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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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Kumari A, Mistretta CM. Anterior and Posterior Tongue Regions and Taste Papillae: Distinct Roles and Regulatory Mechanisms with an Emphasis on Hedgehog Signaling and Antagonism. Int J Mol Sci 2023; 24:4833. [PMID: 36902260 PMCID: PMC10002505 DOI: 10.3390/ijms24054833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/21/2023] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
Sensory receptors across the entire tongue are engaged during eating. However, the tongue has distinctive regions with taste (fungiform and circumvallate) and non-taste (filiform) organs that are composed of specialized epithelia, connective tissues, and innervation. The tissue regions and papillae are adapted in form and function for taste and somatosensation associated with eating. It follows that homeostasis and regeneration of distinctive papillae and taste buds with particular functional roles require tailored molecular pathways. Nonetheless, in the chemosensory field, generalizations are often made between mechanisms that regulate anterior tongue fungiform and posterior circumvallate taste papillae, without a clear distinction that highlights the singular taste cell types and receptors in the papillae. We compare and contrast signaling regulation in the tongue and emphasize the Hedgehog pathway and antagonists as prime examples of signaling differences in anterior and posterior taste and non-taste papillae. Only with more attention to the roles and regulatory signals for different taste cells in distinct tongue regions can optimal treatments for taste dysfunctions be designed. In summary, if tissues are studied from one tongue region only, with associated specialized gustatory and non-gustatory organs, an incomplete and potentially misleading picture will emerge of how lingual sensory systems are involved in eating and altered in disease.
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Affiliation(s)
- Archana Kumari
- Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
| | - Charlotte M. Mistretta
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA
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Fowler BE, Ye J, Humayun S, Lee H, Macpherson LJ. Regional specialization of the tongue revealed by gustatory ganglion imaging. iScience 2022; 25:105700. [PMID: 36582484 PMCID: PMC9792408 DOI: 10.1016/j.isci.2022.105700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/12/2022] [Accepted: 11/29/2022] [Indexed: 12/03/2022] Open
Abstract
Gustatory information is relayed from the anterior tongue by geniculate ganglion neurons and from the posterior tongue by neurons of the petrosal portion of the jugular/nodose/petrosal ganglion complex. Here, we use in vivo calcium imaging in mice to compare the encoding of taste information in the geniculate and petrosal ganglia, at single-neuron resolution. Our data support an anterior/posterior specialization of taste information coding from the tongue to the ganglia, with petrosal neurons more responsive to umami or bitter and less responsive to sweet or salty stimuli than geniculate neurons. We found that umami (50 mM MPG + 1 mM IMP) promotes salivation when applied to the posterior, but not anterior, tongue. This suggests a functional taste map of the mammalian tongue where the anterior and posterior taste pathways are differentially responsive to specific taste qualities, and differentially regulate downstream physiological functions of taste, such as promoting salivation.
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Affiliation(s)
- Bryan E. Fowler
- Department of Neuroscience Developmental and Regenerative Biology, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Jiahao Ye
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
| | - Saima Humayun
- Department of Neuroscience Developmental and Regenerative Biology, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Hojoon Lee
- Department of Neurobiology, Northwestern University, Evanston, IL, USA
| | - Lindsey J. Macpherson
- Department of Neuroscience Developmental and Regenerative Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
- Corresponding author
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Mori Y, Aoki A, Okamoto Y, Isobe T, Ohkawara S, Hanioka N, Tanaka-Kagawa T, Jinno H. Isoform-Specific Quantification of Human Bitter Taste Receptor Transcripts Using Real-Time PCR Analysis. Biol Pharm Bull 2022; 45:1185-1190. [DOI: 10.1248/bpb.b22-00292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Yoko Mori
- Faculty of Pharmacy, Meijo University
| | | | | | - Takashi Isobe
- Faculty of Pharmacy, Yokohama University of Pharmacy
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Abstract
Taste information is encoded in the gustatory nervous system much as in other sensory systems, with notable exceptions. The concept of adequate stimulus is common to all sensory modalities, from somatosensory to auditory, visual, and so forth. That is, sensory cells normally respond only to one particular form of stimulation, the adequate stimulus, such as photons (photoreceptors in the visual system), odors (olfactory sensory neurons in the olfactory system), noxious heat (nociceptors in the somatosensory system), etc. Peripheral sensory receptors transduce the stimulus into membrane potential changes transmitted to the brain in the form of trains of action potentials. How information concerning different aspects of the stimulus such as quality, intensity, and duration are encoded in the trains of action potentials is hotly debated in the field of taste. At one extreme is the notion of labeled line/spatial coding - information for each different taste quality (sweet, salty, sour, etc.) is transmitted along a parallel but separate series of neurons (a "line") that project to focal clusters ("spaces") of neurons in the gustatory cortex. These clusters are distinct for each taste quality. Opposing this are concepts of population/combinatorial coding and temporal coding, where taste information is encrypted by groups of neurons (circuits) and patterns of impulses within these neuronal circuits. Key to population/combinatorial and temporal coding is that impulse activity in an individual neuron does not provide unambiguous information about the taste stimulus. Only populations of neurons and their impulse firing pattern yield that information.
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Affiliation(s)
- Stephen D Roper
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, USA.
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, FL, USA.
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