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Jalaiei A, Asadi MR, Daneshmandpour Y, Rezazadeh M, Ghafouri-Fard S. Clinical, molecular, physiologic, and therapeutic feature of patients with CHRNA4 and CHRNB2 deficiency: A systematic review. J Neurochem 2024. [PMID: 39193833 DOI: 10.1111/jnc.16200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Revised: 07/03/2024] [Accepted: 07/26/2024] [Indexed: 08/29/2024]
Abstract
The α4β2 nAChRs are crucial ion channels that control neurotransmitter release and play a role in various physiologic and pathologic processes. CHRNA4 encodes the α4-nAChRs, while CHRNB2 encodes the β2-nAChRs. Recent studies have found different variants of α4β2-nAChRs in individuals with conditions such as AD, ADHD, ALS, PD, and brain abnormalities. We conducted a scoping review following a six-stage methodology structure and adhering to PRISMA guidelines. We systematically reviewed articles using relevant keywords up to October 2, 2023. In this summary, we cover the clinical symptoms reported, the genes and protein structure of CHRNA4 and CHRNB2, mutations in these genes, inheritance patterns, the functional impact of mutations and polymorphisms in CHRNA4 and CHRNB2, and the epidemiology of these diseases. Recent research indicates that nAChRs may play a significant role in neurodegenerative disorders, possibly impacting neuronal function through yet undiscovered regulatory pathways. Studying how nAChRs interact with disease-related aggregates in neurodegenerative conditions may lead to new treatment options for these disorders.
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Affiliation(s)
- Abbas Jalaiei
- Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad Reza Asadi
- Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yousef Daneshmandpour
- Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Maryam Rezazadeh
- Department of Medical Genetics, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Haufe Y, Loser D, Danker T, Nicke A. Symmetrical Bispyridinium Compounds Act as Open Channel Blockers of Cation-Selective Ion Channels. ACS Pharmacol Transl Sci 2024; 7:771-786. [PMID: 38495220 PMCID: PMC10941285 DOI: 10.1021/acsptsci.3c00308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 03/19/2024]
Abstract
Current treatments against organophosphate poisoning (OPP) do not directly address effects mediated by the overstimulation of nicotinic acetylcholine receptors (nAChR). Non-oxime bispyridinium compounds (BPC) promote acetylcholine esterase-independent recovery of organophosphate-induced paralysis. Here, we test the hypothesis that they act by positive modulatory action on nAChRs. Using two-electrode voltage clamp analysis in combination with mutagenesis and molecular docking analysis, the potency and molecular mode of action of a series of nine BPCs was investigated on human α7 and muscle-type nAChRs expressed in Xenopus laevis oocytes. The investigated BPCs inhibited α7 and/or muscle-type nAChRs with IC50 values in the high nanomolar to high micromolar range. Further analysis of the most potent analogues revealed a noncompetitive, voltage-dependent inhibition. Co-application with the α7-selective positive allosteric modulator PNU120596 and generation of α7/5HT3 receptor chimeras excluded direct interaction with the PNU120596 binding site and binding to the extracellular domain of the α7 nAChR, suggesting that they act as open channel blockers (OCBs). Molecular docking supported by mutagenesis localized the BPC binding area in the outer channel vestibule between the extracellular and transmembrane domains. Analysis of BPC action on other cation-selective channels suggests a rather nonspecific inhibition of pentameric cation channels. BPCs have been shown to ameliorate organophosphate-induced paralysis in vitro and in vivo. Our data support molecular action as OCBs at α7 and muscle-type nAChRs and suggest that their positive physiological effects are more complex than anticipated and require further investigation.
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Affiliation(s)
- Yves Haufe
- Walther
Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany
| | - Dominik Loser
- NMI
Natural and Medical Sciences Institute at the University of Tübingen, 72770 Reutlingen, Germany
| | - Timm Danker
- NMI
Natural and Medical Sciences Institute at the University of Tübingen, 72770 Reutlingen, Germany
| | - Annette Nicke
- Walther
Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany
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3
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Barrantes FJ. Structure and function meet at the nicotinic acetylcholine receptor-lipid interface. Pharmacol Res 2023; 190:106729. [PMID: 36931540 DOI: 10.1016/j.phrs.2023.106729] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 03/08/2023] [Accepted: 03/13/2023] [Indexed: 03/17/2023]
Abstract
The nicotinic acetylcholine receptor (nAChR) is a transmembrane protein that mediates fast intercellular communication in response to the endogenous neurotransmitter acetylcholine. It is the best characterized and archetypal molecule in the superfamily of pentameric ligand-gated ion channels (pLGICs). As a typical transmembrane macromolecule, it interacts extensively with its vicinal lipid microenvironment. Experimental evidence provides a wealth of information on receptor-lipid crosstalk: the nAChR exerts influence on its immediate membrane environment and conversely, the lipid moiety modulates ligand binding, affinity state transitions and gating of ion translocation functions of the receptor protein. Recent cryogenic electron microscopy (cryo-EM) studies have unveiled the occurrence of sites for phospholipids and cholesterol on the lipid-exposed regions of neuronal and electroplax nAChRs, confirming early spectroscopic and affinity labeling studies demonstrating the close contact of lipid molecules with the receptor transmembrane segments. This new data provides structural support to the postulated "lipid sensor" ability displayed by the outer ring of M4 transmembrane domains and their modulatory role on nAChR function, as we postulated a decade ago. Borrowing from the best characterized nAChR, the electroplax (muscle-type) receptor, and exploiting new structural information on the neuronal nAChR, it is now possible to achieve an improved depiction of these sites. In combination with site-directed mutagenesis, single-channel electrophysiology, and molecular dynamics studies, the new structural information delivers a more comprehensive portrayal of these lipid-sensitive loci, providing mechanistic explanations for their ability to modulate nAChR properties and raising the possibility of targetting them in disease.
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Affiliation(s)
- Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Biomedical Research Institute, Faculty of Medical Sciences, Pontifical Catholic University of Argentina (UCA) - Argentine Scientific & Technol. Research Council (CONICET), Av. Alicia Moreau de Justo 1600, C1107AAZ Buenos Aires, Argentina.
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Johnson H, VanHooreweghe M, Satori JA, Chan JD. Schistosomes contain divergent ligand-gated ion channels with an atypical Cys-loop motif. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000694. [PMID: 36713055 PMCID: PMC9874803 DOI: 10.17912/micropub.biology.000694] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/01/1970] [Accepted: 12/20/2022] [Indexed: 01/31/2023]
Abstract
Ligand-gated ion channels (LGICs) are important regulators of neuromuscular function, making them attractive antiparasitic drug targets. While roundworm LGICs are targeted by several anthelmintic classes, flatworm LGICs are less studied. Chromosome-level genome assemblies have recently been released for Schistosoma flatworm species that cause the disease schistosomiasis. These have allowed us to comprehensively predict schistosome LGICs, adding to prior annotations. Analysis of LGIC sequences revealed a clade of receptors lacking cysteines at the eponymous Cys-loop region of the channel. Since these atypical channels are divergent from mammalian LGICs, they may be promising targets to treat diseases caused by parasitic flatworms.
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Affiliation(s)
| | | | | | - John D Chan
- University of Wisconsin - Oshkosh, Oshkosh, WI, USA
,
Correspondence to: John D Chan (
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Choudhary S, Kashyap SS, Martin RJ, Robertson AP. Advances in our understanding of nematode ion channels as potential anthelmintic targets. Int J Parasitol Drugs Drug Resist 2022; 18:52-86. [PMID: 35149380 PMCID: PMC8841521 DOI: 10.1016/j.ijpddr.2021.12.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 12/15/2022]
Abstract
Ion channels are specialized multimeric proteins that underlie cell excitability. These channels integrate with a variety of neuromuscular and biological functions. In nematodes, the physiological behaviors including locomotion, navigation, feeding and reproduction, are regulated by these protein entities. Majority of the antinematodal chemotherapeutics target the ion channels to disrupt essential biological functions. Here, we have summarized current advances in our understanding of nematode ion channel pharmacology. We review cys-loop ligand gated ion channels (LGICs), including nicotinic acetylcholine receptors (nAChRs), acetylcholine-chloride gated ion channels (ACCs), glutamate-gated chloride channels (GluCls), and GABA (γ-aminobutyric acid) receptors, and other ionotropic receptors (transient receptor potential (TRP) channels and potassium ion channels). We have provided an update on the pharmacological properties of these channels from various nematodes. This article catalogs the differences in ion channel composition and resulting pharmacology in the phylum Nematoda. This diversity in ion channel subunit repertoire and pharmacology emphasizes the importance of pursuing species-specific drug target research. In this review, we have provided an overview of recent advances in techniques and functional assays available for screening ion channel properties and their application.
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Affiliation(s)
- Shivani Choudhary
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Sudhanva S Kashyap
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Richard J Martin
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA
| | - Alan P Robertson
- Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
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Yin X, Yang GF, Niu DB, Chen J, Liao M, Cao HQ, Sheng CW. Identification and pharmacological characterization of histamine-gated chloride channels in the fall armyworm, Spodoptera frugiperda. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 140:103698. [PMID: 34848284 DOI: 10.1016/j.ibmb.2021.103698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 11/15/2021] [Accepted: 11/17/2021] [Indexed: 06/13/2023]
Abstract
Histamine-gated chloride channels (HACls) mediate fast inhibitory neurotransmission in invertebrate nervous systems and have important roles in light reception, color processing, temperature preference and light-dark cycle. The fall armyworm, Spodoptera frugiperda is a main destructive pest of grain and row crops. However, the pharmacological characterization of HACls in S. frugiperda remain unknown. In this study, we identified two cDNAs encoding SfHACl1 and SfHACl2 in S. frugiperda. They had similar expression patterns and were most abundantly expressed in the head of larvae and at the egg stage. Electrophysiological analysis with the two-electrode voltage clamp method showed that histamine (HA) and γ-aminobutyric acid (GABA) activated inward currents when SfHACls were singly or collectively expressed with different ratios in Xenopus laevis oocytes. These channels were ≥2000-fold more sensitive to HA than to GABA. They were anion-selective channels, which were highly dependent on changes in external chloride concentrations, but insensitive to changes in external sodium concentrations. The insecticides abamectin (ABM) and emamectin benzoate (EB) also activated these channels with the EC50 to SfHACl1 lower than that to SfHACl2. And the EC50s of ABM and EB to the co-expressed channels gradually increased with increase in the injection ratio of SfHACl2 cRNA. Homology models and docking simulations revealed that HA bound to the large amino-terminal extracellular domain of SfHACl1 and SfHACl2 by forming 4 and 2 hydrogen bonds, respectively. The docking simulations of ABM and EB had similar binding sites in the transmembrane regions. Overall, these findings indicated that HACls act as targets for macrolide, and this study provides theoretical guidance for further derivatization of abamectin insecticides.
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Affiliation(s)
- Xue Yin
- Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China
| | - Guo-Feng Yang
- Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China
| | - Duo-Bang Niu
- Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China
| | - Jiao Chen
- Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, 210028, PR China
| | - Min Liao
- Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China
| | - Hai-Qun Cao
- Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China; Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China.
| | - Cheng-Wang Sheng
- Anhui Province Key Laboratory of Integrated Pest Management on Crops, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China; Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, 230036, PR China.
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7
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Lipovsek M, Marcovich I, Elgoyhen AB. The Hair Cell α9α10 Nicotinic Acetylcholine Receptor: Odd Cousin in an Old Family. Front Cell Neurosci 2021; 15:785265. [PMID: 34867208 PMCID: PMC8634148 DOI: 10.3389/fncel.2021.785265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are a subfamily of pentameric ligand-gated ion channels with members identified in most eumetazoan clades. In vertebrates, they are divided into three subgroups, according to their main tissue of expression: neuronal, muscle and hair cell nAChRs. Each receptor subtype is composed of different subunits, encoded by paralogous genes. The latest to be identified are the α9 and α10 subunits, expressed in the mechanosensory hair cells of the inner ear and the lateral line, where they mediate efferent modulation. α9α10 nAChRs are the most divergent amongst all nicotinic receptors, showing marked differences in their degree of sequence conservation, their expression pattern, their subunit co-assembly rules and, most importantly, their functional properties. Here, we review recent advances in the understanding of the structure and evolution of nAChRs. We discuss the functional consequences of sequence divergence and conservation, with special emphasis on the hair cell α9α10 receptor, a seemingly distant cousin of neuronal and muscle nicotinic receptors. Finally, we highlight potential links between the evolution of the octavolateral system and the extreme divergence of vertebrate α9α10 receptors.
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Affiliation(s)
- Marcela Lipovsek
- Ear Institute, Faculty of Brain Sciences, University College London, London, United Kingdom
| | - Irina Marcovich
- Departments of Otolaryngology & Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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Huang QT, Sheng CW, Jones AK, Jiang J, Tang T, Han ZJ, Zhao CQ. Functional Characteristics of the Lepidopteran Ionotropic GABA Receptor 8916 Subunit Interacting with the LCCH3 or the RDL Subunit. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:11582-11591. [PMID: 34555899 DOI: 10.1021/acs.jafc.1c00385] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The ionotropic γ-aminobutyric acid (iGABA) receptor is commonly considered as a fast inhibitory channel and is an important insecticide target. Since 1990, RDL, LCCH3, and GRD have been successively isolated and found to be potential subunits of the insect iGABA receptor. More recently, one orphan gene named 8916 was found and considered to be another potential iGABA receptor subunit according to its amino acid sequence. However, little information about 8916 has been reported. Here, the 8916 subunit from Chilo suppressalis was studied to determine whether it can form part of a functional iGABA receptor by co-expressing this subunit with CsRDL1 or CsLCCH3 in the Xenopus oocyte system. Cs8916 or CsLCCH3 did not form functional ion channels when expressed alone. However, Cs8916 was able to form heteromeric ion channels when expressed with either CsLCCH3 or CsRDL1. The recombinant heteromeric Cs8916/LCCH3 channel was a cation-selective channel, which was sensitive to GABA or β-alanine. The current of the Cs8916/LCCH3 channel was inhibited by dieldrin, endosulfan, fipronil, or ethiprole. In contrast, fluralaner, broflanilide, and avermectin showed little effect on the Cs8916/LCCH3 channel (IC50s > 10 000 nM). The Cs8916/RDL1 channel was sensitive to GABA, but was significantly different in EC50 and Imax for GABA to those of homomeric CsRDL1. Fluralaner, fipronil, or dieldrin showed antagonistic actions on Cs8916/RDL1. In conclusion, Cs8916 is a potential iGABA receptor subunit, which can interact with CsLCCH3 to generate a cation-selective channel that is sensitive to several insecticides. Also, as Cs8916/RDL1 has a higher EC50 than homomeric CsRDL1, Cs8916 may affect the physiological functions of CsRDL1 and therefore play a role in fine-tuning GABAergic signaling.
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Affiliation(s)
- Qiu Tang Huang
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Cheng Wang Sheng
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Andrew K Jones
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, U.K
| | - Jie Jiang
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Tao Tang
- Institute of Plant Protection, Hunan Academy of Agricultural Sciences, Changsha 410125, P. R. China
| | - Zhao Jun Han
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
| | - Chun Qing Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, P. R. China
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Hashim O, Charvet CL, Toubaté B, Ahmed AAE, Lamassiaude N, Neveu C, Dimier-Poisson I, Debierre-Grockiego F, Dupuy C. Molecular and Functional Characterization of GABA Receptor Subunits GRD and LCCH3 from Human Louse Pediculus Humanus Humanus. Mol Pharmacol 2021; 102:116-127. [PMID: 35858760 PMCID: PMC11037462 DOI: 10.1124/molpharm.122.000499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 04/21/2022] [Accepted: 05/12/2022] [Indexed: 11/22/2022] Open
Abstract
Human louse Pediculus humanus is a cosmopolitan obligatory blood-feeding ectoparasite causing pediculosis and transmitting many bacterial pathogens. Control of infestation is difficult due to the developed resistance to insecticides that mainly target GABA (γ-aminobutyric acid) receptors. Previous work showed that Pediculus humanus humanus (Phh) GABA receptor subunit resistance to dieldrin (RDL) is the target of lotilaner, a synthetic molecule of the isoxazoline chemical class. To enhance our understanding of how insecticides act on GABA receptors, two other GABA receptor subunits were cloned and characterized: three variants of Phh-grd (glycine-like receptor of Drosophila) and one variant of Phh-lcch3 (ligand-gated chloride channel homolog 3). Relative mRNA expression levels of Phh-rdl, Phh-grd, and Phh-lcch3 revealed that they were expressed throughout the developmental stages (eggs, larvae, adults) and in the different parts of adult lice (head, thorax, and abdomen). When expressed individually in the Xenopus oocyte heterologous expression system, Phh-GRD1, Phh-GRD2, Phh-GRD3, and Phh-LCCH3 were unable to reconstitute functional channels, whereas the subunit combinations Phh-GRD1/Phh-LCCH3, Phh-GRD1/Phh-RDL, and Phh-LCCH3/Phh-RDL responded to GABA in a concentration-dependent manner. The three heteromeric receptors were similarly sensitive to the antagonistic effect of picrotoxin and fipronil, whereas Phh-GRD1/Phh-RDL and Phh-LCCH3/Phh-RDL were respectively about 2.5-fold and 5-fold more sensitive to ivermectin than Phh-GRD1/Phh-LCCH3. Moreover, the heteropentameric receptor constituted by Phh-GRD1/Phh-LCCH3 was found to be permeable and highly sensitive to the extracellular sodium concentration. These findings provided valuable additions to our knowledge of the complex nature of GABA receptors in human louse that could help in understanding the resistance pattern to commonly used pediculicides. SIGNIFICANCE STATEMENT: Human louse is an ectoparasite that causes pediculosis and transmits several bacterial pathogens. Emerging strains developed resistance to the commonly used insecticides, especially those targeting GABA receptors. To understand the molecular mechanisms underlying this resistance, two subunits of GABA receptors were cloned and described: Phh-grd and Phh-lcch3. The heteromeric receptor reconstituted with the two subunits was functional in Xenopus oocytes and sensitive to commercially available insecticides. Moreover, both subunits were transcribed throughout the parasite lifecycle.
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Affiliation(s)
- Omar Hashim
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Claude L Charvet
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Berthine Toubaté
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Aimun A E Ahmed
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Nicolas Lamassiaude
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Cédric Neveu
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Isabelle Dimier-Poisson
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Françoise Debierre-Grockiego
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
| | - Catherine Dupuy
- INRAE, Université de Tours, ISP, BioMAP, 37200, Tours, France (O.H., B.T., I.D.-P., F.D.-G., C.D.); Department of Pharmacology, Faculty of Pharmacy, University of Gezira, Wad Madani, Sudan (O.H.); INRAE, Université de Tours, ISP, MPN, 37380, Nouzilly, France (C.L.C., N.L., C.N.); Department of Pharmacology, Albaha University, Alaqiq, Saudi Arabia (A.A.E.A.); and Department of Pharmacology and Toxicology, Omdurman Islamic University, Omdurman, Sudan (A.A.E.A.)
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Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models. J Mol Biol 2021; 433:167128. [PMID: 34224751 DOI: 10.1016/j.jmb.2021.167128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 02/06/2023]
Abstract
The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.
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11
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Structure and gating mechanism of the α7 nicotinic acetylcholine receptor. Cell 2021; 184:2121-2134.e13. [PMID: 33735609 DOI: 10.1016/j.cell.2021.02.049] [Citation(s) in RCA: 137] [Impact Index Per Article: 45.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 01/13/2021] [Accepted: 02/22/2021] [Indexed: 12/13/2022]
Abstract
The α7 nicotinic acetylcholine receptor plays critical roles in the central nervous system and in the cholinergic inflammatory pathway. This ligand-gated ion channel assembles as a homopentamer, is exceptionally permeable to Ca2+, and desensitizes faster than any other Cys-loop receptor. The α7 receptor has served as a prototype for the Cys-loop superfamily yet has proven refractory to structural analysis. We present cryo-EM structures of the human α7 nicotinic receptor in a lipidic environment in resting, activated, and desensitized states, illuminating the principal steps in the gating cycle. The structures also reveal elements that contribute to its function, including a C-terminal latch that is permissive for channel opening, and an anionic ring in the extracellular vestibule that contributes to its high conductance and calcium permeability. Comparisons among the α7 structures provide a foundation for mapping the gating cycle and reveal divergence in gating mechanisms in the Cys-loop receptor superfamily.
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12
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Tian Y, Chen S, Shan Q. Charged residues at the pore extracellular half of the glycine receptor facilitate channel gating: a potential role played by electrostatic repulsion. J Physiol 2020; 598:4643-4661. [PMID: 32844405 DOI: 10.1113/jp279288] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 07/29/2020] [Indexed: 02/05/2023] Open
Abstract
KEY POINTS The Arg271Gln mutation of the glycine receptor (GlyR) causes hereditary hyperekplexia. This mutation dramatically compromises GlyR function; however, the underlying mechanism is not yet known. This study, by employing function and computation methods, proposes that charged residues (including the Arg residue) at the pore extracellular half from each of the five subunits of the homomeric α1 GlyR, create an electrostatic repulsive potential to widen the pore, thereby facilitating channel opening. This mechanism explains how the Arg271Gln mutation, in which the positively charged Arg residue is substituted by the neutral Gln residue, compromises GlyR function. This study furthers our understanding of the biophysical mechanism underlying the Arg271Gln mutation compromising GlyR function. ABSTRACT The R271(19')Q mutation in the α1 subunit of the glycine receptor (GlyR) chloride channel causes hereditary hyperekplexia. This mutation dramatically compromises channel function; however, the underlying mechanism is not yet known. The R271 residue is located at the extracellular half of the channel pore. In this study, an Arg-scanning mutagenesis was performed at the pore extracellular half from the 262(10') to the 272(20') position on the background of the α1 GlyR carrying the hyperekplexia-causing mutation R271(19')Q. It was found that the placement of the Arg residue rescued channel function to an extent inversely correlated with the distance between the residue and the pore central axis (perpendicular to the plane of the lipid bilayer). Accordingly, it was hypothesized that the placed Arg residues from each of the five subunits of the homomeric α1 GlyR create an electrostatic repulsive potential to widen the pore, thereby facilitating channel opening. This hypothesis was quantitatively verified by theoretical computation via exploiting basic laws of electrostatics and thermodynamics, and further supported by more experimental findings that the placement of another positively charged Lys residue or even a negatively charged Asp residue also rescued channel function in the same manner. This study provides a novel mechanism via which charged residues in the pore region facilitate channel gating, not only for the disease-causing 19'R residue in the GlyR, but also potentially for charged residues in the same region of other ion channels.
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Affiliation(s)
- Yao Tian
- Chern Institute of Mathematics, Nankai University, Tianjin, 300071, China
| | - Shijie Chen
- Laboratory for Synaptic Plasticity, Shantou University Medical College, Shantou, Guangdong, 515041, China
| | - Qiang Shan
- Laboratory for Synaptic Plasticity, Shantou University Medical College, Shantou, Guangdong, 515041, China
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13
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Rossokhin A. The general anesthetic etomidate and fenamate mefenamic acid oppositely affect GABA AR and GlyR: a structural explanation. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 49:591-607. [PMID: 32940715 DOI: 10.1007/s00249-020-01464-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 09/03/2020] [Accepted: 09/07/2020] [Indexed: 12/19/2022]
Abstract
GABA and glycine act as inhibitory neurotransmitters in the CNS. Inhibitory neurotransmission is mediated via activation of ionotropic GABAA and glycine receptors. We used a modeling approach to explain the opposite effects of the general anesthetic etomidate (ETM) and fenamate mefenamic acid (MFA) on GABA- and glycine-activated currents recorded in isolated cerebellar Purkinje cells and hippocampal pyramidal neurons, respectively. These drugs potentiated GABAARs but blocked GlyRs. We built a homology model of α1β GlyR based on the cryo-EM structure of open α1 GlyR, used the α1β3γ2 GABAAR structure from the PDB, and applied Monte-Carlo energy minimization to optimize models of receptors and ligand-receptor complexes. In silico docking suggests that ETM/MFA bind at the transmembrane β( +)/α( -) intersubunit interface in GABAAR. Our models predict that the bulky side chain of the highly conserved Arg19' residue at the plus interface side wedges the interface and maintains the conducting receptor state. We hypothesized that MFA/ETM binding at the β( +)/α( -) interface leads to prolongation of receptor life-time in the open state. Having analyzed different GABAAR and GlyR structures available in the PDB, we found that mutual arrangement of the Arg19' and Gln-26' side chains at the plus and minus interface sides, respectively, plays an important role when the receptor switches from the open to closed state. We show that this process is accompanied by narrowing of the intersubunit interfaces, leading to extrusion of the Arg19' side chain from the interface. Our models allow us to explain the lack of GlyR potentiation in our electrophysiological experiments.
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14
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Cottone G, Chiodo L, Maragliano L. Thermodynamics and Kinetics of Ion Permeation in Wild-Type and Mutated Open Active Conformation of the Human α7 Nicotinic Receptor. J Chem Inf Model 2020; 60:5045-5056. [PMID: 32803965 PMCID: PMC8011927 DOI: 10.1021/acs.jcim.0c00549] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
![]()
Molecular
studies of human pentameric ligand-gated ion channels
(LGICs) expressed in neurons and at neuromuscular junctions are of
utmost importance in the development of therapeutic strategies for
neurological disorders. We focus here on the nicotinic acetylcholine
receptor nAChR-α7, a homopentameric channel widely expressed
in the human brain, with a proven role in a wide spectrum of disorders
including schizophrenia and Alzheimer’s disease. By exploiting
an all-atom structural model of the full (transmembrane and extracellular)
protein in the open, agonist-bound conformation we recently developed,
we evaluate the free energy and the mean first passage time of single-ion
permeation using molecular dynamics simulations and the milestoning
method with Voronoi tessellation. The results for the wild-type channel
provide the first available mapping of the potential of mean force
in the full-length α7 nAChR, reveal its expected cationic nature,
and are in good agreement with simulation data for other channels
of the LGIC family and with experimental data on nAChRs. We then investigate
the role of a specific mutation directly related to ion selectivity
in LGICs, the E-1′ → A-1′ substitution at the
cytoplasmatic selectivity filter. We find that the mutation strongly
affects sodium and chloride permeation in opposite directions, leading
to a complete inversion of selectivity, at variance with the limited
experimental results available that classify this mutant as cationic.
We thus provide structural determinants for the observed cationic-to-anionic
inversion, revealing a key role of the protonation state of residue
rings far from the mutation, in the proximity of the hydrophobic channel
gate.
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Affiliation(s)
- Grazia Cottone
- Department of Physics and Chemistry-Emilio Segrè, University of Palermo, Viale delle Scienze Ed. 17, 90128 Palermo, Italy
| | - Letizia Chiodo
- Department of Engineering, Campus Bio-Medico University of Rome, Via Á. del Portillo 21, 00128 Rome, Italy
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.,IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, 16132 Genova, Italy
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15
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Treinin M, Jin Y. Cholinergic transmission in C. elegans: Functions, diversity, and maturation of ACh-activated ion channels. J Neurochem 2020; 158:1274-1291. [PMID: 32869293 DOI: 10.1111/jnc.15164] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 08/13/2020] [Accepted: 08/21/2020] [Indexed: 02/06/2023]
Abstract
Acetylcholine is an abundant neurotransmitter in all animals. Effects of acetylcholine are excitatory, inhibitory, or modulatory depending on the receptor and cell type. Research using the nematode C. elegans has made ground-breaking contributions to the mechanistic understanding of cholinergic transmission. Powerful genetic screens for behavioral mutants or for responses to pharmacological reagents identified the core cellular machinery for synaptic transmission. Pharmacological reagents that perturb acetylcholine-mediated processes led to the discovery and also uncovered the composition and regulators of acetylcholine-activated channels and receptors. From a combination of electrophysiological and molecular cellular studies, we have gained a profound understanding of cholinergic signaling at the levels of synapses, neural circuits, and animal behaviors. This review will begin with a historical overview, then cover in-depth current knowledge on acetylcholine-activated ionotropic receptors, mechanisms regulating their functional expression and their functions in regulating locomotion.
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Affiliation(s)
- Millet Treinin
- Department of Medical Neurobiology, Hadassah Medical school - Hebrew University, Jerusalem, Israel
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
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16
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Henry C, Cens T, Charnet P, Cohen-Solal C, Collet C, van-Dijk J, Guiramand J, de Jésus-Ferreira MC, Menard C, Mokrane N, Roussel J, Thibault JB, Vignes M, Rousset M. Heterogeneous expression of GABA receptor-like subunits LCCH3 and GRD reveals functional diversity of GABA receptors in the honeybee Apis mellifera. Br J Pharmacol 2020; 177:3924-3940. [PMID: 32436264 DOI: 10.1111/bph.15135] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 04/24/2020] [Accepted: 05/09/2020] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Despite a growing awareness, annual losses of honeybee colonies worldwide continue to reach threatening levels for food safety and global biodiversity. Among the biotic and abiotic stresses probably responsible for these losses, pesticides, including those targeting ionotropic GABA receptors, are one of the major drivers. Most insect genomes include the ionotropic GABA receptor subunit gene, Rdl, and two GABA-like receptor subunit genes, Lcch3 and Grd. Most studies have focused on Rdl which forms homomeric GABA-gated chloride channels, and a complete analysis of all possible molecular combinations of GABA receptors is still lacking. EXPERIMENTAL APPROACH We cloned the Rdl, Grd, and Lcch3 genes of Apis mellifera and systematically characterized the resulting GABA receptors expressed in Xenopus oocytes, using electrophysiological assays, fluorescence microscopy and co-immunoprecipitation techniques. KEY RESULTS The cloned subunits interacted with each other, forming GABA-gated heteromeric channels with particular properties. Strikingly, these heteromers were always more sensitive than AmRDL homomer to all the pharmacological agents tested. In particular, when expressed together, Grd and Lcch3 form a non-selective cationic channel that opens at low concentrations of GABA and with sensitivity to insecticides similar to that of homomeric Rdl channels. CONCLUSION AND IMPLICATIONS For off-target species like the honeybee, chronic sublethal exposure to insecticides constitutes a major threat. At these concentration ranges, homomeric RDL receptors may not be the most pertinent target to study and other ionotropic GABA receptor subtypes should be considered in order to understand more fully the molecular mechanisms of sublethal toxicity to insecticides.
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Affiliation(s)
| | - Thierry Cens
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Pierre Charnet
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Claude Collet
- UR 406 Abeilles et Environnement, INRAE, Avignon Cedex 9, France
| | | | | | | | - Claudine Menard
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Nawfel Mokrane
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Julien Roussel
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | | | - Michel Vignes
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Matthieu Rousset
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
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17
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Bertrand D, Wallace TL. A Review of the Cholinergic System and Therapeutic Approaches to Treat Brain Disorders. Curr Top Behav Neurosci 2020; 45:1-28. [PMID: 32451956 DOI: 10.1007/7854_2020_141] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Since its identification over a hundred years ago, the neurotransmitter acetylcholine (ACh) has proven to play an essential role in supporting many diverse functions. Some well-characterized functions include: chemical transmission at the neuromuscular junction; autonomic function in the peripheral nervous system; and, sustained attention, sleep/wake regulation, and learning and memory within the central nervous system. Within the brain, major cholinergic projection pathways from the basal forebrain and the brainstem support these centrally mediated processes, and dysregulation of the cholinergic system is implicated in cognitive decline associated with aging and dementias including Alzheimer's disease. ACh exerts its effects by binding to two different membrane-bound receptor classes: (1) G‑protein coupled muscarinic acetylcholine receptors (mAChRs), and (2) ligand-gated nicotinic acetylcholine receptors (nAChRs). These receptor systems are described in detail within this chapter along with discussion on the successes and failures of synthetic ligands designed to selectively target receptor subtypes for treating brain disorders. New molecular approaches and advances in our understanding of the target biology combined with opportunities to re-purpose existing cholinergic drugs for new indications continue to highlight the exciting opportunities for modulating this system for therapeutic purposes.
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18
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Rossokhin AV, Sharonova IN, Dvorzhak A, Bukanova JV, Skrebitsky VG. The mechanisms of potentiation and inhibition of GABA A receptors by non-steroidal anti-inflammatory drugs, mefenamic and niflumic acids. Neuropharmacology 2019; 160:107795. [PMID: 31560908 DOI: 10.1016/j.neuropharm.2019.107795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 09/02/2019] [Accepted: 09/23/2019] [Indexed: 11/27/2022]
Abstract
Fenamates mefanamic and niflumic acids (MFA and NFA) induced dual potentiating and inhibitory effects on GABA currents recorded in isolated cerebellar Purkinje cells using the whole-cell patch-clamp and fast-application techniques. Regardless of the concentration, both drugs induced a pronounced prolongation of the current response. We demonstrated that the same concentration of drugs can produce both potentiating and inhibitory effects, depending on the GABA concentration, which indicates that both processes take place simultaneously and the net effect depends on the concentrations of both the agonist and fenamate. We found that the NFA-induced block is strongly voltage-dependent. The Woodhull analysis of the block suggests that NFA has two binding sites in the pore - shallow and deep. We built a homology model of the open GABAAR based on the cryo-EM structure of the open α1 GlyR and applied Monte-Carlo energy minimization to optimize the ligand-receptor complexes. A systematic search for MFA/NFA binding sites in the GABAAR pore revealed the existence of two sites, the location of which coincides well with predictions of the Woodhull model. In silico docking suggests that two fenamate molecules are necessary to occlude the pore. We showed that MFA, acting as a PAM, competes with an intravenous anesthetic etomidate for a common binding site. We built structural models of MFA and NFA binding at the transmembrane β(+)/α(-) intersubunit interface. We suggested a hypothesis on the molecular mechanism underlying the prolongation of the receptor lifetime in open state after MFA/NFA binding and β subunit specificity of the fenamate potentiation.
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Affiliation(s)
| | | | - Anton Dvorzhak
- Charité-Universitätsmedizin, Neuroscience Research Center, Berlin, Germany
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19
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Cetin H, Epstein M, Liu WW, Maxwell S, Rodriguez Cruz PM, Cossins J, Vincent A, Webster R, Biggin PC, Beeson D. Muscle acetylcholine receptor conversion into chloride conductance at positive potentials by a single mutation. Proc Natl Acad Sci U S A 2019; 116:21228-21235. [PMID: 31570625 PMCID: PMC6800317 DOI: 10.1073/pnas.1908284116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Charge selectivity forms the basis of cellular excitation or inhibition by Cys-loop ligand-gated ion channels (LGICs), and is essential for physiological receptor function. There are no reports of naturally occurring mutations in LGICs associated with the conversion of charge selectivity. Here, we report on a CHRNA1 mutation (α1Leu251Arg) in a patient with congenital myasthenic syndrome associated with transformation of the muscle acetylcholine receptor (AChR) into an inhibitory channel. Performing patch-clamp experiments, the AChR was found to be converted into chloride conductance at positive potentials, whereas whole-cell currents at negative potentials, although markedly reduced, were still carried by sodium. Umbrella sampling molecular dynamics simulations revealed constriction of the channel pore radius to 2.4 Å as a result of the mutation, which required partial desolvation of the ions in order to permeate the pore. Ion desolvation was associated with an energetic penalty that was compensated for by the favorable electrostatic interaction of the positively charged arginines with chloride. These findings reveal a mechanism for the transformation of the muscle AChR into an inhibitory channel in a clinical context.
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Affiliation(s)
- Hakan Cetin
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
- Department of Neurology, Medical University of Vienna, 1090 Vienna, Austria
| | - Max Epstein
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Wei W Liu
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Susan Maxwell
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Pedro M Rodriguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom
| | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DS, United Kingdom;
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20
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Structural basis for ion selectivity and engineering in channelrhodopsins. Curr Opin Struct Biol 2019; 57:176-184. [PMID: 31174050 DOI: 10.1016/j.sbi.2019.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 01/03/2023]
Abstract
Channelrhodopsins have become an integral part of modern neuroscience approaches due to their ability to control neuronal activity in targeted cell populations. The recent determination of several channelrhodopsin X-ray structures now enables us to study their function with unprecedented molecular precision. We will discuss how these insights can guide the engineering of the ion conducting pathway to increase its selectivity for Cl-, Ca2+, and K+ ions and improve the overall conductance. Engineering such channelrhodopsins would further increase their utility in neuroscience research and beyond by controlling a wider range of physiological events. To thoroughly address this issue, we compare channelrhodopsin structures with structural features of voltage and ligand-gated K+, Cl- and Ca2+ channels and discuss how these could be implemented in channelrhodopsins.
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21
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Feingold D, Knogler L, Starc T, Drapeau P, O'Donnell MJ, Nilson LA, Dent JA. secCl is a cys-loop ion channel necessary for the chloride conductance that mediates hormone-induced fluid secretion in Drosophila. Sci Rep 2019; 9:7464. [PMID: 31097722 PMCID: PMC6522505 DOI: 10.1038/s41598-019-42849-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 04/10/2019] [Indexed: 01/09/2023] Open
Abstract
Organisms use circulating diuretic hormones to control water balance (osmolarity), thereby avoiding dehydration and managing excretion of waste products. The hormones act through G-protein-coupled receptors to activate second messenger systems that in turn control the permeability of secretory epithelia to ions like chloride. In insects, the chloride channel mediating the effects of diuretic hormones was unknown. Surprisingly, we find a pentameric, cys-loop chloride channel, a type of channel normally associated with neurotransmission, mediating hormone-induced transepithelial chloride conductance. This discovery is important because: 1) it describes an unexpected role for pentameric receptors in the membrane permeability of secretory epithelial cells, and 2) it suggests that neurotransmitter-gated ion channels may have evolved from channels involved in secretion.
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Affiliation(s)
- Daniel Feingold
- Department of Biology, McGill University, 1205 Dr. Penfield, Montréal, Québec, H3A 1B1, Canada
| | - Laura Knogler
- Department of Neurosciences, Research Centre of the University of Montréal Hospital Centre, Montréal, Québec, Canada
- Max Planck Institute of Neurobiology, Sensorimotor Control Research Group, Am Klopferspitz 18, Martinsried, 82152, Germany
| | - Tanja Starc
- Institute of Neuroscience, Technische Universität München, Biedersteiner Str. 29, München, Bau 601D-80802, Germany
| | - Pierre Drapeau
- Department of Neurosciences, Research Centre of the University of Montréal Hospital Centre, Montréal, Québec, Canada
| | - Michael J O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada
| | - Laura A Nilson
- Department of Biology, McGill University, 1205 Dr. Penfield, Montréal, Québec, H3A 1B1, Canada
| | - Joseph A Dent
- Department of Biology, McGill University, 1205 Dr. Penfield, Montréal, Québec, H3A 1B1, Canada.
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22
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Harpole TJ, Grosman C. A Crucial Role for Side-Chain Conformation in the Versatile Charge Selectivity of Cys-Loop Receptors. Biophys J 2019; 116:1667-1681. [PMID: 31005237 PMCID: PMC6506641 DOI: 10.1016/j.bpj.2019.03.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 03/18/2019] [Accepted: 03/25/2019] [Indexed: 10/27/2022] Open
Abstract
Whether synaptic transmission is excitatory or inhibitory depends, to a large extent, on whether the ion channels that open upon binding the released neurotransmitter conduct cations or anions. The mechanistic basis of the opposite charge selectivities of Cys-loop receptors has only recently begun to emerge. It is now clear that ionized side chains-whether pore-facing or buried-in the first α-helical turn of the second transmembrane segments underlie this phenomenon and that the electrostatics of backbone atoms are not critically involved. Moreover, on the basis of electrophysiological observations, it has recently been suggested that not only the sign of charged side chains but also their conformation are crucial determinants of cation-anion selectivity. To challenge these ideas with the chemical and structural rigor that electrophysiological observations naturally lack, we performed molecular dynamics, Brownian dynamics, and electrostatics calculations of ion permeation. To this end, we used structural models of the open-channel conformation of the α1 glutamate-gated Cl- channel and the α1 glycine receptor. Our results provided full support to the notion that the conformation of charged sides chains matters for charge selectivity. Indeed, whereas some rotamers of the buried arginines at position 0' conferred high selectivity for anions, others supported the permeation of cations and anions at similar rates or even allowed the faster permeation of cations. Furthermore, we found that modeling glutamates at position -1' of the anion-selective α1 glycine receptor open-state structure-instead of the five native alanines-switches charge selectivity also in a conformation-dependent manner, with some glutamate rotamers being much more effective at conferring selectivity for cations than others. Regarding pore size, we found that the mere expansion of the pore has only a minimal impact on cation-anion selectivity. Overall, these results bring to light the previously unappreciated impact of side-chain conformation on charge selectivity in Cys-loop receptors.
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Affiliation(s)
- Tyler J Harpole
- Center for Biophysics and Quantitative Biology, Urbana, Illinois
| | - Claudio Grosman
- Center for Biophysics and Quantitative Biology, Urbana, Illinois; Department of Molecular and Integrative Physiology, Urbana, Illinois; Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois.
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23
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Changeux JP. Structural Identification of the Nicotinic Receptor Ion Channel. Trends Neurosci 2018; 41:67-70. [DOI: 10.1016/j.tins.2017.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 11/12/2017] [Indexed: 10/18/2022]
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24
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Rossokhin AV. Homology modeling of the transmembrane domain of the GABAA receptor. Biophysics (Nagoya-shi) 2017. [DOI: 10.1134/s0006350917050190] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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25
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Gonzalez-Gutierrez G, Wang Y, Cymes GD, Tajkhorshid E, Grosman C. Chasing the open-state structure of pentameric ligand-gated ion channels. J Gen Physiol 2017; 149:1119-1138. [PMID: 29089419 PMCID: PMC5715906 DOI: 10.1085/jgp.201711803] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 09/14/2017] [Accepted: 10/05/2017] [Indexed: 11/25/2022] Open
Abstract
Members of the pentameric ligand-gated ion channel family have been crystallized in different conformations, including one in which the transmembrane pore is surprisingly wide. Gonzalez-Gutierrez et al. show that the open-channel conformation of animal members is more similar to the models with narrow pores. Remarkable advances have been made toward the structural characterization of ion channels in the last two decades. However, the unambiguous assignment of well-defined functional states to the obtained structural models has proved challenging. In the case of the superfamily of nicotinic-receptor channels (also referred to as pentameric ligand-gated ion channels [pLGICs]), for example, two different types of model of the open-channel conformation have been proposed on the basis of structures solved to resolutions better than 4.0 Å. At the level of the transmembrane pore, the open-state models of the proton-gated pLGIC from Gloeobacter violaceus (GLIC) and the invertebrate glutamate-gated Cl– channel (GluCl) are very similar to each other, but that of the glycine receptor (GlyR) is considerably wider. Indeed, the mean distances between the axis of ion permeation and the Cα atoms at the narrowest constriction of the pore (position −2′) differ by ∼2 Å in these two classes of model, a large difference when it comes to understanding the physicochemical bases of ion conduction and charge selectivity. Here, we take advantage of the extreme open-channel stabilizing effect of mutations at pore-facing position 9′. We find that the I9′A mutation slows down entry into desensitization of GLIC to the extent that macroscopic currents decay only slightly by the end of pH 4.5 solution applications to the extracellular side for several minutes. We crystallize (at pH 4.5) two variants of GLIC carrying this mutation and solve their structures to resolutions of 3.12 Å and 3.36 Å. Furthermore, we perform all-atom molecular dynamics simulations of ion permeation and picrotoxinin block, using the different open-channel structural models. On the basis of these results, we favor the notion that the open-channel structure of pLGICs from animals is much closer to that of the narrow models (of GLIC and GluCl) than it is to that of the GlyR.
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Affiliation(s)
| | - Yuhang Wang
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Gisela D Cymes
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Emad Tajkhorshid
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL.,Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL
| | - Claudio Grosman
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL .,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL.,Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL
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Nemecz Á, Prevost MS, Menny A, Corringer PJ. Emerging Molecular Mechanisms of Signal Transduction in Pentameric Ligand-Gated Ion Channels. Neuron 2017; 90:452-70. [PMID: 27151638 DOI: 10.1016/j.neuron.2016.03.032] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 01/07/2016] [Accepted: 03/24/2016] [Indexed: 10/21/2022]
Abstract
Nicotinic acetylcholine, serotonin type 3, γ-amminobutyric acid type A, and glycine receptors are major players of human neuronal communication. They belong to the family of pentameric ligand-gated ion channels, sharing a highly conserved modular 3D structure. Recently, high-resolution structures of both open- and closed-pore conformations have been solved for a bacterial, an invertebrate, and a vertebrate receptor in this family. These data suggest that a common gating mechanism occurs, coupling neurotransmitter binding to pore opening, but they also pinpoint significant differences among subtypes. In this Review, we summarize the structural and functional data in light of these gating models and speculate about their mechanistic consequences on ion permeation, pathological mutations, as well as functional regulation by orthosteric and allosteric effectors.
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Affiliation(s)
- Ákos Nemecz
- Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France
| | - Marie S Prevost
- Institute of Structural and Molecular Biology, University College London and Birkbeck, Malet Street, London WC1E 7HX, UK
| | - Anaïs Menny
- Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France; Université Pierre et Marie Curie (UPMC), Cellule Pasteur, 75005 Paris, France
| | - Pierre-Jean Corringer
- Channel-Receptors Unit, Institut Pasteur, 75015 Paris, France; CNRS UMR 3571, 75015 Paris, France.
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Gao Y, Eghtesadi S, Liu T. Supramolecular Structures Formation of Polyoxometalates in Solution Driven by Counterion–Macroion Interaction. ADVANCES IN INORGANIC CHEMISTRY 2017. [DOI: 10.1016/bs.adioch.2016.12.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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28
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Zhou Y, Lingle CJ. Engineering differential charge selectivity from a single structural template. Proc Natl Acad Sci U S A 2016; 113:12610-12612. [PMID: 27794117 PMCID: PMC5111640 DOI: 10.1073/pnas.1615847113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2024] Open
Affiliation(s)
- Yu Zhou
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110
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29
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Cymes GD, Grosman C. Identifying the elusive link between amino acid sequence and charge selectivity in pentameric ligand-gated ion channels. Proc Natl Acad Sci U S A 2016; 113:E7106-E7115. [PMID: 27791102 PMCID: PMC5111664 DOI: 10.1073/pnas.1608519113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Among neurotransmitter-gated ion channels, the superfamily of pentameric ligand-gated ion channels (pLGICs) is unique in that its members display opposite permeant-ion charge selectivities despite sharing the same structural fold. Although much effort has been devoted to the identification of the mechanism underlying the cation-versus-anion selectivity of these channels, a careful analysis of past work reveals that discrepancies exist, that different explanations for the same phenomenon have often been put forth, and that no consensus view has yet been reached. To elucidate the molecular basis of charge selectivity for the superfamily as a whole, we performed extensive mutagenesis and electrophysiological recordings on six different cation-selective and anion-selective homologs from vertebrate, invertebrate, and bacterial origin. We present compelling evidence for the critical involvement of ionized side chains-whether pore-facing or buried-rather than backbone atoms and propose a mechanism whereby not only their charge sign but also their conformation determines charge selectivity. Insertions, deletions, and residue-to-residue mutations involving nonionizable residues in the intracellular end of the pore seem to affect charge selectivity by changing the rotamer preferences of the ionized side chains in the first turn of the M2 α-helices. We also found that, upon neutralization of the charged residues in the first turn of M2, the control of charge selectivity is handed over to the many other ionized side chains that decorate the pore. This explains the long-standing puzzle as to why the neutralization of the intracellular-mouth glutamates affects charge selectivity to markedly different extents in different cation-selective pLGICs.
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Affiliation(s)
- Gisela D Cymes
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Claudio Grosman
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801;
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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Takayanagi-Kiya S, Zhou K, Jin Y. Release-dependent feedback inhibition by a presynaptically localized ligand-gated anion channel. eLife 2016; 5:e21734. [PMID: 27782882 PMCID: PMC5102579 DOI: 10.7554/elife.21734] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 10/25/2016] [Indexed: 12/16/2022] Open
Abstract
Presynaptic ligand-gated ion channels (LGICs) have long been proposed to affect neurotransmitter release and to tune the neural circuit activity. However, the understanding of their in vivo physiological action remains limited, partly due to the complexity in channel types and scarcity of genetic models. Here we report that C. elegans LGC-46, a member of the Cys-loop acetylcholine (ACh)-gated chloride (ACC) channel family, localizes to presynaptic terminals of cholinergic motor neurons and regulates synaptic vesicle (SV) release kinetics upon evoked release of acetylcholine. Loss of lgc-46 prolongs evoked release, without altering spontaneous activity. Conversely, a gain-of-function mutation of lgc-46 shortens evoked release to reduce synaptic transmission. This inhibition of presynaptic release requires the anion selectivity of LGC-46, and can ameliorate cholinergic over-excitation in a C. elegans model of excitation-inhibition imbalance. These data demonstrate a novel mechanism of presynaptic negative feedback in which an anion-selective LGIC acts as an auto-receptor to inhibit SV release.
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Affiliation(s)
- Seika Takayanagi-Kiya
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, San Diego, United States
| | - Keming Zhou
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, San Diego, United States
- Howard Hughes Medical Institute, University of California, San Diego, San Diego, United States
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, San Diego, United States
- Howard Hughes Medical Institute, University of California, San Diego, San Diego, United States
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31
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Knoflach F, Hernandez MC, Bertrand D. GABAA receptor-mediated neurotransmission: Not so simple after all. Biochem Pharmacol 2016; 115:10-7. [DOI: 10.1016/j.bcp.2016.03.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/17/2016] [Indexed: 12/28/2022]
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32
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Rossokhin AV, Zhorov BS. Side chain flexibility and the pore dimensions in the GABAA receptor. J Comput Aided Mol Des 2016; 30:559-67. [PMID: 27460059 DOI: 10.1007/s10822-016-9929-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 07/22/2016] [Indexed: 10/21/2022]
Abstract
Permeation of ions through open channels and their accessibility to pore-targeting drugs depend on the pore cross-sectional dimensions, which are known only for static X-ray and cryo-EM structures. Here, we have built homology models of the closed, open and desensitized α1β2γ2 GABAA receptor (GABAAR). The models are based, respectively, on the X-ray structure of α3 glycine receptor (α3 GlyR), cryo-EM structure of α1 GlyR and X-ray structure of β3 GABAAR. We employed Monte Carlo energy minimizations to explore how the pore lumen may increase due to repulsions of flexible side chains from a variable-diameter electroneutral atom (an expanding sphere) pulled through the pore. The expanding sphere computations predicted that the pore diameter averaged along the permeation pathway is larger by approximately 3 Å than that computed for the models with fixed sidechains. Our models predict three major pore constrictions located at the levels of -2', 9' and 20' residues. Residues around the -2' and 9' rings are known to form the desensitization and activation gates of GABAAR. Our computations predict that the 20' ring may also serve as GABAAR gate whose physiological role is unclear. The side chain flexibility of residues -2', 9' and 20' and hence the dimensions of the constrictions depend on the GABAAR functional state.
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Affiliation(s)
- Alexey V Rossokhin
- Research Center of Neurology, RAS, by-str. Obukha 5, Moscow, Russia, 105064.
| | - Boris S Zhorov
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.,Sechenov Institute of Evolutionary Physiology and Biochemistry, RAS, St. Petersburg, Russia
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Abstract
The inhibitory glycine receptor is a ligand-gated chloride channel that exists in developmentally regulated isoforms. These oligomeric transmembrane proteins are composed of variants of the ligand binding α subunit and structural β polypeptides. The agonist and antagonist sites of the α subunits are formed by discontinuous sequence motifs. In the murine genome, the genes encoding the α1 ( Glra1), α3 ( Glra3), and β ( Glyrb) subunit are autosomally located, whereas the α2 ( Glra2) and α4 ( Glra4) genes reside on the X-chromosome. Mutations of glycine receptor genes have been found to underly hypertonic motor disorders in mice and humans. The mouse mutants spasmodic (spd) and oscillator ( spdot) carry recessive mutations of the Glra 1 gene. In the phenotypically similar mouse mutant spastic ( spa), the intronic insertion of a LINE-1 transposable element into the Gyrb gene results in the aberrant splicing and a consecutive loss of glycine receptors. The human neurological disorder hyperekplexia (startle disease, stiff baby syndrome) is caused by point mutations within the α1 subunit gene ( GLRA1) localized in the human chromosomal region 5q31.3. The Neuroscientist 1:130- 141,1995
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Affiliation(s)
- Cord-Michael Becker
- Neurologische Klinik and Zentrum für Molekulare Biologie
Universität Heidelberg Heidelberg, Germany
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34
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Feingold D, Starc T, O'Donnell MJ, Nilson L, Dent JA. The orphan pentameric ligand-gated ion channel pHCl-2 is gated by pH and regulates fluid secretion in Drosophila Malpighian tubules. ACTA ACUST UNITED AC 2016; 219:2629-38. [PMID: 27358471 DOI: 10.1242/jeb.141069] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/13/2016] [Indexed: 12/30/2022]
Abstract
Pentameric ligand-gated ion channels (pLGICs) constitute a large protein superfamily in metazoa whose role as neurotransmitter receptors mediating rapid, ionotropic synaptic transmission has been extensively studied. Although the vast majority of pLGICs appear to be neurotransmitter receptors, the identification of pLGICs in non-neuronal tissues and homologous pLGIC-like proteins in prokaryotes points to biological functions, possibly ancestral, that are independent of neuronal signalling. Here, we report the molecular and physiological characterization of a highly divergent, orphan pLGIC subunit encoded by the pHCl-2 (CG11340) gene, in Drosophila melanogaster We show that pHCl-2 forms a channel that is insensitive to a wide array of neurotransmitters, but is instead gated by changes in extracellular pH. pHCl-2 is expressed in the Malpighian tubules, which are non-innervated renal-type secretory tissues. We demonstrate that pHCl-2 is localized to the apical membrane of the epithelial principal cells of the tubules and that loss of pHCl-2 reduces urine production during diuresis. Our data implicate pHCl-2 as an important source of chloride conductance required for proper urine production, highlighting a novel role for pLGICs in epithelial tissues regulating fluid secretion and osmotic homeostasis.
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Affiliation(s)
- Daniel Feingold
- Department of Biology, McGill University, 1205 Dr Penfield, Montreal, QC, Canada H3A 1B1
| | - Tanja Starc
- Institute of Neuroscience, Technische Universität München, Biedersteiner Strasse 29, München Bau 601D-80802, Germany
| | - Michael J O'Donnell
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1
| | - Laura Nilson
- Department of Biology, McGill University, 1205 Dr Penfield, Montreal, QC, Canada H3A 1B1
| | - Joseph A Dent
- Department of Biology, McGill University, 1205 Dr Penfield, Montreal, QC, Canada H3A 1B1
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35
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Lee BH, Choi SH, Kim HJ, Jung SW, Hwang SH, Pyo MK, Rhim H, Kim HC, Kim HK, Lee SM, Nah SY. Differential Effects of Quercetin and Quercetin Glycosides on Human α7 Nicotinic Acetylcholine Receptor-Mediated Ion Currents. Biomol Ther (Seoul) 2016; 24:410-7. [PMID: 27098860 PMCID: PMC4930285 DOI: 10.4062/biomolther.2015.153] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/28/2015] [Accepted: 01/22/2016] [Indexed: 01/16/2023] Open
Abstract
Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin-3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance α7 nicotinic acetylcholine receptor (α7 nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of α7 nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current (IACh) in Xenopus oocytes expressing the α7 nAChR. IACh was measured with a two-electrode voltage clamp technique. In oocytes injected with α7 nAChR copy RNA, quercetin enhanced IACh, whereas quercetin glycosides inhibited IACh. Quercetin glycosides mediated an inhibition of IACh, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of IACh inhibition by quercetin glycosides was Rutin≥Rham1>Rham2. Quercetin glycosides-mediated IACh enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated IACh inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated α7 nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the α7 nAChR in a differential manner.
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Affiliation(s)
- Byung-Hwan Lee
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
| | - Sun-Hye Choi
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
| | - Hyeon-Joong Kim
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
| | - Seok-Won Jung
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
| | - Sung-Hee Hwang
- Department of Pharmaceutical Engineering, Sangji University, Wonju 26339, Republic of Korea
| | - Mi-Kyung Pyo
- International Ginseng and Herb Research Institute, Geumsan 32724, Republic of Korea
| | - Hyewhon Rhim
- Life Science Division, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
| | - Hyoung-Chun Kim
- Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University, Chunchon 24341, Republic of Korea
| | - Ho-Kyoung Kim
- Mibyeong Research Center, Korea Institute of Oriental Medicine, Daejeon 34054, Republic of Korea
| | - Sang-Mok Lee
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
| | - Seung-Yeol Nah
- Department of Physiology, College of Veterinary Medicine and BioMolecular Informatics Center, Konkuk University, Seoul 05029, Republic of Korea
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Liu L, Sahu ID, McCarrick RM, Lorigan GA. Probing the Secondary Structure of Membrane Peptides Using (2)H-Labeled d(10)-Leucine via Site-Directed Spin-Labeling and Electron Spin Echo Envelope Modulation Spectroscopy. J Phys Chem B 2016; 120:633-40. [PMID: 26735335 DOI: 10.1021/acs.jpcb.5b09040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Previously, we reported an electron spin echo envelope modulation (ESEEM) spectroscopic approach for probing the local secondary structure of membrane proteins and peptides utilizing (2)H isotopic labeling and site-directed spin-labeling (SDSL). In order to probe the secondary structure of a peptide sequence, an amino acid residue (i) side chain was (2)H-labeled, such as (2)H-labeled d10-Leucine, and a cysteine residue was strategically placed at a subsequent nearby position (denoted as i + 1 to i + 4) to which a nitroxide spin label was attached. In order to fully access and demonstrate the feasibility of this new ESEEM approach with (2)H-labeled d10-Leu, four Leu residues within the AChR M2δ peptide were fully mapped out using this ESEEM method. Unique (2)H-ESEEM patterns were observed with the (2)H-labeled d10-Leu for the AChR M2δ α-helical model peptide. For proteins and peptides with an α-helical secondary structure, deuterium modulation can be clearly observed for i ± 3 and i ± 4 samples, but not for i ± 2 samples. Also, a deuterium peak centered at the (2)H Larmor frequency of each i ± 4 sample always had a significantly higher intensity than the corresponding i + 3 sample. This unique feature can be potentially used to distinguish an α-helix from a π-helix or 310-helix. Moreover, (2)H modulation depth for ESEEM samples on Leu10 were significantly enhanced which was consistent with a kinked or curved structural model of the AChR M2δ peptide as suggested by previous MD simulations and NMR experiments.
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Affiliation(s)
- Lishan Liu
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Robert M McCarrick
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
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Structural foundations of optogenetics: Determinants of channelrhodopsin ion selectivity. Proc Natl Acad Sci U S A 2015; 113:822-9. [PMID: 26699459 DOI: 10.1073/pnas.1523341113] [Citation(s) in RCA: 155] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The structure-guided design of chloride-conducting channelrhodopsins has illuminated mechanisms underlying ion selectivity of this remarkable family of light-activated ion channels. The first generation of chloride-conducting channelrhodopsins, guided in part by development of a structure-informed electrostatic model for pore selectivity, included both the introduction of amino acids with positively charged side chains into the ion conduction pathway and the removal of residues hypothesized to support negatively charged binding sites for cations. Engineered channels indeed became chloride selective, reversing near -65 mV and enabling a new kind of optogenetic inhibition; however, these first-generation chloride-conducting channels displayed small photocurrents and were not tested for optogenetic inhibition of behavior. Here we report the validation and further development of the channelrhodopsin pore model via crystal structure-guided engineering of next-generation light-activated chloride channels (iC++) and a bistable variant (SwiChR++) with net photocurrents increased more than 15-fold under physiological conditions, reversal potential further decreased by another ∼ 15 mV, inhibition of spiking faithfully tracking chloride gradients and intrinsic cell properties, strong expression in vivo, and the initial microbial opsin channel-inhibitor-based control of freely moving behavior. We further show that inhibition by light-gated chloride channels is mediated mainly by shunting effects, which exert optogenetic control much more efficiently than the hyperpolarization induced by light-activated chloride pumps. The design and functional features of these next-generation chloride-conducting channelrhodopsins provide both chronic and acute timescale tools for reversible optogenetic inhibition, confirm fundamental predictions of the ion selectivity model, and further elucidate electrostatic and steric structure-function relationships of the light-gated pore.
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Gao Y, Haso F, Szymanowski JES, Zhou J, Hu L, Burns PC, Liu T. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells. Chemistry 2015; 21:18785-90. [DOI: 10.1002/chem.201503773] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Indexed: 11/10/2022]
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Di Maio D, Chandramouli B, Brancato G. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel. PLoS One 2015; 10:e0140258. [PMID: 26465896 PMCID: PMC4605793 DOI: 10.1371/journal.pone.0140258] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/12/2015] [Indexed: 11/29/2022] Open
Abstract
Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested.
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Affiliation(s)
- Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
| | | | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- * E-mail:
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40
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Bertrand D, Lee CHL, Flood D, Marger F, Donnelly-Roberts D. Therapeutic Potential of α7 Nicotinic Acetylcholine Receptors. Pharmacol Rev 2015; 67:1025-73. [DOI: 10.1124/pr.113.008581] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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Pirri JK, Rayes D, Alkema MJ. A Change in the Ion Selectivity of Ligand-Gated Ion Channels Provides a Mechanism to Switch Behavior. PLoS Biol 2015; 13:e1002238. [PMID: 26348462 PMCID: PMC4562599 DOI: 10.1371/journal.pbio.1002238] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 07/30/2015] [Indexed: 11/19/2022] Open
Abstract
Behavioral output of neural networks depends on a delicate balance between excitatory and inhibitory synaptic connections. However, it is not known whether network formation and stability is constrained by the sign of synaptic connections between neurons within the network. Here we show that switching the sign of a synapse within a neural circuit can reverse the behavioral output. The inhibitory tyramine-gated chloride channel, LGC-55, induces head relaxation and inhibits forward locomotion during the Caenorhabditis elegans escape response. We switched the ion selectivity of an inhibitory LGC-55 anion channel to an excitatory LGC-55 cation channel. The engineered cation channel is properly trafficked in the native neural circuit and results in behavioral responses that are opposite to those produced by activation of the LGC-55 anion channel. Our findings indicate that switches in ion selectivity of ligand-gated ion channels (LGICs) do not affect network connectivity or stability and may provide an evolutionary and a synthetic mechanism to change behavior.
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Affiliation(s)
- Jennifer K. Pirri
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Diego Rayes
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, UNS-CONICET, Bahía Blanca, Argentina
| | - Mark J. Alkema
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
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Dani JA. Neuronal Nicotinic Acetylcholine Receptor Structure and Function and Response to Nicotine. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 124:3-19. [PMID: 26472524 DOI: 10.1016/bs.irn.2015.07.001] [Citation(s) in RCA: 173] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) belong to the "Cys-loop" superfamily of ligand-gated ion channels that includes GABAA, glycine, and serotonin (5-HT3) receptors. There are 16 homologous mammalian nAChR subunits encoded by a multigene family. These subunits combine to form many different nAChR subtypes with various expression patterns, diverse functional properties, and differing pharmacological characteristics. Because cholinergic innervation is pervasive and nAChR expression is extremely broad, practically every area of the brain is impinged upon by nicotinic mechanisms. This review briefly examines the structural and functional properties of the receptor/channel complex itself. The review also summarizes activation and desensitization of nAChRs by the low nicotine concentrations obtained from tobacco. Knowledge of the three-dimensional structure and the structural characteristics of channel gating has reached an advanced stage. Likewise, the basic functional properties of the channel also are reasonably well understood. It is these receptor/channel properties that underlie the participation of nAChRs in nearly every anatomical region of the mammalian brain.
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Affiliation(s)
- John A Dani
- Department of Neuroscience, Mahoney Institute for Neurosciences, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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43
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Abstract
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In
this work, we apply the recently developed constant pH molecular
dynamics technique to study protonation equilibria of titratable side
chains in the context of simple transmembrane (TM) helices and explore
the effect of pH on their configurations in membrane bilayers. We
observe that, despite a significant shift toward neutral states, considerable
population of different side chains stay in the charged state that
give rise to pKa values around 9.6 for
Asp and Glu and 4.5 to 6 for His and Lys side chains, respectively.
These charged states are highly stabilized by favorable interactions
between head groups, water molecules, and the charged side chains
that are facilitated by substantial changes in the configuration of
the peptides. The pH dependent configurations and the measured pKa values are in good agreement with relatively
recent solid state NMR measurements. Our results presented here demonstrate
that all-atom constant pH molecular dynamics can be applied to membrane
proteins and peptides to obtain reliable pKa values and pH dependent behavior for these systems.
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Affiliation(s)
- Afra Panahi
- †Department of Chemistry and ‡Biophysics Program, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan, 48109, United States
| | - Charles L Brooks
- †Department of Chemistry and ‡Biophysics Program, University of Michigan, 930 N. University Ave., Ann Arbor, Michigan, 48109, United States
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Jobson MA, Valdez CM, Gardner J, Garcia LR, Jorgensen EM, Beg AA. Spillover transmission is mediated by the excitatory GABA receptor LGC-35 in C. elegans. J Neurosci 2015; 35:2803-16. [PMID: 25673867 PMCID: PMC4323542 DOI: 10.1523/jneurosci.4557-14.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 12/10/2014] [Accepted: 12/23/2014] [Indexed: 11/21/2022] Open
Abstract
Under most circumstances, GABA activates chloride-selective channels and thereby inhibits neuronal activity. Here, we identify a GABA receptor in the nematode Caenorhabditis elegans that conducts cations and is therefore excitatory. Expression in Xenopus oocytes demonstrates that LGC-35 is a homopentameric cation-selective receptor of the cys-loop family exclusively activated by GABA. Phylogenetic analysis suggests that LGC-35 evolved from GABA-A receptors, but the pore-forming domain contains novel molecular determinants that confer cation selectivity. LGC-35 is expressed in muscles and directly mediates sphincter muscle contraction in the defecation cycle in hermaphrodites, and spicule eversion during mating in the male. In the locomotory circuit, GABA release directly activates chloride channels on the muscle to cause muscle relaxation. However, GABA spillover at these synapses activates LGC-35 on acetylcholine motor neurons, which in turn cause muscles to contract, presumably to drive wave propagation along the body. These studies demonstrate that both direct and indirect excitatory GABA signaling plays important roles in regulating neuronal circuit function and behavior in C. elegans.
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Affiliation(s)
- Meghan A Jobson
- Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, Utah 84132, Department of Biology, University of Utah, Salt Lake City, Utah 84132
| | - Chris M Valdez
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, Neuroscience Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Jann Gardner
- Department of Biology, University of Utah, Salt Lake City, Utah 84132
| | - L Rene Garcia
- Department of Biology, Texas A&M University, College Station, Texas 77843, Howard Hughes Medical Institute, Texas A&M University, College Station, Texas 77843
| | - Erik M Jorgensen
- Program in Neuroscience, University of Utah School of Medicine, Salt Lake City, Utah 84132, Department of Biology, University of Utah, Salt Lake City, Utah 84132, Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah 84132, and
| | - Asim A Beg
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109, Neuroscience Program, University of Michigan, Ann Arbor, Michigan 48109,
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45
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Suzuki H, Tani K, Tamura A, Tsukita S, Fujiyoshi Y. Model for the Architecture of Claudin-Based Paracellular Ion Channels through Tight Junctions. J Mol Biol 2015; 427:291-7. [DOI: 10.1016/j.jmb.2014.10.020] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 10/24/2014] [Accepted: 10/29/2014] [Indexed: 12/13/2022]
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46
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The role of the M4 lipid-sensor in the folding, trafficking, and allosteric modulation of nicotinic acetylcholine receptors. Neuropharmacology 2014; 96:157-68. [PMID: 25433148 DOI: 10.1016/j.neuropharm.2014.11.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 10/31/2014] [Accepted: 11/18/2014] [Indexed: 11/24/2022]
Abstract
With the availability of high resolution structural data, increasing attention has focused on the mechanisms by which drugs and endogenous compounds allosterically modulate nicotinic acetylcholine receptor (nAChR) function. Lipids are potent modulators of the nAChR from Torpedo. Membrane lipids influence nAChR function by both conformational selection and kinetic mechanisms, stabilizing varying proportions of pre-existing resting, open, desensitized, and uncoupled conformations, as well as influencing the transitions between these conformational states. Structural and functional data highlight a role for the lipid-exposed M4 transmembrane α-helix of each subunit in lipid sensing, and suggest that lipids influence gating by altering the binding of M4 to the adjacent transmembrane α-helices, M1 and M3. M4 has also been implicated in both the folding and trafficking of nAChRs to the cell surface, as well as in the potentiation of nAChR gating by neurosteroids. Here, we discuss the roles of M4 in the folding, trafficking, and allosteric modulation of nAChRs. We also consider the hypothesis that variable chemistry at the M4-M1/M3 transmembrane α-helical interface in different nAChR subunits governs the capacity for potentiation by activating lipids. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.
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47
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Rossokhin AV, Sharonova IN, Bukanova JV, Kolbaev SN, Skrebitsky VG. Block of GABA(A) receptor ion channel by penicillin: electrophysiological and modeling insights toward the mechanism. Mol Cell Neurosci 2014; 63:72-82. [PMID: 25305478 DOI: 10.1016/j.mcn.2014.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 09/29/2014] [Accepted: 10/07/2014] [Indexed: 11/26/2022] Open
Abstract
GABA(A) receptors (GABA(A)R) mainly mediate fast inhibitory neurotransmission in the central nervous system. Different classes of modulators target GABA(A)R properties. Penicillin G (PNG) belongs to the class of noncompetitive antagonists blocking the open GABA(A)R and is a prototype of β-lactam antibiotics. In this study, we combined electrophysiological and modeling approaches to investigate the peculiarities of PNG blockade of GABA-activated currents recorded from isolated rat Purkinje cells and to predict the PNG binding site. Whole-cell patch-сlamp recording and fast application system was used in the electrophysiological experiments. PNG block developed after channel activation and increased with membrane depolarization suggesting that the ligand binds within the open channel pore. PNG blocked stationary component of GABA-activated currents in a concentration-dependent manner with IC50 value of 1.12mM at -70mV. The termination of GABA and PNG co-application was followed by a transient tail current. Protection of the tail current from bicuculline block and dependence of its kinetic parameters on agonist affinity suggest that PNG acts as a sequential open channel blocker that prevents agonist dissociation while the channel remains blocked. We built the GABA(A)R models based on nAChR and GLIC structures and performed an unbiased systematic search of the PNG binding site. Monte-Carlo energy minimization was used to find the lowest energy binding modes. We have shown that PNG binds close to the intracellular vestibule. In both models the maximum contribution to the energy of ligand-receptor interactions revealed residues located on the level of 2', 6' and 9' rings formed by a bundle of M2 transmembrane segments, indicating that these residues most likely participate in PNG binding. The predicted structural models support the described mechanism of PNG block.
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Affiliation(s)
- Alexey V Rossokhin
- Research Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia.
| | - Irina N Sharonova
- Research Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia
| | - Julia V Bukanova
- Research Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia
| | - Sergey N Kolbaev
- Research Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia
| | - Vladimir G Skrebitsky
- Research Center of Neurology, Russian Academy of Medical Sciences, 105064 Moscow, Russia
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48
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Lipovsek M, Fierro A, Pérez EG, Boffi JC, Millar NS, Fuchs PA, Katz E, Elgoyhen AB. Tracking the molecular evolution of calcium permeability in a nicotinic acetylcholine receptor. Mol Biol Evol 2014; 31:3250-65. [PMID: 25193338 PMCID: PMC4245820 DOI: 10.1093/molbev/msu258] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nicotinic acetylcholine receptors are a family of ligand-gated nonselective cationic channels that participate in fundamental physiological processes at both the central and the peripheral nervous system. The extent of calcium entry through ligand-gated ion channels defines their distinct functions. The α9α10 nicotinic cholinergic receptor, expressed in cochlear hair cells, is a peculiar member of the family as it shows differences in the extent of calcium permeability across species. In particular, mammalian α9α10 receptors are among the ligand-gated ion channels which exhibit the highest calcium selectivity. This acquired differential property provides the unique opportunity of studying how protein function was shaped along evolutionary history, by tracking its evolutionary record and experimentally defining the amino acid changes involved. We have applied a molecular evolution approach of ancestral sequence reconstruction, together with molecular dynamics simulations and an evolutionary-based mutagenesis strategy, in order to trace the molecular events that yielded a high calcium permeable nicotinic α9α10 mammalian receptor. Only three specific amino acid substitutions in the α9 subunit were directly involved. These are located at the extracellular vestibule and at the exit of the channel pore and not at the transmembrane region 2 of the protein as previously thought. Moreover, we show that these three critical substitutions only increase calcium permeability in the context of the mammalian but not the avian receptor, stressing the relevance of overall protein structure on defining functional properties. These results highlight the importance of tracking evolutionarily acquired changes in protein sequence underlying fundamental functional properties of ligand-gated ion channels.
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Affiliation(s)
- Marcela Lipovsek
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N Torres, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Angélica Fierro
- Department of Organic Chemistry, Faculty of Chemistry, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Edwin G Pérez
- Department of Organic Chemistry, Faculty of Chemistry, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan C Boffi
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N Torres, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Neil S Millar
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Paul A Fuchs
- Department of Otolaryngology, Head and Neck Surgery, and Center for Hearing and Balance, The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Eleonora Katz
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N Torres, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Dr. Héctor N Torres, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
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49
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Dong H, Klein ML, Fiorin G. Counterion-Assisted Cation Transport in a Biological Calcium Channel. J Phys Chem B 2014; 118:9668-76. [DOI: 10.1021/jp5059897] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Hao Dong
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Michael L. Klein
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Giacomo Fiorin
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
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50
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White SH, Carter CJ, Magoski NS. A potentially novel nicotinic receptor in Aplysia neuroendocrine cells. J Neurophysiol 2014; 112:446-62. [DOI: 10.1152/jn.00796.2013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nicotinic receptors form a diverse group of ligand-gated ionotropic receptors with roles in both synaptic transmission and the control of excitability. In the bag cell neurons of Aplysia, acetylcholine activates an ionotropic receptor, which passes inward current to produce a long-lasting afterdischarge and hormone release, leading to reproduction. While testing the agonist profile of the cholinergic response, we observed a second current that appeared to be gated only by nicotine and not acetylcholine. The peak nicotine-evoked current was markedly smaller in magnitude than the acetylcholine-induced current, cooperative (Hill value of 2.7), had an EC50 near 500 μM, readily recovered from desensitization, showed Ca2+ permeability, and was blocked by mecamylamine, dihydro-β-erythroidine, or strychnine, but not by α-conotoxin ImI, methyllycaconitine, or hexamethonium. Aplysia transcriptome analysis followed by PCR yielded 20 full-length potential nicotinic receptor subunits. Sixteen of these were predicted to be cation selective, and real-time PCR suggested that 15 of the 16 subunits were expressed to varying degrees in the bag cell neurons. The acetylcholine-induced current, but not the nicotine current, was reduced by double-strand RNA treatment targeted to both subunits ApAChR-C and -E. Conversely, the nicotine-evoked current, but not the acetylcholine current, was lessened by targeting both subunits ApAChR-H and -P. To the best of our knowledge, this is the first report suggesting that a nicotinic receptor is not gated by acetylcholine. Separate receptors may serve as a means to differentially trigger plasticity or safeguard propagation by assuring that only acetylcholine, the endogenous agonist, initiates large enough responses to trigger reproduction.
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Affiliation(s)
- Sean H. White
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Christopher J. Carter
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Neil S. Magoski
- Department of Biomedical and Molecular Sciences, Physiology Graduate Program, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
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