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Gomes JV, Singh-Bhagania S, Cenci M, Chacon Cordon C, Singh M, Butterwick JA. The molecular basis of sugar detection by an insect taste receptor. Nature 2024; 629:228-234. [PMID: 38447670 PMCID: PMC11062906 DOI: 10.1038/s41586-024-07255-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 02/28/2024] [Indexed: 03/08/2024]
Abstract
Animals crave sugars because of their energy potential and the pleasurable sensation of tasting sweetness. Yet all sugars are not metabolically equivalent, requiring mechanisms to detect and differentiate between chemically similar sweet substances. Insects use a family of ionotropic gustatory receptors to discriminate sugars1, each of which is selectively activated by specific sweet molecules2-6. Here, to gain insight into the molecular basis of sugar selectivity, we determined structures of Gr9, a gustatory receptor from the silkworm Bombyx mori (BmGr9), in the absence and presence of its sole activating ligand, D-fructose. These structures, along with structure-guided mutagenesis and functional assays, illustrate how D-fructose is enveloped by a ligand-binding pocket that precisely matches the overall shape and pattern of chemical groups in D-fructose. However, our computational docking and experimental binding assays revealed that other sugars also bind BmGr9, yet they are unable to activate the receptor. We determined the structure of BmGr9 in complex with one such non-activating sugar, L-sorbose. Although both sugars bind a similar position, only D-fructose is capable of engaging a bridge of two conserved aromatic residues that connects the pocket to the pore helix, inducing a conformational change that allows the ion-conducting pore to open. Thus, chemical specificity does not depend solely on the selectivity of the ligand-binding pocket, but it is an emergent property arising from a combination of receptor-ligand interactions and allosteric coupling. Our results support a model whereby coarse receptor tuning is derived from the size and chemical characteristics of the pocket, whereas fine-tuning of receptor activation is achieved through the selective engagement of an allosteric pathway that regulates ion conduction.
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Affiliation(s)
- João Victor Gomes
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | | | - Matthew Cenci
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Carlos Chacon Cordon
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Manjodh Singh
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Joel A Butterwick
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA.
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Schwartz M, Boichot V, Fraichard S, Muradova M, Senet P, Nicolai A, Lirussi F, Bas M, Canon F, Heydel JM, Neiers F. Role of Insect and Mammal Glutathione Transferases in Chemoperception. Biomolecules 2023; 13:biom13020322. [PMID: 36830691 PMCID: PMC9953322 DOI: 10.3390/biom13020322] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/01/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Glutathione transferases (GSTs) are ubiquitous key enzymes with different activities as transferases or isomerases. As key detoxifying enzymes, GSTs are expressed in the chemosensory organs. They fulfill an essential protective role because the chemosensory organs are located in the main entry paths of exogenous compounds within the body. In addition to this protective function, they modulate the perception process by metabolizing exogenous molecules, including tastants and odorants. Chemosensory detection involves the interaction of chemosensory molecules with receptors. GST contributes to signal termination by metabolizing these molecules. By reducing the concentration of chemosensory molecules before receptor binding, GST modulates receptor activation and, therefore, the perception of these molecules. The balance of chemoperception by GSTs has been shown in insects as well as in mammals, although their chemosensory systems are not evolutionarily connected. This review will provide knowledge supporting the involvement of GSTs in chemoperception, describing their localization in these systems as well as their enzymatic capacity toward odorants, sapid molecules, and pheromones in insects and mammals. Their different roles in chemosensory organs will be discussed in light of the evolutionary advantage of the coupling of the detoxification system and chemosensory system through GSTs.
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Affiliation(s)
- Mathieu Schwartz
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Valentin Boichot
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Stéphane Fraichard
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Mariam Muradova
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Patrick Senet
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Université de Bourgogne Franche-Comté, 21078 Dijon, France
| | - Adrien Nicolai
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS, Université de Bourgogne Franche-Comté, 21078 Dijon, France
| | - Frederic Lirussi
- UMR 1231, Lipides Nutrition Cancer, INSERM, 21000 Dijon, France
- UFR des Sciences de Santé, Université de Bourgogne Franche-Comté, 25000 Besançon, France
- Plateforme PACE, Laboratoire de Pharmacologie-Toxicologie, Centre Hospitalo-Universitaire Besançon, 25000 Besançon, France
| | - Mathilde Bas
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Francis Canon
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Jean-Marie Heydel
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
| | - Fabrice Neiers
- Laboratory: Flavour Perception: Molecular Mechanims (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, 21000 Dijon, France
- Correspondence:
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Affiliation(s)
- Anne Tromelin
- CNRS; UMR6265 Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
- INRA; UMR1324 Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
- Université de Bourgogne; UMR Centre des Sciences du Goût et de l'Alimentation; F-21000 Dijon France
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Sbarbati A, Bramanti P, Benati D, Merigo F. The diffuse chemosensory system: exploring the iceberg toward the definition of functional roles. Prog Neurobiol 2010; 91:77-89. [PMID: 20138111 DOI: 10.1016/j.pneurobio.2010.01.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 12/11/2009] [Accepted: 01/27/2010] [Indexed: 01/18/2023]
Abstract
The diffuse chemosensory system (DCS) is an anatomical structure composed of solitary chemosensory cells (SCCs, also called solitary chemoreceptor cells), which have analogies with taste cells but are not aggregated in buds. The concept of DCS has been advanced, after the discovery that cells similar to gustatory elements are present in several organs. The elements forming the DCS share common morphological and biochemical characteristics with the taste cells located in taste buds of the oro-pharyngeal cavity but they are localized in internal organs. In particular, they may express molecules of the chemoreceptorial cascade (e.g. trans-membrane taste receptors, the G-protein alpha-gustducin, PLCbeta2, TRPM5). This article will focus on the mammalian DCS in apparatuses of endodermic origin (i.e. digestive and respiratory systems), which is composed of an enormous number of sensory elements and presents a multiplicity of morphological aspects. Recent research has provided an adequate description of these elements, but the functional role for the DCS in these apparatuses is unknown. The initial findings led to the definition of a DCS structured like an iceberg, with a mysterious "submerged" portion localized in the distal part of endodermic apparatuses. Recent work has focussed on the discovery of this submerged portion, which now appears less puzzling. However, the functional roles of the different cytotypes belonging to the DCS are not well known. Recent studies linked chemosensation of the intraluminal content to local control of absorptive and secretory (exocrine and endocrine) processes. Control of the microbial population and detection of irritants seem to be other possible functions of the DCS. In the light of these new findings, the DCS might be thought to be involved in a wide range of diseases of both the respiratory (e.g. asthma, chronic obstructive pulmonary disease, cystic fibrosis) and digestive apparatuses (absorptive or secretive diseases, dysmicrobism), as well as in systemic diseases (e.g. obesity, diabetes). A description of the functional roles of the DCS might be a first step toward the discovery of therapeutic approaches which target chemosensory mechanisms.
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Affiliation(s)
- Andrea Sbarbati
- Human Anatomy and Histology Section, University of Verona, Medical Faculty, Verona, Italy.
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Markov AV, Kulikov AM. The hypothesis of immune testing of partners—coordinated adaptations and changes in mating preferences. BIOL BULL+ 2006. [DOI: 10.1134/s1062359006030010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Exclusive gene expression, where only one member of a gene or gene cassette family is selected for expression, plays an important role in the establishment of cell identity in several biological systems. Here, we compare four such systems: mating-type switching in fission and budding yeast, where cells choose between expressing one of the two different mating-type cassettes, and immunoglobulin and odorant receptor gene expression in mammals, where the number of gene choices is substantially higher. The underlying mechanisms that establish this selective expression pattern in each system differ in almost every detail. In all four systems, once a successful gene activation event has taken place, a feedback mechanism affects the fate of the cell. In the mammalian systems, feedback is mediated by the expressed cell surface receptor to ensure monoallelic gene expression, whereas in the yeasts, the expressed gene cassette at the mating-type locus affects donor choice during the subsequent switching event.
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Perry BF, Kountakis SE. Subjective improvement of olfactory function after endoscopic sinus surgery for chronic rhinosinusitis. Am J Otolaryngol 2004; 24:366-9. [PMID: 14608567 DOI: 10.1016/s0196-0709(03)00067-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE The purpose of this study was to determine the effect of functional endoscopic sinus surgery (FESS) on subjective olfactory dysfunction in patients with chronic rhinosinusitis. Materials and methods Prospective collection of data on consecutive patients undergoing FESS after failing prolonged medical therapy for chronic rhinosinusitis at a tertiary institution. Patients were asked to grade their olfactory dysfunction from 0 to 10, with 0 representing normal function and 10 complete anosmia. In addition, data such as computed tomography scores, presence or absence of nasal polyps, and the presence or absence of asthma were recorded and analyzed. Patients were followed up to 1 year after surgery. RESULTS Data were collected on 178 patients who had sinus surgery over a 2-year period. The average olfactory dysfunction score before surgery was 4.9. This improved to 0.9 at 1 year after surgery (P =.00). Higher computed tomography scores as per Lund and MacKay correlated with higher olfactory dysfunction scores (r = 0.62, P <.01) and greater improvement after surgery (r = 0.82, P <.01). Asthmatics and patients with polyps had higher subjective olfactory dysfunction scores than nonasthmatics and patients without polyps (6.8 and 7.2 v 4.4 and 4.1, respectively). All groups had subjective improvement at 1 year (2.3 and 1.5 v 0.6 and 0.7, respectively; P =.00). CONCLUSION Patients with subjective olfactory dysfunction despite appropriate medical management for rhinosinusitis benefit from FESS.
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Affiliation(s)
- Brian F Perry
- Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Augusta, GA 30912-4060, USA
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Abstract
The perception of odorant molecules provides the essential information that allows animals to explore their surrounding. We describe here how the external world of scents may sculpt the activity of the first central relay of the olfactory system, i.e., the olfactory bulb. This structure is one of the few brain areas to continuously replace one of its neuronal populations: the local GABAergic interneurons. How the newly generated neurons integrate into a pre-existing neural network and how basic olfactory functions are maintained when a large percentage of neurons are subjected to continuous renewal, are important questions that have recently received new insights. Furthermore, we shall see how the adult neurogenesis is specifically subjected to experience-dependent modulation. In particular, we shall describe the sensitivity of the bulbar neurogenesis to the activity level of sensory inputs from the olfactory epithelium and, in turn, how this neurogenesis may adjust the neural network functioning to optimize odor information processing. Finally, we shall discuss the behavioral consequences of the bulbar neurogenesis and how it may be appropriate for the sense of smell. By maintaining a constitutive turnover of bulbar interneurons subjected to modulation by environmental cues, we propose that adult ongoing neurogenesis in the olfactory bulb is associated with improved olfactory memory. These recent findings not only provide new fuel for the molecular and cellular bases of sensory perception but should also shed light onto cellular bases of learning and memory.
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Affiliation(s)
- Pierre-Marie Lledo
- Laboratory of Perception and Memory, Centre National de la Recherche Scientifique, Unité de Recherche Associée 2182, Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris, France.
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Behrens M, Margolis JW, Margolis FL. Identification of members of the Bex gene family as olfactory marker protein (OMP) binding partners. J Neurochem 2003; 86:1289-96. [PMID: 12911636 DOI: 10.1046/j.1471-4159.2003.01940.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Olfactory marker protein (OMP) expression is a hallmark of mature vertebrate olfactory receptor neurons (ORNs). Evidence for OMP function derives from altered behavioral and electrophysiological activities of OMP-KO mice. The molecular basis for the altered phenotype following the deletion of OMP is still unclear. Recent structural studies predict the involvement of OMP in protein-protein interaction. Here we report the identification of an OMP partner, Bex2, by phage-display screening of an olfactory mucosal cDNA-library. In situ hybridization demonstrates cellular co-localization of OMP mRNA with mRNAs for Bex1, Bex2, and Bex3 in ORNs of olfactory tissue of the mouse. The OMP/Bex interaction has been confirmed by demonstrating the chemical cross-linking of recombinant rat OMP with a synthetic peptide derived from the Bex amino acid sequence. The subcellular localization of Bex and OMP proteins was evaluated in transfected HEK293 cells. Bex is visualized in the nucleus and cytoplasm. Following co-transfection we observed the unexpected presence of some OMP in the nucleus along with Bex. Together, these data argue convincingly that we have identified Bex as an OMP partner whose further characterization will provide insight to the role of OMP and to the mechanism of the OMP/Bex interaction in ORN differentiation and function.
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Affiliation(s)
- Maik Behrens
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD 21201, USA
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