1
|
Felt K, Stauffer M, Salas-Estrada L, Guzzo PR, Xie D, Huang J, Filizola M, Chakrapani S. Structural basis for partial agonism in 5-HT 3A receptors. Nat Struct Mol Biol 2024; 31:598-609. [PMID: 38177669 DOI: 10.1038/s41594-023-01140-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 09/26/2023] [Indexed: 01/06/2024]
Abstract
Hyperactivity of serotonin 3 receptors (5-HT3R) underlies pathologies associated with irritable bowel syndrome and chemotherapy-induced nausea and vomiting. Setrons, a class of high-affinity competitive antagonists, are used in the treatment of these conditions. Although generally effective for chemotherapy-induced nausea and vomiting, the use of setrons for treating irritable bowel syndrome has been impaired by adverse side effects. Partial agonists are now being considered as an alternative strategy, with potentially less severe side effects than full antagonists. However, a structural understanding of how these ligands work is lacking. Here, we present high-resolution cryogenic electron microscopy structures of the mouse 5-HT3AR in complex with partial agonists (SMP-100 and ALB-148471) captured in pre-activated and open-like conformational states. Molecular dynamics simulations were used to assess the stability of drug-binding poses and interactions with the receptor over time. Together, these studies reveal mechanisms for the functional differences between orthosteric partial agonists, full agonists and antagonists of the 5-HT3AR.
Collapse
Affiliation(s)
- Kevin Felt
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | - Madeleine Stauffer
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | - Leslie Salas-Estrada
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Peter R Guzzo
- SciMount Therapeutics (Shenzhen) Co. Ltd., Shenzhen, China
| | - Dejian Xie
- SciMount Therapeutics (Shenzhen) Co. Ltd., Shenzhen, China
| | - Jinkun Huang
- SciMount Therapeutics (Shenzhen) Co. Ltd., Shenzhen, China
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
- Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, OH, USA.
| |
Collapse
|
2
|
Eom S, Jung W, Lee J, Yeom HD, Lee S, Kim C, Park HD, Lee JH. Differential Regulation of Human Serotonin Receptor Type 3A by Chanoclavine and Ergonovine. Molecules 2021; 26:molecules26051211. [PMID: 33668306 PMCID: PMC7956620 DOI: 10.3390/molecules26051211] [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: 12/18/2020] [Revised: 02/18/2021] [Accepted: 02/19/2021] [Indexed: 02/07/2023] Open
Abstract
Irritable bowel syndrome (IBS) is a chronic disease that causes abdominal pain and an imbalance of defecation patterns due to gastrointestinal dysfunction. The cause of IBS remains unclear, but intestinal-brain axis problems and neurotransmitters have been suggested as factors. In this study, chanoclavine, which has a ring structure similar to 5-hydroxytryptamine (5-HT), showed an interaction with the 5-HT3A receptor to regulate IBS. Although its derivatives are known to be involved in neurotransmitter receptors, the molecular physiological mechanism of the interaction between chanoclavine and the 5-HT3A receptor is unknown. Electrophysiological experiments were conducted using a two-electrode voltage-clamp analysis to observe the inhibitory effects of chanoclavine on Xenopus oocytes in which the h5-HT3A receptor was expressed. The co-application of chanoclavine and 5-HT resulted in concentration-dependent, reversible, voltage-independent, and competitive inhibition. The 5-HT3A response induced by 5-HT was blocked by chanoclavine with half-maximal inhibitory response concentration (IC50) values of 107.2 µM. Docking studies suggested that chanoclavine was positioned close F130 and N138 in the 5-HT3A receptor-binding site. The double mutation of F130A and N138A significantly attenuated the interaction of chanoclavine compared to a single mutation or the wild type. These data suggest that F130 and N138 are important sites for ligand binding and activity. Chanoclavine and ergonovine have different effects. Asparagine, the 130th amino acid sequence of the 5-HT3A receptor, and phenylalanine, the 138th, are important in the role of binding chanoclavine, but ergonovine has no interaction with any amino acid sequence of the 5-HT3A receptor. The results of the electrophysiological studies and of in silico simulation showed that chanoclavine has the potential to inhibit the hypergastric stimulation of the gut by inhibiting the stimulation of signal transduction through 5-HT3A receptor stimulation. These findings suggest chanoclavine as a potential antiemetic agent for excessive gut stimulation and offer insight into the mechanisms of 5-HT3A receptor inhibition.
Collapse
Affiliation(s)
- Sanung Eom
- Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea; (S.E.); (J.L.); (S.L.); (C.K.)
| | - Woog Jung
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea;
| | - Jaeeun Lee
- Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea; (S.E.); (J.L.); (S.L.); (C.K.)
| | | | - Shinhui Lee
- Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea; (S.E.); (J.L.); (S.L.); (C.K.)
| | - Chaelin Kim
- Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea; (S.E.); (J.L.); (S.L.); (C.K.)
| | - Heui-Dong Park
- School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea;
- Correspondence: (H.-D.P.); (J.H.L); Tel.: +82-53-950-5774 (H.-D.P.); +82-62-530-2164 (J.H.L.)
| | - Junho H. Lee
- Department of Biotechnology, Chonnam National University, Gwangju 61186, Korea; (S.E.); (J.L.); (S.L.); (C.K.)
- Correspondence: (H.-D.P.); (J.H.L); Tel.: +82-53-950-5774 (H.-D.P.); +82-62-530-2164 (J.H.L.)
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Juza R, Vlcek P, Mezeiova E, Musilek K, Soukup O, Korabecny J. Recent advances with 5-HT 3 modulators for neuropsychiatric and gastrointestinal disorders. Med Res Rev 2020; 40:1593-1678. [PMID: 32115745 DOI: 10.1002/med.21666] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 11/10/2019] [Accepted: 02/11/2020] [Indexed: 12/17/2022]
Abstract
Serotonin (5-hydroxytryptophan [5-HT]) is a biologically active amine expressed in platelets, in gastrointestinal (GI) cells and, to a lesser extent, in the central nervous system (CNS). This biogenic compound acts through the activation of seven 5-HT receptors (5-HT1-7 Rs). The 5-HT3 R is a ligand-gated ion channel belonging to the Cys-loop receptor family. There is a wide variety of 5-HT3 R modulators, but only receptor antagonists (known as setrons) have been used clinically for chemotherapy-induced nausea and vomiting and irritable bowel syndrome treatment. However, since the discovery of the setrons in the mid-1980s, a large number of studies have been published exploring new potential applications due their potency in the CNS and mild side effects. The results of these studies have revealed new potential applications, including the treatment of neuropsychiatric disorders such as schizophrenia, depression, anxiety, and drug abuse. In this review, we provide information related to therapeutic potential of 5-HT3 R antagonists on GI and neuropsychiatric disorders. The major attention is paid to the structure, function, and pharmacology of novel 5-HT3 R modulators developed over the past 10 years.
Collapse
Affiliation(s)
- Radomir Juza
- National Institute of Mental Health, Klecany, Czech Republic
- Department of Chemistry, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Premysl Vlcek
- National Institute of Mental Health, Klecany, Czech Republic
- Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Eva Mezeiova
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Kamil Musilek
- Department of Chemistry, University of Hradec Kralove, Hradec Kralove, Czech Republic
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Ondrej Soukup
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| | - Jan Korabecny
- National Institute of Mental Health, Klecany, Czech Republic
- Biomedical Research Centre, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
| |
Collapse
|
5
|
Basak S, Gicheru Y, Kapoor A, Mayer ML, Filizola M, Chakrapani S. Molecular mechanism of setron-mediated inhibition of full-length 5-HT 3A receptor. Nat Commun 2019; 10:3225. [PMID: 31324772 PMCID: PMC6642186 DOI: 10.1038/s41467-019-11142-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 06/23/2019] [Indexed: 12/27/2022] Open
Abstract
Serotonin receptor (5-HT3AR) is the most common therapeutic target to manage the nausea and vomiting during cancer therapies and in the treatment of irritable bowel syndrome. Setrons, a class of competitive antagonists, cause functional inhibition of 5-HT3AR in the gastrointestinal tract and brainstem, acting as effective anti-emetic agents. Despite their prevalent use, the molecular mechanisms underlying setron binding and inhibition of 5-HT3AR are not fully understood. Here, we present the structure of granisetron-bound full-length 5-HT3AR solved by single-particle cryo-electron microscopy to 2.92 Å resolution. The reconstruction reveals the orientation of granisetron in the orthosteric site with unambiguous density for interacting sidechains. Molecular dynamics simulations and electrophysiology confirm the granisetron binding orientation and the residues central for ligand recognition. Comparison of granisetron-bound 5-HT3AR with the apo and serotonin-bound structures, reveals key insights into the mechanism underlying 5-HT3AR inhibition.
Collapse
Affiliation(s)
- Sandip Basak
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Yvonne Gicheru
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA
| | - Abhijeet Kapoor
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Megan L Mayer
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
| |
Collapse
|
6
|
Jack T, Leuenberger M, Ruepp MD, Vernekar SKV, Thompson AJ, Braga-Lagache S, Heller M, Lochner M. Mapping the Orthosteric Binding Site of the Human 5-HT 3 Receptor Using Photo-cross-linking Antagonists. ACS Chem Neurosci 2019; 10:438-450. [PMID: 30149702 DOI: 10.1021/acschemneuro.8b00327] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The serotonin-gated 5-HT3 receptor is a ligand-gated ion channel. Its location at the synapse in the central and peripheral nervous system has rendered it a prime pharmacological target, for example, for antiemetic drugs that bind with high affinity to the neurotransmitter binding site and prevent the opening of the channel. Advances in structural biology techniques have led to a surge of disclosed three-dimensional receptor structures; however, solving ligand-bound high-resolution 5-HT3 receptor structures has not been achieved to date. Ligand binding poses in the orthosteric binding site have been largely predicted from mutagenesis and docking studies. We report the synthesis of a series of photo-cross-linking compounds whose structures are based on the clinically used antiemetic drug granisetron (Kytril). These displaced [3H]granisetron from the orthosteric binding site with low nanomolar affinities and showed specific photo-cross-linking with the human 5-HT3 receptor. Detailed analysis by protein-MS/MS identified a residue (Met-228) near the tip of binding loop C as the covalent modification site.
Collapse
Affiliation(s)
- Thomas Jack
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Michele Leuenberger
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland
| | - Marc-David Ruepp
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | | | - Andrew J. Thompson
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Sophie Braga-Lagache
- Department of BioMedical Research, Mass Spectrometry and Proteomics Laboratory, University of Bern, Inselspital, 3010 Bern, Switzerland
| | - Manfred Heller
- Department of BioMedical Research, Mass Spectrometry and Proteomics Laboratory, University of Bern, Inselspital, 3010 Bern, Switzerland
| | - Martin Lochner
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland
| |
Collapse
|
7
|
Ladefoged LK, Munro L, Pedersen AJ, Lummis SCR, Bang-Andersen B, Balle T, Schiøtt B, Kristensen AS. Modeling and Mutational Analysis of the Binding Mode for the Multimodal Antidepressant Drug Vortioxetine to the Human 5-HT3A Receptor. Mol Pharmacol 2018; 94:1421-1434. [DOI: 10.1124/mol.118.113530] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Accepted: 09/19/2018] [Indexed: 12/23/2022] Open
|
8
|
Mosesso R, Dougherty DA. A triad of residues is functionally transferrable between 5-HT 3 serotonin receptors and nicotinic acetylcholine receptors. J Biol Chem 2018; 293:2903-2914. [PMID: 29298898 DOI: 10.1074/jbc.m117.810432] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 11/29/2017] [Indexed: 11/06/2022] Open
Abstract
Cys-loop receptors are pentameric ligand-gated ion channels that facilitate communication within the nervous system. Upon neurotransmitter binding, these receptors undergo an allosteric activation mechanism connecting the binding event to the membrane-spanning channel pore, which expands to conduct ions. Some of the earliest steps in this activation mechanism are carried out by residues proximal to the binding site, the relative positioning of which may reflect functional differences among members of the Cys-loop family of receptors. Herein, we investigated key side-chain interactions near the binding site via mutagenesis and two-electrode voltage-clamp electrophysiology in serotonin-gated 5-HT3A receptors (5-HT3ARs) and nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus laevis oocytes. We found that a triad of residues aligning to Thr-152, Glu-209, and Lys-211 in the 5-HT3AR can be exchanged between the homomeric 5-HT3AR and the muscle-type nAChR α-subunit with small functional consequences. Via triple mutant cycle analysis, we demonstrated that this triad forms an interdependent network in the muscle-type nAChR. Furthermore, nAChR-type mutations of the 5-HT3AR affect the affinity of nicotine, a competitive antagonist of 5-HT3ARs, in a cooperative manner. Using mutant cycle analyses between the 5-HT3A triad, loop A residues Asn-101 and Glu-102, β9 residue Lys-197, and the channel gate at Thr-257, we observed that residues in this region are energetically linked to the channel gate and are particularly sensitive to mutations that introduce a net positive charge. This study expands our understanding of the differences and similarities in the activation mechanisms of Cys-loop receptors.
Collapse
Affiliation(s)
- Richard Mosesso
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
| | - Dennis A Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125.
| |
Collapse
|
9
|
Ruepp MD, Wei H, Leuenberger M, Lochner M, Thompson AJ. The binding orientations of structurally-related ligands can differ; A cautionary note. Neuropharmacology 2017; 119:48-61. [PMID: 28137449 PMCID: PMC5464333 DOI: 10.1016/j.neuropharm.2017.01.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 01/13/2017] [Accepted: 01/24/2017] [Indexed: 11/19/2022]
Abstract
Crystal structures can identify ligand-receptor interactions and assist the development of novel therapeutics, but experimental challenges sometimes necessitate the use of homologous proteins. Tropisetron is an orthosteric ligand at both 5-HT3 and α7 nACh receptors and its binding orientation has been determined in the structural homologue AChBP (pdbid: 2WNC). Co-crystallisation with a structurally-related ligand, granisetron, reveals an almost identical orientation (pdbid; 2YME). However, there is a >1000-fold difference in the affinity of tropisetron at 5-HT3 versus α7 nACh receptors, and α7 nACh receptors do not bind granisetron. These striking pharmacological differences prompt questions about which receptor the crystal structures most closely represent and whether the ligand orientations are correct. Here we probe the binding orientation of tropisetron and granisetron at 5-HT3 receptors by in silico modelling and docking, radioligand binding on cysteine-substituted 5-HT3 receptor mutants transiently expressed in HEK 293 cells, and synthetic modification of the ligands. For 15 of the 23 cysteine substitutions, the effects on tropisetron and granisetron were different. Structure-activity relationships on synthesised derivatives of both ligands were also consistent with different orientations, revealing that contrary to the crystallographic evidence from AChBP, the two ligands adopt different orientations in the 5-HT3 receptor binding site. Our results show that even quite structurally similar molecules can adopt different orientations in the same binding site, and that caution may be needed when using homologous proteins to predict ligand binding. The drugs granisetron and tropisetron are structurally similar. Crystals of them bound to AChBP suggest they have similar binding orientations. At 5-HT3R, the effects of mutagenesis indicate that their orientations differ. SAR on both of these drugs also supports different orientations.
Collapse
Affiliation(s)
- Marc-David Ruepp
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Hao Wei
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Michele Leuenberger
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Martin Lochner
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland; Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
| | | |
Collapse
|
10
|
Price KL, Lillestol RK, Ulens C, Lummis SCR. Palonosetron-5-HT 3 Receptor Interactions As Shown by a Binding Protein Cocrystal Structure. ACS Chem Neurosci 2016; 7:1641-1646. [PMID: 27656911 DOI: 10.1021/acschemneuro.6b00132] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Palonosetron is a potent 5-HT3 receptor antagonist and an effective therapeutic agent against emesis. Here we identify the molecular determinants of compound recognition in the receptor binding site by obtaining a high resolution structure of palonosetron bound to an engineered acetylcholine binding protein that mimics the 5-HT3 receptor binding site, termed 5-HTBP, and by examining the potency of palonosetron in a range of 5-HT3 receptors with mutated binding site residues. The structural data indicate that palonosetron forms a tight and effective wedge in the binding pocket, made possible by its rigid tricyclic ring structure and its interactions with binding site residues; it adopts a binding pose that is distinct from the related antiemetics granisetron and tropisetron. The functional data show many residues previously shown to interact with agonists and antagonists in the binding site are important for palonosetron binding, and indicate those of particular importance are W183 (a cation-π interaction and a hydrogen bond) and Y153 (a hydrogen bond). This information, and the availability of the structure of palonosetron bound to 5-HTBP, should aid the development of novel and more efficacious drugs that act via 5-HT3 receptors.
Collapse
Affiliation(s)
- Kerry L. Price
- Department
of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| | - Reidun K. Lillestol
- Department
of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| | - Chris Ulens
- The
Laboratory of Structural Neurobiology, Department of Cellular and
Molecular Medicine, KU Leuven, Herestraat 49,
PB 601, B-3000 Leuven, Belgium
| | - Sarah C. R. Lummis
- Department
of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| |
Collapse
|
11
|
Alix K, Khatri S, Mosier PD, Casterlow S, Yan D, Nyce HL, White MM, Schulte MK, Dukat M. Superagonist, Full Agonist, Partial Agonist, and Antagonist Actions of Arylguanidines at 5-Hydroxytryptamine-3 (5-HT 3) Subunit A Receptors. ACS Chem Neurosci 2016; 7:1565-1574. [PMID: 27533595 DOI: 10.1021/acschemneuro.6b00196] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Introduction of minor variations to the substitution pattern of arylguanidine 5-hydroxytryptamine-3 (5-HT3) receptor ligands resulted in a broad spectrum of functionally-active ligands from antagonist to superagonist. For example, (i) introduction of an additional Cl-substituent(s) to our lead full agonist N-(3-chlorophenyl)guanidine (mCPG, 2; efficacy % = 106) yielded superagonists 7-9 (efficacy % = 186, 139, and 129, respectively), (ii) a positional isomer of 2, p-Cl analog 11, displayed partial agonist actions (efficacy % = 12), and (iii) replacing the halogen atom at the meta or para position with an electron donating OCH3 group or a stronger electron withdrawing (i.e., CF3) group resulted in antagonists 13-16. We posit based on combined mutagenesis, crystallographic, and computational analyses that for the 5-HT3 receptor, the arylguanidines that are better able to simultaneously engage the primary and complementary subunits, thus keeping them in close proximity, have greater agonist character while those that are deficient in this ability are antagonists.
Collapse
Affiliation(s)
- Katie Alix
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Shailesh Khatri
- Department
of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of Sciences, Philadelphia, Pennsylvania 19104, United States
| | - Philip D. Mosier
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Samantha Casterlow
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Dong Yan
- Department
of Biochemistry and Molecular Biology Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Heather L. Nyce
- Department
of Biochemistry and Molecular Biology Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Michael M. White
- Department
of Biochemistry and Molecular Biology Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Marvin K. Schulte
- Department
of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of Sciences, Philadelphia, Pennsylvania 19104, United States
| | - Małgorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| |
Collapse
|
12
|
Lochner M, Thompson AJ. The muscarinic antagonists scopolamine and atropine are competitive antagonists at 5-HT3 receptors. Neuropharmacology 2016; 108:220-8. [PMID: 27108935 PMCID: PMC4920643 DOI: 10.1016/j.neuropharm.2016.04.027] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 03/09/2016] [Accepted: 04/20/2016] [Indexed: 11/30/2022]
Abstract
Scopolamine is a high affinity muscarinic antagonist that is used for the prevention of post-operative nausea and vomiting. 5-HT3 receptor antagonists are used for the same purpose and are structurally related to scopolamine. To examine whether 5-HT3 receptors are affected by scopolamine we examined the effects of this drug on the electrophysiological and ligand binding properties of 5-HT3A receptors expressed in Xenopus oocytes and HEK293 cells, respectively. 5-HT3 receptor-responses were reversibly inhibited by scopolamine with an IC50 of 2.09 μM. Competitive antagonism was shown by Schild plot (pA2 = 5.02) and by competition with the 5-HT3 receptor antagonists [(3)H]granisetron (Ki = 6.76 μM) and G-FL (Ki = 4.90 μM). The related molecule, atropine, similarly inhibited 5-HT evoked responses in oocytes with an IC50 of 1.74 μM, and competed with G-FL with a Ki of 7.94 μM. The reverse experiment revealed that granisetron also competitively bound to muscarinic receptors (Ki = 6.5 μM). In behavioural studies scopolamine is used to block muscarinic receptors and induce a cognitive deficit, and centrally administered concentrations can exceed the IC50 values found here. It is therefore possible that 5-HT3 receptors are also inhibited. Studies that utilise higher concentrations of scopolamine should be mindful of these potential off-target effects.
Collapse
Affiliation(s)
- Martin Lochner
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, Bern, CH-3012, Switzerland.
| | - Andrew J Thompson
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
| |
Collapse
|
13
|
Di Maio D, Chandramouli B, Brancato G. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel. PLoS One 2015; 10:e0140258. [PMID: 26465896 PMCID: PMC4605793 DOI: 10.1371/journal.pone.0140258] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/12/2015] [Indexed: 11/29/2022] Open
Abstract
Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested.
Collapse
Affiliation(s)
- Danilo Di Maio
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
| | | | - Giuseppe Brancato
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
- * E-mail:
| |
Collapse
|
14
|
Price KL, Lillestol RK, Ulens C, Lummis SCR. Varenicline Interactions at the 5-HT3 Receptor Ligand Binding Site are Revealed by 5-HTBP. ACS Chem Neurosci 2015; 6:1151-7. [PMID: 25648658 PMCID: PMC4505686 DOI: 10.1021/cn500369h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cys-loop receptors are the site of action of many therapeutic drugs. One of these is the smoking cessation agent varenicline, which has its major therapeutic effects at nicotinic acetylcholine (nACh) receptors but also acts at 5-HT3 receptors. Here, we report the X-ray crystal structure of the 5-HT binding protein (5-HTBP) in complex with varenicline, and test the predicted interactions by probing the potency of varenicline in a range of mutant 5-HT3 receptors expressed in HEK293 cells and Xenopus oocytes. The structure reveals a range of interactions between varenicline and 5-HTBP. We identified residues within 5 Å of varenicline and substituted the equivalent residues in the 5-HT3 receptor with Ala or a residue with similar chemical properties. Functional characterization of these mutant 5-HT3 receptors, using a fluorescent membrane potential dye in HEK cells and voltage clamp in oocytes, supports interactions between varenicline and the receptor that are similar to those in 5-HTBP. The structure also revealed C-loop closure that was less than in the 5-HT-bound 5-HTBP, and hydrogen bonding between varenicline and the complementary face of the binding pocket via a water molecule, which are characteristics consistent with partial agonist behavior of varenicline in the 5-HT3 receptor. Together, these data reveal detailed insights into the molecular interaction of varenicline in the 5-HT3 receptor.
Collapse
Affiliation(s)
- Kerry L Price
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| | - Reidun K Lillestol
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| | - Chris Ulens
- ‡The Laboratory of Structural Neurobiology, Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, PB 601, B-3000 Leuven, Belgium
| | - Sarah C R Lummis
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, United Kingdom
| |
Collapse
|
15
|
Jiang X, Zhai J, Song D, Qu Q, Li M, Xing L, Miao S. Investigation of the structure of anti-human seminal plasma protein single-chain antibody and its association with linker peptide length. Mol Med Rep 2015; 12:4117-4122. [PMID: 26099852 PMCID: PMC4526083 DOI: 10.3892/mmr.2015.3980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 05/08/2015] [Indexed: 12/03/2022] Open
Abstract
To enhance the activity of seminoprotein single-chain variable fragment (γ-Sm-ScFv) antibodies, modulation of the length of the linker peptide, which connects the variable region of the heavy chain (VH) and the light chain (VL) of single-chain antibodies, was performed in the present study. Homologous modeling of single VH and VL were performed, respectively. Subsequently, modeling of the whole ScFv sequence, which was previously modified with added linkers of different lengths was also performed, and the (Gly4Ser)n peptide chain structure was used as the linker. The similarities between VH and VL prior to and following the addition of the linker were compared by applying the algorithm of protein similarity, based on spherical coordinates layering. In addition, changes in the fore and aft distance, and diffusion radius were calculated using a MATLAB tool, based on which changes in structural stability were analyzed. Finally, the single-chain antibody was assessed in a nude mouse model. When n=3 or n=6, the similarity between the original distance and VH and VL were the highest, and the fore and aft distance and diffusion radius were relatively close. In addition, the nude mouse model indicated that, when n=3 or n=6, the inhibitory rate of the single-chain antibody against tumor cells was significantly higher, compared with the other linker peptides of different lengths. The effect of structural changes of the linker peptides in the single-chain antibodies on the whole antibody molecule was examined at different levels using a combination of mathematical modeling, bioinformatics methods and biological experiments. The findings of the present study may provide a foundation for further investigation into the preparation of single-chain antibodies.
Collapse
Affiliation(s)
- Xin Jiang
- Department of Urology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, P.R. China
| | - Jun Zhai
- Reproductive Center, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, P.R. China
| | - Dongkui Song
- Department of Urology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, P.R. China
| | - Qingshan Qu
- Department of Kidney Transplantation, People's Hospital of Zhengzhou, Zhengzhou, Henan 450003, P.R. China
| | - Ming Li
- Department of Kidney Transplantation, People's Hospital of Zhengzhou, Zhengzhou, Henan 450003, P.R. China
| | - Li Xing
- Department of Kidney Transplantation, People's Hospital of Zhengzhou, Zhengzhou, Henan 450003, P.R. China
| | - Shuzhai Miao
- Department of Kidney Transplantation, People's Hospital of Zhengzhou, Zhengzhou, Henan 450003, P.R. China
| |
Collapse
|
16
|
Thompson AJ, Verheij MHP, Verbeek J, Windhorst AD, de Esch IJP, Lummis SCR. The binding characteristics and orientation of a novel radioligand with distinct properties at 5-HT3A and 5-HT3AB receptors. Neuropharmacology 2014; 86:378-88. [PMID: 25174552 PMCID: PMC4220016 DOI: 10.1016/j.neuropharm.2014.08.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 07/22/2014] [Accepted: 08/09/2014] [Indexed: 12/22/2022]
Abstract
VUF10166 (2-chloro-3-(4-methyl piperazin-1-yl)quinoxaline) is a ligand that binds with high affinity to 5-HT3 receptors. Here we synthesise [(3)H]VUF10166 and characterise its binding properties at 5-HT3A and 5-HT3AB receptors. At 5-HT3A receptors [(3)H]VUF10166 displayed saturable binding with a Kd of 0.18 nM. Kinetic measurements gave monophasic association (6.25 × 10(7) M(-1) min(-1)) and dissociation (0.01 min(-1)) rates that yielded a similar Kd value (0.16 nM). At 5-HT3AB receptors two association (6.15 × 10(-7), 7.23 M(-1) min(-1)) and dissociation (0.024, 0.162 min(-1)) rates were seen, yielding Kd values (0.38 nM and 22 nM) that were consistent with values obtained in saturation (Kd = 0.74 nM) and competition (Ki = 37 nM) binding experiments respectively. At both receptor types, specific binding was inhibited by classical 5-HT3 receptor-selective orthosteric ligands (5-HT, allosetron, d-tubocurarine, granisetron, mCPBG, MDL72222, quipazine), but not by non-competitive antagonists (bilobalide, ginkgolide B, picrotoxin) or competitive ligands of other Cys-loop receptors (ACh, bicuculline, glycine, gabazine). To explore VUF10166 ligand-receptor interactions we used in silico modelling and docking, and tested the predictions using site directed mutagenesis. The data suggest that VUF10166 adopts a similar orientation to 5-HT3 receptor agonists bound in AChBP (varenicline) and 5HTBP (5-HT) crystal structures.
Collapse
Affiliation(s)
| | - Mark H P Verheij
- Amsterdam Institute for Molecules Medicines and Systems (AIMMS), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Joost Verbeek
- VU University Medical Center, Dept Radiology & Nuclear Medicine, Amsterdam, The Netherlands
| | - Albert D Windhorst
- VU University Medical Center, Dept Radiology & Nuclear Medicine, Amsterdam, The Netherlands
| | - Iwan J P de Esch
- Amsterdam Institute for Molecules Medicines and Systems (AIMMS), Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Sarah C R Lummis
- Department of Biochemistry, University of Cambridge, Cambridge, UK.
| |
Collapse
|
17
|
Thompson AJ, Verheij MHP, van Muijlwijk-Koezen JE, Lummis SCR, Leurs R, de Esch IJP. Structure-activity relationships of quinoxaline-based 5-HT3A and 5-HT3AB receptor-selective ligands. ChemMedChem 2013; 8:946-55. [PMID: 23640722 PMCID: PMC4063337 DOI: 10.1002/cmdc.201300032] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 03/15/2013] [Indexed: 12/23/2022]
Abstract
Until recently, discriminating between homomeric 5-HT3A and heteromeric 5-HT3AB receptors was only possible with ligands that bind in the receptor pore. This study describes the first series of ligands that can discriminate between these receptor types at the level of the orthosteric binding site. During a recent fragment screen, 2-chloro-3-(4-methylpiperazin-1-yl)quinoxaline (VUF10166) was identified as a ligand that displays an 83-fold difference in [(3)H]granisetron binding affinity between 5-HT3A and 5-HT3AB receptors. Fragment hit exploration, initiated from VUF10166 and 3-(4-methylpiperazin-1-yl)quinoxalin-2-ol, resulted in a series of compounds with higher affinity at either 5-HT3A or 5-HT3AB receptors. These ligands reveal that a single atom is sufficient to change the selectivity profile of a compound. At the extremes of the new compounds were 2-amino-3-(4-methylpiperazin-1-yl)quinoxaline, which showed 11-fold selectivity for the 5-HT3A receptor, and 2-(4-methylpiperazin-1-yl)quinoxaline, which showed an 8.3-fold selectivity for the 5-HT3AB receptor. These compounds represent novel molecular tools for studying 5-HT3 receptor subtypes and could help elucidate their physiological roles.
Collapse
|
18
|
Duffy NH, Lester HA, Dougherty DA. Ondansetron and granisetron binding orientation in the 5-HT(3) receptor determined by unnatural amino acid mutagenesis. ACS Chem Biol 2012; 7:1738-45. [PMID: 22873819 DOI: 10.1021/cb300246j] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The serotonin type 3 receptor (5-HT(3)R) is a ligand-gated ion channel found in the central and peripheral nervous systems. The 5-HT(3)R is a therapeutic target, and the clinically available drugs ondansetron and granisetron inhibit receptor activity. Their inhibitory action is through competitive binding to the native ligand binding site, although the binding orientation of the drugs at the receptor has been a matter of debate. Here we heterologously express mouse 5-HT(3)A receptors in Xenopus oocytes and use unnatural amino acid mutagenesis to establish a cation-π interaction for both ondansetron and granisetron to tryptophan 183 in the ligand binding pocket. This cation-π interaction establishes a binding orientation for both ondansetron and granisetron within the binding pocket.
Collapse
Affiliation(s)
- Noah H. Duffy
- Division
of Chemistry and Chemical Engineering and ‡Division of Biology, California Institute of Technology,
Pasadena, California 91125, United States
| | - Henry A. Lester
- Division
of Chemistry and Chemical Engineering and ‡Division of Biology, California Institute of Technology,
Pasadena, California 91125, United States
| | - Dennis A. Dougherty
- Division
of Chemistry and Chemical Engineering and ‡Division of Biology, California Institute of Technology,
Pasadena, California 91125, United States
| |
Collapse
|
19
|
Verheij MHP, Thompson AJ, van Muijlwijk-Koezen JE, Lummis SCR, Leurs R, de Esch IJP. Design, synthesis, and structure-activity relationships of highly potent 5-HT₃ receptor ligands. J Med Chem 2012; 55:8603-14. [PMID: 23006041 PMCID: PMC3504484 DOI: 10.1021/jm300801u] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
![]()
The 5-HT3 receptor, a pentameric ligand-gated
ion channel
(pLGIC), is an important therapeutic target. During a recent fragment
screen, 6-chloro-N-methyl-2-(4-methyl-1,4-diazepan-1-yl)quinazolin-4-amine
(1) was identified as a 5-HT3R hit fragment.
Here we describe the synthesis and structure–activity relationships
(SAR) of a series of (iso)quinoline and quinazoline compounds that
were synthesized and screened for 5-HT3R affinity using
a [3H]granisetron displacement assay. These studies resulted
in the discovery of several high affinity ligands of which compound 22 showed the highest affinity (pKi > 10) for the 5-HT3 receptor. The observed SAR is
in
agreement with established pharmacophore models for 5-HT3 ligands and is used for ligand–receptor binding mode prediction
using homology modeling and in silico docking approaches.
Collapse
Affiliation(s)
- Mark H P Verheij
- Leiden/Amsterdam Center of Drug Research-LACDR, Amsterdam Institute for Molecules Medicines and Systems-AIMMS, Division of Medicinal Chemistry, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
20
|
De Rienzo F, Moura Barbosa AJ, Perez MA, Fernandes PA, Ramos MJ, Menziani MC. The extracellular subunit interface of the 5-HT3receptors: a computational alanine scanning mutagenesis study. J Biomol Struct Dyn 2012; 30:280-98. [DOI: 10.1080/07391102.2012.680029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
21
|
Carpenter TS, Lau EY, Lightstone FC. A role for loop F in modulating GABA binding affinity in the GABA(A) receptor. J Mol Biol 2012; 422:310-23. [PMID: 22659322 DOI: 10.1016/j.jmb.2012.05.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 05/08/2012] [Accepted: 05/17/2012] [Indexed: 10/28/2022]
Abstract
The brain's major inhibitory neuroreceptor is the ligand-gated ion channel γ-aminobutyric acid (GABA) type A receptor (GABAR). GABARs exist in a variety of different subunit combinations that act to modulate the physiological behavior of GABAR by altering its pharmacological profile, as well as its affinity for GABA. While the α(1)β(2)γ(2) subtype is one of the most prevalent GABARs, the less populous α(6)β(3)δ subtype has much higher GABA sensitivity. Previous studies identified residues crucial for GABA binding; however, the specific molecular differences responsible for this diverse sensitivity are not known. Furthermore, the role of loop F is a divisive subject, with conflicting evidence for ligand binding function. Using homology modeling, ligand docking, and molecular dynamics simulations, we investigated the GABA binding sites of the two receptor subtypes. Simulations identified seven residues that consistently interacted with GABA in both subtypes: αF65, αR132, βL99, βE155, βR/K196, βY205, and βR207. Residue substitution at position β196 (arginine in α(6)β(3)δ, lysine in α(1)β(2)γ(2)) resulted in a shift in GABA binding. However, the major difference between the two binding sites was the magnitude of loop F involvement, with a greater contribution in the α(6)β(3)δ receptor. Free energy calculations confirm that the α(6)β(3)δ binding pocket has an increased affinity for GABA. Thus, the possible role for loop F across the GABAR family is to modulate GABA affinity.
Collapse
Affiliation(s)
- Timothy S Carpenter
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | | | | |
Collapse
|
22
|
Thompson AJ, Duke RK, Lummis SCR. Binding sites for bilobalide, diltiazem, ginkgolide, and picrotoxinin at the 5-HT3 receptor. Mol Pharmacol 2011; 80:183-90. [PMID: 21505038 PMCID: PMC3127528 DOI: 10.1124/mol.111.071415] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 04/18/2011] [Indexed: 11/22/2022] Open
Abstract
Bilobalide (BB), ginkgolide B (GB), diltiazem (DTZ), and picrotoxinin (PXN) are 5-hydroxytryptamine type 3 (5-HT(3)) receptor antagonists in which the principal sites of action are in the channel. To probe their exact binding locations, 5-HT(3) receptors with substitutions in their pore lining residues were constructed (N-4'Q, E-1'D, S2'A, T6'S, L7'T, L9'V, S12'A, I16'V, D20'E), expressed in Xenopus laevis oocytes, and the effects of the compounds on 5-HT-induced currents were examined. EC(50) values at mutant receptors were less than 6-fold different from those of wild type, indicating that the mutations were well tolerated. BB, GB, DTZ, and PXN had pIC(50) values of 3.33, 3.14, 4.67, and 4.97, respectively. Inhibition by BB and GB was abolished in mutant receptors containing T6'S and S12'A substitutions, but their potencies were enhanced (42- and 125-fold, respectively) in S2'A mutant receptors. S2'A substitution also caused GB ligand trap. PXN potency was modestly enhanced (5-fold) in S2'A, abolished in T6'S, and reduced in L9'V (40-fold) and S12'A (7-fold) receptors. DTZ potency was reduced in L7'T and S12'A receptors (5-fold), and DTZ also displaced [(3)H]granisetron binding, indicating mixed competitive/noncompetitive inhibition. We conclude that regions close to the hydrophobic gate of M2 are important for the inhibitory effects of BB, GB, DTZ, and PXN at the 5-HT(3) receptor; for BB, GB, and PXN, the data show that the 6' channel lining residue is their major site of action, with minor roles for 2', 9', and 12' residues, whereas for DTZ, the 7' and 12' sites are important.
Collapse
Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | | | | |
Collapse
|
23
|
Thompson AJ, Price KL, Lummis SCR. Cysteine modification reveals which subunits form the ligand binding site in human heteromeric 5-HT3AB receptors. J Physiol 2011; 589:4243-57. [PMID: 21708905 PMCID: PMC3180581 DOI: 10.1113/jphysiol.2011.208439] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The ligand binding site of Cys-loop receptors is formed by residues on the principal (+) and complementary (-) faces of adjacent subunits, but the subunits that constitute the binding pocket in many heteromeric receptors are not yet clear. To probe the subunits involved in ligand binding in heteromeric human 5-HT(3)AB receptors, we made cysteine substitutions to the + and - faces of A and B subunits, and measured their functional consequences in receptors expressed in Xenopus oocytes. All A subunit mutations altered or eliminated function. The same pattern of changes was seen at homomeric and heteromeric receptors containing cysteine substitutions at A(R92) (- face), A(L126)(+), A(N128)(+), A(I139)(-), A(Q151)(-) and A(T181)(+), and these receptors displayed further changes when the sulphydryl modifying reagent methanethiosulfonate-ethylammonium (MTSEA) was applied. Modifications of A(R92C)(-)- and A(T181C)(+)-containing receptors were protected by the presence of agonist (5-HT) or antagonist (d-tubocurarine). In contrast modifications of the equivalent B subunit residues did not alter heteromeric receptor function. In addition a double mutant, A(S206C)(-)(/E229C)(+), only responded to 5-HT following DTT treatment in both homomeric and heteromeric receptors, indicating receptor function was inhibited by a disulphide bond between an A+ and an A- interface in both receptor types. Our results are consistent with binding to an A+A- interface at both homomeric and heteromeric human 5-HT(3) receptors, and explain why the competitive pharmacologies of these two receptors are identical.
Collapse
Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | | | | |
Collapse
|
24
|
Machu TK. Therapeutics of 5-HT3 receptor antagonists: current uses and future directions. Pharmacol Ther 2011; 130:338-47. [PMID: 21356241 PMCID: PMC3103470 DOI: 10.1016/j.pharmthera.2011.02.003] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 02/09/2011] [Indexed: 12/14/2022]
Abstract
The 5-Hydroxytryptamine3 (5-HT3) receptor is a member of the cys-loop family of ligand gated ion channels, of which the nicotinic acetylcholine receptor is the prototype. All other 5-HT receptors identified to date are metabotropic receptors. The 5-HT3 receptor is present in the central and peripheral nervous systems, as well as a number of non-nervous tissues. As an ion channel that is permeable to the cations, Na(+), K(+), and Ca(2+), the 5-HT3 receptor mediates fast depolarizing responses in pre- and post-synaptic neurons. As such, 5-HT3 receptor antagonists that are used clinically block afferent and efferent synaptic transmission. The most well established physiological roles of the 5-HT3 receptor are to coordinate emesis and regulate gastrointestinal motility. Currently marketed 5-HT3 receptor antagonists are indicated for the treatment of chemotherapy, radiation, and anesthesia-induced nausea and vomiting, as well as irritable bowel syndrome. Other therapeutic uses that have been explored include pain and drug addiction. The 5-HT3 receptor is one of a number of receptors that play a role in mediating nausea and vomiting, and as such, 5-HT3 receptor antagonists demonstrate the greatest anti-emetic efficacy when administered in combination with other drug classes.
Collapse
Affiliation(s)
- Tina K Machu
- Dept. of Medical Education and Dept. of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Blvd. Fort Worth, TX 76107-2699, USA.
| |
Collapse
|
25
|
Pless SA, Hanek AP, Price KL, Lynch JW, Lester HA, Dougherty DA, Lummis SCR. A cation-π interaction at a phenylalanine residue in the glycine receptor binding site is conserved for different agonists. Mol Pharmacol 2011; 79:742-8. [PMID: 21266487 DOI: 10.1124/mol.110.069583] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cation-π interactions have been demonstrated to play a major role in agonist-binding in Cys-loop receptors. However, neither the aromatic amino acid contributing to this interaction nor its location is conserved among Cys-loop receptors. Likewise, it is not clear how many different agonists of a given receptor form a cation-π interaction or, if they do, whether it is with the same aromatic amino acid as the major physiological agonist. We demonstrated previously that Phe159 in the glycine receptor (GlyR) α1 subunit forms a strong cation-π interaction with the principal agonist, glycine. In the current study, we investigated whether the lower efficacy agonists of the human GlyR β-alanine and taurine also form cation-π interactions with Phe159. By incorporating a series of unnatural amino acids, we found cation-π interactions between Phe159 and the amino groups of β-alanine and taurine. The strengths of these interactions were significantly weaker than for glycine. Modeling studies suggest that β-alanine and taurine are orientated subtly differently in the binding pocket, with their amino groups further from Phe159 than that of glycine. These data therefore show that similar agonists can have similar but not identical orientations and interactions in the binding pocket and provide a possible explanation for the lower potencies of β-alanine and taurine.
Collapse
Affiliation(s)
- Stephan A Pless
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | | | | | | | | | | | | |
Collapse
|
26
|
Poudel KR, Keller DJ, Brozik JA. Single particle tracking reveals corralling of a transmembrane protein in a double-cushioned lipid bilayer assembly. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:320-327. [PMID: 21141848 DOI: 10.1021/la104133m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A predominate question associated with supported bilayer assemblies containing proteins is whether or not the proteins remain active after incorporation. The major cause for concern is that strong interactions with solid supports can render the protein inactive. To address this question, a large transmembrane protein, the serotonin receptor, 5HT(3A), has been incorporated into several supported membrane bilayer assemblies of increasing complexity. The 5HT(3A) receptor has large extracellular domains on both sides of the membrane, which could cause strong interactions. The bilayer assemblies include a simple POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) supported planar bilayer, a “single-cushion” POPC bilayer with a PEG (poly(ethylene glycol)) layer between membrane and support, and a “double-cushion” POPC bilayer with both a PEG layer and a layer of BSA (bovine serum albumin). Single-cushion systems are designed to lift the bilayer from the surface, and double-cushion systems are designed to both lift the membrane and passivate the solid support. As in previously reported work, protein mobilities measured by ensemble fluorescence recovery after photobleaching (FRAP) are quite low, especially in the double-cushion system. But single-particle tracking of fluorescent 5HT(3A) molecules shows that individual proteins in the double-cushion system have quite high local mobilities but are spatially confined within small corralling domains (<r(C)2> 450 nm). Comparisons with the simple POPC membrane and the single-cushion POPC−PEG membrane reveal that BSA both serves to minimize interactions with the solid support and creates the corrals that reduce the long-range (ensemble averaged) mobility of large transmembrane proteins. These results suggest that in double-cushion assemblies proteins with large extra-membrane domains may remain active and unperturbed despite low bulk diffusion constants.
Collapse
Affiliation(s)
- Kumud R Poudel
- Department of Chemistry, Washington State University, PO Box 644630, Pullman, Washington 99164-4630, United States
| | | | | |
Collapse
|
27
|
Moura Barbosa AJ, De Rienzo F, Ramos MJ, Menziani MC. Computational analysis of ligand recognition sites of homo- and heteropentameric 5-HT3 receptors. Eur J Med Chem 2010; 45:4746-60. [DOI: 10.1016/j.ejmech.2010.07.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 06/18/2010] [Accepted: 07/20/2010] [Indexed: 11/25/2022]
|
28
|
Abstract
Cys-loop receptors are membrane-spanning neurotransmitter-gated ion channels that are responsible for fast excitatory and inhibitory transmission in the peripheral and central nervous systems. The best studied members of the Cys-loop family are nACh, 5-HT3, GABAA and glycine receptors. All these receptors share a common structure of five subunits, pseudo-symmetrically arranged to form a rosette with a central ion-conducting pore. Some are cation selective (e.g. nACh and 5-HT3) and some are anion selective (e.g. GABAA and glycine). Each receptor has an extracellular domain (ECD) that contains the ligand-binding sites, a transmembrane domain (TMD) that allows ions to pass across the membrane, and an intracellular domain (ICD) that plays a role in channel conductance and receptor modulation. Cys-loop receptors are the targets for many currently used clinically relevant drugs (e.g. benzodiazepines and anaesthetics). Understanding the molecular mechanisms of these receptors could therefore provide the catalyst for further development in this field, as well as promoting the development of experimental techniques for other areas of neuroscience.In this review, we present our current understanding of Cys-loop receptor structure and function. The ECD has been extensively studied. Research in this area has been stimulated in recent years by the publication of high-resolution structures of nACh receptors and related proteins, which have permitted the creation of many Cys loop receptor homology models of this region. Here, using the 5-HT3 receptor as a typical member of the family, we describe how homology modelling and ligand docking can provide useful but not definitive information about ligand interactions. We briefly consider some of the many Cys-loop receptors modulators. We discuss the current understanding of the structure of the TMD, and how this links to the ECD to allow channel gating, and consider the roles of the ICD, whose structure is poorly understood. We also describe some of the current methods that are beginning to reveal the differences between different receptor states, and may ultimately show structural details of transitions between them.
Collapse
|
29
|
Nyce HL, Stober ST, Abrams CF, White MM. Mapping spatial relationships between residues in the ligand-binding domain of the 5-HT3 receptor using a molecular ruler. Biophys J 2010; 98:1847-55. [PMID: 20441748 DOI: 10.1016/j.bpj.2010.01.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 01/11/2010] [Accepted: 01/14/2010] [Indexed: 12/24/2022] Open
Abstract
The serotonin 5-HT(3) receptor (5-HT(3)R) is a member of the Cys-loop ligand-gated ion channel family. We used a combination of site-directed mutagenesis, homology modeling, and ligand-docking simulations to analyze antagonist-receptor interactions. Mutation of E236, which is near loop C of the binding site, to aspartate prevents expression of the receptor on the cell surface, and no specific ligand binding can be detected. On the other hand, mutation to glutamine, asparagine, or alanine produces receptors that are expressed on the cell surface, but decreases receptor affinity for the competitive antagonist d-tubocurarine (dTC) 5-35-fold. The results of a double-mutant cycle analysis employing a panel of dTC analogs to identify specific points of interactions between the dTC analogs and E236 are consistent with E236 making a direct physical interaction with the 12 -OH of dTC. dTC is a rigid molecule of known three-dimensional structure. Together with previous studies linking other regions of dTC to specific residues in the binding site, these data allow us to define the relative spatial arrangement of three different residues in the ligand-binding site: R92 (loop D), N128 (loop A), and E236 (near loop C). Molecular modeling employing these distance constraints followed by molecular-dynamics simulations produced a dTC/receptor complex consistent with the experimental data. The use of the rigid ligands as molecular rulers in conjunction with double-mutant cycle analysis provides a means of mapping the relative positions of various residues in the ligand-binding site of any ligand-receptor complex, and thus is a useful tool for delineating the architecture of the binding site.
Collapse
Affiliation(s)
- Heather L Nyce
- Department of Biochemistry, Drexel University College of Medicine, Philadelphia, Pennsylvania, USA
| | | | | | | |
Collapse
|
30
|
Agonists and antagonists bind to an A-A interface in the heteromeric 5-HT3AB receptor. Biophys J 2010; 98:1494-502. [PMID: 20409468 DOI: 10.1016/j.bpj.2009.12.4313] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 10/22/2009] [Accepted: 12/02/2009] [Indexed: 11/24/2022] Open
Abstract
The 5-HT3 receptor is a member of the Cys-loop family of transmitter receptors. It can function as a homopentamer (5-HT3A-only subunits) or as a heteropentamer. The 5-HT3AB receptor is the best characterized heteropentamer. This receptor differs from a homopentamer in its kinetics, voltage dependence, and single-channel conductance, but its pharmacology is similar. To understand the contribution of the 5-HT3B subunit to the binding site, we created homology models of 5-HT3AB receptors and docked 5-HT and granisetron into AB, BA, and BB interfaces. To test whether ligands bind in any or all of these interfaces, we mutated amino acids that are important for agonist and antagonist binding in the 5-HT3A subunit to their corresponding residues in the 5-HT3B subunit and vice versa. Changes in [3H]granisetron binding affinity (Kd) and 5-HT EC50 were determined using receptors expressed in HEK-293 cells and Xenopus oocytes, respectively. For all A-to-B mutant receptors, except T181N, antagonist binding was altered or eliminated. Functional studies revealed that either the receptors were nonfunctional or the EC50 values were increased. In B-to-A mutant receptors there were no changes in Kd, although EC50 values and Hill slopes, except for N170T mutant receptors, were similar to those for 5-HT3A receptors. Thus, the experimental data do not support a contribution of the 5-HT3B subunit to the binding pocket, and we conclude that both 5-HT and granisetron bind to an AA binding site in the heteromeric 5-HT3AB receptor.
Collapse
|
31
|
Vernekar SKV, Hallaq HY, Clarkson G, Thompson AJ, Silvestri L, Lummis SCR, Lochner M. Toward biophysical probes for the 5-HT3 receptor: structure-activity relationship study of granisetron derivatives. J Med Chem 2010; 53:2324-8. [PMID: 20146481 PMCID: PMC4166935 DOI: 10.1021/jm901827x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
This report describes the synthesis and biological characterization of novel granisetron derivatives that are antagonists of the human serotonin (5-HT3A) receptor. Some of these substituted granisetron derivatives showed low nanomolar binding affinity and allowed the identification of positions on the granisetron core that might be used as attachment points for biophysical tags. A BODIPY fluorophore was appended to one such position and specifically bound to 5-HT3A receptors in mammalian cells.
Collapse
|
32
|
Rajkumar R, Mahesh R. The auspicious role of the 5-HT3 receptor in depression: a probable neuronal target? J Psychopharmacol 2010; 24:455-69. [PMID: 20123937 DOI: 10.1177/0269881109348161] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The serotonergic mechanisms have been successfully utilized by the majority of antidepressant drug discovery programmes, while the search for newer targets remains persistent. The present review focused on the serotonin type-3 receptor, the only ion channel subtype in the serotonin family. Behavioural, neurochemical, electrophysiological and molecular analyses, including the results from our laboratory, provided substantial evidence that rationalizes the correlation between serotonin type-3 receptor modulation and rodent depressive-like behaviour. Nevertheless, the reports on polymorphism of serotonin type-3 receptor genes and data from clinical studies (on serotonin type-3 receptor antagonists) were insufficient to corroborate the involvement of this receptor in the neurobiology of depression. The preclinical and clinical studies that have contradicted the antidepressant-like effects of serotonin type-3 receptor antagonists and the reasons underlying such disagreement were discussed. Finally, this critical review commended the serotonin type-3 receptor as a candidate neuronal antidepressant drug target.
Collapse
|
33
|
Hazai E, Joshi P, Skoviak EC, Suryanarayanan A, Schulte MK, Bikadi Z. A comprehensive study on the 5-hydroxytryptamine3A receptor binding of agonists serotonin and m-chlorophenylbiguanidine. Bioorg Med Chem 2009; 17:5796-805. [DOI: 10.1016/j.bmc.2009.07.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Revised: 07/06/2009] [Accepted: 07/13/2009] [Indexed: 01/07/2023]
|
34
|
Morelli E, Gemma S, Budriesi R, Campiani G, Novellino E, Fattorusso C, Catalanotti B, Coccone SS, Ros S, Borrelli G, Persico M, Fiorini I, Nacci V, Ioan P, Chiarini A, Hamon M, Cagnotto A, Mennini T, Fracasso C, Colovic M, Caccia S, Butini S. Specific Targeting of Peripheral Serotonin 5-HT3 Receptors. Synthesis, Biological Investigation, and Structure−Activity Relationships. J Med Chem 2009; 52:3548-62. [DOI: 10.1021/jm900018b] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Elena Morelli
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Sandra Gemma
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Roberta Budriesi
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Giuseppe Campiani
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Ettore Novellino
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Caterina Fattorusso
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Bruno Catalanotti
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Salvatore Sanna Coccone
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Sindu Ros
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Giuseppe Borrelli
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Marco Persico
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Isabella Fiorini
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Vito Nacci
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Pierfranco Ioan
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Alberto Chiarini
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Michel Hamon
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Alfredo Cagnotto
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Tiziana Mennini
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Claudia Fracasso
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Milena Colovic
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Silvio Caccia
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| | - Stefania Butini
- European Research Centre for Drug Discovery and Development, Banchi di Sotto 55, 53100 Siena, Italy, Dipartimento Farmaco Chimico Tecnologico, Università di Siena, Via Aldo Moro 53100 Siena, Italy, Dipartimento di Chimica delle Sostanze Naturali (DCSN) e Dipartimento di Chimica Farmaceutica e Tossicologica (DCFT), Università di Napoli “Federico II”, Via D. Montesano 49, 80131 Napoli, Italy, Dipartimento di Scienze Farmaceutiche, Università di Bologna, Via Belmeloro 6, 40126 Bologna, Italy, Neurobiologie
| |
Collapse
|
35
|
de Oliveira-Pierce AN, Zhang R, Machu TK. Colchicine: a novel positive allosteric modulator of the human 5-hydroxytryptamine3A receptor. J Pharmacol Exp Ther 2009; 329:838-47. [PMID: 19188483 DOI: 10.1124/jpet.108.146522] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The actions of colchicine were examined with the two-electrode voltage-clamp technique and radioligand binding assays in mouse and human 5-hydroxytryptamine(3A) receptors (5-HT(3A)Rs) expressed in Xenopus laevis oocytes. Colchicine inhibited 5-hydroxytryptamine (5-HT)-evoked currents in oocytes expressing mouse 5-HT(3A)Rs, with an IC(50) of 59.5 +/- 3 microM. In contrast to the mouse receptor, coapplication of colchicine with 5-HT (<1 microM) strongly enhanced 5-HT-evoked currents in oocytes expressing human 5-HT(3A)Rs. Colchicine applied alone did not induce a detectable current. In the presence of 0.5 microM 5-HT, the potentiation was concentration-dependent and reached the maximum (approximately 100%) when 750 microM colchicine was applied. However, colchicine-dependent inhibition can be observed at 5-HT concentrations > 1 microM. In oocyte membranes expressing mouse or human receptors, binding studies with colchicine (25 nM-1 mM) revealed no displacement of 1-methyl-N-((1R,3r,5S)-9-methyl-9 azabicyclo [3.3.1]nonan-3yl)-1H-indazole-3 carboxamide ([(3)H]BRL-43694), suggesting that actions of colchicine do not occur at the ligand binding domain. Functional effects of colchicine on both receptors occurred in the absence of preincubation and after cold temperature incubation, suggesting that the microtubule-depolymerizing effects of colchicine play no role in modulation of receptor function. Studies with interspecies chimeric receptors demonstrated that the distal one third of the N terminus is responsible for the bidirectional modulation by colchicine. Collectively, these results suggest that colchicine modulates receptor function through loops C and/or F through a gating mechanism.
Collapse
Affiliation(s)
- A N de Oliveira-Pierce
- Department of Pharmacology and Neuroscience, University of North Texas Health Sciences Center, Fort Worth, TX 76107, USA.
| | | | | |
Collapse
|
36
|
Barnes NM, Hales TG, Lummis SC, Peters JA. The 5-HT3 receptor--the relationship between structure and function. Neuropharmacology 2009; 56:273-84. [PMID: 18761359 PMCID: PMC6485434 DOI: 10.1016/j.neuropharm.2008.08.003] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/31/2008] [Accepted: 08/01/2008] [Indexed: 12/15/2022]
Abstract
The 5-hydroxytryptamine type-3 (5-HT3) receptor is a cation-selective ion channel of the Cys-loop superfamily. 5-HT3 receptor activation in the central and peripheral nervous systems evokes neuronal excitation and neurotransmitter release. Here, we review the relationship between the structure and the function of the 5-HT3 receptor. 5-HT3A and 5-HT3B subunits are well established components of 5-HT3 receptors but additional HTR3C, HTR3D and HTR3E genes expand the potential for molecular diversity within the family. Studies upon the relationship between subunit structure and the ionic selectivity and single channel conductances of 5-HT3 receptors have identified a novel domain (the intracellular MA-stretch) that contributes to ion permeation and selectivity. Conventional and unnatural amino acid mutagenesis of the extracellular domain of the receptor has revealed residues, within the principle (A-C) and complementary (D-F) loops, which are crucial to ligand binding. An area requiring much further investigation is the subunit composition of 5-HT3 receptors that are endogenous to neurones, and their regional expression within the central nervous system. We conclude by describing recent studies that have identified numerous HTR3A and HTR3B gene polymorphisms that impact upon 5-HT3 receptor function, or expression, and consider their relevance to (patho)physiology.
Collapse
Affiliation(s)
- Nicholas M. Barnes
- Cellular and Molecular Neuropharmacology Research Group, Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Tim G. Hales
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, USA
| | - Sarah C.R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - John A. Peters
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, The University of Dundee, Dundee DD1 9SY, UK
- Corresponding author. Tel.: +44 01382 660111x33117; fax: +44 01382 667120. E-mail address: (J.A. Peters)
| |
Collapse
|
37
|
A cation-pi interaction in the binding site of the glycine receptor is mediated by a phenylalanine residue. J Neurosci 2008; 28:10937-42. [PMID: 18945901 DOI: 10.1523/jneurosci.2540-08.2008] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cys-loop receptor binding sites characteristically contain many aromatic amino acids. In nicotinic ACh and 5-HT3 receptors, a Trp residue forms a cation-pi interaction with the agonist, whereas in GABA(A) receptors, a Tyr performs this role. The glycine receptor binding site, however, contains predominantly Phe residues. Homology models suggest that two of these Phe side chains, Phe159 and Phe207, and possibly a third, Phe63, are positioned such that they could contribute to a cation-pi interaction with the primary amine of glycine. Here, we test this hypothesis by incorporation of a series of fluorinated Phe derivatives using unnatural amino acid mutagenesis. The data reveal a clear correlation between the glycine EC(50) value and the cation-pi binding ability of the fluorinated Phe derivatives at position 159, but not at positions 207 or 63, indicating a single cation-pi interaction between glycine and Phe159. The data thus provide an anchor point for locating glycine in its binding site, and demonstrate for the first time a cation-pi interaction between Phe and a neurotransmitter.
Collapse
|
38
|
Abstract
The 5-HT3 receptor belongs to a family of therapeutically important neurotransmitter-gated receptors whose ligand binding sites are formed by the convergence of six peptide loops (A-F). Here we have mutated 15 amino acid residues in and around loop B of the 5-HT3 receptor (Ser-177 to Asn-191) to Ala or a residue with similar chemical properties. Changes in [3H]granisetron binding affinity (Kd) and 5-HT EC50 were determined using receptors expressed in human embryonic kidney 293 cells. Substitutions at all but one residue (Thr-181) altered or eliminated binding for one or both mutants. Receptors were nonfunctional or EC50 values were altered for all but two mutants (S182T, I190L). Homology modeling indicates that loop B contributes two residues to a hydrophobic core that faces into the β-sandwich of the subunit, and the experimental data indicate that they are important for both the structure and the function of the receptor. The models also show that close to the apex of the loop (Ser-182 to Ile-190), loop B residues form an extensive network of hydrogen bonds, both with other loop B residues and with adjacent regions of the protein. Overall, the data suggest that loop B has a major role in maintaining the structure of the region by a series of noncovalent interactions that are easily disrupted by amino acid substitutions.
Collapse
|
39
|
Yang LJ, Hou YC, Bai YJ, Yao LB, Su CZ. Analysis of primary structure and modeling of spatial structure of single-chain variable region of antibody against human gastric cancer. Shijie Huaren Xiaohua Zazhi 2008; 16:2333-2336. [DOI: 10.11569/wcjd.v16.i21.2333] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To analyze the sequence of heavy and light chain of the variable region (VH and VL) in the anti-human gastric cancer antibody, select a suitable linker peptide to construct single chain antibody, model the 3-D structure and predict the relationship between its structure and function.
METHODS: Using the sequences of VH and VL, which derived from the phage display library of antibodies against human gastric cancer, a suitable linker peptide was chosen to obtain the primary structure of the single-chain antibody with considering the C-terminal and N-terminal structural character. Furthermore, the 3-D theoretical structure was modeled with computer-guided homology modeling method. The stable spatial conformation of the single-chain variable region was determined with mechanism optimization and molecular dynamic simulation. The structural property and physical-chemical characters were analyzed using the distance geometry, surface electrostatic distribution and solvent accessible surface calculation.
RESULTS: The conformation of the successfully constructed single-chain antibody was stable. Except one amino acid conformation of connecting peptide, others' were reasonable. VL CDR1, CDR2 and VH CDR3 solution accessibility surface area distributed strongly, but VL CDR3, VH CDR1, and CDR2 were comparatively weak. VH CDR3 region had strong electronegativity.
CONCLUSION: The 3-D structure of the created single chain antibody is proved reasonable and reliable.
Collapse
|
40
|
Thompson AJ, Lummis SCR. Calcium modulation of 5-HT3 receptor binding and function. Neuropharmacology 2008; 56:285-91. [PMID: 18675830 DOI: 10.1016/j.neuropharm.2008.07.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Revised: 06/23/2008] [Accepted: 07/08/2008] [Indexed: 10/21/2022]
Abstract
Calcium modulates the 5-HT3 receptor response by reducing peak current amplitude and increasing rates of activation, deactivation and desensitisation, but the binding site(s) and mechanism(s) of this modulation are unknown. Here we study residues that may be involved in calcium binding in two partially overlapping regions of the extracellular domain (E213-E215-E218 and D204-E218-V219). The modulatory effects of calcium were assessed by radioligand binding and whole-cell patch-clamp. Comparisons of [3H]granisetron binding showed an increase in Kd in 10mM calcium that was abolished by the substitutions E213Q, E215Q, D204N and V219L. E218Q mutant receptors displayed no specific binding or function, and immunofluorescence showed that they did not reach the cell surface. E213Q increased inherent rates of desensitisation, but the relative effects of calcium on these rates, and on the reduction in current amplitude, were similar to wild type receptors. Current responses and calcium-mediated effects at E215Q mutant receptors were indistinguishable from wild type. D204N and V219L mutants were non-functional. A calcium impermeable mutant (E277A/S297R) revealed no changes in peak amplitude or kinetics with increased calcium. Our results are consistent with residues D204, E218 and V219 participating in receptor assembly, structure and/or trafficking to the plasma membrane, and we speculate that this might rely upon the stabilising effect of bound calcium. E213, E215, D204 and V219 may contribute to a calcium binding site that is responsible for the calcium-mediated effects on ligand binding. However, the major site for calcium-dependent modulation of the 5-HT3 current is located within the ion channel or cell interior.
Collapse
Affiliation(s)
- Andrew J Thompson
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | | |
Collapse
|
41
|
Price KL, Bower KS, Thompson AJ, Lester HA, Dougherty DA, Lummis SCR. A hydrogen bond in loop A is critical for the binding and function of the 5-HT3 receptor. Biochemistry 2008; 47:6370-7. [PMID: 18498149 PMCID: PMC2649372 DOI: 10.1021/bi800222n] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The binding sites of Cys-loop receptors are formed from at least six loops (A-F). Here we have used mutagenesis, radioligand binding, voltage clamp electrophysiology, and homology modeling to probe the role of two residues in loop A of the 5-HT3 receptor: Asn128 and Glu129. The data show that substitution of Asn128, with a range of alternative natural and unnatural amino acids, changed the EC50 (from approximately 10-fold more potent to approximately 10-fold less potent than that of the wild type), increased the maximal peak current for mCPBG compared to 5-HT (R max) 2-19-fold, and decreased n H, indicating this residue is involved in receptor gating; we propose Asn128 faces away from the binding pocket and plays a role in facilitating transitions between conformational states. Substitutions of Glu129 resulted in functional receptors only when the residue could accept a hydrogen bond, but with both these and other substitutions, no [(3)H]granisetron binding could be detected, indicating a role in ligand binding. We propose that Glu129 faces into the binding pocket, where, through its ability to hydrogen bond, it plays a critical role in ligand binding. Thus, the data support a modified model of the 5-HT3 receptor binding site and show that loop A plays a critical role in both the ligand binding and function of this receptor.
Collapse
Affiliation(s)
- Kerry L Price
- Department of Biochemistry, University of Cambridge, UK
| | | | | | | | | | | |
Collapse
|
42
|
Thompson AJ, Lummis SCR. Antimalarial drugs inhibit human 5-HT(3) and GABA(A) but not GABA(C) receptors. Br J Pharmacol 2008; 153:1686-96. [PMID: 18311193 PMCID: PMC2438262 DOI: 10.1038/bjp.2008.34] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Antimalarial compounds have been previously shown to inhibit rodent nicotinic acetylcholine (nACh) and 5-HT(3) receptors. Here, we extend these studies to include human 5-HT(3A), 5-HT(3AB), GABA(A) alpha1beta2, GABA(A) alpha1beta2gamma2 and GABA(C) rho1 receptors. EXPERIMENTAL APPROACH We examined the effects of quinine, chloroquine and mefloquine on the electrophysiological properties of receptors expressed in Xenopus oocytes. KEY RESULTS 5-HT(3A) receptor responses were inhibited by mefloquine, quinine and chloroquine with IC(50) values of 0.66, 1.06 and 24.3 microM. At 5-HT(3AB) receptors, the potencies of mefloquine (IC(50)=2.7 microM) and quinine (15.8 microM), but not chloroquine (23.6 microM), were reduced. Mefloquine, quinine and chloroquine had higher IC(50) values at GABA(A) alpha1beta2 (98.7, 0.40 and 0.46 mM, respectively) and GABA(A) alpha1beta2gamma2 receptors (0.38, 1.69 and 0.67 mM, respectively). No effect was observed at GABA(C) rho1 receptors. At all 5-HT(3) and GABA(A) receptors, chloroquine displayed competitive behaviour and mefloquine was non-competitive. Quinine was competitive at 5-HT(3A) and GABA(A) receptors, but non-competitive at 5-HT(3AB) receptors. Homology modelling in combination with automated docking suggested orientations of quinine and chloroquine at the GABA(A) receptor binding site. CONCLUSIONS AND IMPLICATIONS The effects of mefloquine, quinine and chloroquine are distinct at GABA(A) and GABA(C) receptors, whereas their effects on 5-HT(3AB) receptors are broadly similar to those at 5-HT(3A) receptors. IC(50) values for chloroquine and mefloquine at 5-HT(3) receptors are close to therapeutic blood concentrations required for malarial treatment, suggesting that their therapeutic use could be extended to include the treatment of 5-HT(3) receptor-related disorders.
Collapse
Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | |
Collapse
|
43
|
Bower KS, Price KL, Sturdee LE, Dayrell M, Dougherty DA, Lummis SC. 5-Fluorotryptamine is a partial agonist at 5-HT3 receptors, and reveals that size and electronegativity at the 5 position of tryptamine are critical for efficient receptor function. Eur J Pharmacol 2008; 580:291-7. [PMID: 18082160 PMCID: PMC2649378 DOI: 10.1016/j.ejphar.2007.11.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 11/09/2007] [Indexed: 11/19/2022]
Abstract
Antagonists, but not agonists, of the 5-HT3 receptor are useful therapeutic agents, and it is possible that partial agonists may also be potentially useful in the clinic. Here we show that 5-fluorotryptamine (5-FT) is a partial agonist at both 5-HT3A and 5-HT3AB receptors with an Rmax (Imax/Imax 5-HT) of 0.64 and 0.45 respectively. It is about 10 fold less potent than 5-HT: EC50=16 and 27 microM, and Ki for displacement of [3H]granisetron binding=0.8 and 1.8 microM for 5-HT3A and 5-HT3AB receptors respectively. We have also explored the potencies and efficacies of tryptamine and a range of 5-substituted tryptamine derivatives. At 5-HT3A receptors tryptamine is a weak (Rmax=0.15), low affinity (EC50=113 microM; Ki=4.8 microM) partial agonist, while 5-chlorotryptamine has a similar affinity to 5-FT (EC50=8.1 microM; Ki=2.7 microM) but is a very weak partial agonist (Rmax=0. 0037). These, and data from 5-methyltryptamine and 5-methoxytryptamine, reveal the importance of size and electronegativity at this location for efficient channel opening.
Collapse
Affiliation(s)
- Kiowa S. Bower
- California Institute of Technology, Pasadena, California, USA
| | - Kerry L. Price
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | - Mariza Dayrell
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | | |
Collapse
|
44
|
Yang LJ, Hou YC, Yao LB, Su CZ. Analysis of primary structure and modeling of spatial structure of heavy chain variable region of antibody against human gastric cancer. Shijie Huaren Xiaohua Zazhi 2008; 16:413-416. [DOI: 10.11569/wcjd.v16.i4.413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To confirm the primary structure of heavy chain variable regions (VH) of antibody against human gastric cancer based on the sequence analysis method and to model its three-dimensional structure using homology modeling method.
METHODS: The VH gene selected from the phage display library of antibodies against human gastric cancer was sequenced and analyzed. Its three-dimensional structure was modeled with computer homology modeling techniques and optimized using molecular mechanism method.
RESULTS: The sequence of VH was in agreement with the characteristics of the mouse antibody variable region. The FR and CDR were determined by Kabat analysis. The spatial structure of the VH was constructed and optimized with molecular mechanism method to obtain the stable 3-D structure.
CONCLUSION: The primary and three-dimensional structures of VH are reasonable and reliable and lay the theoretical foundation for further biological experiments.
Collapse
|
45
|
Thompson AJ, Lochner M, Lummis SCR. The antimalarial drugs quinine, chloroquine and mefloquine are antagonists at 5-HT3 receptors. Br J Pharmacol 2007; 151:666-77. [PMID: 17502851 PMCID: PMC1994240 DOI: 10.1038/sj.bjp.0707238] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The antimalarial compounds quinine, chloroquine and mefloquine affect the electrophysiological properties of Cys-loop receptors and have structural similarities to 5-HT(3) receptor antagonists. They may therefore act at 5-HT(3) receptors. EXPERIMENTAL APPROACH The effects of quinine, chloroquine and mefloquine on electrophysiological and ligand binding properties of 5-HT(3A) receptors expressed in HEK 293 cells and Xenopus oocytes were examined. The compounds were also docked into models of the binding site. KEY RESULTS 5-HT(3) responses were blocked with IC (50) values of 13.4 microM, 11.8 microM and 9.36 microM for quinine, chloroquine and mefloquine. Schild plots indicated quinine and chloroquine behaved competitively with pA (2) values of 4.92 (K (B)=12.0 microM) and 4.97 (K (B)=16.4 microM). Mefloquine displayed weakly voltage-dependent, non-competitive inhibition consistent with channel block. On and off rates for quinine and chloroquine indicated a simple bimolecular reaction scheme. Quinine, chloroquine and mefloquine displaced [(3)H]granisetron with K (i) values of 15.0, 24.2 and 35.7 microM. Docking of quinine into a homology model of the 5-HT(3) receptor binding site located the tertiary ammonium between W183 and Y234, and the quinoline ring towards the membrane, stabilised by a hydrogen bond with E129. For chloroquine, the quinoline ring was positioned between W183 and Y234 and the tertiary ammonium stabilised by interactions with F226. CONCLUSIONS AND IMPLICATIONS This study shows that quinine and chloroquine competitively inhibit 5-HT(3) receptors, while mefloquine inhibits predominantly non-competitively. Both quinine and chloroquine can be docked into a receptor binding site model, consistent with their structural homology to 5-HT(3) receptor antagonists.
Collapse
Affiliation(s)
- A J Thompson
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | | |
Collapse
|
46
|
Abstract
The 5-HT3 receptor is a neurotransmitter-gated ion channel. It is a member of the Cys-loop family of receptors, which also includes nicotinic acetylcholine, glycine and GABAA receptors. Each member of the family consists of an arrangement of five subunits surrounding a central ion-conducting pore. The 5-HT3 receptor binding site is composed of six loops from two adjacent subunits, and the critical ligand binding residues within these loops are well documented. There are a range of 5-HT3 receptor agonists and competitive antagonists, but it is the antagonists that dominate their clinical use. Studies have proposed a range of disease symptoms that might be amenable to 5-HT3 receptor selective compounds; however, so far only the treatment of emesis and irritable bowel syndrome have been fully realised. In this review, the authors look at the structure, function and distribution of 5-HT3 receptors and how this may influence their role in disease. The authors also describe the existing clinical applications of 5-HT3 antagonists and the future potential of these drugs.
Collapse
Affiliation(s)
- Andrew J Thompson
- University of Cambridge, Department of Biochemistry, Tennis Court Road, Cambridge , CB2 1QW, UK
| | - Sarah CR Lummis
- University of Cambridge, Department of Biochemistry, Tennis Court Road, Cambridge , CB2 1QW, UK
| |
Collapse
|
47
|
Peters JA, Carland JE, Cooper MA, Livesey MR, Deeb TZ, Hales TG, Lambert JJ. Novel structural determinants of single-channel conductance in nicotinic acetylcholine and 5-hydroxytryptamine type-3 receptors. Biochem Soc Trans 2007; 34:882-6. [PMID: 17052220 DOI: 10.1042/bst0340882] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Nicotinic ACh (acetylcholine) and 5-HT3 (5-hydroxytryptamine type-3) receptors are cation-selective ion channels of the Cys-loop transmitter-gated ion channel superfamily. Numerous lines of evidence indicate that the channel lining domain of such receptors is formed by the alpha-helical M2 domain (second transmembrane domain) contributed by each of five subunits present within the receptor complex. Specific amino acid residues within the M2 domain have accordingly been demonstrated to influence both single-channel conductance (gamma) and ion selectivity. However, it is now clear from work performed on the homomeric 5-HT3A receptor, heteromeric 5-HT3A/5-HT3B receptor and 5-HT3A/5-HT3B receptor subunit chimaeric constructs that an additional major determinant of gamma resides within a cytoplasmic domain of the receptor termed the MA-stretch (membrane-associated stretch). The MA-stretch, within the M3-M4 loop, is not traditionally thought to be implicated in ion permeation and selection. Here, we describe how such observations extend to a representative neuronal nicotinic ACh receptor composed of alpha4 and beta2 subunits and, by inference, probably other members of the Cys-loop family. In addition, we will attempt to interpret our results within the context of a recently developed atomic scale model of the nicotinic ACh receptor of Torpedo marmorata (marbled electric ray).
Collapse
Affiliation(s)
- J A Peters
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, The University of Dundee, Dundee DD1 9SY, UK.
| | | | | | | | | | | | | |
Collapse
|
48
|
Sullivan NL, Thompson AJ, Price KL, Lummis SCR. Defining the roles of Asn-128, Glu-129 and Phe-130 in loop A of the 5-HT3 receptor. Mol Membr Biol 2007; 23:442-51. [PMID: 17060161 PMCID: PMC2649376 DOI: 10.1080/09687860600831539] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The ligand binding pocket of Cys-loop receptors consists of a number of binding loops termed A-F. Here we examine the 5-HT3 receptor loop A residues Asn-128, Glu-129 and Phe-130 using modelling, mutagenesis, radioligand binding and functional studies on HEK 293 cells. Replacement of Asn-128 results in receptors that have wild type [3H]granisetron binding characteristics but large changes (ranging from a five-fold decrease to a 1500-fold increase) in the 5-HT EC50 when compared to wild type receptors. Phe-130 mutant receptors show both increases and decreases in Kd and EC50 values, depending on the amino acid substituted. The most critical of these residues appears to be Glu-129; its replacement with a range of other amino acids results in non-binding and non-functional receptors. Lack of binding and function in some, but not all, of these receptors is due to poor membrane expression. These data suggest that Glu-129 is important primarily for receptor expression, although it may also play a role in ligand binding; Phe-130 is important for both ligand binding and receptor function, and Asn-128 plays a larger role in receptor function than ligand binding. In light of these results, we have created two new homology models of the 5-HT3 receptor, with alternative positions of loop A. In our preferred model Glu-129 and Phe-130 contribute to the binding site, while the location of Asn-128 immediately behind the binding pocket could contribute to the conformation changes that result in receptor gating. This study provides a new model of the 5-HT3 receptor binding pocket, and also highlights the importance of experimental data to support modelling studies.
Collapse
Affiliation(s)
- Nora L Sullivan
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | | | | |
Collapse
|
49
|
Zettl H, Schubert-Zsilavecz M, Siebert CD. [From cocaine to innovative antiemetics. The medicinal chemistry of 5-ht3 receptor antagonists]. PHARMAZIE IN UNSERER ZEIT 2007; 36:354-61. [PMID: 17722162 DOI: 10.1002/pauz.200700231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Affiliation(s)
- Heiko Zettl
- Institut für Pharmazeutische Chemie, Zentrum für Arzneimittelforschung, Entwicklung und Sicherheit, Max-von-Laue-Str. 9, 60438 Frankfurt
| | | | | |
Collapse
|
50
|
Yang Z, Ney A, Cromer BA, Ng HL, Parker MW, Lynch JW. Tropisetron modulation of the glycine receptor: femtomolar potentiation and a molecular determinant of inhibition. J Neurochem 2006; 100:758-69. [PMID: 17181559 DOI: 10.1111/j.1471-4159.2006.04242.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 5-hydroxytryptamine type-3 receptor antagonist tropisetron is in clinical use as an anti-emetic drug. This compound also exerts both potentiating and inhibitory effects on the glycine receptor chloride channel. The inhibitory effects occur at micromolar concentrations, whereas the potentiating effects are shown here to occur at femtomolar concentrations at the homomeric alpha1 receptor. Potentiation occurred only when tropisetron was applied in the presence of glycine. We also sought to identify molecular determinants of tropisetron inhibition at the alpha1 glycine receptor by serially mutating residues located in or near known ligand-binding sites. We discovered that conservative mutations to N102 ablated tropisetron inhibition without affecting the magnitude or sensitivity of tropisetron potentiation. Several lines of evidence, including a structure-activity analysis of tropisetron, atropine and SB203186, suggest that N102 may bind to the tropisetron tropane nitrogen via H-bonding. Mutation of the N125 residue in the beta subunit, which corresponds to N102 in the alpha1 subunit, had little effect on tropisetron inhibitory potency. These results show that N102 is required for tropisetron inhibition but not potentiation and that inhibitory tropisetron binds in different orientations at different subunit interfaces. To our knowledge, tropisetron is the most exquisitely sensitive modulator yet identified for a cys-loop receptor.
Collapse
Affiliation(s)
- Zhe Yang
- School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
| | | | | | | | | | | |
Collapse
|