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Peverini L, Shi S, Medjebeur K, Corringer PJ. Mapping the molecular motions of 5-HT 3 serotonin-gated channel by voltage-clamp fluorometry. eLife 2024; 12:RP93174. [PMID: 38913422 PMCID: PMC11196107 DOI: 10.7554/elife.93174] [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] [Indexed: 06/25/2024] Open
Abstract
The serotonin-gated ion channel (5-HT3R) mediates excitatory neuronal communication in the gut and the brain. It is the target for setrons, a class of competitive antagonists widely used as antiemetics, and is involved in several neurological diseases. Cryo-electron microscopy (cryo-EM) of the 5-HT3R in complex with serotonin or setrons revealed that the protein has access to a wide conformational landscape. However, assigning known high-resolution structures to actual states contributing to the physiological response remains a challenge. In the present study, we used voltage-clamp fluorometry (VCF) to measure simultaneously, for 5-HT3R expressed at a cell membrane, conformational changes by fluorescence and channel opening by electrophysiology. Four positions identified by mutational screening report motions around and outside the serotonin-binding site through incorporation of cysteine-tethered rhodamine dyes with or without a nearby quenching tryptophan. VCF recordings show that the 5-HT3R has access to four families of conformations endowed with distinct fluorescence signatures: 'resting-like' without ligand, 'inhibited-like' with setrons, 'pre-active-like' with partial agonists, and 'active-like' (open channel) with partial and strong agonists. Data are remarkably consistent with cryo-EM structures, the fluorescence partners matching respectively apo, setron-bound, 5-HT bound-closed, and 5-HT-bound-open conformations. Data show that strong agonists promote a concerted motion of all fluorescently labeled sensors during activation, while partial agonists, especially when loss-of-function mutations are engineered, stabilize both active and pre-active conformations. In conclusion, VCF, though the monitoring of electrophysiologically silent conformational changes, illuminates allosteric mechanisms contributing to signal transduction and their differential regulation by important classes of physiological and clinical effectors.
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Affiliation(s)
- Laurie Peverini
- Institut Pasteur, Université Paris Cité, CNRS UMR 3571, Channel-Receptors UnitParisFrance
| | - Sophie Shi
- Institut Pasteur, Université Paris Cité, CNRS UMR 3571, Channel-Receptors UnitParisFrance
| | - Karima Medjebeur
- Institut Pasteur, Université Paris Cité, CNRS UMR 3571, Channel-Receptors UnitParisFrance
| | - Pierre-Jean Corringer
- Institut Pasteur, Université Paris Cité, CNRS UMR 3571, Channel-Receptors UnitParisFrance
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López-Sánchez U, Munro LJ, Ladefoged LK, Pedersen AJ, Brun CC, Lyngby SM, Baud D, Juillan-Binard C, Pedersen MG, Lummis SCR, Bang-Andersen B, Schiøtt B, Chipot C, Schoehn G, Neyton J, Dehez F, Nury H, Kristensen AS. Structural determinants for activity of the antidepressant vortioxetine at human and rodent 5-HT 3 receptors. Nat Struct Mol Biol 2024:10.1038/s41594-024-01282-x. [PMID: 38698207 DOI: 10.1038/s41594-024-01282-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 03/19/2024] [Indexed: 05/05/2024]
Abstract
Vortioxetine (VTX) is a recently approved antidepressant that targets a variety of serotonin receptors. Here, we investigate the drug's molecular mechanism of operation at the serotonin 5-HT3 receptor (5-HT3R), which features two properties: VTX acts differently on rodent and human 5-HT3R, and VTX appears to suppress any subsequent response to agonists. Using a combination of cryo-EM, electrophysiology, voltage-clamp fluorometry and molecular dynamics, we show that VTX stabilizes a resting inhibited state of the mouse 5-HT3R and an agonist-bound-like state of human 5-HT3R, in line with the functional profile of the drug. We report four human 5-HT3R structures and show that the human receptor transmembrane domain is intrinsically fragile. We also explain the lack of recovery after VTX administration via a membrane partition mechanism.
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Affiliation(s)
- Uriel López-Sánchez
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
- Program in Cellular and Molecular Medicine, Boston Children's Hospital and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Lachlan Jake Munro
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | | | - Anders Juel Pedersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Christian Colding Brun
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Signe Meisner Lyngby
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Delphine Baud
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
| | | | | | - Sarah C R Lummis
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | - Birgit Schiøtt
- Department of Chemistry, Aarhus University, Aarhus, Denmark
| | - Christophe Chipot
- Université de Lorraine, CNRS, LPCT, Nancy, France
- Laboratoire International Associé CNRS and University of Illinois at Urbana-Champaign, Vandoeuvre-les-Nancy, France
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Guy Schoehn
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
| | - Jacques Neyton
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France
| | - Francois Dehez
- Université de Lorraine, CNRS, LPCT, Nancy, France
- Laboratoire International Associé CNRS and University of Illinois at Urbana-Champaign, Vandoeuvre-les-Nancy, France
| | - Hugues Nury
- University Grenoble Alpes, CNRS, CEA, IBS, Grenoble, France.
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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Phylogenetic analyses of 5-hydroxytryptamine 3 (5-HT3) receptors in Metazoa. PLoS One 2023; 18:e0281507. [PMID: 36857360 PMCID: PMC9977066 DOI: 10.1371/journal.pone.0281507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 01/24/2023] [Indexed: 03/02/2023] Open
Abstract
The 5-hydroxytrptamine 3 (5-HT3) receptor is a member of the 'Cys-loop' family and the only pentameric ligand gated ion channel among the serotonin receptors. 5-HT3 receptors play an important role in controlling growth, development, and behaviour in animals. Several 5-HT3 receptor antagonists are used to treat diseases (e.g., irritable bowel syndrome, nausea and emesis). Humans express five different subunits (A-E) enabling a variety of heteromeric receptors to form but all contain 5HT3A subunits. However, the information available about the 5-HT3 receptor subunit occurrence among the metazoan lineages is minimal. In the present article we searched for 5-HT3 receptor subunit homologs from different phyla in Metazoa. We identified more than 1000 5-HT3 receptor subunits in Metazoa in different phyla and undertook simultaneous phylogenetic analysis of 526 5HT3A, 358 5HT3B, 239 5HT3C, 70 5HT3D, and 173 5HT3E sequences. 5-HT3 receptor subunits were present in species belonging to 11 phyla: Annelida, Arthropoda, Chordata, Cnidaria, Echinodermata, Mollusca, Nematoda, Orthonectida, Platyhelminthes, Rotifera and Tardigrada. All subunits were most often identified in Chordata phylum which was strongly represented in searches. Using multiple sequence alignment, we investigated variations in the ligand binding region of the 5HT3A subunit protein sequences in the metazoan lineage. Several critical amino acid residues important for ligand binding (common structural features) are commonly present in species from Nematoda and Platyhelminth gut parasites through to Chordata. Collectively, this better understanding of the 5-HT3 receptor evolutionary patterns raises possibilities of future pharmacological challenges facing Metazoa including effects on parasitic and other species in ecosystems that contain 5-HT3 receptor ligands.
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Heusser SA, Borg CB, Colding JM, Pless SA. Conformational decoupling in acid-sensing ion channels uncovers mechanism and stoichiometry of PcTx1-mediated inhibition. eLife 2022; 11:73384. [PMID: 35156612 PMCID: PMC8871370 DOI: 10.7554/elife.73384] [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: 08/26/2021] [Accepted: 02/11/2022] [Indexed: 01/10/2023] Open
Abstract
Acid-sensing ion channels (ASICs) are trimeric proton-gated cation channels involved in fast synaptic transmission. Pharmacological inhibition of ASIC1a reduces neurotoxicity and stroke infarct volumes, with the cysteine knot toxin psalmotoxin-1 (PcTx1) being one of the most potent and selective inhibitors. PcTx1 binds at the subunit interface in the extracellular domain (ECD), but the mechanism and conformational consequences of the interaction, as well as the number of toxin molecules required for inhibition, remain unknown. Here, we use voltage-clamp fluorometry and subunit concatenation to decipher the mechanism and stoichiometry of PcTx1 inhibition of ASIC1a. Besides the known inhibitory binding mode, we propose PcTx1 to have at least two additional binding modes that are decoupled from the pore. One of these modes induces a long-lived ECD conformation that reduces the activity of an endogenous neuropeptide. This long-lived conformational state is proton-dependent and can be destabilized by a mutation that decreases PcTx1 sensitivity. Lastly, the use of concatemeric channel constructs reveals that disruption of a single PcTx1 binding site is sufficient to destabilize the toxin-induced conformation, while functional inhibition is not impaired until two or more binding sites are mutated. Together, our work provides insight into the mechanism of PcTx1 inhibition of ASICs and uncovers a prolonged conformational change with possible pharmacological implications.
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Affiliation(s)
- Stephanie A Heusser
- Department of Drug Design and Pharmacology, University of Copenhagen, Copehagen, Denmark
| | - Christian B Borg
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Janne M Colding
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Stephan A Pless
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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Basak S, Kumar A, Ramsey S, Gibbs E, Kapoor A, Filizola M, Chakrapani S. High-resolution structures of multiple 5-HT 3AR-setron complexes reveal a novel mechanism of competitive inhibition. eLife 2020; 9:e57870. [PMID: 33063666 PMCID: PMC7655109 DOI: 10.7554/elife.57870] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 10/15/2020] [Indexed: 12/13/2022] Open
Abstract
Serotonin receptors (5-HT3AR) play a crucial role in regulating gut movement, and are the principal target of setrons, a class of high-affinity competitive antagonists, used in the management of nausea and vomiting associated with radiation and chemotherapies. Structural insights into setron-binding poses and their inhibitory mechanisms are just beginning to emerge. Here, we present high-resolution cryo-EM structures of full-length 5-HT3AR in complex with palonosetron, ondansetron, and alosetron. Molecular dynamic simulations of these structures embedded in a fully-hydrated lipid environment assessed the stability of ligand-binding poses and drug-target interactions over time. Together with simulation results of apo- and serotonin-bound 5-HT3AR, the study reveals a distinct interaction fingerprint between the various setrons and binding-pocket residues that may underlie their diverse affinities. In addition, varying degrees of conformational change in the setron-5-HT3AR structures, throughout the channel and particularly along the channel activation pathway, suggests a novel mechanism of competitive inhibition.
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Affiliation(s)
- Sandip Basak
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve UniversityClevelandUnited States
| | - Arvind Kumar
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve UniversityClevelandUnited States
| | - Steven Ramsey
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Eric Gibbs
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve UniversityClevelandUnited States
| | - Abhijeet Kapoor
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount SinaiNew YorkUnited States
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve UniversityClevelandUnited States
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve UniversityClevelandUnited States
- Department of Neuroscience, School of Medicine, Case Western Reserve UniversityClevelandUnited States
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