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Boichot V, Menetrier F, Saliou JM, Lirussi F, Canon F, Folia M, Heydel JM, Hummel T, Menzel S, Steinke M, Hackenberg S, Schwartz M, Neiers F. Characterization of human oxidoreductases involved in aldehyde odorant metabolism. Sci Rep 2023; 13:4876. [PMID: 36966166 PMCID: PMC10039900 DOI: 10.1038/s41598-023-31769-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 03/16/2023] [Indexed: 03/27/2023] Open
Abstract
Oxidoreductases are major enzymes of xenobiotic metabolism. Consequently, they are essential in the chemoprotection of the human body. Many xenobiotic metabolism enzymes have been shown to be involved in chemosensory tissue protection. Among them, some were additionally shown to be involved in chemosensory perception, acting in signal termination as well as in the generation of metabolites that change the activation pattern of chemosensory receptors. Oxidoreductases, especially aldehyde dehydrogenases and aldo-keto reductases, are the first barrier against aldehyde compounds, which include numerous odorants. Using a mass spectrometry approach, we characterized the most highly expressed members of these families in the human nasal mucus sampled in the olfactory vicinity. Their expression was also demonstrated using immunohistochemistry in human epitheliums sampled in the olfactory vicinity. Recombinant enzymes corresponding to three highly expressed human oxidoreductases (ALDH1A1, ALDH3A1, AKR1B10) were used to demonstrate the high enzymatic activity of these enzymes toward aldehyde odorants. The structure‒function relationship set based on the enzymatic parameters characterization of a series of aldehyde odorant compounds was supported by the X-ray structure resolution of human ALDH3A1 in complex with octanal.
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Affiliation(s)
- Valentin Boichot
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France
| | - Franck Menetrier
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France
| | - Jean-Michel Saliou
- CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, UAR CNRS 2014-US Inserm 41-PLBS, University of Lille, Lille, France
| | - Frederic Lirussi
- UMR 1231, Lipides Nutrition Cancer, INSERM, 21000, Dijon, France
- UFR des Sciences de Santé, Université Bourgogne Franche-Comté, 25000, Besançon, France
- Plateforme PACE, Laboratoire de Pharmacologie-Toxicologie, Centre Hospitalo-Universitaire Besançon, 25000, Besançon, France
| | - Francis Canon
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France
| | - Mireille Folia
- Department of Otolaryngology-Head and Neck Surgery, Dijon University Hospital, 21000, Dijon, France
| | - Jean-Marie Heydel
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France
| | - Thomas Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Susanne Menzel
- Smell and Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Maria Steinke
- Chair of Tissue Engineering and Regenerative Medicine, University Hospital Wuerzburg, Roentgenring 11, 97070, Wuerzburg, Germany
- Fraunhofer Institute for Silicate Research ISC, Roentgenring 11, 97070, Wuerzburg, Germany
| | - Stephan Hackenberg
- Department of Otorhinolaryngology-Head and Neck Surgery, RWTH Aachen University Hospital, Aachen, Germany
| | - Mathieu Schwartz
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France.
| | - Fabrice Neiers
- Flavour Perception: Molecular Mechanisms (Flavours), INRAE, CNRS, Institut Agro, Université de Bourgogne Franche-Comté, Dijon, France.
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Nakanishi S, Tsutsui T, Itai N, Denda M. Distinct sets of olfactory receptors highly expressed in different human tissues evaluated by meta-transcriptome analysis: Association of OR10A6 in skin with keratinization. Front Cell Dev Biol 2023; 11:1102585. [PMID: 36776557 PMCID: PMC9909485 DOI: 10.3389/fcell.2023.1102585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 01/16/2023] [Indexed: 01/27/2023] Open
Abstract
Olfactory receptors (ORs) are expressed in many tissues and have multiple functions. However, most studies have focused on individual ORs. Here, we aimed to conduct a comprehensive meta-transcriptome analysis of OR gene expression in human tissues by using open-source tools to search a large, publicly available genotype-tissue expression (GTEx) data set. Analysis of RNA-seq data from GTEx revealed that OR expression patterns were tissue-dependent, and we identified distinct sets of ORs that were highly expressed in 12 tissues, involving 97 ORs in total. Among them, OR5P2, OR5P3 and OR10A6 were associated with skin. We further examined the roles of these ORs in skin by performing weighted gene correlation network analysis (WGCNA) and c3net analysis. WGCNA suggested that the three ORs are involved in epidermal differentiation and water-impermeable barrier homeostasis, and OR10A6 showed the largest gene sub-network in the c3net network. Immunocytochemical examination of human skin keratinocytes revealed a sparse expression pattern of OR10A6, suggesting that it is not uniformly distributed among all keratinocytes. An OR10A6 agonist, 3-phenylpropyl propionate (3PPP), transiently increased intracellular Ca2+ concentration and increased cornified envelope (CE) production in cultured keratinocytes. Knock-down of OR10A6 diminished the effect of 3PPP. Overall, integration of meta-transcriptome analysis and functional analysis uncovered distinct expression patterns of ORs in various human tissues, providing basic data for future studies of the biological functions of highly expressed ORs in individual tissues. Our results further suggest that expression of OR10A6 in skin is related to epidermal differentiation, and OR10A6 may be a potential target for modulation of keratinization.
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Affiliation(s)
- Shinobu Nakanishi
- Shiseido Global Innovation Center, Yokohama, Japan,*Correspondence: Shinobu Nakanishi, ; Taiki Tsutsui,
| | - Taiki Tsutsui
- Shiseido Global Innovation Center, Yokohama, Japan,*Correspondence: Shinobu Nakanishi, ; Taiki Tsutsui,
| | - Nao Itai
- Shiseido Global Innovation Center, Yokohama, Japan
| | - Mitsuhiro Denda
- Institute for Advanced Study of Mathematical Sciences, Meiji University, Tokyo, Japan
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Primacy coding facilitates effective odor discrimination when receptor sensitivities are tuned. PLoS Comput Biol 2019; 15:e1007188. [PMID: 31323033 PMCID: PMC6692051 DOI: 10.1371/journal.pcbi.1007188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 08/13/2019] [Accepted: 06/17/2019] [Indexed: 11/19/2022] Open
Abstract
The olfactory system faces the difficult task of identifying an enormous variety of odors independent of their intensity. Primacy coding, where the odor identity is encoded by the receptor types that respond earliest, might provide a compact and informative representation that can be interpreted efficiently by the brain. In this paper, we analyze the information transmitted by a simple model of primacy coding using numerical simulations and statistical descriptions. We show that the encoded information depends strongly on the number of receptor types included in the primacy representation, but only weakly on the size of the receptor repertoire. The representation is independent of the odor intensity and the transmitted information is useful to perform typical olfactory tasks with close to experimentally measured performance. Interestingly, we find situations in which a smaller receptor repertoire is advantageous for discriminating odors. The model also suggests that overly sensitive receptor types could dominate the entire response and make the whole array useless, which allows us to predict how receptor arrays need to adapt to stay useful during environmental changes. Taken together, we show that primacy coding is more useful than simple binary and normalized coding, essentially because the sparsity of the odor representations is independent of the odor statistics, in contrast to the alternatives. Primacy coding thus provides an efficient odor representation that is independent of the odor intensity and might thus help to identify odors in the olfactory cortex. Humans can identify odors independent of their intensity. Experimental data suggest that this is accomplished by representing the odor identity by the earliest responding receptor types. Using theoretical modeling, we here show that such a primacy code outperforms alternative encodings and allows discriminating odors with close to experimentally measured performance. This performance depends strongly on the number of receptors considered in the primacy code, but the receptor repertoire size is less important. The model also suggests a strong evolutionary pressure on the receptor sensitivities, which could explain observed receptor copy number adaptations. By predicting psycho-physical experiments, the model will thus contribute to our understanding of the olfactory system.
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Rochelle MM, Prévost GJ, Acree TE. Computing Odor Images. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:2219-2225. [PMID: 28285523 DOI: 10.1021/acs.jafc.6b05573] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This perspective examines psychophysical methods that may reveal the algorithms that encode odor images by integrating current data from sensory measurement into a computational model of odor perception. There is evidence that algorithms used by the nervous system to process odor sensations require input from only a few odorants, between three and eight. Furthermore, the number of recognizable odors in foods that contribute anything to the aroma of all foods is approximately 250. This may imply that it is the ratio of a small number of key odorants (KOs) that create a multitude of food odors. Studies with large mixtures of odorants (formulated to be of equal potency) show that a subject's ability to detect individual odorants in these mixtures was vanishingly small. These large mixtures had weak and nondescript but similar odor character. If only a few stimulants are used to represent complex images, it is direct evidence of the simplicity and therefore the tractability of the computational process.
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Affiliation(s)
- Madeleine M Rochelle
- Food Science Department , Cornell University , 411 Tower Road , Ithaca , New York 14853 , United States
| | - Géraldine Julie Prévost
- Food Science Department , Cornell University , 411 Tower Road , Ithaca , New York 14853 , United States
| | - Terry E Acree
- Food Science Department, 347 , Cornell University , 411 Tower Road Ithaca , New York 14853 , United States
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Identification of Chinese Herbal Medicines with Electronic Nose Technology: Applications and Challenges. SENSORS 2017; 17:s17051073. [PMID: 28486407 PMCID: PMC5470463 DOI: 10.3390/s17051073] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/03/2017] [Accepted: 05/03/2017] [Indexed: 12/24/2022]
Abstract
This paper provides a review of the most recent works in machine olfaction as applied to the identification of Chinese Herbal Medicines (CHMs). Due to the wide variety of CHMs, the complexity of growing sources and the diverse specifications of herb components, the quality control of CHMs is a challenging issue. Much research has demonstrated that an electronic nose (E-nose) as an advanced machine olfaction system, can overcome this challenge through identification of the complex odors of CHMs. E-nose technology, with better usability, high sensitivity, real-time detection and non-destructive features has shown better performance in comparison with other analytical techniques such as gas chromatography-mass spectrometry (GC-MS). Although there has been immense development of E-nose techniques in other applications, there are limited reports on the application of E-noses for the quality control of CHMs. The aim of current study is to review practical implementation and advantages of E-noses for robust and effective odor identification of CHMs. It covers the use of E-nose technology to study the effects of growing regions, identification methods, production procedures and storage time on CHMs. Moreover, the challenges and applications of E-nose for CHM identification are investigated. Based on the advancement in E-nose technology, odor may become a new quantitative index for quality control of CHMs and drug discovery. It was also found that more research could be done in the area of odor standardization and odor reproduction for remote sensing.
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Geithe C, Noe F, Kreissl J, Krautwurst D. The Broadly Tuned Odorant Receptor OR1A1 is Highly Selective for 3-Methyl-2,4-nonanedione, a Key Food Odorant in Aged Wines, Tea, and Other Foods. Chem Senses 2016; 42:181-193. [DOI: 10.1093/chemse/bjw117] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Roggatz CC, Lorch M, Hardege JD, Benoit DM. Ocean acidification affects marine chemical communication by changing structure and function of peptide signalling molecules. GLOBAL CHANGE BIOLOGY 2016; 22:3914-3926. [PMID: 27353732 DOI: 10.1111/gcb.13354] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 05/24/2023]
Abstract
Ocean acidification is a global challenge that faces marine organisms in the near future with a predicted rapid drop in pH of up to 0.4 units by the end of this century. Effects of the change in ocean carbon chemistry and pH on the development, growth and fitness of marine animals are well documented. Recent evidence also suggests that a range of chemically mediated behaviours and interactions in marine fish and invertebrates will be affected. Marine animals use chemical cues, for example, to detect predators, for settlement, homing and reproduction. But, while effects of high CO2 conditions on these behaviours are described across many species, little is known about the underlying mechanisms, particularly in invertebrates. Here, we investigate the direct influence of future oceanic pH conditions on the structure and function of three peptide signalling molecules with an interdisciplinary combination of methods. NMR spectroscopy and quantum chemical calculations were used to assess the direct molecular influence of pH on the peptide cues, and we tested the functionality of the cues in different pH conditions using behavioural bioassays with shore crabs (Carcinus maenas) as a model system. We found that peptide signalling cues are susceptible to protonation in future pH conditions, which will alter their overall charge. We also show that structure and electrostatic properties important for receptor binding differ significantly between the peptide forms present today and the protonated signalling peptides likely to be dominating in future oceans. The bioassays suggest an impaired functionality of the signalling peptides at low pH. Physiological changes due to high CO2 conditions were found to play a less significant role in influencing the investigated behaviour. From our results, we conclude that the change of charge, structure and consequently function of signalling molecules presents one possible mechanism to explain altered behaviour under future oceanic pH conditions.
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Affiliation(s)
- Christina C Roggatz
- Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK
| | - Mark Lorch
- Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK
| | - Jörg D Hardege
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Cottingham Road, Hull, HU6 7RX, UK
| | - David M Benoit
- Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK
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Abstract
Natural odors typically consist of many molecules at different concentrations. It is unclear how the numerous odorant molecules and their possible mixtures are discriminated by relatively few olfactory receptors. Using an information theoretic model, we show that a receptor array is optimal for this task if it achieves two possibly conflicting goals: (i) Each receptor should respond to half of all odors and (ii) the response of different receptors should be uncorrelated when averaged over odors presented with natural statistics. We use these design principles to predict statistics of the affinities between receptors and odorant molecules for a broad class of odor statistics. We also show that optimal receptor arrays can be tuned to either resolve concentrations well or distinguish mixtures reliably. Finally, we use our results to predict properties of experimentally measured receptor arrays. Our work can thus be used to better understand natural olfaction, and it also suggests ways to improve artificial sensor arrays.
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Somero GN, Beers JM, Chan F, Hill TM, Klinger T, Litvin SY. What Changes in the Carbonate System, Oxygen, and Temperature Portend for the Northeastern Pacific Ocean: A Physiological Perspective. Bioscience 2015. [DOI: 10.1093/biosci/biv162] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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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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Affiliation(s)
| | - Jörg D. Hardege
- School of Biological, Biomedical, Environmental Sciences, University of Hull, Hull, HU6 7RX, UK
| | - John Terschak
- School of Biological, Biomedical, Environmental Sciences, University of Hull, Hull, HU6 7RX, UK
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Peterlin Z, Firestein S, Rogers ME. The state of the art of odorant receptor deorphanization: a report from the orphanage. ACTA ACUST UNITED AC 2014; 143:527-42. [PMID: 24733839 PMCID: PMC4003190 DOI: 10.1085/jgp.201311151] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The odorant receptors (ORs) provide our main gateway to sensing the world of volatile chemicals. This involves a complex encoding process in which multiple ORs, each of which detects its own set of odorants, work as an ensemble to produce a distributed activation code that is presumably unique to each odorant. One marked challenge to decoding the olfactory code is OR deorphanization, the identification of a set of activating odorants for a particular receptor. Here, we survey various methods used to try to express defined ORs of interest. We also suggest strategies for selecting odorants for test panels to evaluate the functional expression of an OR. Integrating these tools, while retaining awareness of their idiosyncratic limitations, can provide a multi-tiered approach to OR deorphanization, spanning the initial discovery of a ligand to vetting that ligand in a physiologically relevant setting.
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Affiliation(s)
- Zita Peterlin
- Corporate Research and Development, Firmenich Incorporated, Plainsboro, NJ 08536
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Jayanthi KPD, Kempraj V, Aurade RM, Roy TK, Shivashankara KS, Verghese A. Computational reverse chemical ecology: virtual screening and predicting behaviorally active semiochemicals for Bactrocera dorsalis. BMC Genomics 2014; 15:209. [PMID: 24640964 PMCID: PMC4003815 DOI: 10.1186/1471-2164-15-209] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 03/03/2014] [Indexed: 11/16/2022] Open
Abstract
Background Semiochemical is a generic term used for a chemical substance that influences the behaviour of an organism. It is a common term used in the field of chemical ecology to encompass pheromones, allomones, kairomones, attractants and repellents. Insects have mastered the art of using semiochemicals as communication signals and rely on them to find mates, host or habitat. This dependency of insects on semiochemicals has allowed chemical ecologists to develop environment friendly pest management strategies. However, discovering semiochemicals is a laborious process that involves a plethora of behavioural and analytical techniques, making it expansively time consuming. Recently, reverse chemical ecology approach using odorant binding proteins (OBPs) as target for elucidating behaviourally active compounds is gaining eminence. In this scenario, we describe a “computational reverse chemical ecology” approach for rapid screening of potential semiochemicals. Results We illustrate the high prediction accuracy of our computational method. We screened 25 semiochemicals for their binding potential to a GOBP of B. dorsalis using molecular docking (in silico) and molecular dynamics. Parallely, compounds were subjected to fluorescent quenching assays (Experimental). The correlation between in silico and experimental data were significant (r2 = 0.9408; P < 0.0001). Further, predicted compounds were subjected to behavioral bioassays and were found to be highly attractive to insects. Conclusions The present study provides a unique methodology for rapid screening and predicting behaviorally active semiochemicals. This methodology may be developed as a viable approach for prospecting active semiochemicals for pest control, which otherwise is a laborious process.
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Affiliation(s)
| | - Vivek Kempraj
- National Fellow Lab, Division of Entomology and Nematology, Indian Institute of Horticultural Research, Bangalore, India.
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Wyatt T. Introduction to Chemical Signaling in Vertebrates and Invertebrates. Front Neurosci 2014. [DOI: 10.1201/b16511-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Twick I, Lee JA, Ramaswami M. Olfactory habituation in Drosophila-odor encoding and its plasticity in the antennal lobe. PROGRESS IN BRAIN RESEARCH 2014; 208:3-38. [PMID: 24767477 DOI: 10.1016/b978-0-444-63350-7.00001-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
A ubiquitous feature of an animal's response to an odorant is that it declines when the odorant is frequently or continuously encountered. This decline in olfactory response, termed olfactory habituation, can have temporally or mechanistically different forms. The neural circuitry of the fruit fly Drosophila melanogaster's olfactory system is well defined in terms of component cells, which are readily accessible to functional studies and genetic manipulation. This makes it a particularly useful preparation for the investigation of olfactory habituation. In addition, the insect olfactory system shares many architectural and functional similarities with mammalian olfactory systems, suggesting that olfactory mechanisms in insects may be broadly relevant. In this chapter, we discuss the likely mechanisms of olfactory habituation in context of the participating cell types, their connectivity, and their roles in sensory processing. We overview the structure and function of key cell types, the mechanisms that stimulate them, and how they transduce and process odor signals. We then consider how each stage of olfactory processing could potentially contribute to behavioral habituation. After this, we overview a variety of recent mechanistic studies that point to an important role for potentiation of inhibitory synapses in the primary olfactory processing center, the antennal lobe, in driving the reduced response to familiar odorants. Following the discussion of mechanisms for short- and long-term olfactory habituation, we end by considering how these mechanisms may be regulated by neuromodulators, which likely play key roles in the induction, gating, or suppression of habituated behavior, and speculate on the relevance of these processes for other forms of learning and memory.
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Affiliation(s)
- Isabell Twick
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
| | - John Anthony Lee
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
| | - Mani Ramaswami
- School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland; National Centre for Biological Science, Bangalore, India
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Abstract
In the olfactory system of Drosophila melanogaster, it is relatively straightforward to target in vivo measurements of neural activity to specific processing channels. This, together with the numerical simplicity of the Drosophila olfactory system, has produced rapid gains in our understanding of Drosophila olfaction. This review summarizes the neurophysiology of the first two layers of this system: the peripheral olfactory receptor neurons and their postsynaptic targets in the antennal lobe. We now understand in some detail the cellular and synaptic mechanisms that shape odor representations in these neurons. Together, these mechanisms imply that interesting neural adaptations to environmental statistics have occurred. These mechanisms also place some fundamental constraints on early sensory processing that pose challenges for higher brain regions. These findings suggest some general principles with broad relevance to early sensory processing in other modalities.
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Affiliation(s)
- Rachel I Wilson
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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Knaden M, Hansson BS. Mapping odor valence in the brain of flies and mice. Curr Opin Neurobiol 2013; 24:34-8. [PMID: 24492076 DOI: 10.1016/j.conb.2013.08.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/24/2013] [Accepted: 08/14/2013] [Indexed: 11/30/2022]
Abstract
Why are some odors perceived as pleasant while others are not? We review current research on how pleasant and unpleasant odors, that is, odors with positive or negative valence, are processed in the brain of flies and mice. We conclude that in mice pleasant and unpleasant odors are detected via three olfactory subsystems with only one being fully dedicated to unpleasant odors, while the others detect both good and bad odors. Correspondingly, so far no clear segmentation into regions processing exclusively pleasant or unpleasant odors has been identified in the mouse brain. The situation is different in flies, where most odors are sensed via the antenna. Already at the antennal lobe level, that is, the first processing center for olfactory input, odorants seem to be categorized as pleasant or unpleasant. We furthermore discuss why animals at all should make a decision based on olfaction, and why a straightforward and fast processing of odorant valence might be important for survival and reproduction.
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Affiliation(s)
- Markus Knaden
- Max Planck Institute for Chemical Ecology, Hans Knoell Strasse 8, 07745 Jena, Germany
| | - Bill S Hansson
- Max Planck Institute for Chemical Ecology, Hans Knoell Strasse 8, 07745 Jena, Germany.
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Piccoli S, Suku E, Garonzi M, Giorgetti A. Genome-wide Membrane Protein Structure Prediction. Curr Genomics 2013; 14:324-9. [PMID: 24403851 PMCID: PMC3763683 DOI: 10.2174/13892029113149990009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/19/2013] [Accepted: 07/22/2013] [Indexed: 01/25/2023] Open
Abstract
Transmembrane proteins allow cells to extensively communicate with the external world in a very accurate and specific way. They form principal nodes in several signaling pathways and attract large interest in therapeutic intervention, as the majority pharmaceutical compounds target membrane proteins. Thus, according to the current genome annotation methods, a detailed structural/functional characterization at the protein level of each of the elements codified in the genome is also required. The extreme difficulty in obtaining high-resolution three-dimensional structures, calls for computational approaches. Here we review to which extent the efforts made in the last few years, combining the structural characterization of membrane proteins with protein bioinformatics techniques, could help describing membrane proteins at a genome-wide scale. In particular we analyze the use of comparative modeling techniques as a way of overcoming the lack of high-resolution three-dimensional structures in the human membrane proteome.
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Affiliation(s)
- Stefano Piccoli
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Eda Suku
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Marianna Garonzi
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Alejandro Giorgetti
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
- German Research School for Simulation Sciences, Juelich, Germany
- Center for Biomedical Computing (CBMC), University of Verona, strada Le grazie 8, 37134, Verona, Italy
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Abstract
We studied complete dose-response curves for 53 odorants in the third instar larvae of Drosophila melanogaster. All odorants, except one, elicited an attraction response. Some odorants also elicited a decrease from their peak response at higher concentrations. This concentration-dependent decrease in olfactory response could be due to either desensitization or repulsion, 2 possibilities that we cannot distinguish in our current assay. We observed high variations in factors like slopes, thresholds, and peaks of responses that, in agreement with previous studies, suggest that the responses of different receptors are quite different for the similar change in concentration of various ligands. We also observed that lower attraction thresholds predicted higher peak amplitude. This suggests that if odor responses encompassed wider concentration range than can be covered by the dynamic range of a single receptor, then responses tend to be high in magnitude.
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Affiliation(s)
- Sukant Khurana
- National Center for Biological Sciences, GKVK Campus, Bangalore, Karnataka, India.
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Levit A, Barak D, Behrens M, Meyerhof W, Niv MY. Homology model-assisted elucidation of binding sites in GPCRs. Methods Mol Biol 2013; 914:179-205. [PMID: 22976029 DOI: 10.1007/978-1-62703-023-6_11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
G protein-coupled receptors (GPCRs) are important mediators of cell signaling and a major family of drug targets. Despite recent breakthroughs, experimental elucidation of GPCR structures remains a formidable challenge. Homology modeling of 3D structures of GPCRs provides a practical tool for elucidating the structural determinants governing the interactions of these important receptors with their ligands. The working model of the binding site can then be used for virtual screening of additional ligands that may fit this site, for determining and comparing specificity profiles of related receptors, and for structure-based design of agonists and antagonists. The current review presents the protocol and enumerates the steps for modeling and validating the residues involved in ligand binding. The main stages include (a) modeling the receptor structure using an automated fragment-based approach, (b) predicting potential binding pockets, (c) docking known binders, (d) analyzing predicted interactions and comparing with positions that have been shown to bind ligands in other receptors, (e) validating the structural model by mutagenesis.
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Affiliation(s)
- Anat Levit
- Institute of Biochemistry, Food Science, and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, Israel
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23
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Abstract
Mammalian species have evolved a large and diverse number of odorant receptors (ORs). These proteins comprise the largest family of G-protein-coupled receptors (GPCRs) known, amounting to ~1,000-different receptors in the rodent. From the perspective of olfactory coding, the availability of such a vast number of chemosensory receptors poses several fascinating questions; in addition, such a large repertoire provides an attractive biological model to study ligand-receptor interactions. The limited functional expression of these receptors in heterologous systems, however, has greatly hampered attempts to deorphanize them. We have employed a successful approach that combines electrophysiological and imaging techniques to analyze the response profiles of single sensory neurons. Our approach has enabled us to characterize the "odor space" of a population of native aldehyde receptors and the molecular range of a genetically engineered receptor, OR-I7.
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Affiliation(s)
- Richard S Smith
- Department of Biology, University of Maryland, College Park, MD, USA
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24
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Launay G, Sanz G, Pajot-Augy E, Gibrat JF. Modeling of mammalian olfactory receptors and docking of odorants. Biophys Rev 2012; 4:255-269. [PMID: 28510073 DOI: 10.1007/s12551-012-0080-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2012] [Accepted: 05/24/2012] [Indexed: 11/29/2022] Open
Abstract
Olfactory receptors (ORs) belong to the superfamily of G protein-coupled receptors (GPCRs), the second largest class of genes after those related to immunity, and account for about 3 % of mammalian genomes. ORs are present in all multicellular organisms and represent more than half the GPCRs in mammalian species (e.g., the mouse OR repertoire contains >1,000 functional genes). ORs are mainly expressed in the olfactory epithelium where they detect odorant molecules, but they are also expressed in a number of other cells, such as sperm cells, although their functions in these cells remain mostly unknown. It has recently been reported that ORs are present in tumoral tissues where they are expressed at different levels than in healthy tissues. A specific OR is over-expressed in prostate cancer cells, and activation of this OR has been shown to inhibit the proliferation of these cells. Odorant stimulation of some of these receptors results in inhibition of cell proliferation. Even though their biological role has not yet been elucidated, these receptors might constitute new targets for diagnosis and therapeutics. It is important to understand the activation mechanism of these receptors at the molecular level, in particular to be able to predict which ligands are likely to activate a particular receptor ('deorphanization') or to design antagonists for a given receptor. In this review, we describe the in silico methodologies used to model the three-dimensional (3D) structure of ORs (in the more general framework of GPCR modeling) and to dock ligands into these 3D structures.
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Affiliation(s)
- Guillaume Launay
- Equipe interactions hôte-pathogène, Bases Moléculaires et Structurales des Systèmes Infectieux, UMR5086 CNRS/Université de Lyon1, 7 Passage du Vercors, Lyon cedex 07, France
| | - Guenhaël Sanz
- Neurobiologie de l'Olfaction et Modélisation en Imagerie UR1197, INRA, 78350, Jouy-en-Josas, France
| | - Edith Pajot-Augy
- Neurobiologie de l'Olfaction et Modélisation en Imagerie UR1197, INRA, 78350, Jouy-en-Josas, France
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25
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Ferrero DM, Wacker D, Roque MA, Baldwin MW, Stevens RC, Liberles SD. Agonists for 13 trace amine-associated receptors provide insight into the molecular basis of odor selectivity. ACS Chem Biol 2012; 7:1184-9. [PMID: 22545963 DOI: 10.1021/cb300111e] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Trace amine-associated receptors (TAARs) are vertebrate olfactory receptors. However, ligand recognition properties of TAARs remain poorly understood, as most are "orphan receptors" without known agonists. Here, we identify the first ligands for many rodent TAARs and classify these receptors into two subfamilies based on the phylogeny and binding preference for primary or tertiary amines. Some mouse and rat orthologs have similar response profiles, although independent Taar7 gene expansions led to highly related receptors with altered ligand specificities. Using chimeric TAAR7 receptors, we identified an odor contact site in transmembrane helix III that functions as a selectivity filter. Homology models based on the β(2) adrenergic receptor structure indicate spatial proximity of this site to the ligand. Gain-of-function mutations at this site created olfactory receptors with radically altered odor recognition properties. These studies provide new TAAR ligands, valuable tools for studying receptor function, and general insights into the molecular pharmacology of G protein-coupled receptors.
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Affiliation(s)
- David M. Ferrero
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115,
United States
| | - Daniel Wacker
- Department
of Molecular Biology, The Scripps Research Institute, La Jolla, California
92037, United States
| | - Miguel A. Roque
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115,
United States
| | - Maude W. Baldwin
- Department
of Organismic and Evolutionary
Biology, Harvard University, Cambridge,
Massachusetts 02138, United States
| | - Raymond C. Stevens
- Department
of Molecular Biology, The Scripps Research Institute, La Jolla, California
92037, United States
| | - Stephen D. Liberles
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115,
United States
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26
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Fonollosa J, Gutierrez-Galvez A, Marco S. Quality coding by neural populations in the early olfactory pathway: analysis using information theory and lessons for artificial olfactory systems. PLoS One 2012; 7:e37809. [PMID: 22719851 PMCID: PMC3377695 DOI: 10.1371/journal.pone.0037809] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 04/23/2012] [Indexed: 01/08/2023] Open
Abstract
In this article, we analyze the ability of the early olfactory system to detect and discriminate different odors by means of information theory measurements applied to olfactory bulb activity images. We have studied the role that the diversity and number of receptor neuron types play in encoding chemical information. Our results show that the olfactory receptors of the biological system are low correlated and present good coverage of the input space. The coding capacity of ensembles of olfactory receptors with the same receptive range is maximized when the receptors cover half of the odor input space - a configuration that corresponds to receptors that are not particularly selective. However, the ensemble's performance slightly increases when mixing uncorrelated receptors of different receptive ranges. Our results confirm that the low correlation between sensors could be more significant than the sensor selectivity for general purpose chemo-sensory systems, whether these are biological or biomimetic.
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Affiliation(s)
- Jordi Fonollosa
- Department of Electronics, Universitat de Barcelona, Barcelona, Spain
- Artificial Olfaction Group, Institute for Bioengineering of Catalonia, Barcelona, Spain
| | - Agustin Gutierrez-Galvez
- Department of Electronics, Universitat de Barcelona, Barcelona, Spain
- Artificial Olfaction Group, Institute for Bioengineering of Catalonia, Barcelona, Spain
| | - Santiago Marco
- Department of Electronics, Universitat de Barcelona, Barcelona, Spain
- Artificial Olfaction Group, Institute for Bioengineering of Catalonia, Barcelona, Spain
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27
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Reisert J, Zhao H. Perspectives on: information and coding in mammalian sensory physiology: response kinetics of olfactory receptor neurons and the implications in olfactory coding. ACTA ACUST UNITED AC 2012; 138:303-10. [PMID: 21875979 PMCID: PMC3171077 DOI: 10.1085/jgp.201110645] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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28
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Chaput MA, El Mountassir F, Atanasova B, Thomas-Danguin T, Le Bon AM, Perrut A, Ferry B, Duchamp-Viret P. Interactions of odorants with olfactory receptors and receptor neurons match the perceptual dynamics observed for woody and fruity odorant mixtures. Eur J Neurosci 2012; 35:584-97. [PMID: 22304504 DOI: 10.1111/j.1460-9568.2011.07976.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The present study aimed to create a direct bridge between observations on peripheral and central responses to odorant mixtures and their components. Three experiments were performed using mixtures of fruity (isoamyl acetate; ISO) and woody (whiskey lactone; WL) odorants known to contribute to some of the major notes in Burgundy red wine. These experiments consisted of (i) calcium imaging of human embryonic kidney cells (HEK293T) transfected with olfactory receptors (ORs); (ii) single-unit electrophysiological recordings from olfactory receptor neurons (ORNs) and analyses of electro-olfactogram (EOG) responses in the rat nose in vivo; and (iii) psychophysical measurements of the perceived intensity of the mixtures as rated by human subjects. The calcium imaging and electrophysiological results revealed that ISO and WL can act simultaneously on single ORs or ORNs and confirm that receptor responses to mixtures are not the result of a simple sum of the effects of the individual mixture compounds. The addition of WL to ISO principally suppressed the ORN activation induced by ISO alone and was found to enhance this activation in a subset of cases. In the human studies, the addition of high concentrations of WL to ISO decreased the perceived intensity of the ISO. In contrast, the addition of low concentrations of WL enhanced the perceived intensity of the fruity note (ISO) in this mixture, as it enhanced EOG responses in ORNs. Thus, both OR and ORN responses to ISO + WL mixtures faithfully reflected perceptual response changes, so the odour mixture information is set up after the peripheral stage of the olfactory system.
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Affiliation(s)
- M A Chaput
- UMR 5292, Centre de recherche en neurosciences de Lyon, Université de Lyon, CNRS, INSERM, 50 avenue Tony Garnier, F-69366 Lyon, France.
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29
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Olfactory perception as a compass for olfactory neural maps. Trends Cogn Sci 2011; 15:537-45. [PMID: 22001868 DOI: 10.1016/j.tics.2011.09.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 09/22/2011] [Accepted: 09/26/2011] [Indexed: 11/21/2022]
Abstract
The mammalian brain commonly uses structural proximity to reflect proximity in stimulus and perceptual space. Objects or object features that are near each other in physical structure or perception are also near each other in the brain. This generates sensory maps. The topography of olfactory connectivity implies a rudimentary map in the olfactory epithelium, a more intricate map in the olfactory bulb, but no ordered topography is evident in piriform cortex. Currently, we are largely unable to link the ordered topography in epithelium and bulb to meaningful olfactory axes within a strong predictive framework. We argue that the path to uncovering such a predictive framework depends on systematically characterizing olfactory perception, and we describe initial efforts in this direction.
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30
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Abstract
Most natural odors are mixtures and often elicit percepts distinct from those elicited by their constituents. This emergence of a unique odor quality has long been attributed to central processing. Here we show that sophisticated integration of olfactory information begins in olfactory receptor neurons (ORNs) in Drosophila. Odor mixtures are encoded in the temporal dynamics as well as in the magnitudes of ORN responses. ORNs can respond to an inhibitory odorant with different durations depending on the level of background excitation. ORNs respond to mixtures with distinctive temporal dynamics that reflect the physicochemical properties of the constituent odorants. The insect repellent DEET (N,N-diethyl-m-toluamide), which attenuates odor responses of multiple ORNs, differs from an ORN-specific inhibitor in its effects on temporal dynamics. Our analysis reveals a means by which integration of information from odor mixtures begins in ORNs and provides insight into the contribution of inhibitory stimuli to sensory coding.
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31
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Reisert J. Origin of basal activity in mammalian olfactory receptor neurons. J Gen Physiol 2010; 136:529-40. [PMID: 20974772 PMCID: PMC2964517 DOI: 10.1085/jgp.201010528] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 10/01/2010] [Indexed: 01/11/2023] Open
Abstract
Mammalian odorant receptors form a large, diverse group of G protein-coupled receptors that determine the sensitivity and response profile of olfactory receptor neurons. But little is known if odorant receptors control basal and also stimulus-induced cellular properties of olfactory receptor neurons other than ligand specificity. This study demonstrates that different odorant receptors have varying degrees of basal activity, which drives concomitant receptor current fluctuations and basal action potential firing. This basal activity can be suppressed by odorants functioning as inverse agonists. Furthermore, odorant-stimulated olfactory receptor neurons expressing different odorant receptors can have strikingly different response patterns in the later phases of prolonged stimulation. Thus, the influence of odorant receptor choice on response characteristics is much more complex than previously thought, which has important consequences on odor coding and odor information transfer to the brain.
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Affiliation(s)
- Johannes Reisert
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA. jreisert@monell.org
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32
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Abstract
Odor discrimination requires differential expression of odor detectors. In fact, olfactory input to the brain is organized in units (glomeruli) innervated only by olfactory sensory neurons that express the same odorant receptor (OR). Therefore, discriminatory capacity is maximized if each sensory neuron expresses only one allele of a single OR gene, a postulate sometimes canonized as the "one neuron-one receptor rule." OR gene choice appears to result from a hierarchy of processes: differential availability of the alleles of each OR gene, zonal exclusion (or selection), OR gene switching during the initiation of OR gene transcription, and OR-dependent feedback to solidify the choice of one OR gene. The mechanisms underlying these processes are poorly understood, though a few elements are known or suspected. For example, the mechanism of activation of OR gene transcription appears to work in part through a few homeobox transcription factors (Emx2, and perhaps Lhx2) and the Ebf family of transcription factors. Further insights will probably come from several directions, but a promising hypothesis is that epigenetic mechanisms contribute to all levels of the hierarchical control of OR gene expression, especially the repressive events that seem to be necessary to achieve the singularity of OR gene choice.
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Affiliation(s)
- Timothy S McClintock
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY 40536-0298, USA.
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33
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Molecular components of signal amplification in olfactory sensory cilia. Proc Natl Acad Sci U S A 2010; 107:6052-7. [PMID: 20231443 DOI: 10.1073/pnas.0909032107] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The mammalian olfactory system detects an unlimited variety of odorants with a limited set of odorant receptors. To cope with the complexity of the odor world, each odorant receptor must detect many different odorants. The demand for low odor selectivity creates problems for the transduction process: the initial transduction step, the synthesis of the second messenger cAMP, operates with low efficiency, mainly because odorants bind only briefly to their receptors. Sensory cilia of olfactory receptor neurons have developed an unusual solution to this problem. They accumulate chloride ions at rest and discharge a chloride current upon odor detection. This chloride current amplifies the receptor potential and promotes electrical excitation. We have studied this amplification process by examining identity, subcellular localization, and regulation of its molecular components. We found that the Na(+)/K(+)/2Cl(-) cotransporter NKCC1 is expressed in the ciliary membrane, where it mediates chloride accumulation into the ciliary lumen. Gene silencing experiments revealed that the activity of this transporter depends on the kinases SPAK and OSR1, which are enriched in the cilia together with their own activating kinases, WNK1 and WNK4. A second Cl(-) transporter, the Cl(-)/HCO(3)(-) exchanger SLC4A1, is expressed in the cilia and may support Cl(-) accumulation. The calcium-dependent chloride channel TMEM16B (ANO2) provides a ciliary pathway for the excitatory chloride current. These findings describe a specific set of ciliary proteins involved in anion-based signal amplification. They provide a molecular concept for the unique strategy that allows olfactory sensory neurons to operate as efficient transducers of weak sensory stimuli.
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34
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Reed DR, Knaapila A. Genetics of taste and smell: poisons and pleasures. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2010; 94:213-40. [PMID: 21036327 PMCID: PMC3342754 DOI: 10.1016/b978-0-12-375003-7.00008-x] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Eating is dangerous. While food contains nutrients and calories that animals need to produce heat and energy, it may also contain harmful parasites, bacteria, or chemicals. To guide food selection, the senses of taste and smell have evolved to alert us to the bitter taste of poisons and the sour taste and off-putting smell of spoiled foods. These sensory systems help people and animals to eat defensively, and they provide the brake that helps them avoid ingesting foods that are harmful. But choices about which foods to eat are motivated by more than avoiding the bad; they are also motivated by seeking the good, such as fat and sugar. However, just as not everyone is equally capable of sensing toxins in food, not everyone is equally enthusiastic about consuming high-fat, high-sugar foods. Genetic studies in humans and experimental animals strongly suggest that the liking of sugar and fat is influenced by genotype; likewise, the abilities to detect bitterness and the malodors of rotting food are highly variable among individuals. Understanding the exact genes and genetic differences that affect food intake may provide important clues in obesity treatment by allowing caregivers to tailor dietary recommendations to the chemosensory landscape of each person.
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35
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Abstract
Remarkable advances in our understanding of olfactory perception have been made in recent years, including the discovery of new mechanisms of olfactory signaling and new principles of olfactory processing. Here, we discuss the insight that has been gained into the receptors, cells, and circuits that underlie the sense of smell.
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Affiliation(s)
| | | | - John R. Carlson
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven 06520, USA
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