DOCSLIB.ORG

Epilepsy Mutations in Different Regions of the Nav1.2 Channel Cause

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Epilepsy Mutations in Different Regions of the Nav1.2 Channel Cause EPILEPSY MUTATIONS IN DIFFERENT REGIONS OF THE NAV1.2 CHANNEL CAUSE DISTINCT BIOPHYSICAL EFFECTS Emily R. Mason Submitted to the faculty of the University Graduate School in partial fulfillment of the requirements for the degree Doctor of Philosophy in the Department of Pharmacology and Toxicology, Indiana University June 2020 Accepted by the Graduate Faculty of Indiana University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Doctoral Committee ______________________________________ Theodore Cummins, Ph.D., Chair ______________________________________ William Sullivan, Ph.D. March 11, 2020 ______________________________________ Nickolay Brustovetsky, Ph.D. ______________________________________ Patrick Sheets, Ph.D. ______________________________________ Eri Hashino, Ph.D. ii DEDICATION This work is dedicated to patients and their families who struggle with genetically-driven epilepsies. iii ACKNOWLEDGEMENTS I would like to express my deepest gratitude to everyone whose help and support saw me through my graduate work and made this dissertation possible. You are all amazing! First, I want to thank God for His endless love and guidance, as well as for putting so many wholesome and supportive people in my life. Secondly, I would like to thank my family for their love, encouragement, and guidance. My mother, Debra, has been especially important in my entire career path so far. She guided me into the world of biomedical research, recognized that it was a good fit for me, saw that I enjoyed it, encouraged me to stay on this career path, and has helped me navigate every step along the path. My maternal grandmother, Revenna, deserves credit for her work ethic and love of learning, which she has passed down to my mother and me. My dad, Barry, and my sister, Hannah, have been very empathetic and supportive of my research endeavors. Additionally, the love, acceptance, and support that I have always received from all my grandparents and other extended family members has helped to motivate me to always keep moving forward. I would also like to thank all my wonderful friends for their loyalty, support, and encouragement. I would like to acknowledge and thank my mentor, Dr. Cummins, for all of his guidance and support. Thank you for taking time out of your busy schedule to answer my questions and offer thoughtful and very helpful advice. Thank you, also, for giving me opportunities to attend conferences, present posters, present in lab meetings, and iv mentor other students; these things helped me to develop my knowledge base, networking skills, and self-confidence. I would also like to thank my other committee members, Dr. Bill Sullivan, Dr. Nick Brustovetsky, Dr. Patrick Sheets, and Dr. Eri Hashino. Thank you for your support and encouragement, which were much needed and greatly appreciated. Thank you for taking the time to lead me through the planning and completion of my research, papers, and presentations. I would like to thank our collaborators at the University of California Los Angeles, David Geffen School of Medicine: Dr. Stephen Cannon and Dr. FenFen Wu. Thank you for providing valuable content for my first publication and for this dissertation by performing the oocyte electrophysiology experiments and helping me to analyze the resulting data. Thanks to the past and present members of the Cummins lab, Reesha Patel, Cindy Barbosa, Zifan Pei, Yucheng Xiao, James Jackson, Adrienne Jackson, Claudia Pan, Agnes (Zybura) Wardrop, Ashley Frazee, and Patrick Milder for your mentorship, comraderie and encouragement. Thank you for making the lab environment warm and pleasant. I’ve enjoyed working with you! I would like to thank the Pharmacology and Toxicology department for their support. Thanks to the administrative staff, including Lisa King, Amy Lawson, Joanna Plew, and Susan Gunter, for helping me navigate the processes and paperwork involved in my graduate studies and grant submissions. Thanks to all the students, post-docs, v and faculty from the department for your guidance, comraderie, and unique perspectives on both research and life in general. Thanks to the IUSM Graduate Department, especially Tara Hobson and Brandy Woods. Thank you for working hard to ensure that other students and I were well- informed and had smooth and positive experiences throughout our IBMG experience and graduate work. Thank you also for your enthusiasm, encouragement, and for your invaluable assistance in preparing myself for the next steps in my career. I would also like to thank the organizations that funded my dissertation work, including SCN2A Research Foundation, Dravet Syndrome Foundation, Rogcon Biosciences, and the National Institute of Health. *The content of much of this manuscript was adapted from papers published in eNeuro (Mason et al., 2019) and in the International Journal of Molecular Sciences (Mason and Cummins, 2020), both published under the Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/).* vi Emily R. Mason EPILEPSY MUTATIONS IN DIFFERENT REGIONS OF THE NAV1.2 CHANNEL CAUSE DISTINCT BIOPHYSICAL EFFECTS While most cases of epilepsy respond well to common antiepileptic drugs, many genetically-driven epilepsies are refractory to conventional antiepileptic drugs. Over 250 mutations in the Nav1.2 gene (SCN2A) have been implicated in otherwise idiopathic cases of epilepsy, many of which are refractory to traditional antiepileptic drugs. Few of these mutations have been studied in vitro to determine their biophysical effects on the channels, which could reveal why the effects of some are refractory to traditional antiepileptic drugs. The goal of this dissertation was to characterize multiple epilepsy mutations in the SCN2A gene, which I hypothesized would have distinct biophysical effects on the channel’s function. I used patch-clamp electrophysiology to determine the biophysical effects of three SCN2A epilepsy mutations (R1882Q, R853Q, and L835F). Wild-type (WT) or mutant human SCN2A cDNAs were expressed in human embryonic kidney (HEK) cells and subjected to a panel of electrophysiological assays. I predicted that the net effect of each of these mutations was enhancement of channel function; my results regarding the L835F and R1882Q mutations supported this hypothesis. Both mutations enhance persistent current, and R1882Q also impairs fast inactivation. However, examination of the same parameters for the R853Q mutation suggested a decrease of channel function. I hypothesized that the R853Q mutation creates a gating pore in the channel structure through which sodium leaks into the cell when the channel is in its resting conformation. This hypothesis was supported by vii electrophysiological data from Xenopus oocytes, which showed a significant voltage- dependent leak current at negative potentials when they expressed the R853Q mutant channels. This was absent in oocytes expressing WT channels. Overall, these results suggest that individual mutations in the SCN2A gene generate epilepsy via distinct biophysical effects that may require novel and/or tailored pharmacotherapies for effective management. Theodore Cummins, Ph.D., Chair viii TABLE OF CONTENTS LIST OF TABLES .................................................................................................................... xi LIST OF FIGURES ................................................................................................................. xii LIST OF ABBREVIATIONS ................................................................................................... xiii I. INTRODUCTION .................................................................................................................1 Overview ........................................................................................................................1 Voltage-Gated Sodium (Nav) Channel Overview ...........................................................2 Nav Channels of the Brain..............................................................................................7 Epilepsy ..........................................................................................................................9 Nav1.2 and Molecular Mechanisms of Epilepsy ......................................................... 11 Antiepileptic Drug Strategies ...................................................................................... 24 Hypothesis and Experimental Approach/Strategy ..................................................... 30 II. MATERIALS AND METHODS .......................................................................................... 35 DNA Constructs .......................................................................................................... 35 HEK293 Cell Culture .................................................................................................... 35 Transient Transfections .............................................................................................. 35 Generation of Cell Lines Stably Expressing hNav1.2................................................... 36 HEK Electrophysiology ................................................................................................ 36 HEK Voltage Protocols ................................................................................................ 38 Subcloning and Expression in Oocytes ....................................................................... 40 Oocyte Maintenance..................................................................................................
Load more

Recommended publications
  • Potassium Channels in Epilepsy
    Downloaded from http://perspectivesinmedicine.cshlp.org/ on September 28, 2021 - Published by Cold Spring Harbor Laboratory Press Potassium Channels in Epilepsy Ru¨diger Ko¨hling and Jakob Wolfart Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany Correspondence: [email protected] This review attempts to give a concise and up-to-date overview on the role of potassium channels in epilepsies. Their role can be defined from a genetic perspective, focusing on variants and de novo mutations identified in genetic studies or animal models with targeted, specific mutations in genes coding for a member of the large potassium channel family. In these genetic studies, a demonstrated functional link to hyperexcitability often remains elusive. However, their role can also be defined from a functional perspective, based on dy- namic, aggravating, or adaptive transcriptional and posttranslational alterations. In these cases, it often remains elusive whether the alteration is causal or merely incidental. With 80 potassium channel types, of which 10% are known to be associated with epilepsies (in humans) or a seizure phenotype (in animals), if genetically mutated, a comprehensive review is a challenging endeavor. This goal may seem all the more ambitious once the data on posttranslational alterations, found both in human tissue from epilepsy patients and in chronic or acute animal models, are included. We therefore summarize the literature, and expand only on key findings, particularly regarding functional alterations found in patient brain tissue and chronic animal models. INTRODUCTION TO POTASSIUM evolutionary appearance of voltage-gated so- CHANNELS dium (Nav)andcalcium (Cav)channels, Kchan- nels are further diversified in relation to their otassium (K) channels are related to epilepsy newer function, namely, keeping neuronal exci- Psyndromes on many different levels, ranging tation within limits (Anderson and Greenberg from direct control of neuronal excitability and 2001; Hille 2001).
    [Show full text]
  • An Advance About the Genetic Causes of Epilepsy
    E3S Web of Conferences 271, 03068 (2021) https://doi.org/10.1051/e3sconf/202127103068 ICEPE 2021 An advance about the genetic causes of epilepsy Yu Sun1, a, *, †, Licheng Lu2, b, *, †, Lanxin Li3, c, *, †, Jingbo Wang4, d, *, † 1The School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801-3633, US 2High School Affiliated to Shanghai Jiao Tong University, Shanghai, 200441, China 3Applied Biology program, University of British Columbia, Vancouver, V6r3b1, Canada 4School of Chemical Machinery and Safety, Dalian University of Technology, Dalian, 116023, China †These authors contributed equally. Abstract: Human hereditary epilepsy has been found related to ion channel mutations in voltage-gated channels (Na+, K+, Ca2+, Cl-), ligand gated channels (GABA receptors), and G-protein coupled receptors, such as Mass1. In addition, some transmembrane proteins or receptor genes, including PRRT2 and nAChR, and glucose transporter genes, such as GLUT1 and SLC2A1, are also about the onset of epilepsy. The discovery of these genetic defects has contributed greatly to our understanding of the pathology of epilepsy. This review focuses on introducing and summarizing epilepsy-associated genes and related findings in recent decades, pointing out related mutant genes that need to be further studied in the future. 1 Introduction Epilepsy is a neurological disorder characterized by 2 Malfunction of Ion channel epileptic seizures caused by abnormal brain activity. 1 in Functional variation in voltage or ligand-gated ion 100 (50 million people) people are affected by symptoms channel mutations is a major cause of idiopathic epilepsy, of this disorder worldwide, with men, young children, and especially in rare genetic forms.
    [Show full text]
  • Ion Channels 3 1
    r r r Cell Signalling Biology Michael J. Berridge Module 3 Ion Channels 3 1 Module 3 Ion Channels Synopsis Ion channels have two main signalling functions: either they can generate second messengers or they can function as effectors by responding to such messengers. Their role in signal generation is mainly centred on the Ca2 + signalling pathway, which has a large number of Ca2+ entry channels and internal Ca2+ release channels, both of which contribute to the generation of Ca2 + signals. Ion channels are also important effectors in that they mediate the action of different intracellular signalling pathways. There are a large number of K+ channels and many of these function in different + aspects of cell signalling. The voltage-dependent K (KV) channels regulate membrane potential and + excitability. The inward rectifier K (Kir) channel family has a number of important groups of channels + + such as the G protein-gated inward rectifier K (GIRK) channels and the ATP-sensitive K (KATP) + + channels. The two-pore domain K (K2P) channels are responsible for the large background K current. Some of the actions of Ca2 + are carried out by Ca2+-sensitive K+ channels and Ca2+-sensitive Cl − channels. The latter are members of a large group of chloride channels and transporters with multiple functions. There is a large family of ATP-binding cassette (ABC) transporters some of which have a signalling role in that they extrude signalling components from the cell. One of the ABC transporters is the cystic − − fibrosis transmembrane conductance regulator (CFTR) that conducts anions (Cl and HCO3 )and contributes to the osmotic gradient for the parallel flow of water in various transporting epithelia.
    [Show full text]
  • Ion Channels
    UC Davis UC Davis Previously Published Works Title THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: Ion channels. Permalink https://escholarship.org/uc/item/1442g5hg Journal British journal of pharmacology, 176 Suppl 1(S1) ISSN 0007-1188 Authors Alexander, Stephen PH Mathie, Alistair Peters, John A et al. Publication Date 2019-12-01 DOI 10.1111/bph.14749 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California S.P.H. Alexander et al. The Concise Guide to PHARMACOLOGY 2019/20: Ion channels. British Journal of Pharmacology (2019) 176, S142–S228 THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: Ion channels Stephen PH Alexander1 , Alistair Mathie2 ,JohnAPeters3 , Emma L Veale2 , Jörg Striessnig4 , Eamonn Kelly5, Jane F Armstrong6 , Elena Faccenda6 ,SimonDHarding6 ,AdamJPawson6 , Joanna L Sharman6 , Christopher Southan6 , Jamie A Davies6 and CGTP Collaborators 1School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK 2Medway School of Pharmacy, The Universities of Greenwich and Kent at Medway, Anson Building, Central Avenue, Chatham Maritime, Chatham, Kent, ME4 4TB, UK 3Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK 4Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck, A-6020 Innsbruck, Austria 5School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, BS8 1TD, UK 6Centre for Discovery Brain Science, University of Edinburgh, Edinburgh, EH8 9XD, UK Abstract The Concise Guide to PHARMACOLOGY 2019/20 is the fourth in this series of biennial publications. The Concise Guide provides concise overviews of the key properties of nearly 1800 human drug targets with an emphasis on selective pharmacology (where available), plus links to the open access knowledgebase source of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties.
    [Show full text]
  • Genomics Analysis of Potassium Channel Genes in Songbirds Reveals
    Lovell et al. BMC Genomics 2013, 14:470 http://www.biomedcentral.com/1471-2164/14/470 RESEARCH ARTICLE Open Access Genomics analysis of potassium channel genes in songbirds reveals molecular specializations of brain circuits for the maintenance and production of learned vocalizations Peter V Lovell, Julia B Carleton and Claudio V Mello* Abstract Background: A fundamental question in molecular neurobiology is how genes that determine basic neuronal properties shape the functional organization of brain circuits underlying complex learned behaviors. Given the growing availability of complete vertebrate genomes, comparative genomics represents a promising approach to address this question. Here we used genomics and molecular approaches to study how ion channel genes influence the properties of the brain circuitry that regulates birdsong, a learned vocal behavior with important similarities to human speech acquisition. We focused on potassium (K-)Channels, which are major determinants of neuronal cell excitability. Starting with the human gene set of K-Channels, we used cross-species mRNA/protein alignments, and syntenic analysis to define the full complement of orthologs, paralogs, allelic variants, as well as novel loci not previously predicted in the genome of zebra finch (Taeniopygia guttata). We also compared protein coding domains in chicken and zebra finch orthologs to identify genes under positive selective pressure, and those that contained lineage-specific insertions/deletions in functional domains. Finally, we conducted comprehensive in situ hybridizations to determine the extent of brain expression, and identify K-Channel gene enrichments in nuclei of the avian song system. Results: We identified 107 K-Channel finch genes, including 6 novel genes common to non-mammalian vertebrate lineages.
    [Show full text]
  • Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery
    fphar-07-00121 May 7, 2016 Time: 11:45 # 1 REVIEW published: 10 May 2016 doi: 10.3389/fphar.2016.00121 Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery Paola Imbrici1*, Antonella Liantonio1, Giulia M. Camerino1, Michela De Bellis1, Claudia Camerino2, Antonietta Mele1, Arcangela Giustino3, Sabata Pierno1, Annamaria De Luca1, Domenico Tricarico1, Jean-Francois Desaphy3 and Diana Conte1 1 Department of Pharmacy – Drug Sciences, University of Bari “Aldo Moro”, Bari, Italy, 2 Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari “Aldo Moro”, Bari, Italy, 3 Department of Biomedical Sciences and Human Oncology, University of Bari “Aldo Moro”, Bari, Italy In the human genome more than 400 genes encode ion channels, which are transmembrane proteins mediating ion fluxes across membranes. Being expressed in all cell types, they are involved in almost all physiological processes, including sense perception, neurotransmission, muscle contraction, secretion, immune response, cell proliferation, and differentiation. Due to the widespread tissue distribution of ion channels and their physiological functions, mutations in genes encoding ion channel subunits, or their interacting proteins, are responsible for inherited ion channelopathies. These diseases can range from common to very rare disorders and their severity can be mild, Edited by: disabling, or life-threatening. In spite of this, ion channels are the primary target of only Maria Cristina D’Adamo, University of Perugia, Italy about 5% of the marketed drugs suggesting their potential in drug discovery. The current Reviewed by: review summarizes the therapeutic management of the principal ion channelopathies Mirko Baruscotti, of central and peripheral nervous system, heart, kidney, bone, skeletal muscle and University of Milano, Italy Adrien Moreau, pancreas, resulting from mutations in calcium, sodium, potassium, and chloride ion Institut Neuromyogene – École channels.
    [Show full text]
  • Kv5, Kv6, Kv8, and Kv9 Subunits: No Simple Silent Bystanders
    Published January 11, 2016 R e v i e w Kv5, Kv6, Kv8, and Kv9 subunits: No simple silent bystanders Elke Bocksteins Laboratory for Molecular Biophysics, Physiology, and Pharmacology, Department for Biomedical Sciences, University of Antwerp, 2610 Antwerp, Belgium Members of the electrically silent voltage-gated K+ (Kv) subfamilies (Kv5, Kv6, Kv8, and Kv9, collectively identified as electrically silent voltage-gated K+ channel [KvS] subunits) do not form functional homotetrameric channels but assemble with Kv2 subunits into heterotetrameric Kv2/KvS channels with unique biophysical properties. Unlike the ubiquitously expressed Kv2 subunits, KvS subunits show a more restricted expression. This raises the possibility that Kv2/KvS heterotetramers have tissue-specific functions, making them potential targets for the development of novel therapeutic strategies. Here, I provide an overview of the expression of KvS subunits in different tissues and discuss their proposed role in various physiological and pathophysiological processes. This overview demonstrates the importance of KvS subunits and Kv2/KvS heterotetramers in vivo and the importance of considering KvS sub- units and Kv2/KvS heterotetramers in the development of novel treatments. Kv2 channels Downloaded from The voltage-gated K+ (Kv) channel Kv2.1 plays a crucial functions in a host of different excitable and nonexcit- role in many cell types, with its contribution to various able cells depends on Kv2.1 channel diversity, which is processes depending on both its conductive and non-
    [Show full text]
  • Epigenetic Mechanisms Are Involved in the Oncogenic Properties of ZNF518B in Colorectal Cancer
    Epigenetic mechanisms are involved in the oncogenic properties of ZNF518B in colorectal cancer Francisco Gimeno-Valiente, Ángela L. Riffo-Campos, Luis Torres, Noelia Tarazona, Valentina Gambardella, Andrés Cervantes, Gerardo López-Rodas, Luis Franco and Josefa Castillo SUPPLEMENTARY METHODS 1. Selection of genomic sequences for ChIP analysis To select the sequences for ChIP analysis in the five putative target genes, namely, PADI3, ZDHHC2, RGS4, EFNA5 and KAT2B, the genomic region corresponding to the gene was downloaded from Ensembl. Then, zoom was applied to see in detail the promoter, enhancers and regulatory sequences. The details for HCT116 cells were then recovered and the target sequences for factor binding examined. Obviously, there are not data for ZNF518B, but special attention was paid to the target sequences of other zinc-finger containing factors. Finally, the regions that may putatively bind ZNF518B were selected and primers defining amplicons spanning such sequences were searched out. Supplementary Figure S3 gives the location of the amplicons used in each gene. 2. Obtaining the raw data and generating the BAM files for in silico analysis of the effects of EHMT2 and EZH2 silencing The data of siEZH2 (SRR6384524), siG9a (SRR6384526) and siNon-target (SRR6384521) in HCT116 cell line, were downloaded from SRA (Bioproject PRJNA422822, https://www.ncbi. nlm.nih.gov/bioproject/), using SRA-tolkit (https://ncbi.github.io/sra-tools/). All data correspond to RNAseq single end. doBasics = TRUE doAll = FALSE $ fastq-dump -I --split-files SRR6384524 Data quality was checked using the software fastqc (https://www.bioinformatics.babraham. ac.uk /projects/fastqc/). The first low quality removing nucleotides were removed using FASTX- Toolkit (http://hannonlab.cshl.edu/fastxtoolkit/).
    [Show full text]
  • 1 1 2 3 Cell Type-Specific Transcriptomics of Hypothalamic
    1 2 3 4 Cell type-specific transcriptomics of hypothalamic energy-sensing neuron responses to 5 weight-loss 6 7 Fredrick E. Henry1,†, Ken Sugino1,†, Adam Tozer2, Tiago Branco2, Scott M. Sternson1,* 8 9 1Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 10 20147, USA. 11 2Division of Neurobiology, Medical Research Council Laboratory of Molecular Biology, 12 Cambridge CB2 0QH, UK 13 14 †Co-first author 15 *Correspondence to: [email protected] 16 Phone: 571-209-4103 17 18 Authors have no competing interests 19 1 20 Abstract 21 Molecular and cellular processes in neurons are critical for sensing and responding to energy 22 deficit states, such as during weight-loss. AGRP neurons are a key hypothalamic population 23 that is activated during energy deficit and increases appetite and weight-gain. Cell type-specific 24 transcriptomics can be used to identify pathways that counteract weight-loss, and here we 25 report high-quality gene expression profiles of AGRP neurons from well-fed and food-deprived 26 young adult mice. For comparison, we also analyzed POMC neurons, an intermingled 27 population that suppresses appetite and body weight. We find that AGRP neurons are 28 considerably more sensitive to energy deficit than POMC neurons. Furthermore, we identify cell 29 type-specific pathways involving endoplasmic reticulum-stress, circadian signaling, ion 30 channels, neuropeptides, and receptors. Combined with methods to validate and manipulate 31 these pathways, this resource greatly expands molecular insight into neuronal regulation of 32 body weight, and may be useful for devising therapeutic strategies for obesity and eating 33 disorders.
    [Show full text]
  • Heteromeric KV2/KV8.2 Channels Mediate Delayed Rectifier Potassium Currents in Primate Photoreceptors
    3414 • The Journal of Neuroscience, April 4, 2018 • 38(14):3414–3427 Systems/Circuits Heteromeric KV2/KV8.2 Channels Mediate Delayed Rectifier Potassium Currents in Primate Photoreceptors Jacqueline Gayet-Primo,1 Daniel B. Yaeger,3 Roupen A. Khanjian,3 and XTeresa Puthussery1,2,3 1School of Optometry, 2Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California 94720, and 3Casey Eye Institute, Oregon Health & Science University, Portland, Oregon 97239 Silent voltage-gated potassium channel subunits (KVS) interact selectively with members of the KV2 channel family to modify their functional properties. The localization and functional roles of these silent subunits remain poorly understood. Mutations in the KVS subunit, KV8.2 (KCNV2), lead to severe visual impairment in humans, but the basis of these deficits remains unclear. Here, we examined the localization, native interactions, and functional properties of KV8.2-containing channels in mouse, macaque, and human photore- ceptors of either sex. In human retina, KV8.2 colocalized with KV2.1 and KV2.2 in cone inner segments and with KV2.1 in rod inner segments. KV2.1 and KV2.2 could be coimmunoprecipitated with KV8.2 in retinal lysates indicating that these subunits likely interact directly. Retinal KV2.1 was less phosphorylated than cortical KV2.1, a difference expected to alter the biophysical properties of these channels. Using voltage-clamp recordings and pharmacology, we provide functional evidence for Kv2-containing channels in primate rods and cones. We propose that the presence of KV8.2, and low levels of KV2.1 phosphorylation shift the activation range of KV2 channels toalignwiththeoperatingrangeofrodandconephotoreceptors.OurdataindicatearoleforKV2/KV8.2channelsinhumanphotoreceptor function and suggest that the visual deficits in patients with KCNV2 mutations arise from inadequate resting activation of KV channels in rod and cone inner segments.
    [Show full text]
  • Potassium Channels and Their Potential Roles in Substance Use Disorders
    International Journal of Molecular Sciences Review Potassium Channels and Their Potential Roles in Substance Use Disorders Michael T. McCoy † , Subramaniam Jayanthi † and Jean Lud Cadet * Molecular Neuropsychiatry Research Branch, NIDA Intramural Research Program, Baltimore, MD 21224, USA; [email protected] (M.T.M.); [email protected] (S.J.) * Correspondence: [email protected]; Tel.: +1-443-740-2656 † Equal contributions (joint first authors). Abstract: Substance use disorders (SUDs) are ubiquitous throughout the world. However, much re- mains to be done to develop pharmacotherapies that are very efficacious because the focus has been mostly on using dopaminergic agents or opioid agonists. Herein we discuss the potential of using potassium channel activators in SUD treatment because evidence has accumulated to support a role of these channels in the effects of rewarding drugs. Potassium channels regulate neuronal action potential via effects on threshold, burst firing, and firing frequency. They are located in brain regions identified as important for the behavioral responses to rewarding drugs. In addition, their ex- pression profiles are influenced by administration of rewarding substances. Genetic studies have also implicated variants in genes that encode potassium channels. Importantly, administration of potassium agonists have been shown to reduce alcohol intake and to augment the behavioral effects of opioid drugs. Potassium channel expression is also increased in animals with reduced intake of methamphetamine. Together, these results support the idea of further investing in studies that focus on elucidating the role of potassium channels as targets for therapeutic interventions against SUDs. Keywords: alcohol; cocaine; methamphetamine; opioids; pharmacotherapy Citation: McCoy, M.T.; Jayanthi, S.; Cadet, J.L.
    [Show full text]
  • Recurrent Copy Number Changes in Mentally Retarded Children Harbour Genes Involved in Cellular Localization and the Glutamate Receptor Complex
    European Journal of Human Genetics (2010) 18, 39–46 & 2010 Macmillan Publishers Limited All rights reserved 1018-4813/10 $32.00 www.nature.com/ejhg ARTICLE Recurrent copy number changes in mentally retarded children harbour genes involved in cellular localization and the glutamate receptor complex Martin Poot*,1, Marc J Eleveld1, Ruben van ‘t Slot1, Hans Kristian Ploos van Amstel1 and Ron Hochstenbach1 To determine the phenotypic significance of copy number changes (CNCs) in the human genome, we performed genome-wide segmental aneuploidy profiling by BAC-based array-CGH of 278 unrelated patients with multiple congenital abnormalities and mental retardation (MCAMR) and in 48 unaffected family members. In 20 patients, we found de novo CNCs composed of multiple consecutive probes. Of the 125 probes making up these probably pathogenic CNCs, 14 were also found as single CNCs in other patients and 5 in healthy individuals. Thus, these CNCs are not by themselves pathogenic. Almost one out of five patients and almost one out of six healthy individuals in our study cohort carried a gain or a loss for any one of the recently discovered microdeletion/microduplication loci, whereas seven patients and one healthy individual showed losses or gains for at least two different loci. The pathogenic burden resulting from these CNCs may be limited as they were found with similar frequencies among patients and healthy individuals (P¼0.165; Fischer’s exact test), and several individuals showed CNCs at multiple loci. CNCs occurring specifically in our study cohort were enriched for components of the glutamate receptor family (GRIA2, GRIA4, GRIK2 and GRIK4) and genes encoding proteins involved in guiding cell localization during development (ATP1A2, GIRK3, GRIA2, KCNJ3, KCNJ10, KCNK17 and KCNK5).
    [Show full text]