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Persuy MA, Sanz G, Tromelin A, Thomas-Danguin T, Gibrat JF, Pajot-Augy E. Mammalian olfactory receptors: molecular mechanisms of odorant detection, 3D-modeling, and structure-activity relationships. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 130:1-36. [PMID: 25623335 DOI: 10.1016/bs.pmbts.2014.11.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
This chapter describes the main characteristics of olfactory receptor (OR) genes of vertebrates, including generation of this large multigenic family and pseudogenization. OR genes are compared in relation to evolution and among species. OR gene structure and selection of a given gene for expression in an olfactory sensory neuron (OSN) are tackled. The specificities of OR proteins, their expression, and their function are presented. The expression of OR proteins in locations other than the nasal cavity is regulated by different mechanisms, and ORs display various additional functions. A conventional olfactory signal transduction cascade is observed in OSNs, but individual ORs can also mediate different signaling pathways, through the involvement of other molecular partners and depending on the odorant ligand encountered. ORs are engaged in constitutive dimers. Ligand binding induces conformational changes in the ORs that regulate their level of activity depending on odorant dose. When present, odorant binding proteins induce an allosteric modulation of OR activity. Since no 3D structure of an OR has been yet resolved, modeling has to be performed using the closest G-protein-coupled receptor 3D structures available, to facilitate virtual ligand screening using the models. The study of odorant binding modes and affinities may infer best-bet OR ligands, to be subsequently checked experimentally. The relationship between spatial and steric features of odorants and their activity in terms of perceived odor quality are also fields of research that development of computing tools may enhance.
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Affiliation(s)
- Marie-Annick Persuy
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France
| | - Guenhaël Sanz
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France
| | - Anne Tromelin
- INRA UMR 1129 Flaveur, Vision et Comportement du Consommateur, Dijon, France
| | | | - Jean-François Gibrat
- INRA UR1077 Mathématique Informatique et Génome, Domaine de Vilvert, Jouy-en-Josas, France
| | - Edith Pajot-Augy
- INRA UR 1197 NeuroBiologie de l'Olfaction, Domaine de Vilvert, Jouy-en-Josas, France.
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Szebenyi SA, Ogura T, Sathyanesan A, AlMatrouk AK, Chang J, Lin W. Increases in intracellular calcium via activation of potentially multiple phospholipase C isozymes in mouse olfactory neurons. Front Cell Neurosci 2014; 8:336. [PMID: 25374507 PMCID: PMC4204526 DOI: 10.3389/fncel.2014.00336] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 10/01/2014] [Indexed: 11/13/2022] Open
Abstract
Phospholipase C (PLC) and internal Ca(2+) stores are involved in a variety of cellular functions. However, our understanding of PLC in mammalian olfactory sensory neurons (OSNs) is generally limited to its controversial role in odor transduction. Here we employed single-cell Ca(2+) imaging and molecular approaches to investigate PLC-mediated Ca(2+) responses and its isozyme gene transcript expression. We found that the pan-PLC activator m-3M3FBS (25 μM) induces intracellular Ca(2+) increases in vast majority of isolated mouse OSNs tested. Both the response amplitude and percent responding cells depend on m-3M3FBS concentrations. In contrast, the inactive analog o-3M3FBS fails to induce Ca(2+) responses. The m-3M3FBS-induced Ca(2+) increase is blocked by the PLC inhibitor U73122, while its inactive analog U73433 has no effect. Removal of extracellular Ca(2+) does not change significantly the m-3M3FBS-induced Ca(2+) response amplitude. Additionally, in the absence of external Ca(2+), we found that a subset of OSNs respond to an odorant mixture with small Ca(2+) increases, which are significantly suppressed by U73122. Furthermore, using reverse transcription polymerase chain reaction and real-time quantitative polymerase chain reaction, we found that multiple PLC isozyme gene transcripts are expressed in olfactory turbinate tissue in various levels. Using RNA in situ hybridization analysis, we further show expression of β4, γ1, γ2 gene transcripts in OSNs. Taken together, our results establish that PLC isozymes are potent enzymes for mobilizing intracellular Ca(2+) in mouse OSNs and provide molecular insight for PLC isozymes-mediated complex cell signaling and regulation in the peripheral olfactory epithelium.
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Affiliation(s)
- Steven A Szebenyi
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
| | - Tatsuya Ogura
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
| | - Aaron Sathyanesan
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
| | - Abdullah K AlMatrouk
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
| | - Justin Chang
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
| | - Weihong Lin
- Department of Biological Sciences, University of Maryland Baltimore County Baltimore, MD, USA
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Benbernou N, Robin S, Tacher S, Rimbault M, Rakotomanga M, Galibert F. cAMP and IP3 signaling pathways in HEK293 cells transfected with canine olfactory receptor genes. ACTA ACUST UNITED AC 2011; 102 Suppl 1:S47-61. [PMID: 21846747 DOI: 10.1093/jhered/esr033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Olfactory receptors (ORs) expressed at the cell surface of olfactory sensory neurons lining the olfactory epithelium are the first actors of events leading to odor perception and recognition. As for other mammalian ORs, few dog OR have been deorphanized, mainly because of the absence of good methodology and the difficulties encountered to express ORs at the cell surface. Within this work, our aim was 1) to deorphanize a large subset of dog OR and 2) to compare the implication of the 2 main pathways, namely the cAMP and inositol 1,4,5-triphosphate (IP3) pathways, in the transduction of the olfactory message. For this, we used 2 independent tests to assess the importance of each of these 2 pathways and analyzed the responses of 47 canine family 6 ORs to a number of aliphatic compounds. We found these ORs globally capable of inducing intracellular calcium elevation through the IP3 pathway as confirmed by the use of specific inhibitors and/or a cAMP increase in response to aldehyde exposure. We showed that the implication of the cAMP or/and IP3 pathway was dependent upon the ligand-receptor combination rather than on one or the other partner. Finally, by exposing OR-expressing cells to the 21 possible pairs of C6-C12 aliphatic aldehydes, we confirmed that some odorant pairs may have an inhibitory or additive effect. Altogether, these results reinforce the notion that odorant receptor subfamilies may constitute functional units and call for a more systematic use of 2 complementary tests interrogating the cAMP and IP3 pathways when deorphanizing ORs.
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Affiliation(s)
- Naïma Benbernou
- Institute of Genetic and Development of Rennes, CNRS Unité de Recherche Mixte 6061, Faculté de Médecine, Rennes, F-35043 France
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Cholangiocyte cilia express TRPV4 and detect changes in luminal tonicity inducing bicarbonate secretion. Proc Natl Acad Sci U S A 2007; 104:19138-43. [PMID: 18024594 DOI: 10.1073/pnas.0705964104] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cholangiocytes, epithelial cells lining the biliary tree, have primary cilia extending from their apical membrane into the ductal lumen. Although important in disease, cilia also play a vital role in normal cellular functions. We reported that cholangiocyte cilia are sensory organelles responding to mechanical stimuli (i.e., luminal fluid flow) by alterations in intracellular Ca(2+) and cAMP. Because cholangiocyte cilia are also ideally positioned to detect changes in composition and tonicity of bile, we hypothesized that cilia also function as osmosensors. TRPV4, a Ca(2+)-permeable ion channel, has been implicated in signal transduction of osmotic stimuli. Using purified rat cholangiocytes and perfused intrahepatic bile duct units (IBDUs), we found that TRPV4 is expressed on cholangiocyte cilia, and that hypotonicity induces an increase in intracellular Ca(2+) in a TRPV4-, ciliary-, and extracellular calcium-dependent manner. The osmosensation of luminal tonicity by ciliary TRPV4 induces bicarbonate secretion, the main determinant of ductal bile formation, by a mechanism involving apical ATP release. Furthermore, the activation of TRPV4 in vivo, by its specific agonist, 4alphaPDD, induces an increase in bile flow as well as ATP release and bicarbonate secretion. Our results suggest that cholangiocyte primary cilia play an important role in ductal bile formation by acting as osmosensors.
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Cummins SF, De Vries MR, Hill KS, Boehning D, Nagle GT. Gene identification and evidence for expression of G protein alpha subunits, phospholipase C, and an inositol 1,4,5-trisphosphate receptor in Aplysia californica rhinophore. Genomics 2007; 90:110-20. [PMID: 17498918 DOI: 10.1016/j.ygeno.2007.03.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2007] [Revised: 03/28/2007] [Accepted: 03/28/2007] [Indexed: 11/29/2022]
Abstract
In the marine mollusk Aplysia californica, waterborne protein pheromones that are released during egg laying act in concert to stimulate mate attraction. However, molecular information concerning the cellular receptors and signaling mechanisms that may be involved in waterborne peptide and protein pheromonal communication is lacking. As a first step toward examining whether members of the G protein family and phosphoinositide signaling pathway are present in the primary peripheral chemosensory organs (i.e., rhinophores), we isolated five full-length cDNA clones from an A. californica central nervous system cDNA library. These clones encoded (1) the G protein alpha subunits of the Gq, Gi, and Go families, (2) a protein with homology to phospholipase C (PLC) isoforms, and (3) an inositol 1,4,5-trisphosphate receptor (IP3R). The expression of these genes was examined using laser capture microdissection/reverse transcription-polymerase chain reaction and in situ hybridization. All of them are expressed in the rhinophore sensory epithelium, suggesting that Galphaq, Galphai, Galphao, PLC-like protein, and IP3R may be involved in waterborne protein pheromone detection in Aplysia-possibly via a phosphoinositide signaling mechanism.
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Affiliation(s)
- Scott F Cummins
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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Braun T, Voland P, Kunz L, Prinz C, Gratzl M. Enterochromaffin cells of the human gut: sensors for spices and odorants. Gastroenterology 2007; 132:1890-901. [PMID: 17484882 DOI: 10.1053/j.gastro.2007.02.036] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Accepted: 01/30/2007] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Release of serotonin from mucosal enterochromaffin cells triggered by luminal substances is the key event in the regulation of gut motility and secretion. We were interested to know whether nasal olfactory receptors are also expressed in the human gut mucosa by enterochromaffin cells and whether their ligands and odorants present in spices, fragrances, detergents, and cosmetics cause serotonin release. METHODS Receptor expression was studied by the reverse-transcription polymerase chain reaction method in human mucosal enterochromaffin cells isolated by laser microdissection and in a cell line derived from human enterochromaffin cells. Activation of the cells by odorants was investigated by digital fluorescence imaging using the fluorescent Ca(2+) indicator Fluo-4. Serotonin release was measured in culture supernatants by a serotonin enzyme immunoassay and amperometry using carbon fiber microelectrodes placed on single cells. RESULTS We found expression of 4 olfactory receptors in microdissected human mucosal enterochromaffin cells and in a cell line derived from human enterochromaffin cells. Ca(2+) imaging studies revealed that odorant ligands of the identified olfactory receptors cause Ca(2+) influx, elevation of intracellular free Ca(2+) levels, and, consequently, serotonin release. CONCLUSIONS Our results show that odorants present in the luminal environment of the gut may stimulate serotonin release via olfactory receptors present in human enterochromaffin cells. Serotonin controls both gut motility and secretion and is implicated in pathologic conditions such as vomiting, diarrhea, and irritable bowel syndrome. Thus, olfactory receptors are potential novel targets for the treatment of gastrointestinal diseases and motility disorders.
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Affiliation(s)
- Thomas Braun
- Institute of Anatomy, Ludwig Maximilian University Munich, Munich, Germany
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Gorojankina T, Grébert D, Salesse R, Tanfin Z, Caillol M. Study of orexins signal transduction pathways in rat olfactory mucosa and in olfactory sensory neurons-derived cell line Odora: multiple orexin signalling pathways. ACTA ACUST UNITED AC 2007; 141:73-85. [PMID: 17292491 DOI: 10.1016/j.regpep.2006.12.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 12/04/2006] [Accepted: 12/21/2006] [Indexed: 10/23/2022]
Abstract
Orexins A and B (OxA and OxB) are multifunctional neuropeptides implicated in the regulation of energy metabolism, wakefulness but also in a broad range of motivated behaviours. They signal through two G-protein-coupled receptors: orexin receptor 1 and 2 (Ox1R and Ox2R). The orexins and their receptors are present at all levels of the rat olfactory system: epithelium, bulb, piriform cortex but their signalling mechanisms remain unknown. We have studied orexins signal transduction pathways in the rat olfactory mucosa (OM) and in the Odora cell line derived from olfactory sensory neurons and heterologously expressing Ox1R or Ox2R. We have demonstrated by western blot and RT-PCR that multiple components of adenylyl cyclase (AC) and phospholipase C (PLC) signalling pathways were identical in OM and Odora cells. OxA and OxB induced a weak increase in IP3 in OM; they induced a significant rise in cAMP and IP3 in Odora transfected cells, suggesting the activation of AC and PLC pathways. Both OxA and OxB induced intracellular calcium elevation and transient activation of MAP kinases (ERK42/44) in Odora/Ox1R and Odora/Ox2R cells. These results suggest the existence of multiple orexins signalling pathways in Odora cells and probably in OM, corresponding to different possible roles of these peptides.
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Affiliation(s)
- Tatiana Gorojankina
- Unité de Neurobiologie de l'Olfaction et de la Prise Alimentaire, UMR1197 - INRA - Université Paris 11, Equipe Récepteurs et Communication Chimique, CRJ, Domaine de Vilvert, 78352 Jouy-en-Josas Cedex, France
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