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Nguyen H, Glaaser IW, Slesinger PA. Direct modulation of G protein-gated inwardly rectifying potassium (GIRK) channels. Front Physiol 2024; 15:1386645. [PMID: 38903913 PMCID: PMC11187414 DOI: 10.3389/fphys.2024.1386645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/08/2024] [Indexed: 06/22/2024] Open
Abstract
Ion channels play a pivotal role in regulating cellular excitability and signal transduction processes. Among the various ion channels, G-protein-coupled inwardly rectifying potassium (GIRK) channels serve as key mediators of neurotransmission and cellular responses to extracellular signals. GIRK channels are members of the larger family of inwardly-rectifying potassium (Kir) channels. Typically, GIRK channels are activated via the direct binding of G-protein βγ subunits upon the activation of G-protein-coupled receptors (GPCRs). GIRK channel activation requires the presence of the lipid signaling molecule, phosphatidylinositol 4,5-bisphosphate (PIP2). GIRK channels are also modulated by endogenous proteins and other molecules, including RGS proteins, cholesterol, and SNX27 as well as exogenous compounds, such as alcohol. In the last decade or so, several groups have developed novel drugs and small molecules, such as ML297, GAT1508 and GiGA1, that activate GIRK channels in a G-protein independent manner. Here, we aim to provide a comprehensive overview focusing on the direct modulation of GIRK channels by G-proteins, PIP2, cholesterol, and novel modulatory compounds. These studies offer valuable insights into the underlying molecular mechanisms of channel function, and have potential implications for both basic research and therapeutic development.
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Affiliation(s)
| | | | - Paul A. Slesinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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2
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Beverley KM, Barbera N, Levitan I. Dual pattern of cholesterol-induced decoupling of residue-residue interactions of Kir2.2. J Struct Biol 2024; 216:108091. [PMID: 38641256 DOI: 10.1016/j.jsb.2024.108091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 03/28/2024] [Accepted: 04/09/2024] [Indexed: 04/21/2024]
Abstract
Cholesterol is a negative regulator of a variety of ion channels. We have previously shown that cholesterol suppresses Kir2.2 channels via residue-residue uncoupling on the inter-subunit interfaces within the close state of the channels (3JYC). In this study, we extend this analysis to the other known structure of Kir2.2 that is closer to the open state of Kir2.2 channels (3SPI) and provide additional analysis of the residue distances between the uncoupled residues and cholesterol binding domains in the two conformation states of the channels. We found that the general phenomenon of cholesterol binding leading to uncoupling between specific residues is conserved in both channel states but the specific pattern of the uncoupling residues is distinct between the two states and implies different mechanisms. Specifically, we found that cholesterol binding in the 3SPI state results in an uncoupling of residues in three distinct regions; the transmembrane domain, membrane-cytosolic interface, and the cytosolic domain, with the first two regions forming an envelope around PI(4,5)P2 and cholesterol binding sites and the distal region overlapping with the subunit-subunit interface characterized in our previous study of the disengaged state. We also found that this uncoupling is dependent upon the number of cholesterol molecules bound to the channel. We further generated a mutant channel Kir2.2P187V with a single point mutation in a residue proximal to the PI(4,5)P2 binding site, which is predicted to be uncoupled from other residues in its vicinity upon cholesterol binding and found that this mutation abrogates the sensitivity of Kir2.2 to cholesterol changes in the membrane. These findings suggest that cholesterol binding to this conformation state of Kir2.2 channels may destabilize the PI(4,5)P2 interactions with the channels while in the disengaged state the destabilization occurs where the subunits interact. These findings give insight into the structural mechanistic basis for the functional effects of cholesterol binding to the Kir2.2 channel.
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Affiliation(s)
- Katie M Beverley
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | - Nicolas Barbera
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA; Center for Public Health Genomics, Department of Biomedical Engineering, School of Engineering &Applied Science, University of Virginia, Charlottesville, VA 22904, USA
| | - Irena Levitan
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA.
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Moreno-Manuel AI, Macías Á, Cruz FM, Gutiérrez LK, Martínez F, González-Guerra A, Martínez Carrascoso I, Bermúdez-Jimenez FJ, Sánchez-Pérez P, Vera-Pedrosa ML, Ruiz-Robles JM, Bernal JA, Jalife J. The Kir2.1E299V mutation increases atrial fibrillation vulnerability while protecting the ventricles against arrhythmias in a mouse model of short QT syndrome type 3. Cardiovasc Res 2024; 120:490-505. [PMID: 38261726 PMCID: PMC11060485 DOI: 10.1093/cvr/cvae019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 10/24/2023] [Accepted: 12/12/2023] [Indexed: 01/25/2024] Open
Abstract
AIMS Short QT syndrome type 3 (SQTS3) is a rare arrhythmogenic disease caused by gain-of-function mutations in KCNJ2, the gene coding the inward rectifier potassium channel Kir2.1. We used a multidisciplinary approach and investigated arrhythmogenic mechanisms in an in-vivo model of de-novo mutation Kir2.1E299V identified in a patient presenting an extremely abbreviated QT interval and paroxysmal atrial fibrillation. METHODS AND RESULTS We used intravenous adeno-associated virus-mediated gene transfer to generate mouse models, and confirmed cardiac-specific expression of Kir2.1WT or Kir2.1E299V. On ECG, the Kir2.1E299V mouse recapitulated the QT interval shortening and the atrial-specific arrhythmia of the patient. The PR interval was also significantly shorter in Kir2.1E299V mice. Patch-clamping showed extremely abbreviated action potentials in both atrial and ventricular Kir2.1E299V cardiomyocytes due to a lack of inward-going rectification and increased IK1 at voltages positive to -80 mV. Relative to Kir2.1WT, atrial Kir2.1E299V cardiomyocytes had a significantly reduced slope conductance at voltages negative to -80 mV. After confirming a higher proportion of heterotetrameric Kir2.x channels containing Kir2.2 subunits in the atria, in-silico 3D simulations predicted an atrial-specific impairment of polyamine block and reduced pore diameter in the Kir2.1E299V-Kir2.2WT channel. In ventricular cardiomyocytes, the mutation increased excitability by shifting INa activation and inactivation in the hyperpolarizing direction, which protected the ventricle against arrhythmia. Moreover, Purkinje myocytes from Kir2.1E299V mice manifested substantially higher INa density than Kir2.1WT, explaining the abbreviation in the PR interval. CONCLUSION The first in-vivo mouse model of cardiac-specific SQTS3 recapitulates the electrophysiological phenotype of a patient with the Kir2.1E299V mutation. Kir2.1E299V eliminates rectification in both cardiac chambers but protects against ventricular arrhythmias by increasing excitability in both Purkinje-fiber network and ventricles. Consequently, the predominant arrhythmias are supraventricular likely due to the lack of inward rectification and atrial-specific reduced pore diameter of the Kir2.1E299V-Kir2.2WT heterotetramer.
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MESH Headings
- Animals
- Humans
- Mice
- Action Potentials
- Arrhythmias, Cardiac/genetics
- Arrhythmias, Cardiac/physiopathology
- Arrhythmias, Cardiac/metabolism
- Atrial Fibrillation/genetics
- Atrial Fibrillation/physiopathology
- Atrial Fibrillation/metabolism
- Disease Models, Animal
- Genetic Predisposition to Disease
- Heart Rate/genetics
- Heart Ventricles/metabolism
- Heart Ventricles/physiopathology
- Mice, Inbred C57BL
- Mice, Transgenic
- Mutation
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Phenotype
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
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Affiliation(s)
- Ana I Moreno-Manuel
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Álvaro Macías
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Francisco M Cruz
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Lilian K Gutiérrez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Fernando Martínez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Andrés González-Guerra
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Isabel Martínez Carrascoso
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Francisco José Bermúdez-Jimenez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- Department of Cardiology, Hospital Universitario Virgen de las Nieves, 18014 Granada, Spain
| | - Patricia Sánchez-Pérez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | | | - Juan Manuel Ruiz-Robles
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
| | - Juan A Bernal
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - José Jalife
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
- Departments of Internal Medicine and Molecular and Integrative Physiology, Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI 4810, USA
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Sourisseau F, Chahine C, Pouliot V, Cens T, Charnet P, Chahine M. Cloning, functional expression, and pharmacological characterization of inwardly rectifying potassium channels (Kir) from Apis mellifera. Sci Rep 2024; 14:7834. [PMID: 38570597 PMCID: PMC10991380 DOI: 10.1038/s41598-024-58234-0] [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: 12/01/2023] [Accepted: 03/26/2024] [Indexed: 04/05/2024] Open
Abstract
Potassium channels belong to the super family of ion channels and play a fundamental role in cell excitability. Kir channels are potassium channels with an inwardly rectifying property. They play a role in setting the resting membrane potential of many excitable cells including neurons. Although putative Kir channel family genes can be found in the Apis mellifera genome, their functional expression, biophysical properties, and sensitivity to small molecules with insecticidal activity remain to be investigated. We cloned six Kir channel isoforms from Apis mellifera that derive from two Kir genes, AmKir1 and AmKir2, which are present in the Apis mellifera genome. We studied the tissue distribution, the electrophysiological and pharmacological characteristics of three isoforms that expressed functional currents (AmKir1.1, AmKir2.2, and AmKir2.3). AmKir1.1, AmKir2.2, and AmKir2.3 isoforms exhibited distinct characteristics when expressed in Xenopus oocytes. AmKir1.1 exhibited the largest potassium currents and was impermeable to cesium whereas AmKir2.2 and AmKir2.3 exhibited smaller currents but allowed cesium to permeate. AmKir1 exhibited faster opening kinetics than AmKir2. Pharmacological experiments revealed that both AmKir1.1 and AmKir2.2 are blocked by the divalent ion barium, with IC50 values of 10-5 and 10-6 M, respectively. The concentrations of VU041, a small molecule with insecticidal properties required to achieve a 50% current blockade for all three channels were higher than those needed to block Kir channels in other arthropods, such as the aphid Aphis gossypii and the mosquito Aedes aegypti. From this, we conclude that Apis mellifera AmKir channels exhibit lower sensitivity to VU041.
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Affiliation(s)
- Fabien Sourisseau
- CERVO Brain Research Centre, 2601, chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Chaimaa Chahine
- CERVO Brain Research Centre, 2601, chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Valérie Pouliot
- CERVO Brain Research Centre, 2601, chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada
| | - Thierry Cens
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, 1919 Route de Mende, Montpellier, France
| | - Pierre Charnet
- Institut des Biomolécules Max Mousseron (IBMM), CNRS UMR 5247, 1919 Route de Mende, Montpellier, France
| | - Mohamed Chahine
- CERVO Brain Research Centre, 2601, chemin de la Canardière, Quebec City, QC, G1J 2G3, Canada.
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada.
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5
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Delgado-Bermúdez A, Yeste M, Bonet S, Pinart E. Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation. Andrology 2024. [PMID: 38436215 DOI: 10.1111/andr.13606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 01/16/2024] [Accepted: 01/29/2024] [Indexed: 03/05/2024]
Abstract
BACKGROUND Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ). MATERIAL-METHODS The present review includes recent findings on the role of potassium channels in sperm physiology of mammals. RESULTS-DISCUSSION While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs. CONCLUSIONS Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.
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Affiliation(s)
- Ariadna Delgado-Bermúdez
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Marc Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), Barcelona, Spain
| | - Sergi Bonet
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
| | - Elisabeth Pinart
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain
- Department of Biology, Faculty of Sciences, Unit of Cell Biology, University of Girona, Girona, Spain
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6
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Zhao Y, Zhang X, Liu L, Hu F, Chang F, Han Z, Li C. Insights into Activation Dynamics and Functional Sites of Inwardly Rectifying Potassium Channel Kir3.2 by an Elastic Network Model Combined with Perturbation Methods. J Phys Chem B 2024; 128:1360-1370. [PMID: 38308647 DOI: 10.1021/acs.jpcb.3c06739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2024]
Abstract
The inwardly rectifying potassium channel Kir3.2, a member of the inward rectifier potassium (Kir) channel family, exerts important biological functions through transporting potassium ions outside of the cell, during which a large-scale synergistic movement occurs among its different domains. Currently, it is not fully understood how the binding of the ligand to the Kir3.2 channel leads to the structural changes and which key residues are responsible for the channel gating and allosteric dynamics. Here, we construct the Gaussian network model (GNM) of the Kir3.2 channel with the secondary structure and covalent interaction information considered (sscGNM), which shows a better performance in reproducing the channel's flexibility compared with the traditional GNM. In addition, the sscANM-based perturbation method is used to simulate the channel's conformational transition caused by the activator PIP2's binding. By applying certain forces to the PIP2 binding pocket, the coarse-grained calculations generate the similar conformational changes to the experimental observation, suggesting that the topology structure as well as PIP2 binding are crucial to the allosteric activation of the Kir3.2 channel. We also utilize the sscGNM-based thermodynamic cycle method developed by us to identify the key residues whose mutations significantly alter the channel's binding free energy with PIP2. We identify not only the residues important for the specific binding but also the ones critical for the allosteric transition coupled with PIP2 binding. This study is helpful for understanding the working mechanism of Kir3.2 channels and can provide important information for related drug design.
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Affiliation(s)
- Yingchun Zhao
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Xinyu Zhang
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Lamei Liu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Fangrui Hu
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Fubin Chang
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Zhongjie Han
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
| | - Chunhua Li
- Faculty of Environmental and Life Sciences, Beijing University of Technology, Beijing 100124, China
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7
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Beverley KM, Levitan I. Cholesterol regulation of mechanosensitive ion channels. Front Cell Dev Biol 2024; 12:1352259. [PMID: 38333595 PMCID: PMC10850386 DOI: 10.3389/fcell.2024.1352259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/17/2024] [Indexed: 02/10/2024] Open
Abstract
The purpose of this review is to evaluate the role of cholesterol in regulating mechanosensitive ion channels. Ion channels discussed in this review are sensitive to two types of mechanical signals, fluid shear stress and/or membrane stretch. Cholesterol regulates the channels primarily in two ways: 1) indirectly through localizing the channels into cholesterol-rich membrane domains where they interact with accessory proteins and/or 2) direct binding of cholesterol to the channel at specified putative binding sites. Cholesterol may also regulate channel function via changes of the biophysical properties of the membrane bilayer. Changes in cholesterol affect both mechanosensitivity and basal channel function. We focus on four mechanosensitive ion channels in this review Piezo, Kir2, TRPV4, and VRAC channels. Piezo channels were shown to be regulated by auxiliary proteins that enhance channel function in high cholesterol domains. The direct binding mechanism was shown in Kir2.1 and TRPV4 where cholesterol inhibits channel function. Finally, cholesterol regulation of VRAC was attributed to changes in the physical properties of lipid bilayer. Additional studies should be performed to determine the physiological implications of these sterol effects in complex cellular environments.
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Affiliation(s)
- Katie M. Beverley
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States
| | - Irena Levitan
- Division of Pulmonary, Critical Care, Sleep, and Allergy, Department of Medicine, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States
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8
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Nguyen NH, Sarangi S, McChesney EM, Sheng S, Durrant JD, Porter AW, Kleyman TR, Pitluk ZW, Brodsky JL. Genome mining yields putative disease-associated ROMK variants with distinct defects. PLoS Genet 2023; 19:e1011051. [PMID: 37956218 PMCID: PMC10695394 DOI: 10.1371/journal.pgen.1011051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Revised: 12/04/2023] [Accepted: 11/04/2023] [Indexed: 11/15/2023] Open
Abstract
Bartter syndrome is a group of rare genetic disorders that compromise kidney function by impairing electrolyte reabsorption. Left untreated, the resulting hyponatremia, hypokalemia, and dehydration can be fatal, and there is currently no cure. Bartter syndrome type II specifically arises from mutations in KCNJ1, which encodes the renal outer medullary potassium channel, ROMK. Over 40 Bartter syndrome-associated mutations in KCNJ1 have been identified, yet their molecular defects are mostly uncharacterized. Nevertheless, a subset of disease-linked mutations compromise ROMK folding in the endoplasmic reticulum (ER), which in turn results in premature degradation via the ER associated degradation (ERAD) pathway. To identify uncharacterized human variants that might similarly lead to premature degradation and thus disease, we mined three genomic databases. First, phenotypic data in the UK Biobank were analyzed using a recently developed computational platform to identify individuals carrying KCNJ1 variants with clinical features consistent with Bartter syndrome type II. In parallel, we examined genomic data in both the NIH TOPMed and ClinVar databases with the aid of Rhapsody, a verified computational algorithm that predicts mutation pathogenicity and disease severity. Subsequent phenotypic studies using a yeast screen to assess ROMK function-and analyses of ROMK biogenesis in yeast and human cells-identified four previously uncharacterized mutations. Among these, one mutation uncovered from the two parallel approaches (G228E) destabilized ROMK and targeted it for ERAD, resulting in reduced cell surface expression. Another mutation (T300R) was ERAD-resistant, but defects in channel activity were apparent based on two-electrode voltage clamp measurements in X. laevis oocytes. Together, our results outline a new computational and experimental pipeline that can be applied to identify disease-associated alleles linked to a range of other potassium channels, and further our understanding of the ROMK structure-function relationship that may aid future therapeutic strategies to advance precision medicine.
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Affiliation(s)
- Nga H. Nguyen
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Srikant Sarangi
- Paradigm4, Inc., Waltham, Massachusetts, United States of America
| | - Erin M. McChesney
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Shaohu Sheng
- Renal-Electrolyte Division, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Jacob D. Durrant
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Aidan W. Porter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Thomas R. Kleyman
- Renal-Electrolyte Division, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | | | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
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9
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Nguyen NH, Sarangi S, McChesney EM, Sheng S, Porter AW, Kleyman TR, Pitluk ZW, Brodsky JL. Genome mining yields new disease-associated ROMK variants with distinct defects. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.05.539609. [PMID: 37214976 PMCID: PMC10197530 DOI: 10.1101/2023.05.05.539609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bartter syndrome is a group of rare genetic disorders that compromise kidney function by impairing electrolyte reabsorption. Left untreated, the resulting hyponatremia, hypokalemia, and dehydration can be fatal. Although there is no cure for this disease, specific genes that lead to different Bartter syndrome subtypes have been identified. Bartter syndrome type II specifically arises from mutations in the KCNJ1 gene, which encodes the renal outer medullary potassium channel, ROMK. To date, over 40 Bartter syndrome-associated mutations in KCNJ1 have been identified. Yet, their molecular defects are mostly uncharacterized. Nevertheless, a subset of disease-linked mutations compromise ROMK folding in the endoplasmic reticulum (ER), which in turn results in premature degradation via the ER associated degradation (ERAD) pathway. To identify uncharacterized human variants that might similarly lead to premature degradation and thus disease, we mined three genomic databases. First, phenotypic data in the UK Biobank were analyzed using a recently developed computational platform to identify individuals carrying KCNJ1 variants with clinical features consistent with Bartter syndrome type II. In parallel, we examined ROMK genomic data in both the NIH TOPMed and ClinVar databases with the aid of a computational algorithm that predicts protein misfolding and disease severity. Subsequent phenotypic studies using a high throughput yeast screen to assess ROMK function-and analyses of ROMK biogenesis in yeast and human cells-identified four previously uncharacterized mutations. Among these, one mutation uncovered from the two parallel approaches (G228E) destabilized ROMK and targeted it for ERAD, resulting in reduced protein expression at the cell surface. Another ERAD-targeted ROMK mutant (L320P) was found in only one of the screens. In contrast, another mutation (T300R) was ERAD-resistant, but defects in ROMK activity were apparent after expression and two-electrode voltage clamp measurements in Xenopus oocytes. Together, our results outline a new computational and experimental pipeline that can be applied to identify disease-associated alleles linked to a range of other potassium channels, and further our understanding of the ROMK structure-function relationship that may aid future therapeutic strategies. Author Summary Bartter syndrome is a rare genetic disorder characterized by defective renal electrolyte handing, leading to debilitating symptoms and, in some patients, death in infancy. Currently, there is no cure for this disease. Bartter syndrome is divided into five types based on the causative gene. Bartter syndrome type II results from genetic variants in the gene encoding the ROMK protein, which is expressed in the kidney and assists in regulating sodium, potassium, and water homeostasis. Prior work established that some disease-associated ROMK mutants misfold and are destroyed soon after their synthesis in the endoplasmic reticulum (ER). Because a growing number of drugs have been identified that correct defective protein folding, we wished to identify an expanded cohort of similarly misshapen and unstable disease-associated ROMK variants. To this end, we developed a pipeline that employs computational analyses of human genome databases with genetic and biochemical assays. Next, we both confirmed the identity of known variants and uncovered previously uncharacterized ROMK variants associated with Bartter syndrome type II. Further analyses indicated that select mutants are targeted for ER-associated degradation, while another mutant compromises ROMK function. This work sets-the-stage for continued mining for ROMK loss of function alleles as well as other potassium channels, and positions select Bartter syndrome mutations for correction using emerging pharmaceuticals.
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10
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Li E, Kool W, Woolschot L, van der Heyden MAG. Chronic Propafenone Application Increases Functional K IR2.1 Expression In Vitro. Pharmaceuticals (Basel) 2023; 16:ph16030404. [PMID: 36986503 PMCID: PMC10056987 DOI: 10.3390/ph16030404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 02/28/2023] [Accepted: 03/04/2023] [Indexed: 03/30/2023] Open
Abstract
Expression and activity of inwardly rectifying potassium (KIR) channels within the heart are strictly regulated. KIR channels have an important role in shaping cardiac action potentials, having a limited conductance at depolarized potentials but contributing to the final stage of repolarization and resting membrane stability. Impaired KIR2.1 function causes Andersen-Tawil Syndrome (ATS) and is associated with heart failure. Restoring KIR2.1 function by agonists of KIR2.1 (AgoKirs) would be beneficial. The class 1c antiarrhythmic drug propafenone is identified as an AgoKir; however, its long-term effects on KIR2.1 protein expression, subcellular localization, and function are unknown. Propafenone's long-term effect on KIR2.1 expression and its underlying mechanisms in vitro were investigated. KIR2.1-carried currents were measured by single-cell patch-clamp electrophysiology. KIR2.1 protein expression levels were determined by Western blot analysis, whereas conventional immunofluorescence and advanced live-imaging microscopy were used to assess the subcellular localization of KIR2.1 proteins. Acute propafenone treatment at low concentrations supports the ability of propafenone to function as an AgoKir without disturbing KIR2.1 protein handling. Chronic propafenone treatment (at 25-100 times higher concentrations than in the acute treatment) increases KIR2.1 protein expression and KIR2.1 current densities in vitro, which are potentially associated with pre-lysosomal trafficking inhibition.
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Affiliation(s)
- Encan Li
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Willy Kool
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Liset Woolschot
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands
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11
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Jogini V, Jensen MØ, Shaw DE. Gating and modulation of an inward-rectifier potassium channel. J Gen Physiol 2022; 155:213765. [PMID: 36524993 PMCID: PMC9764021 DOI: 10.1085/jgp.202213085] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
Inward-rectifier potassium channels (Kirs) are lipid-gated ion channels that differ from other K+ channels in that they allow K+ ions to flow more easily into, rather than out of, the cell. Inward rectification is known to result from endogenous magnesium ions or polyamines (e.g., spermine) binding to Kirs, resulting in a block of outward potassium currents, but questions remain regarding the structural and dynamic basis of the rectification process and lipid-dependent channel activation. Here, we present the results of long-timescale molecular dynamics simulations starting from a crystal structure of phosphatidylinositol 4,5-bisphosphate (PIP2)-bound chicken Kir2.2 with a non-conducting pore. After introducing a mutation (G178R) that is known to increase the open probability of a homologous channel, we were able to observe transitions to a stably open, ion-conducting pore, during which key conformational changes occurred in the main activation gate and the cytoplasmic domain. PIP2 binding appeared to increase stability of the pore in its open and conducting state, as PIP2 removal resulted in pore closure, with a median closure time about half of that with PIP2 present. To investigate structural details of inward rectification, we simulated spermine binding to and unbinding from the open pore conformation at positive and negative voltages, respectively, and identified a spermine-binding site located near a previously hypothesized site between the pore cavity and the selectivity filter. We also studied the effects of long-range electrostatics on conduction and spermine binding by mutating charged residues in the cytoplasmic domain and found that a finely tuned charge density, arising from basic and acidic residues within the cytoplasmic domain, modulated conduction and rectification.
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Affiliation(s)
| | | | - David E. Shaw
- D. E. Shaw Research, New York, NY, USA,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
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12
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Fernandes CAH, Zuniga D, Fagnen C, Kugler V, Scala R, Péhau-Arnaudet G, Wagner R, Perahia D, Bendahhou S, Vénien-Bryan C. Cryo-electron microscopy unveils unique structural features of the human Kir2.1 channel. SCIENCE ADVANCES 2022; 8:eabq8489. [PMID: 36149965 PMCID: PMC9506730 DOI: 10.1126/sciadv.abq8489] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 08/04/2022] [Indexed: 06/16/2023]
Abstract
We present the first structure of the human Kir2.1 channel containing both transmembrane domain (TMD) and cytoplasmic domain (CTD). Kir2.1 channels are strongly inward-rectifying potassium channels that play a key role in maintaining resting membrane potential. Their gating is modulated by phosphatidylinositol 4,5-bisphosphate (PIP2). Genetically inherited defects in Kir2.1 channels are responsible for several rare human diseases, including Andersen's syndrome. The structural analysis (cryo-electron microscopy), surface plasmon resonance, and electrophysiological experiments revealed a well-connected network of interactions between the PIP2-binding site and the G-loop through residues R312 and H221. In addition, molecular dynamics simulations and normal mode analysis showed the intrinsic tendency of the CTD to tether to the TMD and a movement of the secondary anionic binding site to the membrane even without PIP2. Our results revealed structural features unique to human Kir2.1 and provided insights into the connection between G-loop and gating and the pathological mechanisms associated with this channel.
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Affiliation(s)
- Carlos A. H. Fernandes
- UMR 7590, CNRS, Muséum National d’Histoire Naturelle, IRD, Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, 75005 Paris, France
| | - Dania Zuniga
- UMR 7590, CNRS, Muséum National d’Histoire Naturelle, IRD, Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, 75005 Paris, France
| | - Charline Fagnen
- UMR 7590, CNRS, Muséum National d’Histoire Naturelle, IRD, Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, 75005 Paris, France
| | - Valérie Kugler
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS–University of Strasbourg, Illkirch, Cedex, France
| | - Rosa Scala
- CNRS UMR7370, LP2M, Labex ICST, Faculté de Médecine, Université Côte d’Azur, Nice, France
| | - Gérard Péhau-Arnaudet
- Ultrastructural BioImaging Core Facility/UMR 3528, Institut Pasteur, 75724 Paris Cedex 15, France
| | - Renaud Wagner
- IMPReSs Facility, Biotechnology and Cell Signaling UMR 7242, CNRS–University of Strasbourg, Illkirch, Cedex, France
| | - David Perahia
- Laboratoire de Biologie et Pharmacologie Appliquée, Ecole Normale Supérieure Paris-Saclay, 4 Ave. des Sciences, 91190 Gif-sur-Yvette, France
| | - Saïd Bendahhou
- CNRS UMR7370, LP2M, Labex ICST, Faculté de Médecine, Université Côte d’Azur, Nice, France
| | - Catherine Vénien-Bryan
- UMR 7590, CNRS, Muséum National d’Histoire Naturelle, IRD, Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, IMPMC, Sorbonne Université, 75005 Paris, France
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13
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Lee S, Kang BE, Song YK, Baker BJ. A trafficking motif alters GEVI activity implicating persistent protein interactions at the membrane. BIOPHYSICAL REPORTS 2022; 2:100047. [PMID: 36425771 PMCID: PMC9680705 DOI: 10.1016/j.bpr.2022.100047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 02/18/2022] [Indexed: 11/30/2022]
Abstract
Efficient plasma-membrane expression is critical for genetically encoded voltage indicators (GEVIs). To improve the plasma-membrane expression, we introduced multiple combinations of plasma-membrane trafficking motifs at different positions to members of the Bongwoori family of GEVIs. An improvement from 20% to 27% in the ΔF/F/100 mV depolarization of the plasma membrane was observed when a Golgi transport motif was inserted near the N-terminus in conjunction with an endoplasmic reticulum release motif near the C-terminus of the protein. Unfortunately, this variant was also slower. The weighted tau on of the variant (25 ms) was more than double the original construct (11 ms). The weighted tau off was >20 ms compared with 10 ms for the original GEVI. The voltage range of the GEVI was also shifted to more negative potentials. Insertion of spacer amino acids between the fluorescent-protein domain and the endoplasmic reticulum release motif at the C-terminus rescued the speed of both the tau on and tau off while restoring the voltage range and maintaining the improved voltage-dependent optical signal. These results suggest that while trafficking motifs do improve plasma-membrane expression, they may also mediate persistent associations that affect the functioning of the protein.
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14
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Barbera N, Granados ST, Vanoye CG, Abramova TV, Kulbak D, Ahn SJ, George AL, Akpa BS, Levitan I. Cholesterol-induced suppression of Kir2 channels is mediated by decoupling at the inter-subunit interfaces. iScience 2022; 25:104329. [PMID: 35602957 PMCID: PMC9120057 DOI: 10.1016/j.isci.2022.104329] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/29/2022] [Accepted: 04/26/2022] [Indexed: 12/29/2022] Open
Abstract
Cholesterol is a major regulator of multiple types of ion channels. Although there is increasing information about cholesterol binding sites, the molecular mechanisms through which cholesterol binding alters channel function are virtually unknown. In this study, we used a combination of Martini coarse-grained simulations, a network theory-based analysis, and electrophysiology to determine the effect of cholesterol on the dynamic structure of the Kir2.2 channel. We found that increasing membrane cholesterol reduced the likelihood of contact between specific regions of the cytoplasmic and transmembrane domains of the channel, most prominently at the subunit-subunit interfaces of the cytosolic domains. This decrease in contact was mediated by pairwise interactions of specific residues and correlated to the stoichiometry of cholesterol binding events. The predictions of the model were tested by site-directed mutagenesis of two identified residues-V265 and H222-and high throughput electrophysiology.
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Affiliation(s)
- Nicolas Barbera
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sara T. Granados
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Carlos Guillermo Vanoye
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Tatiana V. Abramova
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Danielle Kulbak
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Sang Joon Ahn
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
| | - Alfred L. George
- Department of Pharmacology; Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Belinda S. Akpa
- Division of Biosciences, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
- Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA
- Molecular Biomedical Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Irena Levitan
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Illinois at Chicago, Chicago, IL 60611, USA
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15
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Santovito D, Weber C. Non-canonical features of microRNAs: paradigms emerging from cardiovascular disease. Nat Rev Cardiol 2022; 19:620-638. [PMID: 35304600 DOI: 10.1038/s41569-022-00680-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/14/2022] [Indexed: 02/08/2023]
Abstract
Research showing that microRNAs (miRNAs) are versatile regulators of gene expression has instigated tremendous interest in cardiovascular research. The overwhelming majority of studies are predicated on the dogmatic notion that miRNAs regulate the expression of specific target mRNAs by inhibiting mRNA translation or promoting mRNA decay in the RNA-induced silencing complex (RISC). These efforts mostly identified and dissected contributions of multiple regulatory networks of miRNA-target mRNAs to cardiovascular pathogenesis. However, evidence from studies in the past decade indicates that miRNAs also operate beyond this canonical paradigm, featuring non-conventional regulatory functions and cellular localizations that have a pathophysiological role in cardiovascular disease. In this Review, we highlight the functional relevance of atypical miRNA biogenesis and localization as well as RISC heterogeneity. Moreover, we delineate remarkable non-canonical examples of miRNA functionality, including direct interactions with proteins beyond the Argonaute family and their role in transcriptional regulation in the nucleus and in mitochondria. We scrutinize the relevance of non-conventional biogenesis and non-canonical functions of miRNAs in cardiovascular homeostasis and pathology, and contextualize how uncovering these non-conventional properties can expand the scope of translational research in the cardiovascular field and beyond.
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Affiliation(s)
- Donato Santovito
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-Universität (LMU), Munich, Germany. .,German Center for Cardiovascular Research (DZHK), partner site Munich Heart Alliance, Munich, Germany. .,Institute for Genetic and Biomedical Research (IRGB), Unit of Milan, National Research Council, Milan, Italy.
| | - Christian Weber
- Institute for Cardiovascular Prevention (IPEK), Ludwig-Maximilians-Universität (LMU), Munich, Germany. .,German Center for Cardiovascular Research (DZHK), partner site Munich Heart Alliance, Munich, Germany. .,Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, Netherlands. .,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
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16
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Gilles O. K + -independent Kir blockade by external Cs + and Ba 2. Physiol Rep 2022; 10:e15200. [PMID: 35274814 PMCID: PMC8915156 DOI: 10.14814/phy2.15200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/14/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023] Open
Abstract
Cations such as Cs+ and Ba2+ are known to block K+ currents by entering an open channel and binding to the selectivity filter, where they obstruct the pore and block diffusion of the permeant ion. This obstruction is voltage- and K+ -dependent and is relieved by the trans permeant ion flux. The present patch-clamp study on Xenopus muscle cells shows that, unlike the voltage-activated K+ (Kv) channels, blockade of the inward rectifier K+ (Kir) channels by external foreign cations results from the combination of pore obstruction with a new and independent mechanism. This new blockade is independent of the K+ concentrations and flux and acts indiscriminately on both the outward and the inward Kir components. External Cs+ and Ba2+ compete for this blockade with free access to common channel sites. These features suggest that the blocking cations do not need to enter the channel for this new mechanism, and should bind to the extracellular side of the channel. When K+ fluxes are flowing outward, the pore obstruction is relieved for both Kir and Kv currents, and the K+ -independent blockade here described is responsible for a selective Kir inhibition, justifying the use of these external cations as tools in cell physiology studies.
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Affiliation(s)
- Ouanounou Gilles
- Université Paris‐SaclayCNRSInstitut des Neurosciences Paris‐SaclaySaclayFrance
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17
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Coyote-Maestas W, Nedrud D, He Y, Schmidt D. Determinants of trafficking, conduction, and disease within a K + channel revealed through multiparametric deep mutational scanning. eLife 2022; 11:76903. [PMID: 35639599 PMCID: PMC9273215 DOI: 10.7554/elife.76903] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 05/27/2022] [Indexed: 01/04/2023] Open
Abstract
A long-standing goal in protein science and clinical genetics is to develop quantitative models of sequence, structure, and function relationships to understand how mutations cause disease. Deep mutational scanning (DMS) is a promising strategy to map how amino acids contribute to protein structure and function and to advance clinical variant interpretation. Here, we introduce 7429 single-residue missense mutations into the inward rectifier K+ channel Kir2.1 and determine how this affects folding, assembly, and trafficking, as well as regulation by allosteric ligands and ion conduction. Our data provide high-resolution information on a cotranslationally folded biogenic unit, trafficking and quality control signals, and segregated roles of different structural elements in fold stability and function. We show that Kir2.1 surface trafficking mutants are underrepresented in variant effect databases, which has implications for clinical practice. By comparing fitness scores with expert-reviewed variant effects, we can predict the pathogenicity of 'variants of unknown significance' and disease mechanisms of known pathogenic mutations. Our study in Kir2.1 provides a blueprint for how multiparametric DMS can help us understand the mechanistic basis of genetic disorders and the structure-function relationships of proteins.
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Affiliation(s)
- Willow Coyote-Maestas
- Department of Biochemistry, Molecular Biology and Biophysics, University of MinnesotaMinneapolisUnited States
| | - David Nedrud
- Department of Biochemistry, Molecular Biology and Biophysics, University of MinnesotaMinneapolisUnited States
| | - Yungui He
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
| | - Daniel Schmidt
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
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18
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Shalomov B, Handklo-Jamal R, Reddy HP, Theodor N, Bera AK, Dascal N. A revised mechanism of action of hyperaldosteronism-linked mutations in cytosolic domains of GIRK4 (KCNJ5). J Physiol 2021; 600:1419-1437. [PMID: 34957562 DOI: 10.1113/jp282690] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 12/21/2021] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Mutations in GIRK4 (KCNJ5) G-protein gated channels cause primary aldosteronism, a major cause of secondary hypertension. The primary mechanism is believed to be loss of K+ selectivity. R52H and E246K, aldosteronism-causing mutations in cytosolic N- and C- termini of GIRK4, were reported to cause loss of K+ selectivity. We show that R52H, E246K and G247R mutations render homotetrameric GIRK channels non-functional. In heterotetrameric context with GIRK1, these mutations impair membrane expression, interaction with Gβγ and open probability, but do not alter K+ selectivity or inward rectification. In human aldosterone-secreting cell line, a GIRK4 opener and overexpression of heterotetrameric GIRK1/4WT , but not over-expression of GIRK1/4 mutants, reduced aldosterone secretion. Aldosteronism-causing mutations in cytosolic domain of GIRK4 are loss-of-function mutations rather than gain-of-function, selectivity-loss mutations. Deciphering of exact biophysical mechanism that impairs the channel is crucial for setting the course of treatment. ABSTRACT G-protein gated, inwardly rectifying potassium channels (GIRK) mediate inhibitory transmission in brain and heart, and are present in adrenal cortex. GIRK4 (KCNJ5) subunits are abundant in the heart and adrenal cortex. Multiple mutations of KCNJ5 cause primary aldosteronism (PA). Mutations in the pore region of GIRK4 cause loss of K+ selectivity, Na+ influx, and depolarization of zona glomerulosa cells followed by hypersecretion of aldosterone. The concept of selectivity loss has been extended to mutations in cytosolic domains of GIRK4 channels, remote from the pore. We expressed aldosteronism-linked GIRK4R52H , GIRK4E246K , and GIRK4G247R mutants in Xenopus oocytes. Whole-cell currents of heterotetrameric GIRK1/4R52H and GIRK1/4E246K channels were greatly reduced compared to GIRK1/4WT . Nevertheless, all heterotetrameric mutants retained full K+ selectivity and inward rectification. When expressed as homotetramers, only GIRK4WT , but none of the mutants, produced whole-cell currents. Confocal imaging, single channel and Förster Resonance Energy Transfer (FRET) analyses showed: 1) reduction of membrane abundance of all mutated channels, especially as homotetramers, 2) impaired interaction with Gβγ subunits, and 3) reduced open probability of GIRK1/4R52H . VU0529331, a GIRK4 opener, activated homotetrameric GIRK4G247R channels, but not GIRK4R52H and GIRK4E246K . In human adrenocortical carcinoma cell line (HAC15), VU0529331 and over-expression of heterotetrameric GIRK1/4WT , but not over-expression of GIRK1/4 mutants, reduced aldosterone secretion. Our results suggest that, contrary to pore mutants of GIRK4, non-pore mutants R52H and E246K mutants are loss-of-function rather than gain-of-function/selectivity-loss mutants. Hence, GIRK4 openers may be a potential course of treatment for patients with cytosolic N- and C-terminal mutations. Abstract Figure: There are two mutations types in KCNJ5 (GIRK4) that can cause excessive secretion of aldosterone, leading to primary aldosteronism. Mutations of the first type render the channel non-selective to monovalent cations and often constitutively active, thus depolarizing the zona granulosa cells. This previously described mechanism underlies the disease-causing effects of mutations of amino acid residues located in the pore region (red color). Blockers of the channel may be useful as potential treatment to reduce aldosterone secretion. Here we show that mutations of the second type, located in the cytosolic domain remote from the pore, act by a different mechanism. They do not alter channel's ion selectivity or rectification but cause poor expression or poor activation by Gβγ, resulting in a reduction in cell's K+ conductance and depolarization. In this case, GIRK4 openers can potentially be useful to prevent the excessive aldosterone secretion. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Boris Shalomov
- Department of Physiology and Pharmacology, School of Medicine, and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Reem Handklo-Jamal
- Department of Physiology and Pharmacology, School of Medicine, and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Haritha P Reddy
- Department of Physiology and Pharmacology, School of Medicine, and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel.,Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, 600036, India
| | - Neta Theodor
- Department of Physiology and Pharmacology, School of Medicine, and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Amal K Bera
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, 600036, India
| | - Nathan Dascal
- Department of Physiology and Pharmacology, School of Medicine, and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 69978, Israel
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19
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Brown KA, Anderson C, Reilly L, Sondhi K, Ge Y, Eckhardt LL. Proteomic Analysis of the Functional Inward Rectifier Potassium Channel (Kir) 2.1 Reveals Several Novel Phosphorylation Sites. Biochemistry 2021; 60:3292-3301. [PMID: 34676745 DOI: 10.1021/acs.biochem.1c00555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Membrane proteins represent a large family of proteins that perform vital physiological roles and represent key drug targets. Despite their importance, bioanalytical methods aiming to comprehensively characterize the post-translational modification (PTM) of membrane proteins remain challenging compared to other classes of proteins in part because of their inherent low expression and hydrophobicity. The inward rectifier potassium channel (Kir) 2.1, an integral membrane protein, is critical for the maintenance of the resting membrane potential and phase-3 repolarization of the cardiac action potential in the heart. The importance of this channel to cardiac physiology is highlighted by the recognition of several sudden arrhythmic death syndromes, Andersen-Tawil and short QT syndromes, which are associated with loss or gain of function mutations in Kir2.1, often triggered by changes in the β-adrenergic tone. Therefore, understanding the PTMs of this channel (particularly β-adrenergic tone-driven phosphorylation) is important for arrhythmia prevention. Here, we developed a proteomic method, integrating both top-down (intact protein) and bottom-up (after enzymatic digestion) proteomic analyses, to characterize the PTMs of recombinant wild-type and mutant Kir2.1, successfully mapping five novel sites of phosphorylation and confirming a sixth site. Our study provides a framework for future work to assess the role of PTMs in regulating Kir2.1 functions.
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Affiliation(s)
- Kyle A Brown
- Department of Surgery, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.,Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Corey Anderson
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Kunal Sondhi
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Ying Ge
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States.,Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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20
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Chen L, He Y, Wang X, Ge J, Li H. Ventricular voltage-gated ion channels: Detection, characteristics, mechanisms, and drug safety evaluation. Clin Transl Med 2021; 11:e530. [PMID: 34709746 PMCID: PMC8516344 DOI: 10.1002/ctm2.530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 07/23/2021] [Accepted: 07/26/2021] [Indexed: 02/06/2023] Open
Abstract
Cardiac voltage-gated ion channels (VGICs) play critical roles in mediating cardiac electrophysiological signals, such as action potentials, to maintain normal heart excitability and contraction. Inherited or acquired alterations in the structure, expression, or function of VGICs, as well as VGIC-related side effects of pharmaceutical drug delivery can result in abnormal cellular electrophysiological processes that induce life-threatening cardiac arrhythmias or even sudden cardiac death. Hence, to reduce possible heart-related risks, VGICs must be acknowledged as important targets in drug discovery and safety studies related to cardiac disease. In this review, we first summarize the development and application of electrophysiological techniques that are employed in cardiac VGIC studies alone or in combination with other techniques such as cryoelectron microscopy, optical imaging and optogenetics. Subsequently, we describe the characteristics, structure, mechanisms, and functions of various well-studied VGICs in ventricular myocytes and analyze their roles in and contributions to both physiological cardiac excitability and inherited cardiac diseases. Finally, we address the implications of the structure and function of ventricular VGICs for drug safety evaluation. In summary, multidisciplinary studies on VGICs help researchers discover potential targets of VGICs and novel VGICs in heart, enrich their knowledge of the properties and functions, determine the operation mechanisms of pathological VGICs, and introduce groundbreaking trends in drug therapy strategies, and drug safety evaluation.
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Affiliation(s)
- Lulan Chen
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Yue He
- Department of CardiologyShanghai Xuhui District Central Hospital & Zhongshan‐xuhui HospitalShanghaiChina
| | - Xiangdong Wang
- Institute of Clinical Science, Zhongshan HospitalFudan UniversityShanghaiChina
| | - Junbo Ge
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
| | - Hua Li
- Department of Cardiology, Shanghai Institute of Cardiovascular DiseasesShanghai Xuhui District Central Hospital & Zhongshan‐xuhui Hospital, Zhongshan Hospital, Fudan UniversityShanghaiChina
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21
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van Aalst E, Wylie BJ. Cholesterol Is a Dose-Dependent Positive Allosteric Modulator of CCR3 Ligand Affinity and G Protein Coupling. Front Mol Biosci 2021; 8:724603. [PMID: 34490352 PMCID: PMC8417553 DOI: 10.3389/fmolb.2021.724603] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Accepted: 07/14/2021] [Indexed: 01/14/2023] Open
Abstract
Cholesterol as an allosteric modulator of G protein-coupled receptor (GPCR) function is well documented. This quintessential mammalian lipid facilitates receptor–ligand interactions and multimerization states. Functionally, this introduces a complicated mechanism for the homeostatic modulation of GPCR signaling. Chemokine receptors are Class A GPCRs responsible for immune cell trafficking through the binding of endogenous peptide ligands. CCR3 is a CC motif chemokine receptor expressed by eosinophils and basophils. It traffics these cells by transducing the signal stimulated by the CC motif chemokine primary messengers 11, 24, and 26. These behaviors are close to the human immunoresponse. Thus, CCR3 is implicated in cancer metastasis and inflammatory conditions. However, there is a paucity of experimental evidence linking the functional states of CCR3 to the molecular mechanisms of cholesterol–receptor cooperativity. In this vein, we present a means to combine codon harmonization and a maltose-binding protein fusion tag to produce CCR3 from E. coli. This technique yields ∼2.6 mg of functional GPCR per liter of minimal media. We leveraged this protein production capability to investigate the effects of cholesterol on CCR3 function in vitro. We found that affinity for the endogenous ligand CCL11 increases in a dose-dependent manner with cholesterol concentration in both styrene:maleic acid lipid particles (SMALPs) and proteoliposomes. This heightened receptor activation directly translates to increased signal transduction as measured by the GTPase activity of the bound G-protein α inhibitory subunit 3 (Gαi3). This work represents a critical step forward in understanding the role of cholesterol-GPCR allostery in regulation of signal transduction.
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Affiliation(s)
- Evan van Aalst
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, United States
| | - Benjamin J Wylie
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, United States
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22
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Kir Channel Molecular Physiology, Pharmacology, and Therapeutic Implications. Handb Exp Pharmacol 2021; 267:277-356. [PMID: 34345939 DOI: 10.1007/164_2021_501] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
For the past two decades several scholarly reviews have appeared on the inwardly rectifying potassium (Kir) channels. We would like to highlight two efforts in particular, which have provided comprehensive reviews of the literature up to 2010 (Hibino et al., Physiol Rev 90(1):291-366, 2010; Stanfield et al., Rev Physiol Biochem Pharmacol 145:47-179, 2002). In the past decade, great insights into the 3-D atomic resolution structures of Kir channels have begun to provide the molecular basis for their functional properties. More recently, computational studies are beginning to close the time domain gap between in silico dynamic and patch-clamp functional studies. The pharmacology of these channels has also been expanding and the dynamic structural studies provide hope that we are heading toward successful structure-based drug design for this family of K+ channels. In the present review we focus on placing the physiology and pharmacology of this K+ channel family in the context of atomic resolution structures and in providing a glimpse of the promising future of therapeutic opportunities.
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23
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Abstract
The physiological heart function is controlled by a well-orchestrated interplay of different ion channels conducting Na+, Ca2+ and K+. Cardiac K+ channels are key players of cardiac repolarization counteracting depolarizating Na+ and Ca2+ currents. In contrast to Na+ and Ca2+, K+ is conducted by many different channels that differ in activation/deactivation kinetics as well as in their contribution to different phases of the action potential. Together with modulatory subunits these K+ channel α-subunits provide a wide range of repolarizing currents with specific characteristics. Moreover, due to expression differences, K+ channels strongly influence the time course of the action potentials in different heart regions. On the other hand, the variety of different K+ channels increase the number of possible disease-causing mutations. Up to now, a plethora of gain- as well as loss-of-function mutations in K+ channel forming or modulating proteins are known that cause severe congenital cardiac diseases like the long-QT-syndrome, the short-QT-syndrome, the Brugada syndrome and/or different types of atrial tachyarrhythmias. In this chapter we provide a comprehensive overview of different K+ channels in cardiac physiology and pathophysiology.
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24
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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25
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Déri S, Borbás J, Hartai T, Hategan L, Csányi B, Visnyovszki Á, Madácsy T, Maléth J, Hegedűs Z, Nagy I, Arora R, Labro AJ, Környei L, Varró A, Sepp R, Ördög B. Impaired cytoplasmic domain interactions cause co-assembly defect and loss of function in the p.Glu293Lys KNCJ2 variant isolated from an Andersen-Tawil syndrome patient. Cardiovasc Res 2021; 117:1923-1934. [PMID: 32810216 DOI: 10.1093/cvr/cvaa249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/16/2020] [Accepted: 08/12/2020] [Indexed: 02/07/2023] Open
Abstract
AIMS Subunit interactions at the cytoplasmic domain interface (CD-I) have recently been shown to control gating in inward rectifier potassium channels. Here we report the novel KCNJ2 variant p.Glu293Lys that has been found in a patient with Andersen-Tawil syndrome type 1 (ATS1), causing amino acid substitution at the CD-I of the inward rectifier potassium channel subunit Kir2.1. Neither has the role of Glu293 in gating control been investigated nor has a pathogenic variant been described at this position. This study aimed to assess the involvement of Glu293 in CD-I subunit interactions and to establish the pathogenic role of the p.Glu293Lys variant in ATS1. METHODS AND RESULTS The p.Glu293Lys variant produced no current in homomeric form and showed dominant-negative effect over wild-type (WT) subunits. Immunocytochemical labelling showed the p.Glu293Lys subunits to distribute in the subsarcolemmal space. Salt bridge prediction indicated the presence of an intersubunit salt bridge network at the CD-I of Kir2.1, with the involvement of Glu293. Subunit interactions were studied by the NanoLuc® Binary Technology (NanoBiT) split reporter assay. Reporter constructs carrying NanoBiT tags on the intracellular termini produced no bioluminescent signal above background with the p.Glu293Lys variant in homomeric configuration and significantly reduced signals in cells co-expressing WT and p.Glu293Lys subunits simultaneously. Extracellularly presented reporter tags, however, generated comparable bioluminescent signals with heteromeric WT and p.Glu293Lys subunits and with homomeric WT channels. CONCLUSIONS Loss of function and dominant-negative effect confirm the causative role of p.Glu293Lys in ATS1. Co-assembly of Kir2.1 subunits is impaired in homomeric channels consisting of p.Glu293Lys subunits and is partially rescued in heteromeric complexes of WT and p.Glu293Lys Kir2.1 variants. These data point to an important role of Glu293 in mediating subunit assembly, as well as in gating of Kir2.1 channels.
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Affiliation(s)
- Szilvia Déri
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Dóm tér 12, PO Box 427, Szeged 6720, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Dóm tér 12, 6720 Szeged, Hungary
| | - János Borbás
- 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Semmelweis u. 8, 6725 Szeged, Hungary
| | - Teodóra Hartai
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Dóm tér 12, PO Box 427, Szeged 6720, Hungary
| | - Lidia Hategan
- 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Semmelweis u. 8, 6725 Szeged, Hungary
| | - Beáta Csányi
- 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Semmelweis u. 8, 6725 Szeged, Hungary
| | - Ádám Visnyovszki
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Dóm tér 12, PO Box 427, Szeged 6720, Hungary
| | - Tamara Madácsy
- 1st Department of Internal Medicine, University of Szeged, Korányi fasor 8-10, 6720 Szeged, Hungary, Hungary
| | - József Maléth
- 1st Department of Internal Medicine, University of Szeged, Korányi fasor 8-10, 6720 Szeged, Hungary, Hungary
| | - Zoltán Hegedűs
- Institute of Biophysics, Biological Research Centre of the Hungarian Academy of Sciences, Temesvári krt. 62, 6726 Szeged, Hungary
- Department of Biochemistry and Medical Chemistry, University of Pécs, Szigeti út 12, 7624 Pécs, Hungary
| | - István Nagy
- Institute of Biochemistry, Biological Research Centre the Hungarian Academy of Sciences, Temesvári krt. 62, 6726 Szeged, Hungary
- Seqomics Biotechnology Ltd, Vállalkozók útja 7, 6782 Mórahalom, Hungary
| | - Rohit Arora
- Department of Veterinary Sciences, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium
| | - Alain J Labro
- Department of Biomedical Sciences, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium
- Department of Basic Medical Sciences, University of Ghent, C. Heymanslaan 10, 9000 Ghent, Belgium
| | - László Környei
- Gottsegen György National Institute of Cardiology, Haller u. 9, 1096 Budapest, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Dóm tér 12, PO Box 427, Szeged 6720, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Dóm tér 12, 6720 Szeged, Hungary
- MTA-SZTE Research Group for Cardiovascular Pharmacology, Hungarian Academy of Sciences, Dóm tér 12, 6720 Szeged, Hungary
| | - Róbert Sepp
- 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Semmelweis u. 8, 6725 Szeged, Hungary
| | - Balázs Ördög
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Dóm tér 12, PO Box 427, Szeged 6720, Hungary
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Fagnen C, Bannwarth L, Zuniga D, Oubella I, De Zorzi R, Forest E, Scala R, Guilbault S, Bendahhou S, Perahia D, Vénien-Bryan C. Unexpected Gating Behaviour of an Engineered Potassium Channel Kir. Front Mol Biosci 2021; 8:691901. [PMID: 34179097 PMCID: PMC8222812 DOI: 10.3389/fmolb.2021.691901] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 05/26/2021] [Indexed: 11/24/2022] Open
Abstract
In this study, we investigated the dynamics and functional characteristics of the KirBac3.1 S129R, a mutated bacterial potassium channel for which the inner pore-lining helix (TM2) was engineered so that the bundle crossing is trapped in an open conformation. The structure of this channel has been previously determined at high atomic resolution. We explored the dynamical characteristics of this open state channel using an in silico method MDeNM that combines molecular dynamics simulations and normal modes. We captured the global and local motions at the mutation level and compared these data with HDX-MS experiments. MDeNM provided also an estimation of the probability of the different opening states that are in agreement with our electrophysiological experiments. In the S129R mutant, the Arg129 mutation releases the two constriction points in the channel that existed in the wild type but interestingly creates another restriction point.
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Affiliation(s)
- Charline Fagnen
- UMR 7590, CNRS, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Université, Paris, France.,Laboratoire de Biologie et de Pharmacologie Appliquée, Ecole Normale Supérieure Paris-Saclay, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
| | - Ludovic Bannwarth
- UMR 7590, CNRS, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Université, Paris, France
| | - Dania Zuniga
- UMR 7590, CNRS, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Université, Paris, France
| | - Iman Oubella
- UMR 7590, CNRS, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Université, Paris, France
| | - Rita De Zorzi
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy
| | - Eric Forest
- IBS University Grenoble Alpes, CNRS, CEA, Grenoble, France
| | - Rosa Scala
- Faculté de Médecine, CNRS UMR7370, LP2M, Labex ICST, University Côte d'Azur, Nice, France
| | - Samuel Guilbault
- Faculté de Médecine, CNRS UMR7370, LP2M, Labex ICST, University Côte d'Azur, Nice, France
| | - Saïd Bendahhou
- Faculté de Médecine, CNRS UMR7370, LP2M, Labex ICST, University Côte d'Azur, Nice, France
| | - David Perahia
- Laboratoire de Biologie et de Pharmacologie Appliquée, Ecole Normale Supérieure Paris-Saclay, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
| | - Catherine Vénien-Bryan
- UMR 7590, CNRS, Muséum National d'Histoire Naturelle, Institut de Minéralogie, Physique des Matériaux et Cosmochimie, IMPMC, Sorbonne Université, Paris, France
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27
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Marmolejo-Murillo LG, Aréchiga-Figueroa IA, Moreno-Galindo EG, Ferrer T, Zamora-Cárdenas R, Navarro-Polanco RA, Sánchez-Chapula JA, Rodríguez-Menchaca AA. Kir4.1/Kir5.1 channels possess strong intrinsic inward rectification determined by a voltage-dependent K+-flux gating mechanism. J Gen Physiol 2021; 153:211949. [PMID: 33822868 PMCID: PMC8025212 DOI: 10.1085/jgp.201912540] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 11/10/2020] [Accepted: 03/16/2021] [Indexed: 11/20/2022] Open
Abstract
Inwardly rectifying potassium (Kir) channels are broadly expressed in both excitable and nonexcitable tissues, where they contribute to a wide variety of cellular functions. Numerous studies have established that rectification of Kir channels is not an inherent property of the channel protein itself, but rather reflects strong voltage dependence of channel block by intracellular cations, such as polyamines and Mg2+. Here, we identify a previously unknown mechanism of inward rectification in Kir4.1/Kir5.1 channels in the absence of these endogenous blockers. This novel intrinsic rectification originates from the voltage-dependent behavior of Kir4.1/Kir5.1, which is generated by the flux of potassium ions through the channel pore; the inward K+-flux induces the opening of the gate, whereas the outward flux is unable to maintain the gate open. This gating mechanism powered by the K+-flux is convergent with the gating of PIP2 because, at a saturating concentration, PIP2 greatly reduces the inward rectification. Our findings provide evidence of the coexistence of two rectification mechanisms in Kir4.1/Kir5.1 channels: the classical inward rectification induced by blocking cations and an intrinsic voltage-dependent mechanism generated by the K+-flux gating.
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Affiliation(s)
- Leticia G Marmolejo-Murillo
- Departamento de Medicina y Nutrición, División de Ciencias de la Salud, Universidad de Guanajuato, León, México
| | - Iván A Aréchiga-Figueroa
- Consejo Nacional de Ciencia y Tecnologia, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
| | - Eloy G Moreno-Galindo
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | - Tania Ferrer
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | | | | | - José A Sánchez-Chapula
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México
| | - Aldo A Rodríguez-Menchaca
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, México.,Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, México
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28
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An D, Peigneur S, Tytgat J. WIN55,212-2, a Dual Modulator of Cannabinoid Receptors and G Protein-Coupled Inward Rectifier Potassium Channels. Biomedicines 2021; 9:484. [PMID: 33924979 PMCID: PMC8146939 DOI: 10.3390/biomedicines9050484] [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: 04/09/2021] [Revised: 04/22/2021] [Accepted: 04/22/2021] [Indexed: 11/16/2022] Open
Abstract
The coupling of cannabinoid receptors, CB1 and CB2, to G protein-coupled inward rectifier potassium channels, GIRK1 and GIRK2, modulates neuronal excitability in the human brain. The present study established and validated the functional expression in a Xenopus laevis oocyte expression system of CB1 and CB2 receptors, interacting with heteromeric GIRK1/2 channels and a regulator of G protein signaling, RGS4. This ex vivo system enables the discovery of a wide range of ligands interacting orthosterically or allosterically with CB1 and/or CB2 receptors. WIN55,212-2, a non-selective agonist of CB1 and CB2, was used to explore the CB1- or CB2-GIRK1/2-RGS4 signaling cascade. We show that WIN55,212-2 activates CB1 and CB2 at low concentrations whereas at higher concentrations it exerts a direct block of GIRK1/2. This illustrates a dual modulatory function, a feature not described before, which helps to explain the adverse effects induced by WIN55,212-2 in vivo. When comparing the effects with other typical cannabinoids such as Δ9-THC, CBD, CP55,940, and rimonabant, only WIN55,212-2 can significantly block GIRK1/2. Interestingly, the inward rectifier potassium channel, IRK1, a non-G protein-coupled potassium channel important for setting the resting membrane voltage and highly similar to GIRK1 and GIRK2, is not sensitive to WIN55,212-2, Δ9-THC, CBD, CP55,940, or rimonabant. From this, it is concluded that WIN55,212-2 selectively blocks GIRK1/2.
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Affiliation(s)
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg, O & N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium;
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg, O & N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium;
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29
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Yang D, Wan X, Dennis AT, Bektik E, Wang Z, Costa MG, Fagnen C, Vénien-Bryan C, Xu X, Gratz DH, Hund TJ, Mohler PJ, Laurita KR, Deschênes I, Fu JD. MicroRNA Biophysically Modulates Cardiac Action Potential by Direct Binding to Ion Channel. Circulation 2021; 143:1597-1613. [PMID: 33590773 PMCID: PMC8132313 DOI: 10.1161/circulationaha.120.050098] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND MicroRNAs (miRs) play critical roles in regulation of numerous biological events, including cardiac electrophysiology and arrhythmia, through a canonical RNA interference mechanism. It remains unknown whether endogenous miRs modulate physiologic homeostasis of the heart through noncanonical mechanisms. METHODS We focused on the predominant miR of the heart (miR1) and investigated whether miR1 could physically bind with ion channels in cardiomyocytes by electrophoretic mobility shift assay, in situ proximity ligation assay, RNA pull down, and RNA immunoprecipitation assays. The functional modulations of cellular electrophysiology were evaluated by inside-out and whole-cell patch clamp. Mutagenesis of miR1 and the ion channel was used to understand the underlying mechanism. The effect on the heart ex vivo was demonstrated through investigating arrhythmia-associated human single nucleotide polymorphisms with miR1-deficient mice. RESULTS We found that endogenous miR1 could physically bind with cardiac membrane proteins, including an inward-rectifier potassium channel Kir2.1. The miR1-Kir2.1 physical interaction was observed in mouse, guinea pig, canine, and human cardiomyocytes. miR1 quickly and significantly suppressed IK1 at sub-pmol/L concentration, which is close to endogenous miR expression level. Acute presence of miR1 depolarized resting membrane potential and prolonged final repolarization of the action potential in cardiomyocytes. We identified 3 miR1-binding residues on the C-terminus of Kir2.1. Mechanistically, miR1 binds to the pore-facing G-loop of Kir2.1 through the core sequence AAGAAG, which is outside its RNA interference seed region. This biophysical modulation is involved in the dysregulation of gain-of-function Kir2.1-M301K mutation in short QT or atrial fibrillation. We found that an arrhythmia-associated human single nucleotide polymorphism of miR1 (hSNP14A/G) specifically disrupts the biophysical modulation while retaining the RNA interference function. It is remarkable that miR1 but not hSNP14A/G relieved the hyperpolarized resting membrane potential in miR1-deficient cardiomyocytes, improved the conduction velocity, and eliminated the high inducibility of arrhythmia in miR1-deficient hearts ex vivo. CONCLUSIONS Our study reveals a novel evolutionarily conserved biophysical action of endogenous miRs in modulating cardiac electrophysiology. Our discovery of miRs' biophysical modulation provides a more comprehensive understanding of ion channel dysregulation and may provide new insights into the pathogenesis of cardiac arrhythmias.
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Affiliation(s)
- Dandan Yang
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Xiaoping Wan
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Adrienne T. Dennis
- Department of Medicine, Heart and Vascular Research Center, The MetroHealth System, Case Western Reserve University, Cleveland, OH 44109, USA
| | - Emre Bektik
- Department of Medicine, Heart and Vascular Research Center, The MetroHealth System, Case Western Reserve University, Cleveland, OH 44109, USA
| | - Zhihua Wang
- Fuwai Hospital Chinese Academy of Medical Sciences, Shenzhen, Shenzhen, China
| | - Mauricio G.S. Costa
- Institute of Mineralogy, Materials Physics and Cosmochemistry, UMR 7590, Sorbonne Université, CNRS, MNHN, Paris F-75005, France
- Oswaldo Cruz Foundation, Scientific Computing Program, Vice Presidency of Education, Information and Communication, Rio de Janeiro, Brazil
| | - Charline Fagnen
- Institute of Mineralogy, Materials Physics and Cosmochemistry, UMR 7590, Sorbonne Université, CNRS, MNHN, Paris F-75005, France
| | - Catherine Vénien-Bryan
- Institute of Mineralogy, Materials Physics and Cosmochemistry, UMR 7590, Sorbonne Université, CNRS, MNHN, Paris F-75005, France
| | - Xianyao Xu
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Departments of Biomedical Engineering and Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Daniel H. Gratz
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Departments of Biomedical Engineering and Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Thomas J. Hund
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Departments of Biomedical Engineering and Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - Peter J. Mohler
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Kenneth R. Laurita
- Department of Medicine, Heart and Vascular Research Center, The MetroHealth System, Case Western Reserve University, Cleveland, OH 44109, USA
| | - Isabelle Deschênes
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Ji-Dong Fu
- The Dorothy M. Davis Heart and Lung Research Institute, Frick Center for Heart Failure and Arrhythmia, Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH 43210, USA
- Department of Medicine, Heart and Vascular Research Center, The MetroHealth System, Case Western Reserve University, Cleveland, OH 44109, USA
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30
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Therapeutic potential of targeting G protein-gated inwardly rectifying potassium (GIRK) channels in the central nervous system. Pharmacol Ther 2021; 223:107808. [PMID: 33476640 DOI: 10.1016/j.pharmthera.2021.107808] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/05/2021] [Indexed: 12/15/2022]
Abstract
G protein-gated inwardly rectifying potassium channels (Kir3/GirK) are important for maintaining resting membrane potential, cell excitability and inhibitory neurotransmission. Coupled to numerous G protein-coupled receptors (GPCRs), they mediate the effects of many neurotransmitters, neuromodulators and hormones contributing to the general homeostasis and particular synaptic plasticity processes, learning, memory and pain signaling. A growing number of behavioral and genetic studies suggest a critical role for the appropriate functioning of the central nervous system, as well as their involvement in many neurologic and psychiatric conditions, such as neurodegenerative diseases, mood disorders, attention deficit hyperactivity disorder, schizophrenia, epilepsy, alcoholism and drug addiction. Hence, GirK channels emerge as a very promising tool to be targeted in the current scenario where these conditions already are or will become a global public health problem. This review examines recent findings on the physiology, function, dysfunction, and pharmacology of GirK channels in the central nervous system and highlights the relevance of GirK channels as a worthful potential target to improve therapies for related diseases.
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31
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Zhao Y, Gameiro-Ros I, Glaaser IW, Slesinger PA. Advances in Targeting GIRK Channels in Disease. Trends Pharmacol Sci 2021; 42:203-215. [PMID: 33468322 DOI: 10.1016/j.tips.2020.12.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 11/30/2020] [Accepted: 12/11/2020] [Indexed: 12/12/2022]
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels are essential regulators of cell excitability in the brain. While they are implicated in a variety of neurological diseases in both human and animal model studies, their therapeutic potential has been largely untapped. Here, we review recent advances in the development of small molecule compounds that specifically modulate GIRK channels and compare them with first-generation compounds that exhibit off-target activity. We describe the method of discovery of these small molecule modulators, their chemical features, and their effects in vivo. These studies provide a promising outlook on the future development of subunit-specific GIRK modulators to regulate neuronal excitability in a brain region-specific manner.
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Affiliation(s)
- Yulin Zhao
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Isabel Gameiro-Ros
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Ian W Glaaser
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Paul A Slesinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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32
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Niu Y, Tao X, Touhara KK, MacKinnon R. Cryo-EM analysis of PIP 2 regulation in mammalian GIRK channels. eLife 2020; 9:e60552. [PMID: 32844743 PMCID: PMC7556866 DOI: 10.7554/elife.60552] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 08/25/2020] [Indexed: 12/16/2022] Open
Abstract
G-protein-gated inward rectifier potassium (GIRK) channels are regulated by G proteins and PIP2. Here, using cryo-EM single particle analysis we describe the equilibrium ensemble of structures of neuronal GIRK2 as a function of the C8-PIP2 concentration. We find that PIP2 shifts the equilibrium between two distinguishable structures of neuronal GIRK (GIRK2), extended and docked, towards the docked form. In the docked form the cytoplasmic domain, to which Gβγ binds, becomes accessible to the cytoplasmic membrane surface where Gβγ resides. Furthermore, PIP2 binding reshapes the Gβγ binding surface on the cytoplasmic domain, preparing it to receive Gβγ. We find that cardiac GIRK (GIRK1/4) can also exist in both extended and docked conformations. These findings lead us to conclude that PIP2 influences GIRK channels in a structurally similar manner to Kir2.2 channels. In Kir2.2 channels, the PIP2-induced conformational changes open the pore. In GIRK channels, they prepare the channel for activation by Gβγ.
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Affiliation(s)
- Yiming Niu
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical InstituteNew YorkUnited States
| | - Xiao Tao
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical InstituteNew YorkUnited States
| | - Kouki K Touhara
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical InstituteNew YorkUnited States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical InstituteNew YorkUnited States
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33
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Towards the Development of AgoKirs: New Pharmacological Activators to Study K ir2.x Channel and Target Cardiac Disease. Int J Mol Sci 2020; 21:ijms21165746. [PMID: 32796537 PMCID: PMC7461056 DOI: 10.3390/ijms21165746] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 12/15/2022] Open
Abstract
Inward rectifier potassium ion channels (IK1-channels) of the Kir2.x family are responsible for maintaining a stable negative resting membrane potential in excitable cells, but also play a role in processes of non-excitable tissues, such as bone development. IK1-channel loss-of-function, either congenital or acquired, has been associated with cardiac disease. Currently, basic research and specific treatment are hindered by the absence of specific and efficient Kir2.x channel activators. However, twelve different compounds, including approved drugs, show off-target IK1 activation. Therefore, these compounds contain valuable information towards the development of agonists of Kir channels, AgoKirs. We reviewed the mechanism of IK1 channel activation of these compounds, which can be classified as direct or indirect activators. Subsequently, we examined the most viable starting points for rationalized drug development and possible safety concerns with emphasis on cardiac and skeletal muscle adverse effects of AgoKirs. Finally, the potential value of AgoKirs is discussed in view of the current clinical applications of potentiators and activators in cystic fibrosis therapy.
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34
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Walczewska-Szewc K, Nowak W. Structural Determinants of Insulin Release: Disordered N-Terminal Tail of Kir6.2 Affects Potassium Channel Dynamics through Interactions with Sulfonylurea Binding Region in a SUR1 Partner. J Phys Chem B 2020; 124:6198-6211. [PMID: 32598150 PMCID: PMC7467719 DOI: 10.1021/acs.jpcb.0c02720] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
![]()
Inward rectifying
potassium ion channels (KATP), sensitive to the
ATP/ADP concentration ratio, play an important, control role in pancreatic
β cells. The channels close upon the increase of this ratio,
which, in turn, triggers insulin release to blood. Numerous mutations
in KATP lead to severe and widespread medical conditions such as diabetes.
The KATP system consists of a pore made of four Kir6.2 subunits and
four accompanying large SUR1 proteins belonging to the ABCC transporters
group. How SUR1 affects KATP function is not yet known; therefore,
we created simplified models of the Kir6.2 tetramer based on recently
determined cryo-EM KATP structures. Using all-atom molecular dynamics
(MD) with the CHARMM36 force field, targeted MD, and molecular docking,
we revealed functionally important rearrangements in the Kir6.2 pore,
induced by the presence of the SUR1 protein. The cytoplasmic domain
of Kir6.2 (CTD) is brought closer to the membrane due to interactions
with SUR1. Each Kir6.2 subunit has a conserved, functionally important,
disordered N-terminal tail. Using molecular docking, we found that
the Kir6.2 tail easily docks to the sulfonylurea drug binding region
located in the adjacent SUR1 protein. We reveal, for the first time,
dynamical behavior of the Kir6.2/SUR1 system, confirming a physiological
role of the Kir6.2 disordered tail, and we indicate structural determinants
of KATP-dependent insulin release from pancreatic β cells.
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Affiliation(s)
- Katarzyna Walczewska-Szewc
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland.,Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń, Poland
| | - Wiesław Nowak
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5, 87-100 Toruń, Poland
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35
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New Structural insights into Kir channel gating from molecular simulations, HDX-MS and functional studies. Sci Rep 2020; 10:8392. [PMID: 32439887 PMCID: PMC7242327 DOI: 10.1038/s41598-020-65246-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 04/29/2020] [Indexed: 11/25/2022] Open
Abstract
Inward rectifier potassium (Kir) channels play diverse and important roles in shaping action potentials in biological membranes. An increasing number of diseases are now known to be directly associated with abnormal Kir function. However, the gating of Kir still remains unknown. To increase our understanding of its gating mechanism, a dynamical view of the entire channel is essential. Here the gating activation was studied using a recent developped in silico method, MDeNM, which combines normal mode analysis and molecular dynamics simulations that showed for the very first time the importance of interrelated collective and localized conformational movements. In particular, we highlighted the role played by concerted movements of the different regions throughout the entire protein, such as the cytoplasmic and transmembrane domains and the slide helices. In addition, the HDX-MS analysis achieved in these studies provided a comprehensive and detailed view of the dynamics associated with open/closed transition of the Kir channel in coherence with the theoretical results. MDeNM gives access to the probability of the different opening states that are in agreement with our electrophysiological experiments. The investigations presented in this article are important to remedy dysfunctional channels and are of interest for designing new pharmacological compounds.
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36
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Handklo-Jamal R, Meisel E, Yakubovich D, Vysochek L, Beinart R, Glikson M, McMullen JR, Dascal N, Nof E, Oz S. Andersen-Tawil Syndrome Is Associated With Impaired PIP 2 Regulation of the Potassium Channel Kir2.1. Front Pharmacol 2020; 11:672. [PMID: 32499698 PMCID: PMC7243181 DOI: 10.3389/fphar.2020.00672] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 04/23/2020] [Indexed: 11/13/2022] Open
Abstract
Andersen-Tawil syndrome (ATS) type-1 is associated with loss-of-function mutations in KCNJ2 gene. KCNJ2 encodes the tetrameric inward-rectifier potassium channel Kir2.1, important to the resting phase of the cardiac action potential. Kir-channels' activity requires interaction with the agonist phosphatidylinositol-4,5-bisphosphate (PIP2). Two mutations were identified in ATS patients, V77E in the cytosolic N-terminal "slide helix" and M307V in the C-terminal cytoplasmic gate structure "G-loop." Current recordings in Kir2.1-expressing HEK cells showed that each of the two mutations caused Kir2.1 loss-of-function. Biotinylation and immunostaining showed that protein expression and trafficking of Kir2.1 to the plasma membrane were not affected by the mutations. To test the functional effect of the mutants in a heterozygote set, Kir2.1 dimers were prepared. Each dimer was composed of two Kir2.1 subunits joined with a flexible linker (i.e. WT-WT, WT dimer; WT-V77E and WT-M307V, mutant dimer). A tetrameric assembly of Kir2.1 is expected to include two dimers. The protein expression and the current density of WT dimer were equally reduced to ~25% of the WT monomer. Measurements from HEK cells and Xenopus oocytes showed that the expression of either WT-V77E or WT-M307V yielded currents of only about 20% compared to the WT dimer, supporting a dominant-negative effect of the mutants. Kir2.1 sensitivity to PIP2 was examined by activating the PIP2 specific voltage-sensitive phosphatase (VSP) that induced PIP2 depletion during current recordings, in HEK cells and Xenopus oocytes. PIP2 depletion induced a stronger and faster decay in Kir2.1 mutant dimers current compared to the WT dimer. BGP-15, a drug that has been demonstrated to have an anti-arrhythmic effect in mice, stabilized the Kir2.1 current amplitude following VSP-induced PIP2 depletion in cells expressing WT or mutant dimers. This study underlines the implication of mutations in cytoplasmic regions of Kir2.1. A newly developed calibrated VSP activation protocol enabled a quantitative assessment of changes in PIP2 regulation caused by the mutations. The results suggest an impaired function and a dominant-negative effect of the Kir2.1 variants that involve an impaired regulation by PIP2. This study also demonstrates that BGP-15 may be beneficial in restoring impaired Kir2.1 function and possibly in treating ATS symptoms.
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Affiliation(s)
| | - Eshcar Meisel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Heart Center, Sheba Medical Center, Ramat-Gan, Israel
| | - Daniel Yakubovich
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Neonatology Department, Schneider Children's Medical Center, Petah-Tikva, Israel
| | | | - Roy Beinart
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Heart Center, Sheba Medical Center, Ramat-Gan, Israel
| | - Michael Glikson
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Heart Center, Sheba Medical Center, Ramat-Gan, Israel
| | | | - Nathan Dascal
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Eyal Nof
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Heart Center, Sheba Medical Center, Ramat-Gan, Israel
| | - Shimrit Oz
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Heart Center, Sheba Medical Center, Ramat-Gan, Israel
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37
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Tobón C, Palacio LC, Chidipi B, Slough DP, Tran T, Tran N, Reiser M, Lin YS, Herweg B, Sayad D, Saiz J, Noujaim S. The Antimalarial Chloroquine Reduces the Burden of Persistent Atrial Fibrillation. Front Pharmacol 2019; 10:1392. [PMID: 31827438 PMCID: PMC6890839 DOI: 10.3389/fphar.2019.01392] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 10/31/2019] [Indexed: 12/31/2022] Open
Abstract
In clinical practice, reducing the burden of persistent atrial fibrillation by pharmacological means is challenging. We explored if blocking the background and the acetylcholine-activated inward rectifier potassium currents (IK1 and IKACh) could be antiarrhythmic in persistent atrial fibrillation. We thus tested the hypothesis that blocking IK1 and IKACh with chloroquine decreases the burden of persistent atrial fibrillation. We used patch clamp to determine the IC50 of IK1 and IKACh block by chloroquine and molecular modeling to simulate the interaction between chloroquine and Kir2.1 and Kir3.1, the molecular correlates of IK1 and IKACh. We then tested, as a proof of concept, if oral chloroquine administration to a patient with persistent atrial fibrillation can decrease the arrhythmia burden. We also simulated the effects of chloroquine in a 3D model of human atria with persistent atrial fibrillation. In patch clamp the IC50 of IK1 block by chloroquine was similar to that of IKACh. A 14-day regimen of oral chloroquine significantly decreased the burden of persistent atrial fibrillation in a patient. Mathematical simulations of persistent atrial fibrillation in a 3D model of human atria suggested that chloroquine prolonged the action potential duration, leading to failure of reentrant excitation, and the subsequent termination of the arrhythmia. The combined block of IK1 and IKACh can be a targeted therapeutic strategy for persistent atrial fibrillation.
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Affiliation(s)
| | | | - Bojjibabu Chidipi
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Diana P Slough
- Department of Chemistry, Tufts University, Medford, MA, United States
| | - Thanh Tran
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Nhi Tran
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Michelle Reiser
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Yu-Shan Lin
- Department of Chemistry, Tufts University, Medford, MA, United States
| | - Bengt Herweg
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Dany Sayad
- Cardiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
| | - Javier Saiz
- Ci2 B, Universitat Politècnica de València, Valencia, Spain
| | - Sami Noujaim
- Molecular Pharmacology and Physiology Department, University of South Florida Morsani College of Medicine, Tampa, FL, United States
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38
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Bernsteiner H, Zangerl-Plessl EM, Chen X, Stary-Weinzinger A. Conduction through a narrow inward-rectifier K + channel pore. J Gen Physiol 2019; 151:1231-1246. [PMID: 31511304 PMCID: PMC6785732 DOI: 10.1085/jgp.201912359] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 07/25/2019] [Accepted: 08/13/2019] [Indexed: 12/17/2022] Open
Abstract
G-protein–gated inwardly rectifying potassium channels are important mediators of inhibitory neurotransmission. Based on microsecond-scale molecular dynamics simulations, Bernsteiner et al. propose novel gating details that may enable K+ flux via a direct knock-on mechanism. Inwardly rectifying potassium (Kir) channels play a key role in controlling membrane potentials in excitable and unexcitable cells, thereby regulating a plethora of physiological processes. G-protein–gated Kir channels control heart rate and neuronal excitability via small hyperpolarizing outward K+ currents near the resting membrane potential. Despite recent breakthroughs in x-ray crystallography and cryo-EM, the gating and conduction mechanisms of these channels are poorly understood. MD simulations have provided unprecedented details concerning the gating and conduction mechanisms of voltage-gated K+ and Na+ channels. Here, we use multi-microsecond–timescale MD simulations based on the crystal structures of GIRK2 (Kir3.2) bound to phosphatidylinositol-4,5-bisphosphate to provide detailed insights into the channel’s gating dynamics, including insights into the behavior of the G-loop gate. The simulations also elucidate the elementary steps that underlie the movement of K+ ions through an inward-rectifier K+ channel under an applied electric field. Our simulations suggest that K+ permeation might occur via direct knock-on, similar to the mechanism recently shown for Kv channels.
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Affiliation(s)
- Harald Bernsteiner
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
| | | | - Xingyu Chen
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
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39
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Robinson CV, Rohacs T, Hansen SB. Tools for Understanding Nanoscale Lipid Regulation of Ion Channels. Trends Biochem Sci 2019; 44:795-806. [PMID: 31060927 PMCID: PMC6729126 DOI: 10.1016/j.tibs.2019.04.001] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 03/23/2019] [Accepted: 04/01/2019] [Indexed: 11/17/2022]
Abstract
Anionic phospholipids are minor but prominent components of the plasma membrane that are necessary for ion channel function. Their persistence in bulk membranes, in particular phosphatidylinositol 4,5-bisphosphate (PIP2), initially suggested they act as channel cofactors. However, recent technologies have established an emerging system of nanoscale signaling to ion channels based on lipid compartmentalization (clustering), direct lipid binding, and local lipid dynamics that allow cells to harness lipid heterogeneity to gate ion channels. The new tools to study lipid binding are set to transform our view of the membrane and answer important questions surrounding ion channel-delimited processes such as mechanosensation.
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Affiliation(s)
- Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Scott B Hansen
- Department of Molecular Medicine, The Scripps Research Institute, Jupiter, FL 33458, USA; Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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40
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Qile M, Ji Y, Houtman MJC, Veldhuis M, Romunde F, Kok B, van der Heyden MAG. Identification of a PEST Sequence in Vertebrate K IR2.1 That Modifies Rectification. Front Physiol 2019; 10:863. [PMID: 31333502 PMCID: PMC6624654 DOI: 10.3389/fphys.2019.00863] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 06/20/2019] [Indexed: 11/13/2022] Open
Abstract
KIR2.1 potassium channels, producing inward rectifier potassium current (IK1), are important for final action potential repolarization and a stable resting membrane potential in excitable cells like cardiomyocytes. Abnormal KIR2.1 function, either decreased or increased, associates with diseases such as Andersen-Tawil syndrome, long and short QT syndromes. KIR2.1 ion channel protein trafficking and subcellular anchoring depends on intrinsic specific short amino acid sequences. We hypothesized that combining an evolutionary based sequence comparison and bioinformatics will identify new functional domains within the C-terminus of the KIR2.1 protein, which function could be determined by mutation analysis. We determined PEST domain signatures, rich in proline (P), glutamic acid (E), serine (S), and threonine (T), within KIR2.1 sequences using the “epestfind” webtool. WT and ΔPEST KIR2.1 channels were expressed in HEK293T and COS-7 cells. Patch-clamp electrophysiology measurements were performed in the inside-out mode on excised membrane patches and the whole cell mode using AxonPatch 200B amplifiers. KIR2.1 protein expression levels were determined by western blot analysis. Immunofluorescence microscopy was used to determine KIR2.1 subcellular localization. An evolutionary conserved PEST domain was identified in the C-terminus of the KIR2.1 channel protein displaying positive PEST scores in vertebrates ranging from fish to human. No similar PEST domain was detected in KIR2.2, KIR2.3, and KIR2.6 proteins. Deletion of the PEST domain in California kingsnake and human KIR2.1 proteins (ΔPEST), did not affect plasma membrane localization. Co-expression of WT and ΔPEST KIR2.1 proteins resulted in heterotetrameric channel formation. Deletion of the PEST domain did not increase protein stability in cycloheximide assays [T½ from 2.64 h (WT) to 1.67 h (ΔPEST), n.s.]. WT and ΔPEST channels, either from human or snake, produced typical IK1, however, human ΔPEST channels displayed stronger intrinsic rectification. The current observations suggest that the PEST sequence of KIR2.1 is not associated with rapid protein degradation, and has a role in the rectification behavior of IK1 channels.
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Affiliation(s)
- Muge Qile
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Yuan Ji
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marien J C Houtman
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marlieke Veldhuis
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Fee Romunde
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Bart Kok
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, Utrecht, Netherlands
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41
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Abstract
Potassium channels that exhibit the property of inward rectification (Kir channels) are present in most cells. Cloning of the first Kir channel genes 25 years ago led to recognition that inward rectification is a consequence of voltage-dependent block by cytoplasmic polyamines, which are also ubiquitously present in animal cells. Upon cellular depolarization, these polycationic metabolites enter the Kir channel pore from the intracellular side, blocking the movement of K+ ions through the channel. As a consequence, high K+ conductance at rest can provide very stable negative resting potentials, but polyamine-mediated blockade at depolarized potentials ensures, for instance, the long plateau phase of the cardiac action potential, an essential feature for a stable cardiac rhythm. Despite much investigation of the polyamine block, where exactly polyamines get to within the Kir channel pore and how the steep voltage dependence arises remain unclear. This Minireview will summarize current understanding of the relevance and molecular mechanisms of polyamine block and offer some ideas to try to help resolve the fundamental issue of the voltage dependence of polyamine block.
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Affiliation(s)
- Colin G Nichols
- From the Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
| | - Sun-Joo Lee
- From the Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, Missouri 63110
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42
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Piermarini PM, Inocente EA, Acosta N, Hopkins CR, Denton JS, Michel AP. Inward rectifier potassium (Kir) channels in the soybean aphid Aphis glycines: Functional characterization, pharmacology, and toxicology. JOURNAL OF INSECT PHYSIOLOGY 2018; 110:57-65. [PMID: 30196125 PMCID: PMC6173977 DOI: 10.1016/j.jinsphys.2018.09.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 09/05/2018] [Accepted: 09/05/2018] [Indexed: 05/21/2023]
Abstract
Inward rectifier K+ (Kir) channels contribute to a variety of physiological processes in insects and are emerging targets for insecticide development. Previous studies on insect Kir channels have primarily focused on dipteran species (e.g., mosquitoes, fruit flies). Here we identify and functionally characterize Kir channel subunits in a hemipteran insect, the soybean aphid Aphis glycines, which is an economically important insect pest and vector of soybeans. From the transcriptome and genome of Ap. glycines we identified two cDNAs, ApKir1 and ApKir2, encoding Kir subunits that were orthologs of insect Kir1 and Kir2, respectively. Notably, a gene encoding a Kir3 subunit was absent from the transcriptome and genome of Ap. glycines, similar to the pea aphid Acyrthosiphon pisum. Heterologous expression of ApKir1 and ApKir2 in Xenopus laevis oocytes enhanced K+-currents in the plasma membrane; these currents were inhibited by barium and the small molecule VU041. Compared to ApKir2, ApKir1 mediated currents that were larger in magnitude, more sensitive to barium, and less inhibited by small molecule VU041. Moreover, ApKir1 exhibited stronger inward rectification compared to ApKir2. Topical application of VU041 in adult aphids resulted in dose-dependent mortality within 24 h that was more efficacious than flonicamid, an established insecticide also known to inhibit Kir channels. We conclude that despite the apparent loss of Kir3 genes in aphid evolution, Kir channels are important to aphid survival and represent a promising target for the development of new insecticides.
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Affiliation(s)
- Peter M Piermarini
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA.
| | - Edna Alfaro Inocente
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
| | - Nuris Acosta
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
| | - Corey R Hopkins
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Jerod S Denton
- Departments of Anesthesiology and Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Andrew P Michel
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH, USA
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43
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Calvo D, Filgueiras-Rama D, Jalife J. Mechanisms and Drug Development in Atrial Fibrillation. Pharmacol Rev 2018; 70:505-525. [PMID: 29921647 PMCID: PMC6010660 DOI: 10.1124/pr.117.014183] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation is a highly prevalent cardiac arrhythmia and the most important cause of embolic stroke. Although genetic studies have identified an increasing assembly of AF-related genes, the impact of these genetic discoveries is yet to be realized. In addition, despite more than a century of research and speculation, the molecular and cellular mechanisms underlying AF have not been established, and therapy for AF, particularly persistent AF, remains suboptimal. Current antiarrhythmic drugs are associated with a significant rate of adverse events, particularly proarrhythmia, which may explain why many highly symptomatic AF patients are not receiving any rhythm control therapy. This review focuses on recent advances in AF research, including its epidemiology, genetics, and pathophysiological mechanisms. We then discuss the status of antiarrhythmic drug therapy for AF today, reviewing molecular mechanisms, and the possible clinical use of some of the new atrial-selective antifibrillatory agents, as well as drugs that target atrial remodeling, inflammation and fibrosis, which are being tested as upstream therapies to prevent AF perpetuation. Altogether, the objective is to highlight the magnitude and endemic dimension of AF, which requires a significant effort to develop new and effective antiarrhythmic drugs, but also improve AF prevention and treatment of risk factors that are associated with AF complications.
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Affiliation(s)
- David Calvo
- Department of Cardiology, Arrhythmia Unit, Hospital Universitario Central de Asturias and Instituto de Investigación Sanitaria del Principado de Asturias, Oviedo, Spain (D.C.); Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain (D.F.-R., J.J.); Department of Cardiology, Arrhythmia Unit, Hospital Clínico Universitario San Carlos, Madrid, Spain (D.F.-R.); Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain (D.F.-R., J.J.); and Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan (J.J.)
| | - David Filgueiras-Rama
- Department of Cardiology, Arrhythmia Unit, Hospital Universitario Central de Asturias and Instituto de Investigación Sanitaria del Principado de Asturias, Oviedo, Spain (D.C.); Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain (D.F.-R., J.J.); Department of Cardiology, Arrhythmia Unit, Hospital Clínico Universitario San Carlos, Madrid, Spain (D.F.-R.); Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain (D.F.-R., J.J.); and Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan (J.J.)
| | - José Jalife
- Department of Cardiology, Arrhythmia Unit, Hospital Universitario Central de Asturias and Instituto de Investigación Sanitaria del Principado de Asturias, Oviedo, Spain (D.C.); Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid, Spain (D.F.-R., J.J.); Department of Cardiology, Arrhythmia Unit, Hospital Clínico Universitario San Carlos, Madrid, Spain (D.F.-R.); Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain (D.F.-R., J.J.); and Center for Arrhythmia Research, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan (J.J.)
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44
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Trezza A, Cicaloni V, Porciatti P, Langella A, Fusi F, Saponara S, Spiga O. From in silico to in vitro: a trip to reveal flavonoid binding on the Rattus norvegicus Kir6.1 ATP-sensitive inward rectifier potassium channel. PeerJ 2018; 6:e4680. [PMID: 29736333 PMCID: PMC5936070 DOI: 10.7717/peerj.4680] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 04/09/2018] [Indexed: 12/18/2022] Open
Abstract
Background ATP-sensitive inward rectifier potassium channels (Kir), are a potassium channel family involved in many physiological processes. KATP dysfunctions are observed in several diseases such as hypoglycaemia, hyperinsulinemia, Prinzmetal angina–like symptoms, cardiovascular diseases. Methods A broader view of the KATP mechanism is needed in order to operate on their regulation, and in this work we clarify the structure of the Rattus norvegicus ATP-sensitive inward rectifier potassium channel 8 (Kir6.1), which has been obtained through a homology modelling procedure. Due to the medical use of flavonoids, a considerable increase in studies on their influence on human health has recently been observed, therefore our aim is to study, through computational methods, the three-dimensional (3D) conformation together with mechanism of action of Kir6.1 with three flavonoids. Results Computational analysis by performing molecular dynamics (MD) and docking simulation on rat 3D modelled structure have been completed, in its closed and open conformation state and in complex with Quercetin, 5-Hydroxyflavone and Rutin flavonoids. Our study showed that only Quercetin and 5-Hydroxyflavone were responsible for a significant down-regulation of the Kir6.1 activity, stabilising it in a closed conformation. This hypothesis was supported by in vitro experiments demonstrating that Quercetin and 5-Hydroxyflavone were capable to inhibit KATP currents of rat tail main artery myocytes recorded by the patch-clamp technique. Conclusion Combined methodological approaches, such as molecular modelling, docking and MD simulations of Kir6.1 channel, used to elucidate flavonoids intrinsic mechanism of action, are introduced, revealing a new potential druggable protein site.
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Affiliation(s)
- Alfonso Trezza
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Vittoria Cicaloni
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy.,Toscana Life Sciences Foundation, Siena, Italy
| | - Piera Porciatti
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Andrea Langella
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
| | - Fabio Fusi
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Simona Saponara
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Ottavia Spiga
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy
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45
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OSR1 regulates a subset of inward rectifier potassium channels via a binding motif variant. Proc Natl Acad Sci U S A 2018; 115:3840-3845. [PMID: 29581290 DOI: 10.1073/pnas.1802339115] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The with-no-lysine (K) (WNK) signaling pathway to STE20/SPS1-related proline- and alanine-rich kinase (SPAK) and oxidative stress-responsive 1 (OSR1) kinase is an important mediator of cell volume and ion transport. SPAK and OSR1 associate with upstream kinases WNK 1-4, substrates, and other proteins through their C-terminal domains which interact with linear R-F-x-V/I sequence motifs. In this study we find that SPAK and OSR1 also interact with similar affinity with a motif variant, R-x-F-x-V/I. Eight of 16 human inward rectifier K+ channels have an R-x-F-x-V motif. We demonstrate that two of these channels, Kir2.1 and Kir2.3, are activated by OSR1, while Kir4.1, which does not contain the motif, is not sensitive to changes in OSR1 or WNK activity. Mutation of the motif prevents activation of Kir2.3 by OSR1. Both siRNA knockdown of OSR1 and chemical inhibition of WNK activity disrupt NaCl-induced plasma membrane localization of Kir2.3. Our results suggest a mechanism by which WNK-OSR1 enhance Kir2.1 and Kir2.3 channel activity by increasing their plasma membrane localization. Regulation of members of the inward rectifier K+ channel family adds functional and mechanistic insight into the physiological impact of the WNK pathway.
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46
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Tian W, Liang J. On quantification of geometry and topology of protein pockets and channels for assessing mutation effects. ... IEEE-EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL AND HEALTH INFORMATICS. IEEE-EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL AND HEALTH INFORMATICS 2018; 2018:263-266. [PMID: 30272056 PMCID: PMC6157619 DOI: 10.1109/bhi.2018.8333419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Geometric and topological features of proteins such as voids, pockets and channels are important for protein functions. We discuss a method for visualizing protein pockets and channels based on orthogonal spheres computed from alpha shapes of the protein structures, and how metric properties of channel surfaces can be mapped. In addition, we discuss how structurally prominent sites, such as constriction sties in channels, can be computed, which may help to understand protein functions and mutation effects, with implications in developing novel therapeutic interventions.
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Affiliation(s)
- Wei Tian
- Bioinformatics Program, Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Jie Liang
- Bioinformatics Program, Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
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47
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Takemoto Y, Slough DP, Meinke G, Katnik C, Graziano ZA, Chidipi B, Reiser M, Alhadidy MM, Ramirez R, Salvador-Montañés O, Ennis S, Guerrero-Serna G, Haburcak M, Diehl C, Cuevas J, Jalife J, Bohm A, Lin YS, Noujaim SF. Structural basis for the antiarrhythmic blockade of a potassium channel with a small molecule. FASEB J 2018; 32:1778-1793. [PMID: 29162702 DOI: 10.1096/fj.201700349r] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The acetylcholine-activated inward rectifier potassium current ( IKACh) is constitutively active in persistent atrial fibrillation (AF). We tested the hypothesis that the blocking of IKACh with the small molecule chloroquine terminates persistent AF. We used a sheep model of tachypacing-induced, persistent AF, molecular modeling, electrophysiology, and structural biology approaches. The 50% inhibition/inhibitory concentration of IKACh block with chloroquine, measured by patch clamp, was 1 μM. In optical mapping of sheep hearts with persistent AF, 1 μM chloroquine restored sinus rhythm. Molecular modeling suggested that chloroquine blocked the passage of a hydrated potassium ion through the intracellular domain of Kir3.1 (a molecular correlate of IKACh) by interacting with residues D260 and F255, in proximity to I228, Q227, and L299. 1H 15N heteronuclear single-quantum correlation of purified Kir3.1 intracellular domain confirmed the modeling results. F255, I228, Q227, and L299 underwent significant chemical-shift perturbations upon drug binding. We then crystallized and solved a 2.5 Å X-ray structure of Kir3.1 with F255A mutation. Modeling of chloroquine binding to the mutant channel suggested that the drug's binding to the pore becomes off centered, reducing its ability to block a hydrated potassium ion. Patch clamp validated the structural and modeling data, where the F255A and D260A mutations significantly reduced IKACh block by chloroquine. With the use of numerical and structural biology approaches, we elucidated the details of how a small molecule could block an ion channel and exert antiarrhythmic effects. Chloroquine binds the IKACh channel at a site formed by specific amino acids in the ion-permeation pathway, leading to decreased IKACh and the subsequent termination of AF.-Takemoto, Y., Slough, D. P., Meinke, G., Katnik, C., Graziano, Z. A., Chidipi, B., Reiser, M., Alhadidy, M. M., Ramirez, R., Salvador-Montañés, O., Ennis, S., Guerrero-Serna, G., Haburcak, M., Diehl, C., Cuevas, J., Jalife, J., Bohm, A., Lin,Y.-S., Noujaim, S. F. Structural basis for the antiarrhythmic blockade of a potassium channel with a small molecule.
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Affiliation(s)
- Yoshio Takemoto
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.,Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan, USA
| | - Diana P Slough
- Department of Chemistry, Tufts University, Medford, Massachusetts, USA
| | - Gretchen Meinke
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Christopher Katnik
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
| | | | - Bojjibabu Chidipi
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
| | - Michelle Reiser
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
| | - Mohammed M Alhadidy
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
| | - Rafael Ramirez
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Steven Ennis
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Marian Haburcak
- Department of Biology, Brandeis University, Waltham, Massachusetts, USA
| | - Carl Diehl
- Saromics Biostructures, Copenhagen, Denmark; and
| | - Javier Cuevas
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
| | - Jose Jalife
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, Michigan, USA.,Centro de Nacional de Investigaciones Cardiovasculares Carlos III and Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares , Madrid, Spain
| | - Andrew Bohm
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Yu-Shan Lin
- Department of Chemistry, Tufts University, Medford, Massachusetts, USA
| | - Sami F Noujaim
- Molecular Pharmacology and Physiology Department, University of South Florida, Tampa, Florida, USA
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48
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Principalli MA, Lemel L, Rongier A, Godet AC, Langer K, Revilloud J, Darré L, Domene C, Vivaudou M, Moreau CJ. Functional mapping of the N-terminal arginine cluster and C-terminal acidic residues of Kir6.2 channel fused to a G protein-coupled receptor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2144-2153. [PMID: 28757124 DOI: 10.1016/j.bbamem.2017.07.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 07/06/2017] [Accepted: 07/26/2017] [Indexed: 10/19/2022]
Abstract
Ion channel-coupled receptors (ICCRs) are original man-made ligand-gated ion channels created by fusion of G protein-coupled receptors (GPCRs) to the inward-rectifier potassium channel Kir6.2. GPCR conformational changes induced by ligand binding are transduced into electrical current by the ion channel. This functional coupling is closely related to the length of the linker region formed by the GPCR C-terminus (C-ter) and Kir6.2N-terminus (N-ter). Manipulating the GPCR C-ter length allows to finely tune the channel regulation, both in amplitude and sign (opening or closing Kir6.2). In this work, we demonstrate that the primary sequence of the channel N-terminal domain is an additional parameter for the functional coupling with GPCRs. As for all Kir channels, a cluster of basic residues is present in the N-terminal domain of Kir6.2 and is composed of 5 arginines which are proximal to the GPCR C-ter in the fusion proteins. Using a functional mapping approach, we demonstrate the role of specific arginines (R27 and R32) for the function of ICCRs, indicating that the position and not the cluster of positively-charged arginines is critical for the channel regulation by the GPCR. Following observations provided by molecular dynamics simulation, we explore the hypothesis of interaction of these arginines with acidic residues, and using site-directed mutagenesis, we identified aspartate D307 and glutamate E308 residues as critical for the function of ICCRs. These results demonstrate the critical role of the N-terminal and C-terminal charged residues of Kir6.2 for its allosteric regulation by the fused GPCR.
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Affiliation(s)
- Maria A Principalli
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Laura Lemel
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Anaëlle Rongier
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Anne-Claire Godet
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Karla Langer
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Jean Revilloud
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Leonardo Darré
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK
| | - Carmen Domene
- Department of Chemistry, King's College London, Britannia House, 7 Trinity Street, London SE1 1DB, UK; Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK
| | - Michel Vivaudou
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France
| | - Christophe J Moreau
- Institut de Biologie Structurale (IBS), Univ. Grenoble Alpes, CEA, CNRS, LabEx ICST, 71, avenue des Martyrs, CS10090, F-38044 Grenoble, France.
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49
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Yuan HX, Yan K, Hou DY, Zhang ZY, Wang H, Wang X, Zhang J, Xu XR, Liang YH, Zhao WS, Xu L, Zhang L. Whole exome sequencing identifies a KCNJ12 mutation as a cause of familial dilated cardiomyopathy. Medicine (Baltimore) 2017; 96:e7727. [PMID: 28816949 PMCID: PMC5571686 DOI: 10.1097/md.0000000000007727] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Dilated cardiomyopathy (DCM) is characterized by left ventricular dilation, and is associated with systolic dysfunction and increased action potential duration. Approximately 50% of DCM cases are caused by inherited gene mutations with genetic and phenotypic heterogeneity. Next generation sequencing may be useful in screening unknown mutations in such cases.A family was identified with DCM, in which the affected family members developed heart failure, arrhythmia, and sudden death. Probands and 4 affected family members underwent whole exome sequencing (WES), bioinformatics methods, and gene annotation to identify potentially causative variants. The Sanger sequencing method was used to verify the candidate mutation.WES yielded 2,238,831 variations. KCNJ12 (p.Glu334del) was identified as a candidate mutation, and the heterozygous mutation was verified by Sanger sequencing.Our study emphasizes the application of WES in identifying causative mutations in DCM. This report is the first to describe the KCNJ12 gene as a cause of DCM in patients.
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Affiliation(s)
- Hai-Xin Yuan
- Basic Medical Research Center, Beijing Chao-Yang Hospital, Capital Medical University
| | - Kai Yan
- Biomarker Technologies Company
| | - Dong-Yan Hou
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Zhi-Yong Zhang
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Hua Wang
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Xin Wang
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Juan Zhang
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Xiao-Rong Xu
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Yan-Hong Liang
- Department of General Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Wen-Shu Zhao
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Lin Xu
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
| | - Lin Zhang
- Heart Failure Center, Department of Cardiology, Beijing Chao-Yang Hospital, Capital Medical University
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50
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Hydrocinnamic Acid Inhibits the Currents of WT and SQT3 Syndrome-Related Mutants of Kir2.1 Channel. J Membr Biol 2017; 250:425-432. [PMID: 28660286 DOI: 10.1007/s00232-017-9964-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 06/01/2017] [Indexed: 01/27/2023]
Abstract
Gain of function in mutations, D172N and E299V, of Kir2.1 will induce type III short QT syndrome. In our previous work, we had identified that a mixture of traditional Chinese medicine, styrax, is a blocker of Kir2.1. Here, we determined a monomer, hydrocinnamic acid (HA), as the effective component from 18 compounds of styrax. Our data show that HA can inhibit the currents of Kir2.1 channel in both excised inside-out and whole-cell patch with the IC50 of 5.21 ± 1.02 and 10.08 ± 0.46 mM, respectively. The time course of HA blockage and washout are 2.3 ± 0.6 and 10.5 ± 2.6 s in the excised inside-out patch. Moreover, HA can also abolish the currents of D172N and E299V with the IC50 of 6.66 ± 0.57 and 5.81 ± 1.10 mM for D172N and E299V, respectively. Molecular docking results determine that HA binds with Kir2.1 at K182, K185, and K188, which are phosphatidylinositol 4,5-bisphosphate (PIP2) binding residues. Our results indicate that HA competes with PIP2 to bind with Kir2.1 and inhibits the currents.
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