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Manville RW, Alfredo Freites J, Sidlow R, Tobias DJ, Abbott GW. Native American ataxia medicines rescue ataxia-linked mutant potassium channel activity via binding to the voltage sensing domain. Nat Commun 2023; 14:3281. [PMID: 37280215 DOI: 10.1038/s41467-023-38834-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 05/17/2023] [Indexed: 06/08/2023] Open
Abstract
There are currently no drugs known to rescue the function of Kv1.1 voltage-gated potassium channels carrying loss-of-function sequence variants underlying the inherited movement disorder, Episodic Ataxia 1 (EA1). The Kwakwaka'wakw First Nations of the Pacific Northwest Coast used Fucus gardneri (bladderwrack kelp), Physocarpus capitatus (Pacific ninebark) and Urtica dioica (common nettle) to treat locomotor ataxia. Here, we show that extracts of these plants enhance wild-type Kv1.1 current, especially at subthreshold potentials. Screening of their constituents revealed that gallic acid and tannic acid similarly augment wild-type Kv1.1 current, with submicromolar potency. Crucially, the extracts and their constituents also enhance activity of Kv1.1 channels containing EA1-linked sequence variants. Molecular dynamics simulations reveal that gallic acid augments Kv1.1 activity via a small-molecule binding site in the extracellular S1-S2 linker. Thus, traditional Native American ataxia treatments utilize a molecular mechanistic foundation that can inform small-molecule approaches to therapeutically correcting EA1 and potentially other Kv1.1-linked channelopathies.
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Affiliation(s)
- Rían W Manville
- Bioelectricity Laboratory, Dept. of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
| | | | | | - Douglas J Tobias
- Department of Chemistry, University of California, Irvine, CA, USA
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Dept. of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA.
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2
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Paulhus K, Glasscock E. Novel Genetic Variants Expand the Functional, Molecular, and Pathological Diversity of KCNA1 Channelopathy. Int J Mol Sci 2023; 24:8826. [PMID: 37240170 PMCID: PMC10219020 DOI: 10.3390/ijms24108826] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/11/2023] [Accepted: 05/13/2023] [Indexed: 05/28/2023] Open
Abstract
The KCNA1 gene encodes Kv1.1 voltage-gated potassium channel α subunits, which are crucial for maintaining healthy neuronal firing and preventing hyperexcitability. Mutations in the KCNA1 gene can cause several neurological diseases and symptoms, such as episodic ataxia type 1 (EA1) and epilepsy, which may occur alone or in combination, making it challenging to establish simple genotype-phenotype correlations. Previous analyses of human KCNA1 variants have shown that epilepsy-linked mutations tend to cluster in regions critical for the channel's pore, whereas EA1-associated mutations are evenly distributed across the length of the protein. In this review, we examine 17 recently discovered pathogenic or likely pathogenic KCNA1 variants to gain new insights into the molecular genetic basis of KCNA1 channelopathy. We provide the first systematic breakdown of disease rates for KCNA1 variants in different protein domains, uncovering potential location biases that influence genotype-phenotype correlations. Our examination of the new mutations strengthens the proposed link between the pore region and epilepsy and reveals new connections between epilepsy-related variants, genetic modifiers, and respiratory dysfunction. Additionally, the new variants include the first two gain-of-function mutations ever discovered for KCNA1, the first frameshift mutation, and the first mutations located in the cytoplasmic N-terminal domain, broadening the functional and molecular scope of KCNA1 channelopathy. Moreover, the recently identified variants highlight emerging links between KCNA1 and musculoskeletal abnormalities and nystagmus, conditions not typically associated with KCNA1. These findings improve our understanding of KCNA1 channelopathy and promise to enhance personalized diagnosis and treatment for individuals with KCNA1-linked disorders.
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Affiliation(s)
| | - Edward Glasscock
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, USA;
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3
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Erro R, Magrinelli F, Bhatia KP. Paroxysmal movement disorders: Paroxysmal dyskinesia and episodic ataxia. HANDBOOK OF CLINICAL NEUROLOGY 2023; 196:347-365. [PMID: 37620078 DOI: 10.1016/b978-0-323-98817-9.00033-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
Paroxysmal movement disorders have traditionally been classified into paroxysmal dyskinesia (PxD), which consists in attacks of involuntary movements (mainly dystonia and/or chorea) without loss of consciousness, and episodic ataxia (EA), which features spells of cerebellar dysfunction with or without interictal neurological manifestations. In this chapter, PxD will be discussed first according to the trigger-based classification, thus reviewing clinical, genetic, and molecular features of paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia, and paroxysmal exercise-induced dyskinesia. EA will be presented thereafter according to their designated gene or genetic locus. Clinicogenetic similarities among paroxysmal movement disorders have progressively emerged, which are herein highlighted along with growing evidence that their pathomechanisms overlap those of epilepsy and migraine. Advances in our comprehension of the biological pathways underlying paroxysmal movement disorders, which involve ion channels as well as proteins associated with the vesical synaptic cycle or implicated in neuronal energy metabolism, may represent the cornerstone for defining a shared pathophysiologic framework and developing target-specific therapies.
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Affiliation(s)
- Roberto Erro
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", Neuroscience Section, University of Salerno, Baronissi, Salerno, Italy
| | - Francesca Magrinelli
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Kailash P Bhatia
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
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4
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McGahan K, Keener J. Modeling the kinetics of heteromeric potassium channels. Front Cell Neurosci 2022; 16:1036813. [DOI: 10.3389/fncel.2022.1036813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 10/24/2022] [Indexed: 11/11/2022] Open
Abstract
Mechanistic mathematical modeling has long been used as a tool for answering questions in cellular physiology. To mathematically describe cellular processes such as cell excitability, volume regulation, neurotransmitter release, and hormone secretion requires accurate descriptions of ion channel kinetics. One class of ion channels currently lacking a physiological model framework is the class of channels built with multiple different potassium protein subunits called heteromeric voltage gated potassium channels. Here we present a novel mathematical model for heteromeric potassium channels that captures both the number and type of protein subunits present in each channel. Key model assumptions are validated by showing our model is the reduction of a Markov model and through observations about voltage clamp data. We then show our model's success in replicating kinetic properties of concatemeric channels with different numbers of Kv1.1 and Kv1.2 subunits. Finally, through comparisons with multiple expression experiments across multiple voltage gated potassium families, we use the model to make predictions about the importance and effect of genetic mutations in heteromeric channel formation.
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5
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Dinoi G, Morin M, Conte E, Mor Shaked H, Coppola MA, D’Adamo MC, Elpeleg O, Liantonio A, Hartmann I, De Luca A, Blunck R, Russo A, Imbrici P. Clinical and Functional Study of a De Novo Variant in the PVP Motif of Kv1.1 Channel Associated with Epilepsy, Developmental Delay and Ataxia. Int J Mol Sci 2022; 23:ijms23158079. [PMID: 35897654 PMCID: PMC9331732 DOI: 10.3390/ijms23158079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/15/2022] [Accepted: 07/18/2022] [Indexed: 02/05/2023] Open
Abstract
Mutations in the KCNA1 gene, encoding the voltage-gated potassium channel Kv1.1, have been associated with a spectrum of neurological phenotypes, including episodic ataxia type 1 and developmental and epileptic encephalopathy. We have recently identified a de novo variant in KCNA1 in the highly conserved Pro-Val-Pro motif within the pore of the Kv1.1 channel in a girl affected by early onset epilepsy, ataxia and developmental delay. Other mutations causing severe epilepsy are located in Kv1.1 pore domain. The patient was initially treated with a combination of antiepileptic drugs with limited benefit. Finally, seizures and ataxia control were achieved with lacosamide and acetazolamide. The aim of this study was to functionally characterize Kv1.1 mutant channel to provide a genotype–phenotype correlation and discuss therapeutic options for KCNA1-related epilepsy. To this aim, we transfected HEK 293 cells with Kv1.1 or P403A cDNAs and recorded potassium currents through whole-cell patch-clamp. P403A channels showed smaller potassium currents, voltage-dependent activation shifted by +30 mV towards positive potentials and slower kinetics of activation compared with Kv1.1 wild-type. Heteromeric Kv1.1+P403A channels, resembling the condition of the heterozygous patient, confirmed a loss-of-function biophysical phenotype. Overall, the functional characterization of P403A channels correlates with the clinical symptoms of the patient and supports the observation that mutations associated with severe epileptic phenotype cluster in a highly conserved stretch of residues in Kv1.1 pore domain. This study also strengthens the beneficial effect of acetazolamide and sodium channel blockers in KCNA1 channelopathies.
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Affiliation(s)
- Giorgia Dinoi
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
| | - Michael Morin
- Department of Physics, Université de Montréal, Montreal, QC H3C 3J7, Canada; (M.M.); (R.B.)
- CIRCA, Center for Interdisciplinary Research on Brain and Learning, Université de Montréal, Montreal, QC H3C 3J7, Canada
| | - Elena Conte
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
| | - Hagar Mor Shaked
- Department of Genetics, Hadassah Medical Center, Jerusalem 91120, Israel; (H.M.S.); (O.E.)
| | - Maria Antonietta Coppola
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
| | | | - Orly Elpeleg
- Department of Genetics, Hadassah Medical Center, Jerusalem 91120, Israel; (H.M.S.); (O.E.)
| | - Antonella Liantonio
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
| | - Inbar Hartmann
- Pediatric Neurology Clinic, Shamir Medical Center (Assaf Harofeh), Zerifin 7033001, Israel;
| | - Annamaria De Luca
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
| | - Rikard Blunck
- Department of Physics, Université de Montréal, Montreal, QC H3C 3J7, Canada; (M.M.); (R.B.)
- CIRCA, Center for Interdisciplinary Research on Brain and Learning, Université de Montréal, Montreal, QC H3C 3J7, Canada
- Department of Pharmacology and Physiology, Université de Montréal, Montreal, QC H3C 3J7, Canada
| | - Angelo Russo
- Child Neurology Unit, IRCCS, Institute of Neurological Sciences of Bologna, 40139 Bologna, Italy;
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy; (G.D.); (E.C.); (M.A.C.); (A.L.); (A.D.L.)
- Correspondence:
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Musculoskeletal Features without Ataxia Associated with a Novel de novo Mutation in KCNA1 Impairing the Voltage Sensitivity of Kv1.1 Channel. Biomedicines 2021; 9:biomedicines9010075. [PMID: 33466780 PMCID: PMC7829709 DOI: 10.3390/biomedicines9010075] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/02/2021] [Accepted: 01/06/2021] [Indexed: 02/06/2023] Open
Abstract
The KCNA1 gene encodes the α subunit of the voltage-gated Kv1.1 potassium channel that critically regulates neuronal excitability in the central and peripheral nervous systems. Mutations in KCNA1 have been classically associated with episodic ataxia type 1 (EA1), a movement disorder triggered by physical and emotional stress. Additional features variably reported in recent years include epilepsy, myokymia, migraine, paroxysmal dyskinesia, hyperthermia, hypomagnesemia, and cataplexy. Interestingly, a few individuals with neuromyotonia, either isolated or associated with skeletal deformities, have been reported carrying variants in the S2–S3 transmembrane segments of Kv1.1 channels in the absence of any other symptoms. Here, we have identified by whole-exome sequencing a novel de novo variant, T268K, in KCNA1 in a boy displaying recurrent episodes of neuromyotonia, muscle hypertrophy, and skeletal deformities. Through functional analysis in heterologous cells and structural modeling, we show that the mutation, located at the extracellular end of the S3 helix, causes deleterious effects, disrupting Kv1.1 function by altering the voltage dependence of activation and kinetics of deactivation, likely due to abnormal interactions with the voltage sensor in the S4 segment. Our study supports previous evidence suggesting that specific residues within the S2 and S3 segments of Kv1.1 result in a distinctive phenotype with predominant musculoskeletal presentation.
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Koźmiński W, Pera J. Involvement of the Peripheral Nervous System in Episodic Ataxias. Biomedicines 2020; 8:biomedicines8110448. [PMID: 33105744 PMCID: PMC7690566 DOI: 10.3390/biomedicines8110448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/04/2022] Open
Abstract
Episodic ataxias comprise a group of inherited disorders, which have a common hallmark—transient attacks of ataxia. The genetic background is heterogeneous and the causative genes are not always identified. Furthermore, the clinical presentation, including intraictal and interictal symptoms, as well as the retention and progression of neurological deficits, is heterogeneous. Spells of ataxia can be accompanied by other symptoms—mostly from the central nervous system. However, in some of episodic ataxias involvement of peripheral nervous system is a part of typical clinical picture. This review intends to provide an insight into involvement of peripheral nervous system in episodic ataxias.
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Affiliation(s)
- Wojciech Koźmiński
- Department of Neurology, University Hospital, ul. Jakubowskiego 2, 30-688 Krakow, Poland;
| | - Joanna Pera
- Department of Neurology, Jagiellonian University Medical College, ul. Botaniczna 3, 31-503 Krakow, Poland
- Correspondence:
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8
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A Common Kinetic Property of Mutations Linked to Episodic Ataxia Type 1 Studied in the Shaker Kv Channel. Int J Mol Sci 2020; 21:ijms21207602. [PMID: 33066705 PMCID: PMC7589002 DOI: 10.3390/ijms21207602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 12/21/2022] Open
Abstract
(1) Background: Episodic ataxia type 1 is caused by mutations in the KCNA1 gene encoding for the voltage-gated potassium channel Kv1.1. There have been many mutations in Kv1.1 linked to episodic ataxia reported and typically investigated by themselves or in small groups. The aim of this article is to determine whether we can define a functional parameter common to all Kv1.1 mutants that have been linked to episodic ataxia. (2) Methods: We introduced the disease mutations linked to episodic ataxia in the drosophila analog of Kv1.1, the Shaker Kv channel, and expressed the channels in Xenopus oocytes. Using the cut-open oocyte technique, we characterized the gating and ionic currents. (3) Results: We found that the episodic ataxia mutations variably altered the different gating mechanisms described for Kv channels. The common characteristic was a conductance voltage relationship and inactivation shifted to less polarized potentials. (4) Conclusions: We suggest that a combination of a prolonged action potential and slowed and incomplete inactivation leads to development of ataxia when Kv channels cannot follow or adapt to high firing rates.
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9
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Giunti P, Mantuano E, Frontali M. Episodic Ataxias: Faux or Real? Int J Mol Sci 2020; 21:ijms21186472. [PMID: 32899446 PMCID: PMC7555854 DOI: 10.3390/ijms21186472] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 11/22/2022] Open
Abstract
The term Episodic Ataxias (EA) was originally used for a few autosomal dominant diseases, characterized by attacks of cerebellar dysfunction of variable duration and frequency, often accompanied by other ictal and interictal signs. The original group subsequently grew to include other very rare EAs, frequently reported in single families, for some of which no responsible gene was found. The clinical spectrum of these diseases has been enormously amplified over time. In addition, episodes of ataxia have been described as phenotypic variants in the context of several different disorders. The whole group is somewhat confused, since a strong evidence linking the mutation to a given phenotype has not always been established. In this review we will collect and examine all instances of ataxia episodes reported so far, emphasizing those for which the pathophysiology and the clinical spectrum is best defined.
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Affiliation(s)
- Paola Giunti
- Laboratory of Neurogenetics, Department of Molecular Neuroscience, UCL Institute of Neurology, London WC2N 5DU, UK
- Correspondence: (P.G.); (M.F.)
| | - Elide Mantuano
- Laboratory of Neurogenetics, Institute of Translational Pharmacology, National Research Council of Italy, 00133 Rome, Italy;
| | - Marina Frontali
- Laboratory of Neurogenetics, Institute of Translational Pharmacology, National Research Council of Italy, 00133 Rome, Italy;
- Correspondence: (P.G.); (M.F.)
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10
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Ahn H, Ko TS. The Genetic Relationship between Paroxysmal Movement Disorders and Epilepsy. ANNALS OF CHILD NEUROLOGY 2020. [DOI: 10.26815/acn.2020.00073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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11
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Yuan H, Yuan H, Wang Q, Ye W, Yao R, Xu W, Liu Y. Two novel KCNA1 variants identified in two unrelated Chinese families affected by episodic ataxia type 1 and neurodevelopmental disorders. Mol Genet Genomic Med 2020; 8:e1434. [PMID: 32705822 PMCID: PMC7549609 DOI: 10.1002/mgg3.1434] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 06/03/2020] [Accepted: 07/11/2020] [Indexed: 12/19/2022] Open
Abstract
Background Pathogenic KCNA1 variants have been linked to episodic ataxia type 1 (EA1), a rare neurological syndrome characterized by continuous myokymia and attacks of generalized ataxia that can be triggered by fever, abrupt movements, emotional stress, and fatigue. Currently, over 40 KCNA1 variants have been identified in individuals with EA1. Methods A male patient displayed partial seizures in addition to EA1 symptoms, often triggered by fever. A sibling presented with typical EA1 symptoms, seizures, and learning difficulties. In addition, the older brother displayed cognitive impairment, developmental delay, and slurred speech, which were absent in his younger sister. Whole‐exome sequencing was performed for the patients. Results A novel de novo missense variant in KCNA1 (p.Ala261Thr) was identified in the male patient, which is located in a base of the 3rd transmembrane domain (S3). The other novel KCNA1 variant (p.Gly376Ser) was identified in the sibling and was inherited from an unaffected father with low‐level mosaicism. The variant was located in the S5–S6 extracellular linker of the voltage sensor domain of the Kv channel. Next, we systematically reviewed the available clinical phenotypes of individuals with EA1 and observed that individuals with KCNA1 variants at the C‐terminus were more likely to suffer from seizures and neurodevelopmental disorders than those with variants at the N‐terminus. Conclusion Our study expands the mutation spectrum of KCNA1 and improves our understanding of the genotype–phenotype correlations of KCNA1. Definitive genetic diagnosis is beneficial for the genetic counseling and clinical management of individuals with EA1.
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Affiliation(s)
- Haiming Yuan
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Huihua Yuan
- Dongguan Maternal and Child Health Care HospitalDongguanChina
| | - Qingming Wang
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Wanhua Ye
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Ruixia Yao
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Wanfang Xu
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Yanhui Liu
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
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12
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Imbrici P, Nematian-Ardestani E, Hasan S, Pessia M, Tucker SJ, D'Adamo MC. Altered functional properties of a missense variant in the TRESK K + channel (KCNK18) associated with migraine and intellectual disability. Pflugers Arch 2020; 472:923-930. [PMID: 32394190 DOI: 10.1007/s00424-020-02382-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/16/2020] [Accepted: 04/22/2020] [Indexed: 12/16/2022]
Abstract
Mutations in the KCNK18 gene that encodes the TRESK K2P potassium channel have previously been linked with typical familial migraine with aura. Recently, an atypical clinical case has been reported in which a male individual carrying the p.Trp101Arg (W101R) missense mutation in the KCNK18 gene was diagnosed with intellectual disability and migraine with brainstem aura. Here we report the functional characterization of this new missense variant. This mutation is located in a highly conserved residue close to the selectivity filter, and our results show although these mutant channels retain their K+ selectivity and calcineurin-dependent regulation, the variant causes an overall dramatic loss of TRESK channel function as well as an initial dominant-negative effect when co-expressed with wild-type channels in Xenopus laevis oocytes. The dramatic functional consequences of this mutation thereby support a potentially pathogenic role for this variant and provide further insight into the relationship between the structure and function of this ion channel.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Ehsan Nematian-Ardestani
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta
| | - Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Mauro Pessia
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.,Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Maria Cristina D'Adamo
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.
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13
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Altamura C, Desaphy JF, Conte D, De Luca A, Imbrici P. Skeletal muscle ClC-1 chloride channels in health and diseases. Pflugers Arch 2020; 472:961-975. [PMID: 32361781 DOI: 10.1007/s00424-020-02376-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/18/2020] [Accepted: 03/31/2020] [Indexed: 12/14/2022]
Abstract
In 1970, the study of the pathomechanisms underlying myotonia in muscle fibers isolated from myotonic goats highlighted the importance of chloride conductance for skeletal muscle function; 20 years later, the human ClC-1 chloride channel has been cloned; last year, the crystal structure of human protein has been solved. Over the years, the efforts of many researchers led to significant advances in acknowledging the role of ClC-1 in skeletal muscle physiology and the mechanisms through which ClC-1 dysfunctions lead to impaired muscle function. The wide spectrum of pathophysiological conditions associated with modification of ClC-1 activity, either as the primary cause, such as in myotonia congenita, or as a secondary adaptive mechanism in other neuromuscular diseases, supports the idea that ClC-1 is relevant to preserve not only for skeletal muscle excitability, but also for skeletal muscle adaptation to physiological or harmful events. Improving this understanding could open promising avenues toward the development of selective and safe drugs targeting ClC-1, with the aim to restore normal muscle function. This review summarizes the most relevant research on ClC-1 channel physiology, associated diseases, and pharmacology.
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Affiliation(s)
- Concetta Altamura
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari "Aldo Moro", Bari, Italy
| | - Jean-Francois Desaphy
- Department of Biomedical Sciences and Human Oncology, School of Medicine, University of Bari "Aldo Moro", Bari, Italy
| | - Diana Conte
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy.
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14
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D’Adamo MC, Liantonio A, Rolland JF, Pessia M, Imbrici P. Kv1.1 Channelopathies: Pathophysiological Mechanisms and Therapeutic Approaches. Int J Mol Sci 2020; 21:ijms21082935. [PMID: 32331416 PMCID: PMC7215777 DOI: 10.3390/ijms21082935] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 04/19/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
Kv1.1 belongs to the Shaker subfamily of voltage-gated potassium channels and acts as a critical regulator of neuronal excitability in the central and peripheral nervous systems. KCNA1 is the only gene that has been associated with episodic ataxia type 1 (EA1), an autosomal dominant disorder characterized by ataxia and myokymia and for which different and variable phenotypes have now been reported. The iterative characterization of channel defects at the molecular, network, and organismal levels contributed to elucidating the functional consequences of KCNA1 mutations and to demonstrate that ataxic attacks and neuromyotonia result from cerebellum and motor nerve alterations. Dysfunctions of the Kv1.1 channel have been also associated with epilepsy and kcna1 knock-out mouse is considered a model of sudden unexpected death in epilepsy. The tissue-specific association of Kv1.1 with other Kv1 members, auxiliary and interacting subunits amplifies Kv1.1 physiological roles and expands the pathogenesis of Kv1.1-associated diseases. In line with the current knowledge, Kv1.1 has been proposed as a novel and promising target for the treatment of brain disorders characterized by hyperexcitability, in the attempt to overcome limited response and side effects of available therapies. This review recounts past and current studies clarifying the roles of Kv1.1 in and beyond the nervous system and its contribution to EA1 and seizure susceptibility as well as its wide pharmacological potential.
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Affiliation(s)
- Maria Cristina D’Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
| | - Antonella Liantonio
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
| | | | - Mauro Pessia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain Po Box 17666, UAE
| | - Paola Imbrici
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
- Correspondence:
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15
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Clinical Spectrum of KCNA1 Mutations: New Insights into Episodic Ataxia and Epilepsy Comorbidity. Int J Mol Sci 2020; 21:ijms21082802. [PMID: 32316562 PMCID: PMC7215408 DOI: 10.3390/ijms21082802] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 12/13/2022] Open
Abstract
Mutations in the KCNA1 gene, which encodes voltage-gated Kv1.1 potassium channel α-subunits, cause a variety of human diseases, complicating simple genotype–phenotype correlations in patients. KCNA1 mutations are primarily associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1). However, some patients have EA1 in combination with epilepsy, whereas others have epilepsy alone. KCNA1 mutations can also cause hypomagnesemia and paroxysmal dyskinesia in rare cases. Why KCNA1 variants are associated with such phenotypic heterogeneity in patients is not yet understood. In this review, literature databases (PubMed) and public genetic archives (dbSNP and ClinVar) were mined for known pathogenic or likely pathogenic mutations in KCNA1 to examine whether patterns exist between mutation type and disease manifestation. Analyses of the 47 deleterious KCNA1 mutations that were identified revealed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein. In addition, insights from animal models of KCNA1 channelopathy were considered, as well as the possible influence of genetic modifiers on disease expressivity and severity. Elucidation of the complex relationship between KCNA1 variants and disease will enable better diagnostic risk assessment and more personalized therapeutic strategies for KCNA1 channelopathy.
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16
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Rogers A, Golumbek P, Cellini E, Doccini V, Guerrini R, Wallgren-Pettersson C, Thuresson AC, Gurnett CA. De novo KCNA1 variants in the PVP motif cause infantile epileptic encephalopathy and cognitive impairment similar to recurrent KCNA2 variants. Am J Med Genet A 2018; 176:1748-1752. [PMID: 30055040 DOI: 10.1002/ajmg.a.38840] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/15/2018] [Accepted: 04/19/2018] [Indexed: 11/08/2022]
Abstract
Derangements in voltage-gated potassium channel function are responsible for a range of paroxysmal neurologic disorders. Pathogenic variants in the KCNA1 gene, which encodes the voltage-gated potassium channel Kv1.1, are responsible for Episodic Ataxia Type 1 (EA1). Patients with EA1 have an increased incidence of epilepsy, but KCNA1 variants have not been described in epileptic encephalopathy. Here, we describe four patients with infantile-onset epilepsy and cognitive impairment who harbor de novo KCNA1 variants located within the Kv-specific Pro-Val-Pro (PVP) motif which is essential for channel gating. The first two patients have KCNA1 variants resulting in (p.Pro405Ser) and (p.Pro405Leu), respectively, and a set of identical twins has a variant affecting a nearby residue (p.Pro403Ser). Notably, recurrent de novo variants in the paralogous PVP motif of KCNA2 have previously been shown to abolish channel function and also cause early-onset epileptic encephalopathy. Importantly, this report extends the range of phenotypes associated with KCNA1 variants to include epileptic encephalopathy when the PVP motif is involved.
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Affiliation(s)
- Amanda Rogers
- Department of Neurology, Washington University in St. Louis, St. Louis, Missouri
| | - Paul Golumbek
- Department of Neurology, Washington University in St. Louis, St. Louis, Missouri
| | - Elena Cellini
- Anna Meyer Children's Hospital, University of Florence, Firenze, Italy
| | - Viola Doccini
- Anna Meyer Children's Hospital, University of Florence, Firenze, Italy
| | - Renzo Guerrini
- Anna Meyer Children's Hospital, University of Florence, Firenze, Italy
| | - Carina Wallgren-Pettersson
- Department of Medical and Clinical Genetics, Folkhaelsan Institute of Genetics, University of Helsinki, Helsinki, Finland
| | - Ann-Charlotte Thuresson
- Science for Life Laboratory, Department of Immunology, Genetics, and Pathology, Uppsala University, Uppsala, Sweden
| | - Christina A Gurnett
- Department of Neurology, Washington University in St. Louis, St. Louis, Missouri
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17
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Karalok ZS, Megaro A, Cenciarini M, Guven A, Hasan SM, Taskin BD, Imbrici P, Ceylaner S, Pessia M, D'Adamo MC. Identification of a New de Novo Mutation Underlying Regressive Episodic Ataxia Type I. Front Neurol 2018; 9:587. [PMID: 30140249 PMCID: PMC6094999 DOI: 10.3389/fneur.2018.00587] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Accepted: 06/29/2018] [Indexed: 11/29/2022] Open
Abstract
Episodic ataxia type 1 (EA1), a Shaker-like K+channelopathy, is a consequence of genetic anomalies in the KCNA1 gene that lead to dysfunctions in the voltage-gated K+ channel Kv1. 1. Generally, KCNA1 mutations are inherited in an autosomal dominant manner. Here we report the clinical phenotype of an EA1 patient characterized by ataxia attacks that decrease in frequency with age, and eventually leading to therapy discontinuation. A new de novo mutation (c.932G>A) that changed a highly conserved glycine residue into an aspartate (p.G311D) was identified by using targeted next-generation sequencing. The conserved glycine is located in the S4–S5 linker, a crucial domain controlling Kv1.1 channel gating. In silico analyses predicted the mutation deleterious. Heterologous expression of the mutant (Kv1.1-G311D) channels resulted in remarkably decreased amplitudes of measured current, confirming the identified variant is pathogenic. Collectively, these findings corroborate the notion that EA1 also results from de novo variants and point out that regardless of the mutation-induced deleterious loss of Kv1.1 channel function the ataxia phenotype may improve spontaneously.
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Affiliation(s)
- Zeynep S Karalok
- Department of Pediatric Neurology, Ankara Children's Hematology Oncology Research and Training Hospital, Ankara, Turkey
| | - Alfredo Megaro
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Marta Cenciarini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Alev Guven
- Department of Pediatric Neurology, Ankara Children's Hematology Oncology Research and Training Hospital, Ankara, Turkey
| | - Sonia M Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait, Kuwait
| | - Birce D Taskin
- Department of Pediatric Neurology, Ankara Children's Hematology Oncology Research and Training Hospital, Ankara, Turkey
| | - Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | | | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy.,Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
| | - Maria C D'Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
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18
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Zima L, Ceulemans S, Reiner G, Galosi S, Chen D, Sahagian M, Haas RH, Hyland K, Friedman J. Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes. Ann Clin Transl Neurol 2018; 5:996-1010. [PMID: 30128325 PMCID: PMC6093839 DOI: 10.1002/acn3.597] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/28/2018] [Accepted: 05/29/2018] [Indexed: 11/07/2022] Open
Abstract
Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis‐characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.
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Affiliation(s)
- Laura Zima
- University of Nebraska Medical Center Omaha Nebraska
| | - Sophia Ceulemans
- Division of Neurology Rady Children's Hospital San Diego California
| | - Gail Reiner
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Serena Galosi
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California.,Department of Human Neuroscience Child Neurology and Psychiatry Sapienza University Rome Italy
| | - Dillon Chen
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Michelle Sahagian
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Richard H Haas
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Pediatrics University of California San Diego San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Keith Hyland
- Medical Neurogenetics Laboratories Atlanta Georgia
| | - Jennifer Friedman
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Pediatrics University of California San Diego San Diego California.,Department of Neurosciences University of California San Diego San Diego California.,Rady Children's Institute for Genomic Medicine San Diego California
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19
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Hasan S, Hunter T, Hunter G, Pessia M, D'Adamo MC. Commentary: A channelopathy mutation in the voltage-sensor discloses contributions of a conserved phenylalanine to gating properties of Kv1.1 channels and ataxia. Front Cell Neurosci 2018; 12:174. [PMID: 29973872 PMCID: PMC6019458 DOI: 10.3389/fncel.2018.00174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Accepted: 06/04/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Sonia Hasan
- Department of Physiology, Faculty of Medicine Kuwait University, Kuwait City, Kuwait
| | - Therese Hunter
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery University of Malta, Msida, Malta
| | - Gary Hunter
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery University of Malta, Msida, Malta
| | - Mauro Pessia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery University of Malta, Msida, Malta.,Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine University of Perugia, Perugia, Italy
| | - Maria Cristina D'Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery University of Malta, Msida, Malta
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20
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Hasan S, Bove C, Silvestri G, Mantuano E, Modoni A, Veneziano L, Macchioni L, Hunter T, Hunter G, Pessia M, D'Adamo MC. A channelopathy mutation in the voltage-sensor discloses contributions of a conserved phenylalanine to gating properties of Kv1.1 channels and ataxia. Sci Rep 2017; 7:4583. [PMID: 28676720 PMCID: PMC5496848 DOI: 10.1038/s41598-017-03041-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/21/2017] [Indexed: 01/21/2023] Open
Abstract
Channelopathy mutations prove informative on disease causing mechanisms and channel gating dynamics. We have identified a novel heterozygous mutation in the KCNA1 gene of a young proband displaying typical signs and symptoms of Episodic Ataxia type 1 (EA1). This mutation is in the S4 helix of the voltage-sensing domain and results in the substitution of the highly conserved phenylalanine 303 by valine (p.F303V). The contributions of F303 towards K+ channel voltage gating are unclear and here have been assessed biophysically and by performing structural analysis using rat Kv1.2 coordinates. We observed significant positive shifts of voltage-dependence, changes in the activation, deactivation and slow inactivation kinetics, reduced window currents, and decreased current amplitudes of both Kv1.1 and Kv1.1/1.2 channels. Structural analysis revealed altered interactions between F303V and L339 and I335 of the S5 helix of a neighboring subunit. The substitution of an aromatic phenylalanine with an aliphatic valine within the voltage-sensor destabilizes the open state of the channel. Thus, F303 fine-tunes the Kv1.1 gating properties and contributes to the interactions between the S4 segment and neighboring alpha helices. The resulting channel's loss of function validates the clinical relevance of the mutation for EA1 pathogenesis.
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Affiliation(s)
- Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Safat, 13110, Kuwait
| | - Cecilia Bove
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Gabriella Silvestri
- Institute of Neurology, Catholic University of Sacred Heart, Fondazione Gemelli, Rome, Italy
| | - Elide Mantuano
- Institute of Translational Pharmacology, National Research Council of Italy, Rome, Italy
| | - Anna Modoni
- Institute of Neurology, Catholic University of Sacred Heart, Fondazione Gemelli, Rome, Italy
| | - Liana Veneziano
- Institute of Translational Pharmacology, National Research Council of Italy, Rome, Italy
| | - Lara Macchioni
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy
| | - Therese Hunter
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Gary Hunter
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia, Perugia, Italy.,Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta
| | - Maria Cristina D'Adamo
- Faculty of Medicine & Surgery, Department of Physiology & Biochemistry, University of Malta, MSD 2080, Msida, Malta.
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21
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Imbrici P, Altamura C, Gualandi F, Mangiatordi GF, Neri M, De Maria G, Ferlini A, Padovani A, D'Adamo MC, Nicolotti O, Pessia M, Conte D, Filosto M, Desaphy JF. A novel KCNA1 mutation in a patient with paroxysmal ataxia, myokymia, painful contractures and metabolic dysfunctions. Mol Cell Neurosci 2017; 83:6-12. [PMID: 28666963 DOI: 10.1016/j.mcn.2017.06.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 04/05/2017] [Accepted: 06/25/2017] [Indexed: 11/26/2022] Open
Abstract
Episodic ataxia type 1 (EA1) is a human dominant neurological syndrome characterized by continuous myokymia, episodic attacks of ataxic gait and spastic contractions of skeletal muscles that can be triggered by emotional stress and fatigue. This rare disease is caused by missense mutations in the KCNA1 gene coding for the neuronal voltage gated potassium channel Kv1.1, which contributes to nerve cell excitability in the cerebellum, hippocampus, cortex and peripheral nervous system. We identified a novel KCNA1 mutation, E283K, in an Italian proband presenting with paroxysmal ataxia and myokymia aggravated by painful contractures and metabolic dysfunctions. The E283K mutation is located in the S3-S4 extracellular linker belonging to the voltage sensor domain of Kv channels. In order to test whether the E283K mutation affects Kv1.1 biophysical properties we transfected HEK293 cells with WT or mutant cDNAs alone or in a 1:1 combination, and recorded relative potassium currents in the whole-cell configuration of patch-clamp. Mutant E283K channels display voltage-dependent activation shifted by 10mV toward positive potentials and kinetics of activation slowed by ~2 fold compared to WT channels. Potassium currents resulting from heteromeric WT/E283K channels show voltage-dependent gating and kinetics of activation intermediate between WT and mutant homomeric channels. Based on homology modeling studies of the mutant E283K, we propose a molecular explanation for the reduced voltage sensitivity and slow channel opening. Overall, our results suggest that the replacement of a negatively charged residue with a positively charged lysine at position 283 in Kv1.1 causes a drop of potassium current that likely accounts for EA-1 symptoms in the heterozygous carrier.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari Aldo Moro, Bari, Italy.
| | - Concetta Altamura
- Department of Pharmacy - Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Francesca Gualandi
- Logistic Unit of Medical Genetics, Department of Medical Sciences, University-Hospital of Ferrara, Italy
| | | | - Marcella Neri
- Logistic Unit of Medical Genetics, Department of Medical Sciences, University-Hospital of Ferrara, Italy
| | | | - Alessandra Ferlini
- Logistic Unit of Medical Genetics, Department of Medical Sciences, University-Hospital of Ferrara, Italy
| | - Alessandro Padovani
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology, ASST "Spedali Civili", and University of Brescia, Brescia, Italy
| | - Maria Cristina D'Adamo
- Faculty of Medicine, Department of Physiology and Biochemistry, University of Malta, MSD-2080 Msida, Malta
| | - Orazio Nicolotti
- Department of Pharmacy - Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Mauro Pessia
- Faculty of Medicine, Department of Physiology and Biochemistry, University of Malta, MSD-2080 Msida, Malta; Department of Experimental Medicine, Section of Physiology & Biochemistry, University of Perugia School of Medicine, Perugia, Italy
| | - Diana Conte
- Department of Pharmacy - Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Massimiliano Filosto
- Center for Neuromuscular Diseases and Neuropathies, Unit of Neurology, ASST "Spedali Civili", and University of Brescia, Brescia, Italy
| | - Jean-Francois Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari Aldo Moro, Bari, Italy
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22
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Chen SH, Fu SJ, Huang JJ, Tang CY. The episodic ataxia type 1 mutation I262T alters voltage-dependent gating and disrupts protein biosynthesis of human Kv1.1 potassium channels. Sci Rep 2016; 6:19378. [PMID: 26778656 PMCID: PMC4726062 DOI: 10.1038/srep19378] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 12/07/2015] [Indexed: 01/08/2023] Open
Abstract
Voltage-gated potassium (Kv) channels are essential for setting neuronal membrane excitability. Mutations in human Kv1.1 channels are linked to episodic ataxia type 1 (EA1). The EA1-associated mutation I262T was identified from a patient with atypical phenotypes. Although a previous report has characterized its suppression effect, several key questions regarding the impact of the I262T mutation on Kv1.1 as well as other members of the Kv1 subfamily remain unanswered. Herein we show that the dominant-negative effect of I262T on Kv1.1 current expression is not reversed by co-expression with Kvβ1.1 or Kvβ2 subunits. Biochemical examinations indicate that I262T displays enhanced protein degradation and impedes membrane trafficking of Kv1.1 wild-type subunits. I262T appears to be the first EA1 mutation directly associated with impaired protein stability. Further functional analyses demonstrate that I262T changes the voltage-dependent activation and Kvβ1.1-mediated inactivation, uncouples inactivation from activation gating, and decelerates the kinetics of cumulative inactivation of Kv1.1 channels. I262T also exerts similar dominant effects on the gating of Kv1.2 and Kv1.4 channels. Together our data suggest that I262T confers altered channel gating and reduced functional expression of Kv1 channels, which may account for some of the phenotypes of the EA1 patient.
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Affiliation(s)
- Szu-Han Chen
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ssu-Ju Fu
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Jing-Jia Huang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chih-Yung Tang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
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23
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D'Adamo MC, Hasan S, Guglielmi L, Servettini I, Cenciarini M, Catacuzzeno L, Franciolini F. New insights into the pathogenesis and therapeutics of episodic ataxia type 1. Front Cell Neurosci 2015; 9:317. [PMID: 26347608 PMCID: PMC4541215 DOI: 10.3389/fncel.2015.00317] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/30/2015] [Indexed: 11/13/2022] Open
Abstract
Episodic ataxia type 1 (EA1) is a K+channelopathy characterized by a broad spectrum of symptoms. Generally, patients may experience constant myokymia and dramatic episodes of spastic contractions of the skeletal muscles of the head, arms, and legs with loss of both motor coordination and balance. During attacks additional symptoms may be reported such as vertigo, blurred vision, diplopia, nausea, headache, diaphoresis, clumsiness, stiffening of the body, dysarthric speech, and difficulty in breathing. These episodes may be precipitated by anxiety, emotional stress, fatigue, startle response or sudden postural changes. Epilepsy is overrepresented in EA1. The disease is inherited in an autosomal dominant manner, and genetic analysis of several families has led to the discovery of a number of point mutations in the voltage-dependent K+ channel gene KCNA1 (Kv1.1), on chromosome 12p13. To date KCNA1 is the only gene known to be associated with EA1. Functional studies have shown that these mutations impair Kv1.1 channel function with variable effects on channel assembly, trafficking and biophysics. Despite the solid evidence obtained on the molecular mechanisms underlying EA1, how these cause dysfunctions within the central and peripheral nervous systems circuitries remains elusive. This review summarizes the main breakthrough findings in EA1, discusses the neurophysiological mechanisms underlying the disease, current therapies, future challenges and opens a window onto the role of Kv1.1 channels in central nervous system (CNS) and peripheral nervous system (PNS) functions.
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Affiliation(s)
- Maria Cristina D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Sonia Hasan
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Luca Guglielmi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Ilenio Servettini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Marta Cenciarini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
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24
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Imbrici P, Altamura C, Pessia M, Mantegazza R, Desaphy JF, Camerino DC. ClC-1 chloride channels: state-of-the-art research and future challenges. Front Cell Neurosci 2015; 9:156. [PMID: 25964741 PMCID: PMC4410605 DOI: 10.3389/fncel.2015.00156] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/08/2015] [Indexed: 01/06/2023] Open
Abstract
The voltage-dependent ClC-1 chloride channel belongs to the CLC channel/transporter family. It is a homodimer comprising two individual pores which can operate independently or simultaneously according to two gating modes, the fast and the slow gate of the channel. ClC-1 is preferentially expressed in the skeletal muscle fibers where the presence of an efficient Cl(-) homeostasis is crucial for the correct membrane repolarization and propagation of action potential. As a consequence, mutations in the CLCN1 gene cause dominant and recessive forms of myotonia congenita (MC), a rare skeletal muscle channelopathy caused by abnormal membrane excitation, and clinically characterized by muscle stiffness and various degrees of transitory weakness. Elucidation of the mechanistic link between the genetic defects and the disease pathogenesis is still incomplete and, at this time, there is no specific treatment for MC. Still controversial is the subcellular localization pattern of ClC-1 channels in skeletal muscle as well as its modulation by some intracellular factors. The expression of ClC-1 in other tissues such as in brain and heart and the possible assembly of ClC-1/ClC-2 heterodimers further expand the physiological properties of ClC-1 and its involvement in diseases. A recent de novo CLCN1 truncation mutation in a patient with generalized epilepsy indeed postulates an unexpected role of this channel in the control of neuronal network excitability. This review summarizes the most relevant and state-of-the-art research on ClC-1 chloride channels physiology and associated diseases.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Concetta Altamura
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Mauro Pessia
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | - Renato Mantegazza
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
| | | | - Diana Conte Camerino
- Department of Pharmacy - Drug Sciences, University of Bari “Aldo Moro”,Bari, Italy
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Karcz A, Allen PD, Walton J, Ison JR, Kopp-Scheinpflug C. Auditory deficits of Kcna1 deletion are similar to those of a monaural hearing impairment. Hear Res 2015; 321:45-51. [PMID: 25602577 DOI: 10.1016/j.heares.2015.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 12/29/2014] [Accepted: 01/07/2015] [Indexed: 11/28/2022]
Abstract
Kv1.1 subunits of low voltage-activated (Kv) potassium channels are encoded by the Kcna1 gene and crucially determine the synaptic integration window to control the number and temporal precision of action potentials in the auditory brainstem of mammals and birds. Prior electrophysiological studies showed that auditory signaling is compromised in monaural as well as in binaural neurons of the auditory brainstem in Kv1.1 knockout mice (Kcna1(-/-)). Here we examine the behavioral effects of Kcna1 deletion on sensory tasks dependent on either binaural processing (detecting the movement of a sound source across the azimuth), monaural processing (detecting a gap in noise), as well as binaural summation of the acoustic startle reflex (ASR). Hearing thresholds measured by auditory brainstem responses (ABR) do not differ between genotypes, but our data show a much stronger performance of wild type mice (+/+) in each test during binaural hearing which was lost by temporarily inducing a unilateral hearing loss (through short term blocking of one ear) thus remarkably, leaving no significant difference between binaural and monaural hearing in Kcna1(-/-) mice. These data suggest that the behavioral effect of Kv1.1 deletion is primarily to impede binaural integration and thus to mimic monaural hearing.
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Affiliation(s)
- Anita Karcz
- Carl-Ludwig-Institute for Physiology, University of Leipzig, Medical School, Germany
| | - Paul D Allen
- Department of Neurobiology and Anatomy, School of Medicine & Dentistry, University of Rochester, NY, USA
| | - Joseph Walton
- Department of Communication Sciences and Disorders, University of South Florida, 4202 Fowler Av., Tampa, Fl 32620, USA
| | - James R Ison
- Department of Neurobiology and Anatomy, School of Medicine & Dentistry, University of Rochester, NY, USA; Department of Brain & Cognitive Sciences, University of Rochester, NY, USA
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D'Adamo MC, Gallenmüller C, Servettini I, Hartl E, Tucker SJ, Arning L, Biskup S, Grottesi A, Guglielmi L, Imbrici P, Bernasconi P, Di Giovanni G, Franciolini F, Catacuzzeno L, Pessia M, Klopstock T. Novel phenotype associated with a mutation in the KCNA1(Kv1.1) gene. Front Physiol 2015; 5:525. [PMID: 25642194 PMCID: PMC4295438 DOI: 10.3389/fphys.2014.00525] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/20/2014] [Indexed: 11/13/2022] Open
Abstract
Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with short attacks of cerebellar ataxia and dysarthria, and may also show interictal myokymia. Episodes can be triggered by emotional or physical stress, startle response, sudden postural change or fever. Here we describe a 31-year-old man displaying markedly atypical symptoms, including long-lasting attacks of jerking muscle contractions associated with hyperthermia, severe migraine, and a relatively short-sleep phenotype. A single nucleotide change in KCNA1 (c.555C>G) was identified that changes a highly conserved residue (p.C185W) in the first transmembrane segment of the voltage-gated K(+) channel Kv1.1. The patient is heterozygous and the mutation was inherited from his asymptomatic mother. Next generation sequencing revealed no variations in the CACNA1A, CACNB4, KCNC3, KCNJ10, PRRT2 or SCN8A genes of either the patient or mother, except for a benign variant in SLC1A3. Functional analysis of the p.C185W mutation in KCNA1 demonstrated a deleterious dominant-negative phenotype where the remaining current displayed slower activation kinetics, subtle changes in voltage-dependence and faster recovery from slow inactivation. Structural modeling also predicts the C185W mutation to be functionally deleterious. This description of novel clinical features, associated with a Kv1.1 mutation highlights a possibly unrecognized relationship between K(+) channel dysfunction, hyperthermia and migraine in EA1, and suggests that thorough assessments for these symptoms should be carefully considered for all patients affected by EA1.
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Affiliation(s)
- Maria C D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy ; Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy
| | - Constanze Gallenmüller
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany ; German Network for Mitochondrial Disorders (mitoNET) Ludwigshafen, Germany ; DZNE - German Center for Neurodegenerative Diseases Munich, Germany
| | - Ilenio Servettini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy
| | - Elisabeth Hartl
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford Oxford, UK
| | - Larissa Arning
- Department of Human Genetics, Ruhr-University Bochum Bochum, Germany
| | - Saskia Biskup
- Center for Genomics and Transcriptomics (CeGaT) GmbH Tübingen Tübingen, Germany
| | - Alessandro Grottesi
- Department of Supercomputing Applications and Innovation, CINECA (Consorzio Inter-Universitario per il Calcolo Automatico) Rome, Italy
| | - Luca Guglielmi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy
| | - Paola Imbrici
- Department of Pharmacy, University of Bari Bari, Italy
| | - Pia Bernasconi
- Neurology IV - Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute "Carlo Besta" Milan, Italy
| | - Giuseppe Di Giovanni
- Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy ; Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta Msida, Malta
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy ; Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy
| | - Thomas Klopstock
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany ; German Network for Mitochondrial Disorders (mitoNET) Ludwigshafen, Germany ; DZNE - German Center for Neurodegenerative Diseases Munich, Germany ; German Center for Vertigo and Balance Disorders Munich, Germany
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27
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D’Adamo MC, Di Giovanni G, Pessia M. Animal Models of Episodic Ataxia Type 1 (EA1). Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00051-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Kipfer S, Strupp M. The Clinical Spectrum of Autosomal-Dominant Episodic Ataxias. Mov Disord Clin Pract 2014; 1:285-290. [PMID: 30713867 DOI: 10.1002/mdc3.12075] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 06/16/2014] [Accepted: 06/20/2014] [Indexed: 11/06/2022] Open
Abstract
Autosomal-dominant episodic ataxias (EAs) represent a clinically and genetically heterogeneous group of disorders characterized by recurrent episodes of cerebellar ataxia (CA). Ataxia episodes are usually of short duration and often triggered by specific stimuli. There are currently seven classified subtypes of EA. EA types 1 and 2 have the highest prevalence and are therefore the clinically most relevant. Between attacks, EA 1 is associated with myokymia. In EA 2, often an interictal downbeat nystagmus with other cerebellar ocular dysfunctions is present; patients with EA 2 may display slowly progessive ataxia and vermian atrophy. EA 1 and 2 are both channelopathies, affecting the potassium channel gene, KCNA1, in EA 1 and the PQ calcium channel-encoding gene, CACNA1A, in EA 2. The types EA 3 to 7 are very rare and have to be further elucidated. Here, we review the historical, clinical, and genetic aspects of autosomal-dominant EAs and their current treatment, focusing on EA 1 and 2.
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Affiliation(s)
- Stefan Kipfer
- Department of Neurology Kantonsspital Olten Switzerland
| | - Michael Strupp
- Department of Neurology and German Center for Vertigo and Balance Disorders University Hospital Munich Munich Germany
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Graves TD, Cha YH, Hahn AF, Barohn R, Salajegheh MK, Griggs RC, Bundy BN, Jen JC, Baloh RW, Hanna MG. Episodic ataxia type 1: clinical characterization, quality of life and genotype-phenotype correlation. ACTA ACUST UNITED AC 2014; 137:1009-18. [PMID: 24578548 DOI: 10.1093/brain/awu012] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Episodic ataxia type 1 is considered a rare neuronal ion channel disorder characterized by brief attacks of unsteadiness and dizziness with persistent myokymia. To characterize the natural history, develop outcome measures for future clinical trials, and correlate genotype with phenotype, we undertook an international, prospective, cross-sectional study. Thirty-nine individuals (51% male) were enrolled: median age 37 years (range 15-65 years). We identified 10 different pathogenic point mutations in KCNA1 that accounted for the genetic basis of 85% of the cohort. Participants with KCNA1 mutations were more likely to have a positive family history. Analysis of the total cohort showed that the first episode of ataxia occurred before age 20 in all but one patient, with an average age of onset of 7.9 years. Physical exertion, emotional stress and environmental temperature were the most common triggers for attacks. Attack frequency ranged from daily to monthly, even with the same KCNA1 genotype. Average attack duration was in the order of minutes. Ten participants (26%) developed permanent cerebellar signs, which were related to disease duration. The average Scale for the Assessment and Rating of Ataxia score (SARA, a standardized measure of cerebellar dysfunction on clinical examination, scores range from 0-40) was an average of 3.15 for all participants (range 0-14), but was only 2 in those with isolated episodic ataxia compared with 7.7 in those with progressive cerebellar ataxia in addition to episodic ataxia. Thirty-seven participants completed the SF-36, a quality of life survey; all eight domain norm-based average scores (mean=50) were below normal with mental health being the lowest (41.3) in those with mutation positive episodic ataxia type 1. Scores on SF-36 correlated negatively with attack frequency. Of the 39 participants in the study, 33 harboured mutations in KCNA1 whereas the remaining six had no mutation identified. Episodic ataxia type 1 phenocopies have not been described previously and we report their clinical features, which appear to be different to those with a KCNA1 mutation. This large prospective study of both genetically confirmed episodic ataxia type 1 and episodic ataxia type 1 phenocopies provides detailed baseline characteristics of these disorders and their impact on participants. We found that attacks had a significant effect on quality of life. Unlike previous studies, we found that a significant number of individuals with genetically confirmed episodic ataxia type 1 (21%) had accumulated persistent cerebellar symptoms and signs. These data will enable the development of outcome measures for clinical trials of treatment.
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Affiliation(s)
- Tracey D Graves
- 1 MRC Centre for Neuromuscular Disease, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
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30
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D'Adamo MC, Catacuzzeno L, Di Giovanni G, Franciolini F, Pessia M. K(+) channelepsy: progress in the neurobiology of potassium channels and epilepsy. Front Cell Neurosci 2013; 7:134. [PMID: 24062639 PMCID: PMC3772396 DOI: 10.3389/fncel.2013.00134] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/06/2013] [Indexed: 12/19/2022] Open
Abstract
K(+) channels are important determinants of seizure susceptibility. These membrane proteins, encoded by more than 70 genes, make the largest group of ion channels that fine-tune the electrical activity of neuronal and non-neuronal cells in the brain. Their ubiquity and extremely high genetic and functional diversity, unmatched by any other ion channel type, place K(+) channels as primary targets of genetic variations or perturbations in K(+)-dependent homeostasis, even in the absence of a primary channel defect. It is therefore not surprising that numerous inherited or acquired K(+) channels dysfunctions have been associated with several neurologic syndromes, including epilepsy, which often generate confusion in the classification of the associated diseases. Therefore, we propose to name the K(+) channels defects underlying distinct epilepsies as "K(+) channelepsies," and introduce a new nomenclature (e.g., Kx.y-channelepsy), following the widely used K(+) channel classification, which could be also adopted to easily identify other channelopathies involving Na(+) (e.g., Nav x.y-phenotype), Ca(2+) (e.g., Cav x.y-phenotype), and Cl(-) channels. Furthermore, we discuss novel genetic defects in K(+) channels and associated proteins that underlie distinct epileptic phenotypes in humans, and analyze critically the recent progress in the neurobiology of this disease that has also been provided by investigations on valuable animal models of epilepsy. The abundant and varied lines of evidence discussed here strongly foster assessments for variations in genes encoding for K(+) channels and associated proteins in patients with idiopathic epilepsy, provide new avenues for future investigations, and highlight these proteins as critical pharmacological targets.
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Key Words
- Potassium channels: [Kv1, Kv2, Kv3, Kv4, Kv8, Kv11(HERG), KCa1.1, Kvβ1, Kvβ2, KChIP LGI1, Kir1-Kir7 (GIRK, KATP)]
- autism–epilepsy
- channelopathies
- temporal lobe epilepsy
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Affiliation(s)
- Maria Cristina D'Adamo
- Faculty of Medicine, Section of Human Physiology, Department of Internal Medicine, University of Perugia Perugia, Italy ; Istituto Euro Mediterraneo di Scienza e Tecnologia, IEMEST Palermo, Italy
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Zhu J, Alsaber R, Zhao J, Ribeiro-Hurley E, Thornhill WB. Characterization of the Kv1.1 I262T and S342I mutations associated with episodic ataxia 1 with distinct phenotypes. Arch Biochem Biophys 2012; 524:99-105. [PMID: 22609616 DOI: 10.1016/j.abb.2012.05.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 10/28/2022]
Abstract
Episodic ataxia type 1 (EA-1) is an autosomal dominant neurological disorder caused by mutations in the potassium channel Kv1.1. Two EA-1 mutations, I262T and S342I, have been identified with unique clinical phenotypes, but their functional and biochemical properties have not been fully investigated. Here we characterized these two mutations in transfected mammalian cells both electrophysiologically and biochemically. We found that the I262T mutation resulted in a ∼7-fold reduction in the K+ current amplitude compared with wild type channels, whereas the S342I mutation produced an apparent nonfunctional channel when expressed alone. Co-expression of wild type and mutant channels showed that both I262T and S342I exerted dominant-negative effects on wild type function. The protein expression analysis showed that I262T resulted in ∼2-fold decrease in surface protein levels of Kv1.1, which partially contributed to the decreased surface conductance density, whereas the S342I mutation showed no effects on surface protein expression. Conservative amino acid substitution experiments suggest that the wild type amino acids at these two positions are required for normal channel function. Our results broaden the knowledge of EA-1 mutations and the underlying mechanisms of the associated disorder.
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Affiliation(s)
- Jing Zhu
- Department of Biological Sciences and Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
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32
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Matilla-Dueñas A. Machado-Joseph disease and other rare spinocerebellar ataxias. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 724:172-88. [PMID: 22411243 DOI: 10.1007/978-1-4614-0653-2_14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The spinocerebellar ataxias (SCAs) are a group of neurodegenerative diseases characterised by progressive lack of motor coordination leading to major disability. SCAs show high clinical, genetic, molecular and epidemiological variability. In the last one decade, the intensive scientific research devoted to the SCAs is resulting in clear advances and a better understanding on the genetic and nongenetic factors contributing to their pathogenesis which are facilitating the diagnosis, prognosis and development of new therapies. The scope of this chapter is to provide an updated information on Machado-Joseph disease (MJD), the most frequent SCA subtype worldwide and other rare spinocerebellar ataxias including dentatorubral-pallidoluysian atrophy (DRPLA), the X-linked fragile X tremor and ataxia syndrome (FXTAS) and the nonprogressive episodic forms of inherited ataxias (EAs). Furthermore, the different therapeutic strategies that are currently being investigated to treat the ataxia and non-ataxia symptoms in SCAs are also described.
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33
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Ishida S, Sakamoto Y, Nishio T, Baulac S, Kuwamura M, Ohno Y, Takizawa A, Kaneko S, Serikawa T, Mashimo T. Kcna1-mutant rats dominantly display myokymia, neuromyotonia and spontaneous epileptic seizures. Brain Res 2011; 1435:154-66. [PMID: 22206926 DOI: 10.1016/j.brainres.2011.11.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 11/04/2011] [Accepted: 11/08/2011] [Indexed: 11/30/2022]
Abstract
Mutations in the KCNA1 gene, which encodes for the α subunit of the voltage-gated potassium channel Kv1.1, cause episodic ataxia type 1 (EA1). EA1 is a dominant human neurological disorder characterized by variable phenotypes of brief episodes of ataxia, myokymia, neuromyotonia, and associated epilepsy. Animal models for EA1 include Kcna1-deficient mice, which recessively display severe seizures and die prematurely, and V408A-knock-in mice, which dominantly exhibit stress-induced loss of motor coordination. In the present study, we have identified an N-ethyl-N-nitrosourea-mutagenized rat, named autosomal dominant myokymia and seizures (ADMS), with a missense mutation (S309T) in the voltage-sensor domain, S4, of the Kcna1 gene. ADMS rats dominantly exhibited myokymia, neuromyotonia and generalized tonic-clonic seizures. They also showed cold stress-induced tremor, neuromyotonia, and motor incoordination. Expression studies of homomeric and heteromeric Kv1.1 channels in HEK cells and Xenopus oocytes, showed that, although S309T channels are transferred to the cell membrane surface, they remained non-functional in terms of their biophysical properties, suggesting a dominant-negative effect of the S309T mutation on potassium channel function. ADMS rats provide a new model, distinct from previously reported mouse models, for studying the diverse functions of Kv1.1 in vivo, as well as for understanding the pathology of EA1.
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Affiliation(s)
- Saeko Ishida
- Institute of Laboratory animals, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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Imbrici P, D'Adamo MC, Grottesi A, Biscarini A, Pessia M. Episodic ataxia type 1 mutations affect fast inactivation of K+ channels by a reduction in either subunit surface expression or affinity for inactivation domain. Am J Physiol Cell Physiol 2011; 300:C1314-22. [PMID: 21307345 DOI: 10.1152/ajpcell.00456.2010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Episodic ataxia type 1 (EA1) is an autosomal dominant disorder characterized by continuous myokymia and episodic attacks of ataxia. Mutations in the gene KCNA1 that encodes the voltage-gated potassium channel Kv1.1 are responsible for EA1. In several brain areas, Kv1.1 coassembles with Kv1.4, which confers N-type inactivating properties to heteromeric channels. It is therefore likely that the rate of inactivation will be determined by the number of Kv1.4 inactivation particles, as set by the precise subunit stoichiometry. We propose that EA1 mutations affect the rate of N-type inactivation either by reduced subunit surface expression, giving rise to a reduced number of Kv1.1 subunits in heterotetramer Kv1.1-Kv1.4 channels, or by reduced affinity for the Kv1.4 inactivation domain. To test this hypothesis, quantified amounts of mRNA for Kv1.4 or Kv1.1 containing selected EA1 mutations either in the inner vestibule of Kv1.1 on S6 or in the transmembrane regions were injected into Xenopus laevis oocytes and the relative rates of inactivation and stoichiometry were determined. The S6 mutations, V404I and V408A, which had normal surface expression, reduced the rate of inactivation by a decreased affinity for the inactivation domain while the mutations I177N in S1 and E325D in S5, which had reduced subunit surface expression, increased the rate of N-type inactivation due to a stoichiometric increase in the number of Kv1.4 subunits.
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Affiliation(s)
- Paola Imbrici
- Section of Human Physiology, Dept. of Internal Medicine, University of Perugia School of Medicine, Via del Giochetto, Perugia, Italy
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Graves TD, Rajakulendran S, Zuberi SM, Morris HR, Schorge S, Hanna MG, Kullmann DM. Nongenetic factors influence severity of episodic ataxia type 1 in monozygotic twins. Neurology 2010; 75:367-72. [PMID: 20660867 DOI: 10.1212/wnl.0b013e3181ea9ee3] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Episodic ataxia type 1 (EA1) is a monogenic channelopathy caused by mutations of the potassium channel gene KCNA1. Affected individuals carrying the same mutation can exhibit considerable variability in the severity of ataxia, neuromyotonia, and other associated features. We investigated the phenotypic heterogeneity of EA1 in 2 sets of identical twins to determine the contribution of environmental factors to disease severity. One of the mutations was also found in a distantly related family, providing evidence of the influence of genetic background on the EA1 phenotype. METHODS We evaluated 3 families with an EA1 phenotype, 2 of which included monozygotic twins. We sequenced the KCNA1 gene and studied the biophysical consequences of the mutations in HEK cells. RESULTS We identified a new KCNA1 mutation in each pair of twins. Both pairs reported striking differences in the clinical severity of symptoms. The F414S mutation identified in one set of twins also occurred in a distantly related family in which seizures complicated the EA1 phenotype. The other twins had an R307C mutation, the first EA1 mutation to affect an arginine residue in the voltage-sensor domain. Both mutants when expressed exerted a dominant-negative effect on wild-type channels. CONCLUSION These results broaden the range of KCNA1 mutations and reveal an unexpectedly large contribution of nongenetic factors to phenotypic variability in EA1. The occurrence of epilepsy in 1 of 2 families with the F414S mutation suggests an interplay of KCNA1 with other genetic factors.
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Affiliation(s)
- T D Graves
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, University College London, Queen Square, London, United Kingdom
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36
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Vanhaesebrouck AE, Van Soens I, Poncelet L, Duchateau L, Bhatti S, Polis I, Diels S, Van Ham L. Clinical and electrophysiological characterization of myokymia and neuromyotonia in Jack Russell Terriers. J Vet Intern Med 2010; 24:882-9. [PMID: 20492485 DOI: 10.1111/j.1939-1676.2010.0525.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Generalized myokymia and neuromyotonia (M/NM) in Jack Russell Terriers (JRTs) is related to peripheral nerve hyperexcitability syndrome in humans, a symptom complex resulting from diverse etiologies. OBJECTIVE Clinical and electrodiagnostic evaluation is used to narrow the list of possible etiological diagnoses in JRTs with M/NM. ANIMALS Nine healthy JRTs and 8 affected JRTs. METHODS A prospective study was conducted comparing clinical and electrophysiological characteristics in 8 JRTs affected by M/NM with 9 healthy JRT controls. RESULTS All affected dogs except 1 had clinical signs typical of hereditary ataxia (HA). In 6 dogs, neuromyotonic discharges were recorded during electromyogram. Motor nerve conduction studies showed an axonal neuropathy in only 1 affected dog. Compared with controls, brainstem auditory-evoked potentials (BAEP) showed prolonged latencies (P<.05) accompanied by the disappearance of wave components in 3 dogs. Onset latencies of tibial sensory-evoked potentials (SEP) recorded at the lumbar intervertebral level were delayed in the affected group (P<.001). The BAEP and SEP results of the only neuromyotonic dog without ataxia were normal. CONCLUSIONS AND CLINICAL IMPORTANCE The BAEP and spinal SEP abnormalities observed in JRTs with M/NM were associated with the presence of HA. Therefore, these electrophysiological findings presumably arise from the neurodegenerative changes characterizing HA and do not directly elucidate the pathogenesis of M/NM. An underlying neuronal ion channel dysfunction is thought to be the cause of M/NM in JRTs.
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Affiliation(s)
- A E Vanhaesebrouck
- Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
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