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Kawabata Y, Takai S, Sanematsu K, Iwata S, Kawabata F, Kanematsu T, Jimi E, Shigemura N. The G protein-coupled receptor GPRC5C is a saccharide sensor with a novel 'off' response. FEBS Lett 2023; 597:2006-2016. [PMID: 37418589 DOI: 10.1002/1873-3468.14695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/15/2023] [Accepted: 06/16/2023] [Indexed: 07/09/2023]
Abstract
GPRC5C is an orphan G protein-coupled receptor (GPCR) that belongs to the class C GPCR family. Although GPRC5C is expressed in various organs, its function and ligand are still undetermined. We found that GPRC5C is expressed in mouse taste cells, enterocytes, and pancreatic α-cells. In functional imaging assays, HEK293 cells heterologously expressing GPRC5C and the chimeric G protein α subunit Gα16-gust44 showed robust intracellular Ca2+ increases in response to monosaccharides, disaccharides, and a sugar alcohol, but not an artificial sweetener or sweet-tasting amino acid. Notably, Ca2+ increases occurred after washout, not during stimulation. Our findings suggest that GPRC5C has receptor properties which lead to novel 'off' responses to saccharide detachment and may work as an internal or external chemosensor specifically tuned to natural sugars.
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Affiliation(s)
- Yuko Kawabata
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Shingo Takai
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
- Dent-Craniofacial Development and Regeneration Center, Kyushu University, Fukuoka, Japan
| | - Keisuke Sanematsu
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
- Oral Health/Brain Health/Total Health Research Center, Kyushu University, Fukuoka, Japan
- Research and Development Center for Five-Sense Devices Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
| | - Shusuke Iwata
- Department of Oral Physiology, Asahi University School of Dentistry, Mizuho, Japan
| | - Fuminori Kawabata
- Physiology of Domestic Animals, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Japan
| | - Takashi Kanematsu
- Division of Oral Biological Sciences, Department of Cell Biology, Aging Science, and Pharmacology, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Eijiro Jimi
- Oral Health/Brain Health/Total Health Research Center, Kyushu University, Fukuoka, Japan
- Laboratory of Molecular and Cellular Biochemistry, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
- Research and Development Center for Five-Sense Devices Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
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2
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Oike A, Iwata S, Hirayama A, Ono Y, Nagasato Y, Kawabata Y, Takai S, Sanematsu K, Wada N, Shigemura N. Bisphosphonate affects the behavioral responses to HCl by disrupting farnesyl diphosphate synthase in mouse taste bud and tongue epithelial cells. Sci Rep 2022; 12:21246. [PMID: 36481783 PMCID: PMC9732047 DOI: 10.1038/s41598-022-25755-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 12/05/2022] [Indexed: 12/13/2022] Open
Abstract
Little is known about the molecular mechanisms underlying drug-induced taste disorders, which can cause malnutrition and reduce quality of life. One of taste disorders is known adverse effects of bisphosphonates, which are administered as anti-osteoporotic drugs. Therefore, the present study evaluated the effects of risedronate (a bisphosphonate) on taste bud cells. Expression analyses revealed that farnesyl diphosphate synthase (FDPS, a key enzyme in the mevalonate pathway) was present in a subset of mouse taste bud and tongue epithelial cells, especially type III sour-sensitive taste cells. Other mevalonate pathway-associated molecules were also detected in mouse taste buds. Behavioral analyses revealed that mice administered risedronate exhibited a significantly enhanced aversion to HCl but not for other basic taste solutions, whereas the taste nerve responses were not affected by risedronate. Additionally, the taste buds of mice administered risedronate exhibited significantly lower mRNA expression of desmoglein-2, an integral component of desmosomes. Taken together, these findings suggest that risedronate may interact directly with FDPS to inhibit the mevalonate pathway in taste bud and tongue epithelial cells, thereby affecting the expression of desmoglein-2 related with epithelial barrier function, which may lead to alterations in behavioral responses to HCl via somatosensory nerves.
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Affiliation(s)
- Asami Oike
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan ,grid.177174.30000 0001 2242 4849Section of Interdisciplinary Dentistry, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Shusuke Iwata
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan ,grid.177174.30000 0001 2242 4849Research and Development Center for Five-Sense Devices, Kyushu University, Fukuoka, Japan
| | - Ayaka Hirayama
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yurika Ono
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuki Nagasato
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuko Kawabata
- grid.177174.30000 0001 2242 4849Department of Cell Biology, Aging Science, and Pharmacology, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Shingo Takai
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Keisuke Sanematsu
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan ,grid.177174.30000 0001 2242 4849Research and Development Center for Five-Sense Devices, Kyushu University, Fukuoka, Japan ,grid.177174.30000 0001 2242 4849Oral Health/Brain Health/Total Health Research Center, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Naohisa Wada
- grid.177174.30000 0001 2242 4849Section of Interdisciplinary Dentistry, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Noriatsu Shigemura
- grid.177174.30000 0001 2242 4849Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan ,grid.177174.30000 0001 2242 4849Research and Development Center for Five-Sense Devices, Kyushu University, Fukuoka, Japan
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3
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Kulesh B, Reese BE, Keeley PW. Contraction of axonal and dendritic fields in Sox5-deficient cone bipolar cells is accompanied by axonal sprouting and dendritic hyper-innervation of pedicles. Front Neuroanat 2022; 16:944706. [PMID: 36093292 PMCID: PMC9459848 DOI: 10.3389/fnana.2022.944706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 07/04/2022] [Indexed: 11/25/2022] Open
Abstract
Multiple factors regulate the differentiation of neuronal morphology during development, including interactions with afferents, targets, and homotypic neighbors, as well as cell-intrinsic transcriptional regulation. Retinal bipolar cells provide an exemplary model system for studying the control of these processes, as there are 15 transcriptionally and morphologically distinct types, each extending their dendritic and axonal arbors in respective strata within the synaptic layers of the retina. Here we have examined the role of the transcription factor Sox5 in the control of the morphological differentiation of one type of cone bipolar cell (CBC), the Type 7 cell. We confirm selective expression of SOX5 in this single bipolar cell type, emerging at the close of the first post-natal week, prior to morphological differentiation. Conditional knockout mice were generated by crossing a bipolar cell-specific cre-expressing line with mice carrying floxed Sox5 alleles, as well as the Gustducin-gfp reporter which labels Type 7 CBCs. Loss of SOX5 was confirmed in the bipolar cell stratum, in GFP+ Type 7 cells. Such SOX5-deficient Type 7 cells differentiate axonal and dendritic arbors that are each reduced in areal extent. The axonal arbors exhibit sprouting in the inner plexiform layer (IPL), thereby extending their overall radial extent, while the dendritic arbors connect with fewer cone pedicles in the outer plexiform layer, showing an increase in the average number of dendritic contacts at each pedicle. SOX5-deficient Type 7 CBCs should therefore exhibit smaller receptive fields derived from fewer if now hyper-innervated pedicles, transmitting their signals across a broader depth through the IPL.
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Affiliation(s)
- Bridget Kulesh
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Benjamin E. Reese
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Patrick W. Keeley
- Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA, United States
- *Correspondence: Patrick W. Keeley
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Yamada Y, Takai S, Watanabe Y, Osaki A, Kawabata Y, Oike A, Hirayama A, Iwata S, Sanematsu K, Tabata S, Shigemura N. Gene expression profiling of α-gustducin-expressing taste cells in mouse fungiform and circumvallate papillae. Biochem Biophys Res Commun 2021; 557:206-212. [PMID: 33872990 DOI: 10.1016/j.bbrc.2021.04.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 04/08/2021] [Indexed: 11/27/2022]
Abstract
Taste buds are complex sensory organs embedded in the epithelium of fungiform papillae (FP) and circumvallate papillae (CV). The sweet, bitter, and umami tastes are sensed by type II taste cells that express taste receptors (Tas1rs and Tas2rs) coupled with the taste G-protein α-gustducin. Recent studies revealed that the taste response profiles of α-gustducin-expressing cells are different between FP and CV, but which genes could generate such distinctive cell characteristics are still largely unknown. We performed a comprehensive transcriptome analysis on α-gustducin-expressing cells in mouse FP and CV by single-cell RNA sequencing combined with fluorescence-activated cell sorting. Transcriptome profiles of the α-gustducin-expressing cells showed various expression patterns of taste receptors. Our clustering analysis defined the specific cell populations derived from FP or CV based on their distinct gene expression. Immunohistochemistry confirmed the specific expression of galectin-3, encoded by Lgals3, which was recognized as a differentially expressed gene in the transcriptome analysis. Our work provides fundamental knowledge toward understanding the genetic heterogeneity of type II cells, potentially revealing differential characterization of FP and CV taste bud cells.
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Affiliation(s)
- Yu Yamada
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Laboratory of Functional Anatomy, Graduate School of Biosource and Bioenvironmental Science, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka-city, Fukuoka, 819-0395, Japan
| | - Shingo Takai
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan.
| | - Yu Watanabe
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Section of Implant and Rehabilitative Dentistry, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan
| | - Ayana Osaki
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Section of Interdisciplinary Dentistry, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, 812-8582, Fukuoka, Japan
| | - Yuko Kawabata
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan
| | - Asami Oike
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Section of Interdisciplinary Dentistry, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, 812-8582, Fukuoka, Japan
| | - Ayaka Hirayama
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Section of Orthodontics and Dentofacial Orthopedics, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan
| | - Shusuke Iwata
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Research and Development Center for Five-Sense Devices Taste and Odor Sensing, Kyushu University, 744, Nishi-ku, Fukuoka-city, Fukuoka, 819-0395, Japan
| | - Keisuke Sanematsu
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; OBT Research Center, Graduate School of Dental Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Research and Development Center for Five-Sense Devices Taste and Odor Sensing, Kyushu University, 744, Nishi-ku, Fukuoka-city, Fukuoka, 819-0395, Japan
| | - Shoji Tabata
- Laboratory of Functional Anatomy, Graduate School of Biosource and Bioenvironmental Science, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka-city, Fukuoka, 819-0395, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka-city, Fukuoka, 812-8582, Japan; Research and Development Center for Five-Sense Devices Taste and Odor Sensing, Kyushu University, 744, Nishi-ku, Fukuoka-city, Fukuoka, 819-0395, Japan.
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5
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Nguyen QT, Beck Coburn GE, Valentino A, Karabucak B, Tizzano M. Mouse Mandibular Retromolar Taste Buds Associated With a Mucus Salivary Gland. Chem Senses 2021; 46:6226126. [PMID: 33855345 DOI: 10.1093/chemse/bjab019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We have characterized a recently rediscovered chemosensory structure at the rear of the mandibular mucosa in the mouse oral cavity originally reported in the 1980s. This consists of unorganized taste buds, not contained within troughs, associated with the ducts of an underlying minor salivary gland. Using whole-mount preparations of transgenic mice expressing green fluorescent protein under the promoter of taste-signaling-specific genes, we determined that the structure contains taste bud clusters and salivary gland orifices at the rear of each mandible, distal to the last molar and anterior to the ascending ramus. Immunohistochemical analysis shows in the retromolar taste buds expression of the taste receptors Tas2R131 and T1R3 and taste cascade molecules TrpM5, PLCβ2, and GNAT3, consistent with type II taste cells, and expression of GAD1, consistent with type III taste cells. Furthermore, the neuronal marker, calcitonin gene-related peptide, in retromolar mucosa tissue wrapping around TrpM5+ taste buds was observed. RT-PCR showed that retromolar taste buds express all 3 mouse tas1r genes, 28 of the 35 tas2r genes, and taste transduction signaling genes gnat3, plcb2, and trpm5, making the retromolar taste buds similar to other lingual and palate taste buds. Finally, histochemistry demonstrated that the mandibular retromolar secretory gland is a minor salivary gland of mucous type. The mandibular retromolar taste structure may thus play a role in taste sensation and represent a potential novel pharmacological target for taste disorders.
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Affiliation(s)
- Quan T Nguyen
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Grace E Beck Coburn
- Department of Endodontics, The Robert Schattner Center, University of Pennsylvania, School of Dental Medicine, 240 South 40th Street, Philadelphia, PA 19104-6030, USA
| | - Amber Valentino
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Bekir Karabucak
- Department of Endodontics, The Robert Schattner Center, University of Pennsylvania, School of Dental Medicine, 240 South 40th Street, Philadelphia, PA 19104-6030, USA
| | - Marco Tizzano
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
- Department of Endodontics, The Robert Schattner Center, University of Pennsylvania, School of Dental Medicine, 240 South 40th Street, Philadelphia, PA 19104-6030, USA
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6
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Larson ED, Vandenbeuch A, Anderson CB, Kinnamon SC. GAD65Cre Drives Reporter Expression in Multiple Taste Cell Types. Chem Senses 2021; 46:bjab033. [PMID: 34160573 PMCID: PMC8276891 DOI: 10.1093/chemse/bjab033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In taste buds, Type I cells represent the majority of cells (50-60%) and primarily have a glial-like function in taste buds. However, recent studies suggest that they have additional sensory and signaling functions including amiloride-sensitive salt transduction, oxytocin modulation of taste, and substance P mediated GABA release. Nonetheless, the overall function of Type I cells in transduction and signaling remains unclear, primarily because of the lack of a reliable reporter for this cell type. GAD65 expression is specific to Type I taste cells and GAD65 has been used as a Cre driver to study Type I cells in salt taste transduction. To test the specificity of transgene-driven expression, we crossed GAD65Cre mice with floxed tdTomato and Channelrhodopsin (ChR2) lines and examined the progeny with immunochemistry, chorda tympani recording, and calcium imaging. We report that while many tdTomato+ taste cells express NTPDase2, a specific marker of Type I cells, we see some expression of tdTomato in both Gustducin and SNAP25-positive taste cells. We also see ChR2 in cells just outside the fungiform taste buds. Chorda tympani recordings in the GAD65Cre/ChR2 mice show large responses to blue light. Furthermore, several isolated tdTomato-positive taste cells responded to KCl depolarization with increases in intracellular calcium, indicating the presence of voltage-gated calcium channels. Taken together, these data suggest that GAD65Cre mice drive expression in multiple taste cell types and thus cannot be considered a reliable reporter of Type I cell function.
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Affiliation(s)
- Eric D Larson
- Department of Otolaryngology, University of Colorado Anschutz Medical Campus and Rocky Mountain Taste and Smell Center, Aurora, CO, USA
| | - Aurelie Vandenbeuch
- Department of Otolaryngology, University of Colorado Anschutz Medical Campus and Rocky Mountain Taste and Smell Center, Aurora, CO, USA
| | - Catherine B Anderson
- Department of Otolaryngology, University of Colorado Anschutz Medical Campus and Rocky Mountain Taste and Smell Center, Aurora, CO, USA
| | - Sue C Kinnamon
- Department of Otolaryngology, University of Colorado Anschutz Medical Campus and Rocky Mountain Taste and Smell Center, Aurora, CO, USA
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Masamoto M, Mitoh Y, Kobashi M, Shigemura N, Yoshida R. Effects of bitter receptor antagonists on behavioral lick responses of mice. Neurosci Lett 2020; 730:135041. [PMID: 32413538 DOI: 10.1016/j.neulet.2020.135041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 10/24/2022]
Abstract
Bitter taste receptors TAS2Rs detect noxious compounds in the oral cavity. Recent heterologous expression studies reported that some compounds function as antagonists for human TAS2Rs. For examples, amino acid derivatives such as γ-aminobutyric acid (GABA) and Nα,Nα-bis(carboxymethyl)-L-Lysine (BCML) blocked responses to quinine mediated by human TAS2R4. Probenecid inhibited responses to phenylthiocarbamide mediated by human TAS2R38. In this study, we investigated the effects of these human bitter receptor antagonists on behavioral lick responses of mice to elucidate whether these compounds also function as bitter taste blockers. In short-term (10 s) lick tests, concentration-dependent lick responses to bitter compounds (quinine-HCl, denatonium and phenylthiourea) were not affected by the addition of GABA or BCML. Probenecid reduced aversive lick responses to denatonium and phenylthiourea but not to quinine-HCl. In addition, taste cell responses to phenylthiourea were inhibited by probenecid. These results suggest some bitter antagonists of human TAS2Rs can work for bitter sense of mouse.
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Affiliation(s)
- Michimasa Masamoto
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan
| | - Yoshihiro Mitoh
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan
| | - Motoi Kobashi
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Ryusuke Yoshida
- Department of Oral Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8525, Japan.
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Sensing Senses: Optical Biosensors to Study Gustation. SENSORS 2020; 20:s20071811. [PMID: 32218129 PMCID: PMC7180777 DOI: 10.3390/s20071811] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 12/11/2022]
Abstract
The five basic taste modalities, sweet, bitter, umami, salty and sour induce changes of Ca2+ levels, pH and/or membrane potential in taste cells of the tongue and/or in neurons that convey and decode gustatory signals to the brain. Optical biosensors, which can be either synthetic dyes or genetically encoded proteins whose fluorescence spectra depend on levels of Ca2+, pH or membrane potential, have been used in primary cells/tissues or in recombinant systems to study taste-related intra- and intercellular signaling mechanisms or to discover new ligands. Taste-evoked responses were measured by microscopy achieving high spatial and temporal resolution, while plate readers were employed for higher throughput screening. Here, these approaches making use of fluorescent optical biosensors to investigate specific taste-related questions or to screen new agonists/antagonists for the different taste modalities were reviewed systematically. Furthermore, in the context of recent developments in genetically encoded sensors, 3D cultures and imaging technologies, we propose new feasible approaches for studying taste physiology and for compound screening.
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Abstract
The study of taste has been guided throughout much of its history by the conceptual framework of psychophysics, where the focus was on quantification of the subjective experience of the taste sensations. By the mid-20th century, data from physiologic studies had accumulated sufficiently to assemble a model for the function of receptors that must mediate the initial stimulus of tastant molecules in contact with the tongue. But the study of taste as a receptor-mediated event did not gain momentum until decades later when the actual receptor proteins and attendant signaling mechanisms were identified and localized to the highly specialized taste-responsive cells of the tongue. With those discoveries a new opportunity to examine taste as a function of receptor activity has come into focus. Pharmacology is the science designed specifically for the experimental interrogation and quantitative characterization of receptor function at all levels of inquiry from molecules to behavior. This review covers the history of some of the major concepts that have shaped thinking and experimental approaches to taste, the seminal discoveries that have led to elucidation of receptors for taste, and how applying principles of receptor pharmacology can enhance understanding of the mechanisms of taste physiology and perception.
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Affiliation(s)
- R Kyle Palmer
- Opertech Bio, Inc., Pennovation Center, Philadelphia, Pennsylvania
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10
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Yoshida R, Takai S, Sanematsu K, Margolskee RF, Shigemura N, Ninomiya Y. Bitter Taste Responses of Gustducin-positive Taste Cells in Mouse Fungiform and Circumvallate Papillae. Neuroscience 2017; 369:29-39. [PMID: 29113930 DOI: 10.1016/j.neuroscience.2017.10.047] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/24/2017] [Accepted: 10/30/2017] [Indexed: 12/22/2022]
Abstract
Bitter taste serves as an important signal for potentially poisonous compounds in foods to avoid their ingestion. Thousands of compounds are estimated to taste bitter and presumed to activate taste receptor cells expressing bitter taste receptors (Tas2rs) and coupled transduction components including gustducin, phospholipase Cβ2 (PLCβ2) and transient receptor potential channel M5 (TRPM5). Indeed, some gustducin-positive taste cells have been shown to respond to bitter compounds. However, there has been no systematic characterization of their response properties to multiple bitter compounds and the role of transduction molecules in these cells. In this study, we investigated bitter taste responses of gustducin-positive taste cells in situ in mouse fungiform (anterior tongue) and circumvallate (posterior tongue) papillae using transgenic mice expressing green fluorescent protein in gustducin-positive cells. The overall response profile of gustducin-positive taste cells to multiple bitter compounds (quinine, denatonium, cyclohexamide, caffeine, sucrose octaacetate, tetraethylammonium, phenylthiourea, L-phenylalanine, MgSO4, and high concentration of saccharin) was not significantly different between fungiform and circumvallate papillae. These bitter-sensitive taste cells were classified into several groups according to their responsiveness to multiple bitter compounds. Bitter responses of gustducin-positive taste cells were significantly suppressed by inhibitors of TRPM5 or PLCβ2. In contrast, several bitter inhibitors did not show any effect on bitter responses of taste cells. These results indicate that bitter-sensitive taste cells display heterogeneous responses and that TRPM5 and PLCβ2 are indispensable for eliciting bitter taste responses of gustducin-positive taste cells.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; OBT Research Center, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
| | - Shingo Takai
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Keisuke Sanematsu
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | | | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
| | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Monell Chemical Senses Center, Philadelphia, PA, USA; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
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Yoshida R, Shin M, Yasumatsu K, Takai S, Inoue M, Shigemura N, Takiguchi S, Nakamura S, Ninomiya Y. The Role of Cholecystokinin in Peripheral Taste Signaling in Mice. Front Physiol 2017; 8:866. [PMID: 29163209 PMCID: PMC5671461 DOI: 10.3389/fphys.2017.00866] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/16/2017] [Indexed: 11/13/2022] Open
Abstract
Cholecystokinin (CCK) is a gut hormone released from enteroendocrine cells. CCK functions as an anorexigenic factor by acting on CCK receptors expressed on the vagal afferent nerve and hypothalamus with a synergistic interaction between leptin. In the gut, tastants such as amino acids and bitter compounds stimulate CCK release from enteroendocrine cells via activation of taste transduction pathways. CCK is also expressed in taste buds, suggesting potential roles of CCK in taste signaling in the peripheral taste organ. In the present study, we focused on the function of CCK in the initial responses to taste stimulation. CCK was coexpressed with type II taste cell markers such as Gα-gustducin, phospholipase Cβ2, and transient receptor potential channel M5. Furthermore, a small subset (~30%) of CCK-expressing taste cells expressed a sweet/umami taste receptor component, taste receptor type 1 member 3, in taste buds. Because type II taste cells are sweet, umami or bitter taste cells, the majority of CCK-expressing taste cells may be bitter taste cells. CCK-A and -B receptors were expressed in both taste cells and gustatory neurons. CCK receptor knockout mice showed reduced neural responses to bitter compounds compared with wild-type mice. Consistently, intravenous injection of CCK-Ar antagonist lorglumide selectively suppressed gustatory nerve responses to bitter compounds. Intravenous injection of CCK-8 transiently increased gustatory nerve activities in a dose-dependent manner whereas administration of CCK-8 did not affect activities of bitter-sensitive taste cells. Collectively, CCK may be a functionally important neurotransmitter or neuromodulator to activate bitter nerve fibers in peripheral taste tissues.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.,OBT Research Center, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan
| | - Misa Shin
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.,Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Keiko Yasumatsu
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.,Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
| | - Shingo Takai
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan
| | - Mayuko Inoue
- OBT Research Center, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.,Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan
| | - Soichi Takiguchi
- National Kyushu Cancer Center, Institute for Clinical Research, Fukuoka, Japan
| | - Seiji Nakamura
- Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan.,Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan.,Monell Chemical Senses Center, Philadelphia, PA, United States
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12
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Abstract
Retinal bipolar cells spread their dendritic arbors to tile the retinal surface, extending them to the tips of the dendritic fields of their homotypic neighbors, minimizing dendritic overlap. Such uniform nonredundant dendritic coverage of these populations would suggest a degree of spatial order in the properties of their somal distributions, yet few studies have examined the patterning in retinal bipolar cell mosaics. The present study examined the organization of two types of cone bipolar cells in the mouse retina, the Type 2 cells and the Type 4 cells, and compared their spatial statistical properties with those of the horizontal cells and the cholinergic amacrine cells, as well as to random simulations of cells matched in density and constrained by soma size. The Delauney tessellation of each field was computed, from which nearest neighbor distances and Voronoi domain areas were extracted, permitting a calculation of their respective regularity indexes (RIs). The spatial autocorrelation of the field was also computed, from which the effective radius and packing factor (PF) were determined. Both cone bipolar cell types were found to be less regular and less efficiently packed than either the horizontal cells or cholinergic amacrine cells. Furthermore, while the latter two cell types had RIs and PFs in excess of those for their matched random simulations, the two types of cone bipolar cells had spatial statistical properties comparable to random distributions. An analysis of single labeled cone bipolar cells revealed dendritic arbors frequently skewed to one side of the soma, as would be expected from a randomly distributed population of cells with dendrites that tile. Taken together, these results suggest that, unlike the horizontal cells or cholinergic amacrine cells which minimize proximity to one another, cone bipolar cell types are constrained only by their physical size.
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13
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Yoshida R, Noguchi K, Shigemura N, Jyotaki M, Takahashi I, Margolskee RF, Ninomiya Y. Leptin Suppresses Mouse Taste Cell Responses to Sweet Compounds. Diabetes 2015; 64:3751-62. [PMID: 26116698 PMCID: PMC4876703 DOI: 10.2337/db14-1462] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 06/16/2015] [Indexed: 01/19/2023]
Abstract
Leptin is known to selectively suppress neural and behavioral responses to sweet-tasting compounds. However, the molecular basis for the effect of leptin on sweet taste is not known. Here, we report that leptin suppresses sweet taste via leptin receptors (Ob-Rb) and KATP channels expressed selectively in sweet-sensitive taste cells. Ob-Rb was more often expressed in taste cells that expressed T1R3 (a sweet receptor component) than in those that expressed glutamate-aspartate transporter (a marker for Type I taste cells) or GAD67 (a marker for Type III taste cells). Systemically administered leptin suppressed taste cell responses to sweet but not to bitter or sour compounds. This effect was blocked by a leptin antagonist and was absent in leptin receptor-deficient db/db mice and mice with diet-induced obesity. Blocking the KATP channel subunit sulfonylurea receptor 1, which was frequently coexpressed with Ob-Rb in T1R3-expressing taste cells, eliminated the effect of leptin on sweet taste. In contrast, activating the KATP channel with diazoxide mimicked the sweet-suppressing effect of leptin. These results indicate that leptin acts via Ob-Rb and KATP channels that are present in T1R3-expressing taste cells to selectively suppress their responses to sweet compounds.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Kenshi Noguchi
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan Section of Orthodontics and Dentofacial Orthopedics, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Masafumi Jyotaki
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | - Ichiro Takahashi
- Section of Orthodontics and Dentofacial Orthopedics, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan
| | | | - Yuzo Ninomiya
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan
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14
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Takai S, Yasumatsu K, Inoue M, Iwata S, Yoshida R, Shigemura N, Yanagawa Y, Drucker DJ, Margolskee RF, Ninomiya Y. Glucagon-like peptide-1 is specifically involved in sweet taste transmission. FASEB J 2015; 29:2268-80. [PMID: 25678625 DOI: 10.1096/fj.14-265355] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/22/2015] [Indexed: 11/11/2022]
Abstract
Five fundamental taste qualities (sweet, bitter, salty, sour, umami) are sensed by dedicated taste cells (TCs) that relay quality information to gustatory nerve fibers. In peripheral taste signaling pathways, ATP has been identified as a functional neurotransmitter, but it remains to be determined how specificity of different taste qualities is maintained across synapses. Recent studies demonstrated that some gut peptides are released from taste buds by prolonged application of particular taste stimuli, suggesting their potential involvement in taste information coding. In this study, we focused on the function of glucagon-like peptide-1 (GLP-1) in initial responses to taste stimulation. GLP-1 receptor (GLP-1R) null mice had reduced neural and behavioral responses specifically to sweet compounds compared to wild-type (WT) mice. Some sweet responsive TCs expressed GLP-1 and its receptors were expressed in gustatory neurons. GLP-1 was released immediately from taste bud cells in response to sweet compounds but not to other taste stimuli. Intravenous administration of GLP-1 elicited transient responses in a subset of sweet-sensitive gustatory nerve fibers but did not affect other types of fibers, and this response was suppressed by pre-administration of the GLP-1R antagonist Exendin-4(3-39). Thus GLP-1 may be involved in normal sweet taste signal transmission in mice.
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Affiliation(s)
- Shingo Takai
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Keiko Yasumatsu
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Mayuko Inoue
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Shusuke Iwata
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Ryusuke Yoshida
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Noriatsu Shigemura
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Yuchio Yanagawa
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Daniel J Drucker
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Robert F Margolskee
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Yuzo Ninomiya
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
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15
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Xiong G, Redding K, Chen B, Cohen AS, Cohen NA. Non-specific immunostaining by a rabbit antibody against gustducin α subunit in mouse brain. J Histochem Cytochem 2014; 63:79-87. [PMID: 25411190 DOI: 10.1369/0022155414562838] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gustducin is a guanosine nucleotide-binding protein functionally coupled with taste receptors and thus originally identified in taste cells of the tongue. Recently, bitter taste receptors and gustducin have been detected in the airways, digestive tracts and brain. The existing studies showing taste receptors and gustducin in the brain were carried out exclusively on frozen sections. In order to avoid the technical shortcomings associated with frozen sectioning, we performed immunofluorescence staining using vibratome-cut sections from mouse brains. Using a rabbit gustducin antibody, we could not detect neurons or astrocytes as reported previously. Rather, we found dense fibers in the nucleus accumbens and periventricular areas. We assumed these staining patterns to be specific after confirmation with conventional negative control staining. For the verification of this finding, we stained gustducin knockout mouse brain and tongue sections with the same rabbit gustducin antibody. Whereas negative staining was confirmed in the tongue, intensive fibers were constantly stained in the brain. Moreover, immunostaining with a goat gustducin antibody could not demonstrate the fibers in the brain tissue. The present study implies a cross immunoreaction that occurs with the rabbit gustducin antibody in mouse brain samples, suggesting that the conventional negative controls may not be sufficient when an immunostaining pattern is to be verified.
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Affiliation(s)
- Guoxiang Xiong
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania (GX, ASC)
| | - Kevin Redding
- Monell Chemical Senses Center, Philadelphia, Pennsylvania (KR)
| | - Bei Chen
- Departments of Otorhinolaryngology - Head and Neck Surgery, University of Pennsylvania, Philadelphia, Pennsylvania (BC, NAC)
| | - Akiva S Cohen
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania (GX, ASC),Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania (ASC)
| | - Noam A Cohen
- Departments of Otorhinolaryngology - Head and Neck Surgery, University of Pennsylvania, Philadelphia, Pennsylvania (BC, NAC)
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16
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Hoon M, Okawa H, Della Santina L, Wong ROL. Functional architecture of the retina: development and disease. Prog Retin Eye Res 2014; 42:44-84. [PMID: 24984227 DOI: 10.1016/j.preteyeres.2014.06.003] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 06/08/2014] [Accepted: 06/22/2014] [Indexed: 12/22/2022]
Abstract
Structure and function are highly correlated in the vertebrate retina, a sensory tissue that is organized into cell layers with microcircuits working in parallel and together to encode visual information. All vertebrate retinas share a fundamental plan, comprising five major neuronal cell classes with cell body distributions and connectivity arranged in stereotypic patterns. Conserved features in retinal design have enabled detailed analysis and comparisons of structure, connectivity and function across species. Each species, however, can adopt structural and/or functional retinal specializations, implementing variations to the basic design in order to satisfy unique requirements in visual function. Recent advances in molecular tools, imaging and electrophysiological approaches have greatly facilitated identification of the cellular and molecular mechanisms that establish the fundamental organization of the retina and the specializations of its microcircuits during development. Here, we review advances in our understanding of how these mechanisms act to shape structure and function at the single cell level, to coordinate the assembly of cell populations, and to define their specific circuitry. We also highlight how structure is rearranged and function is disrupted in disease, and discuss current approaches to re-establish the intricate functional architecture of the retina.
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Affiliation(s)
- Mrinalini Hoon
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Haruhisa Okawa
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Luca Della Santina
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA
| | - Rachel O L Wong
- Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, WA 98195, USA.
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17
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Pepino MY, Bradley D, Eagon JC, Sullivan S, Abumrad NA, Klein S. Changes in taste perception and eating behavior after bariatric surgery-induced weight loss in women. Obesity (Silver Spring) 2014; 22:E13-20. [PMID: 24167016 PMCID: PMC4000290 DOI: 10.1002/oby.20649] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 10/15/2013] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Roux-en-Y gastric bypass (RYGB) surgery causes greater weight loss than laparoscopic adjustable gastric banding (LAGB). We tested the hypothesis that RYGB has weight loss-independent effects on taste perception, which influence eating behavior and contribute to the greater weight loss. METHODS Subjects were studied before and after ∼20% weight loss induced by RYGB (n = 17) or LAGB (n = 10). The following have been evaluated: taste sensitivity for sweet, salty and savory stimuli, sucrose and monosodium glutamate (MSG) preferences, sweetness palatability, eating behavior, and expression of taste-related genes in biopsies of fungiform papillae. RESULTS Weight loss induced by both procedures caused the same decrease in: preferred sucrose concentration (-12 ± 10%), perceived sweetness of sucrose (-7 ± 5%), cravings for sweets and fast-foods (-22 ± 5%), influence of emotions (-27 ± 5%), and external food cues (-30 ± 4%) on eating behavior, and expression of α-gustducin in fungiform papillae (all P values <0.05). RYGB, but not LAGB, shifted sweetness palatability from pleasant to unpleasant when repetitively tasting sucrose (P = 0.05). Neither procedure affected taste detection thresholds nor MSG preferences. CONCLUSIONS LAGB and RYGB cause similar alterations in eating behaviors, when weight loss is matched. These changes in eating behavior were not associated with changes in taste sensitivity, suggesting other, as yet unknown, mechanisms are involved.
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Affiliation(s)
- Marta Yanina Pepino
- Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
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18
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Extrasensory perception: odorant and taste receptors beyond the nose and mouth. Pharmacol Ther 2013; 142:41-61. [PMID: 24280065 DOI: 10.1016/j.pharmthera.2013.11.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 11/04/2013] [Indexed: 12/22/2022]
Abstract
G protein-coupled receptors (GPCRs) represent the largest family of transmembrane receptors and are prime therapeutic targets. The odorant and taste receptors account for over half of the GPCR repertoire, yet they are generally excluded from large-scale, drug candidate analyses. Accumulating molecular evidence indicates that the odorant and taste receptors are widely expressed throughout the body and functional beyond the oronasal cavity - with roles including nutrient sensing, autophagy, muscle regeneration, regulation of gut motility, protective airway reflexes, bronchodilation, and respiratory disease. Given this expanding array of actions, the restricted perception of these GPCRs as mere mediators of smell and taste is outdated. Moreover, delineation of the precise actions of odorant and taste GPCRs continues to be hampered by the relative paucity of selective and specific experimental tools, as well as the lack of defined receptor pharmacology. In this review, we summarize the evidence for expression and function of odorant and taste receptors in tissues beyond the nose and mouth, and we highlight their broad potential in physiology and pathophysiology.
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20
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Immunohistochemical detection of TAS2R38 protein in human taste cells. PLoS One 2012; 7:e40304. [PMID: 22792271 PMCID: PMC3391245 DOI: 10.1371/journal.pone.0040304] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 06/05/2012] [Indexed: 12/14/2022] Open
Abstract
The sense of taste plays an important role in the evaluation of the nutrient composition of consumed food. Bitter taste in particular is believed to serve a warning function against the ingestion of poisonous substances. In the past years enormous progress was made in the characterization of bitter taste receptors, including their gene expression patterns, pharmacological features and presumed physiological roles in gustatory as well as in non-gustatory tissues. However, due to a lack in TAS2R-specifc antibodies the localization of receptor proteins within gustatory tissues has never been analyzed. In the present study we have screened a panel of commercially available antisera raised against human bitter taste receptors by immunocytochemical experiments. One of these antisera was found to be highly specific for the human bitter taste receptor TAS2R38. We further demonstrate that this antibody is able to detect heterologously expressed TAS2R38 protein on Western blots. The antiserum is, however, not able to interfere significantly with TAS2R38 function in cell based calcium imaging analyses. Most importantly, we were able to demonstrate the presence of TAS2R38 protein in human gustatory papillae. Using double immunofluorescence we show that TAS2R38-positive cells form a subpopulation of PLCbeta2 expressing cells. On a subcellular level the localization of this bitter taste receptor is neither restricted to the cell surface nor particularly enriched at the level of the microvilli protruding into the pore region of the taste buds, but rather evenly distributed over the entire cell body.
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21
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Nosrat IV, Margolskee RF, Nosrat CA. Targeted taste cell-specific overexpression of brain-derived neurotrophic factor in adult taste buds elevates phosphorylated TrkB protein levels in taste cells, increases taste bud size, and promotes gustatory innervation. J Biol Chem 2012; 287:16791-800. [PMID: 22442142 DOI: 10.1074/jbc.m111.328476] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is the most potent neurotrophic factor in the peripheral taste system during embryonic development. It is also expressed in adult taste buds. There is a lack of understanding of the role of BDNF in the adult taste system. To address this, we generated novel transgenic mice in which transgene expression was driven by an α-gustducin promoter coupling BDNF expression to the postnatal expression of gustducin in taste cells. Immunohistochemistry revealed significantly stronger BDNF labeling in taste cells of high BDNF-expressing mouse lines compared with controls. We show that taste buds in these mice are significantly larger and have a larger number of taste cells compared with controls. To examine whether innervation was affected in Gust-BDNF mice, we used antibodies to neural cell adhesion molecule (NCAM) and ATP receptor P2X3. The total density of general innervation and specifically the gustatory innervation was markedly increased in high BDNF-expressing mice compared with controls. TrkB and NCAM gene expression in laser capture microdissected taste epithelia were significantly up-regulated in these mice. Up-regulation of TrkB transcripts in taste buds and elevated taste cell-specific TrkB phosphorylation in response to increased BDNF levels indicate that BDNF controls the expression and activation of its high affinity receptor in taste cells. This demonstrates a direct taste cell function for BDNF. BDNF also orchestrates and maintains taste bud innervation. We propose that the Gust-BDNF transgenic mouse models can be employed to further dissect the specific roles of BDNF in the adult taste system.
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Affiliation(s)
- Irina V Nosrat
- University of Tennessee Health Science Center, College of Medicine, Memphis, Tennessee 38163, USA
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22
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Abstract
The role of bitter taste receptors has changed considerably over the past years. While initially considered to have predominantly, or even exclusively, gustatory functions, numerous recent reports addressed nongustatory actions of TAS2R s. One site of extraoral bitter taste receptor expression is the respiratory system. It was demonstrated that bitter taste receptors are located in the nasal respiratory epithelium, as well as in ciliated cells of lung epithelium, where they affect respiratory functions in response to noxious stimuli. Another site of TAS2R gene expression is the gastrointestinal tract. Here, bitter compounds are suspected to regulate via activation of TAS2Rs metabolic and digestive functions.The present article focuses on general pharmacological features and signal transduction components of mammalian TAS2Rs and summarizes current knowledge on Tas2r gene function in respiratory and gastrointestinal systems on the expense of a detailed description of gustatory bitter taste perception, which has been the subject of recent reviews.
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Zhang Y, Kolli T, Hivley R, Jaber L, Zhao FI, Yan J, Herness S. Characterization of the expression pattern of adrenergic receptors in rat taste buds. Neuroscience 2010; 169:1421-37. [PMID: 20478367 DOI: 10.1016/j.neuroscience.2010.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 05/03/2010] [Accepted: 05/11/2010] [Indexed: 12/01/2022]
Abstract
Taste buds signal the presence of chemical stimuli in the oral cavity to the central nervous system using both early transduction mechanisms, which allow single cells to be depolarized via receptor-mediated signaling pathways, and late transduction mechanisms, which involve extensive cell-to-cell communication among the cells in the bud. The latter mechanisms, which involve a large number of neurotransmitters and neuropeptides, are less well understood. Among neurotransmitters, multiple lines of evidence suggest that norepinephrine plays a yet unknown role in the taste bud. This study investigated the expression pattern of adrenergic receptors in the rat posterior taste bud. Expression of alpha1A, alpha1B, alpha1D, alpha2A, alpha2B, alpha2C, beta1, and the beta2 adrenoceptor subtypes was observed in taste buds using RT-PCR and immunocytochemical techniques. Taste buds also expressed the biosynthetic enzyme for norepinephrine, dopamine beta-hydroxylase (DbetaH), as well as the norepinephrine transporter. Further, expression of the epinephrine synthetic enzyme, phenylethanolamine N-methyltransferase (PNMT), was observed suggesting a possible role for this transmitter in the bud. Phenotyping adrenoceptor expression patterns with double labeling experiments to gustducin, synaptosomal-associated protein 25 (SNAP-25), and neural cell adhesion molecule (NCAM) suggests they are prominently expressed in subsets of cells known to express taste receptor molecules but segregated from cells known to have synapses with the afferent nerve fiber. Alpha and beta adrenoceptors co-express with one another in unique patterns as observed with immunocytochemistry and single cell reverse transcription polymerase chain reaction (RT-PCR). These data suggest that single cells express multiple adrenergic receptors and that adrenergic signaling may be particularly important in bitter, sweet, and umami taste qualities. In summary, adrenergic signaling in the taste bud occurs through complex pathways that include presynaptic and postsynaptic receptors and likely play modulatory roles in processing of gustatory information similar to other peripheral sensory systems such as the retina, cochlea, and olfactory bulb.
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Affiliation(s)
- Y Zhang
- Department of Physiology and Pathophysiology, Key Laboratory of Environment and Genes Related to Diseases, Ministry of Education, School of Medicine, Xi'an Jiaotong University, 76# West Yanta Road, Xi'an 710061, PR China
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Puthussery T, Gayet-Primo J, Taylor WR. Localization of the calcium-binding protein secretagogin in cone bipolar cells of the mammalian retina. J Comp Neurol 2010; 518:513-25. [PMID: 20020539 DOI: 10.1002/cne.22234] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Secretagogin, a recently cloned member of the EF-hand family of calcium binding proteins, was localized in the mouse, rat, and rabbit retina using immunofluorescence immunohistochemistry. Secretagogin is expressed in subpopulations of ON and OFF cone bipolar cells; however, no immunoreactivity was observed in rod bipolar cells in any of these species. Using subtype-specific markers and mice expressing green fluorescent protein (GFP) within specific cell classes, we found that secretagogin is expressed in Types 2, 3, 4, 5, 6 and possibly Type 8 cone bipolar cells in the mouse retina. The expression pattern in the rat retina differs slightly with expression in cone bipolar cell Types 2, 5, 6, 7, and 8. Evaluation of secretagogin in the developing mouse retina revealed expression as early as postnatal day 6, with OFF cone bipolar cells showing secretagogin expression prior to the ON cone bipolar cells. Secretagogin is a useful marker of cone bipolar cells for studying alterations in bipolar cell morphology during development and degeneration. Further work will be necessary to elucidate the functional role of this protein in bipolar cells.
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Affiliation(s)
- Theresa Puthussery
- Casey Eye Institute, Department of Ophthalmology, Oregon Health and Sciences University, Portland, Oregon 97239, USA.
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Yoshida R, Ninomiya Y. New Insights into the Signal Transmission from Taste Cells to Gustatory Nerve Fibers. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 279:101-34. [DOI: 10.1016/s1937-6448(10)79004-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Lu Q, Ivanova E, Pan ZH. Characterization of green fluorescent protein-expressing retinal cone bipolar cells in a 5-hydroxytryptamine receptor 2a transgenic mouse line. Neuroscience 2009; 163:662-8. [PMID: 19589372 PMCID: PMC2769501 DOI: 10.1016/j.neuroscience.2009.07.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 07/01/2009] [Accepted: 07/02/2009] [Indexed: 10/20/2022]
Abstract
Retinal bipolar cells relay visual information from photoreceptors to third-order retinal neurons. Bipolar cells, comprising multiple types, play an essential role in segregating visual information into multiple parallel pathways in the retina. The identification of molecular markers that can label specific retinal bipolar cells could facilitate the investigation of bipolar cell functions in the retina. Transgenic mice with specific cell type(s) labeled with green fluorescent protein (GFP) have become a powerful tool for morphological and functional studies of neurons in the CNS, including the retina. In this study, we report a 5-hydroxytryptamine receptor 2a (5-HTR2a) transgenic mouse line in which expression of GFP was observed in two populations of bipolar cells in the retina. Based on the terminal stratification and immunostaining, all the strongly GFP-labeled bipolar cells were found to be type 4 cone bipolar cells. A small population of weakly labeled bipolar cells was also observed, which may represent type 8 or 9 cone bipolar cells. GFP expression in retinal cone bipolar cells was seen as early as postnatal day 5. In addition, despite severe retinal degeneration due to the presence of the rd1 mutation in this transgenic line, the density of GFP-labeled cone bipolar cells remained stable up to at least 6 months of age. This transgenic mouse line will be a useful tool for the study of type 4 cone bipolar cells in the retina under both normal and disease conditions.
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Affiliation(s)
- Q Lu
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 540 East Canfield Avenue, Detroit, MI 48201, USA
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27
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Yoshida R, Miyauchi A, Yasuo T, Jyotaki M, Murata Y, Yasumatsu K, Shigemura N, Yanagawa Y, Obata K, Ueno H, Margolskee RF, Ninomiya Y. Discrimination of taste qualities among mouse fungiform taste bud cells. J Physiol 2009; 587:4425-39. [PMID: 19622604 PMCID: PMC2766648 DOI: 10.1113/jphysiol.2009.175075] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 07/17/2009] [Indexed: 11/08/2022] Open
Abstract
Multiple lines of evidence from molecular studies indicate that individual taste qualities are encoded by distinct taste receptor cells. In contrast, many physiological studies have found that a significant proportion of taste cells respond to multiple taste qualities. To reconcile this apparent discrepancy and to identify taste cells that underlie each taste quality, we investigated taste responses of individual mouse fungiform taste cells that express gustducin or GAD67, markers for specific types of taste cells. Type II taste cells respond to sweet, bitter or umami tastants, express taste receptors, gustducin and other transduction components. Type III cells possess putative sour taste receptors, and have well elaborated conventional synapses. Consistent with these findings we found that gustducin-expressing Type II taste cells responded best to sweet (25/49), bitter (20/49) or umami (4/49) stimuli, while all GAD67 (Type III) taste cells examined (44/44) responded to sour stimuli and a portion of them showed multiple taste sensitivities, suggesting discrimination of each taste quality among taste bud cells. These results were largely consistent with those previously reported with circumvallate papillae taste cells. Bitter-best taste cells responded to multiple bitter compounds such as quinine, denatonium and cyclohexamide. Three sour compounds, HCl, acetic acid and citric acid, elicited responses in sour-best taste cells. These results suggest that taste cells may be capable of recognizing multiple taste compounds that elicit similar taste sensation. We did not find any NaCl-best cells among the gustducin and GAD67 taste cells, raising the possibility that salt sensitive taste cells comprise a different population.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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28
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Beites CL, Hollenbeck PLW, Kim J, Lovell-Badge R, Lander AD, Calof AL. Follistatin modulates a BMP autoregulatory loop to control the size and patterning of sensory domains in the developing tongue. Development 2009; 136:2187-97. [PMID: 19474151 DOI: 10.1242/dev.030544] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The regenerative capacity of many placode-derived epithelial structures makes them of interest for understanding the molecular control of epithelial stem cells and their niches. Here, we investigate the interaction between the developing epithelium and its surrounding mesenchyme in one such system, the taste papillae and sensory taste buds of the mouse tongue. We identify follistatin (FST) as a mesenchymal factor that controls size, patterning and gustatory cell differentiation in developing taste papillae. FST limits expansion and differentiation of Sox2-expressing taste progenitor cells and negatively regulates the development of taste papillae in the lingual epithelium: in Fst(-/-) tongue, there is both ectopic development of Sox2-expressing taste progenitors and accelerated differentiation of gustatory cells. Loss of Fst leads to elevated activity and increased expression of epithelial Bmp7; the latter effect is consistent with BMP7 positive autoregulation, a phenomenon we demonstrate directly. We show that FST and BMP7 influence the activity and expression of other signaling systems that play important roles in the development of taste papillae and taste buds. In addition, using computational modeling, we show how aberrations in taste papillae patterning in Fst(-/-) mice could result from disruption of an FST-BMP7 regulatory circuit that normally suppresses noise in a process based on diffusion-driven instability. Because inactivation of Bmp7 rescues many of the defects observed in Fst(-/-) tongue, we conclude that interactions between mesenchyme-derived FST and epithelial BMP7 play a central role in the morphogenesis, innervation and maintenance of taste buds and their stem/progenitor cells.
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Affiliation(s)
- Crestina L Beites
- Department of Anatomy and Neurobiology and Center for Complex Biological Systems, University of California, Irvine, CA 92697, USA
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Ota MS, Kaneko Y, Kondo K, Ogishima S, Tanaka H, Eto K, Kondo T. Combined in silico and in vivo analyses reveal role of Hes1 in taste cell differentiation. PLoS Genet 2009; 5:e1000443. [PMID: 19343206 PMCID: PMC2655725 DOI: 10.1371/journal.pgen.1000443] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Accepted: 03/02/2009] [Indexed: 11/19/2022] Open
Abstract
The sense of taste is of critical importance to animal survival. Although studies of taste signal transduction mechanisms have provided detailed information regarding taste receptor calcium signaling molecules (TRCSMs, required for sweet/bitter/umami taste signal transduction), the ontogeny of taste cells is still largely unknown. We used a novel approach to investigate the molecular regulation of taste system development in mice by combining in silico and in vivo analyses. After discovering that TRCSMs colocalized within developing circumvallate papillae (CVP), we used computational analysis of the upstream regulatory regions of TRCSMs to investigate the possibility of a common regulatory network for TRCSM transcription. Based on this analysis, we identified Hes1 as a likely common regulatory factor, and examined its function in vivo. Expression profile analyses revealed that decreased expression of nuclear HES1 correlated with expression of type II taste cell markers. After stage E18, the CVP of Hes1(-/) (-) mutants displayed over 5-fold more TRCSM-immunoreactive cells than did the CVP of their wild-type littermates. Thus, according to our composite analyses, Hes1 is likely to play a role in orchestrating taste cell differentiation in developing taste buds.
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Affiliation(s)
- Masato S. Ota
- Section of Molecular Craniofacial Embryology, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Kondo Research Unit, Neuro-Developmental Disorder Research Group, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan
| | - Yoshiyuki Kaneko
- Department of Bioinformatics, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Kaori Kondo
- Section of Molecular Craniofacial Embryology, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
- Kondo Research Unit, Neuro-Developmental Disorder Research Group, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan
| | - Soichi Ogishima
- Department of Bioinformatics, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Hiroshi Tanaka
- Department of Bioinformatics, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Kazuhiro Eto
- Section of Molecular Craniofacial Embryology, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
| | - Takashi Kondo
- Kondo Research Unit, Neuro-Developmental Disorder Research Group, Brain Science Institute, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan
- * E-mail:
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Abstract
Bitter taste in mammals is achieved by a family of approximately 30 bitter taste receptor genes. The main function of bitter taste is to protect the organism against the ingestion of, frequently bitter, toxic food metabolites. The field of taste research has advanced rapidly during the last several years. This is especially true for the G-protein-coupled-receptor-mediated taste qualities, sweet, umami, and bitter. This review summarizes current knowledge of bitter taste receptor gene expression, signal transduction, the structure-activity relationship of bitter taste receptor proteins, as well as their variability leading to a high degree of individualization of this taste quality in mammals.
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Affiliation(s)
- M Behrens
- German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, Nuthetal, 14558, Germany.
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Jang HJ, Kokrashvili Z, Theodorakis MJ, Carlson OD, Kim BJ, Zhou J, Kim HH, Xu X, Chan SL, Juhaszova M, Bernier M, Mosinger B, Margolskee RF, Egan JM. Gut-expressed gustducin and taste receptors regulate secretion of glucagon-like peptide-1. Proc Natl Acad Sci U S A 2007; 104:15069-74. [PMID: 17724330 PMCID: PMC1986614 DOI: 10.1073/pnas.0706890104] [Citation(s) in RCA: 742] [Impact Index Per Article: 43.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1), released from gut endocrine L cells in response to glucose, regulates appetite, insulin secretion, and gut motility. How glucose given orally, but not systemically, induces GLP-1 secretion is unknown. We show that human duodenal L cells express sweet taste receptors, the taste G protein gustducin, and several other taste transduction elements. Mouse intestinal L cells also express alpha-gustducin. Ingestion of glucose by alpha-gustducin null mice revealed deficiencies in secretion of GLP-1 and the regulation of plasma insulin and glucose. Isolated small bowel and intestinal villi from alpha-gustducin null mice showed markedly defective GLP-1 secretion in response to glucose. The human L cell line NCI-H716 expresses alpha-gustducin, taste receptors, and several other taste signaling elements. GLP-1 release from NCI-H716 cells was promoted by sugars and the noncaloric sweetener sucralose, and blocked by the sweet receptor antagonist lactisole or siRNA for alpha-gustducin. We conclude that L cells of the gut "taste" glucose through the same mechanisms used by taste cells of the tongue. Modulating GLP-1 secretion in gut "taste cells" may provide an important treatment for obesity, diabetes and abnormal gut motility.
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Affiliation(s)
- Hyeung-Jin Jang
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Zaza Kokrashvili
- Department of Neuroscience, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1065, New York, NY 10029
| | - Michael J. Theodorakis
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Olga D. Carlson
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Byung-Joon Kim
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Jie Zhou
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Hyeon Ho Kim
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Xiangru Xu
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Sic L. Chan
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Magdalena Juhaszova
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Michel Bernier
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
| | - Bedrich Mosinger
- Department of Neuroscience, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1065, New York, NY 10029
| | - Robert F. Margolskee
- Department of Neuroscience, Mount Sinai School of Medicine, 1425 Madison Avenue, Box 1065, New York, NY 10029
- To whom correspondence should be addressed. E-mail:
| | - Josephine M. Egan
- *National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224; and
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Romanov RA, Rogachevskaja OA, Bystrova MF, Jiang P, Margolskee RF, Kolesnikov SS. Afferent neurotransmission mediated by hemichannels in mammalian taste cells. EMBO J 2007; 26:657-67. [PMID: 17235286 PMCID: PMC1794384 DOI: 10.1038/sj.emboj.7601526] [Citation(s) in RCA: 265] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Accepted: 12/05/2006] [Indexed: 01/06/2023] Open
Abstract
In mammalian taste buds, ionotropic P2X receptors operate in gustatory nerve endings to mediate afferent inputs. Thus, ATP secretion represents a key aspect of taste transduction. Here, we characterized individual vallate taste cells electrophysiologically and assayed their secretion of ATP with a biosensor. Among electrophysiologically distinguishable taste cells, a population was found that released ATP in a manner that was Ca(2+) independent but voltage-dependent. Data from physiological and pharmacological experiments suggested that ATP was released from taste cells via specific channels, likely to be connexin or pannexin hemichannels. A small fraction of ATP-secreting taste cells responded to bitter compounds, indicating that they express taste receptors, their G-protein-coupled and downstream transduction elements. Single cell RT-PCR revealed that ATP-secreting taste cells expressed gustducin, TRPM5, PLCbeta2, multiple connexins and pannexin 1. Altogether, our data indicate that tastant-responsive taste cells release the neurotransmitter ATP via a non-exocytotic mechanism dependent upon the generation of an action potential.
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Affiliation(s)
- Roman A Romanov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Olga A Rogachevskaja
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Marina F Bystrova
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Peihua Jiang
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY, USA
| | - Robert F Margolskee
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, NY, USA
| | - Stanislav S Kolesnikov
- Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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Bartel DL, Sullivan SL, Lavoie EG, Sévigny J, Finger TE. Nucleoside triphosphate diphosphohydrolase-2 is the ecto-ATPase of type I cells in taste buds. J Comp Neurol 2006; 497:1-12. [PMID: 16680780 PMCID: PMC2212711 DOI: 10.1002/cne.20954] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The presence of one or more calcium-dependent ecto-ATPases (enzymes that hydrolyze extracellular 5'-triphosphates) in mammalian taste buds was first shown histochemically. Recent studies have established that dominant ecto-ATPases consist of enzymes now called nucleoside triphosphate diphosphohydrolases (NTPDases). Massively parallel signature sequencing (MPSS) from murine taste epithelium provided molecular evidence suggesting that NTPDase2 is the most likely member present in mouse taste papillae. Immunocytochemical and enzyme histochemical staining verified the presence of NTPDase2 associated with plasma membranes in a large number of cells within all mouse taste buds. To determine which of the three taste cell types expresses this enzyme, double-label assays were performed with antisera directed against the glial glutamate/aspartate transporter (GLAST), the transduction pathway proteins phospholipase Cbeta2 (PLCbeta2) or the G-protein subunit alpha-gustducin, and serotonin (5HT) as markers of type I, II, and III taste cells, respectively. Analysis of the double-labeled sections indicates that NTPDase2 immunoreactivity is found on cell processes that often envelop other taste cells, reminiscent of type I cells. In agreement with this observation, NTPDase2 was located to the same membrane as GLAST, indicating that this enzyme is present in type I cells. The presence of ecto-ATPase in taste buds likely reflects the importance of ATP as an intercellular signaling molecule in this system.
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Affiliation(s)
- Dianna L Bartel
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado 80045-6511, USA
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Ivanova E, Müller U, Wässle H. Characterization of the glycinergic input to bipolar cells of the mouse retina. Eur J Neurosci 2006; 23:350-64. [PMID: 16420443 DOI: 10.1111/j.1460-9568.2005.04557.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Glycine and gamma-aminobutyric acid (GABA) are the major inhibitory transmitters of the mammalian retina, and bipolar cells receive GABAergic and glycinergic inhibition from multiple amacrine cell types. Here we evaluated the functional properties and subunit composition of glycine receptors (GlyRs) in bipolar cells. Patch-clamp recordings were performed from retinal slices of wild-type, GlyRalpha1-deficient (Glra1(spd-ot)) and GlyRalpha3-deficient (Glra3(-/-)) mice. Whole-cell currents following glycine application and spontaneous inhibitory postsynaptic currents (IPSCs) were analysed. During the recordings the cells were filled with Alexa 488 and, thus, unequivocally identified. Glycine-induced currents of bipolar cells were picrotoxinin-insensitive and thus represent heteromeric channels composed of alpha and beta subunits. Glycine-induced currents and IPSCs were absent from all bipolar cells of Glra1(spd-ot) mice, indicating that GlyRalpha1 is an essential subunit of bipolar cell GlyRs. By comparing IPSCs of bipolar cells in wild-type and Glra3(-/-) mice, no statistically significant differences were found. OFF-cone bipolar (CB) cells receive a strong glycinergic input from AII amacrine cells, that is preferentially based on the fast alpha1beta-containing channels (mean decay time constant tau = 5.9 +/- 1.4 ms). We did not observe glycinergic IPSCs in ON-CB cells and could elicit only small, if any, glycinergic currents. Rod bipolar cells receive a prominent glycinergic input that is mainly mediated by alpha1beta-containing channels (tau = 5.5 +/- 1.6 ms). Slow IPSCs, the characteristic of GlyRs containing the alpha2 subunit, were not observed in bipolar cells. Thus, different bipolar cell types receive kinetically fast glycinergic inputs, preferentially mediated by GlyRs composed of alpha1 and beta subunits.
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Affiliation(s)
- Elena Ivanova
- Department Neuroanatomy, Max-Planck-Institute for Brain Research, Frankfurt/Main, Germany
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35
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Kim JW, Roberts C, Maruyama Y, Berg S, Roper S, Chaudhari N. Faithful Expression of GFP from the PLCβ2 Promoter in a Functional Class of Taste Receptor Cells. Chem Senses 2006; 31:213-9. [PMID: 16394244 DOI: 10.1093/chemse/bjj021] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Phospholipase C-type beta2 (PLCbeta2) is expressed in a subset of cells within mammalian taste buds. This enzyme is involved in the transduction of sweet, bitter, and umami stimuli and thus is believed to be a marker for gustatory sensory receptor cells. We have developed transgenic mice expressing green fluorescent protein (GFP) under the control of the PLCbeta2 promoter to enable one to identify these cells and record their physiological activity in living preparations. Expression of GFP (especially in lines with more than one copy integrated) is strong enough to be detected in intact tissue preparations using epifluorescence microscopy. By immunohistochemistry, we confirmed that the overwhelming majority of cells expressing GFP are those that endogenously express PLCbeta2. Expression of the GFP transgene in circumvallate papillae occurs at about the same time during development as endogenous PLCbeta2 expression. When loaded with a calcium-sensitive dye in situ, GFP-positive taste cells produce typical Ca2+ responses to a taste stimulus, the bitter compound cycloheximide. These PLCbeta2 promoter-GFP transgenic lines promise to be useful for studying taste transduction, sensory signal processing, and taste bud development.
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Affiliation(s)
- Joung Woul Kim
- Department of Physiology and Biophysics, University of Miami Miller School of Medicine (RMSB 4040), 1600 NW 10th Avenue, Miami, FL 33136, USA
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Morgan JL, Dhingra A, Vardi N, Wong ROL. Axons and dendrites originate from neuroepithelial-like processes of retinal bipolar cells. Nat Neurosci 2005; 9:85-92. [PMID: 16341211 DOI: 10.1038/nn1615] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 11/16/2005] [Indexed: 11/09/2022]
Abstract
The cellular mechanisms underlying axogenesis and dendritogenesis are not completely understood. The axons and dendrites of retinal bipolar cells, which contact their synaptic partners within specific laminae in the inner and outer retina, provide a good system for exploring these issues. Using transgenic mice expressing enhanced green fluorescent protein (GFP) in a subset of bipolar cells, we determined that axonal and dendritic arbors of these interneurons develop directly from apical and basal processes attached to the outer and inner limiting membranes, respectively. Selective stabilization of processes contributed to stratification of axonal and dendritic arbors within the appropriate synaptic layer. This unusual mode of axogenesis and dendritogenesis from neuroepithelial-like processes may act to preserve neighbor-neighbor relationships in synaptic wiring between the outer and inner retina.
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Affiliation(s)
- Josh L Morgan
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
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37
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Spector AC. The functional organization of the peripheral gustatory system: Lessons from behavior. PROGRESS IN PSYCHOBIOLOGY AND PHYSIOLOGICAL PSYCHOLOGY 2005. [DOI: 10.1016/s0363-0951(03)80008-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Landin AM, Kim JW, Chaudhari N. Liposome-mediated transfection of mature taste cells. ACTA ACUST UNITED AC 2005; 65:12-21. [PMID: 16003761 DOI: 10.1002/neu.20157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The introduction and expression of exogenous DNA in neurons is valuable for analyzing a range of cellular and molecular processes in the periphery, e.g., the roles of transduction-related proteins, the impact of growth factors on development and differentiation, and the function of promoters specific to cell type. However, sensory receptor cells, particularly chemosensory cells, have been difficult to transfect. We have successfully introduced plasmids expressing green and Discosoma Red fluorescent proteins (GFP and DsRed) into rat taste buds in primary culture. Transfection efficiency increased when delaminated taste epithelium was redigested with fresh protease, suggesting that a protective barrier of extracellular matrix surrounding taste cells may normally be present. Because taste buds are heterogeneous aggregates of cells, we used alpha-gustducin, neuronal cell adhesion molecule (NCAM), and neuronal ubiquitin carboxyl terminal hydrolase (PGP9.5), markers for defined subsets of mature taste cells, to demonstrate that liposome-mediated transfection targets multiple taste cell types. After testing eight commercially available lipids, we identified one, Transfast, that is most effective on taste cells. We also demonstrate the effectiveness of two common "promiscuous" promoters and one promoter that taste cells use endogenously. These studies should permit ex vivo strategies for studying development and cellular function in taste cells.
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Affiliation(s)
- Ana Marie Landin
- Department of Physiology and Biophysics, University of Miami School of Medicine, 1600 NW 10th Ave., Miami, FL 33136, USA
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Abstract
A family of approximately 30 TAS2R bitter taste receptors has been identified in mammals. Their genes evolved through adaptive diversification and are linked to chromosomal loci known to influence bitter taste in mice and humans. The agonists for various TAS2Rs have been identified and all of them were established as bitter tastants. TAS2Rs are broadly tuned to detect multiple bitter substances, explaining, in part, how mammals can recognize numerous bitter compounds with a limited set of receptors. The TAS2Rs are expressed in a subset of taste receptor cells, which are distinct from those mediating responses to other taste qualities. However, cells devoted to the detection of sweet, umami, and bitter stimuli share common signal transduction components. Transgenic expression of a human TAS2R in sweet or bitter taste receptor-expressing cells of mice induced either strong attraction or aversion to the receptor's cognate bitter tastant. Thus, dedicated taste receptor cells appear to function as broadly tuned detectors for bitter substances and are wired to elicit aversive behavior.
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Affiliation(s)
- Wolfgang Meyerhof
- German Institute of Human Nutrition Potsdam-Rehbrücke, Department of Molecular Genetics, Arthur-Scheunert-Allee 114-1 16, 14558 Nuthetal, Germany.
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Pérez CA, Margolskee RF, Kinnamon SC, Ogura T. Making sense with TRP channels: store-operated calcium entry and the ion channel Trpm5 in taste receptor cells. Cell Calcium 2003; 33:541-9. [PMID: 12765699 DOI: 10.1016/s0143-4160(03)00059-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The sense of taste plays a critical role in the life and nutritional status of organisms. During the last decade, several molecules involved in taste detection and transduction have been identified, providing a better understanding of the molecular physiology of taste receptor cells. However, a comprehensive catalogue of the taste receptor cell signaling machinery is still unavailable. We have recently described the occurrence of calcium signaling mechanisms in taste receptor cells via apparent store-operated channels and identified Trpm5, a novel candidate taste transduction element belonging to the mammalian family of transient receptor potential channels. Trpm5 is expressed in a tissue-restricted manner, with high levels in gustatory tissue. In taste cells, Trpm5 is co-expressed with taste-signaling molecules such as alpha-gustducin, Ggamma(13), phospholipase C beta(2) and inositol 1,4,5-trisphosphate receptor type III. Biophysical studies of Trpm5 heterologously expressed in Xenopus oocytes and mammalian CHO-K1 cells indicate that it functions as a store-operated channel that mediates capacitative calcium entry. The role of store-operated channels and Trpm5 in capacitative calcium entry in taste receptor cells in response to bitter compounds is discussed.
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Affiliation(s)
- Cristian A Pérez
- Department of Physiology & Biophysics, Howard Hughes Medical Institute, Mount Sinai School of Medicine, New York University, New York, NY 10029, USA.
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Medler KF, Margolskee RF, Kinnamon SC. Electrophysiological characterization of voltage-gated currents in defined taste cell types of mice. J Neurosci 2003; 23:2608-17. [PMID: 12684446 PMCID: PMC6742075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2002] [Revised: 12/23/2002] [Accepted: 01/17/2003] [Indexed: 03/01/2023] Open
Abstract
Despite extensive immunological characterization of the cells within taste buds, little is known about the functional significance of the different cell types. In this study, we use taste cells isolated from mouse vallate and foliate papillae to characterize voltage-gated currents in the three principal elongate types of taste cells: type I, II, and III. Cell types are identified by using antibodies to external epitopes [antigen H for type I cells, antigen A for type II cells, and neural cell adhesion molecule (NCAM) for type III cells]. In addition, we identify the subset of type II cells that contains alpha-gustducin, a G-protein involved in bitter transduction, by using transgenic mice expressing green fluorescent protein under the control of the gustducin promoter. Our results indicate that antigen H-immunoreactive (-IR) cells and many of the antigen A-IR cells have small voltage-gated inward Na(+) and outward K(+) currents but no voltage-gated Ca(2+) currents. In contrast, a subset of antigen A-IR cells and all NCAM-IR cells have large inward Na(+) and outward K(+) currents as well as voltage-gated Ca(2+) currents. Unexpectedly, all gustducin-expressing cells lacked voltage-gated Ca(2+) currents, suggesting that these cells use mechanisms other than classical synapses to communicate signals to the brain.
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Affiliation(s)
- Kathryn F Medler
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA.
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Huang L, Max M, Margolskee RF, Su H, Masland RH, Euler T. G protein subunit G gamma 13 is coexpressed with G alpha o, G beta 3, and G beta 4 in retinal ON bipolar cells. J Comp Neurol 2003; 455:1-10. [PMID: 12454992 DOI: 10.1002/cne.10396] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We investigated the expression of Ggamma13, a recently discovered G protein subunit, and a selection of Gbeta subunits in retinal bipolar cells, by using a transgenic mouse strain in which green fluorescent protein is strongly expressed in a single type of cone bipolar cell. The cells have ON morphology, and patch-clamp recordings in slices confirmed that they are of the physiological ON type. Immunohistochemistry showed that Ggamma13 is expressed in rod bipolar cells and ON cone bipolar cells, where it is colocalized in the dendrites with Galphaomicron. ON and OFF cone bipolar cells and rod bipolar cells were identified among dissociated cells by their green fluorescence and/or distinct morphology. Hybridization of single-cell polymerase chain reaction products with cDNA probes for G protein subunits Gbeta1 to 5 showed that Gbeta3, Gbeta4, and Ggamma13 are coexpressed in ON bipolar cells but not present in OFF bipolar cells. Gbeta1, 2, and 5 are expressed in partially overlapping subpopulations of cone bipolar cells. Ggamma13 and Gbeta3 and/or Gbeta4, thus, seem selectively to participate in signal transduction by ON bipolar cells.
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Affiliation(s)
- Liquan Huang
- Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, New York 10029, USA
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Pérez CA, Huang L, Rong M, Kozak JA, Preuss AK, Zhang H, Max M, Margolskee RF. A transient receptor potential channel expressed in taste receptor cells. Nat Neurosci 2002; 5:1169-76. [PMID: 12368808 DOI: 10.1038/nn952] [Citation(s) in RCA: 428] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2002] [Accepted: 09/09/2002] [Indexed: 11/09/2022]
Abstract
We used differential screening of cDNAs from individual taste receptor cells to identify candidate taste transduction elements in mice. Among the differentially expressed clones, one encoded Trpm5, a member of the mammalian family of transient receptor potential (TRP) channels. We found Trpm5 to be expressed in a restricted manner, with particularly high levels in taste tissue. In taste cells, Trpm5 was coexpressed with taste-signaling molecules such as alpha-gustducin, Ggamma13, phospholipase C-beta2 (PLC-beta2) and inositol 1,4,5-trisphosphate receptor type III (IP3R3). Our heterologous expression studies of Trpm5 indicate that it functions as a cationic channel that is gated when internal calcium stores are depleted. Trpm5 may be responsible for capacitative calcium entry in taste receptor cells that respond to bitter and/or sweet compounds.
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Affiliation(s)
- Cristian A Pérez
- Howard Hughes Medical Institute, Mount Sinai School of Medicine, New York University, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA
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Zhao FL, Lu SG, Herness S. Dual actions of caffeine on voltage-dependent currents and intracellular calcium in taste receptor cells. Am J Physiol Regul Integr Comp Physiol 2002; 283:R115-29. [PMID: 12069937 DOI: 10.1152/ajpregu.00410.2001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the numerous stimuli representing the taste quality of bitterness are known to be transduced through multiple mechanisms, recent studies have suggested an unpredicted complexity of the transduction pathways for individual bitter stimuli. To investigate this notion more thoroughly, a single prototypic bitter stimulus, caffeine, was studied by using patch-clamp and ratiometric imaging techniques on dissociated rat taste receptor cells. At behaviorally relevant concentrations, caffeine produced strong inhibition of outwardly and inwardly rectifying potassium currents. Caffeine additionally inhibited calcium current, produced a weaker inhibition of sodium current, and was without effect on chloride current. Consistent with its effects on voltage-dependent currents, caffeine caused a broadening of the action potential and an increase of the input resistance. Caffeine was an effective stimulus for elevation of intracellular calcium. This elevation was concentration dependent, independent of extracellular calcium or ryanodine, and dependent on intracellular stores as evidenced by thapsigargin treatment. These dual actions on voltage-activated ionic currents and intracellular calcium levels suggest that a single taste stimulus, caffeine, utilizes multiple transduction mechanisms.
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Affiliation(s)
- Fang-Li Zhao
- Department of Oral Biology, College of Dentistry, Ohio State University, 305 West 12th Avenue, Columbus, OH 43210, USA
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Ogura T, Margolskee RF, Kinnamon SC. Taste receptor cell responses to the bitter stimulus denatonium involve Ca2+ influx via store-operated channels. J Neurophysiol 2002; 87:3152-5. [PMID: 12037215 DOI: 10.1152/jn.2002.87.6.3152] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies in rat and mouse have shown that brief exposure to the bitter stimulus denatonium induces an increase in [Ca2+]i due to Ca2+ release from intracellular Ca2+ stores, rather than Ca2+ influx. We report here that prolonged exposure to denatonium induces sustained increases in [Ca2+]i that are dependent on Ca2+ influx. Similar results were obtained from taste cells of the mudpuppy, Necturus maculosus, as well as green fluorescent protein (GFP) tagged gustducin-expressing taste cells of transgenic mice. In a subset of mudpuppy taste cells, prolonged exposure to denatonium induced oscillatory Ca2+ responses. Depletion of Ca2+ stores by thapsigargin also induced Ca2+ influx, suggesting that Ca2+ store-operated channels (SOCs) are present in both mudpuppy taste cells and gustducin-expressing taste cells of mouse. Further, treatment with thapsigargin prevented subsequent responses to denatonium, suggesting that the SOCs were the source of the Ca2+ influx. These data suggest that SOCs may contribute to bitter taste transduction and to regulation of Ca2+ homeostasis in taste cells.
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Affiliation(s)
- Tatsuya Ogura
- Department of Anatomy and Neurobiology, Colorado State University, Fort Collins, Colorado 80523, USA.
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Ruiz-Avila L, Wong GT, Damak S, Margolskee RF. Dominant loss of responsiveness to sweet and bitter compounds caused by a single mutation in alpha -gustducin. Proc Natl Acad Sci U S A 2001; 98:8868-73. [PMID: 11447270 PMCID: PMC37527 DOI: 10.1073/pnas.151235798] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Biochemical and genetic studies have implicated alpha-gustducin as a key component in the transduction of both bitter or sweet taste. Yet, alpha-gustducin-null mice are not completely unresponsive to bitter or sweet compounds. To gain insights into how gustducin mediates responses to bitter and sweet compounds, and to elicit the nature of the gustducin-independent pathways, we generated a dominant-negative form of alpha-gustducin and expressed it as a transgene from the alpha-gustducin promoter in both wild-type and alpha-gustducin-null mice. A single mutation, G352P, introduced into the C-terminal region of alpha-gustducin critical for receptor interaction rendered the mutant protein unresponsive to activation by taste receptor, but left its other functions intact. In control experiments, expression of wild-type alpha-gustducin as a transgene in alpha-gustducin-null mice fully restored responsiveness to bitter and sweet compounds, formally proving that the targeted deletion of the alpha-gustducin gene caused the taste deficits of the null mice. In contrast, transgenic expression of the G352P mutant did not restore responsiveness of the null mice to either bitter or sweet compounds. Furthermore, in the wild-type background, the mutant transgene inhibited endogenous alpha-gustducin's interactions with taste receptors, i.e., it acted as a dominant-negative. That the mutant transgene further diminished the residual bitter and sweet taste responsiveness of the alpha-gustducin-null mice suggests that other guanine nucleotide-binding regulatory proteins expressed in the alpha-gustducin lineage of taste cells mediate these responses.
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Affiliation(s)
- L Ruiz-Avila
- Howard Hughes Medical Institute, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, One Gustave L. Levy Place, New York, NY 10029, USA.
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Abstract
Acid and salt responses of taste cells induced by natural stimulation have not been investigated with exception of early studies with conventional microelectrode method, due to the toxicity of high concentration of salt or low pH of acid stimuli applied to isolated taste cells. This indicates that the application of rapid and localized stimulation to the apical membrane of taste cells is necessary for recording of natural responses to salt or acid stimuli using patch clamp technique. Recently we have developed a procedure to accomplish the quasi-natural condition including rapid, localized stimuli to the apical receptive membrane and the maintenance of taste bud polarity. In this review, we present our recent results obtained under quasi-natural condition using patch clamp techniques, comparing with the previously proposed hypothesis. One of our major finding is the fact that the acid-induced responses of taste cells in the mouse fungiform papillae are never suppressed by amiloride but an apical proton-gated conductance and a basolateral Cl(-) conductance possibly contribute to sour transduction. On the other hand, salt-induced responses are suppressed by amiloride, although the salt-induced responses recorded from a single cell involve both amiloride-sensitive and -insensitive components. Furthermore, the amiloride-insensitive component of salt responses possibly consists of multiple subcomponents including an apical sodium-gated nonselective cation conductance and a basolateral Cl(-) conductance. Recent reports also support the hypothesis that both acid and salt responses require specific receptor mechanisms of inorganic cations such as H(+) and Na(+) at the apical receptive membrane.
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Affiliation(s)
- T Miyamoto
- Department of Physiology, Nagasaki University School of Dentistry, 1-7-1 Sakamoto, 852-8588, Nagasaki, Japan.
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Abstract
The gustatory system of mammals can sense four basic taste qualities, bitter, sweet, salty and sour, as well as umami, the taste of glutamate. Previous studies suggested that the detection of bitter and sweet tastants by taste receptor cells in the mouth is likely to involve G-protein-coupled receptors. Although two putative G-protein-coupled bitter/sweet taste receptors have been identified, the chemical diversity of bitter and sweet compounds leads one to expect that there is a larger number of different receptors. Here we report the identification of a family of candidate taste receptors (the TRBs) that are members of the G-protein-coupled receptor superfamily and that are specifically expressed by taste receptor cells. A cluster of genes encoding human TRBs is located adjacent to a Prp gene locus, which in mouse is tightly linked to the SOA genetic locus that is involved in detecting the bitter compound sucrose octaacetate. Another TRB gene is found on a human contig assigned to chromosome 5p15, the location of a genetic locus (PROP) that controls the detection of the bitter compound 6-n-propyl-2-thiouracil in humans.
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Affiliation(s)
- H Matsunami
- Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Huang L, Shanker YG, Dubauskaite J, Zheng JZ, Yan W, Rosenzweig S, Spielman AI, Max M, Margolskee RF. Ggamma13 colocalizes with gustducin in taste receptor cells and mediates IP3 responses to bitter denatonium. Nat Neurosci 1999; 2:1055-62. [PMID: 10570481 DOI: 10.1038/15981] [Citation(s) in RCA: 246] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Gustducin is a transducin-like G protein selectively expressed in taste receptor cells. The alpha subunit of gustducin (alpha-gustducin) is critical for transduction of responses to bitter or sweet compounds. We identified a G-protein gamma subunit (Ggamma13) that colocalized with alpha-gustducin in taste receptor cells. Of 19 alpha-gustducin/Ggamma13-positive taste receptor cells profiled, all expressed the G protein beta3 subunit (Gbeta3); approximately 80% also expressed Gbeta1. Gustducin heterotrimers (alpha-gustducin/Gbeta1/Ggamma13) were activated by taste cell membranes plus bitter denatonium. Antibodies against Ggamma13 blocked the denatonium-induced increase of inositol trisphosphate (IP3) in taste tissue. We conclude that gustducin heterotrimers transduce responses to bitter and sweet compounds via alpha-gustducin's regulation of phosphodiesterase (PDE) and Gbetagamma's activation of phospholipase C (PLC).
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Affiliation(s)
- L Huang
- Howard Hughes Medical Institute, Mount Sinai School of Medicine of New York University, Box 1677, One Gustave L. Levy Place, New York, New York 10029, USA
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