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Burtscher V, Mount J, Huang J, Cowgill J, Chang Y, Bickel K, Chen J, Yuan P, Chanda B. Structural basis for hyperpolarization-dependent opening of human HCN1 channel. Nat Commun 2024; 15:5216. [PMID: 38890331 PMCID: PMC11189445 DOI: 10.1038/s41467-024-49599-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 06/11/2024] [Indexed: 06/20/2024] Open
Abstract
Hyperpolarization and cyclic nucleotide (HCN) activated ion channels are critical for the automaticity of action potentials in pacemaking and rhythmic electrical circuits in the human body. Unlike most voltage-gated ion channels, the HCN and related plant ion channels activate upon membrane hyperpolarization. Although functional studies have identified residues in the interface between the voltage-sensing and pore domain as crucial for inverted electromechanical coupling, the structural mechanisms for this unusual voltage-dependence remain unclear. Here, we present cryo-electron microscopy structures of human HCN1 corresponding to Closed, Open, and a putative Intermediate state. Our structures reveal that the downward motion of the gating charges past the charge transfer center is accompanied by concomitant unwinding of the inner end of the S4 and S5 helices, disrupting the tight gating interface observed in the Closed state structure. This helix-coil transition at the intracellular gating interface accompanies a concerted iris-like dilation of the pore helices and underlies the reversed voltage dependence of HCN channels.
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Affiliation(s)
- Verena Burtscher
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Jonathan Mount
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jian Huang
- Department of Chemistry, University of Massachusetts, Amherst, MA, USA
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
- Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Kathleen Bickel
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA
| | - Jianhan Chen
- Department of Chemistry, University of Massachusetts, Amherst, MA, USA
| | - Peng Yuan
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, USA.
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, MO, USA.
- Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, USA.
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Lin JL, Chang Y, Tewari D, Cowgill J, Chanda B. Mapping the contribution of the C-linker domain to gating polarity in CNBD channels. Biophys J 2024:S0006-3495(24)00284-4. [PMID: 38678368 DOI: 10.1016/j.bpj.2024.04.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/23/2024] [Accepted: 04/22/2024] [Indexed: 04/29/2024] Open
Abstract
Ion channels of the cyclic nucleotide-binding domain (CNBD) family play a crucial role in the regulation of key biological processes, such as photoreception and pacemaking activity in the heart. These channels exhibit high sequence and structural similarity but differ greatly in their functional responses to membrane potential. The CNBD family includes hyperpolarization-activated ion channels and depolarization-activated ether-à-go-go channels. Structural and functional studies show that the differences in the coupling interface between these two subfamilies' voltage-sensing domain and pore domain may underlie their differential response to membrane polarity. However, other structural components may also contribute to defining the polarity differences in activation. Here, we focus on the role of the C-terminal domain, which interacts with elements in both the pore and voltage-sensing domains. By generating a series of chimeras involving the C-terminal domain derived from distant members of the CNBD family, we find that the nature of the C-termini profoundly influences the gating polarity of these ion channels. Scanning mutagenesis of the C-linker region, a helix-turn-helix motif connecting the pore helix to the CNBD, reveals that residues at the intersubunit interface between the C-linkers are crucial for hyperpolarization-dependent activation. These findings highlight the unique and unexpected role of the intersubunit interface of the C-linker region in regulating the gating polarity of voltage-gated ion channels.
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Affiliation(s)
- Jenna L Lin
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri; Graduate Program in Biochemistry, Biophysics, & Structural Biology, Washington University School of Medicine, St. Louis, Missouri
| | - Yongchang Chang
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Debanjan Tewari
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - John Cowgill
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri.
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Houdayer C, Phillips AM, Chabbert M, Bourreau J, Maroofian R, Houlden H, Richards K, Saadi NW, Dad'ová E, Van Bogaert P, Rupin M, Keren B, Charles P, Smol T, Riquet A, Pais L, O'Donnell-Luria A, VanNoy GE, Bayat A, Møller RS, Olofsson K, Abou Jamra R, Syrbe S, Dasouki M, Seaver LH, Sullivan JA, Shashi V, Alkuraya FS, Poss AF, Spence JE, Schnur RE, Forster IC, Mckenzie CE, Simons C, Wang M, Snell P, Kothur K, Buckley M, Roscioli T, Elserafy N, Dauriat B, Procaccio V, Henrion D, Lenaers G, Colin E, Verbeek NE, Van Gassen KL, Legendre C, Bonneau D, Reid CA, Howell KB, Ziegler A, Legros C. Mono and biallelic variants in HCN2 cause severe neurodevelopmental disorders. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.03.19.24303984. [PMID: 38562733 PMCID: PMC10984036 DOI: 10.1101/2024.03.19.24303984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Hyperpolarization activated Cyclic Nucleotide (HCN) gated channels are crucial for various neurophysiological functions, including learning and sensory functions, and their dysfunction are responsible for brain disorders, such as epilepsy. To date, HCN2 variants have only been associated with mild epilepsy and recently, one monoallelic missense variant has been linked to developmental and epileptic encephalopathy. Here, we expand the phenotypic spectrum of HCN2- related disorders by describing twenty-one additional individuals from fifteen unrelated families carrying HCN2 variants. Seventeen individuals had developmental delay/intellectual disability (DD/ID), two had borderline DD/ID, and one had borderline DD. Ten individuals had epilepsy with DD/ID, with median age of onset of 10 months, and one had epilepsy with normal development. Molecular diagnosis identified thirteen different pathogenic HCN2 variants, including eleven missense variants affecting highly conserved amino acids, one frameshift variant, and one in-frame deletion. Seven variants were monoallelic of which five occurred de novo, one was not maternally inherited, one was inherited from a father with mild learning disabilities, and one was of unknown inheritance. The remaining six variants were biallelic, with four homozygous and two compound heterozygous variants. Functional studies using two-electrode voltage-clamp recordings in Xenopus laevis oocytes were performed on three monoallelic variants, p.(Arg324His), p.(Ala363Val), and p.(Met374Leu), and three biallelic variants, p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp). The p.(Arg324His) variant induced a strong increase of HCN2 conductance, while p.(Ala363Val) and p.(Met374Leu) displayed dominant negative effects, leading to a partial loss of HCN2 channel function. By confocal imaging, we found that the p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp) pathogenic variants impaired membrane trafficking, resulting in a complete loss of HCN2 elicited currents in Xenopus oocytes. Structural 3D-analysis in depolarized and hyperpolarized states of HCN2 channels, revealed that the pathogenic variants p.(His205Gln), p.(Ser409Leu), p.(Arg324Cys), p.(Asn369Ser) and p.(Gly460Asp) modify molecular interactions altering HCN2 function. Taken together, our data broadens the clinical spectrum associated with HCN2 variants, and disclose that HCN2 is involved in developmental encephalopathy with or without epilepsy.
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Kazmierska-Grebowska P, Jankowski MM, MacIver MB. Missing Puzzle Pieces in Dementia Research: HCN Channels and Theta Oscillations. Aging Dis 2024; 15:22-42. [PMID: 37450922 PMCID: PMC10796085 DOI: 10.14336/ad.2023.0607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 06/07/2023] [Indexed: 07/18/2023] Open
Abstract
Increasing evidence indicates a role of hyperpolarization activated cation (HCN) channels in controlling the resting membrane potential, pacemaker activity, memory formation, sleep, and arousal. Their disfunction may be associated with the development of epilepsy and age-related memory decline. Neuronal hyperexcitability involved in epileptogenesis and EEG desynchronization occur in the course of dementia in human Alzheimer's Disease (AD) and animal models, nevertheless the underlying ionic and cellular mechanisms of these effects are not well understood. Some suggest that theta rhythms involved in memory formation could be used as a marker of memory disturbances in the course of neurogenerative diseases, including AD. This review focusses on the interplay between hyperpolarization HCN channels, theta oscillations, memory formation and their role(s) in dementias, including AD. While individually, each of these factors have been linked to each other with strong supportive evidence, we hope here to expand this linkage to a more inclusive picture. Thus, HCN channels could provide a molecular target for developing new therapeutic agents for preventing and/or treating dementia.
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Affiliation(s)
| | - Maciej M. Jankowski
- Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
- BioTechMed Center, Multimedia Systems Department, Faculty of Electronics, Telecommunications, and Informatics, Gdansk University of Technology, Gdansk, Poland.Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland.
| | - M. Bruce MacIver
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of of Medicine, Stanford University, CA, USA.
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DiFrancesco JC, Ragona F, Murano C, Frosio A, Melgari D, Binda A, Calamaio S, Prevostini R, Mauri M, Canafoglia L, Castellotti B, Messina G, Gellera C, Previtali R, Veggiotti P, Milanesi R, Barbuti A, Solazzi R, Freri E, Granata T, Rivolta I. A novel de novo HCN2 loss-of-function variant causing developmental and epileptic encephalopathy treated with a ketogenic diet. Epilepsia 2023; 64:e222-e228. [PMID: 37746765 DOI: 10.1111/epi.17777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 09/20/2023] [Accepted: 09/20/2023] [Indexed: 09/26/2023]
Abstract
Missense variants of hyperpolarization-activated, cyclic nucleotide-gated (HCN) ion channels cause variable phenotypes, ranging from mild generalized epilepsy to developmental and epileptic encephalopathy (DEE). Although variants of HCN1 are an established cause of DEE, those of HCN2 have been reported in generalized epilepsies. Here we describe the first case of DEE caused by the novel de novo heterozygous missense variant c.1379G>A (p.G460D) of HCN2. Functional characterization in transfected HEK293 cells and neonatal rat cortical neurons revealed that HCN2 p.G460D currents were strongly reduced compared to wild-type, consistent with a dominant negative loss-of-function effect. Immunofluorescence staining showed that mutant channels are retained within the cell and do not reach the membrane. Moreover, mutant HCN2 also affect HCN1 channels, by reducing the Ih current expressed by the HCN1-HCN2 heteromers. Due to the persistence of frequent seizures despite pharmacological polytherapy, the patient was treated with a ketogenic diet, with a significant and long-lasting reduction of episodes. In vitro experiments conducted in a ketogenic environment demonstrated that the clinical improvement observed with this dietary regimen was not mediated by a direct action on HCN2 activity. These results expand the clinical spectrum related to HCN2 channelopathies, further broadening our understanding of the pathogenesis of DEE.
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Affiliation(s)
| | - Francesca Ragona
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Carmen Murano
- School of Medicine and Surgery, University of Milano-Bicocca, Milan Center for Neuroscience (NeuroMI), Monza, Italy
| | - Anthony Frosio
- IMTC - Institute of Molecular and Translational Cardiology, San Donato Milanese, Italy
| | - Dario Melgari
- IMTC - Institute of Molecular and Translational Cardiology, San Donato Milanese, Italy
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Milan Center for Neuroscience (NeuroMI), Monza, Italy
| | - Serena Calamaio
- IMTC - Institute of Molecular and Translational Cardiology, San Donato Milanese, Italy
| | - Rachele Prevostini
- IMTC - Institute of Molecular and Translational Cardiology, San Donato Milanese, Italy
| | - Mario Mauri
- School of Medicine and Surgery, University of Milano-Bicocca, Milan Center for Neuroscience (NeuroMI), Monza, Italy
| | - Laura Canafoglia
- Integrated Diagnostics for Epilepsy, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Barbara Castellotti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Giuliana Messina
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Cinzia Gellera
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Roberto Previtali
- Pediatric Neurology Unit, V. Buzzi Hospital, University of Milan, Milan, Italy
| | | | - Raffaella Milanesi
- Department of Veterinary Medicine and Animal Science, University of Milan, Lodi, Italy
| | - Andrea Barbuti
- The Cell Physiology MiLab, Department of Biosciences, University of Milano, Milan, Italy
| | - Roberta Solazzi
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Freri
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Ilaria Rivolta
- School of Medicine and Surgery, University of Milano-Bicocca, Milan Center for Neuroscience (NeuroMI), Monza, Italy
- IMTC - Institute of Molecular and Translational Cardiology, San Donato Milanese, Italy
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6
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Crunelli V, David F, Morais TP, Lorincz ML. HCN channels and absence seizures. Neurobiol Dis 2023; 181:106107. [PMID: 37001612 DOI: 10.1016/j.nbd.2023.106107] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/20/2023] [Accepted: 03/25/2023] [Indexed: 03/31/2023] Open
Abstract
Hyperpolarization-activation cyclic nucleotide-gated (HCN) channels were for the first time implicated in absence seizures (ASs) when an abnormal Ih (the current generated by these channels) was reported in neocortical layer 5 neurons of a mouse model. Genetic studies of large cohorts of children with Childhood Absence Epilepsy (where ASs are the only clinical symptom) have identified only 3 variants in HCN1 (one of the genes that code for the 4 HCN channel isoforms, HCN1-4), with one (R590Q) mutation leading to loss-of-function. Due to the multi-faceted effects that HCN channels exert on cellular excitability and neuronal network dynamics as well as their modulation by environmental factors, it has been difficult to identify the detailed mechanism by which different HCN isoforms modulate ASs. In this review, we systematically and critically analyze evidence from established AS models and normal non-epileptic animals with area- and time-selective ablation of HCN1, HCN2 and HCN4. Notably, whereas knockout of rat HCN1 and mouse HCN2 leads to the expression of ASs, the pharmacological block of all HCN channel isoforms abolishes genetically determined ASs. These seemingly contradictory results could be reconciled by taking into account the well-known opposite effects of Ih on cellular excitability and network function. Whereas existing evidence from mouse and rat AS models indicates that pan-HCN blockers may provide a novel approach for the treatment of human ASs, the development of HCN isoform-selective drugs would greatly contribute to current research on the role for these channels in ASs generation and maintenance as well as offer new potential clinical applications.
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Affiliation(s)
- Vincenzo Crunelli
- Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK.
| | - Francois David
- Integrative Neuroscience and Cognition Center, Paris University, Paris, France
| | - Tatiana P Morais
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, Malta University, Msida, Malta
| | - Magor L Lorincz
- Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK; Department of Physiology, Szeged University, Szeged, Hungary.
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Depolarization and Hyperexcitability of Cortical Motor Neurons after Spinal Cord Injury Associates with Reduced HCN Channel Activity. Int J Mol Sci 2023; 24:ijms24054715. [PMID: 36902146 PMCID: PMC10003573 DOI: 10.3390/ijms24054715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/24/2023] [Accepted: 02/25/2023] [Indexed: 03/05/2023] Open
Abstract
A spinal cord injury (SCI) damages the axonal projections of neurons residing in the neocortex. This axotomy changes cortical excitability and results in dysfunctional activity and output of infragranular cortical layers. Thus, addressing cortical pathophysiology after SCI will be instrumental in promoting recovery. However, the cellular and molecular mechanisms of cortical dysfunction after SCI are poorly resolved. In this study, we determined that the principal neurons of the primary motor cortex layer V (M1LV), those suffering from axotomy upon SCI, become hyperexcitable following injury. Therefore, we questioned the role of hyperpolarization cyclic nucleotide gated channels (HCN channels) in this context. Patch clamp experiments on axotomized M1LV neurons and acute pharmacological manipulation of HCN channels allowed us to resolve a dysfunctional mechanism controlling intrinsic neuronal excitability one week after SCI. Some axotomized M1LV neurons became excessively depolarized. In those cells, the HCN channels were less active and less relevant to control neuronal excitability because the membrane potential exceeded the window of HCN channel activation. Care should be taken when manipulating HCN channels pharmacologically after SCI. Even though the dysfunction of HCN channels partakes in the pathophysiology of axotomized M1LV neurons, their dysfunctional contribution varies remarkably between neurons and combines with other pathophysiological mechanisms.
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Kessi M, Peng J, Duan H, He H, Chen B, Xiong J, Wang Y, Yang L, Wang G, Kiprotich K, Bamgbade OA, He F, Yin F. The Contribution of HCN Channelopathies in Different Epileptic Syndromes, Mechanisms, Modulators, and Potential Treatment Targets: A Systematic Review. Front Mol Neurosci 2022; 15:807202. [PMID: 35663267 PMCID: PMC9161305 DOI: 10.3389/fnmol.2022.807202] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 04/06/2022] [Indexed: 12/04/2022] Open
Abstract
Background Hyperpolarization-activated cyclic nucleotide-gated (HCN) current reduces dendritic summation, suppresses dendritic calcium spikes, and enables inhibitory GABA-mediated postsynaptic potentials, thereby suppressing epilepsy. However, it is unclear whether increased HCN current can produce epilepsy. We hypothesized that gain-of-function (GOF) and loss-of-function (LOF) variants of HCN channel genes may cause epilepsy. Objectives This systematic review aims to summarize the role of HCN channelopathies in epilepsy, update genetic findings in patients, create genotype–phenotype correlations, and discuss animal models, GOF and LOF mechanisms, and potential treatment targets. Methods The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, for all years until August 2021. Results We identified pathogenic variants of HCN1 (n = 24), HCN2 (n = 8), HCN3 (n = 2), and HCN4 (n = 6) that were associated with epilepsy in 74 cases (43 HCN1, 20 HCN2, 2 HCN3, and 9 HCN4). Epilepsy was associated with GOF and LOF variants, and the mechanisms were indeterminate. Less than half of the cases became seizure-free and some developed drug-resistant epilepsy. Of the 74 cases, 12 (16.2%) died, comprising HCN1 (n = 4), HCN2 (n = 2), HCN3 (n = 2), and HCN4 (n = 4). Of the deceased cases, 10 (83%) had a sudden unexpected death in epilepsy (SUDEP) and 2 (16.7%) due to cardiopulmonary failure. SUDEP affected more adults (n = 10) than children (n = 2). HCN1 variants p.M234R, p.C329S, p.V414M, p.M153I, and p.M305L, as well as HCN2 variants p.S632W and delPPP (p.719–721), were associated with different phenotypes. HCN1 p.L157V and HCN4 p.R550C were associated with genetic generalized epilepsy. There are several HCN animal models, pharmacological targets, and modulators, but precise drugs have not been developed. Currently, there are no HCN channel openers. Conclusion We recommend clinicians to include HCN genes in epilepsy gene panels. Researchers should explore the possible underlying mechanisms for GOF and LOF variants by identifying the specific neuronal subtypes and neuroanatomical locations of each identified pathogenic variant. Researchers should identify specific HCN channel openers and blockers with high binding affinity. Such information will give clarity to the involvement of HCN channelopathies in epilepsy and provide the opportunity to develop targeted treatments.
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Affiliation(s)
- Miriam Kessi
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
- Department of Pediatrics, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Haolin Duan
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Hailan He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Baiyu Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Juan Xiong
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Ying Wang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Lifen Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Guoli Wang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Karlmax Kiprotich
- Department of Epidemiology and Medical Statistics, School of Public Health, Moi University, Eldoret, Kenya
| | - Olumuyiwa A. Bamgbade
- Department of Anesthesiology and Pharmacology, University of British Columbia, Vancouver, BC, Canada
| | - Fang He
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, China
- *Correspondence: Fei Yin
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Mayar S, Memarpoor-Yazdi M, Makky A, Eslami Sarokhalil R, D'Avanzo N. Direct Regulation of Hyperpolarization-Activated Cyclic-Nucleotide Gated (HCN1) Channels by Cannabinoids. Front Mol Neurosci 2022; 15:848540. [PMID: 35465092 PMCID: PMC9019169 DOI: 10.3389/fnmol.2022.848540] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 02/21/2022] [Indexed: 11/24/2022] Open
Abstract
Cannabinoids are a broad class of molecules that act primarily on neurons, affecting pain sensation, appetite, mood, learning, and memory. In addition to interacting with specific cannabinoid receptors (CBRs), cannabinoids can directly modulate the function of various ion channels. Here, we examine whether cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC), the most prevalent phytocannabinoids in Cannabis sativa, can regulate the function of hyperpolarization-activated cyclic-nucleotide-gated (HCN1) channels independently of CBRs. HCN1 channels were expressed in Xenopus oocytes since they do not express CBRs, and the effects of cannabinoid treatment on HCN1 currents were examined by a two-electrode voltage clamp. We observe opposing effects of CBD and THC on HCN1 current, with CBD acting to stimulate HCN1 function, while THC inhibited current. These effects persist in HCN1 channels lacking the cyclic-nucleotide binding domain (HCN1ΔCNBD). However, changes to membrane fluidity, examined by treating cells with TX-100, inhibited HCN1 current had more pronounced effects on the voltage-dependence and kinetics of activation than THC, suggesting this is not the primary mechanism of HCN1 regulation by cannabinoids. Our findings may contribute to the overall understanding of how cannabinoids may act as promising therapeutic molecules for the treatment of several neurological disorders in which HCN function is disturbed.
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Liu XR, Xu XX, Lin SM, Fan CY, Ye TT, Tang B, Shi YW, Su T, Li BM, Yi YH, Luo JH, Liao WP. GRIN2A Variants Associated With Idiopathic Generalized Epilepsies. Front Mol Neurosci 2021; 14:720984. [PMID: 34720871 PMCID: PMC8551482 DOI: 10.3389/fnmol.2021.720984] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 08/30/2021] [Indexed: 12/16/2022] Open
Abstract
Objective: The objective of this study is to explore the role of GRIN2A gene in idiopathic generalized epilepsies and the potential underlying mechanism for phenotypic variation. Methods: Whole-exome sequencing was performed in a cohort of 88 patients with idiopathic generalized epilepsies. Electro-physiological alterations of the recombinant N-methyl-D-aspartate receptors (NMDARs) containing GluN2A mutants were examined using two-electrode voltage-clamp recordings. The alterations of protein expression were detected by immunofluorescence staining and biotinylation. Previous studies reported that epilepsy related GRIN2A missense mutations were reviewed. The correlation among phenotypes, functional alterations, and molecular locations was analyzed. Results: Three novel heterozygous missense GRIN2A mutations (c.1770A > C/p.K590N, c.2636A > G/p.K879R, and c.3199C > T/p.R1067W) were identified in three unrelated cases. Electrophysiological analysis demonstrated R1067W significantly increased the current density of GluN1/GluN2A NMDARs. Immunofluorescence staining indicated GluN2A mutants had abundant distribution in the membrane and cytoplasm. Western blotting showed the ratios of surface and total expression of the three GluN2A-mutants were significantly increased comparing to the wild type. Further analysis on the reported missense mutations demonstrated that mutations with severe gain-of-function were associated with epileptic encephalopathy, while mutations with mild gain of function were associated with mild phenotypes, suggesting a quantitative correlation between gain-of-function and phenotypic severity. The mutations located around transmembrane domains were more frequently associated with severe phenotypes and absence seizure-related mutations were mostly located in carboxyl-terminal domain, suggesting molecular sub-regional effects. Significance: This study revealed GRIN2A gene was potentially a candidate pathogenic gene of idiopathic generalized epilepsies. The functional quantitative correlation and the molecular sub-regional implication of mutations helped in explaining the relatively mild clinical phenotypes and incomplete penetrance associated with GRIN2A variants.
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Affiliation(s)
- Xiao-Rong Liu
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Xing-Xing Xu
- Department of Physiology, Wenzhou Medical University, Wenzhou, China
| | - Si-Mei Lin
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Cui-Ying Fan
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Ting-Ting Ye
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Bin Tang
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yi-Wu Shi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Tao Su
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Bing-Mei Li
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yong-Hong Yi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Jian-Hong Luo
- NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, School of Brain Science and Brain Medicine, Zhejiang University School of Medicine, Hangzhou, China
| | - Wei-Ping Liao
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
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11
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Rodríguez-Ortiz R, Matínez-Torres A. Mutants of the Zebrafish K + Channel Hcn2b Exhibit Epileptic-like Behaviors. Int J Mol Sci 2021; 22:ijms222111471. [PMID: 34768904 PMCID: PMC8584164 DOI: 10.3390/ijms222111471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/06/2021] [Accepted: 10/21/2021] [Indexed: 02/02/2023] Open
Abstract
Epilepsy is a chronic neurological disorder that affects 50 million people worldwide. The most common form of epilepsy is idiopathic, where most of the genetic defects of this type of epilepsy occur in ion channels. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are activated by membrane hyperpolarization, and are mainly expressed in the heart and central and peripheral nervous systems. In humans, four HCN genes have been described, and emergent clinical data shows that dysfunctional HCN channels are involved in epilepsy. Danio rerio has become a versatile organism to model a wide variety of diseases. In this work, we used CRISPR/Cas9 to generate hcn2b mutants in zebrafish, and characterized them molecularly and behaviorally. We obtained an hcn2b mutant allele with an 89 bp deletion that produced a premature stop codon. The mutant exhibited a high mortality rate in its life span, probably due to its sudden death. We did not detect heart malformations or important heart rate alterations. Absence seizures and moderate seizures were observed in response to light. These seizures rarely caused instant death. The results show that mutations in the Hcn2b channel are involved in epilepsy and provide evidence of the advantages of zebrafish to further our understanding of the pathogenesis of epilepsy.
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Affiliation(s)
- Roberto Rodríguez-Ortiz
- Cátedras CONACyT—Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus UNAM-Juriquilla, Universidad Nacional Autónoma de México, Querétaro CP 76230, Mexico
- Correspondence: (R.R.-O.); (A.M.-T.); Tel.: +52-442-238-1064 (R.R.-O. & A.M.-T.)
| | - Ataúlfo Matínez-Torres
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus UNAM-Juriquilla, Universidad Nacional Autónoma de México, Querétaro CP 76230, Mexico
- Correspondence: (R.R.-O.); (A.M.-T.); Tel.: +52-442-238-1064 (R.R.-O. & A.M.-T.)
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12
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Yu H, Gall B, Newman M, Hathaway Q, Brundage K, Ammer A, Mathers P, Siderovski D, Hull RW. Contribution of HCN1 variant to sinus bradycardia: A case report. J Arrhythm 2021; 37:1337-1347. [PMID: 34621433 PMCID: PMC8485797 DOI: 10.1002/joa3.12598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 06/08/2021] [Accepted: 06/26/2021] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Missense mutations in the hyperpolarization-activated cyclic nucleotide-modulated (HCN) channel 4 (HCN4) are one of the genetic causes of cardiac sinus bradycardia. OBJECTIVE To investigate possible HCN4 channel mutation in a young patient with profound sinus bradycardia. METHODS Direct sequencing of HCN4 and whole-exome sequencing were performed on DNA samples from the indexed patient (P), the patient's son (PS), and a family unrelated healthy long-distance running volunteer (V). Resting heart rate was 31 bpm for P, 67 bpm for PS, and 50 bpm for V. Immunoblots, flow cytometry, and immunocytofluorescence confocal imaging were used to study cellular distribution of channel variants. Patch-clamp electrophysiology was used to investigate the properties of mutant HCN1 channels. RESULTS In P no missense mutations were found in the HCN4 gene; instead, we found two heterozygous variants in the HCN1 gene: deletion of an N-terminal glycine triplet (72GGG74, "N-del") and a novel missense variant, P851A, in the C-terminal region. N-del variant was found before and shared by PS. These two variations were not found in V. Compared to wild type, N-del and P851A reduced cell surface expression and negatively shifted voltage-activation with slower activation kinetics. CONCLUSION Decreased channel activity HCN1 mutant channel makes it unable to contribute to early depolarization of sinus node action potential, thus likely a main cause of the profound sinus bradycardia in this patient.
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Affiliation(s)
- Hangang Yu
- Department of Physiology and PharmacologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - Bryan Gall
- Department of Physiology and PharmacologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
- Present address:
Variant Curator at NateraSan CarlosCAUSA
| | - Mackenzie Newman
- Department of Physiology and PharmacologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - Quincy Hathaway
- Department of Exercise PhysiologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - Kathleen Brundage
- Department of Microbiology, Immunology & Cell BiologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - Amanda Ammer
- Department of Microbiology, Immunology & Cell BiologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - Peter Mathers
- Department of NeuroscienceSchool of MedicineWest Virginia UniversityMorgantownWVUSA
| | - David Siderovski
- Department of Physiology and PharmacologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
- Present address:
Pharmacology & NeuroscienceUniversity of North TexasDentonTXUSA
| | - Robert W. Hull
- Department of CardiologySchool of MedicineWest Virginia UniversityMorgantownWVUSA
- Present address:
Department of CardiologyMon General HospitalMorgantownWVUSA
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13
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Porro A, Abbandonato G, Veronesi V, Russo A, Binda A, Antolini L, Granata T, Castellotti B, Marini C, Moroni A, DiFrancesco JC, Rivolta I. Do the functional properties of HCN1 mutants correlate with the clinical features in epileptic patients? PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:147-155. [PMID: 34310985 DOI: 10.1016/j.pbiomolbio.2021.07.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/14/2021] [Accepted: 07/20/2021] [Indexed: 10/20/2022]
Abstract
The altered function of the Hyperpolarization-activated Cyclic-Nucleotide-gated (HCN) ion channels plays an important role in the pathogenesis of epilepsy in humans. In particular, HCN1 missense mutations have been recently identified in patients with different epileptic phenotypes, varying from mild to severe. Their electrophysiological characterization shows that mutated channels can act both with loss-of-function and gain-of-function mechanisms of action, without an evident correlation with the phenotype. In search for a correlation between clinical features and biophysical properties of the mutations, in this work we considered sixteen HCN1 mutations, found in eighteen Early Infantile Epileptic Encephalopathy (EIEE) patients. Statistical analysis did not establish any significant correlation between the clinical parameters and the current properties of the mutant channels. The lack of significance of our results could depend on the small number of mutations analyzed, epilepsy-associated with certainty. With the progressive increase of Next Generation Sequencing in patients with early-onset epilepsy, it is expected that the number of patients with HCN1 mutations will grow steadily. Functional characterization of epilepsy-associated HCN1 mutations remains a fundamental tool for a better understanding of the pathogenetic mechanisms leading to the disease in humans.
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Affiliation(s)
| | | | - Valentina Veronesi
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Alberto Russo
- Department of Biosciences, University of Milan, Milan, Italy.
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Laura Antolini
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.
| | - Barbara Castellotti
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.
| | - Carla Marini
- Department of Child Neuropsychiatry, Children's Hospital, Ancona, Italy.
| | - Anna Moroni
- Department of Biosciences, University of Milan, Milan, Italy.
| | - Jacopo C DiFrancesco
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Department of Neurology, Epilepsy Center, ASST San Gerardo Hospital, University of Milano- Bicocca, Monza, Italy.
| | - Ilaria Rivolta
- School of Medicine and Surgery and Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy.
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14
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Iacone Y, Morais TP, David F, Delicata F, Sandle J, Raffai T, Parri HR, Weisser JJ, Bundgaard C, Klewe IV, Tamás G, Thomsen MS, Crunelli V, Lőrincz ML. Systemic administration of ivabradine, a hyperpolarization-activated cyclic nucleotide-gated channel inhibitor, blocks spontaneous absence seizures. Epilepsia 2021; 62:1729-1743. [PMID: 34018186 PMCID: PMC9543052 DOI: 10.1111/epi.16926] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 04/27/2021] [Accepted: 04/27/2021] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are known to be involved in the generation of absence seizures (ASs), and there is evidence that cortical and thalamic HCN channel dysfunctions may have a proabsence role. Many HCN channel blockers are available, but their role in ASs has been investigated only by localized brain injection or in in vitro model systems due to their limited brain availability. Here, we investigated the effect on ASs of orally administered ivabradine (an HCN channel blocker approved for the treatment of heart failure in humans) following injection of the P-glycoprotein inhibitor elacridar, which is known to increase penetration into the brain of drug substrates for this efflux transporter. The action of ivabradine was also tested following in vivo microinjection into the cortical initiation network (CIN) of the somatosensory cortex and in the thalamic ventrobasal nucleus (VB) as well as on cortical and thalamocortical neurons in brain slices. METHODS We used electroencephalographic recordings in freely moving Genetic Absence Epilepsy Rats From Strasbourg (GAERSs) to assess the action of oral administration of ivabradine, with and without elacridar, on ASs. Ivabradine was also microinjected into the CIN and VB of GAERSs in vivo and applied to Wistar CIN and GAERS VB slices while recording patch-clamped cortical Layer 5/6 and thalamocortical neurons, respectively. RESULTS Oral administration of ivabradine markedly and dose-dependently reduced ASs. Ivabradine injection into CIN abolished ASs and elicited small-amplitude 4-7-Hz waves (without spikes), whereas in the VB it was less potent. Moreover, ivabradine applied to GAERS VB and Wistar CIN slices selectively decreased HCN channel-dependent properties of cortical Layer 5/6 pyramidal and thalamocortical neurons, respectively. SIGNIFICANCE These results provide the first demonstration of the antiabsence action of a systemically administered HCN channel blocker, indicating the potential of this class of drugs as a novel therapeutic avenue for ASs.
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Affiliation(s)
- Yasmine Iacone
- Neuroscience ResearchH. Lundbeck A/S, ValbyCopenhagenDenmark
- Biomedical SciencesFaculty of Health and Medical SciencesCopenhagen UniversityCopenhagenDenmark
| | - Tatiana P. Morais
- Neuroscience DivisionSchool of BiosciencesCardiff UniversityCardiffUK
| | - François David
- Integrative Neuroscience and Cognition CenterUniversity of ParisParisFrance
| | | | - Joanna Sandle
- Department of Anatomy, Physiology, and NeuroscienceMTA‐SZTE Research Group for Cortical MicrocircuitsUniversity of SzegedSzegedHungary
| | - Timea Raffai
- Department of Physiology, Anatomy, and NeuroscienceFaculty of SciencesUniversity of SzegedSzegedHungary
- Department of PhysiologyFaculty of MedicineUniversity of SzegedSzegedHungary
| | | | | | | | | | - Gábor Tamás
- Department of Anatomy, Physiology, and NeuroscienceMTA‐SZTE Research Group for Cortical MicrocircuitsUniversity of SzegedSzegedHungary
| | | | - Vincenzo Crunelli
- Neuroscience DivisionSchool of BiosciencesCardiff UniversityCardiffUK
- Department of Physiology and BiochemistryFaculty of Medicine and SurgeryUniversity of MaltaMsidaMalta
| | - Magor L. Lőrincz
- Neuroscience DivisionSchool of BiosciencesCardiff UniversityCardiffUK
- Department of Physiology, Anatomy, and NeuroscienceFaculty of SciencesUniversity of SzegedSzegedHungary
- Department of PhysiologyFaculty of MedicineUniversity of SzegedSzegedHungary
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15
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Loss of HCN2 in Dorsal Hippocampus of Young Adult Mice Induces Specific Apoptosis of the CA1 Pyramidal Neuron Layer. Int J Mol Sci 2021; 22:ijms22136699. [PMID: 34206649 PMCID: PMC8269412 DOI: 10.3390/ijms22136699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/08/2021] [Accepted: 06/18/2021] [Indexed: 11/20/2022] Open
Abstract
Neurons inevitably rely on a proper repertoire and distribution of membrane-bound ion-conducting channels. Among these proteins, the family of hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels possesses unique properties giving rise to the corresponding Ih-current that contributes to various aspects of neural signaling. In mammals, four genes (hcn1-4) encode subunits of HCN channels. These subunits can assemble as hetero- or homotetrameric ion-conducting channels. In order to elaborate on the specific role of the HCN2 subunit in shaping electrical properties of neurons, we applied an Adeno-associated virus (AAV)-mediated, RNAi-based knock-down strategy of hcn2 gene expression both in vitro and in vivo. Electrophysiological measurements showed that HCN2 subunit knock-down resulted in specific yet anticipated changes in Ih-current properties in primary hippocampal neurons and, in addition, corroborated that the HCN2 subunit participates in postsynaptic signal integration. To further address the role of the HCN2 subunit in vivo, we injected recombinant (r)AAVs into the dorsal hippocampus of young adult male mice. Behavioral and biochemical analyses were conducted to assess the contribution of HCN2-containing channels in shaping hippocampal network properties. Surprisingly, knock-down of hcn2 expression resulted in a severe degeneration of the CA1 pyramidal cell layer, which did not occur in mice injected with control rAAV constructs. This finding might pinpoint to a vital and yet unknown contribution of HCN2 channels in establishing or maintaining the proper function of CA1 pyramidal neurons of the dorsal hippocampus.
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16
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Concepcion FA, Khan MN, Ju Wang JD, Wei AD, Ojemann JG, Ko AL, Shi Y, Eng JK, Ramirez JM, Poolos NP. HCN Channel Phosphorylation Sites Mapped by Mass Spectrometry in Human Epilepsy Patients and in an Animal Model of Temporal Lobe Epilepsy. Neuroscience 2021; 460:13-30. [PMID: 33571596 DOI: 10.1016/j.neuroscience.2021.01.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/07/2021] [Accepted: 01/26/2021] [Indexed: 10/22/2022]
Abstract
Because hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels modulate the excitability of cortical and hippocampal principal neurons, these channels play a key role in the hyperexcitability that occurs during the development of epilepsy after a brain insult, or epileptogenesis. In epileptic rats generated by pilocarpine-induced status epilepticus, HCN channel activity is downregulated by two main mechanisms: a hyperpolarizing shift in gating and a decrease in amplitude of the current mediated by HCN channels, Ih. Because these mechanisms are modulated by various phosphorylation signaling pathways, we hypothesized that phosphorylation changes occur at individual HCN channel amino acid residues (phosphosites) during epileptogenesis. We collected CA1 hippocampal tissue from male Sprague Dawley rats made epileptic by pilocarpine-induced status epilepticus, and age-matched naïve controls. We also included resected human brain tissue containing epileptogenic zones (EZs) where seizures arise for comparison to our chronically epileptic rats. After enrichment for HCN1 and HCN2 isoforms by immunoprecipitation and trypsin in-gel digestion, the samples were analyzed by mass spectrometry. We identified numerous phosphosites from HCN1 and HCN2 channels, representing a novel survey of phosphorylation sites within HCN channels. We found high levels of HCN channel phosphosite homology between humans and rats. We also identified a novel HCN1 channel phosphosite S791, which underwent significantly increased phosphorylation during the chronic epilepsy stage. Heterologous expression of a phosphomimetic mutant, S791D, replicated a hyperpolarizing shift in Ih gating seen in neurons from chronically epileptic rats. These results show that HCN1 channel phosphorylation is altered in epilepsy and may be of pathogenic importance.
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Affiliation(s)
- F A Concepcion
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, WA, United States
| | - M N Khan
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, WA, United States
| | - J-D Ju Wang
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA, United States
| | - A D Wei
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA, United States
| | - J G Ojemann
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA, United States; Department of Neurological Surgery, University of Washington, Seattle, WA, United States
| | - A L Ko
- Department of Neurological Surgery, University of Washington, Seattle, WA, United States
| | - Y Shi
- Department of Electrical and Computer Engineering, University of Washington, Seattle, WA, United States
| | - J K Eng
- Proteomics Resource, University of Washington, Seattle, WA, United States
| | - J-M Ramirez
- Seattle Children's Research Institute, Center for Integrative Brain Research, Seattle, WA, United States; Department of Neurological Surgery, University of Washington, Seattle, WA, United States
| | - N P Poolos
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, WA, United States.
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17
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Han Y, Lyman KA, Foote KM, Chetkovich DM. The structure and function of TRIP8b, an auxiliary subunit of hyperpolarization-activated cyclic-nucleotide gated channels. Channels (Austin) 2020; 14:110-122. [PMID: 32189562 PMCID: PMC7153792 DOI: 10.1080/19336950.2020.1740501] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 02/18/2020] [Accepted: 02/21/2020] [Indexed: 02/08/2023] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed throughout the mammalian central nervous system (CNS). These channels have been implicated in a wide range of diseases, including Major Depressive Disorder and multiple subtypes of epilepsy. The diversity of functions that HCN channels perform is in part attributable to differences in their subcellular localization. To facilitate a broad range of subcellular distributions, HCN channels are bound by auxiliary subunits that regulate surface trafficking and channel function. One of the best studied auxiliary subunits is tetratricopeptide-repeat containing, Rab8b-interacting protein (TRIP8b). TRIP8b is an extensively alternatively spliced protein whose only known function is to regulate HCN channels. TRIP8b binds to HCN pore-forming subunits at multiple interaction sites that differentially regulate HCN channel function and subcellular distribution. In this review, we summarize what is currently known about the structure and function of TRIP8b isoforms with an emphasis on the role of this auxiliary subunit in health and disease.
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Affiliation(s)
- Ye Han
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kyle A. Lyman
- Department of Neurology, Stanford University, Palo Alto, CA, USA
| | - Kendall M. Foote
- Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Dane M. Chetkovich
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN, USA
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18
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Santoro B, Shah MM. Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels as Drug Targets for Neurological Disorders. Annu Rev Pharmacol Toxicol 2020; 60:109-131. [PMID: 31914897 DOI: 10.1146/annurev-pharmtox-010919-023356] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are voltage-gated ion channels that critically modulate neuronal activity. Four HCN subunits (HCN1-4) have been cloned, each having a unique expression profile and distinctive effects on neuronal excitability within the brain. Consistent with this, the expression and function of these subunits are altered in diverse ways in neurological disorders. Here, we review current knowledge on the structure and distribution of the individual HCN channel isoforms, their effects on neuronal activity under physiological conditions, and how their expression and function are altered in neurological disorders, particularly epilepsy, neuropathic pain, and affective disorders. We discuss the suitability of HCN channels as therapeutic targets and how drugs might be strategically designed to specifically act on particular isoforms. We conclude that medicines that target individual HCN isoforms and/or their auxiliary subunit, TRIP8b, may provide valuable means of treating distinct neurological conditions.
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Affiliation(s)
- Bina Santoro
- Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | - Mala M Shah
- Department of Pharmacology, School of Pharmacy, University College London, London WC1N 1AX, United Kingdom;
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19
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Hernandez-Ronquillo L, Miranzadeh Mahabadi H, Moien-Afshari F, Wu A, Auer R, Zherebitskiy V, Borowsky R, Mickleborough M, Huntsman R, Vrbancic M, Cayabyab FS, Taghibiglou C, Carter A, Tellez-Zenteno JF. The Concept of an Epilepsy Brain Bank. Front Neurol 2020; 11:833. [PMID: 32973652 PMCID: PMC7468480 DOI: 10.3389/fneur.2020.00833] [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: 04/17/2020] [Accepted: 07/03/2020] [Indexed: 12/31/2022] Open
Abstract
Epilepsy comprises more than 40 clinical syndromes affecting millions of patients and families worldwide. To decode the molecular and pathological framework of epilepsy researchers, need reliable human epilepsy and control brain samples. Brain bank organizations collecting and supplying well-documented clinically and pathophysiologically tissue specimens are important for high-quality neurophysiology and neuropharmacology studies for epilepsy and other neurological diseases. New development in molecular mechanism and new treatment methods for neurological disorders have evoked increased demands for human brain tissue. An epilepsy brain bank is a storage source for both the frozen samples as well as the formaldehyde fixed paraffin embedded (FFPE) tissue from epilepsy surgery resections. In 2014, the University of Saskatchewan have started collecting human epilepsy brain tissues for the first time in Canada. This review highlights the necessity and importance of Epilepsy Brain bank that provides unique access for research to valuable source of brain tissue and blood samples from epilepsy patients.
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Affiliation(s)
- Lizbeth Hernandez-Ronquillo
- Saskatchewan Epilepsy Program, Division of Neurology, Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Hajar Miranzadeh Mahabadi
- Department of Anatomy, Physiology and Pharmacology, College of Medicine University of Saskatchewan, Saskatoon, SK, Canada
| | | | - Adam Wu
- Division of Neurosurgery, Department of Surgery, University of Saskatchewan, Saskatoon, SK, Canada
| | - Roland Auer
- Department of Pathology and Laboratory Medicine, Royal University Hospital, Saskatchewan Health Region, University of Saskatchewan, Saskatoon, SK, Canada
| | - Viktor Zherebitskiy
- Department of Pathology and Laboratory Medicine, Royal University Hospital, Saskatchewan Health Region, University of Saskatchewan, Saskatoon, SK, Canada
| | - Ron Borowsky
- Cognitive Neuroscience Laboratory, Department of Psychology, College of Arts and Science, University of Saskatchewan, Saskatoon, SK, Canada
| | - Marla Mickleborough
- Cognitive Neuroscience Laboratory, Department of Psychology, College of Arts and Science, University of Saskatchewan, Saskatoon, SK, Canada
| | - Richard Huntsman
- Division of Pediatric Neurology, Department of Pediatrics, University of Saskatchewan, Saskatoon, SK, Canada
| | - Mirna Vrbancic
- Department of Clinical Health Psychology, Ellis Hall, Royal University Hospital, Saskatoon, SK, Canada
| | - Francisco S Cayabyab
- Division of Neurosurgery, Department of Surgery, University of Saskatchewan, Saskatoon, SK, Canada
| | - Changiz Taghibiglou
- Department of Anatomy, Physiology and Pharmacology, College of Medicine University of Saskatchewan, Saskatoon, SK, Canada
| | - Alexandra Carter
- Saskatchewan Epilepsy Program, Division of Neurology, Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
| | - Jose F Tellez-Zenteno
- Saskatchewan Epilepsy Program, Division of Neurology, Department of Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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20
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Rivolta I, Binda A, Masi A, DiFrancesco JC. Cardiac and neuronal HCN channelopathies. Pflugers Arch 2020; 472:931-951. [PMID: 32424620 DOI: 10.1007/s00424-020-02384-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 04/21/2020] [Accepted: 04/24/2020] [Indexed: 12/31/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed as four different isoforms (HCN1-4) in the heart and in the central and peripheral nervous systems. In the voltage range of activation, HCN channels carry an inward current mediated by Na+ and K+, termed If in the heart and Ih in neurons. Altered function of HCN channels, mainly HCN4, is associated with sinus node dysfunction and other arrhythmias such as atrial fibrillation, ventricular tachycardia, and atrioventricular block. In recent years, several data have also shown that dysfunctional HCN channels, in particular HCN1, but also HCN2 and HCN4, can play a pathogenic role in epilepsy; these include experimental data from animal models, and data collected over genetic mutations of the channels identified and characterized in epileptic patients. In the central nervous system, alteration of the Ih current could predispose to the development of neurodegenerative diseases such as Parkinson's disease; since HCN channels are widely expressed in the peripheral nervous system, their dysfunctional behavior could also be associated with the pathogenesis of neuropathic pain. Given the fundamental role played by the HCN channels in the regulation of the discharge activity of cardiac and neuronal cells, the modulation of their function for therapeutic purposes is under study since it could be useful in various pathological conditions. Here we review the present knowledge of the HCN-related channelopathies in cardiac and neurological diseases, including clinical, genetic, therapeutic, and physiopathological aspects.
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Affiliation(s)
- Ilaria Rivolta
- School of Medicine and Surgery, Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy
| | - Anna Binda
- School of Medicine and Surgery, Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy
| | - Alessio Masi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), section of Pharmacology and Toxicology, University of Florence, Florence, Italy
| | - Jacopo C DiFrancesco
- School of Medicine and Surgery, Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy. .,Department of Neurology, ASST San Gerardo Hospital, University of Milano-Bicocca, Via Pergolesi, 33, 20900, Monza, MB, Italy.
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21
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Wang ZJ, Blanco I, Hayoz S, Brelidze TI. The HCN domain is required for HCN channel cell-surface expression and couples voltage- and cAMP-dependent gating mechanisms. J Biol Chem 2020; 295:8164-8173. [PMID: 32341127 DOI: 10.1074/jbc.ra120.013281] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 04/23/2020] [Indexed: 11/06/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are major regulators of synaptic plasticity and rhythmic activity in the heart and brain. Opening of HCN channels requires membrane hyperpolarization and is further facilitated by intracellular cyclic nucleotides (cNMPs). In HCN channels, membrane hyperpolarization is sensed by the membrane-spanning voltage sensor domain (VSD), and the cNMP-dependent gating is mediated by the intracellular cyclic nucleotide-binding domain (CNBD) connected to the pore-forming S6 transmembrane segment via the C-linker. Previous functional analysis of HCN channels has suggested a direct or allosteric coupling between the voltage- and cNMP-dependent activation mechanisms. However, the specifics of this coupling remain unclear. The first cryo-EM structure of an HCN1 channel revealed that a novel structural element, dubbed the HCN domain (HCND), forms a direct structural link between the VSD and C-linker-CNBD. In this study, we investigated the functional significance of the HCND. Deletion of the HCND prevented surface expression of HCN2 channels. Based on the HCN1 structure analysis, we identified Arg237 and Gly239 residues on the S2 of the VSD that form direct interactions with Ile135 on the HCND. Disrupting these interactions abolished HCN2 currents. We also identified three residues on the C-linker-CNBD (Glu478, Gln482, and His559) that form direct interactions with residues Arg154 and Ser158 on the HCND. Disrupting these interactions affected both voltage- and cAMP-dependent gating of HCN2 channels. These findings indicate that the HCND is necessary for the cell-surface expression of HCN channels and provides a functional link between voltage- and cAMP-dependent mechanisms of HCN channel gating.
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Affiliation(s)
- Ze-Jun Wang
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D. C., USA
| | - Ismary Blanco
- Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, D. C., USA
| | - Sebastien Hayoz
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D. C., USA
| | - Tinatin I Brelidze
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, D. C., USA .,Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, D. C., USA
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22
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Thomas M, Ranjith G, Radhakrishnan A, Arun Anirudhan V. Effects of HCN2 Mutations on Dendritic Excitability and Synaptic Plasticity: A Computational Study. Neuroscience 2019; 423:148-161. [DOI: 10.1016/j.neuroscience.2019.10.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 10/07/2019] [Accepted: 10/09/2019] [Indexed: 12/12/2022]
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23
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Foote KM, Lyman KA, Han Y, Michailidis IE, Heuermann RJ, Mandikian D, Trimmer JS, Swanson GT, Chetkovich DM. Phosphorylation of the HCN channel auxiliary subunit TRIP8b is altered in an animal model of temporal lobe epilepsy and modulates channel function. J Biol Chem 2019; 294:15743-15758. [PMID: 31492750 DOI: 10.1074/jbc.ra119.010027] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/30/2019] [Indexed: 12/14/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is a prevalent neurological disorder with many patients experiencing poor seizure control with existing anti-epileptic drugs. Thus, novel insights into the mechanisms of epileptogenesis and identification of new drug targets can be transformative. Changes in ion channel function have been shown to play a role in generating the aberrant neuronal activity observed in TLE. Previous work demonstrates that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate neuronal excitability and are mislocalized within CA1 pyramidal cells in a rodent model of TLE. The subcellular distribution of HCN channels is regulated by an auxiliary subunit, tetratricopeptide repeat-containing Rab8b-interacting protein (TRIP8b), and disruption of this interaction correlates with channel mislocalization. However, the molecular mechanisms responsible for HCN channel dysregulation in TLE are unclear. Here we investigated whether changes in TRIP8b phosphorylation are sufficient to alter HCN channel function. We identified a phosphorylation site at residue Ser237 of TRIP8b that enhances binding to HCN channels and influences channel gating by altering the affinity of TRIP8b for the HCN cytoplasmic domain. Using a phosphospecific antibody, we demonstrate that TRIP8b phosphorylated at Ser237 is enriched in CA1 distal dendrites and that phosphorylation is reduced in the kainic acid model of TLE. Overall, our findings indicate that the TRIP8b-HCN interaction can be modulated by changes in phosphorylation and suggest that loss of TRIP8b phosphorylation may affect HCN channel properties during epileptogenesis. These results highlight the potential of drugs targeting posttranslational modifications to restore TRIP8b phosphorylation to reduce excitability in TLE.
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Affiliation(s)
- Kendall M Foote
- Davee Department of Neurology and Clinical Neurosciences, Northwestern University, Chicago, Illinois 60611.,Department of Pharmacology, Northwestern University, Chicago, Illinois 60611.,Vanderbilt University Medical Center Department of Neurology, Nashville, Tennessee 37232
| | - Kyle A Lyman
- Davee Department of Neurology and Clinical Neurosciences, Northwestern University, Chicago, Illinois 60611.,Vanderbilt University Medical Center Department of Neurology, Nashville, Tennessee 37232.,Department of Medicine, Stanford University, Palo Alto, California 94305
| | - Ye Han
- Davee Department of Neurology and Clinical Neurosciences, Northwestern University, Chicago, Illinois 60611.,Vanderbilt University Medical Center Department of Neurology, Nashville, Tennessee 37232
| | - Ioannis E Michailidis
- Vanderbilt University Medical Center Department of Neurology, Nashville, Tennessee 37232
| | - Robert J Heuermann
- Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Danielle Mandikian
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616
| | - James S Trimmer
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616.,Department of Physiology and Membrane Biology, University of California, Davis, California 95616
| | - Geoffrey T Swanson
- Department of Pharmacology, Northwestern University, Chicago, Illinois 60611.,Department of Neurobiology, Northwestern University, Evanston, Illinois 60208
| | - Dane M Chetkovich
- Vanderbilt University Medical Center Department of Neurology, Nashville, Tennessee 37232
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24
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DiFrancesco JC, Castellotti B, Milanesi R, Ragona F, Freri E, Canafoglia L, Franceschetti S, Ferrarese C, Magri S, Taroni F, Costa C, Labate A, Gambardella A, Solazzi R, Binda A, Rivolta I, Di Gennaro G, Casciato S, D’Incerti L, Barbuti A, DiFrancesco D, Granata T, Gellera C. HCN ion channels and accessory proteins in epilepsy: genetic analysis of a large cohort of patients and review of the literature. Epilepsy Res 2019; 153:49-58. [DOI: 10.1016/j.eplepsyres.2019.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/01/2019] [Accepted: 04/08/2019] [Indexed: 11/28/2022]
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25
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Lussier Y, Fürst O, Fortea E, Leclerc M, Priolo D, Moeller L, Bichet DG, Blunck R, D'Avanzo N. Disease-linked mutations alter the stoichiometries of HCN-KCNE2 complexes. Sci Rep 2019; 9:9113. [PMID: 31235733 PMCID: PMC6591248 DOI: 10.1038/s41598-019-45592-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 06/11/2019] [Indexed: 12/21/2022] Open
Abstract
The four hyperpolarization-activated cylic-nucleotide gated (HCN) channel isoforms and their auxiliary subunit KCNE2 are important in the regulation of peripheral and central neuronal firing and the heartbeat. Disruption of their normal function has been implicated in cardiac arrhythmias, peripheral pain, and epilepsy. However, molecular details of the HCN-KCNE2 complexes are unknown. Using single-molecule subunit counting, we determined that the number of KCNE2 subunits in complex with the pore-forming subunits of human HCN channels differs with each HCN isoform and is dynamic with respect to concentration. These interactions can be altered by KCNE2 gene-variants with functional implications. The results provide an additional consideration necessary to understand heart rhythm, pain, and epileptic disorders.
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Affiliation(s)
- Yoann Lussier
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Oliver Fürst
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Eva Fortea
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Marc Leclerc
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Dimitri Priolo
- Department of Physics, Université de Montréal, Montréal, Canada
| | - Lena Moeller
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Canada
| | - Daniel G Bichet
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Rikard Blunck
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada.,Department of Physics, Université de Montréal, Montréal, Canada
| | - Nazzareno D'Avanzo
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada. .,Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Canada.
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26
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Jepson JEC, Praschberger R, Krishnakumar SS. Mechanisms of Neurological Dysfunction in GOSR2 Progressive Myoclonus Epilepsy, a Golgi SNAREopathy. Neuroscience 2019; 420:41-49. [PMID: 30954670 DOI: 10.1016/j.neuroscience.2019.03.057] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 03/22/2019] [Accepted: 03/26/2019] [Indexed: 10/27/2022]
Abstract
Successive fusion events between transport vesicles and their target membranes mediate trafficking of secreted, membrane- and organelle-localised proteins. During the initial steps of this process, termed the secretory pathway, COPII vesicles bud from the endoplasmic reticulum (ER) and fuse with the cis-Golgi membrane, thus depositing their cargo. This fusion step is driven by a quartet of SNARE proteins that includes the cis-Golgi t-SNARE Membrin, encoded by the GOSR2 gene. Mis-sense mutations in GOSR2 result in Progressive Myoclonus Epilepsy (PME), a severe neurological disorder characterised by ataxia, myoclonus and seizures in the absence of significant cognitive impairment. However, given the ubiquitous and essential function of ER-to-Golgi transport, why GOSR2 mutations cause neurological dysfunction and not lethality or a broader range of developmental defects has remained an enigma. Here we highlight new work that has shed light on this issue and incorporate insights into canonical and non-canonical secretory trafficking pathways in neurons to speculate as to the cellular and molecular mechanisms underlying GOSR2 PME. This article is part of a Special Issue entitled: SNARE proteins: a long journey of science in brain physiology and pathology: from molecular.
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Affiliation(s)
- James E C Jepson
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK.
| | - Roman Praschberger
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK
| | - Shyam S Krishnakumar
- Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK; Department of Cell Biology, Yale School of Medicine, New Haven, CT, USA
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27
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Tanguay J, Callahan KM, D'Avanzo N. Characterization of drug binding within the HCN1 channel pore. Sci Rep 2019; 9:465. [PMID: 30679654 PMCID: PMC6345760 DOI: 10.1038/s41598-018-37116-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 11/29/2018] [Indexed: 11/09/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels mediate rhythmic electrical activity of cardiac pacemaker cells, and in neurons play important roles in setting resting membrane potentials, dendritic integration, neuronal pacemaking, and establishing action potential threshold. Block of HCN channels slows the heart rate and is currently used to treat angina. However, HCN block also provides a promising approach to the treatment of neuronal disorders including epilepsy and neuropathic pain. While several molecules that block HCN channels have been identified, including clonidine and its derivative alinidine, lidocaine, mepivacaine, bupivacaine, ZD7288, ivabradine, zatebradine, and cilobradine, their low affinity and lack of specificity prevents wide-spread use. Different studies suggest that the binding sites of these inhibitors are located in the inner vestibule of HCN channels, but the molecular details of their binding remain unknown. We used computational docking experiments to assess the binding sites and mode of binding of these inhibitors against the recently solved atomic structure of human HCN1 channels, and a homology model of the open pore derived from a closely related CNG channel. We identify a possible hydrophobic groove in the pore cavity that plays an important role in conformationally restricting the location and orientation of drugs bound to the inner vestibule. Our results also help explain the molecular basis of the low-affinity binding of these inhibitors, paving the way for the development of higher affinity molecules.
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Affiliation(s)
- Jérémie Tanguay
- Department of Physics, Université de Montréal, Montréal, Canada
| | - Karen M Callahan
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada
| | - Nazzareno D'Avanzo
- Department of Pharmacology and Physiology, Université de Montréal, Montréal, Canada.
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28
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Lehnhoff J, Strauss U, Wierschke S, Grosser S, Pollali E, Schneider UC, Holtkamp M, Dehnicke C, Deisz RA. The anticonvulsant lamotrigine enhances Ih in layer 2/3 neocortical pyramidal neurons of patients with pharmacoresistant epilepsy. Neuropharmacology 2019; 144:58-69. [DOI: 10.1016/j.neuropharm.2018.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 09/19/2018] [Accepted: 10/05/2018] [Indexed: 11/29/2022]
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29
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Liu X, Zhang L, Jin L, Tan Y, Li W, Tang J. HCN2 contributes to oxaliplatin-induced neuropathic pain through activation of the CaMKII/CREB cascade in spinal neurons. Mol Pain 2018; 14:1744806918778490. [PMID: 29806529 PMCID: PMC5974562 DOI: 10.1177/1744806918778490] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Emerging evidence showed that hyperpolarization-activated cation channels (HCN) participate in the development of inflammatory and neuropathic pain. However, the role of HCN2 in oxaliplatin-induced neuropathic pain remains unknown. Here, we found that HCN2 expression was upregulated in a rat model of oxaliplatin-induced neuropathic pain. Intrathecal injection of ZD7288, an HCN specific inhibitor, decreased the HCN2 level, as well as weakened the neuropathic pain behaviors compared to naive rats. Besides, mechanistic studies revealed that the expression of the spinal N-methyl-D-aspartate receptor subunit 2B was increased after oxaliplatin administration and was reduced by ZD7288 administration. The nociceptive behaviors were reversed by NR2B antagonist Ro 25–6981 in HCN2-overexpression rats. Furthermore, the underlying cellular mechanism demonstrated that ZD7288 administration restrained the enhanced activation of the neuronal calcium–calmodulin-dependent kinase II (CaMKII)/cyclic adenosine monophosphate response element-binding protein cascade after oxaliplatin administration. Moreover, pretreatment of CaMKII inhibitor KN-93 suppressed the nociceptive behaviors, as well as NR2B upregulation induced by overexpression of HCN2. In a word, HCN2 is conducive to oxaliplatin-induced neuropathic pain by activating the neuronal CaMKII/CREB cascade.
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Affiliation(s)
- Xiaoyu Liu
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
| | - Lidong Zhang
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
| | - Li Jin
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
| | - Yuanhui Tan
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
| | - Weiyan Li
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
- Weiyan Li and Jun Tang, Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, 305 East Zhongshan Road, Nanjing, Jiangsu Province 210002, P.R. China. Emails: ;
| | - Jun Tang
- Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, P.R. China
- Weiyan Li and Jun Tang, Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, 305 East Zhongshan Road, Nanjing, Jiangsu Province 210002, P.R. China. Emails: ;
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30
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Campostrini G, DiFrancesco JC, Castellotti B, Milanesi R, Gnecchi-Ruscone T, Bonzanni M, Bucchi A, Baruscotti M, Ferrarese C, Franceschetti S, Canafoglia L, Ragona F, Freri E, Labate A, Gambardella A, Costa C, Gellera C, Granata T, Barbuti A, DiFrancesco D. A Loss-of-Function HCN4 Mutation Associated With Familial Benign Myoclonic Epilepsy in Infancy Causes Increased Neuronal Excitability. Front Mol Neurosci 2018; 11:269. [PMID: 30127718 PMCID: PMC6089338 DOI: 10.3389/fnmol.2018.00269] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 07/16/2018] [Indexed: 01/03/2023] Open
Abstract
HCN channels are highly expressed and functionally relevant in neurons and increasing evidence demonstrates their involvement in the etiology of human epilepsies. Among HCN isoforms, HCN4 is important in cardiac tissue, where it underlies pacemaker activity. Despite being expressed also in deep structures of the brain, mutations of this channel functionally shown to be associated with epilepsy have not been reported yet. Using Next Generation Sequencing for the screening of patients with idiopathic epilepsy, we identified the p.Arg550Cys (c.1648C>T) heterozygous mutation on HCN4 in two brothers affected by benign myoclonic epilepsy of infancy. Functional characterization in heterologous expression system and in neurons showed that the mutation determines a loss of function of HCN4 contribution to activity and an increase of neuronal discharge, potentially predisposing to epilepsy. Expressed in cardiomyocytes, mutant channels activate at slightly more negative voltages than wild-type (WT), in accordance with borderline bradycardia. While HCN4 variants have been frequently associated with cardiac arrhythmias, these data represent the first experimental evidence that functional alteration of HCN4 can also be involved in human epilepsy through a loss-of-function effect and associated increased neuronal excitability. Since HCN4 appears to be highly expressed in deep brain structures only early during development, our data provide a potential explanation for a link between dysfunctional HCN4 and infantile epilepsy. These findings suggest that it may be useful to include HCN4 screening to extend the knowledge of the genetic causes of infantile epilepsies, potentially paving the way for the identification of innovative therapeutic strategies.
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Affiliation(s)
- Giulia Campostrini
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Jacopo C DiFrancesco
- Clinical Neurophysiology and Epilepsy Center, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.,Laboratory of Neurobiology, Department of Neurology, Milan Center for Neuroscience, San Gerardo Hospital, University of Milano-Bicocca, Monza, Italy
| | - Barbara Castellotti
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Raffaella Milanesi
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | | | - Mattia Bonzanni
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Annalisa Bucchi
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Mirko Baruscotti
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Carlo Ferrarese
- Laboratory of Neurobiology, Department of Neurology, Milan Center for Neuroscience, San Gerardo Hospital, University of Milano-Bicocca, Monza, Italy
| | - Silvana Franceschetti
- Clinical Neurophysiology and Epilepsy Center, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Laura Canafoglia
- Clinical Neurophysiology and Epilepsy Center, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Francesca Ragona
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Freri
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Angelo Labate
- Institute of Neurology, Università degli Studi Magna Græcia di Catanzaro, Catanzaro, Italy
| | - Antonio Gambardella
- Institute of Neurology, Università degli Studi Magna Græcia di Catanzaro, Catanzaro, Italy
| | - Cinzia Costa
- Neurology Unit, Ospedale S. Maria della Misericordia, Department of Medicine, University of Perugia, Perugia, Italy
| | - Cinzia Gellera
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Andrea Barbuti
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
| | - Dario DiFrancesco
- Molecular Physiology and Neurobiology, The PaceLab, Department of Biosciences, Università degli Studi di Milano, Milan, Italy
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31
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David F, Çarçak N, Furdan S, Onat F, Gould T, Mészáros Á, Di Giovanni G, Hernández VM, Chan CS, Lőrincz ML, Crunelli V. Suppression of Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel Function in Thalamocortical Neurons Prevents Genetically Determined and Pharmacologically Induced Absence Seizures. J Neurosci 2018; 38:6615-6627. [PMID: 29925625 PMCID: PMC6067077 DOI: 10.1523/jneurosci.0896-17.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 04/13/2018] [Accepted: 05/05/2018] [Indexed: 12/31/2022] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and the Ih current they generate contribute to the pathophysiological mechanisms of absence seizures (ASs), but their precise role in neocortical and thalamic neuronal populations, the main components of the network underlying AS generation, remains controversial. In diverse genetic AS models, Ih amplitude is smaller in neocortical neurons and either larger or unchanged in thalamocortical (TC) neurons compared with nonepileptic strains. A lower expression of neocortical HCN subtype 1 channels is present in genetic AS-prone rats, and HCN subtype 2 knock-out mice exhibit ASs. Furthermore, whereas many studies have characterized Ih contribution to "absence-like" paroxysmal activity in vitro, no data are available on the specific role of cortical and thalamic HCN channels in behavioral seizures. Here, we show that the pharmacological block of HCN channels with the antagonist ZD7288 applied via reverse microdialysis in the ventrobasal thalamus (VB) of freely moving male Genetic Absence Epilepsy Rats from Strasbourg decreases TC neuron firing and abolishes spontaneous ASs. A similar effect is observed on γ-hydroxybutyric acid-elicited ASs in normal male Wistar rats. Moreover, thalamic knockdown of HCN channels via virally delivered shRNA into the VB of male Stargazer mice, another genetic AS model, decreases spontaneous ASs and Ih-dependent electrophysiological properties of VB TC neurons. These findings provide the first evidence that block of TC neuron HCN channels prevents ASs and suggest that any potential anti-absence therapy that targets HCN channels should carefully consider the opposite role for cortical and thalamic Ih in the modulation of absence seizures.SIGNIFICANCE STATEMENT Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play critical roles in the fine-tuning of cellular and network excitability and have been suggested to be a key element of the pathophysiological mechanism underlying absence seizures. However, the precise contribution of HCN channels in neocortical and thalamic neuronal populations to these nonconvulsive seizures is still controversial. In the present study, pharmacological block and genetic suppression of HCN channels in thalamocortical neurons in the ventrobasal thalamic nucleus leads to a marked reduction in absence seizures in one pharmacological and two genetic rodent models of absence seizures. These results provide the first evidence that block of TC neuron HCN channels prevents absence seizures.
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Affiliation(s)
- François David
- Neuroscience Division, School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom,
- Lyon Neuroscience Research Center, CNRS UMR 5292-INSERM U1028-Université Claude Bernard, 69008 Lyon, France
| | - Nihan Çarçak
- Neuroscience Division, School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
- Department of Pharmacology, Faculty of Pharmacy, Istanbul University, Istanbul, Turkey
| | - Szabina Furdan
- Department of Physiology, Anatomy, and Neuroscience, University of Szeged, Szeged 6726, Hungary
| | - Filiz Onat
- Department of Pharmacology and Clinical 34452 Pharmacology, Marmara University School of Medicine, Istanbul 81326, Turkey
| | - Timothy Gould
- Neuroscience Division, School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Ádám Mészáros
- Department of Physiology, Anatomy, and Neuroscience, University of Szeged, Szeged 6726, Hungary
| | - Giuseppe Di Giovanni
- Department of Physiology and Biochemistry, University of Malta, Msida MSD 2080, Malta, and
| | - Vivian M Hernández
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Robert H Lurie Medical Research Center, Chicago, Illinois 60611
| | - C Savio Chan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Robert H Lurie Medical Research Center, Chicago, Illinois 60611
| | - Magor L Lőrincz
- Department of Physiology, Anatomy, and Neuroscience, University of Szeged, Szeged 6726, Hungary
| | - Vincenzo Crunelli
- Neuroscience Division, School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom,
- Department of Physiology and Biochemistry, University of Malta, Msida MSD 2080, Malta, and
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Binda A, Panariti A, Barbuti A, Murano C, Dal Magro R, Masserini M, Re F, Rivolta I. Modulation of the intrinsic neuronal excitability by multifunctional liposomes tailored for the treatment of Alzheimer's disease. Int J Nanomedicine 2018; 13:4059-4071. [PMID: 30034232 PMCID: PMC6047604 DOI: 10.2147/ijn.s161563] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose Nanotechnologies turned out to be promising in the development of diagnostic and therapeutic approaches toward neurodegenerative disorders. However, only a very scant number of nanodevices until now proved to be effective on preclinical animal models. Although specific tests in vivo are available to assess the potential toxicity of these nanodevices on cognitive functions, those to evaluate their biosafety in vitro on neurons are still to be improved. Materials and methods We utilized the patch-clamp technique on primary cultures of cortical neural cells isolated from neonatal rats, aiming to evaluate their electrical properties after the incubation with liposomes (mApoE-PA-LIPs), previously proved able to cross the blood–brain barrier and to be effective on mouse models of Alzheimer’s disease (AD), both in the absence and in the presence of β-amyloid peptide oligomers. Results Data show a high degree of biocompatibility, evaluated by lactate dehydrogenase (LDH) release and MTT assay, and the lack of cellular internalization. After the incubation with mApoE-PA-LIPs, neuronal membranes show an increase in the input resistance (from 724.14±76 MΩ in untreated population to 886.06±86 MΩ in the treated one), a reduction in the rheobase current (from 29.6±3 to 24.2±3 pA in untreated and treated, respectively), and an increase of the firing frequency, consistent with an ultimate increase in intrinsic excitability. Data obtained after co-incubation of mApoE-PA-LIPs with β-amyloid peptide oligomers suggest a retention of liposome efficacy. Conclusion These data suggest the ability of liposomes to modulate neuronal electrical properties and are compatible with the previously demonstrated amelioration of cognitive functions induced by treatment of AD mice with liposomes. We conclude that this electrophysiological approach could represent a useful tool for nanomedicine to evaluate the effect of nanoparticles on intrinsic neuronal excitability.
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Affiliation(s)
- Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy,
| | - Alice Panariti
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy,
| | - Andrea Barbuti
- Department of Biosciences, The PaceLab and Interuniversity Center of Molecular Medicine and Applied Biophysics (CIMMBA), University of Milan, Milano, Italy
| | - Carmen Murano
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy,
| | - Roberta Dal Magro
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy,
| | - Massimo Masserini
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy, .,Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy, .,Nanomedicine Center NANOMIB, University of Milano-Bicocca, Milano, Italy,
| | - Francesca Re
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy, .,Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy, .,Nanomedicine Center NANOMIB, University of Milano-Bicocca, Milano, Italy,
| | - Ilaria Rivolta
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy, .,Milan Center for Neuroscience (NeuroMI), University of Milano-Bicocca, Monza, Italy, .,Nanomedicine Center NANOMIB, University of Milano-Bicocca, Milano, Italy,
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Bonzanni M, DiFrancesco JC, Milanesi R, Campostrini G, Castellotti B, Bucchi A, Baruscotti M, Ferrarese C, Franceschetti S, Canafoglia L, Ragona F, Freri E, Labate A, Gambardella A, Costa C, Rivolta I, Gellera C, Granata T, Barbuti A, DiFrancesco D. A novel de novo HCN1 loss-of-function mutation in genetic generalized epilepsy causing increased neuronal excitability. Neurobiol Dis 2018; 118:55-63. [PMID: 29936235 DOI: 10.1016/j.nbd.2018.06.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 06/11/2018] [Accepted: 06/15/2018] [Indexed: 11/26/2022] Open
Abstract
The causes of genetic epilepsies are unknown in the majority of patients. HCN ion channels have a widespread expression in neurons and increasing evidence demonstrates their functional involvement in human epilepsies. Among the four known isoforms, HCN1 is the most expressed in the neocortex and hippocampus and de novo HCN1 point mutations have been recently associated with early infantile epileptic encephalopathy. So far, HCN1 mutations have not been reported in patients with idiopathic epilepsy. Using a Next Generation Sequencing approach, we identified the de novo heterozygous p.Leu157Val (c.469C > G) novel mutation in HCN1 in an adult male patient affected by genetic generalized epilepsy (GGE), with normal cognitive development. Electrophysiological analysis in heterologous expression model (CHO cells) and in neurons revealed that L157V is a loss-of-function, dominant negative mutation causing reduced HCN1 contribution to net inward current and responsible for an increased neuronal firing rate and excitability, potentially predisposing to epilepsy. These data represent the first evidence that autosomal dominant missense mutations of HCN1 can also be involved in GGE, without the characteristics of epileptic encephalopathy reported previously. It will be important to include HCN1 screening in patients with GGE, in order to extend the knowledge of the genetic causes of idiopathic epilepsies, thus paving the way for the identification of innovative therapeutic strategies.
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Affiliation(s)
- Mattia Bonzanni
- Dept. of Biosciences, The PaceLab, University of Milano, Milano, Italy
| | - Jacopo C DiFrancesco
- Clinical Neurophysiology and Epilepsy Center, "C. Besta" Neurological Institute, Milano, Italy; Dept. of Neurology, San Gerardo Hospital, Laboratory of Neurobiology, Milan Center for Neuroscience, University of Milano-Bicocca, Monza, Italy.
| | | | | | - Barbara Castellotti
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, "C. Besta" Neurological Institute, Milano, Italy
| | - Annalisa Bucchi
- Dept. of Biosciences, The PaceLab, University of Milano, Milano, Italy
| | - Mirko Baruscotti
- Dept. of Biosciences, The PaceLab, University of Milano, Milano, Italy
| | - Carlo Ferrarese
- Dept. of Neurology, San Gerardo Hospital, Laboratory of Neurobiology, Milan Center for Neuroscience, University of Milano-Bicocca, Monza, Italy
| | - Silvana Franceschetti
- Clinical Neurophysiology and Epilepsy Center, "C. Besta" Neurological Institute, Milano, Italy
| | - Laura Canafoglia
- Clinical Neurophysiology and Epilepsy Center, "C. Besta" Neurological Institute, Milano, Italy
| | - Francesca Ragona
- Dept. of Pediatric Neuroscience, "C. Besta" Neurological Institute, Milano, Italy
| | - Elena Freri
- Dept. of Pediatric Neuroscience, "C. Besta" Neurological Institute, Milano, Italy
| | - Angelo Labate
- Institute of Neurology, University "Magna Graecia", Catanzaro, Italy
| | | | - Cinzia Costa
- Neurology Unit, Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia, Perugia, Italy
| | - Ilaria Rivolta
- School of Medicine and Surgery, Milan Center for Neuroscience and Nanomedicine Center, University of Milano-Bicocca, Monza, Italy
| | - Cinzia Gellera
- Unit of Genetics of Neurodegenerative and Metabolic Diseases, "C. Besta" Neurological Institute, Milano, Italy
| | - Tiziana Granata
- Dept. of Pediatric Neuroscience, "C. Besta" Neurological Institute, Milano, Italy
| | - Andrea Barbuti
- Dept. of Biosciences, The PaceLab, University of Milano, Milano, Italy.
| | - Dario DiFrancesco
- Dept. of Biosciences, The PaceLab, University of Milano, Milano, Italy
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Kawasaki Y, Saito M, Won J, Bae JY, Sato H, Toyoda H, Kuramoto E, Kogo M, Tanaka T, Kaneko T, Oh SB, Bae YC, Kang Y. Inhibition of GluR Current in Microvilli of Sensory Neurons via Na +-Microdomain Coupling Among GluR, HCN Channel, and Na +/K + Pump. Front Cell Neurosci 2018; 12:113. [PMID: 29740287 PMCID: PMC5928758 DOI: 10.3389/fncel.2018.00113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 04/06/2018] [Indexed: 11/13/2022] Open
Abstract
Glutamatergic dendritic EPSPs evoked in cortical pyramidal neurons are depressed by activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels expressed in dendritic spines. This depression has been attributed to shunting effects of HCN current (Ih) on input resistance or Ih deactivation. Primary sensory neurons in the rat mesencephalic trigeminal nucleus (MTN) have the somata covered by spine-like microvilli that express HCN channels. In rat MTN neurons, we demonstrated that Ih enhancement apparently diminished the glutamate receptor (GluR) current (IGluR) evoked by puff application of glutamate/AMPA and enhanced a transient outward current following IGluR (OT-IGluR). This suggests that some outward current opposes inward IGluR. The IGluR inhibition displayed a U-shaped voltage-dependence with a minimal inhibition around the resting membrane potential, suggesting that simple shunting effects or deactivation of Ih cannot explain the U-shaped voltage-dependence. Confocal imaging of Na+ revealed that GluR activation caused an accumulation of Na+ in the microvilli, which can cause a negative shift of the reversal potential for Ih (Eh). Taken together, it was suggested that IGluR evoked in MTN neurons is opposed by a transient decrease or increase in standing inward or outward Ih, respectively, both of which can be caused by negative shifts of Eh, as consistent with the U-shaped voltage-dependence of the IGluR inhibition and the OT-IGluR generation. An electron-microscopic immunohistochemical study revealed the colocalization of HCN channels and glutamatergic synapses in microvilli of MTN neurons, which would provide a morphological basis for the functional interaction between HCN and GluR channels. Mathematical modeling eliminated the possibilities of the involvements of Ih deactivation and/or shunting effect and supported the negative shift of Eh which causes the U-shaped voltage-dependent inhibition of IGluR.
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Affiliation(s)
- Yasuhiro Kawasaki
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Mitsuru Saito
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Jonghwa Won
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, South Korea
| | - Jin Young Bae
- Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Hajime Sato
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Hiroki Toyoda
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Eriko Kuramoto
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Mikihiko Kogo
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
| | - Takuma Tanaka
- Department of Computational Intelligence and Systems Science, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan
| | - Takeshi Kaneko
- Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Seog Bae Oh
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, South Korea
| | - Yong Chul Bae
- Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Youngnam Kang
- Department of Neuroscience and Oral Physiology, Graduate School of Dentistry, Osaka University, Osaka, Japan
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35
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Zhao Z, Li L, Gu H. Dynamical Mechanism of Hyperpolarization-Activated Non-specific Cation Current Induced Resonance and Spike-Timing Precision in a Neuronal Model. Front Cell Neurosci 2018; 12:62. [PMID: 29568262 PMCID: PMC5852126 DOI: 10.3389/fncel.2018.00062] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 02/20/2018] [Indexed: 01/23/2023] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated cation current (Ih) plays important roles in the achievement of many physiological/pathological functions in the nervous system by modulating the electrophysiological activities, such as the rebound (spike) to hyperpolarization stimulations, subthreshold membrane resonance to sinusoidal currents, and spike-timing precision to stochastic factors. In the present paper, with increasing gh (conductance of Ih), the rebound (spike) and subthreshold resonance appear and become stronger, and the variability of the interspike intervals (ISIs) becomes lower, i.e., the enhancement of spike-timing precision, which are simulated in a conductance-based theoretical model and well explained by the nonlinear concept of bifurcation. With increasing gh, the stable node to stable focus, to coexistence behavior, and to firing via the codimension-1 bifurcations (Hopf bifurcation, saddle-node bifurcation, saddle-node bifurcations on an invariant circle, and saddle homoclinic orbit) and codimension-2 bifurcations such as Bogdanov-Takens (BT) point related to the transition between saddle-node and Hopf bifurcations, are acquired with 1- and 2-parameter bifurcation analysis. The decrease of variability of ISIs with increasing gh is induced by the fast decrease of the standard deviation of ISIs, which is related to the increase of the capacity of resisting noisy disturbance due to the firing becomes far away from the bifurcation point. The enhancement of the rebound (spike) with increasing gh builds up a relationship to the decrease of the capacity of resisting disturbance like the hyperpolarization stimulus as the resting state approaches the bifurcation point. The “typical”-resonance and non-resonance appear in the parameter region of the stable focus and node far away from the bifurcation points, respectively. The complex or “strange” dynamics, such as the “weak”-resonance for the stable node near the transition point between the stable node and focus and the non-resonance for the stable focus close to the codimension-1 and −2 bifurcation points, are discussed.
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Affiliation(s)
- Zhiguo Zhao
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China.,School of Basic Science, Henan Institute of Technology, Xinxiang, China
| | - Li Li
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China
| | - Huaguang Gu
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China
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Oyrer J, Maljevic S, Scheffer IE, Berkovic SF, Petrou S, Reid CA. Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies. Pharmacol Rev 2018; 70:142-173. [PMID: 29263209 DOI: 10.1124/pr.117.014456] [Citation(s) in RCA: 163] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/02/2017] [Indexed: 12/19/2022] Open
Abstract
Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.
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Affiliation(s)
- Julia Oyrer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Snezana Maljevic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Ingrid E Scheffer
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Samuel F Berkovic
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Melbourne, Australia (J.O., S.M., I.E.S., S.P., C.A.R.); Department of Medicine, Austin Health, University of Melbourne, Heidelberg West, Melbourne, Australia (I.E.S., S.F.B.); and Department of Paediatrics, University of Melbourne, Royal Children's Hospital, Melbourne, Australia (I.E.S.)
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Sartiani L, Mannaioni G, Masi A, Novella Romanelli M, Cerbai E. The Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels: from Biophysics to Pharmacology of a Unique Family of Ion Channels. Pharmacol Rev 2017; 69:354-395. [PMID: 28878030 DOI: 10.1124/pr.117.014035] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 07/07/2017] [Indexed: 12/22/2022] Open
Abstract
Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels are important members of the voltage-gated pore loop channels family. They show unique features: they open at hyperpolarizing potential, carry a mixed Na/K current, and are regulated by cyclic nucleotides. Four different isoforms have been cloned (HCN1-4) that can assemble to form homo- or heterotetramers, characterized by different biophysical properties. These proteins are widely distributed throughout the body and involved in different physiologic processes, the most important being the generation of spontaneous electrical activity in the heart and the regulation of synaptic transmission in the brain. Their role in heart rate, neuronal pacemaking, dendritic integration, learning and memory, and visual and pain perceptions has been extensively studied; these channels have been found also in some peripheral tissues, where their functions still need to be fully elucidated. Genetic defects and altered expression of HCN channels are linked to several pathologies, which makes these proteins attractive targets for translational research; at the moment only one drug (ivabradine), which specifically blocks the hyperpolarization-activated current, is clinically available. This review discusses current knowledge about HCN channels, starting from their biophysical properties, origin, and developmental features, to (patho)physiologic role in different tissues and pharmacological modulation, ending with their present and future relevance as drug targets.
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Affiliation(s)
- Laura Sartiani
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Guido Mannaioni
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Alessio Masi
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Maria Novella Romanelli
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
| | - Elisabetta Cerbai
- Department of Neurosciences, Psychology, Drug Research, and Child Health, University of Florence, Firenze, Italy
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Wu SZ, Ye H, Yang XG, Lu ZL, Qu Q, Qu J. Case-control pharmacogenetic study of HCN1/HCN2 variants and genetic generalized epilepsies. Clin Exp Pharmacol Physiol 2017; 45:226-233. [PMID: 29047147 DOI: 10.1111/1440-1681.12877] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 10/06/2017] [Accepted: 10/12/2017] [Indexed: 11/27/2022]
Abstract
Epilepsy is a common complex neurological disorder, and some forms are resistant to drug treatment. The HCN1/HCN2 genes encode hyperpolarization-activated cyclic nucleotide-gated channels, which play important roles in the electrophysiology of neurons. We investigated the association between HCN1/HCN2 variants and drug resistance or the risk of genetic generalized epilepsies (GGEs). We used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to assess nine variants of HCN1/HCN2 in 284 healthy participants and 483 GGEs (279 drug-responsive, 204 drug-resistant). Frequencies of HCN2 rs7255568 and rs3752158 G alleles differed in GGEs and in controls (P = .039, P = .027, respectively). The frequency of HCN2 haplotype (CAC) was higher in patients than controls (P = .046). The frequency of the HCN1 rs10462087 CC+CT genotype was lower in patients with childhood absence epilepsy (CAE) than controls (P = .047). Rs7255568 was associated with the risk of CAE (P = .028) and juvenile myoclonic epilepsy (JME) (P = .02). Rs3752158 was associated with the risk of generalized tonic-clonic seizures, JME, and febrile seizures (all P < .05). The frequency of the HCN2 haplotype (CAC) was higher in patients with JME (P = .015) and in those with febrile seizures (P = .024) than in controls. No significant association was found between HCN1/HCN2 alleles, genotypes or haplotypes, and drug resistance in patients. After Bonferroni's multiple comparisons correction, only the HCN2 rs3752158 C allele and GC+CC genotype frequencies in patients with JME were higher than those in controls (19.2% vs 11.6%, odds ratio (OR) = 1.71, 95% CI = 1.18-2.32), P = .004 < 0.05/9; 36% vs 22.2%, OR = 1.62(1.18-2.23), P = .003 < 0.05/9). Our study suggests that HCN2 rs3752158 is involved in the susceptibility to JME.
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Affiliation(s)
- Shu-Zhi Wu
- Department of Neurology, The Third Clinical Institute Affiliated to Wenzhou Medical University & Wenzhou People's Hospital, Wenzhou, China
| | - Hua Ye
- Department of Neurology, The Third Clinical Institute Affiliated to Wenzhou Medical University & Wenzhou People's Hospital, Wenzhou, China
| | - Xiao-Guo Yang
- Department of Neurology, The Third Clinical Institute Affiliated to Wenzhou Medical University & Wenzhou People's Hospital, Wenzhou, China
| | - Zhi-Li Lu
- Department of Pathology, Hunan Cancer Hospital, Central South University, Changsha, China
| | - Qiang Qu
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, China
| | - Jian Qu
- Department of Pharmacy, The Second Xiangya Hospital, Central South University, Changsha, China.,Institute of Clinical Pharmacy, Central South University, Changsha, China
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Li M, Maljevic S, Phillips AM, Petrovski S, Hildebrand MS, Burgess R, Mount T, Zara F, Striano P, Schubert J, Thiele H, Nürnberg P, Wong M, Weisenberg JL, Thio LL, Lerche H, Scheffer IE, Berkovic SF, Petrou S, Reid CA. Gain-of-functionHCN2variants in genetic epilepsy. Hum Mutat 2017; 39:202-209. [DOI: 10.1002/humu.23357] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 09/06/2017] [Accepted: 10/10/2017] [Indexed: 12/26/2022]
Affiliation(s)
- Melody Li
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
| | - Snezana Maljevic
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
| | - A. Marie Phillips
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
- School of Biosciences; The University of Melbourne; Parkville Victoria Australia
| | - Slave Petrovski
- Epilepsy Research Centre; Department of Medicine; The University of Melbourne; Austin Health Heidelberg Victoria Australia
| | - Michael S. Hildebrand
- Epilepsy Research Centre; Department of Medicine; The University of Melbourne; Austin Health Heidelberg Victoria Australia
| | - Rosemary Burgess
- Epilepsy Research Centre; Department of Medicine; The University of Melbourne; Austin Health Heidelberg Victoria Australia
| | - Therese Mount
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
| | - Federico Zara
- Laboratory of Neurogenetics; Department of Neuroscience; Institute “G. Gaslini”; Genoa Italy
| | - Pasquale Striano
- Pediatric Neurology and Muscular Diseases Unit; Department of Neurosciences; Institute “G. Gaslini”; Genoa Italy
| | - Julian Schubert
- University of Tübingen, Department of Neurology and Epileptology; Hertie Institute for Clinical Brain Research; Tübingen Germany
| | - Holger Thiele
- Cologne Centre for Genomics; University of Cologne; Cologne Germany
| | - Peter Nürnberg
- Cologne Centre for Genomics; University of Cologne; Cologne Germany
| | - Michael Wong
- Department of Neurology; Washington University School of Medicine and St. Louis Children's Hospital; St Louis Missouri
| | - Judith L. Weisenberg
- Department of Neurology; Washington University School of Medicine and St. Louis Children's Hospital; St Louis Missouri
| | - Liu Lin Thio
- Department of Neurology; Washington University School of Medicine and St. Louis Children's Hospital; St Louis Missouri
| | - Holger Lerche
- University of Tübingen, Department of Neurology and Epileptology; Hertie Institute for Clinical Brain Research; Tübingen Germany
| | - Ingrid E. Scheffer
- Epilepsy Research Centre; Department of Medicine; The University of Melbourne; Austin Health Heidelberg Victoria Australia
| | - Samuel F. Berkovic
- Epilepsy Research Centre; Department of Medicine; The University of Melbourne; Austin Health Heidelberg Victoria Australia
| | - Steven Petrou
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
| | - Christopher A. Reid
- Florey Institute of Neuroscience and Mental Health; The University of Melbourne; Parkville Victoria Australia
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Becker F, Reid CA, Hallmann K, Tae HS, Phillips AM, Teodorescu G, Weber YG, Kleefuss-Lie A, Elger C, Perez-Reyes E, Petrou S, Kunz WS, Lerche H, Maljevic S. Functional variants in HCN4 and CACNA1H may contribute to genetic generalized epilepsy. Epilepsia Open 2017; 2:334-342. [PMID: 29588962 PMCID: PMC5862120 DOI: 10.1002/epi4.12068] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/23/2017] [Indexed: 01/11/2023] Open
Abstract
Objective Genetic generalized epilepsy (GGE) encompasses seizure disorders characterized by spike‐and‐wave discharges (SWD) originating within thalamo‐cortical circuits. Hyperpolarization‐activated (HCN) and T‐type Ca2+ channels are key modulators of rhythmic activity in these brain regions. Here, we screened HCN4 and CACNA1H genes for potentially contributory variants and provide their functional analysis. Methods Targeted gene sequencing was performed in 20 unrelated familial cases with different subtypes of GGE, and the results confirmed in 230 ethnically matching controls. Selected variants in CACNA1H and HCN4 were functionally assessed in tsA201 cells and Xenopus laevis oocytes, respectively. Results We discovered a novel CACNA1H (p.G1158S) variant in two affected members of a single family. One of them also carried an HCN4 (p.P1117L) variant inherited from the unaffected mother. In a separate family, an HCN4 variant (p.E153G) was identified in one of several affected members. Voltage‐clamp analysis of CACNA1H (p.G1158S) revealed a small but significant gain‐of‐function, including increased current density and a depolarizing shift of steady‐state inactivation. HCN4 p.P1117L and p.G153E both caused a hyperpolarizing shift in activation and reduced current amplitudes, resulting in a loss‐of‐function. Significance Our results are consistent with a model suggesting cumulative contributions of subtle functional variations in ion channels to seizure susceptibility and GGE.
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Affiliation(s)
- Felicitas Becker
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany.,RKU-University Neurology Clinic of Ulm Ulm Germany
| | - Christopher A Reid
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
| | - Kerstin Hallmann
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Han-Shen Tae
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia.,Present address: Illawarra Health and Medical Research Institute (IHMRI) University of Wollongong Wollongong New South Wales Australia
| | - A Marie Phillips
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia.,School of Biosciences The University of Melbourne Melbourne Victoria Australia
| | - Georgeta Teodorescu
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Yvonne G Weber
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Ailing Kleefuss-Lie
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Christian Elger
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Edward Perez-Reyes
- Department of Pharmacology University of Virginia Charlottesville Virginia U.S.A
| | - Steven Petrou
- The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
| | - Wolfram S Kunz
- Department of Neurology and Epileptology University of Bonn Medical Center Bonn Germany
| | - Holger Lerche
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany
| | - Snezana Maljevic
- Department of Neurology and Epileptology Hertie-Institute for Clinical Brain-Research University of Tübingen Tübingen Germany.,The Florey Institute of Neuroscience and Mental Health Melbourne Victoria Australia
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Carbone C, Costa A, Provensi G, Mannaioni G, Masi A. The Hyperpolarization-Activated Current Determines Synaptic Excitability, Calcium Activity and Specific Viability of Substantia Nigra Dopaminergic Neurons. Front Cell Neurosci 2017; 11:187. [PMID: 28701928 PMCID: PMC5487410 DOI: 10.3389/fncel.2017.00187] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 06/16/2017] [Indexed: 12/28/2022] Open
Abstract
Differential vulnerability between Substantia Nigra pars compacta (SNpc) and Ventral Tegmental Area (VTA) dopaminergic (DAergic) neurons is a hallmark of Parkinson’s disease (PD). Understanding the molecular bases of this key histopathological aspect would foster the development of much-needed disease-modifying therapies. Non-heterogeneous DAergic degeneration is present in both toxin-based and genetic animal models, suggesting that cellular specificity, rather than causing factors, constitutes the background for differential vulnerability. In this regard, we previously demonstrated that MPP+, a neurotoxin able to cause selective nigrostriatal degeneration in animal rodents and primates, inhibits the Hyperpolarization-activated current (Ih) in SNpc DAergic neurons and that pharmacological Ih antagonism causes potentiation of evoked Excitatory post-synaptic potentials (EPSPs). Of note, the magnitude of such potentiation is greater in the SNpc subfield, consistent with higher Ih density. In the present work, we show that Ih block-induced synaptic potentiation leads to the amplification of somatic calcium responses (SCRs) in vitro. This effect is specific for the SNpc subfield and largely mediated by L-Type calcium channels, as indicated by sensitivity to the CaV 1 blocker isradipine. Furthermore, Ih is downregulated by low intracellular ATP and determines the efficacy of GABAergic inhibition in SNpc DAergic neurons. Finally, we show that stereotaxic administration of Ih blockers causes SNpc-specific neurodegeneration and hemiparkinsonian motor phenotype in rats. During PD progression, Ih downregulation may result from mitochondrial dysfunction and, in concert with PD-related disinhibition of excitatory inputs, determine a SNpc-specific disease pathway.
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Affiliation(s)
- Carmen Carbone
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Alessia Costa
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Gustavo Provensi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Guido Mannaioni
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy.,Toxicology Unit, Azienda Ospedaliero-Universitaria CareggiFlorence, Italy
| | - Alessio Masi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy.,Toxicology Unit, Azienda Ospedaliero-Universitaria CareggiFlorence, Italy
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42
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Avanzini G, Mantegazza M, Terragni B, Canafoglia L, Scalmani P, Franceschetti S. The impact of genetic and experimental studies on classification and therapy of the epilepsies. Neurosci Lett 2017; 667:17-26. [PMID: 28522348 DOI: 10.1016/j.neulet.2017.05.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/12/2017] [Accepted: 05/13/2017] [Indexed: 10/19/2022]
Abstract
Different types of epilepsy are associated with gene mutations, in which seizures can be the only symptom (genetic epilepsies) or be one of the elements of complex clinical pictures that are often progressive over time (epileptic or epileptogenic encephalopathies). In epileptogenic encephalopathies, epileptic seizures and other neurological and cognitive signs are symptoms of genetically determined neuropathological or neurochemical disorders. In epileptic encephalopathies, epileptic activity itself is thought to contribute to severe cognitive and behavioral impairments above and beyond what might be expected from the underlying pathology alone. The distinction is conceptually clear and clinically relevant, as the different categories have a different prognosis in terms of both epilepsy and associated neurological and cognitive picture, but the boundaries are sometimes difficult to define in the clinical practice. Here we review the genetic epilepsies from the clinician perspective. A monogenic inheritance has been defined only in a minority of idiopathic epilepsies making improper to rename genetic the category of idiopathic epilepsies, until the presumptive multigenic mechanism will be demonstrated. A search for gene mutations must be done in any patient with candidate genetic types of epilepsy or epileptic/epileptogenic encephalopathy (e.g. familial forms) to complete the diagnostic process, define the prognosis and optimize the therapy. Advanced methods are available to express the gene variant in experimental model systems and test its effect on the properties of the affected protein, on neuronal excitability and on phenotypes in model organisms, and may help in identifying treatments with compatible action mechanisms. The influence of genetic studies on epilepsy taxonomy is now a matter of discussion: their impact on the international classification of the epilepsies will hopefully be defined soon.
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Affiliation(s)
- Giuliano Avanzini
- Dept. of Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy.
| | - Massimo Mantegazza
- Institute of Molecular and Cellular Pharmacology (IPMC), CNRS UMR7275, 06560, Valbonne-Sophia, Antipolis, France; University Côte d'Azur (UCA), 06560, Valbonne-Sophia, Antipolis, France
| | - Benedetta Terragni
- Dept. of Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Laura Canafoglia
- Dept. of Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Paolo Scalmani
- Dept. of Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
| | - Silvana Franceschetti
- Dept. of Neurophysiology and Diagnostic Epileptology, Foundation IRCCS Neurological Institute C. Besta, 20133 Milan, Italy
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Ion Channel Genes and Epilepsy: Functional Alteration, Pathogenic Potential, and Mechanism of Epilepsy. Neurosci Bull 2017; 33:455-477. [PMID: 28488083 DOI: 10.1007/s12264-017-0134-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 02/20/2017] [Indexed: 01/29/2023] Open
Abstract
Ion channels are crucial in the generation and modulation of excitability in the nervous system and have been implicated in human epilepsy. Forty-one epilepsy-associated ion channel genes and their mutations are systematically reviewed. In this paper, we analyzed the genotypes, functional alterations (funotypes), and phenotypes of these mutations. Eleven genes featured loss-of-function mutations and six had gain-of-function mutations. Nine genes displayed diversified funotypes, among which a distinct funotype-phenotype correlation was found in SCN1A. These data suggest that the funotype is an essential consideration in evaluating the pathogenicity of mutations and a distinct funotype or funotype-phenotype correlation helps to define the pathogenic potential of a gene.
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Parker AR, Welch MA, Forster LA, Tasneem SM, Dubhashi JA, Baro DJ. SUMOylation of the Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 2 Increases Surface Expression and the Maximal Conductance of the Hyperpolarization-Activated Current. Front Mol Neurosci 2017; 9:168. [PMID: 28127275 PMCID: PMC5226956 DOI: 10.3389/fnmol.2016.00168] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 12/26/2016] [Indexed: 11/13/2022] Open
Abstract
Small Ubiquitin-like Modifier (SUMO) is a ∼10 kDa peptide that can be post-translationally added to a lysine (K) on a target protein to facilitate protein–protein interactions. Recent studies have found that SUMOylation can be regulated in an activity-dependent manner and that ion channel SUMOylation can alter the biophysical properties and surface expression of the channel. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channel surface expression can be regulated in an activity-dependent manner through unknown processes. We hypothesized that SUMOylation might influence the surface expression of HCN2 channels. In this manuscript, we show that HCN2 channels are SUMOylated in the mouse brain. Baseline levels of SUMOylation were also observed for a GFP-tagged HCN2 channel stably expressed in Human embryonic kidney (Hek) cells. Elevating GFP-HCN2 channel SUMOylation above baseline in Hek cells led to an increase in surface expression that augmented the hyperpolarization-activated current (Ih) mediated by these channels. Increased SUMOylation did not alter Ih voltage-dependence or kinetics of activation. There are five predicted intracellular SUMOylation sites on HCN2. Site-directed mutagenesis indicated that more than one K on the GFP-HCN2 channel was SUMOylated. Enhancing SUMOylation at one of the five predicted sites, K669, led to the increase in surface expression and IhGmax. The role of SUMOylation at additional sites is currently unknown. The SUMOylation site at K669 is also conserved in HCN1 channels. Aberrant SUMOylation has been linked to neurological diseases that also display alterations in HCN1 and HCN2 channel expression, such as seizures and Parkinson’s disease. This work is the first report that HCN channels can be SUMOylated and that this can regulate surface expression and Ih.
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Affiliation(s)
- Anna R Parker
- Department of Biology, Georgia State University Atlanta, GA, USA
| | - Meghyn A Welch
- Department of Biology, Georgia State University Atlanta, GA, USA
| | - Lori A Forster
- Neuroscience Institute, Georgia State University Atlanta, GA, USA
| | - Sarah M Tasneem
- Department of Biology, Georgia State University Atlanta, GA, USA
| | | | - Deborah J Baro
- Department of Biology, Georgia State UniversityAtlanta, GA, USA; Neuroscience Institute, Georgia State UniversityAtlanta, GA, USA
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45
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HCN2 ion channels: basic science opens up possibilities for therapeutic intervention in neuropathic pain. Biochem J 2016; 473:2717-36. [DOI: 10.1042/bcj20160287] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 05/18/2016] [Indexed: 01/22/2023]
Abstract
Nociception — the ability to detect painful stimuli — is an invaluable sense that warns against present or imminent damage. In patients with chronic pain, however, this warning signal persists in the absence of any genuine threat and affects all aspects of everyday life. Neuropathic pain, a form of chronic pain caused by damage to sensory nerves themselves, is dishearteningly refractory to drugs that may work in other types of pain and is a major unmet medical need begging for novel analgesics. Hyperpolarisation-activated cyclic nucleotide (HCN)-modulated ion channels are best known for their fundamental pacemaker role in the heart; here, we review data demonstrating that the HCN2 isoform acts in an analogous way as a ‘pacemaker for pain’, in that its activity in nociceptive neurons is critical for the maintenance of electrical activity and for the sensation of chronic pain in pathological pain states. Pharmacological block or genetic deletion of HCN2 in sensory neurons provides robust pain relief in a variety of animal models of inflammatory and neuropathic pain, without any effect on normal sensation of acute pain. We discuss the implications of these findings for our understanding of neuropathic pain pathogenesis, and we outline possible future opportunities for the development of efficacious and safe pharmacotherapies in a range of chronic pain syndromes.
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46
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Zhang XX, Min XC, Xu XL, Zheng M, Guo LJ. ZD7288, a selective hyperpolarization-activated cyclic nucleotide-gated channel blocker, inhibits hippocampal synaptic plasticity. Neural Regen Res 2016; 11:779-86. [PMID: 27335562 PMCID: PMC4904469 DOI: 10.4103/1673-5374.182705] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The selective hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyrimidinium chloride (ZD7288) blocks the induction of long-term potentiation in the perforant path–CA3 region in rat hippocampus in vivo. To explore the mechanisms underlying the action of ZD7288, we recorded excitatory postsynaptic potentials in perforant path–CA3 synapses in male Sprague-Dawley rats. We measured glutamate content in the hippocampus and in cultured hippocampal neurons using high performance liquid chromatography, and determined intracellular Ca2+ concentration [Ca2+]i) using Fura-2. ZD7288 inhibited the induction and maintenance of long-term potentiation, and these effects were mirrored by the nonspecific HCN channel blocker cesium. ZD7288 also decreased glutamate release in hippocampal tissue and in cultured hippocampal neurons. Furthermore, ZD7288 attenuated glutamate-induced rises in [Ca2+]i in a concentration-dependent manner and reversed 8-Br-cAMP-mediated facilitation of these glutamate-induced [Ca2+]i rises. Our results suggest that ZD7288 inhibits hippocampal synaptic plasticity both glutamate release and resultant [Ca2+]i increases in rat hippocampal neurons.
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Affiliation(s)
- Xiao-Xue Zhang
- Department of Laboratory Medicine, Affiliated Pu'ai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Xiao-Chun Min
- Department of Laboratory Medicine, Affiliated Pu'ai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Xu-Lin Xu
- Department of Pharmacology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Min Zheng
- School of Biomedical Engineering, Hubei University of Science and Technology, Xianning, Hubei Province, China
| | - Lian-Jun Guo
- Department of Pharmacology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
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Itoh M, Ishihara K, Nakashima N, Takano M. The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels contain multiple S-palmitoylation sites. J Physiol Sci 2016; 66:241-8. [PMID: 26546007 PMCID: PMC10717812 DOI: 10.1007/s12576-015-0420-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 10/18/2015] [Indexed: 11/26/2022]
Abstract
Expression of hyperpolarization-activated cyclic nucleotide-gated channels (HCN1-4) on distal dendrites of neurons is suggested to modify synaptic integration in the central nervous system. However, the mechanisms of dendritic localization are not fully understood. Recent studies have revealed that S-palmitoylation plays an important role in the enrichment of various molecules at the postsynaptic membrane. Thus, we performed an acyl-biotinyl exchange assay, and found that HCN1, HCN2, and HCN4, but not HCN3, were S-palmitoylated in HEK293 cells. Mutation of multiple intracellular cysteine residues at the N-terminus of HCN2 was required for complete inhibition of S-palmitoylation. However, this mutagenesis had a minimal effect on surface expression of HCN2 proteins or electrophysiological properties of HCN2 current when expressed in HEK293 cells or in Xenopus oocytes. These findings provide insight into the physiological roles of S-palmitoylation of HCN channels in native neurons.
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Affiliation(s)
- Masayuki Itoh
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, 67 Asahimachi, Kurume, Fukuoka, 830-0011, Japan.
| | - Keiko Ishihara
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, 67 Asahimachi, Kurume, Fukuoka, 830-0011, Japan
| | - Noriyuki Nakashima
- Department of Physiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Makoto Takano
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, 67 Asahimachi, Kurume, Fukuoka, 830-0011, Japan
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48
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Brennan GP, Baram TZ, Poolos NP. Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channels in Epilepsy. Cold Spring Harb Perspect Med 2016; 6:a022384. [PMID: 26931806 DOI: 10.1101/cshperspect.a022384] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Epilepsy is a common brain disorder characterized by the occurrence of spontaneous seizures. These bursts of synchronous firing arise from abnormalities of neuronal networks. Excitability of individual neurons and neuronal networks is largely governed by ion channels and, indeed, abnormalities of a number of ion channels resulting from mutations or aberrant expression and trafficking underlie several types of epilepsy. Here, we focus on the hyperpolarization-activated cyclic nucleotide-gated ion (HCN) channels that conduct Ih current. This conductance plays complex and diverse roles in the regulation of neuronal and network excitability. We describe the normal function of HCN channels and discuss how aberrant expression, assembly, trafficking, and posttranslational modifications contribute to experimental and human epilepsy.
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Affiliation(s)
- Gary P Brennan
- Department of Pediatrics, University of California-Irvine, Irvine, California 92697-4475
| | - Tallie Z Baram
- Department of Pediatrics, University of California-Irvine, Irvine, California 92697-4475 Departments of Anatomy/Neurobiology and Neurology, University of California-Irvine, Irvine, California 92697-4475
| | - Nicholas P Poolos
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, Washington 98104
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Heuermann RJ, Jaramillo TC, Ying SW, Suter BA, Lyman KA, Han Y, Lewis AS, Hampton TG, Shepherd GMG, Goldstein PA, Chetkovich DM. Reduction of thalamic and cortical Ih by deletion of TRIP8b produces a mouse model of human absence epilepsy. Neurobiol Dis 2016; 85:81-92. [PMID: 26459112 PMCID: PMC4688217 DOI: 10.1016/j.nbd.2015.10.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 09/22/2015] [Accepted: 10/08/2015] [Indexed: 12/19/2022] Open
Abstract
Absence seizures occur in several types of human epilepsy and result from widespread, synchronous feedback between the cortex and thalamus that produces brief episodes of loss of consciousness. Genetic rodent models have been invaluable for investigating the pathophysiological basis of these seizures. Here, we identify tetratricopeptide-containing Rab8b-interacting protein (TRIP8b) knockout mice as a new model of absence epilepsy, featuring spontaneous spike-wave discharges on electroencephalography (EEG) that are the electrographic hallmark of absence seizures. TRIP8b is an auxiliary subunit of the hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels, which have previously been implicated in the pathogenesis of absence seizures. In contrast to mice lacking the pore-forming HCN channel subunit HCN2, TRIP8b knockout mice exhibited normal cardiac and motor function and a less severe seizure phenotype. Evaluating the circuit that underlies absence seizures, we found that TRIP8b knockout mice had significantly reduced HCN channel expression and function in thalamic-projecting cortical layer 5b neurons and thalamic relay neurons, but preserved function in inhibitory neurons of the reticular thalamic nucleus. Our results expand the known roles of TRIP8b and provide new insight into the region-specific functions of TRIP8b and HCN channels in constraining cortico-thalamo-cortical excitability.
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Affiliation(s)
- Robert J Heuermann
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Thomas C Jaramillo
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Shui-Wang Ying
- C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Medical College of Cornell University, 1300 York Ave., Room A-1050, New York, New York 10021, USA.
| | - Benjamin A Suter
- Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Kyle A Lyman
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Ye Han
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Alan S Lewis
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Thomas G Hampton
- Mouse Specifics, Inc., 2 Central Street, Level 1 Suite 1, Framingham, MA 01701, USA.
| | - Gordon M G Shepherd
- Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
| | - Peter A Goldstein
- C.V. Starr Laboratory for Molecular Neuropharmacology, Department of Anesthesiology, Weill Medical College of Cornell University, 1300 York Ave., Room A-1050, New York, New York 10021, USA.
| | - Dane M Chetkovich
- Davee Department of Neurology and Clinical Neurosciences, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA; Department of Physiology, Feinberg School of Medicine, Northwestern University, 303 E. Chicago Ave., Ward Building, Room 10-201, Chicago, IL 60611, USA.
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Novella Romanelli M, Sartiani L, Masi A, Mannaioni G, Manetti D, Mugelli A, Cerbai E. HCN Channels Modulators: The Need for Selectivity. Curr Top Med Chem 2016; 16:1764-91. [PMID: 26975509 PMCID: PMC5374843 DOI: 10.2174/1568026616999160315130832] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 08/04/2015] [Accepted: 08/05/2015] [Indexed: 12/27/2022]
Abstract
Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, the molecular correlate of the hyperpolarization-activated current (If/Ih), are membrane proteins which play an important role in several physiological processes and various pathological conditions. In the Sino Atrial Node (SAN) HCN4 is the target of ivabradine, a bradycardic agent that is, at the moment, the only drug which specifically blocks If. Nevertheless, several other pharmacological agents have been shown to modulate HCN channels, a property that may contribute to their therapeutic activity and/or to their side effects. HCN channels are considered potential targets for developing drugs to treat several important pathologies, but a major issue in this field is the discovery of isoform-selective compounds, owing to the wide distribution of these proteins into the central and peripheral nervous systems, heart and other peripheral tissues. This survey is focused on the compounds that have been shown, or have been designed, to interact with HCN channels and on their binding sites, with the aim to summarize current knowledge and possibly to unveil useful information to design new potent and selective modulators.
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Affiliation(s)
- Maria Novella Romanelli
- University of Florence, Department of Neurosciences, Psychology, Drug Research and Child's Health, Section of Pharmaceutical and Nutraceutical Sciences, via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy.
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