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Nagasaka T, Hata T, Shindo K, Adachi Y, Takeuchi M, Saito K, Takiyama Y. Morphological Alterations of the Sarcotubular System in Permanent Myopathy of Hereditary Hypokalemic Periodic Paralysis with a Mutation in the CACNA1S Gene. J Neuropathol Exp Neurol 2021; 79:1276-1292. [PMID: 33184660 DOI: 10.1093/jnen/nlaa098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
We investigated the immunohistochemical localization of several proteins related to excitation-contraction coupling and ultrastructural alterations of the sarcotubular system in biopsied muscles from a father and a daughter in a family with permanent myopathy with hypokalemic periodic paralysis (PMPP) due to a mutation in calcium channel CACNA1S; p. R1239H hetero. Immunostaining for L-type calcium channels (LCaC) showed linear hyper-stained regions indicating proliferation of longitudinal t-tubules. The margin of vacuoles was positive for ryanodine receptor, LCaC, calsequestrin (CASQ) 1, CASQ 2, SR/ER Ca2+-ATPase (SERCA) 1, SERCA2, dysferlin, dystrophin, α-actinin, LC3, and LAMP 1. Electron microscopy indicated that the vacuoles mainly originated from the sarcoplasmic reticulum (SR). These findings indicate impairment of the muscle contraction system related to Ca2+ dynamics, remodeling of t-tubules and muscle fiber repair. We speculate that PMPP in patients with a CACNA1S mutation might start with abnormal SR function due to impaired LCaC. Subsequent induction of muscular contractile abnormalities and the vacuoles formed by fused SR in the repair process including autophagy might result in permanent myopathy. Our findings may facilitate prediction of the pathomechanisms of PMPP seen on morphological observation.
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Affiliation(s)
- Takamura Nagasaka
- Department of Neurology, Faculty of Medicine, University of Yamanashi, Chuou-city, Yamanashi, Japan
| | - Takanori Hata
- Department of Neurology, Faculty of Medicine, University of Yamanashi, Chuou-city, Yamanashi, Japan
| | - Kazumasa Shindo
- Department of Neurology, Faculty of Medicine, University of Yamanashi, Chuou-city, Yamanashi, Japan
| | - Yoshiki Adachi
- Department of Neurology, Matsue Medical Center, National Hospital Organization, Shimane, Japan
| | | | - Kayoko Saito
- Institute of Medical Genetics, Tokyo Women's University, Tokyo, Japan
| | - Yoshihisa Takiyama
- Department of Neurology, Faculty of Medicine, University of Yamanashi, Chuou-city, Yamanashi, Japan
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Sadeh TT, Black GC, Manson F. A Review of Genetic and Physiological Disease Mechanisms Associated With Cav1 Channels: Implications for Incomplete Congenital Stationary Night Blindness Treatment. Front Genet 2021; 12:637780. [PMID: 33584831 PMCID: PMC7876387 DOI: 10.3389/fgene.2021.637780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 01/12/2021] [Indexed: 11/13/2022] Open
Abstract
Calcium channels are crucial to a number of cellular functions. The high voltage-gated calcium channel family comprise four heteromeric channels (Cav1.1-1.4) that function in a similar manner, but that have distinct expression profiles. Three of the pore-forming α1 subunits are located on autosomes and the forth on the X chromosome, which has consequences for the type of pathogenic mutation and the disease mechanism associated with each gene. Mutations in this family of channels are associated with malignant hyperthermia (Cav1.1), various QT syndromes (Cav1.2), deafness (Cav1.3), and incomplete congenital stationary night blindness (iCSNB; Cav1.4). In this study we performed a bioinformatic analysis on reported mutations in all four Cav α1 subunits and correlated these with variant frequency in the general population, phenotype and the effect on channel conductance to produce a comprehensive composite Cav1 mutation analysis. We describe regions of mutation clustering, identify conserved residues that are mutated in multiple family members and regions likely to cause a loss- or gain-of-function in Cav1.4. Our research highlights that therapeutic treatments for each of the Cav1 channels will have to consider channel-specific mechanisms, especially for the treatment of X-linked iCSNB.
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Affiliation(s)
- Tal T Sadeh
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Graeme C Black
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom.,Manchester Centre for Genomic Medicine, Manchester Academic Health Sciences Centre, Manchester University NHS Foundation Trust, St Mary's Hospital, Manchester, United Kingdom
| | - Forbes Manson
- Division of Evolution and Genomic Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
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Desaphy JF, Altamura C, Vicart S, Fontaine B. Targeted Therapies for Skeletal Muscle Ion Channelopathies: Systematic Review and Steps Towards Precision Medicine. J Neuromuscul Dis 2021; 8:357-381. [PMID: 33325393 PMCID: PMC8203248 DOI: 10.3233/jnd-200582] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Skeletal muscle ion channelopathies include non-dystrophic myotonias (NDM), periodic paralyses (PP), congenital myasthenic syndrome, and recently identified congenital myopathies. The treatment of these diseases is mainly symptomatic, aimed at reducing muscle excitability in NDM or modifying triggers of attacks in PP. OBJECTIVE This systematic review collected the evidences regarding effects of pharmacological treatment on muscle ion channelopathies, focusing on the possible link between treatments and genetic background. METHODS We searched databases for randomized clinical trials (RCT) and other human studies reporting pharmacological treatments. Preclinical studies were considered to gain further information regarding mutation-dependent drug effects. All steps were performed by two independent investigators, while two others critically reviewed the entire process. RESULTS For NMD, RCT showed therapeutic benefits of mexiletine and lamotrigine, while other human studies suggest some efficacy of various sodium channel blockers and of the carbonic anhydrase inhibitor (CAI) acetazolamide. Preclinical studies suggest that mutations may alter sensitivity of the channel to sodium channel blockers in vitro, which has been translated to humans in some cases. For hyperkalemic and hypokalemic PP, RCT showed efficacy of the CAI dichlorphenamide in preventing paralysis. However, hypokalemic PP patients carrying sodium channel mutations may have fewer benefits from CAI compared to those carrying calcium channel mutations. Few data are available for treatment of congenital myopathies. CONCLUSIONS These studies provided limited information about the response to treatments of individual mutations or groups of mutations. A major effort is needed to perform human studies for designing a mutation-driven precision medicine in muscle ion channelopathies.
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Affiliation(s)
- Jean-François Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari Aldo Moro, Bari, Italy
| | - Savine Vicart
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, Assistance Publique Hôpitaux de Paris, Centre de Recherche en Myologie-UMR 974, Reference center in neuro-muscular channelopathies, Institute of Myology, Hôpital Universitaire Pitié-Salpêtrière, Paris, France
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Farooque U, Cheema AY, Kumar R, Saini G, Kataria S. Primary Periodic Paralyses: A Review of Etiologies and Their Pathogeneses. Cureus 2020; 12:e10112. [PMID: 33005530 PMCID: PMC7523540 DOI: 10.7759/cureus.10112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Periodic paralyses are a group of disorders characterized by episodes of muscle paralyses. They are mainly divided as primary (hereditary) and secondary (acquired) periodic paralyses. Primary periodic paralyses occur as a result of mutations in genes encoding subunits of muscle membrane channel proteins such as sodium, calcium, and potassium channels, resulting in impairment of their properties. Primary periodic paralyses are further classified on the basis of affected ion channels and other associated complications. Some of these periodic paralyses are hyperkalemic periodic paralysis (Na-channel mutation), hypokalemic periodic paralysis (Na- or Ca-channel mutation), Andersen’s syndrome (K-channel mutation), etc.
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Flucher BE. Skeletal muscle Ca V1.1 channelopathies. Pflugers Arch 2020; 472:739-754. [PMID: 32222817 PMCID: PMC7351834 DOI: 10.1007/s00424-020-02368-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/06/2020] [Accepted: 03/17/2020] [Indexed: 12/15/2022]
Abstract
CaV1.1 is specifically expressed in skeletal muscle where it functions as voltage sensor of skeletal muscle excitation-contraction (EC) coupling independently of its functions as L-type calcium channel. Consequently, all known CaV1.1-related diseases are muscle diseases and the molecular and cellular disease mechanisms relate to the dual functions of CaV1.1 in this tissue. To date, four types of muscle diseases are known that can be linked to mutations in the CACNA1S gene or to splicing defects. These are hypo- and normokalemic periodic paralysis, malignant hyperthermia susceptibility, CaV1.1-related myopathies, and myotonic dystrophy type 1. In addition, the CaV1.1 function in EC coupling is perturbed in Native American myopathy, arising from mutations in the CaV1.1-associated protein STAC3. Here, we first address general considerations concerning the possible roles of CaV1.1 in disease and then discuss the state of the art regarding the pathophysiology of the CaV1.1-related skeletal muscle diseases with an emphasis on molecular disease mechanisms.
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Affiliation(s)
- Bernhard E Flucher
- Department of Physiology and Medical Biophysics, Medical University Innsbruck, Schöpfstraße 41, A6020, Innsbruck, Austria.
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Allard B, Fuster C. When muscle Ca 2+ channels carry monovalent cations through gating pores: insights into the pathophysiology of type 1 hypokalaemic periodic paralysis. J Physiol 2018; 596:2019-2027. [PMID: 29572832 DOI: 10.1113/jp274955] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 03/12/2018] [Indexed: 12/22/2022] Open
Abstract
Patients suffering from type 1 hypokalaemic periodic paralysis (HypoPP1) experience attacks of muscle paralysis associated with hypokalaemia. The disease arises from missense mutations in the gene encoding the α1 subunit of the dihydropyridine receptor (DHPR), a protein complex anchored in the tubular membrane of skeletal muscle fibres which controls the release of Ca2+ from sarcoplasmic reticulum and also functions as a Ca2+ channel. The vast majority of mutations consist of the replacement of one of the outer arginines in S4 segments of the α1 subunit by neutral residues. Early studies have shown that muscle fibres from HypoPP1 patients are abnormally depolarized at rest in low K+ to the point of inducing muscle inexcitability. The relationship between HypoPP1 mutations and depolarization has long remained unknown. More recent investigations conducted in the closely structurally related voltage-gated Na+ and K+ channels have shown that comparable S4 arginine substitutions gave rise to elevated inward currents at negative potentials called gating pore currents. Experiments performed in muscle fibres from different models revealed such an inward resting current through HypoPP1 mutated Ca2+ channels. In mouse fibres transfected with HypoPP1 mutated channels, the elevated resting current was found to carry H+ for the R1239H arginine-to-histidine mutation in a S4 segment and Na+ for the V876E HypoPP1 mutation, which has the peculiarity of not being located in S4 segments. Muscle paralysis probably results from the presence of a gating pore current associated with hypokalaemia for both mutations, possibly aggravated by external acidosis for the R1239H mutation.
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Affiliation(s)
- Bruno Allard
- Institut NeuroMyoGene, Université de Lyon, Université Lyon 1, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France
| | - Clarisse Fuster
- Institut NeuroMyoGene, Université de Lyon, Université Lyon 1, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622 Villeurbanne, France
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Wu F, Quinonez M, DiFranco M, Cannon SC. Stac3 enhances expression of human Ca V1.1 in Xenopus oocytes and reveals gating pore currents in HypoPP mutant channels. J Gen Physiol 2018; 150:475-489. [PMID: 29386226 PMCID: PMC5839724 DOI: 10.1085/jgp.201711962] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 01/03/2018] [Indexed: 01/24/2023] Open
Abstract
Hypokalemic periodic paralysis (HypoPP) is thought to be caused by an aberrant inward current through the voltage sensors of mutant Na+ or Ca2+ channels. Wu et al. use Stac3 to enhance the membrane expression of two HypoPP CaV1.1 mutants in oocytes and find that both support gating pore currents. Mutations of CaV1.1, the pore-forming subunit of the L-type Ca2+ channel in skeletal muscle, are an established cause of hypokalemic periodic paralysis (HypoPP). However, functional assessment of HypoPP mutant channels has been hampered by difficulties in achieving sufficient plasma membrane expression in cells that are not of muscle origin. In this study, we show that coexpression of Stac3 dramatically increases the expression of human CaV1.1 (plus α2-δ1b and β1a subunits) at the plasma membrane of Xenopus laevis oocytes. In voltage-clamp studies with the cut-open oocyte clamp, we observe ionic currents on the order of 1 μA and gating charge displacements of ∼0.5–1 nC. Importantly, this high expression level is sufficient to ascertain whether HypoPP mutant channels are leaky because of missense mutations at arginine residues in S4 segments of the voltage sensor domains. We show that R528H and R528G in S4 of domain II both support gating pore currents, but unlike other R/H HypoPP mutations, R528H does not conduct protons. Stac3-enhanced membrane expression of CaV1.1 in oocytes increases the throughput for functional studies of disease-associated mutations and is a new platform for investigating the voltage-dependent properties of CaV1.1 without the complexity of the transverse tubule network in skeletal muscle.
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Affiliation(s)
- Fenfen Wu
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marbella Quinonez
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marino DiFranco
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Stephen C Cannon
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
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Fuster C, Perrot J, Berthier C, Jacquemond V, Allard B. Elevated resting H + current in the R1239H type 1 hypokalaemic periodic paralysis mutated Ca 2+ channel. J Physiol 2017; 595:6417-6428. [PMID: 28857175 DOI: 10.1113/jp274638] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/28/2017] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Missense mutations in the gene encoding the α1 subunit of the skeletal muscle voltage-gated Ca2+ channel induce type 1 hypokalaemic periodic paralysis, a poorly understood neuromuscular disease characterized by episodic attacks of paralysis associated with low serum K+ . Acute expression of human wild-type and R1239H HypoPP1 mutant α1 subunits in mature mouse muscles showed that R1239H fibres displayed Ca2+ currents of reduced amplitude and larger resting leak inward current increased by external acidification. External acidification also produced intracellular acidification at a higher rate in R1239H fibres and inhibited inward rectifier K+ currents. These data suggest that the R1239H mutation induces an elevated leak H+ current at rest flowing through a gating pore and could explain why paralytic attacks preferentially occur during the recovery period following muscle exercise. ABSTRACT Missense mutations in the gene encoding the α1 subunit of the skeletal muscle voltage-gated Ca2+ channel induce type 1 hypokalaemic periodic paralysis, a poorly understood neuromuscular disease characterized by episodic attacks of paralysis associated with low serum K+ . The present study aimed at identifying the changes in muscle fibre electrical properties induced by acute expression of the R1239H hypokalaemic periodic paralysis human mutant α1 subunit of Ca2+ channels in a mature muscle environment to better understand the pathophysiological mechanisms involved in this disorder. We transferred genes encoding wild-type and R1239H mutant human Ca2+ channels into hindlimb mouse muscle by electroporation and combined voltage-clamp and intracellular pH measurements on enzymatically dissociated single muscle fibres. As compared to fibres expressing wild-type α1 subunits, R1239H mutant-expressing fibres displayed Ca2+ currents of reduced amplitude and a higher resting leak inward current that was increased by external acidification. External acidification also produced intracellular acidification at a higher rate in R1239H fibres and inhibited inward rectifier K+ currents. These data indicate that the R1239H mutation induces an elevated leak H+ current at rest flowing through a gating pore created by the mutation and that external acidification favours onset of muscle paralysis by potentiating H+ depolarizing currents and inhibiting resting inward rectifier K+ currents. Our results could thus explain why paralytic attacks preferentially occur during the recovery period following intense muscle exercise.
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Affiliation(s)
- Clarisse Fuster
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622, Villeurbanne, France
| | - Jimmy Perrot
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622, Villeurbanne, France
| | - Christine Berthier
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622, Villeurbanne, France
| | - Vincent Jacquemond
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622, Villeurbanne, France
| | - Bruno Allard
- Institut NeuroMyoGene, Université Lyon 1, Université de Lyon, UMR CNRS 5310, Inserm U1217, 43 bd du 11 Novembre 1918, 69622, Villeurbanne, France
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Abstract
Familial disorders of skeletal muscle excitability were initially described early in the last century and are now known to be caused by mutations of voltage-gated ion channels. The clinical manifestations are often striking, with an inability to relax after voluntary contraction (myotonia) or transient attacks of severe weakness (periodic paralysis). An essential feature of these disorders is fluctuation of symptoms that are strongly impacted by environmental triggers such as exercise, temperature, or serum K(+) levels. These phenomena have intrigued physiologists for decades, and in the past 25 years the molecular lesions underlying these disorders have been identified and mechanistic studies are providing insights for therapeutic strategies of disease modification. These familial disorders of muscle fiber excitability are "channelopathies" caused by mutations of a chloride channel (ClC-1), sodium channel (NaV1.4), calcium channel (CaV1.1), and several potassium channels (Kir2.1, Kir2.6, and Kir3.4). This review provides a synthesis of the mechanistic connections between functional defects of mutant ion channels, their impact on muscle excitability, how these changes cause clinical phenotypes, and approaches toward therapeutics.
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Affiliation(s)
- Stephen C Cannon
- Department of Physiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
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Yang B, Yang Y, Tu W, Shen Y, Dong Q. A rare case of unilateral adrenal hyperplasia accompanied by hypokalaemic periodic paralysis caused by a novel dominant mutation in CACNA1S: features and prognosis after adrenalectomy. BMC Urol 2014; 14:96. [PMID: 25430699 PMCID: PMC4259161 DOI: 10.1186/1471-2490-14-96] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Accepted: 11/20/2014] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Acute hypokalaemic paralysis is characterised by acute flaccid muscle weakness and has a complex aetiological spectrum. Herein we report, for the first time, a case of unilateral adrenal hyperplasia accompanied by hypokalaemic periodic paralysis type I resulting from a novel dominant mutation in CACNA1S. We present the clinical features and prognosis after adrenalectomy in this case. CASE PRESENTATION A 43-year-old Han Chinese male presented with severe hypokalaemic paralysis that remitted after taking oral potassium. The patient had suffered from periodic attacks of hypokalaemic paralysis for more than 20 years. A computed tomography (CT) scan of the abdomen showed a nodular mass on the left adrenal gland, although laboratory examination revealed the patient had not developed primary aldosteronism. The patient underwent a left adrenalectomy 4 days after admission, and the pathological examination further confirmed a 1.1 cm benign nodule at the periphery of the adrenal gland. Three months after the adrenalectomy, a paralytic attack recurred and the patient asked for assistance from the Department of Medical Genetics. His family history showed that two uncles, one brother, and a nephew also had a history of periodic paralysis, although their symptoms were milder. The patient's CACNA1S and SCN4A genes were sequenced, and a novel missense mutation, c.1582C > T (p.Arg528Cys), in CACNA1S was detected. Detection of the mutation in five adult male family members, including three with periodic paralysis and two with no history of the disease, indicated that this mutation caused hypokalaemic periodic paralysis type I in his family. Follow-up 2 years after adrenalectomy showed that the serum potassium concentration was increased between paralyses and the number and severity of paralytic attacks were significantly decreased. CONCLUSION We identified a novel dominant mutation, c.1582C > T (p.Arg528Cys), in CACNA1S that causes hypokalaemic periodic paralysis. The therapeutic effect of adrenalectomy indicated that unilateral adrenal hyperplasia might make paralytic attacks more serious and more frequent by decreasing serum potassium. This finding suggests that the surgical removal of hyperplastic tissues might relieve the symptoms of patients with severe hypokalaemic paralysis caused by other incurable diseases, even if the adrenal lesion does not cause primary aldosteronism.
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Affiliation(s)
| | | | | | | | - Qiang Dong
- Department of Urology, West China Hospital, Sichuan University, Chengdu 610041, China.
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Simms BA, Zamponi GW. Neuronal voltage-gated calcium channels: structure, function, and dysfunction. Neuron 2014; 82:24-45. [PMID: 24698266 DOI: 10.1016/j.neuron.2014.03.016] [Citation(s) in RCA: 420] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Voltage-gated calcium channels are the primary mediators of depolarization-induced calcium entry into neurons. There is great diversity of calcium channel subtypes due to multiple genes that encode calcium channel α1 subunits, coassembly with a variety of ancillary calcium channel subunits, and alternative splicing. This allows these channels to fulfill highly specialized roles in specific neuronal subtypes and at particular subcellular loci. While calcium channels are of critical importance to brain function, their inappropriate expression or dysfunction gives rise to a variety of neurological disorders, including, pain, epilepsy, migraine, and ataxia. This Review discusses salient aspects of voltage-gated calcium channel function, physiology, and pathophysiology.
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Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
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Frank CA. How voltage-gated calcium channels gate forms of homeostatic synaptic plasticity. Front Cell Neurosci 2014; 8:40. [PMID: 24592212 PMCID: PMC3924756 DOI: 10.3389/fncel.2014.00040] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/28/2014] [Indexed: 01/15/2023] Open
Abstract
Throughout life, animals face a variety of challenges such as developmental growth, the presence of toxins, or changes in temperature. Neuronal circuits and synapses respond to challenges by executing an array of neuroplasticity paradigms. Some paradigms allow neurons to up- or downregulate activity outputs, while countervailing ones ensure that outputs remain within appropriate physiological ranges. A growing body of evidence suggests that homeostatic synaptic plasticity (HSP) is critical in the latter case. Voltage-gated calcium channels gate forms of HSP. Presynaptically, the aggregate data show that when synapse activity is weakened, homeostatic signaling systems can act to correct impairments, in part by increasing calcium influx through presynaptic CaV2-type channels. Increased calcium influx is often accompanied by parallel increases in the size of active zones and the size of the readily releasable pool of presynaptic vesicles. These changes coincide with homeostatic enhancements of neurotransmitter release. Postsynaptically, there is a great deal of evidence that reduced network activity and loss of calcium influx through CaV1-type calcium channels also results in adaptive homeostatic signaling. Some adaptations drive presynaptic enhancements of vesicle pool size and turnover rate via retrograde signaling, as well as de novo insertion of postsynaptic neurotransmitter receptors. Enhanced calcium influx through CaV1 after network activation or single cell stimulation can elicit the opposite response-homeostatic depression via removal of excitatory receptors. There exist intriguing links between HSP and calcium channelopathies-such as forms of epilepsy, migraine, ataxia, and myasthenia. The episodic nature of some of these disorders suggests alternating periods of stable and unstable function. Uncovering information about how calcium channels are regulated in the context of HSP could be relevant toward understanding these and other disorders.
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Affiliation(s)
- C Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine Iowa City, IA, USA
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Bandschapp O, Iaizzo PA. Pathophysiologic and anesthetic considerations for patients with myotonia congenita or periodic paralyses. Paediatr Anaesth 2013; 23:824-33. [PMID: 23802937 DOI: 10.1111/pan.12217] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/29/2013] [Indexed: 12/13/2022]
Abstract
Myotonia congenita and periodic paralyses are hereditary skeletal muscle channelopathies. In these disorders, various channel defects in the sarcolemma lead to a severely disturbed membrane excitability of the affected skeletal muscles. The clinical picture can range from severe myotonic reactions (e.g., masseter spasm, opisthotonus) to attacks of weakness and paralysis. Provided here is a short overview of the pathomechanisms behind such wide-ranging phenotypic presentations in these patients, followed by recommendations concerning the management of anesthesia in such populations.
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Affiliation(s)
- Oliver Bandschapp
- Department of Anesthesia, Surgical Intensive Care, Prehospital Emergency Medicine and Pain Therapy, University Hospital Basel, Basel, Switzerland.
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Wu F, Mi W, Hernández-Ochoa EO, Burns DK, Fu Y, Gray HF, Struyk AF, Schneider MF, Cannon SC. A calcium channel mutant mouse model of hypokalemic periodic paralysis. J Clin Invest 2012. [PMID: 23187123 DOI: 10.1172/jci66091] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Hypokalemic periodic paralysis (HypoPP) is a familial skeletal muscle disorder that presents with recurrent episodes of severe weakness lasting hours to days associated with reduced serum potassium (K+). HypoPP is genetically heterogeneous, with missense mutations of a calcium channel (Ca(V)1.1) or a sodium channel (Na(V)1.4) accounting for 60% and 20% of cases, respectively. The mechanistic link between Ca(V)1.1 mutations and the ictal loss of muscle excitability during an attack of weakness in HypoPP is unknown. To address this question, we developed a mouse model for HypoPP with a targeted Ca(V)1.1 R528H mutation. The Ca(V)1.1 R528H mice had a HypoPP phenotype for which low K+ challenge produced a paradoxical depolarization of the resting potential, loss of muscle excitability, and weakness. A vacuolar myopathy with dilated transverse tubules and disruption of the triad junctions impaired Ca2+ release and likely contributed to the mild permanent weakness. Fibers from the Ca(V)1.1 R528H mouse had a small anomalous inward current at the resting potential, similar to our observations in the Na(V)1.4 R669H HypoPP mouse model. This "gating pore current" may be a common mechanism for paradoxical depolarization and susceptibility to HypoPP arising from missense mutations in the S4 voltage sensor of either calcium or sodium channels.
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Affiliation(s)
- Fenfen Wu
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813, USA
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Jurkat-Rott K, Groome J, Lehmann-Horn F. Pathophysiological role of omega pore current in channelopathies. Front Pharmacol 2012; 3:112. [PMID: 22701429 PMCID: PMC3372090 DOI: 10.3389/fphar.2012.00112] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Accepted: 05/23/2012] [Indexed: 12/12/2022] Open
Abstract
In voltage-gated cation channels, a recurrent pattern for mutations is the neutralization of positively charged residues in the voltage-sensing S4 transmembrane segments. These mutations cause dominant ion channelopathies affecting many tissues such as brain, heart, and skeletal muscle. Recent studies suggest that the pathogenesis of associated phenotypes is not limited to alterations in the gating of the ion-conducting alpha pore. Instead, aberrant so-called omega currents, facilitated by the movement of mutated S4 segments, also appear to contribute to symptoms. Surprisingly, these omega currents conduct cations with varying ion selectivity and are activated in either a hyperpolarized or depolarized voltage range. This review gives an overview of voltage sensor channelopathies in general and focuses on pathogenesis of skeletal muscle S4 disorders for which current knowledge is most advanced.
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Rajakulendran S, Kaski D, Hanna MG. Neuronal P/Q-type calcium channel dysfunction in inherited disorders of the CNS. Nat Rev Neurol 2012; 8:86-96. [PMID: 22249839 DOI: 10.1038/nrneurol.2011.228] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The past two decades have witnessed the emergence of a new and expanding field of neurological diseases--the genetic ion channelopathies. These disorders arise from mutations in genes that encode ion channel subunits, and manifest as paroxysmal attacks involving the brain or spinal cord, and/or muscle. The voltage-gated P/Q-type calcium channel (P/Q channel) is highly expressed in the cerebellum, hippocampus and cortex of the mammalian brain. The P/Q channel has a fundamental role in mediating fast synaptic transmission at central and peripheral nerve terminals. Autosomal dominant mutations in the CACNA1A gene, which encodes voltage-gated P/Q-type calcium channel subunit α(1) (the principal pore-forming subunit of the P/Q channel) are associated with episodic and progressive forms of cerebellar ataxia, familial hemiplegic migraine, vertigo and epilepsy. This Review considers, from both a clinical and genetic perspective, the various neurological phenotypes arising from inherited P/Q channel dysfunction, with a focus on recent advances in the understanding of the pathogenetic mechanisms underlying these disorders.
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Affiliation(s)
- Sanjeev Rajakulendran
- Medical Research Council Center for Neuromuscular Diseases, Box 102, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK
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Kim H, Hwang H, Cheong HI, Park HW. Hypokalemic periodic paralysis; two different genes responsible for similar clinical manifestations. KOREAN JOURNAL OF PEDIATRICS 2011; 54:473-6. [PMID: 22253645 PMCID: PMC3254894 DOI: 10.3345/kjp.2011.54.11.473] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 04/07/2011] [Accepted: 06/25/2011] [Indexed: 11/27/2022]
Abstract
Primary hypokalemic periodic paralysis (HOKPP) is an autosomal dominant disorder manifesting as recurrent periodic flaccid paralysis and concomitant hypokalemia. HOKPP is divided into type 1 and type 2 based on the causative gene. Although 2 different ion channels have been identified as the molecular genetic cause of HOKPP, the clinical manifestations between the 2 groups are similar. We report the cases of 2 patients with HOKPP who both presented with typical clinical manifestations, but with mutations in 2 different genes (CACNA1Sp.Arg528His and SCN4A p.Arg672His). Despite the similar clinical manifestations, there were differences in the response to acetazolamide treatment between certain genotypes of SCN4A mutations and CACNA1S mutations. We identified p.Arg672His in the SCN4A gene of patient 2 immediately after the first attack through a molecular genetic testing strategy. Molecular genetic diagnosis is important for genetic counseling and selecting preventive treatment.
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Affiliation(s)
- Hunmin Kim
- Department of Pediatrics, Seoul National University Bundang Hospital, Seongnam, Korea
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Striessnig J, Bolz HJ, Koschak A. Channelopathies in Cav1.1, Cav1.3, and Cav1.4 voltage-gated L-type Ca2+ channels. Pflugers Arch 2010; 460:361-74. [PMID: 20213496 PMCID: PMC2883925 DOI: 10.1007/s00424-010-0800-x] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 02/03/2010] [Accepted: 02/05/2010] [Indexed: 12/24/2022]
Abstract
Voltage-gated Ca2+ channels couple membrane depolarization to Ca2+-dependent intracellular signaling events. This is achieved by mediating Ca2+ ion influx or by direct conformational coupling to intracellular Ca2+ release channels. The family of Cav1 channels, also termed L-type Ca2+ channels (LTCCs), is uniquely sensitive to organic Ca2+ channel blockers and expressed in many electrically excitable tissues. In this review, we summarize the role of LTCCs for human diseases caused by genetic Ca2+ channel defects (channelopathies). LTCC dysfunction can result from structural aberrations within their pore-forming alpha1 subunits causing hypokalemic periodic paralysis and malignant hyperthermia sensitivity (Cav1.1 alpha1), incomplete congenital stationary night blindness (CSNB2; Cav1.4 alpha1), and Timothy syndrome (Cav1.2 alpha1; reviewed separately in this issue). Cav1.3 alpha1 mutations have not been reported yet in humans, but channel loss of function would likely affect sinoatrial node function and hearing. Studies in mice revealed that LTCCs indirectly also contribute to neurological symptoms in Ca2+ channelopathies affecting non-LTCCs, such as Cav2.1 alpha1 in tottering mice. Ca2+ channelopathies provide exciting disease-related molecular detail that led to important novel insight not only into disease pathophysiology but also to mechanisms of channel function.
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Affiliation(s)
- Jörg Striessnig
- Pharmacology and Toxicology, Institute of Pharmacy, and Center for Molecular Biosciences, University of Innsbruck, Peter-Mayr-Strasse 1, 6020, Innsbruck, Austria.
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Abstract
Mutations of voltage-gated ion channels cause several channelopathies of skeletal muscle, which present clinically with myotonia, periodic paralysis, or a combination of both. Expression studies have revealed both loss-of-function and gain-of-function defects for the currents passed by mutant channels. In many cases, these functional changes could be mechanistically linked to the defects of fibre excitability underlying myotonia or periodic paralysis. One remaining enigma was the basis for depolarization-induced weakness in hypokalaemic periodic paralysis (HypoPP) arising from mutations in either sodium or calcium channels. Curiously, 14 of 15 HypoPP mutations are at arginines in S4 voltage sensors, and recent observations show that these substitutions support an alternative pathway for ion conduction, the gating pore, that may be the source of the aberrant depolarization during an attack of paralysis.
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Affiliation(s)
- Stephen C Cannon
- Department of Neurology and Program in Neuroscience, 5323 Harry Hines Blvd, UT Southwestern Medical Center, Dallas, TX 75390-8813, USA.
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Matthews E, Hanna MG. Muscle channelopathies: does the predicted channel gating pore offer new treatment insights for hypokalaemic periodic paralysis? J Physiol 2010; 588:1879-86. [PMID: 20123788 DOI: 10.1113/jphysiol.2009.186627] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Hypokalaemic periodic paralysis (hypoPP) is the archetypal skeletal muscle channelopathy caused by dysfunction of one of two sarcolemmal ion channels, either the sodium channel Nav1.4 or the calcium channel Cav1.1. Clinically, hypoPP is characterised by episodes of often severe flaccid muscle paralysis, in which the muscle fibre membrane becomes electrically inexcitable, and which may be precipitated by low serum potassium levels. Initial functional characterisation of hypoPP mutations failed to adequately explain the pathomechanism of the disease. Recently, as more pathogenic mutations involving loss of positive charge have been identified in the S4 segments of either channel, the hypothesis that an abnormal gating pore current may be important has emerged. Such an aberrant gating pore current has been identified in mutant Nav1.4 channels and has prompted potentially significant advances in this area. The carbonic anhydrase inhibitor acetazolamide has been used as a treatment for hypokalaemic periodic paralysis for over 40 years but its precise therapeutic mechanism of action is unclear. In this review we summarise the recent advances in the understanding of the molecular pathophysiology of hypoPP and consider how these may relate to the reported beneficial effects of acetazolamide. We also consider potential areas for future therapeutic development.
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Affiliation(s)
- E Matthews
- MRC Centre for Neuromuscular Disease, University College London Hospitals/University College London, UCL, Institute of Neurology, London, UK
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Parness J, Bandschapp O, Girard T. The Myotonias and Susceptibility to Malignant Hyperthermia. Anesth Analg 2009; 109:1054-64. [DOI: 10.1213/ane.0b013e3181a7c8e5] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Struyk AF, Markin VS, Francis D, Cannon SC. Gating pore currents in DIIS4 mutations of NaV1.4 associated with periodic paralysis: saturation of ion flux and implications for disease pathogenesis. ACTA ACUST UNITED AC 2008; 132:447-64. [PMID: 18824591 PMCID: PMC2553391 DOI: 10.1085/jgp.200809967] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
S4 voltage–sensor mutations in CaV1.1 and NaV1.4 channels cause the human muscle disorder hypokalemic periodic paralysis (HypoPP). The mechanism whereby these mutations predispose affected sarcolemma to attacks of sustained depolarization and loss of excitability is poorly understood. Recently, three HypoPP mutations in the domain II S4 segment of NaV1.4 were shown to create accessory ionic permeation pathways, presumably extending through the aqueous gating pore in which the S4 segment resides. However, there are several disparities between reported gating pore currents from different investigators, including differences in ionic selectivity and estimates of current amplitude, which in turn have important implications for the pathological relevance of these aberrant currents. To clarify the features of gating pore currents arising from different DIIS4 mutants, we recorded gating pore currents created by HypoPP missense mutations at position R666 in the rat isoform of Nav1.4 (the second arginine from the outside, at R672 in human NaV1.4). Extensive measurements were made for the index mutation, R666G, which created a gating pore that was permeable to K+ and Na+. This current had a markedly shallow slope conductance at hyperpolarized voltages and robust inward rectification, even when the ionic gradient strongly favored outward ionic flow. These characteristics were accounted for by a barrier model incorporating a voltage-gated permeation pathway with a single cation binding site oriented near the external surface of the electrical field. The amplitude of the R666G gating pore current was similar to the amplitude of a previously described proton-selective current flowing through the gating pore in rNaV1.4-R663H mutant channels. Currents with similar amplitude and cation selectivity were also observed in R666S and R666C mutant channels, while a proton-selective current was observed in R666H mutant channels. These results add support to the notion that HypoPP mutations share a common biophysical profile comprised of a low-amplitude inward current at the resting potential that may contribute to the pathological depolarization during attacks of weakness.
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Affiliation(s)
- Arie F Struyk
- Department of Neurology, University of Texas-Southwestern Medical Center, Dallas, TX 75390, USA.
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Abstract
OBJECTIVE To review the current knowledge about primary periodic paralyses (PPs). RESULTS Periodic paralyses are a heterogeneous group of disorders, clinically characterized by episodes of flaccid muscle weakness, occurring at irregular intervals. PPs are divided into primary (hereditary) and secondary (acquired) forms of which the secondary PPs are much more common than the primary PPs. Primary PPs are due to mutations in genes encoding for subunits of channel proteins of the skeletal muscle membrane, such as the muscular sodium, potassium or calcium channels, or the SCL4A1 protein. Primary PPs include entities such as hyperkalemic PP, hypokalemic PP, paramyotonia congenita von Eulenburg, Andersen's syndrome, thyrotoxic PP, distal renal tubular acidosis, X-linked episodic muscle weakness syndrome and congenital myasthenic syndromes. Attacks of weakness or myotonia may be triggered or enhanced by vigorous exercise, cold, potassium-rich food, emotional stress, drugs such as glucocorticosteroids, insulin or diuretics, or pregnancy. Depending on the pathomechanism, episodes of weakness may respond to mild exercise, ingestion of potassium, carbohydrates, salbutamol, calcium gluconate, thiazide diuretics, carboanhydrase inhibitors, such as acetazolamide or dichlorphenamine, and episodes may be prevented by avoidance of potassium-rich food, or drugs, which increase serum potassium. CONCLUSION This review presents and discusses current knowledge and recent advances in the etiology, molecular genetics, genotype-phenotype correlations, pathogenesis, diagnosis and treatment of primary PPs.
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Affiliation(s)
- J Finsterer
- Neurological Department, Krankenanstalt Rudolfstiftung, Vienna, Austria.
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Abstract
Periodic paralyses are rare diseases characterized by severe episodes of muscle weakness concomitant to variations in blood potassium levels. It is thus usual to differentiate hypokalemic, normokalemic, and hyperkalemic periodic paralysis. Except for thyrotoxic hypokalemic periodic paralysis and periodic paralyses secondary to permanent changes of blood potassium levels, all of these diseases are of genetic origin, transmitted with an autosomal-dominant mode of inheritance. Periodic paralyses are channelopathies, that is, diseases caused by mutations in genes encoding ion channels. The culprit genes encode for potassium, calcium, and sodium channels. Mutations of the potassium and calcium channel genes cause periodic paralysis of the same type (Andersen-Tawil syndrome or hypokalemic periodic paralysis). In contrast, distinct mutations in the muscle sodium channel gene are responsible for all different types of periodic paralyses (hyper-, normo-, and hypokalemic). The physiological consequences of the mutations have been studied by patch-clamp techniques and electromyography (EMG). Globally speaking, ion channel mutations modify the cycle of muscle membrane excitability which results in a loss of function (paralysis). Clinical physiological studies using EMG have shown a good correlation between symptoms and EMG parameters, enabling the description of patterns that greatly enhance molecular diagnosis accuracy. The understanding of the genetics and pathophysiology of periodic paralysis has contributed to refine and rationalize therapeutic intervention and will be without doubts the basis of further advances.
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Affiliation(s)
- Bertrand Fontaine
- INSERM, UMR 546, Paris, France; Université Pierre et Marie Curie-Paris 6, UMR S546 and Assistance Publique-Hôpitaux de Paris, Centre de référence des canalopathies musculaires, Groupe Hospitalier Pitié-Salpêtrière, Paris, France
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Abstract
Since the initial identification of native calcium currents, significant progress has been made towards our understanding of the molecular and cellular contributions of voltage-gated calcium channels in multiple physiological processes. Moreover, we are beginning to comprehend their pathophysiological roles through both naturally occurring channelopathies in humans and mice and through targeted gene deletions. The data illustrate that small perturbations in voltage-gated calcium channel function induced by genetic alterations can affect a wide variety of mammalian developmental, physiological and behavioral functions. At least in those instances wherein the channelopathies can be attributed to gain-of-function mechanisms, the data point towards new therapeutic strategies for developing highly selective calcium channel antagonists.
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Fontaine B, Fournier E, Sternberg D, Vicart S, Tabti N. Hypokalemic periodic paralysis: a model for a clinical and research approach to a rare disorder. Neurotherapeutics 2007; 4:225-32. [PMID: 17395132 DOI: 10.1016/j.nurt.2007.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Rare diseases have attracted little attention in the past from physicians and researchers. The situation has recently changed for several reasons. First, patient associations have successfully advocated their cause to institutions and governments. They were able to argue that, taken together, rare diseases affect approximately 10% of the population in developed countries. Second, almost 80% of rare diseases are of genetic origin. Advances in genetics have enabled the identification of the causative genes. Unprecedented financial support has been dedicated to research on rare diseases, as well as to the development of referral centers aimed at improving the quality of care. This expenditure of resources is justified by the experience in cystic fibrosis, which demonstrated that improved care delivered by specialized referral centers resulted in a dramatic increase of life expectancy. Moreover, clinical referral centers offer the unique possibility of developing high quality clinical research studies, not otherwise possible because of the geographic dispersion of patients. This is the case in France where national referral centers for rare diseases were created, including one for muscle channelopathies. The aim of this center is to develop appropriate care, clinical research, and teaching on periodic paralysis and myotonia. In this review, we plan to demonstrate how research has improved our knowledge of hypokalemic periodic paralysis and the way we evaluate, advise, and treat patients. We also advocate for the establishment of international collaborations, which are mandatory for the follow-up of cohorts and conduct of definitive therapeutic trials in rare diseases.
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Affiliation(s)
- Bertrand Fontaine
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR S546, Paris, France.
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29
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Felix R. Calcium channelopathies. Neuromolecular Med 2007; 8:307-18. [PMID: 16775382 DOI: 10.1385/nmm:8:3:307] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2005] [Revised: 11/30/1999] [Accepted: 01/20/2006] [Indexed: 11/11/2022]
Abstract
Intracellular calcium ([Ca2+]i) is highly regulated in eukaryotic cells. The free [Ca2+]i is approximately four orders of magnitude less than that in the extracellular environment. It is, therefore, an electrochemical gradient favoring Ca2+ entry, and transient cellular activation increasing Ca2+ permeability will lead to a transient increase in [Ca2+]i. These transient rises of [Ca2+]i trigger or regulate diverse intracellular events, including metabolic processes, muscle contraction, secretion of hormones and neurotransmitters, cell differentiation, and gene expression. Hence, changes in [Ca2+]i act as a second messenger system coordinating modifications in the external environment with intracellular processes. Notably, information on the molecular genetics of the membrane channels responsible for the influx of Ca2+ ions has led to the discovery that mutations in these proteins are linked to human disease. Ca2+ channel dysfunction is now known to be the basis for several neurological and muscle disorders such as migraine, ataxia, and periodic paralysis. In contrast to other types of genetic diseases, Ca2+ channelopathies can be studied with precision by electrophysiological methods, and in some cases, the results have been highly rewarding with a biophysical phenotype that correlates with the ultimate clinical phenotype. This review outlines recent advances in genetic, molecular, and pathophysiological aspects of human Ca2+ channelopathies.
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Affiliation(s)
- Ricardo Felix
- Department of Cell Biology, Center for Research and Advanced Studies, National Polytechnic Institute (Cinvestav-IPN), Mexico City, Mexico.
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Kuzmenkin A, Hang C, Kuzmenkina E, Jurkat-Rott K. Gating of the HypoPP-1 mutations: II. Effects of a calcium-channel agonist BayK 8644. Pflugers Arch 2007; 454:605-14. [PMID: 17333247 DOI: 10.1007/s00424-007-0228-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Revised: 11/23/2006] [Accepted: 01/31/2007] [Indexed: 11/28/2022]
Abstract
L-type calcium-channel mutations causing hypokalemic periodic paralysis type 1 (HypoPP-1) have pronounced "loss-of-function" features and stabilize the less-selective second open state O(2), as we demonstrated in the companion paper. Here, we compared the effects of the L-type calcium-channel activator (+/-)BayK 8644 (BayK) on the heterologously expressed wild-type (WT) calcium channel, rabbit Cav1.2 HypoPP-1 analogs, and two double mutants (R650H/R1362H, R650H/R1362G). Our goal was to elucidate (1) whether the "loss-of-function" in HypoPP-1 can be compensated by BayK application, (2) how the less-selective open state is affected by BayK in WT and HypoPP-1 mutants, as well as (3) to gain an insight into BayK mechanism of action. Ionic currents were examined by whole-cell patch-clamp and analyzed by the global-fitting procedure. Our results imply that (1) BayK promotes channel activation, but equalized the differences among the WT and mutants, thus attenuating HypoPP-related effects on activation and deactivation; (2) BayK binds to the first open state O(1), and then serves as a catalyst for O(2) formation; (3) binding of BayK is impaired in the HypoPP mutants, thus affecting the formation of the less-selective second open state; (4) BayK affects cooperativity between the single HypoPP-1 mutations at all stages of the channel gating; and (5) BayK favoring of O(2) lowers calcium-channel selectivity.
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Affiliation(s)
- Alexey Kuzmenkin
- Department of Applied Physiology, University of Ulm, 89069 Ulm, Germany
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Kuzmenkin A, Hang C, Kuzmenkina E, Jurkat-Rott K. Gating of the HypoPP-1 mutations: I. Mutant-specific effects and cooperativity. Pflugers Arch 2007; 454:495-505. [PMID: 17333249 DOI: 10.1007/s00424-007-0225-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2006] [Revised: 12/15/2006] [Accepted: 01/29/2007] [Indexed: 11/25/2022]
Abstract
Hypokalemic periodic paralysis type 1 (HypoPP-1) is a hereditary muscular disorder caused by point mutations in the gene encoding the voltage-gated Ca(2+) channel alpha subunit (Ca(v)1.1). Despite extensive research, the results on HypoPP-1 mutations are minor and controversial, as it is difficult to analyse Ca(2+) channel activation macroscopically due to an existence of two open states. In this study, we heterologously expressed the wild-type and HypoPP-1 mutations introduced into the rabbit cardiac Ca(2+) channel (R650H, R1362H, R1362G) in HEK-293 cells. To examine the cooperative effects of the mutations on channel gating, we expressed two double mutants (R650H/R1362H, R650H/R1362G). We performed whole-cell patch-clamp and, to obtain more information, applied a global fitting procedure whereby several current traces elicited by different potentials were simultaneously fit to the kinetic model containing four closed, two open and two inactivated states. We found that all HypoPP-1 mutations have "loss-of-function" features: D4/S4 mutations shift the equilibrium to the closed states, which results in reduced open probability, shorter openings and, therefore, in smaller currents, and the D2/S4 mutant slows the activation. In addition, HypoPP-1 histidine mutants favored the second open state O(2) with a possibly lower channel selectivity. Cooperativity between the D2/S4 and D4/S4 HypoPP-1 mutations manifested in dominant effects of the D4/S4 mutations on kinetics of the double mutants, suggesting different roles of D2/S4 and D4/S4 voltage sensors in the gating of voltage-gated calcium channels.
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Affiliation(s)
- Alexey Kuzmenkin
- Department of Applied Physiology, University of Ulm, 89081, Ulm, Germany.
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32
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Voltage-gated calcium channels, calcium signaling, and channelopathies. CALCIUM - A MATTER OF LIFE OR DEATH 2007. [DOI: 10.1016/s0167-7306(06)41005-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Jurkat-Rott K, Lehmann-Horn F. Paroxysmal muscle weakness: the familial periodic paralyses. J Neurol 2006; 253:1391-8. [PMID: 17139526 DOI: 10.1007/s00415-006-0339-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Accepted: 06/26/2006] [Indexed: 11/28/2022]
Abstract
The familial periodic paralyses (PP) were commonly considered to be benign diseases since frequency and severity of the paralytic attacks decrease in adulthood. However, with increasing age, a third of the patients develop permanent weakness and muscle degeneration with fatty replacement. Another complication, cardiac arrhythmia, can result from the dyskalemia during paralytic attacks. The familial PP are typical dominant ion channelopathies: the function of the mutant muscular channel is compensated in the interictal state but defective under certain conditions which then cause flaccid weakness. A triggering factor is the level of serum potassium, the extracellular ion decisive for membrane excitability. In hyper- and hypokalemic periodic paralysis, the mutations are specifically located in the voltage-gated sodium and calcium channels which are essential for action potential generation or excitation-contraction coupling. The common mechanism for the membrane inexcitability during paralytic attacks is a transient membrane depolarization that inactivates the sodium channels which are then no longer available for action potential generation. For the third PP type, the Andersen syndrome, the responsible gene is also expressed in cardiac muscle, and, independently of paralytic attacks, the hazard of ventricular arrhythmias is inherent. The gene product, an inwardly rectifying potassium channel, is responsible for maintaining the resting membrane potential, and all known mutations cause dominant-negative effects on the tetrameric channel complexes. In this article the clinical consequences of the mutations and the therapeutic strategies for all three types of PP are reported.
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Affiliation(s)
- Karin Jurkat-Rott
- Dept of Applied Physiology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
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Abstract
Ion channelopathies are a diverse array of human disorders caused by mutations in ion channel genes. This review focuses on the pathogenic mechanisms of channelopathies affecting skeletal muscle and brain arising from mutations of voltage-gated ion channels and fast ligand-gated ion channels expressed at the surface membrane. Derangements in channel function alter the electrical excitability of the cell and thereby increase susceptibility to transient symptomatic attacks including myasthenia, periodic paralysis, myotonic stiffness, seizures, headache, dyskinesia, or episodic ataxia. Although these disorders are rare, they stand out as exemplary cases for which disease pathogenesis can be traced from a point mutation to altered protein function, to altered cellular activity, and to clinical phenotype. The study of these disorders has provided insights on channel structure-function relations, the physiological roles of ion channels, and rational approaches toward therapeutic intervention for many disorders of cellular excitability.
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Affiliation(s)
- Stephen C Cannon
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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Jurkat-Rott K, Lehmann-Horn F. Muscle channelopathies and critical points in functional and genetic studies. J Clin Invest 2005; 115:2000-9. [PMID: 16075040 PMCID: PMC1180551 DOI: 10.1172/jci25525] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Muscle channelopathies are caused by mutations in ion channel genes, by antibodies directed against ion channel proteins, or by changes of cell homeostasis leading to aberrant splicing of ion channel RNA or to disturbances of modification and localization of channel proteins. As ion channels constitute one of the only protein families that allow functional examination on the molecular level, expression studies of putative mutations have become standard in confirming that the mutations cause disease. Functional changes may not necessarily prove disease causality of a putative mutation but could be brought about by a polymorphism instead. These problems are addressed, and a more critical evaluation of the underlying genetic data is proposed.
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Oz M, Alptekin A, Tchugunova Y, Dinc M. Effects of saturated long-chain N-acylethanolamines on voltage-dependent Ca2+ fluxes in rabbit T-tubule membranes. Arch Biochem Biophys 2005; 434:344-51. [PMID: 15639235 DOI: 10.1016/j.abb.2004.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Revised: 11/04/2004] [Indexed: 11/29/2022]
Abstract
The effects of saturated long-chain (C: 16-22) N-acylethanolamines and a series of saturated fatty acids with the same length of carbon chains were investigated on depolarization-induced (45)Ca(2+) fluxes mediated by voltage-dependent Ca(2+) channels in transverse tubule membrane vesicles from rabbit skeletal muscle. Vesicles were loaded with (45)Ca(2+) and membrane potentials were generated by establishing potassium gradients across the vesicle using the ionophore valinomycin. Arachidonoylethanolamide and docosaenoylethanolamide but not palmitoylethanolamide and stearoylethanolamide (all 10 microM) caused a significant inhibition of depolarization-induced (45)Ca(2+) fluxes and specific binding of [(3)H]Isradipine to transverse tubule membranes. On the other hand, saturated fatty acids including palmitic, stearic, arachidic, and docosanoic acids (all 10 microM) were ineffective in functional and radioligand binding experiments. Additional experiments using endocannabinoid metabolites suggested that whereas ethanolamine and arachidic acids were ineffective, arachidonoylethanolamide inhibited Ca(2+) effluxes and specific binding of [(3)H]Isradipine. Further studies indicated that only those fatty acids containing ethanolamine as a head group and having a chain length of more than 18 carbons were effective in inhibiting depolarization-induced Ca(2+) effluxes and specific binding of [(3)H]Isradipine. In conclusion, results indicate that depending on the chain length and the head group of fatty acid, N-acylethanolamines have differential effects on the function of voltage-dependent Ca(2+) channels and on the specific binding of [(3)H]Isradipine in skeletal muscle membranes.
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Affiliation(s)
- Murat Oz
- National Institute on Drug Abuse, Cellular Neurobiology Section, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
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Wang Q, Liu M, Xu C, Tang Z, Liao Y, Du R, Li W, Wu X, Wang X, Liu P, Zhang X, Zhu J, Ren X, Ke T, Wang Q, Yang J. Novel CACNA1S mutation causes autosomal dominant hypokalemic periodic paralysis in a Chinese family. J Mol Med (Berl) 2005; 83:203-8. [PMID: 15726306 PMCID: PMC1579762 DOI: 10.1007/s00109-005-0638-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2004] [Accepted: 12/06/2004] [Indexed: 10/25/2022]
Abstract
Hypokalemic periodic paralysis (HypoPP) is an autosomal dominant disorder which is characterized by periodic attacks of muscle weakness associated with a decrease in the serum potassium level. The skeletal muscle calcium channel alpha-subunit gene CACNA1S is a major disease-causing gene for HypoPP, however, only three specific HypoPP-causing mutations, Arg528His, Arg1,239His and Arg1,239Gly, have been identified in CACNA1S to date. In this study, we studied a four-generation Chinese family with HypoPP with 43 living members and 19 affected individuals. Linkage analysis showed that the causative mutation in the family is linked to the CACNA1S gene with a LOD score of 6.7. DNA sequence analysis revealed a heterozygous C to G transition at nucleotide 1,582, resulting in a novel 1,582C-->G (Arg528Gly) mutation. The Arg528Gly mutation co-segregated with all affected individuals in the family, and was not present in 200 matched normal controls. The penetrance of the Arg528Gly mutation was complete in male mutation carriers, however, a reduced penetrance of 83% (10/12) was observed in female carriers. No differences were detected for age-at-onset and severity of the disease (frequency of symptomatic attacks per year) between male and female patients. Oral intake of KCl is effective in blocking the symptomatic attacks. This study identifies a novel Arg528Gly mutation in the CACNA1S gene that causes HypoPP in a Chinese family, expands the spectrum of mutations causing HypoPP, and demonstrates a gender difference in the penetrance of the disease.
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Affiliation(s)
- Qiufen Wang
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- Institute of Cardiovascular Disease, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- Center for Molecular Genetics, Department of Molecular Cardiology, Lerner Research Institute, The Cleveland Clinic Foundation, and Department of Molecular Medicine and Department of Pathology, Case Western Reserve University, Cleveland, OH, 44195, USA
- e-mail:
| | - Mugen Liu
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Chunsheng Xu
- Neurology, Binzhou Medical College Hospital, Binzhou, Shandong, 256603, China
| | - Zhaohui Tang
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Yuhua Liao
- Institute of Cardiovascular Disease, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Rong Du
- Institute of Cardiovascular Disease, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
| | - Wei Li
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xiaoyan Wu
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xu Wang
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Ping Liu
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xianqin Zhang
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Jianfang Zhu
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Xiang Ren
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Tie Ke
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
| | - Qing Wang
- Center for Molecular Genetics, Department of Molecular Cardiology, Lerner Research Institute, The Cleveland Clinic Foundation, and Department of Molecular Medicine and Department of Pathology, Case Western Reserve University, Cleveland, OH, 44195, USA
| | - Junguo Yang
- Center for Human Genome Research Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China
- Institute of Cardiovascular Disease, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China
- e-mail:
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Oz M, Tchugunova Y, Dinc M. Differential effects of endogenous and synthetic cannabinoids on voltage-dependent calcium fluxes in rabbit T-tubule membranes: comparison with fatty acids. Eur J Pharmacol 2004; 502:47-58. [PMID: 15464089 DOI: 10.1016/j.ejphar.2004.08.052] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 08/09/2004] [Accepted: 08/27/2004] [Indexed: 10/26/2022]
Abstract
The effects of cannabinoid receptor ligands including 2-arachidonoylglycerol, R-methanandamide, Delta9-THC (Delta9-tetrahydrocannabinol), WIN 55,212-2 [4,5-dihydro-2-methyl-4(4-morpholinylmethyl)-1-(1-naphthalenylcarbonyl)-6H-pyrrolo[3,2,1ij]quinolin-6-one], CP 55,940 ([1alpha,2beta-(R)-5alpha]-(-)-5-(1,1-dimethyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl-phenol]) and a series of fatty acids on depolarization-induced Ca2+ effluxes mediated by voltage-dependent Ca2+ channels were investigated comparatively in transverse tubule membrane vesicles from rabbit skeletal muscle. Vesicles were loaded with 45Ca2+ and membrane potentials were generated by establishing potassium gradients across the vesicle using the ionophore valinomycin. Endocannabinoids, 2-arachidonoylglycerol and R-methanandamide (all 10 microM), inhibited depolarization-induced Ca2+ effluxes and specific binding of [3H]PN 200-110 (isradipine) to transverse tubule membranes. On the other hand, synthetic cannabinoids, including CP 55,940, WIN 55,212-2, and Delta9-THC (all 10 microM), were ineffective. Additional experiments using endocannabinoid metabolites suggested that whereas ethanolamine and glycerol were ineffective, arachidonic acid inhibited Ca2+ effluxes and specific binding of [3H]PN 200-110. Further studies indicated that only those fatty acids containing two or more double bonds were effective in inhibiting depolarization-induced Ca2+ effluxes and specific binding of [3H]PN 200-110. These results indicate that endocannabinoids, but not synthetic cannabinoids, directly inhibit the function of voltage-dependent calcium channels (VDCCs) and modulate the specific binding of calcium channel ligands of the dihydropyridine (DHP) class.
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Affiliation(s)
- Murat Oz
- National Institute on Drug Abuse, National Institutes of Health, DHHS, Intramural Research Program, Cellular Neurobiology Branch, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
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Jurkat-Rott K, Lehmann-Horn F. Electrophysiology and molecular pharmacology of muscle channelopathies. Rev Neurol (Paris) 2004; 160:S43-8. [PMID: 15269660 DOI: 10.1016/s0035-3787(04)71005-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As voltage-gated ion channels are essential for membrane excitation, it is not surprising that mutations in the respective channel genes cause diseases characterised by altered cell excitability. Skeletal muscle was the first tIssue in which such diseases, namely the myotonias and periodic paralyses, were recognised as ion channelopathies. The detection of the functional defect that is brought about by the disease-causing mutation is essential for the understanding of the pathology. Much progress on the road to this aim was achieved by the combination of molecular biology and electrophysiological patch clamp techniques. The functional expression of the mutations in expression systems allows to study the functional alterations of mutant channels and to develop new strategies for the therapy of ion channelopathies, e.g. by designing drugs that specifically suppress the effects of malfunctioning channels.
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Affiliation(s)
- K Jurkat-Rott
- Department of Physiology, Ulm University, Ulm, Germany
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Ikezoe K, Furuya H, Ohyagi Y, Osoegawa M, Nishino I, Nonaka I, Kira JI. Dysferlin expression in tubular aggregates: their possible relationship to endoplasmic reticulum stress. Acta Neuropathol 2003; 105:603-9. [PMID: 12664320 DOI: 10.1007/s00401-003-0686-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2002] [Accepted: 01/15/2003] [Indexed: 10/25/2022]
Abstract
Dysferlin is a newly identified sarcolemmal protein related to Miyoshi myopathy and limb-girdle muscular dystrophy. Although its function is still unknown, it is inferred from the presence of C2 domains and a transmembrane domain in its sequence that dysferlin may be expressed or located not only at the sarcolemma but also in other membranous organelles to interact with Ca(2+). Tubular aggregates (TAs) are derived from sarcoplasmic reticulum (SR) and found in various myopathies, especially in those related to disturbed intra-sarcoplasmic Ca(2+) homeostasis. To clarify the expression of dysferlin in TAs and the relationship among TA formation, dysferlin expression, and endoplasmic reticulum (ER) stress, we examined the expression of dysferlin and other sarcolemmal proteins by immunohistochemistry in 12 muscle biopsy specimens with TAs from 11 cases of periodic paralysis and 1 case of myalgia/cramps syndrome. Moreover, the expression of glucose-regulated protein 78 (GRP78) and GRP94, which are up-regulated under ER stress, was also examined by immunohistochemistry and immunoblotting. TAs showed strong expression of dysferlin. GRP78 and GRP94 were also intensely expressed in TAs. Total amounts of GRP78 and GRP94 were significantly increased in muscles with TAs compared with normal controls. These results indicate that muscles with TAs seem to be under ER stress, probably resulting from disturbed intra-sarcoplasmic Ca(2+) homeostasis. Strong expression of dysferlin in TAs suggests the possibility that it is located not only at the sarcolemma but also in the SR, at least in the pathological conditions.
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Affiliation(s)
- Koji Ikezoe
- Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University 60, 812-8582, Fukuoka, Japan.
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Chapter 23 Skeletal muscle channelopathies: myotonias, periodic paralyses and malignant hyperthermia. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-4231(09)70133-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Jospin M, Jacquemond V, Mariol MC, Ségalat L, Allard B. The L-type voltage-dependent Ca2+ channel EGL-19 controls body wall muscle function in Caenorhabditis elegans. J Cell Biol 2002; 159:337-48. [PMID: 12391025 PMCID: PMC2173050 DOI: 10.1083/jcb.200203055] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2002] [Revised: 08/30/2002] [Accepted: 09/08/2002] [Indexed: 11/22/2022] Open
Abstract
Caenorhabditis elegans is a powerful model system widely used to investigate the relationships between genes and complex behaviors like locomotion. However, physiological studies at the cellular level have been restricted by the difficulty to dissect this microscopic animal. Thus, little is known about the properties of body wall muscle cells used for locomotion. Using in situ patch clamp technique, we show that body wall muscle cells generate spontaneous spike potentials and develop graded action potentials in response to injection of positive current of increasing amplitude. In the presence of K+ channel blockers, membrane depolarization elicited Ca2+ currents inhibited by nifedipine and exhibiting Ca2+-dependent inactivation. Our results give evidence that the Ca2+ channel involved belongs to the L-type class and corresponds to EGL-19, a putative Ca2+ channel originally thought to be a member of this class on the basis of genomic data. Using Ca2+ fluorescence imaging on patch-clamped muscle cells, we demonstrate that the Ca2+ transients elicited by membrane depolarization are under the control of Ca2+ entry through L-type Ca2+ channels. In reduction of function egl-19 mutant muscle cells, Ca2+ currents displayed slower activation kinetics and provided a significantly smaller Ca2+ entry, whereas the threshold for Ca2+ transients was shifted toward positive membrane potentials.
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Affiliation(s)
- Maëlle Jospin
- Physiologie des Eléments Excitables, Centre National de la Recherche Scientifique UMR 5123, Université C. Bernard Lyon I, 43 boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
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Abstract
Ion channels are complex proteins that span the lipid bilayer of the cell membrane, where they orchestrate the electrical signals necessary for normal function of the central nervous system, peripheral nerve, and both skeletal and cardiac muscle. The role of ion channel defects in the pathogenesis of numerous disorders, many of them neuromuscular, has become increasingly apparent over the last decade. Progress in molecular biology has allowed cloning and expression of genes that encode channel proteins, while comparable advances in biophysics, including patch-clamp electrophysiology and related techniques, have made the study of expressed proteins at the level of single channel molecules possible. Understanding the molecular basis of ion channel function and dysfunction will facilitate both the accurate classification of these disorders and the rational development of specific therapeutic interventions. This review encompasses clinical, genetic, and pathophysiological aspects of ion channels disorders, focusing mainly on those with neuromuscular manifestations.
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Affiliation(s)
- Kleopas A Kleopa
- Department of Neurology, University of Pennsylvania School of Medicine, 122 College Hall, Philadelphia, PA 19104, USA
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Abstract
The periodic paralyses are rare disorders of skeletal muscle characterized by episodic attacks of weakness due to intermittent failure of electrical excitability. Familial forms of periodic paralysis are all caused by mutations in genes coding for voltage-gated ion channels. New discoveries in the past 2 years have broadened our views on the diversity of phenotypes produced by mutations of a single channel gene and have led to the identification of potassium channel mutations, in addition to those previously found in sodium and calcium channels. This review focuses on the clinical features, molecular genetic defects, and pathophysiologic mechanisms that underlie familial periodic paralysis.
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Affiliation(s)
- Stephen C Cannon
- Department of Neurology, Massachusetts General Hospital/Wellman 423, 50 Blossom Street, Boston, MA 02114, USA.
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Kuzmenkin A, Muncan V, Jurkat-Rott K, Hang C, Lerche H, Lehmann-Horn F, Mitrovic N. Enhanced inactivation and pH sensitivity of Na(+) channel mutations causing hypokalaemic periodic paralysis type II. Brain 2002; 125:835-43. [PMID: 11912116 DOI: 10.1093/brain/awf071] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hypokalaemic periodic paralysis (hypoPP) is a dominantly inherited muscle disorder characterized by episodes of flaccid weakness. Previous genetic studies revealed mutations in the voltage-gated calcium channel alpha1-subunit (CACNA1S gene) in families with hypoPP (type I). Electrophysiological studies on these mutants in different expression systems could not explain the pathophysiology of the disease. In addition, several mutations (Arg669His, Arg672His, Arg672Gly and Arg672Ser) in the voltage sensor of the skeletal muscle sodium channel alpha-subunit (SCN4A gene) have been found in families with hypoPP (type II). For Arg672Gly/His a fast inactivation defect was described, and for Arg669His an impairment of slow inactivation was reported. Except for the substitution for serine, we have now expressed all mutants in a human cell-line and studied them electrophysiologically. Patch-clamp recordings show an enhanced fast inactivation for all three mutations, whereas two of them reveal enhanced slow inactivation. This may reduce the number of functional sodium channels at resting membrane potential and contribute to the long-lasting periods of paralysis experienced by hypoPP patients. The gating of both histidine mutants (Arg669His, Arg672His) can be modulated by changes of extra- or intracellular pH. The inactivation defects of Arg669His and Arg672His can be alleviated by low pH to a significant degree, suggesting that the decrease of pH in muscle cells (e.g. during muscle work) might lead to an auto-compensation of functional defects. This may explain a delay or prevention of paralytic attacks in patients by slight physical activity. Moreover, the histidine residues may be the target for a potential therapeutic action by acetazolamide.
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Affiliation(s)
- Alexey Kuzmenkin
- Department of Applied Physiology, University of Ulm, D-89069 Ulm, Germany
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Dias da Silva MR, Cerutti JM, Tengan CH, Furuzawa GK, Vieira TCA, Gabbai AA, Maciel RMB. Mutations linked to familial hypokalaemic periodic paralysis in the calcium channel alpha1 subunit gene (Cav1.1) are not associated with thyrotoxic hypokalaemic periodic paralysis. Clin Endocrinol (Oxf) 2002; 56:367-75. [PMID: 11940049 DOI: 10.1046/j.1365-2265.2002.01481.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate whether patients with thyrotoxic hypokalaemic periodic paralysis (THPP) have the same molecular defect in the calcium channel gene described in familial hypokalaemic periodic paralysis (FHPP), as the symptoms of both diseases are comparable, we analysed, in patients with THPP, the presence of mutations R528H, R1239H and R1239G on the S4 voltage-sensing transmembrane segment of the alpha1 subunit of the calcium channel gene (Cav1.1). DESIGN AND PATIENTS Genomic DNA was extracted from peripheral blood from 14 patients with THPP, 13 sporadic cases and one with a family history. An FHPP family was selected as a positive control. The exons bearing the described mutations were amplified by PCR, screened by single-strand conformation polymorphism (SSCP), and further sequenced. MEASUREMENTS THPP was diagnosed both clinically and through laboratory tests, all patients having elevated levels of thyroid hormones (T4, T3 or free T4), suppressed TSH and plasma potassium below 3 small middle dot5 mmol/l. RESULTS No evidence of the described mutations was found in patients with THPP. Furthermore, we did not detect any mutations in any of the four full S4 voltage-sensing transmembrane segments of Cav1 small middle dot1 (DIS4, DIIS4, DIIIS4 and DIVS4) by direct sequencing. However, close to the R528H mutation, we identified two single nucleotide polymorphisms at nucleotides 1551 and 1564 in both familial and sporadic cases with THPP. In addition, we were able to detect the R528H mutation in the DIIS4 transmembrane segment in all members of the FHPP family. CONCLUSION Mutations linked to familial hypokalaemic periodic paralysis in the calcium channel alpha1 subunit gene (Cav1.1) are not associated with thyrotoxic hypokalaemic periodic paralysis. However, polymorphisms in nucleotides 1551 and 1564 in the exon 11 were found in patients with familial hypokalaemic periodic paralysis and thyrotoxic hypokalaemic periodic paralysis in higher frequency than in controls. The polymorphisms identified within the Cav1.1 gene are associated with thyrotoxic hypokalaemic periodic paralysis and represent a novel finding.
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Affiliation(s)
- Magnus R Dias da Silva
- Department of Medicine, Laboratory of Molecular Endocrinology, Division of Endocrinology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil
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Lehmann-Horn F, Jurkat-Rott K, Rüdel R. Periodic paralysis: understanding channelopathies. Curr Neurol Neurosci Rep 2002; 2:61-9. [PMID: 11898585 DOI: 10.1007/s11910-002-0055-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Familial periodic paralyses are typical channelopathies (i.e., caused by functional disturbances of ion channel proteins). The episodes of flaccid muscle weakness observed in these disorders are due to underexcitability of sarcolemma leading to a silent electromyogram and the lack of action potentials even upon electrical stimulation. Interictally, ion channel malfunction is well compensated, so that special exogenous or endogenous triggers are required to produce symptoms in the patients. An especially obvious trigger is the level of serum potassium (K+), the ion responsible for resting membrane potential and degree of excitability. The clinical symptoms can be caused by mutations in genes coding for ion channels that mediate different functions for maintaining the resting potential or propagating the action potential, the basis of excitability. The phenotype is determined by the type of functional defect brought about by the mutations, rather than the channel effected, because the contrary phenotypes hyperkalemic periodic paralysis (HyperPP) and hypokalemic periodic paralysis (HypoPP) may be caused by point mutations in the same gene. Still, the common mechanism for inexcitability in all known episodic-weakness phenotypes is a long-lasting depolarization that inactivates sodium ion (Na+) channels, initiating the action potential.
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Affiliation(s)
- Frank Lehmann-Horn
- Department of Physiology, Ulm University, Albert-Einstein-Allee II, Ulm 89069, Germany.
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Desaphy JF, De Luca A, Tricarico D, Pierno S, Conte Camerino D. Ion channels in muscle and cardiac hereditary diseases: from gene dysfunction to pharmacological therapy. 10-11 March 2000, Bari, Italy. Neuromuscul Disord 2001; 11:583-8. [PMID: 11525889 DOI: 10.1016/s0960-8966(01)00189-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- J F Desaphy
- Unit of Pharmacology, Department of Pharmaco-Biology, Faculty of Pharmacy, University of Bari, Via Orabona 4 - campus, 70125 Bari, Italy
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Tricarico D, Barbieri M, Conte Camerino D. Acetazolamide opens the muscular K Ca 2+ channel: A novel mechanism of action that may explain the therapeutic effect of the drug in hypokalemic periodic paralysis. Ann Neurol 2001. [DOI: 10.1002/1531-8249(200009)48:3<304::aid-ana4>3.0.co;2-a] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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The human skeletal muscle Na channel mutation R669H associated with hypokalemic periodic paralysis enhances slow inactivation. J Neurosci 2001. [PMID: 11102465 DOI: 10.1523/jneurosci.20-23-08610.2000] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Missense mutations of the human skeletal muscle voltage-gated Na channel (hSkM1) underlie a variety of diseases, including hyperkalemic periodic paralysis (HyperPP), paramyotonia congenita, and potassium-aggravated myotonia. Another disorder of sarcolemmal excitability, hypokalemic periodic paralysis (HypoPP), which is usually caused by missense mutations of the S4 voltage sensors of the L-type Ca channel, was associated recently in one family with a mutation in the outermost arginine of the IIS4 voltage sensor (R669H) of hSkM1 (Bulman et al., 1999). Intriguingly, an arginine-to-histidine mutation at the homologous position in the L-type Ca(2+) channel (R528H) is a common cause of HypoPP. We have studied the gating properties of the hSkM1-R669H mutant Na channel experimentally in human embryonic kidney cells and found that it has no significant effects on activation or fast inactivation but does cause an enhancement of slow inactivation. R669H channels exhibit an approximately 10 mV hyperpolarized shift in the voltage dependence of slow inactivation and a twofold to fivefold prolongation of recovery after prolonged depolarization. In contrast, slow inactivation is often disrupted in HyperPP-associated Na channel mutants. These results demonstrate that, in R669H-associated HypoPP, enhanced slow inactivation does not preclude, and may contribute to, prolonged attacks of weakness and add support to previous evidence implicating the IIS4 voltage sensor in slow-inactivation gating.
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