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Lee CK, Nguyen HS, Kang SJ, Jeong SW. Cellular and Molecular Mechanisms Underlying Altered Excitability of Cardiac Efferent Neurons in Cirrhotic Rats. Biomedicines 2024; 12:1722. [PMID: 39200187 PMCID: PMC11351538 DOI: 10.3390/biomedicines12081722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2024] [Revised: 07/30/2024] [Accepted: 07/30/2024] [Indexed: 09/02/2024] Open
Abstract
Patients with cirrhosis often exhibit cardiac autonomic dysfunction (CAD), characterized by enhanced cardiac sympathetic activity and diminished cardiac vagal tone, leading to increased morbidity and mortality. This study delineates the cellular and molecular mechanisms associated with altered neuronal activities causing cirrhosis-induced CAD. Biliary and nonbiliary cirrhotic rats were produced by common bile duct ligation (CBDL) and intraperitoneal injections of thioacetamide (TAA), respectively. Three weeks after CBDL or TAA injection, the assessment of heart rate variability revealed autonomic imbalance in cirrhotic rats. We observed increased excitability in stellate ganglion (SG) neurons and decreased excitability in intracardiac ganglion (ICG) neurons in cirrhotic rats compared to sham-operated controls. Additionally, threshold, rheobase, and action potential duration exhibited opposite alterations in SG and ICG neurons, along with changes in afterhyperpolarization duration. A- and M-type K⁺ channels were significantly downregulated in SG neurons, while M-type K⁺ channels were upregulated, with downregulation of the N- and L-type Ca2⁺ channels in the ICG neurons of cirrhotic rats, both in transcript expression and functional activity. Collectively, these findings suggest that cirrhosis induces an imbalance between cardiac sympathetic and parasympathetic neuronal activities via the differential regulation of K+ and Ca2+ channels. Thus, cirrhosis-induced CAD may be associated with impaired autonomic efferent functions within the homeostatic reflex arc that regulates cardiac functions.
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Affiliation(s)
| | | | | | - Seong-Woo Jeong
- Laboratory of Molecular Neurophysiology, Department of Physiology, Yonsei University Wonju College of Medicine, Wonju 26426, Republic of Korea; (C.-K.L.); (H.S.N.); (S.J.K.)
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2
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Bhat S, Rousseau J, Michaud C, Lourenço CM, Stoler JM, Louie RJ, Clarkson LK, Lichty A, Koboldt DC, Reshmi SC, Sisodiya SM, Hoytema van Konijnenburg EMM, Koop K, van Hasselt PM, Démurger F, Dubourg C, Sullivan BR, Hughes SS, Thiffault I, Tremblay ES, Accogli A, Srour M, Blunck R, Campeau PM. Mono-allelic KCNB2 variants lead to a neurodevelopmental syndrome caused by altered channel inactivation. Am J Hum Genet 2024; 111:761-777. [PMID: 38503299 PMCID: PMC11023922 DOI: 10.1016/j.ajhg.2024.02.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 02/23/2024] [Accepted: 02/25/2024] [Indexed: 03/21/2024] Open
Abstract
Ion channels mediate voltage fluxes or action potentials that are central to the functioning of excitable cells such as neurons. The KCNB family of voltage-gated potassium channels (Kv) consists of two members (KCNB1 and KCNB2) encoded by KCNB1 and KCNB2, respectively. These channels are major contributors to delayed rectifier potassium currents arising from the neuronal soma which modulate overall excitability of neurons. In this study, we identified several mono-allelic pathogenic missense variants in KCNB2, in individuals with a neurodevelopmental syndrome with epilepsy and autism in some individuals. Recurrent dysmorphisms included a broad forehead, synophrys, and digital anomalies. Additionally, we selected three variants where genetic transmission has not been assessed, from two epilepsy studies, for inclusion in our experiments. We characterized channel properties of these variants by expressing them in oocytes of Xenopus laevis and conducting cut-open oocyte voltage clamp electrophysiology. Our datasets indicate no significant change in absolute conductance and conductance-voltage relationships of most disease variants as compared to wild type (WT), when expressed either alone or co-expressed with WT-KCNB2. However, variants c.1141A>G (p.Thr381Ala) and c.641C>T (p.Thr214Met) show complete abrogation of currents when expressed alone with the former exhibiting a left shift in activation midpoint when expressed alone or with WT-KCNB2. The variants we studied, nevertheless, show collective features of increased inactivation shifted to hyperpolarized potentials. We suggest that the effects of the variants on channel inactivation result in hyper-excitability of neurons, which contributes to disease manifestations.
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Affiliation(s)
- Shreyas Bhat
- Center for Interdisciplinary Research on Brain and Learning (CIRCA), Department of Physics and Department of Pharmacology and Physiology, Université de Montréal, Montréal, QC, Canada
| | - Justine Rousseau
- Centre de Recherche Du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, QC H3T 1C5, Canada
| | - Coralie Michaud
- Centre de Recherche Du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, QC H3T 1C5, Canada
| | | | - Joan M Stoler
- Division of Genetics and Genomics, Boston Children's Hospital, Boston, MA, USA
| | | | | | - Angie Lichty
- Greenwood Genetic Center, Greenwood, SC 29646, USA
| | - Daniel C Koboldt
- Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, USA
| | - Shalini C Reshmi
- Steve and Cindy Rasmussen Institute for Genomic Medicine at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pathology and Laboratory Medicine, Nationwide Children's Hospital, Columbus, OH, USA
| | - Sanjay M Sisodiya
- Department of Clinical and Experimental Epilepsy, University College London Queen Square Institute of Neurology, London WC1N 3BG, UK
| | | | - Klaas Koop
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Peter M van Hasselt
- Department of Genetics, Section Metabolic Diagnostics, University Medical Center Utrecht, Utrecht, the Netherlands
| | | | - Christèle Dubourg
- Department of Molecular Genetics and Genomics, Rennes University Hospital, Rennes, France; Université de Rennes, CNRS, IGDR, UMR 6290 Rennes, France
| | - Bonnie R Sullivan
- Division of Clinical Genetics, Department of Pediatrics, Children's Mercy Kansas City, Kansas City, MO, USA
| | - Susan S Hughes
- Division of Clinical Genetics, Department of Pediatrics, Children's Mercy Kansas City, Kansas City, MO, USA
| | - Isabelle Thiffault
- Departments of Pediatrics and of Pathology and Laboratory Medicine, Children's Mercy Kansas City, Kansas City, MO, USA
| | - Elisabeth Simard Tremblay
- Department of Neurology and Neurosurgery, McGill University Health Centre, Montréal, QC, Canada; Department of Pediatrics, Division of Pediatric Neurology, McGill University, Montréal, QC, Canada
| | - Andrea Accogli
- Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Centre, Montréal, QC, Canada; Department of Human Genetics, Faculty of Medicine, McGill University, Montral, QC H3A 1B1, Canada
| | - Myriam Srour
- Department of Pediatrics, Division of Pediatric Neurology, McGill University, Montréal, QC, Canada; Department of Human Genetics, Faculty of Medicine, McGill University, Montral, QC H3A 1B1, Canada
| | - Rikard Blunck
- Center for Interdisciplinary Research on Brain and Learning (CIRCA), Department of Physics and Department of Pharmacology and Physiology, Université de Montréal, Montréal, QC, Canada.
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3
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Ryu H, Kim M, Park H, Choi HK, Chung C. Stress-induced translation of KCNB1 contributes to the enhanced synaptic transmission of the lateral habenula. Front Cell Neurosci 2023; 17:1278847. [PMID: 38193032 PMCID: PMC10773861 DOI: 10.3389/fncel.2023.1278847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 10/05/2023] [Indexed: 01/10/2024] Open
Abstract
The lateral habenula (LHb) is a well-established brain region involved in depressive disorders. Synaptic transmission of the LHb neurons is known to be enhanced by stress exposure; however, little is known about genetic modulators within the LHb that respond to stress. Using recently developed molecular profiling methods by phosphorylated ribosome capture, we obtained transcriptome profiles of stress responsive LHb neurons during acute physical stress. Among such genes, we found that KCNB1 (Kv2.1 channel), a delayed rectifier and voltage-gated potassium channel, exhibited increased expression following acute stress exposure. To determine the roles of KCNB1 on LHb neurons during stress, we injected short hairpin RNA (shRNA) against the kcnb1 gene to block its expression prior to stress exposure. We observed that the knockdown of KCNB1 altered the basal firing pattern of LHb neurons. Although KCNB1 blockade did not rescue despair-like behaviors in acute learned helplessness (aLH) animals, we found that KCNB1 knockdown prevented the enhancement of synaptic strength in LHb neuron after stress exposure. This study suggests that KCNB1 may contribute to shape stress responses by regulating basal firing patterns and neurotransmission intensity of LHb neurons.
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Affiliation(s)
- Hakyun Ryu
- Department of Biological Sciences, Konkuk University, Seoul, Republic of Korea
| | - Minseok Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea
| | - Hoyong Park
- Department of Biological Sciences, Konkuk University, Seoul, Republic of Korea
| | - Han Kyoung Choi
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Republic of Korea
| | - ChiHye Chung
- Department of Biological Sciences, Konkuk University, Seoul, Republic of Korea
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4
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Casas M, Murray KD, Hino K, Vierra NC, Simó S, Trimmer JS, Dixon RE, Dickson EJ. NPC1-dependent alterations in K V2.1-Ca V1.2 nanodomains drive neuronal death in models of Niemann-Pick Type C disease. Nat Commun 2023; 14:4553. [PMID: 37507375 PMCID: PMC10382591 DOI: 10.1038/s41467-023-39937-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 07/04/2023] [Indexed: 07/30/2023] Open
Abstract
Lysosomes communicate through cholesterol transfer at endoplasmic reticulum (ER) contact sites. At these sites, the Niemann Pick C1 cholesterol transporter (NPC1) facilitates the removal of cholesterol from lysosomes, which is then transferred to the ER for distribution to other cell membranes. Mutations in NPC1 result in cholesterol buildup within lysosomes, leading to Niemann-Pick Type C (NPC) disease, a progressive and fatal neurodegenerative disorder. The molecular mechanisms connecting NPC1 loss to NPC-associated neuropathology remain unknown. Here we show both in vitro and in an animal model of NPC disease that the loss of NPC1 function alters the distribution and activity of voltage-gated calcium channels (CaV). Underlying alterations in calcium channel localization and function are KV2.1 channels whose interactions drive calcium channel clustering to enhance calcium entry and fuel neurotoxic elevations in mitochondrial calcium. Targeted disruption of KV2-CaV interactions rescues aberrant CaV1.2 clustering, elevated mitochondrial calcium, and neurotoxicity in vitro. Our findings provide evidence that NPC is a nanostructural ion channel clustering disease, characterized by altered distribution and activity of ion channels at membrane contacts, which contribute to neurodegeneration.
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Affiliation(s)
- Maria Casas
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Karl D Murray
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
- Department of Psychiatry & Behavioral Sciences, School of Medicine, University of California, Davis, CA, USA
| | - Keiko Hino
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA, USA
| | - Nicholas C Vierra
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Sergi Simó
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA, USA
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA.
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5
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Gray M, Santin JM. Series resistance errors in whole cell voltage clamp measured directly with dual patch-clamp recordings: not as bad as you think. J Neurophysiol 2023; 129:1177-1190. [PMID: 37073967 PMCID: PMC10190937 DOI: 10.1152/jn.00476.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 04/11/2023] [Accepted: 04/13/2023] [Indexed: 04/20/2023] Open
Abstract
Whole cell patch clamp has provided much insight into the function of voltage-gated ion channels in central neurons. However, voltage errors caused by the resistance of the recording electrode [series resistance (Rs)] limit its application to relatively small ionic currents. Ohm's law is often applied to estimate and correct the membrane potential for these voltage errors. We tested this assumption in brainstem motoneurons of adult frogs with dual patch-clamp recordings, one performing whole cell voltage clamp of K+ currents and the other directly recording the membrane potential. We hypothesized that Ohm's law-based correction would approximate the measured voltage error. We found that voltage errors averaged <5 mV for currents considered to be large for patch clamp (∼7-13 nA) and <10 mV for massive currents thought to be experimentally intractable (25-30 nA), each error falling within commonly accepted inclusion limits. In most cases Ohm's law-based correction overpredicted these measured voltage errors by roughly 2.5-fold. Consequently, the use of Ohm's law to correct for voltage errors led to erroneous current-voltage (I-V) relationships, showing the greatest distortion for inactivating currents. Finally, recordings with low electrode Rs compensated moderately by the amplifier circuitry appeared to have smaller voltage errors than those with larger Rs and high compensation despite the same "effective Rs" and current magnitude. Therefore, when Rs is low, large currents may be studied with better-than-expected voltage control. These results suggest that patch-clamp may be used to study ionic currents often interpreted to be off limits because of size.NEW & NOTEWORTHY Voltage errors occur in whole cell voltage clamp. We make, to our knowledge, the first direct measurements of these errors and find that voltage errors are far smaller than standard calculations would predict. Since voltage errors were often minimal during the measurement of large ion channel currents, this technique may be applied to large neurons of adults to gain insight into ion channel function across the life span and progression of disease.
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Affiliation(s)
- Michael Gray
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States
| | - Joseph M Santin
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States
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6
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Dixon RE, Trimmer JS. Endoplasmic Reticulum-Plasma Membrane Junctions as Sites of Depolarization-Induced Ca 2+ Signaling in Excitable Cells. Annu Rev Physiol 2023; 85:217-243. [PMID: 36202100 PMCID: PMC9918718 DOI: 10.1146/annurev-physiol-032122-104610] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Membrane contact sites between endoplasmic reticulum (ER) and plasma membrane (PM), or ER-PM junctions, are found in all eukaryotic cells. In excitable cells they play unique roles in organizing diverse forms of Ca2+ signaling as triggered by membrane depolarization. ER-PM junctions underlie crucial physiological processes such as excitation-contraction coupling, smooth muscle contraction and relaxation, and various forms of activity-dependent signaling and plasticity in neurons. In many cases the structure and molecular composition of ER-PM junctions in excitable cells comprise important regulatory feedback loops linking depolarization-induced Ca2+ signaling at these sites to the regulation of membrane potential. Here, we describe recent findings on physiological roles and molecular composition of native ER-PM junctions in excitable cells. We focus on recent studies that provide new insights into canonical forms of depolarization-induced Ca2+ signaling occurring at junctional triads and dyads of striated muscle, as well as the diversity of ER-PM junctions in these cells and in smooth muscle and neurons.
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Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
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7
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Richter-Laskowska M, Trybek P, Delfino DV, Wawrzkiewicz-Jałowiecka A. Flavonoids as Modulators of Potassium Channels. Int J Mol Sci 2023; 24:1311. [PMID: 36674825 PMCID: PMC9861088 DOI: 10.3390/ijms24021311] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/02/2023] [Accepted: 01/04/2023] [Indexed: 01/12/2023] Open
Abstract
Potassium channels are widely distributed integral proteins responsible for the effective and selective transport of K+ ions through the biological membranes. According to the existing structural and mechanistic differences, they are divided into several groups. All of them are considered important molecular drug targets due to their physiological roles, including the regulation of membrane potential or cell signaling. One of the recent trends in molecular pharmacology is the evaluation of the therapeutic potential of natural compounds and their derivatives, which can exhibit high specificity and effectiveness. Among the pharmaceuticals of plant origin, which are potassium channel modulators, flavonoids appear as a powerful group of biologically active substances. It is caused by their well-documented anti-oxidative, anti-inflammatory, anti-mutagenic, anti-carcinogenic, and antidiabetic effects on human health. Here, we focus on presenting the current state of knowledge about the possibilities of modulation of particular types of potassium channels by different flavonoids. Additionally, the biological meaning of the flavonoid-mediated changes in the activity of K+ channels will be outlined. Finally, novel promising directions for further research in this area will be proposed.
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Affiliation(s)
- Monika Richter-Laskowska
- The Centre for Biomedical Engineering, Łukasiewicz Research Network—Krakow Institute of Technology, 30-418 Krakow, Poland
| | - Paulina Trybek
- Faculty of Science and Technology, University of Silesia in Katowice, 41-500 Chorzów, Poland
| | | | - Agata Wawrzkiewicz-Jałowiecka
- Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland
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Activity-dependent endoplasmic reticulum Ca 2+ uptake depends on Kv2.1-mediated endoplasmic reticulum/plasma membrane junctions to promote synaptic transmission. Proc Natl Acad Sci U S A 2022; 119:e2117135119. [PMID: 35862456 PMCID: PMC9335237 DOI: 10.1073/pnas.2117135119] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The endoplasmic reticulum (ER) extends throughout the neuron as a continuous organelle, and its dysfunction is associated with several neurological disorders. During electrical activity, the ER takes up Ca2+ from the cytosol, which has been shown to support synaptic transmission. This close choreography of ER Ca2+ uptake with electrical activity suggests functional coupling of the ER to sources of voltage-gated Ca2+ entry through an unknown mechanism. We report that a nonconducting role for Kv2.1 through its ER binding domain is necessary for ER Ca2+ uptake during neuronal activity. Loss of Kv2.1 profoundly disables neurotransmitter release without altering presynaptic voltage. This suggests that Kv2.1-mediated signaling hubs play an important neurobiological role in Ca2+ handling and synaptic transmission independent of ion conduction. The endoplasmic reticulum (ER) forms a continuous and dynamic network throughout a neuron, extending from dendrites to axon terminals, and axonal ER dysfunction is implicated in several neurological disorders. In addition, tight junctions between the ER and plasma membrane (PM) are formed by several molecules including Kv2 channels, but the cellular functions of many ER-PM junctions remain unknown. Recently, dynamic Ca2+ uptake into the ER during electrical activity was shown to play an essential role in synaptic transmission. Our experiments demonstrate that Kv2.1 channels are necessary for enabling ER Ca2+ uptake during electrical activity, as knockdown (KD) of Kv2.1 rendered both the somatic and axonal ER unable to accumulate Ca2+ during electrical stimulation. Moreover, our experiments demonstrate that the loss of Kv2.1 in the axon impairs synaptic vesicle fusion during stimulation via a mechanism unrelated to voltage. Thus, our data demonstrate that a nonconducting role of Kv2.1 exists through its binding to the ER protein VAMP-associated protein (VAP), which couples ER Ca2+ uptake with electrical activity. Our results further suggest that Kv2.1 has a critical function in neuronal cell biology for Ca2+ handling independent of voltage and reveals a critical pathway for maintaining ER lumen Ca2+ levels and efficient neurotransmitter release. Taken together, these findings reveal an essential nonclassical role for both Kv2.1 and the ER-PM junctions in synaptic transmission.
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9
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Marquis MJ, Sack JT. Mechanism of use-dependent Kv2 channel inhibition by RY785. J Gen Physiol 2022; 154:e202112981. [PMID: 35435946 PMCID: PMC9195051 DOI: 10.1085/jgp.202112981] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 03/01/2022] [Accepted: 03/30/2022] [Indexed: 01/21/2023] Open
Abstract
Understanding the mechanism by which ion channel modulators act is critical for interpretation of their physiological effects and can provide insight into mechanisms of ion channel gating. The small molecule RY785 is a potent and selective inhibitor of Kv2 voltage-gated K+ channels that has a use-dependent onset of inhibition. Here, we investigate the mechanism of RY785 inhibition of rat Kv2.1 (Kcnb1) channels heterologously expressed in CHO-K1 cells. We find that 1 µM RY785 block eliminates Kv2.1 current at all physiologically relevant voltages, inhibiting ≥98% of the Kv2.1 conductance. Both onset of and recovery from RY785 inhibition require voltage sensor activation. Intracellular tetraethylammonium, a classic open-channel blocker, competes with RY785 inhibition. However, channel opening itself does not appear to alter RY785 access. Gating current measurements reveal that RY785 inhibits a component of voltage sensor activation and accelerates voltage sensor deactivation. We propose that voltage sensor activation opens a path into the central cavity of Kv2.1 where RY785 binds and promotes voltage sensor deactivation, trapping itself inside. This gated-access mechanism in conjunction with slow kinetics of unblock supports simple interpretation of RY785 effects: channel activation is required for block by RY785 to equilibrate, after which trapped RY785 will simply decrease the Kv2 conductance density.
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Affiliation(s)
- Matthew James Marquis
- Department of Physiology & Membrane Biology, University of California, Davis, Davis, CA
| | - Jon T. Sack
- Department of Physiology & Membrane Biology, University of California, Davis, Davis, CA
- Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA
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10
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Nakai-Shimoda H, Himeno T, Okawa T, Miura-Yura E, Sasajima S, Kato M, Yamada Y, Morishita Y, Tsunekawa S, Kato Y, Seino Y, Inoue R, Kondo M, Seino S, Naruse K, Kato K, Mizukami H, Nakamura J, Kamiya H. Kir6.2-deficient mice develop somatosensory dysfunction and axonal loss in the peripheral nerves. iScience 2022; 25:103609. [PMID: 35005553 PMCID: PMC8719014 DOI: 10.1016/j.isci.2021.103609] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/27/2021] [Accepted: 12/08/2021] [Indexed: 10/26/2022] Open
Abstract
Glucose-responsive ATP-sensitive potassium channels (KATP) are expressed in a variety of tissues including nervous systems. The depolarization of the membrane potential induced by glucose may lead to hyperexcitability of neurons and induce excitotoxicity. However, the roles of KATP in the peripheral nervous system (PNS) are poorly understood. Here, we determine the roles of KATP in the PNS using KATP-deficient (Kir6.2-deficient) mice. We demonstrate that neurite outgrowth of dorsal root ganglion (DRG) neurons was reduced by channel closers sulfonylureas. However, a channel opener diazoxide elongated the neurite. KATP subunits were expressed in mouse DRG, and expression of certain subunits including Kir6.2 was increased in diabetic mice. In Kir6.2-deficient mice, the current perception threshold, thermal perception threshold, and sensory nerve conduction velocity were impaired. Electron microscopy revealed a reduction of unmyelinated and small myelinated fibers in the sural nerves. In conclusion, KATP may contribute to the development of peripheral neuropathy.
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Affiliation(s)
- Hiromi Nakai-Shimoda
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Tatsuhito Himeno
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan.,Department of Innovative Diabetes Therapy, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Tetsuji Okawa
- Department of Endocrinology, Gifu Prefectural Tajimi Hospital, Tajimi 507-8522, Japan
| | - Emiri Miura-Yura
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Sachiko Sasajima
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Makoto Kato
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Yuichiro Yamada
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Yoshiaki Morishita
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Shin Tsunekawa
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Yoshiro Kato
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Yusuke Seino
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake 470-1192, Aichi, Japan
| | - Rieko Inoue
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Masaki Kondo
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Susumu Seino
- Division of Molecular and Metabolic Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0047, Japan
| | - Keiko Naruse
- Department of Internal Medicine, Aichi Gakuin University School of Dentistry, Nagoya 464-0821, Japan
| | - Koichi Kato
- Department of Medicine, Aichi Gakuin University School of Pharmacy, Nagoya 464-8650, Japan
| | - Hiroki Mizukami
- Department of Pathology and Molecular Medicine, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan
| | - Jiro Nakamura
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan.,Department of Innovative Diabetes Therapy, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
| | - Hideki Kamiya
- Division of Diabetes, Department of Internal Medicine, Aichi Medical University School of Medicine, Nagakute 480-1185, Japan
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11
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Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
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Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
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12
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Thapa P, Stewart R, Sepela RJ, Vivas O, Parajuli LK, Lillya M, Fletcher-Taylor S, Cohen BE, Zito K, Sack JT. EVAP: A two-photon imaging tool to study conformational changes in endogenous Kv2 channels in live tissues. J Gen Physiol 2021; 153:212666. [PMID: 34581724 PMCID: PMC8480965 DOI: 10.1085/jgp.202012858] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 09/03/2021] [Indexed: 12/29/2022] Open
Abstract
A primary goal of molecular physiology is to understand how conformational changes of proteins affect the function of cells, tissues, and organisms. Here, we describe an imaging method for measuring the conformational changes of the voltage sensors of endogenous ion channel proteins within live tissue, without genetic modification. We synthesized GxTX-594, a variant of the peptidyl tarantula toxin guangxitoxin-1E, conjugated to a fluorophore optimal for two-photon excitation imaging through light-scattering tissue. We term this tool EVAP (Endogenous Voltage-sensor Activity Probe). GxTX-594 targets the voltage sensors of Kv2 proteins, which form potassium channels and plasma membrane–endoplasmic reticulum junctions. GxTX-594 dynamically labels Kv2 proteins on cell surfaces in response to voltage stimulation. To interpret dynamic changes in fluorescence intensity, we developed a statistical thermodynamic model that relates the conformational changes of Kv2 voltage sensors to degree of labeling. We used two-photon excitation imaging of rat brain slices to image Kv2 proteins in neurons. We found puncta of GxTX-594 on hippocampal CA1 neurons that responded to voltage stimulation and retain a voltage response roughly similar to heterologously expressed Kv2.1 protein. Our findings show that EVAP imaging methods enable the identification of conformational changes of endogenous Kv2 voltage sensors in tissue.
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Affiliation(s)
- Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Robert Stewart
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Rebecka J Sepela
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Oscar Vivas
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Laxmi K Parajuli
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Mark Lillya
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Sebastian Fletcher-Taylor
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Bruce E Cohen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA.,Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Karen Zito
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA
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13
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Yang YS, Choi JH, Rah JC. Hypoxia with inflammation and reperfusion alters membrane resistance by dynamically regulating voltage-gated potassium channels in hippocampal CA1 neurons. Mol Brain 2021; 14:147. [PMID: 34556177 PMCID: PMC8461870 DOI: 10.1186/s13041-021-00857-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/07/2021] [Indexed: 02/01/2023] Open
Abstract
Hypoxia typically accompanies acute inflammatory responses in patients and animal models. However, a limited number of studies have examined the effect of hypoxia in combination with inflammation (Hypo-Inf) on neural function. We previously reported that neuronal excitability in hippocampal CA1 neurons decreased during hypoxia and greatly rebounded upon reoxygenation. We attributed this altered excitability mainly to the dynamic regulation of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels and input resistance. However, the molecular mechanisms underlying input resistance changes by Hypo-Inf and reperfusion remained unclear. In the present study, we found that a change in the density of the delayed rectifier potassium current (IDR) can explain the input resistance variability. Furthermore, voltage-dependent inactivation of A-type potassium (IA) channels shifted in the depolarizing direction during Hypo-Inf and reverted to normal upon reperfusion without a significant alteration in the maximum current density. Our results indicate that changes in the input resistance, and consequently excitability, caused by Hypo-Inf and reperfusion are at least partially regulated by the availability and voltage dependence of KV channels. Moreover, these results suggest that selective KV channel modulators can be used as potential neuroprotective drugs to minimize hypoxia- and reperfusion-induced neuronal damage.
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Affiliation(s)
- Yoon-Sil Yang
- Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062 South Korea
| | - Joon Ho Choi
- Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062 South Korea
| | - Jong-Cheol Rah
- Korea Brain Research Institute, 61 Cheomdan-ro, Dong-gu, Daegu, 41062 South Korea
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, 333 Techno Jungang-daero, Dalseong-gun, Daegu, 42988 South Korea
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14
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Li Z, Dong W, Zhang X, Lu JM, Mei YA, Hu C. Protein Kinase C Controls the Excitability of Cortical Pyramidal Neurons by Regulating Kv2.2 Channel Activity. Neurosci Bull 2021; 38:135-148. [PMID: 34542799 PMCID: PMC8821747 DOI: 10.1007/s12264-021-00773-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 05/11/2021] [Indexed: 02/03/2023] Open
Abstract
The family of voltage-gated potassium Kv2 channels consists of the Kv2.1 and Kv2.2 subtypes. Kv2.1 is constitutively highly phosphorylated in neurons and its function relies on its phosphorylation state. Whether the function of Kv2.2 is also dependent on its phosphorylation state remains unknown. Here, we investigated whether Kv2.2 channels can be phosphorylated by protein kinase C (PKC) and examined the effects of PKC-induced phosphorylation on their activity and function. Activation of PKC inhibited Kv2.2 currents and altered their steady-state activation in HEK293 cells. Point mutations and specific antibodies against phosphorylated S481 or S488 demonstrated the importance of these residues for the PKC-dependent modulation of Kv2.2. In layer II pyramidal neurons in cortical slices, activation of PKC similarly regulated native Kv2.2 channels and simultaneously reduced the frequency of action potentials. In conclusion, this study provides the first evidence to our knowledge that PKC-induced phosphorylation of the Kv2.2 channel controls the excitability of cortical pyramidal neurons.
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Affiliation(s)
- Zhaoyang Li
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
| | - Wenhao Dong
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
| | - Xinyuan Zhang
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
| | - Jun-Mei Lu
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
| | - Yan-Ai Mei
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
| | - Changlong Hu
- State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and School of Life Sciences, Fudan University, Shanghai, 200438 China
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15
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Zhang Y, Zhang Y, Wang Z, Sun Y, Jiang X, Xue M, Yu Y, Tao J. Suppression of delayed rectifier K + channels by gentamicin induces membrane hyperexcitability through JNK and PKA signaling pathways in vestibular ganglion neurons. Biomed Pharmacother 2021; 135:111185. [PMID: 33422932 DOI: 10.1016/j.biopha.2020.111185] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/20/2020] [Accepted: 12/26/2020] [Indexed: 01/11/2023] Open
Abstract
Aminoglycoside antibiotics, such as gentamicin, are known to have vestibulotoxic effects, including ataxia and disequilibrium. To date, however, the underlying cellular and molecular mechanisms are still unclear. In this study, we determined the role of gentamicin in regulating the sustained delayed rectifier K+ current (IDR) and membrane excitability in vestibular ganglion (VG) neurons in mice. Our results showed that the application of gentamicin to VG neurons decreased the IDR in a concentration-dependent manner, while the transient outward A-type K+ current (IA) remained unaffected. The decrease in IDR induced by gentamicin was independent of G-protein activity and led to a hyperpolarizing shift of the inactivation Vhalf. The analysis of phospho-c-Jun N-terminal kinase (p-JNK) revealed that gentamicin significantly stimulated JNK, while p-ERK and p-p38 remained unaffected. Blocking Kv1 channels with α-dendrotoxin or pretreating VG neurons with the JNK inhibitor II abrogated the gentamicin-induced decrease in IDR. Antagonism of JNK signaling attenuated the gentamicin-induced stimulation of PKA activity, whereas PKA inhibition prevented the IDR response induced by gentamicin. Moreover, gentamicin significantly increased the number of action potentials fired in both phasic and tonic firing type neurons; pretreating VG neurons with the JNK inhibitor II and the blockade of the IDR abolished this effect. Taken together, our results demonstrate that gentamicin decreases the IDR through a G-protein-independent but JNK and PKA-mediated signaling pathways. This gentamicin-induced IDR response mediates VG neuronal hyperexcitability and might contribute to its pharmacological vestibular effects.
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Affiliation(s)
- Yunmei Zhang
- Department of Otolaryngology, the First Affiliated Hospital of Soochow University, Suzhou 215006, PR China; Department of Physiology and Neurobiology & Centre for Ion Channelopathy, Medical College of Soochow University, Suzhou 215123, PR China
| | - Yuan Zhang
- Department of Geriatrics & Institute of Neuroscience, the Second Affiliated Hospital of Soochow University, Suzhou 215004, PR China; Department of Physiology and Neurobiology & Centre for Ion Channelopathy, Medical College of Soochow University, Suzhou 215123, PR China
| | - Zizhang Wang
- Department of Head and Neck Surgery, Shaanxi Provincial Tumor Hospital, the Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, PR China
| | - Yufang Sun
- Department of Physiology and Neurobiology & Centre for Ion Channelopathy, Medical College of Soochow University, Suzhou 215123, PR China
| | - Xinghong Jiang
- Department of Physiology and Neurobiology & Centre for Ion Channelopathy, Medical College of Soochow University, Suzhou 215123, PR China
| | - Man Xue
- Suzhou Institute for Drug Control, Suzhou 215000, PR China
| | - Yafeng Yu
- Department of Otolaryngology, the First Affiliated Hospital of Soochow University, Suzhou 215006, PR China.
| | - Jin Tao
- Department of Physiology and Neurobiology & Centre for Ion Channelopathy, Medical College of Soochow University, Suzhou 215123, PR China; Jiangsu Key Laboratory of Neuropsychiatric Diseases, Soochow University, Suzhou 215123, PR China.
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16
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Di Lascio S, Benfante R, Cardani S, Fornasari D. Research Advances on Therapeutic Approaches to Congenital Central Hypoventilation Syndrome (CCHS). Front Neurosci 2021; 14:615666. [PMID: 33510615 PMCID: PMC7835644 DOI: 10.3389/fnins.2020.615666] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/17/2020] [Indexed: 12/11/2022] Open
Abstract
Congenital central hypoventilation syndrome (CCHS) is a genetic disorder of neurodevelopment, with an autosomal dominant transmission, caused by heterozygous mutations in the PHOX2B gene. CCHS is a rare disorder characterized by hypoventilation due to the failure of autonomic control of breathing. Until now no curative treatment has been found. PHOX2B is a transcription factor that plays a crucial role in the development (and maintenance) of the autonomic nervous system, and in particular the neuronal structures involved in respiratory reflexes. The underlying pathogenetic mechanism is still unclear, although studies in vivo and in CCHS patients indicate that some neuronal structures may be damaged. Moreover, in vitro experimental data suggest that transcriptional dysregulation and protein misfolding may be key pathogenic mechanisms. This review summarizes latest researches that improved the comprehension of the molecular pathogenetic mechanisms responsible for CCHS and discusses the search for therapeutic intervention in light of the current knowledge about PHOX2B function.
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Affiliation(s)
- Simona Di Lascio
- Department of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, Milan, Italy
| | - Roberta Benfante
- Department of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, Milan, Italy.,CNR-Institute of Neuroscience, Milan, Italy.,NeuroMi-Milan Center for Neuroscience, University of Milano Bicocca, Milan, Italy
| | - Silvia Cardani
- Department of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, Milan, Italy
| | - Diego Fornasari
- Department of Medical Biotechnology and Translational Medicine (BIOMETRA), Università degli Studi di Milano, Milan, Italy.,CNR-Institute of Neuroscience, Milan, Italy
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17
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Wang W, Yin H, Feng N, Wang L, Wang X. Inhibitory effects of antidepressant fluoxetine on cloned Kv2.1 potassium channel expressed in HEK293 cells. Eur J Pharmacol 2020; 878:173097. [PMID: 32278853 DOI: 10.1016/j.ejphar.2020.173097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 03/08/2020] [Accepted: 04/01/2020] [Indexed: 11/15/2022]
Abstract
It is well demonstrated that antidepressant fluoxetine has significant inhibitory effects on voltage-gated potassium channels. So far, the concise regulation of fluoxetine on Kv2.1, the predominant delayed rectifier potassium channel subtype in the central nervous system, are rarely reported. Here patch-clamp recording was used to investigate the inhibitory effects of fluoxetine on Kv2.1 potassium channels stably expressed in HEK293 cells. The results showed fluoxetine dose-dependently suppressed Kv2.1 currents with an IC50 of 51.3 μM. At the test potential positive to +50 mV, fluoxetine 50 μM voltage-dependently suppressed Kv2.1 currents with an electrical distance δ of 0.28. Moreover, fluoxetine 50 μM did not affect the activation process of Kv2.1, but reduced the decay time constant τinact and obviously accelerated the inactivation process of Kv2.1 and left-shifted the half-maximal inactivation potential of Kv2.1 potassium channel by 9.8 mV. Fluoxetine 50 μM notably delayed the recovery process of Kv2.1 from inactivation with increased time constants. In addition, fluoxetine 50 μM use-dependently inhibited Kv2.1 currents at different frequencies. In conclusion, the inhibition of Kv2.1 by fluoxetine was concentration-dependent, voltage-dependent and use-dependent. The accelerated steady-state inactivation of Kv2.1 channels induced by fluoxetine might be ascribed to the delay of the recovery process of Kv2.1.
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Affiliation(s)
- Weiping Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Huajing Yin
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Nan Feng
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Ling Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Xiaoliang Wang
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
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18
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Nascimento F, Broadhead MJ, Tetringa E, Tsape E, Zagoraiou L, Miles GB. Synaptic mechanisms underlying modulation of locomotor-related motoneuron output by premotor cholinergic interneurons. eLife 2020; 9:e54170. [PMID: 32081133 PMCID: PMC7062467 DOI: 10.7554/elife.54170] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 02/20/2020] [Indexed: 01/15/2023] Open
Abstract
Spinal motor networks are formed by diverse populations of interneurons that set the strength and rhythmicity of behaviors such as locomotion. A small cluster of cholinergic interneurons, expressing the transcription factor Pitx2, modulates the intensity of muscle activation via 'C-bouton' inputs to motoneurons. However, the synaptic mechanisms underlying this neuromodulation remain unclear. Here, we confirm in mice that Pitx2+ interneurons are active during fictive locomotion and that their chemogenetic inhibition reduces the amplitude of motor output. Furthermore, after genetic ablation of cholinergic Pitx2+ interneurons, M2 receptor-dependent regulation of the intensity of locomotor output is lost. Conversely, chemogenetic stimulation of Pitx2+ interneurons leads to activation of M2 receptors on motoneurons, regulation of Kv2.1 channels and greater motoneuron output due to an increase in the inter-spike afterhyperpolarization and a reduction in spike half-width. Our findings elucidate synaptic mechanisms by which cholinergic spinal interneurons modulate the final common pathway for motor output.
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Affiliation(s)
- Filipe Nascimento
- School of Psychology and Neuroscience, University of St AndrewsSt AndrewsUnited Kingdom
| | | | - Efstathia Tetringa
- Center of Basic Research, Biomedical Research Foundation of the Academy of AthensAthensGreece
| | - Eirini Tsape
- Center of Basic Research, Biomedical Research Foundation of the Academy of AthensAthensGreece
| | - Laskaro Zagoraiou
- Center of Basic Research, Biomedical Research Foundation of the Academy of AthensAthensGreece
| | - Gareth Brian Miles
- School of Psychology and Neuroscience, University of St AndrewsSt AndrewsUnited Kingdom
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19
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Yu W, Shin MR, Sesti F. Complexes formed with integrin-α5 and KCNB1 potassium channel wild type or epilepsy-susceptibility variants modulate cellular plasticity via Ras and Akt signaling. FASEB J 2019; 33:14680-14689. [PMID: 31682765 DOI: 10.1096/fj.201901792r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Voltage-gated potassium (K+) channel subfamily B member 1 (KCNB1, Kv2.1) and integrin-α5 form macromolecular complexes-named integrin-α5-KCNB1 complexes (IKCs)-in the human brain, but their function was poorly understood. Here we report that membrane depolarization triggered IKC intracellular signals mediated by small GTPases of the Ras subfamily and protein kinase B (Akt) to advance the development of filopodia and lamellipodia in Chinese hamster ovary cells, stimulate their motility, and enhance neurite outgrowth in mouse neuroblastoma Neuro2a cells. Five KCNB1 mutants (L211P, R312H G379R, G381R, and F416L) linked to severe infancy or early-onset epileptic encephalopathy exhibited markedly defective conduction. However, although L211P, G379R, and G381R normally engaged Ras/Akt and stimulated cell migration, R312H and F416L failed to activate Ras/Akt signaling and did not enhance cell migration. Taken together, these data suggest that IKCs modulate cellular plasticity via Ras and Akt signaling. As such, defective IKCs may cause epilepsy through mechanisms other than dysregulated excitability such as, for example, abnormal neuronal development and resulting synaptic connectivity.-Yu, W., Shin, M. R., Sesti, F. Complexes formed with integrin-α5 and KCNB1 potassium channel wild type or epilepsy-susceptibility variants modulate cellular plasticity via Ras and Akt signaling.
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Affiliation(s)
- Wei Yu
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, New Jersey, USA
| | - Mi Ryung Shin
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, New Jersey, USA
| | - Federico Sesti
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, New Jersey, USA
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20
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Montalbetti N, Rooney JG, Rued AC, Carattino MD. Molecular determinants of afferent sensitization in a rat model of cystitis with urothelial barrier dysfunction. J Neurophysiol 2019; 122:1136-1146. [PMID: 31314637 DOI: 10.1152/jn.00306.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The internal surface of the urinary bladder is covered by the urothelium, a stratified epithelium that forms an impermeable barrier to urinary solutes. Increased urothelial permeability is thought to contribute to symptom generation in several forms of cystitis by sensitizing bladder afferents. In this report we investigate the physiological mechanisms that mediate bladder afferent hyperexcitability in a rat model of cystitis induced by overexpression in the urothelium of claudin-2 (Cldn2), a tight junction-associated protein upregulated in bladder biopsies from patients with interstitial cystitis/bladder pain syndrome. Patch-clamp studies showed that overexpression of Cldn2 in the urothelium sensitizes a population of isolectin GS-IB4-negative [IB4(-)] bladder sensory neurons with tetrodotoxin-sensitive (TTX-S) action potentials. Gene expression analysis revealed a significant increase in mRNA levels of the delayed-rectifier voltage-gated K+ channel (Kv)2.2 and the accessory subunit Kv9.1 in this population of bladder sensory neurons. Consistent with this finding, Kv2/Kv9.1 channel activity was greater in IB4(-) bladder sensory neurons from rats overexpressing Cldn2 in the urothelium than in control counterparts. Likewise, current density of TTX-S voltage-gated Na+ (Nav) channels was greater in sensitized neurons than in control counterparts. Significantly, guangxitoxin-1E (GxTX-1E), a selective blocker of Kv2 channels, blunted the repetitive firing of sensitized IB4(-) sensory neurons. In summary, our studies indicate that an increase in the activity of TTX-S Nav and Kv2/Kv9.1 channels mediates repetitive firing of sensitized bladder sensory neurons in rats with increased urothelial permeability.NEW & NOTEWORTHY Hyperexcitability of sensitized bladder sensory neurons in a rat model of interstitial cystitis/bladder pain syndrome (IC/BPS) results from increased activity of tetrodotoxin-sensitive voltage-gated Na+ and delayed-rectifier voltage-gated K+ (Kv)2/Kv9.1 channels. Of major significance, our studies indicate that Kv2/Kv9.1 channels play a major role in symptom generation in this model of IC/BPS by maintaining the sustained firing of the sensitized bladder sensory neurons.
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Affiliation(s)
- Nicolas Montalbetti
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - James G Rooney
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Anna C Rued
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Marcelo D Carattino
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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21
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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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22
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Romer SH, Deardorff AS, Fyffe REW. A molecular rheostat: Kv2.1 currents maintain or suppress repetitive firing in motoneurons. J Physiol 2019; 597:3769-3786. [DOI: 10.1113/jp277833] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 05/29/2019] [Indexed: 12/26/2022] Open
Affiliation(s)
- Shannon H. Romer
- Neuroscience, Cell Biology & PhysiologyBoonshoft School of MedicineWright State University Fairborn OH 45435 USA
- Oak Ridge Institute for Science and EducationEnvironmental Health Effects LaboratoryNavy Medical Research Unit‐DaytonWright‐Patterson Air Force Base OH 45433 USA
| | - Adam S. Deardorff
- Neuroscience, Cell Biology & PhysiologyBoonshoft School of MedicineWright State University Fairborn OH 45435 USA
- Neurology, Boonshoft School of MedicineWright State University Dayton OH 45409 USA
| | - Robert E. W. Fyffe
- Neuroscience, Cell Biology & PhysiologyBoonshoft School of MedicineWright State University Fairborn OH 45435 USA
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23
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Liu L, Bonventre JV, Rittenhouse AR. cPLA2α-/- sympathetic neurons exhibit increased membrane excitability and loss of N-Type Ca2+ current inhibition by M1 muscarinic receptor signaling. PLoS One 2018; 13:e0201322. [PMID: 30557348 PMCID: PMC6296557 DOI: 10.1371/journal.pone.0201322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 07/11/2018] [Indexed: 11/18/2022] Open
Abstract
Group IVa cytosolic phospholipase A2 (cPLA2α) mediates GPCR-stimulated arachidonic acid (AA) release from phosphatidylinositol 4,5-bisphosphate (PIP2) located in plasma membranes. We previously found in superior cervical ganglion (SCG) neurons that PLA2 activity is required for voltage-independent N-type Ca2+ (N-) current inhibition by M1 muscarinic receptors (M1Rs). These findings are at odds with an alternative model, previously observed for M-current inhibition, where PIP2 dissociation from channels and subsequent metabolism by phospholipase C suffices for current inhibition. To resolve cPLA2α’s importance, we have investigated its role in mediating voltage-independent N-current inhibition (~40%) that follows application of the muscarinic agonist oxotremorine-M (Oxo-M). Preincubation with different cPLA2α antagonists or dialyzing cPLA2α antibodies into cells minimized N-current inhibition by Oxo-M, whereas antibodies to Ca2+-independent PLA2 had no effect. Taking a genetic approach, we found that SCG neurons from cPLA2α-/- mice exhibited little N-current inhibition by Oxo-M, confirming a role for cPLA2α. In contrast, cPLA2α antibodies or the absence of cPLA2α had no effect on voltage-dependent N-current inhibition by M2/M4Rs or on M-current inhibition by M1Rs. These findings document divergent M1R signaling mediating M-current and voltage-independent N-current inhibition. Moreover, these differences suggest that cPLA2α acts locally to metabolize PIP2 intimately associated with N- but not M-channels. To determine cPLA2α’s functional importance more globally, we examined action potential firing of cPLA2α+/+ and cPLA2α-/- SCG neurons, and found decreased latency to first firing and interspike interval resulting in a doubling of firing frequency in cPLA2α-/- neurons. These unanticipated findings identify cPLA2α as a tonic regulator of neuronal membrane excitability.
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Affiliation(s)
- Liwang Liu
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Joseph V. Bonventre
- Harvard Institute of Medicine, Harvard Medical School & Brigham and Women's Hospital, Boston, Massachusetts, United States of America
| | - Ann R. Rittenhouse
- Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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24
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Pisupati A, Mickolajczyk KJ, Horton W, van Rossum DB, Anishkin A, Chintapalli SV, Li X, Chu-Luo J, Busey G, Hancock WO, Jegla T. The S6 gate in regulatory Kv6 subunits restricts heteromeric K + channel stoichiometry. J Gen Physiol 2018; 150:1702-1721. [PMID: 30322883 PMCID: PMC6279357 DOI: 10.1085/jgp.201812121] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 07/03/2018] [Accepted: 09/26/2018] [Indexed: 11/24/2022] Open
Abstract
Atypical substitutions in the S6 activation gate sequence distinguish “regulatory” Kv subunits, which cannot homotetramerize due to T1 self-incompatibility. Pisupati et al. show that such substitutions in Kv6 work together with self-incompatibility to restrict Kv2:Kv6 heteromeric stoichiometry to 3:1. The Shaker-like family of voltage-gated K+ channels comprises four functionally independent gene subfamilies, Shaker (Kv1), Shab (Kv2), Shaw (Kv3), and Shal (Kv4), each of which regulates distinct aspects of neuronal excitability. Subfamily-specific assembly of tetrameric channels is mediated by the N-terminal T1 domain and segregates Kv1–4, allowing multiple channel types to function independently in the same cell. Typical Shaker-like Kv subunits can form functional channels as homotetramers, but a group of mammalian Kv2-related genes (Kv5.1, Kv6s, Kv8s, and Kv9s) encodes subunits that have a “silent” or “regulatory” phenotype characterized by T1 self-incompatibility. These channels are unable to form homotetramers, but instead heteromerize with Kv2.1 or Kv2.2 to diversify the functional properties of these delayed rectifiers. While T1 self-incompatibility predicts that these heterotetramers could contain up to two regulatory (R) subunits, experiments show a predominance of 3:1R stoichiometry in which heteromeric channels contain a single regulatory subunit. Substitution of the self-compatible Kv2.1 T1 domain into the regulatory subunit Kv6.4 does not alter the stoichiometry of Kv2.1:Kv6.4 heteromers. Here, to identify other channel structures that might be responsible for favoring the 3:1R stoichiometry, we compare the sequences of mammalian regulatory subunits to independently evolved regulatory subunits from cnidarians. The most widespread feature of regulatory subunits is the presence of atypical substitutions in the highly conserved consensus sequence of the intracellular S6 activation gate of the pore. We show that two amino acid substitutions in the S6 gate of the regulatory subunit Kv6.4 restrict the functional stoichiometry of Kv2.1:Kv6.4 to 3:1R by limiting the formation and function of 2:2R heteromers. We propose a two-step model for the evolution of the asymmetric 3:1R stoichiometry, which begins with evolution of self-incompatibility to establish the regulatory phenotype, followed by drift of the activation gate consensus sequence under relaxed selection to limit stoichiometry to 3:1R.
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Affiliation(s)
- Aditya Pisupati
- Department of Biology, Pennsylvania State University, University Park, PA.,Medical Scientist Training Program, College of Medicine, Pennsylvania State University, Hershey, PA
| | - Keith J Mickolajczyk
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA
| | - William Horton
- Department of Animal Science, Pennsylvania State University, University Park, PA
| | - Damian B van Rossum
- The Jake Gittlen Laboratories for Cancer Research, College of Medicine, Pennsylvania State University, Hershey, PA.,Division of Experimental Pathology, Department of Pathology, College of Medicine, Pennsylvania State University, Hershey, PA
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD
| | - Sree V Chintapalli
- Arkansas Children's Nutrition Center and Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR
| | - Xiaofan Li
- Department of Biology, Pennsylvania State University, University Park, PA
| | - Jose Chu-Luo
- Department of Biology, Pennsylvania State University, University Park, PA
| | - Gregory Busey
- Department of Biology, Pennsylvania State University, University Park, PA
| | - William O Hancock
- Department of Biomedical Engineering, Pennsylvania State University, University Park, PA
| | - Timothy Jegla
- Department of Biology, Pennsylvania State University, University Park, PA .,Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA
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25
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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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26
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Cleavage of potassium channel Kv2.1 by BACE2 reduces neuronal apoptosis. Mol Psychiatry 2018; 23:1542-1554. [PMID: 29703946 DOI: 10.1038/s41380-018-0060-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 02/24/2018] [Accepted: 03/13/2018] [Indexed: 12/20/2022]
Abstract
Potassium channel Kv2.1 regulates potassium current in cortical neurons and potassium efflux is necessary for cell apoptosis. As a major component of delayed rectifier current potassium channels, Kv2.1 forms clusters in the membrane of hippocampal neurons. BACE2 is an aspartyl protease to cleave APP to prevent the generation of Aβ, a central component of neuritic plaques in Alzheimer's brain. We now identified Kv2.1 as a novel substrate of BACE2. We found that BACE2 cleaved Kv2.1 at Thr376, Ala717, and Ser769 sites and disrupted Kv2.1 clustering on cell membrane, resulting in decreased Ik of Kv2.1 and a hyperpolarizing shift in primary neurons. Furthermore, we discovered that the BACE2-cleaved Kv2.1 forms, Kv2.1-1-375, Kv2.1-1-716, and Kv2.1-1-768, depressed the delayed rectifier Ik surge and reduced neuronal apoptosis. Our study suggests that BACE2 plays a neuroprotective role by cleavage of Kv2.1 to prevent the outward potassium currents, a potential new target for Alzheimer's treatment.
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27
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Wang JZ, Long C, Li KY, Xu HT, Yuan LL, Wu GY. Potent block of potassium channels by MEK inhibitor U0126 in primary cultures and brain slices. Sci Rep 2018; 8:8808. [PMID: 29892075 PMCID: PMC5995919 DOI: 10.1038/s41598-018-27235-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 05/29/2018] [Indexed: 12/05/2022] Open
Abstract
U0126 (1,4-diamino-2,3-dicyano-1,4-bis (2-aminophenylthio) butadiene), a widely used mitogen-activated protein kinase kinase (MEK) inhibitor, was found to accelerate voltage-gated K+ channel (KV) inactivation in heterologous cells expressing several types of KV. The goal of this study was to examine whether U0126 at a concentration thought to specifically inhibit MEK signaling also inhibits KV in native neurons of primary cultures or brain slices. U0126 caused a dose-dependent inhibition of both the transient (IA) and sustained (IDR) components of K+ currents in hippocampal neurons. U0126 also exhibited much higher potency on the IA and IDR than the classical KV blockers 4-aminopyridine (4-AP) and tetraethylammonium (TEA). Consistent with its inhibitory effect on KV, U0126 broadened action potential duration, profoundly affected the repolarizing phase, and dramatically reduced firing frequency in response to current pulse injections. Despite the potent and reversible action of U0126 on Kv channels, PD98059, a structurally-unrelated MEK inhibitor, did not induce such an effect, suggesting U0126 may act independently of MEK inhibition. Together, these results raise cautions for using U0126 as a specific inhibitor for studying MEK signaling in neurons; on the other hand, further studies on the blocking mechanisms of U0126 as a potent inhibitor of KV may provide useful insights into the structure-function relationship of KV in general.
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Affiliation(s)
- Jin-Zhao Wang
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Cheng Long
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
| | - Kai-Yuan Li
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Hua-Tai Xu
- Institute of Neuroscience, Chinese Academy of Sciences, 320 Yue Yang Road, Shanghai, 200031, China
| | - Li-Lian Yuan
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, 50312, USA
| | - Gang-Yi Wu
- School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
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28
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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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29
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Zhu J, Zang S, Chen X, Jiang L, Gu A, Cheng J, Zhang L, Wang J, Xiao H. Involvement of the delayed rectifier outward potassium channel Kv2.1 in methamphetamine-induced neuronal apoptosis via the p38 mitogen-activated protein kinase signaling pathway. J Appl Toxicol 2018; 38:696-704. [PMID: 29297590 DOI: 10.1002/jat.3576] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 11/06/2017] [Accepted: 11/11/2017] [Indexed: 01/08/2023]
Abstract
Methamphetamine (Meth) is an illicit psychostimulant with high abuse potential and severe neurotoxicity. Recent studies have shown that dysfunctions in learning and memory induced by Meth may partially reveal the mechanisms of neuronal channelopathies. Kv2.1, the primary delayed rectifying potassium channel in neurons, is responsible for mediating apoptotic current surge. However, whether Kv2.1 is involved in Meth-mediated neural injury remains unknown. In the present study, the treatment of primary cultured hippocampal neurons with Meth indicated that Meth induced a time- and dose-dependent augmentation of Kv2.1 protein expression, accompanied by elevated cleaved-caspase 3 and declined bcl-2/bax ratio. The blockage of Kv2.1 with the inhibitor GxTx-1E or the knockdown of the channel noticeably abrogated the pro-apoptotic effects mediated by Meth, demonstrating the specific roles of Kv2.1 in Meth-mediated neural damage. Additionally, the p38 mitogen-activated protein kinase (MAPK) signaling was demonstrated to be involved in Meth-mediated Kv2.1 upregulation and in the subsequent pro-apoptotic effects, as treatment with a p38 MAPK inhibitor significantly attenuated Meth-mediated Kv2.1 upregulation and cell apoptosis. Of note, PRE-084, a sigma-1 receptor agonist, obviously attenuated Meth-induced upregulation of Kv2.1 expression, neural apoptosis and p38 MAPK activation. Taken together, these results reveal a novel mechanism involved in Meth-induced neural death with implications for therapeutic interventions for Meth users.
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Affiliation(s)
- Jingying Zhu
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China.,Wuxi Center for Disease Control and Prevention, 499 Jincheng Road, Liangxi District, Wuxi, Jiangsu, 214023, China
| | - Songsong Zang
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
| | - Xufeng Chen
- Department of Emergency Medicine, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Lei Jiang
- Department of Emergency Medicine, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Aihua Gu
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
| | - Jie Cheng
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
| | - Li Zhang
- Children's Hospital of Nanjing Medical University, 72 Guangzhou Road, Nanjing, Jiangsu, 210029, China
| | - Jun Wang
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
| | - Hang Xiao
- Key Lab of Modern Toxicology (NJMU), Ministry of Education; Department of Toxicology, School of Public Health, Nanjing Medical University, 818 Tianyuan East Road, Nanjing, Jiangsu, 211166, China
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30
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Navidhamidi M, Ghasemi M, Mehranfard N. Epilepsy-associated alterations in hippocampal excitability. Rev Neurosci 2018; 28:307-334. [PMID: 28099137 DOI: 10.1515/revneuro-2016-0059] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/03/2016] [Indexed: 11/15/2022]
Abstract
The hippocampus exhibits a wide range of epilepsy-related abnormalities and is situated in the mesial temporal lobe, where limbic seizures begin. These abnormalities could affect membrane excitability and lead to overstimulation of neurons. Multiple overlapping processes refer to neural homeostatic responses develop in neurons that work together to restore neuronal firing rates to control levels. Nevertheless, homeostatic mechanisms are unable to restore normal neuronal excitability, and the epileptic hippocampus becomes hyperexcitable or hypoexcitable. Studies show that there is hyperexcitability even before starting recurrent spontaneous seizures, suggesting although hippocampal hyperexcitability may contribute to epileptogenesis, it alone is insufficient to produce epileptic seizures. This supports the concept that the hippocampus is not the only substrate for limbic seizure onset, and a broader hyperexcitable limbic structure may contribute to temporal lobe epilepsy (TLE) seizures. Nevertheless, seizures also occur in conditions where the hippocampus shows a hypoexcitable phenotype. Since TLE seizures most often originate in the hippocampus, it could therefore be assumed that both hippocampal hypoexcitability and hyperexcitability are undesirable states that make the epileptic hippocampal network less stable and may, under certain conditions, trigger seizures.
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31
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Coordinate expression of pan-neuronal and functional signature genes in sympathetic neurons. Cell Tissue Res 2017; 370:227-241. [PMID: 28936781 DOI: 10.1007/s00441-017-2688-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/27/2017] [Indexed: 12/20/2022]
Abstract
Neuron subtypes of the mature nervous system differ in the expression of characteristic marker genes while they share the expression of generic neuronal genes. The regulatory logic that maintains subtype-specific and pan-neuronal genes is not well understood. To begin to address this issue, we analyze RNA sequencing results from whole sympathetic ganglia and single sympathetic neurons in the mouse. We focus on gene products involved in the neuronal cytoskeleton, neurotransmitter synthesis and storage, transmitter release and reception and electrical information processing. We find a particular high correlation in the expression of stathmin 2 and several members of the tubulin beta family, classical pan-neuronal markers. Noradrenergic transmitter-synthesizing enzymes and transporters are also well correlated in their cellular transcript levels. In addition, noradrenergic marker transcript levels correlate well with selected pan-neuronal markers. Such a correlation in transcript levels is also seen between a number of selected ion channel, receptor and synaptic protein genes. These results provide the foundation for the analyses of the coordinated expression of downstream target genes in nerve cells.
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32
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Inhibition of Metabotropic Glutamate Receptor Subtype 1 Alters the Excitability of the Commissural Pyramidal Neuron in the Rat Anterior Cingulate Cortex after Chronic Constriction Injury to the Sciatic Nerve. Anesthesiology 2017; 127:515-533. [PMID: 28422818 DOI: 10.1097/aln.0000000000001654] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Abstract
Background
Inhibition of the metabotropic glutamate receptor subtype 1 in the anterior cingulate cortex has an analgesic effect during sustained nociceptive hypersensitivity. However, the specific changes in different subtypes of anterior cingulate cortex layer 5 pyramidal neurons, as well as the distinct effect of metabotropic glutamate receptor subtype 1 inhibition on different neuronal subtypes, have not been well studied.
Methods
Retrograde labeling combined with immunofluorescence, whole cell clamp recording, and behavioral tests combined with RNA interference were performed in a rat model of chronic constriction injury to the sciatic nerve.
Results
Commissural layer 5 pyramidal neurons (projecting to the contralateral cortex) existed in the anterior cingulate cortex. The voltage-gated potassium channel subunit 2–mediated current in these neurons were substantially reduced after chronic constriction injury (current densities at +30 mV for the sham, and chronic constriction injury neurons were [mean ± SD] 10.22 ± 3.42 pA/pF vs. 5.58 ± 2.71 pA/pF, respectively; n = 11; P < 0.01), which increased the spike width and fast afterhyperpolarization potential, resulting in hyperexcitability. Inhibition of metabotropic glutamate receptor subtype 1 alleviated the down-regulation of voltage-gated potassium channel subunit 2 currents (current density increased by 8.11 ± 3.22 pA/pF; n = 7; P < 0.01). Furthermore, knockdown of voltage-gated potassium channel subunit 2 current in the commissural neurons attenuated the analgesic effect of metabotropic glutamate receptor subtype 1 inhibition (n = 6 rats; P < 0.05).
Conclusions
The effect of metabotropic glutamate receptor subtype 1 inhibition on commissural anterior cingulate cortex layer 5 pyramidal neurons is likely different with the modification of previously studied hyperpolarization-activated/cyclic nucleotide-gated channel-dependent neurons but relies on the alteration of voltage-gated potassium channel subunit 2 currents. These results will contribute to a better understanding of the therapeutic role of metabotropic glutamate receptor subtype 1 in chronic pain.
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33
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Justice JA, Schulien AJ, He K, Hartnett KA, Aizenman E, Shah NH. Disruption of K V2.1 somato-dendritic clusters prevents the apoptogenic increase of potassium currents. Neuroscience 2017; 354:158-167. [PMID: 28461216 DOI: 10.1016/j.neuroscience.2017.04.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 03/01/2017] [Accepted: 04/21/2017] [Indexed: 12/27/2022]
Abstract
As the predominant mediator of the delayed rectifier current, KV2.1 is an important regulator of neuronal excitability. KV2.1, however, also plays a well-established role in apoptotic cell death. Apoptogenic stimuli induce syntaxin-dependent trafficking of KV2.1, resulting in an augmented delayed rectifier current that acts as a conduit for K+ efflux required for pro-apoptotic protease/nuclease activation. Recent evidence suggests that KV2.1 somato-dendritic clusters regulate the formation of endoplasmic reticulum-plasma membrane junctions that function as scaffolding sites for plasma membrane trafficking of ion channels, including KV2.1. However, it is unknown whether KV2.1 somato-dendritic clusters are required for apoptogenic trafficking of KV2.1. By overexpression of a protein derived from the C-terminus of the cognate channel KV2.2 (KV2.2CT), we induced calcineurin-independent disruption of KV2.1 somato-dendritic clusters in rat cortical neurons, without altering the electrophysiological properties of the channel. We observed that KV2.2CT-expressing neurons are less susceptible to oxidative stress-induced cell death. Critically, expression of KV2.2CT effectively blocked the increased current density of the delayed rectifier current associated with oxidative injury, supporting a vital role of KV2.1-somato-dendritic clusters in apoptogenic increases in KV2.1-mediated currents.
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Affiliation(s)
- Jason A Justice
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
| | - Anthony J Schulien
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Kai He
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Karen A Hartnett
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Elias Aizenman
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Niyathi H Shah
- Department of Neurobiology and Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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Dougalis AG, Matthews GAC, Liss B, Ungless MA. Ionic currents influencing spontaneous firing and pacemaker frequency in dopamine neurons of the ventrolateral periaqueductal gray and dorsal raphe nucleus (vlPAG/DRN): A voltage-clamp and computational modelling study. J Comput Neurosci 2017; 42:275-305. [PMID: 28367595 PMCID: PMC5403876 DOI: 10.1007/s10827-017-0641-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 10/28/2016] [Accepted: 03/13/2017] [Indexed: 01/31/2023]
Abstract
Dopamine (DA) neurons of the ventrolateral periaqueductal gray (vlPAG) and dorsal raphe nucleus (DRN) fire spontaneous action potentials (APs) at slow, regular patterns in vitro but a detailed account of their intrinsic membrane properties responsible for spontaneous firing is currently lacking. To resolve this, we performed a voltage-clamp electrophysiological study in brain slices to describe their major ionic currents and then constructed a computer model and used simulations to understand the mechanisms behind autorhythmicity in silico. We found that vlPAG/DRN DA neurons exhibit a number of voltage-dependent currents activating in the subthreshold range including, a hyperpolarization-activated cation current (IH), a transient, A-type, potassium current (IA), a background, ‘persistent’ (INaP) sodium current and a transient, low voltage activated (LVA) calcium current (ICaLVA). Brain slice pharmacology, in good agreement with computer simulations, showed that spontaneous firing occurred independently of IH, IA or calcium currents. In contrast, when blocking sodium currents, spontaneous firing ceased and a stable, non-oscillating membrane potential below AP threshold was attained. Using the DA neuron model we further show that calcium currents exhibit little activation (compared to sodium) during the interspike interval (ISI) repolarization while, any individual potassium current alone, whose blockade positively modulated AP firing frequency, is not required for spontaneous firing. Instead, blockade of a number of potassium currents simultaneously is necessary to eliminate autorhythmicity. Repolarization during ISI is mediated initially via the deactivation of the delayed rectifier potassium current, while a sodium background ‘persistent’ current is essentially indispensable for autorhythmicity by driving repolarization towards AP threshold.
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Affiliation(s)
- Antonios G Dougalis
- MRC London Institute of Medical Sciences (LMS), Du Cane Road, London, W12 0NN, UK.,Institute of Clinical Sciences (ICS), Imperial College London, Faculty of Medicine, Du Cane Road, London, W12 0NN, UK.,Institute of Applied Physiology, University of Ulm, Faculty of Medicine, 89073, Ulm, Germany
| | - Gillian A C Matthews
- MRC London Institute of Medical Sciences (LMS), Du Cane Road, London, W12 0NN, UK.,Institute of Clinical Sciences (ICS), Imperial College London, Faculty of Medicine, Du Cane Road, London, W12 0NN, UK.,Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Birgit Liss
- Institute of Applied Physiology, University of Ulm, Faculty of Medicine, 89073, Ulm, Germany
| | - Mark A Ungless
- MRC London Institute of Medical Sciences (LMS), Du Cane Road, London, W12 0NN, UK. .,Institute of Clinical Sciences (ICS), Imperial College London, Faculty of Medicine, Du Cane Road, London, W12 0NN, UK.
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35
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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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36
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Wang HY, Wang W, Liu YW, Li MY, Liang TY, Li JY, Hu HM, Lu Y, Yao C, Ye YY, Wang YZ, Zhang SZ. Role of KCNB1 in the prognosis of gliomas and autophagy modulation. Sci Rep 2017; 7:14. [PMID: 28144039 PMCID: PMC5428316 DOI: 10.1038/s41598-017-00045-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 12/20/2016] [Indexed: 12/13/2022] Open
Abstract
Increasing evidence suggests that ion channel genes play an important role in the progression of gliomas. However, the mechanisms by which ion channel genes influence the progression of glioma are not fully understood. We identified KCNB1 as a novel ion gene, associated with malignant progression and favorable overall survival (OS) and progression-free survival (PFS) in glioma patients from three datasets (CGGA, GSE16011 and REMBRANDT). Moreover, we characterized a novel function of autophagy induction accompanied by increased apoptosis and reduced proliferation and invasion of glioma cells for KCNB1. KEGG pathway analysis and in vitro studies suggested that the ERK pathway is involved in KCNB1-mediated regulation of autophagy, which was confirmed by inhibition of KCNB1-induced autophagy by using a selective ERK1/2 inhibitor (U0126) or siERK1/2. In vivo studies showed that KCNB1 induced autophagy while inhibiting tumor growth and increasing survival. Overall, our studies define KCNB1 as a novel prognostic factor for gliomas that exerts its tumor suppressive function through autophagy induction.
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Affiliation(s)
- Hao-Yuan Wang
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Chinese Glioma Cooperative Group (CGCG), Beijing, China
| | - Wen Wang
- Chinese Glioma Cooperative Group (CGCG), Beijing, China.,Department of Neurosurgery, The Second Affiliated Hospital of Soochow University, Suzhou, China.,Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Yan-Wei Liu
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Chinese Glioma Cooperative Group (CGCG), Beijing, China.,Department of Radiation Therapy, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Ming-Yang Li
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Chinese Glioma Cooperative Group (CGCG), Beijing, China.,Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Ting-Yu Liang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Chinese Glioma Cooperative Group (CGCG), Beijing, China
| | - Ji-Ye Li
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Hui-Min Hu
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China.,Chinese Glioma Cooperative Group (CGCG), Beijing, China
| | - Yang Lu
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Chen Yao
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Yong-Yi Ye
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.,The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Yong-Zhi Wang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, China. .,Chinese Glioma Cooperative Group (CGCG), Beijing, China. .,Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
| | - Shi-Zhong Zhang
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China. .,The National Key Clinical Specialty, The Engineering Technology Research Center of Education Ministry of China Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
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37
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Hönigsperger C, Nigro MJ, Storm JF. Physiological roles of Kv2 channels in entorhinal cortex layer II stellate cells revealed by Guangxitoxin-1E. J Physiol 2017; 595:739-757. [PMID: 27562026 PMCID: PMC5285721 DOI: 10.1113/jp273024] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Accepted: 08/19/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Kv2 channels underlie delayed-rectifier potassium currents in various neurons, although their physiological roles often remain elusive. Almost nothing is known about Kv2 channel functions in medial entorhinal cortex (mEC) neurons, which are involved in representing space, memory formation, epilepsy and dementia. Stellate cells in layer II of the mEC project to the hippocampus and are considered to be space-representing grid cells. We used the new Kv2 blocker Guangxitoxin-1E (GTx) to study Kv2 functions in these neurons. Voltage clamp recordings from mEC stellate cells in rat brain slices showed that GTx inhibited delayed-rectifier K+ current but not transient A-type current. In current clamp, GTx had multiple effects: (i) increasing excitability and bursting at moderate spike rates but reducing firing at high rates; (ii) enhancing after-depolarizations; (iii) reducing the fast and medium after-hyperpolarizations; (iv) broadening action potentials; and (v) reducing spike clustering. GTx is a useful tool for studying Kv2 channels and their functions in neurons. ABSTRACT The medial entorhinal cortex (mEC) is strongly involved in spatial navigation, memory, dementia and epilepsy. Although potassium channels shape neuronal activity, their roles in mEC are largely unknown. We used the new Kv2 blocker Guangxitoxin-1E (GTx; 10-100 nm) in rat brain slices to investigate Kv2 channel functions in mEC layer II stellate cells (SCs). These neurons project to the hippocampus and are considered to be grid cells representing space. Voltage clamp recordings from SCs nucleated patches showed that GTx inhibited a delayed rectifier K+ current activating beyond -30 mV but not transient A-type current. In current clamp, GTx (i) had almost no effect on the first action potential but markedly slowed repolarization of late spikes during repetitive firing; (ii) enhanced the after-depolarization (ADP); (iii) reduced fast and medium after-hyperpolarizations (AHPs); (iv) strongly enhanced burst firing and increased excitability at moderate spike rates but reduced spiking at high rates; and (v) reduced spike clustering and rebound potentials. The changes in bursting and excitability were related to the altered ADPs and AHPs. Kv2 channels strongly shape the activity of mEC SCs by affecting spike repolarization, after-potentials, excitability and spike patterns. GTx is a useful tool and may serve to further clarify Kv2 channel functions in neurons. We conclude that Kv2 channels in mEC SCs are important determinants of intrinsic properties that allow these neurons to produce spatial representation. The results of the present study may also be important for the accurate modelling of grid cells.
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Affiliation(s)
| | - Maximiliano J. Nigro
- Department of PhysiologyInstitute of Basal Medical SciencesUniversity of OsloOsloNorway
- Department of Physiology and NeuroscienceNeuroscience InstituteNew York UniversityNew York, NYUSA
| | - Johan F. Storm
- Department of PhysiologyInstitute of Basal Medical SciencesUniversity of OsloOsloNorway
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38
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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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Zhang YZ, Zhang R, Zeng XZ, Song CY. The inhibitory effect of propofol on Kv2.1 potassium channel in rat parietal cortical neurons. Neurosci Lett 2016; 616:93-7. [PMID: 26828304 DOI: 10.1016/j.neulet.2016.01.058] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 12/24/2015] [Accepted: 01/26/2016] [Indexed: 11/16/2022]
Abstract
Excessive K(+) efflux via activated voltage-gated K(+) channels can deplete intracellular K(+) and lead to long-lasting membrane depolarization which will promote neuronal apoptosis during ischemia/hypoxia injury. The Kv2.1 potassium channel was the major component of delayed rectifier potassium current (Ik) in pyramidal neurons in cortex and hippocampus. The neuronal protective effect of propofol has been proved. Delayed rectifier potassium current (Ik) has been shown to have close relationship with neuronal damage. The study was designed to test the inhibitory effect of propofol on Kv2.1 potassium channel in rat parietal cortical neurons. Whole-cell patch clamp recordings and Western blot analysis were used to investigate the electrophysiological function and protein expression of Kv2.1 in rat parietal cortical neurons after propofol treatment. We found that propofol concentration-dependently inhibited Ik in pyramidal neurons. Propofol also caused a downward shift of the I-V curve of Ik at 30μM concentration. Propofol significantly inhibited the expression of Kv2.1 protein level at 30μM, 50μM, 100μM concentration. In conclusion, our data showed that propofol could inhibit Ik, probably via depressing the expression of Kv2.1 protein in rat cerebral parietal cortical neurons.
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Affiliation(s)
- Yan-Zhuo Zhang
- Department of Anesthesiology, China and Heilongjiang Key Laboratory for Anesthesia and Critical Care, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, China
| | - Rui Zhang
- Department of Anesthesiology, China and Heilongjiang Key Laboratory for Anesthesia and Critical Care, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, China
| | - Xian-Zhang Zeng
- Department of Anesthesiology, China and Heilongjiang Key Laboratory for Anesthesia and Critical Care, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, China
| | - Chun-Yu Song
- Department of Anesthesiology, China and Heilongjiang Key Laboratory for Anesthesia and Critical Care, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, China.
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40
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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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41
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Kitamura N, Sakamoto K, Ono T, Kimura J. THE INHIBITORY EFFECT OF PACLITAXEL ON (Kv2.1) K+ CURRENT IN H9c2 CELLS. Fukushima J Med Sci 2015; 61:47-53. [PMID: 25994081 DOI: 10.5387/fms.2014-34] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Using the whole-cell voltage clamp technique, we investigated the effect of paclitaxel, an anticancer agent which promotes microtubule formation, on K(+) current in H9c2 cells originated from rat embryonic cardiac myocytes. Paclitaxel inhibited Kv2.1 voltage-dependent K(+) current (IKur) with ultra-rapidly activating and slowly inactivating kinetics in a concentration-dependent manner. The inhibitory effect of paclitaxel on IKur was time-dependent and more marked at 200 ms after the onset than at the beginning of the depolarizing pulse. The IC50 value of paclitaxel was 1.1 µM at 200 ms. The time-dependent inhibition suggests that paclitaxel might be an open channel blocker of Kv2.1. This inhibition of Kv2.1 may be involved in the adverse effects of paclitaxel on cardiac and neuronal cells.
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Affiliation(s)
- Naoko Kitamura
- Department of Pharmacology, Fukushima Medical University, School of Medicine
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42
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Angel-Chavez LI, Acosta-Gómez EI, Morales-Avalos M, Castro E, Cruzblanca H. Forskolin suppresses delayed-rectifier K+ currents and enhances spike frequency-dependent adaptation of sympathetic neurons. PLoS One 2015; 10:e0126365. [PMID: 25962132 PMCID: PMC4427186 DOI: 10.1371/journal.pone.0126365] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/01/2015] [Indexed: 11/30/2022] Open
Abstract
In signal transduction research natural or synthetic molecules are commonly used to target a great variety of signaling proteins. For instance, forskolin, a diterpene activator of adenylate cyclase, has been widely used in cellular preparations to increase the intracellular cAMP level. However, it has been shown that forskolin directly inhibits some cloned K+ channels, which in excitable cells set up the resting membrane potential, the shape of action potential and regulate repetitive firing. Despite the growing evidence indicating that K+ channels are blocked by forskolin, there are no studies yet assessing the impact of this mechanism of action on neuron excitability and firing patterns. In sympathetic neurons, we find that forskolin and its derivative 1,9-Dideoxyforskolin, reversibly suppress the delayed rectifier K+ current (IKV). Besides, forskolin reduced the spike afterhyperpolarization and enhanced the spike frequency-dependent adaptation. Given that IKV is mostly generated by Kv2.1 channels, HEK-293 cells were transfected with cDNA encoding for the Kv2.1 α subunit, to characterize the mechanism of forskolin action. Both drugs reversible suppressed the Kv2.1-mediated K+ currents. Forskolin inhibited Kv2.1 currents and IKV with an IC50 of ~32 μM and ~24 µM, respectively. Besides, the drug induced an apparent current inactivation and slowed-down current deactivation. We suggest that forskolin reduces the excitability of sympathetic neurons by enhancing the spike frequency-dependent adaptation, partially through a direct block of their native Kv2.1 channels.
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Affiliation(s)
- Luis I. Angel-Chavez
- Departamento de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Ciudad Juárez, Chih. 32310, México
| | - Eduardo I. Acosta-Gómez
- Departamento de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Ciudad Juárez, Ciudad Juárez, Chih. 32310, México
| | - Mario Morales-Avalos
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
| | - Elena Castro
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
| | - Humberto Cruzblanca
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Col. 28045, México
- * E-mail:
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Li XT, Li XQ, Hu XM, Qiu XY. The Inhibitory Effects of Ca2+ Channel Blocker Nifedipine on Rat Kv2.1 Potassium Channels. PLoS One 2015; 10:e0124602. [PMID: 25893973 PMCID: PMC4404097 DOI: 10.1371/journal.pone.0124602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/04/2015] [Indexed: 11/26/2022] Open
Abstract
It is well documented that nifedipine, a commonly used dihydropyridine Ca2+ channel blocker, has also significant interactions with voltage-gated K+ (Kv) channels. But to date, little is known whether nifedipine exerted an action on Kv2.1 channels, a member of the Shab subfamily with slow inactivation. In the present study, we explored the effects of nifedipine on rat Kv2.1 channels expressed in HEK293 cells. Data from whole-cell recording showed that nifedipine substantially reduced Kv2.1 currents with the IC50 value of 37.5 ± 5.7 μM and delayed the time course of activation without effects on the activation curve. Moreover, this drug also significantly shortened the duration of inactivation and deactivation of Kv2.1 currents in a voltage-dependent manner. Interestingly, the half-maximum inactivation potential (V1/2) of Kv2.1 currents was -11.4 ± 0.9 mV in control and became -38.5 ± 0.4 mV after application of 50 μM nifedipine. The large hyperpolarizing shift (27 mV) of the inactivation curve has not been reported previously and may result in more inactivation for outward delayed rectifier K+ currents mediated by Kv2.1 channels at repolarization phases. The Y380R mutant significantly increased the binding affinity of nifedipine to Kv2.1 channels, suggesting an interaction of nifedipine with the outer mouth region of this channel. The data present here will be helpful to understand the diverse effects exerted by nifedipine on various Kv channels.
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Affiliation(s)
- Xian-Tao Li
- Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, China
- * E-mail:
| | - Xiao-Qing Li
- Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, China
| | - Xi-Mu Hu
- South-Central University for Nationalities, Wuhan, China
| | - Xiao-Yue Qiu
- South-Central University for Nationalities, Wuhan, China
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Peers C, Boyle JP. Oxidative modulation of K+ channels in the central nervous system in neurodegenerative diseases and aging. Antioxid Redox Signal 2015; 22:505-21. [PMID: 25333910 DOI: 10.1089/ars.2014.6007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
SIGNIFICANCE Oxidative stress and damage are well-established components of neurodegenerative diseases, contributing to neuronal death during disease progression. Here, we consider key K(+) channels as target proteins that can undergo oxidative modulation, describe what is understood about how this influences disease progression, and consider regulation of these channels by gasotransmitters as a means of cellular protection. RECENT ADVANCES Oxidative regulation of the delayed rectifier Kv2.1 and the Ca(2+)- and voltage-sensitive BK channel are established, but recent studies contest how their redox sensitivity contributes to altered excitability, progression of neurodegenerative diseases, and healthy aging. CRITICAL ISSUES Both Kv2.1 and BK channels have recently been established as target proteins for regulation by the gasotransmitters carbon monoxide and hydrogen sulfide. Establishing the molecular basis of such regulation, and exactly how this influences excitability and vulnerability to apoptotic cell death will determine whether such regulation can be exploited for therapeutic benefit. FUTURE DIRECTIONS Developing a more comprehensive picture of the oxidative modulation of K(+) channels (and, indeed, other ion channels) within the central nervous system in health and disease will enable us to better understand processes associated with healthy aging as well as distinct processes underlying progression of neurodegenerative diseases. Advances in the growing understanding of how gasotransmitters can regulate ion channels, including redox-sensitive K(+) channels, are a research priority for this field, and will establish their usefulness in design of future approaches for the treatment of such diseases.
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Affiliation(s)
- Chris Peers
- Division of Cardiovascular and Diabetes Research, Leeds Institute of Cardiovascular and Metabolic Medicine (LICAMM), Faculty of Medicine and Health, University of Leeds , Leeds, United Kingdom
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Springer MG, Kullmann PHM, Horn JP. Virtual leak channels modulate firing dynamics and synaptic integration in rat sympathetic neurons: implications for ganglionic transmission in vivo. J Physiol 2014; 593:803-23. [PMID: 25398531 DOI: 10.1113/jphysiol.2014.284125] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 11/04/2014] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS The synaptic organization of paravertebral sympathetic ganglia enables them to relay activity from the spinal cord to the periphery and thereby control autonomic functions, including blood pressure and body temperature. The present experiments were done to reconcile conflicting observations in tissue culture, intact isolated ganglia and living animals. By recording intracellularly from dissociated neurons and intact ganglia, we found that when electrode damage makes cells leaky it could profoundly distort cellular excitability and the integration of synaptic potentials. The experiments relied on the dynamic clamp method, which allows the creation of virtual ion channels by injecting current into a cell based upon a mathematical model and using rapid feedback between the model and cell. The results support the hypothesis that sympathetic ganglia can produce a 2.4-fold amplification of presynaptic activity. This could aid understanding of the neural hyperactivity that is believed to drive high blood pressure in some patients. ABSTRACT The excitability of rat sympathetic neurons and integration of nicotinic EPSPs were compared in primary cell culture and in the acutely isolated intact superior cervical ganglion using whole cell patch electrode recordings. When repetitive firing was classified by Hodgkin's criteria in cultured cells, 18% displayed tonic class 1 excitability, 36% displayed adapting class 2 excitability and 46% displayed phasic class 3 excitability. In the intact ganglion, 71% of cells were class 1 and 29% were class 2. This diverges from microelectrode reports that nearly 100% of superior cervical ganglion neurons show phasic class 3 firing. The hypothesis that the disparity between patch and microelectrode data arises from a shunt conductance was tested using the dynamic clamp in cell culture. Non-depolarizing shunts of 3-10 nS converted cells from classes 1 and 2 to class 3 dynamics with current-voltage relations that replicated microelectrode data. Primary and secondary EPSPs recorded from the intact superior cervical ganglion were modelled as virtual synapses in cell culture using the dynamic clamp. Stimulating sympathetic neurons with virtual synaptic activity, designed to replicate in vivo recordings of EPSPs in muscle vasoconstrictor neurons, produced a 2.4-fold amplification of presynaptic activity. This gain in postsynaptic output did not differ between neurons displaying the three classes of excitability. Mimicry of microelectrode damage by virtual leak channels reduced and eventually obliterated synaptic gain by inhibiting summation of subthreshold EPSPs. These results provide a framework for interpreting sympathetic activity recorded from intact animals and support the hypothesis that paravertebral ganglia function as activity-dependent amplifiers of spinal output from preganglionic circuitry.
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Affiliation(s)
- Mitchell G Springer
- Department of Neurobiology and Center for Neuroscience, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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Domain Structure and Conformational Changes in rat KV2.1 ion Channel. J Neuroimmune Pharmacol 2014; 9:727-39. [DOI: 10.1007/s11481-014-9565-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 09/03/2014] [Indexed: 01/26/2023]
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Wang W, Wang Y, Zhang C, Sun M, Zhu X. Effect of sodium ferulate on delayed rectifier K + currents in PC12 cells. Exp Ther Med 2014; 8:983-987. [PMID: 25120634 PMCID: PMC4113652 DOI: 10.3892/etm.2014.1806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 06/03/2014] [Indexed: 11/14/2022] Open
Abstract
In order to investigate the effect of sodium ferulate (SF) on voltage-activated K+ channels, the delayed rectifier K+ current (Ik) in PC12 rat pheochromocytoma cells was recorded using the automated patch-clamp method. The results indicated that following the application of SF, the Ik in PC12 cells was significantly decreased in a concentration-dependent manner. The analysis of activation kinetic curves and inactivation kinetic curves of Ik showed that SF had an effect on the activation and inactivation kinetics. Following the application of 15.3 μM SF, the activation curve of the Ik of PC12 cells was shifted to positive potentials and the inactivation curve of the Ik of PC12 cells was shifted to negative potentials. This study revealed that the delayed rectifier K+ currents of PC12 cells were inhibited following SF treatment in a concentration-dependent manner. The mechanism may be associated with the delayed activation and enhanced inactivation of Ik-associated channels.
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Affiliation(s)
- Wei Wang
- Basic Medical Department, School of Pharmacy, Yantai University, Yantai, Shandong 264005, P.R. China
| | - Yuyun Wang
- Basic Medical Department, School of Pharmacy, Yantai University, Yantai, Shandong 264005, P.R. China
| | - Chunlei Zhang
- Basic Medical Department, School of Pharmacy, Yantai University, Yantai, Shandong 264005, P.R. China
| | - Mengmeng Sun
- Basic Medical Department, School of Pharmacy, Yantai University, Yantai, Shandong 264005, P.R. China
| | - Xiaoyin Zhu
- Basic Medical Department, School of Pharmacy, Yantai University, Yantai, Shandong 264005, P.R. China
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Effects of SKF83959 on the excitability of hippocampal CA1 pyramidal neurons: a modeling study. Acta Pharmacol Sin 2014; 35:738-51. [PMID: 24858313 DOI: 10.1038/aps.2014.23] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 03/03/2014] [Indexed: 12/31/2022] Open
Abstract
AIM 3-Methyl-6-chloro-7,8-hydroxy-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959) have been shown to affect several types of voltage-dependent channels in hippocampal pyramidal neurons. The aim of this study was to determine how modulation of a individual type of the channels by SKF83959 contributes to the overall excitability of CA1 pyramidal neurons during either direct current injections or synaptic activation. METHODS Rat hippocampal slices were prepared. The kinetics of voltage-dependent Na(+) channels and neuronal excitability and depolarization block in CA1 pyramidal neurons were examined using whole-cell recording. A realistic mathematical model of hippocampal CA1 pyramidal neuron was used to simulate the effects of SKF83959 on neuronal excitability. RESULTS SKF83959 (50 μmol/L) shifted the inactivation curve of Na(+) current by 10.3 mV but had no effect on the activation curve in CA1 pyramidal neurons. The effects of SKF83959 on passive membrane properties, including a decreased input resistance and depolarized resting potential, predicted by our simulations were in agreement with the experimental data. The simulations showed that decreased excitability of the soma by SKF83959 (examined with current injection at the soma) was only observed when the membrane potential was compensated to the control levels, whereas the decreased dendritic excitability (examined with current injection at the dendrite) was found even without membrane potential compensation, which led to a decreased number of action potentials initiated at the soma. Moreover, SKF83959 significantly facilitated depolarization block in CA1 pyramidal neurons. SKF83959 decreased EPSP temporal summation and, of physiologically greater relevance, the synaptic-driven firing frequency. CONCLUSION SKF83959 decreased the excitability of CA1 pyramidal neurons even though the drug caused the membrane potential depolarization. The results may reveal a partial mechanism for the drug's anti-Parkinsonian effects and may also suggest that SKF83959 has a potential antiepileptic effect.
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Frolov RV, Singh S. Celecoxib and ion channels: a story of unexpected discoveries. Eur J Pharmacol 2014; 730:61-71. [PMID: 24630832 DOI: 10.1016/j.ejphar.2014.02.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 01/28/2014] [Accepted: 02/18/2014] [Indexed: 10/25/2022]
Abstract
Celecoxib (Celebrex), a highly popular selective inhibitor of cyclooxygenase-2, can modulate ion channels and alter functioning of neurons and myocytes at clinically relevant concentrations independently of cyclooxygenase inhibition. In experimental systems varying from Drosophila to primary mammalian and human cell lines, celecoxib inhibits many voltage-activated Na(+), Ca(2+), and K(+) channels, including NaV1.5, L- and T-type Ca(2+) channels, KV1.5, KV2.1, KV4.3, KV7.1, KV11.1 (hERG), while stimulating other K(+) channels-KV7.2-5 and, possibly, KV11.1 (hERG) channels under certain conditions. In this review, we summarize the information currently available on the effects of celecoxib on ion channels, examine mechanistic aspects of drug action and the concomitant changes at the cellular and organ levels, and discuss these findings in the therapeutic context.
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Affiliation(s)
- Roman V Frolov
- Department of Physical Sciences, Division of Biophysics, University of Oulu, PO Box 3000, 90014 Oulun Yliopisto, Finland.
| | - Satpal Singh
- Department of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, NY 14214, USA
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Kirizs T, Kerti-Szigeti K, Lorincz A, Nusser Z. Distinct axo-somato-dendritic distributions of three potassium channels in CA1 hippocampal pyramidal cells. Eur J Neurosci 2014; 39:1771-83. [PMID: 24606584 PMCID: PMC4150533 DOI: 10.1111/ejn.12526] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 01/24/2014] [Accepted: 01/27/2014] [Indexed: 12/21/2022]
Abstract
Potassium channels comprise the most diverse family of ion channels and play critical roles in a large variety of physiological and pathological processes. In addition to their molecular diversity, variations in their distributions and densities on the axo-somato-dendritic surface of neurons are key parameters in determining their functional impact. Despite extensive electrophysiological and anatomical investigations, the exact location and densities of most K+ channels in small subcellular compartments are still unknown. Here we aimed at providing a quantitative surface map of two delayed-rectifier (Kv1.1 and Kv2.1) and one G-protein-gated inwardly rectifying (Kir3.2) K+ channel subunits on hippocampal CA1 pyramidal cells (PCs). Freeze-fracture replica immunogold labelling was employed to determine the relative densities of these K+ channel subunits in 18 axo-somato-dendritic compartments. Significant densities of the Kv1.1 subunit were detected on axon initial segments (AISs) and axon terminals, with an approximately eight-fold lower density in the latter compartment. The Kv2.1 subunit was found in somatic, proximal dendritic and AIS plasma membranes at approximately the same densities. This subunit has a non-uniform plasma membrane distribution; Kv2.1 clusters are frequently adjacent to, but never overlap with, GABAergic synapses. A quasi-linear increase in the Kir3.2 subunit density along the dendrites of PCs was detected, showing no significant difference between apical dendritic shafts, oblique dendrites or dendritic spines at the same distance from the soma. Our results demonstrate that each subunit has a unique cell-surface distribution pattern, and predict their differential involvement in synaptic integration and output generation at distinct subcellular compartments.
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Affiliation(s)
- Tekla Kirizs
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony Street 43, Budapest, Hungary
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