCN) are added into Pb(SCN)2 precursor to improve the microstructure of CH3NH3PbI3-x(SCN)x perovskite layers and performance of the as-prepared PSCs. At the optimum concentrations of alkali thiocyanates as additives, the as-prepared NaSCN-modified and KSCN-modified PSCs demonstrate the efficiencies of 16.59% and 15.63% respectively, being much higher than 12.73% of the reference PSCs without additives. This improvement is primarily ascribed to the enhanced electron transport, reduced recombination rates and much improved microstructures with large grain size and low defect density at grain boundaries. Importantly, it is revealed that the modified PSCs at the optimized concentrations of alkali thiocyanates additives exhibit remarkably improved stability than the reference PSCs against humid circumstance, and a continuous exposure to humid air without encapsulation over 45 days only records about 5% degradation of the efficiency. These findings provide a facile approach to fabricate efficient and stable PSCs by low processing temperature in ambient air, both of which are highly preferred for future practical applications of PSCs.

Evidence for Dual Binding Sites for 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in Insect Sodium Channels*

Science.gov (United States)

Du, Yuzhe; Nomura, Yoshiko; Zhorov, Boris S.; Dong, Ke

2016-01-01

1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), the first organochlorine insecticide, and pyrethroid insecticides are sodium channel agonists. Although the use of DDT is banned in most of the world due to its detrimental impact on the ecosystem, indoor residual spraying of DDT is still recommended for malaria control in Africa. Development of resistance to DDT and pyrethroids is a serious global obstacle for managing disease vectors. Mapping DDT binding sites is necessary for understanding mechanisms of resistance and modulation of sodium channels by structurally different ligands. The pioneering model of the housefly sodium channel visualized the first receptor for pyrethroids, PyR1, in the II/III domain interface and suggested that DDT binds within PyR1. Previously, we proposed the second pyrethroid receptor, PyR2, at the I/II domain interface. However, whether DDT binds to both pyrethroid receptor sites remains unknown. Here, using computational docking of DDT into the Kv1.2-based mosquito sodium channel model, we predict that two DDT molecules can bind simultaneously within PyR1 and PyR2. The bulky trichloromethyl group of each DDT molecule fits snugly between four helices in the bent domain interface, whereas two p-chlorophenyl rings extend into two wings of the interface. Model-driven mutagenesis and electrophysiological analysis confirmed these propositions and revealed 10 previously unknown DDT-sensing residues within PyR1 and PyR2. Our study proposes a dual DDT-receptor model and provides a structural background for rational development of new insecticides. PMID:26637352

ASIC and ENaC type sodium channels: conformational states and the structures of the ion selectivity filters.

Science.gov (United States)

Hanukoglu, Israel

2017-02-01

The acid-sensing ion channels (ASICs) and epithelial sodium channels (ENaC) are members of a superfamily of channels that play critical roles in mechanosensation, chemosensation, nociception, and regulation of blood volume and pressure. These channels look and function like a tripartite funnel that directs the flow of Na + ions into the cytoplasm via the channel pore in the membrane. The subunits that form these channels share a common structure with two transmembrane segments (TM1 and TM2) and a large extracellular part. In most vertebrates, there are five paralogous genes that code for ASICs (ASIC1-ASIC5), and four for ENaC subunits alpha, beta, gamma, and delta (α, β, γ, and δ). While ASICs can form functional channels as a homo- or heterotrimer, ENaC functions as an obligate heterotrimer composed of α-β-γ or β-γ-δ subunits. The structure of ASIC has been determined in several conformations, including desensitized and open states. This review presents a comparison of the structures of these states using easy-to-understand molecular models of the full complex, the central tunnel that includes an outer vestibule, the channel pore, and ion selectivity filter. The differences in the secondary, tertiary, and quaternary structures of the states are summarized to pinpoint the conformational changes responsible for channel opening. Results of site-directed mutagenesis studies of ENaC subunits are examined in light of ASIC1 models. Based on these comparisons, a molecular model for the selectivity filter of ENaC is built by in silico mutagenesis of an ASIC1 structure. These models suggest that Na + ions pass through the filter in a hydrated state. © 2016 Federation of European Biochemical Societies.

Contrasting oxygen-effects in the inactivation of ribonuclease A by N3, (SCN)-2 and OH radicals

International Nuclear Information System (INIS)

Pruetz, W.A.

1979-01-01

N 3 exhibits higher efficiency than OH in the inactivation of RNase in de-acerated (neutral) aqueous solution. In O 2 -saturated solution the OH-induced inactivation is enhanced, but N 3 and (SCN) - 2 become remarkably inefficient. Our results suggest that semi-oxidized tyrosine, the predominant initial defect induced by N 3 and (SCN) - 2 but not by OH, can be re-reduced upon reaction with O - 2 or cysteine. (orig.) [de

Sodium Overload Due To a Persistent Current That Attenuates The Arrhythmogenic Potential of a Novel LQT3 Mutation

Directory of Open Access Journals (Sweden)

Adrien eMoreau

2013-10-01

Full Text Available Long QT syndrome (LQTS is a congenital abnormality of cardiac repolarization that manifests as a prolonged QT interval on 12-lead electrocardiograms. The syndrome may lead to syncope and sudden death from ventricular tachyarrhythmias known as torsades de pointes. An increased persistent Na+ current is known to cause a Ca2+ overload in case of ischemia for example. Such increased Na+ persistent current is also usually associated to the LQT3 syndrome. The purpose of this study was to investigate the pathological consequences of a novel mutation in a family affected by LQTS. The impact of biophysical defects on cellular homeostasis are also investigated.Genomic DNA was extracted from blood samples, and a combination of PCR and DNA sequencing of several LQTS-linked genes was used to identify mutations. The mutation was reproduced in vitro and was characterized using the patch clamp technique and in silico quantitative analysis.A novel mutation (Q1476R was identified on the SCN5A gene encoding the cardiac Na+ channel. Cells expressing the Q1476R mutation exhibited biophysical alterations, including a shift of SS inactivation and a significant increase in the persistent Na+ current. The in silico analysis confirmed the arrhythmogenic character of the Q1476R mutation. It further revealed that the increase in persistent Na+ current causes a frequency-dependent Na+ overload in cardiomyocytes co-expressing WT and mutant Nav1.5 channels, that, in turn, exerts a moderating effect on the lengthening of the action potential duration caused by the mutation.The Q1476R mutation in SCN5A results in a three-fold increase in the window current and a persistent inward Na+ current. These biophysical defects may expose the carrier of the mutation to arrhythmias that occur preferentially in the patient at rest or during tachycardia. However, the Na+ overload counterbalances the gain-of-function of the mutation and is beneficial in that it prevents severe arrhythmias at

Domain IV voltage-sensor movement is both sufficient and rate limiting for fast inactivation in sodium channels.

Science.gov (United States)

Capes, Deborah L; Goldschen-Ohm, Marcel P; Arcisio-Miranda, Manoel; Bezanilla, Francisco; Chanda, Baron

2013-08-01

Voltage-gated sodium channels are critical for the generation and propagation of electrical signals in most excitable cells. Activation of Na(+) channels initiates an action potential, and fast inactivation facilitates repolarization of the membrane by the outward K(+) current. Fast inactivation is also the main determinant of the refractory period between successive electrical impulses. Although the voltage sensor of domain IV (DIV) has been implicated in fast inactivation, it remains unclear whether the activation of DIV alone is sufficient for fast inactivation to occur. Here, we functionally neutralize each specific voltage sensor by mutating several critical arginines in the S4 segment to glutamines. We assess the individual role of each voltage-sensing domain in the voltage dependence and kinetics of fast inactivation upon its specific inhibition. We show that movement of the DIV voltage sensor is the rate-limiting step for both development and recovery from fast inactivation. Our data suggest that activation of the DIV voltage sensor alone is sufficient for fast inactivation to occur, and that activation of DIV before channel opening is the molecular mechanism for closed-state inactivation. We propose a kinetic model of sodium channel gating that can account for our major findings over a wide voltage range by postulating that DIV movement is both necessary and sufficient for fast inactivation.

The epithelial sodium channel γ-subunit is processed proteolytically in human kidney

DEFF Research Database (Denmark)

Langkilde, Rikke Zachar; Skjødt, Karsten; Marcussen, Niels

2015-01-01

The epithelial sodium channel (ENaC) of the kidney is necessary for extracellular volume homeostasis and normal arterial BP. Activity of ENaC is enhanced by proteolytic cleavage of the gamma-subunit and putative release of a 43-amino acid inhibitory tract from the gamma-subunit ectodomain. We......ENaC was detected consistently only in tissue from patients with proteinuria and observed in collecting ducts. In conclusion, human kidney gammaENaC is subject to proteolytic cleavage, yielding fragments compatible with furin cleavage, and proteinuria is associated with cleavage at the putative prostasin...

Characterization of the binding of the Ptychodiscus brevis neurotoxin T17 to sodium channels in rat brain synaptosomes

International Nuclear Information System (INIS)

Poli, M.A.

1985-01-01

The lipid-soluble polyether neurotoxins isolated from the marine dinoflagellate Ptychodiscus brevis (formerly Gymnodinium breve) have been determined to bind to a unique receptor site associated with the voltage-sensitive sodium channel in rat brain synaptosomes. Reduction of the C 42 aldehyde function of T34 to the alcohol function of T17 using NaB 3 H 4 yielded 3 H-T17 with a specific activity of 15 Ci;/mmol. Using this specific probe, binding to sodium channels was measured at 4 0 CC, 22 0 C, and 37 0 C. Rosenthal analysis of the binding data yielded a K/sub d/ of 2.9 nM and B/sub max/ of 6.8 pmoles 3 H-T17 per mg of synaptosomal protein at 4 0 C. Both K/sub d/ and B/sub max/ were found to be temperature dependent. Depolarization of the synaptosomes by osmotic lysis resulted in the loss of 34% of the available receptor sites, with no decrease in binding affinity. Unlabeled T17, T34, and synthetic T17 (reduced T34) were equipotent in their ability to displace 3 H-T17 from its specific receptor site. Competition experiments using natural toxin probes specific for sites I-IV on the voltage-sensitive sodium channel demonstrate that 3 H-T17 does not bind to any of the previously-described neurotoxin receptor sites. A fifth site is proposed

Characterization of the binding of the Ptychodiscus brevis neurotoxin T17 to sodium channels in rat brain synaptosomes

Energy Technology Data Exchange (ETDEWEB)

Poli, M.A.

1985-01-01

The lipid-soluble polyether neurotoxins isolated from the marine dinoflagellate Ptychodiscus brevis (formerly Gymnodinium breve) have been determined to bind to a unique receptor site associated with the voltage-sensitive sodium channel in rat brain synaptosomes. Reduction of the C/sub 42/ aldehyde function of T34 to the alcohol function of T17 using NaB/sup 3/H/sub 4/ yielded /sup 3/H-T17 with a specific activity of 15 Ci;/mmol. Using this specific probe, binding to sodium channels was measured at 4/sup 0/CC, 22/sup 0/C, and 37/sup 0/C. Rosenthal analysis of the binding data yielded a K/sub d/ of 2.9 nM and B/sub max/ of 6.8 pmoles /sup 3/H-T17 per mg of synaptosomal protein at 4/sup 0/C. Both K/sub d/ and B/sub max/ were found to be temperature dependent. Depolarization of the synaptosomes by osmotic lysis resulted in the loss of 34% of the available receptor sites, with no decrease in binding affinity. Unlabeled T17, T34, and synthetic T17 (reduced T34) were equipotent in their ability to displace /sup 3/H-T17 from its specific receptor site. Competition experiments using natural toxin probes specific for sites I-IV on the voltage-sensitive sodium channel demonstrate that /sup 3/H-T17 does not bind to any of the previously-described neurotoxin receptor sites. A fifth site is proposed.

Nanomolar bifenthrin alters synchronous Ca2+ oscillations and cortical neuron development independent of sodium channel activity.

Science.gov (United States)

Cao, Zhengyu; Cui, Yanjun; Nguyen, Hai M; Jenkins, David Paul; Wulff, Heike; Pessah, Isaac N

2014-04-01

Bifenthrin, a relatively stable type I pyrethroid that causes tremors and impairs motor activity in rodents, is broadly used. We investigated whether nanomolar bifenthrin alters synchronous Ca(2+) oscillations (SCOs) necessary for activity-dependent dendritic development. Primary mouse cortical neurons were cultured 8 or 9 days in vitro (DIV), loaded with the Ca(2+) indicator Fluo-4, and imaged using a Fluorescence Imaging Plate Reader Tetra. Acute exposure to bifenthrin rapidly increased the frequency of SCOs by 2.7-fold (EC50 = 58 nM) and decreased SCO amplitude by 36%. Changes in SCO properties were independent of modifications in voltage-gated sodium channels since 100 nM bifenthrin had no effect on the whole-cell Na(+) current, nor did it influence neuronal resting membrane potential. The L-type Ca(2+) channel blocker nifedipine failed to ameliorate bifenthrin-triggered SCO activity. By contrast, the metabotropic glutamate receptor (mGluR)5 antagonist MPEP [2-methyl-6-(phenylethynyl)pyridine] normalized bifenthrin-triggered increase in SCO frequency without altering baseline SCO activity, indicating that bifenthrin amplifies mGluR5 signaling independent of Na(+) channel modification. Competitive [AP-5; (-)-2-amino-5-phosphonopentanoic acid] and noncompetitive (dizocilpine, or MK-801 [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate]) N-methyl-d-aspartate antagonists partially decreased both basal and bifenthrin-triggered SCO frequency increase. Bifenthrin-modified SCO rapidly enhanced the phosphorylation of cAMP response element-binding protein (CREB). Subacute (48 hours) exposure to bifenthrin commencing 2 DIV-enhanced neurite outgrowth and persistently increased SCO frequency and reduced SCO amplitude. Bifenthrin-stimulated neurite outgrowth and CREB phosphorylation were dependent on mGluR5 activity since MPEP normalized both responses. Collectively these data identify a new mechanism by which bifenthrin potently alters Ca(2

Identification of Novel Voltage-Gated Sodium Channel Mutations in Human Head and Body Lice (Phthiraptera: Pediculidae).

Science.gov (United States)

Firooziyan, Samira; Sadaghianifar, Ali; Taghilou, Behrooz; Galavani, Hossein; Ghaffari, Eslam; Gholizadeh, Saber

2017-09-01

In recent years, the increase of head louse infestation in Iran (7.4%) and especially in West-Azerbaijan Province (248%) has raised the hypothesis of insecticide resistance development. There are different mechanisms of resistance to various groups of insecticides, and knockdown resistance (kdr) is a prominent mechanism of resistance to pyrethroids, an insecticide group which is used conventionally for pediculosis control. For detection of kdr-type well-known amino acid substitutions (M815I-T917I-L920F) and additional sodium channel mutations potentially associated with kdr resistance in head and body lice, louse populations were collected from West-Azerbaijan and Zanjan Provinces of Iran. Six novel mutations were found to be located in the IIS1-2 extracellular loop (H813P) and IIS5 (I927F, L928A, R929V, L930M, and L932M) of the α-subunit. Genotyping results showed that all specimens (100%) have at least one of these or the well-known mutations. Therefore, the presence of kdr-related and novel mutations in the sodium channel is likely to be the reason for the frequent use of pyrethroid insecticides due to treatment failure against lice. Further studies are now required to evaluate the prevalence of the kdr-like mutant allele for monitoring of insecticide resistance and the management of head and body lice in other provinces of the country. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evidence for Dual Binding Sites for 1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in Insect Sodium Channels.

Science.gov (United States)

Du, Yuzhe; Nomura, Yoshiko; Zhorov, Boris S; Dong, Ke

2016-02-26

1,1,1-Trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), the first organochlorine insecticide, and pyrethroid insecticides are sodium channel agonists. Although the use of DDT is banned in most of the world due to its detrimental impact on the ecosystem, indoor residual spraying of DDT is still recommended for malaria control in Africa. Development of resistance to DDT and pyrethroids is a serious global obstacle for managing disease vectors. Mapping DDT binding sites is necessary for understanding mechanisms of resistance and modulation of sodium channels by structurally different ligands. The pioneering model of the housefly sodium channel visualized the first receptor for pyrethroids, PyR1, in the II/III domain interface and suggested that DDT binds within PyR1. Previously, we proposed the second pyrethroid receptor, PyR2, at the I/II domain interface. However, whether DDT binds to both pyrethroid receptor sites remains unknown. Here, using computational docking of DDT into the Kv1.2-based mosquito sodium channel model, we predict that two DDT molecules can bind simultaneously within PyR1 and PyR2. The bulky trichloromethyl group of each DDT molecule fits snugly between four helices in the bent domain interface, whereas two p-chlorophenyl rings extend into two wings of the interface. Model-driven mutagenesis and electrophysiological analysis confirmed these propositions and revealed 10 previously unknown DDT-sensing residues within PyR1 and PyR2. Our study proposes a dual DDT-receptor model and provides a structural background for rational development of new insecticides. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Flow-injection spectrophotometric determination of captopril in pharmaceutical formulations using a new solid-phase reactor containing AgSCN immobilized in a polyurethane resin

Directory of Open Access Journals (Sweden)

Fernando Campanhã Vicentini

2012-06-01

Full Text Available A simple flow-injection analysis procedure was developed for determining captopril in pharmaceutical formulations employing a novel solid-phase reactor containing silver thiocyanate immobilized in a castor oil derivative polyurethane resin. The method was based on silver mercaptide formation between the captopril and Ag(I in the solid-phase reactor. During such a reaction, the SCN- anion was released and reacted with Fe3+, which generated the FeSCN2+ complex that was continuously monitored at 480 nm. The analytical curve was linear in the captopril concentration range from 3.0 × 10-4 mol L-1 to 1.1 × 10-3 mol L-1 with a detection limit of 8.0 × 10-5 mol L-1. Recoveries between 97.5% and 103% and a relative standard deviation of 2% for a solution containing 6.0 × 10-4 mol L-1 captopril (n = 12 were obtained. The sample throughput was 40 h-1 and the results obtained for captopril in pharmaceutical formulations using this procedure and those obtained using a pharmacopoeia procedure were in agreement at a 95% confidence level.Um procedimento simples de análise por injeção em fluxo foi desenvolvido para a determinação de captopril em formulações farmacêuticas empregando um novo reator em fase sólida contendo tiocianato de prata imobilizado em resina poliuretana obtida a partir de óleo de mamona. O método foi baseado na formação de um mercapto composto de prata, no reator em fase sólida, obtido entre o captopril e Ag (I imobilizada. Durante a reação, íons SCN- eram liberados e reagiam com Fe3+, gerando o complexo FeSCN2+, que foi continuamente monitorado em 480 nm. A curva analítica foi linear no intervalo de concentração de captopril entre 3,0 × 10-4 a 1,1 × 10-3 mol L-1 com um limite de detecção de 8,0 × 10-5 mol L-1. Recuperações entre 97,5-103% e desvio padrão relativo de 2% para uma solução contendo 6,0 × 10-4 mol L-1 de captopril (n = 12 foram obtidos. A frequência de amostragem foi de 40 h-1 e os resultados

Development of 68Ga-SCN-DOTA-Capsaicin as an Imaging Agent Targeting Apoptosis and Cell Cycle Arrest in Breast Cancer.

Science.gov (United States)

Lee, Jun Young; Lee, Sang-Yeun; Kim, Gun Gyun; Hur, Min Goo; Yang, Seung Dae; Park, Jeong-Hoon; Kim, Sang Wook

2017-06-01

68 Ga-labeled capsaicin using a DOTA (1,4,7,10-tetraazocyclododecane-N,N',N″,N'″-tetraacetic acid) derivative [ 68 Ga-SCN-Benzyl(Bn)-DOTA-capsaicin] was studied for the diagnosis of breast cancers, such as MCF-7 and SK-BR-3. The standard compound, 69 Ga-SCN-Bn-DOTA-capsaicin, was also prepared and characterized by spectroscopic analysis. The binding affinity of 68 Ga-SCN-Bn-DOTA-capsaicin was evaluated by using breast cancer cell lines (MCF-7, SK-BR-3) and colon cancer cell (CT-26); the biodistribution was carried out by using MCF-7-bearing nude mice, after which the positron emission tomography (PET) images were obtained at different time intervals (15-120 minutes). 68 Ga-SCN-Bn-DOTA-capsaicin showed a cellular uptake of 0.93% Injected Dose (ID) after 30 minutes of incubation, whereas 68 Ga-SCN-Bn-DOTA showed a lower uptake of 0.25% ID. The tumor-to-blood ID/g% ratios increased and were found to be 0.49, 0.22, and 0.77 for 15, 30, and 60 minutes, respectively. The small-animal PET study showed that the uptake of 68 Ga-SCN-Bn-DOTA-capsaicin was higher in the tumor regions even at 30 minutes after injection. These results suggest that 68 Ga-SCN-Bn-DOTA-capsaicin is a potential targeting agent for PET imaging of MCF-7.

MiR-30b Attenuates Neuropathic Pain by Regulating Voltage-Gated Sodium Channel Nav1.3 in Rats

Directory of Open Access Journals (Sweden)

Songxue Su

2017-05-01

Full Text Available Nav1.3 is a tetrodotoxin-sensitive isoform among voltage-gated sodium channels that are closely associated with neuropathic pain. It can be up-regulated following nerve injury, but its biological function remains uncertain. MicroRNAs (miRNAs are endogenous non-coding RNAs that can regulate post-transcriptional gene expression by binding with their target mRNAs. Using Target Scan software, we discovered that SCN3A is the major target of miR-30b, and we then determined whether miR-30b regulated the expression of Nav1.3 by transfecting miR-30b agomir through the stimulation of TNF-α or by transfecting miR-30b antagomir in primary dorsal root ganglion (DRG neurons. The spinal nerve ligation (SNL model was used to determine the contribution of miR-30b to neuropathic pain, to evaluate changes in Nav1.3 mRNA and protein expression, and to understand the sensitivity of rats to mechanical and thermal stimuli. Our results showed that miR-30b agomir transfection down-regulated Nav1.3 mRNA stimulated with TNF-α in primary DRG neurons. Moreover, miR-30b overexpression significantly attenuated neuropathic pain induced by SNL, with decreases in the expression of Nav1.3 mRNA and protein both in DRG neurons and spinal cord. Activation of Nav1.3 caused by miR-30b antagomir was identified. These data suggest that miR-30b is involved in the development of neuropathic pain, probably by regulating the expression of Nav1.3, and might be a novel therapeutic target for neuropathic pain.Perspective: This study is the first to explore the important role of miR-30b and Nav1.3 in spinal nerve ligation-induced neuropathic pain, and our evidence may provide new insight for improving therapeutic approaches to pain.

A remarkably stable TipE gene cluster: evolution of insect Para sodium channel auxiliary subunits

Directory of Open Access Journals (Sweden)

Li Jia

2011-11-01

Full Text Available Abstract Background First identified in fruit flies with temperature-sensitive paralysis phenotypes, the Drosophila melanogaster TipE locus encodes four voltage-gated sodium (NaV channel auxiliary subunits. This cluster of TipE-like genes on chromosome 3L, and a fifth family member on chromosome 3R, are important for the optional expression and functionality of the Para NaV channel but appear quite distinct from auxiliary subunits in vertebrates. Here, we exploited available arthropod genomic resources to trace the origin of TipE-like genes by mapping their evolutionary histories and examining their genomic architectures. Results We identified a remarkably conserved synteny block of TipE-like orthologues with well-maintained local gene arrangements from 21 insect species. Homologues in the water flea, Daphnia pulex, suggest an ancestral pancrustacean repertoire of four TipE-like genes; a subsequent gene duplication may have generated functional redundancy allowing gene losses in the silk moth and mosquitoes. Intronic nesting of the insect TipE gene cluster probably occurred following the divergence from crustaceans, but in the flour beetle and silk moth genomes the clusters apparently escaped from nesting. Across Pancrustacea, TipE gene family members have experienced intronic nesting, escape from nesting, retrotransposition, translocation, and gene loss events while generally maintaining their local gene neighbourhoods. D. melanogaster TipE-like genes exhibit coordinated spatial and temporal regulation of expression distinct from their host gene but well-correlated with their regulatory target, the Para NaV channel, suggesting that functional constraints may preserve the TipE gene cluster. We identified homology between TipE-like NaV channel regulators and vertebrate Slo-beta auxiliary subunits of big-conductance calcium-activated potassium (BKCa channels, which suggests that ion channel regulatory partners have evolved distinct lineage

Distribution of cardiac sodium channels in clusters potentiates ephaptic interactions in the intercalated disc.

Science.gov (United States)

Hichri, Echrak; Abriel, Hugues; Kucera, Jan P

2018-02-15

It has been proposed that ephaptic conduction, relying on interactions between the sodium (Na + ) current and the extracellular potential in intercalated discs, might contribute to cardiac conduction when gap junctional coupling is reduced, but this mechanism is still controversial. In intercalated discs, Na + channels form clusters near gap junction plaques, but the functional significance of these clusters has never been evaluated. In HEK cells expressing cardiac Na + channels, we show that restricting the extracellular space modulates the Na + current, as predicted by corresponding simulations accounting for ephaptic effects. In a high-resolution model of the intercalated disc, clusters of Na + channels that face each other across the intercellular cleft facilitate ephaptic impulse transmission when gap junctional coupling is reduced. Thus, our simulations reveal a functional role for the clustering of Na + channels in intercalated discs, and suggest that rearrangement of these clusters in disease may influence cardiac conduction. It has been proposed that ephaptic interactions in intercalated discs, mediated by extracellular potentials, contribute to cardiac impulse propagation when gap junctional coupling is reduced. However, experiments demonstrating ephaptic effects on the cardiac Na + current (I Na ) are scarce. Furthermore, Na + channels form clusters around gap junction plaques, but the electrophysiological significance of these clusters has never been investigated. In patch clamp experiments with HEK cells stably expressing human Na v 1.5 channels, we examined how restricting the extracellular space modulates I Na elicited by an activation protocol. In parallel, we developed a high-resolution computer model of the intercalated disc to investigate how the distribution of Na + channels influences ephaptic interactions. Approaching the HEK cells to a non-conducting obstacle always increased peak I Na at step potentials near the threshold of I Na activation

Differential distribution of the sodium-activated potassium channels slick and slack in mouse brain.

Science.gov (United States)

Rizzi, Sandra; Knaus, Hans-Günther; Schwarzer, Christoph

2016-07-01

The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are high-conductance potassium channels of the Slo family. In neurons, Slick and Slack channels are involved in the generation of slow afterhyperpolarization, in the regulation of firing patterns, and in setting and stabilizing the resting membrane potential. The distribution and subcellular localization of Slick and Slack channels in the mouse brain have not yet been established in detail. The present study addresses this issue through in situ hybridization and immunohistochemistry. Both channels were widely distributed and exhibited distinct distribution patterns. However, in some brain regions, their expression overlapped. Intense Slick channel immunoreactivity was observed in processes, varicosities, and neuronal cell bodies of the olfactory bulb, granular zones of cortical regions, hippocampus, amygdala, lateral septal nuclei, certain hypothalamic and midbrain nuclei, and several regions of the brainstem. The Slack channel showed primarily a diffuse immunostaining pattern, and labeling of cell somata and processes was observed only occasionally. The highest Slack channel expression was detected in the olfactory bulb, lateral septal nuclei, basal ganglia, and distinct areas of the midbrain, brainstem, and cerebellar cortex. In addition, comparing our data obtained from mouse brain with a previously published study on rat brain revealed some differences in the expression and distribution of Slick and Slack channels in these species. J. Comp. Neurol. 524:2093-2116, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc.

THE PRESENCE OF A B SUBUNIT INCREASES SENSITIVITY OF SODIUM CHANNEL NAV1.3, BUT NOT NAV1.2, TO TYPE II PYRETHROIDS.

Science.gov (United States)

Voltage-sensitive sodium channels (VSSCs) are a primary target of pyrethroid insecticides. VSSCs are comprised of a pore-forming ¿ and auxillary ß subunits, and multiple isoforms of both subunit types exist. The sensitivity of different isoform combinations to pyrethroids has not...

Molecular cloning of ion channels in Felis catus that are related to periodic paralyses in man: a contribution to the understanding of the genetic susceptibility to feline neck ventroflexion and paralysis

Directory of Open Access Journals (Sweden)

Marlyn Zapata

2014-07-01

Full Text Available Neck ventroflexion in cats has different causes; however, the most common is the hypokalemia associated with flaccid paralysis secondary to chronic renal failure. In humans, the most common causes of acute flaccid paralysis are hypokalemia precipitated by thyrotoxicosis and familial forms linked to mutations in sodium, potassium, and calcium channel genes. Here, we describe the sequencing and analysis of skeletal muscle ion channels in Felis catus that could be related to periodic paralyses in humans, contributing to the understanding of the genetic susceptibility to feline neck ventroflexion and paralysis. We studied genomic DNA from eleven cats, including five animals that were hyperthyroid with hypokalemia, although only one presented with muscle weakness, and six healthy control domestic cats. We identified the ion channel ortholog genes KCNJ2, KCNJ12, KCNJ14, CACNA1S and SCN4A in the Felis catus genome, together with several polymorphic variants. Upon comparative alignment with other genomes, we found that Felis catus provides evidence for a high genomic conservation of ion channel sequences. Although we hypothesized that neck ventroflexion in cats could be associated with a thyrotoxic or familial periodic paralysis channel mutation, we did not identify any previously detected human channel mutation in the hyperthyroid cat presenting hypokalemia. However, based on the small number of affected cats in this study, we cannot yet rule out this molecular mechanism. Notwithstanding, hyperthyroidism should still be considered as a differential diagnosis in hypokalemic feline paralysis.

Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes.

Science.gov (United States)

Feldman, Chris R; Brodie, Edmund D; Brodie, Edmund D; Pfrender, Michael E

2012-03-20

Natural selection often produces convergent changes in unrelated lineages, but the degree to which such adaptations occur via predictable genetic paths is unknown. If only a limited subset of possible mutations is fixed in independent lineages, then it is clear that constraint in the production or function of molecular variants is an important determinant of adaptation. We demonstrate remarkably constrained convergence during the evolution of resistance to the lethal poison, tetrodotoxin, in six snake species representing three distinct lineages from around the globe. Resistance-conferring amino acid substitutions in a voltage-gated sodium channel, Na(v)1.4, are clustered in only two regions of the protein, and a majority of the replacements are confined to the same three positions. The observed changes represent only a small fraction of the experimentally validated mutations known to increase Na(v)1.4 resistance to tetrodotoxin. These results suggest that constraints resulting from functional tradeoffs between ion channel function and toxin resistance led to predictable patterns of evolutionary convergence at the molecular level. Our data are consistent with theoretical predictions and recent microcosm work that suggest a predictable path is followed during an adaptive walk along a mutational landscape, and that natural selection may be frequently constrained to produce similar genetic outcomes even when operating on independent lineages.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

Directory of Open Access Journals (Sweden)

Yang Li

Full Text Available Voltage-gated sodium (Nav channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions, a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

Science.gov (United States)

Li, Yang; Liu, Huihui; Xia, Mengdie; Gong, Haipeng

2016-01-01

Voltage-gated sodium (Nav) channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions), a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh) to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group.

Identification of an alternative knockdown resistance (kdr)-like mutation, M918L, and a novel mutation, V1010A, in the Thrips tabaci voltage-gated sodium channel gene.

Science.gov (United States)

Wu, Meixiang; Gotoh, Hiroki; Waters, Timothy; Walsh, Douglas B; Lavine, Laura Corley

2014-06-01

Knockdown resistance (kdr) has been identified as a main mechanism against pyrethroid insecticides in many arthropod pests including in the onion thrips, Thrips tabaci. To characterize and identify pyrethroid-resistance in onion thrips in Washington state, we conducted insecticide bioassays and sequenced a region of the voltage gated sodium channel gene from several different T. tabaci populations. Field collected Thrips tabaci were found to have large variations in resistance to the pyrethroid insecticide lambda-cyhalothrin. We identified two single nucleotide substitutions in our analysis of a partial sequence of the T. tabaci voltage-gated sodium channel gene. One mutation resulted in the non-synonymous substitution of methionine with leucine (M918L), which is well known to be responsible for super knockdown resistance in some pest species. Another non-synonymous substitution, a valine (GTT) to alanine (GCT) replacement at amino acid 1010 (V1010A) was identified in our study and was associated with lambda-cyhalothrin resistance. We have characterized a known kdr mutation and identified a novel mutation in the voltage-gated sodium channel gene of Thrips tabaci associated with resistance to lambda-cyhalothrin. This gene region and these mutations are expected to be useful in the development of a diagnostic test to detect kdr resistance in many onion thrips populations. © 2013 Society of Chemical Industry.

The Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) voltage-gated sodium channel and mutations associated with pyrethroid resistance in field-collected adult males.

Science.gov (United States)

Hopkins, B W; Pietrantonio, P V

2010-05-01

Helicoverpa zea is one of the most costly insect pests of food and fiber crops throughout the Americas. Pyrethroid insecticides are widely applied for its control as they are effective and relatively inexpensive; however, resistance to pyrethroids threatens agricultural systems sustainability because alternative insecticides are often more expensive or less effective. Although pyrethroid resistance has been identified in this pest since 1990, the mechanisms of resistance have not yet been elucidated at the molecular level. Pyrethroids exert their toxicity by prolonging the open state of the voltage-gated sodium channel. Here we report the cDNA sequence of the H. zea sodium channel alpha-subunit homologous to the para gene from Drosophila melanogaster. In field-collected males which were resistant to cypermethrin as determined by the adult vial test, we identify known resistance-conferring mutations L1029H and V421M, along with two novel mutations at the V421 residue, V421A and V421G. An additional mutation, I951V, may be the first example of a pyrethroid resistance mutation caused by RNA editing. Identification of the sodium channel cDNA sequence will allow for testing hypotheses on target-site resistance for insecticides acting on this channel through modeling and expression studies. Understanding the mechanisms responsible for resistance will greatly improve our ability to identify and predict resistance, as well as preserve susceptibility to pyrethroid insecticides. Copyright 2010 Elsevier Ltd. All rights reserved.

Microrheology and microstructure of water-in-water emulsions containing sodium caseinate and locust bean gum.

Science.gov (United States)

Moschakis, Thomas; Chantzos, Nikos; Biliaderis, Costas G; Dickinson, Eric

2018-05-23

The mechanical response on the microscale of phase-separated water-in-water emulsions containing sodium caseinate (SCN) and locust bean gum (LBG) has been monitored by confocal laser scanning microscopy and particle tracking microrheology. Mixed biopolymer systems exhibiting phase-separated micro-regions were enriched in either protein or polysaccharide in the continuous or dispersed phase, depending on the weight ratio of the two biopolymers. Measurements of the tracking of charged probe particles revealed that the local rheological properties of protein-rich regions were considerably lower than that of LBG-rich domains for all the biopolymer ratios examined. At pH 7 in the absence of added salt, the viscosity of the protein-rich regions was little affected by an increase in overall LBG concentration, which is consistent with the phase separation mechanism in the mixed solution of charged (SCN) and uncharged (LBG) biopolymers being dominated by the relative entropy of the counter-ions associated with the charged protein molecules. Addition of salt was found to produce an enhancement in the level of thermodynamic incompatibility, leading to faster and more pronounced phase separation, and altering the micro-viscosity of protein-rich regions. At high ionic strength, it was also noted that there was a pronounced accumulation of incorporated probe particles at the liquid-liquid interface. The microrheological properties of the SCN-rich regions were found to be substantially pH-dependent in the range 7 > pH > 5.4. By adjusting the acidification conditions and the biopolymer ratio, discrete protein-based microspheres were generated with potential applications as a functional food ingredient.

Distinct interactions of Na+ and Ca2+ ions with the selectivity filter of the bacterial sodium channel NaVAb

International Nuclear Information System (INIS)

Ke, Song; Zangerl, Eva-Maria; Stary-Weinzinger, Anna

2013-01-01

Highlights: ► Ca 2+ translocates slowly in the filter, due to lack of “loose” knock-on mechanism. ► Identification of a high affinity binding site in Na V Ab selectivity filter. ► Changes of EEEE locus triggered by electrostatic interactions with Ca 2+ ions. -- Abstract: Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. In this study, we use molecular dynamics simulations and free energy calculations to investigate how the bacterial sodium channel Na V Ab (Arcobacter butzleri) differentiates between Na + and Ca 2+ ions. Multiple nanosecond molecular dynamics simulations revealed distinct binding patterns for these two cations in the selectivity filter and suggested a high affinity calcium binding site formed by backbone atoms of residues Leu-176 and Thr-175 (S CEN ) in the sodium channel selectivity filter

A Switchable Molecular Dielectric with Two Sequential Reversible Phase Transitions: [(CH3)4P]4[Mn(SCN)6].

Science.gov (United States)

Li, Qiang; Shi, Ping-Ping; Ye, Qiong; Wang, Hui-Ting; Wu, De-Hong; Ye, Heng-Yun; Fu, Da-Wei; Zhang, Yi

2015-11-16

A new organic-inorganic hybrid switchable and tunable dielectric compound, [(CH3)4P]4[Mn(SCN)6] (1), exhibits three distinct dielectric states above room temperature and undergoes two reversible solid-state phase transitions, including a structural phase transition at 330 K and a ferroelastic phase transition with the Aizu notation of mmmF2/m at 352 K. The variable-temperature structural analyses disclose that the origin of the phase transitions and dielectric anomalies can be ascribed to the reorientation or motion of both the [(CH3)4P](+) cations and [Mn(SCN)6](4-) anions in solid-state crystals.

Unusual Voltage-Gated Sodium Currents as Targets for Pain.

Science.gov (United States)

Barbosa, C; Cummins, T R

2016-01-01

Pain is a serious health problem that impacts the lives of many individuals. Hyperexcitability of peripheral sensory neurons contributes to both acute and chronic pain syndromes. Because voltage-gated sodium currents are crucial to the transmission of electrical signals in peripheral sensory neurons, the channels that underlie these currents are attractive targets for pain therapeutics. Sodium currents and channels in peripheral sensory neurons are complex. Multiple-channel isoforms contribute to the macroscopic currents in nociceptive sensory neurons. These different isoforms exhibit substantial variations in their kinetics and pharmacology. Furthermore, sodium current complexity is enhanced by an array of interacting proteins that can substantially modify the properties of voltage-gated sodium channels. Resurgent sodium currents, atypical currents that can enhance recovery from inactivation and neuronal firing, are increasingly being recognized as playing potentially important roles in sensory neuron hyperexcitability and pain sensations. Here we discuss unusual sodium channels and currents that have been identified in nociceptive sensory neurons, describe what is known about the molecular determinants of the complex sodium currents in these neurons. Finally, we provide an overview of therapeutic strategies to target voltage-gated sodium currents in nociceptive neurons. Copyright © 2016 Elsevier Inc. All rights reserved.

Direct evidence that scorpion α-toxins (site-3 modulate sodium channel inactivation by hindrance of voltage-sensor movements.

Directory of Open Access Journals (Sweden)

Zhongming Ma

Full Text Available The position of the voltage-sensing transmembrane segment, S4, in voltage-gated ion channels as a function of voltage remains incompletely elucidated. Site-3 toxins bind primarily to the extracellular loops connecting transmembrane helical segments S1-S2 and S3-S4 in Domain 4 (D4 and S5-S6 in Domain 1 (D1 and slow fast-inactivation of voltage-gated sodium channels. As S4 of the human skeletal muscle voltage-gated sodium channel, hNav1.4, moves in response to depolarization from the resting to the inactivated state, two D4S4 reporters (R2C and R3C, Arg1451Cys and Arg1454Cys, respectively move from internal to external positions as deduced by reactivity to internally or externally applied sulfhydryl group reagents, methane thiosulfonates (MTS. The changes in reporter reactivity, when cycling rapidly between hyperpolarized and depolarized voltages, enabled determination of the positions of the D4 voltage-sensor and of its rate of movement. Scorpion α-toxin binding impedes D4S4 segment movement during inactivation since the modification rates of R3C in hNav1.4 with methanethiosulfonate (CH3SO2SCH2CH2R, where R = -N(CH33 (+ trimethylammonium, MTSET and benzophenone-4-carboxamidocysteine methanethiosulfonate (BPMTS were slowed ~10-fold in toxin-modified channels. Based upon the different size, hydrophobicity and charge of the two reagents it is unlikely that the change in reactivity is due to direct or indirect blockage of access of this site to reagent in the presence of toxin (Tx, but rather is the result of inability of this segment to move outward to the normal extent and at the normal rate in the toxin-modified channel. Measurements of availability of R3C to internally applied reagent show decreased access (slower rates of thiol reaction providing further evidence for encumbered D4S4 movement in the presence of toxins consistent with the assignment of at least part of the toxin binding site to the region of D4S4 region of the voltage

Inhibition of HERG potassium channels by celecoxib and its mechanism.

Directory of Open Access Journals (Sweden)

Roman V Frolov

Full Text Available Celecoxib (Celebrex, a widely prescribed selective inhibitor of cyclooxygenase-2, can modulate ion channels independently of cyclooxygenase inhibition. Clinically relevant concentrations of celecoxib can affect ionic currents and alter functioning of neurons and myocytes. In particular, inhibition of Kv2.1 channels by celecoxib leads to arrhythmic beating of Drosophila heart and of rat heart cells in culture. However, the spectrum of ion channels involved in human cardiac excitability differs from that in animal models, including mammalian models, making it difficult to evaluate the relevance of these observations to humans. Our aim was to examine the effects of celecoxib on hERG and other human channels critically involved in regulating human cardiac rhythm, and to explore the mechanisms of any observed effect on the hERG channels.Celecoxib inhibited the hERG, SCN5A, KCNQ1 and KCNQ1/MinK channels expressed in HEK-293 cells with IC(50s of 6.0 µM, 7.5 µM, 3.5 µM and 3.7 µM respectively, and the KCND3/KChiP2 channels expressed in CHO cells with an IC(50 of 10.6 µM. Analysis of celecoxib's effects on hERG channels suggested gating modification as the mechanism of drug action.The above channels play a significant role in drug-induced long QT syndrome (LQTS and short QT syndrome (SQTS. Regulatory guidelines require that all new drugs under development be tested for effects on the hERG channel prior to first administration in humans. Our observations raise the question of celecoxib's potential to induce cardiac arrhythmias or other channel related adverse effects, and make a case for examining such possibilities.

X-ray diffraction and chemical bonding

International Nuclear Information System (INIS)

Bats, J.W.

1976-01-01

Chemical bonds are investigated in sulfamic acid (H 3 N-SO 3 ), sodium sulfonlate dihydrate (H 2 NC 6 H 4 SO 3 Na.2H 2 O), 2,5-dimercaptothiadiazole (HS-C 2 N 2 S-SH), sodium cyanide dihydrate (NaCN.2H 2 O), sodium thiocyanate (NaSCN) and ammonium thiocyanate (NH 4 SCN) by X-ray diffraction, and if necessary completed with neutron diffraction. Crystal structures and electron densities are determined together with bond length and angles. Also the effects of thermal motion are discussed

Effects of the β1 auxiliary subunit on modification of Rat Na{sub v}1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin

Energy Technology Data Exchange (ETDEWEB)

He, Bingjun [College of Life Sciences, Nankai University, Tianjin 300071 (China); Soderlund, David M., E-mail: dms6@cornell.edu [Department of Entomology, Cornell University, Geneva, NY 14456 (United States)

2016-01-15

We expressed rat Na{sub v}1.6 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 Na{sub v}1.6 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 Na{sub v}1.6 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. - Highlights: • We expressed Na{sub v}1.6 sodium channels with or without β1 subunits in HEK293 cells. • Tefluthrin and deltamethrin

RING finger protein 121 facilitates the degradation and membrane localization of voltage-gated sodium channels

Science.gov (United States)

Ogino, Kazutoyo; Low, Sean E.; Yamada, Kenta; Saint-Amant, Louis; Zhou, Weibin; Muto, Akira; Asakawa, Kazuhide; Nakai, Junichi; Kawakami, Koichi; Kuwada, John Y.; Hirata, Hiromi

2015-01-01

Following their synthesis in the endoplasmic reticulum (ER), voltage-gated sodium channels (NaV) are transported to the membranes of excitable cells, where they often cluster, such as at the axon initial segment of neurons. Although the mechanisms by which NaV channels form and maintain clusters have been extensively examined, the processes that govern their transport and degradation have received less attention. Our entry into the study of these processes began with the isolation of a new allele of the zebrafish mutant alligator, which we found to be caused by mutations in the gene encoding really interesting new gene (RING) finger protein 121 (RNF121), an E3-ubiquitin ligase present in the ER and cis-Golgi compartments. Here we demonstrate that RNF121 facilitates two opposing fates of NaV channels: (i) ubiquitin-mediated proteasome degradation and (ii) membrane localization when coexpressed with auxiliary NaVβ subunits. Collectively, these results indicate that RNF121 participates in the quality control of NaV channels during their synthesis and subsequent transport to the membrane. PMID:25691753

Kinetics of photocurrent generation and an efficient charge separation of a dye-sensitized n-Cu2O/p-CuSCN junction photoelectrode in a solid-state photovoltaic cell

International Nuclear Information System (INIS)

Fernando, C A N; Kumara, N T R N; Gamage, T N

2010-01-01

A Cu/n-Cu 2 O/dye/p-CuSCN junction photoelectrode is fabricated to produce a solid-state dye-sensitized photovoltaic cell. Samples are characterized by XRD, SEM and surface resistivity measurements. Photocurrent generation is found due to light absorption of n-Cu 2 O thin film and dye sensitization between p-CuSCN and the dye. Kinetics of the photocurrent generation of the dye sensitization is studied solving the rate equations by the iteration method obtaining a relationship for the photocurrent quantum efficiency (Φ) depending on the surface concentration (D o ) of the dye and the rate constants of the reactions with connection to the dye sensitization process. The solution obtained in the steady state by iteration is found to be of the form Φ = AD o −BD o 2 (A and B are constants related to the reaction rates of the photocurrent generation process and the concentration of the n-Cu 2 O film). The variation of the n-Cu 2 O concentration with photocurrent is presented. A photocurrent enhancement is observed for the Cu/n-Cu 2 O/dye/p-CuSCN photovoltaic cell compared to that of Cu/n-Cu 2 O, Cu/p-CuSCN/dye and Cu/n-Cu 2 O/p-CuSCN photovoltaic cells. Good rectification characteristics are observed for the Cu/n-Cu 2 O/p-CuSCN photoelectrode compared to that of Cu/n-Cu 2 O and Cu/p-CuSCN photoelectrodes. Photocurrent enhancement is found due to the efficient charge separation process at the n–p junction. Energy band structures of the n–p junction are proposed according to the onset potentials which are used to discuss the mechanism of the efficient charge separation suppressing the recombination process

Measurement and correlation of vapour pressures of pyridine and thiophene with [EMIM][SCN] ionic liquid

International Nuclear Information System (INIS)

Khelassi-Sefaoui, Asma; Mutelet, Fabrice; Mokbel, Ilham; Jose, Jacques; Negadi, Latifa

2014-01-01

Highlights: • VLE of (pyridine + [EMIM][SCN]), or (thiophene + [EMIM][SCN]) binary mixtures were measured. • The investigated temperatures are 273 K to 363 K. • The PC-SAFT equation of state has been used to correlate the vapour pressures of the binary systems. - Abstract: In this work (vapour + liquid) equilibrium (VLE) measurements were performed on binary systems of the ionic liquid 1-ethyl-3-methylimidazolium thiocynate [EMIM][SCN] with thiophene or pyridine at pressures close to the atmospheric pressure using a static device at temperatures between 273 K and 363 K. Experimental data were correlated by the PC-SAFT EoS. The binary interaction parameters k ij were optimised on experimental VLE data. The results obtained for the two binary mixtures studied in this paper indicate that the PC-SAFT EoS can be used to represent systems containing ionic liquids

Pitfalls in genetic testing: the story of missed SCN1A mutations

OpenAIRE

Djémié, T.; Weckhuysen, S.; von Spiczak, S.; Carvill, G. L.; Jaehn, J.; Anttonen, A-K; Brilstra, E.; Caglayan, H. S.; de Kovel, C. G.; Depienne, C.; Gaily, E.; Gennaro, E.; Giraldez, B. G.; Gormley, P.; Guerrero-López, R.

2016-01-01

BACKGROUND: Sanger sequencing, still the standard technique for genetic testing in most diagnostic laboratories and until recently widely used in research, is gradually being complemented by next-generation sequencing (NGS). No single mutation detection technique is however perfect in identifying all mutations. Therefore, we wondered to what extent inconsistencies between Sanger sequencing and NGS affect the molecular diagnosis of patients. Since mutations in SCN1A, the major gene implicated ...

Pitfalls in genetic testing : the story of missed SCN1A mutations

OpenAIRE

Djémié, Tania; Weckhuysen, Sarah; von Spiczak, Sarah; Carvill, Gemma L; Jaehn, Johanna; Anttonen, Anna-Kaisa; Brilstra, Eva; Caglayan, Hande S; de Kovel, Carolien G; Depienne, Christel; Gaily, Eija; Gennaro, Elena; Giraldez, Beatriz G; Gormley, Padhraig; Guerrero-López, Rosa

2016-01-01

BACKGROUND: Sanger sequencing, still the standard technique for genetic testing in most diagnostic laboratories and until recently widely used in research, is gradually being complemented by next-generation sequencing (NGS). No single mutation detection technique is however perfect in identifying all mutations. Therefore, we wondered to what extent inconsistencies between Sanger sequencing and NGS affect the molecular diagnosis of patients. Since mutations in SCN1A, the major gene implicated ...

RNAi-mediated knockdown of the voltage gated sodium ion channel TcNav causes mortality in Tribolium castaneum.

Science.gov (United States)

Abd El Halim, Hesham M; Alshukri, Baida M H; Ahmad, Munawar S; Nakasu, Erich Y T; Awwad, Mohammed H; Salama, Elham M; Gatehouse, Angharad M R; Edwards, Martin G

2016-07-14

The voltage-gated sodium ion channel (VGSC) belongs to the largest superfamily of ion channels. Since VGSCs play key roles in physiological processes they are major targets for effective insecticides. RNA interference (RNAi) is widely used to analyse gene function, but recently, it has shown potential to contribute to novel strategies for selectively controlling agricultural insect pests. The current study evaluates the delivery of dsRNA targeted to the sodium ion channel paralytic A (TcNav) gene in Tribolium castaneum as a viable means of controlling this insect pest. Delivery of TcNav dsRNA caused severe developmental arrest with larval mortalities up to 73% post injection of dsRNA. Injected larvae showed significant (p < 0.05) knockdown in gene expression between 30-60%. Expression was also significantly (p < 0.05) reduced in pupae following injection causing 30% and 42% knockdown for early and late pupal stages, respectively. Oral delivery of dsRNA caused dose-dependant mortalities of between 19 and 51.34%; this was accompanied by significant (p < 0.05) knockdown in gene expression following 3 days of continuous feeding. The majority of larvae injected with, or fed, dsRNA died during the final larval stage prior to pupation. This work provides evidence of a viable RNAi-based strategy for insect control.

Brugada Syndrome: Are we doing enough to prevent sudden death?

International Nuclear Information System (INIS)

Buksh, Jahangir A.; Al-Hersi, Ahmad S.; Al-Nozha, Mansour M.

2007-01-01

Burgada syndrome (BS) is an inherited arrythmogenic disease characterized by typical ECG changes in the form of an SR pattern in VI to V2, and ST segment elevation in VI to V3 and prolongation of the QT interval in right precordial leads. This syndrome carries an increased risk of sudden death due to arrhythmias. This disease was first described in 1992 by Joseph Brugada et al and was named Brugada syndrome by Yan and Antzelvich in 1996. By 2003 more than 600 patients had been reported by Brugada et al and hundreds by others. A genetic aspect to BS is now recognized and been linked to the alpha subunit of the cardiac sodium channel gene SCN5A. Over five dozen mutations in SCN5A have been identified. Accentuation of the right ventricular notch under pathophysiological conditions leads to exaggeration of the J-wave or J-point elevation and a saddle-shaped configuration of the repolarisation waves. Diagnosis is essentially by electrocardiogram either by spontaneous changes or by provocation by sodium channel blockers drugs, e.g., procainamide, flecainide. The role of electrophysiological studies in induction of arrhythmia in asymptomatic individuals by electron beam computed tomography and signal-averaged electrocardiogram is not settled. Unfortunately, an effective drug is not available is not available at present, but quinidine has a place in treatment. New promising drugs are emerging like cilostazol and tedisamil. At present, implantation of an ICD is the only effective means of preventing sudden death. (author)

Temperature fluctuation of sodium in annular flow channel heated by single-pin with blockage

International Nuclear Information System (INIS)

Miyazaki, Keiji; Kimura, Jiro; Ogawa, Masuro; Okada, Toshio

1978-01-01

Root mean square (RMS) value and power spectral density (PSD) of temperature fluctuation were measured with use of forced-circulating sodium in an annular channel (6.5 mm I.D., 20mm O.D.) with concentric disk to simulate blockage (about 80%) of sodium flow. The experimental range of the heat flux was 40 -- 150 W/cm 2 and the bulk flow velocity 0.14--0.41m/sec (Re=7.7x10 3 --2.3x10 4 ) under a temperature of 500--800 0 C. The RMS value measured at the exit of heating section (150mm downstream from the blockage) is larger by a factor of 2 -- 3 than that in the wake (10 -- 20mm downstream from the blockage), marking a few deg.C for a heat flux of 105W/cm 2 and a flow velocity of 0.27m/sec. The RMS value is proportional to the wall-to-bulk-fluid temperature difference in heat transfer, presenting the similar dependence on the heat flux and flow velocity. The fluctuations of temperature are greatly attenuated in the upper unheated section where the radial temperature gradient is absent, and consequently it is suggested that the fluctuations of temperature should be caused by the local turbulence of flow, such as a vortex street due to blockage in the present experiment, under the presence of large gradient of temperature near the heating surface. (auth.)

Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage.

Science.gov (United States)

Zaika, Oleg; Palygin, Oleg; Tomilin, Viktor; Mamenko, Mykola; Staruschenko, Alexander; Pochynyuk, Oleh

2016-02-15

Potassium Kir4.1/5.1 channels are abundantly expressed at the basolateral membrane of principal cells in the cortical collecting duct (CCD), where they are thought to modulate transport rates by controlling transepithelial voltage. Insulin and insulin-like growth factor-1 (IGF-1) stimulate apically localized epithelial sodium channels (ENaC) to augment sodium reabsorption in the CCD. However, little is known about their actions on potassium channels localized at the basolateral membrane. In this study, we implemented patch-clamp analysis in freshly isolated murine CCD to assess the effect of these hormones on Kir4.1/5.1 at both single channel and cellular levels. We demonstrated that K(+)-selective conductance via Kir4.1/5.1 is the major contributor to the macroscopic current recorded from the basolateral side in principal cells. Acute treatment with 10 μM amiloride (ENaC blocker), 100 nM tertiapin-Q (TPNQ; ROMK inhibitor), and 100 μM ouabain (Na(+)-K(+)-ATPase blocker) failed to produce a measurable effect on the macroscopic current. In contrast, Kir4.1 inhibitor nortriptyline (100 μM), but not fluoxetine (100 μM), virtually abolished whole cell K(+)-selective conductance. Insulin (100 nM) markedly increased the open probability of Kir4.1/5.1 and nortriptyline-sensitive whole cell current, leading to significant hyperpolarization of the basolateral membrane. Inhibition of the phosphatidylinositol 3-kinase cascade with LY294002 (20 μM) abolished action of insulin on Kir4.1/5.1. IGF-1 had similar stimulatory actions on Kir4.1/5.1-mediated conductance only when applied at a higher (500 nM) concentration and was ineffective at 100 nM. We concluded that both insulin and, to a lesser extent, IGF-1 activate Kir4.1/5.1 channel activity and open probability to hyperpolarize the basolateral membrane, thereby facilitating Na(+) reabsorption in the CCD. Copyright © 2016 the American Physiological Society.

Coupled-channel optical calculation of electron-atom scattering: elastic scattering from sodium at 20 to 150 eV

International Nuclear Information System (INIS)

Bray, Igor; Konovalov, D.A.; McCarthy, I.E.

1991-04-01

A coupled-channel optical method for electron-atom scattering is applied to elastic electron-sodium scattering at energies of 20, 22.1, 54.4, 100, and 150 eV. It is demonstrated that the effect of all the inelastic channels on elastic scattering may be well reproduced by the 'ab initio' calculated complex non-local polarization potential. Whilst the experiments generally agree at small angles and therefore agree on the total elastic cross section, there is considerable discrepancy at intermediate and backward angles. 9 refs., 2 tabs., 1 fig

Infantile Pain Episodes Associated with Novel Nav1.9 Mutations in Familial Episodic Pain Syndrome in Japanese Families.

Science.gov (United States)

Okuda, Hiroko; Noguchi, Atsuko; Kobayashi, Hatasu; Kondo, Daiki; Harada, Kouji H; Youssefian, Shohab; Shioi, Hirotomo; Kabata, Risako; Domon, Yuki; Kubota, Kazufumi; Kitano, Yutaka; Takayama, Yasunori; Hitomi, Toshiaki; Ohno, Kousaku; Saito, Yoshiaki; Asano, Takeshi; Tominaga, Makoto; Takahashi, Tsutomu; Koizumi, Akio

2016-01-01

Painful peripheral neuropathy has been correlated with various voltage-gated sodium channel mutations in sensory neurons. Recently Nav1.9, a voltage-gated sodium channel subtype, has been established as a genetic influence for certain peripheral pain syndromes. In this study, we performed a genetic study in six unrelated multigenerational Japanese families with episodic pain syndrome. Affected participants (n = 23) were characterized by infantile recurrent pain episodes with spontaneous mitigation around adolescence. This unique phenotype was inherited in an autosomal-dominant mode. Linkage analysis was performed for two families with 12 affected and nine unaffected members, and a single locus was identified on 3p22 (LOD score 4.32). Exome analysis (n = 14) was performed for affected and unaffected members in these two families and an additional family. Two missense variants were identified: R222H and R222S in SCN11A. Next, we generated a knock-in mouse model harboring one of the mutations (R222S). Behavioral tests (Hargreaves test and cold plate test) using R222S and wild-type C57BL/6 (WT) mice, young (8-9 weeks old; n = 10-12 for each group) and mature (36-38 weeks old; n = 5-6 for each group), showed that R222S mice were significantly (p pain. The mouse model developed here will be useful for drug screening for familial episodic pain syndrome associated with SCN11A mutations.

Guanidinium Toxins and Their Interactions with Voltage-Gated Sodium Ion Channels

Directory of Open Access Journals (Sweden)

Lorena M. Durán-Riveroll

2017-10-01

Full Text Available Guanidinium toxins, such as saxitoxin (STX, tetrodotoxin (TTX and their analogs, are naturally occurring alkaloids with divergent evolutionary origins and biogeographical distribution, but which share the common chemical feature of guanidinium moieties. These guanidinium groups confer high biological activity with high affinity and ion flux blockage capacity for voltage-gated sodium channels (NaV. Members of the STX group, known collectively as paralytic shellfish toxins (PSTs, are produced among three genera of marine dinoflagellates and about a dozen genera of primarily freshwater or brackish water cyanobacteria. In contrast, toxins of the TTX group occur mainly in macrozoa, particularly among puffer fish, several species of marine invertebrates and a few terrestrial amphibians. In the case of TTX and analogs, most evidence suggests that symbiotic bacteria are the origin of the toxins, although endogenous biosynthesis independent from bacteria has not been excluded. The evolutionary origin of the biosynthetic genes for STX and analogs in dinoflagellates and cyanobacteria remains elusive. These highly potent molecules have been the subject of intensive research since the latter half of the past century; first to study the mode of action of their toxigenicity, and later as tools to characterize the role and structure of NaV channels, and finally as therapeutics. Their pharmacological activities have provided encouragement for their use as therapeutants for ion channel-related pathologies, such as pain control. The functional role in aquatic and terrestrial ecosystems for both groups of toxins is unproven, although plausible mechanisms of ion channel regulation and chemical defense are often invoked. Molecular approaches and the development of improved detection methods will yield deeper understanding of their physiological and ecological roles. This knowledge will facilitate their further biotechnological exploitation and point the way towards

Identification of potential novel interaction partners of the sodium-activated potassium channels Slick and Slack in mouse brain.

Science.gov (United States)

Rizzi, Sandra; Schwarzer, Christoph; Kremser, Leopold; Lindner, Herbert H; Knaus, Hans-Günther

2015-12-01

The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are paralogous channels of the Slo family of high-conductance potassium channels. Slick and Slack channels are widely distributed in the mammalian CNS and they play a role in slow afterhyperpolarization, generation of depolarizing afterpotentials and in setting and stabilizing the resting potential. In the present study we used a combined approach of (co)-immunoprecipitation studies, Western blot analysis, double immunofluorescence and mass spectrometric sequencing in order to investigate protein-protein interactions of the Slick and Slack channels. The data strongly suggest that Slick and Slack channels co-assemble into identical cellular complexes. Double immunofluorescence experiments revealed that Slick and Slack channels co-localize in distinct mouse brain regions. Moreover, we identified the small cytoplasmic protein beta-synuclein and the transmembrane protein 263 (TMEM 263) as novel interaction partners of both, native Slick and Slack channels. In addition, the inactive dipeptidyl-peptidase (DPP 10) and the synapse associated protein 102 (SAP 102) were identified as constituents of the native Slick and Slack channel complexes in the mouse brain. This study presents new insights into protein-protein interactions of native Slick and Slack channels in the mouse brain.

Acid-sensing ion and epithelial sodium channels do not contribute to the mechanoreceptor component of the exercise pressor reflex

OpenAIRE

McCord, Jennifer L.; Hayes, Shawn G.; Kaufman, Marc P.

2008-01-01

Amiloride, injected into the popliteal artery, has been reported to attenuate the reflex pressor response to static contraction of the triceps surae muscles. Both mechanical and metabolic stimuli arising in contracting skeletal muscle are believed to evoke this effect, which has been named the exercise pressor reflex. Amiloride blocks both acid-sensing ion channels, as well as epithelial sodium channels. Nevertheless, amiloride is thought to block the metabolic stimulus to the reflex, because...

Loss of Sodium-Activated Potassium Channel Slack and FMRP Differentially Affect Social Behavior in Mice.

Science.gov (United States)

Bausch, Anne E; Ehinger, Rebekka; Straubinger, Julia; Zerfass, Patrick; Nann, Yvette; Lukowski, Robert

2018-05-31

The sodium-activated potassium channel Slack (Slo2.2) is widely expressed in central and peripheral neurons where it is supposed to shape firing properties important for neuronal excitability. Slack activity is enhanced by interaction with the Fragile-X-Mental-Retardation-Protein (FMRP) and loss of FMRP leads to decreased sodium-activated potassium currents in medial nucleus of the trapezoid body neurons of the Fmr1-knockout (KO) mouse representing a mouse model of the human Fragile-X-Syndrome (FXS) and autism. Autism is a frequent comorbidity of FXS, but it is unclear whether Slack is involved in autistic or related conditions of FXS in vivo. By applying a wide range of behavioral tests, we compared social and autism-related behaviors in Slack- and FMRP-deficient mice. In our hands, as expected, FMRP-deficiency causes autism-related behavioral changes in nesting and in a marble-burying test. In contrast, Slack-deficient males exhibited specific abnormalities in sociability in direct and indirect social interaction tests. Hence, we show for the first time that a proper Slack channel function is mandatory for normal social behavior in mice. Nevertheless, as deficits in social behaviors seem to occur independently from each other in FMRP and Slack null mutants, we conclude that Slack is not involved in the autistic phenotype of FMRP KO mice. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Association Between IL1B and SCN1A Polymorphism and Febrile Seizures in Children in Siberia

Directory of Open Access Journals (Sweden)

Maria A. Stroganova

2017-06-01

Full Text Available Background: Febrile seizures (FS are a benign, age-dependent, genetically determined state, in which the child’s brain is susceptible to epileptic seizures occurring in response to hyperthermia. We assessed whether polymorphisms of IL1B and SCN1A genes, encoding the proinflammatory cytokine IL1B and SCN1A, respectively, could help to predict FS development and find a new way to treat FS. Methods: We examined 121 children with FS and 30 children with HTS aged from 3 to 36 months. SNPs rs1143634 and rs16944 of IL1B gene, and rs3812718 and rs16851603 of SCN1A gene were determined by quantitative real-time PCR. Results: The analysis for rs1143634 revealed an association between the CC genotype and increased risk of FS development (OR 6.56; P=0.0008 against the background of acute respiratory viral infection. The same result was obtained for rs16944 (OR 3.13; P=0.04 and an association of two homozygous genotypes CC/CC. For rs3812718, the carriage of heterozygous genotype CT demonstrated a direct relationship with FS development (OR 44.95; P=0.000. Conclusion: Children with high FS risk need preventive treatment and joint observation of a pediatrician, pediatric infectionist, and a neurologist-epileptologist.

Parallel evolution of tetrodotoxin resistance in three voltage-gated sodium channel genes in the garter snake Thamnophis sirtalis.

Science.gov (United States)

McGlothlin, Joel W; Chuckalovcak, John P; Janes, Daniel E; Edwards, Scott V; Feldman, Chris R; Brodie, Edmund D; Pfrender, Michael E; Brodie, Edmund D

2014-11-01

Members of a gene family expressed in a single species often experience common selection pressures. Consequently, the molecular basis of complex adaptations may be expected to involve parallel evolutionary changes in multiple paralogs. Here, we use bacterial artificial chromosome library scans to investigate the evolution of the voltage-gated sodium channel (Nav) family in the garter snake Thamnophis sirtalis, a predator of highly toxic Taricha newts. Newts possess tetrodotoxin (TTX), which blocks Nav's, arresting action potentials in nerves and muscle. Some Thamnophis populations have evolved resistance to extremely high levels of TTX. Previous work has identified amino acid sites in the skeletal muscle sodium channel Nav1.4 that confer resistance to TTX and vary across populations. We identify parallel evolution of TTX resistance in two additional Nav paralogs, Nav1.6 and 1.7, which are known to be expressed in the peripheral nervous system and should thus be exposed to ingested TTX. Each paralog contains at least one TTX-resistant substitution identical to a substitution previously identified in Nav1.4. These sites are fixed across populations, suggesting that the resistant peripheral nerves antedate resistant muscle. In contrast, three sodium channels expressed solely in the central nervous system (Nav1.1-1.3) showed no evidence of TTX resistance, consistent with protection from toxins by the blood-brain barrier. We also report the exon-intron structure of six Nav paralogs, the first such analysis for snake genes. Our results demonstrate that the molecular basis of adaptation may be both repeatable across members of a gene family and predictable based on functional considerations. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Deep Ultraviolet Copper(I) Thiocyanate (CuSCN) Photodetectors Based on Coplanar Nanogap Electrodes Fabricated via Adhesion Lithography

KAUST Repository

Wyatt-Moon, Gwenhivir

2017-11-28

Adhesion lithography (a-Lith) is a versatile fabrication technique used to produce asymmetric coplanar electrodes separated by a <15 nm nanogap. Here, we use a-Lith to fabricate deep ultraviolet (DUV) photodetectors by combining coplanar asymmetric nanogap electrode architectures (Au/Al) with solution-processable wide-band-gap (3.5–3.9 eV) p-type semiconductor copper(I) thiocyanate (CuSCN). Because of the device’s unique architecture, the detectors exhibit high responsivity (≈79 A W–1) and photosensitivity (≈720) when illuminated with a DUV-range (λpeak = 280 nm) light-emitting diode at 220 μW cm–2. Interestingly, the photosensitivity of the photodetectors remains fairly high (≈7) even at illuminating intensities down to 0.2 μW cm–2. The scalability of the a-Lith process combined with the unique properties of CuSCN paves the way to new forms of inexpensive, yet high-performance, photodetectors that can be manufactured on arbitrary substrate materials including plastic.

Deep Ultraviolet Copper(I) Thiocyanate (CuSCN) Photodetectors Based on Coplanar Nanogap Electrodes Fabricated via Adhesion Lithography

KAUST Repository

Wyatt-Moon, Gwenhivir; Georgiadou, Dimitra G; Semple, James; Anthopoulos, Thomas D.

2017-01-01

Adhesion lithography (a-Lith) is a versatile fabrication technique used to produce asymmetric coplanar electrodes separated by a <15 nm nanogap. Here, we use a-Lith to fabricate deep ultraviolet (DUV) photodetectors by combining coplanar asymmetric nanogap electrode architectures (Au/Al) with solution-processable wide-band-gap (3.5–3.9 eV) p-type semiconductor copper(I) thiocyanate (CuSCN). Because of the device’s unique architecture, the detectors exhibit high responsivity (≈79 A W–1) and photosensitivity (≈720) when illuminated with a DUV-range (λpeak = 280 nm) light-emitting diode at 220 μW cm–2. Interestingly, the photosensitivity of the photodetectors remains fairly high (≈7) even at illuminating intensities down to 0.2 μW cm–2. The scalability of the a-Lith process combined with the unique properties of CuSCN paves the way to new forms of inexpensive, yet high-performance, photodetectors that can be manufactured on arbitrary substrate materials including plastic.

Multi-country Survey Revealed Prevalent and Novel F1534S Mutation in Voltage-Gated Sodium Channel (VGSC Gene in Aedes albopictus.

Directory of Open Access Journals (Sweden)

Jiabao Xu

2016-05-01

Full Text Available Aedes albopictus is an important dengue vector because of its aggressive biting behavior and rapid spread out of its native home range in Southeast Asia. Pyrethroids are widely used for adult mosquito control, and resistance to pyrethroids should be carefully monitored because vector control is the only effective method currently available to prevent dengue transmission. The voltage-gated sodium channel gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr. Previous studies reported various mutations in the voltage-gated sodium channel (VGSC gene, but the spatial distribution of kdr mutations in Ae. albopictus has not been systematically examined, and the association between kdr mutation and phenotypic resistance has not been established.A total of 597 Ae. albopictus individuals from 12 populations across Asia, Africa, America and Europe were examined for mutations in the voltage-gated sodium channel gene. Three domains for a total of 1,107 bp were sequenced for every individual. Two populations from southern China were examined for pyrethroid resistance using the World Health Organization standard tube bioassay, and the association between kdr mutations and phenotypic resistance was tested.A total of 29 synonymous mutations were found across domain II, III and IV of the VGSC gene. Non-synonymous mutations in two codons of the VGSC gene were detected in 5 populations from 4 countries. A novel mutation at 1532 codon (I1532T was found in Rome, Italy with a frequency of 19.7%. The second novel mutation at codon 1534 (F1534S was detected in southern China and Florida, USA with a frequency ranging from 9.5-22.6%. The WHO insecticide susceptibility bioassay found 90.1% and 96.1% mortality in the two populations from southern China, suggesting resistance and probable resistance. Positive association between kdr mutations with deltamethrin resistance was established in these two populations.Two novel kdr

Multi-country Survey Revealed Prevalent and Novel F1534S Mutation in Voltage-Gated Sodium Channel (VGSC) Gene in Aedes albopictus.

Science.gov (United States)

Xu, Jiabao; Bonizzoni, Mariangela; Zhong, Daibin; Zhou, Guofa; Cai, Songwu; Li, Yiji; Wang, Xiaoming; Lo, Eugenia; Lee, Rebecca; Sheen, Roger; Duan, Jinhua; Yan, Guiyun; Chen, Xiao-Guang

2016-05-01

Aedes albopictus is an important dengue vector because of its aggressive biting behavior and rapid spread out of its native home range in Southeast Asia. Pyrethroids are widely used for adult mosquito control, and resistance to pyrethroids should be carefully monitored because vector control is the only effective method currently available to prevent dengue transmission. The voltage-gated sodium channel gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr). Previous studies reported various mutations in the voltage-gated sodium channel (VGSC) gene, but the spatial distribution of kdr mutations in Ae. albopictus has not been systematically examined, and the association between kdr mutation and phenotypic resistance has not been established. A total of 597 Ae. albopictus individuals from 12 populations across Asia, Africa, America and Europe were examined for mutations in the voltage-gated sodium channel gene. Three domains for a total of 1,107 bp were sequenced for every individual. Two populations from southern China were examined for pyrethroid resistance using the World Health Organization standard tube bioassay, and the association between kdr mutations and phenotypic resistance was tested. A total of 29 synonymous mutations were found across domain II, III and IV of the VGSC gene. Non-synonymous mutations in two codons of the VGSC gene were detected in 5 populations from 4 countries. A novel mutation at 1532 codon (I1532T) was found in Rome, Italy with a frequency of 19.7%. The second novel mutation at codon 1534 (F1534S) was detected in southern China and Florida, USA with a frequency ranging from 9.5-22.6%. The WHO insecticide susceptibility bioassay found 90.1% and 96.1% mortality in the two populations from southern China, suggesting resistance and probable resistance. Positive association between kdr mutations with deltamethrin resistance was established in these two populations. Two novel kdr mutations, I1532T

Chronic ciguatoxin treatment induces synaptic scaling through voltage gated sodium channels in cortical neurons.

Science.gov (United States)

Martín, Víctor; Vale, Carmen; Rubiolo, Juan A; Roel, Maria; Hirama, Masahiro; Yamashita, Shuji; Vieytes, Mercedes R; Botana, Luís M

2015-06-15

Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10-13 days in vitro (DIV) cortical neurons to the synthetic ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin increased the mRNA levels of both Arc and Egr1, the effect of CTX 3C in NaV channels, membrane potential, firing activity, miniature excitatory postsynaptic currents (mEPSCs), and glutamate receptors expression in cortical neurons after a 24 h exposure was evaluated using electrophysiological and western blot approaches. The data presented here show that CTX 3C induced an upregulation of Arc and Egr1 that was prevented by previous coincubation of the neurons with the NaV channel blocker tetrodotoxin. In addition, chronic CTX 3C caused a concentration-dependent shift in the activation voltage of NaV channels to more negative potentials and produced membrane potential depolarization. Moreover, 24 h treatment of cortical neurons with 5 nM CTX 3C decreased neuronal firing and induced synaptic scaling mechanisms, as evidenced by a decrease in the amplitude of mEPSCs and downregulation in the protein level of glutamate receptors that was also prevented by tetrodotoxin

Solution-processed inorganic copper(I) thiocyanate (CuSCN) hole transporting layers for efficient p–i–n perovskite solar cells

KAUST Repository

Zhao, Kui

2015-08-27

CuSCN is a highly transparent, highly stable, low cost and easy to solution process HTL that is proposed as a low cost replacement to existing organic and inorganic metal oxide hole transporting materials. Here, we demonstrate hybrid organic-inorganic perovskite-based p-i-n planar heterojunction solar cells using a solution-processed copper(I) thiocyanate (CuSCN) bottom hole transporting layer (HTL). CuSCN, with its high workfunction, increases the open circuit voltage (Voc) by 0.23 V to 1.06 V as compared with devices based on the well-known poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (0.83 V), resulting in a superior power conversion efficiency (PCE) of 10.8% without any notable hysteresis. Photoluminescence measurements suggest a similar efficiency of charge transfer at HTL/perovskite interface as PEDOT:PSS. However, we observe more efficient light harvesting in the presence of CuSCN at shorter wavelengths despite PEDOT:PSS being more transparent. Further investigation of the microstructure and morphology reveals differences in the crystallographic texture of the polycrystalline perovskite film, suggesting somewhat modified perovskite growth on the surface of CuSCN. The successful demonstration of the solution-processed inorganic HTL using simple and low temperature processing routes bodes well for the development of reliable and efficient flexible p-i-n perovskite modules or for integration as a front cell in hybrid tandem solar cells.

The antipsychotic drug loxapine is an opener of the sodium-activated potassium channel slack (Slo2.2).

Science.gov (United States)

Biton, B; Sethuramanujam, S; Picchione, Kelly E; Bhattacharjee, A; Khessibi, N; Chesney, F; Lanneau, C; Curet, O; Avenet, P

2012-03-01

Sodium-activated potassium (K(Na)) channels have been suggested to set the resting potential, to modulate slow after-hyperpolarizations, and to control bursting behavior or spike frequency adaptation (Trends Neurosci 28:422-428, 2005). One of the genes that encodes K(Na) channels is called Slack (Kcnt1, Slo2.2). Studies found that Slack channels were highly expressed in nociceptive dorsal root ganglion neurons and modulated their firing frequency (J Neurosci 30:14165-14172, 2010). Therefore, Slack channel openers are of significant interest as putative analgesic drugs. We screened the library of pharmacologically active compounds with recombinant human Slack channels expressed in Chinese hamster ovary cells, by using rubidium efflux measurements with atomic absorption spectrometry. Riluzole at 500 μM was used as a reference agonist. The antipsychotic drug loxapine and the anthelmintic drug niclosamide were both found to activate Slack channels, which was confirmed by using manual patch-clamp analyses (EC(50) = 4.4 μM and EC(50) = 2.9 μM, respectively). Psychotropic drugs structurally related to loxapine were also evaluated in patch-clamp experiments, but none was found to be as active as loxapine. Loxapine properties were confirmed at the single-channel level with recombinant rat Slack channels. In dorsal root ganglion neurons, loxapine was found to behave as an opener of native K(Na) channels and to increase the rheobase of action potential. This study identifies new K(Na) channel pharmacological tools, which will be useful for further Slack channel investigations.

Skeletal Muscle Na+ Channel Disorders

Directory of Open Access Journals (Sweden)

Dina eSimkin

2011-10-01

Full Text Available Five inherited human disorders affecting skeletal muscle contraction have been traced to mutations in the gene encoding the voltage-gated sodium channel Nav1.4. The main symptoms of these disorders are myotonia or periodic paralysis caused by changes in skeletal muscle fiber excitability. Symptoms of these disorders vary from mild or latent disease to incapacitating or even death in severe cases. As new human sodium channel mutations corresponding to disease states become discovered, the importance of understanding the role of the sodium channel in skeletal muscle function and disease state grows.

Optimization of In Vitro Techniques for Distinguishing between Live and Dead Second Stage Juveniles of Heterodera glycines and Meloidogyne incognita.

Directory of Open Access Journals (Sweden)

Ni Xiang

Full Text Available Heterodera glycines (Soybean Cyst nematode, or SCN and Meloidogyne incognita (Root-Knot nematode, or RKN are two damaging plant-parasitic nematodes on important field crops. Developing a quick method to distinguish between live and dead SCN and RKN second stage juveniles (J2 is vital for high throughput screening of pesticides or biological compounds against SCN and RKN. The in vitro assays were conducted in 96-well plates to determine the optimum chemical stimulus to distinguish between live and dead SCN and RKN J2. Sodium carbonate (Na2CO3, sodium bicarbonate (NaHCO3, and sodium hydroxide (NaOH were evaluated for the nematode response to see if these compounds can help distinguish between viable from the dead J2. Results indicated that live SCN J2 responded equally (P ≤ 0.05 to 1 μl Na2CO3 and 10 μl NaHCO3 in 100 μl of water at pH = 10. Live SCN J2 responded by twisting their bodies in a curling shape and increasing rate of movements within 2 minutes of exposure. The twisting activity continued for up to 30 minutes. Live RKN J2 responded by increasing activity with the application of 1 μl NaOH in 100 μl of water at pH = 10 also in the 2 minutes to 30 minutes time frame. Furthermore, in growth chamber tests to confirm the infectivity of live SCN. The live SCN as determined by exposure to 1 μl of Na2CO3 indicated 60.5% of the SCN J2 were alive and of those, 29.5% were infective and entered the soybean roots. The 1 μl of NaOH stimulus revealed that 75.2% RKN J2 were alive and of those, 14.9% were infective and entered soybean roots. These results confirmed that 1 μl of Na2CO3 added to 100 μl suspension of SCN J2 and 1 μl of NaOH added to 100 μl suspension of RKN J2 are the effective stimuli for rapidly distinguishing between live and dead SCN and RKN J2 in vitro. SCN and RKN J2 responded differently to different compounds.

Effects of Photoperiod Extension on Clock Gene and Neuropeptide RNA Expression in the SCN of the Soay Sheep.

Directory of Open Access Journals (Sweden)

Hugues Dardente

Full Text Available In mammals, changing daylength (photoperiod is the main synchronizer of seasonal functions. The photoperiodic information is transmitted through the retino-hypothalamic tract to the suprachiasmatic nuclei (SCN, site of the master circadian clock. To investigate effects of day length change on the sheep SCN, we used in-situ hybridization to assess the daily temporal organization of expression of circadian clock genes (Per1, Per2, Bmal1 and Fbxl21 and neuropeptides (Vip, Grp and Avp in animals acclimated to a short photoperiod (SP; 8h of light and at 3 or 15 days following transfer to a long photoperiod (LP3, LP15, respectively; 16h of light, achieved by an acute 8-h delay of lights off. We found that waveforms of SCN gene expression conformed to those previously seen in LP acclimated animals within 3 days of transfer to LP. Mean levels of expression for Per1-2 and Fbxl21 were nearly 2-fold higher in the LP15 than in the SP group. The expression of Vip was arrhythmic and unaffected by photoperiod, while, in contrast to rodents, Grp expression was not detectable within the sheep SCN. Expression of the circadian output gene Avp cycled robustly in all photoperiod groups with no detectable change in phasing. Overall these data suggest that synchronizing effects of light on SCN circadian organisation proceed similarly in ungulates and in rodents, despite differences in neuropeptide gene expression.

Sodium voiding analysis in Kalimer

International Nuclear Information System (INIS)

Chang, Won-Pyo; Jeong, Kwan-Seong; Hahn, Dohee

2001-01-01

A sodium boiling model has been developed for calculations of the void reactivity feedback as well as the fuel and cladding temperatures in the KALIMER core after onset of sodium boiling. The sodium boiling in liquid metal reactors using sodium as coolant should be modeled because of phenomenon difference observed from that in light water reactor systems. The developed model is a multiple -bubble slug ejection model. It allows a finite number of bubbles in a channel at any time. Voiding is assumed to result from formation of bubbles that fill the whole cross section of the coolant channel except for liquid film left on the cladding surface. The vapor pressure, currently, is assumed to be uniform within a bubble. The present study is focused on not only demonstration of the sodium voiding behavior predicted by the developed model, but also confirmation on qualitative acceptance for the model. In results, the model catches important phenomena for sodium boiling, while further effort should be made for the complete analysis. (author)

Electrochemical Performance of a V2O5 Cathode for a Sodium Ion Battery

Science.gov (United States)

Van Nghia, Nguyen; Long, Pham Duy; Tan, Ta Anh; Jafian, Samuel; Hung, I.-Ming

2017-06-01

In this paper, layered vanadium pentoxide (V2O5) is employed as a cathode material for a sodium ion battery. The V2O5 particle sizes range from 200 nm to 500 nm and the shapes of the aggregated V2O5 particles are non-homogeneous and irregular. The material exhibits a first discharge capacity of approximately 208.1 mAh g-1. The structure of V2O5 changes to a NaxV2O5 structure after Na+ insertion at the first discharge; the structure of NaxV2O5 remains stable␣during cycling. After 40 cycles, the discharge capacity retains 61.2% of the capacity of the second cycle. The capacity of V2O5 at a high charge/discharge current rate of 1.0 C is 49.1% of capacity at 0.1 C. Furthermore, the capacity returns to the initial value as the discharge rate returns to 0.1 C. The results of electrochemical performance tests indicate that V2O5 is a potential cathode material for sodium ion batteries.

A Gate Hinge Controls the Epithelial Calcium Channel TRPV5

OpenAIRE

van der Wijst, Jenny; Leunissen, Elizabeth H.; Blanchard, Maxime G.; Venselaar, Hanka; Verkaart, Sjoerd; Paulsen, Candice E.; Bindels, Ren? J.; Hoenderop, Joost G.

2017-01-01

TRPV5 is unique within the large TRP channel family for displaying a high Ca2+ selectivity together with Ca2+-dependent inactivation. Our study aims to uncover novel insights into channel gating through in-depth structure-function analysis. We identify an exceptional tryptophan (W583) at the terminus of the intracellular pore that is unique for TRPV5 (and TRPV6). A combination of site-directed mutagenesis, biochemical and electrophysiological analysis, together with homology modeling, demonst...

Solution-processed p-type copper(I) thiocyanate (CuSCN) for low-voltage flexible thin-film transistors and integrated inverter circuits

KAUST Repository

Petti, Luisa

2017-03-17

We report on low operating voltage thin-film transistors (TFTs) and integrated inverters based on copper(I) thiocyanate (CuSCN) layers processed from solution at low temperature on free-standing plastic foils. As-fabricated coplanar bottom-gate and staggered top-gate TFTs exhibit hole-transporting characteristics with average mobility values of 0.0016 cm2 V−1 s−1 and 0.013 cm2 V−1 s−1, respectively, current on/off ratio in the range 102–104, and maximum operating voltages between −3.5 and −10 V, depending on the gate dielectric employed. The promising TFT characteristics enable fabrication of unipolar NOT gates on flexible free-standing plastic substrates with voltage gain of 3.4 at voltages as low as −3.5 V. Importantly, discrete CuSCN transistors and integrated logic inverters remain fully functional even when mechanically bent to a tensile radius of 4 mm, demonstrating the potential of the technology for flexible electronics.

Sodium-water reaction in double pool LMFBR, (5)

International Nuclear Information System (INIS)

Yoshida, Kazuo; Kumagai, Hiromichi; Nishi, Yoshihisa; Uotani, Masaki

1990-01-01

Experiments were conducted using a 1/5 scale model of the Double Pool in order to evaluate a pressure rise caused by a large scale sodium-water reaction. The experiments were focused on the pressure rise caused by the piston motion of liquid sodium. It appeared from the results that the magnitude of this pressure rise depends on the depth of reaction point, and that a pressure rise more than 1 MPa would arise in the real Double Pool plant. A new design of steam generator is proposed to mitigate the pressure rise. (author)

Solution-processed p-type copper(I) thiocyanate (CuSCN) for low-voltage flexible thin-film transistors and integrated inverter circuits

KAUST Repository

Petti, Luisa; Pattanasattayavong, Pichaya; Lin, Yen-Hung; Mü nzenrieder, Niko; Cantarella, Giuseppe; Yaacobi-Gross, Nir; Yan, Feng; Trö ster, Gerhard; Anthopoulos, Thomas D.

2017-01-01

, depending on the gate dielectric employed. The promising TFT characteristics enable fabrication of unipolar NOT gates on flexible free-standing plastic substrates with voltage gain of 3.4 at voltages as low as −3.5 V. Importantly, discrete CuSCN transistors

Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

Energy Technology Data Exchange (ETDEWEB)

Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); Niermann, T.; Lehmann, M. [Technische Universität Berlin, Institut für Optik und Atomare Physik, Straße des 17. Juni 135, 10623 Berlin (Germany); Thapa, S. B.; Haeberlen, M.; Storck, P. [SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); BTU Cottbus, Konrad-Zuse-Str. 1, 03046 Cottbus (Germany)

2015-11-16

We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

Homogeneous distribution of large-conductance calcium-dependent potassium channels on soma and apical dendrite of rat neocortical layer 5 pyramidal neurons.

Science.gov (United States)

Benhassine, Narimane; Berger, Thomas

2005-02-01

Voltage-gated conductances on dendrites of layer 5 pyramidal neurons participate in synaptic integration and output generation. We investigated the properties and the distribution of large-conductance calcium-activated potassium channels (BK channels) in this cell type using excised patches in acute slice preparations of rat somatosensory cortex. BK channels were characterized by their large conductance and sensitivity to the specific blockers paxilline and iberiotoxin. BK channels showed a pronounced calcium-dependence with a maximal opening probability of 0.69 at 10 microm and 0.42 at 3 microm free calcium. Their opening probability and transition time constants between open and closed states are voltage-dependent. At depolarized potentials, BK channel gating is described by two open and one closed states. Depolarization increases the opening probability due to a prolongation of the open time constant and a shortening of the closed time constant. Calcium-dependence and biophysical properties of somatic and dendritic BK channels were identical. The presence of BK channels on the apical dendrite of layer 5 pyramidal neurons was shown by immunofluorescence. Patch-clamp recordings revealed a homogeneous density of BK channels on the soma and along the apical dendrite up to 850 microm with a mean density of 1.9 channels per microm(2). BK channels are expressed either isolated or in clusters containing up to four channels. This study shows the presence of BK channels on dendrites. Their activation might modulate the shape of sodium and calcium action potentials, their propagation along the dendrite, and thereby the electrotonic distance between the somatic and dendritic action potential initiation zones.

Large scale experiments with a 5 MW sodium/air heat exchanger for decay heat removal

International Nuclear Information System (INIS)

Stehle, H.; Damm, G.; Jansing, W.

1994-01-01

Sodium experiments in the large scale test facility ILONA were performed to demonstrate proper operation of a passive decay heat removal system for LMFBRs based on pure natural convection flow. Temperature and flow distributions on the sodium and the air side of a 5 MW sodium/air heat exchanger in a natural draught stack were measured during steady state and transient operation in good agreement with calculations using a two dimensional computer code ATTICA/DIANA. (orig.)

Pyrethroid resistance in Sitophilus zeamais is associated with a mutation (T929I) in the voltage-gated sodium channel.

Science.gov (United States)

Araújo, Rúbia A; Williamson, Martin S; Bass, Christopher; Field, Linda M; Duce, Ian R

2011-08-01

The maize weevil, Sitophilus zeamais, is the most important pest affecting stored grain in Brazil and its control relies heavily on the use of insecticides. The intensive use of compounds such as the pyrethroids has led to the emergence of resistance, and previous studies have suggested that resistance to both pyrethroids and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) may result from reduced sensitivity of the insecticide target, the voltage-gated sodium channel. To identify the molecular mechanisms underlying pyrethroid resistance in S. zeamais, the domain II region of the voltage-gated sodium channel (para-orthologue) gene was amplified by PCR and sequenced from susceptible and resistant laboratory S. zeamais strains that were selected with a discriminating dose of DDT. A single point mutation, T929I, was found in the para gene of the resistant S. zeamais populations and its presence in individual weevils was strongly associated with survival after DDT exposure. This is the first identification of a target-site resistance mutation in S. zeamais and unusually it is a super-kdr type mutation occurring in the absence of the more common kdr (L1014F) substitution. A high-throughput assay based on TaqMan single nucleotide polymorphism genotyping was developed for sensitive detection of the mutation and used to screen field-collected strains of S. zeamais. This showed that the mutation is present at low frequency in field populations and is a useful tool for informing control strategies. © 2011 The Authors. Insect Molecular Biology © 2011 The Royal Entomological Society.

Ab-initio studies of the Sc adsorption and the ScN thin film formation on the GaN(000-1)-(2 × 2) surface

International Nuclear Information System (INIS)

Guerrero-Sánchez, J.; Sánchez-Ochoa, F.; Cocoletzi, Gregorio H.; Rivas-Silva, J.F.; Takeuchi, Noboru

2013-01-01

First principles total energy calculations have been performed to investigate the initial stages of the Sc adsorption and ScN thin film formation on the GaN(000-1)-(2 × 2) surface. Studies are done within the periodic density functional theory as implemented in the PWscf code of the Quantum ESPRESSO package. The Sc adsorption at high symmetry sites results in the bridge site as the most stable structure. When a Sc monolayer is deposited above the surface the T4 site results as the most stable geometry. The Sc migration into the first Ga monolayer induces the Ga displaced ad-atom to be adsorbed at the T4-2 site. A ScN bilayer may be obtained under the Ga monolayer. Finally a ScN bilayer may be formed in the wurtzite phase above the surface. The formation energy plots show that in the moderate Ga-rich conditions we obtain the formation of a ScN bilayer under the gallium monolayer. However at N-rich conditions the formation of ScN bilayer above the surface is the most favorable structure. We report the density of states to explain the electronic structure of the most favorable geometries. - Highlights: • Studies of the initial stages in the formation of Sc and ScN structures on GaN • In the adsorption of Sc on the GaN the Br site is the most favorable geometry. • When a Sc replaces a Ga of the first monolayer the displaced Ga occupies a T4-2 site. • For Ga-rich conditions there is formation of ScN under the Ga monolayer. • In N-rich conditions there is formation of ScN in the wurtzite phase

Tarantula huwentoxin-IV inhibits neuronal sodium channels by binding to receptor site 4 and trapping the domain ii voltage sensor in the closed configuration.

Science.gov (United States)

Xiao, Yucheng; Bingham, Jon-Paul; Zhu, Weiguo; Moczydlowski, Edward; Liang, Songping; Cummins, Theodore R

2008-10-03

Peptide toxins with high affinity, divergent pharmacological functions, and isoform-specific selectivity are powerful tools for investigating the structure-function relationships of voltage-gated sodium channels (VGSCs). Although a number of interesting inhibitors have been reported from tarantula venoms, little is known about the mechanism for their interaction with VGSCs. We show that huwentoxin-IV (HWTX-IV), a 35-residue peptide from tarantula Ornithoctonus huwena venom, preferentially inhibits neuronal VGSC subtypes rNav1.2, rNav1.3, and hNav1.7 compared with muscle subtypes rNav1.4 and hNav1.5. Of the five VGSCs examined, hNav1.7 was most sensitive to HWTX-IV (IC(50) approximately 26 nM). Following application of 1 microm HWTX-IV, hNav1.7 currents could only be elicited with extreme depolarizations (>+100 mV). Recovery of hNav1.7 channels from HWTX-IV inhibition could be induced by extreme depolarizations or moderate depolarizations lasting several minutes. Site-directed mutagenesis analysis indicated that the toxin docked at neurotoxin receptor site 4 located at the extracellular S3-S4 linker of domain II. Mutations E818Q and D816N in hNav1.7 decreased toxin affinity for hNav1.7 by approximately 300-fold, whereas the reverse mutations in rNav1.4 (N655D/Q657E) and the corresponding mutations in hNav1.5 (R812D/S814E) greatly increased the sensitivity of the muscle VGSCs to HWTX-IV. Our data identify a novel mechanism for sodium channel inhibition by tarantula toxins involving binding to neurotoxin receptor site 4. In contrast to scorpion beta-toxins that trap the IIS4 voltage sensor in an outward configuration, we propose that HWTX-IV traps the voltage sensor of domain II in the inward, closed configuration.

CFD Modeling of Sodium-Oxide Deposition in Sodium-Cooled Fast Reactor Compact Heat Exchangers

Energy Technology Data Exchange (ETDEWEB)

Tatli, Emre; Ferroni, Paolo; Mazzoccoli, Jason

2015-09-02

The possible use of compact heat exchangers (HXs) in sodium-cooled fast reactors (SFR) employing a Brayton cycle is promising due to their high power density and resulting small volume in comparison with conventional shell-and-tube HXs. However, the small diameter of their channels makes them more susceptible to plugging due to Na2O deposition during accident conditions. Although cold traps are designed to reduce oxygen impurity levels in the sodium coolant, their failure, in conjunction with accidental air ingress into the sodium boundary, could result in coolant oxygen levels that are above the saturation limit in the cooler parts of the HX channels. This can result in Na2O crystallization and the formation of solid deposits on cooled channel surfaces, limiting or even blocking coolant flow. The development of analysis tools capable of modeling the formation of these deposits in the presence of sodium flow will allow designers of SFRs to properly size the HX channels so that, in the scenario mentioned above, the reactor operator has sufficient time to detect and react to the affected HX. Until now, analytical methodologies to predict the formation of these deposits have been developed, but never implemented in a high-fidelity computational tool suited to modern reactor design techniques. This paper summarizes the challenges and the current status in the development of a Computational Fluid Dynamics (CFD) methodology to predict deposit formation, with particular emphasis on sensitivity studies on some parameters affecting deposition.

A selectivity filter at the intracellular end of the acid-sensing ion channel pore

DEFF Research Database (Denmark)

Lynagh, Timothy; Flood, Emelie; Boiteux, Céline

2017-01-01

Increased extracellular proton concentrations during neurotransmission are converted to excitatory sodium influx by acid-sensing ion channels (ASICs). 10-fold sodium/potassium selectivity in ASICs has long been attributed to a central constriction in the channel pore, but experimental verificatio...... at the "GAS belt" in the central constriction. Instead, we identified a band of glutamate and aspartate side chains at the lower end of the pore that enables preferential sodium conduction....

Hydrogen Sulfide Prevents Advanced Glycation End-Products Induced Activation of the Epithelial Sodium Channel

Directory of Open Access Journals (Sweden)

Qiushi Wang

2015-01-01

Full Text Available Advanced glycation end-products (AGEs are complex and heterogeneous compounds implicated in diabetes. Sodium reabsorption through the epithelial sodium channel (ENaC at the distal nephron plays an important role in diabetic hypertension. Here, we report that H2S antagonizes AGEs-induced ENaC activation in A6 cells. ENaC open probability (PO in A6 cells was significantly increased by exogenous AGEs and that this AGEs-induced ENaC activity was abolished by NaHS (a donor of H2S and TEMPOL. Incubating A6 cells with the catalase inhibitor 3-aminotriazole (3-AT mimicked the effects of AGEs on ENaC activity, but did not induce any additive effect. We found that the expression levels of catalase were significantly reduced by AGEs and both AGEs and 3-AT facilitated ROS uptake in A6 cells, which were significantly inhibited by NaHS. The specific PTEN and PI3K inhibitors, BPV(pic  and LY294002, influence ENaC activity in AGEs-pretreated A6 cells. Moreover, after removal of AGEs from AGEs-pretreated A6 cells for 72 hours, ENaC PO remained at a high level, suggesting that an AGEs-related “metabolic memory” may be involved in sodium homeostasis. Our data, for the first time, show that H2S prevents AGEs-induced ENaC activation by targeting the ROS/PI3K/PTEN pathway.

COMMD1 regulates the delta epithelial sodium channel (δENaC) through trafficking and ubiquitination

International Nuclear Information System (INIS)

Chang, Tina; Ke, Ying; Ly, Kevin; McDonald, Fiona J.

2011-01-01

Highlights: → The COMM domain of COMMD1 mediates binding to δENaC. → COMMD1 reduces the cell surface population of δENaC. → COMMD1 increases the population of δENaC-ubiquitin. → Both endogenous and transfected δENaC localize with COMMD1 and transferrin suggesting they are located in early/recycling endosomes. -- Abstract: The delta subunit of the epithelial sodium channel (δENaC) is a member of the ENaC/degenerin family of ion channels. δENaC is distinct from the related α-, β- and γENaC subunits, known for their role in sodium homeostasis and blood pressure control, as δENaC is expressed in brain neurons and activated by external protons. COMMD1 (copper metabolism Murr1 domain 1) was previously found to associate with and downregulate δENaC activity. Here, we show that COMMD1 interacts with δENaC through its COMM domain. Co-expression of δENaC with COMMD1 significantly reduced δENaC surface expression, and led to an increase in δENaC ubiquitination. Immunocytochemical and confocal microscopy studies show that COMMD1 promoted localization of δENaC to the early/recycling endosomal pool where the two proteins were localized together. These results suggest that COMMD1 downregulates δENaC activity by reducing δENaC surface expression through promoting internalization of surface δENaC to an intracellular recycling pool, possibly via enhanced ubiquitination.

COMMD1 regulates the delta epithelial sodium channel ({delta}ENaC) through trafficking and ubiquitination

Energy Technology Data Exchange (ETDEWEB)

Chang, Tina; Ke, Ying; Ly, Kevin [Department of Physiology, University of Otago, P.O. Box 913, Dunedin 9054 (New Zealand); McDonald, Fiona J., E-mail: fiona.mcdonald@otago.ac.nz [Department of Physiology, University of Otago, P.O. Box 913, Dunedin 9054 (New Zealand)

2011-08-05

Highlights: {yields} The COMM domain of COMMD1 mediates binding to {delta}ENaC. {yields} COMMD1 reduces the cell surface population of {delta}ENaC. {yields} COMMD1 increases the population of {delta}ENaC-ubiquitin. {yields} Both endogenous and transfected {delta}ENaC localize with COMMD1 and transferrin suggesting they are located in early/recycling endosomes. -- Abstract: The delta subunit of the epithelial sodium channel ({delta}ENaC) is a member of the ENaC/degenerin family of ion channels. {delta}ENaC is distinct from the related {alpha}-, {beta}- and {gamma}ENaC subunits, known for their role in sodium homeostasis and blood pressure control, as {delta}ENaC is expressed in brain neurons and activated by external protons. COMMD1 (copper metabolism Murr1 domain 1) was previously found to associate with and downregulate {delta}ENaC activity. Here, we show that COMMD1 interacts with {delta}ENaC through its COMM domain. Co-expression of {delta}ENaC with COMMD1 significantly reduced {delta}ENaC surface expression, and led to an increase in {delta}ENaC ubiquitination. Immunocytochemical and confocal microscopy studies show that COMMD1 promoted localization of {delta}ENaC to the early/recycling endosomal pool where the two proteins were localized together. These results suggest that COMMD1 downregulates {delta}ENaC activity by reducing {delta}ENaC surface expression through promoting internalization of surface {delta}ENaC to an intracellular recycling pool, possibly via enhanced ubiquitination.

Investigations of the Navβ1b sodium channel subunit in human ventricle; functional characterization of the H162P Brugada Syndrome mutant

DEFF Research Database (Denmark)

Yuan, Lei; Koivumaki, Jussi; Liang, Bo

2014-01-01

Brugada Syndrome (BrS) is a rare inherited disease which can give rise to ventricular arrhythmia and ultimately sudden cardiac death. Numerous loss-of-function mutations in the cardiac sodium channel Nav1.5 have been associated with BrS. However, few mutations in the auxiliary Navβ1-4 subunits ha...... density was reduced by 48 % (-645±151 vs - 334±71 pA/pF), V1/2 steady-state inactivation shifted by -6.7 mV (-70.3±1.5 vs. -77.0±2.8 mV), and time-dependent recovery from inactivation slowed by more than 50% as compared to co-expression with Navβ1b WT. Computer simulations revealed...

Severe myoclonic epilepsy of infancy (Dravet syndrome: Clinical and genetic features of nine Turkish patients

Directory of Open Access Journals (Sweden)

Meral Özmen

2011-01-01