1
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Chojnacka W, Teng J, Kim JJ, Jensen AA, Hibbs RE. Structural insights into GABA A receptor potentiation by Quaalude. Nat Commun 2024; 15:5244. [PMID: 38898000 PMCID: PMC11187190 DOI: 10.1038/s41467-024-49471-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 05/31/2024] [Indexed: 06/21/2024] Open
Abstract
Methaqualone, a quinazolinone marketed commercially as Quaalude, is a central nervous system depressant that was used clinically as a sedative-hypnotic, then became a notorious recreational drug in the 1960s-80s. Due to its high abuse potential, medical use of methaqualone was eventually prohibited, yet it persists as a globally abused substance. Methaqualone principally targets GABAA receptors, which are the major inhibitory neurotransmitter-gated ion channels in the brain. The restricted status and limited accessibility of methaqualone have contributed to its pharmacology being understudied. Here, we use cryo-EM to localize the GABAA receptor binding sites of methaqualone and its more potent derivative, PPTQ, to the same intersubunit transmembrane sites targeted by the general anesthetics propofol and etomidate. Both methaqualone and PPTQ insert more deeply into subunit interfaces than the previously-characterized modulators. Binding of quinazolinones to this site results in widening of the extracellular half of the ion-conducting pore, following a trend among positive allosteric modulators in destabilizing the hydrophobic activation gate in the pore as a mechanism for receptor potentiation. These insights shed light on the underexplored pharmacology of quinazolinones and further elucidate the molecular mechanisms of allosteric GABAA receptor modulation through transmembrane binding sites.
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Affiliation(s)
- Weronika Chojnacka
- Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, USA
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
| | - Jinfeng Teng
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
| | - Jeong Joo Kim
- Protein Structure and Function, Loxo@Lilly, Louisville, CO, USA
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Ryan E Hibbs
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA.
- Department of Pharmacology, University of California San Diego, La Jolla, CA, USA.
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2
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Mortensen M, Bright DP, Fagotti J, Dorovykh V, Cerna B, Smart TG. Forty Years Searching for Neurosteroid Binding Sites on GABA A Receptors. Neuroscience 2024:S0306-4522(24)00257-4. [PMID: 38852898 DOI: 10.1016/j.neuroscience.2024.06.002] [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: 04/04/2024] [Revised: 05/31/2024] [Accepted: 06/03/2024] [Indexed: 06/11/2024]
Abstract
Brain inhibition is a vital process for controlling and sculpting the excitability of the central nervous system in healthy individuals. This level of control is provided over several timescales and involves the neurotransmitter GABA acting at inhibitory synapses to: rapidly inhibit neurons by activating the GABAA receptor; over a slower timescale, to tonically activate extrasynaptic GABAA receptors to provide a low level of background inhibition; and finally, to activate G-protein coupled GABAB receptors to control transmitter release by inhibiting presynaptic Ca2+ channels whilst providing postsynaptic inhibition via K+ channel activation. From this plethora of roles for GABA and its receptors, the GABAA receptor isoform is of major interest due to its dynamic functional plasticity, which in part, is due to being targeted by modulatory brain neurosteroids derived from sex and stress hormones. This family of neurosteroids can, depending on their structure, potentiate, activate and also inhibit the activity of GABAA receptors to affect brain inhibition. This review tracks the methods that have been deployed in probing GABAA receptors, and charts the sterling efforts made by several groups to locate the key neurosteroid binding sites that affect these important receptors. Increasing our knowledge of these binding sites will greatly facilitate our understanding of the physiological roles of neurosteroids and will help to advance their use as novel therapeutics to combat debilitating brain diseases.
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Affiliation(s)
- Martin Mortensen
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom
| | - Damian P Bright
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom
| | - Juliane Fagotti
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom
| | - Valentina Dorovykh
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom
| | - Barbora Cerna
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom
| | - Trevor G Smart
- University College London, Dept Neuroscience, Physiology & Pharmacology, Gower Street, London WC1E 6BT, United Kingdom.
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3
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Bukanova JV, Solntseva EI, Skrebitsky VG. Factors promoting the release of picrotoxin from the trap in the GABA(A) receptor pore. Neurochem Int 2024; 175:105703. [PMID: 38395151 DOI: 10.1016/j.neuint.2024.105703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/31/2024] [Accepted: 02/21/2024] [Indexed: 02/25/2024]
Abstract
Picrotoxin (PTX), a convulsant of plant origin, has been used in many studies as research tool. PTX is the open channel blocker of the GABAA receptor (GABAAR). Being in the pore, PTX initiates transfer of the channel to the closed state and thus it falls into the "trap". The consequence of this PTX trapping is so-called aftereffect, i.e. continuation of the blockade of the GABA-induced chloride current (IGABA) after removal of PTX from the external solution. The present work shows that the positive allosteric modulators (PAMs) of the GABAA receptor, allopregnanolone (Allo) and zolpidem (Zolp) as well as a high concentration of GABA shortened the PTX aftereffect. Experiments were carried out on isolated Purkinje neurons of the rat cerebellum using the whole-cell patch-clamp method. IGABA was induced by applications of 5 μM GABA (EC30) for 1 s with 30 s intervals. 50 μM PTX completely blocked IGABA, and recovery upon PTX washout occurred with a time constant (τrec) of 20.2 min. 1 μM Allo reduced the blocking effect of PTX by 30% and accelerated the recovery of IGABA by almost 10 times (τrec = 2.4 min). 0.5 μM Zolp did not change the IGABA block in the presence of PTX but accelerated the recovery of IGABA by more than 3 times (τrec = 5.6 min). Increasing the GABA concentration to 20 μM did not change the blocking effect of PTX, but accelerated recovery by 6 times (τrec = 3.3 min). The mechanism of the shortening of the PTX aftereffect is presumably the expansion of the GABAAR pore in the presence of PAMs and a high concentration of the agonist and, as a consequence, the escape of PTX from the "trap". The work describes new pharmacological properties of Allo and Zolp.
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Affiliation(s)
- Julia V Bukanova
- Brain Research Institute, Research Center of Neurology, Moscow, Russia
| | - Elena I Solntseva
- Brain Research Institute, Research Center of Neurology, Moscow, Russia.
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4
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Bharambe N, Li Z, Seiferth D, Balakrishna AM, Biggin PC, Basak S. Cryo-EM structures of prokaryotic ligand-gated ion channel GLIC provide insights into gating in a lipid environment. Nat Commun 2024; 15:2967. [PMID: 38580666 PMCID: PMC10997623 DOI: 10.1038/s41467-024-47370-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 03/28/2024] [Indexed: 04/07/2024] Open
Abstract
GLIC, a proton-activated prokaryotic ligand-gated ion channel, served as a model system for understanding the eukaryotic counterparts due to their structural and functional similarities. Despite extensive studies conducted on GLIC, the molecular mechanism of channel gating in the lipid environment requires further investigation. Here, we present the cryo-EM structures of nanodisc-reconstituted GLIC at neutral and acidic pH in the resolution range of 2.6 - 3.4 Å. In our apo state at pH 7.5, the extracellular domain (ECD) displays conformational variations compared to the existing apo structures. At pH 4.0, three distinct conformational states (C1, C2 and O states) are identified. The protonated structures exhibit a compacted and counter-clockwise rotated ECD compared with our apo state. A gradual widening of the pore in the TMD is observed upon reducing the pH, with the widest pore in O state, accompanied by several layers of water pentagons. The pore radius and molecular dynamics (MD) simulations suggest that the O state represents an open conductive state. We also observe state-dependent interactions between several lipids and proteins that may be involved in the regulation of channel gating. Our results provide comprehensive insights into the importance of lipids impact on gating.
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Affiliation(s)
- Nikhil Bharambe
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - Zhuowen Li
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore
| | - David Seiferth
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Philip C Biggin
- Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, UK
| | - Sandip Basak
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore, 639798, Singapore.
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5
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Burke SM, Avstrikova M, Noviello CM, Mukhtasimova N, Changeux JP, Thakur GA, Sine SM, Cecchini M, Hibbs RE. Structural mechanisms of α7 nicotinic receptor allosteric modulation and activation. Cell 2024; 187:1160-1176.e21. [PMID: 38382524 PMCID: PMC10950261 DOI: 10.1016/j.cell.2024.01.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/05/2023] [Accepted: 01/22/2024] [Indexed: 02/23/2024]
Abstract
The α7 nicotinic acetylcholine receptor is a pentameric ligand-gated ion channel that plays an important role in cholinergic signaling throughout the nervous system. Its unique physiological characteristics and implications in neurological disorders and inflammation make it a promising but challenging therapeutic target. Positive allosteric modulators overcome limitations of traditional α7 agonists, but their potentiation mechanisms remain unclear. Here, we present high-resolution structures of α7-modulator complexes, revealing partially overlapping binding sites but varying conformational states. Structure-guided functional and computational tests suggest that differences in modulator activity arise from the stable rotation of a channel gating residue out of the pore. We extend the study using a time-resolved cryoelectron microscopy (cryo-EM) approach to reveal asymmetric state transitions for this homomeric channel and also find that a modulator with allosteric agonist activity exploits a distinct channel-gating mechanism. These results define mechanisms of α7 allosteric modulation and activation with implications across the pentameric receptor superfamily.
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Affiliation(s)
- Sean M Burke
- Molecular Biophysics Graduate Program, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mariia Avstrikova
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, 67081 Strasbourg Cedex, France
| | - Colleen M Noviello
- Department of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nuriya Mukhtasimova
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55902, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55902, USA
| | - Jean-Pierre Changeux
- Neuroscience Department, Institut Pasteur, Collège de France, 75015 Paris, France
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA
| | - Steven M Sine
- Receptor Biology Laboratory, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55902, USA; Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic College of Medicine, Rochester, MN 55902, USA; Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN 55902, USA.
| | - Marco Cecchini
- Institut de Chimie de Strasbourg, UMR7177, CNRS, Université de Strasbourg, 67081 Strasbourg Cedex, France.
| | - Ryan E Hibbs
- Department of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA; Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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6
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Tong G, Griffin S, Sader A, Crowell AB, Beavers K, Watson J, Buchan Z, Chen S, Shenvi RA. C5 methylation confers accessibility, stability and selectivity to picrotoxinin. Nat Commun 2023; 14:8308. [PMID: 38097583 PMCID: PMC10721898 DOI: 10.1038/s41467-023-44030-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 11/28/2023] [Indexed: 12/17/2023] Open
Abstract
Minor changes to complex structures can exert major influences on synthesis strategy and functional properties. Here we explore two parallel series of picrotoxinin (PXN, 1) analogs and identify leads with selectivity between mammalian and insect ion channels. These are the first SAR studies of PXN despite its >100-year history and are made possible by advances in total synthesis. We observe a remarkable stabilizing effect of a C5 methyl, which completely blocks C15 alcoholysis via destabilization of an intermediate twist-boat conformer; suppression of this secondary hydrolysis pathway increases half-life in plasma. C5 methylation also decreases potency against vertebrate ion channels (γ-Aminobutyric acid type A (GABAA) receptors) but maintains or increases antagonism of homologous invertebrate GABA-gated chloride channels (resistance to dieldrin (RDL) receptors). Optimal 5MePXN analogs appear to change the PXN binding pose within GABAARs by disruption of a hydrogen bond network. These discoveries were made possible by the lower synthetic burden of 5MePXN (2) and were illuminated by the parallel analog series, which allowed characterization of the role of the synthetically simplifying C5 methyl in channel selectivity. These are the first SAR studies to identify changes to PXN that increase the GABAA-RDL selectivity index.
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Affiliation(s)
- Guanghu Tong
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, California, 92037, USA
| | - Samantha Griffin
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, Indiana, 46268, USA
| | - Avery Sader
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, Indiana, 46268, USA
| | - Anna B Crowell
- Department of Chemistry and Biochemistry, Oberlin College, 119 Woodland Street, Oberlin, Ohio, 44074, USA
| | - Ken Beavers
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, Indiana, 46268, USA
| | - Jerry Watson
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, Indiana, 46268, USA
| | - Zachary Buchan
- Corteva Agriscience, 9330 Zionsville Road, Indianapolis, Indiana, 46268, USA
| | - Shuming Chen
- Department of Chemistry and Biochemistry, Oberlin College, 119 Woodland Street, Oberlin, Ohio, 44074, USA.
| | - Ryan A Shenvi
- Department of Chemistry, Scripps Research, 10550 North Torrey Pines Road, La Jolla, California, 92037, USA.
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7
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Cowgill J, Fan C, Haloi N, Tobiasson V, Zhuang Y, Howard RJ, Lindahl E. Structure and dynamics of differential ligand binding in the human ρ-type GABA A receptor. Neuron 2023; 111:3450-3464.e5. [PMID: 37659407 DOI: 10.1016/j.neuron.2023.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 08/01/2023] [Accepted: 08/07/2023] [Indexed: 09/04/2023]
Abstract
The neurotransmitter γ-aminobutyric acid (GABA) drives critical inhibitory processes in and beyond the nervous system, partly via ionotropic type-A receptors (GABAARs). Pharmacological properties of ρ-type GABAARs are particularly distinctive, yet the structural basis for their specialization remains unclear. Here, we present cryo-EM structures of a lipid-embedded human ρ1 GABAAR, including a partial intracellular domain, under apo, inhibited, and desensitized conditions. An apparent resting state, determined first in the absence of modulators, was recapitulated with the specific inhibitor (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid and blocker picrotoxin and provided a rationale for bicuculline insensitivity. Comparative structures, mutant recordings, and molecular simulations with and without GABA further explained the sensitized but slower activation of ρ1 relative to canonical subtypes. Combining GABA with picrotoxin also captured an apparent uncoupled intermediate state. This work reveals structural mechanisms of gating and modulation with applications to ρ-specific pharmaceutical design and to our biophysical understanding of ligand-gated ion channels.
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Affiliation(s)
- John Cowgill
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden
| | - Chen Fan
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden
| | - Nandan Haloi
- Department of Applied Physics, SciLifeLab, KTH Royal Institute of Technology, 17121 Solna, Sweden
| | - Victor Tobiasson
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden
| | - Yuxuan Zhuang
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden.
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, SciLifeLab, Stockholm University, 17121 Solna, Sweden; Department of Applied Physics, SciLifeLab, KTH Royal Institute of Technology, 17121 Solna, Sweden.
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8
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Liu X, Wang W. Asymmetric gating of a human hetero-pentameric glycine receptor. Nat Commun 2023; 14:6377. [PMID: 37821459 PMCID: PMC10567788 DOI: 10.1038/s41467-023-42051-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 09/28/2023] [Indexed: 10/13/2023] Open
Abstract
Hetero-pentameric Cys-loop receptors constitute a major type of neurotransmitter receptors that enable signal transmission and processing in the nervous system. Despite intense investigations into their working mechanism and pharmaceutical potentials, how neurotransmitters activate these receptors remains unclear due to the lack of high-resolution structural information in the activated open state. Here we report near-atomic resolution structures resolved in digitonin consistent with all principle functional states of the human α1β GlyR, which is a major Cys-loop receptor that mediates inhibitory neurotransmission in the central nervous system of adults. Glycine binding induces cooperative and symmetric structural rearrangements in the neurotransmitter-binding extracellular domain but asymmetrical pore dilation in the transmembrane domain. Symmetric response in the extracellular domain is consistent with electrophysiological data showing cooperative glycine activation and contribution from both α1 and β subunits. A set of functionally essential but differentially charged amino acid residues in the transmembrane domain of the α1 and β subunits explains asymmetric activation. These findings provide a foundation for understanding how the gating of the Cys-loop receptor family members diverges to accommodate specific physiological environments.
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Affiliation(s)
- Xiaofen Liu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Weiwei Wang
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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9
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Mortensen M, Xu Y, Shehata MA, Krall J, Ernst M, Frølund B, Smart TG. Pregnenolone sulfate analogues differentially modulate GABA A receptor closed/desensitised states. Br J Pharmacol 2023; 180:2482-2499. [PMID: 37194503 PMCID: PMC10952582 DOI: 10.1111/bph.16143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 02/07/2023] [Accepted: 05/05/2023] [Indexed: 05/18/2023] Open
Abstract
BACKGROUND AND PURPOSE GABAA receptors are regulated by numerous classes of allosteric modulators. However, regulation of receptor macroscopic desensitisation remains largely unexplored and may offer new therapeutic opportunities. Here, we report the emerging potential for modulating desensitisation with analogues of the endogenous inhibitory neurosteroid, pregnenolone sulfate. EXPERIMENTAL APPROACH New pregnenolone sulfate analogues were synthesised incorporating various heterocyclic substitutions located at the C-21 position on ring D. The pharmacological profiles of these compounds were assessed using electrophysiology and recombinant GABAA receptors together with mutagenesis, molecular dynamics simulations, structural modelling and kinetic simulations. KEY RESULTS All seven analogues retained a negative allosteric modulatory capability whilst exhibiting diverse potencies. Interestingly, we observed differential effects on GABA current decay by compounds incorporating either a six- (compound 5) or five-membered heterocyclic ring (compound 6) on C-21, which was independent of their potencies as inhibitors. We propose that differences in molecular charges, and the targeted binding of analogues to specific states of the GABAA receptor, are the most likely cause of the distinctive functional profiles. CONCLUSIONS AND IMPLICATIONS Our findings reveal that heterocyclic addition to inhibitory neurosteroids not only affected their potency and macroscopic efficacy but also affected innate receptor mechanisms that underlie desensitisation. Acute modulation of macroscopic desensitisation will determine the degree and duration of GABA inhibition, which are vital for the integration of neural circuit activity. Discovery of this form of modulation could present an opportunity for next-generation GABAA receptor drug design and development.
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Affiliation(s)
- Martin Mortensen
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
| | - Yue Xu
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Mohamed A. Shehata
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Jacob Krall
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
- Present address:
Xellia Pharmaceuticals ApSCopenhagenDenmark
| | - Margot Ernst
- Department of Pathology of the Nervous System, Center for Brain ResearchMedical University of ViennaViennaAustria
| | - Bente Frølund
- Department of Drug Design and Pharmacology, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Trevor G. Smart
- Department of Neuroscience, Physiology and PharmacologyUniversity College LondonLondonUK
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10
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Asahi M, Yamato K, Ozoe F, Ozoe Y. External amino acid residues of insect GABA receptor channels dictate the action of the isoxazoline ectoparasiticide fluralaner. PEST MANAGEMENT SCIENCE 2023; 79:4078-4082. [PMID: 37288963 DOI: 10.1002/ps.7606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/05/2023] [Accepted: 06/08/2023] [Indexed: 06/09/2023]
Abstract
BACKGROUND Fluralaner is the first isoxazoline ectoparasiticide developed to protect companion animals from fleas and ticks. Fluralaner primarily inhibits arthropod γ-aminobutyric acid receptors (GABARs), which are ligand-gated ion channels comprising five subunits arranged around the channel pore. We previously reported that the action site of fluralaner resides at the M1-M3 transmembrane interface between adjacent GABAR subunits. To investigate whether fluralaner interacts with the second transmembrane segment (M2) located deep in the interface, we generated four housefly RDL GABAR mutants with non-conservative amino acid substitutions in the M2 region. RESULTS Electrophysiological analysis of GABARs expressed in Xenopus oocytes indicated that S313A and S314A mutants exhibited fluralaner sensitivities similar to that of the wild type. M312S mutant exhibited approximately seven-fold lower sensitivity than that of the wild type. Notably, the N316L mutant was almost insensitive to fluralaner. CONCLUSION The findings of this study indicate that the conserved external amino acid residues of insect GABAR channels play a critical role in the antagonistic effect of fluralaner. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Miho Asahi
- Biological Research Laboratories, Nissan Chemical Corporation, Shiraoka, Saitama, Japan
| | - Kohei Yamato
- Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, Japan
| | - Fumiyo Ozoe
- Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, Japan
- Interdisciplinary Institute for Science Research, Organization for Research and Academic Information, Shimane University, Matsue, Shimane, Japan
| | - Yoshihisa Ozoe
- Faculty of Life and Environmental Sciences, Shimane University, Matsue, Shimane, Japan
- Interdisciplinary Institute for Science Research, Organization for Research and Academic Information, Shimane University, Matsue, Shimane, Japan
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11
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Solntseva EI, Bukanova JV, Kondratenko R, Kudova E. Corticosteroids as Selective and Effective Modulators of Glycine Receptors. ACS Chem Neurosci 2023; 14:3132-3142. [PMID: 37584305 PMCID: PMC10485894 DOI: 10.1021/acschemneuro.3c00287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 08/07/2023] [Indexed: 08/17/2023] Open
Abstract
The mechanism of the negative impact of corticosteroids on the induction and progress of mental illness remains unclear. In this work, we studied the effects of corticosteroids on the activity of neuronal glycine receptors (GlyR) and GABA-A receptors (GABAAR) by measuring the chloride current induced by the application of GABA (2 or 5 μM) to isolated cerebellar Purkinje cells (IGABA) and by the application of glycine (100 μM) to pyramidal neurons of the rat hippocampus (IGly). It was found that corticosterone, 5α-dihydrodeoxycorticosterone, allotetrahydrocorticosterone, cortisol, and 17α,21-dihydroxypregnenolone were able to accelerate the desensitization of the IGly at physiological concentrations (IC50 values varying from 0.39 to 0.72 μM). Next, cortisone, 11-deoxycortisol, 11-deoxycorticosterone, 5β-dihydrodeoxycorticosterone, and tetrahydrocorticosterone accelerated the desensitization of IGly with IC50 values varying from 10.3 to 15.2 μM. Allotetrahydrocorticosterone and tetrahydrocorticosterone potentiated the IGABA albeit with high EC50 values (18-23 μM). The rest of the steroids had no effect on IGABA in the range of concentrations of 1-100 μM. Finally, our study has suggested a structural relationship of the 3β-hydroxyl group/3-oxo group with the selective modulatory activity on GlyRs in contrast to the 3α-hydroxyl group that is pivotal for GABAARs. In summary, our results suggest that increased GlyR desensitization by corticosteroids may contribute to brain dysfunction under chronic stress and identify corticosteroids for further development as selective modulators of GlyRs.
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Affiliation(s)
- Elena I. Solntseva
- Functional
Synaptology Laboratory, Brain Research Institute,
Research Center of Neurology, Moscow 125367, Russia
| | - Julia V. Bukanova
- Functional
Synaptology Laboratory, Brain Research Institute,
Research Center of Neurology, Moscow 125367, Russia
| | - Rodion Kondratenko
- Functional
Synaptology Laboratory, Brain Research Institute,
Research Center of Neurology, Moscow 125367, Russia
| | - Eva Kudova
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 166 10, Czech Republic
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12
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Kłopotowski K, Michałowski MA, Gos M, Mosiądz D, Czyżewska MM, Mozrzymas JW. Mutation of valine 53 at the interface between extracellular and transmembrane domains of the β 2 principal subunit affects the GABA A receptor gating. Eur J Pharmacol 2023; 947:175664. [PMID: 36934960 DOI: 10.1016/j.ejphar.2023.175664] [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: 11/17/2022] [Revised: 02/09/2023] [Accepted: 03/16/2023] [Indexed: 03/21/2023]
Abstract
GABAA receptors (gamma-aminobutyric acid type A receptors) are pentameric ligand-gated ion channels mediating inhibition in adult mammalian brains. Their static structure has been intensely studied in the past years but the underlying molecular activatory mechanisms remain obscure. The interface between extracellular and transmembrane domains has been recognized as a key player in the receptor gating. However, the role of the valine 53 in the β1-β2 loop of the principal subunit (β2) remains controversial showing differences compared to homologous residues in some cys-loop counterparts such as nAChR. To address the role of the β2V53 residue in the α1β2γ2L receptor gating, we performed high resolution macroscopic and single-channel recordings. To explore underlying molecular mechanisms a variety of substituting amino acids were investigated: Glutamate and Lysine (different electric charge), Alanine (aliphatic, larger than Valine) and Histidine (same residue as in homologous α1H55). We report that mutation of the β2V53 residue results in alterations of nearly all gating transitions including opening/closing, preactivation and desensitization. A dramatic gating impairment was observed for glutamate substitution (β2V53E) but β2V53K mutation had a weak effect. The impact of histidine substitution was also small while β2V53A markedly affected the receptor but to a smaller extent than β2V53E. Considering available structures in desensitized and bicuculline blocked shut states we propose that strongly detrimental effect of β2V53E mutation on receptor activation results from electrostatic interaction between the glutamate and β2K274 on the loop M2-M3 which stabilizes the receptor in the shut state. We conclude that β2V53 is strongly involved in mechanisms underlying the receptor gating.
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Affiliation(s)
- Karol Kłopotowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland.
| | - Michał A Michałowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Michalina Gos
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland
| | - Daniela Mosiądz
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Marta M Czyżewska
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland
| | - Jerzy W Mozrzymas
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chałubińskiego 3a, Wrocław, Dolnośląskie, PL 50-368, Poland; University of Wroclaw, Department of Molecular Physiology and Neurobiology, Sienkiewicza 21, Wrocław, Dolnośląskie, Pl 50-335, Poland.
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13
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Gibbs E, Klemm E, Seiferth D, Kumar A, Ilca SL, Biggin PC, Chakrapani S. Conformational transitions and allosteric modulation in a heteromeric glycine receptor. Nat Commun 2023; 14:1363. [PMID: 36914669 PMCID: PMC10011588 DOI: 10.1038/s41467-023-37106-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/02/2023] [Indexed: 03/16/2023] Open
Abstract
Glycine Receptors (GlyRs) provide inhibitory neuronal input in the spinal cord and brainstem, which is critical for muscle coordination and sensory perception. Synaptic GlyRs are a heteromeric assembly of α and β subunits. Here we present cryo-EM structures of full-length zebrafish α1βBGlyR in the presence of an antagonist (strychnine), agonist (glycine), or agonist with a positive allosteric modulator (glycine/ivermectin). Each structure shows a distinct pore conformation with varying degrees of asymmetry. Molecular dynamic simulations found the structures were in a closed (strychnine) and desensitized states (glycine and glycine/ivermectin). Ivermectin binds at all five interfaces, but in a distinct binding pose at the β-α interface. Subunit-specific features were sufficient to solve structures without a fiduciary marker and to confirm the 4α:1β stoichiometry recently observed. We also report features of the extracellular and intracellular domains. Together, our results show distinct compositional and conformational properties of α1βGlyR and provide a framework for further study of this physiologically important channel.
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Affiliation(s)
- Eric Gibbs
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Emily Klemm
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - David Seiferth
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Arvind Kumar
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Serban L Ilca
- New York Structural Biology Center, New York, NY, 10027, USA
- Simons Electron Microscopy Center, New York, NY, 10027, USA
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
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14
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Liu X, Wang W. Asymmetric gating of a human hetero-pentameric glycine receptor. RESEARCH SQUARE 2023:rs.3.rs-2386831. [PMID: 36711971 PMCID: PMC9882600 DOI: 10.21203/rs.3.rs-2386831/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Hetero-pentameric Cys-loop receptors constitute a major type of neurotransmitter receptors that enable signal transmission and processing in the nervous system. Despite intense investigations in their working mechanism and pharmaceutical potentials, how neurotransmitters activate these receptors remain unclear due to the lack of high-resolution structural information in the activated open state. Here we report near-atomic resolution structures in all principle functional states of the human α1β GlyR, which is a major Cys-loop receptor that mediates inhibitory neurotransmission in the central nervous system of adults. Glycine binding induced cooperative and symmetric structural rearrangements in the neurotransmitter-binding extracellular domain, but asymmetrical pore dilation in the transmembrane domain. Symmetric response in the extracellular domain is consistent with electrophysiological data showing similar contribution to activation from all the α1 and β subunits. A set of functionally essential but differentially charged amino-acid residues in the transmembrane domain of the α1 and β subunits explains asymmetric activation. These findings point to a gating mechanism that is distinct from homomeric receptors but more compatible with heteromeric GlyRs being clustered at synapses through β subunit-scaffolding protein interactions. Such mechanism provides foundation for understanding how gating of the Cys-loop receptor members diverge to accommodate specific physiological environment.
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Affiliation(s)
- Xiaofen Liu
- University of Texas Southwestern Medical Center
| | - Weiwei Wang
- University of Texas Southwestern Medical Center
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15
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Goldschen-Ohm MP. Benzodiazepine Modulation of GABA A Receptors: A Mechanistic Perspective. Biomolecules 2022; 12:biom12121784. [PMID: 36551212 PMCID: PMC9775625 DOI: 10.3390/biom12121784] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 11/23/2022] [Accepted: 11/26/2022] [Indexed: 12/05/2022] Open
Abstract
Benzodiazepines (BZDs) are a class of widely prescribed psychotropic drugs that target GABAA receptors (GABAARs) to tune inhibitory synaptic signaling throughout the central nervous system. Despite knowing their molecular target for over 40 years, we still do not fully understand the mechanism of modulation at the level of the channel protein. Nonetheless, functional studies, together with recent cryo-EM structures of GABAA(α1)2(βX)2(γ2)1 receptors in complex with BZDs, provide a wealth of information to aid in addressing this gap in knowledge. Here, mechanistic interpretations of functional and structural evidence for the action of BZDs at GABAA(α1)2(βX)2(γ2)1 receptors are reviewed. The goal is not to describe each of the many studies that are relevant to this discussion nor to dissect in detail all the effects of individual mutations or perturbations but rather to highlight general mechanistic principles in the context of recent structural information.
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16
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Kaczor PT, Michałowski MA, Mozrzymas JW. α 1 Proline 277 Residues Regulate GABA AR Gating through M2-M3 Loop Interaction in the Interface Region. ACS Chem Neurosci 2022; 13:3044-3056. [PMID: 36219829 PMCID: PMC9634794 DOI: 10.1021/acschemneuro.2c00401] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Cys-loop receptors are a superfamily of transmembrane, pentameric receptors that play a crucial role in mammalian CNS signaling. Physiological activation of these receptors is typically initiated by neurotransmitter binding to the orthosteric binding site, located at the extracellular domain (ECD), which leads to the opening of the channel pore (gate) at the transmembrane domain (TMD). Whereas considerable knowledge on molecular mechanisms of Cys-loop receptor activation was gathered for the acetylcholine receptor, little is known with this respect about the GABAA receptor (GABAAR), which mediates cellular inhibition. Importantly, several static structures of GABAAR were recently described, paving the way to more in-depth molecular functional studies. Moreover, it has been pointed out that the TMD-ECD interface region plays a crucial role in transduction of conformational changes from the ligand binding site to the channel gate. One of the interface structures implicated in this transduction process is the M2-M3 loop with a highly conserved proline (P277) residue. To address this issue specifically for α1β2γ2L GABAAR, we choose to substitute proline α1P277 with amino acids with different physicochemical features such as electrostatic charge or their ability to change the loop flexibility. To address the functional impact of these mutations, we performed macroscopic and single-channel patch-clamp analyses together with modeling. Our findings revealed that mutation of α1P277 weakly affected agonist binding but was critical for all transitions of GABAAR gating: opening/closing, preactivation, and desensitization. In conclusion, we provide evidence that conservative α1P277 at the interface is strongly involved in regulating the receptor gating.
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17
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GABA A receptor proline 273 at the interdomain interface of the β 2 subunit regulates entry into desensitization and opening/closing transitions. Life Sci 2022; 308:120943. [PMID: 36096246 DOI: 10.1016/j.lfs.2022.120943] [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: 05/31/2022] [Revised: 08/29/2022] [Accepted: 09/06/2022] [Indexed: 11/23/2022]
Abstract
AIMS GABAA receptors belong to Cys-loop ion channel family and mediate inhibition in the brain. Despite the abundance of structural data on receptor structure, the molecular scenarios of activation are unknown. In this study we investigated the role of a β2P273 residue in channel gating transitions. This residue is located in a central position of the M2-M3 linker of the interdomain interface, expected to be predisposed to interact with another interfacial element, the β1-β2 loop of the extracellular side. The interactions occurring on this interface have been reported to couple agonist binding to channel gating. MAIN METHODS We recorded micro- and macroscopic current responses of recombinant GABAA receptors mutated at the β2P273 residue (to A, K, E) to saturating GABA. Electrophysiological data served as basis to kinetic modeling, used to decipher which gating transition were affected by mutations. KEY FINDINGS Mutations of this residue impaired macroscopic desensitization and accelerated current deactivation with P273E mutant showing greatest deviation from wild-type. Single-channel analysis revealed alterations mainly in short-lived shut times and shortening of openings, resulting in dramatic changes in intraburst open probability. Kinetic modeling indicated that β2P273 mutants show diminished entry into desensitized and open states as well as faster channel closing transitions. SIGNIFICANCE In conclusion, we demonstrate that β2P273 of the M2-M3 linker is a crucial element of the ECD-TMD interface regulating the receptor's ability to undergo late gating transitions. Henceforth, this region could be an important target for new pharmacological tools affecting GABAAR-mediated inhibition.
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18
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Kumar A, Kindig K, Rao S, Zaki AM, Basak S, Sansom MSP, Biggin PC, Chakrapani S. Structural basis for cannabinoid-induced potentiation of alpha1-glycine receptors in lipid nanodiscs. Nat Commun 2022; 13:4862. [PMID: 35982060 PMCID: PMC9388682 DOI: 10.1038/s41467-022-32594-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 08/08/2022] [Indexed: 11/23/2022] Open
Abstract
Nociception and motor coordination are critically governed by glycine receptor (GlyR) function at inhibitory synapses. Consequentially, GlyRs are attractive targets in the management of chronic pain and in the treatment of several neurological disorders. High-resolution mechanistic details of GlyR function and its modulation are just emerging. While it has been known that cannabinoids such as Δ9-tetrahydrocannabinol (THC), the principal psychoactive constituent in marijuana, potentiate GlyR in the therapeutically relevant concentration range, the molecular mechanism underlying this effect is still not understood. Here, we present Cryo-EM structures of full-length GlyR reconstituted into lipid nanodisc in complex with THC under varying concentrations of glycine. The GlyR-THC complexes are captured in multiple conformational states that reveal the basis for THC-mediated potentiation, manifested as different extents of opening at the level of the channel pore. Taken together, these structural findings, combined with molecular dynamics simulations and functional analysis, provide insights into the potential THC binding site and the allosteric coupling to the channel pore.
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Affiliation(s)
- Arvind Kumar
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kayla Kindig
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Shanlin Rao
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Sandip Basak
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Philip C Biggin
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
- Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
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19
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β subunits of GABA A receptors form proton-gated chloride channels: Insights into the molecular basis. Commun Biol 2022; 5:784. [PMID: 35922471 PMCID: PMC9349252 DOI: 10.1038/s42003-022-03720-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 07/14/2022] [Indexed: 11/17/2022] Open
Abstract
Gamma-aminobutyric acid type A receptors (GABAARs) are ligand gated channels mediating inhibition in the central nervous system. Here, we identify a so far undescribed function of β-subunit homomers as proton-gated anion channels. Mutation of a single H267A in β3 subunits completely abolishes channel activation by protons. In molecular dynamic simulations of the β3 crystal structure protonation of H267 increased the formation of hydrogen bonds between H267 and E270 of the adjacent subunit leading to a pore stabilising ring formation and accumulation of Cl- within the transmembrane pore. Conversion of these residues in proton insensitive ρ1 subunits transfers proton-dependent gating, thus highlighting the role of this interaction in proton sensitivity. Activation of chloride and bicarbonate currents at physiological pH changes (pH50 is in the range 6- 6.3) and kinetic studies suggest a physiological role in neuronal and non-neuronal tissues that express beta subunits, and thus as potential novel drug target. Beta subunits of GABAA receptors are unexpectedly shown to form homomeric proton gated ion channels attributable to a single histidine residue.
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20
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Solntseva EI, Bukanova JV, Skrebitsky VG, Kudova E. Pregnane neurosteroids exert opposite effects on GABA and glycine-induced chloride current in isolated rat neurons. Hippocampus 2022; 32:552-563. [PMID: 35703084 DOI: 10.1002/hipo.23449] [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: 02/21/2022] [Revised: 05/16/2022] [Accepted: 06/01/2022] [Indexed: 11/11/2022]
Abstract
The ability of endogenous neurosteroids (NSs) with pregnane skeleton modified at positions C-3 and C-5 to modulate the functional activity of inhibitory glycine receptors (GlyR) and ionotropic ɣ-aminobutyric acid receptors (GABAA R) was estimated. The glycine and GABA-induced chloride current (IGly and IGABA ) were measured in isolated pyramidal neurons of the rat hippocampus and in isolated rat cerebellar Purkinje cells, respectively. Our experiments demonstrated that pregnane NSs affected IGABA and IGly in a different manner. At low concentrations (up to 5 μM), tested pregnane NSs increased or did not change the peak amplitude of the IGABA , but reduced the IGly by decreasing the peak amplitude and/or accelerating desensitization. Namely, allopregnanolone (ALLO), epipregnanolone (EPI), pregnanolone (PA), pregnanolone sulfate (PAS) and 5β-dihydroprogesterone (5β-DHP) enhanced the IGABA in Purkinje cells. Dose-response curves plotted in the concentration range from 1 nM to 100 μM were smooth for EPI and 5β-DHP, but bell-shaped for ALLO, PA and PAS. The peak amplitude of the IGly was reduced by PA, PAS, and 5α- and 5β-DHP. In contrast, ALLO, ISO and EPI did not modulate it. Dose-response curves for the inhibition of the IGly peak amplitude were smooth for all active compounds. All NSs accelerated desensitization of the IGly . The dose-response relationship for this effect was smooth for ALLO, PA, PAS and 5β-DHP, but it was U-shaped for EPI, 5α-DHP and ISO. These results, together with our previous results on NSs with androstane skeleton, offer comprehensive overview for understanding the mechanisms of effects of NSs on IGly and IGABA .
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Affiliation(s)
- Elena I Solntseva
- Functional Synaptology Laboratory, Brain Research Department, Research Center of Neurology, Moscow, Russia
| | - Julia V Bukanova
- Functional Synaptology Laboratory, Brain Research Department, Research Center of Neurology, Moscow, Russia
| | - Vladimir G Skrebitsky
- Functional Synaptology Laboratory, Brain Research Department, Research Center of Neurology, Moscow, Russia
| | - Eva Kudova
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
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21
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de Bartolomeis A, Vellucci L, Austin MC, De Simone G, Barone A. Rational and Translational Implications of D-Amino Acids for Treatment-Resistant Schizophrenia: From Neurobiology to the Clinics. Biomolecules 2022; 12:biom12070909. [PMID: 35883465 PMCID: PMC9312470 DOI: 10.3390/biom12070909] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 06/25/2022] [Accepted: 06/26/2022] [Indexed: 12/13/2022] Open
Abstract
Schizophrenia has been conceptualized as a neurodevelopmental disorder with synaptic alterations and aberrant cortical–subcortical connections. Antipsychotics are the mainstay of schizophrenia treatment and nearly all share the common feature of dopamine D2 receptor occupancy, whereas glutamatergic abnormalities are not targeted by the presently available therapies. D-amino acids, acting as N-methyl-D-aspartate receptor (NMDAR) modulators, have emerged in the last few years as a potential augmentation strategy in those cases of schizophrenia that do not respond well to antipsychotics, a condition defined as treatment-resistant schizophrenia (TRS), affecting almost 30–40% of patients, and characterized by serious cognitive deficits and functional impairment. In the present systematic review, we address with a direct and reverse translational perspective the efficacy of D-amino acids, including D-serine, D-aspartate, and D-alanine, in poor responders. The impact of these molecules on the synaptic architecture is also considered in the light of dendritic spine changes reported in schizophrenia and antipsychotics’ effect on postsynaptic density proteins. Moreover, we describe compounds targeting D-amino acid oxidase and D-aspartate oxidase enzymes. Finally, other drugs acting at NMDAR and proxy of D-amino acids function, such as D-cycloserine, sarcosine, and glycine, are considered in the light of the clinical burden of TRS, together with other emerging molecules.
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Affiliation(s)
- Andrea de Bartolomeis
- Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, 80131 Naples, Italy; (L.V.); (G.D.S.); (A.B.)
- Correspondence: ; Tel.: +39-081-7463673 or +39-081-7463884 or +39-3662745592; Fax: +39-081-7462644
| | - Licia Vellucci
- Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, 80131 Naples, Italy; (L.V.); (G.D.S.); (A.B.)
| | - Mark C. Austin
- Clinical Psychopharmacology Program, College of Pharmacy, Idaho State University, Pocatello, ID 83209, USA;
| | - Giuseppe De Simone
- Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, 80131 Naples, Italy; (L.V.); (G.D.S.); (A.B.)
| | - Annarita Barone
- Laboratory of Translational and Molecular Psychiatry and Unit of Treatment-Resistant Psychosis, Section of Psychiatry, Department of Neuroscience, Reproductive Sciences and Dentistry, University of Naples Federico II, 80131 Naples, Italy; (L.V.); (G.D.S.); (A.B.)
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22
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Sikstus S, Benkherouf AY, Soini SL, Uusi-Oukari M. The Influence of AA29504 on GABA A Receptor Ligand Binding Properties and Its Implications on Subtype Selectivity. Neurochem Res 2022; 47:667-678. [PMID: 34727270 PMCID: PMC8847198 DOI: 10.1007/s11064-021-03475-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 09/03/2021] [Accepted: 10/27/2021] [Indexed: 10/26/2022]
Abstract
The unique pharmacological properties of δ-containing γ-aminobutyric acid type A receptors (δ-GABAARs) make them an attractive target for selective and persistent modulation of neuronal excitability. However, the availability of selective modulators targeting δ-GABAARs remains limited. AA29504 ([2-amino-4-(2,4,6-trimethylbenzylamino)-phenyl]-carbamic acid ethyl ester), an analog of K+ channel opener retigabine, acts as an agonist and a positive allosteric modulator (Ago-PAM) of δ-GABAARs. Based on electrophysiological studies using recombinant receptors, AA29504 was found to be a more potent and effective agonist in δ-GABAARs than in γ2-GABAARs. In comparison, AA29504 positively modulated the activity of recombinant δ-GABAARs more effectively than γ2-GABAARs, with no significant differences in potency. The impact of AA29504's efficacy- and potency-associated GABAAR subtype selectivity on radioligand binding properties remain unexplored. Using [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate ([3H]EBOB) binding assay, we found no difference in the modulatory potency of AA29504 on GABA- and THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol)-induced responses between native forebrain GABAARs of wild type and δ knock-out mice. In recombinant receptors expressed in HEK293 cells, AA29504 showed higher efficacy on δ- than γ2-GABAARs in the GABA-independent displacement of [3H]EBOB binding. Interestingly, AA29504 showed a concentration-dependent stimulation of [3H]muscimol binding to γ2-GABAARs, which was absent in δ-GABAARs. This was explained by AA29504 shifting the low-affinity γ2-GABAAR towards a higher affinity desensitized state, thereby rising new sites capable of binding GABAAR agonists with low nanomolar affinity. Hence, the potential of AA29504 to act as a desensitization-modifying allosteric modulator of γ2-GABAARs deserves further investigation for its promising influence on shaping efficacy, duration and plasticity of GABAAR synaptic responses.
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Affiliation(s)
- Sylvia Sikstus
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Ali Y Benkherouf
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Sanna L Soini
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland
| | - Mikko Uusi-Oukari
- Integrative Physiology and Pharmacology, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20014, Turku, Finland.
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23
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Felsztyna I, Villarreal MA, García DA, Miguel V. Insect RDL Receptor Models for Virtual Screening: Impact of the Template Conformational State in Pentameric Ligand-Gated Ion Channels. ACS OMEGA 2022; 7:1988-2001. [PMID: 35071887 PMCID: PMC8771969 DOI: 10.1021/acsomega.1c05465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
The RDL receptor is one of the most relevant protein targets for insecticide molecules. It belongs to the pentameric ligand-gated ion channel (pLGIC) family. Given that the experimental structures of pLGICs are difficult to obtain, homology modeling has been extensively used for these proteins, particularly for the RDL receptor. However, no detailed assessments of the usefulness of homology models for virtual screening (VS) have been carried out for pLGICs. The aim of this study was to evaluate which are the determinant factors for a good VS performance using RDL homology models, specially analyzing the impact of the template conformational state. Fifteen RDL homology models were obtained based on different pLGIC templates representing the closed, open, and desensitized states. A retrospective VS process was performed on each model, and their performance in the prioritization of active ligands was assessed. In addition, the three best-performing models among each of the conformations were subjected to molecular dynamics simulations (MDS) in complex with a representative active ligand. The models showed variations in their VS performance parameters that were related to the structural properties of the binding site. VS performance tended to improve in more constricted binding cavities. The best performance was obtained with a model based on a template in the closed conformation. MDS confirmed that the closed model was the one that best represented the interactions with an active ligand. These results imply that different templates should be evaluated and the structural variations between their channel conformational states should be specially examined, providing guidelines for the application of homology modeling for VS in other proteins of the pLGIC family.
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Affiliation(s)
- Iván Felsztyna
- Facultad
de Ciencias Exactas, Físicas y Naturales, Departamento de Química.
Cátedra de Química Biológica, Universidad Nacional de Córdoba, Córdoba 5016, Argentina
- Instituto
de Investigaciones Biológicas y Tecnológicas (IIByT), CONICET-Universidad Nacional de Córdoba, Córdoba 5016, Argentina
| | - Marcos A. Villarreal
- Facultad
de Ciencias Químicas, Departamento de Química Teórica
y Computacional, Universidad Nacional de
Córdoba, Córdoba 5016, Argentina
- Instituto
de Investigaciones en Físico-Química de Córdoba
(INFIQC), CONICET-Universidad Nacional de
Córdoba, Córdoba 5016, Argentina
| | - Daniel A. García
- Facultad
de Ciencias Exactas, Físicas y Naturales, Departamento de Química.
Cátedra de Química Biológica, Universidad Nacional de Córdoba, Córdoba 5016, Argentina
- Instituto
de Investigaciones Biológicas y Tecnológicas (IIByT), CONICET-Universidad Nacional de Córdoba, Córdoba 5016, Argentina
| | - Virginia Miguel
- Facultad
de Ciencias Exactas, Físicas y Naturales, Departamento de Química.
Cátedra de Química Biológica, Universidad Nacional de Córdoba, Córdoba 5016, Argentina
- Instituto
de Investigaciones Biológicas y Tecnológicas (IIByT), CONICET-Universidad Nacional de Córdoba, Córdoba 5016, Argentina
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24
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Madjroh N, Mellou E, Davies PA, Söderhielm PC, Jensen AA. Discovery and functional characterization of N-(thiazol-2-yl)-benzamide analogs as the first class of selective antagonists of the Zinc-Activated Channel (ZAC). Biochem Pharmacol 2021; 193:114782. [PMID: 34560054 PMCID: PMC9979163 DOI: 10.1016/j.bcp.2021.114782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/08/2021] [Accepted: 09/13/2021] [Indexed: 10/20/2022]
Abstract
The Zinc-Activated Channel (ZAC) is an atypical member of the Cys-loop receptor (CLR) superfamily of pentameric ligand-gated ion channels, with its very different endogenous agonists and signalling properties. In this study, a compound library screening at ZAC resulted in the identification of 2-(5-bromo-2-chlorobenzamido)-4-methylthiazole-5-methyl ester (1) as a novel ZAC antagonist. The structural determinants for ZAC activity in 1 were investigated by functional characterization of 61 analogs at ZAC expressed in Xenopus oocytes by two-electrode voltage clamp electrophysiology, and couple of analogs exerting more potent ZAC inhibition than 1 were identified (IC50 values: 1-3 μM). 1 and N-(4-(tert-butyl)thiazol-2-yl)-3-fluorobenzamide (5a, TTFB) were next applied in studies of the functional properties and the mode of action of this novel class of ZAC antagonists. TTFB was a roughly equipotent antagonist of Zn+- and H+-evoked ZAC signaling and of spontaneous ZAC activity, and the slow on-set of its channel block suggested that its ZAC inhibition is state-dependent. TTFB was found to be a selective ZAC antagonist, exhibiting no significant agonist, antagonist or modulatory activity at 5-HT3A, α3β4 nicotinic acetylcholine, α1β2γ2S GABAA or α1 glycine receptors at 30 μM. 1 displayed largely non-competitive antagonism of Zn2+-induced ZAC signalling, and TTFB was demonstrated to target the transmembrane and/or intracellular domains of the receptor, which collectively suggests that the N-(thiazol-2-yl)-benzamide analog acts a negative allosteric modulator of ZAC. We propose that this first class of selective ZAC antagonists could constitute useful pharmacological tools in future explorations of the presently poorly elucidated physiological functions governed by this CLR.
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Affiliation(s)
- Nawid Madjroh
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Eleni Mellou
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Paul A. Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Pella C. Söderhielm
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Anders A. Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark,Corresponding author. (A.A. Jensen)
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25
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Madjroh N, Mellou E, Æbelø L, Davies PA, Söderhielm PC, Jensen AA. Probing the molecular basis for signal transduction through the Zinc-Activated Channel (ZAC). Biochem Pharmacol 2021; 193:114781. [PMID: 34560053 DOI: 10.1016/j.bcp.2021.114781] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/11/2021] [Accepted: 09/13/2021] [Indexed: 12/18/2022]
Abstract
The molecular basis for the signal transduction through the classical Cys-loop receptors (CLRs) has been delineated in great detail. The Zinc-Activated Channel (ZAC) constitutes a so far poorly elucidated fifth branch of the CLR superfamily, and in this study we explore the molecular mechanisms underlying ZAC signaling in Xenopus oocytes by two-electrode voltage clamp electrophysiology. In studies of chimeric receptors fusing either the extracellular domain (ECD) or the transmembrane/intracellular domain (TMD-ICD) of ZAC with the complementary domains of 5-HT3A serotonin or α1 glycine receptors, serotonin and Zn2+/H+ evoked robust concentration-dependent currents in 5-HT3A/ZAC- and ZAC/α1-Gly-expressing oocytes, respectively, suggesting that Zn2+ and protons activate ZAC predominantly through its ECD. The molecular basis for Zn2+-mediated ZAC signaling was probed further by introduction of mutations of His, Cys, Glu and Asp residues in this domain, but as none of the mutants tested displayed substantially impaired Zn2+ functionality compared to wild-type ZAC, the location of the putative Zn2+ binding site(s) in the ECD was not identified. Finally, the functional importance of Leu246 (Leu9') in the transmembrane M2 α-helix of ZAC was investigated by Ala, Val, Ile and Thr substitutions. In concordance with findings for this highly conserved residue in classical CLRs, the ZACL9'X mutants exhibited left-shifted agonist concentration-response relationships, markedly higher degrees of spontaneous activity and slower desensitization kinetics compared to wild-type ZAC. In conclusion, while ZAC is an atypical CLR in terms of its (identified) agonists and channel characteristics, its signal transduction seems to undergo similar conformational transitions as those in the classical CLR.
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Affiliation(s)
- Nawid Madjroh
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Ø 2100, Denmark
| | - Eleni Mellou
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Ø 2100, Denmark
| | - Laura Æbelø
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Ø 2100, Denmark
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, United States
| | - Pella C Söderhielm
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Ø 2100, Denmark
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen Ø 2100, Denmark.
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26
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Nakao T, Banba S. Important amino acids for function of the insect Rdl GABA receptor. PEST MANAGEMENT SCIENCE 2021; 77:3753-3762. [PMID: 33002317 DOI: 10.1002/ps.6121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/24/2020] [Accepted: 10/01/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Insect Rdl GABA receptor is an important insecticide target. To design a novel insecticide, studies on the structures of homologous pentameric ligand-gated ion channels provide information about important amino acids that are necessary for the function of insect Rdl GABA receptors. RESULTS L9'A, T12'A, T13'A, T13'S, M15'S, and M15'N mutations in the Drosophila Rdl GABA receptor subunit caused the protein to spontaneously adopt the open state conformation. In contrast, the S16'A, S16'T, S17'A, and S17'H mutant homomers showed the same levels of agonist and antagonist sensitivity as the wild-type receptor. The G336M mutation in the Drosophila Rdl GABA receptor abolished the agonist activities of ivermectin and milbemectin, but the F339M mutation did not. Additionally, the F339M mutation caused spontaneous opening of the receptor. In the Drosophila Rdl model, the hydrophobic girdle plays an important role in stabilization of the closed state. Mutations which decrease hydrophobic interactions resulted in spontaneous opening, supporting the importance of the hydrophobic girdle for keeping the channel closed. Through a mutational study of transmembrane 3 (TM3) cytoplasmic domain and Rdl GABA receptor modeling, hydrophobic interactions between TM3 and TM4 and intersubunit interaction were demonstrated to be important for channel gating. Alternatively, the intrasubunit interaction between TM2 and TM3 domains were less important for channel gating in case of Drosophila Rdl GABA receptor. CONCLUSION This study demonstrates important amino acids critical to the function of the Drosophila Rdl GABA receptor based on the mutational studies and Drosophila Rdl GABA receptor modeling approach. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Toshifumi Nakao
- Organic Chemistry G, Agrochemicals Research Center, Mitsui Chemicals Agro, Inc., Chiba, Japan
| | - Shinichi Banba
- Organic Chemistry G, Agrochemicals Research Center, Mitsui Chemicals Agro, Inc., Chiba, Japan
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27
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Terejko K, Michałowski MA, Iżykowska I, Dominik A, Brzóstowicz A, Mozrzymas JW. Mutations at the M2 and M3 Transmembrane Helices of the GABA ARs α 1 and β 2 Subunits Affect Primarily Late Gating Transitions Including Opening/Closing and Desensitization. ACS Chem Neurosci 2021; 12:2421-2436. [PMID: 34101432 PMCID: PMC8291490 DOI: 10.1021/acschemneuro.1c00151] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
![]()
GABA type A receptors
(GABAARs) belong to the pentameric
ligand-gated ion channel (pLGIC) family and play a crucial role in
mediating inhibition in the adult mammalian brain. Recently, a major
progress in determining the static structure of GABAARs
was achieved, although precise molecular scenarios underlying conformational
transitions remain unclear. The ligand binding sites (LBSs) are located
at the extracellular domain (ECD), very distant from the receptor
gate at the channel pore. GABAAR gating is complex, comprising
three major categories of transitions: openings/closings, preactivation,
and desensitization. Interestingly, mutations at, e.g., the ligand
binding site affect not only binding but often also more than one
gating category, suggesting that structural determinants for distinct
conformational transitions are shared. Gielen and co-workers (2015)
proposed that the GABAAR desensitization gate is located
at the second and third transmembrane segment. However, studies of
our and others’ groups indicated that other parts of the GABAAR macromolecule might be involved in this process. In the
present study, we asked how selected point mutations (β2G254V, α1G258V, α1L300V,
and β2L296V) at the M2 and M3 transmembrane segments
affect gating transitions of the α1β2γ2 GABAAR. Using high resolution macroscopic
and single-channel recordings and analysis, we report that these substitutions,
besides affecting desensitization, also profoundly altered openings/closings,
having some minor effect on preactivation and agonist binding. Thus,
the M2 and M3 segments primarily control late gating transitions of
the receptor (desensitization, opening/closing), providing a further
support for the concept of diffuse gating mechanisms for conformational
transitions of GABAAR.
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Affiliation(s)
- Katarzyna Terejko
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Michał A. Michałowski
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
- Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335 Wrocław, Poland
| | - Ilona Iżykowska
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Anna Dominik
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Aleksandra Brzóstowicz
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
| | - Jerzy W. Mozrzymas
- Department of Biophysics and Neuroscience, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368 Wrocław, Poland
- Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335 Wrocław, Poland
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28
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Kłopotowski K, Czyżewska MM, Mozrzymas JW. Glycine substitution of α1F64 residue at the loop D of GABA A receptor impairs gating - Implications for importance of binding site-channel gate linker rigidity. Biochem Pharmacol 2021; 192:114668. [PMID: 34216603 DOI: 10.1016/j.bcp.2021.114668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/27/2021] [Accepted: 06/28/2021] [Indexed: 12/29/2022]
Abstract
GABAA receptors (GABAARs) play a crucial role in mediating inhibition in adult mammalian brains. In the recent years, an impressive progress in revealing the static structure of GABAARs was achieved but the molecular mechanisms underlying their conformational transitions remain elusive. Phenylalanine 64 (α1F64) is located at the loop D of the orthosteric binding site of GABAAR and was found to directly interact with GABA molecule. Mutations of α1F64 were demonstrated to affect not only binding but also some gating properties. Loop D is a rigid β strand which seems to be particularly suitable to convey activatory signaling from the ligand binding site (LBS) to the gate at the channel pore. To test this scenario, we have investigated the substitution of α1F64 with glycine, the smallest amino acid, widely recognized as a rigidity "reducer" of protein structures. To this end, we assessed the impact of the α1F64G mutation in the α1β2γ2L type of GABAARs on gating properties by analyzing both macroscopic responses to rapid agonist applications and single-channel currents. We found that this substitution dramatically altered all gating features of the receptor (opening/closing, preactivation and desensitization) which contrasts with markedly weaker effects of previously considered substitutions (α1F64L and α1F64A). In particular, α1F64G mutation practically abolished the desensitization process. At the same time, the α1F64G mutant maintained gating integrity manifested as single-channel activity in the form of clusters. We conclude that rigidity of the loop D plays a crucial role in conveying the activation signal from the LBS to the channel gate.
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Affiliation(s)
- Karol Kłopotowski
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland.
| | - Marta M Czyżewska
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland
| | - Jerzy W Mozrzymas
- Wroclaw Medical University, Department of Biophysics and Neuroscience, Chalubinskiego 3A, Wroclaw, Dolnośląskie PL 50-368, +48 71 784 15 51, Poland.
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29
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Rook ML, Miaro M, Couch T, Kneisley DL, Musgaard M, MacLean DM. Mutation of a conserved glutamine residue does not abolish desensitization of acid-sensing ion channel 1. THE JOURNAL OF GENERAL PHYSIOLOGY 2021; 153:212203. [PMID: 34061161 PMCID: PMC8167889 DOI: 10.1085/jgp.202012855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 05/13/2021] [Indexed: 12/14/2022]
Abstract
Desensitization is a common feature of ligand-gated ion channels, although the molecular cause varies widely between channel types. Mutations that greatly reduce or nearly abolish desensitization have been described for many ligand-gated ion channels, including glutamate, GABA, glycine, and nicotinic receptors, but not for acid-sensing ion channels (ASICs) until recently. Mutating Gln276 to a glycine (Q276G) in human ASIC1a was reported to mostly abolish desensitization at both the macroscopic and the single channel levels, potentially providing a valuable tool for subsequent studies. However, we find that in both human and chicken ASIC1, the effect of Q276G is modest. In chicken ASIC1, the equivalent Q277G slightly reduces desensitization when using pH 6.5 as a stimulus but desensitizes, essentially like wild-type, when using more acidic pH values. In addition, steady-state desensitization is intact, albeit right-shifted, and recovery from desensitization is accelerated. Molecular dynamics simulations indicate that the Gln277 side chain participates in a hydrogen bond network that might stabilize the desensitized conformation. Consistent with this, destabilizing this network with the Q277N or Q277L mutations largely mimics the Q277G phenotype. In human ASIC1a, the Q276G mutation also reduces desensitization, but not to the extent reported previously. Interestingly, the kinetic consequences of Q276G depend on the human variant used. In the common G212 variant, Q276G slows desensitization, while in the rare D212 variant desensitization accelerates. Our data reveal that while the Q/G mutation does not abolish or substantially impair desensitization as previously reported, it does point to unexpected differences between chicken and human ASICs and the need for careful scrutiny before using this mutation in future studies.
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Affiliation(s)
- Matthew L Rook
- Graduate Program in Cellular and Molecular Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
| | - Megan Miaro
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Tyler Couch
- Graduate Program in Cellular and Molecular Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
| | - Dana L Kneisley
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
| | - Maria Musgaard
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - David M MacLean
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY
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30
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Murgia F, Gagliano A, Tanca MG, Or-Geva N, Hendren A, Carucci S, Pintor M, Cera F, Cossu F, Sotgiu S, Atzori L, Zuddas A. Metabolomic Characterization of Pediatric Acute-Onset Neuropsychiatric Syndrome (PANS). Front Neurosci 2021; 15:645267. [PMID: 34121984 PMCID: PMC8194687 DOI: 10.3389/fnins.2021.645267] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 04/27/2021] [Indexed: 01/21/2023] Open
Abstract
Introduction PANS is a controversial clinical entity, consisting of a complex constellation of psychiatric symptoms, adventitious changes, and expression of various serological alterations, likely sustained by an autoimmune/inflammatory disease. Detection of novel biomarkers of PANS is highly desirable for both diagnostic and therapeutic management of affected patients. Analysis of metabolites has proven useful in detecting biomarkers for other neuroimmune-psychiatric diseases. Here, we utilize the metabolomics approach to determine whether it is possible to define a specific metabolic pattern in patients affected by PANS compared to healthy subjects. Design This observational case-control study tested consecutive patients referred for PANS between June 2019 to May 2020. A PANS diagnosis was confirmed according to the PANS working criteria (National Institute of Mental Health [NIMH], 2010). Healthy age and sex-matched subjects were recruited as controls. Methods Thirty-four outpatients referred for PANS (mean age 9.5 years; SD 2.9, 71% male) and 25 neurotypical subjects matched for age and gender, were subjected to metabolite analysis. Serum samples were obtained from each participant and were analyzed using Nuclear Magnetic Resonance (NMR) spectroscopy. Subsequently, multivariate and univariate statistical analyses and Receiver Operator Curves (ROC) were performed. Results Separation of the samples, in line with the presence of PANS diagnosis, was observed by applying a supervised model (R2X = 0.44, R2Y = 0.54, Q2 = 0.44, p-value < 0.0001). The significantly altered variables were 2-Hydroxybutyrate, glycine, glutamine, histidine, tryptophan. Pathway analysis indicated that phenylalanine, tyrosine, and tryptophan metabolism, as well as glutamine and glutamate metabolism, exhibited the largest deviations from neurotypical controls. Conclusion We found a unique plasma metabolic profile in PANS patients, significantly differing from that of healthy children, that suggests the involvement of specific patterns of neurotransmission (tryptophan, glycine, histamine/histidine) as well as a more general state of neuroinflammation and oxidative stress (glutamine, 2-Hydroxybutyrate, and tryptophan-kynurenine pathway) in the disorder. This metabolomics study offers new insights into biological mechanisms underpinning the disorder and supports research of other potential biomarkers implicated in PANS.
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Affiliation(s)
- Federica Murgia
- Clinical Metabolomics Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Antonella Gagliano
- Child and Adolescent Neuropsychiatry Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,Child and Adolescent Neuropsychiatry Unit, "A. Cao" Peditric Hosptal, "G. Brotzu" Hospital Trust, Cagliari, Italy
| | - Marcello G Tanca
- Child and Adolescent Neuropsychiatry Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Noga Or-Geva
- Interdepartmental Program in Immunology, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, United States
| | - Aran Hendren
- Clinical Metabolomics Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Sara Carucci
- Child and Adolescent Neuropsychiatry Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,Child and Adolescent Neuropsychiatry Unit, "A. Cao" Peditric Hosptal, "G. Brotzu" Hospital Trust, Cagliari, Italy
| | - Manuela Pintor
- Child and Adolescent Neuropsychiatry Unit, "A. Cao" Peditric Hosptal, "G. Brotzu" Hospital Trust, Cagliari, Italy
| | - Francesca Cera
- Child and Adolescent Neuropsychiatry Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Fausto Cossu
- Paediatric Clinic, "A. Cao" Hospital, Cagliari, Italy
| | - Stefano Sotgiu
- Child Neuropsychiatry Unit, Department of Medical, Surgical and Experimental Sciences, University of Sassari, Sassari, Italy
| | - Luigi Atzori
- Clinical Metabolomics Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | - Alessandro Zuddas
- Child and Adolescent Neuropsychiatry Unit, Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy.,Child and Adolescent Neuropsychiatry Unit, "A. Cao" Peditric Hosptal, "G. Brotzu" Hospital Trust, Cagliari, Italy
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31
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Madjroh N, Davies PA, Smalley JL, Kristiansen U, Söderhielm PC, Jensen AA. Delineation of the functional properties exhibited by the Zinc-Activated Channel (ZAC) and its high-frequency Thr 128Ala variant (rs2257020) in Xenopus oocytes. Pharmacol Res 2021; 169:105653. [PMID: 33962015 DOI: 10.1016/j.phrs.2021.105653] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/23/2021] [Accepted: 04/27/2021] [Indexed: 11/28/2022]
Abstract
The signalling characteristics of the Zinc-Activated Channel (ZAC), a member of the Cys-loop receptor (CLR) superfamily, are presently poorly elucidated. The ZACN polymorphism c.454G>A encoding for the Thr128Ala variation in ZAC is found in extremely high allele frequencies across ethnicities. In this, the first study of ZAC in Xenopus oocytes by TEVC electrophysiology, ZACThr128 and ZACAla128 exhibited largely comparable pharmacological and signalling characteristics, but interestingly the Zn2+- and H+-evoked current amplitudes in ZACAla128-oocytes were dramatically smaller than those in ZACThr128-oocytes. While the variation thus appeared to impact cell surface expression and/or channel properties of ZAC, the similar expression properties exhibited by ZACThr128 and ZACAla128 in transfected mammalian cells indicated that their distinct functionalities could arise from the latter. In co-expression experiments, wild-type and variant ZAC subunits assembled efficiently into "heteromeric" complexes in HEK293 cells, while the concomitant presence of ZACAla128 in ZACThr128:ZACAla128-oocytes did not exert a dominant negative effect on agonist-evoked current amplitudes compared to those in ZACThr128-oocytes. Finally, the structural determinants of the functional importance of the 1-hydroxyethyl side-chain of Thr128 appeared to be subtle, as agonist-evoked current amplitudes in ZACSer128-, ZACVal128- and ZACIle128-oocytes also were substantially lower than those in ZACThr128-oocytes. In conclusion, the functional properties exhibited by ZAC in this work substantiate the notion of it being an atypical CLR. While the impact of the Thr128Ala variation on ZAC functionality in oocytes is striking, it remains to be investigated whether and to which extent this translates into an in vivo setting and thus could constitute a source of inter-individual variation in ZAC physiology.
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Affiliation(s)
- Nawid Madjroh
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Paul A Davies
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Joshua L Smalley
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Uffe Kristiansen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Pella C Söderhielm
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark
| | - Anders A Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen Ø, Denmark.
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32
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Field M, Dorovykh V, Thomas P, Smart TG. Physiological role for GABA A receptor desensitization in the induction of long-term potentiation at inhibitory synapses. Nat Commun 2021; 12:2112. [PMID: 33837214 PMCID: PMC8035410 DOI: 10.1038/s41467-021-22420-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 03/03/2021] [Indexed: 01/03/2023] Open
Abstract
GABAA receptors (GABAARs) are pentameric ligand-gated ion channels distributed throughout the brain where they mediate synaptic and tonic inhibition. Following activation, these receptors undergo desensitization which involves entry into long-lived agonist-bound closed states. Although the kinetic effects of this state are recognised and its structural basis has been uncovered, the physiological impact of desensitization on inhibitory neurotransmission remains unknown. Here we describe an enduring form of long-term potentiation at inhibitory synapses that elevates synaptic current amplitude for 24 h following desensitization of GABAARs in response to agonist exposure or allosteric modulation. Using receptor mutants and allosteric modulators we demonstrate that desensitization of GABAARs facilitates their phosphorylation by PKC, which increases the number of receptors at inhibitory synapses. These observations provide a physiological relevance to the desensitized state of GABAARs, acting as a signal to regulate the efficacy of inhibitory synapses during prolonged periods of inhibitory neurotransmission.
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Affiliation(s)
- Martin Field
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Valentina Dorovykh
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
| | - Philip Thomas
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, UCL, London, UK.
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33
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Hernandez CC, Tian X, Hu N, Shen W, Catron MA, Yang Y, Chen J, Jiang Y, Zhang Y, Macdonald RL. Dravet syndrome-associated mutations in GABRA1, GABRB2 and GABRG2 define the genetic landscape of defects of GABA A receptors. Brain Commun 2021; 3:fcab033. [PMID: 34095830 PMCID: PMC8176149 DOI: 10.1093/braincomms/fcab033] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 01/07/2021] [Accepted: 01/14/2021] [Indexed: 12/29/2022] Open
Abstract
Dravet syndrome is a rare, catastrophic epileptic encephalopathy that begins in the first year of life, usually with febrile or afebrile hemiclonic or generalized tonic-clonic seizures followed by status epilepticus. De novo variants in genes that mediate synaptic transmission such as SCN1A and PCDH19 are often associated with Dravet syndrome. Recently, GABAA receptor subunit genes (GABRs) encoding α1 (GABRA1), β3 (GABRB3) and γ2 (GABRG2), but not β2 (GABRB2) or β1 (GABRB1), subunits are frequently associated with Dravet syndrome or Dravet syndrome-like phenotype. We performed next generation sequencing on 870 patients with Dravet syndrome and identified nine variants in three different GABRs. Interestingly, the variants were all in genes encoding the most common GABAA receptor, the α1β2γ2 receptor. Mutations in GABRA1 (c.644T>C, p. L215P; c.640C>T, p. R214C; c.859G>A; V287I; c.641G>A, p. R214H) and GABRG2 (c.269C>G, p. T90R; c.1025C>T, p. P342L) presented as de novo cases, while in GABRB2 two variants were de novo (c.992T>C, p. F331S; c.542A>T, p. Y181F) and one was autosomal dominant and inherited from the maternal side (c.990_992del, p.330_331del). We characterized the effects of these GABR variants on GABAA receptor biogenesis and channel function. We found that defects in receptor gating were the common deficiency of GABRA1 and GABRB2 Dravet syndrome variants, while mainly trafficking defects were found with the GABRG2 (c.269C>G, p. T90R) variant. It seems that variants in α1 and β2 subunits are less tolerated than in γ2 subunits, since variant α1 and β2 subunits express well but were functionally deficient. This suggests that all of these GABR variants are all targeting GABR genes that encode the assembled α1β2γ2 receptor, and regardless of which of the three subunits are mutated, variants in genes coding for α1, β2 and γ2 receptor subunits make them candidate causative genes in the pathogenesis of Dravet syndrome.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48198, USA
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - XiaoJuan Tian
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing 100045, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Mackenzie A Catron
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37240, USA
| | - Ying Yang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Jiaoyang Chen
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing 100069, China
| | - Yuehua Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
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34
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Kim JJ, Hibbs RE. Direct Structural Insights into GABA A Receptor Pharmacology. Trends Biochem Sci 2021; 46:502-517. [PMID: 33674151 DOI: 10.1016/j.tibs.2021.01.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/08/2021] [Accepted: 01/25/2021] [Indexed: 12/18/2022]
Abstract
GABAA receptors are pentameric ligand-gated ion channels that mediate most fast neuronal inhibition in the brain. In addition to their important physiological roles, they are noteworthy in their rich pharmacology; prominent drugs used for anxiety, insomnia, and general anesthesia act through positive modulation of GABAA receptors. Direct structural information for how these drugs work was absent until recently. Efforts in structural biology over the past few years have revealed how important drug classes and natural products interact with the GABAA receptor, providing a foundation for studies in dynamics and structure-guided drug design. Here, we review recent developments in GABAA receptor structural pharmacology, focusing on subunit assemblies of the receptor found at synapses.
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Affiliation(s)
- Jeong Joo Kim
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Mediatory role of the dopaminergic system through D1 receptor on glycine-induced hypophagia in neonatal broiler-type chickens. Amino Acids 2021; 53:461-470. [PMID: 33649971 DOI: 10.1007/s00726-021-02963-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 02/19/2021] [Indexed: 10/22/2022]
Abstract
The present study aimed to examine the mediatory role of the dopaminergic system in the food intake induced by intracerebroventricular (ICV) injection of glycine in neonatal 3-h feed-deprived (FD3) meat-type chickens. In the first and second experiments, birds were ICV injected using low and high doses of glycine (50, 100 and 200 nmol) and strychnine (50, 100 and 200 nmol), respectively. In experiments 3-9, the behaviorally subeffective doses of dopamine (10 nmol), 6-OHDA (2.5 nmol), SCH 23,390 (D1 antagonist; 5 nmol), AMI-193 (D2 antagonist; 5 nmol), NGB2904 (D3 antagonist; 6.4 nmol) and L-741,742 (D4 antagonist; 6 nmol) were, respectively, co-administrated with glycine (200 nmol) in FD3 5-day-old chicks to investigate possible interplay of dopamine receptors in glycine-induced feeding behavior. Then, cumulative food intake based on body weight percentage (%BW) was determined at 30, 60 and 120 min after the injection. According to the results, dopamine significantly boosted the hypophagia induced by glycine at all-time intervals (p ≤ 0.001). These results combined with the previous findings suggest an interplay between dopamine and glycine in chicken's brain in which D1 receptor-mediated food intake induced by glycine.
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36
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Yu J, Zhu H, Lape R, Greiner T, Du J, Lü W, Sivilotti L, Gouaux E. Mechanism of gating and partial agonist action in the glycine receptor. Cell 2021; 184:957-968.e21. [PMID: 33567265 PMCID: PMC8115384 DOI: 10.1016/j.cell.2021.01.026] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/16/2020] [Accepted: 01/15/2021] [Indexed: 12/14/2022]
Abstract
Ligand-gated ion channels mediate signal transduction at chemical synapses and transition between resting, open, and desensitized states in response to neurotransmitter binding. Neurotransmitters that produce maximum open channel probabilities (Po) are full agonists, whereas those that yield lower than maximum Po are partial agonists. Cys-loop receptors are an important class of neurotransmitter receptors, yet a structure-based understanding of the mechanism of partial agonist action has proven elusive. Here, we study the glycine receptor with the full agonist glycine and the partial agonists taurine and γ-amino butyric acid (GABA). We use electrophysiology to show how partial agonists populate agonist-bound, closed channel states and cryo-EM reconstructions to illuminate the structures of intermediate, pre-open states, providing insights into previously unseen conformational states along the receptor reaction pathway. We further correlate agonist-induced conformational changes to Po across members of the receptor family, providing a hypothetical mechanism for partial and full agonist action at Cys-loop receptors.
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Affiliation(s)
- Jie Yu
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Hongtao Zhu
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Remigijus Lape
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK
| | - Timo Greiner
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK
| | - Juan Du
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Wei Lü
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Lucia Sivilotti
- Department of Neuroscience, Physiology and Pharmacology, University College London, Medical Sciences Building, Gower Street, London WC1E 6BT, UK.
| | - Eric Gouaux
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Howard Hughes Medical Institute, Oregon Health & Science University, Portland, OR 97239, USA.
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37
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Kaczor PT, Wolska AD, Mozrzymas JW. α 1 Subunit Histidine 55 at the Interface between Extracellular and Transmembrane Domains Affects Preactivation and Desensitization of the GABA A Receptor. ACS Chem Neurosci 2021; 12:562-572. [PMID: 33471498 PMCID: PMC7875458 DOI: 10.1021/acschemneuro.0c00781] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
![]()
The
GABAA receptor is a member of the Cys-loop family
and plays a crucial role in the adult mammalian brain inhibition.
Although the static structure of this receptor is emerging, the molecular
mechanisms underlying its conformational transitions remain elusive.
It is known that in the Cys-loop receptors, the interface between
extracellular and transmembrane domains plays a key role in transmitting
the “activation wave” down to the channel gate in the
pore. It has been previously reported that histidine 55 (H55), located
centrally at the interfacial β1−β2 loop of the
α1 subunit, is important in the receptor activation,
but it is unknown which specific gating steps it is affecting. In
the present study, we addressed this issue by taking advantage of
the state-of-the-art macroscopic and single-channel recordings together
with extensive modeling. Considering that H55 is known to affect the
local electrostatic landscape and because it is neighbored by two
negatively charged aspartates, a well conserved feature in the α
subunits, we considered substitution with negative (E) and positive
(K) residues. We found that these mutations markedly affected the
receptor gating, altering primarily preactivation and desensitization
transitions. Importantly, opposite effects were observed for these
two mutations strongly suggesting involvement of electrostatic interactions.
Single-channel recordings suggested also a minor effect on opening/closing
transitions which did not depend on the electric charge of the substituting
amino acid. Altogether, we demonstrate that H55 mutations affect primarily
preactivation and desensitization most likely by influencing local
electrostatic interactions at the receptor interface.
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Affiliation(s)
- Przemyslaw T. Kaczor
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Aleksandra D. Wolska
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
| | - Jerzy W. Mozrzymas
- Department of Biophysics and Neuroscience, Wroclaw Medical University, Chalubinskiego 3a, Wroclaw, Dolnoślaskie 50-368, Poland
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Subunit-Specific Photocontrol of Glycine Receptors by Azobenzene-Nitrazepam Photoswitcher. eNeuro 2021; 8:ENEURO.0294-20.2020. [PMID: 33298457 PMCID: PMC7877471 DOI: 10.1523/eneuro.0294-20.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 11/04/2020] [Accepted: 11/23/2020] [Indexed: 12/24/2022] Open
Abstract
Photopharmacology is a unique approach that through a combination of photochemistry methods and advanced life science techniques allows the study and control of specific biological processes, ranging from intracellular pathways to brain circuits. Recently, a first photochromic channel blocker of anion-selective GABAA receptors, the azobenzene-nitrazepam-based photochromic compound (Azo-NZ1), has been described. In the present study, using patch-clamp technique in heterologous system and in mice brain slices, site-directed mutagenesis and molecular modeling we provide evidence of the interaction of Azo-NZ1 with glycine receptors (GlyRs) and determine the molecular basis of this interaction. Glycinergic synaptic neurotransmission determines an important inhibitory drive in the vertebrate nervous system and plays a crucial role in the control of neuronal circuits in the spinal cord and brain stem. GlyRs are involved in locomotion, pain sensation, breathing, and auditory function, as well as in the development of such disorders as hyperekplexia, epilepsy, and autism. Here, we demonstrate that Azo-NZ1 blocks in a UV-dependent manner the activity of α2 GlyRs (GlyR2), while being barely active on α1 GlyRs (GlyR1). The site of Azo-NZ1 action is in the chloride-selective pore of GlyR at the 2’ position of transmembrane helix 2 and amino acids forming this site determine the difference in Azo-NZ1 blocking activity between GlyR2 and GlyR1. This subunit-specific modulation is also shown on motoneurons of brainstem slices from neonatal mice that switch during development from expressing “fetal” GlyR2 to “adult” GlyR1 receptors.
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39
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Gomila AMJ, Rustler K, Maleeva G, Nin-Hill A, Wutz D, Bautista-Barrufet A, Rovira X, Bosch M, Mukhametova E, Petukhova E, Ponomareva D, Mukhamedyarov M, Peiretti F, Alfonso-Prieto M, Rovira C, König B, Bregestovski P, Gorostiza P. Photocontrol of Endogenous Glycine Receptors In Vivo. Cell Chem Biol 2020; 27:1425-1433.e7. [PMID: 32846115 DOI: 10.1016/j.chembiol.2020.08.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 04/14/2020] [Accepted: 08/04/2020] [Indexed: 12/15/2022]
Abstract
Glycine receptors (GlyRs) are indispensable for maintaining excitatory/inhibitory balance in neuronal circuits that control reflexes and rhythmic motor behaviors. Here we have developed Glyght, a GlyR ligand controlled with light. It is selective over other Cys-loop receptors, is active in vivo, and displays an allosteric mechanism of action. The photomanipulation of glycinergic neurotransmission opens new avenues to understanding inhibitory circuits in intact animals and to developing drug-based phototherapies.
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Affiliation(s)
- Alexandre M J Gomila
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain
| | - Karin Rustler
- University of Regensburg, Institute of Organic Chemistry, Regensburg 93053, Germany
| | - Galyna Maleeva
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain; Aix-Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille 13005, France
| | - Alba Nin-Hill
- University of Barcelona, Department of Inorganic and Organic Chemistry, Institute of Theoretical Chemistry (IQTCUB), Barcelona 08028, Spain
| | - Daniel Wutz
- University of Regensburg, Institute of Organic Chemistry, Regensburg 93053, Germany
| | - Antoni Bautista-Barrufet
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain
| | - Xavier Rovira
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain
| | - Miquel Bosch
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain
| | - Elvira Mukhametova
- Aix-Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille 13005, France; Kazan Federal University, Open Lab of Motor Neurorehabilitation, Kazan, Russia
| | - Elena Petukhova
- Institute of Neurosciences, Kazan State Medical University, Kazan, Russia
| | - Daria Ponomareva
- Institute of Neurosciences, Kazan State Medical University, Kazan, Russia
| | | | - Franck Peiretti
- Aix Marseille Université, INSERM 1263, INRA 1260, C2VN, Marseille, France
| | - Mercedes Alfonso-Prieto
- Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Computational Biomedicine, Forschungszentrum Jülich, 52425 Jülich, Germany; Cécile and Oskar Vogt Institute for Brain Research, Medical Faculty, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Carme Rovira
- University of Barcelona, Department of Inorganic and Organic Chemistry, Institute of Theoretical Chemistry (IQTCUB), Barcelona 08028, Spain; Catalan Institution for Research and Advanced Studies (ICREA), Barcelona 08003 Spain.
| | - Burkhard König
- University of Regensburg, Institute of Organic Chemistry, Regensburg 93053, Germany.
| | - Piotr Bregestovski
- Aix-Marseille Université, INSERM, INS, Institut de Neurosciences des Systèmes, Marseille 13005, France; Institute of Neurosciences, Kazan State Medical University, Kazan, Russia.
| | - Pau Gorostiza
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Barcelona 08028, Spain; Catalan Institution for Research and Advanced Studies (ICREA), Barcelona 08003 Spain; CIBER-BBN, Madrid 28001 Spain.
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40
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Solntseva EI, Bukanova JV, Kondratenko RV, Skrebitsky VG. Copper Ions Reduce the Effect of Protons on Desensitization of Glycine Receptors. Bull Exp Biol Med 2020; 169:791-794. [PMID: 33098514 DOI: 10.1007/s10517-020-04980-w] [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: 03/02/2020] [Indexed: 11/28/2022]
Abstract
Chloride current (IGly) evoked by the rapid (600 msec) application of glycine on isolated pyramidal neurons of the rat hippocampus was recorded using the patch clamp technique. We studied the effect of individual or combined application of copper ions (Cu2+) and protons (H+) on IGly. It was found that both Cu2+ (10 μM) and H+ (pH 7.0 and 6.0) applied separately caused a fast and reversible effect on IGly that included two components: a decrease in peak amplitude (Ipeak) and a decrease in the desensitization time constant (τdes). During combined application, the effects on Ipeak were additive, which indicates the independence of the mechanisms of these effects. At the same time, the effect of combined application of Cu2+ and H+ on τdes was not additive and sometimes a slowdown of the total desensitization was observed. The latter result suggests that H+ and Cu2+ can play the role of mutual antagonists when they affect the desensitization of GlyR.
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41
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Gielen M, Barilone N, Corringer PJ. The desensitization pathway of GABA A receptors, one subunit at a time. Nat Commun 2020; 11:5369. [PMID: 33097732 PMCID: PMC7585415 DOI: 10.1038/s41467-020-19218-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 09/17/2020] [Indexed: 01/05/2023] Open
Abstract
GABAA receptors mediate most inhibitory synaptic transmission in the brain of vertebrates. Following GABA binding and fast activation, these receptors undergo a slower desensitization, the conformational pathway of which remains largely elusive. To explore the mechanism of desensitization, we used concatemeric α1β2γ2 GABAA receptors to selectively introduce gain-of-desensitization mutations one subunit at a time. A library of twenty-six mutant combinations was generated and their bi-exponential macroscopic desensitization rates measured. Introducing mutations at the different subunits shows a strongly asymmetric pattern with a key contribution of the γ2 subunit, and combining mutations results in marked synergistic effects indicating a non-concerted mechanism. Kinetic modelling indeed suggests a pathway where subunits move independently, the desensitization of two subunits being required to occlude the pore. Our work thus hints towards a very diverse and labile conformational landscape during desensitization, with potential implications in physiology and pharmacology.
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Affiliation(s)
- Marc Gielen
- Channel Receptors Unit, Institut Pasteur, CNRS UMR 3571, 25 rue du Docteur Roux, 75015, Paris, France.
- Sorbonne Université, 21 rue de l'École de Médecine, 75006, Paris, France.
| | - Nathalie Barilone
- Channel Receptors Unit, Institut Pasteur, CNRS UMR 3571, 25 rue du Docteur Roux, 75015, Paris, France
| | - Pierre-Jean Corringer
- Channel Receptors Unit, Institut Pasteur, CNRS UMR 3571, 25 rue du Docteur Roux, 75015, Paris, France
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42
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Grau-Bové X, Tomlinson S, O’Reilly AO, Harding NJ, Miles A, Kwiatkowski D, Donnelly MJ, Weetman D. Evolution of the Insecticide Target Rdl in African Anopheles Is Driven by Interspecific and Interkaryotypic Introgression. Mol Biol Evol 2020; 37:2900-2917. [PMID: 32449755 PMCID: PMC7530614 DOI: 10.1093/molbev/msaa128] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The evolution of insecticide resistance mechanisms in natural populations of Anopheles malaria vectors is a major public health concern across Africa. Using genome sequence data, we study the evolution of resistance mutations in the resistance to dieldrin locus (Rdl), a GABA receptor targeted by several insecticides, but most notably by the long-discontinued cyclodiene, dieldrin. The two Rdl resistance mutations (296G and 296S) spread across West and Central African Anopheles via two independent hard selective sweeps that included likely compensatory nearby mutations, and were followed by a rare combination of introgression across species (from A. gambiae and A. arabiensis to A. coluzzii) and across nonconcordant karyotypes of the 2La chromosomal inversion. Rdl resistance evolved in the 1950s as the first known adaptation to a large-scale insecticide-based intervention, but the evolutionary lessons from this system highlight contemporary and future dangers for management strategies designed to combat development of resistance in malaria vectors.
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Affiliation(s)
- Xavier Grau-Bové
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Sean Tomlinson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Centre for Health Informatics, Computing and Statistics, Lancaster University, Lancaster, United Kingdom
| | - Andrias O O’Reilly
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Nicholas J Harding
- Big Data Institute, University of Oxford, Li Ka Shing Centre for Health Information and Discovery, Oxford, United Kingdom
| | - Alistair Miles
- Big Data Institute, University of Oxford, Li Ka Shing Centre for Health Information and Discovery, Oxford, United Kingdom
- Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Dominic Kwiatkowski
- Big Data Institute, University of Oxford, Li Ka Shing Centre for Health Information and Discovery, Oxford, United Kingdom
- Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Martin J Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Wellcome Sanger Institute, Hinxton, United Kingdom
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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43
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Kim JJ, Gharpure A, Teng J, Zhuang Y, Howard RJ, Zhu S, Noviello CM, Walsh RM, Lindahl E, Hibbs RE. Shared structural mechanisms of general anaesthetics and benzodiazepines. Nature 2020; 585:303-308. [PMID: 32879488 PMCID: PMC7486282 DOI: 10.1038/s41586-020-2654-5] [Citation(s) in RCA: 164] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/01/2020] [Indexed: 01/17/2023]
Abstract
Most general anaesthetics and classical benzodiazepine drugs act through positive modulation of γ-aminobutyric acid type A (GABAA) receptors to dampen neuronal activity in the brain1-5. However, direct structural information on the mechanisms of general anaesthetics at their physiological receptor sites is lacking. Here we present cryo-electron microscopy structures of GABAA receptors bound to intravenous anaesthetics, benzodiazepines and inhibitory modulators. These structures were solved in a lipidic environment and are complemented by electrophysiology and molecular dynamics simulations. Structures of GABAA receptors in complex with the anaesthetics phenobarbital, etomidate and propofol reveal both distinct and common transmembrane binding sites, which are shared in part by the benzodiazepine drug diazepam. Structures in which GABAA receptors are bound by benzodiazepine-site ligands identify an additional membrane binding site for diazepam and suggest an allosteric mechanism for anaesthetic reversal by flumazenil. This study provides a foundation for understanding how pharmacologically diverse and clinically essential drugs act through overlapping and distinct mechanisms to potentiate inhibitory signalling in the brain.
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Affiliation(s)
- Jeong Joo Kim
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Anant Gharpure
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jinfeng Teng
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yuxuan Zhuang
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Rebecca J Howard
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Shaotong Zhu
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Colleen M Noviello
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Richard M Walsh
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
- Department of Applied Physics, Swedish e-Science Research Center, KTH Royal Institute of Technology, Solna, Sweden
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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44
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Thompson MJ, Baenziger JE. Structural basis for the modulation of pentameric ligand-gated ion channel function by lipids. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183304. [DOI: 10.1016/j.bbamem.2020.183304] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 03/20/2020] [Accepted: 04/05/2020] [Indexed: 10/24/2022]
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45
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Mechanisms of activation and desensitization of full-length glycine receptor in lipid nanodiscs. Nat Commun 2020; 11:3752. [PMID: 32719334 PMCID: PMC7385131 DOI: 10.1038/s41467-020-17364-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 06/25/2020] [Indexed: 12/31/2022] Open
Abstract
Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Glycine receptors (GlyRs) are key players in mediating fast inhibitory neurotransmission at these synapses. While previous high-resolution structures have provided insights into the molecular architecture of GlyR, several mechanistic questions pertaining to channel function are still unanswered. Here, we present Cryo-EM structures of the full-length GlyR protein complex reconstituted into lipid nanodiscs that are captured in the unliganded (closed), glycine-bound (open and desensitized), and allosteric modulator-bound conformations. A comparison of these states reveals global conformational changes underlying GlyR channel gating and modulation. The functional state assignments were validated by molecular dynamics simulations, and the observed permeation events are in agreement with the anion selectivity and conductance of GlyR. These studies provide the structural basis for gating, ion selectivity, and single-channel conductance properties of GlyR in a lipid environment. Glycinergic synapses play a central role in motor control and pain processing in the central nervous system. Here, authors present cryo-EM structures of the full-length glycine receptors (GlyRs) reconstituted into lipid nanodiscs in the unliganded, glycine-bound and allosteric modulator-bound conformations and reveal global conformational changes underlying GlyR channel gating and modulation.
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Olander ER, Janzen D, Villmann C, Jensen AA. Comparison of biophysical properties of α1β2 and α3β2 GABAA receptors in whole-cell patch-clamp electrophysiological recordings. PLoS One 2020; 15:e0234080. [PMID: 32479525 PMCID: PMC7263626 DOI: 10.1371/journal.pone.0234080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 05/18/2020] [Indexed: 12/28/2022] Open
Abstract
In the present study we have characterized the biophysical properties of wild-type (WT) α1β2 and α3β2 GABAA receptors and probed the molecular basis for the observed differences. The activation and desensitization behavior and the residual currents of the receptors expressed in HEK293 cells were determined in whole-cell patch clamp recordings. Kinetic parameters of α1β2 and α3β2 activation differed significantly, with α1β2 and α3β2 exhibiting rise times (10–90%) of 24 ± 2 ms and 51 ± 7 ms, respectively. In contrast, the two receptors exhibited largely comparable desensitization behavior with decay currents that could be fitted to exponential functions with two or three components. Most notably, the two receptor compositions displayed different degrees of desentization, with the residual currents of α1β2 and α3β2 constituting 34 ± 2% and 21 ± 2% of the peak current, respectively. The respective contributions of the extracellular domains and the transmembrane/intracellular domains of the α-subunit to these physiological profiles were next assessed in recordings from cells expressing αβ2 receptors comprising chimeric α-subunits. The rise times displayed by α1ECD/α3TMDβ2 and α3ECD/α1TMDβ2 receptors were intermediate to those of WT α1β2 and WT α3β2, and the distribution of the different components of the current decays exhibited by the two chimeric receptors followed the same pattern as the two WT receptors. The residual current exhibited by α1ECD/α3TMDβ2 (23 ± 3%) was similar to that of α3β2 but significantly different from that of α1β2, whereas the residual current displayed by α3ECD/α1TMDβ2 (27 ± 2%) was intermediate to and did not differ significantly from either of the WT receptors. This points to molecular differences in the transmembrane/intracellular domains of the α-subunit as the main determinants of the observed differences in receptor physiology between α1β2 and α3β2 receptors.
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Affiliation(s)
- Emma Rie Olander
- Institute for Clinical Neurobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Dieter Janzen
- Institute for Clinical Neurobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Carmen Villmann
- Institute for Clinical Neurobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
- * E-mail: (CV); (AAJ)
| | - Anders A. Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail: (CV); (AAJ)
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Chemogenetics a robust approach to pharmacology and gene therapy. Biochem Pharmacol 2020; 175:113889. [DOI: 10.1016/j.bcp.2020.113889] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 02/26/2020] [Indexed: 12/20/2022]
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Sanchis-Juan A, Hasenahuer MA, Baker JA, McTague A, Barwick K, Kurian MA, Duarte ST, Carss KJ, Thornton J, Raymond FL. Structural analysis of pathogenic missense mutations in GABRA2 and identification of a novel de novo variant in the desensitization gate. Mol Genet Genomic Med 2020; 8:e1106. [PMID: 32347641 PMCID: PMC7336760 DOI: 10.1002/mgg3.1106] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/29/2019] [Accepted: 12/10/2019] [Indexed: 12/19/2022] Open
Abstract
Background Cys‐loop receptors control neuronal excitability in the brain and their dysfunction results in numerous neurological disorders. Recently, six missense variants in GABRA2, a member of this family, have been associated with early infantile epileptic encephalopathy (EIEE). We identified a novel de novo missense variant in GABRA2 in a patient with EIEE and performed protein structural analysis of the seven variants. Methods The novel variant was identified by trio whole‐genome sequencing. We performed protein structural analysis of the seven variants, and compared them to previously reported pathogenic mutations at equivalent positions in other Cys‐loop receptors. Additionally, we studied the distribution of disease‐associated variants in the transmembrane helices of these proteins. Results The seven variants are in the transmembrane domain, either close to the desensitization gate, the activation gate, or in inter‐subunit interfaces. Six of them have pathogenic mutations at equivalent positions in other Cys‐loop receptors, emphasizing the importance of these residues. Also, pathogenic mutations are more common in the pore‐lining helix, consistent with this region being highly constrained for variation in control populations. Conclusion Our study reports a novel pathogenic variant in GABRA2, characterizes the regions where pathogenic mutations are in the transmembrane helices, and underscores the value of considering sequence, evolutionary, and structural information as a strategy for variant interpretation of novel missense mutations.
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Affiliation(s)
- Alba Sanchis-Juan
- Department of Haematology, University of Cambridge, NHS Blood and Transplant Centre, Cambridge, UK.,NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK
| | - Marcia A Hasenahuer
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK.,Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - James A Baker
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Amy McTague
- Developmental Neurosciences, Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Katy Barwick
- Developmental Neurosciences, Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Manju A Kurian
- Developmental Neurosciences, Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Sofia T Duarte
- Hospital Dona Estefânia, Centro Hospitalar de Lisboa Central, Lisbon, Portugal
| | | | - Keren J Carss
- Department of Haematology, University of Cambridge, NHS Blood and Transplant Centre, Cambridge, UK.,NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK
| | - Janet Thornton
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - F Lucy Raymond
- NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK.,Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
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Rahman MM, Teng J, Worrell BT, Noviello CM, Lee M, Karlin A, Stowell MHB, Hibbs RE. Structure of the Native Muscle-type Nicotinic Receptor and Inhibition by Snake Venom Toxins. Neuron 2020; 106:952-962.e5. [PMID: 32275860 DOI: 10.1016/j.neuron.2020.03.012] [Citation(s) in RCA: 121] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 01/13/2020] [Accepted: 03/15/2020] [Indexed: 12/28/2022]
Abstract
The nicotinic acetylcholine receptor, a pentameric ligand-gated ion channel, converts the free energy of binding of the neurotransmitter acetylcholine into opening of its central pore. Here we present the first high-resolution structure of the receptor type found in muscle-endplate membrane and in the muscle-derived electric tissues of fish. The native receptor was purified from Torpedo electric tissue and functionally reconstituted in lipids optimal for cryo-electron microscopy. The receptor was stabilized in a closed state by the binding of α-bungarotoxin. The structure reveals the binding of a toxin molecule at each of two subunit interfaces in a manner that would block the binding of acetylcholine. It also reveals a closed gate in the ion-conducting pore, formed by hydrophobic amino acid side chains, located ∼60 Å from the toxin binding sites. The structure provides a framework for understanding gating in ligand-gated channels and how mutations in the acetylcholine receptor cause congenital myasthenic syndromes.
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Affiliation(s)
- Md Mahfuzur Rahman
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jinfeng Teng
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Brady T Worrell
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Colleen M Noviello
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Myeongseon Lee
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA
| | - Arthur Karlin
- Center for Molecular Recognition & Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Michael H B Stowell
- Department of Molecular, Cellular & Developmental Biology, University of Colorado, Boulder, CO 80309, USA.
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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Bukanova JV, Solntseva EI, Kudova E. Neurosteroids as Selective Inhibitors of Glycine Receptor Activity: Structure-Activity Relationship Study on Endogenous Androstanes and Androstenes. Front Mol Neurosci 2020; 13:44. [PMID: 32265652 PMCID: PMC7098970 DOI: 10.3389/fnmol.2020.00044] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/04/2020] [Indexed: 12/21/2022] Open
Abstract
The ability of androstane and androstene neurosteroids with modifications at C-17, C-5, and C-3 (compounds 1-9) to influence the functional activity of inhibitory glycine and γ-aminobutyric acid (GABA) receptors was estimated. The glycine- and GABA-induced chloride current (IGly and IGABA) were measured in isolated pyramidal neurons of the rat hippocampus and isolated rat cerebellar Purkinje cells, correspondingly, using the patch-clamp technique. Our results demonstrate that all the nine neurosteroids display similar biological activity, namely, they strongly inhibited IGly and weakly inhibited IGABA. The threshold concentration of neurosteroids inducing effects on IGly was 0.1 μM, and for effects on IGABA was 10–50 μM. Moreover, our compounds accelerated desensitization of the IGly with the IC50 values varying from 0.12 to 0.49 μM and decreased the peak amplitude with IC50 values varying from 16 to 22 μM. Interestingly, our study revealed that only compounds 4 (epiandrosterone) and 8 (dehydroepiandrosterone) were able to cause a significant change in IGABA in 10 μM concentration. Moreover, compounds 3 (testosterone), 5 (epitestosterone), 6 (dihydroandrostenedione), and 9 (etiocholanedione) did not modulate IGABA up to the concentration of 50 μM. Thus, we conclude that compounds 3, 5, 6, and 9 may be identified as selective modulators of IGly. Our results offer new avenues of investigation in the field of drug-like selective modulators of IGly.
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Affiliation(s)
| | | | - Eva Kudova
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czechia
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