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Ray S, Stampf JL, Kudlacek O, Yang JW, Schicker KW, Graf Y, Losgott T, Boehm S, Salzer I. A triple cysteine motif as major determinant of the modulation of neuronal K V7 channels by the paracetamol metabolite N-acetyl-p-benzo quinone imine. Br J Pharmacol 2024; 181:2851-2868. [PMID: 38657956 DOI: 10.1111/bph.16380] [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: 10/20/2023] [Revised: 02/19/2024] [Accepted: 03/10/2024] [Indexed: 04/26/2024] Open
Abstract
BACKGROUND AND PURPOSE The analgesic action of paracetamol involves KV7 channels, and its metabolite N-acetyl-p-benzo quinone imine (NAPQI), a cysteine modifying reagent, was shown to increase currents through such channels in nociceptors. Modification of cysteine residues by N-ethylmaleimide, H2O2, or nitric oxide has been found to modulate currents through KV7 channels. The study aims to identify whether, and if so which, cysteine residues in neuronal KV7 channels might be responsible for the effects of NAPQI. EXPERIMENTAL APPROACH To address this question, we used a combination of perforated patch-clamp recordings, site-directed mutagenesis, and mass spectrometry applied to recombinant KV7.1 to KV7.5 channels. KEY RESULTS Currents through the cardiac subtype KV7.1 were reduced by NAPQI. Currents through all other subtypes were increased, either by an isolated shift of the channel voltage dependence to more negative values (KV7.3) or by such a shift combined with increased maximal current levels (KV7.2, KV7.4, KV7.5). A stretch of three cysteine residues in the S2-S3 linker region of KV7.2 was necessary and sufficient to mediate these effects. CONCLUSION AND IMPLICATION The paracetamol metabolite N-acetyl-p-benzo quinone imine (NAPQI) modifies cysteine residues of KV7 subunits and reinforces channel gating in homomeric and heteromeric KV7.2 to KV7.5, but not in KV7.1 channels. In KV7.2, a triple cysteine motif located within the S2-S3 linker region mediates this reinforcement that can be expected to reduce the excitability of nociceptors and to mediate antinociceptive actions of paracetamol.
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Affiliation(s)
- Sutirtha Ray
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jan-Luca Stampf
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Oliver Kudlacek
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Klaus W Schicker
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Yvonne Graf
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Thomas Losgott
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Stefan Boehm
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Isabella Salzer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Graziano B, Wang L, White OR, Kaplan DH, Fernandez-Abascal J, Bianchi L. Glial KCNQ K + channels control neuronal output by regulating GABA release from glia in C. elegans. Neuron 2024; 112:1832-1847.e7. [PMID: 38460523 PMCID: PMC11156561 DOI: 10.1016/j.neuron.2024.02.013] [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: 10/04/2023] [Revised: 01/22/2024] [Accepted: 02/16/2024] [Indexed: 03/11/2024]
Abstract
KCNQs are voltage-gated K+ channels that control neuronal excitability and are mutated in epilepsy and autism spectrum disorder (ASD). KCNQs have been extensively studied in neurons, but their function in glia is unknown. Using voltage, calcium, and GABA imaging, optogenetics, and behavioral assays, we show here for the first time in Caenorhabditis elegans (C. elegans) that glial KCNQ channels control neuronal excitability by mediating GABA release from glia via regulation of the function of L-type voltage-gated Ca2+ channels. Further, we show that human KCNQ channels have the same role when expressed in nematode glia, underscoring conservation of function across species. Finally, we show that pathogenic loss-of-function and gain-of-function human KCNQ2 mutations alter glia-to-neuron GABA signaling in distinct ways and that the KCNQ channel opener retigabine exerts rescuing effects. This work identifies glial KCNQ channels as key regulators of neuronal excitability via control of GABA release from glia.
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Affiliation(s)
- Bianca Graziano
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Lei Wang
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Olivia R White
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Daryn H Kaplan
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Jesus Fernandez-Abascal
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA
| | - Laura Bianchi
- Department Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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3
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Liu E, Pang K, Liu M, Tan X, Hang Z, Mu S, Han W, Yue Q, Comai S, Sun J. Activation of Kv7 channels normalizes hyperactivity of the VTA-NAcLat circuit and attenuates methamphetamine-induced conditioned place preference and sensitization in mice. Mol Psychiatry 2023; 28:5183-5194. [PMID: 37604975 DOI: 10.1038/s41380-023-02218-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 08/02/2023] [Accepted: 08/04/2023] [Indexed: 08/23/2023]
Abstract
The brain circuit projecting from the ventral tegmental area (VTA) to the nucleus accumbens lateral shell (NAcLat) has a key role in methamphetamine (MA) addiction. As different dopamine (DA) neuron subpopulations in the VTA participate in different neuronal circuits, it is a challenge to isolate these DA neuron subtypes. Using retrograde tracing and Patch-seq, we isolated DA neurons in the VTA-NAcLat circuit in MA-treated mice and performed gene expression profiling. Among the differentially expressed genes, KCNQ genes were dramatically downregulated. KCNQ genes encode Kv7 channel proteins, which modulate neuronal excitability. Injection of both the Kv7.2/3 agonist ICA069673 and the Kv7.4 agonist fasudil into the VTA attenuated MA-induced conditioned place preference and locomotor sensitization and decreased neuronal excitability. Increasing Kv7.2/3 activity decreased neural oscillations, synaptic plasticity and DA release in the VTA-NacLat circuit in MA-treated mice. Furthermore, overexpression of only Kv7.3 channels in the VTA-NacLat circuit was sufficient to attenuate MA-induced reward behavior and decrease VTA neuron excitability. Activation of Kv7 channels in the VTA may become a novel treatment strategy for MA abuse.
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Affiliation(s)
- E Liu
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Kunkun Pang
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
- Department of Ultrasound, The Second Hospital of Shandong University, Jinan, Shandong, China
| | - Min Liu
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Xu Tan
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Zhaofang Hang
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Shouhong Mu
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Weikai Han
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Qingwei Yue
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China
| | - Stefano Comai
- Department of Psychiatry, McGill University, Montréal, QC, Canada
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Jinhao Sun
- Department of Anatomy and Neurobiology, Shandong University School of Basic Medicine, Jinan, Shandong, China.
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Mészáros B, Csoti A, Szanto TG, Telek A, Kovács K, Toth A, Volkó J, Panyi G. The hEag1 K + Channel Inhibitor Astemizole Stimulates Ca 2+ Deposition in SaOS-2 and MG-63 Osteosarcoma Cultures. Int J Mol Sci 2022; 23:ijms231810533. [PMID: 36142445 PMCID: PMC9504018 DOI: 10.3390/ijms231810533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 08/27/2022] [Accepted: 09/06/2022] [Indexed: 11/29/2022] Open
Abstract
The hEag1 (Kv10.1) K+ channel is normally found in the brain, but it is ectopically expressed in tumor cells, including osteosarcoma. Based on the pivotal role of ion channels in osteogenesis, we tested whether pharmacological modulation of hEag1 may affect osteogenic differentiation of osteosarcoma cell lines. Using molecular biology (RT-PCR), electrophysiology (patch-clamp) and pharmacology (astemizole sensitivity, IC50 = 0.135 μM) we demonstrated that SaOS-2 osteosarcoma cells also express hEag1 channels. SaOS-2 cells also express to KCa1.1 K+ channels as shown by mRNA expression and paxilline sensitivity of the current. The inhibition of hEag1 (2 μM astemizole) or KCa1.1 (1 mM TEA) alone did not induce Ca2+ deposition in SaOS-2 cultures, however, these inhibitors, at identical concentrations, increased Ca2+ deposition evoked by the classical or pathological (inorganic phosphate, Pi) induction pathway without causing cytotoxicity, as reported by three completer assays (LDH release, MTT assay and SRB protein assay). We observed a similar effect of astemizole on Ca2+ deposition in MG-63 osteosarcoma cultures as well. We propose that the increase in the osteogenic stimuli-induced mineral matrix formation of osteosarcoma cell lines by inhibiting hEag1 may be a useful tool to drive terminal differentiation of osteosarcoma.
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Affiliation(s)
- Beáta Mészáros
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
- MTA-DE Cell Biology and Signaling Research Group, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Agota Csoti
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Tibor G. Szanto
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Andrea Telek
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Katalin Kovács
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Agnes Toth
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Julianna Volkó
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Life Science Building, Egyetem Ter 1, H-4032 Debrecen, Hungary
- Correspondence: ; Tel.: +36-52-258603; Fax: +36-52-532201
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5
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Baculis BC, Kesavan H, Weiss AC, Kim EH, Tracy GC, Ouyang W, Tsai NP, Chung HJ. Homeostatic regulation of extracellular signal-regulated kinase 1/2 activity and axonal K v7.3 expression by prolonged blockade of hippocampal neuronal activity. Front Cell Neurosci 2022; 16:838419. [PMID: 35966206 PMCID: PMC9366003 DOI: 10.3389/fncel.2022.838419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 07/04/2022] [Indexed: 11/17/2022] Open
Abstract
Homeostatic plasticity encompasses the mechanisms by which neurons stabilize their synaptic strength and excitability in response to prolonged and destabilizing changes in their network activity. Prolonged activity blockade leads to homeostatic scaling of action potential (AP) firing rate in hippocampal neurons in part by decreased activity of N-Methyl-D-Aspartate receptors and subsequent transcriptional down-regulation of potassium channel genes including KCNQ3 which encodes Kv7.3. Neuronal Kv7 channels are mostly heterotetramers of Kv7.2 and Kv7.3 subunits and are highly enriched at the axon initial segment (AIS) where their current potently inhibits repetitive and burst firing of APs. However, whether a decrease in Kv7.3 expression occurs at the AIS during homeostatic scaling of intrinsic excitability and what signaling pathway reduces KCNQ3 transcript upon prolonged activity blockade remain unknown. Here, we report that prolonged activity blockade in cultured hippocampal neurons reduces the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) followed by a decrease in the activation of brain-derived neurotrophic factor (BDNF) receptor, Tropomyosin receptor kinase B (TrkB). Furthermore, both prolonged activity blockade and prolonged pharmacological inhibition of ERK1/2 decrease KCNQ3 and BDNF transcripts as well as the density of Kv7.3 and ankyrin-G at the AIS. Collectively, our findings suggest that a reduction in the ERK1/2 activity and subsequent transcriptional down-regulation may serve as a potential signaling pathway that links prolonged activity blockade to homeostatic control of BDNF-TrkB signaling and Kv7.3 density at the AIS during homeostatic scaling of AP firing rate.
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Affiliation(s)
- Brian C. Baculis
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Harish Kesavan
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Amanda C. Weiss
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Edward H. Kim
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Gregory C. Tracy
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Wenhao Ouyang
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Nien-Pei Tsai
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
| | - Hee Jung Chung
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
- Institute of Genomic Biology, University of Illinois at Urbana-Champaign, Champaign, IL, United States
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6
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Liu S, Guo P, Wang K, Zhang S, Li Y, Shen J, Mei L, Ye Y, Zhang Q, Yang H. General Pharmacological Activation Mechanism of K + Channels Bypassing Channel Gates. J Med Chem 2022; 65:10285-10299. [PMID: 35878013 DOI: 10.1021/acs.jmedchem.1c02115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Under the known pharmacological activation mechanisms, activators allosterically or directly open potassium channel gates. However, herein, molecular dynamics simulations on TREK-1, a member of the channel class gated at the filter, suggested that negatively charged activators act with a gate-independent mechanism where compounds increase currents by promoting ions passing through the central cavity. Then, based on studies of KCNQ2, we uncovered that this noncanonical activation mechanism is shared by the other channel class gated at the helix-bundle crossing. Rational drug design found a novel KCNQ2 agonist, CLE030, which stably binds to the central cavity. Functional analysis, molecular dynamics simulations, and calculations of the potential of mean force revealed that the carbonyl oxygen of CLE030 influences permeant ions in the central cavity to contribute to its activation effects. Together, this study discovered a ligand-to-ion activation mechanism for channels that bypasses their gates and thus is conserved across subfamilies with different gates.
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Affiliation(s)
- Shijie Liu
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Peipei Guo
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Kun Wang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Shaoying Zhang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Ya Li
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Juwen Shen
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Lianghe Mei
- Suzhou Institute of Drug Innovation, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Suzhou, Jiangsu 215123, China
| | - Yangliang Ye
- Suzhou AlphaMa Biotechnology Co., Ltd., Suzhou, Jiangsu 215123, China
| | - Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, School of Life Sciences, East China Normal University, Shanghai 200241, China
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Mosca I, Rivolta I, Labalme A, Ambrosino P, Castellotti B, Gellera C, Granata T, Freri E, Binda A, Lesca G, DiFrancesco JC, Soldovieri MV, Taglialatela M. Functional Characterization of Two Variants at the Intron 6—Exon 7 Boundary of the KCNQ2 Potassium Channel Gene Causing Distinct Epileptic Phenotypes. Front Pharmacol 2022; 13:872645. [PMID: 35770094 PMCID: PMC9234691 DOI: 10.3389/fphar.2022.872645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/10/2022] [Indexed: 11/13/2022] Open
Abstract
Pathogenic variants in KCNQ2 encoding for Kv7.2 potassium channel subunits have been found in patients affected by widely diverging epileptic phenotypes, ranging from Self-Limiting Familial Neonatal Epilepsy (SLFNE) to severe Developmental and Epileptic Encephalopathy (DEE). Thus, understanding the pathogenic molecular mechanisms of KCNQ2 variants and their correlation with clinical phenotypes has a relevant impact on the clinical management of these patients. In the present study, the genetic, biochemical, and functional effects prompted by two variants, each found in a non-familial SLNE or a DEE patient but both affecting nucleotides at the KCNQ2 intron 6-exon 7 boundary, have been investigated to test whether and how they affected the splicing process and to clarify whether such mechanism might play a pathogenetic role in these patients. Analysis of KCNQ2 mRNA splicing in patient-derived lymphoblasts revealed that the SLNE-causing intronic variant (c.928-1G > C) impeded the use of the natural splice site, but lead to a 10-aa Kv7.2 in frame deletion (Kv7.2 p.G310Δ10); by contrast, the DEE-causing exonic variant (c.928G > A) only had subtle effects on the splicing process at this site, thus leading to the synthesis of a full-length subunit carrying the G310S missense variant (Kv7.2 p.G310S). Patch-clamp recordings in transiently-transfected CHO cells and primary neurons revealed that both variants fully impeded Kv7.2 channel function, and exerted strong dominant-negative effects when co-expressed with Kv7.2 and/or Kv7.3 subunits. Notably, Kv7.2 p.G310S, but not Kv7.2 p.G310Δ10, currents were recovered upon overexpression of the PIP2-synthesizing enzyme PIP5K, and/or CaM; moreover, currents from heteromeric Kv7.2/Kv7.3 channels incorporating either Kv7.2 mutant subunits were differentially regulated by changes in PIP2 availability, with Kv7.2/Kv7.2 G310S/Kv7.3 currents showing a greater sensitivity to PIP2 depletion when compared to those from Kv7.2/Kv7.2 G310Δ10/Kv7.3 channels. Altogether, these results suggest that the two variants investigated differentially affected the splicing process at the intron 6-exon 7 boundary, and led to the synthesis of Kv7.2 subunits showing a differential sensitivity to PIP2 and CaM regulation; more studies are needed to clarify how such different functional properties contribute to the widely-divergent clinical phenotypes.
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Affiliation(s)
- Ilaria Mosca
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
| | - Ilaria Rivolta
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Audrey Labalme
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Paolo Ambrosino
- Department of Science and Technology (DST), University of Sannio, Benevento, Italy
| | - Barbara Castellotti
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Cinzia Gellera
- Unit of Medical Genetics and Neurogenetics, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Tiziana Granata
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Elena Freri
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
| | - Anna Binda
- School of Medicine and Surgery, University of Milano-Bicocca, Monza-Center for Neuroscience (NeuroMI), Milan, Italy
| | - Gaetan Lesca
- Department of Medical Genetics, Hospices Civils de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Jacopo C. DiFrancesco
- Department of Pediatric Neuroscience, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy
- Department of Neurology, ASST “San Gerardo” Hospital, University of Milano-Bicocca, Monza, Italy
| | - Maria Virginia Soldovieri
- Department of Medicine and Health Science “V. Tiberio”, University of Molise, Campobasso, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
| | - Maurizio Taglialatela
- Department of Neuroscience, University of Naples “Federico II”, Naples, Italy
- *Correspondence: Maria Virginia Soldovieri, ; Maurizio Taglialatela,
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8
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Abstract
KCNQ2 and KCNQ3 channels are associated with multiple neurodevelopmental disorders and are also therapeutic targets for neurological and neuropsychiatric diseases. For more than two decades, it has been thought that most KCNQ channels in the brain are either KCNQ2/3 or KCNQ3/5 heteromers. Here, we investigated the potential heteromeric compositions of KCNQ2-containing channels. We applied split-intein protein trans-splicing to form KCNQ2/5 tandems and coexpressed these with and without KCNQ3. Unexpectedly, we found that KCNQ2/5 tandems form functional channels independent of KCNQ3 in heterologous cells. Using mass spectrometry, we went on to demonstrate that KCNQ2 associates with KCNQ5 in native channels in the brain, even in the absence of KCNQ3. Additionally, our functional heterologous expression data are consistent with the formation of KCNQ2/3/5 heteromers. Thus, the composition of KCNQ channels is more diverse than has been previously recognized, necessitating a re-examination of the genotype/phenotype relationship of KCNQ2 pathogenic variants.
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Stincic TL, Bosch MA, Hunker AC, Juarez B, Connors AM, Zweifel LS, Rønnekleiv OK, Kelly MJ. CRISPR knockdown of Kcnq3 attenuates the M-current and increases excitability of NPY/AgRP neurons to alter energy balance. Mol Metab 2021; 49:101218. [PMID: 33766732 PMCID: PMC8093934 DOI: 10.1016/j.molmet.2021.101218] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 03/12/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVE Arcuate nucleus neuropeptide Y/agouti-related peptide (NPY/AgRP) neurons drive ingestive behavior. The M-current, a subthreshold non-inactivating potassium current, plays a critical role in regulating NPY/AgRP neuronal excitability. Fasting decreases while 17β-estradiol increases the M-current by regulating the mRNA expression of Kcnq2, 3, and 5 (Kv7.2, 3, and 5) channel subunits. Incorporating KCNQ3 into heteromeric channels has been considered essential to generate a robust M-current. Therefore, we investigated the behavioral and physiological effects of selective Kcnq3 deletion from NPY/AgRP neurons. METHODS We used a single adeno-associated viral vector containing a recombinase-dependent Staphylococcus aureus Cas9 with a single-guide RNA to selectively delete Kcnq3 in NPY/AgRP neurons. Single-cell quantitative measurements of mRNA expression and whole-cell patch clamp experiments were conducted to validate the selective knockdown. Body weight, food intake, and locomotor activity were measured in male mice to assess disruptions in energy balance. RESULTS The virus reduced the expression of Kcnq3 mRNA without affecting Kcnq2 or Kcnq5. The M-current was attenuated, causing NPY/AgRP neurons to be more depolarized, exhibit a higher input resistance, and require less depolarizing current to fire action potentials, indicative of increased excitability. Although the resulting decrease in the M-current did not overtly alter ingestive behavior, it significantly reduced the locomotor activity as measured by open-field testing. Control mice on a high-fat diet exhibited an enhanced M-current and increased Kcnq2 and Kcnq3 expression, but the M-current remained significantly attenuated in KCNQ3 knockdown animals. CONCLUSIONS The M-current plays a critical role in modulating the intrinsic excitability of NPY/AgRP neurons that is essential for maintaining energy homeostasis.
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Affiliation(s)
- Todd L Stincic
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA.
| | - Martha A Bosch
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Avery C Hunker
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, 98195, USA
| | - Barbara Juarez
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA
| | - Ashley M Connors
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Larry S Zweifel
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, 98195, USA; Department of Pharmacology, University of Washington, Seattle, WA, 98195, USA
| | - Oline K Rønnekleiv
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA; Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, 97006, USA
| | - Martin J Kelly
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA; Division of Neuroscience, Oregon National Primate Research Center, Beaverton, OR, 97006, USA.
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10
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Kim KW, Suh BC. Ethanol inhibits Kv7.2/7.3 channel open probability by reducing the PI(4,5)P2 sensitivity of Kv7.2 subunit. BMB Rep 2021. [PMID: 33408002 PMCID: PMC8249878 DOI: 10.5483/bmbrep.2021.54.6.231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Ethanol often causes critical health problems by altering the neuro-nal activities of the central and peripheral nerve systems. One of the cellular targets of ethanol is the plasma membrane proteins including ion channels and receptors. Recently, we reported that ethanol elevates membrane excitability in sympathetic neurons by inhibiting Kv7.2/7.3 channels in a cell type-specific manner. Even though our studies revealed that the inhibitory effects of ethanol on the Kv7.2/7.3 channel was diminished by the increase of plasma membrane phosphatidylinositol 4,5-bisphosphate (PI (4,5)P2), the molecular mechanism of ethanol on Kv7.2/7.3 channel inhibition remains unclear. By investigating the kinetics of Kv7.2/7.3 current in high K+ solution, we found that ethanol inhibited Kv7.2/7.3 channels through a mechanism distinct from that of tetraethylammonium (TEA) which enters into the pore and blocks the gate of the channels. Using a non-stationary noise analysis (NSNA), we demonstrated that the inhibitory effect of ethanol is the result of reduction of open probability (PO) of the Kv7.2/7.3 channel, but not of a single channel current (i) or channel number (N). Finally, ethanol selectively facilitated the kinetics of Kv7.2 current suppression by voltage-sensing phosphatase (VSP)-induced PI(4,5)P2 depletion, while it slowed down Kv7.2 current recovery from the VSP-induced inhibition. Together our results suggest that ethanol regulates neuronal activity through the reduction of open probability and PI(4,5)P2 sensitivity of Kv7.2/7.3 channels.
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Affiliation(s)
- Kwon-Woo Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Byung-Chang Suh
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
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11
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Naffaa MM, Al-Ewaidat OA. Ligand modulation of KCNQ-encoded (K V7) potassium channels in the heart and nervous system. Eur J Pharmacol 2021; 906:174278. [PMID: 34174270 DOI: 10.1016/j.ejphar.2021.174278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/06/2021] [Accepted: 06/18/2021] [Indexed: 10/21/2022]
Abstract
KCNQ-encoded (KV7) potassium channels are diversely distributed in the human tissues, associated with many physiological processes and pathophysiological conditions. These channels are increasingly used as drug targets for treating diseases. More selective and potent molecules on various types of the KV7 channels are desirable for appropriate therapies. The recent knowledge of the structure and function of human KCNQ-encoded channels makes it more feasible to achieve these goals. This review discusses the role and mechanism of action of many molecules in modulating the function of the KCNQ-encoded potassium channels in the heart and nervous system. The effects of these compounds on KV7 channels help to understand their involvement in many diseases, and to search for more selective and potent ligands to be used in the treatment of many disorders such as various types of cardiac arrhythmias, epilepsy, and pain.
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Affiliation(s)
- Moawiah M Naffaa
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA; Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
| | - Ola A Al-Ewaidat
- Faculty of Medicine, The University of Jordan, Amman, 11942, Jordan
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12
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Springer K, Varghese N, Tzingounis AV. Flexible Stoichiometry: Implications for KCNQ2- and KCNQ3-Associated Neurodevelopmental Disorders. Dev Neurosci 2021; 43:191-200. [PMID: 33794528 PMCID: PMC8440324 DOI: 10.1159/000515495] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/25/2021] [Indexed: 11/19/2022] Open
Abstract
KCNQ2 and KCNQ3 pathogenic channel variants have been associated with a spectrum of developmentally regulated diseases that vary in age of onset, severity, and whether it is transient (i.e., benign familial neonatal seizures) or long-lasting (i.e., developmental and epileptic encephalopathy). KCNQ2 and KCNQ3 channels have also emerged as a target for novel antiepileptic drugs as their activation could reduce epileptic activity. Consequently, a great effort has taken place over the last 2 decades to understand the mechanisms that control the assembly, gating, and modulation of KCNQ2 and KCNQ3 channels. The current view that KCNQ2 and KCNQ3 channels assemble as heteromeric channels (KCNQ2/3) forms the basis of our understanding of KCNQ2 and KCNQ3 channelopathies and drug design. Here, we review the evidence that supports the formation of KCNQ2/3 heteromers in neurons. We also highlight functional and transcriptomic studies that suggest channel composition might not be necessarily fixed in the nervous system, but rather is dynamic and flexible, allowing some neurons to express KCNQ2 and KCNQ3 homomers. We propose that to fully understand KCNQ2 and KCNQ3 channelopathies, we need to adopt a more flexible view of KCNQ2 and KCNQ3 channel stoichiometry, which might differ across development, brain regions, cell types, and disease states.
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Affiliation(s)
- Kristen Springer
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Nissi Varghese
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Anastasios V Tzingounis
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
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13
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Wu X, Larsson HP. Insights into Cardiac IKs (KCNQ1/KCNE1) Channels Regulation. Int J Mol Sci 2020; 21:ijms21249440. [PMID: 33322401 PMCID: PMC7763278 DOI: 10.3390/ijms21249440] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/05/2020] [Accepted: 12/09/2020] [Indexed: 12/19/2022] Open
Abstract
The delayed rectifier potassium IKs channel is an important regulator of the duration of the ventricular action potential. Hundreds of mutations in the genes (KCNQ1 and KCNE1) encoding the IKs channel cause long QT syndrome (LQTS). LQTS is a heart disorder that can lead to severe cardiac arrhythmias and sudden cardiac death. A better understanding of the IKs channel (here called the KCNQ1/KCNE1 channel) properties and activities is of great importance to find the causes of LQTS and thus potentially treat LQTS. The KCNQ1/KCNE1 channel belongs to the superfamily of voltage-gated potassium channels. The KCNQ1/KCNE1 channel consists of both the pore-forming subunit KCNQ1 and the modulatory subunit KCNE1. KCNE1 regulates the function of the KCNQ1 channel in several ways. This review aims to describe the current structural and functional knowledge about the cardiac KCNQ1/KCNE1 channel. In addition, we focus on the modulation of the KCNQ1/KCNE1 channel and its potential as a target therapeutic of LQTS.
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14
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Maghera J, Li J, Lamothe SM, Braun M, Appendino JP, Au PYB, Kurata HT. Familial neonatal seizures caused by the Kv7.3 selectivity filter mutation T313I. Epilepsia Open 2020; 5:562-573. [PMID: 33336127 PMCID: PMC7733659 DOI: 10.1002/epi4.12438] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 08/14/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022] Open
Abstract
OBJECTIVE A spectrum of seizure disorders is linked to mutations in Kv7.2 and Kv7.3 channels. Linking functional effects of identified mutations to their clinical presentation requires ongoing characterization of newly identified variants. In this study, we identified and functionally characterized a previously unreported mutation in the selectivity filter of Kv7.3. METHODS Next-generation sequencing was used to identify the Kv7.3[T313I] mutation in a family affected by neonatal seizures. Electrophysiological approaches were used to characterize the functional effects of this mutation on ion channels expressed in Xenopus laevis oocytes. RESULTS Substitution of residue 313 from threonine to isoleucine (Kv7.3[T313I]) likely disrupts a critical intersubunit hydrogen bond. Characterization of the mutation in homomeric Kv7.3 channels demonstrated a total loss of channel function. Assembly in heteromeric channels (with Kv7.2) leads to modest suppression of total current when expressed in Xenopus laevis oocytes. Using a Kv7 activator with distinct effects on homomeric Kv7.2 vs heteromeric Kv7.2/Kv7.3 channels, we demonstrated that assembly of Kv7.2 and Kv7.3[T313I] generates functional channels. SIGNIFICANCE Biophysical and clinical effects of the T313I mutation are consistent with Kv7.3 mutations previously identified in cases of pharmacoresponsive self-limiting neonatal epilepsy. These findings expand our description of functionally characterized Kv7 channel variants and report new methods to distinguish molecular mechanisms of channel mutations.
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Affiliation(s)
- Jasmine Maghera
- Department of PharmacologyAlberta Diabetes InstituteUniversity of AlbertaEdmontonABCanada
| | - Jingru Li
- Department of PharmacologyAlberta Diabetes InstituteUniversity of AlbertaEdmontonABCanada
| | - Shawn M. Lamothe
- Department of PharmacologyAlberta Diabetes InstituteUniversity of AlbertaEdmontonABCanada
| | - Marvin Braun
- Division of Child NeurologyDepartment of PediatricsWeill Cornell MedicineNew YorkNYUSA
| | - Juan P. Appendino
- Section of NeurologyDepartment of PediatricsCumming School of MedicineUniversity of Calgary, and Alberta Children’s HospitalCalgaryABCanada
| | - P. Y. Billie Au
- Department of Medical GeneticsCumming School of MedicineAlberta Children’s Hospital Research InstituteUniversity of CalgaryCalgaryABCanada
| | - Harley T. Kurata
- Department of PharmacologyAlberta Diabetes InstituteUniversity of AlbertaEdmontonABCanada
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15
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The M-current works in tandem with the persistent sodium current to set the speed of locomotion. PLoS Biol 2020; 18:e3000738. [PMID: 33186352 PMCID: PMC7688130 DOI: 10.1371/journal.pbio.3000738] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 11/25/2020] [Accepted: 10/13/2020] [Indexed: 01/20/2023] Open
Abstract
The central pattern generator (CPG) for locomotion is a set of pacemaker neurons endowed with inherent bursting driven by the persistent sodium current (INaP). How they proceed to regulate the locomotor rhythm remained unknown. Here, in neonatal rodents, we identified a persistent potassium current critical in regulating pacemakers and locomotion speed. This current recapitulates features of the M-current (IM): a subthreshold noninactivating outward current blocked by 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride (XE991) and enhanced by N-(2-chloro-5-pyrimidinyl)-3,4-difluorobenzamide (ICA73). Immunostaining and mutant mice highlight an important role of Kv7.2-containing channels in mediating IM. Pharmacological modulation of IM regulates the emergence and the frequency regime of both pacemaker and CPG activities and controls the speed of locomotion. Computational models captured these results and showed how an interplay between IM and INaP endows the locomotor CPG with rhythmogenic properties. Overall, this study provides fundamental insights into how IM and INaP work in tandem to set the speed of locomotion.
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16
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Rivas-Ramírez P, Reboreda A, Rueda-Ruzafa L, Herrera-Pérez S, Lamas JA. Contribution of KCNQ and TREK Channels to the Resting Membrane Potential in Sympathetic Neurons at Physiological Temperature. Int J Mol Sci 2020; 21:E5796. [PMID: 32806753 PMCID: PMC7461115 DOI: 10.3390/ijms21165796] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 07/31/2020] [Accepted: 08/10/2020] [Indexed: 12/19/2022] Open
Abstract
The ionic mechanisms controlling the resting membrane potential (RMP) in superior cervical ganglion (SCG) neurons have been widely studied and the M-current (IM, KCNQ) is one of the key players. Recently, with the discovery of the presence of functional TREK-2 (TWIK-related K+ channel 2) channels in SCG neurons, another potential main contributor for setting the value of the resting membrane potential has appeared. In the present work, we quantified the contribution of TREK-2 channels to the resting membrane potential at physiological temperature and studied its role in excitability using patch-clamp techniques. In the process we have discovered that TREK-2 channels are sensitive to the classic M-current blockers linopirdine and XE991 (IC50 = 0.310 ± 0.06 µM and 0.044 ± 0.013 µM, respectively). An increase from room temperature (23 °C) to physiological temperature (37 °C) enhanced both IM and TREK-2 currents. Likewise, inhibition of IM by tetraethylammonium (TEA) and TREK-2 current by XE991 depolarized the RMP at room and physiological temperatures. Temperature rise also enhanced adaptation in SCG neurons which was reduced due to TREK-2 and IM inhibition by XE991 application. In summary, TREK-2 and M currents contribute to the resting membrane potential and excitability at room and physiological temperature in the primary culture of mouse SCG neurons.
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Affiliation(s)
- Paula Rivas-Ramírez
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain; (P.R.-R.); (L.R.-R.); (S.H.-P.)
| | - Antonio Reboreda
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain; (P.R.-R.); (L.R.-R.); (S.H.-P.)
- Functional Architecture of Memory Department, Leibniz-Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Lola Rueda-Ruzafa
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain; (P.R.-R.); (L.R.-R.); (S.H.-P.)
| | - Salvador Herrera-Pérez
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain; (P.R.-R.); (L.R.-R.); (S.H.-P.)
| | - Jose Antonio Lamas
- Department of Functional Biology and Health Sciences, Faculty of Biology-CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain; (P.R.-R.); (L.R.-R.); (S.H.-P.)
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17
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Li J, Maghera J, Lamothe SM, Marco EJ, Kurata HT. Heteromeric Assembly of Truncated Neuronal Kv7 Channels: Implications for Neurologic Disease and Pharmacotherapy. Mol Pharmacol 2020; 98:192-202. [DOI: 10.1124/mol.120.119644] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 06/11/2020] [Indexed: 12/19/2022] Open
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18
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Rivas-Ramírez P, Reboreda A, Rueda-Ruzafa L, Herrera-Pérez S, Lamas JA. PIP 2 Mediated Inhibition of TREK Potassium Currents by Bradykinin in Mouse Sympathetic Neurons. Int J Mol Sci 2020; 21:ijms21020389. [PMID: 31936257 PMCID: PMC7014146 DOI: 10.3390/ijms21020389] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/30/2019] [Accepted: 01/02/2020] [Indexed: 12/17/2022] Open
Abstract
Bradykinin (BK), a hormone inducing pain and inflammation, is known to inhibit potassium M-currents (IM) and to increase the excitability of the superior cervical ganglion (SCG) neurons by activating the Ca2+-calmodulin pathway. M-current is also reduced by muscarinic agonists through the depletion of membrane phosphatidylinositol 4,5-biphosphate (PIP2). Similarly, the activation of muscarinic receptors inhibits the current through two-pore domain potassium channels (K2P) of the “Tandem of pore-domains in a Weakly Inward rectifying K+ channel (TWIK)-related channels” (TREK) subfamily by reducing PIP2 in mouse SCG neurons (mSCG). The aim of this work was to test and characterize the modulation of TREK channels by bradykinin. We used the perforated-patch technique to investigate riluzole (RIL) activated currents in voltage- and current-clamp experiments. RIL is a drug used in the palliative treatment of amyotrophic lateral sclerosis and, in addition to blocking voltage-dependent sodium channels, it also selectively activates the K2P channels of the TREK subfamily. A cell-attached patch-clamp was also used to investigate TREK-2 single channel currents. We report here that BK reduces spike frequency adaptation (SFA), inhibits the riluzole-activated current (IRIL), which flows mainly through TREK-2 channels, by about 45%, and reduces the open probability of identified single TREK-2 channels in cultured mSCG cells. The effect of BK on IRIL was precluded by the bradykinin receptor (B2R) antagonist HOE-140 (d-Arg-[Hyp3, Thi5, d-Tic7, Oic8]BK) but also by diC8PIP2 which prevents PIP2 depletion when phospholipase C (PLC) is activated. On the contrary, antagonizing inositol triphosphate receptors (IP3R) using 2-aminoethoxydiphenylborane (2-APB) or inhibiting protein kinase C (PKC) with bisindolylmaleimide did not affect the inhibition of IRIL by BK. In conclusion, bradykinin inhibits TREK-2 channels through the activation of B2Rs resulting in PIP2 depletion, much like we have demonstrated for muscarinic agonists. This mechanism implies that TREK channels must be relevant for the capture of information about pain and visceral inflammation.
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19
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Abstract
Here, I recount some adventures that I and my colleagues have had over some 60 years since 1957 studying the effects of drugs and neurotransmitters on neuronal excitability and ion channel function, largely, but not exclusively, using sympathetic neurons as test objects. Studies include effects of centrally active drugs on sympathetic transmission; neuronal action and neuroglial uptake of GABA in the ganglia and brain; the action of muscarinic agonists on sympathetic neurons; the action of bradykinin on neuroblastoma-derived cells; and the identification of M-current as a target for muscarinic action, including experiments to determine its distribution, molecular composition, neurotransmitter sensitivity, and intracellular regulation by phospholipids and their hydrolysis products. Techniques used include electrophysiological recording (extracellular, intracellular microelectrode, whole-cell, and single-channel patch-clamp), autoradiography, messenger RNA and complementary DNA expression, antibody injection, antisense knockdown, and membrane-targeted lipidated peptides. I finish with some recollections about my scientific career, funding, and changes in laboratory life and pharmacology research over the past 60 years.
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Affiliation(s)
- David A. Brown
- Departments of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, United Kingdom
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20
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Carver CM, Hastings SD, Cook ME, Shapiro MS. Functional responses of the hippocampus to hyperexcitability depend on directed, neuron-specific KCNQ2 K + channel plasticity. Hippocampus 2019; 30:435-455. [PMID: 31621989 DOI: 10.1002/hipo.23163] [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] [Received: 05/08/2019] [Revised: 07/24/2019] [Accepted: 08/30/2019] [Indexed: 12/14/2022]
Abstract
M-type (KCNQ2/3) K+ channels play dominant roles in regulation of active and passive neuronal discharge properties such as resting membrane potential, spike-frequency adaptation, and hyper-excitatory states. However, plasticity of M-channel expression and function in nongenetic forms of epileptogenesis are still not well understood. Using transgenic mice with an EGFP reporter to detect expression maps of KCNQ2 mRNA, we assayed hyperexcitability-induced alterations in KCNQ2 transcription across subregions of the hippocampus. Pilocarpine and pentylenetetrazol chemoconvulsant models of seizure induction were used, and brain tissue examined 48 hr later. We observed increases in KCNQ2 mRNA in CA1 and CA3 pyramidal neurons after chemoconvulsant-induced hyperexcitability at 48 hr, but no significant change was observed in dentate gyrus (DG) granule cells. Using chromogenic in situ hybridization assays, changes to KCNQ3 transcription were not detected after hyper-excitation challenge, but the results for KCNQ2 paralleled those using the KCNQ2-mRNA reporter mice. In mice 7 days after pilocarpine challenge, levels of KCNQ2 mRNA were similar in all regions to those from control mice. In brain-slice electrophysiology recordings, CA1 pyramidal neurons demonstrated increased M-current amplitudes 48 hr after hyperexcitability; however, there were no significant changes to DG granule cell M-current amplitude. Traumatic brain injury induced significantly greater KCNQ2 expression in the hippocampal hemisphere that was ipsilateral to the trauma. In vivo, after a secondary challenge with subconvulsant dose of pentylenetetrazole, control mice were susceptible to tonic-clonic seizures, whereas mice administered the M-channel opener retigabine were protected from such seizures. This study demonstrates that increased excitatory activity promotes KCNQ2 upregulation in the hippocampus in a cell-type specific manner. Such novel ion channel expressional plasticity may serve as a compensatory mechanism after a hyperexcitable event, at least in the short term. The upregulation described could be potentially leveraged in anticonvulsant enhancement of KCNQ2 channels as therapeutic target for preventing onset of epileptogenic seizures.
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Affiliation(s)
- Chase M Carver
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Shayne D Hastings
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Mileah E Cook
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
| | - Mark S Shapiro
- Department of Cellular and Integrative Physiology, University of Texas Health San Antonio, San Antonio, Texas
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21
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Lauritano A, Moutton S, Longobardi E, Tran Mau‐Them F, Laudati G, Nappi P, Soldovieri MV, Ambrosino P, Cataldi M, Jouan T, Lehalle D, Maurey H, Philippe C, Miceli F, Vitobello A, Taglialatela M. A novel homozygous KCNQ3 loss-of-function variant causes non-syndromic intellectual disability and neonatal-onset pharmacodependent epilepsy. Epilepsia Open 2019; 4:464-475. [PMID: 31440727 PMCID: PMC6698674 DOI: 10.1002/epi4.12353] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/04/2019] [Accepted: 07/28/2019] [Indexed: 12/18/2022] Open
Abstract
OBJECTIVE Heterozygous variants in KCNQ2 or, more rarely, KCNQ3 genes are responsible for early-onset developmental/epileptic disorders characterized by heterogeneous clinical presentation and course, genetic transmission, and prognosis. While familial forms mostly include benign epilepsies with seizures starting in the neonatal or early-infantile period, de novo variants in KCNQ2 or KCNQ3 have been described in sporadic cases of early-onset encephalopathy (EOEE) with pharmacoresistant seizures, various age-related pathological EEG patterns, and moderate/severe developmental impairment. All pathogenic variants in KCNQ2 or KCNQ3 occur in heterozygosity. The aim of this work was to report the clinical, molecular, and functional properties of a new KCNQ3 variant found in homozygous configuration in a 9-year-old girl with pharmacodependent neonatal-onset epilepsy and non-syndromic intellectual disability. METHODS Exome sequencing was used for genetic investigation. KCNQ3 transcript and subunit expression in fibroblasts was analyzed with quantitative real-time PCR and Western blotting or immunofluorescence, respectively. Whole-cell patch-clamp electrophysiology was used for functional characterization of mutant subunits. RESULTS A novel single-base duplication in exon 12 of KCNQ3 (NM_004519.3:c.1599dup) was found in homozygous configuration in the proband born to consanguineous healthy parents; this frameshift variant introduced a premature termination codon (PTC), thus deleting a large part of the C-terminal region. Mutant KCNQ3 transcript and protein abundance was markedly reduced in primary fibroblasts from the proband, consistent with nonsense-mediated mRNA decay. The variant fully abolished the ability of KCNQ3 subunits to assemble into functional homomeric or heteromeric channels with KCNQ2 subunits. SIGNIFICANCE The present results indicate that a homozygous KCNQ3 loss-of-function variant is responsible for a severe phenotype characterized by neonatal-onset pharmacodependent seizures, with developmental delay and intellectual disability. They also reveal difference in genetic and pathogenetic mechanisms between KCNQ2- and KCNQ3-related epilepsies, a crucial observation for patients affected with EOEE and/or developmental disabilities.
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Affiliation(s)
- Anna Lauritano
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Sebastien Moutton
- Reference Center for Developmental Anomalies, Department of Medical GeneticsDijon University HospitalDijonFrance
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
| | - Elena Longobardi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Frédéric Tran Mau‐Them
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Giusy Laudati
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Piera Nappi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | | | - Paolo Ambrosino
- Division of Pharmacology, Department of Science and TechnologyUniversity of SannioBeneventoItaly
| | - Mauro Cataldi
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Thibaud Jouan
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Daphné Lehalle
- Reference Center for Developmental Anomalies, Department of Medical GeneticsDijon University HospitalDijonFrance
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
| | - Hélène Maurey
- Service de Neurologie PédiatriqueAPHP, Hôpital Universitaire BicêtreLe Kremlin‐BicêtreFrance
| | - Christophe Philippe
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Francesco Miceli
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
| | - Antonio Vitobello
- INSERM U1231, LNC UMR1231 GADBurgundy UniversityDijonFrance
- Laboratoire de Génétique, Innovation en Diagnostic Génomique des Maladies Rares UF6254, Plateau Technique de BiologieCHU DijonDijonFrance
| | - Maurizio Taglialatela
- Division of Pharmacology, Department of NeuroscienceUniversity of Naples “Federico II”NaplesItaly
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22
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Sun H, Lin AH, Ru F, Patil MJ, Meeker S, Lee LY, Undem BJ. KCNQ/M-channels regulate mouse vagal bronchopulmonary C-fiber excitability and cough sensitivity. JCI Insight 2019; 4:124467. [PMID: 30721152 DOI: 10.1172/jci.insight.124467] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 01/29/2019] [Indexed: 01/06/2023] Open
Abstract
Increased airway vagal sensory C-fiber activity contributes to the symptoms of inflammatory airway diseases. The KCNQ/Kv7/M-channel is a well-known determinant of neuronal excitability, yet whether it regulates the activity of vagal bronchopulmonary C-fibers and airway reflex sensitivity remains unknown. Here we addressed this issue using single-cell RT-PCR, patch clamp technique, extracellular recording of single vagal nerve fibers innervating the mouse lungs, and telemetric recording of cough in free-moving mice. Single-cell mRNA analysis and biophysical properties of M-current (IM) suggest that KCNQ3/Kv7.3 is the major M-channel subunit in mouse nodose neurons. The M-channel opener retigabine negatively shifted the voltage-dependent activation of IM, leading to membrane hyperpolarization, increased rheobase, and suppression of both evoked and spontaneous action potential (AP) firing in nodose neurons in an M-channel inhibitor XE991-sensitive manner. Retigabine also markedly suppressed the α,β-methylene ATP-induced AP firing in nodose C-fiber terminals innervating the mouse lungs, and coughing evoked by irritant gases in awake mice. In conclusion, KCNQ/M-channels play a role in regulating the excitability of vagal airway C-fibers at both the cell soma and nerve terminals. Drugs that open M-channels in airway sensory afferents may relieve the sufferings associated with pulmonary inflammatory diseases such as chronic coughing.
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Affiliation(s)
- Hui Sun
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - An-Hsuan Lin
- Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
| | - Fei Ru
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Mayur J Patil
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Sonya Meeker
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Lu-Yuan Lee
- Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
| | - Bradley J Undem
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Gq-Coupled Muscarinic Receptor Enhancement of KCNQ2/3 Channels and Activation of TRPC Channels in Multimodal Control of Excitability in Dentate Gyrus Granule Cells. J Neurosci 2018; 39:1566-1587. [PMID: 30593498 DOI: 10.1523/jneurosci.1781-18.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 12/17/2018] [Accepted: 12/20/2018] [Indexed: 12/21/2022] Open
Abstract
KCNQ (Kv7, "M-type") K+ channels and TRPC (transient receptor potential, "canonical") cation channels are coupled to neuronal discharge properties and are regulated via Gq/11-protein-mediated signals. Stimulation of Gq/11-coupled receptors both consumes phosphatidylinositol 4,5-bisphosphate (PIP2) via phosphalipase Cβ hydrolysis and stimulates PIP2 synthesis via rises in Ca2+ i and other signals. Using brain-slice electrophysiology and Ca2+ imaging from male and female mice, we characterized threshold K+ currents in dentate gyrus granule cells (DGGCs) and CA1 pyramidal cells, the effects of Gq/11-coupled muscarinic M1 acetylcholine (M1R) stimulation on M current and on neuronal discharge properties, and elucidated the intracellular signaling mechanisms involved. We observed disparate signaling cascades between DGGCs and CA1 neurons. DGGCs displayed M1R enhancement of M-current, rather than suppression, due to stimulation of PIP2 synthesis, which was paralleled by increased PIP2-gated G-protein coupled inwardly rectifying K+ currents as well. Deficiency of KCNQ2-containing M-channels ablated the M1R-induced enhancement of M-current in DGGCs. Simultaneously, M1R stimulation in DGGCs induced robust increases in [Ca2+]i, mostly due to TRPC currents, consistent with, and contributing to, neuronal depolarization and hyperexcitability. CA1 neurons did not display such multimodal signaling, but rather M current was suppressed by M1R stimulation in these cells, similar to the previously described actions of M1R stimulation on M-current in peripheral ganglia that mostly involves PIP2 depletion. Therefore, these results point to a pleiotropic network of cholinergic signals that direct cell-type-specific, precise control of hippocampal function with strong implications for hyperexcitability and epilepsy.SIGNIFICANCE STATEMENT At the neuronal membrane, protein signaling cascades consisting of ion channels and metabotropic receptors govern the electrical properties and neurotransmission of neuronal networks. Muscarinic acetylcholine receptors are G-protein-coupled metabotropic receptors that control the excitability of neurons through regulating ion channels, intracellular Ca2+ signals, and other second-messenger cascades. We have illuminated previously unknown actions of muscarinic stimulation on the excitability of hippocampal principal neurons that include M channels, TRPC (transient receptor potential, "canonical") cation channels, and powerful regulation of lipid metabolism. Our results show that these signaling pathways, and mechanisms of excitability, are starkly distinct between peripheral ganglia and brain, and even between different principal neurons in the hippocampus.
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24
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Gollasch M, Welsh DG, Schubert R. Perivascular adipose tissue and the dynamic regulation of K v 7 and K ir channels: Implications for resistant hypertension. Microcirculation 2018; 25. [PMID: 29211322 DOI: 10.1111/micc.12434] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 11/30/2017] [Indexed: 12/20/2022]
Abstract
Resistant hypertension is defined as high blood pressure that remains uncontrolled despite treatment with at least three antihypertensive drugs at adequate doses. Resistant hypertension is an increasingly common clinical problem in older age, obesity, diabetes, sleep apnea, and chronic kidney disease. Although the direct vasodilator minoxidil was introduced in the early 1970s, only recently has this drug been shown to be particularly effective in a subgroup of patients with treatment-resistant or uncontrolled hypertension. This pharmacological approach is interesting from a mechanistic perspective as minoxidil is the only clinically used K+ channel opener today, which targets a subclass of K+ channels, namely KATP channels in VSMCs. Beside KATP channels, two other classes of VSMC K+ channels could represent novel effective targets for treatment of resistant hypertension, namely Kv 7 (KCNQ) and inward rectifier potassium (Kir 2.1) channels. Interestingly, these channels are unique among VSMC potassium channels. First, both have been implicated in the control of microvascular tone by perivascular adipose tissue. Second, they exhibit biophysical properties strongly controlled and regulated by membrane voltage, but not intracellular calcium. This review focuses on Kv 7 (Kv 7.1-5) and Kir (Kir 2.1) channels in VSMCs as potential novel drug targets for treatment of resistant hypertension, particularly in comorbid conditions such as obesity and metabolic syndrome.
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Affiliation(s)
- Maik Gollasch
- Medical Clinic for Nephrology and Internal Intensive Care, Charité Campus Virchow Klinikum, Experimental and Clinical Research Center (ECRC) - a joint cooperation between the Charité - University Medicine Berlin and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Donald G Welsh
- Department of Physiology and Pharmacology, Western University, London, ON, Canada
| | - Rudolf Schubert
- Centre for Biomedicine and Medical Technology Mannheim (CBTM), Research Division Cardiovascular Physiology, Medical Faculty Mannheim, Heidelberg University, Heidelberg, Germany
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25
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Eid BG, Gurney AM. Zinc pyrithione activates K+ channels and hyperpolarizes the membrane of rat pulmonary artery smooth muscle cells. PLoS One 2018; 13:e0192699. [PMID: 29474372 PMCID: PMC5824988 DOI: 10.1371/journal.pone.0192699] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 01/29/2018] [Indexed: 01/09/2023] Open
Abstract
The membrane potential helps determine pulmonary artery smooth muscle cell (PASMC) contraction. The Kv7 channel activators, retigabine and flupirtine, are thought to dilate pulmonary arteries by hyperpolarising PASMC. Zinc pyrithione activates Kv7 channels by a mechanism distinct from retigabine and with different Kv7 subunit selectivity. This study aimed to determine if zinc pyrithione selectively activates Kv7 channels in rat PASMC to evoke pulmonary artery dilation. Zinc pyrithione relaxed pulmonary arteries with half-maximal effect at 4.3μM. At 10μM it activated pronounced voltage-dependent K+ current and hyperpolarized PASMCs by around 10mV. Tetraethylammonium ions (TEA, 10mM) and paxilline (1μM) abolished both the current and hyperpolarisation. XE991 (10μM) blocked the hyperpolarization and reduced the current by 30%. Iberiotoxin (50nM) had no effect on the hyperpolarisation, but reduced the current by 40%. The XE991-sensitive current activated with an exponential time course (time constant 17ms), whereas the iberiotoxin-sensitive current followed a bi-exponential time course (time constants 6 and 57ms), suggesting that the drugs blocked different components of the zinc pyrithione-induced current. Zinc pyrithione therefore appears to activate at least two types of K+ channel in PASMC; an XE991, TEA and paxilline-sensitive Kv7 channel and a TEA, paxilline and iberiotoxin-sensitive BKCa channel. Both could contribute to the relaxing effect of zinc pyrithione on pulmonary artery.
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Affiliation(s)
- Basma G. Eid
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Alison M. Gurney
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
- * E-mail:
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26
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Dierich M, Evers S, Wilke BU, Leitner MG. Inverse Modulation of Neuronal K v12.1 and K v11.1 Channels by 4-Aminopyridine and NS1643. Front Mol Neurosci 2018; 11:11. [PMID: 29440988 PMCID: PMC5797642 DOI: 10.3389/fnmol.2018.00011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 01/09/2018] [Indexed: 01/24/2023] Open
Abstract
The three members of the ether-à-go-go-gene-like (Elk; Kv12.1-Kv12.3) family of voltage-gated K+ channels are predominantly expressed in neurons, but only little information is available on their physiological relevance. It was shown that Kv12.2 channels modulate excitability of hippocampal neurons, but no native current could be attributed to Kv12.1 and Kv12.3 subunits yet. This may appear somewhat surprising, given high expression of their mRNA transcripts in several brain areas. Native Kv12 currents may have been overlooked so far due to limited knowledge on their biophysical properties and lack of specific pharmacology. Except for Kv12.2, appropriate genetically modified mouse models have not been described; therefore, identification of Kv12-mediated currents in native cell types must rely on characterization of unique properties of the channels. We focused on recombinant human Kv12.1 to identify distinct properties of these channels. We found that Kv12.1 channels exhibited significant mode shift of activation, i.e., stabilization of the voltage sensor domain in a “relaxed” open state after prolonged channel activation. This mode shift manifested by a slowing of deactivation and, most prominently, a significant shift of voltage dependence to hyperpolarized potentials. In contrast to related Kv11.1, mode shift was not sensitive to extracellular Na+, which allowed for discrimination between these isoforms. Sensitivity of Kv12.1 and Kv11.1 to the broad-spectrum K+ antagonist 4-aminopyridine was similar. However, 4-AP strongly activated Kv12.1 channels, but it was an inhibitor of Kv11 channels. Interestingly, the agonist of Kv11 channels NS1643 also differentially modulated the activity of these channels, i.e., NS1643 activated Kv11.1, but strongly inhibited Kv12.1 channels. Thus, these closely related channels are distinguished by inverse pharmacological profiles. In summary, we identified unique biophysical and pharmacological properties of Kv12.1 channels and established straightforward experimental protocols to characterize Kv12.1-mediated currents. Identification of currents in native cell types with mode shift that are activated through 4-AP and inhibited by NS1643 can provide strong evidence for contribution of Kv12.1 to whole cell currents.
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Affiliation(s)
- Marlen Dierich
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Saskia Evers
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Bettina U Wilke
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany
| | - Michael G Leitner
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University of Marburg, Marburg, Germany.,Division of Physiology, Department of Physiology and Medical Physics, Innsbruck Medical University, Innsbruck, Austria
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27
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Ambrosino P, Freri E, Castellotti B, Soldovieri MV, Mosca I, Manocchio L, Gellera C, Canafoglia L, Franceschetti S, Salis B, Iraci N, Miceli F, Ragona F, Granata T, DiFrancesco JC, Taglialatela M. Kv7.3 Compound Heterozygous Variants in Early Onset Encephalopathy Reveal Additive Contribution of C-Terminal Residues to PIP2-Dependent K+ Channel Gating. Mol Neurobiol 2018; 55:7009-7024. [DOI: 10.1007/s12035-018-0883-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 01/08/2018] [Indexed: 11/28/2022]
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SMIT1 Modifies KCNQ Channel Function and Pharmacology by Physical Interaction with the Pore. Biophys J 2017; 113:613-626. [PMID: 28793216 DOI: 10.1016/j.bpj.2017.06.055] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 05/26/2017] [Accepted: 06/12/2017] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated potassium channels of the KCNQ (Kv7) subfamily are essential for control of cellular excitability and repolarization in a wide range of cell types. Recently, we and others found that some KCNQ channels functionally and physically interact with sodium-dependent solute transporters, including myo-inositol transporters SMIT1 and SMIT2, potentially facilitating various modes of channel-transporter signal integration. In contrast to indirect effects such as channel regulation by SMIT-transported, myo-inositol-derived phosphatidylinositol 4,5-bisphosphate (PIP2), the mechanisms and functional consequences of the physical interaction of channels with transporters have been little studied. Here, using co-immunoprecipitation with different channel domains, we found that SMIT1 binds to the KCNQ2 pore module. We next tested the effects of SMIT1 co-expression, in the absence of extracellular myo-inositol or other SMIT1 substrates, on fundamental functional attributes of KCNQ2, KCNQ2/3, KCNQ1, and KCNQ1-KCNE1 channels. Without exception, SMIT1 altered KCNQ ion selectivity, sensitivity to extracellular K+, and pharmacology, consistent with an impact on conformation of the KCNQ pore. SMIT1 also altered the gating kinetics and/or voltage dependence of KCNQ2, KCNQ2/3, and KCNQ1-KCNE1. In contrast, SMIT1 had no effect on Kv1.1 (KCNA1) gating, ion selectivity, or pharmacology. We conclude that, independent of its transport activity and indirect regulatory mechanisms involving inositol-derived increases in PIP2, SMIT1, and likely other related sodium-dependent solute transporters, regulates KCNQ channel ion selectivity, gating, and pharmacology by direct physical interaction with the pore module.
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29
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Di Cesare Mannelli L, Lucarini E, Micheli L, Mosca I, Ambrosino P, Soldovieri MV, Martelli A, Testai L, Taglialatela M, Calderone V, Ghelardini C. Effects of natural and synthetic isothiocyanate-based H 2S-releasers against chemotherapy-induced neuropathic pain: Role of Kv7 potassium channels. Neuropharmacology 2017; 121:49-59. [PMID: 28431970 DOI: 10.1016/j.neuropharm.2017.04.029] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Revised: 03/21/2017] [Accepted: 04/17/2017] [Indexed: 01/02/2023]
Abstract
Hydrogen sulfide (H2S) is a crucial signaling molecule involved in several physiological and pathological processes. Nonetheless, the role of this gasotransmitter in the pathogenesis and treatment of neuropathic pain is controversial. The aim of the present study was to investigate the pain relieving profile of a series of slow releasing H2S donors (the natural allyl-isothiocyanate and the synthetics phenyl- and carboxyphenyl-isothiocyanate) in animal models of neuropathic pain induced by paclitaxel or oxaliplatin, anticancer drugs characterized by a dose-limiting neurotoxicity. The potential contribution of Kv7 potassium channels modulation was also studied. Mice were treated with paclitaxel (2.0 mg kg-1) i.p. on days 1, 3, 5 and 7; oxaliplatin (2.4 mg kg-1) was administered i.p. on days 1-2, 5-9, 12-14. Behavioral tests were performed on day 15. In both models, single subcutaneous administrations of H2S donors (1.33, 4.43, 13.31 μmol kg-1) reduced the hypersensitivity to cold non-noxious stimuli (allodynia-related measurement). The prototypical H2S donor NaHS was also effective. Activity was maintained after i.c.v. administrations. On the contrary, the S-lacking molecule allyl-isocyanate did not increase pain threshold; the H2S-binding molecule hemoglobin abolished the pain-relieving effects of isothiocyanates and NaHS. The anti-neuropathic properties of H2S donors were reverted by the Kv7 potassium channel blocker XE991. Currents carried by Kv7.2 homomers and Kv7.2/Kv7.3 heteromers expressed in CHO cells were potentiated by H2S donors. Sistemically- or centrally-administered isothiocyanates reduced chemotherapy-induced neuropathic pain by releasing H2S. Activation of Kv7 channels largely mediate the anti-neuropathic effect.
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Affiliation(s)
- Lorenzo Di Cesare Mannelli
- Dept. of Neuroscience, Psychology, Drug Research and Child Health - Neurofarba - Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, Florence, Italy.
| | - Elena Lucarini
- Dept. of Neuroscience, Psychology, Drug Research and Child Health - Neurofarba - Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, Florence, Italy
| | - Laura Micheli
- Dept. of Neuroscience, Psychology, Drug Research and Child Health - Neurofarba - Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, Florence, Italy
| | - Ilaria Mosca
- Dept. of Medicine and Health Science, University of Molise, Via Francesco De Sanctis, 1 Campobasso, Italy
| | - Paolo Ambrosino
- Dept. of Medicine and Health Science, University of Molise, Via Francesco De Sanctis, 1 Campobasso, Italy
| | - Maria Virginia Soldovieri
- Dept. of Medicine and Health Science, University of Molise, Via Francesco De Sanctis, 1 Campobasso, Italy
| | - Alma Martelli
- Dept. of Pharmacy, University of Pisa, Via Bonanno 6, Pisa, Italy
| | - Lara Testai
- Dept. of Pharmacy, University of Pisa, Via Bonanno 6, Pisa, Italy
| | - Maurizio Taglialatela
- Dept. of Medicine and Health Science, University of Molise, Via Francesco De Sanctis, 1 Campobasso, Italy; Section of Pharmacology, Department of Neuroscience, University of Naples Federico II, Via Pansini 5, Naples, Italy
| | | | - Carla Ghelardini
- Dept. of Neuroscience, Psychology, Drug Research and Child Health - Neurofarba - Pharmacology and Toxicology Section, University of Florence, Viale Pieraccini 6, Florence, Italy
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30
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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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31
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Affiliation(s)
- Maik Gollasch
- Medical Clinic for Nephrology and Internal Intensive Care, Charité Campus Virchow Klinikum, and Experimental and Clinical Research Center, a joint cooperation of the Charité – University Medicine Berlin and Max Delbrück Center for Molecular Medicine in the Helmholtz Association, 13125 Berlin, Germany;
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32
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Early-onset epileptic encephalopathy caused by a reduced sensitivity of Kv7.2 potassium channels to phosphatidylinositol 4,5-bisphosphate. Sci Rep 2016; 6:38167. [PMID: 27905566 PMCID: PMC5131271 DOI: 10.1038/srep38167] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/04/2016] [Indexed: 12/17/2022] Open
Abstract
Kv7.2 and Kv7.3 subunits underlie the M-current, a neuronal K+ current characterized by an absolute functional requirement for phosphatidylinositol 4,5-bisphosphate (PIP2). Kv7.2 gene mutations cause early-onset neonatal seizures with heterogeneous clinical outcomes, ranging from self-limiting benign familial neonatal seizures to severe early-onset epileptic encephalopathy (Kv7.2-EE). In this study, the biochemical and functional consequences prompted by a recurrent variant (R325G) found independently in four individuals with severe forms of neonatal-onset EE have been investigated. Upon heterologous expression, homomeric Kv7.2 R325G channels were non-functional, despite biotin-capture in Western blots revealed normal plasma membrane subunit expression. Mutant subunits exerted dominant-negative effects when incorporated into heteromeric channels with Kv7.2 and/or Kv7.3 subunits. Increasing cellular PIP2 levels by co-expression of type 1γ PI(4)P5-kinase (PIP5K) partially recovered homomeric Kv7.2 R325G channel function. Currents carried by heteromeric channels incorporating Kv7.2 R325G subunits were more readily inhibited than wild-type channels upon activation of a voltage-sensitive phosphatase (VSP), and recovered more slowly upon VSP switch-off. These results reveal for the first time that a mutation-induced decrease in current sensitivity to PIP2 is the primary molecular defect responsible for Kv7.2-EE in individuals carrying the R325G variant, further expanding the range of pathogenetic mechanisms exploitable for personalized treatment of Kv7.2-related epilepsies.
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Zhang X, An H, Li J, Zhang Y, Liu Y, Jia Z, Zhang W, Chu L, Zhang H. Selective activation of vascular K v 7.4/K v 7.5 K + channels by fasudil contributes to its vasorelaxant effect. Br J Pharmacol 2016; 173:3480-3491. [PMID: 27677924 DOI: 10.1111/bph.13639] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Revised: 09/13/2016] [Accepted: 09/15/2016] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND AND PURPOSE Kv 7 (Kv 7.1-7.5) channels play an important role in the regulation of neuronal excitability and the cardiac action potential. Growing evidence suggests Kv 7.4/Kv 7.5 channels play a crucial role in regulating vascular smooth muscle contractility. Most of the reported Kv 7 openers have shown poor selectivity across these five subtypes. In this study, fasudil - a drug used for cerebral vasospasm - has been found to be a selective opener of Kv 7.4/Kv 7.5 channels. EXPERIMENTAL APPROACH A perforated whole-cell patch technique was used to record the currents and membrane potential. Homology modelling and a docking technique were used to investigate the interaction between fasudil and the Kv 7.4 channel. An isometric tension recording technique was used to assess the vascular tension. KEY RESULTS Fasudil selectively and potently enhanced Kv 7.4 and Kv 7.4/Kv 7.5 currents expressed in HEK293 cells, and shifted the voltage-dependent activation curve in a more negative direction. Fasudil did not affect either Kv 7.2 and Kv 7.2/Kv 7.3 currents expressed in HEK293 cells, the native neuronal M-type K+ currents, or the resting membrane potential in small rat dorsal root ganglia neurons. The Val248 in S5 and Ile308 in S6 segment of Kv 7.4 were critical for this activating effect of fasudil. Fasudil relaxed precontracted rat small arteries in a concentration-dependent fashion; this effect was antagonized by the Kv 7 channel blocker XE991. CONCLUSIONS AND IMPLICATIONS These results suggest that fasudil is a selective Kv 7.4/Kv 7.5 channel opener and provide a new dimension for developing selective Kv 7 modulators and a new prospective for the use, action and mechanism of fasudil.
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Affiliation(s)
- Xuan Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China.,Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China.,Department of Pharmacology, Institution of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang, China
| | - Hailong An
- Key Laboratory of Molecular Biophysics, Hebei Province; Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Junwei Li
- Key Laboratory of Molecular Biophysics, Hebei Province; Institute of Biophysics, School of Sciences, Hebei University of Technology, Tianjin, China
| | - Yuanyuan Zhang
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Yang Liu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China.,Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Zhanfeng Jia
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Wei Zhang
- Department of Pharmacology, Institution of Chinese Integrative Medicine, Hebei Medical University, Shijiazhuang, China
| | - Li Chu
- Department of Pharmacology, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
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Zwart R, Reed H, Clarke S, Sher E. A novel muscarinic receptor-independent mechanism of KCNQ2/3 potassium channel blockade by Oxotremorine-M. Eur J Pharmacol 2016; 791:221-228. [PMID: 27590358 DOI: 10.1016/j.ejphar.2016.08.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 08/30/2016] [Accepted: 08/30/2016] [Indexed: 10/21/2022]
Abstract
Inhibition of KCNQ (Kv7) potassium channels by activation of muscarinic acetylcholine receptors has been well established, and the ion currents through these channels have been long known as M-currents. We found that this cross-talk can be reconstituted in Xenopus oocytes by co-transfection of human recombinant muscarinic M1 receptors and KCNQ2/3 potassium channels. Application of the muscarinic acetylcholine receptor agonist Oxotremorine-methiodide (Oxo-M) between voltage pulses to activate KCNQ2/3 channels caused inhibition of the subsequent KCNQ2/3 responses. This effect of Oxo-M was blocked by the muscarinic acetylcholine receptor antagonist atropine. We also found that KCNQ2/3 currents were inhibited when Oxo-M was applied during an ongoing KCNQ2/3 response, an effect that was not blocked by atropine, suggesting that Oxo-M inhibits KCNQ2/3 channels directly. Indeed, also in oocytes that were transfected with only KCNQ2/3 channels, but not with muscarinic M1 receptors, Oxo-M inhibited the KCNQ2/3 response. These results show that besides the usual muscarinic acetylcholine receptor-mediated inhibition, Oxo-M also inhibits KCNQ2/3 channels by a direct mechanism. We subsequently tested xanomeline, which is a chemically distinct muscarinic acetylcholine receptor agonist, and oxotremorine, which is a close analogue of Oxo-M. Both compounds inhibited KCNQ2/3 currents via activation of M1 muscarinic acetylcholine receptors but, in contrast to Oxo-M, they did not directly inhibit KCNQ2/3 channels. Xanomeline and oxotremorine do not contain a positively charged trimethylammonium moiety that is present in Oxo-M, suggesting that such a charged moiety could be a crucial component mediating this newly described direct inhibition of KCNQ2/3 channels.
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Affiliation(s)
- Ruud Zwart
- Eli Lilly and Company, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham GU20 6PH, United Kingdom.
| | - Hannah Reed
- Eli Lilly and Company, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham GU20 6PH, United Kingdom
| | - Sophie Clarke
- Eli Lilly and Company, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham GU20 6PH, United Kingdom
| | - Emanuele Sher
- Eli Lilly and Company, Lilly Research Centre, Erl Wood Manor, Sunninghill Road, Windlesham GU20 6PH, United Kingdom
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Yang JE, Song MS, Shen Y, Ryu PD, Lee SY. The Role of KV7.3 in Regulating Osteoblast Maturation and Mineralization. Int J Mol Sci 2016; 17:407. [PMID: 26999128 PMCID: PMC4813262 DOI: 10.3390/ijms17030407] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 03/02/2016] [Accepted: 03/10/2016] [Indexed: 11/19/2022] Open
Abstract
KCNQ (KV7) channels are voltage-gated potassium (KV) channels, and the function of KV7 channels in muscles, neurons, and sensory cells is well established. We confirmed that overall blockade of KV channels with tetraethylammonium augmented the mineralization of bone-marrow-derived human mesenchymal stem cells during osteogenic differentiation, and we determined that KV7.3 was expressed in MG-63 and Saos-2 cells at the mRNA and protein levels. In addition, functional KV7 currents were detected in MG-63 cells. Inhibition of KV7.3 by linopirdine or XE991 increased the matrix mineralization during osteoblast differentiation. This was confirmed by alkaline phosphatase, osteocalcin, and osterix in MG-63 cells, whereas the expression of Runx2 showed no significant change. The extracellular glutamate secreted by osteoblasts was also measured to investigate its effect on MG-63 osteoblast differentiation. Blockade of KV7.3 promoted the release of glutamate via the phosphorylation of extracellular signal-regulated kinase 1/2-mediated upregulation of synapsin, and induced the deposition of type 1 collagen. However, activation of KV7.3 by flupirtine did not produce notable changes in matrix mineralization during osteoblast differentiation. These results suggest that KV7.3 could be a novel regulator in osteoblast differentiation.
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Affiliation(s)
- Ji Eun Yang
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
| | - Min Seok Song
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
| | - Yiming Shen
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
| | - Pan Dong Ryu
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
| | - So Yeong Lee
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea.
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Engholm M, Pinilla E, Mogensen S, Matchkov V, Hedegaard ER, Chen H, Mulvany MJ, Simonsen U. Involvement of transglutaminase 2 and voltage-gated potassium channels in cystamine vasodilatation in rat mesenteric small arteries. Br J Pharmacol 2016; 173:839-55. [PMID: 26603619 DOI: 10.1111/bph.13393] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Revised: 10/13/2015] [Accepted: 11/10/2015] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND AND PURPOSE Vasodilatation may contribute to the neuroprotective and vascular anti-remodelling effect of the tissue transglutaminase 2 (TG2) inhibitor cystamine. Here, we hypothesized that inhibition of TG2 followed by blockade of smooth muscle calcium entry and/or inhibition of Rho kinase underlies cystamine vasodilatation. EXPERIMENTAL APPROACH We used rat mesenteric small arteries and RT-PCR, immunoblotting, and measurements of isometric wall tension, intracellular Ca(2+) ([Ca(2+)]i ), K(+) currents (patch clamp), and phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and myosin regulatory light chain, in our experiments. KEY RESULTS RT-PCR and immunoblotting revealed expression of TG2 in mesenteric small arteries. Cystamine concentration-dependently inhibited responses to phenylephrine, 5-HT and U46619 and for extracellular potassium. Selective inhibitors of TG2, LDN 27129 and T101, also inhibited phenylephrine contraction. An inhibitor of PLC suppressed cystamine relaxation. Cystamine relaxed and reduced [Ca(2+)]i in phenylephrine-contracted arteries. In potassium-contracted arteries, cystamine induced less relaxation without changing [Ca(2+)]i , and these relaxations were blocked by mitochondrial complex inhibitors. Blockers of Kv 7 channels, XE991 and linopirdine, inhibited cystamine relaxation and increases in voltage-dependent smooth muscle currents. Cystamine and the Rho kinase inhibitor Y27632 reduced basal MYPT1-Thr(855) phosphorylation, but only Y27632 reduced phenylephrine-induced increases in MYPT1-Thr(855) and myosin regulatory light chain phosphorylation. CONCLUSIONS AND IMPLICATIONS Cystamine induced vasodilatation by inhibition of receptor-coupled TG2, leading to opening of Kv channels and reduction of intracellular calcium, and by activation of a pathway sensitive to inhibitors of the mitochondrial complexes I and III. Both pathways may contribute to the antihypertensive and neuroprotective effect of cystamine.
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Affiliation(s)
- Morten Engholm
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Estéfano Pinilla
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Susie Mogensen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Vladimir Matchkov
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Elise Røge Hedegaard
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Hua Chen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Michael J Mulvany
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, Aarhus University, Denmark
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Choveau FS, Zhang J, Bierbower SM, Sharma R, Shapiro MS. The Role of the Carboxyl Terminus Helix C-D Linker in Regulating KCNQ3 K+ Current Amplitudes by Controlling Channel Trafficking. PLoS One 2015; 10:e0145367. [PMID: 26692086 PMCID: PMC4687061 DOI: 10.1371/journal.pone.0145367] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/01/2015] [Indexed: 12/18/2022] Open
Abstract
In the central and peripheral nervous system, the assembly of KCNQ3 with KCNQ2 as mostly heteromers, but also homomers, underlies “M-type” currents, a slowly-activating voltage-gated K+ current that plays a dominant role in neuronal excitability. KCNQ3 homomers yield much smaller currents compared to KCNQ2 or KCNQ4 homomers and KCNQ2/3 heteromers. This smaller current has been suggested to result either from divergent channel surface expression or from a pore that is more unstable in KCNQ3. Channel surface expression has been shown to be governed by the distal part of the C-terminus in which helices C and D are critical for channel trafficking and assembly. A sequence alignment of this region in KCNQ channels shows that KCNQ3 possesses a longer linker between helix C and D compared to the other KCNQ subunits. Here, we investigate the role of the extra residues of this linker on KCNQ channel expression. Deletion of these residues increased KCNQ3 current amplitudes. Total internal reflection fluorescence imaging and plasma membrane protein assays suggest that the increase in current is due to a higher surface expression of the channels. Conversely, introduction of the extra residues into the linker between helices C and D of KCNQ4 reduced current amplitudes by decreasing the number of KCNQ4 channels at the plasma membrane. Confocal imaging suggests a higher fraction of channels, which possess the extra residues of helix C-D linker, were retained within the endoplasmic reticulum. Such retention does not appear to lead to protein accumulation and activation of the unfolded protein response that regulates protein folding and maintains endoplasmic reticulum homeostasis. Taken together, we conclude that extra helix C-D linker residues play a role in KCNQ3 current amplitudes by controlling the exit of the channel from the endoplasmic reticulum.
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Affiliation(s)
- Frank S. Choveau
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Jie Zhang
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Sonya M. Bierbower
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Ramaswamy Sharma
- Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
| | - Mark S. Shapiro
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America
- * E-mail:
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Gründemann J, Clark BA. Calcium-Activated Potassium Channels at Nodes of Ranvier Secure Axonal Spike Propagation. Cell Rep 2015; 12:1715-22. [PMID: 26344775 PMCID: PMC4590545 DOI: 10.1016/j.celrep.2015.08.022] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 06/22/2015] [Accepted: 08/05/2015] [Indexed: 12/01/2022] Open
Abstract
Functional connectivity between brain regions relies on long-range signaling by myelinated axons. This is secured by saltatory action potential propagation that depends fundamentally on sodium channel availability at nodes of Ranvier. Although various potassium channel types have been anatomically localized to myelinated axons in the brain, direct evidence for their functional recruitment in maintaining node excitability is scarce. Cerebellar Purkinje cells provide continuous input to their targets in the cerebellar nuclei, reliably transmitting axonal spikes over a wide range of rates, requiring a constantly available pool of nodal sodium channels. We show that the recruitment of calcium-activated potassium channels (IK, KCa3.1) by local, activity-dependent calcium (Ca2+) influx at nodes of Ranvier via a T-type voltage-gated Ca2+ current provides a powerful mechanism that likely opposes depolarizing block at the nodes and is thus pivotal to securing continuous axonal spike propagation in spontaneously firing Purkinje cells. Activity-dependent node of Ranvier Ca2+ influx in Purkinje cell axons Cav and KCa3.1 channels required for axonal spike propagation Nodal KCa3.1 channels provide repolarizing drive to sustain axonal spike propagation
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Affiliation(s)
- Jan Gründemann
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK
| | - Beverley A Clark
- Wolfson Institute for Biomedical Research, University College London, Gower Street, London WC1E 6BT, UK.
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Rivas-Ramírez P, Cadaveira-Mosquera A, Lamas JA, Reboreda A. Muscarinic modulation of TREK currents in mouse sympathetic superior cervical ganglion neurons. Eur J Neurosci 2015; 42:1797-807. [PMID: 25899939 DOI: 10.1111/ejn.12930] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 03/30/2015] [Accepted: 04/20/2015] [Indexed: 01/05/2023]
Abstract
Muscarinic receptors play a key role in the control of neurotransmission in the autonomic ganglia, which has mainly been ascribed to the regulation of potassium M-currents and voltage-dependent calcium currents. Muscarinic agonists provoke depolarization of the membrane potential and a reduction in spike frequency adaptation in postganglionic neurons, effects that may be explained by M-current inhibition. Here, we report the presence of a riluzole-activated current (IRIL ) that flows through the TREK-2 channels, and that is also inhibited by muscarinic agonists in neurons of the mouse superior cervical ganglion (mSCG). The muscarinic agonist oxotremorine-M (Oxo-M) inhibited the IRIL by 50%, an effect that was abolished by pretreatment with atropine or pirenzepine, but was unaffected in the presence of himbacine. Moreover, these antagonists had similar effects on single-channel TREK-2 currents. IRIL inhibition was unaffected by pretreatment with pertussis toxin. The protein kinase C blocker bisindolylmaleimide did not have an effect, and neither did the inositol triphosphate antagonist 2-aminoethoxydiphenylborane. Nevertheless, the IRIL was markedly attenuated by the phospholipase C (PLC) inhibitor ET-18-OCH3. Finally, the phosphatidylinositol-3-kinase/phosphatidylinositol-4-kinase inhibitor wortmannin strongly attenuated the IRIL , whereas blocking phosphatidylinositol 4,5-bisphosphate (PIP2 ) depletion consistently prevented IRIL inhibition by Oxo-M. These results demonstrate that TREK-2 currents in mSCG neurons are inhibited by muscarinic agonists that activate M1 muscarinic receptors, reducing PIP2 levels via a PLC-dependent pathway. The similarities between the signaling pathways regulating the IRIL and the M-current in the same neurons reflect an important role of this new pathway in the control of autonomic ganglia excitability.
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Affiliation(s)
- P Rivas-Ramírez
- Department of Functional Biology and Health Sciences, Faculty of Biology - CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
| | - A Cadaveira-Mosquera
- Department of Functional Biology and Health Sciences, Faculty of Biology - CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
| | - J A Lamas
- Department of Functional Biology and Health Sciences, Faculty of Biology - CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
| | - A Reboreda
- Department of Functional Biology and Health Sciences, Faculty of Biology - CINBIO-IBIV, University of Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
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40
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Tong WC, Tribe RM, Smith R, Taggart MJ. Computational modeling reveals key contributions of KCNQ and hERG currents to the malleability of uterine action potentials underpinning labor. PLoS One 2014; 9:e114034. [PMID: 25474527 PMCID: PMC4256391 DOI: 10.1371/journal.pone.0114034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 11/03/2014] [Indexed: 11/19/2022] Open
Abstract
The electrical excitability of uterine smooth muscle cells is a key determinant of the contraction of the organ during labor and is manifested by spontaneous, periodic action potentials (APs). Near the end of term, APs vary in shape and size reflecting an ability to change the frequency, duration and amplitude of uterine contractions. A recent mathematical model quantified several ionic features of the electrical excitability in uterine smooth muscle cells. It replicated many of the experimentally recorded uterine AP configurations but its limitations were evident when trying to simulate the long-duration bursting APs characteristic of labor. A computational parameter search suggested that delayed rectifying K(+) currents could be a key model component requiring improvement to produce the longer-lasting bursting APs. Of the delayed rectifying K(+) currents family it is of interest that KCNQ and hERG channels have been reported to be gestationally regulated in the uterus. These currents exhibit features similar to the broadly defined uterine IK1 of the original mathematical model. We thus formulated new quantitative descriptions for several I(KCNQ) and I(hERG). Incorporation of these currents into the uterine cell model enabled simulations of the long-lasting bursting APs. Moreover, we used this modified model to simulate the effects of different contributions of I(KCNQ) and I(hERG) on AP form. Our findings suggest that the alterations in expression of hERG and KCNQ channels can potentially provide a mechanism for fine tuning of AP forms that lends a malleability for changing between plateau-like and long-lasting bursting-type APs as uterine cells prepare for parturition.
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Affiliation(s)
- Wing-Chiu Tong
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Rachel M. Tribe
- Division of Women's Health, King's College London and King's Health Partners, London, United Kingdom
| | - Roger Smith
- Hunter Medical Research Institute, University of Newcastle, New Lambton, New South Wales, Australia
| | - Michael J. Taggart
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
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41
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Tano JY, Gollasch M. Calcium-activated potassium channels in ischemia reperfusion: a brief update. Front Physiol 2014; 5:381. [PMID: 25339909 PMCID: PMC4186282 DOI: 10.3389/fphys.2014.00381] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/13/2014] [Indexed: 12/24/2022] Open
Abstract
Ischemia and reperfusion (IR) injury constitutes one of the major causes of cardiovascular morbidity and mortality. The discovery of new therapies to block/mediate the effects of IR is therefore an important goal in the biomedical sciences. Dysfunction associated with IR involves modification of calcium-activated potassium channels (KCa) through different mechanisms, which are still under study. Respectively, the KCa family, major contributors to plasma membrane calcium influx in cells and essential players in the regulation of the vascular tone are interesting candidates. This family is divided into two groups including the large conductance (BKCa) and the small/intermediate conductance (SKCa/IKCa) K(+) channels. In the heart and brain, these channels have been described to offer protection against IR injury. BKCa and SKCa channels deserve special attention since new data demonstrate that these channels are also expressed in mitochondria. More studies are however needed to fully determine their potential use as therapeutic targets.
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Affiliation(s)
- Jean-Yves Tano
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
| | - Maik Gollasch
- Experimental and Clinical Research Center, Charité University Medicine - Max Delbrück Center (MDC) for Molecular Medicine Berlin, Germany ; Nephrology/Intensive Care Section, Charité University Medicine Berlin, Germany
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42
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Anderson UA, Carson C, Johnston L, Joshi S, Gurney AM, McCloskey KD. Functional expression of KCNQ (Kv7) channels in guinea pig bladder smooth muscle and their contribution to spontaneous activity. Br J Pharmacol 2014; 169:1290-304. [PMID: 23586426 PMCID: PMC3746117 DOI: 10.1111/bph.12210] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 03/15/2013] [Accepted: 03/26/2013] [Indexed: 12/30/2022] Open
Abstract
Background and Purpose The aim of the study was to determine whether KCNQ channels are functionally expressed in bladder smooth muscle cells (SMC) and to investigate their physiological significance in bladder contractility. Experimental Approach KCNQ channels were examined at the genetic, protein, cellular and tissue level in guinea pig bladder smooth muscle using RT-PCR, immunofluorescence, patch-clamp electrophysiology, calcium imaging, detrusor strip myography, and a panel of KCNQ activators and inhibitors. Key Results KCNQ subtypes 1–5 are expressed in bladder detrusor smooth muscle. Detrusor strips typically displayed TTX-insensitive myogenic spontaneous contractions that were increased in amplitude by the KCNQ channel inhibitors XE991, linopirdine or chromanol 293B. Contractility was inhibited by the KCNQ channel activators flupirtine or meclofenamic acid (MFA). The frequency of Ca2+-oscillations in SMC contained within bladder tissue sheets was increased by XE991. Outward currents in dispersed bladder SMC, recorded under conditions where BK and KATP currents were minimal, were significantly reduced by XE991, linopirdine, or chromanol, and enhanced by flupirtine or MFA. XE991 depolarized the cell membrane and could evoke transient depolarizations in quiescent cells. Flupirtine (20 μM) hyperpolarized the cell membrane with a simultaneous cessation of any spontaneous electrical activity. Conclusions and Implications These novel findings reveal the role of KCNQ currents in the regulation of the resting membrane potential of detrusor SMC and their important physiological function in the control of spontaneous contractility in the guinea pig bladder.
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Affiliation(s)
- U A Anderson
- Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
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43
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Tano JY, Schleifenbaum J, Gollasch M. Perivascular adipose tissue, potassium channels, and vascular dysfunction. Arterioscler Thromb Vasc Biol 2014; 34:1827-30. [PMID: 25012133 DOI: 10.1161/atvbaha.114.303032] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Perivascular adipose tissue has been recognized unequivocally as a major player in the pathology of metabolic and cardiovascular diseases. Through its production of adipokines and the release of other thus far unidentified factors, this recently discovered adipose tissue modulates vascular regulation and the myogenic response. After the discovery of its ability to diminish the vessel's response to vasoconstrictors, a new paradigm established adipose-derived relaxing factor (ADRF) as a paracrine smooth muscle cells' potassium channel opener that could potentially help combat vascular dysfunction. This review will discuss the role of ADRF in vascular dysfunction in obesity and hypertension, the different potassium channels that can be activated by this factor, and describes new pharmacological tools that can mimic the ADRF effect and thus can be beneficial against vascular dysfunction in cardiovascular disease.
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Affiliation(s)
- Jean-Yves Tano
- From the Experimental and Clinical Research Center, Berlin-Buch, Germany; and Nephrology/Intensive Care Section, Charité Campus Virchow, Berlin, Germany.
| | - Johanna Schleifenbaum
- From the Experimental and Clinical Research Center, Berlin-Buch, Germany; and Nephrology/Intensive Care Section, Charité Campus Virchow, Berlin, Germany
| | - Maik Gollasch
- From the Experimental and Clinical Research Center, Berlin-Buch, Germany; and Nephrology/Intensive Care Section, Charité Campus Virchow, Berlin, Germany
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44
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King CH, Lancaster E, Salomon D, Peles E, Scherer SS. Kv7.2 regulates the function of peripheral sensory neurons. J Comp Neurol 2014; 522:3262-80. [PMID: 24687876 DOI: 10.1002/cne.23595] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 03/27/2014] [Accepted: 03/28/2014] [Indexed: 11/08/2022]
Abstract
The Kv7 (KCNQ) family of voltage-gated K(+) channels regulates cellular excitability. The functional role of Kv7.2 has been hampered by the lack of a viable Kcnq2-null animal model. In this study, we generated homozygous Kcnq2-null sensory neurons using the Cre-Lox system; in these mice, Kv7.2 expression is absent in the peripheral sensory neurons, whereas the expression of other molecular components of nodes (including Kv7.3), paranodes, and juxtaparanodes is not altered. The conditional Kcnq2-null animals exhibit normal motor performance but have increased thermal hyperalgesia and mechanical allodynia. Whole-cell patch recording technique demonstrates that Kcnq2-null sensory neurons have increased excitability and reduced spike frequency adaptation. Taken together, our results suggest that the loss of Kv7.2 activity increases the excitability of primary sensory neurons.
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Affiliation(s)
- Chih H King
- Department of Neuroscience, The University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, 19104
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45
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Battefeld A, Tran BT, Gavrilis J, Cooper EC, Kole MHP. Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons. J Neurosci 2014; 34:3719-32. [PMID: 24599470 PMCID: PMC3942587 DOI: 10.1523/jneurosci.4206-13.2014] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/27/2014] [Accepted: 01/30/2014] [Indexed: 12/14/2022] Open
Abstract
Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na(v)) channels in the axonal initial segment and nodes of Ranvier. The local biophysical properties of these K(v)7 channels and the functional impact of colocalization with Na(v) channels remain poorly understood. Here, we quantitatively examined K(v)7 channels in myelinated axons of rat neocortical pyramidal neurons using high-resolution confocal imaging and patch-clamp recording. K(v)7.2 and 7.3 immunoreactivity steeply increased within the distal two-thirds of the axon initial segment and was mirrored by the conductance density estimates, which increased from ~12 (proximal) to 150 pS μm(-2) (distal). The axonal initial segment and nodal M-currents were similar in voltage dependence and kinetics, carried by K(v)7.2/7.3 heterotetramers, 4% activated at the resting membrane potential and rapidly activated with single-exponential time constants (~15 ms at 28 mV). Experiments and computational modeling showed that while somatodendritic K(v)7 channels are strongly activated by the backpropagating action potential to attenuate the afterdepolarization and repetitive firing, axonal K(v)7 channels are minimally recruited by the forward-propagating action potential. Instead, in nodal domains K(v)7.2/7.3 channels were found to increase Na(v) channel availability and action potential amplitude by stabilizing the resting membrane potential. Thus, K(v)7 clustering near axonal Na(v) channels serves specific and context-dependent roles, both restraining initiation and enhancing conduction of the action potential.
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Affiliation(s)
- Arne Battefeld
- Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, 1105 BA, Amsterdam, The Netherlands
| | - Baouyen T. Tran
- Baylor College of Medicine, Baylor Plaza, Houston, Texas 77030
| | - Jason Gavrilis
- Eccles Institute for Neuroscience, The Australian National University, Canberra 0200, Australian Capital Territory, Australia, and
- Department of Audiology and Speech Pathology, University of Melbourne, Melbourne, Victoria 3010, Australia
| | | | - Maarten H. P. Kole
- Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, 1105 BA, Amsterdam, The Netherlands
- Eccles Institute for Neuroscience, The Australian National University, Canberra 0200, Australian Capital Territory, Australia, and
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Robbins J, Passmore GM, Abogadie FC, Reilly JM, Brown DA. Effects of KCNQ2 gene truncation on M-type Kv7 potassium currents. PLoS One 2013; 8:e71809. [PMID: 23977150 PMCID: PMC3748097 DOI: 10.1371/journal.pone.0071809] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 07/02/2013] [Indexed: 11/23/2022] Open
Abstract
The KCNQ2 gene product, Kv7.2, is a subunit of the M-channel, a low-threshold voltage-gated K+ channel that regulates mammalian and human neuronal excitability. Spontaneous mutations one of the KCNQ2 genes cause disorders of neural excitability such as Benign Familial Neonatal Seizures. However there appear to be no reports in which both human KCNQ2 genes are mutated. We therefore asked what happens to M-channel function when both KCNQ2 genes are disrupted. We addressed this using sympathetic neurons isolated from mice in which the KCNQ2 gene was truncated at a position corresponding to the second transmembrane domain of the Kv7.2 protein. Since homozygote KCNQ2−/− mice die postnatally, experiments were largely restricted to neurons from late embryos. Quantitative PCR revealed an absence of KCNQ2 mRNA in ganglia from KCNQ2−/− embryos but 100–120% increase of KCNQ3 and KCNQ5 mRNAs; KCNQ2+/− ganglia showed ∼30% less KCNQ2 mRNA than wild-type (+/+) ganglia but 40–50% more KCNQ3 and KCNQ5 mRNA. Neurons from KCNQ2−/− embryos showed a complete absence of M-current, even after applying the Kv7 channel enhancer, retigabine. Neurons from heterozygote KCNQ2+/− embryos had ∼60% reduced M-current. In contrast, M-currents in neurons from adult KCNQ2+/− mice were no smaller than those in neurons from wild-type mice. Measurements of tetraethylammonium block did not indicate an increased expression of Kv7.5-containing subunits, implying a compensatory increase in Kv7.2 expression from the remaining KCNQ2 gene. We conclude that mouse embryonic M-channels have an absolute requirement for Kv7.2 subunits for functionality, that the reduced M-channel activity in heterozygote KCNQ2+/− mouse embryos results primarily from a gene-dosage effect, and that there is a compensatory increase in Kv7.2 expression in adult mice.
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Affiliation(s)
- Jon Robbins
- Wolfson Centre for Age Related Disease, King's College London, London, United Kingdom
- * E-mail:
| | - Gayle M. Passmore
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Fe C. Abogadie
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- Health Innovations Research Institute, Royal Melbourne Institute of Technology University, Victoria, Australia
| | - Joanne M. Reilly
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - David A. Brown
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
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Kv3.4 potassium channel-mediated electrosignaling controls cell cycle and survival of irradiated leukemia cells. Pflugers Arch 2013; 465:1209-21. [PMID: 23443853 DOI: 10.1007/s00424-013-1249-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 01/29/2013] [Accepted: 02/08/2013] [Indexed: 10/27/2022]
Abstract
Aberrant ion channel expression in the plasma membrane is characteristic for many tumor entities and has been attributed to neoplastic transformation, tumor progression, metastasis, and therapy resistance. The present study aimed to define the function of these "oncogenic" channels for radioresistance of leukemia cells. Chronic myeloid leukemia cells were irradiated (0-6 Gy X ray), ion channel expression and activity, Ca(2+)- and protein signaling, cell cycle progression, and cell survival were assessed by quantitative reverse transcriptase-polymerase chain reaction, patch-clamp recording, fura-2 Ca(2+)-imaging, immunoblotting, flow cytometry, and clonogenic survival assays, respectively. Ionizing radiation-induced G2/M arrest was preceded by activation of Kv3.4-like voltage-gated potassium channels. Channel activation in turn resulted in enhanced Ca(2+) entry and subsequent activation of Ca(2+)/calmodulin-dependent kinase-II, and inactivation of the phosphatase cdc25B and the cyclin-dependent kinase cdc2. Accordingly, channel inhibition by tetraethylammonium and blood-depressing substance-1 and substance-2 or downregulation by RNA interference led to release from radiation-induced G2/M arrest, increased apoptosis, and decreased clonogenic survival. Together, these findings indicate the functional significance of voltage-gated K(+) channels for the radioresistance of myeloid leukemia cells.
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Abstract
Kv7 (KCNQ) potassium channel openers (enhancers) decrease neuropathic pain in experimental models. Here we show that C-fibers, and their associated small-diameter neurons in the dorsal root ganglia (both IB4- and TrkA-positive), expressed Kv7.5. In contrast, C-fibers did not express detectable levels of Kv7.2 or Kv7.3, which are instead localized to nodes of Ranvier and the cell bodies of large sensory neurons. These data suggest that Kv7.5 provides the primary M current in nociceptive neurons.
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Affiliation(s)
- Chih H King
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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Pore determinants of KCNQ3 K+ current expression. Biophys J 2012; 102:2489-98. [PMID: 22713564 DOI: 10.1016/j.bpj.2012.04.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 03/30/2012] [Accepted: 04/06/2012] [Indexed: 11/23/2022] Open
Abstract
KCNQ3 homomeric channels yield very small macroscopic currents compared with other KCNQ channels or KCNQ2/3 heteromers. Two disparate regions of the channels--the C-terminus and the pore region--have been implicated in governing KCNQ current amplitudes. We previously showed that the C-terminus plays a secondary role compared with the pore region. Here, we confirm the critical role of the pore region in determining KCNQ3 currents. We find that mutations at the 312 position in the pore helix of KCNQ3 (I312E, I312K, and I312R) dramatically decreased KCNQ3 homomeric currents as well as heteromeric KCNQ2/3 currents. Evidence that these mutants were expressed in the heteromers includes shifted TEA sensitivity compared with KCNQ2 homomers. To test for differential membrane protein expression, we performed total internal reflection fluorescence imaging, which revealed only small differences that do not underlie the differences in macroscopic currents. To determine whether this mechanism generalizes to other KCNQ channels, we tested the effects of analogous mutations at the conserved I273 position in KCNQ2, with similar results. Finally, we performed homology modeling of the pore region of wild-type and mutant KCNQ3 channels to investigate the putative structural mechanism mediating these results. The modeling suggests that the lack of current in I312E, I312K, and I312R KCNQ3 channels is due to pore helix-selectivity filter interactions that lock the selectivity filter in a nonconductive conformation.
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Abstract
UNLABELLED Visceral fat has been linked to metabolic disturbances and increased risk for cardiovascular disease and type 2 diabetes. Recent studies propose a paracrine role for periadventitial adipose tissue in the control of arterial vascular tone. This regulation depends on the anatomical integrity of the vessels and involves a transferable mediator(s) (adipokine) released from either periadventitial adipocytes or perivascular adipose tissue. Although a number of adipokines with vasoactive properties have been identified, a still unidentified adipocyte-derived relaxing factor (ADRF) plays a major role in the periadventitial vasoregulation of visceral arteries, such as the aorta and mesenteric arteries. ADRF is released by visceral periadventitial adipocytes and primarily produces endothelium-independent vasorelaxation by opening voltage-dependent (K(v) ) K(+) channels in the plasma membrane of smooth muscle cells. At least in part, KCNQ (K(v) 7) channels could represent the subtype of K(v) channels involved. Glibenclamide-sensitive K(ATP) channels are not involved or play a minor role. The 'third gas', namely H(2) S, could represent ADRF. Alterations in the paracrine control of arterial tone by visceral periadventitial adipose tissue have been found in animal models of hypertension and metabolic disease. ADRF, or perhaps its putative targets, might represent exciting new targets for the development of drugs for treatment of cardiovascular and metabolic disorders. LINKED ARTICLES This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.
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Affiliation(s)
- Maik Gollasch
- Medical Clinic for Nephrology and Internal Intensive Care, Charité Campus Virchow Klinikum, Experimental and Clinical Research Center (ECRC) and Max-Delbrück Center for Molecular Medicine, Berlin, Germany.
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