1
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Michálek O, King GF, Pekár S. Prey specificity of predatory venoms. Biol Rev Camb Philos Soc 2024. [PMID: 38991997 DOI: 10.1111/brv.13120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Revised: 07/01/2024] [Accepted: 07/03/2024] [Indexed: 07/13/2024]
Abstract
Venom represents a key adaptation of many venomous predators, allowing them to immobilise prey quickly through chemical rather than physical warfare. Evolutionary arms races between prey and a predator are believed to be the main factor influencing the potency and composition of predatory venoms. Predators with narrowly restricted diets are expected to evolve specifically potent venom towards their focal prey, with lower efficacy on alternative prey. Here, we evaluate hypotheses on the evolution of prey-specific venom, focusing on the effect of restricted diet, prey defences, and prey resistance. Prey specificity as a potential evolutionary dead end is also discussed. We then provide an overview of the current knowledge on venom prey specificity, with emphasis on snakes, cone snails, and spiders. As the current evidence for venom prey specificity is still quite limited, we also overview the best approaches and methods for its investigation and provide a brief summary of potential model groups. Finally, possible applications of prey-specific toxins are discussed.
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Affiliation(s)
- Ondřej Michálek
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, Brno, 611 37, Czech Republic
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St. Lucia, Queensland, 4072, Australia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Queensland, St. Lucia, Queensland, 4072, Australia
| | - Stano Pekár
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, Brno, 611 37, Czech Republic
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2
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Munaron L, Chinigò G, Scarpellino G, Ruffinatti FA. The fallacy of functional nomenclature in the kingdom of biological multifunctionality: physiological and evolutionary considerations on ion channels. J Physiol 2024; 602:2367-2381. [PMID: 37635695 DOI: 10.1113/jp284422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
Living organisms are multiscale complex systems that have evolved high degrees of multifunctionality and redundancy in the structure-function relationship. A number of factors, only in part determined genetically, affect the jobs of proteins. The overall structural organization confers unique molecular properties that provide the potential to perform a pattern of activities, some of which are co-opted by specific environments. The variety of multifunctional proteins is expanding, but most cases are handled individually and according to the still dominant 'one structure-one function' approach, which relies on the attribution of canonical names typically referring to the first task identified for a given protein. The present topical review focuses on the multifunctionality of ion channels as a paradigmatic example. Mounting evidence reports the ability of many ion channels (including members of voltage-dependent, ligand-gated and transient receptor potential families) to exert biological effects independently of their ion conductivity. 'Functionally based' nomenclature (the practice of naming a protein or family of proteins based on a single purpose) is a conceptual bias for three main reasons: (i) it increases the amount of ambiguity, deceiving our understanding of the multiple contributions of biomolecules that is the heart of the complexity; (ii) it is in stark contrast to protein evolution dynamics, largely based on multidomain arrangement; and (iii) it overlooks the crucial role played by the microenvironment in adjusting the actions of cell structures and in tuning protein isoform diversity to accomplish adaptational requirements. Biological information in protein physiology is distributed among different entwined layers working as the primary 'locus' of natural selection and of evolutionary constraints.
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Affiliation(s)
- Luca Munaron
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
| | - Giorgia Chinigò
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
| | - Giorgia Scarpellino
- Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy
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3
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Ahmad M, Johnson TG, Flerin M, Duarte F, Langton MJ. Responsive Anionophores with AND Logic Multi-Stimuli Activation. Angew Chem Int Ed Engl 2024; 63:e202403314. [PMID: 38517056 DOI: 10.1002/anie.202403314] [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: 02/16/2024] [Revised: 03/19/2024] [Accepted: 03/21/2024] [Indexed: 03/23/2024]
Abstract
Artificial ion transport systems have emerged as an important class of compounds that promise applications in chemotherapeutics as anticancer agents or to treat channelopathies. Stimulus-responsive systems that offer spatiotemporally controlled activity for targeted applications remain rare. Here we utilize dynamic hydrogen bonding interactions of a 4,6-dihydroxy-isophthalamide core to generate a modular platform enabling access to stimuli-responsive ion transporters that can be activated in response to a wide variety of external stimuli, including light, redox, and enzymes, with excellent OFF-ON activation profiles. Alkylation of the two free hydroxyl groups with stimulus-responsive moieties locks the amide bonds through intramolecular hydrogen bonding and hence makes them unavailable for anion binding and transport. Triggering using a particular stimulus to cleave both cages reverses the hydrogen bonding arrangement, to generate a highly preorganized anion binding cavity for efficient transmembrane transport. Integration of two cages that are responsive to orthogonal stimuli enables multi-stimuli activation, where both stimuli are required to trigger transport in an AND logic process. Importantly, the strategy provides a facile method to post-functionalize the highly active transporter core with a variety of stimulus-responsive moieties for targeted activation with multiple triggers.
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Affiliation(s)
- Manzoor Ahmad
- Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Toby G Johnson
- Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Martin Flerin
- Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Fernanda Duarte
- Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
| | - Matthew J Langton
- Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, UK
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4
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Pagán OR. The complexities of ligand/receptor interactions: Exploring the role of molecular vibrations and quantum tunnelling. Bioessays 2024; 46:e2300195. [PMID: 38459808 DOI: 10.1002/bies.202300195] [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: 10/20/2023] [Revised: 01/19/2024] [Accepted: 02/19/2024] [Indexed: 03/10/2024]
Abstract
Molecular vibrations and quantum tunneling may link ligand binding to the function of pharmacological receptors. The well-established lock-and-key model explains a ligand's binding and recognition by a receptor; however, a general mechanism by which receptors translate binding into activation, inactivation, or modulation remains elusive. The Vibration Theory of Olfaction was proposed in the 1930s to explain this subset of receptor-mediated phenomena by correlating odorant molecular vibrations to smell, but a mechanism was lacking. In the 1990s, inelastic electron tunneling was proposed as a plausible mechanism for translating molecular vibration to odorant physiology. More recently, studies of ligands' vibrational spectra and the use of deuterated ligand analogs have provided helpful information to study this admittedly controversial hypothesis in metabotropic receptors other than olfactory receptors. In the present work, based in part on published experiments from our laboratory using planarians as an experimental organism, I will present a rationale and possible experimental approach for extending this idea to ligand-gated ion channels.
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Affiliation(s)
- Oné R Pagán
- Department of Biology, West Chester University, West Chester, Pennsylvania, USA
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5
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Murphy EA, Kleiner FH, Helliwell KE, Wheeler GL. Channels of Evolution: Unveiling Evolutionary Patterns in Diatom Ca 2+ Signalling. PLANTS (BASEL, SWITZERLAND) 2024; 13:1207. [PMID: 38732422 PMCID: PMC11085791 DOI: 10.3390/plants13091207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/09/2024] [Accepted: 04/15/2024] [Indexed: 05/13/2024]
Abstract
Diatoms are important primary producers in marine and freshwater environments, but little is known about the signalling mechanisms they use to detect changes in their environment. All eukaryotic organisms use Ca2+ signalling to perceive and respond to environmental stimuli, employing a range of Ca2+-permeable ion channels to facilitate the movement of Ca2+ across cellular membranes. We investigated the distribution of different families of Ca2+ channels in diatom genomes, with comparison to other members of the stramenopile lineage. The four-domain voltage-gated Ca2+ channels (Cav) are present in some centric diatoms but almost completely absent in pennate diatoms, whereas single-domain voltage-gated EukCatA channels were found in all diatoms. Glutamate receptors (GLRs) and pentameric ligand-gated ion channels (pLGICs) also appear to have been lost in several pennate species. Transient receptor potential (TRP) channels are present in all diatoms, but have not undergone the significant expansion seen in brown algae. All diatom species analysed lacked the mitochondrial uniporter (MCU), a highly conserved channel type found in many eukaryotes, including several stramenopile lineages. These results highlight the unique Ca2+-signalling toolkit of diatoms and indicate that evolutionary gains or losses of different Ca2+ channels may contribute to differences in cellular-signalling mechanisms between species.
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Affiliation(s)
- Eleanor A. Murphy
- Marine Biological Association, Plymouth PL1 2PB, UK (K.E.H.)
- School of Biological Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | | | - Katherine E. Helliwell
- Marine Biological Association, Plymouth PL1 2PB, UK (K.E.H.)
- Department of Biosciences, University of Exeter, Exeter EX4 4QD, UK
| | - Glen L. Wheeler
- Marine Biological Association, Plymouth PL1 2PB, UK (K.E.H.)
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6
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Sandberg JW, Santiago-McRae E, Ennis J, Brannigan G. The density-threshold affinity: Calculating lipid binding affinities from unbiased coarse-grained molecular dynamics simulations. Methods Enzymol 2024; 701:47-82. [PMID: 39025580 DOI: 10.1016/bs.mie.2024.03.008] [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] [Indexed: 07/20/2024]
Abstract
Many membrane proteins are sensitive to their local lipid environment. As structural methods for membrane proteins have improved, there is growing evidence of direct, specific binding of lipids to protein surfaces. Unfortunately the workhorse of understanding protein-small molecule interactions, the binding affinity for a given site, is experimentally inaccessible for these systems. Coarse-grained molecular dynamics simulations can be used to bridge this gap, and are relatively straightforward to learn. Such simulations allow users to observe spontaneous binding of lipids to membrane proteins and quantify localized densities of individual lipids or lipid fragments. In this chapter we outline a protocol for extracting binding affinities from these localized distributions, known as the "density threshold affinity." The density threshold affinity uses an adaptive and flexible definition of site occupancy that alleviates the need to distinguish between "bound'' lipids and bulk lipids that are simply diffusing through the site. Furthermore, the method allows "bead-level" resolution that is suitable for the case where lipids share binding sites, and circumvents ambiguities about a relevant reference state. This approach provides a convenient and straightforward method for comparing affinities of a single lipid species for multiple sites, multiple lipids for a single site, and/or a single lipid species modeled using multiple forcefields.
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Affiliation(s)
- Jesse W Sandberg
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Ezry Santiago-McRae
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Jahmal Ennis
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, United States; Department of Physics, Rutgers University, Camden, NJ, United States.
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7
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Van Renterghem C, Nemecz Á, Medjebeur K, Corringer P. Short-chain mono-carboxylates as negative modulators of allosteric transitions in Gloeobacter violaceus ligand-gated ion channel, and impact of a pre-β5 strand (Loop Ω) double mutation on crotonate, not butyrate effect. Physiol Rep 2024; 12:e15916. [PMID: 38343277 PMCID: PMC10859675 DOI: 10.14814/phy2.15916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 12/24/2023] [Accepted: 01/03/2024] [Indexed: 02/15/2024] Open
Abstract
Using the bacterial proton-activated pentameric receptor-channel Gloeobacter violaceus ligand-gated ion channel (GLIC): (1) We characterize saturated, mono-carboxylates as negative modulators of GLIC (as previously shown for crotonate; Alqazzaz et al., Biochemistry, 2016, 55, 5947). Butyrate and crotonate have indistinguishable properties regarding negative modulation of wt GLIC. (2) We identify a locus in the pre-β5 strand (Loop Ω) whose mutation inverses the effect of the mono-carboxylate crotonate from negative to positive modulation of the allosteric transitions, suggesting an involvement of the pre-β5 strand in coupling the extracellular orthotopic receptor to pore gating. (3) As an extension to the previously proposed "in series" mechanism, we suggest that a orthotopic/orthosteric site-vestibular site-Loop Ω-β5-β6 "sandwich"-Pro-Loop/Cys-Loop series may be an essential component of orthotopic/orthosteric compound-elicited gating control in this pentameric ligand-gated ion channel, on top of which compounds targeting the vestibular site may provide modulation.
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Affiliation(s)
| | - Ákos Nemecz
- Channel‐Receptors Unit, Institut Pasteur, CNRS UMR3571Université Paris CitéParisFrance
| | - Karima Medjebeur
- Channel‐Receptors Unit, Institut Pasteur, CNRS UMR3571Université Paris CitéParisFrance
| | - Pierre‐Jean Corringer
- Channel‐Receptors Unit, Institut Pasteur, CNRS UMR3571Université Paris CitéParisFrance
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8
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Pitman C, Santiago-McRae E, Lohia R, Bassi K, Joseph TT, Hansen MEB, Brannigan G. The blobulator: a webtool for identification and visual exploration of hydrophobic modularity in protein sequences. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.15.575761. [PMID: 38293114 PMCID: PMC10827107 DOI: 10.1101/2024.01.15.575761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Motivation Clusters of hydrophobic residues are known to promote structured protein stability and drive protein aggregation. Recent work has shown that identifying contiguous hydrophobic residue clusters (termed "blobs") has proven useful in both intrinsically disordered protein (IDP) simulation and human genome studies. However, a graphical interface was unavailable. Results Here, we present the blobulator: an interactive and intuitive web interface to detect intrinsic modularity in any protein sequence based on hydrophobicity. We demonstrate three use cases of the blobulator and show how identifying blobs with biologically relevant parameters provides useful information about a globular protein, two orthologous membrane proteins, and an IDP. Other potential applications are discussed, including: predicting protein segments with critical roles in tertiary interactions, providing a definition of local order and disorder with clear edges, and aiding in predicting protein features from sequence. Availability The blobulator GUI can be found at www.blobulator.branniganlab.org, and the source code with pip installable command line tool can be found on GitHub at www.GitHub.com/BranniganLab/blobulator.
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Affiliation(s)
- Connor Pitman
- Center for Computational and Integrative Biology, Rutgers University-Camden, 201 Broadway, 08103, NJ, USA
| | - Ezry Santiago-McRae
- Center for Computational and Integrative Biology, Rutgers University-Camden, 201 Broadway, 08103, NJ, USA
| | - Ruchi Lohia
- Department of Physiology, University of Toronto, 1 King's College Circle, M5S 1A8, Toronto, Ontario, Canada
| | - Kaitlin Bassi
- Center for Computational and Integrative Biology, Rutgers University-Camden, 201 Broadway, 08103, NJ, USA
| | - Thomas T Joseph
- Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, JMB 305, 3620 Hamilton Walk, 19104, PA, USA
| | - Matthew E B Hansen
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Blvd, 19104, PA, USA
| | - Grace Brannigan
- Center for Computational and Integrative Biology, Rutgers University-Camden, 201 Broadway, 08103, NJ, USA
- Department of Physics, Rutgers University-Camden, 201 Broadway, 08103, NJ, USA
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9
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Menzikov SA, Zaichenko DM, Moskovtsev AA, Morozov SG, Kubatiev AA. Phenols and GABA A receptors: from structure and molecular mechanisms action to neuropsychiatric sequelae. Front Pharmacol 2024; 15:1272534. [PMID: 38303988 PMCID: PMC10831359 DOI: 10.3389/fphar.2024.1272534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 01/03/2024] [Indexed: 02/03/2024] Open
Abstract
γ-Aminobutyric acid type A receptors (GABAARs) are members of the pentameric ligand-gated ion channel (pLGIC) family, which are widespread throughout the invertebrate and vertebrate central nervous system. GABAARs are engaged in short-term changes of the neuronal concentrations of chloride (Cl-) and bicarbonate (HCO3 -) ions by their passive permeability through the ion channel pore. GABAARs are regulated by various structurally diverse phenolic substances ranging from simple phenols to complex polyphenols. The wide chemical and structural variability of phenols suggest similar and different binding sites on GABAARs, allowing them to manifest themselves as activators, inhibitors, or allosteric ligands of GABAAR function. Interest in phenols is associated with their great potential for GABAAR modulation, but also with their subsequent negative or positive role in neurological and psychiatric disorders. This review focuses on the GABAergic deficit hypotheses during neurological and psychiatric disorders induced by various phenols. We summarize the structure-activity relationship of general phenol groups concerning their differential roles in the manifestation of neuropsychiatric symptoms. We describe and analyze the role of GABAAR subunits in manifesting various neuropathologies and the molecular mechanisms underlying their modulation by phenols. Finally, we discuss how phenol drugs can modulate GABAAR activity via desensitization and resensitization. We also demonstrate a novel pharmacological approach to treat neuropsychiatric disorders via regulation of receptor phosphorylation/dephosphorylation.
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10
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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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11
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Bampali K, Koniuszewski F, Vogel FD, Fabjan J, Andronis C, Lekka E, Virvillis V, Seidel T, Delaunois A, Royer L, Rolf MG, Giuliano C, Traebert M, Roussignol G, Fric-Bordat M, Mazelin-Winum L, Bryant SD, Langer T, Ernst M. GABA A receptor-mediated seizure liabilities: a mixed-methods screening approach. Cell Biol Toxicol 2023; 39:2793-2819. [PMID: 37093397 PMCID: PMC10693519 DOI: 10.1007/s10565-023-09803-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: 12/08/2022] [Accepted: 03/09/2023] [Indexed: 04/25/2023]
Abstract
GABAA receptors, members of the pentameric ligand-gated ion channel superfamily, are widely expressed in the central nervous system and mediate a broad range of pharmaco-toxicological effects including bidirectional changes to seizure threshold. Thus, detection of GABAA receptor-mediated seizure liabilities is a big, partly unmet need in early preclinical drug development. This is in part due to the plethora of allosteric binding sites that are present on different subtypes of GABAA receptors and the critical lack of screening methods that detect interactions with any of these sites. To improve in silico screening methods, we assembled an inventory of allosteric binding sites based on structural data. Pharmacophore models representing several of the binding sites were constructed. These models from the NeuroDeRisk IL Profiler were used for in silico screening of a compiled collection of drugs with known GABAA receptor interactions to generate testable hypotheses. Amoxapine was one of the hits identified and subjected to an array of in vitro assays to examine molecular and cellular effects on neuronal excitability and in vivo locomotor pattern changes in zebrafish larvae. An additional level of analysis for our compound collection is provided by pharmacovigilance alerts using FAERS data. Inspired by the Adverse Outcome Pathway framework, we postulate several candidate pathways leading from specific binding sites to acute seizure induction. The whole workflow can be utilized for any compound collection and should inform about GABAA receptor-mediated seizure risks more comprehensively compared to standard displacement screens, as it rests chiefly on functional data.
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Affiliation(s)
- Konstantina Bampali
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090, Vienna, Austria
| | - Filip Koniuszewski
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090, Vienna, Austria
| | - Florian D Vogel
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090, Vienna, Austria
| | - Jure Fabjan
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090, Vienna, Austria
| | | | | | | | - Thomas Seidel
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090, Vienna, Austria
| | - Annie Delaunois
- UCB Biopharma SRL, Chemin du Foriest, Braine-L'Alleud, Belgium
| | - Leandro Royer
- UCB Biopharma SRL, Chemin du Foriest, Braine-L'Alleud, Belgium
| | - Michael G Rolf
- R&D Biopharmaceuticals, Astra Zeneca, Pepparedsleden 1, 431 83, Mölndal, Sweden
| | - Chiara Giuliano
- R&D Biopharmaceuticals, Astra Zeneca, Fleming Building (B623), Babraham Research Park, Babraham, Cambridgeshire, CB22 3AT, UK
| | - Martin Traebert
- Novartis Institutes for Biomedical Research, Fabrikstrasse 2, CH-4056, Basel, Switzerland
| | | | | | | | - Sharon D Bryant
- Inte:Ligand GmbH, Mariahilferstrasse 74B/11, 1070, Vienna, Austria
| | - Thierry Langer
- Department of Pharmaceutical Sciences, Division of Pharmaceutical Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090, Vienna, Austria
| | - Margot Ernst
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090, Vienna, Austria.
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12
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Vallés AS, Barrantes FJ. Nicotinic Acetylcholine Receptor Dysfunction in Addiction and in Some Neurodegenerative and Neuropsychiatric Diseases. Cells 2023; 12:2051. [PMID: 37626860 PMCID: PMC10453526 DOI: 10.3390/cells12162051] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 07/20/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
The cholinergic system plays an essential role in brain development, physiology, and pathophysiology. Herein, we review how specific alterations in this system, through genetic mutations or abnormal receptor function, can lead to aberrant neural circuitry that triggers disease. The review focuses on the nicotinic acetylcholine receptor (nAChR) and its role in addiction and in neurodegenerative and neuropsychiatric diseases and epilepsy. Cholinergic dysfunction is associated with inflammatory processes mainly through the involvement of α7 nAChRs expressed in brain and in peripheral immune cells. Evidence suggests that these neuroinflammatory processes trigger and aggravate pathological states. We discuss the preclinical evidence demonstrating the therapeutic potential of nAChR ligands in Alzheimer disease, Parkinson disease, schizophrenia spectrum disorders, and in autosomal dominant sleep-related hypermotor epilepsy. PubMed and Google Scholar bibliographic databases were searched with the keywords indicated below.
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Affiliation(s)
- Ana Sofía Vallés
- Bahía Blanca Institute of Biochemical Research (UNS-CONICET), Bahía Blanca 8000, Argentina;
| | - Francisco J. Barrantes
- Biomedical Research Institute (BIOMED), Faculty of Medical Sciences, Pontifical Catholic University of Argentina—National Scientific and Technical Research Council, Av. Alicia Moreau de Justo 1600, Buenos Aires C1107AFF, Argentina
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13
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Hernando G, Turani O, Rodriguez Araujo N, Bouzat C. The diverse family of Cys-loop receptors in Caenorhabditis elegans: insights from electrophysiological studies. Biophys Rev 2023; 15:733-750. [PMID: 37681094 PMCID: PMC10480131 DOI: 10.1007/s12551-023-01080-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 06/18/2023] [Indexed: 09/09/2023] Open
Abstract
Cys-loop receptors integrate a large family of pentameric ligand-gated ion channels that mediate fast ionotropic responses in vertebrates and invertebrates. Their vital role in converting neurotransmitter recognition into an electrical impulse makes these receptors essential for a great variety of physiological processes. In vertebrates, the Cys-loop receptor family includes the cation-selective channels, nicotinic acetylcholine and 5-hydroxytryptamine type 3 receptors, and the anion-selective channels, GABAA and glycine receptors, whereas in invertebrates, the repertoire is significantly larger. The free-living nematode Caenorhabditis elegans has the largest known Cys-loop receptor family as well as unique receptors that are absent in vertebrates and constitute attractive targets for anthelmintic drugs. Given the large number and variety of Cys-loop receptor subunits and the multiple possible ways of subunit assembly, C. elegans offers a large diversity of receptors although only a limited number of them have been characterized to date. C. elegans has emerged as a powerful model for the study of the nervous system and human diseases as well as a model for antiparasitic drug discovery. This nematode has also shown promise in the pharmaceutical industry search for new therapeutic compounds. C. elegans is therefore a powerful model organism to explore the biology and pharmacology of Cys-loop receptors and their potential as targets for novel therapeutic interventions. In this review, we provide a comprehensive overview of what is known about the function of C. elegans Cys-loop receptors from an electrophysiological perspective.
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Affiliation(s)
- Guillermina Hernando
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina
| | - Ornella Turani
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina
| | - Noelia Rodriguez Araujo
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina
| | - Cecilia Bouzat
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga Km 7, 8000 Bahía Blanca, Argentina
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14
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Papke RL, Quadri M, Gulsevin A. Silent agonists for α7 nicotinic acetylcholine receptors. Pharmacol Res 2023; 190:106736. [PMID: 36940890 DOI: 10.1016/j.phrs.2023.106736] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 03/07/2023] [Accepted: 03/14/2023] [Indexed: 03/23/2023]
Abstract
We discuss models for the activation and desensitization of α7 nicotinic acetylcholine receptors (nAChRs) and the effects of efficacious type II positive allosteric modulators (PAMs) that destabilize α7 desensitized states. Type II PAMs such as PNU-120596 can be used to distinguish inactive compounds from silent agonists, compounds that produce little or no channel activation but stabilize the non-conducting conformations associated with desensitization. We discuss the effects of α7 nAChRs in cells of the immune system and their roles in modulating inflammation and pain through what has come to be known as the cholinergic anti-inflammatory system (CAS). Cells controlling CAS do not generate ion channel currents but rather respond to α7 drugs by modulating intracellular signaling pathways analogous to the effects of metabotropic receptors. Metabotropic signaling by α7 receptors appears to be mediated by receptors in nonconducting conformations and can be accomplished by silent agonists. We discuss electrophysiological structure-activity relationships for α7 silent agonists and their use in cell-based and in vivo assays for CAS regulation. We discuss the strongly desensitizing partial agonist GTS-21 and its effectiveness in modulation of CAS. We also review the properties of the silent agonist NS6740, which is remarkably effective at maintaining α7 receptors in PAM-sensitive desensitized states. Most silent agonists bind to sites overlapping those for orthosteric agonists, but some appear to bind to allosteric sites. Finally, we discuss α9⁎ nAChRs and their potential role in CAS, and ligands that will be useful in defining and distinguishing the specific roles of α7 and α9 in CAS.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG).
| | - Marta Quadri
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG)
| | - Alican Gulsevin
- Department of Pharmacology and Therapeutics, University of Florida, PO Box 100267 Gainesville, FL 32610 USA (RLP); Olon S.p.A., Strada Rivoltana, Km 6/7 - 20053 Rodano (MI) - ITALY (MQ); Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA, 37212 (AG)
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15
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Barrantes FJ. Structure and function meet at the nicotinic acetylcholine receptor-lipid interface. Pharmacol Res 2023; 190:106729. [PMID: 36931540 DOI: 10.1016/j.phrs.2023.106729] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 03/08/2023] [Accepted: 03/13/2023] [Indexed: 03/17/2023]
Abstract
The nicotinic acetylcholine receptor (nAChR) is a transmembrane protein that mediates fast intercellular communication in response to the endogenous neurotransmitter acetylcholine. It is the best characterized and archetypal molecule in the superfamily of pentameric ligand-gated ion channels (pLGICs). As a typical transmembrane macromolecule, it interacts extensively with its vicinal lipid microenvironment. Experimental evidence provides a wealth of information on receptor-lipid crosstalk: the nAChR exerts influence on its immediate membrane environment and conversely, the lipid moiety modulates ligand binding, affinity state transitions and gating of ion translocation functions of the receptor protein. Recent cryogenic electron microscopy (cryo-EM) studies have unveiled the occurrence of sites for phospholipids and cholesterol on the lipid-exposed regions of neuronal and electroplax nAChRs, confirming early spectroscopic and affinity labeling studies demonstrating the close contact of lipid molecules with the receptor transmembrane segments. This new data provides structural support to the postulated "lipid sensor" ability displayed by the outer ring of M4 transmembrane domains and their modulatory role on nAChR function, as we postulated a decade ago. Borrowing from the best characterized nAChR, the electroplax (muscle-type) receptor, and exploiting new structural information on the neuronal nAChR, it is now possible to achieve an improved depiction of these sites. In combination with site-directed mutagenesis, single-channel electrophysiology, and molecular dynamics studies, the new structural information delivers a more comprehensive portrayal of these lipid-sensitive loci, providing mechanistic explanations for their ability to modulate nAChR properties and raising the possibility of targetting them in disease.
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Affiliation(s)
- Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Biomedical Research Institute, Faculty of Medical Sciences, Pontifical Catholic University of Argentina (UCA) - Argentine Scientific & Technol. Research Council (CONICET), Av. Alicia Moreau de Justo 1600, C1107AAZ Buenos Aires, Argentina.
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16
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Elgoyhen AB. The α9α10 acetylcholine receptor: a non-neuronal nicotinic receptor. Pharmacol Res 2023; 190:106735. [PMID: 36931539 DOI: 10.1016/j.phrs.2023.106735] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/06/2023] [Accepted: 03/14/2023] [Indexed: 03/17/2023]
Abstract
Within the superfamily of pentameric ligand-gated ion channels, cholinergic nicotinic receptors (nAChRs) were classically identified to mediate synaptic transmission in the nervous system and the neuromuscular junction. The α9 and α10 nAChR subunits were the last ones to be identified. Surprisingly, they do not fall into the dichotomic neuronal/muscle classification of nAChRs. They assemble into heteropentamers with a well-established function as canonical ion channels in inner ear hair cells, where they mediate central nervous system control of auditory and vestibular sensory processing. The present review includes expression, pharmacological, structure-function, molecular evolution and pathophysiological studies, that define receptors composed from α9 and α10 subunits as distant and distinct members within the nAChR family. Thus, although α9 and α10 were initially included within the neuronal subdivision of nAChR subunits, they form a distinct clade within the phylogeny of nAChRs. Following the classification of nAChR subunits based on their main synaptic site of action, α9 and α10 should receive a name in their own right.
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Affiliation(s)
- Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490, Buenos Aires 1428, Argentina.
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17
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Tribiños F, Cuevas P, Cornejo I, Sepúlveda FV, Cid LP. A new family of glutamate-gated chloride channels in parasitic sea louse Caligus rogercresseyi: A subunit refractory to activation by ivermectin is dominant in heteromeric assemblies. PLoS Pathog 2023; 19:e1011188. [PMID: 36917600 PMCID: PMC10038264 DOI: 10.1371/journal.ppat.1011188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 03/24/2023] [Accepted: 02/07/2023] [Indexed: 03/16/2023] Open
Abstract
Sea louse ectoparasitosis is a major threat to fish aquaculture. Avermectins such as ivermectin and emamectin have been effectively used against sea louse infestation, but the emergence of resistance has limited their use. A better understanding of the molecular targets of avermectins is essential to the development of novel treatment strategies or new, more effective drugs. Avermectins are known to act by inhibiting neurotransmission through allosteric activation of glutamate-gated chloride channels (GluCls). We have investigated the GluCl subunit present in Caligus rogercresseyi, a sea louse affecting aquaculture in the Southern hemisphere. We identify four new subunits, CrGluCl-B to CrGluCl-E, and characterise them functionally. CrGluCl-A (previously reported as CrGluClα), CrGluCl-B and CrGluCl-C all function as glutamate channel receptors with different sensitivities to the agonist, but in contrast to subunit -A and -C, CrGluCl-B is not activated by ivermectin but is rather antagonised by the drug. CrGluCl-D channel appears active in the absence of any stimulation by glutamate or ivermectin and CrGluCl-E does not exhibit any activity. Notably, the expression of CrGluCl-B with either -A or -C subunits gives rise to receptors unresponsive to ivermectin and showing altered response to glutamate, suggesting that coexpression has led to the preferential formation of heteromers to which the presence of CrGluCl-B confers the property of ivermectin-activation refractoriness. Furthermore, there was evidence for heteromer formation with novel properties only when coexpressing pairs E/C and D/B CrGluCl subtypes. Site-directed mutagenesis shows that three transmembrane domain residues contribute to the lack of activation by ivermectin, most crucially Gln 15' in M2, with mutation Q15'T (the residue present in ivermectin-activated subunits A and C) conferring ivermectin activation to CrGluCl-B. The differential response to avermectin of these Caligus rogercresseyi GluClsubunits, which are highly conserved in the Northern hemisphere sea louse Lepeophtheirus salmonis, could have an influence on the response of these parasites to treatment with macrocyclic lactones. They could serve as molecular markers to assess susceptibility to existing treatments and might be useful molecular targets in the search for novel antiparasitic drugs.
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Affiliation(s)
| | | | - Isabel Cornejo
- Centro de Estudios Científicos (CECs), Valdivia, Chile
- Facultad de Ciencias para el Cuidado de la Salud, Universidad San Sebastián, Valdivia, Chile
| | - Francisco V Sepúlveda
- Centro de Estudios Científicos (CECs), Valdivia, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile
| | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Valdivia, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Valdivia, Chile
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18
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Phenotypic Profiling of Macrocyclic Lactones on Parasitic Schistosoma Flatworms. Antimicrob Agents Chemother 2023; 67:e0123022. [PMID: 36695583 PMCID: PMC9933704 DOI: 10.1128/aac.01230-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Macrocyclic lactones are front-line therapies for parasitic roundworm infections; however, there are no comprehensive studies on the activity of this drug class against parasitic flatworms. Ivermectin is well known to be inactive against flatworms. However, the structure-activity relationship of macrocyclic lactones may vary across phyla, and it is entirely possible other members of this drug class do in fact show antiparasitic activity on flatworms. For example, there are several reports hinting at the anti-schistosomal activity of doramectin and moxidectin. To explore this class further, we developed an automated imaging assay combined with measurement of lactate levels from worm media. This assay was applied to the screening of 21 macrocyclic lactones (avermectins, milbemycins, and others such as spinosyns) against adult schistosomes. These in vitro assays identified several macrocyclic lactones (emamectin, milbemycin oxime, and the moxidectin metabolite 23-ketonemadectin) that caused contractile paralysis and lack of lactate production. Several of these were also active against miracidia, which infect the snail intermediate host. Hits prioritized from these in vitro assays were administered to mice harboring patent schistosome infections. However, no reduction in worm burden was observed. Nevertheless, these data show the utility of a multiplexed in vitro screening platform to quantitatively assess drug action and exclude inactive compounds from a chemical series before proceeding to in vivo studies. While the prototypical macrocyclic lactone ivermectin displays minimal activity against adult Schistosoma mansoni, this family of compounds does contain schistocidal compounds which may serve as a starting point for development of new anti-flatworm chemotherapies.
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19
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Johnson H, VanHooreweghe M, Satori JA, Chan JD. Schistosomes contain divergent ligand-gated ion channels with an atypical Cys-loop motif. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000694. [PMID: 36713055 PMCID: PMC9874803 DOI: 10.17912/micropub.biology.000694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/01/1970] [Accepted: 12/20/2022] [Indexed: 01/31/2023]
Abstract
Ligand-gated ion channels (LGICs) are important regulators of neuromuscular function, making them attractive antiparasitic drug targets. While roundworm LGICs are targeted by several anthelmintic classes, flatworm LGICs are less studied. Chromosome-level genome assemblies have recently been released for Schistosoma flatworm species that cause the disease schistosomiasis. These have allowed us to comprehensively predict schistosome LGICs, adding to prior annotations. Analysis of LGIC sequences revealed a clade of receptors lacking cysteines at the eponymous Cys-loop region of the channel. Since these atypical channels are divergent from mammalian LGICs, they may be promising targets to treat diseases caused by parasitic flatworms.
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Affiliation(s)
| | | | | | - John D Chan
- University of Wisconsin - Oshkosh, Oshkosh, WI, USA
,
Correspondence to: John D Chan (
)
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20
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Biophysical characterization of calcium-binding and modulatory-domain dynamics in a pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2022; 119:e2210669119. [PMID: 36480474 PMCID: PMC9897478 DOI: 10.1073/pnas.2210669119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) perform electrochemical signal transduction in organisms ranging from bacteria to humans. Among the prokaryotic pLGICs, there is architectural diversity involving N-terminal domains (NTDs) not found in eukaryotic relatives, exemplified by the calcium-sensitive channel (DeCLIC) from a Desulfofustis deltaproteobacterium, which has an NTD in addition to the canonical pLGIC structure. Here, we have characterized the structure and dynamics of DeCLIC through cryoelectron microscopy (cryo-EM), small-angle neutron scattering (SANS), and molecular dynamics (MD) simulations. In the presence and absence of calcium, cryo-EM yielded structures with alternative conformations of the calcium-binding site. SANS profiles further revealed conformational diversity at room temperature beyond that observed in static structures, shown through MD to be largely attributable to rigid-body motions of the NTD relative to the protein core, with expanded and asymmetric conformations improving the fit of the SANS data. This work reveals the range of motion available to the DeCLIC NTD and calcium-binding site, expanding the conformational landscape of the pLGIC family. Further, these findings demonstrate the power of combining low-resolution scattering, high-resolution structural, and MD simulation data to elucidate interfacial interactions that are highly conserved in the pLGIC family.
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21
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Lummis SCR, Dougherty DA. Expression of Mutant Glycine Receptors in Xenopus Oocytes Using Canonical and Non-Canonical Amino Acids Reveals Distinct Roles of Conserved Proline Residues. MEMBRANES 2022; 12:1012. [PMID: 36295771 PMCID: PMC9607081 DOI: 10.3390/membranes12101012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
Pentameric ligand-gated ion channels (pLGIC) play important roles in fast neuronal signal transmission. Functional receptors are pentamers, with each subunit having an extracellular domain (ECD), a transmembrane domain (TMD) and an intracellular domain. The binding of the agonist to the ECD induces a structural change that is transduced to the TMD to open the channel. Molecular details of this process are emerging, but a comprehensive understanding is still lacking. Proline (Pro) is one amino acid that has attracted much interest; its unusual features generate bends in loops and kinks and bulges in helices, which can be essential for function in some pLGICs. Here, we explore the roles of four conserved Pros in the glycine receptor (GlyR), creating substitutions with canonical and noncanonical amino acids, characterizing them using two electrode voltage clamp electrophysiology in Xenopus oocytes, and interpreting changes in receptor parameters using structural data from the open and closed states of the receptor. The data reveal that for efficient function, the Pro in the α1β1 loop is needed to create a turn and to be the correct size and shape to interact with nearby residues; the peptide bond of the Pro in the Cys-loop requires the cis conformation; and the Pros in loop A and M1 allow efficient function because of their reduced hydrogen bonding capacity. These data are broadly consistent with data from other pLGICs, and therefore likely represent the important features of these Pros in all members of the family.
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Affiliation(s)
- Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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22
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Gallagher CI, Ha DA, Harvey RJ, Vandenberg RJ. Positive Allosteric Modulators of Glycine Receptors and Their Potential Use in Pain Therapies. Pharmacol Rev 2022; 74:933-961. [PMID: 36779343 PMCID: PMC9553105 DOI: 10.1124/pharmrev.122.000583] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 04/26/2022] [Accepted: 05/13/2022] [Indexed: 11/22/2022] Open
Abstract
Glycine receptors are ligand-gated ion channels that mediate synaptic inhibition throughout the mammalian spinal cord, brainstem, and higher brain regions. They have recently emerged as promising targets for novel pain therapies due to their ability to produce antinociception by inhibiting nociceptive signals within the dorsal horn of the spinal cord. This has greatly enhanced the interest in developing positive allosteric modulators of glycine receptors. Several pharmaceutical companies and research facilities have attempted to identify new therapeutic leads by conducting large-scale screens of compound libraries, screening new derivatives from natural sources, or synthesizing novel compounds that mimic endogenous compounds with antinociceptive activity. Advances in structural techniques have also led to the publication of multiple high-resolution structures of the receptor, highlighting novel allosteric binding sites and providing additional information for previously identified binding sites. This has greatly enhanced our understanding of the functional properties of glycine receptors and expanded the structure activity relationships of novel pharmacophores. Despite this, glycine receptors are yet to be used as drug targets due to the difficulties in obtaining potent, selective modulators with favorable pharmacokinetic profiles that are devoid of side effects. This review presents a summary of the structural basis for how current compounds cause positive allosteric modulation of glycine receptors and discusses their therapeutic potential as analgesics. SIGNIFICANCE STATEMENT: Chronic pain is a major cause of disability, and in Western societies, this will only increase as the population ages. Despite the high level of prevalence and enormous socioeconomic burden incurred, treatment of chronic pain remains limited as it is often refractory to current analgesics, such as opioids. The National Institute for Drug Abuse has set finding effective, safe, nonaddictive strategies to manage chronic pain as their top priority. Positive allosteric modulators of glycine receptors may provide a therapeutic option.
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Affiliation(s)
- Casey I Gallagher
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Damien A Ha
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Harvey
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
| | - Robert J Vandenberg
- Molecular Biomedicine, School of Medical Sciences, University of Sydney, Sydney, Australia (C.I.G., D.A.H., R.J.V.) and Biomedical Science, School of Health and Behavioural Sciences and Sunshine Coast Health Institute, University of the Sunshine Coast, Maroochydore, Australia (R.J.H.)
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23
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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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Calahorro F, Chapman M, Dudkiewicz K, Holden-Dye L, O'Connor V. PharmacoGenetic targeting of a C. elegans essential neuron provides an in vivo screening for novel modulators of nematode ion channel function. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2022; 186:105152. [PMID: 35973757 DOI: 10.1016/j.pestbp.2022.105152] [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: 02/28/2022] [Revised: 05/18/2022] [Accepted: 06/16/2022] [Indexed: 06/15/2023]
Abstract
Chemical or drug treatments are successfully used to treat parasitic nematode infections that impact human, animal and plant health. Many of these exert their effects through modifying neural function underpinning behaviours essential for parasite viability. Selectivity against the parasite may be achieved through distinct pharmacological properties of the parasite nervous system, as exemplified by the success of the ivermectin which target a glutamate-gated chloride channel found only in invertebrates. Despite the success of the ivermectins, emerging resistance and concerns around eco-toxicity are driving the search for new nematocidal chemicals or drugs. Here, we describe the potential of a 5-HT-gated chloride channel MOD-1, which is involved in vital parasite behaviours with constrained distribution in the invertebrate phyla. This ion channel has potential pharmacophores that could be targeted by new nematocidal chemicals and drugs. We have developed a microtiter based bioassay for MOD-1 pharmacology based on its ectopic expression in the Caenorhabditis elegans essential neuron M4. We have termed this technology 'PhaGeM4' for 'Pharmacogenetic targeting of M4 neuron'. Exposure of transgenic worms harbouring ectopically expressed MOD-1 to 5-HT results in developmental arrest. By additional expression of a fluorescence marker in body wall muscle to monitor growth we demonstrate that this assay is suitable for the identification of receptor agonists and antagonists. Indeed, the developmental progression is a robustly quantifiable bioassay that resolves MOD-1 activation by quipazine, 5-carboxyamidotryptamine and fluoxetine and highlight methiothepin as a potent antagonist. This assay has the intrinsic ability to highlight compounds with optimal bioavailability and furthermore to filter out off-target effects. It can be extended to the investigation of other classes of membrane receptors and modulators of neuronal excitation. This approach based on heterologous modulation of the essential M4 neuron function offers a route to discover new effective and selective anthelmintics potentially less confounded by disruptive environmental impact.
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Affiliation(s)
- Fernando Calahorro
- School of Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton SO17 1BJ, UK.
| | - Mark Chapman
- School of Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton SO17 1BJ, UK
| | - Katarzyna Dudkiewicz
- School of Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton SO17 1BJ, UK
| | - Lindy Holden-Dye
- School of Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton SO17 1BJ, UK
| | - Vincent O'Connor
- School of Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton SO17 1BJ, UK
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Fraccaroli L, Ruiz MD, Perdomo VG, Clausi AN, Balcazar DE, Larocca L, Carrillo C. Broadening the spectrum of ivermectin: Its effect on Trypanosoma cruzi and related trypanosomatids. Front Cell Infect Microbiol 2022; 12:885268. [PMID: 35967842 PMCID: PMC9366347 DOI: 10.3389/fcimb.2022.885268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 07/05/2022] [Indexed: 11/22/2022] Open
Abstract
Chagas disease is an endemic American parasitosis, caused by Trypanosoma cruzi. The current therapies, benznidazole (BZN) and nifurtimox (NFX), show limited efficacy and multiple side effects. Thus, there is a need to develop new trypanocidal strategies. Ivermectin (IVM) is a broad-spectrum antiparasitic drug with low human and veterinary toxicity with effects against T. brucei and Leishmania spp. Considering this and its relatively low cost, we evaluate IVM as a potential repurposed trypanocidal drug on T. cruzi and other trypanosomatids. We found that IVM affected, in a dose-dependent manner, the proliferation of T. cruzi epimastigotes as well as the amastigotes and trypomastigotes survival. The Selectivity Index for the amastigote stage with respect to Vero cells was 12. The IVM effect was also observed in Phytomonas jma 066 and Leishmania mexicana proliferation but not in Crithidia fasciculata. On the epimastigote stage, the IVM effect was trypanostatic at 50 μM but trypanocidal at 100 μM. The assays of the drug combinations of IVM with BNZ or NFX showed mainly additive effects among combinations. In silico studies showed that classical structures belonging to glutamate-gated Cl channels, the most common IVM target, are absent in kinetoplastids. However, we found in the studied trypanosomatid genomes one copy for putative IMPα and IMPβ, potential targets for IVM. The putative IMPα genes (with 76% similarity) showed conserved Armadillo domains but lacked the canonical IMPβ binding sequence. These results allowed us to propose a novel molecular target in T. cruzi and suggest IVM as a good candidate for drug repurposing in the Chagas disease context.
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Affiliation(s)
- Laura Fraccaroli
- Laboratorio de Biología Molecular y Bioquímica en Trypanosoma cruzi y otros agentes infecciosos, CONICET for Instituto de Ciencia y Tecnología (ICT) Milstein - Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
- *Correspondence: Laura Fraccaroli, ; Carolina Carrillo,
| | - María Daniela Ruiz
- Laboratorio de Biología Molecular y Bioquímica en Trypanosoma cruzi y otros agentes infecciosos, CONICET for Instituto de Ciencia y Tecnología (ICT) Milstein - Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Virginia Gabriela Perdomo
- Área Parasitología, Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina
| | - Agustina Nicole Clausi
- Laboratorio de Biología Molecular y Bioquímica en Trypanosoma cruzi y otros agentes infecciosos, CONICET for Instituto de Ciencia y Tecnología (ICT) Milstein - Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Darío Emmanuel Balcazar
- Área Parasitología, Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina
| | - Luciana Larocca
- Laboratorio de Biología Molecular y Bioquímica en Trypanosoma cruzi y otros agentes infecciosos, CONICET for Instituto de Ciencia y Tecnología (ICT) Milstein - Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Carolina Carrillo
- Laboratorio de Biología Molecular y Bioquímica en Trypanosoma cruzi y otros agentes infecciosos, CONICET for Instituto de Ciencia y Tecnología (ICT) Milstein - Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
- *Correspondence: Laura Fraccaroli, ; Carolina Carrillo,
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26
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Tessier CJG, Sturgeon RM, Emlaw JR, McCluskey GD, Pérez-Areales FJ, daCosta CJB. Ancestral acetylcholine receptor β-subunit forms homopentamers that prime before opening spontaneously. eLife 2022; 11:76504. [PMID: 35781368 PMCID: PMC9365395 DOI: 10.7554/elife.76504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 06/21/2022] [Indexed: 11/13/2022] Open
Abstract
Human adult muscle-type acetylcholine receptors are heteropentameric ion channels formed from two α-subunits, and one each of the β-, d-, and e-subunits. To form functional channels, the subunits must assemble with one another in a precise stoichiometry and arrangement. Despite being different, the four subunits share a common ancestor that is presumed to have formed homopentamers. The extent to which the properties of the modern-day receptor result from its subunit complexity is unknown. Here we discover that a reconstructed ancestral muscle-type β-subunit can form homopentameric ion channels. These homopentamers open spontaneously and display single-channel hallmarks of muscle-type acetylcholine receptor activity. Our findings attest to the homopentameric origin of the muscle-type acetylcholine receptor, and demonstrate that signature features of its function are both independent of agonist and do not necessitate the complex heteropentameric architecture of the modern-day protein.
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Affiliation(s)
| | - R Michel Sturgeon
- Center for Chemical and Synthetic Biology, University of Ottawa, Ottawa, Canada
| | - Johnathon R Emlaw
- Center for Chemical and Synthetic Biology, University of Ottawa, Ottawa, Canada
| | - Gregory D McCluskey
- Center for Chemical and Synthetic Biology, University of Ottawa, Ottawa, Canada
| | | | - Corrie J B daCosta
- Center for Chemical and Synthetic Biology, University of Ottawa, Ottawa, Canada
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27
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Gao X, Zhang M, Lyu M, Lin S, Luo X, You W, Ke C. Role of Bmal1 in mediating the cholinergic system to regulate the behavioral rhythm of nocturnal marine molluscs. Comput Struct Biotechnol J 2022; 20:2815-2830. [PMID: 35765646 PMCID: PMC9189711 DOI: 10.1016/j.csbj.2022.05.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 05/17/2022] [Accepted: 05/19/2022] [Indexed: 11/18/2022] Open
Abstract
The circadian differential expression of AchE was identified using TMT quantitative proteomics; It was found that the Ach concentration and the expression levels of AchE and Bmal1 exhibit circadian cosine rhythm; The full-length sequences of AchE and nAchR were obtained by cloning technique and made available for phylogenetic analysis; The movement distance and duration of abalone increased after the injection of neostigmine methylsulfate as the AchE inhibitor; Bmal1 as the core circadian clock gene was proven to bind to AchE and nAchR, thereby regulating the movement behavior of abalone.
The circadian rhythm is one of the most general and important rhythms in biological organisms. In this study, continuous 24-h video recordings showed that the cumulative movement distance and duration of the abalone, Haliotis discus hannai, reached their maximum values between 20:00–00:00, but both were significantly lower between 08:00–12:00 than at any other time of day or night (P < 0.05). To investigate the causes of these diel differences in abalone movement behavior, their cerebral ganglia were harvested at 00:00 (group D) and 12:00 (group L) to screen for differentially expressed proteins using tandem mass tagging (TMT) quantitative proteomics. Seventy-five significantly different proteins were identified in group D vs. group L. The differences in acetylcholinesterase (AchE) expression levels between day- and nighttime and the key role in the cholinergic nervous system received particular attention during the investigation. A cosine rhythm analysis found that the concentration of acetylcholine (Ach) and the expression levels of AchE tended to be low during the day and high at night, and high during the day and low at night, respectively. However, the rhythmicity of the diel expression levels of acetylcholine receptor (nAchR) appeared to be insignificant (P > 0.05). Following the injection of three different concentrations of neostigmine methylsulfate, as an AchE inhibitor, the concentration of Ach in the hemolymph, and the expression levels of nAchR in the cerebral ganglia increased significantly (P < 0.05). Four hours after drug injection, the cumulative movement distance and duration of abalones were significantly higher than those in the uninjected control group, and the group injected with saline (P < 0.05). The expression levels of the core diurnal clock Bmal1 over a 24-h period also tended to be high during the day and low at night. First, a co-immunoprecipitation assay demonstrated the binding between Bmal1 and AchE or nAchR. A dual-luciferase gene test and electrophoretic mobility shift assay showed that Bmal1 bound to the promoter regions of AchE and nAchR. Twenty-four hours after silencing the Bmal1 gene, the expression levels of AchE and nAchR decreased significantly compared to those of the dsEGFP and PBS control groups, further showing that Bmal1 mediates the cholinergic system to regulate the behavioral rhythm of abalone. These findings shed light on the endocrine mechanism regulating the rhythmic behavior of abalone, and provide a reference for understanding the life history adaptation strategies of nocturnal organisms and the proliferation and protection of bottom dwelling economically important organisms.
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Affiliation(s)
- Xiaolong Gao
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Mo Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Mingxin Lyu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Shihui Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Xuan Luo
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Weiwei You
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
| | - Caihuan Ke
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
- Fujian Key Laboratory of Genetics and Breeding of Marine Organisms, Xiamen University, Xiamen, China
- Corresponding author.
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28
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Lipovsek M, Marcovich I, Elgoyhen AB. The Hair Cell α9α10 Nicotinic Acetylcholine Receptor: Odd Cousin in an Old Family. Front Cell Neurosci 2021; 15:785265. [PMID: 34867208 PMCID: PMC8634148 DOI: 10.3389/fncel.2021.785265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 10/25/2021] [Indexed: 11/13/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are a subfamily of pentameric ligand-gated ion channels with members identified in most eumetazoan clades. In vertebrates, they are divided into three subgroups, according to their main tissue of expression: neuronal, muscle and hair cell nAChRs. Each receptor subtype is composed of different subunits, encoded by paralogous genes. The latest to be identified are the α9 and α10 subunits, expressed in the mechanosensory hair cells of the inner ear and the lateral line, where they mediate efferent modulation. α9α10 nAChRs are the most divergent amongst all nicotinic receptors, showing marked differences in their degree of sequence conservation, their expression pattern, their subunit co-assembly rules and, most importantly, their functional properties. Here, we review recent advances in the understanding of the structure and evolution of nAChRs. We discuss the functional consequences of sequence divergence and conservation, with special emphasis on the hair cell α9α10 receptor, a seemingly distant cousin of neuronal and muscle nicotinic receptors. Finally, we highlight potential links between the evolution of the octavolateral system and the extreme divergence of vertebrate α9α10 receptors.
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Affiliation(s)
- Marcela Lipovsek
- Ear Institute, Faculty of Brain Sciences, University College London, London, United Kingdom
| | - Irina Marcovich
- Departments of Otolaryngology & Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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29
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Nin-Hill A, Mueller NPF, Molteni C, Rovira C, Alfonso-Prieto M. Photopharmacology of Ion Channels through the Light of the Computational Microscope. Int J Mol Sci 2021; 22:12072. [PMID: 34769504 PMCID: PMC8584574 DOI: 10.3390/ijms222112072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 10/31/2021] [Accepted: 11/02/2021] [Indexed: 12/13/2022] Open
Abstract
The optical control and investigation of neuronal activity can be achieved and carried out with photoswitchable ligands. Such compounds are designed in a modular fashion, combining a known ligand of the target protein and a photochromic group, as well as an additional electrophilic group for tethered ligands. Such a design strategy can be optimized by including structural data. In addition to experimental structures, computational methods (such as homology modeling, molecular docking, molecular dynamics and enhanced sampling techniques) can provide structural insights to guide photoswitch design and to understand the observed light-regulated effects. This review discusses the application of such structure-based computational methods to photoswitchable ligands targeting voltage- and ligand-gated ion channels. Structural mapping may help identify residues near the ligand binding pocket amenable for mutagenesis and covalent attachment. Modeling of the target protein in a complex with the photoswitchable ligand can shed light on the different activities of the two photoswitch isomers and the effect of site-directed mutations on photoswitch binding, as well as ion channel subtype selectivity. The examples presented here show how the integration of computational modeling with experimental data can greatly facilitate photoswitchable ligand design and optimization. Recent advances in structural biology, both experimental and computational, are expected to further strengthen this rational photopharmacology approach.
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Affiliation(s)
- Alba Nin-Hill
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028 Barcelona, Spain; (A.N.-H.); (C.R.)
| | - Nicolas Pierre Friedrich Mueller
- Institute for Advanced Simulations IAS-5 and Institute of Neuroscience and Medicine INM-9, Computational Biomedicine, Forschungszentrum Jülich, 52425 Jülich, Germany;
- Faculty of Mathematics and Natural Sciences, Heinrich-Heine-University Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany
| | - Carla Molteni
- Physics Department, King’s College London, London WC2R 2LS, UK;
| | - Carme Rovira
- Departament de Química Inorgànica i Orgànica (Secció de Química Orgànica) and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, 08028 Barcelona, Spain; (A.N.-H.); (C.R.)
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08020 Barcelona, Spain
| | - Mercedes Alfonso-Prieto
- Institute for Advanced Simulations 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, University Hospital Düsseldorf, Medical Faculty, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
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30
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Timsit Y, Grégoire SP. Towards the Idea of Molecular Brains. Int J Mol Sci 2021; 22:ijms222111868. [PMID: 34769300 PMCID: PMC8584932 DOI: 10.3390/ijms222111868] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 02/06/2023] Open
Abstract
How can single cells without nervous systems perform complex behaviours such as habituation, associative learning and decision making, which are considered the hallmark of animals with a brain? Are there molecular systems that underlie cognitive properties equivalent to those of the brain? This review follows the development of the idea of molecular brains from Darwin’s “root brain hypothesis”, through bacterial chemotaxis, to the recent discovery of neuron-like r-protein networks in the ribosome. By combining a structural biology view with a Bayesian brain approach, this review explores the evolutionary labyrinth of information processing systems across scales. Ribosomal protein networks open a window into what were probably the earliest signalling systems to emerge before the radiation of the three kingdoms. While ribosomal networks are characterised by long-lasting interactions between their protein nodes, cell signalling networks are essentially based on transient interactions. As a corollary, while signals propagated in persistent networks may be ephemeral, networks whose interactions are transient constrain signals diffusing into the cytoplasm to be durable in time, such as post-translational modifications of proteins or second messenger synthesis. The duration and nature of the signals, in turn, implies different mechanisms for the integration of multiple signals and decision making. Evolution then reinvented networks with persistent interactions with the development of nervous systems in metazoans. Ribosomal protein networks and simple nervous systems display architectural and functional analogies whose comparison could suggest scale invariance in information processing. At the molecular level, the significant complexification of eukaryotic ribosomal protein networks is associated with a burst in the acquisition of new conserved aromatic amino acids. Knowing that aromatic residues play a critical role in allosteric receptors and channels, this observation suggests a general role of π systems and their interactions with charged amino acids in multiple signal integration and information processing. We think that these findings may provide the molecular basis for designing future computers with organic processors.
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Affiliation(s)
- Youri Timsit
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO UM110, 13288 Marseille, France
- Research Federation for the Study of Global Ocean Systems Ecology and Evolution, FR2022/Tara GOSEE, 3 rue Michel-Ange, 75016 Paris, France
- Correspondence:
| | - Sergeant-Perthuis Grégoire
- Institut de Mathématiques de Jussieu—Paris Rive Gauche (IMJ-PRG), UMR 7586, CNRS-Université Paris Diderot, 75013 Paris, France;
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31
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Ahmad M, Chattopadhayay S, Mondal D, Vijayakanth T, Talukdar P. Stimuli-Responsive Anion Transport through Acylhydrazone-Based Synthetic Anionophores. Org Lett 2021; 23:7319-7324. [PMID: 34519509 DOI: 10.1021/acs.orglett.1c02249] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photoswitchable acylhydrazone-based synthetic anionophores are reported. Single-crystal X-ray structure and 1H NMR titration studies confirmed the chloride binding in solid and solution states. The ion transport activity of 1a was greatly attenuated through a phototriggered E to Z photoisomerization process, and the photoisomerized deactivated state showed high kinetic stability due to an intramolecular hydrogen bond. Switchable "OFF-ON" transport activity was achieved by the application of light and acid-catalyzed reactivation process.
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Affiliation(s)
- Manzoor Ahmad
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India
| | - Sandip Chattopadhayay
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India
| | - Debashis Mondal
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India
| | - Thangavel Vijayakanth
- The Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Pinaki Talukdar
- Department of Chemistry, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India
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32
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Lefebvre SN, Taly A, Menny A, Medjebeur K, Corringer PJ. Mutational analysis to explore long-range allosteric couplings involved in a pentameric channel receptor pre-activation and activation. eLife 2021; 10:60682. [PMID: 34590583 PMCID: PMC8504973 DOI: 10.7554/elife.60682] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 09/29/2021] [Indexed: 01/23/2023] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) mediate chemical signaling through a succession of allosteric transitions that are yet not completely understood as intermediate states remain poorly characterized by structural approaches. In a previous study on the prototypic bacterial proton-gated channel GLIC, we generated several fluorescent sensors of the protein conformation that report a fast transition to a pre-active state, which precedes the slower process of activation with pore opening. Here, we explored the phenotype of a series of allosteric mutations, using simultaneous steady-state fluorescence and electrophysiological measurements over a broad pH range. Our data, fitted to a three-state Monod-Wyman-Changeux model, show that mutations at the subunit interface in the extracellular domain (ECD) principally alter pre-activation, while mutations in the lower ECD and in the transmembrane domain principally alter activation. We also show that propofol alters both transitions. Data are discussed in the framework of transition pathways generated by normal mode analysis (iModFit). It further supports that pre-activation involves major quaternary compaction of the ECD, and suggests that activation involves principally a reorganization of a ‘central gating region’ involving a contraction of the ECD β-sandwich and the tilt of the channel lining M2 helix.
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Affiliation(s)
- Solène N Lefebvre
- Institut Pasteur, Université de Paris, CNRS UMR 3571,Channel-Receptors Unit, Paris, France.,Sorbonne Université, Collège doctoral, Paris, France
| | - Antoine Taly
- Institut de Biologie Physico-chimique, Fondation Edmond de Rothschild, PSL Research University, Paris, France.,Laboratoire de Biochimie Théorique, CNRS, Université de Paris, UPR 9080, Paris, France
| | - Anaïs Menny
- Institut Pasteur, Université de Paris, CNRS UMR 3571,Channel-Receptors Unit, Paris, France.,Sorbonne Université, Collège doctoral, Paris, France
| | - Karima Medjebeur
- Institut Pasteur, Université de Paris, CNRS UMR 3571,Channel-Receptors Unit, Paris, France
| | - Pierre-Jean Corringer
- Institut Pasteur, Université de Paris, CNRS UMR 3571,Channel-Receptors Unit, Paris, France
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33
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Pursuing High-Resolution Structures of Nicotinic Acetylcholine Receptors: Lessons Learned from Five Decades. Molecules 2021; 26:molecules26195753. [PMID: 34641297 PMCID: PMC8510392 DOI: 10.3390/molecules26195753] [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: 08/28/2021] [Revised: 09/19/2021] [Accepted: 09/20/2021] [Indexed: 01/04/2023] Open
Abstract
Since their discovery, nicotinic acetylcholine receptors (nAChRs) have been extensively studied to understand their function, as well as the consequence of alterations leading to disease states. Importantly, these receptors represent pharmacological targets to treat a number of neurological and neurodegenerative disorders. Nevertheless, their therapeutic value has been limited by the absence of high-resolution structures that allow for the design of more specific and effective drugs. This article offers a comprehensive review of five decades of research pursuing high-resolution structures of nAChRs. We provide a historical perspective, from initial structural studies to the most recent X-ray and cryogenic electron microscopy (Cryo-EM) nAChR structures. We also discuss the most relevant structural features that emerged from these studies, as well as perspectives in the field.
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34
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Rovšnik U, Zhuang Y, Forsberg BO, Carroni M, Yvonnesdotter L, Howard RJ, Lindahl E. Dynamic closed states of a ligand-gated ion channel captured by cryo-EM and simulations. Life Sci Alliance 2021; 4:e202101011. [PMID: 34210687 PMCID: PMC8326787 DOI: 10.26508/lsa.202101011] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 11/25/2022] Open
Abstract
Ligand-gated ion channels are critical mediators of electrochemical signal transduction across evolution. Biophysical and pharmacological characterization of these receptor proteins relies on high-quality structures in multiple, subtly distinct functional states. However, structural data in this family remain limited, particularly for resting and intermediate states on the activation pathway. Here, we report cryo-electron microscopy (cryo-EM) structures of the proton-activated Gloeobacter violaceus ligand-gated ion channel (GLIC) under three pH conditions. Decreased pH was associated with improved resolution and side chain rearrangements at the subunit/domain interface, particularly involving functionally important residues in the β1-β2 and M2-M3 loops. Molecular dynamics simulations substantiated flexibility in the closed-channel extracellular domains relative to the transmembrane ones and supported electrostatic remodeling around E35 and E243 in proton-induced gating. Exploration of secondary cryo-EM classes further indicated a low-pH population with an expanded pore. These results allow us to define distinct protonation and activation steps in pH-stimulated conformational cycling in GLIC, including interfacial rearrangements largely conserved in the pentameric channel family.
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Affiliation(s)
- Urška Rovšnik
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Yuxuan Zhuang
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Björn O Forsberg
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Marta Carroni
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Linnea Yvonnesdotter
- 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
| | - Erik Lindahl
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, Solna, Sweden
- Department of Applied Physics, Science for Life Laboratory, Kungliga Tekniska Högskolan Royal Institute of Technology, Solna, Sweden
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35
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Moroz LL, Nikitin MA, Poličar PG, Kohn AB, Romanova DY. Evolution of glutamatergic signaling and synapses. Neuropharmacology 2021; 199:108740. [PMID: 34343611 DOI: 10.1016/j.neuropharm.2021.108740] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 12/13/2022]
Abstract
Glutamate (Glu) is the primary excitatory transmitter in the mammalian brain. But, we know little about the evolutionary history of this adaptation, including the selection of l-glutamate as a signaling molecule in the first place. Here, we used comparative metabolomics and genomic data to reconstruct the genealogy of glutamatergic signaling. The origin of Glu-mediated communications might be traced to primordial nitrogen and carbon metabolic pathways. The versatile chemistry of L-Glu placed this molecule at the crossroad of cellular biochemistry as one of the most abundant metabolites. From there, innovations multiplied. Many stress factors or injuries could increase extracellular glutamate concentration, which led to the development of modular molecular systems for its rapid sensing in bacteria and archaea. More than 20 evolutionarily distinct families of ionotropic glutamate receptors (iGluRs) have been identified in eukaryotes. The domain compositions of iGluRs correlate with the origins of multicellularity in eukaryotes. Although L-Glu was recruited as a neuro-muscular transmitter in the early-branching metazoans, it was predominantly a non-neuronal messenger, with a possibility that glutamatergic synapses evolved more than once. Furthermore, the molecular secretory complexity of glutamatergic synapses in invertebrates (e.g., Aplysia) can exceed their vertebrate counterparts. Comparative genomics also revealed 15+ subfamilies of iGluRs across Metazoa. However, most of this ancestral diversity had been lost in the vertebrate lineage, preserving AMPA, Kainate, Delta, and NMDA receptors. The widespread expansion of glutamate synapses in the cortical areas might be associated with the enhanced metabolic demands of the complex brain and compartmentalization of Glu signaling within modular neuronal ensembles.
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Affiliation(s)
- Leonid L Moroz
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA; Departments of Neuroscience and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA.
| | - Mikhail A Nikitin
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119991, Russia; Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127994, Russia
| | - Pavlin G Poličar
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA; Faculty of Computer and Information Science, University of Ljubljana, SI-1000, Ljubljana, Slovenia
| | - Andrea B Kohn
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA
| | - Daria Y Romanova
- Cellular Neurobiology of Learning Lab, Institute of Higher Nervous Activity and Neurophysiology, Moscow, 117485, Russia.
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36
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Elephants in the Dark: Insights and Incongruities in Pentameric Ligand-gated Ion Channel Models. J Mol Biol 2021; 433:167128. [PMID: 34224751 DOI: 10.1016/j.jmb.2021.167128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 02/06/2023]
Abstract
The superfamily of pentameric ligand-gated ion channels (pLGICs) comprises key players in electrochemical signal transduction across evolution, including historic model systems for receptor allostery and targets for drug development. Accordingly, structural studies of these channels have steadily increased, and now approach 250 depositions in the protein data bank. This review contextualizes currently available structures in the pLGIC family, focusing on morphology, ligand binding, and gating in three model subfamilies: the prokaryotic channel GLIC, the cation-selective nicotinic acetylcholine receptor, and the anion-selective glycine receptor. Common themes include the challenging process of capturing and annotating channels in distinct functional states; partially conserved gating mechanisms, including remodeling at the extracellular/transmembrane-domain interface; and diversity beyond the protein level, arising from posttranslational modifications, ligands, lipids, and signaling partners. Interpreting pLGIC structures can be compared to describing an elephant in the dark, relying on touch alone to comprehend the many parts of a monumental beast: each structure represents a snapshot in time under specific experimental conditions, which must be integrated with further structure, function, and simulations data to build a comprehensive model, and understand how one channel may fundamentally differ from another.
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37
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Signal transduction through Cys-loop receptors is mediated by the nonspecific bumping of closely apposed domains. Proc Natl Acad Sci U S A 2021; 118:2021016118. [PMID: 33785596 DOI: 10.1073/pnas.2021016118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
One of the most fundamental questions in the field of Cys-loop receptors (pentameric ligand-gated ion channels, pLGICs) is how the affinity for neurotransmitters and the conductive/nonconductive state of the transmembrane pore are correlated despite the ∼60-Å distance between the corresponding domains. Proposed mechanisms differ, but they all converge into the idea that interactions between wild-type side chains across the extracellular-transmembrane-domain (ECD-TMD) interface are crucial for this phenomenon. Indeed, the successful design of fully functional chimeras that combine intact ECD and TMD modules from different wild-type pLGICs has commonly been ascribed to the residual conservation of sequence that exists at the level of the interfacial loops even between evolutionarily distant parent channels. Here, using mutagenesis, patch-clamp electrophysiology, and radiolabeled-ligand binding experiments, we studied the effect of eliminating this residual conservation of sequence on ion-channel function and cell-surface expression. From our results, we conclude that proper state interconversion ("gating") does not require conservation of sequence-or even physicochemical properties-across the ECD-TMD interface. Wild-type ECD and TMD side chains undoubtedly interact with their surroundings, but the interactions between them-straddling the interface-do not seem to be more important for gating than those occurring elsewhere in the protein. We propose that gating of pLGICs requires, instead, that the overall structure of the interfacial loops be conserved, and that their relative orientation and distance be the appropriate ones for changes in one side to result in changes in the other, in a phenomenon akin to the nonspecific "bumping" of closely apposed domains.
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38
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Marcovich I, Moglie MJ, Carpaneto Freixas AE, Trigila AP, Franchini LF, Plazas PV, Lipovsek M, Elgoyhen AB. Distinct Evolutionary Trajectories of Neuronal and Hair Cell Nicotinic Acetylcholine Receptors. Mol Biol Evol 2021; 37:1070-1089. [PMID: 31821508 PMCID: PMC7086180 DOI: 10.1093/molbev/msz290] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The expansion and pruning of ion channel families has played a crucial role in the evolution of nervous systems. Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels with distinct roles in synaptic transmission at the neuromuscular junction, the central and peripheral nervous system, and the inner ear. Remarkably, the complement of nAChR subunits has been highly conserved along vertebrate phylogeny. To ask whether the different subtypes of receptors underwent different evolutionary trajectories, we performed a comprehensive analysis of vertebrate nAChRs coding sequences, mouse single-cell expression patterns, and comparative functional properties of receptors from three representative tetrapod species. We found significant differences between hair cell and neuronal receptors that were most likely shaped by the differences in coexpression patterns and coassembly rules of component subunits. Thus, neuronal nAChRs showed high degree of coding sequence conservation, coupled to greater coexpression variance and conservation of functional properties across tetrapod clades. In contrast, hair cell α9α10 nAChRs exhibited greater sequence divergence, narrow coexpression pattern, and great variability of functional properties across species. These results point to differential substrates for random change within the family of gene paralogs that relate to the segregated roles of nAChRs in synaptic transmission.
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Affiliation(s)
- Irina Marcovich
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo J Moglie
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Agustín E Carpaneto Freixas
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Anabella P Trigila
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Lucia F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Paola V Plazas
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Marcela Lipovsek
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Centre for Developmental Neurobiology, King's College London, Institute of Psychiatry, Psychology and Neuroscience, Guy's Campus, London, United Kingdom
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
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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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40
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Draguhn A, Mallatt JM, Robinson DG. Anesthetics and plants: no pain, no brain, and therefore no consciousness. PROTOPLASMA 2021; 258:239-248. [PMID: 32880005 PMCID: PMC7907021 DOI: 10.1007/s00709-020-01550-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 08/26/2020] [Indexed: 05/05/2023]
Abstract
Plants have a rich variety of interactions with their environment, including adaptive responses mediated by electrical signaling. This has prompted claims that information processing in plants is similar to that in animals and, hence, that plants are conscious, intelligent organisms. In several recent reports, the facts that general anesthetics cause plants to lose their sensory responses and behaviors have been taken as support for such beliefs. These lipophilic substances, however, alter multiple molecular, cellular, and systemic functions in almost every organism. In humans and other animals with complex brains, they eliminate the experience of pain and disrupt consciousness. The question therefore arises: do plants feel pain and have consciousness? In this review, we discuss what can be learned from the effects of anesthetics in plants. For this, we describe the mechanisms and structural prerequisites for pain sensations in animals and show that plants lack the neural anatomy and all behaviors that would indicate pain. By explaining the ubiquitous and diverse effects of anesthetics, we discuss whether these substances provide any empirical or logical evidence for "plant consciousness" and whether it makes sense to study the effects of anesthetics on plants for this purpose. In both cases, the answer is a resounding no.
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Affiliation(s)
- Andreas Draguhn
- Institute for Physiology and Pathophysiology, Medical Faculty, University of Heidelberg, 69120, Heidelberg, Germany
| | - Jon M Mallatt
- The University of Washington WWAMI Medical Education Program, The University of Idaho, Moscow, ID, 83844, USA
| | - David G Robinson
- Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, D-69120, Heidelberg, Germany.
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41
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Islas-Weinstein L, Marquina-Castillo B, Mata-Espinosa D, Paredes-González IS, Chávez J, Balboa L, Marín Franco JL, Guerrero-Romero D, Barrios-Payan JA, Hernandez-Pando R. The Cholinergic System Contributes to the Immunopathological Progression of Experimental Pulmonary Tuberculosis. Front Immunol 2021; 11:581911. [PMID: 33679685 PMCID: PMC7930380 DOI: 10.3389/fimmu.2020.581911] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 12/22/2020] [Indexed: 01/08/2023] Open
Abstract
The cholinergic system is present in both bacteria and mammals and regulates inflammation during bacterial respiratory infections through neuronal and non-neuronal production of acetylcholine (ACh) and its receptors. However, the presence of this system during the immunopathogenesis of pulmonary tuberculosis (TB) in vivo and in its causative agent Mycobacterium tuberculosis (Mtb) has not been studied. Therefore, we used an experimental model of progressive pulmonary TB in BALB/c mice to quantify pulmonary ACh using high-performance liquid chromatography during the course of the disease. In addition, we performed immunohistochemistry in lung tissue to determine the cellular expression of cholinergic system components, and then administered nicotinic receptor (nAChR) antagonists to validate their effect on lung bacterial burden, inflammation, and pro-inflammatory cytokines. Finally, we subjected Mtb cultures to colorimetric analysis to reveal the production of ACh and the effect of ACh and nAChR antagonists on Mtb growth. Our results show high concentrations of ACh and expression of its synthesizing enzyme choline acetyltransferase (ChAT) during early infection in lung epithelial cells and macrophages. During late progressive TB, lung ACh upregulation was even higher and coincided with ChAT and α7 nAChR subunit expression in immune cells. Moreover, the administration of nAChR antagonists increased pro-inflammatory cytokines, reduced bacillary loads and synergized with antibiotic therapy in multidrug resistant TB. Finally, in vitro studies revealed that the bacteria is capable of producing nanomolar concentrations of ACh in liquid culture. In addition, the administration of ACh and nicotinic antagonists to Mtb cultures induced or inhibited bacterial proliferation, respectively. These results suggest that Mtb possesses a cholinergic system and upregulates the lung non-neuronal cholinergic system, particularly during late progressive TB. The upregulation of the cholinergic system during infection could aid both bacterial growth and immunomodulation within the lung to favor disease progression. Furthermore, the therapeutic efficacy of modulating this system suggests that it could be a target for treating the disease.
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Affiliation(s)
- Leon Islas-Weinstein
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
| | - Brenda Marquina-Castillo
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
| | - Dulce Mata-Espinosa
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
| | - Iris S. Paredes-González
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
| | - Jaime Chávez
- Department of Bronchial Hyperreactivity, National Institute of Respiratory Diseases (Mexico), Mexico City, Mexico
| | - Luciana Balboa
- Laboratorio de Inmunología de Enfermedades Respiratorias, Instituto de Medicina Experimental del National Scientific and Technical Research Council (CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina
| | - José Luis Marín Franco
- Laboratorio de Inmunología de Enfermedades Respiratorias, Instituto de Medicina Experimental del National Scientific and Technical Research Council (CONICET), Academia Nacional de Medicina, Buenos Aires, Argentina
| | - Daniel Guerrero-Romero
- Departamento de Matemáticas, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Jorge Alberto Barrios-Payan
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
| | - Rogelio Hernandez-Pando
- Division of Experimental Pathology, Department of Pathology, National Institute of Medical Sciences and Nutrition Salvador Zubirán, México City, Mexico
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Asymmetric opening of the homopentameric 5-HT 3A serotonin receptor in lipid bilayers. Nat Commun 2021; 12:1074. [PMID: 33594077 PMCID: PMC7887223 DOI: 10.1038/s41467-021-21016-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 01/06/2021] [Indexed: 12/13/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) of the Cys-loop receptor family are key players in fast signal transduction throughout the nervous system. They have been shown to be modulated by the lipid environment, however the underlying mechanism is not well understood. We report three structures of the Cys-loop 5-HT3A serotonin receptor (5HT3R) reconstituted into saposin-based lipid bilayer discs: a symmetric and an asymmetric apo state, and an asymmetric agonist-bound state. In comparison to previously published 5HT3R conformations in detergent, the lipid bilayer stabilises the receptor in a more tightly packed, ‘coupled’ state, involving a cluster of highly conserved residues. In consequence, the agonist-bound receptor conformation adopts a wide-open pore capable of conducting sodium ions in unbiased molecular dynamics (MD) simulations. Taken together, we provide a structural basis for the modulation of 5HT3R by the membrane environment, and a model for asymmetric activation of the receptor. Pentameric ligand-gated ion channels (pLGICs) are key players in neurotransmission and have been shown to be modulated by the lipid environment, however the underlying mechanism is not well understood. Here, the authors report structures of the pLGIC 5-HT3A serotonin receptor reconstituted into lipid bilayer discs and reveal lipid–protein interactions as well as asymmetric activation of the homopentameric receptor.
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43
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Baker BW, Dougherty DA, Lummis SCR. Proline Residues Contribute to Efficient GABA p Receptor Function. ACS Chem Neurosci 2020; 11:4215-4222. [PMID: 33201686 DOI: 10.1021/acschemneuro.0c00483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
GABAp receptors are homomeric pentameric ligand-gated ion channels (pLGICs) and are useful for probing the molecular details of the mechanism of action in this important protein family. Here, we explore the role of proline (Pro) residues by creating mutant receptors, expressing them in HEK293 cells, and using fluorescent membrane potential sensitive dye to monitor receptor activity. The data revealed that 3 of the Pro-to-alanine substitutions resulted in nonfunctional receptors (one in the Cys-loop, one in loop A and one in the β2-β3 loop), 7 resulted in increased EC50 values, and the remaining 13 resulted in receptors with properties similar to WT receptors. Further exploration of the nonfunctional mutants using expression in Xenopus laevis oocytes and whole-cell voltage-clamp electrophysiology, incorporating both canonical and noncanonical amino acids, revealed that the Pro in the Cys-loop had a preference for analogues with a high intrinsic cis bias, the Pro in loop A required a ring, and the β2-β3 loop Pro contributes to expression. The data from the Cys-loop Pro are consistent with those from other pLGICs, while those of the loop A Pro and some of the other Pros surprisingly differ. Thus, overall, the data clarify the roles of many of the Pros in the GABAp receptor and also suggest that caution must be applied in using data from one receptor to understand molecular details of all pLGICs.
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Affiliation(s)
- Benjamin W. Baker
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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44
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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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45
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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: 18] [Impact Index Per Article: 4.5] [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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46
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Lynch C, Rao S, Sansom MSP. Water in Nanopores and Biological Channels: A Molecular Simulation Perspective. Chem Rev 2020; 120:10298-10335. [PMID: 32841020 PMCID: PMC7517714 DOI: 10.1021/acs.chemrev.9b00830] [Citation(s) in RCA: 88] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Indexed: 12/18/2022]
Abstract
This Review explores the dynamic behavior of water within nanopores and biological channels in lipid bilayer membranes. We focus on molecular simulation studies, alongside selected structural and other experimental investigations. Structures of biological nanopores and channels are reviewed, emphasizing those high-resolution crystal structures, which reveal water molecules within the transmembrane pores, which can be used to aid the interpretation of simulation studies. Different levels of molecular simulations of water within nanopores are described, with a focus on molecular dynamics (MD). In particular, models of water for MD simulations are discussed in detail to provide an evaluation of their use in simulations of water in nanopores. Simulation studies of the behavior of water in idealized models of nanopores have revealed aspects of the organization and dynamics of nanoconfined water, including wetting/dewetting in narrow hydrophobic nanopores. A survey of simulation studies in a range of nonbiological nanopores is presented, including carbon nanotubes, synthetic nanopores, model peptide nanopores, track-etched nanopores in polymer membranes, and hydroxylated and functionalized nanoporous silica. These reveal a complex relationship between pore size/geometry, the nature of the pore lining, and rates of water transport. Wider nanopores with hydrophobic linings favor water flow whereas narrower hydrophobic pores may show dewetting. Simulation studies over the past decade of the behavior of water in a range of biological nanopores are described, including porins and β-barrel protein nanopores, aquaporins and related polar solute pores, and a number of different classes of ion channels. Water is shown to play a key role in proton transport in biological channels and in hydrophobic gating of ion channels. An overall picture emerges, whereby the behavior of water in a nanopore may be predicted as a function of its hydrophobicity and radius. This informs our understanding of the functions of diverse channel structures and will aid the design of novel nanopores. Thus, our current level of understanding allows for the design of a nanopore which promotes wetting over dewetting or vice versa. However, to design a novel nanopore, which enables fast, selective, and gated flow of water de novo would remain challenging, suggesting a need for further detailed simulations alongside experimental evaluation of more complex nanopore systems.
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Affiliation(s)
- Charlotte
I. Lynch
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, U.K.
| | - Shanlin Rao
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, U.K.
| | - Mark S. P. Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, U.K.
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Hughes ME, Mesoy SM, Capes E, Lummis SCR. Many Proline Residues in the Extracellular Domain Contribute to Glycine Receptor Function. ACS Chem Neurosci 2020; 11:2658-2665. [PMID: 32786326 DOI: 10.1021/acschemneuro.0c00320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Prolines in signaling proteins are of particular interest because they have a range of unique properties that may be critical for function. Here we show that many proline residues in the extracellular domain (ECD) of the glycine receptor are involved in the correct functioning of this ligand-gated ion channel. We explore their role by creating mutant receptors, expressing them in cells, and using fluorescent membrane potential sensitive dye to monitor receptor activity. We then interpret the changes in receptor parameters using structural information from the open and closed states of the receptor. The data reveal that substitution with alanine of ten of the 13 Pro residues in the ECD alters the function of the receptor: one substitution ablates function, six cause a decrease in the EC50, and three cause an increase. Only three of these mutants result in EC50 values similar to WT. The nonfunctional mutant, Pro30Ala, was further probed in oocytes, and the data suggest a role in both expression and function. Examination of the locations of sensitive Pro residues in the receptor and identification of potential interactions with nearby residues reveal how these residues could contribute to the correct functioning of this typical pentameric ligand-gated ion channel.
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Affiliation(s)
- Merryn E. Hughes
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, U.K
| | - Susanne M. Mesoy
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, U.K
| | - Emily Capes
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, U.K
| | - Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, U.K
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Stroebel D, Paoletti P. Architecture and function of NMDA receptors: an evolutionary perspective. J Physiol 2020; 599:2615-2638. [PMID: 32786006 DOI: 10.1113/jp279028] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 07/21/2020] [Indexed: 12/20/2022] Open
Abstract
Ionotropic glutamate receptors (iGluRs) are a major class of ligand-gated ion channels that are widespread in the living kingdom. Their critical role in excitatory neurotransmission and brain function of arthropods and vertebrates has made them a compelling subject of interest for neurophysiologists and pharmacologists. This is particularly true for NMDA receptor (NMDARs), a subclass of iGluRs that act as central drivers of synaptic plasticity in the CNS. How and when the unique properties of NMDARs arose during evolution, and how they relate to the evolution of the nervous system, remain open questions. Recent years have witnessed a boom in both genomic and structural data, such that it is now possible to analyse the evolution of iGluR genes on an unprecedented scale and within a solid molecular framework. In this review, combining insights from phylogeny, atomic structure and physiological and mechanistic data, we discuss how evolution of NMDAR motifs and sequences shaped their architecture and functionalities. We trace differences and commonalities between NMDARs and other iGluRs, emphasizing a few distinctive properties of the former regarding ligand binding and gating, permeation, allosteric modulation and intracellular signalling. Finally, we speculate on how specific molecular properties of iGuRs arose to supply new functions to the evolving structure of the nervous system, from early metazoan to present mammals.
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Affiliation(s)
- David Stroebel
- Ecole Normale Supérieure, CNRS, INSERM, Institute de Biologie de l'Ecole Normale Supérieure (IBENS), Université PSL, Paris, France
| | - Pierre Paoletti
- Ecole Normale Supérieure, CNRS, INSERM, Institute de Biologie de l'Ecole Normale Supérieure (IBENS), Université PSL, Paris, France
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Ahmad M, Metya S, Das A, Talukdar P. A Sandwich Azobenzene-Diamide Dimer for Photoregulated Chloride Transport. Chemistry 2020; 26:8703-8708. [PMID: 32129531 DOI: 10.1002/chem.202000400] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Indexed: 12/15/2022]
Abstract
There has been a tremendous evolution for artificial ion transport systems, especially gated synthetic systems, which closely mimic their natural congeners. Herein, we demonstrate a trans-azobenzene-based photoregulatory anionophoric system that transports chloride by forming a sandwich dimeric complex. Further studies confirmed a carrier-mediated chloride-anion antiport mechanism, and the supramolecular interactions involved in chloride recognition within the sandwich complex were revealed from theoretical studies. Reversible trans-cis photoisomerization of the azobenzene was achieved without any significant contribution from the thermal cis→trans isomerization at room temperature. Photoregulatory transport activity across the lipid bilayer membrane inferred an outstanding off-on response of the azobenzene photoswitch.
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Affiliation(s)
- Manzoor Ahmad
- Chemistry Department, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India
| | - Surajit Metya
- Chemistry Department, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India
| | - Aloke Das
- Chemistry Department, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India
| | - Pinaki Talukdar
- Chemistry Department, Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune, 411008, Maharashtra, India
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Structural basis for allosteric transitions of a multidomain pentameric ligand-gated ion channel. Proc Natl Acad Sci U S A 2020; 117:13437-13446. [PMID: 32482881 DOI: 10.1073/pnas.1922701117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) are allosteric receptors that mediate rapid electrochemical signal transduction in the animal nervous system through the opening of an ion pore upon binding of neurotransmitters. Orthologs have been found and characterized in prokaryotes and they display highly similar structure-function relationships to eukaryotic pLGICs; however, they often encode greater architectural diversity involving additional amino-terminal domains (NTDs). Here we report structural, functional, and normal-mode analysis of two conformational states of a multidomain pLGIC, called DeCLIC, from a Desulfofustis deltaproteobacterium, including a periplasmic NTD fused to the conventional ligand-binding domain (LBD). X-ray structure determination revealed an NTD consisting of two jelly-roll domains interacting across each subunit interface. Binding of Ca2+ at the LBD subunit interface was associated with a closed transmembrane pore, with resolved monovalent cations intracellular to the hydrophobic gate. Accordingly, DeCLIC-injected oocytes conducted currents only upon depletion of extracellular Ca2+; these were insensitive to quaternary ammonium block. Furthermore, DeCLIC crystallized in the absence of Ca2+ with a wide-open pore and remodeled periplasmic domains, including increased contacts between the NTD and classic LBD agonist-binding sites. Functional, structural, and dynamical properties of DeCLIC paralleled those of sTeLIC, a pLGIC from another symbiotic prokaryote. Based on these DeCLIC structures, we would reclassify the previous structure of bacterial ELIC (the first high-resolution structure of a pLGIC) as a "locally closed" conformation. Taken together, structures of DeCLIC in multiple conformations illustrate dramatic conformational state transitions and diverse regulatory mechanisms available to ion channels in pLGICs, particularly involving Ca2+ modulation and periplasmic NTDs.
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