1
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Lee WW, Lee CG, Ki CS. KCNJ3 is a novel candidate gene for autosomal dominant pure hereditary spastic paraplegia identified using whole genome sequencing. Am J Med Genet B Neuropsychiatr Genet 2024:e32984. [PMID: 38597354 DOI: 10.1002/ajmg.b.32984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 03/05/2024] [Accepted: 04/02/2024] [Indexed: 04/11/2024]
Abstract
Hereditary spastic paraplegia (HSP) is a group of familial diseases characterized by progressive corticospinal tract degeneration. Clinically, patients present with lower-limb spasticity and weakness. To date, more than 80 genetic HSP types have been identified. Despite advances in molecular genetics, novel HSP gene discoveries are ongoing, with a low genetic diagnostic yield. In this study, we aimed to determine pathogenic variants in a family with HSP, which was not diagnosed through conventional genetic testing. We clinically characterized a large family and conducted whole genome sequencing (WGS) analysis of four affected and three unaffected individuals in the family to identify the genetic cause of HSP. This family had autosomal dominant pure (uncomplicated) late childhood-onset HSP. The patients' symptoms accelerated between the ages of 20 and 30. Brain magnetic resonance images typically showed white matter changes, a thin corpus callosum, and cerebellar atrophy. We identified a heterozygous missense variant, KCNJ3 c.1297T>G (p.Leu433Val), through WGS and family genetic analysis, confirmed by Sanger sequencing. We suggest that the identification of KCNJ3 c.1297T>G (p.Leu433Val) constitutes the discovery of a potential novel gene responsible for HSP in this family. This is the first study to report the possible role of a KCNJ3 variant in HSP pathogenesis. Our findings further expand the phenotypic and genotypic spectrum of HSP.
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Affiliation(s)
- Woong-Woo Lee
- Department of Neurology, Nowon Eulji Medical Center, Eulji University School of Medicine, Seoul, Republic of Korea
| | - Cha Gon Lee
- Department of Pediatrics, Nowon Eulji Medical Center, Eulji University School of Medicine, Seoul, Republic of Korea
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2
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Stott JB, Greenwood IA. G protein βγ regulation of KCNQ-encoded voltage-dependent K channels. Front Physiol 2024; 15:1382904. [PMID: 38655029 PMCID: PMC11035767 DOI: 10.3389/fphys.2024.1382904] [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: 02/06/2024] [Accepted: 03/25/2024] [Indexed: 04/26/2024] Open
Abstract
The KCNQ family is comprised of five genes and the expression products form voltage-gated potassium channels (Kv7.1-7.5) that have a major impact upon cellular physiology in many cell types. Each functional Kv7 channel forms as a tetramer that often associates with proteins encoded by the KCNE gene family (KCNE1-5) and is critically reliant upon binding of phosphatidylinositol bisphosphate (PIP2) and calmodulin. Other modulators like A-kinase anchoring proteins, ubiquitin ligases and Ca-calmodulin kinase II alter Kv7 channel function and trafficking in an isoform specific manner. It has now been identified that for Kv7.4, G protein βγ subunits (Gβγ) can be added to the list of key regulators and is paramount for channel activity. This article provides an overview of this nascent field of research, highlighting themes and directions for future study.
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Affiliation(s)
| | - Iain A. Greenwood
- Vascular Biology Research Group, Institute of Molecular and Clinical Sciences, St George’s University of London, London, United Kingdom
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3
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Lei M, Salvage SC, Jackson AP, Huang CLH. Cardiac arrhythmogenesis: roles of ion channels and their functional modification. Front Physiol 2024; 15:1342761. [PMID: 38505707 PMCID: PMC10949183 DOI: 10.3389/fphys.2024.1342761] [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: 11/22/2023] [Accepted: 01/22/2024] [Indexed: 03/21/2024] Open
Abstract
Cardiac arrhythmias cause significant morbidity and mortality and pose a major public health problem. They arise from disruptions in the normally orderly propagation of cardiac electrophysiological activation and recovery through successive cardiomyocytes in the heart. They reflect abnormalities in automaticity, initiation, conduction, or recovery in cardiomyocyte excitation. The latter properties are dependent on surface membrane electrophysiological mechanisms underlying the cardiac action potential. Their disruption results from spatial or temporal instabilities and heterogeneities in the generation and propagation of cellular excitation. These arise from abnormal function in their underlying surface membrane, ion channels, and transporters, as well as the interactions between them. The latter, in turn, form common regulatory targets for the hierarchical network of diverse signaling mechanisms reviewed here. In addition to direct molecular-level pharmacological or physiological actions on these surface membrane biomolecules, accessory, adhesion, signal transduction, and cytoskeletal anchoring proteins modify both their properties and localization. At the cellular level of excitation-contraction coupling processes, Ca2+ homeostatic and phosphorylation processes affect channel activity and membrane excitability directly or through intermediate signaling. Systems-level autonomic cellular signaling exerts both acute channel and longer-term actions on channel expression. Further upstream intermediaries from metabolic changes modulate the channels both themselves and through modifying Ca2+ homeostasis. Finally, longer-term organ-level inflammatory and structural changes, such as fibrotic and hypertrophic remodeling, similarly can influence all these physiological processes with potential pro-arrhythmic consequences. These normal physiological processes may target either individual or groups of ionic channel species and alter with particular pathological conditions. They are also potentially alterable by direct pharmacological action, or effects on longer-term targets modifying protein or cofactor structure, expression, or localization. Their participating specific biomolecules, often clarified in experimental genetically modified models, thus constitute potential therapeutic targets. The insights clarified by the physiological and pharmacological framework outlined here provide a basis for a recent modernized drug classification. Together, they offer a translational framework for current drug understanding. This would facilitate future mechanistically directed therapeutic advances, for which a number of examples are considered here. The latter are potentially useful for treating cardiac, in particular arrhythmic, disease.
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Affiliation(s)
- Ming Lei
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Samantha C. Salvage
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Antony P. Jackson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L.-H. Huang
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
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4
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Cheng L, Xia F, Li Z, Shen C, Yang Z, Hou H, Sun S, Feng Y, Yong X, Tian X, Qin H, Yan W, Shao Z. Structure, function and drug discovery of GPCR signaling. MOLECULAR BIOMEDICINE 2023; 4:46. [PMID: 38047990 PMCID: PMC10695916 DOI: 10.1186/s43556-023-00156-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 11/06/2023] [Indexed: 12/05/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are versatile and vital proteins involved in a wide array of physiological processes and responses, such as sensory perception (e.g., vision, taste, and smell), immune response, hormone regulation, and neurotransmission. Their diverse and essential roles in the body make them a significant focus for pharmaceutical research and drug development. Currently, approximately 35% of marketed drugs directly target GPCRs, underscoring their prominence as therapeutic targets. Recent advances in structural biology have substantially deepened our understanding of GPCR activation mechanisms and interactions with G-protein and arrestin signaling pathways. This review offers an in-depth exploration of both traditional and recent methods in GPCR structure analysis. It presents structure-based insights into ligand recognition and receptor activation mechanisms and delves deeper into the mechanisms of canonical and noncanonical signaling pathways downstream of GPCRs. Furthermore, it highlights recent advancements in GPCR-related drug discovery and development. Particular emphasis is placed on GPCR selective drugs, allosteric and biased signaling, polyphamarcology, and antibody drugs. Our goal is to provide researchers with a thorough and updated understanding of GPCR structure determination, signaling pathway investigation, and drug development. This foundation aims to propel forward-thinking therapeutic approaches that target GPCRs, drawing upon the latest insights into GPCR ligand selectivity, activation, and biased signaling mechanisms.
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Affiliation(s)
- Lin Cheng
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
- Department of Otolaryngology Head and Neck Surgery, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, 610000, China
| | - Fan Xia
- Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Ziyan Li
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Chenglong Shen
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Zhiqian Yang
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Hanlin Hou
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Suyue Sun
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Yuying Feng
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Xihao Yong
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Xiaowen Tian
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Hongxi Qin
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China
| | - Wei Yan
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
| | - Zhenhua Shao
- Division of Nephrology and Kidney Research Institute, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
- Tianfu Jincheng Laboratory, Frontiers Medical Center, Chengdu, 610212, China.
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5
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Li C, Yang Y. Advancements in the study of inward rectifying potassium channels on vascular cells. Channels (Austin) 2023; 17:2237303. [PMID: 37463317 PMCID: PMC10355679 DOI: 10.1080/19336950.2023.2237303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/20/2023] [Accepted: 07/04/2023] [Indexed: 07/20/2023] Open
Abstract
Inward rectifier potassium channels (Kir channels) exist in a variety of cells and are involved in maintaining resting membrane potential and signal transduction in most cells, as well as connecting metabolism and membrane excitability of body cells. It is closely related to normal physiological functions of body and the occurrence and development of some diseases. Although the functional expression of Kir channels and their role in disease have been studied, they have not been fully elucidated. In this paper, the functional expression of Kir channels in vascular endothelial cells and smooth muscle cells and their changes in disease states were reviewed, especially the recent research progress of Kir channels in stem cells was introduced, in order to have a deeper understanding of Kir channels in vascular tissues and provide new ideas and directions for the treatment of related ion channel diseases.
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Affiliation(s)
- Chunshu Li
- Key Lab of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yan Yang
- Key Lab of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Lab of Sichuan Province, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
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6
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Jo A, Deniz S, Xu J, Duvoisin RM, DeVries SH, Zhu Y. A sign-inverted receptive field of inhibitory interneurons provides a pathway for ON-OFF interactions in the retina. Nat Commun 2023; 14:5937. [PMID: 37741839 PMCID: PMC10517963 DOI: 10.1038/s41467-023-41638-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 09/11/2023] [Indexed: 09/25/2023] Open
Abstract
A fundamental organizing plan of the retina is that visual information is divided into ON and OFF streams that are processed in separate layers. This functional dichotomy originates in the ON and OFF bipolar cells, which then make excitatory glutamatergic synapses onto amacrine and ganglion cells in the inner plexiform layer. We have identified an amacrine cell (AC), the sign-inverting (SI) AC, that challenges this fundamental plan. The glycinergic, ON-stratifying SI-AC has OFF light responses. In opposition to the classical wiring diagrams, it receives inhibitory inputs from glutamatergic ON bipolar cells at mGluR8 synapses, and excitatory inputs from an OFF wide-field AC at electrical synapses. This "inhibitory ON center - excitatory OFF surround" receptive-field of the SI-AC allows it to use monostratified dendrites to conduct crossover inhibition and push-pull activation to enhance light detection by ACs and RGCs in the dark and feature discrimination in the light.
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Affiliation(s)
- Andrew Jo
- Departments of Ophthalmology and Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Sercan Deniz
- Departments of Ophthalmology and Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Jian Xu
- Departments of Ophthalmology and Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA
| | - Robert M Duvoisin
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Steven H DeVries
- Departments of Ophthalmology and Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.
| | - Yongling Zhu
- Departments of Ophthalmology and Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.
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7
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Pandey M, Zhang JH, Adikaram PR, Kittock C, Lue N, Awe A, Degner K, Jacob N, Staples J, Thomas R, Kohnen AB, Ganesan S, Kabat J, Chen CK, Simonds WF. Specific regulation of mechanical nociception by Gβ5 involves GABA-B receptors. JCI Insight 2023; 8:e134685. [PMID: 37219953 PMCID: PMC10371342 DOI: 10.1172/jci.insight.134685] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 05/19/2023] [Indexed: 05/24/2023] Open
Abstract
Mechanical, thermal, and chemical pain sensation is conveyed by primary nociceptors, a subset of sensory afferent neurons. The intracellular regulation of the primary nociceptive signal is an area of active study. We report here the discovery of a Gβ5-dependent regulatory pathway within mechanical nociceptors that restrains antinociceptive input from metabotropic GABA-B receptors. In mice with conditional knockout (cKO) of the gene that encodes Gβ5 (Gnb5) targeted to peripheral sensory neurons, we demonstrate the impairment of mechanical, thermal, and chemical nociception. We further report the specific loss of mechanical nociception in Rgs7-Cre+/- Gnb5fl/fl mice but not in Rgs9-Cre+/- Gnb5fl/fl mice, suggesting that Gβ5 might specifically regulate mechanical pain in regulator of G protein signaling 7-positive (Rgs7+) cells. Additionally, Gβ5-dependent and Rgs7-associated mechanical nociception is dependent upon GABA-B receptor signaling since both were abolished by treatment with a GABA-B receptor antagonist and since cKO of Gβ5 from sensory cells or from Rgs7+ cells potentiated the analgesic effects of GABA-B agonists. Following activation by the G protein-coupled receptor Mrgprd agonist β-alanine, enhanced sensitivity to inhibition by baclofen was observed in primary cultures of Rgs7+ sensory neurons harvested from Rgs7-Cre+/- Gnb5fl/fl mice. Taken together, these results suggest that the targeted inhibition of Gβ5 function in Rgs7+ sensory neurons might provide specific relief for mechanical allodynia, including that contributing to chronic neuropathic pain, without reliance on exogenous opioids.
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Affiliation(s)
- Mritunjay Pandey
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Jian-Hua Zhang
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Poorni R. Adikaram
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Claire Kittock
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Nicole Lue
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Adam Awe
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Katherine Degner
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Nirmal Jacob
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Jenna Staples
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Rachel Thomas
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Allison B. Kohnen
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Sundar Ganesan
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Juraj Kabat
- Research Technologies Branch, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Ching-Kang Chen
- Department of Molecular Medicine, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA
| | - William F. Simonds
- Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (NIH), Bethesda, Maryland, USA
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Huang CLH, Lei M. Cardiomyocyte electrophysiology and its modulation: current views and future prospects. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220160. [PMID: 37122224 PMCID: PMC10150219 DOI: 10.1098/rstb.2022.0160] [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: 01/16/2023] [Accepted: 03/10/2023] [Indexed: 05/02/2023] Open
Abstract
Normal and abnormal cardiac rhythms are of key physiological and clinical interest. This introductory article begins from Sylvio Weidmann's key historic 1950s microelectrode measurements of cardiac electrophysiological activity and Singh & Vaughan Williams's classification of cardiotropic targets. It then proceeds to introduce the insights into cardiomyocyte function and its regulation that subsequently emerged and their therapeutic implications. We recapitulate the resulting view that surface membrane electrophysiological events underlying cardiac excitation and its initiation, conduction and recovery constitute the final common path for the cellular mechanisms that impinge upon this normal or abnormal cardiac electrophysiological activity. We then consider progress in the more recently characterized successive regulatory hierarchies involving Ca2+ homeostasis, excitation-contraction coupling and autonomic G-protein signalling and their often reciprocal interactions with the surface membrane events, and their circadian rhythms. Then follow accounts of longer-term upstream modulation processes involving altered channel expression, cardiomyocyte energetics and hypertrophic and fibrotic cardiac remodelling. Consideration of these developments introduces each of the articles in this Phil. Trans. B theme issue. The findings contained in these articles translate naturally into recent classifications of cardiac electrophysiological targets and drug actions, thereby encouraging future iterations of experimental cardiac electrophysiological discovery, and testing directed towards clinical management. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - Ming Lei
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK
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van Wyk M, Kleinlogel S. A visual opsin from jellyfish enables precise temporal control of G protein signalling. Nat Commun 2023; 14:2450. [PMID: 37117224 PMCID: PMC10147646 DOI: 10.1038/s41467-023-38231-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 04/20/2023] [Indexed: 04/30/2023] Open
Abstract
Phototransduction is mediated by distinct types of G protein cascades in different animal taxa: bilateral invertebrates typically utilise the Gαq pathway whereas vertebrates typically utilise the Gαt(i/o) pathway. By contrast, photoreceptors in jellyfish (Cnidaria) utilise the Gαs intracellular pathway, similar to olfactory transduction in mammals1. How this habitually slow pathway has adapted to support dynamic vision in jellyfish remains unknown. Here we study a light-sensing protein (rhodopsin) from the box jellyfish Carybdea rastonii and uncover a mechanism that dramatically speeds up phototransduction: an uninterrupted G protein-coupled receptor - G protein complex. Unlike known G protein-coupled receptors (GPCRs), this rhodopsin constitutively binds a single downstream Gαs partner to enable G-protein activation and inactivation within tens of milliseconds. We use this GPCR in a viral gene therapy to restore light responses in blind mice.
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Affiliation(s)
- Michiel van Wyk
- Department of Biomedical Research, University of Bern, Bern, Switzerland.
- Institute of Physiology, University of Bern, Bern, Switzerland.
| | - Sonja Kleinlogel
- Department of Biomedical Research, University of Bern, Bern, Switzerland.
- Institute of Physiology, University of Bern, Bern, Switzerland.
- Roche Pharma and Early Development, Neuroscience and Rare Diseases, Roche Innovation Center, F. Hoffmann-La Roche Ltd, Basel, Switzerland.
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Ortiz MI, Cariño-Cortés R, Castañeda-Hernández G, Medina-Solís CE. Effect of nitric oxide-cyclic GMP-K + channel pathway blockers, naloxone and metformin, on the antinociception induced by the diuretic pamabrom. Can J Physiol Pharmacol 2023; 101:41-51. [PMID: 36318824 DOI: 10.1139/cjpp-2022-0277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Pamabrom is a diuretic that is effective in treating premenstrual syndrome and primary dysmenorrhea. The aim of this study was to examine the effect of metformin and modulators of the opioid receptor-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-K+ channel pathway on the local antinociception induced by pamabrom. The rat paw 1% formalin test was used to assess the effects. Rats were treated with local administration of pamabrom (200-800 µg/paw) or indomethacin (200-800 µg/paw). The antinociception of pamabrom or indomethacin was evaluated with and without the local pretreatment of the blockers. Local administration of pamabrom and indomethacin produced dose-dependent antinociception during the second phase of the test. Local pretreatment of the paws with naloxone (50 µg/paw), l-nitro-arginine methyl ester (10-100 µg/paw), or 1H-(1,2,4)-oxadiazolo[4,2-a]quinoxalin-1-one (10-100 µg/paw) reverted the antinociception induced by local pamabrom, but not of indomethacin. Similarly, the K+ channel blockers glibenclamide, glipizide, 4-aminopyridine, tetraethylammonium, charybdotoxin, or apamin reverted the pamabrom-induced antinociception, but not of indomethacin. Metformin significantly blocked the antinociception of pamabrom and indomethacin. Our data suggest that pamabrom could activate the opioid receptor-NO-cGMP-K+ channel pathway to produce its peripheral antinociception in the formalin test. Likewise, a biguanide-dependent mechanism could be activated by pamabrom and indomethacin to generate antinociception.
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Affiliation(s)
- Mario I Ortiz
- Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Raquel Cariño-Cortés
- Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Gilberto Castañeda-Hernández
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Carlo Eduardo Medina-Solís
- Área Académica de Odontología del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
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Campos-Ríos A, Rueda-Ruzafa L, Lamas JA. The Relevance of GIRK Channels in Heart Function. MEMBRANES 2022; 12:1119. [PMID: 36363674 PMCID: PMC9698958 DOI: 10.3390/membranes12111119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/06/2022] [Accepted: 11/07/2022] [Indexed: 06/16/2023]
Abstract
Among the large number of potassium-channel families implicated in the control of neuronal excitability, G-protein-gated inwardly rectifying potassium channels (GIRK/Kir3) have been found to be a main factor in heart control. These channels are activated following the modulation of G-protein-coupled receptors and, although they have been implicated in different neurological diseases in both human and animal studies of the central nervous system, the therapeutic potential of different subtypes of these channel families in cardiac conditions has remained untapped. As they have emerged as a promising potential tool to treat a variety of conditions that disrupt neuronal homeostasis, many studies have started to focus on these channels as mediators of cardiac dynamics, thus leading to research into their implication in cardiovascular conditions. Our aim is to review the latest advances in GIRK modulation in the heart and their role in the cardiovascular system.
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Affiliation(s)
- Ana Campos-Ríos
- CINBIO, Laboratory of Neuroscience, University of Vigo, 36310 Vigo, Spain
- Laboratory of Neuroscience, Galicia Sur Health Research Institute (IISGS), 15706 Vigo, Spain
| | - Lola Rueda-Ruzafa
- Department of Nursing Science, Physiotherapy and Medicine, Faculty of Health Sciences, University of Almeria, 04120 Almeria, Spain
| | - José Antonio Lamas
- CINBIO, Laboratory of Neuroscience, University of Vigo, 36310 Vigo, Spain
- Laboratory of Neuroscience, Galicia Sur Health Research Institute (IISGS), 15706 Vigo, Spain
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12
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Szczurowska E, Szánti-Pintér E, Randáková A, Jakubík J, Kudova E. Allosteric Modulation of Muscarinic Receptors by Cholesterol, Neurosteroids and Neuroactive Steroids. Int J Mol Sci 2022; 23:13075. [PMID: 36361865 PMCID: PMC9656441 DOI: 10.3390/ijms232113075] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/21/2022] [Accepted: 10/24/2022] [Indexed: 11/24/2023] Open
Abstract
Muscarinic acetylcholine receptors are membrane receptors involved in many physiological processes. Malfunction of muscarinic signaling is a cause of various internal diseases, as well as psychiatric and neurologic conditions. Cholesterol, neurosteroids, neuroactive steroids, and steroid hormones are molecules of steroid origin that, besides having well-known genomic effects, also modulate membrane proteins including muscarinic acetylcholine receptors. Here, we review current knowledge on the allosteric modulation of muscarinic receptors by these steroids. We give a perspective on the research on the non-genomic effects of steroidal compounds on muscarinic receptors and drug development, with an aim to ultimately exploit such knowledge.
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Affiliation(s)
- Ewa Szczurowska
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Namesti 2, Prague 6, 166 10 Prague, Czech Republic
| | - Eszter Szánti-Pintér
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Namesti 2, Prague 6, 166 10 Prague, Czech Republic
| | - Alena Randáková
- Institute of Physiology, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Jan Jakubík
- Institute of Physiology, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic
| | - Eva Kudova
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo Namesti 2, Prague 6, 166 10 Prague, Czech Republic
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13
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Kleschevnikov AM. Enhanced GIRK2 channel signaling in Down syndrome: A feasible role in the development of abnormal nascent neural circuits. Front Genet 2022; 13:1006068. [PMID: 36171878 PMCID: PMC9510977 DOI: 10.3389/fgene.2022.1006068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 08/24/2022] [Indexed: 11/24/2022] Open
Abstract
The most distinctive feature of Down syndrome (DS) is moderate to severe cognitive impairment. Genetic, molecular, and neuronal mechanisms of this complex DS phenotype are currently under intensive investigation. It is becoming increasingly clear that the abnormalities arise from a combination of initial changes caused by triplication of genes on human chromosome 21 (HSA21) and later compensatory adaptations affecting multiple brain systems. Consequently, relatively mild initial cognitive deficits become pronounced with age. This pattern of changes suggests that one approach to improving cognitive function in DS is to target the earliest critical changes, the prevention of which can change the ‘trajectory’ of the brain development and reduce the destructive effects of the secondary alterations. Here, we review the experimental data on the role of KCNJ6 in DS-specific brain abnormalities, focusing on a putative role of this gene in the development of abnormal neural circuits in the hippocampus of genetic mouse models of DS. It is suggested that the prevention of these early abnormalities with pharmacological or genetic means can ameliorate cognitive impairment in DS.
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14
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Jin L, Guo Y, Chen J, Wen Z, Jiang Y, Qian J. Lactate receptor HCAR1 regulates cell growth, metastasis and maintenance of cancer‑specific energy metabolism in breast cancer cells. Mol Med Rep 2022; 26:268. [PMID: 35775372 PMCID: PMC9260879 DOI: 10.3892/mmr.2022.12784] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 05/30/2022] [Indexed: 11/06/2022] Open
Abstract
Under aerobic conditions, the preferential use of anaerobic glycolysis by tumour cells leads to a high level of lactate accumulation in tumour microenvironment. Lactate acts not only as a cellular energy source but also as a signalling molecule that regulates cancer cell growth, metastasis and metabolism. It has been reported that a G‑protein‑coupled receptor for lactate named hydroxycarboxylic acid receptor 1 (HCAR1) is highly expressed in numerous types of cancer, but the detailed mechanism remains unclear. In the present study, it was reported that HCAR1 is highly expressed in breast cancer cells. Genetic deletion of HCAR1 in MCF7 cells leads to reduced cell proliferation and migration. Moreover, it was observed that knockout (KO) of HCAR1 attenuated the expression and activity of phosphofructokinase and hexokinase, key rate‑limiting enzymes in glycolysis. Using an extracellular flux analyzer, it was showed that KO of HCAR1 promoted a metabolic shift towards a decreased glycolysis state, as evidenced by a decreased extracellular acidification rate and increased oxygen consumption rate in MCF7 cells. Taken together, our results suggested that lactate acts through HCAR1 as a metabolic regulator in breast cancer cells that may be therapeutically exploited.
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Affiliation(s)
- Lili Jin
- Huzhou Key Laboratory of Molecular Medicine, Huzhou Central Hospital, Huzhou Hospital Affiliated with Zhejiang University, Huzhou, Zhejiang 313000, P.R. China
| | - Yanan Guo
- Huzhou University Schools of Nursing and Medicine, Huzhou University, Huzhou, Zhejiang 313000, P.R. China
| | - Jiawen Chen
- Huzhou University Schools of Nursing and Medicine, Huzhou University, Huzhou, Zhejiang 313000, P.R. China
| | - Zhenzhen Wen
- Huzhou University Schools of Nursing and Medicine, Huzhou University, Huzhou, Zhejiang 313000, P.R. China
| | - Yibin Jiang
- Huzhou University Schools of Nursing and Medicine, Huzhou University, Huzhou, Zhejiang 313000, P.R. China
| | - Jing Qian
- Huzhou University Schools of Nursing and Medicine, Huzhou University, Huzhou, Zhejiang 313000, P.R. China
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15
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Luo H, Marron Fernandez de Velasco E, Wickman K. Neuronal G protein-gated K + channels. Am J Physiol Cell Physiol 2022; 323:C439-C460. [PMID: 35704701 PMCID: PMC9362898 DOI: 10.1152/ajpcell.00102.2022] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to PIP2, phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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16
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Ferré S, Ciruela F, Dessauer CW, González-Maeso J, Hébert TE, Jockers R, Logothetis DE, Pardo L. G protein-coupled receptor-effector macromolecular membrane assemblies (GEMMAs). Pharmacol Ther 2022; 231:107977. [PMID: 34480967 PMCID: PMC9375844 DOI: 10.1016/j.pharmthera.2021.107977] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 08/11/2021] [Accepted: 08/17/2021] [Indexed: 12/12/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest group of receptors involved in cellular signaling across the plasma membrane and a major class of drug targets. The canonical model for GPCR signaling involves three components - the GPCR, a heterotrimeric G protein and a proximal plasma membrane effector - that have been generally thought to be freely mobile molecules able to interact by 'collision coupling'. Here, we synthesize evidence that supports the existence of GPCR-effector macromolecular membrane assemblies (GEMMAs) comprised of specific GPCRs, G proteins, plasma membrane effector molecules and other associated transmembrane proteins that are pre-assembled prior to receptor activation by agonists, which then leads to subsequent rearrangement of the GEMMA components. The GEMMA concept offers an alternative and complementary model to the canonical collision-coupling model, allowing more efficient interactions between specific signaling components, as well as the integration of the concept of GPCR oligomerization as well as GPCR interactions with orphan receptors, truncated GPCRs and other membrane-localized GPCR-associated proteins. Collision-coupling and pre-assembled mechanisms are not exclusive and likely both operate in the cell, providing a spectrum of signaling modalities which explains the differential properties of a multitude of GPCRs in their different cellular environments. Here, we explore the unique pharmacological characteristics of individual GEMMAs, which could provide new opportunities to therapeutically modulate GPCR signaling.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Addiction, Intramural Research Program, NIH, DHHS, Baltimore, MD, USA.
| | - Francisco Ciruela
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, IDIBELL, University of Barcelona, L’Hospitalet de Llobregat, Spain
| | - Carmen W. Dessauer
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Javier González-Maeso
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Terence E. Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec
| | - Ralf Jockers
- University of Paris, Institute Cochin, INSERM, CNRS, Paris, France
| | - Diomedes E. Logothetis
- Laboratory of Electrophysiology, Departments of Pharmaceutical Sciences, Chemistry and Chemical Biology and Center for Drug Discovery, School of Pharmacy at the Bouvé College of Health Sciences and College of Science, Northeastern University, Boston, Massachusetts, USA
| | - Leonardo Pardo
- Laboratory of Computational Medicine, Biostatistics Unit, Faculty of Medicine, Autonomous University of Barcelona, Bellaterra, Spain
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17
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Kleschevnikov A. GIRK2 Channels in Down Syndrome and Alzheimer's Disease. Curr Alzheimer Res 2022; 19:819-829. [PMID: 36567290 DOI: 10.2174/1567205020666221223122110] [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: 08/13/2022] [Revised: 11/26/2022] [Accepted: 11/29/2022] [Indexed: 12/27/2022]
Abstract
Cognitive impairment in Down syndrome (DS) results from the abnormal expression of hundreds of genes. However, the impact of KCNJ6, a gene located in the middle of the 'Down syndrome critical region' of chromosome 21, seems to stand out. KCNJ6 encodes GIRK2 (KIR3.2) subunits of G protein-gated inwardly rectifying potassium channels, which serve as effectors for GABAB, m2, 5HT1A, A1, and many other postsynaptic metabotropic receptors. GIRK2 subunits are heavily expressed in neocortex, cerebellum, and hippocampus. By controlling resting membrane potential and neuronal excitability, GIRK2 channels may thus affect both synaptic plasticity and stability of neural circuits in the brain regions important for learning and memory. Here, we discuss recent experimental data regarding the role of KCNJ6/GIRK2 in neuronal abnormalities and cognitive impairment in models of DS and Alzheimer's disease (AD). The results compellingly show that signaling through GIRK2 channels is abnormally enhanced in mouse genetic models of Down syndrome and that partial suppression of GIRK2 channels with pharmacological or genetic means can restore synaptic plasticity and improve impaired cognitive functions. On the other hand, signaling through GIRK2 channels is downregulated in AD models, such as models of early amyloidopathy. In these models, reduced GIRK2 channel signaling promotes neuronal hyperactivity, causing excitatory-inhibitory imbalance and neuronal death. Accordingly, activation of GABAB/GIRK2 signaling by GIRK channel activators or GABAB receptor agonists may reduce Aβ-induced hyperactivity and subsequent neuronal death, thereby exerting a neuroprotective effect in models of AD.
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18
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Ortiz MI, Cariño-Cortés R, Muñoz Pérez VM, Medina-Solís CE, Castañeda-Hernández G. Citral inhibits the nociception in the rat formalin test: Effect of metformin and blockers of opioid receptor and the NO-cGMP-K+ channel pathway. Can J Physiol Pharmacol 2021; 100:306-313. [PMID: 34826228 DOI: 10.1139/cjpp-2021-0458] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objective of the present study was to scrutinize the effect of nitric oxide (NO), cGMP, potassium channel blockers and metformin on the citral-produced peripheral antinociception. The rat paw 1% formalin test was used to assess nociception and antinociception. Rats were treated with local peripheral administration of citral (10-100 µg/paw). The antinociception of citral (100 µg/paw) was evaluated with and without the local pretreatment of naloxone, NG-L-nitro-arginine methyl ester (L-NAME, a NO synthesis inhibitor), 1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one (ODQ, a soluble guanylyl cyclase inhibitor), metformin, opioid receptors antagonists, and K+ channel blockers. Injection of citral in the rat paw significantly decreased the nociceptive effect of formalin administration during the two phases of the test. Local pretreatment of the paws with L-NAME and ODQ did not reduced the citral-induced antinociception. Glipizide or glibenclamide (Kir6.1-2; ATP-sensitive K+ channel blockers), tetraethylammonium or 4-aminopyridine (KV; voltage-gated K+ channel blockers) or charybdotoxin (KCa1.1; big conductance calcium-activated K+ channel blocker) or apamin (KCa2.1-3; small conductance Ca2+-activated K+ channel antagonist), or metformin, but not the opioid antagonists, reduced the antinociception of citral. Citral produced peripheral antinociception during both phases of the formalin test. These effects were due to the activation of K+ channels and a biguanide-dependent mechanism.
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Affiliation(s)
- Mario I Ortiz
- Universidad Autonoma del Estado de Hidalgo, 27781, Área Académica de Medicina del Instituto de Ciencias de la Salud, Laboratorio de Farmacología, Dr. Eliseo Ramírez Ulloa 400, Col. Doctores, Pachuca, Hidalgo, Mexico, 42090;
| | - Raquel Cariño-Cortés
- Área Académica de Medicina del Instituto de Ciencias de la Salud. Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico, Pachuca, HIdalgo, Mexico;
| | - Victor Manuel Muñoz Pérez
- Autonomous University of Hidalgo State, 27781, Reproductive Biology, Eliseo Ramírez Ulloa 400, Doctores, Pachuca, Pachuca, Mexico, 42000.,Mexico;
| | - Carlo E Medina-Solís
- Universidad Autónoma del Estado de Hidalgo Instituto de Ciencias de la Salud, 103794, Pachuca, Hidalgo, Mexico;
| | - Gilberto Castañeda-Hernández
- Centro de Investigacion y de Estudios Avanzados del IPN, 42576, Department of Pharmacology, Ciudad de Mexico, Mexico, 07360;
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19
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Bony AR, McArthur JR, Finol-Urdaneta RK, Adams DJ. Analgesic α-conotoxins modulate native and recombinant GIRK1/2 channels via activation of GABA B receptors and reduce neuroexcitability. Br J Pharmacol 2021; 179:179-198. [PMID: 34599513 DOI: 10.1111/bph.15690] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 08/25/2021] [Accepted: 08/30/2021] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND AND PURPOSE Activation of GIRK channels via G protein-coupled GABAB receptors has been shown to attenuate nociceptive transmission. The analgesic α-conotoxin Vc1.1 activates GABAB receptors resulting in inhibition of Cav 2.2 and Cav 2.3 channels in mammalian primary afferent neurons. Here, we investigated the effects of analgesic α-conotoxins on recombinant and native GIRK-mediated K+ currents and on neuronal excitability. EXPERIMENTAL APPROACH The effects of analgesic α-conotoxins, Vc1.1, RgIA, and PeIA, were investigated on inwardly-rectifying K+ currents in HEK293T cells recombinantly co-expressing either heteromeric human GIRK1/2 or homomeric GIRK2 subunits, with GABAB receptors. The effects of α-conotoxin Vc1.1 and baclofen were studied on GIRK-mediated K+ currents and the passive and active electrical properties of adult mouse dorsal root ganglion neurons. KEY RESULTS Analgesic α-conotoxins Vc1.1, RgIA, and PeIA potentiate inwardly-rectifying K+ currents in HEK293T cells recombinantly expressing human GIRK1/2 channels and GABAB receptors. GABAB receptor-dependent GIRK channel potentiation by Vc1.1 and baclofen occurs via a pertussis toxin-sensitive G protein and is inhibited by the selective GABAB receptor antagonist CGP 55845. In adult mouse dorsal root ganglion neurons, GABAB receptor-dependent GIRK channel potentiation by Vc1.1 and baclofen hyperpolarizes the cell membrane potential and reduces excitability. CONCLUSIONS AND IMPLICATIONS This is the first report of GIRK channel potentiation via allosteric α-conotoxin Vc1.1-GABAB receptor agonism, leading to decreased neuronal excitability. Such action potentially contributes to the analgesic effects of Vc1.1 and baclofen observed in vivo.
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Affiliation(s)
- Anuja R Bony
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Jeffrey R McArthur
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - Rocio K Finol-Urdaneta
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
| | - David J Adams
- Illawarra Health and Medical Research Institute (IHMRI), University of Wollongong, Wollongong, NSW, Australia
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20
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Encephalopathy-causing mutations in Gβ 1 ( GNB1) alter regulation of neuronal GIRK channels. iScience 2021; 24:103018. [PMID: 34522861 PMCID: PMC8426278 DOI: 10.1016/j.isci.2021.103018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/04/2021] [Accepted: 08/18/2021] [Indexed: 11/24/2022] Open
Abstract
Mutations in the GNB1 gene, encoding the Gβ1 subunit of heterotrimeric G proteins, cause GNB1 Encephalopathy. Patients experience seizures, pointing to abnormal activity of ion channels or neurotransmitter receptors. We studied three Gβ1 mutations (K78R, I80N and I80T) using computational and functional approaches. In heterologous expression models, these mutations did not alter the coupling between G protein-coupled receptors to Gi/o, or the Gβγ regulation of the neuronal voltage-gated Ca2+ channel CaV2.2. However, the mutations profoundly affected the Gβγ regulation of the G protein-gated inwardly rectifying potassium channels (GIRK, or Kir3). Changes were observed in Gβ1 protein expression levels, Gβγ binding to cytosolic segments of GIRK subunits, and in Gβγ function, and included gain-of-function for K78R or loss-of-function for I80T/N, which were GIRK subunit-specific. Our findings offer new insights into subunit-dependent gating of GIRKs by Gβγ, and indicate diverse etiology of GNB1 Encephalopathy cases, bearing a potential for personalized treatment. GIRK channels are key players affected by GNB1 mutations under study (K78R and I80N/T) Effects of mutations (LoF or GoF) are channel subunit composition-specific The findings help to understand the GNB1 encephalopathy and to devise treatments The results yield new insights into mechanisms of Gβγ regulation of GIRKs
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21
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Zou S, Qiu S, Su S, Zhang J, Sun J, Wang Y, Shi C, Xu Y. Inhibitory G-protein-mediated modulation of slow delayed rectifier potassium channels contributes to increased susceptibility to arrhythmogenesis in aging heart. Heart Rhythm 2021; 18:2197-2209. [PMID: 34536591 DOI: 10.1016/j.hrthm.2021.09.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/20/2021] [Accepted: 09/08/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND Slow delayed rectifier potassium current (IKs) is an important component of repolarization reserve during sympathetic nerve excitement. However, little is known about age-related functional changes of IKs and its involvement in age-dependent arrhythmogenesis. OBJECTIVE The purpose of this study was to investigate age-related alteration of the IKs response to β-adrenergic receptor (βAR) activation. METHODS Dunkin-Hartley guinea pigs were used. Whole-cell patch-clamp recording was used to record K+ currents. Optical mapping of membrane potential was performed in ex vivo heart. RESULTS There was no difference in IKs density in ventricular cardiomyocytes between young and old guinea pigs. However, in contrast to IKs potentiation in young hearts, isoproterenol (ISO) evoked an acute inhibition on IKs in a concentration-dependent manner in old guinea pig hearts. The β2AR antagonist, but not β1AR antagonist, reversed the inhibitory response. Preincubation of cardiomyocytes with the inhibitory G protein (Gi) inhibitor pertussis toxin (PTX) also reversed the inhibitory response. In HEK293 cells cotransfected with cloned IKs channel and β2AR, ISO enhanced the current but reduced it when cells were cotransfected with Gi2, and PTX restored the ISO-induced excitatory response. Moreover, in aging cardiomyocytes, Gβγ inhibitor gallein, PLC inhibitor U73122, or protein kinase C inhibitor Bis-1 prevented the reduction of IKs by ISO. Furthermore, cardiac-specific Gi2 overexpression in young guinea pigs predisposed the heart to ventricular tachyarrhythmias. PTX pretreatment protected the hearts from ventricular arrhythmias. CONCLUSION βAR activation acutely induces an inhibitory IKs response in aging guinea pig hearts through β2AR-Gi signaling, which contributes to increased susceptibility to arrhythmogenesis in aging hearts.
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Affiliation(s)
- Sihao Zou
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Suhua Qiu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Shi Su
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jiali Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Jinglei Sun
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yuhong Wang
- Institute of Masteria Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Chenxia Shi
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China
| | - Yanfang Xu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei, China.
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22
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Stepniewski TM, Mancini A, Ågren R, Torrens-Fontanals M, Semache M, Bouvier M, Sahlholm K, Breton B, Selent J. Mechanistic insights into dopaminergic and serotonergic neurotransmission - concerted interactions with helices 5 and 6 drive the functional outcome. Chem Sci 2021; 12:10990-11003. [PMID: 34522296 PMCID: PMC8386650 DOI: 10.1039/d1sc00749a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 06/15/2021] [Indexed: 01/14/2023] Open
Abstract
Brain functions rely on neurotransmitters that mediate communication between billions of neurons. Disruption of this communication can result in a plethora of psychiatric and neurological disorders. In this work, we combine molecular dynamics simulations, live-cell biosensor and electrophysiological assays to investigate the action of the neurotransmitter dopamine at the dopaminergic D2 receptor (D2R). The study of dopamine and closely related chemical probes reveals how neurotransmitter binding translates into the activation of distinct subsets of D2R effectors (i.e.: Gi2, GoB, Gz and β-arrestin 2). Ligand interactions with key residues in TM5 (S5.42) and TM6 (H6.55) in the D2R binding pocket yield a dopamine-like coupling signature, whereas exclusive TM5 interaction is typically linked to preferential G protein coupling (in particular GoB) over β-arrestin. Further experiments for serotonin receptors indicate that the reported molecular mechanism is shared by other monoaminergic neurotransmitter receptors. Ultimately, our study highlights how sequence variation in position 6.55 is used by nature to fine-tune β-arrestin recruitment and in turn receptor signaling and internalization of neurotransmitter receptors.
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Affiliation(s)
- Tomasz Maciej Stepniewski
- Research Programme on Biomedical Informatics (GRIB), Hospital del Mar Medical Research Institute (IMIM) - Pompeu Fabra University (UPF) Dr Aiguader 88 Barcelona E-08003 Spain
- InterAx Biotech AG, PARK InnovAARE 5234 Villigen Switzerland
| | - Arturo Mancini
- Domain Therapeutics NA Inc 7171 Frederick-Banting Saint-Laurent (QC) H4S 1Z9 Canada
| | - Richard Ågren
- Department of Neuroscience, Karolinska Institute Stockholm Sweden
| | - Mariona Torrens-Fontanals
- Research Programme on Biomedical Informatics (GRIB), Hospital del Mar Medical Research Institute (IMIM) - Pompeu Fabra University (UPF) Dr Aiguader 88 Barcelona E-08003 Spain
| | - Meriem Semache
- Domain Therapeutics NA Inc 7171 Frederick-Banting Saint-Laurent (QC) H4S 1Z9 Canada
| | - Michel Bouvier
- Department of Biochemistry and Molecular Medicine, Université de Montréal Montreal QC H3C 3J7 Canada
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal Montréal Québec H3T 1J4 Canada
| | - Kristoffer Sahlholm
- Department of Neuroscience, Karolinska Institute Stockholm Sweden
- Department of Integrative Medical Biology, Wallenberg Centre for Molecular Medicine, Umeå University 90187 Umeå Sweden
| | - Billy Breton
- Domain Therapeutics NA Inc 7171 Frederick-Banting Saint-Laurent (QC) H4S 1Z9 Canada
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal Montréal Québec H3T 1J4 Canada
| | - Jana Selent
- Research Programme on Biomedical Informatics (GRIB), Hospital del Mar Medical Research Institute (IMIM) - Pompeu Fabra University (UPF) Dr Aiguader 88 Barcelona E-08003 Spain
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23
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Ortiz MI, Cariño-Cortés R, Muñoz-Pérez VM, Salas-Casas A, Castañeda-Hernández G. Role of the NO-cGMP-K + channels pathway in the peripheral antinociception induced by α-bisabolol. Can J Physiol Pharmacol 2021; 99:1048-1056. [PMID: 33857384 DOI: 10.1139/cjpp-2020-0744] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The aim of this study was to examine if the peripheral antinociception of α-bisabolol involves the participation of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) synthesis followed by K+ channel opening in the formalin test. Wistar rats were injected in the dorsal surface of the right hind paw with formalin (1%). Rats received a subcutaneous injection into the dorsal surface of the paw of vehicles or increasing doses of α-bisabolol (100-300 µg/paw). To determine whether the peripheral antinociception induced by α-bisabolol was mediated by either the opioid receptors or the NO-cGMP-K+ channels pathway, the effect of pretreatment (10 min before formalin injection) with the appropriate vehicles, naloxone, naltrexone, NG-nitro-l-arginine methyl ester (L-NAME), 1H-[1,2,4]-oxadiazolo[4,2-a]quinoxalin-1-one (ODQ), glibenclamide, glipizide, apamin, charybdotoxin, tetraethylammonium, or 4-aminopyridine on the antinociceptive effects induced by local peripheral α-bisabolol (300 µg/paw) were assessed. α-Bisabolol produced antinociception during both phases of the formalin test. α-Bisabolol antinociception was blocked by L-NAME, ODQ, and all the K+ channels blockers. The peripheral antinociceptive effect produced by α-bisabolol was not blocked by the opioid receptor inhibitors. α-Bisabolol was able to active the NO-cGMP-K+ channels pathway to produce its antinoceptive effect. The participation of opioid receptors in the peripheral local antinociception induced by α-bisabolol is excluded.
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Affiliation(s)
- Mario I Ortiz
- Área Académica de Medicina del Instituto de Ciencias de la Salud. Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Raquel Cariño-Cortés
- Área Académica de Medicina del Instituto de Ciencias de la Salud. Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Víctor M Muñoz-Pérez
- Área Académica de Medicina del Instituto de Ciencias de la Salud. Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Andrés Salas-Casas
- Área Académica de Gerontología del Instituto de Ciencias de la Salud. Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Gilberto Castañeda-Hernández
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
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Dopamine D 2 Receptor Agonist Binding Kinetics-Role of a Conserved Serine Residue. Int J Mol Sci 2021; 22:ijms22084078. [PMID: 33920848 PMCID: PMC8071183 DOI: 10.3390/ijms22084078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/06/2021] [Accepted: 04/13/2021] [Indexed: 01/03/2023] Open
Abstract
The forward (kon) and reverse (koff) rate constants of drug–target interactions have important implications for therapeutic efficacy. Hence, time-resolved assays capable of measuring these binding rate constants may be informative to drug discovery efforts. Here, we used an ion channel activation assay to estimate the kons and koffs of four dopamine D2 receptor (D2R) agonists; dopamine (DA), p-tyramine, (R)- and (S)-5-OH-dipropylaminotetralin (DPAT). We further probed the role of the conserved serine S1935.42 by mutagenesis, taking advantage of the preferential interaction of (S)-, but not (R)-5-OH-DPAT with this residue. Results suggested similar koffs for the two 5-OH-DPAT enantiomers at wild-type (WT) D2R, both being slower than the koffs of DA and p-tyramine. Conversely, the kon of (S)-5-OH-DPAT was estimated to be higher than that of (R)-5-OH-DPAT, in agreement with the higher potency of the (S)-enantiomer. Furthermore, S1935.42A mutation lowered the kon of (S)-5-OH-DPAT and reduced the potency difference between the two 5-OH-DPAT enantiomers. Kinetic Kds derived from the koff and kon estimates correlated well with EC50 values for all four compounds across four orders of magnitude, strengthening the notion that our assay captured meaningful information about binding kinetics. The approach presented here may thus prove valuable for characterizing D2R agonist candidate drugs.
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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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Calebiro D, Koszegi Z, Lanoiselée Y, Miljus T, O'Brien S. G protein-coupled receptor-G protein interactions: a single-molecule perspective. Physiol Rev 2020; 101:857-906. [PMID: 33331229 DOI: 10.1152/physrev.00021.2020] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
G protein-coupled receptors (GPCRs) regulate many cellular and physiological processes, responding to a diverse range of extracellular stimuli including hormones, neurotransmitters, odorants, and light. Decades of biochemical and pharmacological studies have provided fundamental insights into the mechanisms of GPCR signaling. Thanks to recent advances in structural biology, we now possess an atomistic understanding of receptor activation and G protein coupling. However, how GPCRs and G proteins interact in living cells to confer signaling efficiency and specificity remains insufficiently understood. The development of advanced optical methods, including single-molecule microscopy, has provided the means to study receptors and G proteins in living cells with unprecedented spatio-temporal resolution. The results of these studies reveal an unexpected level of complexity, whereby GPCRs undergo transient interactions among themselves as well as with G proteins and structural elements of the plasma membrane to form short-lived signaling nanodomains that likely confer both rapidity and specificity to GPCR signaling. These findings may provide new strategies to pharmaceutically modulate GPCR function, which might eventually pave the way to innovative drugs for common diseases such as diabetes or heart failure.
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Affiliation(s)
- Davide Calebiro
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Zsombor Koszegi
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Yann Lanoiselée
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Tamara Miljus
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
| | - Shannon O'Brien
- Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, United Kingdom; Centre of Membrane Proteins and Receptors (COMPARE), Universities of Nottingham and Birmingham, Birmingham, United Kingdom
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Ortiz MI, Cariño-Cortés R, Castañeda-Hernández G. Participation of the opioid receptor - nitric oxide - cGMP - K + channel pathway in the peripheral antinociceptive effect of nalbuphine and buprenorphine in rats. Can J Physiol Pharmacol 2020; 98:753-762. [PMID: 33095677 DOI: 10.1139/cjpp-2020-0104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The aim of this study was to examine if the peripheral antinociceptive effects of the opioid agonist/antagonist nalbuphine and buprenorphine involve the sequential participation of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) synthesis followed by K+ channel opening in the formalin test. Wistar rats (180-220 g) were injected in the dorsal surface of the right hind paw with formalin (1%). Rats received a subcutaneous (s.c.) injection into the dorsal surface of the paw of vehicles or increasing doses of nalbuphine (50-200 μg/paw) or buprenorphine (1-5 μg/paw) 20 min before formalin injection into the paw. Nalbuphine antinociception was reversed by the s.c. injection into the paw of the inhibitor of NO synthesis (NG-nitro-l-arginine methyl ester (L-NAME)), by the inhibitor of guanylyl cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ)), by the Kir6.1-2, ATP-sensitive K+ channel inhibitors (glibenclamide and glipizide), by the KCa2.1-3, small conductance Ca2+-activated K+ channel blocker (apamin), by the KCa1.1, large conductance Ca2+-activated K+ channel blocker (charybdotoxin), and by the KV, voltage-dependent K+ channel inhibitors (4-aminopyridine (4-AP) and tetraethylammonium chloride (TEA)). The antinociceptive effect produced by buprenorphine was blocked by the s.c. injection of 4-AP and TEA but not by L-NAME, ODQ, glibenclamide, glipizide, apamin, or charybdotoxin. The present results provide evidence for differences in peripheral mechanisms of action between these opioid drugs.
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Affiliation(s)
- Mario I Ortiz
- Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Raquel Cariño-Cortés
- Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
| | - Gilberto Castañeda-Hernández
- Departamento de Farmacología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
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Histamine H3 Receptor Activation Modulates Glutamate Release in the Corticostriatal Synapse by Acting at CaV2.1 (P/Q-Type) Calcium Channels and GIRK (KIR3) Potassium Channels. Cell Mol Neurobiol 2020; 42:817-828. [DOI: 10.1007/s10571-020-00980-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 10/06/2020] [Indexed: 01/24/2023]
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Kir3 channel blockade in the cerebellar cortex suppresses performance of classically conditioned Purkinje cell responses. Sci Rep 2020; 10:15654. [PMID: 32973240 PMCID: PMC7515874 DOI: 10.1038/s41598-020-72581-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 09/03/2020] [Indexed: 11/23/2022] Open
Abstract
In the eyeblink conditioning paradigm, cerebellar Purkinje cells learn to respond to the conditional stimulus with an adaptively timed pause in its spontaneous firing. Evidence suggests that the pause is elicited by glutamate released from parallel fibers and acting on metabotropic receptors (mGluR7) which initiates a delayed-onset suppression of firing. We suggested that G protein activation of hyperpolarizing Kir3 channels (or ‘GIRK’, G protein-coupled inwardly-rectifying K+ channels) could be part of such a mechanism. Application of the Kir3 antagonist Tertiapin-LQ locally in the superficial layers of the cerebellar cortex in decerebrate ferrets suppressed normal performance of Purkinje cell pause responses to the conditional stimulus. Importantly, there was no detectable effect on spontaneous firing. These findings suggest that intact functioning of Kir3 channels in the cerebellar cortex is required for normal conditioned Purkinje cell responses.
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30
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Berlin S, Artzy E, Handklo-Jamal R, Kahanovitch U, Parnas H, Dascal N, Yakubovich D. A Collision Coupling Model Governs the Activation of Neuronal GIRK1/2 Channels by Muscarinic-2 Receptors. Front Pharmacol 2020; 11:1216. [PMID: 32903404 PMCID: PMC7435011 DOI: 10.3389/fphar.2020.01216] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/24/2020] [Indexed: 01/14/2023] Open
Abstract
The G protein-activated Inwardly Rectifying K+-channel (GIRK) modulates heart rate and neuronal excitability. Following G-Protein Coupled Receptor (GPCR)-mediated activation of heterotrimeric G proteins (Gαβγ), opening of the channel is obtained by direct binding of Gβγ subunits. Interestingly, GIRKs are solely activated by Gβγ subunits released from Gαi/o-coupled GPCRs, despite the fact that all receptor types, for instance Gαq-coupled, are also able to provide Gβγ subunits. It is proposed that this specificity and fast kinetics of activation stem from pre-coupling (or pre-assembly) of proteins within this signaling cascade. However, many studies, including our own, point towards a diffusion-limited mechanism, namely collision coupling. Here, we set out to address this long-standing question by combining electrophysiology, imaging, and mathematical modeling. Muscarinic-2 receptors (M2R) and neuronal GIRK1/2 channels were coexpressed in Xenopus laevis oocytes, where we monitored protein surface expression, current amplitude, and activation kinetics. Densities of expressed M2R were assessed using a fluorescently labeled GIRK channel as a molecular ruler. We then incorporated our results, along with available kinetic data reported for the G-protein cycle and for GIRK1/2 activation, to generate a comprehensive mathematical model for the M2R-G-protein-GIRK1/2 signaling cascade. We find that, without assuming any irreversible interactions, our collision coupling kinetic model faithfully reproduces the rate of channel activation, the changes in agonist-evoked currents and the acceleration of channel activation by increased receptor densities.
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Affiliation(s)
- Shai Berlin
- Department of Neuroscience, Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Etay Artzy
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv-Yafo, Israel
| | - Reem Handklo-Jamal
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv-Yafo, Israel
| | - Uri Kahanovitch
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv-Yafo, Israel
| | - Hanna Parnas
- Silberman Institute of Life Sciences, Hebrew University, Jerusalem, Israel
| | - Nathan Dascal
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv-Yafo, Israel
| | - Daniel Yakubovich
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv-Yafo, Israel.,Department of Neonatology, Schneider Children's Hospital, Petah Tikva, Israel
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31
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Huang CLH, Wu L, Jeevaratnam K, Lei M. Update on antiarrhythmic drug pharmacology. J Cardiovasc Electrophysiol 2020; 31:579-592. [PMID: 31930579 DOI: 10.1111/jce.14347] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/22/2019] [Accepted: 01/03/2020] [Indexed: 12/28/2022]
Abstract
Cardiac arrhythmias constitute a major public health problem. Pharmacological intervention remains mainstay to their clinical management. This, in turn, depends upon systematic drug classification schemes relating their molecular, cellular, and systems effects to clinical indications and therapeutic actions. This approach was first pioneered in the 1960s Vaughan-Williams classification. Subsequent progress in cardiac electrophysiological understanding led to a lag between the fundamental science and its clinical translation, partly addressed by The working group of the European Society of Cardiology (1991), which, however, did not emerge with formal classifications. We here utilize the recent Revised Oxford Classification Scheme to review antiarrhythmic drug pharmacology. We survey drugs and therapeutic targets offered by the more recently characterized ion channels, transporters, receptors, intracellular Ca2+ handling, and cell signaling molecules. These are organized into their strategic roles in cardiac electrophysiological function. Following analysis of the arrhythmic process itself, we consider (a) pharmacological agents directly targeting membrane function, particularly the Na+ and K+ ion channels underlying depolarizing and repolarizing events in the cardiac action potential. (b) We also consider agents that modify autonomic activity that, in turn, affects both the membrane and (c) the Ca2+ homeostatic and excitation-contraction coupling processes linking membrane excitation to contractile activation. Finally, we consider (d) drugs acting on more upstream energetic and structural remodeling processes currently the subject of clinical trials. Such systematic correlations of drug actions and arrhythmic mechanisms at different molecular to systems levels of cardiac function will facilitate current and future antiarrhythmic therapy.
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Affiliation(s)
- Christopher L-H Huang
- Department of Biochemistry and Physiological Laboratory, University of Cambridge, Cambridge, UK.,Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Lin Wu
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Cardiology, Peking University First Hospital, Beijing, China
| | | | - Ming Lei
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Pharmacology, University of Oxford, Oxford, UK
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32
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Xu Y, Cantwell L, Molosh AI, Plant LD, Gazgalis D, Fitz SD, Dustrude ET, Yang Y, Kawano T, Garai S, Noujaim SF, Shekhar A, Logothetis DE, Thakur GA. The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents. J Biol Chem 2020; 295:3614-3634. [PMID: 31953327 DOI: 10.1074/jbc.ra119.011527] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/09/2020] [Indexed: 01/31/2023] Open
Abstract
G-protein-gated inwardly-rectifying K+ (GIRK) channels are targets of Gi/o-protein-signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential. Here, we report on a highly-specific, potent, and efficacious activator of brain GIRK1/2 channels. Using a chemical screen and electrophysiological assays, we found that this activator, the bromothiophene-substituted small molecule GAT1508, is specific for brain-expressed GIRK1/2 channels rather than for cardiac GIRK1/4 channels. Computational models predicted a GAT1508-binding site validated by experimental mutagenesis experiments, providing insights into how urea-based compounds engage distant GIRK1 residues required for channel activation. Furthermore, we provide computational and experimental evidence that GAT1508 is an allosteric modulator of channel-phosphatidylinositol 4,5-bisphosphate interactions. Through brain-slice electrophysiology, we show that subthreshold GAT1508 concentrations directly stimulate GIRK currents in the basolateral amygdala (BLA) and potentiate baclofen-induced currents. Of note, GAT1508 effectively extinguished conditioned fear in rodents and lacked cardiac and behavioral side effects, suggesting its potential for use in pharmacotherapy for post-traumatic stress disorder. In summary, our findings indicate that the small molecule GAT1508 has high specificity for brain GIRK1/2 channel subunits, directly or allosterically activates GIRK1/2 channels in the BLA, and facilitates fear extinction in a rodent model.
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Affiliation(s)
- Yu Xu
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Lucas Cantwell
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Andrei I Molosh
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Leigh D Plant
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Stephanie D Fitz
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Erik T Dustrude
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Yuchen Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Takeharu Kawano
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Sumanta Garai
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Sami F Noujaim
- Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida 33612
| | - Anantha Shekhar
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202.
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115.
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115.
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Jacobson DA, Shyng SL. Ion Channels of the Islets in Type 2 Diabetes. J Mol Biol 2019; 432:1326-1346. [PMID: 31473158 DOI: 10.1016/j.jmb.2019.08.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/19/2019] [Accepted: 08/21/2019] [Indexed: 02/06/2023]
Abstract
Ca2+ is an essential signal for pancreatic β-cell function. Ca2+ plays critical roles in numerous β-cell pathways such as insulin secretion, transcription, metabolism, endoplasmic reticulum function, and the stress response. Therefore, β-cell Ca2+ handling is tightly controlled. At the plasma membrane, Ca2+ entry primarily occurs through voltage-dependent Ca2+ channels. Voltage-dependent Ca2+ channel activity is dependent on orchestrated fluctuations in the plasma membrane potential or voltage, which are mediated via the activity of many ion channels. During the pathogenesis of type 2 diabetes the β-cell is exposed to stressful conditions, which result in alterations of Ca2+ handling. Some of the changes in β-cell Ca2+ handling that occur under stress result from perturbations in ion channel activity, expression or localization. Defective Ca2+ signaling in the diabetic β-cell alters function, limits insulin secretion and exacerbates hyperglycemia. In this review, we focus on the β-cell ion channels that control Ca2+ handling and how they impact β-cell dysfunction in type 2 diabetes.
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Affiliation(s)
- David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 7415 MRB4 (Langford), 2213 Garland Avenue, Nashville, TN 37232, USA.
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, L224, MRB 624, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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Wu V, Yeerna H, Nohata N, Chiou J, Harismendy O, Raimondi F, Inoue A, Russell RB, Tamayo P, Gutkind JS. Illuminating the Onco-GPCRome: Novel G protein-coupled receptor-driven oncocrine networks and targets for cancer immunotherapy. J Biol Chem 2019; 294:11062-11086. [PMID: 31171722 DOI: 10.1074/jbc.rev119.005601] [Citation(s) in RCA: 118] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are the largest gene family of cell membrane-associated molecules mediating signal transmission, and their involvement in key physiological functions is well-established. The ability of GPCRs to regulate a vast array of fundamental biological processes, such as cardiovascular functions, immune responses, hormone and enzyme release from endocrine and exocrine glands, neurotransmission, and sensory perception (e.g. vision, odor, and taste), is largely due to the diversity of these receptors and the layers of their downstream signaling circuits. Dysregulated expression and aberrant functions of GPCRs have been linked to some of the most prevalent human diseases, which renders GPCRs one of the top targets for pharmaceutical drug development. However, the study of the role of GPCRs in tumor biology has only just begun to make headway. Recent studies have shown that GPCRs can contribute to the many facets of tumorigenesis, including proliferation, survival, angiogenesis, invasion, metastasis, therapy resistance, and immune evasion. Indeed, GPCRs are widely dysregulated in cancer and yet are underexploited in oncology. We present here a comprehensive analysis of GPCR gene expression, copy number variation, and mutational signatures in 33 cancer types. We also highlight the emerging role of GPCRs as part of oncocrine networks promoting tumor growth, dissemination, and immune evasion, and we stress the potential benefits of targeting GPCRs and their signaling circuits in the new era of precision medicine and cancer immunotherapies.
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Affiliation(s)
- Victoria Wu
- Department of Pharmacology, UCSD Moores Cancer Center, La Jolla, California 92093
| | - Huwate Yeerna
- Department of Medicine, UCSD Moores Cancer Center, La Jolla, California 92093
| | - Nijiro Nohata
- Department of Pharmacology, UCSD Moores Cancer Center, La Jolla, California 92093
| | - Joshua Chiou
- Department of Pediatrics, University of California San Diego School of Medicine, La Jolla, California 92093
| | - Olivier Harismendy
- Department of Medicine, UCSD Moores Cancer Center, La Jolla, California 92093.,Department of Medicine, UCSD Moores Cancer Center, La Jolla, California 92093
| | - Francesco Raimondi
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Asuka Inoue
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
| | - Robert B Russell
- CellNetworks, Bioquant, Heidelberg University, Im Neuenheimer Feld 267, 69120 Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Heidelberg University, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
| | - Pablo Tamayo
- Department of Medicine, UCSD Moores Cancer Center, La Jolla, California 92093
| | - J Silvio Gutkind
- Department of Pharmacology, UCSD Moores Cancer Center, La Jolla, California 92093
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Carmi I, De Battista M, Maddalena L, Carroll EC, Kienzler MA, Berlin S. Holographic two-photon activation for synthetic optogenetics. Nat Protoc 2019; 14:864-900. [PMID: 30804570 DOI: 10.1038/s41596-018-0118-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 12/17/2018] [Indexed: 12/25/2022]
Abstract
Optogenetic tools provide users the ability to photocontrol the activity of cells. Commonly, activation is achieved by expression of proteins from photosynthetic organisms, for example, microbial opsins (e.g., ChR2). Alternatively, a sister approach, synthetic optogenetics, enables photocontrol over proteins of mammalian origin by use of photoswitches, visible light (typically), and genetic modification. Thus, synthetic optogenetics facilitates interrogation of native neuronal signaling mechanisms. However, the poor tissue penetration of visible wavelengths impedes the use of the technique in tissue, as two-photon excitation (2PE) is typically required to access the near-infrared window. Here, we describe an alternative technique that uses 2PE-compatible photoswitches (section 1) for photoactivation of genetically modified glutamate receptors (section 2). Furthermore, for fast, multi-region photoactivation, we describe the use of 2P-digital holography (2P-DH) (section 3). We detail how to combine 2P-DH and synthetic optogenetics with electrophysiology, or with red fluorescence Ca2+ recordings, for all-optical neural interrogation. The time required to complete the methods, aside from obtaining the necessary reagents and illumination equipment, is ~3 weeks.
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Affiliation(s)
- Ido Carmi
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Marco De Battista
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Laura Maddalena
- Department of Imaging Physics, Delft University of Technology, Delft, the Netherlands
| | - Elizabeth C Carroll
- Department of Imaging Physics, Delft University of Technology, Delft, the Netherlands
| | | | - Shai Berlin
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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Mutual action by Gγ and Gβ for optimal activation of GIRK channels in a channel subunit-specific manner. Sci Rep 2019; 9:508. [PMID: 30679535 PMCID: PMC6346094 DOI: 10.1038/s41598-018-36833-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 11/29/2018] [Indexed: 01/06/2023] Open
Abstract
The tetrameric G protein-gated K+ channels (GIRKs) mediate inhibitory effects of neurotransmitters that activate Gi/o-coupled receptors. GIRKs are activated by binding of the Gβγ dimer, via contacts with Gβ. Gγ underlies membrane targeting of Gβγ, but has not been implicated in channel gating. We observed that, in Xenopus oocytes, expression of Gγ alone activated homotetrameric GIRK1* and heterotetrameric GIRK1/3 channels, without affecting the surface expression of GIRK or Gβ. Gγ and Gβ acted interdependently: the effect of Gγ required the presence of ambient Gβ and was enhanced by low doses of coexpressed Gβ, whereas excess of either Gβ or Gγ imparted suboptimal activation, possibly by sequestering the other subunit “away” from the channel. The unique distal C-terminus of GIRK1, G1-dCT, was important but insufficient for Gγ action. Notably, GIRK2 and GIRK1/2 were not activated by Gγ. Our results suggest that Gγ regulates GIRK1* and GIRK1/3 channel’s gating, aiding Gβ to trigger the channel’s opening. We hypothesize that Gγ helps to relax the inhibitory effect of a gating element (“lock”) encompassed, in part, by the G1-dCT; GIRK2 acts to occlude the effect of Gγ, either by setting in motion the same mechanism as Gγ, or by triggering an opposing gating effect.
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Goswami S. G protein-coupled receptor signaling in cardiovascular system: Specificity versus diversity. JOURNAL OF THE PRACTICE OF CARDIOVASCULAR SCIENCES 2019. [DOI: 10.4103/jpcs.jpcs_37_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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38
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Abstract
BACKGROUND Among his major cardiac electrophysiological contributions, Miles Vaughan Williams (1918-2016) provided a classification of antiarrhythmic drugs that remains central to their clinical use. METHODS We survey implications of subsequent discoveries concerning sarcolemmal, sarcoplasmic reticular, and cytosolic biomolecules, developing an expanded but pragmatic classification that encompasses approved and potential antiarrhythmic drugs on this centenary of his birth. RESULTS We first consider the range of pharmacological targets, tracking these through to cellular electrophysiological effects. We retain the original Vaughan Williams Classes I through IV but subcategorize these divisions in light of more recent developments, including the existence of Na+ current components (for Class I), advances in autonomic (often G protein-mediated) signaling (for Class II), K+ channel subspecies (for Class III), and novel molecular targets related to Ca2+ homeostasis (for Class IV). We introduce new classes based on additional targets, including channels involved in automaticity, mechanically sensitive ion channels, connexins controlling electrotonic cell coupling, and molecules underlying longer-term signaling processes affecting structural remodeling. Inclusion of this widened range of targets and their physiological sequelae provides a framework for a modernized classification of established antiarrhythmic drugs based on their pharmacological targets. The revised classification allows for the existence of multiple drug targets/actions and for adverse, sometimes actually proarrhythmic, effects. The new scheme also aids classification of novel drugs under investigation. CONCLUSIONS We emerge with a modernized classification preserving the simplicity of the original Vaughan Williams framework while aiding our understanding and clinical management of cardiac arrhythmic events and facilitating future developments in this area.
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Affiliation(s)
- Ming Lei
- Department of Pharmacology, University of Oxford, United Kingdom (M.L., D.A.T.)
- Key Laboratory of Medical Electrophysiology of the Ministry of Education and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China (M.L., L.W.)
| | - Lin Wu
- Department of Cardiology, Peking University First Hospital, Beijing, China (L.W.)
- Key Laboratory of Medical Electrophysiology of the Ministry of Education and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China (M.L., L.W.)
| | - Derek A Terrar
- Department of Pharmacology, University of Oxford, United Kingdom (M.L., D.A.T.)
| | - Christopher L-H Huang
- Physiological Laboratory (C.L.-H.H.), University of Cambridge, United Kingdom
- Department of Biochemistry (C.L.-H.H.). University of Cambridge, United Kingdom
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Inhibitory Signaling to Ion Channels in Hippocampal Neurons Is Differentially Regulated by Alternative Macromolecular Complexes of RGS7. J Neurosci 2018; 38:10002-10015. [PMID: 30315127 DOI: 10.1523/jneurosci.1378-18.2018] [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] [Received: 05/30/2018] [Revised: 09/01/2018] [Accepted: 09/26/2018] [Indexed: 12/14/2022] Open
Abstract
The neuromodulatory effects of GABA on pyramidal neurons are mediated by GABAB receptors (GABABRs) that signal via a conserved G-protein-coupled pathway. Two prominent effectors regulated by GABABRs include G-protein inwardly rectifying K+ (GIRK) and P/Q/N type voltage-gated Ca2+ (CaV2) ion channels that control excitability and synaptic output of these neurons, respectively. Regulator of G-protein signaling 7 (RGS7) has been shown to control GABAB effects, yet the specificity of its impacts on effector channels and underlying molecular mechanisms is poorly understood. In this study, we show that hippocampal RGS7 forms two distinct complexes with alternative subunit configuration bound to either membrane protein R7BP (RGS7 binding protein) or orphan receptor GPR158. Quantitative biochemical experiments show that both complexes account for targeting nearly the entire pool of RGS7 to the plasma membrane. We analyzed the effect of genetic elimination in mice of both sexes and overexpression of various components of RGS7 complex by patch-clamp electrophysiology in cultured neurons and brain slices. We report that RGS7 prominently regulates GABABR signaling to CaV2, in addition to its known involvement in modulating GIRK. Strikingly, only complexes containing R7BP, but not GPR158, accelerated the kinetics of both GIRK and CaV2 modulation by GABABRs. In contrast, GPR158 overexpression exerted the opposite effect and inhibited RGS7-assisted temporal modulation of GIRK and CaV2 by GABA. Collectively, our data reveal mechanisms by which distinctly composed macromolecular complexes modulate the activity of key ion channels that mediate the inhibitory effects of GABA on hippocampal CA1 pyramidal neurons.SIGNIFICANCE STATEMENT This study identifies the contributions of distinct macromolecular complexes containing a major G-protein regulator to controlling key ion channel function in hippocampal neurons with implications for understanding molecular mechanisms underlying synaptic plasticity, learning, and memory.
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40
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Dickson PE, Roy TA, McNaughton KA, Wilcox TD, Kumar P, Chesler EJ. Systems genetics of sensation seeking. GENES BRAIN AND BEHAVIOR 2018; 18:e12519. [PMID: 30221471 PMCID: PMC6399063 DOI: 10.1111/gbb.12519] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 09/09/2018] [Accepted: 09/11/2018] [Indexed: 02/06/2023]
Abstract
Sensation seeking is a multifaceted, heritable trait which predicts the development of substance use and abuse in humans; similar phenomena have been observed in rodents. Genetic correlations among sensation seeking and substance use indicate shared biological mechanisms, but the genes and networks underlying these relationships remain elusive. Here, we used a systems genetics approach in the BXD recombinant inbred mouse panel to identify shared genetic mechanisms underlying substance use and preference for sensory stimuli, an intermediate phenotype of sensation seeking. Using the operant sensation seeking (OSS) paradigm, we quantified preference for sensory stimuli in 120 male and 127 female mice from 62 BXD strains and the C57BL/6J and DBA/2J founder strains. We used relative preference for the active and inactive levers to dissociate preference for sensory stimuli from locomotion and exploration phenotypes. We identified genomic regions on chromosome 4 (155.236‐155.742 Mb) and chromosome 13 (72.969‐89.423 Mb) associated with distinct behavioral components of OSS. Using publicly available behavioral data and mRNA expression data from brain regions involved in reward processing, we identified (a) genes within these behavioral QTL exhibiting genome‐wide significant cis‐eQTL and (b) genetic correlations among OSS phenotypes, ethanol phenotypes and mRNA expression. From these analyses, we nominated positional candidates for behavioral QTL associated with distinct OSS phenotypes including Gnb1 and Mef2c. Genetic covariation of Gnb1 expression, preference for sensory stimuli and multiple ethanol phenotypes suggest that heritable variation in Gnb1 expression in reward circuitry partially underlies the widely reported relationship between sensation seeking and substance use.
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Affiliation(s)
- Price E. Dickson
- Center for Systems Neurogenetics of AddictionThe Jackson LaboratoryBar HarborMaine
| | - Tyler A. Roy
- Center for Systems Neurogenetics of AddictionThe Jackson LaboratoryBar HarborMaine
| | | | - Troy D. Wilcox
- Center for Systems Neurogenetics of AddictionThe Jackson LaboratoryBar HarborMaine
| | - Padam Kumar
- Center for Systems Neurogenetics of AddictionThe Jackson LaboratoryBar HarborMaine
| | - Elissa J. Chesler
- Center for Systems Neurogenetics of AddictionThe Jackson LaboratoryBar HarborMaine
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41
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Ågren R, Århem P, Nilsson J, Sahlholm K. The Beta-Arrestin-Biased Dopamine D2 Receptor Ligand, UNC9994, Is a Partial Agonist at G-Protein-Mediated Potassium Channel Activation. Int J Neuropsychopharmacol 2018; 21:1102-1108. [PMID: 29986044 PMCID: PMC6276031 DOI: 10.1093/ijnp/pyy059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 07/03/2018] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Previous evidence suggests that UNC9994 is a beta-arrestin2-selective agonist at the dopamine D2 receptor, lacking ability both to activate and antagonize G protein-dependent signaling. However, this has only been reported by one laboratory using a single assay. METHODS We used G protein-coupled inward rectifier potassium channel activation in Xenopus oocytes to investigate UNC9994-induced modulation of G protein-dependent signaling at dopamine D2 receptor and dopamine D3 receptor. RESULTS At dopamine D2 receptor, UNC9994 induced G protein-coupled inward rectifier potassium channel currents that were 15% of the maximal response to dopamine, with an EC50 of 185 nM. At dopamine D3 receptor, the ligand elicited 89% of the maximal dopamine response with an EC50 of 62 nM. Pertussis toxin abolished G protein-coupled inward rectifier potassium channel activation. Furthermore, UNC9994 antagonized dopamine-induced G protein-coupled inward rectifier potassium channel activation at dopamine D2 receptor. CONCLUSIONS UNC9994 modulates G protein-coupled inward rectifier potassium channel channel activation via pertussis toxin-sensitive G proteins at dopamine D2 receptor and dopamine D3 receptor. These findings may have implications for the interpretation of data obtained with this ligand.
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Affiliation(s)
- Richard Ågren
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden,Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Peter Århem
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Johanna Nilsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden,Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Kristoffer Sahlholm
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden,Correspondence: Kristoffer Sahlholm, PhD, Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177, Stockholm, Sweden ()
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42
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Radnikow G, Feldmeyer D. Layer- and Cell Type-Specific Modulation of Excitatory Neuronal Activity in the Neocortex. Front Neuroanat 2018; 12:1. [PMID: 29440997 PMCID: PMC5797542 DOI: 10.3389/fnana.2018.00001] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 01/04/2018] [Indexed: 01/08/2023] Open
Abstract
From an anatomical point of view the neocortex is subdivided into up to six layers depending on the cortical area. This subdivision has been described already by Meynert and Brodmann in the late 19/early 20. century and is mainly based on cytoarchitectonic features such as the size and location of the pyramidal cell bodies. Hence, cortical lamination is originally an anatomical concept based on the distribution of excitatory neuron. However, it has become apparent in recent years that apart from the layer-specific differences in morphological features, many functional properties of neurons are also dependent on cortical layer or cell type. Such functional differences include changes in neuronal excitability and synaptic activity by neuromodulatory transmitters. Many of these neuromodulators are released from axonal afferents from subcortical brain regions while others are released intrinsically. In this review we aim to describe layer- and cell-type specific differences in the effects of neuromodulator receptors in excitatory neurons in layers 2–6 of different cortical areas. We will focus on the neuromodulator systems using adenosine, acetylcholine, dopamine, and orexin/hypocretin as examples because these neuromodulator systems show important differences in receptor type and distribution, mode of release and functional mechanisms and effects. We try to summarize how layer- and cell type-specific neuromodulation may affect synaptic signaling in cortical microcircuits.
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Affiliation(s)
- Gabriele Radnikow
- Research Centre Jülich, Institute of Neuroscience and Medicine, INM-10, Jülich, Germany
| | - Dirk Feldmeyer
- Research Centre Jülich, Institute of Neuroscience and Medicine, INM-10, Jülich, Germany.,Department of Psychiatry, Psychotherapy and Psychosomatics, Medical School, RWTH Aachen University, Aachen, Germany.,Jülich-Aachen Research Alliance - Translational Brain Medicine, Jülich, Germany
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43
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Dascal N, Rubinstein M. Lithium reduces the span of G protein-activated K + (GIRK) channel inhibition in hippocampal neurons. Bipolar Disord 2017; 19:568-574. [PMID: 28895268 DOI: 10.1111/bdi.12536] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 07/20/2017] [Indexed: 01/01/2023]
Abstract
OBJECTIVES Lithium (Li+ ) is one of the most widely used treatments for bipolar disorder (BD). However, the molecular and neuronal basis of BD, as well as the mechanisms of Li+ actions are poorly understood. Cellular and biochemical studies identified G proteins as being among the cellular targets for Li+ action, while genetic studies indicated an association with the KCNJ3 gene, which encodes the G protein-activated inwardly rectifying K+ (GIRK) channels. GIRK channels regulate neuronal excitability by mediating the inhibitory effects of multiple neurotransmitters and contribute to the resting potassium conductance. Here, we explored the effects of therapeutic dose of Li+ on neuronal excitability and the role of GIRK channels in Li+ actions. METHODS Effects of Li+ on excitability were studied in hippocampal brain slices using whole-cell electrophysiological recordings. RESULTS A therapeutic dose of Li+ (1 mM) dually regulated the function of GIRK channels in hippocampal slices. Li+ hyperpolarized the resting membrane potential of hippocampal CA1 pyramidal neurons and prolonged the latency to reach the action potential threshold and peak. These effects were abolished in the presence of tertiapin, a specific GIRK channel blocker, and at doses above the therapeutic window (2 mM). In contrast, Li+ reduced GIRK channel opening induced by GABAB receptor (GABAB R) activation, causing reduced hyperpolarization of the membrane potential, attenuated reduction of input resistance, and a smaller decrease of neuronal firing. CONCLUSIONS A therapeutic dose of Li+ reduces the span of GIRK channel-mediated inhibition due to enhancement of basal GIRK currents and inhibition of GABAB R evoked responses, providing an important link between Li+ action, neuronal excitability, and cellular and genetic targets of BD.
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Affiliation(s)
- Nathan Dascal
- The Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Moran Rubinstein
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,The Goldschleger Eye Research Institute, Sheba Medical Center, Tel Hashomer, Israel.,The Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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44
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Prolonged seizure activity causes caspase dependent cleavage and dysfunction of G-protein activated inwardly rectifying potassium channels. Sci Rep 2017; 7:12313. [PMID: 28951616 PMCID: PMC5615076 DOI: 10.1038/s41598-017-12508-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 09/08/2017] [Indexed: 01/09/2023] Open
Abstract
Recurrent high-frequency epileptic seizures cause progressive hippocampal sclerosis, which is associated with caspase-3 activation and NMDA receptor-dependent excitotoxicity. However, the identity of caspase-3 substrates that contribute to seizure-induced hippocampal atrophy remains largely unknown. Here, we show that prolonged high-frequency epileptiform discharges in cultured hippocampal neurons leads to caspase-dependent cleavage of GIRK1 and GIRK2, the major subunits of neuronal G protein-activated inwardly rectifying potassium (GIRK) channels that mediate membrane hyperpolarization and synaptic inhibition in the brain. We have identified caspase-3 cleavage sites in GIRK1 (387ECLD390) and GIRK2 (349YEVD352). The YEVD motif is highly conserved in GIRK2-4, and located within their C-terminal binding sites for Gβγ proteins that mediate membrane-delimited GIRK activation. Indeed, the cleaved GIRK2 displays reduced binding to Gβγ and cannot coassemble with GIRK1. Loss of an ER export motif upon cleavage of GIRK2 abolishes surface and current expression of GIRK2 homotetramic channels. Lastly, kainate-induced status epilepticus causes GIRK1 and GIRK2 cleavage in the hippocampus in vivo. Our findings are the first to show direct cleavage of GIRK1 and GIRK2 subunits by caspase-3, and suggest the possible role of caspase-3 mediated down-regulation of GIRK channel function and expression in hippocampal neuronal injury during prolonged epileptic seizures.
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45
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Mule NK, Orjuela Leon AC, Falck JR, Arand M, Marowsky A. 11,12 -Epoxyeicosatrienoic acid (11,12 EET) reduces excitability and excitatory transmission in the hippocampus. Neuropharmacology 2017; 123:310-321. [DOI: 10.1016/j.neuropharm.2017.05.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/25/2017] [Accepted: 05/13/2017] [Indexed: 12/19/2022]
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46
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Kahanovitch U, Berlin S, Dascal N. Collision coupling in the GABA
B
receptor–G protein–GIRK signaling cascade. FEBS Lett 2017; 591:2816-2825. [DOI: 10.1002/1873-3468.12756] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2017] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Uri Kahanovitch
- Department of Physiology and Pharmacology Sackler School of Medicine Tel Aviv University Israel
| | - Shai Berlin
- Department of Physiology and Pharmacology Sackler School of Medicine Tel Aviv University Israel
| | - Nathan Dascal
- Department of Physiology and Pharmacology Sackler School of Medicine Tel Aviv University Israel
- Sagol School of Neuroscience Tel Aviv University Israel
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Berlin S, Isacoff EY. Synapses in the spotlight with synthetic optogenetics. EMBO Rep 2017; 18:677-692. [PMID: 28396573 DOI: 10.15252/embr.201744010] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/02/2017] [Accepted: 03/09/2017] [Indexed: 12/15/2022] Open
Abstract
Membrane receptors and ion channels respond to various stimuli and relay that information across the plasma membrane by triggering specific and timed processes. These include activation of second messengers, allowing ion permeation, and changing cellular excitability, to name a few. Gaining control over equivalent processes is essential to understand neuronal physiology and pathophysiology. Recently, new optical techniques have emerged proffering new remote means to control various functions of defined neuronal populations by light, dubbed optogenetics. Still, optogenetic tools do not typically address the activity of receptors and channels native to neurons (or of neuronal origin), nor gain access to their signaling mechanisms. A related method-synthetic optogenetics-bridges this gap by endowing light sensitivity to endogenous neuronal receptors and channels by the appending of synthetic, light-receptive molecules, or photoswitches. This provides the means to photoregulate neuronal receptors and channels and tap into their native signaling mechanisms in select regions of the neurons, such as the synapse. This review discusses the development of synthetic optogenetics as a means to study neuronal receptors and channels remotely, in their natural environment, with unprecedented spatial and temporal precision, and provides an overview of tool design, mode of action, potential clinical applications and insights and achievements gained.
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Affiliation(s)
- Shai Berlin
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa, Israel
| | - Ehud Y Isacoff
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA.,Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.,Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
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48
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Trads JB, Burgstaller J, Laprell L, Konrad DB, de la Osa de la Rosa L, Weaver CD, Baier H, Trauner D, Barber DM. Optical control of GIRK channels using visible light. Org Biomol Chem 2017; 15:76-81. [DOI: 10.1039/c6ob02153k] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We have developed the photoswitchable GIRK channel agonistVLOGO, which permits the precise control of GIRK channels using visible light.
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Affiliation(s)
- Julie B. Trads
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
- Center for DNA Nanotechnology
| | | | - Laura Laprell
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
| | - David B. Konrad
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
| | - Luis de la Osa de la Rosa
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
| | - C. David Weaver
- Department of Pharmacology and Institute of Chemical Biology
- Vanderbilt University School of Medicine
- Nashville
- USA
| | - Herwig Baier
- Max Planck Institute of Neurobiology
- 82152 Martinsried
- Germany
| | - Dirk Trauner
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
| | - David M. Barber
- Department of Chemistry and Center for Integrated Protein Science
- Ludwig Maximilians University Munich
- 81377 Munich
- Germany
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49
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Povstyan OV, Barrese V, Stott JB, Greenwood IA. Synergistic interplay of Gβγ and phosphatidylinositol 4,5-bisphosphate dictates Kv7.4 channel activity. Pflugers Arch 2016; 469:213-223. [PMID: 27981364 PMCID: PMC5222924 DOI: 10.1007/s00424-016-1916-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 11/22/2016] [Accepted: 11/24/2016] [Indexed: 11/30/2022]
Abstract
Kv7.4 channels are key determinants of arterial contractility and cochlear mechanosensation that, like all Kv7 channels, have an obligatory requirement for phosphatidylinositol 4,5-bisphosphate (PIP2). βγ G proteins (Gβγ) have been identified as novel positive regulators of Kv7.4. The present study ascertained whether Gβγ increased Kv7.4 open probability through an increased sensitivity to PIP2. In HEK cells stably expressing Kv7.4, PIP2 or Gβγ increased open probability in a concentration dependent manner. Depleting PIP2 prevented any Gβγ-mediated stimulation whilst an array of Gβγ inhibitors prohibited any PIP2-induced current enhancement. A combination of PIP2 and Gβγ at sub-efficacious concentrations increased channel open probability considerably. The stimulatory effects of three Kv7.2-7.5 channel activators were also lost by PIP2 depletion or Gβγ inhibitors. This study alters substantially our understanding of the fundamental processes that dictate Kv7.4 activity, revealing a more complex and subtle paradigm where the reliance on local phosphoinositide is dictated by interaction with Gβγ.
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Affiliation(s)
- Oleksandr V Povstyan
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, UK
| | - Vincenzo Barrese
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, UK
| | - Jennifer B Stott
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, UK
| | - Iain A Greenwood
- Vascular Biology Research Centre, Molecular and Clinical Sciences Institute, St George's, University of London, London, SW17 0RE, UK.
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50
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Barber DM, Schönberger M, Burgstaller J, Levitz J, Weaver CD, Isacoff EY, Baier H, Trauner D. Optical control of neuronal activity using a light-operated GIRK channel opener (LOGO). Chem Sci 2015; 7:2347-2352. [PMID: 28090283 PMCID: PMC5234268 DOI: 10.1039/c5sc04084a] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
G-protein coupled inwardly rectifying potassium channels (GIRKs) are ubiquitously expressed throughout the human body and are an integral part of inhibitory signal transduction pathways. Upon binding of Gβγ subunits released from G-protein coupled receptors (GPCRs), GIRK channels open and reduce the activity of excitable cells via hyperpolarization. As such, they play a role in cardiac output, the coordination of movement and cognition. Due to their involvement in a multitude of pathways, the precision control of GIRK channels is an important endeavour. Here, we describe the development of the photoswitchable agonist LOGO (the Light Operated GIRK-channel Opener), which activates GIRK channels in the dark and is rapidly deactivated upon exposure to long wavelength UV irradiation. LOGO is the first K+ channel opener and selectively targets channels that contain the GIRK1 subunit. It can be used to optically silence action potential firing in dissociated hippocampal neurons and LOGO exhibits activity in vivo, controlling the motility of zebrafish larvae in a light dependent fashion. We envisage that LOGO will be a valuable research tool to dissect the function of GIRK channels from other GPCR dependent signalling pathways.
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Affiliation(s)
- David M Barber
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Matthias Schönberger
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Jessica Burgstaller
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Joshua Levitz
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
| | - C David Weaver
- Department of Pharmacology and Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Ehud Y Isacoff
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA; Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Herwig Baier
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Dirk Trauner
- Department of Chemistry and Center for Integrated Protein Science, Ludwig Maximilians University Munich, Butenandtstraße 5-13, 81377 Munich, Germany
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