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Sodium channelopathies

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https://www.readbyqxmd.com/read/29037745/genetics-update-monogenetics-polygene-disorders-and-the-quest-for-modifying-genes
#1
REVIEW
Joseph D Symonds, Sameer M Zuberi
The genetic channelopathies are a broad collection of diseases. Many ion channel genes demonstrate wide phenotypic pleiotropy, but nonetheless concerted efforts have been made to characterise genotype-phenotype relationships. In this review we give an overview of the factors that influence genotype-phenotype relationships across this group of diseases as a whole, using specific individual channelopathies as examples. We suggest reasons for the limitations observed in these relationships. We discuss the role of ion channel variation in polygenic disease and highlight research that has contributed to unravelling the complex aetiological nature of these conditions...
October 13, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28986244/expression-of-recombinant-%C3%AE-toxin-bmkm9-from-scorpion-buthus-martensii-karsch-and-its-functional-characterization-on-sodium-channels
#2
Fan Yang, Shuang Liu, Yaoyun Zhang, Chenhu Qin, Lingna Xu, Wenhua Li, Zhijian Cao, Wenxin Li, Yingliang Wu
Scorpion toxins are invaluable pharmacological tools for studying ion channels and potential drugs for channelopathies. The long-chain toxins from scorpion venom with four disulfide bridges exhibit their unusual bioactivity or biotoxicity by acting on the sodium channels. However, the functional properties of most toxins are still unclear due to their tiny amounts in crude venom and their challenging production by chemical and gene engineering techniques. Here, we expressed one of the long-chain α-toxins, BmKM9, found in the venom of the scorpion Buthus martensii Karsch and characterized its pharmacological properties on sodium channels...
October 3, 2017: Peptides
https://www.readbyqxmd.com/read/28965172/gating-pore-currents-in-sodium-channels
#3
J R Groome, A Moreau, L Delemotte
Voltage-gated sodium channels belong to the superfamily of voltage-gated cation channels. Their structure is based on domains comprising a voltage sensor domain (S1-S4 segments) and a pore domain (S5-S6 segments). Mutations in positively charged residues of the S4 segments may allow protons or cations to pass directly through the gating pore constriction of the voltage sensor domain; these anomalous currents are referred to as gating pore or omega (ω) currents. In the skeletal muscle disorder hypokalemic periodic paralysis, and in arrhythmic dilated cardiomyopathy, inherited mutations of S4 arginine residues promote omega currents that have been shown to be a contributing factor in the pathogenesis of these sodium channel disorders...
October 1, 2017: Handbook of Experimental Pharmacology
https://www.readbyqxmd.com/read/28965168/cardiac-arrhythmias-related-to-sodium-channel-dysfunction
#4
Eleonora Savio-Galimberti, Mariana Argenziano, Charles Antzelevitch
The voltage-gated cardiac sodium channel (Nav1.5) is a mega-complex comprised of a pore-forming α subunit and 4 ancillary β-subunits together with numerous protein partners. Genetic defects in the form of rare variants in one or more sodium channel-related genes can cause a loss- or gain-of-function of sodium channel current (INa) leading to the manifestation of various disease phenotypes, including Brugada syndrome, long QT syndrome, progressive cardiac conduction disease, sick sinus syndrome, multifocal ectopic Purkinje-related premature contractions, and atrial fibrillation...
October 1, 2017: Handbook of Experimental Pharmacology
https://www.readbyqxmd.com/read/28964108/stochastic-spontaneous-calcium-release-events-and-sodium-channelopathies-promote-ventricular-arrhythmias
#5
Fernando O Campos, Yohannes Shiferaw, Edward J Vigmond, Gernot Plank
Premature ventricular complexes (PVCs), the first initiating beats of a variety of cardiac arrhythmias, have been associated with spontaneous calcium release (SCR) events at the cell level. However, the mechanisms underlying the degeneration of such PVCs into arrhythmias are not fully understood. The objective of this study was to investigate the conditions under which SCR-mediated PVCs can lead to ventricular arrhythmias. In particular, we sought to determine whether sodium (Na(+)) current loss-of-function in the structurally normal ventricles provides a substrate for unidirectional conduction block and reentry initiated by SCR-mediated PVCs...
September 2017: Chaos
https://www.readbyqxmd.com/read/28956012/flecainide-ameliorates-arrhythmogenicity-through-ncx-flux-in-andersen-tawil-syndrome-ips-cell-derived-cardiomyocytes
#6
Yusuke Kuroda, Shinsuke Yuasa, Yasuhide Watanabe, Shogo Ito, Toru Egashira, Tomohisa Seki, Tetsuhisa Hattori, Seiko Ohno, Masaki Kodaira, Tomoyuki Suzuki, Hisayuki Hashimoto, Shinichiro Okata, Atsushi Tanaka, Yoshiyasu Aizawa, Mitsushige Murata, Takeshi Aiba, Naomasa Makita, Tetsushi Furukawa, Wataru Shimizu, Itsuo Kodama, Satoshi Ogawa, Norito Kokubun, Hitoshi Horigome, Minoru Horie, Kaichiro Kamiya, Keiichi Fukuda
Andersen-Tawil syndrome (ATS) is a rare inherited channelopathy. The cardiac phenotype in ATS is typified by a prominent U wave and ventricular arrhythmia. An effective treatment for this disease remains to be established. We reprogrammed somatic cells from three ATS patients to generate induced pluripotent stem cells (iPSCs). Multi-electrode arrays (MEAs) were used to record extracellular electrograms of iPSC-derived cardiomyocytes, revealing strong arrhythmic events in the ATS-iPSC-derived cardiomyocytes...
March 2017: Biochemistry and Biophysics Reports
https://www.readbyqxmd.com/read/28940424/n1366s-mutation-of-human-skeletal-muscle-sodium-channel-causes-paramyotonia-congenita
#7
Qing Ke, Jia Ye, Siyang Tang, Jin Wang, Benyan Luo, Fang Ji, Xu Zhang, Ye Yu, Xiaoyang Cheng, Yuezhou Li
Paramyotonia congenita is an autosomal dominant skeletal muscle channelopathy caused by missense mutations in SCN4A, the gene encoding the α subunit of the human skeletal muscle voltage-gated sodium channel NaV1.4. Here, we report a three-generation family in which six members present clinical symptoms of paramyotonia congenita characterized by a marked worsening of myotonia by cold and by the presence of clear episodes of paralysis. We identified a novel mutation in SCN4A (Asn-1366-Ser, N1366S) in all patients in the family but not in healthy relatives or in 500 normal control subjects...
September 20, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28939973/sodium-channelopathies-of-skeletal-muscle
#8
Stephen C Cannon
The NaV1.4 sodium channel is highly expressed in skeletal muscle, where it carries almost all of the inward Na(+) current that generates the action potential, but is not present at significant levels in other tissues. Consequently, mutations of SCN4A encoding NaV1.4 produce pure skeletal muscle phenotypes that now include six allelic disorders: sodium channel myotonia, paramyotonia congenita, hyperkalemic periodic paralysis, hypokalemic periodic paralysis, congenital myasthenia, and congenital myopathy with hypotonia...
September 23, 2017: Handbook of Experimental Pharmacology
https://www.readbyqxmd.com/read/28927993/voltage-gated-sodium-channel-%C3%AE-subunits-the-power-outside-the-pore-in-brain-development-and-disease
#9
REVIEW
Jacob M Hull, Lori L Isom
Voltage gated sodium channels (VGSCs) were first identified in terms of their role in the upstroke of the action potential. The underlying proteins were later identified as saxitoxin and scorpion toxin receptors consisting of α and β subunits. We now know that VGSCs are heterotrimeric complexes consisting of a single pore forming α subunit joined by two β subunits; a noncovalently linked β1 or β3 and a covalently linked β2 or β4 subunit. VGSC α subunits contain all the machinery necessary for channel cell surface expression, ion conduction, voltage sensing, gating, and inactivation, in one central, polytopic, transmembrane protein...
September 16, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28757052/genetics-update-monogenetics-polygene-disorders-and-the-quest-for-modifying-genes
#10
REVIEW
Joseph D Symonds, Sameer M Zuberi
The genetic channelopathies are a broad collection of diseases. Many ion channel genes demonstrate wide phenotypic pleiotropy, but nonetheless concerted efforts have been made to characterise genotype-phenotype relationships. In this review we give an overview of the factors that influence genotype-phenotype relationships across this group of diseases as a whole, using specific individual channelopathies as examples. We suggest reasons for the limitations observed in these relationships. We discuss the role of ion channel variation in polygenic disease and highlight research that has contributed to unravelling the complex aetiological nature of these conditions...
July 27, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28756098/phenotypic-variability-in-lqt3-human-induced-pluripotent-stem-cell-derived-cardiomyocytes-and-their-response-to-antiarrhythmic-pharmacologic-therapy-an-in-silico-approach
#11
Michelangelo Paci, Elisa Passini, Stefano Severi, Jari Hyttinen, Blanca Rodriguez
BACKGROUND: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are in vitro models with the clear advantages of their human origin and suitability for human disease investigations. However, limitations include their incomplete characterization and variability reported in different cell lines and laboratories. OBJECTIVE: The purpose of this study was to investigate in silico ionic mechanisms potentially explaining the phenotypic variability of hiPSC-CMs in long QT syndrome type 3 (LQT3) and their response to antiarrhythmic drugs...
July 27, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/28662944/skeletal-muscle-channelopathies-rare-disorders-with-common-pediatric-symptoms
#12
Emma Matthews, Arpana Silwal, Richa Sud, Michael G Hanna, Adnan Y Manzur, Francesco Muntoni, Pinki Munot
OBJECTIVE: To ascertain the presenting symptoms of children with skeletal muscle channelopathies to promote early diagnosis and treatment. STUDY DESIGN: Retrospective case review of 38 children with a skeletal muscle channelopathy attending the specialist pediatric neuromuscular service at Great Ormond Street Hospital over a 15-year period. RESULTS: Gait disorder and leg cramps are a frequent presentation of myotonic disorders (19 of 29). Strabismus or extraocular myotonia (9 of 19) and respiratory and/or bulbar symptoms (11 of 19) are common among those with sodium channelopathy...
September 2017: Journal of Pediatrics
https://www.readbyqxmd.com/read/28637969/development-of-a-patient-derived-induced-pluripotent-stem-cell-model-for-the-investigation-of-scn5a-d1275n-related-cardiac-sodium-channelopathy
#13
Mamoru Hayano, Takeru Makiyama, Tsukasa Kamakura, Hiroshi Watanabe, Kenichi Sasaki, Shunsuke Funakoshi, Yimin Wuriyanghai, Suguru Nishiuchi, Takeshi Harita, Yuta Yamamoto, Hirohiko Kohjitani, Sayako Hirose, Fumika Yokoi, Jiarong Chen, Osamu Baba, Takahiro Horie, Kazuhisa Chonabayashi, Seiko Ohno, Futoshi Toyoda, Yoshinori Yoshida, Koh Ono, Minoru Horie, Takeshi Kimura
BACKGROUND: TheSCN5Agene encodes the α subunit of the cardiac voltage-gated sodium channel, NaV1.5. The missense mutation, D1275N, has been associated with a range of unusual phenotypes associated with reduced NaV1.5 function, including cardiac conduction disease and dilated cardiomyopathy. Curiously, the reported biophysical properties ofSCN5A-D1275N channels vary with experimental system.Methods and Results:First, using a human embryonic kidney (HEK) 293 cell-based heterologous expression system, theSCN5A-D1275N channels showed similar maximum sodium conductance but a significantly depolarizing shift of activation gate (+10 mV) compared to wild type...
June 20, 2017: Circulation Journal: Official Journal of the Japanese Circulation Society
https://www.readbyqxmd.com/read/28597987/trafficking-and-localization-to-the-plasma-membrane-of-nav-1-5-promoted-by-the-%C3%AE-2-subunit-is-defective-due-to-a-%C3%AE-2-mutation-associated-with-brugada-syndrome
#14
Gemma Dulsat, Sonia Palomeras, Eric Cortada, Helena Riuró, Ramon Brugada, Marcel Vergés
BACKGROUND INFORMATION: Cardiac channelopathies arise by mutations in genes encoding ion channel subunits. One example is Brugada Syndrome (BrS), which causes arrhythmias and sudden death. BrS is often associated with mutations in SCN5A, encoding Nav 1.5, the α subunit of the major cardiac voltage-gated sodium channel. This channel forms a protein complex including one or two associated β subunits as well as other proteins. RESULTS: We analyzed regulation of Nav 1...
June 9, 2017: Biology of the Cell
https://www.readbyqxmd.com/read/28571716/post-translational-dysfunctions-in-channelopathies-of-the-nervous-system
#15
REVIEW
Benedetta Terragni, Paolo Scalmani, Silvana Franceschetti, Sandrine Cestèle, Massimo Mantegazza
Channelopathies comprise various diseases caused by defects of ion channels. Modifications of their biophysical properties are common and have been widely studied. However, ion channels are heterogeneous multi-molecular complexes that are extensively modulated and undergo a maturation process comprising numerous steps of structural modifications and intracellular trafficking. Perturbations of these processes can give rise to aberrant channels that cause pathologies. Here we review channelopathies of the nervous system associated with dysfunctions at the post-translational level (folding, trafficking, degradation, subcellular localization, interactions with associated proteins and structural post-translational modifications)...
May 29, 2017: Neuropharmacology
https://www.readbyqxmd.com/read/28557061/classification-of-involuntary-movements-in-dogs-myoclonus-and-myotonia
#16
REVIEW
M Lowrie, L Garosi
Myoclonus is a sudden brief, involuntary muscle jerk. Of all the movement disorders, myoclonus is the most difficult to encapsulate into any simple framework. On the one hand, a classification system is required that is clinically useful to aid in guiding diagnosis and treatment. On the other hand, there is need for a system that organizes current knowledge regarding biological mechanisms to guide scientific research. These 2 needs are distinct, making it challenging to develop a robust classification system suitable for all purposes...
July 2017: Journal of Veterinary Internal Medicine
https://www.readbyqxmd.com/read/28552867/an-unusual-case-of-sodium-channel-myotonia-with-transient-weakness-upon-initiating-movements-which-is-characteristic-in-becker-disease
#17
Junpei Yamamoto, Keiichi Hokkoku, Yuki Hatanaka, Shunichi Sakoda, Jun-Hui Yuan, Masahiro Sonoo
We reported a 32-year-old man who was a sporadic case of myotonic syndrome with muscle stiffness or transient weakness of limbs upon initiating movements after rest. On examination, he showed painless myotonia with warm-up phenomenon, Hercules-like hypertrophic musculature and myotonic discharges in EMG. The clinical findings resembled to those of Becker disease rather than Thomsen disease. But electrodiagnosis suggested sodium channel myotonia instead of chloride channelopathy. Genetic testing detected a novel missense mutation (p...
June 28, 2017: Rinshō Shinkeigaku, Clinical Neurology
https://www.readbyqxmd.com/read/28536668/brugada-syndrome-in-a-patient-with-vascular-ehlers-danlos-syndrome-sudden-death-risk-amplified
#18
Jason D'Souza, Divyanshu Malhotra, Aditya Goud, Chanukya Dahagam, George Everett
The vast majority of sudden cardiac arrests occur in patients with structural heart disease and in approximately 10% of the cases, it can occur in those with structurally normal hearts. Brugada syndrome is an autosomal dominant sodium channelopathy that has been implicated in sudden deaths. Given their low prevalence, our knowledge about Brugada syndrome is still evolving. Apart from schizophrenia, there have been no reports of associated medical conditions. We recently encountered a patient with vascular Ehlers-Danlos syndrome who was also found to have Brugada syndrome...
April 19, 2017: Curēus
https://www.readbyqxmd.com/read/28527083/shared-mechanisms-of-epilepsy-migraine-and-affective-disorders
#19
Davide Zarcone, Simona Corbetta
Since the nineteenth century several clinical features have been observed in common between migraine and epilepsy (such as episodic attacks, triggering factors, presence of aura, frequent familiarity), but only in recent years researchers have really engaged in finding a common pathogenic mechanism. From studies of disease incidence, we understand how either migraine among patients with epilepsy or epilepsy among migraine patients are more frequent than in the general population. This association may result from a direct causality, by the same environmental risk factors and/or by a common genetic susceptibility...
May 2017: Neurological Sciences
https://www.readbyqxmd.com/read/28470179/autoimmune-channelopathies-as-a-novel-mechanism-in-cardiac-arrhythmias
#20
REVIEW
Pietro Enea Lazzerini, Pier Leopoldo Capecchi, Franco Laghi-Pasini, Mohamed Boutjdir
Cardiac arrhythmias confer a considerable burden of morbidity and mortality in industrialized countries. Although coronary artery disease and heart failure are the prevalent causes of cardiac arrest, in 5-15% of patients, structural abnormalities at autopsy are absent. In a proportion of these patients, mutations in genes encoding cardiac ion channels are documented (inherited channelopathies), but, to date, the molecular autopsy is negative in nearly 70% of patients. Emerging evidence indicates that autoimmunity is involved in the pathogenesis of cardiac arrhythmias...
September 2017: Nature Reviews. Cardiology
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