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Ciotu CI, Tsantoulas C, Meents J, Lampert A, McMahon SB, Ludwig A, Fischer MJM. Noncanonical Ion Channel Behaviour in Pain. Int J Mol Sci 2019; 20:E4572. [PMID: 31540178 PMCID: PMC6770626 DOI: 10.3390/ijms20184572] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/09/2019] [Accepted: 09/12/2019] [Indexed: 12/19/2022] Open
Abstract
Ion channels contribute fundamental properties to cell membranes. Although highly diverse in conductivity, structure, location, and function, many of them can be regulated by common mechanisms, such as voltage or (de-)phosphorylation. Primarily considering ion channels involved in the nociceptive system, this review covers more novel and less known features. Accordingly, we outline noncanonical operation of voltage-gated sodium, potassium, transient receptor potential (TRP), and hyperpolarization-activated cyclic nucleotide (HCN)-gated channels. Noncanonical features discussed include properties as a memory for prior voltage and chemical exposure, alternative ion conduction pathways, cluster formation, and silent subunits. Complementary to this main focus, the intention is also to transfer knowledge between fields, which become inevitably more separate due to their size.
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Affiliation(s)
- Cosmin I Ciotu
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | | | - Jannis Meents
- Institute of Physiology, University Hospital RWTH Aachen, 52074 Aachen, Germany
| | - Angelika Lampert
- Institute of Physiology, University Hospital RWTH Aachen, 52074 Aachen, Germany
| | - Stephen B McMahon
- Wolfson Centre for Age-Related Diseases, King's College London, London SE1 1UR, UK
| | - Andreas Ludwig
- Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Michael J M Fischer
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria.
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Vullhorst D, Buonanno A. NMDA Receptors Regulate Neuregulin 2 Binding to ER-PM Junctions and Ectodomain Release by ADAM10 [corrected]. Mol Neurobiol 2019; 56:8345-8363. [PMID: 31240601 DOI: 10.1007/s12035-019-01659-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 05/20/2019] [Indexed: 12/13/2022]
Abstract
Unprocessed pro-neuregulin 2 (pro-NRG2) accumulates on neuronal cell bodies at junctions between the endoplasmic reticulum and plasma membrane (ER-PM junctions). NMDA receptors (NMDARs) trigger NRG2 ectodomain shedding from these sites followed by activation of ErbB4 receptor tyrosine kinases, and ErbB4 signaling cell-autonomously downregulates intrinsic excitability of GABAergic interneurons by reducing voltage-gated sodium channel currents. NMDARs also promote dispersal of Kv2.1 clusters from ER-PM junctions and cause a hyperpolarizing shift in its voltage-dependent channel activation, suggesting that NRG2/ErbB4 and Kv2.1 work together to regulate intrinsic interneuron excitability in an activity-dependent manner. Here we explored the cellular processes underlying NMDAR-dependent NRG2 shedding in cultured rat hippocampal neurons. We report that NMDARs control shedding by two separate but converging mechanisms. First, NMDA treatment disrupts binding of pro-NRG2 to ER-PM junctions by post-translationally modifying conserved Ser/Thr residues in its intracellular domain. Second, using a mutant NRG2 protein that cannot be modified at these residues and that fails to accumulate at ER-PM junctions, we demonstrate that NMDARs also directly promote NRG2 shedding by ADAM-type metalloproteinases. Using pharmacological and shRNA-mediated knockdown, and metalloproteinase overexpression, we unexpectedly find that ADAM10, but not ADAM17/TACE, is the major NRG2 sheddase acting downstream of NMDAR activation. Together, these findings reveal how NMDARs exert tight control over the NRG2/ErbB4 signaling pathway, and suggest that NRG2 and Kv2.1 are co-regulated components of a shared pathway that responds to elevated extracellular glutamate levels.
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Affiliation(s)
- Detlef Vullhorst
- Section on Molecular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 35 Lincoln Drive, Room 2C-1000, Bethesda, MD, 20892, USA
| | - Andres Buonanno
- Section on Molecular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 35 Lincoln Drive, Room 2C-1000, Bethesda, MD, 20892, USA.
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53
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The Role of the Voltage-Gated Potassium Channel Proteins Kv8.2 and Kv2.1 in Vision and Retinal Disease: Insights from the Study of Mouse Gene Knock-Out Mutations. eNeuro 2019; 6:eN-NWR-0032-19. [PMID: 30820446 PMCID: PMC6393689 DOI: 10.1523/eneuro.0032-19.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 02/01/2019] [Accepted: 02/04/2019] [Indexed: 11/21/2022] Open
Abstract
Mutations in the KCNV2 gene, which encodes the voltage-gated K+ channel protein Kv8.2, cause a distinctive form of cone dystrophy with a supernormal rod response (CDSRR). Kv8.2 channel subunits only form functional channels when combined in a heterotetramer with Kv2.1 subunits encoded by the KCNB1 gene. The CDSRR disease phenotype indicates that photoreceptor adaptation is disrupted. The electroretinogram (ERG) response of affected individuals shows depressed rod and cone activity, but what distinguishes this disease is the supernormal rod response to a bright flash of light. Here, we have utilized knock-out mutations of both genes in the mouse to study the pathophysiology of CDSRR. The Kv8.2 knock-out (KO) mice show many similarities to the human disorder, including a depressed a-wave and an elevated b-wave response with bright light stimulation. Optical coherence tomography (OCT) imaging and immunohistochemistry indicate that the changes in six-month-old Kv8.2 KO retinae are largely limited to the outer nuclear layer (ONL), while outer segments appear intact. In addition, there is a significant increase in TUNEL-positive cells throughout the retina. The Kv2.1 KO and double KO mice also show a severely depressed a-wave, but the elevated b-wave response is absent. Interestingly, in all three KO genotypes, the c-wave is totally absent. The differential response shown here of these KO lines, that either possess homomeric channels or lack channels completely, has provided further insights into the role of K+ channels in the generation of the a-, b-, and c-wave components of the ERG.
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54
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Corbin-Leftwich A, Small HE, Robinson HH, Villalba-Galea CA, Boland LM. A Xenopus oocyte model system to study action potentials. J Gen Physiol 2018; 150:1583-1593. [PMID: 30266757 PMCID: PMC6219683 DOI: 10.1085/jgp.201812146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/10/2018] [Indexed: 12/23/2022] Open
Abstract
Voltage-gated Na+ and K+ channels are known to underlie the temporal characteristics of action potentials. Corbin-Leftwich et al. establish reliable action potential recordings from Xenopus oocytes coexpressing these channels and show how different K+ channel subtypes can modulate excitability. Action potentials (APs) are the functional units of fast electrical signaling in excitable cells. The upstroke and downstroke of an AP is generated by the competing and asynchronous action of Na+- and K+-selective voltage-gated conductances. Although a mixture of voltage-gated channels has been long recognized to contribute to the generation and temporal characteristics of the AP, understanding how each of these proteins function and are regulated during electrical signaling remains the subject of intense research. AP properties vary among different cellular types because of the expression diversity, subcellular location, and modulation of ion channels. These complexities, in addition to the functional coupling of these proteins by membrane potential, make it challenging to understand the roles of different channels in initiating and “temporally shaping” the AP. Here, to address this problem, we focus our efforts on finding conditions that allow reliable AP recordings from Xenopus laevis oocytes coexpressing Na+ and K+ channels. As a proof of principle, we show how the expression of a variety of K+ channel subtypes can modulate excitability in this minimal model system. This approach raises the prospect of studies on the modulation of APs by pharmacological or biological means with a controlled background of Na+ and K+ channel expression.
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Affiliation(s)
| | - Hannah E Small
- Department of Biology, University of Richmond, Richmond, VA
| | | | - Carlos A Villalba-Galea
- Department of Physiology and Biophysics, Virginia Commonwealth University, School of Medicine, Richmond, VA .,Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA
| | - Linda M Boland
- Department of Biology, University of Richmond, Richmond, VA
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Kirmiz M, Palacio S, Thapa P, King AN, Sack JT, Trimmer JS. Remodeling neuronal ER-PM junctions is a conserved nonconducting function of Kv2 plasma membrane ion channels. Mol Biol Cell 2018; 29:2410-2432. [PMID: 30091655 PMCID: PMC6233057 DOI: 10.1091/mbc.e18-05-0337] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The endoplasmic reticulum (ER) and plasma membrane (PM) form junctions crucial to ion and lipid signaling and homeostasis. The Kv2.1 ion channel is localized at ER–PM junctions in brain neurons and is unique among PM proteins in its ability to remodel these specialized membrane contact sites. Here, we show that this function is conserved between Kv2.1 and Kv2.2, which differ in their biophysical properties, modulation, and cellular expression. Kv2.2 ER–PM junctions are present at sites deficient in the actin cytoskeleton, and disruption of the actin cytoskeleton affects their spatial organization. Kv2.2-containing ER–PM junctions overlap with those formed by canonical ER–PM tethers. The ability of Kv2 channels to remodel ER–PM junctions is unchanged by point mutations that eliminate their ion conduction but eliminated by point mutations within the Kv2-specific proximal restriction and clustering (PRC) domain that do not impact their ion channel function. The highly conserved PRC domain is sufficient to transfer the ER–PM junction–remodeling function to another PM protein. Last, brain neurons in Kv2 double-knockout mice have altered ER–PM junctions. Together, these findings demonstrate a conserved in vivo function for Kv2 family members in remodeling neuronal ER–PM junctions that is distinct from their canonical role as ion-conducting channels shaping neuronal excitability.
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Affiliation(s)
- Michael Kirmiz
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Stephanie Palacio
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616
| | - Anna N King
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - James S Trimmer
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616.,Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616
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Abstract
Exome and targeted sequencing have revolutionized clinical diagnosis. This has been particularly striking in epilepsy and neurodevelopmental disorders, for which new genes or new variants of preexisting candidate genes are being continuously identified at increasing rates every year. A surprising finding of these efforts is the recognition that gain of function potassium channel variants are actually associated with certain types of epilepsy, such as malignant migrating partial seizures of infancy or early-onset epileptic encephalopathy. This development has been difficult to understand as traditionally potassium channel loss-of-function, not gain-of-function, has been associated with hyperexcitability disorders. In this article, we describe the current state of the field regarding the gain-of-function potassium channel variants associated with epilepsy (KCNA2, KCNB1, KCND2, KCNH1, KCNH5, KCNJ10, KCNMA1, KCNQ2, KCNQ3, and KCNT1) and speculate on the possible cellular mechanisms behind the development of seizures and epilepsy in these patients. Understanding how potassium channel gain-of-function leads to epilepsy will provide new insights into the inner working of neural circuits and aid in developing new therapies.
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Affiliation(s)
- Zachary Niday
- Dept. of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269, USA
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Identification of VAPA and VAPB as Kv2 Channel-Interacting Proteins Defining Endoplasmic Reticulum-Plasma Membrane Junctions in Mammalian Brain Neurons. J Neurosci 2018; 38:7562-7584. [PMID: 30012696 DOI: 10.1523/jneurosci.0893-18.2018] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/01/2018] [Accepted: 07/07/2018] [Indexed: 11/21/2022] Open
Abstract
Membrane contacts between endoplasmic reticulum (ER) and plasma membrane (PM), or ER-PM junctions, are ubiquitous in eukaryotic cells and are platforms for lipid and calcium signaling and homeostasis. Recent studies have revealed proteins crucial to the formation and function of ER-PM junctions in non-neuronal cells, but little is known of the ER-PM junctions prominent in aspiny regions of mammalian brain neurons. The Kv2.1 voltage-gated potassium channel is abundantly clustered at ER-PM junctions in brain neurons and is the first PM protein that functions to organize ER-PM junctions. However, the molecular mechanism whereby Kv2.1 localizes to and remodels these junctions is unknown. We used affinity immunopurification and mass spectrometry-based proteomics on brain samples from male and female WT and Kv2.1 KO mice and identified the resident ER vesicle-associated membrane protein-associated proteins isoforms A and B (VAPA and VAPB) as prominent Kv2.1-associated proteins. Coexpression with Kv2.1 or its paralog Kv2.2 was sufficient to recruit VAPs to ER-PM junctions. Multiplex immunolabeling revealed colocalization of Kv2.1 and Kv2.2 with endogenous VAPs at ER-PM junctions in brain neurons from male and female mice in situ and in cultured rat hippocampal neurons, and KO of VAPA in mammalian cells reduces Kv2.1 clustering. The association of VAPA with Kv2.1 relies on a "two phenylalanines in an acidic tract" (FFAT) binding domain on VAPA and a noncanonical phosphorylation-dependent FFAT motif comprising the Kv2-specific clustering or PRC motif. These results suggest that Kv2.1 localizes to and organizes neuronal ER-PM junctions through an interaction with VAPs.SIGNIFICANCE STATEMENT Our study identified the endoplasmic reticulum (ER) proteins vesicle-associated membrane protein-associated proteins isoforms A and B (VAPA and VAPB) as proteins copurifying with the plasma membrane (PM) Kv2.1 ion channel. We found that expression of Kv2.1 recruits VAPs to ER-PM junctions, specialized membrane contact sites crucial to distinct aspects of cell function. We found endogenous VAPs at Kv2.1-mediated ER-PM junctions in brain neurons and other mammalian cells and that knocking out VAPA expression disrupts Kv2.1 clustering. We identified domains of VAPs and Kv2.1 necessary and sufficient for their association at ER-PM junctions. Our study suggests that Kv2.1 expression in the PM can affect ER-PM junctions via its phosphorylation-dependent association to ER-localized VAPA and VAPB.
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Activating Transcription Factor 4 (ATF4) Regulates Neuronal Activity by Controlling GABA BR Trafficking. J Neurosci 2018; 38:6102-6113. [PMID: 29875265 DOI: 10.1523/jneurosci.3350-17.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 05/29/2018] [Accepted: 05/31/2018] [Indexed: 11/21/2022] Open
Abstract
Activating Transcription Factor 4 (ATF4) has been postulated as a key regulator of learning and memory. We previously reported that specific hippocampal ATF4 downregulation causes deficits in synaptic plasticity and memory and reduction of glutamatergic functionality. Here we extend our studies to address ATF4's role in neuronal excitability. We find that long-term ATF4 knockdown in cultured rat hippocampal neurons significantly increases the frequency of spontaneous action potentials. This effect is associated with decreased functionality of metabotropic GABAB receptors (GABABRs). Knocking down ATF4 results in significant reduction of GABABR-induced GIRK currents and increased mIPSC frequency. Furthermore, reducing ATF4 significantly decreases expression of membrane-exposed, but not total, GABABR 1a and 1b subunits, indicating that ATF4 regulates GABABR trafficking. In contrast, ATF4 knockdown has no effect on surface expression of GABABR2s, several GABABR-coupled ion channels or β2 and γ2 GABAARs. Pharmacologic manipulations confirmed the relationship between GABABR functionality and action potential frequency in our cultures. Specifically, the effects of ATF4 downregulation cited above are fully rescued by transcriptionally active, but not by transcriptionally inactive, shRNA-resistant, ATF4. We previously reported that ATF4 promotes stabilization of the actin-regulatory protein Cdc42 by a transcription-dependent mechanism. To test the hypothesis that this action underlies the mechanism by which ATF4 loss affects neuronal firing rates and GABABR trafficking, we downregulated Cdc42 and found that this phenocopies the effects of ATF4 knockdown on these properties. In conclusion, our data favor a model in which ATF4, by regulating Cdc42 expression, affects trafficking of GABABRs, which in turn modulates the excitability properties of neurons.SIGNIFICANCE STATEMENT GABAB receptors (GABABRs), the metabotropic receptors for the inhibitory neurotransmitter GABA, have crucial roles in controlling the firing rate of neurons. Deficits in trafficking/functionality of GABABRs have been linked to a variety of neurological and psychiatric conditions, including epilepsy, anxiety, depression, schizophrenia, addiction, and pain. Here we show that GABABRs trafficking is influenced by Activating Transcription Factor 4 (ATF4), a protein that has a pivotal role in hippocampal memory processes. We found that ATF4 downregulation in hippocampal neurons reduces membrane-bound GABABR levels and thereby increases intrinsic excitability. These effects are mediated by loss of the small GTPase Cdc42 following ATF4 downregulation. These findings reveal a critical role for ATF4 in regulating the modulation of neuronal excitability by GABABRs.
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Heteromeric K V2/K V8.2 Channels Mediate Delayed Rectifier Potassium Currents in Primate Photoreceptors. J Neurosci 2018; 38:3414-3427. [PMID: 29483285 DOI: 10.1523/jneurosci.2440-17.2018] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Revised: 01/18/2018] [Accepted: 02/11/2018] [Indexed: 01/17/2023] Open
Abstract
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 photoreceptors 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 to align with the operating range of rod and cone photoreceptors. Our data indicate a role for KV2/KV8.2 channels in human photoreceptor 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.SIGNIFICANCE STATEMENT Mutations in a voltage-gated potassium channel subunit, KV8.2, underlie a blinding inherited photoreceptor dystrophy, indicating an important role for these channels in human vision. Here, we have defined the localization and subunit interactions of KV8.2 channels in primate photoreceptors. We show that the KV8.2 subunit interacts with different Kv2 channels in rods and cones, giving rise to potassium currents with distinct functional properties. Our results provide a molecular basis for retinal dysfunction in patients with mutations in the KCNV2 gene encoding KV8.2.
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60
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Myshkin MY, Paramonov AS, Kulbatskii DS, Lyukmanova EN, Kirpichnikov MP, Shenkarev ZO. “Divide and conquer” approach to the structural studies of multidomain ion channels by the example of isolated voltage sensing domains of human Kv2.1 and Nav1.4 channels. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2018. [DOI: 10.1134/s1068162017060103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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61
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Bishop HI, Cobb MM, Kirmiz M, Parajuli LK, Mandikian D, Philp AM, Melnik M, Kuja-Panula J, Rauvala H, Shigemoto R, Murray KD, Trimmer JS. Kv2 Ion Channels Determine the Expression and Localization of the Associated AMIGO-1 Cell Adhesion Molecule in Adult Brain Neurons. Front Mol Neurosci 2018; 11:1. [PMID: 29403353 PMCID: PMC5780429 DOI: 10.3389/fnmol.2018.00001] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/03/2018] [Indexed: 12/20/2022] Open
Abstract
Voltage-gated K+ (Kv) channels play important roles in regulating neuronal excitability. Kv channels comprise four principal α subunits, and transmembrane and/or cytoplasmic auxiliary subunits that modify diverse aspects of channel function. AMIGO-1, which mediates homophilic cell adhesion underlying neurite outgrowth and fasciculation during development, has recently been shown to be an auxiliary subunit of adult brain Kv2.1-containing Kv channels. We show that AMIGO-1 is extensively colocalized with both Kv2.1 and its paralog Kv2.2 in brain neurons across diverse mammals, and that in adult brain, there is no apparent population of AMIGO-1 outside of that colocalized with these Kv2 α subunits. AMIGO-1 is coclustered with Kv2 α subunits at specific plasma membrane (PM) sites associated with hypolemmal subsurface cisternae at neuronal ER:PM junctions. This distinct PM clustering of AMIGO-1 is not observed in brain neurons of mice lacking Kv2 α subunit expression. Moreover, in heterologous cells, coexpression of either Kv2.1 or Kv2.2 is sufficient to drive clustering of the otherwise uniformly expressed AMIGO-1. Kv2 α subunit coexpression also increases biosynthetic intracellular trafficking and PM expression of AMIGO-1 in heterologous cells, and analyses of Kv2.1 and Kv2.2 knockout mice show selective loss of AMIGO-1 expression and localization in neurons lacking the respective Kv2 α subunit. Together, these data suggest that in mammalian brain neurons, AMIGO-1 is exclusively associated with Kv2 α subunits, and that Kv2 α subunits are obligatory in determining the correct pattern of AMIGO-1 expression, PM trafficking and clustering.
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Affiliation(s)
- Hannah I Bishop
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Melanie M Cobb
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Michael Kirmiz
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Laxmi K Parajuli
- Center for Neuroscience, University of California, Davis, Davis, CA, United States.,Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki, Japan
| | - Danielle Mandikian
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Ashleigh M Philp
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Mikhail Melnik
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | | | - Heikki Rauvala
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Ryuichi Shigemoto
- Division of Cerebral Structure, National Institute for Physiological Sciences, Okazaki, Japan
| | - Karl D Murray
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States.,Center for Neuroscience, University of California, Davis, Davis, CA, United States
| | - James S Trimmer
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States.,Department Physiology and Membrane Biology, University of California, Davis, Davis, CA, United States
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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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Marini C, Romoli M, Parrini E, Costa C, Mei D, Mari F, Parmeggiani L, Procopio E, Metitieri T, Cellini E, Virdò S, De Vita D, Gentile M, Prontera P, Calabresi P, Guerrini R. Clinical features and outcome of 6 new patients carrying de novo KCNB1 gene mutations. NEUROLOGY-GENETICS 2017; 3:e206. [PMID: 29264397 PMCID: PMC5733250 DOI: 10.1212/nxg.0000000000000206] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2017] [Accepted: 09/07/2017] [Indexed: 01/01/2023]
Abstract
Objective To describe electroclinical features and outcome of 6 patients harboring KCNB1 mutations. Methods Clinical, EEG, neuropsychological, and brain MRI data analysis. Targeted next-generation sequencing of a 95 epilepsy gene panel. Results The mean age at seizure onset was 11 months. The mean follow-up of 11.3 years documented that 4 patients following an infantile phase of frequent seizures became seizure free; the mean age at seizure offset was 4.25 years. Epilepsy phenotypes comprised West syndrome in 2 patients, infantile-onset unspecified generalized epilepsy, myoclonic and photosensitive eyelid myoclonia epilepsy resembling Jeavons syndrome, Lennox-Gastaut syndrome, and focal epilepsy with prolonged occipital or clonic seizures in each and every one. Five patients had developmental delay prior to seizure onset evolving into severe intellectual disability with absent speech and autistic traits in one and stereotypic hand movements with impulse control disorder in another. The patient with Jeavons syndrome evolved into moderate intellectual disability. Mutations were de novo, 4 missense and 2 nonsense, 5 were novel, and 1 resulted from somatic mosaicism. Conclusions KCNB1-related manifestations include a spectrum of infantile-onset generalized or focal seizures whose combination leads to early infantile epileptic encephalopathy including West, Lennox-Gastaut, and Jeavons syndromes. Long-term follow-up highlights that following a stormy phase, seizures subside or cease and treatment may be eased or withdrawn. Cognitive and motor functions are almost always delayed prior to seizure onset and evolve into severe, persistent impairment. Thus, KCNB1 mutations are associated with diffuse brain dysfunction combining seizures, motor, and cognitive impairment.
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Affiliation(s)
- Carla Marini
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Michele Romoli
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Elena Parrini
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Cinzia Costa
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Davide Mei
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Francesco Mari
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Lucio Parmeggiani
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Elena Procopio
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Tiziana Metitieri
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Elena Cellini
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Simona Virdò
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Dalila De Vita
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Mattia Gentile
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Paolo Prontera
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Paolo Calabresi
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
| | - Renzo Guerrini
- Pediatric Neurology Unit (C.M., E.P., D.M., F.M., T.M., E.C., S.V., D.D.V., R.G.), Neurogenetics and Neurobiology Laboratories, Neuroscience Department, A. Meyer Pediatric Hospital, University of Florence; Neurology Unit (M.R., C.C., P.C.), Department of Medicine, University of Perugia, Ospedale S. Maria della Misericordia; Child Neurology Service (L.P.), Hospital of Bolzano; Metabolic Unit (E.P.), A. Meyer Pediatric Hospital, Florence; Medical Genetics Unit (M.G.), Azienda Sanitaria Locale Bari; Neonatology Unit and Prenatal Diagnosis (P.P.), Medical Genetic Unit, Ospedale S. Maria della Misericordia, Perugia; Department of Experimental Neurosciences (P.C.), "Istituto di Ricovero e Cura a Carattere Scientifico," IRCCS Santa Lucia Foundation, Rome; and IRCCS Stella Maris Foundation (R.G.), Calambrone, Pisa, Italy
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Attention-deficit/hyperactivity disorder associated with KChIP1 rs1541665 in Kv channels accessory proteins. PLoS One 2017; 12:e0188678. [PMID: 29176790 PMCID: PMC5703492 DOI: 10.1371/journal.pone.0188678] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 11/10/2017] [Indexed: 12/16/2022] Open
Abstract
Attention-deficit/hyperactivity disorder (ADHD) is an early onset childhood neurodevelopmental disorder with high heritability. A number of genetic risk factors and environment factors have been implicated in the pathogenesis of ADHD. Genes encoding for subtypes of voltage-dependent K channels (Kv) and accessory proteins to these channels have been identified in genome-wide association studies (GWAS) of ADHD. We conducted a two-stage case–control study to investigate the associations between five key genes (KChIP4, KChIP1, DPP10, FHIT, and KCNC1) and the risk of developing ADHD. In the discovery stage comprising 256 cases and 372 controls, KChIP1 rs1541665 and FHIT rs3772475 were identified; they were further genotyped in the validation stage containing 328cases and 431 controls.KChIP1 rs1541665 showed significant association with a risk of ADHD at both stages, with CC vs TT odds ratio (OR) = 1.961, 95% confidence interval (CI) = 1.366–2.497, in combined analyses (P-FDR = 0.007). Moreover, we also found rs1541665 involvement in ADHD-I subtype (OR (95% CI) = 2.341(1.713, 3.282), and Hyperactive index score (P = 0.005) in combined samples.Intriguingly, gene-environmental interactions analysis consistently revealed the potential interactionsof rs1541665 collaboratingwith maternal stress pregnancy (Pmul = 0.021) and blood lead (Padd = 0.017) to modify ADHD risk. In conclusion, the current study provides evidence that genetic variants of Kv accessory proteins may contribute to the susceptibility of ADHD.Further studies with different ethnicitiesare warranted to produce definitive conclusions.
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Effects of Acyclovir and IVIG on Behavioral Outcomes after HSV1 CNS Infection. Behav Neurol 2017; 2017:5238402. [PMID: 29358844 PMCID: PMC5735307 DOI: 10.1155/2017/5238402] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 09/06/2017] [Accepted: 09/16/2017] [Indexed: 12/27/2022] Open
Abstract
Herpes simplex virus 1 (HSV) encephalitis (HSE) has serious neurological complications, involving behavioral and cognitive impairments that cause significant morbidity and a reduced quality of life. We showed that HSE results from dysregulated central nervous system (CNS) inflammatory responses. We hypothesized that CNS inflammation is casually involved in behavioral abnormalities after HSE and that treatment with ACV and pooled human immunoglobulin (IVIG), an immunomodulatory drug, would improve outcomes compared to mice treated with phosphate buffered saline (PBS) or ACV alone. Anxiety levels were high in HSV-infected PBS and ACV-treated mice compared to mice treated with ACV + IVIG, consistent with reports implicating inflammation in anxiety induced by lipopolysaccharide (LPS) or stress. Female, but not male, PBS-treated mice were cognitively impaired, and unexpectedly, ACV was protective, while the inclusion of IVIG surprisingly antagonized ACV's beneficial effects. Distinct serum proteomic profiles were observed for male and female mice, and the antagonistic effects of ACV and IVIG on behavior were paralleled by similar changes in the serum proteome of ACV- and ACV + IVIG-treated mice. We conclude that inflammation and other factors mediate HSV-induced behavioral impairments and that the effects of ACV and IVIG on behavior involve novel mechanisms.
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de Kovel CGF, Syrbe S, Brilstra EH, Verbeek N, Kerr B, Dubbs H, Bayat A, Desai S, Naidu S, Srivastava S, Cagaylan H, Yis U, Saunders C, Rook M, Plugge S, Muhle H, Afawi Z, Klein KM, Jayaraman V, Rajagopalan R, Goldberg E, Marsh E, Kessler S, Bergqvist C, Conlin LK, Krok BL, Thiffault I, Pendziwiat M, Helbig I, Polster T, Borggraefe I, Lemke JR, van den Boogaardt MJ, Møller RS, Koeleman BPC. Neurodevelopmental Disorders Caused by De Novo Variants in KCNB1 Genotypes and Phenotypes. JAMA Neurol 2017; 74:1228-1236. [PMID: 28806457 DOI: 10.1001/jamaneurol.2017.1714] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Importance Knowing the range of symptoms seen in patients with a missense or loss-of-function variant in KCNB1 and how these symptoms correlate with the type of variant will help clinicians with diagnosis and prognosis when treating new patients. Objectives To investigate the clinical spectrum associated with KCNB1 variants and the genotype-phenotype correlations. Design, Setting, and Participants This study summarized the clinical and genetic information of patients with a presumed pathogenic variant in KCNB1. Patients were identified in research projects or during clinical testing. Information on patients from previously published articles was collected and authors contacted if feasible. All patients were seen at a clinic at one of the participating institutes because of presumed genetic disorder. They were tested in a clinical setting or included in a research project. Main Outcomes and Measures The genetic variant and its inheritance and information on the patient's symptoms and characteristics in a predefined format. All variants were identified with massive parallel sequencing and confirmed with Sanger sequencing in the patient. Absence of the variant in the parents could be confirmed with Sanger sequencing in all families except one. Results Of 26 patients (10 female, 15 male, 1 unknown; mean age at inclusion, 9.8 years; age range, 2-32 years) with developmental delay, 20 (77%) carried a missense variant in the ion channel domain of KCNB1, with a concentration of variants in region S5 to S6. Three variants that led to premature stops were located in the C-terminal and 3 in the ion channel domain. Twenty-one of 25 patients (84%) had seizures, with 9 patients (36%) starting with epileptic spasms between 3 and 18 months of age. All patients had developmental delay, with 17 (65%) experiencing severe developmental delay; 14 (82%) with severe delay had behavioral problems. The developmental delay was milder in 4 of 6 patients with stop variants and in a patient with a variant in the S2 transmembrane element rather than the S4 to S6 region. Conclusions and Relevance De novo KCNB1 missense variants in the ion channel domain and loss-of-function variants in this domain and the C-terminal likely cause neurodevelopmental disorders with or without seizures. Patients with presumed pathogenic variants in KCNB1 have a variable phenotype. However, the type and position of the variants in the protein are (imperfectly) correlated with the severity of the disorder.
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Affiliation(s)
- Carolien G F de Kovel
- Department of Genetics, University Medical Center Utrecht, Utrecht, the Netherlands.,Department of Language and Genetics, Max Planck Institute for Psycholinguistics, Nijmegen, the Netherlands
| | - Steffen Syrbe
- Division of Child Neurology and Inherited Metabolic Diseases, Department of General Pediatrics, Center for Pediatrics and Adolescent Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - Eva H Brilstra
- Department of Genetics, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Nienke Verbeek
- Department of Genetics, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Bronwyn Kerr
- Institute of Evolution, Systems and Genomics, Faculty of Medical and Human Sciences, University of Manchester, Manchester, England.,Manchester Centre For Genomic Medicine, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester, England.,Manchester Academic Health Science Centre, Manchester, England
| | - Holly Dubbs
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Allan Bayat
- Department of Pediatrics, University Hospital of Hvidovre, Copenhagen, Denmark
| | - Sonal Desai
- Department of Neurogenetics, Kennedy Krieger Institute, Baltimore, Maryland
| | - Sakkubai Naidu
- Department of Neurology and Pediatrics, Johns Hopkins School of Medicine, Baltimore, Maryland.,Hugo Moser Research Institute, Kennedy Krieger Institute, Baltimore, Maryland
| | | | - Hande Cagaylan
- Department of Molecular Biology and Genetics, Bogaziçi University, Istanbul, Turkey
| | - Uluc Yis
- Division of Child Neurology, Department of Pediatrics, School of Medicine, Dokuz Eylül University, İzmir, Turkey
| | - Carol Saunders
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, Children's Mercy Hospital, Kansas City, Missouri.,Department of Pediatrics, Children's Mercy Hospital, Kansas City, Missouri.,Pediatric Pathology and Laboratory Medicine, University of Missouri-Kansas City School of Medicine, Kansas City
| | - Martin Rook
- Department of Medical Physiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Susanna Plugge
- Department of Biomedical Sciences, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Hiltrud Muhle
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian Albrechts University, Kiel, Germany
| | - Zaid Afawi
- Department of Physiology and Pharmacology, Tel Aviv University Medical School, Ramat Aviv, Israel
| | - Karl-Martin Klein
- Department of Neurology, Epilepsy Center Frankfurt Rhine-Main, Center of Neurology and Neurosurgery, University Hospital, Goethe-University Frankfurt, Frankfurt, Germany
| | - Vijayakumar Jayaraman
- Division of Genomic Diagnostics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Ramakrishnan Rajagopalan
- Division of Genomic Diagnostics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Ethan Goldberg
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Eric Marsh
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Sudha Kessler
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Christina Bergqvist
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Laura K Conlin
- Division of Genomic Diagnostics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Bryan L Krok
- Division of Genomic Diagnostics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Isabelle Thiffault
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, Children's Mercy Hospital, Kansas City, Missouri.,Department of Pediatrics, Children's Mercy Hospital, Kansas City, Missouri
| | - Manuela Pendziwiat
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian Albrechts University, Kiel, Germany
| | - Ingo Helbig
- Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.,University Medical Center Schleswig-Holstein, Christian Albrechts University, Kiel, Germany
| | - Tilman Polster
- Epilepsiezentrum Bethel, Krankenhaus Mara, Kinderepileptologie, Bielefeld, Germany
| | - Ingo Borggraefe
- Department of Pediatric Neurology, Developmental Medicine and Social Pediatrics Dr. von Hauner's Children's Hospital, University of Munich, Munich, Germany
| | - Johannes R Lemke
- Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany
| | | | - Rikke S Møller
- Danish Epilepsy Centre, Dianalund, Denmark.,Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark
| | - Bobby P C Koeleman
- Department of Genetics, University Medical Center Utrecht, Utrecht, the Netherlands
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Trafficking of Kv2.1 Channels to the Axon Initial Segment by a Novel Nonconventional Secretory Pathway. J Neurosci 2017; 37:11523-11536. [PMID: 29042434 DOI: 10.1523/jneurosci.3510-16.2017] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 09/09/2017] [Indexed: 02/07/2023] Open
Abstract
Kv2.1 is a major delayed-rectifier voltage-gated potassium channel widely expressed in neurons of the CNS. Kv2.1 localizes in high-density cell-surface clusters in the soma and proximal dendrites as well as in the axon initial segment (AIS). Given the crucial roles of both of these compartments in integrating signal input and then generating output, this localization of Kv2.1 is ideal for regulating the overall excitability of neurons. Here we used fluorescence recovery after photobleaching imaging, mutagenesis, and pharmacological interventions to investigate the molecular mechanisms that control the localization of Kv2.1 in these two different membrane compartments in cultured rat hippocampal neurons of mixed sex. Our data uncover a unique ability of Kv2.1 channels to use two molecularly distinct trafficking pathways to accomplish this. Somatodendritic Kv2.1 channels are targeted by the conventional secretory pathway, whereas axonal Kv2.1 channels are targeted by a nonconventional trafficking pathway independent of the Golgi apparatus. We further identified a new AIS trafficking motif in the C-terminus of Kv2.1, and show that putative phosphorylation sites in this region are critical for the restricted and clustered localization in the AIS. These results indicate that neurons can regulate the expression and clustering of Kv2.1 in different membrane domains independently by using two distinct localization mechanisms, which would allow neurons to precisely control local membrane excitability.SIGNIFICANCE STATEMENT Our study uncovered a novel mechanism that targets the Kv2.1 voltage-gated potassium channel to two distinct trafficking pathways and two distinct subcellular destinations: the somatodendritic plasma membrane and that of the axon initial segment. We also identified a distinct motif, including putative phosphorylation sites, that is important for the AIS localization. This raises the possibility that the destination of a channel protein can be dynamically regulated via changes in post-translational modification, which would impact the excitability of specific membrane compartments.
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Heterogeneity in Kv2 Channel Expression Shapes Action Potential Characteristics and Firing Patterns in CA1 versus CA2 Hippocampal Pyramidal Neurons. eNeuro 2017; 4:eN-NWR-0267-17. [PMID: 28856240 PMCID: PMC5569380 DOI: 10.1523/eneuro.0267-17.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/03/2017] [Accepted: 08/09/2017] [Indexed: 01/07/2023] Open
Abstract
The CA1 region of the hippocampus plays a critical role in spatial and contextual memory, and has well-established circuitry, function and plasticity. In contrast, the properties of the flanking CA2 pyramidal neurons (PNs), important for social memory, and lacking CA1-like plasticity, remain relatively understudied. In particular, little is known regarding the expression of voltage-gated K+ (Kv) channels and the contribution of these channels to the distinct properties of intrinsic excitability, action potential (AP) waveform, firing patterns and neurotransmission between CA1 and CA2 PNs. In the present study, we used multiplex fluorescence immunolabeling of mouse brain sections, and whole-cell recordings in acute mouse brain slices, to define the role of heterogeneous expression of Kv2 family Kv channels in CA1 versus CA2 pyramidal cell excitability. Our results show that the somatodendritic delayed rectifier Kv channel subunits Kv2.1, Kv2.2, and their auxiliary subunit AMIGO-1 have region-specific differences in expression in PNs, with the highest expression levels in CA1, a sharp decrease at the CA1-CA2 boundary, and significantly reduced levels in CA2 neurons. PNs in CA1 exhibit a robust contribution of Guangxitoxin-1E-sensitive Kv2-based delayed rectifier current to AP shape and after-hyperpolarization potential (AHP) relative to that seen in CA2 PNs. Our results indicate that robust Kv2 channel expression confers a distinct pattern of intrinsic excitability to CA1 PNs, potentially contributing to their different roles in hippocampal network function.
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Zhang C, Deng Y, Lei Y, Zhao J, Wei W, Li Y. Effects of selenium on myocardial apoptosis by modifying the activity of mitochondrial STAT3 and regulating potassium channel expression. Exp Ther Med 2017; 14:2201-2205. [PMID: 28962142 PMCID: PMC5609099 DOI: 10.3892/etm.2017.4716] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 06/19/2017] [Indexed: 01/21/2023] Open
Abstract
The present study investigated the effects of myocardial mitochondrial signal transduction and activator of transcription 3 (STAT3), succinate dehydrogenase activity and changes of potassium channel expression on cardiomyocyte apoptosis under low selenium conditions. Primary cultured cardiomyocytes from neonatal mice were divided into the non-toxic control group (0.1 µM sodium selenite) and low selenium treatment group (0.05 µM sodium selenite) according to different selenium concentrations. The expression of mitochondrial STAT3, p-STAT3, p-Kv1.2 potassium channel and apoptosis-related proteins, Bax and Bcl-2, were assessed by immunoblotting. Succinate dehydrogenase activity was measured by spectrophotometry. Flow cytometry was used to detect cardiomyocyte apoptosis. Low selenium treatment reduced the expression of p-STAT3, but did not affect the expression of STAT3. In addition, low selenium treatment reduced the activity of mitochondrial STAT3 and succinate dehydrogenase in cardiomyocytes, leading to injury of myocardial mitochondria. Compared with the control group, low selenium conditions reduced the activity of p-Kv1.2 and reduced the normal electrophysiological function of cardiomyocytes. In the low selenium-treated group, the expression of Bax protein increased, whereas the expression of Bcl-2 protein decreased. The apoptotic rate increased. In conclusion, selenium deficiency in cardiomyocytes leads to decreased potassium channel expression and decreased mitochondrial STAT3 activity and mitochondrial function, which in turn promotes the apoptosis of cardiomyocytes.
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Affiliation(s)
- Changjiang Zhang
- Cardiovascular Disease Center, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
| | - Yinzhi Deng
- Department of Gastroenterology, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
| | - Yuhua Lei
- Cardiovascular Disease Center, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
| | - Jingbo Zhao
- Cardiovascular Disease Center, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
| | - Wen Wei
- Cardiovascular Disease Center, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
| | - Yuanhong Li
- Cardiovascular Disease Center, Central Hospital of Enshi Autonomous Prefecture, Enshi, Hubei 445000, P.R. China
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70
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Targeting a Potassium Channel/Syntaxin Interaction Ameliorates Cell Death in Ischemic Stroke. J Neurosci 2017; 37:5648-5658. [PMID: 28483976 DOI: 10.1523/jneurosci.3811-16.2017] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/25/2017] [Accepted: 05/01/2017] [Indexed: 12/12/2022] Open
Abstract
The voltage-gated K+ channel Kv2.1 has been intimately linked with neuronal apoptosis. After ischemic, oxidative, or inflammatory insults, Kv2.1 mediates a pronounced, delayed enhancement of K+ efflux, generating an optimal intracellular environment for caspase and nuclease activity, key components of programmed cell death. This apoptosis-enabling mechanism is initiated via Zn2+-dependent dual phosphorylation of Kv2.1, increasing the interaction between the channel's intracellular C-terminus domain and the SNARE (soluble N-ethylmaleimide-sensitive factor activating protein receptor) protein syntaxin 1A. Subsequently, an upregulation of de novo channel insertion into the plasma membrane leads to the critical enhancement of K+ efflux in damaged neurons. Here, we investigated whether a strategy designed to interfere with the cell death-facilitating properties of Kv2.1, specifically its interaction with syntaxin 1A, could lead to neuroprotection following ischemic injury in vivo The minimal syntaxin 1A-binding sequence of Kv2.1 C terminus (C1aB) was first identified via a far-Western peptide screen and used to create a protherapeutic product by conjugating C1aB to a cell-penetrating domain. The resulting peptide (TAT-C1aB) suppressed enhanced whole-cell K+ currents produced by a mutated form of Kv2.1 mimicking apoptosis in a mammalian expression system, and protected cortical neurons from slow excitotoxic injury in vitro, without influencing NMDA-induced intracellular calcium responses. Importantly, intraperitoneal administration of TAT-C1aB in mice following transient middle cerebral artery occlusion significantly reduced ischemic stroke damage and improved neurological outcome. These results provide strong evidence that targeting the proapoptotic function of Kv2.1 is an effective and highly promising neuroprotective strategy.SIGNIFICANCE STATEMENT Kv2.1 is a critical regulator of apoptosis in central neurons. It has not been determined, however, whether the cell death-enabling function of this K+ channel can be selectively targeted to improve neuronal survival following injury in vivo The experiments presented here demonstrate that the cell death-specific role of Kv2.1 can be uniquely modulated to provide neuroprotection in an animal model of acute ischemic stroke. We thus reveal a novel therapeutic strategy for neurological disorders that are accompanied by Kv2.1-facilitated forms of cell death.
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Oxidation of KCNB1 potassium channels triggers apoptotic integrin signaling in the brain. Cell Death Dis 2017; 8:e2737. [PMID: 28383553 PMCID: PMC5477583 DOI: 10.1038/cddis.2017.160] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 03/10/2017] [Accepted: 03/13/2017] [Indexed: 12/20/2022]
Abstract
Oxidative modification of the voltage-gated potassium (K+) channel KCNB1 promotes apoptosis in the neurons of cortex and hippocampus through a signaling pathway mediated by Src tyrosine kinases. How oxidation of the channel is transduced into Src recruitment and activation, however, was not known. Here we show that the apoptotic signal originates from integrins, which form macromolecular complexes with KCNB1 channels. The initial stimulus is transduced to Fyn and possibly other Src family members by focal adhesion kinase (FAK). Thus KCNB1 and integrin alpha chain V (integrin-α5) coimmunoprecipitated in the mouse brain and these interactions were retained upon channel's oxidation. Pharmacological inhibition of integrin signaling or FAK suppressed apoptosis induced by oxidation of KCNB1, as well as FAK and Src/Fyn activation. Most importantly, the activation of the integrin-FAK-Src/Fyn cascade was negligible in the presence of non-oxidizable C73A KCNB1 mutant channels, even though they normally interacted with integrin-α5. This leads us to conclude that the transition between the non-oxidized and oxidized state of KCNB1 activates integrin signaling. KCNB1 oxidation may favor integrin clustering, thereby facilitating the recruitment and activation of FAK and Src/Fyn kinases.
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Yang YS, Jeon SC, Kim DK, Eun SY, Jung SC. Chronic Ca 2+ influx through voltage-dependent Ca 2+ channels enhance delayed rectifier K + currents via activating Src family tyrosine kinase in rat hippocampal neurons. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2017; 21:259-265. [PMID: 28280420 PMCID: PMC5343060 DOI: 10.4196/kjpp.2017.21.2.259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 01/20/2017] [Accepted: 01/23/2017] [Indexed: 12/14/2022]
Abstract
Excessive influx and the subsequent rapid cytosolic elevation of Ca2+ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic Ca2+ level in normal as well as pathological conditions. Delayed rectifier K+ channels (IDR channels) play a role to suppress membrane excitability by inducing K+ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under Ca2+-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of IDR channels to hyperexcitable conditions induced by high Ca2+ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high Ca2+-treatment significantly increased the amplitude of IDR without changes of gating kinetics. Nimodipine but not APV blocked Ca2+-induced IDR enhancement, confirming that the change of IDR might be targeted by Ca2+ influx through voltage-dependent Ca2+ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated IDR enhancement was not affected by either Ca2+-induced Ca2+ release (CICR) or small conductance Ca2+-activated K+ channels (SK channels). Furthermore, PP2 but not H89 completely abolished IDR enhancement under high Ca2+ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for Ca2+-mediated IDR enhancement. Thus, SFKs may be sensitive to excessive Ca2+ influx through VDCCs and enhance IDR to activate a neuroprotective mechanism against Ca2+-mediated hyperexcitability in neurons.
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Affiliation(s)
- Yoon-Sil Yang
- Department of Physiology, School of Medicine, Jeju National University, Jeju 63243, Korea
| | - Sang-Chan Jeon
- Department of Physiology, School of Medicine, Jeju National University, Jeju 63243, Korea
| | - Dong-Kwan Kim
- Department of Physiology, College of Medicine, Konyang University, Daejeon 35365, Korea
| | - Su-Yong Eun
- Department of Physiology, School of Medicine, Jeju National University, Jeju 63243, Korea.; Institute of Medical Science, Jeju National University, Jeju 63243, Korea
| | - Sung-Cherl Jung
- Department of Physiology, School of Medicine, Jeju National University, Jeju 63243, Korea.; Institute of Medical Science, Jeju National University, Jeju 63243, Korea
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CaMKII modulates sodium current in neurons from epileptic Scn2a mutant mice. Proc Natl Acad Sci U S A 2017; 114:1696-1701. [PMID: 28137877 DOI: 10.1073/pnas.1615774114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Monogenic epilepsies with wide-ranging clinical severity have been associated with mutations in voltage-gated sodium channel genes. In the Scn2aQ54 mouse model of epilepsy, a focal epilepsy phenotype is caused by transgenic expression of an engineered NaV1.2 mutation displaying enhanced persistent sodium current. Seizure frequency and other phenotypic features in Scn2aQ54 mice depend on genetic background. We investigated the neurophysiological and molecular correlates of strain-dependent epilepsy severity in this model. Scn2aQ54 mice on the C57BL/6J background (B6.Q54) exhibit a mild disorder, whereas animals intercrossed with SJL/J mice (F1.Q54) have a severe phenotype. Whole-cell recording revealed that hippocampal pyramidal neurons from B6.Q54 and F1.Q54 animals exhibit spontaneous action potentials, but F1.Q54 neurons exhibited higher firing frequency and greater evoked activity compared with B6.Q54 neurons. These findings correlated with larger persistent sodium current and depolarized inactivation in neurons from F1.Q54 animals. Because calcium/calmodulin protein kinase II (CaMKII) is known to modify persistent current and channel inactivation in the heart, we investigated CaMKII as a plausible modulator of neuronal sodium channels. CaMKII activity in hippocampal protein lysates exhibited a strain-dependence in Scn2aQ54 mice with higher activity in F1.Q54 animals. Heterologously expressed NaV1.2 channels exposed to activated CaMKII had enhanced persistent current and depolarized channel inactivation resembling the properties of F1.Q54 neuronal sodium channels. By contrast, inhibition of CaMKII attenuated persistent current, evoked a hyperpolarized channel inactivation, and suppressed neuronal excitability. We conclude that CaMKII-mediated modulation of neuronal sodium current impacts neuronal excitability in Scn2aQ54 mice and may represent a therapeutic target for the treatment of epilepsy.
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Latypova X, Matsumoto N, Vinceslas-Muller C, Bézieau S, Isidor B, Miyake N. Novel KCNB1 mutation associated with non-syndromic intellectual disability. J Hum Genet 2016; 62:569-573. [PMID: 27928161 DOI: 10.1038/jhg.2016.154] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 10/22/2016] [Accepted: 11/03/2016] [Indexed: 11/09/2022]
Abstract
Potassium voltage-gated channel subfamily B member 1 (KCNB1) encodes Kv2.1 potassium channel of crucial role in hippocampal neuron excitation homeostasis. KCNB1 mutations are known to cause early-onset infantile epilepsy. To date, 10 KCNB1 mutations have been described in 11 patients. Using whole-exome sequencing, we identified a novel de novo missense (c.1132G>C, p.V378L) KCNB1 mutation in a patient with global developmental delay, intellectual disability, severe speech impairment, but no episode of epilepsy until the lastly examined age of 6 years old. Furthermore, she showed neuropsychiatric symptoms including hyperactivity with irritability, heteroaggressiveness, psychomotor instability and agitation. Our observation might expand the phenotypic spectrum of KCNB1-related phenotypes and raises the issue of the occurrence of the epileptic phenotype.
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Affiliation(s)
- Xénia Latypova
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nantes, Nantes, France
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Cécile Vinceslas-Muller
- Service de Pédiatrie, Hôpital Mère-Enfant, Centre Hospitalier Universitaire de Nantes, Nantes, France
| | - Stéphane Bézieau
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nantes, Nantes, France
| | - Bertrand Isidor
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nantes, Nantes, France.,INSERM, UMR-957, Laboratoire de Physiopathologie de la Résorption Osseuse et thérapie des tumeurs osseuses primitives, Nantes, France
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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Yu W, Parakramaweera R, Teng S, Gowda M, Sharad Y, Thakker-Varia S, Alder J, Sesti F. Oxidation of KCNB1 Potassium Channels Causes Neurotoxicity and Cognitive Impairment in a Mouse Model of Traumatic Brain Injury. J Neurosci 2016; 36:11084-11096. [PMID: 27798188 PMCID: PMC5098843 DOI: 10.1523/jneurosci.2273-16.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 08/25/2016] [Accepted: 09/07/2016] [Indexed: 01/08/2023] Open
Abstract
The delayed rectifier potassium (K+) channel KCNB1 (Kv2.1), which conducts a major somatodendritic current in cortex and hippocampus, is known to undergo oxidation in the brain, but whether this can cause neurodegeneration and cognitive impairment is not known. Here, we used transgenic mice harboring human KCNB1 wild-type (Tg-WT) or a nonoxidable C73A mutant (Tg-C73A) in cortex and hippocampus to determine whether oxidized KCNB1 channels affect brain function. Animals were subjected to moderate traumatic brain injury (TBI), a condition characterized by extensive oxidative stress. Dasatinib, a Food and Drug Administration-approved inhibitor of Src tyrosine kinases, was used to impinge on the proapoptotic signaling pathway activated by oxidized KCNB1 channels. Thus, typical lesions of brain injury, namely, inflammation (astrocytosis), neurodegeneration, and cell death, were markedly reduced in Tg-C73A and dasatinib-treated non-Tg animals. Accordingly, Tg-C73A mice and non-Tg mice treated with dasatinib exhibited improved behavioral outcomes in motor (rotarod) and cognitive (Morris water maze) assays compared to controls. Moreover, the activity of Src kinases, along with oxidative stress, were significantly diminished in Tg-C73A brains. Together, these data demonstrate that oxidation of KCNB1 channels is a contributing mechanism to cellular and behavioral deficits in vertebrates and suggest a new therapeutic approach to TBI. SIGNIFICANCE STATEMENT This study provides the first experimental evidence that oxidation of a K+ channel constitutes a mechanism of neuronal and cognitive impairment in vertebrates. Specifically, the interaction of KCNB1 channels with reactive oxygen species plays a major role in the etiology of mouse model of traumatic brain injury (TBI), a condition associated with extensive oxidative stress. In addition, a Food and Drug Administration-approved drug ameliorates the outcome of TBI in mouse, by directly impinging on the toxic pathway activated in response to oxidation of the KCNB1 channel. These findings elucidate a basic mechanism of neurotoxicity in vertebrates and might lead to a new therapeutic approach to TBI in humans, which, despite significant efforts, is a condition that remains without effective pharmacological treatments.
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Affiliation(s)
- Wei Yu
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Randika Parakramaweera
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Shavonne Teng
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Manasa Gowda
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Yashsavi Sharad
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Smita Thakker-Varia
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Janet Alder
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Federico Sesti
- Department of Neuroscience and Cell Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
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76
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Stas JI, Bocksteins E, Jensen CS, Schmitt N, Snyders DJ. The anticonvulsant retigabine suppresses neuronal K V2-mediated currents. Sci Rep 2016; 6:35080. [PMID: 27734968 PMCID: PMC5062084 DOI: 10.1038/srep35080] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 09/20/2016] [Indexed: 11/09/2022] Open
Abstract
Enhancement of neuronal M-currents, generated through KV7.2-KV7.5 channels, has gained much interest for its potential in developing treatments for hyperexcitability-related disorders such as epilepsy. Retigabine, a KV7 channel opener, has proven to be an effective anticonvulsant and has recently also gained attention due to its neuroprotective properties. In the present study, we found that the auxiliary KCNE2 subunit reduced the KV7.2-KV7.3 retigabine sensitivity approximately 5-fold. In addition, using both mammalian expression systems and cultured hippocampal neurons we determined that low μM retigabine concentrations had ‘off-target’ effects on KV2.1 channels which have recently been implicated in apoptosis. Clinical retigabine concentrations (0.3–3 μM) inhibited KV2.1 channel function upon prolonged exposure. The suppression of the KV2.1 conductance was only partially reversible. Our results identified KV2.1 as a new molecular target for retigabine, thus giving a potential explanation for retigabine’s neuroprotective properties.
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Affiliation(s)
- Jeroen I Stas
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, 2610 Antwerp, Belgium.,Ion Channel Group, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Elke Bocksteins
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, 2610 Antwerp, Belgium
| | - Camilla S Jensen
- Ion Channel Group, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Nicole Schmitt
- Ion Channel Group, Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Dirk J Snyders
- Laboratory for Molecular Biophysics, Physiology and Pharmacology, Department of Biomedical Sciences, University of Antwerp, CDE, Universiteitsplein 1, 2610 Antwerp, Belgium
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77
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Thiffault I, Speca DJ, Austin DC, Cobb MM, Eum KS, Safina NP, Grote L, Farrow EG, Miller N, Soden S, Kingsmore SF, Trimmer JS, Saunders CJ, Sack JT. A novel epileptic encephalopathy mutation in KCNB1 disrupts Kv2.1 ion selectivity, expression, and localization. ACTA ACUST UNITED AC 2016; 146:399-410. [PMID: 26503721 PMCID: PMC4621747 DOI: 10.1085/jgp.201511444] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A missense mutation in the pore-forming α subunit of a delayed rectifier Kv channel is associated with epileptic encephalopathy, alters the cation selectivity of voltage-gated currents, and disrupts channel expression and localization. The epileptic encephalopathies are a group of highly heterogeneous genetic disorders. The majority of disease-causing mutations alter genes encoding voltage-gated ion channels, neurotransmitter receptors, or synaptic proteins. We have identified a novel de novo pathogenic K+ channel variant in an idiopathic epileptic encephalopathy family. Here, we report the effects of this mutation on channel function and heterologous expression in cell lines. We present a case report of infantile epileptic encephalopathy in a young girl, and trio-exome sequencing to determine the genetic etiology of her disorder. The patient was heterozygous for a de novo missense variant in the coding region of the KCNB1 gene, c.1133T>C. The variant encodes a V378A mutation in the α subunit of the Kv2.1 voltage-gated K+ channel, which is expressed at high levels in central neurons and is an important regulator of neuronal excitability. We found that expression of the V378A variant results in voltage-activated currents that are sensitive to the selective Kv2 channel blocker guangxitoxin-1E. These voltage-activated Kv2.1 V378A currents were nonselective among monovalent cations. Striking cell background–dependent differences in expression and subcellular localization of the V378A mutation were observed in heterologous cells. Further, coexpression of V378A subunits and wild-type Kv2.1 subunits reciprocally affects their respective trafficking characteristics. A recent study reported epileptic encephalopathy-linked missense variants that render Kv2.1 a tonically activated, nonselective cation channel that is not voltage activated. Our findings strengthen the correlation between mutations that result in loss of Kv2.1 ion selectivity and development of epileptic encephalopathy. However, the strong voltage sensitivity of currents from the V378A mutant indicates that the loss of voltage-sensitive gating seen in all other reported disease mutants is not required for an epileptic encephalopathy phenotype. In addition to electrophysiological differences, we suggest that defects in expression and subcellular localization of Kv2.1 V378A channels could contribute to the pathophysiology of this KCNB1 variant.
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Affiliation(s)
- Isabelle Thiffault
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108
| | - David J Speca
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - Daniel C Austin
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - Melanie M Cobb
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - Kenneth S Eum
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - Nicole P Safina
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108
| | - Lauren Grote
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108
| | - Emily G Farrow
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108
| | - Neil Miller
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108
| | - Sarah Soden
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108
| | - Stephen F Kingsmore
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108
| | - James S Trimmer
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616 Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
| | - Carol J Saunders
- Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 Center for Pediatric Genomic Medicine, Department of Pathology and Laboratory Medicine, and Department of Pediatrics, Children's Mercy Hospital, Kansas City, MO 64108 University of Missouri-Kansas City School of Medicine, Kansas City, MO 64108
| | - Jon T Sack
- Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616 Department of Neurobiology, Physiology and Behavior, Department of Physiology and Membrane Biology, and Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA 95616
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78
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Sesti F. Oxidation of K(+) Channels in Aging and Neurodegeneration. Aging Dis 2016; 7:130-5. [PMID: 27114846 PMCID: PMC4809605 DOI: 10.14336/ad.2015.0901] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/01/2015] [Indexed: 01/26/2023] Open
Abstract
Reversible regulation of proteins by reactive oxygen species (ROS) is an important mechanism of neuronal plasticity. In particular, ROS have been shown to act as modulatory molecules of ion channels-which are key to neuronal excitability-in several physiological processes. However ROS are also fundamental contributors to aging vulnerability. When the level of excess ROS increases in the cell during aging, DNA is damaged, proteins are oxidized, lipids are degraded and more ROS are produced, all culminating in significant cell injury. From this arose the idea that oxidation of ion channels by ROS is one of the culprits for neuronal aging. Aging-dependent oxidative modification of voltage-gated potassium (K(+)) channels was initially demonstrated in the nematode Caenorhabditis elegans and more recently in the mammalian brain. Specifically, oxidation of the delayed rectifier KCNB1 (Kv2.1) and of Ca(2+)- and voltage sensitive K(+) channels have been established suggesting that their redox sensitivity contributes to altered excitability, progression of healthy aging and of neurodegenerative disease. Here I discuss the implications that oxidation of K(+) channels by ROS may have for normal aging, as well as for neurodegenerative disease.
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Affiliation(s)
- Federico Sesti
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ 08854, USA
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79
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Distinct Cell- and Layer-Specific Expression Patterns and Independent Regulation of Kv2 Channel Subtypes in Cortical Pyramidal Neurons. J Neurosci 2016; 35:14922-42. [PMID: 26538660 DOI: 10.1523/jneurosci.1897-15.2015] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED The Kv2 family of voltage-gated potassium channel α subunits, comprising Kv2.1 and Kv2.2, mediate the bulk of the neuronal delayed rectifier K(+) current in many mammalian central neurons. Kv2.1 exhibits robust expression across many neuron types and is unique in its conditional role in modulating intrinsic excitability through changes in its phosphorylation state, which affect Kv2.1 expression, localization, and function. Much less is known of the highly related Kv2.2 subunit, especially in forebrain neurons. Here, through combined use of cortical layer markers and transgenic mouse lines, we show that Kv2.1 and Kv2.2 are localized to functionally distinct cortical cell types. Kv2.1 expression is consistently high throughout all cortical layers, especially in layer (L) 5b pyramidal neurons, whereas Kv2.2 expression is primarily limited to neurons in L2 and L5a. In addition, L4 of primary somatosensory cortex is strikingly devoid of Kv2.2 immunolabeling. The restricted pattern of Kv2.2 expression persists in Kv2.1-KO mice, suggesting distinct cell- and layer-specific functions for these two highly related Kv2 subunits. Analyses of endogenous Kv2.2 in cortical neurons in situ and recombinant Kv2.2 expressed in heterologous cells reveal that Kv2.2 is largely refractory to stimuli that trigger robust, phosphorylation-dependent changes in Kv2.1 clustering and function. Immunocytochemistry and voltage-clamp recordings from outside-out macropatches reveal distinct cellular expression patterns for Kv2.1 and Kv2.2 in intratelencephalic and pyramidal tract neurons of L5, indicating circuit-specific requirements for these Kv2 paralogs. Together, these results support distinct roles for these two Kv2 channel family members in mammalian cortex. SIGNIFICANCE STATEMENT Neurons within the neocortex are arranged in a laminar architecture and contribute to the input, processing, and/or output of sensory and motor signals in a cell- and layer-specific manner. Neurons of different cortical layers express diverse populations of ion channels and possess distinct intrinsic membrane properties. Here, we show that the Kv2 family members Kv2.1 and Kv2.2 are expressed in distinct cortical layers and pyramidal cell types associated with specific corticostriatal pathways. We find that Kv2.1 and Kv2.2 exhibit distinct responses to acute phosphorylation-dependent regulation in brain neurons in situ and in heterologous cells in vitro. These results identify a molecular mechanism that contributes to heterogeneity in cortical neuron ion channel function and regulation.
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80
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81
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Peltola MA, Kuja-Panula J, Liuhanen J, Võikar V, Piepponen P, Hiekkalinna T, Taira T, Lauri SE, Suvisaari J, Kulesskaya N, Paunio T, Rauvala H. AMIGO-Kv2.1 Potassium Channel Complex Is Associated With Schizophrenia-Related Phenotypes. Schizophr Bull 2016; 42:191-201. [PMID: 26240432 PMCID: PMC4681558 DOI: 10.1093/schbul/sbv105] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The enormous variability in electrical properties of neurons is largely affected by a multitude of potassium channel subunits. Kv2.1 is a widely expressed voltage-dependent potassium channel and an important regulator of neuronal excitability. The Kv2.1 auxiliary subunit AMIGO constitutes an integral part of the Kv2.1 channel complex in brain and regulates the activity of the channel. AMIGO and Kv2.1 localize to the distinct somatodendritic clusters at the neuronal plasma membrane. Here we have created and characterized a mouse line lacking the AMIGO gene. Absence of AMIGO clearly reduced the amount of the Kv2.1 channel protein in mouse brain and altered the electrophysiological properties of neurons. These changes were accompanied by behavioral and pharmacological abnormalities reminiscent of those identified in schizophrenia. Concomitantly, we have detected an association of a rare, population-specific polymorphism of KV2.1 (KCNB1) with human schizophrenia in a genetic isolate enriched with schizophrenia. Our study demonstrates the involvement of AMIGO-Kv2.1 channel complex in schizophrenia-related behavioral domains in mice and identifies KV2.1 (KCNB1) as a strong susceptibility gene for schizophrenia spectrum disorders in humans.
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Affiliation(s)
- Marjaana A. Peltola
- Neuroscience Center, University of Helsinki, Helsinki, Finland;,*To whom correspondence should be addressed; Neuroscience Center, PO Box 56 (Viikinkaari 4), FI-00014 University of Helsinki, Helsinki, Finland; tel: +358-2941-57649, fax: +358-2941-57620, e-mail:
| | | | - Johanna Liuhanen
- Public Health Genomics Unit, National Institute for Health and Welfare, Helsinki, Finland
| | - Vootele Võikar
- Neuroscience Center, University of Helsinki, Helsinki, Finland
| | - Petteri Piepponen
- Division of Pharmacology and Toxicology, University of Helsinki, Helsinki, Finland
| | - Tero Hiekkalinna
- Public Health Genomics Unit, National Institute for Health and Welfare, Helsinki, Finland;,Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
| | - Tomi Taira
- Neuroscience Center, University of Helsinki, Helsinki, Finland;,Department of Biosciences, University of Helsinki, Helsinki, Finland;,Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Sari E. Lauri
- Neuroscience Center, University of Helsinki, Helsinki, Finland;,Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - Jaana Suvisaari
- Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Helsinki, Finland
| | | | - Tiina Paunio
- Public Health Genomics Unit, National Institute for Health and Welfare, Helsinki, Finland;,Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland;,Department of Psychiatry, Institute of Clinical Medicine, University of Helsinki, Helsinki, Finland
| | - Heikki Rauvala
- Neuroscience Center, University of Helsinki, Helsinki, Finland
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82
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Saitsu H, Akita T, Tohyama J, Goldberg-Stern H, Kobayashi Y, Cohen R, Kato M, Ohba C, Miyatake S, Tsurusaki Y, Nakashima M, Miyake N, Fukuda A, Matsumoto N. De novo KCNB1 mutations in infantile epilepsy inhibit repetitive neuronal firing. Sci Rep 2015; 5:15199. [PMID: 26477325 PMCID: PMC4609934 DOI: 10.1038/srep15199] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/21/2015] [Indexed: 11/09/2022] Open
Abstract
The voltage-gated Kv2.1 potassium channel encoded by KCNB1 produces the major delayed rectifier potassium current in pyramidal neurons. Recently, de novo heterozygous missense KCNB1 mutations have been identified in three patients with epileptic encephalopathy and a patient with neurodevelopmental disorder. However, the frequency of KCNB1 mutations in infantile epileptic patients and their effects on neuronal activity are yet unknown. We searched whole exome sequencing data of a total of 437 patients with infantile epilepsy, and found novel de novo heterozygous missense KCNB1 mutations in two patients showing psychomotor developmental delay and severe infantile generalized seizures with high-amplitude spike-and-wave electroencephalogram discharges. The mutation located in the channel voltage sensor (p.R306C) disrupted sensitivity and cooperativity of the sensor, while the mutation in the channel pore domain (p.G401R) selectively abolished endogenous Kv2 currents in transfected pyramidal neurons, indicating a dominant-negative effect. Both mutants inhibited repetitive neuronal firing through preventing production of deep interspike voltages. Thus KCNB1 mutations can be a rare genetic cause of infantile epilepsy, and insufficient firing of pyramidal neurons would disturb both development and stability of neuronal circuits, leading to the disease phenotypes.
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Affiliation(s)
- Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Tenpei Akita
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Jun Tohyama
- Department of Pediatrics, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | | | - Yu Kobayashi
- Department of Pediatrics, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Roni Cohen
- Epilepsy Center, Schneider's Children Medical Center, Petah Tiqwa, Israel
| | - Mitsuhiro Kato
- Department of Pediatrics, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Mitsuko Nakashima
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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83
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He K, McCord MC, Hartnett KA, Aizenman E. Regulation of Pro-Apoptotic Phosphorylation of Kv2.1 K+ Channels. PLoS One 2015; 10:e0129498. [PMID: 26115091 PMCID: PMC4482604 DOI: 10.1371/journal.pone.0129498] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 05/08/2015] [Indexed: 12/12/2022] Open
Abstract
Caspase activity during apoptosis is inhibited by physiological concentrations of intracellular K+. To enable apoptosis in injured cortical and hippocampal neurons, cellular loss of this cation is facilitated by the insertion of Kv2.1 K+ channels into the plasma membrane via a Zn2+/CaMKII/SNARE-dependent process. Pro-apoptotic membrane insertion of Kv2.1 requires the dual phosphorylation of the channel by Src and p38 at cytoplasmic N- and C-terminal residues Y124 and S800, respectively. In this study, we investigate if these phosphorylation sites are mutually co-regulated, and whether putative N- and C-terminal interactions, possibly enabled by Kv2.1 intracellular cysteine residues C73 and C710, influence the phosphorylation process itself. Studies were performed with recombinant wild type and mutant Kv2.1 expressed in Chinese hamster ovary (CHO) cells. Using immunoprecipitated Kv2.1 protein and phospho-specific antibodies, we found that an intact Y124 is required for p38 phosphorylation of S800, and, importantly, that Src phosphorylation of Y124 facilitates the action of the p38 at the S800 residue. Moreover, the actions of Src on Kv2.1 are substantially decreased in the non-phosphorylatable S800A channel mutant. We also observed that mutations of either C73 or C710 residues decreased the p38 phosphorylation at S800 without influencing the actions of Src on tyrosine phosphorylation of Kv2.1. Surprisingly, however, apoptotic K+ currents were suppressed only in cells expressing the Kv2.1(C73A) mutant but not in those transfected with Kv2.1(C710A), suggesting a possible structural alteration in the C-terminal mutant that facilitates membrane insertion. These results show that intracellular N-terminal domains critically regulate phosphorylation of the C-terminal of Kv2.1, and vice versa, suggesting possible new avenues for modifying the apoptotic insertion of these channels during neurodegenerative processes.
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Affiliation(s)
- Kai He
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Meghan C. McCord
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Karen A. Hartnett
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
| | - Elias Aizenman
- Department of Neurobiology, University of Pittsburgh School of Medicine, E1456 BST, 3500 Terrace St., Pittsburgh, PA, 15261, United States of America
- * E-mail:
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84
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Trimmer JS. Subcellular localization of K+ channels in mammalian brain neurons: remarkable precision in the midst of extraordinary complexity. Neuron 2015; 85:238-56. [PMID: 25611506 DOI: 10.1016/j.neuron.2014.12.042] [Citation(s) in RCA: 155] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Potassium channels (KChs) are the most diverse ion channels, in part due to extensive combinatorial assembly of a large number of principal and auxiliary subunits into an assortment of KCh complexes. Their structural and functional diversity allows KChs to play diverse roles in neuronal function. Localization of KChs within specialized neuronal compartments defines their physiological role and also fundamentally impacts their activity, due to localized exposure to diverse cellular determinants of channel function. Recent studies in mammalian brain reveal an exquisite refinement of KCh subcellular localization. This includes axonal KChs at the initial segment, and near/within nodes of Ranvier and presynaptic terminals, dendritic KChs found at sites reflecting specific synaptic input, and KChs defining novel neuronal compartments. Painting the remarkable diversity of KChs onto the complex architecture of mammalian neurons creates an elegant picture of electrical signal processing underlying the sophisticated function of individual neuronal compartments, and ultimately neurotransmission and behavior.
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Affiliation(s)
- James S Trimmer
- Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616, USA; Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA 95616, USA.
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85
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Chemoselective tarantula toxins report voltage activation of wild-type ion channels in live cells. Proc Natl Acad Sci U S A 2014; 111:E4789-96. [PMID: 25331865 DOI: 10.1073/pnas.1406876111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Electrically excitable cells, such as neurons, exhibit tremendous diversity in their firing patterns, a consequence of the complex collection of ion channels present in any specific cell. Although numerous methods are capable of measuring cellular electrical signals, understanding which types of ion channels give rise to these signals remains a significant challenge. Here, we describe exogenous probes which use a novel mechanism to report activity of voltage-gated channels. We have synthesized chemoselective derivatives of the tarantula toxin guangxitoxin-1E (GxTX), an inhibitory cystine knot peptide that binds selectively to Kv2-type voltage gated potassium channels. We find that voltage activation of Kv2.1 channels triggers GxTX dissociation, and thus GxTX binding dynamically marks Kv2 activation. We identify GxTX residues that can be replaced by thiol- or alkyne-bearing amino acids, without disrupting toxin folding or activity, and chemoselectively ligate fluorophores or affinity probes to these sites. We find that GxTX-fluorophore conjugates colocalize with Kv2.1 clusters in live cells and are released from channels activated by voltage stimuli. Kv2.1 activation can be detected with concentrations of probe that have a trivial impact on cellular currents. Chemoselective GxTX mutants conjugated to dendrimeric beads likewise bind live cells expressing Kv2.1, and the beads are released by channel activation. These optical sensors of conformational change are prototype probes that can indicate when ion channels contribute to electrical signaling.
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86
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Torkamani A, Bersell K, Jorge BS, Bjork RL, Friedman JR, Bloss CS, Cohen J, Gupta S, Naidu S, Vanoye CG, George AL, Kearney JA. De novo KCNB1 mutations in epileptic encephalopathy. Ann Neurol 2014; 76:529-540. [PMID: 25164438 DOI: 10.1002/ana.24263] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Numerous studies have demonstrated increased load of de novo copy number variants or single nucleotide variants in individuals with neurodevelopmental disorders, including epileptic encephalopathies, intellectual disability, and autism. METHODS We searched for de novo mutations in a family quartet with a sporadic case of epileptic encephalopathy with no known etiology to determine the underlying cause using high-coverage whole exome sequencing (WES) and lower-coverage whole genome sequencing. Mutations in additional patients were identified by WES. The effect of mutations on protein function was assessed in a heterologous expression system. RESULTS We identified a de novo missense mutation in KCNB1 that encodes the KV 2.1 voltage-gated potassium channel. Functional studies demonstrated a deleterious effect of the mutation on KV 2.1 function leading to a loss of ion selectivity and gain of a depolarizing inward cation conductance. Subsequently, we identified 2 additional patients with epileptic encephalopathy and de novo KCNB1 missense mutations that cause a similar pattern of KV 2.1 dysfunction. INTERPRETATION Our genetic and functional evidence demonstrate that KCNB1 mutation can result in early onset epileptic encephalopathy. This expands the locus heterogeneity associated with epileptic encephalopathies and suggests that clinical WES may be useful for diagnosis of epileptic encephalopathies of unknown etiology.
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Affiliation(s)
- Ali Torkamani
- The Scripps Translational Science Institute, Scripps Health and The Scripps Research Institute, San Diego, CA 92037
| | - Kevin Bersell
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - Benjamin S Jorge
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN 37232, USA
| | - Robert L Bjork
- Pediatrics, Scripps Health, San Diego, CA 92037, USA.,Sea Breeze Pediatrics, APC, San Diego, CA
| | - Jennifer R Friedman
- Departments of Neurosciences and Pediatrics, University of California, San Diego, San Diego, CA 92093, USA
| | - Cinnamon S Bloss
- The Scripps Translational Science Institute, Scripps Health and The Scripps Research Institute, San Diego, CA 92037
| | - Julie Cohen
- Kennedy Krieger Institute, Baltimore, MD 21205
| | - Siddharth Gupta
- Kennedy Krieger Institute, Baltimore, MD 21205.,Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Sakkubai Naidu
- Kennedy Krieger Institute, Baltimore, MD 21205.,Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Carlos G Vanoye
- Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA.,Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Alfred L George
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA.,Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA.,Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
| | - Jennifer A Kearney
- Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA.,Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611
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87
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Mandikian D, Bocksteins E, Parajuli LK, Bishop HI, Cerda O, Shigemoto R, Trimmer JS. Cell type-specific spatial and functional coupling between mammalian brain Kv2.1 K+ channels and ryanodine receptors. J Comp Neurol 2014; 522:3555-74. [PMID: 24962901 DOI: 10.1002/cne.23641] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 06/17/2014] [Accepted: 06/20/2014] [Indexed: 11/08/2022]
Abstract
The Kv2.1 voltage-gated K+ channel is widely expressed throughout mammalian brain, where it contributes to dynamic activity-dependent regulation of intrinsic neuronal excitability. Here we show that somatic plasma membrane Kv2.1 clusters are juxtaposed to clusters of intracellular ryanodine receptor (RyR) Ca2+ -release channels in mouse brain neurons, most prominently in medium spiny neurons (MSNs) of the striatum. Electron microscopy-immunogold labeling shows that in MSNs, plasma membrane Kv2.1 clusters are adjacent to subsurface cisternae, placing Kv2.1 in close proximity to sites of RyR-mediated Ca2+ release. Immunofluorescence labeling in transgenic mice expressing green fluorescent protein in specific MSN populations reveals the most prominent juxtaposed Kv2.1:RyR clusters in indirect pathway MSNs. Kv2.1 in both direct and indirect pathway MSNs exhibits markedly lower levels of labeling with phosphospecific antibodies directed against the S453, S563, and S603 phosphorylation site compared with levels observed in neocortical neurons, although labeling for Kv2.1 phosphorylation at S563 was significantly lower in indirect pathway MSNs compared with those in the direct pathway. Finally, acute stimulation of RyRs in heterologous cells causes a rapid hyperpolarizing shift in the voltage dependence of activation of Kv2.1, typical of Ca2+ /calcineurin-dependent Kv2.1 dephosphorylation. Together, these studies reveal that striatal MSNs are distinct in their expression of clustered Kv2.1 at plasma membrane sites juxtaposed to intracellular RyRs, as well as in Kv2.1 phosphorylation state. Differences in Kv2.1 expression and phosphorylation between MSNs in direct and indirect pathways provide a cell- and circuit-specific mechanism for coupling intracellular Ca2+ release to phosphorylation-dependent regulation of Kv2.1 to dynamically impact intrinsic excitability.
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Affiliation(s)
- Danielle Mandikian
- Department of Neurobiology, Physiology and Behavior, University of California Davis, Davis, California, 95616
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88
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Zhao X, Kuja-Panula J, Sundvik M, Chen YC, Aho V, Peltola MA, Porkka-Heiskanen T, Panula P, Rauvala H. Amigo adhesion protein regulates development of neural circuits in zebrafish brain. J Biol Chem 2014; 289:19958-75. [PMID: 24904058 DOI: 10.1074/jbc.m113.545582] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The Amigo protein family consists of three transmembrane proteins characterized by six leucine-rich repeat domains and one immunoglobulin-like domain in their extracellular moieties. Previous in vitro studies have suggested a role as homophilic adhesion molecules in brain neurons, but the in vivo functions remain unknown. Here we have cloned all three zebrafish amigos and show that amigo1 is the predominant family member expressed during nervous system development in zebrafish. Knockdown of amigo1 expression using morpholino oligonucleotides impairs the formation of fasciculated tracts in early fiber scaffolds of brain. A similar defect in fiber tract development is caused by mRNA-mediated expression of the Amigo1 ectodomain that inhibits adhesion mediated by the full-length protein. Analysis of differentiated neural circuits reveals defects in the catecholaminergic system. At the behavioral level, the disturbed formation of neural circuitry is reflected in enhanced locomotor activity and in the inability of the larvae to perform normal escape responses. We suggest that Amigo1 is essential for the development of neural circuits of zebrafish, where its mechanism involves homophilic interactions within the developing fiber tracts and regulation of the Kv2.1 potassium channel to form functional neural circuitry that controls locomotion.
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Affiliation(s)
| | | | - Maria Sundvik
- From the Neuroscience Center, Institute of Biomedicine/Anatomy, and
| | - Yu-Chia Chen
- From the Neuroscience Center, Institute of Biomedicine/Anatomy, and
| | - Vilma Aho
- Institute of Biomedicine/Physiology, University of Helsinki, Helsinki FIN-00014, Finland
| | | | - Tarja Porkka-Heiskanen
- Institute of Biomedicine/Physiology, University of Helsinki, Helsinki FIN-00014, Finland
| | - Pertti Panula
- From the Neuroscience Center, Institute of Biomedicine/Anatomy, and
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